Download - ECE 659 Fundamentals of Semiconductor Fabrication (May,Sze-2004)

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Fundamentals of Semiconductor Fabr icat ion

Fundamentals of Semiconductor Fabrication

GARY S. MAY Alsc.~mln F~ntta<lnlinn Pmfesror ,%b<,nl ofEleariro1 ond Cnmn1,ucr Enginerri,q a o r c l a l m ~ f i r ~ t f ~ of Trrhn~~logg Atlnnm. Gore in

SIMON M. SZE c~rc Choir I'rufi.?sor &',,lbnol Cltino lirng Ll t~ iwmlt~) &hri,8nnl Xnno n,vicc Lnlromforipr Ilrincl,!r. Toilcon

JOHN WllN & SONS. INC.

p d u ~ t c s o r fi&t-!t~ pcl(illiate studends in ph!si~s. chrmin~y e b e r i d cw*rr--rine. rI<.rn- ic;d e#>ginrering. md nratrrial. ricncc. 'The book r a n lx, t~u.cl conwlaic.nt1y i r k ;I

selncstrr-lcngtlu mum on integrated circuit fabriation. Such a arm%. ~ n ; q o r rlvd? ncA Iw rirmarnpnnird by ~s mrequisite lnlnratol).. Tllc test can alw u r \ r xs a rcfcr<,nc~. fo# nradicinc cnCinrcrr and scientists in the srnirun&iaor indust% .. .,

Clrrtpter I gives n brief historical o\.enimv of rnajar wrniconduaor <lr-irr-- and irr\ technolop dcvrlaprnentr. ;r\ \\,ell as an intrwluction to hmic i:~bricntion stvp-. Ch;lplrr 2 deals \,it11 cnstal ermvih twl~ninues. The next sc.\rd irlhimtcn nm oreanimd xn,nl- . ., ing to a hpid fnhrir;ttion .wplm& Cbapter3 presents siliror;oxid;<tian. Photolrtlwzmp!~ nnd etcllieg RrC <Lisct~ssed in Cbaplerr 4 and 5. reslxrti\.elp Chnptcrs (5 end 7 pn.'a.nt line prilnnl). tccbniqaes lor tlte intrrvludion oidopmts: djfilstoru m d inn implxnv.~tt:on. Thc final c1111ptcr on inclili\idaal process steps. Clrnptcr S. cows \arioor rnr t lml~ of thin film drporition. The final three chapters focus on h m d . sornrnati\.c topic-. Clrap:,.r 9 tics tlnr indi\irlunl nrocrss stens toceth~r hv nmmting tlw o m s flmrs for critic-.$ om- . " , . - . ccss technologies. integrated de\ices. and micmelwtrid n,ech;miotl syr)slr.rnr, \IE\IS>. Chapter 10i!~tralt1cesldcl~-le~~el iintemtedcircnit n,ae!~laawine bsarr. inc lad ine~~l t~ . hid testing. p~cknging, 6-ss mntrol, and )irld. Fimdl?, ~ l l ; r ~ t r ; l l d i ~ ~ m e s t!~r fut~xre outlook ant1 cl~dlrng~..s for the scn~icanductor indsstn,

Ench cln;eter iwCins\vith an intmludion and n list ollenminr rods and mnclard- ~. .- with ssun>rnan;of in~portnnt mnwptr. Solved cst:lmple pml~Iems arc pro\idrd t lrmo~h- out. and sareested l~omnrark nmhlems anwar ;kt the end of the chantrr 'ill? mnwirt . . . . of process siniulation is presented in scwml chapters. usin< the popular SI'PRE\I and PROLITI-I sohmre p~cljlges s application \rhic!er. 3 t a ~ t r ~ of this wtii\-arr h i n t m d d to supplement, but nM replace. l~aming the fcnndarncntnl rnnwptr ;~swciat<d \\it!, nticro- electrnnic5 pmcessing.

A complete set of detailed solutions to all endd-ol-chapter prnblen~s klr hecn p r c pared. This instntctori manual & ad lah le to d l ndopting k a l h 'Ill? fio~rn in tlw tmt are also availnhle. in electronic Cornat. fmrn the puhl is l~~r at the fr>Illlo\\ine \\r.hritr: l ~ t ~ ~ / ~ ~ ~ ~ ~ ~ ~ . ~ ~ i l e y c a ~ ~ n l l e g e I ~ n a ~ .

in~l<.btrd to Xlr. S. Erdor for trcl8nic;d editins of tlte manurrcript. 51%. Iris Lin for hp- ingtlw m:ay rc\islon nftl~edmlt. :tnd \ I s . Y. C. Y:ingofthv S~nriconductor L~hhorntary N:tlirmal Cl~iaoTung Univcnily\vlto fc~rnisltcd tltc hundnrls oftrxhnid illunntion~ ~,v.d in t l ~ r l m k .

M Jolrn\Viley :rsd Son%.\vr wish to thank hlr. \V 7lol,rin. uhn encoum~d us to un<b..r- tnkc tllc proirct. S. hl. Sw \rirlles also 1 0 arknm\.lr.dnc the Snrine Fo>iedation of t l~r

CHAPTER 1

Introduction 1

1.1 Scmimn~l~~ctor Materials 2 1.2 Sc~mimnrl!nctor Devices 2 1.3 Senlimnductor Process TecIlnolow 5

1.3.1 Key Semimndrrctor Trchnologirs 5

1.3.2 T ~ c h n o l o p Trends 8 1.4 Rsic Fabrimtion Stcps 11

1..I.1 Oxidalion 11 1.4.2 Pl,o1olithoCnph)~

Etcl>ing 13 1.4.3 Diffusion itnd ton

Implantation 14 1.4.4 Xfetslli.,.?tion 14

1.5 Su~nlnaty 14 Refrrrncrs 15

3.2 Imperit?. Rrdistrihatinn r h Oxidation 50

3.3 %larking Proprtim of Silic* Dioxide 51

3.4 0.6rle Qu;dity 53 3.5 Oxiclc Tlricknrrs Characteni.~tron j4

3.6 Onidation S~rnt!lntion 54 3.i Summary 57

References 58 Prohlemr 59

CHAPTER 4

Photolithography 60

4.1 Optical Lithography 60 4.1.1 The Clean Room (

4.1.2 Eymsan: Tools 6? 4.1.3 hlxsb 65 4.1.4 Photorericl 61

CHAPTER 2 4.1.5 Patten) Transfer i Crystal Growth 17 4.1.6 Resolution Enh;mc~.rl,r~~r

2.1 Silicon C y t n l C m \ t h fmm the Tnhniqurs 72 Melt 18 4.2 Next-Cencntiun Litllwraphir

2.1.1 Slartinp 'faterial 18 >Icthmk iR 2.1.2 The Cmchnlski TechniW 18 4.2.1 Elrctron Bern Lithm,phy id 2.1.3 Distribution of Dopant 19 4.2.2 Extwm? L'ltr.\\iolet 2.1.4 Effective Segregation L i t h ~ t p h y i6

Cocllicient 22 4.2.3 X-R;)y L i l l a , w p I ~ ~ i8 2.2 Silicon Float-7~ne Process 24 4.2.4 Ion Ream Litllopphy 79

2.3 G'aAs Cqrtni Gro\rtl~ Trcl~niques 26 4.2.5 ~ ~ ~ ~ > ~ r i ~ ~ ~ of \ ; L ~ ~ C ~ I B S

2.3.1 Starting Xlateriitls 26 L i t h ~ n p h i c hlctlm& 80

2.3.2 Cq51.11 Cm\*l~ Tccltnilues 30 4.3 Pl~o to l i tho~pl ty Sin~ul.~tion 81

2.4 hfaterial Cllarncteriz%tion 31 4.4 Sttmmat?. 83 2.41 \\5tfer Shaping 31 Ilcfrrmcrs 83

2.4.2 C q ~ t n l Cl~ar.lcteriation 33 Problrn~s 54 2.5 Summaty 38

References 39 CHAPTER s Pmhlems 39 Etching 8s

5.1 \Vrl Clte~nicxl Etchins 8 5 CHAPTER 3 5.1.1 Silimn Etcl~ins S6

Silicon Oxidation 41 5.1.2 Silicon Dioxidr Etcltit~? S i 5.1.3 Silicon Sitridr, ; u ~ d Pol\silirnn

3.1 Tl~ermal Oddntion Procrss 42 E t c h i n ~ SS 3.1.1 Kinetics of Cro\eh 42 5.1.4 .~ l~tmiaant I?tcl~ins SS 3.1.2 Thin Olidr Gm\ttli 49 5 . 5 Callintn hrsrnidr Etchin? SS

di L Contents

5.2 I)? Etchins 89 3.2.1 Pl;sntn Ft~n<lnmentals 90 3.2.3 Elclt hlrcha~ism. Plsamil

Ili;~q~ortics. and End-Point Control 91

5.2.3 Reactive Pl;~sma Etcl~ing Trrhnhlom ln t l Equ ipn~~nt 93

5.2.4 Resrli\.c Pl:nma Elcl~ing r\pplicntions 97

5.3 E t c l~ Sinlrll:~tinn 101 i:! s1111111113. 10.2

RrSiwac~~s 103 Pmbl~tns 103

CHAPTER 6

Diffusion 105

6.1 Rz i r Diffusion Prm,ss 106 6.1.1 IliNtnsion Eqtaation 107 6.1.2 Diffusion Profilrs 109 6.1.3 Evaltvation of DiNosrd

Lq!vrs 113 6.2 Extrinsic 1)iNusion 114

fi.2.l Cor1rrnlmlion-l3rpen(Ie111 UN,ei\ih 115

6 . 2 IliN~lsian Profilm 117 6 . L ~ t r r a l l)iflt~sion 118 4 I>ilfi8siort Sin~ulation 120 6.5 Summ;\r). 121

IicSr~rrnccs 122 I'rnhlra~s 122

CHAPTER 7

Ion Implantation 124

7.1 R:~nge of lnnplantetl Ions 125 7.1.1 Ion Dislril,ution 125 i.. Ion Slopping 127 I . Ic~n C l~ i tnnr l in~ 130

i .2 Impl:~nt l l an lng~ anrl ,\nnr;llins 131 7.2.1 Implant Dnuna~e 131 i.2.2 r\nn~aliag 134

i .3 Implantation-llcInte<l Processes 136 - .

8 ..I. I ilultipl+ Irnplantatio~~ ;tnd il:~skirtg I 3 6 - . 3 . 2 li lt-Anel? Ion lanpl;tnt:~tion 138 - . 1..%.3 l l i c l ~ - E ! ~ v ~ a n ~ l lligl~-C;n~rrcnt Implnnt;\tior~ 139

4 In11 Inlpl:ttntiiti(~n Sitna~li~tiou 140 - - I . Sumn~;rry 141

Ilcfi.n.nc~s 142 I'r~l>l,~rns 142

CHAPTER 8

Film Deposition 144

8.1 EpiI;~xial Grou<h Tr.rhniqtars 144 8.1.1 Cllcn~ical Vapor I>rpositio~~ 8.1.2 >lolcculnr Bvam E p i l ; ~ ~ 141

8.2 Stmdarrr and Defvcts in Epitaxid La\m 152

9.2.1 Lqtticx.-Xlatcl~ed and Stnincd- I~ayer E p i k ~ y 152

8.2.2 Def rc t in Epit i~xi i~l Layers 1 8.3 Diclrctric Deposition 155

8.3.1 Silican Dioxide 156 8.3.2 Silicon Si t r i~ lc 160 8.3.3 Lir>\r.-Dirlrctric-Constant

Xlatrrinls 162 8.3.4 Flig11-l)irluctric-Constant

\latc,rials 164 8.4 Po$silicun I)rpsition 165 8.5 hlet;xlli)i~tion 167

S.5.1 Pll)sic;tl \';tpor Deposition 167 8.3.2 Cllcnlical \'capor Deposition 16 8.5.3 Alnmien~n~ hlt:t:~llimtian 169 8.5.4 Copper hlrtell iz~tion I 7 3 8.5.5 Silicirlp 175

8.6 Drposition Simn~latiort 177 8.7 Sttr~~n,:~ry 177

References 179 Pml,lems 180

CHAPTER 9

Process Integration 182

9.1 P~(5ive Components 184 9.1.1 Tl l r I n t ~ g ~ ~ t e d Circuit

Hesirtar 184 9.1.2 Tl l r ln t tyc t t r~ l Circuit

Cep;lcitor 185 9.1.3 The Iut<yratrd Circuit

Indllch,r 187 9.2 Bipolar Tecllnolng?. IS8

9.2.1 l'hr R:rsic I'sl,ric;rlion Process I 8 9

9.2.2 Diplrctric Isoliition 192 9.2.3 SPIT-Aligned Doul~le-Pol!lilicon

B ip la r Stn~rtures 193 9.3 hlOSFET TCL.IIIIOIU~ 196

9.3.1 Tlw Bsic Ftthricatio~t Prcress 196

9.3.2 Mrn lon Dr\irr,s 199 9.3.3 CMOS ' r rc l~noloe 203 9.3.4 BiCMOS Trc l~nnlne 210

9.4 hlESFI7I"r,~rl~nalo~ 212

9.5 XIELIS T o c b n o l ~ 21 9.5.1 Ralk >~icromach~nxn~ st;, 95.2 Surf;$w >licromarl,ioin~ 215 '1.5.3 LICi\ Pr r .$ r 215

9.6 P r o w s Simulnliots 218 9 . i Summar). 223

Rrf<.n.nct.s 223 Prnl,lrlas 224

CHAPTER 10

IC Manufacturing 226

l APPENDIX 1

List of Symbols 26s

t APPENDIX B

International System of Units IS1 Units) 2fis

l APPENDIX ( Unit Prefixes 21

l APPENDIX D

Greek Alphabet 271

10.1 Elcclrinl Testing 227 l APPENDIX E

10.1.1 Trst Stn~eturn 227 10.1.2 Final Test 228 Physical Constants 273

10.2 Pach@ng 228 t APPENDIX F 10.2.1 D i r Separation 230 10.2.2 P;skngr T!ys 230

Properties of Si and GaAs at 300 K 275

10.2.3 h1t;trhment t APPENDIX G >lrtlmlolog$es 232

10.7 Statistical Prnrss Control 237 Some Properties of the Error Function f

10.3.1 Cnntrol Cl~arts Tor l APPENDIX H r\~trihtntw 237 Basic Kinetic Theory of Gases r s l

10.3.2 C m m l Cli;lrts krr \'ari?l~lcs 239 10.4 St;ttislical Eqwri~ncntal Drsip 242 tAPPENDIX I

L0:l.l Comptring Distrihutic~m W.2 10.4.2 Anal!sis of \';~rianw 243

SUPREM Commands 2s3

IO.4.3 Fs~isto~id D rs i p r 246 APPENDIX J 10.5 Siel(l 250 Running PRDLITH 287

105.1 l.'anctionnl Yiekl 250 10.5.2 P:ar.tmrlrir Yirld 254 b APPENDIX K

10.6 C o n , p u l ~ r - ~ n t ~ C + t ~ l Percentage Points of the t b~nnounon blanufald~tring 256

CHAPTER 11

Future Trends and Challenges 259

11.1 Cl~allrngrs for ln lep~t ion 259 11.I.L ~ ! l ~ n ~ s l ~ ~ ~ l l o ~ v Jttnclinn

Fnnl~;tlion 261 11.1.2 Ultr.ttltin Oxid,. 261 11.1.3 Silicidr Formation 261 11.1.4 Nva. ilatrrial- k,r

I ~ ~ t c r m n n t ~ ~ l i o a "-1 I l . l .5 1'owt.r Limitntions 261 I 1 . 6 SO1 i l ~ t r h ~ ~ t i o n 262

11.1 S!~trla-an-;t-CI~ip 2F^ 11.3 S n ~ r n m s ~ 204

H<*G-.n~nc~.s 261 l't~,l,l,~,l,s 264

t APPENDIX L Percentage Points of the FDimibution 3 1

Chapter 1. lnlroduction

TIlt. wort inlportant de j iw foradv;tncrd i n t e p t r d circuits is tile MOSFET (~ner;d- ,~yi~lr.-srlllilr~l~~I~Irt~~r licld.mll,vt transistor). \vhirh n a s n~portell I I ~ R ~ d ~ n g and Ali~ll:~" i l l l!)(il), 1.3 slloi,s tllr fin1 rlr\iw t~singa t l~rr~~~al ly<)xidize~l silicon s~~hstmte. Tile d,-dcr. Ira :I g:~tr lrr~gl, of 20 ~ I I I ;aal a F t r od#lc tllicknrss of 100 nm (1 nln = 10-'cn1). Tllc hsrr kt.\.l>olcs arr the s o ~ ~ r c r :md delis contacts. and tllc top elongated a r m is the alinrnin~,tt~ Satt. fi:tpo~ttcd t l l r o n ~ l ~ a mrtal ~n-k. i \ l tho~~gl~ prestmt-rl;~y 5IOSFETs I I I I ~ lxvtl a-.dn! clo~m lo tltp cl~.(~p-st~l~ndcmn rr@nle. th? clloi<~* of silimn :lnd tllemidl!. pwtn silicon dio\i<lc usrd in tlw lint hIOSFET rr~anins tllc innst important combination of n,atrri:ds. Tllr \IOSFET:III~ relatctl intrgctted circuits ~lo~vconstitule ;lhont 90% ofthe wmirnnduaor d e t i c ~ nlarkrt. ,111 oltc~cnlall XIOSFET \tit11 a cll;tnnrl lpngt11 of 15 nm 1l.w lrrs ~ l r n ~ o n s t c ~ t ~ u l ~ ~ ~ t I ~ " T l ~ i s d r ~ i c r n n sm.c;u Ill? b;wis for the most nd\anwd intrmntrd circltit cllips mnhining obrr or!? trillion (>lo1') dedws.

In 1962. Hall ct itl." lint acl~icvecl I:~sins in semiconductors. In 1963. KmemerlL and :\lfem\.a~al Ksxinov" proposwl tllr itck.rnstmchlre 1:lser. These prnposds Inid the f o ~ ~ n - dation Lrr nimlrn~ I:~.er dindes. \vhicI~ can h r oprratr(l mntin~tously at room tcn~perature. L x r r rlimlcs arc tlto key conlponents for ;I n i d r mnge of applications, inclrlrling <li$tnl xirlm disk%. optic:il-filler co~nm~naication. I;~ter printing. and atmospheric pollu- linn monitorinc.

Tllrw important micm\r~\rde\icrs\r,err invcntrd or rr;lli7,.d in thr tl,rrc ,ran, fir. fin1 ~ I ~ \ i ~ * u = ~ tlte t r ;u~sfemlclcdmn ~Iimlc (TEI): a ~ w c ~ l n ~ ~;,,~,,di,,+,, irl;r.ntprl 13. Gllon"ill 196% TIlr TI:13 is I I W ~ r.xtmrivrly in stdcl~ millinlrlrr.\,II,C applimli~ms clrtection s>Ttenls. remote mntrol5. m d microt~avc test instn~mcnts. rile S , . ~ ~ , ~ , I is ill? IXIp,VlTdi~le: its oprntior~\rm~ fiat o1,xn.d jnlll~ston d.8" i n ~ x j . I\I~:\TT diodrs can genecrtc t l ~ r l~igllest rnntin~~o~~s-t\; lre (CT\:J power at millimrtcr.,varc rre. qurllcies of:1ll selnimndllacrr deices. TI11.yare ~ ~ s e t l in radar qrntpnls ancl a l ; ~ ~ s,.ite,ns. The tllirtl dc\ iw is tlre XIESFET imrtal-sm~icondta:tor lielcl+llect transitor). invrntwl I? 5,le;al"in 19%. It is a kt.?<Ie\ice for t n n ~ ~ o l i t l ~ i c m i c m ~ a ~ r int ror~tal drorits ~.\!\IIcI . . ,

All IlnpOrtmt semicond~~ctor mrnmol?. cle\iw \\-a$ invented Ijv I;:iltnx and ~z,.:' i n 1967. Tl~is is thl. nonvolatile semimn(luctur nlernon. ( ~ T ' s ~ I ). \vI,~c:I, an rct;tin its infom.ttion \vl~en t11e p u r e r supply is nvitclml 011. ~ l t h o ~ ~ g l ~ it i5 similar to a rnn\.cn. tionnl XfOSFET, the major dillerencr is tl~eadriition of:l.'flmtinp.pte"inrvl~icl~ scmiper. tnancrit ellarge storage is possible. Recause of its attril~t~tes of nor~rolatilit~ Iiigh debiee dcmsity low power cuns~lrnption. and electrical rewit7ititbility (i.e.. thr stored c l~ : r~c . n n he removed hy appl!ine voltage to the contml gate), tltr X\'S>I 11s k r n t n e the ilon~i- nant memory for portatlle riectrnnic n5tems stacll a the wllulnr nllone. nolelvnk mm- ~~~.~ ...... puler. digital camen, and smart card.

.A limitins cace of the floating-gate nonvolatile nlemoy is t l ~ c s i n ~ l e - e l e d r ~ ~ mern- ory cell (SElfC) . u.l~icl~ is obtnined by reducing the Irngth oftlte floatis? p t e to "Itrd. slnall rlilnrnsionc (e.g.. 10 nnl). At this dmer~lion. uhen an ~ lechnn m o w i r ~ t o t l ~ ~ flmtillg gate. the potential of thegate\rili be dtrrrcl so that it uill prrvent the entnncr o f w o t l ~ e ~ rlcctmn. T l ~ e SEhlC is tile ~lllimatr floating-gate nlernol?. cell. sinw need only one electron for information storage. The oprcttion o fa SEhlC at mom teeprrnture15-.s Cra (lcmonstrated by Y:~no et al." in 19% The SE5IC cxn s e w as t l ~ e baris far the mort advancrd sen~imnductor nlmlories. \!*hie11 can mntain over one trillion hits.

The cl~a%e-co~~pled dc,dcr (CCD) u a s inwnted by h y l e and Snritll" is 1970. CCD is llsed exieosiwly ill \illen c;lnler;lr and in optical sencing applications, The resonant hm- nrli~lp d i ~ l e (RTD) n.a lint stulbed by Cllang el d.?' in 1974. RTD is the b:lciv for n~oct quwtun~-rffrct dedws.~d~icl~o~~redremrlyl~i~l~ d m s i h ul tnhi~l~rpnul . andenl~nscd filnctionality. I x ~ t ~ ~ s e it pcrnlits a p a t l y rr(lun.d na~nlwr of drtices to perforn~ a given circnit h~nbion. In 19SO. \ l i m ~ ~ c t e t ; ~ l . ~ d o r l o ~ l the 5IODFETinrxl1~latio11-cl~I TK.I<I- ellrct tnnsistor). \Yitl~ tile proper selection of l~eternj!s~~bion in:lteri:ll%. thr \IODFET is the fatest field-eNect tcmsklor.

Sincr t l ~ e invcntior~ of t l ~ e bipolar transistor in 1947. t l ~ e nunllx=r and \ari?hofrpmi- rnnductor devices Il:>ve i ~ ~ c r e a e d t r em~ndn~~s ly as ad\;~nccd t c r l ~ n o l q , no\. materi~lr. anrl brnrnlrncd compmllnaion lln? lwaeell :tpplicd to tlle creation of nrwtlr~icices. I-lmrm~r. one rnnpeIling question remains: \\lvat pnmsses are r q ~ ~ i r c d to mnstn~ct tl~ese won- drotls de\ices frnnr b:lsic sen~icondt~ctor m~~terials?

SEMICONDUCTOR PROCESS TECHNOLOGY Key Semiconductor Technologies

Figure 1.3 Tltc linl t ~ ~ ~ l . ~ l - c ~ r i ~ l c . - r ~ ~ ~ ~ ~ i i i ~ n c I ~ ~ r ~ ~ ~ r lic.l<l-a.&~rt l r ;~sr i \~or ' ' tl,hotwaph rnultey of )I..lI l~~lnnlrm~.s.l

\lnoy important semimnductor trchnolo@cs I I~ IW lwen dcri\rd f m ~ n pm'ssrs inwntc~l centt~ries ago. For e s : ~ n ~ p l ~ . 111" p n l h of n ~ ~ ~ t a l l i c q s t l l s in n h~rnact. *:as pionct.ml try ~ f ~ ~ ; ~ ~ ~ ~ li,ins tllp , \~s ten l sl~nrcs of LZliP Uctor i lllore tl1.11 2IXW) !rats ~?n."Tliw p r w s s urn itred to p ~ o d n w nrlxln steel in l~ re l~r ;~ ted fomd-cllnfl fltmaws. :\notllrr Pralnple is tllr litlloCnpllY p-s, wl~iel~ \V;IS i n v r n t ~ ~ l in 1795. In tltis o r i$~~i~ l pr-<. tllp p,ttenl, or iln;lge. ,,.- tr.\,,f~rrrd frnm s stone platr ilitho!.'' This section nltlsidrn

,he ,,,,lrrtonrr o ~ t w ~ l l l n ~ s ~ ~ ~ that U,PW applied for the Ant tilne to s~lni~-nduc*or pm- ,,.sr,,r <,r , ~ ~ ~ l ~ ~ 1 Fii;cl~~y for s r ~ ~ ~ i m n d u c t o r dr\iw filhrintioll.

s , , ~ ? kc, a,,,,irnnc[urtor tcrllnolot$.ics ; ~ r t listed in Table 1.2 in chmeol?!ir:~l ord I,, 1~,1,. c:Lwl,c,i&:' <~,,,~lo~wcl a li~luid-solid lnonon>~nponent pal11 twhniqt (,;nrl,r.~ski Sn,,,r)r is tilr pnn.s~ ,,srd to most of the cnstals lion1 \dl ic l~ silic ,,:,fr.s :,rr prwlncyd. :\notIlrr Font l~ trcbniqse \ m c de\.elopd by Rnygmw" in 1 9 n,,. Rnclwt:ut twhsique been 11srd rxtensi\rly for tltr qm!tl~ ol gi~llinm aneni .... I -I..,.UI .mnlmlnnd rcnlimnductor cnst;lls, hltl~oogh the sen l imnd~~r to r pmpert

rr. I?.

011

15

<,,a<, ,. ,~.~. .. ......=.. ~~~~~

s,lirnn I,..~\.~ hn , , ~ ( I ~ I V strldied sin; e~lrly IWO, tllr stucly of srmirnl~ductol- m pn,,,, ds ,,:,c nqlc*ed for.; lonetinle. In 1952. \ ~ r l k r i " ~ ~ o t e d that gallium anpnidr a n,l,ltcy{ ,,I.\: rn,,,pun& semimnducton. I-lr \%;IS ahlr to prr<lict tlreir c h a ~ l c t iaio and to thrn1 e.Trimr~~tnll!: T t ~ h ~ ~ o l o g and dc\ices nsing tllese conlpollr Il:t\.r r i l le h e n acii\vly sturlird.

TIl? dilii~sion of impurity ntolns in sen~iconducton is inlportnllt for d c d m p m s s - inq %,sic difilnon 1 1 1 ~ ~ \\;u m n s i d e r ~ l I?\. F i c P in 1%. The idea of using clifi~don tCyhniqun to *Iter tllp hp- of rnndurtivih in silicon \xu disclosed in a patrnt in 1952 h PCAnn.' In 1957. the ancient I i t h o g m p l ~ ~ p m s s ~ s applied to semimndlldor d<+ice I.hric3tion hy Andnls." He used photos~nsili\~e, etch-resistant po!\nl?n [pboloresisl) for p t t r m tnnsfrr. L i t l l p p l l y is a key t e c h n o l ~ forthe semiconductor ind~lstly The mn- tintled mo\\tl~ of the indttstn 11% heen the direct result of i~npmved litllogmpllic tech- ~ ~ o l ~ . ' L i t h o ~ ~ h y b &o a signifirmt economic Factor. currently repwsmting over 3%

TABLE 11 Key Smiconducmr Tachnologiar

Y Twhnolop. i\uthor(r)An\~ntor(s) Rrl

191s Cmhmlsli ~ s t a l p v i h Czoehralski 24 1 R~idmnan cnstA mmtth Brid~man 29 . .

III-\, rnmpounds Diffucion Lith-phir photomrist Chide ma~linq Ep i tnd C\D ~ \ i h Ion implantation Ilyhri<l inlwatnl cirnzit \lonolithir intrpted circuit Planar pnm,rs CMOS DRAM Pol!%Iirnn self-Aimed mte \lW,\D D n etchinx \lolm~lar h a m ep ik~y \lirropnrccrsor i4W1 Twnch iolrlinn Chemiml mcchnnical polishin< Cnnncr inl~rmnntd

\Velkpr Pfann .&ndns F m h and Derrick Sheftal. Kokorirh. and Kn~ilov Shockley Kill? Nn)rr llwrni \\hnlmr md Sah Dcnnard Keruin. Klrin. and Samw \lanam+t and Simpsnn Inin:, Lemons, and Bohor Cho Hoff et a!. Rune. >lomore. ant1 Ns&atnrho D:a\lui c.1 al. Pamnmak et a l ~

1.3 Semiconductor ProcessTechnolo~ 4 7

Tllp odd? rnaski~g n i r t h ~ l xlns drrt.loprtl by Frnsd~ anrl Drrrick" in 1957. nw-? fo11n11 illat an oxidr 1:1yrr c;ln p r w n t mast impllril) :ktnnlr fronl diffnsisg t l t n ~ n ~ l ~ it. Is thp S I I ~ P y(>:Ir. 111~. (.pil:~~iilj krox\tl~ p r ~ ~ i - s s I>:L-(TI 011 1111. chrmir:d \ . . l p r d~pnsition tpclt- niquc \ \ . i ~v dr\.rInp~!.SIIC~~LI r t ill. '" Epita\?. d ~ r i v r d froln l l ~ r (;reeli\vor<L~ cpi. me:nn. ins "on." and toxir. nlrstlitlS "ikrno~gen~c~~t." dvseribrs s lwItnitlttc of cnstal grmtilt to form a tlrin 1;lyrr of romic~,~al~lctor inntmals on 111,. r~~rfcmcv of n cnst:d that IIX a 1;tttic-c stnxcturrr irlcntic~l to th:~t of t11r cnst;tl. This ~ncll~rxl is immrt;lnt lor thr imnwc.mmt of dr\icr prrfonnnnce ;tnd tllc crcation o l novrl dmiw stnldun.r. In 1959. ;t mOina-n- t a n intevatedcircuit \\'m mad^ I)\. Kill>?' It mntilin<.d onr biw1:~r tmnsisto~ threr r ~ d s - . . . . . ~~~~~~~

tom. and on? rapleitor, all lnxle in grrrnanit~nr ;and c~,anrctnl lx \$irr hnndine-;! I ~ h r i d . . circuit. Also in i959. No!r.r" l~ro&,srd the monolithic IC I,? tlbrinting all ~lc\icr.r in a sinelr s r ~ n i r n n t l ~ ~ a o r s r~ la tn t r (nrottr~lilirl~ mems sin el^ slnnr.") ;and mnnc<tiiiine tllr dr*iws I>\. :iIunrinu~n ~~~rtalliz;~linn. I'i~!nrc 1.4 shows the first mo~~olill~ic IC of a flir)-flop rircnit . . mntnining six dr\icrs. Thc altaninmn intrrmn~~cdtion Lines urnnhkl innl hy rtchingevap o n t r d nlonlin~~ln lawrover thr entire or i~lr snrfam. \wine thr l i l h m n l ~ i c lrchni<n~r. TIkrrr . , inrrotions l:url tlw foendntion for the napid gro\\ill of tlre inicrwlcctmnics industn.. . .

The plannrprocrss ns drvrloprd hy Hwn~i"in 19fiO. In this p m s s , an midr layer is formed OII ;i srtniconductor sarbce. \\Ftll the h ~ l n of ;I litllom;mltv nrocess. m r t i n r . . . , . of the oxide CITI Ix rrmo\.e<l ;uld \rindo\\s cut in the o d e . Ilnpurity atoms \\ill r l ihs r only througll the eqxwxl seniimnd~stor sn~&~re, and ,)-,I jrnnctions s i l l fonn in the odde wiado\r. nrens.

t. rip. ,,,,,,i,~cui, r , i t~,r IC ilscn-;rsnl. t r d ~ s o l q 11:s nlo\wl f m n ~ NXfOS (nrl~annt ,,FI. 1. I,, \ I ( I\ ,,,,,,,ll~,.,llmt,ln. hlOSFKTI. \~.lliclb e ~ ~ ~ p k n s Lx)111 NSlOS zlntl PJIO

:.~. !,,,,,,.,i \~(i\l:t:T~ t,, ion,l t~,r kxjc c~It~na.nts. ChIOS cvnept \\;rq pmpost*~l I]? i t ,,!! ,<. .,,,,I <,,I , , t,, lw;, TIl,. ;i~lx:tnka:c* c>fC:\lOS t~~clmolnq is that I ~ ~ c ~ ~ ~ ~ I I ~ ~ ~ I I I s ~ K I \ V

< ,7 t l~ i t . ,~! t ctnmv!at t~nh tit~n~t: t l~v t~insilion ftvln on<, statt, to ~1110titer l<,.g., fro111 0 to 1) .cr,ri ,in,,, w n lxttlr. rumnt Ix.h\rro tr.t~aitCms. itllouing po\\vr mnsu~nption to hr lllin- ,:.,.r.,! C\IOS tvrlmnlrr,? ic 1111. c!o~sinsnt t t ~ ~ l ~ 1 1 o l t q for arh;aln'd ICs.

11, 1'H%7. :el ixt~jrni;tnt h\n.eh~ln~~nt circl~it. tllr cl!~~ialaic random a w n Inmion Dl< \ \ I . I-.~1 insvxttrtl 11, Dt.nnanl." The mrmoyci~l l contains onp SIOSFET and one

c ii.~~>.-,lr~r.~w <-.lpxilor. Tllr SIOSFET wmvs is n stilclt to c l l ; q or d i x h a ~ e ttlle clpac- i ! , )~ :\ltIt011"t 11 lIH.\\l i* \mlatik, iuld IOIIInnes mlstiw!y l l i ~ l l po\%vr. we e h ~ e c t lllat I>I{ . \ \ I \ \ r i l l n,nlin18r to hr lllr lint cl~oice anlong \ariulls st*n~iconductor memulies for nr , l lp~rl ; thl~~ rllrtmnic r?sle!ns i n the &rrcswablr fllturc.

rir illq)m\t. IIC.\KY pcrformann.. the lwl~silimr~ self-aligned gate pmrrss uw pm- pos<yI 1,) i;en\it~ el ;<I." in 1969. Tl~is prm~,ss not only improwd dmin. rrliabilih blrt .$w wlltoul pcwitir r;~p.lr<tia~ws. Alsn in 1969. the i n v h l o ~ ; e ~ i c c l ~ r ~ n i c a l tnpm d e p ritinn t \IOO'DI inrll~al\r:r< detr lopd by >l:svaw8il :ual Si~n~son." This it a\.?? impor- 1.w rpii;t\ial qo?n\\il~ trclrniqnr for r ~ , m ~ w i ~ n d scmimnducton such as CaAs.

i tint. clr\im <lin~rnsions \wre reduced. the d? etcliing tecl~nique WIS drveloped tn n-pl:m-\rrt rllr~ni~xil rtcl~ine for hi~li-lidrlihpattem tmsfer. This tmliniqae \\as ini- tt;hlml by I n i n ~ r t al." in 1971 usinza CFJO: gay n ~ i x t ~ ~ r e to etch silicon wafers. Another imp'RxIt tc.cltniqae de\.cloprd in the same )par b)- ClioA' \\-a molecalar k n m epitay. Tltix tt.i-lmiqltr hils tllr atl\-,rrrhqe of near-perfect vertical mntml of co~n~osition and dop- inr rlnua to ;~to!nir r!im?nsions. It is responsiblr for the creation of numemos pllotonic dc\ims and qaamtum-rffrn dr!in>s.

111 1971. lllr first ~nicmprwssor\t~as made I?\. Hoff r t al..*a.l~o put tile entire cen- t ~ t l p m r i n x itnit (CPti) of a sirnplr computer on one ellip. It u x a four-bit rnicro- pnxrssor (1ntt.l -IWl. sllm\n in F i ~ l r e 1.5, nit11 n chip size of 3 mm by 4 mm. and it mnl;~innl TXXO \IOSFETs. It \r;lr fahricatetl by a,>-cl~annel pol!silicon gate pmcess using 1111 j-pni d r s i v n ~ l r . This micropmssor prrfonned a$ well as tllosr in S30n.WO lBhl mnil>tttrn uf tllr ~ i ~ r l y 19~Xk--e;;rll of\r.hic& needed n CPU the sizz of a large desk. This \rxs ;I major I~renkil~rougl~ for tllr sen~icond~rtor i n d ~ ~ s t n Currently. tl~icropmcessors m!rctittrtc thp lap~est se:ment of the inrhlstry

Sinw tlw ri~rly 1950s. many new tccl~nalogies have been developed to meet 111 vquirmlmts of ewr-sltrinking minimum feature lengths. Three key tecl~nologies nr trenclt isolation. rl~rmical mecl~aninl polishing. and copper interconnect. Trencli isola tion 1 ~ 1 , n o l o ~ . \v:s intrmhlrrd by Rung el al." in 19%' to isolate CMOS dr\ices. This :ipprnach rvrnhtally replacml ill1 o t l i ~ r isolation mctl~mls. In 19S9. the chen~ic%I mechan- ictl polisl~in~ n~rll~wl\\:rs d~vrloped Iy Daari n al." far ~lobnl planarilation ofthe inter- Lwrrlirlwtria. ntis k a 1 ; ~ p m r s - for mtdtilmrl metallization. At snd,micron dimensions. a \\i~lrly Lnmvt~ hilure nlecl~anisn~ is rlrctromigration. wllich is the t n l l s p r t of metal in- thrnuzlr a rnn<l~tctor d ~ i e to the passage ofanelectricill current. ~ l t l ~ o u g l l aluminum h;a ht-rn used sinm, t l ~ r early 196~1s a% intrrmnnrct n~atrrial. it suffers from electromi- $ration at l ~ i q l ~ rlrrtrical amrrrnt. Coppcr intrrmnnect was intmd~lced in 1993 by P.IRKZCLI~ r t al." to rrplnw nlominurn for minimum1 fnture lengla approaclling 103 nni. Tliis I m k mnsidrn all the trcl~nolqies listed in Table 1.2.

132 Technology Trends

Sinw htv Ixyinninenftl~r tnicrns!rdmnics e n . tllr smallest linmvirlth (or the minimun f-.shlrr i~n?l l l ' nf:al intrgalrd c imi l Ilas I w n r e d ~ ~ m d nt a lilt? ofahlnt 13% per year'

Figure 1.5 1'1.. lint ~ n ~ ~ r r ~ ~ n r ~ s r r ~ r ' (I'l~otrrq;tpi~ uuarirsyof lntcl Corp.1

At that ntc , the n~inimum feature length \\ill shrink to alwttt 50 nni in tlie !Far 1010. Debice miniat~rriziition resnlts in m l o n d unit cost prr circuit funnion. For example. tltr cost 1x.r bit of memoly chips 11;s 11nl\rd em? 2 !ran for suwssiw genrr.16011~ of DRAM circoits. r\s (levice (linlensions d~crmsr . tlrc intrinsic svitclting time drcre;rc~s. Dcrirr. speed has iniprovrd I,? four orden of ma,pit,~de s i n e 1959. Hiqhcr spreds lrld to cxpnndrd 1C limctional tllrougl~put rates. I n tl~r f u t ~ t r ~ , di@t:d ICs \\ill be iil>le to perform data processing and numrticnl computation at terahit-l)er-semnrl rates. As dc\ims k m e s smnller. thq. consume less p w r . n~r rc fnr r , dc\im tniniat>1ri7~1tion :also d u c r s tlw m e n f used for nicli nvitcltinr! olwmtion. Tltc r n r r ~ dissipntcd pcr Io*c cntc h a ..~- -~~~~ n .. . clccrr.lsed I)? over on? million limes sinn. 19%.

r?imsro 1 (icl,n\\r l l ~ cmnllmti;~ inerras? oftllr ;tciusl DHA>I rlrrlsih%mas lhr !ria . .&,... ...... ~ . .~~~ "ffint pmlndio,l fWnl ]9 i i to 2000. nlr rlrnsi~~incrcscs by a factor o f? c\m. IS ~nontls. [ftrentk mnti,~,,c, DR,\\I dc~~sit).\~iill incn.:~sc lo 8 Gb in tllr!'car20(Li ;ulrl to 64 Ch nrmllld 1IIe 2012. l?iymrc, 1.7 s l l m ~ t l ~ r eWnentiid incw:se ofnl icmpmswr mlllpat*io~;~l tm,Tr, ~ ~ ~ ~ ~ , ~ , ~ i ~ ~ ~ ~ ~ ~ pP.cr in~n.;srs I,? a fador o f ? c S % y IS nlollt~ls. Cltmnt!\: 3 ~.,...;..,.-1.,.,1 ,.Y.N,,,,:~I mlnnl,t(.r 1,;~s the SB~IP mntpatntionnl p w r :s tlut of *I CR4Y I

1.4 Basic Fabrication Steps 4 I 1

Fieurc 1.8 illoshtes the emnth ntmes fordiflewnl lecl~nnlamdriven:" A1 Ute hnin- ning of tlw nuo~l#m~ ~ I t ~ l r ~ ~ n ~ ~ em ~1950-lCI:O . tlw bnpl~tr t r~~~~s i s to r u:ts tltc twlt~nol. om. ~lri%r.r. I.'rnn~ 10711 to I!J!XI. tllr DR,\.\l and llw nlivnrnmn.<sor l,:~wl on 510.5 ~ l n i r r r ,., n r r e tltr t c c l ~ n t ~ l o ~ ; driven because of tllr npid grnntl~ of p ~ n o n a l cornpaten and

b 1.4 BASIC FABRICATION STEPS Today planar technologv is used e\iensiveIy for IC Fnhrintion. Fiplms 1.9 and 1.10 show the major steps o fa plnnnr pmcrss. Tllrsr steps isclt~de o\idntion. p l ~ o t o l i t h o ~ p p l ~ ~ etchins. ion impl;ination. ned tnrtdliwtian. This r~~clion dcscrilws tlinr steps briefly blow detailed disrt~ssions can 1w fol~~lcl in CI~:,pten 3 10 S: Chapter 9 describes lllc inregfit- tion of tllcsr unit p r w s steps to Torn) sernimnduetor de\iws.

1.4.1 Oxidation

rile rlP,vlopmcnt ],igh.qanlih silimn d i o 6 6 (SiO,) 11% l l c lp l to rsti~hlisl~ the C~OIII-

inane ,,r~i in tllr p m ~ , l ~ i o l , ufmnl~n~mi;il ICs. (anpnlh SiO, hlnctions as :m inculator

1.4 Basic Fabrication Steps 4 ID

Figun 1.9 lo) A bare n-t?pe Si wafer ib) An a d d d Si wafer hy &y or ~ c t oddation fr \pplimtiun ofn+rt, tdl Rnin flrr;ure thmqh the mark.

in a number ofdnim s t~ctures orar a barrier to dflusion or implantation during devil fahriration. In the fahriation ofap-n junction iFig. 1.9). the SiOI film is used to defir ole junction awa.

Therr are hvo SiO, methods. dl). and \vet oxidation, depending on whetha dl). o9yrn or w t e r \ a p r k us&. Dry oddation is usually used to form thin oxides I

a h i m . stnlmlr? h ~ r s e of its eoocl Si-SiO, interfam cl~mcteristin. \vliereas wpt or dation is a d for tl~icker la!~rs l m u s ~ * of its higher p \ t h rate. F ip re 1.90 sllows sfMon of a haw Si wfer T C : I I ~ for oddation. Aftcr the oddation prapss. a SiO, layer formed all owr the a l fer surfam. For simplicity, F i ~ r e 1.91, shmm only the upper su faw of an oxidi7~d ~ ~ f v r . \lore details on oddation ma!. he found in Chapter 3.

cl Mnll '+LA cn

Figure 1.10 (0) Thr \clfer after the drwlopment. lh) Thexalcr aRer SiO, remud. (c) The final result aftcr a complete lithngraphic pnxrrs. (d! A p-r jtnnclian is farmed in the diffusion or implantation pmcsr. ( r ) Thc >rafer after inctdlintion. (fi A p-r, junction lner the romplcte pmcrssc's.

Photolith

I - - -r the solv<

Fig mask usi

- A.

ography and Etching

Another technology, calledphntolitlmogra~rlmy, is used to define thegeometry of thep-n junction. ARer the fonnntion of SiO,. the wafer is coated \rith an ulha\iolet ( W l liglit-sensitive ninterid d l m l apholnmivl. which is spun on thewnler surfacehya high- GWPA winner. ARenvard (Fig. I.*). the mafer is baked at about 80°C to 100°C to &\?

.nt oul of the resist and to harden the resist for imnpmpd ad~esion. Ire 1.91 shoua the next step. ~vhich is to e.xpose the &r tlvough a pttemml ng a Ul'light snum. The eqmed =@on of the pllotorwistcoahduder under-

&- i s c~ten~ical ~ x t i o a depencIingon the Qpeof mist. 7he area* to w ~ t b m c s p ~ l y n e ~ e d and difficnlt to remmFe in anetchant. Thepohmerized e o n retnainsdnn the \v.~fer is placed in a developer. \\,hem$ the unexposed region (under theopaque area) clissolws a~ld \\il41es away.

FiOln 1 . l h il~mr- the \\afer nller the development. The \\?tier is agoin baked tr 111l'c: I,, ISIPC for 20 minutes to enhnnw the adhesion and i~npmve t11e resistancr t~

s ~ t l ~ w ~ , ~ ~ ~ t rtrhing pnxrss. Then, inn etch I I S ~ I I ~ 011lk.red I~yclrofl~~orie acid (AF) n,rrm\r.< 11w ~ ~ s ~ r o t n t ~ l Si0: s~ l r f iw (Fig. l.lW!. h t l y , the rt-sist is stripped a\myby r c1lctnic:d wlnt~ion or an opSrn pl;uma s!strm. F i g u r ~ 1.101. shn\n t l ~ e finid rs111t of a

\\?tl,o~t oxide (R uindow) :titer the l i t l ~ o p ~ p h y p m s s . The wafer is no\\. read! fi,r fornlinS thrl+n junction hy a cliffusion or ion in~plantation p m s . Photolithnppl~! .and t.trl,inc sw drsrrihrcl nlorr thnrn~l<hly in C h a p t ~ n 4 and 5. respctively.

1.43 Diffusion and Ion Implantation

I" rhr (liflwion s ~ r t l l ~ l , tlre senlimnductor surfam not protected by the oxide is expo! to;, sonme rrilh a hiell concvntration ofopposite-typ? ilnpt!rih The impurity mo\r,s il the wnnimntlucturcnJt;il h sulid-st21te diffusion. 111 ion in~plmtation. tllr intended i~n l rityis intmluct~l into thr semiconductor hy awleraling the impuric ions to a high e a r Iewl ant1 then impl.mtieg the ions in the srrnicond~stor The SiO, la!w sen.es .u a b rier to i m p ~ ~ r i y (liITwio~~ or ion irnpl.mtiation. Alter the difilsior~ or in~plantation p m s . the IM iunction is formed. as shown in Firmre L.IM. Due to lntrrd diffusion . , t~nl>unt~e< or 1.1tecd s t n ~ l e ofttnplant<.d ions. 111,. ~ d t h o I ' t I~~ .~~- repon is s l i c l ~ t l ~ t rv

t lun the \<?nclo\v openin<. Diffttsa~\ ;,ad ion i ~ n ~ l ; u ~ r a t b o ~ ~ arc disct!s5ed in C:I\;~pter and 7. rr.specti\vly,

1.4.4 Metallization

.\ftrr difircion or ion implanlation. ;I m~,l$lization pmcess is uwd to form ohlnic cont;l and i n t r n o n n ~ t ~ o ~ l r IFbe L.lOr). \ktd films can Iw formed IIV d~\sic.~l \.;*nor dew%it .. . or chemical \apor deposition. The p l ~ o t o l i t l ~ o p ~ h y p a s s is again used to define fmnt mntact. \vhich is sltmvm in Figure 1.1% A similar metallimtion step is performed the back m n h a rrithout udne a l i thmphsprorrss. Nonnallv. a lmv-temwrahlre (<.-%I' . . . . anneal aaukl dw be perfokecl to promote low-resistan& contacts L h w e n the mt Ia!rn and the senlimnductor. Uetallimtion is discussed in more detail in Chapter 8.

ied 1tO 1u- '3 ar- m.

,L,>

ion the on .-~

r 1.5 SUMMARY %miconductor devices haw an enormous impact on our society and the global econom! brcause they sewe as the fnundntion of the largest industry in the world-the electron i a industr).

This intmducton. chapter has presented a historical ro iew of major semicondt~cto dmices. from the first stutly nf the metal-semiconductor mntad in 1874 to the iabricatio~ ofan ultrasmall 15-nm hlOSFET in 2001. Of particular importann are the invention o the hipolar trmsistor in 1947, which ushered in the modem electronics era: the devel opnient of the hlOSFET in 19fiO. whiclr is the most important d m i n for integrated cir cuir : and the invention of the nonwlatile semiconductor Inenlory in i%i, wl~ich ha h w n the technolog\. driver of the electronin indust? since 1990.

This chapter also described key semimnd!~ctor technologies. The origins of tlt, trchnolo$es mn h t r a e d hack as far a% hm millennia. Of particular importance are < lwlopn~en t of the l i t l ~ o p p h i c photoresist in 1957, which estaMished the \?sic pan,

ese

tmmfrr p m s s for semimn;luctir deices: the in\rntion of the integrated circuit i;l 1 9 ~ ~ ulwch wu wminal to th- npid ero , r t l~ of the micmelectronia industn.: and the dwel . .. ,. ~ .~~~ oprnrntt of t l ~ e DRAN in 1967 and the n ~ i c r o p m s s o r in 1071. which constitute t111 h\n Iaq-t spmnrnts of the sen~icantl~rctor industry

In this lank. each chapter dmls wit11 II k<.y IC fal,rir;~tion p r m s s strp or s~rlnlpl~n. o f s t ~ ~ ) s . l:ncli c11aptt.r is prcsrnted in a clnlrnnd cohrrent f:ahion \*tl>on~t l ~ c n ~ v rrliantr on lllc original litc.r:ltnre. I l n \ % ~ ~ r ~ r . e few iallxniant paprn ir? listrrl at tltc r.n'cl ofr:ach cl~apter for n.frrrncr and for f ~ ~ r t l ~ r r rradinp.

.. .u^ru+ctmnlc.\lnrkef IhDo," B ~ n k . Elmm!~ lnd. Asur.. \\:rhinetoa. IIC. 2MO

Ind. Tnl~nnl. A

"lltrtrd in S. .\I

i5. In?l., Il.indtu, T ' x n . ZOO.

I . Sa,. Ed.. .%nrlurnd~~rfor k l c n Rnvrdnc

4. R. K. Sp. Corn1,fNr Ctrirlr 10 Smllmnar,rror mmlc<r. YFCnr-trill. Scrv York 1w5.

5. F Dmun.-Ulxr die Stmmleilu*ng duwh Scl>>\clrlmcldc~: A n n N>yr C h m ~ . 151.554 (18741.

6. H. J , nmmd. 'A N o s on Carbmrmclutn: U'arun. l sdd . 19, SY) ilwi!.

7 . J. Rmltw and \\'. H. Rnttdn. 71wTnnsislor, nSrrnlmndtnnnr Ttiodr:Pl~!,r. Rm.. 71. %N iIPllii.

8. IF S l ~ o e M ~ , The l l~wn. of," June dudon mrl lw ~unnion Tmri.sfan: 8 4 syrr Te1t.I.. 28, 43.5 119191.

8 J. Ebm. 'Fo~~rTcrmlna1~wr-p-n TNni,torr''Pm. IRE. 40. I361 119i21.

10. D. Sf. Chapin, C. S. Fcrllrr mcl C. I. Pmmn. 'A Sm. Silirnn p-n Jlnnnion Pl~nlocell for Compnirlc Solar Rrrlirtion il~lo Elrrttinl Pmsrr-J. i\l~l,l Phhyr. 25.676 i I Y 3 1 .

11. !I. Kmrmcz Tllrnr).ofn \\iclr-Gap Emitter forTc~nriston: Pm. IRE. 45. 1535 (1957).

I?. L Eub. "Sw Phrnomcnon ill Sam~~Grrmoniu!~>p-n J~~nrlinnr.'Pl~p. Rn. . 109. rfi3 (1931.

13. D. Kdmgand M. 51. Aldla Tilimn-Silimn Diotick S u d k ~ . Dnicc:in IRE Dcvirr Rrrrarln Confirmrr. P i l ~ . h u r J ~ . 19Ca iTl~r p p r n n l r lo~rld in Be(. 3.1

14. R. Yu. ct td..'tS nm Gat? h.nmll Pimar CIlOSTmntisloi lEEE IEDW Trclrnlml mgen. \ Ihh inson . DC. p. 937 iZWI1.

15. R. S. Ilrll. el al.. 'Cohewet L i ~ h l Erniction fmm C.& Juttnionr:l%p. Rn.. It!,.. 9.366 119621.

16. $1. Kmrmrr:A P m p im,jtmnninn InFlicrn Lwlrrrs: Pnx. IEEE. 51, l ib2 iIW31.

17.1. A l k . m n n d R. F. Ki o n d l ~ l o r h w r \ ~ i l l t Elwitiol P~rrnpinx: US.S.R. Patc.nt 181. - - (3, OW.').

18. J. 8. Cunn. -~ficm\m\~w O~lllrliun~ ofCt#mnl in Ill-\'Srmirnndanun.~S~M Slnrr Cmma8m.. 1. &I (1Sii3). 19. R. L Jolmrton. B. C. Dekla . jr. and n. C. Calm.-A Sil'imn Dicx(x(, .\(icnnmr~ M U ~ N : &I1 SI(*I. Tech.].. 4.1.369 1ILK5). 20. C. A. Atead. -Seholth. B,unr.r G ~ l e Firld E a r t Trmsi~lar' Prw IEEE. 5.1. MYI: i IW?) .

1' ib b duprw I. Introduction

a I (-,, I ,~ J J I . -I:,,, -arrn mr ~ I , ~ I I , , ~ ,kr ~ t i r t d l i * ; l t i o ~ ~ ~ w c I ~ ~ ~ i n d i ~ ) R ~ i ~ drr .Vetdlr.* 2' Fh:, ,'!,<", 9% 21".lY1%1.

, p \r R,,,(~.,,~, -c,.nvn PI,,*I,~ p~mprmw sinqlc Cnstdr o lmqr tm. .Antimom): Rbmufb. .I..!I~~~,,,, ~~i.lil,lllln. ?AIC. i~nd 'Ill>.- Pnx A,,). . d . . l * r W . 60. 303 11925).

,n 11 \I;.I\,.~ -i'h.. sru. 11Jrlritc.n~k~ \i.rhIndnngen.- Z Snllrrlomh. 7% 744 ( I s%) .

.il . nrl. .l'rll.r DiiT~~tion.-~nn. Nlyr Lp:. 170.59 IlW!.

2 .!r c Nmn. .s,.mkunduaor S i ~ d Tntnrlnans Do*..- 11.S. hllrnt ?.59:.mq iI(152).

,a j &nilnl,. -~.~hnc-rtmn olsrm~crmrl~mor Dt-im: US. P.1tcn13.1B.Rl7 (filnl 1s;; p n l d 1W).

3 c 1, F&, -,I 1. I)P,,~&, -SU&Y ~ k ~ r r t i o n Sc,lmiw Ulckinp duriq Diffwion in Stlimn.' U l n n r h m . L x . IOI. 5l7 i1957).

.35 s s Sh,fid. S. Kobririh.dA.\. Kntilm,-Crm~thafSi~pl~~C~rtd in)?rrnfSllimn and ~ - . ~ , , ~ i ~ ~ ~ th.-Y~pr I'l,av; Rtrll A m 1 Sc( L~.S.S.R. Phyr Srr. 21, 140 00571.

if, \\' SLoeLln. Tominq S~tnimncltmnr Dniw lonk Bo!nlunlmmt.' US. P3tml2.7S7.56.I (I=).

2: 1 S. h l l h -1mmlron oltllr istqnlrd Cimtit.- IEEE Trnns. Urermta IkcFs . ED-93,646 (19761: I' s P.a,.ot 3.li9.743 ~ P n l lu59, p n t r d lW1

3, R S Sqtr. .Scmimndu<tor lhimmd.Lrad Slmnum.- U.S. RIcnt 2,(191,8ii (filed I s9 ; prontcd 1*11.

? J. .4. llcrmi. -Pfannr S~licon Tr-ton m l Di&: IRE br . U M m n B r i m >I?#., \Vshlngton. DC I IW

40 F \I. \btm .md C T. S&. -sanwlrt Lqio Urillg Firhl.ENcd blrtd.O~de .%mimndunor Ttinl-: T-1, I)I: IEEE 1.1. Ldi,l.Yn!c Cimrir Ccr?{, p. 32 (IW!.

41 R. > I Lkntunl. -Field Efft" Tnnmtor \lrmory" U.S. Palrnl3.3%7.%6 (film1 1967: g ~ l l r l IW) .

42 R. E. Krn~in . D. L lilcin. .md J. C. Lmw. -hlrtllal lor hfabing XIIS Slmc3arc.' U.S. Pntenl3.475.234 ,1m, .

*7 11. >I. \Isnr-il and.!\! I. Lmpmn. 7 h c Uw olMetd.Orgmie in lhc P~cpnntionofkmimnductor >Iatc.ti~l%. I. Epitslld CrlLunl-\'Compounds:]. UrrrmrBem. Sr. 116. 17% il%39I.

U. S \t. Ininq. K. E Lrmanr. and C. E. B o b . *Cs Pk-ma Vapor Etdkit* P m a : U.S. Paten1 D.615.W ;19711.

6. .&. Y. Cho. 'Film i k ~ i t i o n I,? >lnlnuhr Beam T-hniqur:] I'm. W. T ' t d . 8.S31 09il).

4G lltr immlm d l b ~ ~ mlnopmlor arc W. F.. HOB F, Fogin. S. Yarar. and 2.1. Shimn. For a profile of \I. E lloR w*. Pmtmit? In S i l h R. Shtrr. p. l i i . YIT Press. Camhtirlp. 1%7.

47 R. Rune 11. Yomow. and Y~ Szgahlh. TkepTmeh lrolvld CMOS Dr\icrr.- Ted,. Cfg, IEEE Inl. U s a m hmr .!lrrt. p. 237 119'121.

45 R. D;n?m. d d.. 'A SM Plra%tintian Tcrhttiqur., U11ng n Comhinllion of RlE md Chrmld > I w h m l Poli'h ICYPI: Trrlt. D i g IEEE In,. Urnmn &,ins h f m . p. 61 (1959).

49 1. I'n~awm~k. el d.. -lli,ch Pc&m.mw Diclwirin and P-sw for ULSl lnlrrmnncdion Xvhnolwn.' Tmh Die. IEEE ln f Flmmn D w l n , >fro.. p. 2fil (IW).

50. Tldr Inrrmnlimol Twhndoin/ Rmrlmpfm Srminmdt,dm. Srmimndt~+or Ind. A m . . San Jmc. 1999.

51. >I=nroh:Fl*h Llrmnn.Technol~: Pnx Inr. Urerrnn Dcr<cz$ Zfarpr Symp.. S. Hdndtu. T.+ t lW1

CHAPT d 2 ~ r y s t a l Growth

The hvo most important semimnductors for rliscretr d e r i m and i n s p t e d circuits are silimn and gnll i t~~n arscnide. This chapter descrilxs tlw mrnnam trchniques for e rmine singlr c y t a l s of t h ~ s e t \w semimnductors. The h a i c process flow frnm starting matr- rials to polisllrd wafers is sho\\n in Fiarre 2.1. The startine m a ~ e r i a l s ~ i l i m n diosidr for a silimn \vafer. and gallium and arsenic lorn galli~rm arsenide anfrr--re chrmically pm- wssed to form a ~liell-narih~ool\mn~talline sernimnd~rctor fmm \vhiclt sinele cn.itds arc ~. . ,. . , " . gro\wl. The sin Jr+qslal ingots are s l~aprd to define the diameter of the material and are a t t e t l into \vafers. Thcse unfers are elcltctl and plislted to pmddc smootl~. spml- Iar surfaces upon a.lticlt devices will be made. This cllspter m r r n tlle fnllm~iing tapin:

B a i c tecl~niqurs to gro\v silimn and Gu\s single-cvstJ ingots

\\'afer-shaping steps from ingots to plislted \~-fers

\\'afer charactelimtion in tenns of its e l e a r i d and mechanical pmpe~ties

Figure 21 Pnxr.is Om*. fm~n starting material to lr~lir l~nl \*;lkr

R p a 23 XYCmm 1 I2 in.) and UW-mnl (16 in1 C7achrdslri-grm\n rilimn ineots. (I'hoto m u t c w of Shin-Et-I H.mtht.i Cs.. li,Ly>.)

TABLE 21 Eauililwium Sesmsation Cwfficients for Oo~anta in Silicon

Consider a cnxtal !wing pow fmm a melt hadng an initial w e i k ~ t J1.witl1 an initial dopine concvntntion C,, in the melt he . . the wriqht of the dopant per I g of ntelt). :it a S\I.I, point of ~ r m v t h u.lten a cnlstal of weight .\I Ilaq heen ~ro\<ql. the antaunt of clqxu>t n.nlaj~ling in thr mrlt thy\\eigl~t) ir S For an incwnlrntal itlrlount oftl tr cnstal ~ 1 1 1 \vcielbt d l . the <nmspndin ,q re(ltmion of the clopant ( 4 s ) fmn, 11s melt is C.r/,ll. \vI>rrp C , i s tl~r chpine cancrntntion in the cnskll (I>? u,e$hti:

7 2.1 Silicon Crystal Grmmh from the Melt 4 21

Nrnv, the rcnlnining \\,\.rigl~t of tllc mclt is .\I,,- dl. and the c l ~ ~ i n ~ c o n w n t r a t i o n in tllc liquid (by a~right). C,, is @\.iS11 IF

Cornhining El'. 5 nnrl6 and substitl~ting C,/Cl = I ; , yields

C i \ m the initid weigl~t of the dopant. C,,\l,,. \vc can intrpnte Eq, 7:

Soldng L.,. .. ...., ,-ml)ining with Eq. 6 gives

Fi,gure 2.4 illustrates t l ~ r doping distrihetion ns a furwtion oftlle [r~ction solidified (l(Jf/,\I,) for sevrrd segregation mficients? ' As cr)std gmulh pmgresses, the compmition initiall? at k,,Cn\sill increaqe continually for k,,c 1 and decrease continually fork,,> I. \ \ l ~ e n k,, E 1. R uniform impurih distrihation can be obtained.

b EXAMPLE 1

A silimn incot. which shottld contain 10'" lnmn stornskm'. is to be grmn by the C,cchr;rlrb 1 ~ ~ 1 3 ~ nique. \\laat mnrcntration of l n m s atoms sho<~lrl bc in the melt to gitr the reqtrinvl c~mwntm- lion in the ingot? If the initid load of rilimn in ihr mnril,le is M kg. hm\, mans .wms of k ~ m n (atomic \\right 10.81 slto~xld lr iddcd? V I P density of molten silimn is 2.53 glcm'.

SOLUTlON Tal,lt. 2.1 shmvs that the s e p p t i n n melEdcnt I;., for boron is 0.8. \Vc nwlmc that C, = L,C, thmuphout the p l h . Thus. tbr. initid mnwntntion of lnmn in tllr melt should be

lo1^ - = 1.25x101^ homn .~lom-lcm' 0.8

Sin- the amount of homn rnnwntntion ir u, small. thp \r,lo~!nr of mrlt can ht. wln~lrtrd front thc weight of silicon. filerrk,r<.. thlc \nhnrnr of ((n ksof silicon is

-= 60x10' 2 . 3 7 ~ I O ~ C ~ ' 2.53

The total the mclt b

. ..v........ n'x2.37xI0'cm'=2.96~10~ honm atoms

so that

~nvnll amount of lnmn needed to d o y sllrll it brpe hwd of rillc~*l. 4

tr b Cbronr 2 Cwal Growth 21 Silicon Cwal Growth from the Men 4 23

Figm 24 Cunpr for p i h fmm the melt shmring the doping mnmntratian in a solid as a titnaion of the fmc(ion rolidifid.'

21.4 Effective Segregation Coefficient

\\lrik the crystal is W n s . dopants rn constantly being rej&ed into Ole melt (for I;,> 1). If the rejection rate is higher than the rats at which the dopant can he transported awny hy diffusion or stirring. then a concentration p ~ l i e n t will develop at the interface. ac illustrated in Figure 2.5. The segregation coefficient (given in Section 2.1.3) is k,, = C,/C,(C \Ye can define an effrrtivc x p q a t i o n mcffident k,. which is the ratio of C, and the imp) ri& concentration far a m y from the interfaw:

Consider a sniall. \irtuslly s tapant l a y of melt \\<th uidth S in which the only flow is that n q u i d to replace the cqstal k i n g uitlidra\m fmm the melt. Outside this stag- nant layvr. the dopint conwntntion ha< a constant value CI. Inside the layer. the dop- IIIC mncvritration a n k drscrihrd h\. the stea~ly-state continuiF equation:

Figurn 25 Doping clislrihtntion near the did-melt intc+ee

where D is the dopant diffusion coefficient in the melt, v is thr cns td p x i h velwih and C is the lo pi rig concentration in tlie melt.

The solution of Eq. 1 1 is

\\,liere A, and A, are constants to be determined I)y the houndan conditions. n i e first houndaryconrlition is tliat C = C, (0) nt x = 0. The sccond honnrlnn~mndition is lhr mn- s rw~t ion o f t l ~ r toktl ~ ~ t ~ ~ ~ ~ l r r o l t l o p n n t s : tl1:lt is.tl~es~tnioftl~cch)~.mt l l ~ ~ ~ r s ~ t t11e interface niust In. mro. Rw~mnri~lerine tllr ~lifft~sion of~lonnnl ~ t o ~ n - in t11r mrlt .n(.eh%6ne ~, " diffi~sion in the solid). \ve Imve

Substituting these boundary conditions into Eq. 12 and noting that C = C, at x = 6giei\~s

The doping mstnnrlnon in the crystal is given hy the a n t e c.,l,rt.>.nv,, .s in Eq. 9. eswpt that k, is rcplawd I)! k,. \'slues ofk. are laqer than tl~ose olk,, and can appmicl~ 1 for I q r values oftlie gm\v~li paranietrr vS/D Uniform dnping rlistribution (k. + I) in the cqstal cm Ix obtained hy emplqving a higli pull cite and a lmv mc~tioa s p n l (sinm 6 is invrndy pmportionnl to the mtation sped) . r\notherappmncli to acliievt. 11nifon11 doping is to add ultrapure pol>~mtnllinr silicon mntinuously lo tile lnclt so that the illitial doping concentration is maintninetl.

* 2.2 SILICON FLOAT-ZONE PROCESS Tllrf?<xrf-:~,r> 11 Lu a s 4 to q \ v silimn that l e r~ lower mntalnin;ltion than tllat

tw~n~~.%!l\~ o!tt Ilr ~ r , ~ - I ~ r n l & i tterl~niqar. .i scl~e~~lat ic srhlp of t l ~ r flot~t-zone

p n x r v ic .;In< n. ?.fin. A li igI~-~urih ~ n l ! ~ s t a l l i n r mil with a sred cnstnl at

:I,,. 1,~ttnrn IS z ~ r t c t urt .I xrtiind pnsitiou ;utd mtstc~l. The md is i.ncIosr~l in aquartz enw- !,r \\ltl~in \vl!idt IVI inrlf a t r n ~ ~ ~ l l e w (arqon) b tnaintxind. During the operation, a small n,,qr ,.I i , ~ u . ~ n t i , , , ~ t m in 1~1ictl11 oftltr cp31:tl is kept molten I? i~ rxl io-freq~~e~~cy iRF) Ilc.ttPr. wltirh is inn& fmnt 1111. scwl up\ranl co 1l1;1t t l ~ i s j l m t i t ~ ~ ~ : ~ ~ traverses the lengt.111

tht. rnl. nlf. n~r!ltrn silicon is wklincd hy surklff tetlsion iwhveen tbe nleltillg ar-' v n r i r ) ~ rolid-dlirnn inn?. h the floatir~q zone mows up\rnnl, single-cnstd silicon f n w .n tI,v ronv\ retw.ttin< md xid p \ v s :s an extmsion of tbe seed cnxtal. hlaterials \vi hiSI,,,r misli\it i~s cnl Ir ohtain~y{ fmm the float-zone p m s s than frnm the Czncllral! ~ n u ~ q Iw:~nre the fornler GIJI hr used to pt~ri& the cnstal inow easily Furtliern~o~ 1 1 t t y 110 cntcihlr is ux'd in thr flatt-zone p m ~ s s . there ic no contamination from t .rucihle (;s \\ill) C,ncl~~&li qmvih). ,\t the present time, float-zone cr)~txls arc. us, n.unlv for hinh-prn\rr. Ili~It-\nltage :edcwic~s. ultrre high-resistivity materials are wquirf

TC, r\;llrnatc tllr (lopinS dicmhution ofn flmt-zone prorrss. consider a simplified niorl ;~c shrnrn in Fiqurp .'.MI. The initial trlnifon~t doping concentration in the rod is C, ( \rrielttl. L is t l ~ r lenzth of the molten zone i1t a distance x along the m l . A is thc cro spainnd areaof thv m l . p,, ic the specific d~11sityofsilicon, and S is tlie aniolmt ofclopa

e molten zone. i\s tlie zone tmverses a distance dr. the amount of dopa resent in tI18 ddnl to it at ti11 tI,e rplm

11s :~d\:,nnn?end is (: .p,,A dr a l t ~ n x s Ill.? ;llnount ofc!op.int n.tllo\.cd trc ~tsn? vtnl rs I , SddLI. ~ I I C * R . I , a llte r&divc. ~cyrqalioll mefirtent. Tllt

Rf mil -0

t 1.1 lh)

RF 26 flmt-nmrb pnxvw In1 Schematic rrhlp fbl Simple, m d r l lor dopine nalt~ation

el. 13).

FS-

cnt

2.2 Silicon Flost.Zone Pmcerr 4 25

so that

I

I&=j dS . , C,,P.IA -(k.s!L) (ICn)

\vIlew S,, = C,,p,,AL is the antount ofclopant in the rnne wllcn it first fnnnrtl at tllr frnnt end of t l ~ c rod. Frnni Eq. I&, wr oljtain

Since C. (the (loping concentration in the c y t a l at the wtreating end) is given hy C. = kJSIAp,&). then

C. = ~, [ l - l ( l -k~) -~""] 0 8 ) Figure 2 . i shows t l ~ e doping concentration versus t l ~ e solidified zone lengtll for\arious V ~ L I P S of li,.

These hvo crystal p n t h tecliniques can a l a he used to remove imparitics. A rnm. parison of Figtre 2.7 wit11 Figure 2.4 shows that a s in~le pass in the flost-mne p r w r r does not pmluce as much p~~ri l int ion nc a single Czwl~nlski p \ \ t h . For example. for k, = k. = 0.1. C,/C,, is smaller over nlost of the solidified ingot made by the C d t n l s k i grm~tli. How'ever, multiple float-zone pacses can be prrformrd on a rod muell more earily than a cnstal can hr grnvn. the end region cropped on. and rrgm\cn fmm the zs~lt. F i g ~ r e 2.8 sho\vs the itxipurity distribution for an element \ i t h b,. = 0.1 anrr a nun~lxr of succrssive passes of the lane along t l a length of the ml.' Note tl~at tltcrr is a sub- stantial reduction of impsrity conffnlrntion in the mil after each pns. Tl~rreforr. the float-zone process is ideally suited for c y t d purifimtion. n ~ i s pmcess is also died tlte zort~-,$nii~g techniqt~r. \rllirb cnn prn\idc a "3. I~igll purity Inelof the raw materid.

If it is desirable to dope the rod nther than purify it, m ~ ~ s i d e r the a q e in \vhicIr all the dopants are introduced in the first lane (S,, = C,Ap&) and thr initial mtlcentratio~~ C, is negligibly small. Equation l i gives

Since C, :

Therefore, if k@L is small. C, \vill renlain nearly constant tvitl~ distnncr ex* at t l ~ e rnd that is last to solidi(v

For crrtain mitching d~\ices , s ~ t c l ~ as lti,e,lk-\olt;lge tb!~iston. large clip arms arp . quently an entire \,.;~fcr for a singlr de\ice. This size impuses stringent mlllire. the uniformity of the starting material. To obtain ltoo~yeneous distribution of I float-aoae silicon slim tllal 11:s a11 avemgc doping conceiltntion wvll I~lav ..., ,,.l...,ed a~rlount is izsrd. T l ~ c slice is then irradiated with thennal neutrnss. This pm-

wss, c~l led t~nrtmn irmdiation. givrr rise to rractiond tnmsm~~tation ofsilicon intoplms- pllonrs ancl dopes the silimn 11-1)p:

2.3 GaAs lh Techniques 4 27

I I c,;c,>= 1 . ( I 4 . b I..'''.

T,, = I 6.r ull c.a~n-.r

""I / 1 I I I I l l I I I 2 3 4 5 6 7 6 9

Salidinrd zont. b.nsfla dl.

Figun U Cllnr.~ for ihr float-mne p-sr shm\ing dr~pin~conccntmtion in the solid as a hlnaion of wlhlificd mne ltqths.'

The 11;Jf-life o f t l ~ r intrrmnliate rlrrnrnt Si:: is 2.62 ho~ln . Bemuse t l ~ e penetntion depth of nrutrnns in silimn is alnot 100 cnl, doping is v e n lmifonn t l l rnuklo~~t the slice. F i p m 2.9 mmparcs t l ~ r latrnl rcsistibih disirib~~tions i n con\.c*ntionally do~xul silimn and in ~ i l i ~ , n dojxul I? neutmn irn<lintion.'Sotr that t11r rrsisti\ity \anations for the neu. tmn-imaliatrd silirnn are lnuch smaller tllitn 1110s~ for tile mnvcntio~~idly d o p l silicon.

2.3 GaAs CRYSTAL GROWTH TECHNIQUES 23.1 Starting Materials

Tllr starlint iniatrrid% for thr s\ntl~esis n i lnlycnmmllin~ gallium anenide arc the ele- ntrnt.d. rl~t.n~ic~lly ~ I I ~ P p l l i ~ ~ l l r ;ln<l :trsrnic. B r c ~ ~ l s e gdliem arsenidr is a mmbinalion I)( hvo t~li~tvriids, its Ivl~it\ior is ilifferrnt imm tll;d of :I single materid slncl~ ns silicon. TIM. I r l r smr of 3 mrnl,in;tti<m mn hr dt.scriln.l I,? a p h a r cliagrarn. A ,>lmav~ is n state

Crystal Grow

1

Solidifinl mne lmptlt' df,

Figure 28 R~el:~tivr irnpuri? concentration rrmtr ,me lensh for a numnkr dpnrw. 1. ~l~~nolc r the 7onr lcn#l,.'

(e.g., "lid, liquid, or gaseous) in which a material may exist. Al~lto.~c flingram shmvs thr ~lationsllip brhveen the h \a m ~ n p n e n t s . gallium and anenic. .lc n h~tlction of tern- pefilture.

Figure 2.10 sl~ows the p b a e d i a p n i of the pllitlan-:~nenic ?s l~n l . The ahscissa rrpresents \-drious mlnpsitions oftlle h%'n mlnpnents ill ternls ofatomic percrnl (!rnK"? scale) or perrrnt (upper scale)." Considrr a rrlelt that is initidl!, ofmn~position x (e.g.. 85 atomic percent arsenic, nr sho\vn in Fig. 2.10). \\'11en tile t e ~ n p r e ~ t ~ l r r is low- ererl, its mmposition will rrlnain k x ~ l until the liquidus line is rcacl~ed. At cllr Flint iTi.x).

of50 ~ t ~ n ~ i c percent arsenic (ir.. galliuln anenide) uill I v e n to solirlifv.

b EXAMPLE 2

riprr 2.10, consiller a ~ f i n i t i ~ l mmporilios C,. (\\vi!$>l prm,nl w;*l*,) th;ll is nxllwl fnm~ T* (on ill,. li,l,,i~l,,s !in<!) 10 T,,. Find 11,e lctclion of I IK melt thi8t nit1 wlidific~~.

SOLLmON At T,. 11, is ihr urixht of thc listlid. ,\I. is thr w i $ l t of llw wlid (i r... G.&I. and C! C. the r,,nwn~mtions "f dopant in thr liquid and ihr rcllid. rrspvclivt.ly. !..~r.n.lort,. ihc

,vrieh~s ,,fnnrnir in (Ilr liqurl ilnll ~ l i ~ l inns AI,C, ;md .\l,C.. rerpcli\r.!\- Rrc*t~rr ~ I I I ' Ink11 urrenic

&rn 29 (ol T ~ i d lateral rerirlhiirit). m o u a o n m a eonwntionally doped silimn. fh) Silimn dnprd neulm imliation.'

Atomic 5 m m i e

f ipnrZl0 Phaw &amm for the yallium-nmnk .sytcm.'

23 G a b Cvfiul GrmhTschnlguss 4 29

md I are 1l1c lmgths of lh. Ix\n lines meanwed fmm C., s~ the liquic .-.,-.-... cly As o n lw swot fnrm Fiplnrr2.10. alnntt I ( ~ . o f t h r mrlt is w,lhl

Unlike silimn. whicl~ h a a relatively lo\<-vapor pr~sstnre at its melting point (apprr,r- irnately 104atm ;a 1412'C). arsenic has much higller wpor pwssurrs at the meltingpoin~ o f g d l i ~ ~ m m n i d e (1240°C). In its wpor phae. awnicllas ,\s, and&, a s i ~ ~ major spreies. Figure 2.11 slaws the vapor prcss~~res of galliu~n and anenic along the liquidus curve? Also S I I O ~ ~ for mnip.*nn is the vapor prcss~~re of silimn. The v a p r pressun, cunpr lor gallium m n i d e are double valued. n~ r dvlled runes arc for arsenic-rid, gallium arsenide melt (riglit side of liquidus line in Fig. 2.10). and the solid cunrr are for &Iiurn-rich gallium arscnide melt (left side ofliquidw line in ,is a larger amount of arsenic in an arsenic-rich nielt than in a ga ;enic 0% and As,)

Fig. 2.10). I! Iliam-licl~ rn

Fipurs I11 Panid pressam of gailitr~n and arrenic owr rdlium m n i d c ar a fun*ion af tern. pmtnw.' Also ~ho\vn is the partid pressnm olrilimn.

- 30 Chsptrr 2. Cryrml Gmwlh

,,,.ill h. ,..,,,,,"A tllr arsenicrich melt. thus resulting in a lligllermpor pressllre. 1

, , , , , i ~ . , ~ .,rru,errrt rT~ai,~ the Iliglrer \;vpor pressure of gallium i n a ~Ilium-rich sot,. tll;+t lullc Ir,fure the mt4ting point is r e ~ r h ~ l , the surface lilyen of liquid ~all ios .ir\rr)i<l,* !nil\. drmn~pose into e;~lli~tni and arsenic. Brcnase the \"dpor press~lres of gal hill,r :wnic:mS R.tiNerpst. 1)~.rr is a preferential loss of the more \vlatile arsenic s p i e r ;utJ the liquid k o n ~ r s galliutn ric11.

X, 5~i\lltlt~siz~ g:~Ilium ;trsmidr, an encuated, sealed qttartz hlbe s)stem wit11 a hvo tl.aepr.li,~w htn~arr is c ~ n ~ m o n l ~ usd . Tlie high-purity arsenic is placed in a graphit$ bo:,t anrl l~eatrrl to 610DC to 620°C. \rfIlereas the l~igI~-poritygdliue~ is placed in mothe vtphite boat ;mid heated to slightly above the gallit~rn nrsenide melting temperaton , I ? - I ~ L I ~ ~ ~ O ' C ~ . Undrr tl~ese mnditions. an ovprprrssore of arsenic is cstablislled (a) t~ mlsc the tm~cport ofalr*nic\-apor to thegdliun~ itlelt. mnvertingit intogalliunl arsmide anrl ihr to prevent dnun~position of the g~d1i11m anenide wl~ile it is being formed in 111, fi~rn:~ce. \\hen the nielt cools. :t high-purity polycqstalli~~e gallit~m arsenirlr resolts. Tlti sews ar tile raw matetell to grow single-crystal ~allium arsenide.'

232 Crystal Growth Techniques

There are h\o tecl~niques for Cmk cqstal growth: tbe C~ocbralski technique and th Bdcrnon tt~ltnirpre. .\lost gallium menide h p \ n by the Brirlpm tecl~nique. Have\.e~ tllr C ~ o c l ~ d s k trcltniqor is more popular for the growth of larger-diameter Garb ingob

For Czochralsk ero\rzl~ of galliun~ arsenide, the basic puller is identical to tl~at lo nbwn Hm\.twr. tupn,\rnt drmmpition of thr mrlr cl~~ringcn.it.d p \ \ l l l , a Lqllid ennp atlrtlon n ~ r t l ~ ~ l is rnmlm~l. Thr ltnui~lrncansul;mt is ;I 111oltrn lmmn tnoude (R.0.1 la\? ~ ~ a .. . ,. , about 1 cm thick. Xlolten lmmn trioxide is inert to the galliuni anenide surface and senre - w amp to m e r t l ~ e melt. This cap prevents demmposition ofthe gallirlm arsenide a Ion: a the oressure on its surface is hieher than 1 atm (760 Torr). Because boron hioxide ccal ~ ~

0

di.wlve silicon dioride, the fieed-silica crueihlc is replaced with a graphite cmcihle. To ohtain the desired doping concentration in the grown ctytal of GaAs. cadmiun

and .dnc are commonly used forp-hpe materials. \vhere.u selenium, silicon, and telluriun are treed for n-Qpe materials. For semiinsulating Gals, the material is undoped. The equi librium srgregation coefficients for dopants in G d s are listed in Table 2.2. Similar t, those in Si. most of the segregation coefficients are less than 1. The expressions derive, pre\iously Ibr Si (Eqs. 4 to 1.5) are equally applicable to Gals.

TABLE L2 Equilibrium Ssgmgation Costliciami for Dopant. in GaAs

hp.mt k,, T!V

Br 3 1' \ I< 0.1 P Zn I x 10.' P C 0.8 ' / P Si I.= x 10.' n/p

Ge 2.8 x 10-1 "/P S 0.5 n .% 5.0 x ~tr ' 18

Sn 5.2 x lo'? n Te 6.8 x LO-? n Cr 1.03 x lo' Semiinsulating Fr 1.0 x 10.' Semiinsulating

2.4 Material Characterization 4 31

Figure 212 Bridgman tcchniquc for grwing sinelr-c~~tal gallium mnidc, nncl a trmpmturr profile of the itln,;lc+.

Figure 2.12 shows a Bridgman system in wl~icl~ a hvo-7nne furnam is uspd for g m - ing single-cnst~l gallinm arsenide. The left-hand zone is held at a temwratore (anoror-

v . " is made ofquartz, and the boat is made ofgr~pldte. In operation, the boat is loadrd\rith a charge of po1ycr)l;talline gallir~m arsenide. \\it11 the arsenic kept at the other end of the t u l ~ .

As the filmam is rno\~e<l tmtuxl the rigl~t, the melt mols at one end. Usuall!: tl~ere is aseecl placed at the left end ofthe b a ~ t toestablish aspeeificcqstal ori~ntrtion. T l ~ p p d - ud freezing (solidification) of the melt allm\s a single cnstal to pmpa,pte at the liqui<l-solid interface. Eventually, a single cqstal of gallit~m anenidc b ~ \ \ I I . Tlie impnrih distribution c ~ n he descrilwrl essentially ly Eqs. 9 and 1.5. \vlrere the p \ r t h rat? is given In t l~e traversing speed of the furnace.

b 2.4 MATERIAL CHARACTERIZATION 2.4.1 Wafer Shaping

After a cqstal is grown. the first shaping opention is to remove the seed and the otlwr end of t l~e insot. \vl~ich is I ;L .~ to solidify' The n r ~ t operntion is to grind tllr surhce so that the dianleter ofthe materi;tl is drfinml. After that, one or nlorc fill regionsireplllld along the lm$I~ of the ingot. Thrsr regions, orJa1.v. nrark tile specific cyta l orientation of tlir ingot and the ~ ~ n d n c t i \ i h t!yc ofthe inaterid. The l:qtsst flat. the prilnay

f i r , allows a 111rr11anic1l locator in automntic p m s s i ~ l g equiplnent to pmitios tile \%lfer and to orient the dc.\in-s relati\.e to the cqstal. Othcr soiall+r fl:~ts. cded.scm~tdan~~at.~. are grotmd to irlentif). the ori~nlatioli and conducti\ih hy of the cqskal. :w sho~~m ill F i p w 2.13. For cyst;~ls\\itl~ diamrtrn rqud toor Lqcr tl1m200 mm. no fli~ts are p d . Intrad. a small gmove is ground along the lengtll of the insot.

2.4 Material Charactemation 4 33

-. T .

IlWI ..t,l* llOOlp.hF

Figun 213 ldentihin~ flats on r remimnductor \%afer.

Thr ingot is thrn rrarly to he sliwd hy diamond saw into wafers. Slicing deter- mines fonr\\:ifrr pa~mrten:ntrfncro~~~ntntio~~ (e.g.. c l l I > or <Inn>): thickr~css (e.g., O..iO.7 tnta. de-pnding on wifer diameter): toper. \vIiich is the xvnfer thicl;lless variations from one rnd to another: and how. \vIiich is the surf:lcc conatllre of the \Vafrr, mest~red from the wntrr of the wafer to its rdge.

After slicinc. lmtll sides of tlie \vafrr are laPprd wing a mixture ofAl,Oj and glyc-

7 - - and mntantinated redons can l r ren~o\wl I y chemical etching (srr C11:lptrr 5). The find step of nafrr shaping is polishing. Its porpse is to proxidr n snlooth, specl~lar s~~rface \\here dr\iw fr;~turcs can I r rlrfined h? pl~otolitlio~rapl~ic processes (see Chapter 4). F i ~ r r 2.14 shows 2.70-~nm (8 in.) snrl 400-mm (16 in.) lmlislied silimn wnfers in cas- srttes. T.shlr 2.3 sllous the specifications for 125.. 1.50.. 200.. and 3.70-~n~n dilmeter pol- ishcrl silicon aafen from the Srmimndnctor Equipment and Materials Institute (SEMI). Ar mrntionrrl pmiowly for l a p q s t a l ( 2 2M ; i t r y ~ ~k~ineter), no flats nrr p t ~ n d ; insirad. a m v e marlr on the edce of the \\afer for msitionine and orinitation oumoses. ., . .

Gallium awniclr is a more fnyile material than silimn. Altla~ngh thr bmic shaping oprration of gallium arsrnidc is es<entiall!. tlir wnlr ;L% that for silimn. grratrr care mu hc rscmsel ill gallium arsrnidc \\:+lr pr~pac~tion. The t a t r ofpJlinn~ ;trsrnide technc q r n . is wl~tivrly primitiw mrnplwl with that of silicnn. Howrvcr. the tech~~olog of gro~ Ill-V rnnipo~~nds lixs :~<hannrl partly luc~usr of the ad\nncvs in silimli tec l~nnlo~,

Figure 2.14 200-1,lrn (S inr.1 and 41M1-mm i i G in.) polished silieon wfen in mqrttcr. (I'l~,to murtrry oFShin-Etmr Ilrnth,lai Co.. ToLyo.)

TABLE 2.3 - Panmete

Diameter (mm) ThicAmcsr (mm) Prima? flat length (mm) Scmndnry flat length (mm)

Bmv (ttrn) Total ~hickncss \ariatic Sud-ce oricntntio~?

led Monocynallins Silico~

j trim 150 mm

1%+1 I.%+ l 0.60.65 O . t E 4 . i 40-45 55-m 25-30 35-40

ca SO

0) + I 0 Ssme I + 1 Sntnc

e n o t l i l .7l~,i '35 N A N,\ 30 10 Same Same

m+1 0 i.m.Ti5 9 A NA c3a < LO Samr S a m

NA. not a?lil8blr

24.2 Crystal Characteriza"

Crystal Defects A real c ~ s t a l (sacl~ ;ls a silicon wafer) dilfen from the ideal end in iniportant \\;I:S. It is finite: tll~ls. surfnce atoms are izicosipletrly Imaderl. Furthemiore. it 1 1 s defras, wl~icl~ strongly influr~ice the electrical. alrcl~a~~ical. and opticd prnprrtirs of the sr~t~imnductor. There are fourcategories ofdefects: point defrcts. line drfkcts. Rreadefrcls. and \ul- utile defects.

Figure 2.15 sho\rs sewml foniis ofpoint d~fccts."' Any foreigi atom incorlm~~trd into t l ~ r latticv at ritlier a s~lbstitl~tional sitr [ i .~. . at a regilar lattice sitr (Fig. .'.I%)] or as interstitial site 1i.e.. behvcen wplzl:lr lattice sites (Fig. .?.1511)] is a point dc.frct. A missi~~gatoln in the lattiw creates avac:1119 also mnsidrretl :I point dcfect (Fik 2.1%).

(c) (d)

FigM 215 Point defecb. (0 ) St~I>stitutional impuriy (b) Intemitial impurity (c) httice \ l e n n ~ . ( d ) FrrnlteI-h~x defect."

.4 host atom that is situated behveen regular lattice sites and adiacent to a vacancy nlled 3 Fwnkeldrfed ~ F I Z . 2.1511. Point drfrcts art. particularly itlllwrt;~nt subjects i t l~e h e t i n ofod(l.ttion ;tnd (IrNt~r~on proxsres. Thesr topin arr mnsirlerc(l in Chnpte~ 3 and 6. respecti\~ely.

The neb class of defects is the line defect, also called a dislocntion." There are h\, hpes of dislocations: the edge and screw types. Figure 2.16a is a schematic represer tation ofan e d ~ e dislocation in acuhic lattice. An ednplane ofatoms AB is inserted int the lattice. The line of the dislocation \auld be perpendicular to the plane of the p. The scre\rs dislocation may ire mnsidered as being produced by cutting the crystal p \vaytl~mugh and pushing the upperpart one lattice spacing over. as shmtn in F ipre 2.: Line defects in desices are unclesinhle bemuse they act as precipitation sites for me lic impurities. \&ch mayde,pde dexice performwcr.

A m drf&f~ r e p e n t a large-area dircontinaih in the lattice. T ~ i d defects are h and grain Lmuntlaries. ?icinnin,o represents a change in the cy ta l orientation acro plane. A gelin houndan isa tmsition behveen cly~tals havineno particular orientati, rrlntionslt~p tonne motla.r. Sl~cln (lefrch aplpnrd~~rine,cnst;J mvt1~ . ,\nother 3n.a cIr is tl~e.~nrkir~pfo~tb 'In t h ~ c drfw. thr aachne wnucnrrofnu aton~ic lmpr ir intrrnln . ~, c? , ~ ~~~ ,~~ ~ - - . ~ ~ . ~ ~ ~ , In Fiprre 2 . l i the sequpnce of atoms in the stack is ABCARC .... If a part of layer missing. the defect is rdlrd an intrinric stacking fault (Fig. 2.170). If an e d n plane inserted behvees layers R and C. it is an extrinsicstacking ranlt (Fig. 2.lib). Such del rnay appear during cnstd gro\\th. Cqstals having these area clefects are not usahle integrated circuit nlanllfachlre and are discarded.

age. #art- 161,. .*..IL

A is ects for

(a) 6,

Figure 2.16 ( 0 ) Edge nntl (h) screw cssloration formation in cubic cnrt;tlr?

(a) 6 1

Figure 217 Stacklng kalts in srmicond~xfor la) Intrinsic stxl jnq Fault ihl Edrimic ctcklng fi,nlt."

Precipitates of impurities or dopant atoms m&e up tile fonrth cl;~<< of defeas: col- Iriiled/ccls. These defects arise beause of the inl~errnt roluhilify of the irnpurih in the host lattice. There is a s p ~ ~ i f i c mncpntmtion of iolporit). that the lrost lattice c.m xmpt in a soli(l solution of itself and the inlpurih. Figure 2.18 sho\\s solubilit\. \?nus temper- atrw for a mrieh of elements in silicon." The soluhilih of most i~npurities (~r(.reue6 with decreasing telnpmh~re. Thus, iran imparit!. is intmduml to thc n~;r\ im~~~n mn- centntion allo\ved hy its soluhilih at a given tempemture, imd the cpstal is then cwkd to n lonvr tralper.ltore. the cnstd can only achirvr ;an eqailibrion~ st:ttr I,! precipitnt- ing the iolpurih atoms in excess of the sohhilih Ir\vl. Ilo\\?\rr. the \ululnr nlislllatcll behveen the host latticc and the precipitates resalts in dislor.ltio!~s.

hlntetial Properties Tal>le 2.4 mmpares silimn chandrristin md the r~yuirenlcnts forillte~ltc(1 cimiit trdl- nolo9 I~nving rron. tllnn 10' mmpnnrnts. \vlliclt is referred to as el:rn/n~~~-~rn/r irl:r- gmlioa (ULSI)."" The remimlaludor mntrrial prolwrties listed in Tcahle 2.4 C ~ I I be n~r;m~rnl by \;~riota mptltnls. Thr rcshtitih is I I I ~ U I I W I ly th~fm~r-p~irlt l~ndn. 1nt~t~ln1."

24 Material Characterization 4 07

:u~rl tnaw impurities stlc11 n< o x y p ~ and carbon in silicon n n be wal!7rrl by the secondat ion mms spwhmmpic (SIXIS) trchnigtr d rsc r ik l in Cl~apter 6. Note that dthoogl~ cu~ wnt ~ip~hil i t i rs cm mwt inmtoftl~e u d r r rpffificltions listed in Tahle 2.3, manyi!npm\v ~rirnts :arc nrrdrd to satisfy the rtrincent requirements for ULSl t e c h n o l ~ . "

Thr ni?:ca and n r l m ~ ~ cnncrntrations irrr s~~hstantially liigl~er in Czocl~rdsld cq: talc than in floiat-zonr cr)stak 1wn11sr of the dissnl~~tion of o y s e n from the s i l in c n el,lc anrl t m n p r t nfclrhon to thr mrlt fmtn t l ~ r ~ x p l u t e srLurptor d~~ringciytnl p v t l T t p i d nlartmn ~enwntrations m g e from 10'" to a l ~ o ~ ~ t IO"ato~ndcn~'. and c,~rhon nton ill ~ilicon n m ~ p y suhmh~tional laltirrsites. TIIP prpsrnw ofnrlwn is ~~ndesirahlr 1m11r

TABLE 24 Cornpariron ol Silicon Material Chanmerlulm d Raqulmntr lor UlSl

CI~:~mcl~ti~lim

Hesirtibity (antimony) t t - h p (ohmentl 0.00,%10 - 0.f~1t-0.02 Hcsisti\4h (Inran) p - 1 9 (nhm.cn~) 0.OILi-50 144M 5-50 and np Renirti\ity pndicnt (fi,ltr-pint pmlr) (%I 5-10 20 xcn ipp~nitl 5-25 Sot cktcdnl Unifom

c~mln>llnl Carlxm (ppmal 1-5 0.1-1 <().I DisLrntion (lrfom processing) ( v r cm') I; 500 5 .UKI < I Diameter (mm! Up to 200 Up to 100 Up to 300 Slim Imvfpm) 5 25 I; 25 < 5 Slice laper (pm) I; 15 I; 15 <S Sltrfac* flihtnerr (pm) 5 5 5 5 c I Ilr!:lry!netnl intpltrities (ppltn) 5 1 5 0.01 <(IIX)I

ppma. p r F r znlllmn atom$ ppha parts p r billton atoms.

a aos w e formation of clefrcts. Ppical oqxen mnmntrations range fmm 10'' to 10'' ntomslcm'. Oygen, ho\ever, has 11otl1 deleterious and kneficid eflects. It can act as a donor. <bstortine t l ~ c resisti\itv of the cns td caused h\f intrntional doninr. On the other ,, L 7

l~and, o q e n in an interstitial lattice site can increasr the yield strength of silicon. In addition, the precipitates ofo.yp;en due to the solubility rffvct can lx i w d for

gettering. Getfenng is :I general terlll nleaning a proct*ss that removes harrnf~~l inlpurities or defects iron> the rr$on in a svafer \vltere de\ices are fahrimted. \ \ l ~ r n the safer is sn1)jrcted to 11islr-temperature treatnlent (e.g.. 105O'C in S,). oygen evaporates from the surfam. This lo\vers the oyo,en mntent near thc surC,ace. The treatrncnt creates s defect-free iorden~lded) zone for dmiw fabrication. assl~oun in the inset of Rgrrc 2.19.' Additional thern~al c!.cles can he wed to promote t l ~ r ionnation ofoi?xen prrcipitatrr in tltr interior o f t l ~ e \ r ~ ~ f e r for getteringof impnrities. The depth of the defect-frre zone depends on t l ~ e time and tenlprratrlrc of the tlkcnnal nl?,clc and on the diff!~ri\ih ofon.. gen in silicon. hle;~ct!rrd r r s ~ ~ l t s for the den~tded zone nrr sl~o\\n i n F i y r e 2.19.' It ic possible to obtain Czocl~mlsLi cqstals of silimn that are \irtnaIly frrc of dislmtions.

Comtnerci:d melt-sro\\m n,alerials o f g a l l i ~ ~ n ~ arsenidr are 11ea\ily (vnlitniinat~~l by the cn~cihle. tlmvever, for pl~otonic appliwtions. moct wq~tirelnrnb cidl forhca\iIydoped materials (brhveen 10'' and 10'" cm-'i. For integrated circnits or for discrrte MESFET devices. undoprd gallil~n~ an en id^ n n be used ;I,, the StartillR tnntrrial with a rrsisti\it). of 10"R-cm. Oqpen is an ondesir.~hle implllityis C : k Lrcal~se it a n fonn aclffpdonor level. \vhicl~ mntlibutcs to a trapping rba%p in the balk of the substrate iu~d incrr.lsc5 its resistiuity Oxygen mnt;tn~innlion can ~nini~nizcd by using p p h i t r crucibles for melt grovll~. The clisloc:~tion content for C~ocI~~~lsld-grn\m galb~rr~r arsr.nidt- cnztals is nhoat hvo onlen of mapit~zdr Itigher than that for silimn. For Bridgman Club cl).st;~ls. the dislncation <lensity is abut an or<brr of m ; t ~ n i t ~ ~ d r lower than that for C./.ochr.&Li- ~ o t v n GiAs cn~tnls .

Problems 4 39

2.5 SUMMARY Se\r,r.d trc$nirI~ws arc inxilahlr to p \ v single cnstals of silirnn and gallit~m menide. For silicnn mst:ll<. sand (Si0,l is n ~ r d to pnxl l~cc pol!.cnstallinr silicon, r\.lriclt l h ~ n sen?s as tllc nta. m:tt~.ri$ in a CxoclmilrLi ppellrr. s w d cns ta l x i t l l the desired orientation is tlrerl to ~v n l a q e incot fmm the melt. ( h e r W% of silicon c n s t a l a re prepared I I ~ this twllniq~le. Dlvrin: cns t~ l l ~ o \ r t h . the dopnnt in the cns ta l \till r r d i s t r i h t ~ t ~ . A hy p ~ f i ~ n ~ e t r r is ~ I I P swrczation co(.flicirnt. that is. t h r ratio of t h r dopant mnc rn tn t i on in l l ~ r o l i d to that in tltr 111eIt. Sinw most of tlrr cwflicienh arc I s $ t l ~ :u~ 1. d ~ e lrlelt l rconles pmfrrscivrI\- enriched \\it11 th? dopant .2c 111r cnstal m\\s. . .

. ~ n o t h r r , g a ~ i l i t r c l t ~ ~ i q t ~ e for silicon ic t h r float-zone prncpss. I t offrrs lmvcr con- taminatior~ tlt;m t h t nonrr:rll\.ohtained frorl~ tlw C.mhralsl j t rchnio t~e . Float-zone cn5-

~ ~ ~ ~~~~ ~

tals a r r (llrnl nl;linly for hiell-po\vc.r. Iriolr-\alla<r (1c~drr.s wltere I~ip11-rcsistivih materiais arc rrquirecl.

To m:kv GI&<. chrmic.dly pu r r <allit~m and arsenic arc used a< the starting mn ri.11~ that arc , > ~ ~ t l ~ e ~ i z r d t o form pn$cnstallinr C;rAs. S i n d r cnstals of Gar\s m a w n n l hytlie (:znclindsh l tr l~niqw=. I Imn*r,\rr. a l i qu idennps~~ lnn t (c .g. BIO,) is requi to pn-vcnt cl8.mmprition o f (:~L.\s at tlw pm\vtl~ tpmpw;ttttrc, :\notl>rr trchniclae is 1111 Rridcm;m prr~r.sq. wltirlr urrs a hrrrzorlr hrn;~cv for grathl;rl solidilicatioa of the melt

.\rtt.r t i cn-la1 is gro\\n. it llsuzdl? S w s thmlr~h a:ifrr-sllapinS operations to five a1 t%n<l p r h l c t of hieI11\ polished n~tI;.rs uitll a s p i f i e d cl iam~trr . thickr~css, and surfno oricnl.~tinn. For r~.t!~,plc.. 2IKI-!nm silicon \vairrs for a MOSFET falrriration l inr sl~otlld 11:nr :i ilinmctcr r r f ? r N l t 1 mm. :I t l t i r b~ rc s oflJ.725 .i fJ.01 mln. ;tnrl ;I snrLrct. orirntzt- tmn oi I ( Y j l i 1''. \\:+fin v i th diarnctrrs I n r ~ r r than 200 nlm ;Ire lwing man~lfactorcd for futt~n. i n t w ~ t c ~ l rirnrits. Tllrir sw i l ;mt ion< are l i ~ l ~ r ! in Tahlp 2.3.

A r r i~ l cr)rt;d has clckcts l l~a t i s f l ~ ~ e n w the elc~utric;~l. mrclts~timl. :~nd optir;~l p n p rrl irs o f t h r s rmi~o l ld l~do r . Tlwsr clrfrcts arc p i n t rlrftctr, l i n ~ clcfcrts, arc;, ileG.rts. :~nd \nlclna. (l~.i,,as. Tllis chapter a l u ~ disrtrsa.<l trtcans to nrinimin. st~clt d,.ii.ris. F ~ j r tllr more clrln:tn<ling LiLSl :~l>plirntions. 1111. dislrmtion ~ l r n s i ~ y must hr 1c.n tln;ns 1 p r r sqtuan' nn t i a l r t r r . O111t~r imlwrl;ml rrqltirrmrnls a rc lislrd in Td,lt. 2.4.

b REFERENCES I . C. \I: Pr.tm... *Cylsl Crcm.11~ ctnd \\il,.r Pn.pr.lllon'sl~rl -Eplt*r): in, S. \I. Sr,.. Ed . \7.51 Trrl$ndoc!,. Yd:r.nv-llill, SnvSnr4. 19%.

2 T Ah,. 'Silimn Cr)\ld* for Cim-Ril Snlr Intr~ntios: InT. S. 5Ims. Ed,. Ilondlml nr Smtimndt~rc~~n. \bl. 3. Elmirr Cipnw 13. V,. AnnacnlamSllu. Sol*. 1IF)I

3 \\'. R. R!m)sn. Slllnd Scmlmnrltddor TrJ8ndqY. \IGm~~~.llill. Sw S,&. IV(15.

4 \\'. C.. Phnn, &nr ilrlrlnp, 2nrl Ed.. \\?It7 S~rnv Sol*. 1%.

5. E. \\' n,d \I. S Llmuller.-Phorplooms Dqinqof Silimn by 5lraaof X'ulnln lrrxli;~li,n: Tmnl €l<nrun Dnlws. ED-23. W:3 119761.

6. \< Ilm-rn. Conalfafina "[Biwry A&nlr. 5lcC.r~~v-Illll. ScaSork ID;',

7. S. K. ChsndLi. \'LV F01,Hmtion PHlltil,let. \\ilr): Sw Sol*. I'l's3.

8. J. R. Arlhur.-bpor Prrssumr and Pha<c Equllihria in lhr Cds S>slcm~]. Plop Chml .W&. 28. 225: Il~X,71.

9. 8 . El-Krrrh. F~~ndn,?vnInlr oJSrmlconrlr,dor Fmrrr(,ag T<cbnnlog.y. K1tnrr.r .Ao&~~uie. Rnrton. IVI5

10. c A. \\'en n. u. PIdy* O J S ~ ~ M ~ . \ICCW.II~II. s~.~sorl i I(M.

It. F. A. Tnmmhorc. 'Solid Snluhilitier oflrnp~dty Elrmmt~ m Crnnanitm md Silime.-Brll Syn Twlr I.. 39. 205 1 ISCS): 8 . Iiull. Prq~~Hin~fC~r loNinr Stlimn. ISSPEC. Lnndnn. I!r51.

12. Y Sfnlnrdlitr. 7 r m d of Silimn Suhslmlc Trchnoloxicr for 0 '5 pru Dnim.- Pnx. lrLS1 Tmhnd ! l ' ~ l t " , , llrrnolulu (1996l.

13. 'Thr lr~lmmllnnnl Trr l l dop l Rmdrl1~111 JOT SO)tIrndt~do~~. Srmimnduaor Imlurtry Anacl~linn. Sm Jou. CA. ?MI.

1.1. \\. F I k ; ~ l l ~ . I. C. C. Tui, and R. D. Plt~mmrr. Edc.. pltkl Rrf~mnm ~lnnaaiJor Englnrm. \lit% SCW Yvrk, I!W.

b PROBLEMS

SECllON 2.1: SILICON CRY-AL CRO\\TII FRO\l THE MELT

1. Plot the d~rpinsdistril,ation of amnic at distancvs of 10. ?0.30.4tl. and 15 cni fmm the surd in n silicon Ingot 50 em long that hm h~rn ptollrd fmm n molt \\ith an initial loping mncerttratior> of 10'' mn-'.

2. In silicon. the Isttiw mnrhnt is 5.43 A. ,Lsnnnr s 1t;vd-rphrre m<xlrl. (1) Calmlstc the nditls of n rilimn alom. (1,) Delrrnrin~ the drnsily of rilic~nn atoms in ;~tovns~on'. lcl U c the Awgadrn mnst;mt to find the drnsity of rilim,n.

3. Asuming that a 1O.k~ p a n silimn c h ; q c is e s d . \vhal is lhr ;tmount of hnmn t l ~ l l mtul h, ;td<lcrl to prt thr lx,ron-dolxd silimn to hnre r resirtivity~~fO.0L R.r.8" ahm onr-htlf of the ingot is p \ n P

4. ,\ silimn \eafer I mm lltick 1n:lrinp a diameter of 11K) rnm ronln~inr 5.41 ntgofhn,n mi- lormly distril,nlrd in n~hs t ih~t io~~nl ritrs. Find ( a ) dlr lnron mnn.ntralion in :aluslr'cm' md 11,) the ;m.r;yr dirlntrr ix.hrrcn imron aloms.

5, ~ 1 , ~ %.e~ cMtd ,,scyl in tllr c ~ ~ I , ~ I s ~ ~ p m c r s is itn~dh nwktrl dm,n to a snvall dio~n.-

trr (5.5 m,ni ;a to i,,itia~c dislmti~,n.frcc p ~ i l n . Iftllr critinl.)idd stnm!tl~ silicol, is 2 x I@ ptcm'. cJcal;ttr the il~syirnun~ lm@h of r silimn isgot 1(Xl 111111 in di.111~-

trr that e;nn he nrpp,nnl hy stnelt r XYYI.

~fc,, 1 1 ~ c,,lrt ~ i t h ~ c/c,,\illae for k,,. 0.05 in the Cznchdsk tmhnirlac.

i, ,, (-nrl,d,~i.p,n m3,.rl h do+ ~ i t h h>mn \\It). is the lw,n,n mnrrnlntion isrg at tllr i.ul r ~ x l of the m-td than at the scwl i.nd2

9. trh, is the innputin mnrrntr~tion Isqt-r in the cvntcr of the s;~frr than at its pvrinwt

S E ~ O N 2.:: SluCON FLOAT-ZONE PROCESS

g, \G uu the flwt-mnr pmm- to pt!rifva silicon inpt that r~mtains a uniforn ydliun~ ,yImntrati~n 01'5 x 1U"cm~'. One pss ir mndr with ;I moltrt> zone 2 cm long. (Xrr N+I.,~ CI~\PAKV is the rrrulting g;dlium wnwntntion h.lcnv5 x 10" cm"?

10. ~ n , m E,I. I$ find the C/C,, tdnlur at .dL r I and 2 >\it11 k, - 0.3.

I I. Ifpr.n ah~upt.jtmdiovt dicdcs we iabtinted tising the silimn mncridr sbovn in Fip 2 Y. find the pncntilqr ch;tngc (of hmskdmw~ \nlt;agrr for the mnvmtionnllydopd si clrn and the nrutmn.irr.uli~td silicnn.

SECTlON 2.3: GMS CRYSTAL GRO\Wli TECHNIQUES

12. Fmm F i ~ m 2.10. ifC. ir 20%. \\hat fme(ion of thr liquid will remain at T,?

13. Fmm Fimm 2.1 1. rrplain \vhy ihc C:L* liquid alu-a!~ hcromes gdlium nich.

SECnOS 2.4: S1ATERI.U C 1 l N i . 4 ~ R M l l O N

14. The eqtzilihium derityof\rr;myn, is giwn by N exp(-E,lkTj. $\hem N is the densit rrmimnd~rctor atoms and E, is thc enewof formation Calmalate n, in rilimn at 2i°C. SM'C. md I2MVC. .<<solme E, = 2.3 r!'.

15. Am~me ihc enerp of fornation (E,) of a F renkc l -h~ de fm to be 1.1 eV and ertirnat the <b.fert dcntih at 27'C and IXnDC. Thr e~l~rilihrirnm density ofFrrnke!-hpe defca! giwn by

", =@t-~,"' \%here X k rhc atomicdtm"tyof silimn (em"). and X'is the density of awilnhle intea tid s i t s [em-') and is represented by A" = I x I F c'"' 'Tcm".

16. llmv many chips of m a 4M mm' em k placed on a wafer 3M mm in dinmctcr? Explair !our arsumptionr rrganlinq the chip shape and t tnu .4 udcr perimeter

Si l icon Oxidation

hlmy difTcrent kin& of thin films arc used to hhricnte discrete dr\ires m d in lep ted Orc~~its, inclt~~lingtl~cnndoddcr, dielectriclayen, polycr)ddlinc silimn. and mrt:~l f i ls~s. Figure 3.1 slio\r.t a sclie~natic \imv of a mn\.cntion;kl silimn n-cltannel XIOSFET tlrat lrsrs d l four p u p s of films. n i p first important Illin film from the thertnal oxide grot~p is thr g:lte oxide in)~r. under \vl~icll a mnduding chmnel can In. formc~l *ln.hveeo t h ~ source and t l ~ e drain. A related layer is the firlrl odrle. whidi pm\i(les isolation from otl~er devices. Rot11 gate and field asides genenll!. arr p n by a thennal oxidation p m r s s lwcause only tl~crmal oddation can provide t l ~ r hi~hestq~ndity oddcs I~a\ing tile lowest interface t n p densities.

This chapter m v e n the follmsining topics:

The thermal oddntion process used to fonn silimn dioxide (Si0:)

Inipurit). redistribution during oxidation

hlaterid properties and tl~icknness mensuremmt tecl~nir~ues for SiOi films

3.1 Thermal Oxidation Process 4 ID

b 3.1 THERMAL OXIDATION PROCESS . ~

Srn,imn,~urton lW oddized by ,srious methods. These include thermid oxidation. ,~l,an,,.la.r,,ir;,~ a t ,~ imt ion . ;,nd pl;rcma-~nl~anml c l a m i d wpor deposition (PECVD. -, ~ ] , : ~ ~ t ~ . ~ 5;. hrnullq tllrsr n r tha l s , l l ~ r n ~ ~ n l oddation is I)? far the Itlost imprl;lnt fi,r silims dr\im. lt i s l keyp-s~ in n ~ o d e n ~ silimn intrgrat~dcircoit tcclmoluv. For cdli,,,n :Inenide. I , ~ ~ ~ \ . ~ . ~ . thern~$ o s i h ~ t i o ~ ~ results in gened ly no~stoid~iu~netr ic RIIII! TI,,. ,,\irl,? pmfidP prrlfftric;ll inrul;~tion and w n ~ i c o ~ ~ d u d o r surf.acc prntection: h rnn ~ t , , . ~ ~ ,,\idCI aw nrPI!. in ~ d l i u m menide t r c l lno lo~ . Consequently. tlris clmple m n r m t ~ t t ~ c on the thermal od11.1tion of silicon.

basic thenn;~1 oxidation apparatus is shown in Figure 3.2.' The reactor mnsbi of a y p s i ~ t ~ I I ~ t - - l ~ e : ~ t ~ I f u n ~ m . a O.lit~drid f ~ l - q ~ a ~ tube containing the silicon w d e ~ hrkl t r r t i d l ? in a slotted qu.uh 1m:tt. and a soclm of either pure (I? oqgcn o r pur uatrr\-npor Thr loadinr: rnrl oftllr fum:~ce h t k protrudes into a wriical flour hood \viler

filtrrr,l flmr.or.zir is m;tint;tinecl. Flmv is dirrctrd as sho\\n by the arrmv in Figure 32 The. haxl duct-sdust and particulate matter in the air surrounding then&n :md mir itnizes oontamination durine \\-afrr loading. Tlre Oxidation trmper.~ture is generdly i the m e c of9M'C to 1EOO'C. ;md the hpid gas flow rate b shout 1 Wmin. The ox .~~~ .. - cL7tioo {stem uses micmpmcesson to replate the gas flmv sequenm, to contml the auk matic inwrtion and remmd of silicon \\dbrs. to mmp the temperature up (i.e.. to increa. tile hlrnaw trmpenture linearly) from a lo\\. t~tnperature to the osidation temperatut wr that tht- xclfrn \rill not \ r q due to sudden tenlpenture change, to maintain the ox &tion t r ~ m p n h r r e to within +1"C, and to n m p t l ~ r temperature down \vl~en oxidntia is mmplrtvd.

3.1.1 Kinetics of Gmwth

The follm\+ng rhrmical reactiom describe the thermal oddation of silicon in o x e n (I oddation) or \rater \apor (\vet osih?tion):

Si (solid) + 0, (gas) + SiO? (solid) (

Si (solidl + 2H10 (gas) + SiOI (solid) + 2H2 (gas) (1

The s i l imn~i l iwn dioddc intrrfaw nlovrs into tlle silimn (luring the orirl;itiot~ prow<<. This creatrs 11 frrsh i n t e d ~ r r region, aitll sudacr contamination on t l ~ r orictinal silicr,n en(1in.q up on tI~r osi~l? s~lrfaw. T l ~ r cb.nsitirs anti molrrul;~r \v r i c l~ t rrf i l imn anrl sili. con dioside are use11 in tl~r follon,ing vr;tmplc to shmnv tlrat gro\ving an orhlr of tltirk- nrss x consunles a layer of silirwn 0.44.r thick (Fig. 0.3).

EXAMPLE 1

If n silirnn nddr layer of thickness x is Lmnnn 11s thrrmal oxidation. what is t l ~ v thickncrs ofnlicl,n Ix.ise; mns~~mnl? The inoln~tlar weight of Si is 25.9 g/m/mol, and the denity ~ r f Si is 2.1 cIcm'. The roncsponding \alurr krr SiO? are Cfi.09 g/rnol :~nd 2.21 C/cm'.

SOLUTION The wllrnrnc of I mol of silimn i~

Molecular weight of Si - 2R.9"mol = 12.06 cm'/mo~ Dznrityof Si 2.33 g/em'

Thr \nlt~mc of 1 rnol of silicon dioxide is

Molrmlsr wcicht of SiO, - M).h9 glmol =27.18 m'/mol

Dc,nsih of SiO, 221 glrm'

Sinoe 1 mol of rilimn is mnvrrted to I mol of rilicon dimide.

Thickness of Sixarea - \'olumc of l mol of Si - Thicknrsr uf SiO: xarcn \'olameof l mnl of SiO,

'Ihiekmesofsilirnn = 0.44 (tbicknnr dSi0,I. For c~xmple. t o p v a silicon diooac l;i>rral 11x1 nln. a In!-r of W nm of rilinrn is w,nrumed. 4

internuclear distance is 1.6 A. and the oqge~e.-to-oq'ge~~ internucleardihu~cr is 2.i?i(. These tetra11edr.1 are joined at tbeirmmen I,yoq$en bridges in a \?riehof\\TI>5 tu fonn the various p11;ies or stntctures of silimn dioxide (also ridled siliro). Silica h:i se\.crd cqstalline stnlrtlrres (e .~. . quiutz) and an anlorphor~s stmcturc. \ \ l ~ r n silicon is t h e d y ovidized. the silicon diodde structare is an~orphous. T)pic;llly an~orphoos silia~ 11;s a density of "2.1 g/cmi. compared nit11 2.67 girm' for qaartr.

EJlal0.t

R#om 32 Schematic m* wiion ofa nristanrr-heated oddation filmace

3.1 Thermal Oxidation Process 4 45

(c)

Kgun 3.4 (01 R:~sir \tn!rtnrd unit of silimn dinedr. (1,) T~~wlimensh~nal wrrpst~nl:tlion of s ,tv4rvz cnxt.<I latfirv (rl T\mdimcnsion.<l rrrpreseotatinn of tllr nmorpl,ous stntcturr of silirnn ,l,<,,i<lr,'

Tl~e h;lricdifTrrence hrh\w~l the cnstallinr and nmorphous struch~m ic that the fol nirr ic a primlir stn~ctun.. edmdingover nlan~molrmles.\vI~erex~ the h e r has noppn nlir anniIln, at dlII. E i q t n ? 3.d) is;\ h~vdzner~401d wllen~atic d i i m ofaqllartz cqstdlin- ctnlctum nurle upof rinqs witll sixsilimn atoms. Fipre3.kicn hmlimensional schematic dism.1111 of ~ I I I amoml~o~a stnlctirre sl~o\\n for m~nnariron. In the arnornhous sm~cture. then. is still :a lentleny to frmn cha~~cteristic rings !vitll six silimn atoms. Sote that the dmnlpho~~s stnlctnw in Fig~re 3 . 4 ~ is quitc oppn 1m11se only 43% of the spqw is ~ I I

pirrl I>? silirnn dioxide moleo~les. The rrlnti\el?open stmatt. accounts for the lo\c~rden sih and :~llmrr n mrirhof imp~~rities (sucl~ ;L? srxli~~m) to enterand diffiw readily tl~rnug tlw silims~ ~liosicl~~ la,~r.

Tlir hinrtics of tl~ernlal oxidation of silicon mn he studied hated on a simple md~lc illnstnted in Figure 3.5.' A silimn rlicr mntacts the osidizinp species (oqxen or \rate \npur'l. rc~s!t~tin~ in a srldacr cnncentratinn of C,, n~o!en~lrdcm' for these sprcies. TI1 ~namlit~~cle of C., rqtjlls tlcc equilihri~~m balk concentration of the species nt the oxida tion tr.mIrr.lttlrc-. The rqllilihri~~m mncentmtion gr~~erally is proprtiorial to the palti; pnsntrr of thr okidaflt ntlj;lc~nt to the oside srtrf:lo?. At 1000'C and at a pressure of :ttm. tIw mnc~mtr.~tinn C, is 5.2 x 10"' molmulerlcni' for dry oqyen and 3 x 10' molrr~~lrJcni ' for \v;atcr vapor.

The oxi~lizin~ y c i r s diffi~ses t l ~ m ~ ~ c h the silicon dioxide Ia!pr. res~~lting in a mn c~~ntratinn C~ :tt tlw sttrfam, of silimn. Tltr flclr F, can he \\7ittrn ac

\vltem D is tltr difft~sion cwNicknt ufthr oxididnx Species. and x is the thickness of the mirlr 1.w-r aln-arl!. prrsrot.

Figurn 3.5 Raic mdcl for the thermal avidatinn of rilimn.:

At the silicon surface, the oxidizing species mcts cl~emicaaly\~th silimn. Assuming the rate of reaction is proportional to t11c concentration of the sppcies at the silimn rur- face. the fllu F, is given I]?

F:=< (4)

\rrllere xis the sudxe reaction nte mnstant for odrlation. At t l~e stead? state. F, = Fl = F Combining Eqs. 3 and 4 gives

The reactior~ of the oxididng species ~4t11 silimn fonns silimn dioxide. Let C, be the rntmher of molecules of the oxidizing species in a unit volume of the oside. Thcrr am 2.2 x 10" silimn dioxide molwaledcnl" in tllr oxide, nrld add one oqxen molrcule (OJ to each silimn &oxide molecule. \!,hewas we add htv \rater molecules (H:O) to r;tcl~ SiO, niolecule. Therefore. C, for oxidation in d v oqsen is 2.2 x 10" cm-'. and for oddation in water vapr it is hsice this nomher (4.4 x 10'cm-'). Tl~t~s. the gmtth nte of the oxide layer thiclinrss is given by

\\'e om solve this diKerenti$ eqlmtion s11hjrc-l to the initid condition. x(O) = d,, %\llere rl, is the initid oxide tl~ichmess: (1, can also he r e g ~ r d d a the thicLness of oxide layer grown in an earlier oxidation step. Solving Eq. 6 )ielrls the general wlationship for the oxidation of silimn.

, 2 0 ZDC, .r- t-.I=-(rtr) (71 h. CI

afl~ere r e (d 5 + ZDd,lr,,/~)C,C2DC,, wlticl~ represents a time modinarc shift to ~ I I I I ~

for the initial odd" l :q~r dv The oxide thicknrss after an oxidi7jng time f is @wn hy - 7

4 8 F Chapter 3. Siccon Oxidation 3.1 Thermal Oxidation Process 4 40

IMOlTiK-1 )

Fipun 3.7 Parabolic n tc constant versm temperature.'

,Althoud~ oxides p \ m in dr). oqxen haw the best elearical properties. mnsider- ably more time is required to grow the same oxide tl~ickness at a given temperattlre in d n a n r e n than in\\.ater tapor. For relatively thin oxides sucl~ as the gate oxide i n a blOS- FET (hpi~111y S2O nm). dr). oxidation is used. However, for thicker oxides such as field oxides (2 20 nm ) in SIOS integrated circuits, and for bipolar debices, oxidation in water \apor (or steam) is used to pmridr both adequate isolation and passivation.

F i p r e 3.8 shm\s the e v r i m e n t a l results of silicon dioxide tlrickness as a function of reaction time and tempratare for h\v substrate orientations." Under a gives oxidation mn~lition, tlre oxide thickmcss grown on a (111) suhstrate is largt-r than that grovn on a (100) suhstrate l m u s e of tlte larger linear rate const'mt of the (111) orientation. Xotr that for a given tempmhlre and time. the oxide film obtained usinswet oxidation is a b u t 5 to 10 times thicker than that using dry oxidation.

A $limn smple is oddiad in dry 0, nt 1200'C for 1 hour. (a) \%at in the thickness of the ox pmn? (h! Ilm~.mt~ch additional timc is required t o p 0 . l pm more oddc in \ b e t 0 2 a t 1200'

SOLUnON (a) Fmm Tahlc 3.2. lhr %alaes of the n tc constants for d ~ y 0: at 12009C are

.A = 0.01 pm B = 0.045 pm'h

and r = 0.027 h. Using these panmcten in Eq. 11. \vr ohtain an odde thickness of

r = 0.196 pm

(hr Fmm Tahlc 3.1. the \dtler of the rate constants for wet 0: at 1200°C are

A = 0.05 um B = 0.72 unlZ/h

ide 'C?

Odhlion finsr r ~ r r

(h)

Figura 3.8 E ~ ~ ~ i m c n l a l mrults oisilimn di06,ic thickmess s a fimrtion of rraction time rnd tcmpcr~ture for two n ~ h r ~ n l r orirntatinns. i n ) Crwtih in d ~ a y ~ m . ~ h l Grcmth i n slrrm.

Sine ,I,, = 0 196 pm fmm thr fin! rtcp. \re haw

d: + A4. - r = (di +2D4, W)C, PDC, = - B - 0.067 h

~h~ final drdnrl t l l i c ~ e s is = (1, + 0.1 ilm = Oe96 film. Ilsisg lhrre pann1c.h.a in Eq. 11. \w obtain ;m adclitiosi~l oridation tin)? of

r = 0.76 h = 4.53 nbin 4

3.12 Thin Oxide Growth

R e l ~ t i \ ~ l ~ slow Cro$vllb mtrs nwst lrr used to repmltlcihly ~ r n u . thin mid? filllls of pw- cise tllichrss. \T:lrions approacl~es to a c l ~ i ~ w surlt slo\v p a i l l n t r s 11mr bwa rt.lmrtcd. inclu1]inx gma*l, i n (IO. 0: at inmosphrric prcssare and lo\v~.r trl1qwntan.s IstN"C 10 gm0c) : pro,,tl, nt tllan ilttn~spl~cric prrsst~n.: grn\til~ in rr(111d p~rtiill prrssurrs of^, I?\. dilarnt incl-t g.~, such X\.2. Ar, or He. losctlt~.r -it11 lhv 3- mnt~, , i r , s tllr. o\idiinx sprcil.s: and thr usr ofcr,n~~msitr midr films. \\it11 thr q;~tc.c~icll' fillnS n,,lsisti,lg of lil!vr 01. tlwrnnlly grn\\n SiO, ;a111 en o\-rrli~yer of SiO: Sro\\n I>!

.SO * haonr 3 Silicon Oxidation 3.3 Masking Propanies of Silicon Oioxida 4 51

rhrrnirrl \a lnr rlcpositios (CVI)). Ilmrr\rr. the inxinstreim~ nl)proncl~ for gate odder 10 t t n 1,; ntn tl~ick is tu cm\v the oxide liln~ at iatn~ospltt.rir pNhSS1lN' and lo\ver t cmpra t t~ws , \ r x ~ < : to tnrvcI. \\ill, tlti.; apprn.~cll. pnm.ssiag using m ~ l r n ~ trriirnl odd:ttion fur- rl.tn.r c;ur rnnv n~nnrlt~cihlr. Ilicl~-<~ualit\. 10-nm odrlt,s to \\illkin 0.1 nnl acmss thr \rnfrr. - . . . .

It $)is nntrd t.;~rlit.~. tlkat for Jn odrl;!tion. then, is i1n apparently mpid oddation tllat @r.s r i r to an initi.tl nxi,\c, thickst~ss d,, of nholtt 20 nnt. 'Tl~errfore. the sirnplc mwlrl l m ~ c ~ n t v d in Swtiol~ 3.1.1 is not \:tli,l for ~Ino~icla t inn \\it11 an nddr thirl;nws lrss than o r C Y ~ , , : ~ to 20 n n ~ . For IILSI. tl~r ability to ~gm~m\v thin (-5220 ntn). uniform. high-quslity n.pnxl~lcihlr pak oxi~lrs I t i s h m m r inrrea-in~k. in~pnrtsnt. Illis stxiion lrriefly cnnsidpn thv Lmn\tlt inc~ltanklt~r of s11r11 tllin oxides.

In t l ~ rtrly stact. o fqo \ \ ih in r ln oudntion. there is a large conlpresive stress in thp o<d<. lmrr that n ~ l u c r s the o n s e n cliffusion mflicient in the oxirlr. 11s the oddr ' . I r m m r r thicker. the t m s r is mdtm-rl hrr:ttnsr of the viscous flmv of silica, and the diffusion rwflktmt ill :,onrnach its strrss-free wltte. I l t e r e f o ~ ~ . for thin oides. t h ~ \PIIIP . . .~ of ll!ret:~~ Ir. sl!flici~ntly sn~all that \w GIII nrgIect the Ann in Eq. 11 ant! olttain

b 3.2 IMPURITY REDISTRIBUTION DURING OXIDATION Dop:mt impurities nrlr the silicon s11rfacx2 \\ill Iw redistrihut~d during thermal oddation Thr m l i ~ t r i h ~ ~ t i o e clrpntls on sc\.cral facton. \Vhm hta solid p l ~ z r s are brought tqether. irnpv~rityin onr solid d l redistrib~~te behvern t l ~ r hru solids until it rearlles eq,tilihrium. This is similar in the pretious discussion in Chapter 2 on impurih retlistri- h ~ ~ t i o r ~ in c n s t d ~ \ V I I I fmm t l ~ r inelt. The ratio ofthe eqsilihriam conmsntntion of the ilap~~rity in the silicon to that in the silicon dioxide is callt~l thr srgmgotio 3 8 1

and is rlcfinnl

1. = Equilibri~nn concentration of inlpurih. in silimn Equilihrit~nn conwntrat io~~ of impurih in SiO,

.I sewn11 factor that inf l~~enrrs in~pnrity distribution is thqt the impuriv m y (liffuse rapidly thro11~11 the silicon dioxide ant1 e s r a p to the ~ W W I I S amhient. Tftl~e lbffusi\ih of t l a inlpllrih in silicon dioxide h inr-ge. this fador \\%I1 h~ important. A thin! factor in the ~ ~ i s t r i b l l t i o n prim-5 is tllilt the o<de is .w\ ing. ant! tllus tltr inunr t ln behveen the silicon and the ndde is a r l \ m r i n ~ into t l ~ r silicon as a function of time. The relative cttr of tl~is ial\ance mmpawd \,it11 the cliffa~sinn mtr of the impurity thn1p11 t l ~ e oxide is important in r l ~ l ~ n n i n i n ~ tllr r t e n t of the N-<listribr~tion. Xotr that even if the segre- pt inn m f i c i e n t of :UI i~np~nrihequals u n i h ram? r ~ l i s t r i b ~ l t b e of the impurih in the silimn will still lakc: pl:~rr. As indicitt~l in F i g ~ r e 3.3. thr oxidr layer will Iw ;tlnut hviw

thirk :lz tlrr silimn layer it repl;~mi. n~erefore . the same amount of imptwity\\"ll nmv h. di.;tril>~ttr<l in 3 lawer volamr. n*r t~ l t in~ in depiction of the impurity from the silimn.

Fo~rr pos.;ihlc n.~Iistrihution prn1Trv.r a w ill~~rtratpd in F i p r r 3.8.' n ~ c w p m s s e s mn in.rlmsilird into hvorn~lps . Inone p o p , the odde takes !lptlle impurity (Figs. 3 . 9 and 1, for I; 1) . In c;lrh mv. ull:lt i1aplr.n~ rleplals on llmv ~lpidly the irnpurihcln diffuse thrnltgh the nxirlr.. I n gmop I . 1116. silimn sr~rf:~cv is ileplrtnl of impuriticr: an ex;tmplc is inmn. \sit11 I i~pprnxir~~.~trly rq!rnl tr, 0.3. Rapid &lTnzsion of the in~purity thrn11~1~ tllc silicon dinside

r (pml r ipml

(4 (dl

Figum 3.9 Four dillemnt rues nf impurity redishihation in rilimn duc to therntd od<htion'

increases the amount ofdepletion: an exan~ple is homn-doped silicon heated in a h d m . gen ambient. becnnre hydrogen in sil ico~~ ~liodde enh.ulws the difhsi\ity of bomn. In mar, 2. I; is s e a t e r than mihi. so the odde reiects the i n ~ n ~ ~ r i h : lftlifitsion ofthe inmu- ~. . <. . , r i v through the silicon diodde is relatively sfoiv, the impurih piles up near t l r silikn snrfarr: ao exan~ple is phosphoms. with k :~pprndnlntdy equal to 10. \ \ l ~ c n diffusion thmugh the silicon dioxide is rapid, so much impurity may escapr fmtn the solid to the gaseous ambient that the overall effect ,rill he a depletion of t l ~ r impurih rmmple is gallium, with k appmdmntely equal to 90.

The redirtribatecl dopant imp~rities in silimrt cboddr are selrlont elec+ri~illl\. active. Ho\ve\.er. wtlistrihution in silicon IBCU an import;mt rlTect on processing and d w i w per- formnnce. For eu~nmle. nonuniform clovant distribution \rill inodih the interpretation of the mensurnnents of interlaw trip prnprties. and the ch.wge of the snrf.~ce con- centntion will nnodib tllc tl~reshold volt:tpe and deiire contad resirtancr.

b3 .3 MASKING PROPERTIES OF SILICON DIOXIDE A silicon iliodde layer can also pmtidr a selrctivc nlwk again.1 t1ie diffusion ofdopan;altl at clr\atnl tenlpmhtrcs, e ~ 3 . usehl pmpn?. in IC hbrication. Pdcporition ofdopu!ts (see Chapter fi). \vhethrr it lw I,? ion ilnplantation. d~rn~ic -d dillusion. or .spin-on trrh- niql~es. hTicdly resalts in n dopnnt source at or npar the surface of the odde. During ;I

52 b Chapter 3. Silicon Oxidation

stdscqrsnt high-tenIperarure uriw-itt step. ~Iiffusion in oxide-ninsked regions must I sI0\v rnouCh nit11 reslrct to diITusion in tlte silico~t to prewnt dopnnts from difl~eil thmtteh tlw oddr lnnsk to tlte silimu surface. The q u i r r d thickness 111t1yh dctennin~ rxF"nlcntally I?,. n~e;auring the wide tllickness nccesai? to prevent the illersion ol liclttl\. doFd silicon substr.ltc of opposite ~~~tchtcti\ity at a particular tempcnlhlre at t i ; ~ ~ ~ . ' ~ ~ ~ i ~ : ~ l l y , oxides used for m;ukng coolmon in~puritics are 0.5 to 1.0 pm thick.

Tl~e \Tllrues of &Nttrion mnstw~ts for \n"oun <lopants in SiO, depend an the m centn~tion. pmpertirs. anrl structure. of tlze oxide. Talrle 3.3 lists <liffi~sion mnstnnts f \Niour cotntnon dopants. and Fipn. 3.10gi~i\~s the oxirh? tlticLness requir~l to ttiask Imn and pltosplronts as function of cliffusion time and tcrnperature. Notr that SiO, is !nut morv eff,~rti\r for nvaljng baron than pltospl~on~s. Xevertltrlesr, tlte diff~tsivitics of Sh. As, and 13 it1 SiO? arc all ortlrn of tnapit~tde less tlian their corresponding val~as silicon. w the!. ;uc all comp:atil>le wit11 midr mnsking. Tlds is not t ~ e . I~owcver, lor ( or Al. Silicon nitride is itsrtl :zc an alternative mnrking mnterial for these rlements.

- Romn

0.1 1.0 10 IM ntlT,sicm time (I,,)

Figun 3.10 Thiehnr orrilimn dio.ridr nredcd to maqk lnron and phrxphoms diffi~sions a hamion <ddifiusion time :and lcmpcratm=.

- 3.4 Oxide Ouality 4 53

w 3.4 OXIDE QUALITY Oxides I I S C ~ for mucrking are usually grow, by \ r~ t oxiclation. A gpical g rou~ l~ cvcle mnsists of a sequence of dg.\vet-dr). oxid:ltion%. Mcxt orthe prmvtlt in strclt a WI~IP~CV; r n q j r n

in the \vet phase, sillce tile SiO, growill rate is mllcll higller when water is uspd ar. thl. oxidant. Dn. oxidation. hou,ever, res~~lts in a Itisher-qualit? oxide that is denser and 1~;~s a ltidter brcak(lo\~n wltage (.%I0 M\'/cm). It is for tlirsermwns tltnt the thin gate oxirln in h!OS dexicrs are us11;tlly forn~ed using dry oxidation.

hlOS devices are also affected Iry charges in the oxide and traps at tlte Si0,-Si interface. Tlte ba%ic clwification of these traps and cl~arges is shrnvn in Figure 3.11. T l ~ q are the interface tnpped charge, Lxcd oxide charge. oxide trapped cltarge. and mol~ile ionic cltarge."

Interface trapped charges (Q,) are due to tile Si0,-Si intrrface properties and are dependent on tltr clletnical composition of this interface. Tltr tnps are located at the 50,-Si interface, with ener~ystates in thes den 1)ande;rn. Tile interfant trao

<, . densih (i.e.. number of inteaace tnps per ~d p r c.\.\') k orienhttion depr;. llrnt. In silicon uith a c1lXb c y t d orienta~,~.a. .,#terface trap densih is ahout m order of nlapiturle smaller than Illat in tlte <I1 l>orientation. Present-day \IOS dmices with tlienn:Jly grown silicon dioxide on silicon have most of the interface t rappl charges passimted by low-temperat~~re (150°C) hy11rogc.n annealing (see Cl~npter 7). The \due of Q,, for <IN)>-oriented silicon can he Im\.as 10"'cm-'. wl~icl~ :unonnts to about one interrace trapped charge per 10' s~triace atoms. For <Ill>-orient~l silicon. P,, is ahout 10" cm-'.

Tlte kxed cltnrge (Q,) is located within approximately 3 nm of the Si0:-Si interhce. This charge is fixed and very dimcult to charge or discl~arge. Generally, Q, is positive and depends on oxidation ant1 annealing conditions and on silicon orientation. It 1 1 s l ~ c n s a ~ e s t e d that wllen tlte oxidation is stoppd. some ionic silicon is left near the inter- filce. These ions. along\vitll uncompleted s i \ i ~ n bond5 (e.g.. Si-Si or Si-0 hanrk) at the

in the positive interface cltarge. Q , m he repnled .u a chaqe sllrct surface, may reslrlt

.U c Cbnom I SlLcon Oxidetion 3.6 Oxidation Simulation 4 55

Irratrrl at t l ~ r SiO,Si isterClm.. T>?ic:ll k~ed oxide cl~arpc ilnuities for ;I n ~ r r f ~ ~ l l ~ twatc s,o,-si illtrrf;l'y. s,dm~ an- illnut In'" cm-' for a <100> sttrf;ar and alnllt 5 X 10'" cnl fi,r ;t starf,~c~.. R m u s r of the lo\ver \~1111rs nf C),, a ~ ~ d Q,. t11e <100> orientation pn-frm.i fbr silimn hlOSFETs.

( h t l r t ~ a ~ ~ ~ l rhnrgrs I Q , . ~ an~as.;ociatrd uith defects in thr silimn dioxide. The: C ! I : I ~ I ~X-RII Ix. c rea td . for c*x:~mplr. I>? x-ray radiation or 11igI1-eorrg rlrctron 1m11 hanln>rnt. Tl,r traps art* dirlril,tttc-tl insidr t l ~ e ori(lp li~!rr. h.lost procrss-rr!at(~d Q, IF n.nto\wI hv Lnv-trn~p.r;~ture anneding.

\loIriIe ionic cl~arst.s (Q,!. \vhirl~ r r s ~ ~ l t f m ~ n contiunination from sodium or nth, ;~l l i~l i inns. are mohilr \\ititin tltr oridr t~ndr r ctisml trmpcnilrlrrr (e.g., >100'CI and l ~ i g l ~ rlcyirir field oprraticm~s. TRIW mnt;nnin;~tion I,? ;dk:di n~rtnl ions may cause stahilit?.prob- lrrlls in <t.nli<nn<luctor clr\icvr o p m l t < ~ l tlndrr l~igI~-hia% and high-tenlperat~~rr mndi- tionx. Untlcr thew mnditinns mol~ilz ionic cll;~rgr.: can n ~ o v ~ hark iind fort11 t l~rougl~ the nxido l;aycr :m<l r:luw th red~ol~ l vnltap s l ~ i l t . Tl~mrrfore. scpci;tl altrntion mtlst In. p i

the rliteir~ation of ntohile ions in iit.\icr C~lnic:~tion. For ~ ~ ~ r n p l e . the r k t s nf sadit~l met.~mio:ttion r;ln lw n-drlucd by addillg cl~lorine during oxidation. Cl~lnrine imtnob lkes hlr sntliu~n i n ~ ~ s . A s~n:~ll nn lo~~nt (6% or lrss! of ; u J ~ \ r l r o ~ ~ s llCl in the ori<lizinc c: n n accnmplisl linear ;an<! pari

I tl~is, hut th lholic nh n

,~. <.

I, pn.scnncv ofchlorine during dr).oridntion incre;ws I~otlt tl nnstants. leading t o n highrr ~ro\r . t l~ r:$tr.

b 3.5 OXIDE THICKNESS CHARACTERIZATION Prrltap< tlte sitnplrst mrtl~ml for drtermining tlw t l ~ i c k n r ~ s of an oxidv is to mmp:tn 11 mlnr of t h r uxf8.r a i th a w6.rrnn. rwlnr rh;trt. cltcl) .AS tlw OILP in T.~hl(* 3 - t L \ \ l ~ e n 3

o n i d r - m l ~ l uafcr is illunlinatcvl \\it11 white liellt wrpendiallar to the surface, the l i ~ h t . . . prnctnltrc tile oxide ;mcl is rrllcctcd hy the u~~rlerlying silimn \\afer. Constnlcti\.e intcr- k.rrnw It.ntLc to ~ n l ~ m c r m e n t o f a wrtiun ~v:~vrl rnet l~ of rrflected liel~t. and the mlor ,- of thr wafer mrrespnnd~ to that uavrlrngth. For example. a \safer witl~ a 500-am sili- m n dinride I a y r uill appear hlur m r n . . .

Clearl!: mlor chart <omparirons i r e suhjcctive and nrr therefore not the most ace, nlte m ~ c l ~ ; ~ n i s ~ n for drtrrminine oxide thicknrss. A more aceorate measurrtnent w n t

Prnjlr~~nrrnj ir a wr). mnnnon methwl of film thicknrss menwrrment. In this trcl nique. a sten fri~ture in the mown or dt:msited lilm is t int r ~ a t r r l . pitl~er lw n~nskin <- ~. ~

during drposition or ln.rtcl~ing aftrnwrcl. Tllr pmfilometer then drags a line stylus acm: lltr filn~ snrf l l~ ' (see Fie. 3.12)'. \\lien tllr stylrm e ~ ~ r a ~ ~ n t r r s n step. a signal variatiu intlintes t l ~ c step I~eigbt. This infom~ation is t l ~ r n displn?ed on a ch;lrt remrtler o r CR scrrrn. Fil~ns of tl~icLnrsses of less than 100 nm to greater t l~an 5 pin can I* nnlrnsnrr with this instrument.

Ulipwmr?nj ir anothrr tridrh used measurement tcclmip~e that is hxwd on the polar- ization rhangrs that m a r \vhm ligl~t is reflected from or transmitted tl~rouglr a medi~am. Change* in polari7~tion are a f~lnction of the. opt inl proprrties of the mat~ria l (i.e.. its m m p h ~ s rrfr;lrtive inrlircs). it$ thirLnrss, anrl tllp ~ w v ~ l m g i l ~ and angle of incidcnrr of t l ~ r lieht lwan) relative tn the sl~rf:~ct. n o r n ~ d . T l ~ r s r (li&.rencrs in politri7ation are I I I ~ ;

s t ~ r r ~ l hy an ellipomrtcr. and tl~r c~xirlc tl~irkncss can t l ~ r n Iw ra lc~~l ;~ t rd .

TABLE x4 Color Chon for Thenallv Cmrm SIO, Film Observed Perpendicularly undn Dayligk n~omrced Lightinn

\ ' i c r l ~ t n~ Rvd ,ir,lr \'i"I"t Ill..., .<"I

Tl~irhes< Color 2nd Co~nm~.sts Ipn) (idor i m ~ L_IJT~IIIII.~,LS

T:m 0.GS "nlakb- (11n1 lllna. I ~ , I lnnl,.dinc Ilr,~\vr~ l u 4 a ? n t tiolvt ;mcl 1,ltlc. grr,rs: Dmk \iolrt to r-I \ic~lct ;~ppc.arr morr lckr a i l ~ i x t t l n .

R q d blue Iwtnv~n tiold rwl and I>ltw ~~~~~~ Light I,lttc to mrt;dlir blur :twl lc<>k\ gn>>i<I3 I

>lt.IRllie 10 \.PV Ii~ht 0.72 liluc pn.rn to gncn lrluirc llnwdi yvllr~n gr~.ce rl.ii "Yt.lltn,i~lr"

I.irl>t gold ctr )rllmr.: 0.54 Onnsc lr;~tb<.r broad fix ocmgc) sliql~tly rnc~t.nIlir Ori2 S;oln~rn (:old n i t I> 5li~ht 0.&5 DDI. liph~ n,<l \iolct y<.llcn\. <,mr,r" 0 . Vsnlr,

Omnpc to inrlnn 0.hi R l s a &let Hrd \iolrl 0.69 BInv Bluc to \iolrt l,Ita: I Illuv gn.m Blur 1)))s Dtdl yvIlo\\, p - c n Rita to blue w e n 0.9i Yt,lLnv to "!rll<n\i~b' I.icltt p e n 0.W Oritnp Cn.m to )rllmnv prcm 1.00 Carnation pink Scllmv prerrm 1.02 \?otrt n:d Crt..l.n y,llow 10.5 R C ~ \ioIct Y?llrn\. l(K \lolet Liqlnt orange I.0i Rltw \inlet

C;trnntinn nink 1.10 Cncn 1.11 Yvllmv crrcn 1.11 Crwn 1.18 \5ol<~t

.,.,.L ..,,... 1.19 R n l \iolet

Blue 1.21 \Fcdrt m l

Rlt!e g r ~ c , ! > 1.24 Ctrnation pink to ulmon

C h c n (l,ro:td) 1.25 0r.tnge Yvll<nv g"Y.11 1.23 'T,~ll,n\isl,- C w m )r.llmn\, I . Sk, bhtr to p v n I ~ l l s

Ycllmv t r l "!rlln~~ish" (not ycllrnv h a 1 1 . 0 Ornnev

c 3.6 OXIDATION SIMULATION

u in thr position tvhrrr !vllmv is tr, k. eqwctvd: at tinlcs b8ppc.m to 1%.

AT trend* trnr~tnl miniaturiirntinn mntinup ancl the s a l e olintegntion of ICs incwasr amlratr b ~ m v l c d ~ r ofonr-. hvo-, and thrrr~limensionnl r t n ~ c t m d ininnnation rep;ar<li~ir

1.45 \'iol~t 1.16 Rlur. !ioh!t

light cwrlny gri~v or mrlrlllc) I.i(l H i t ~ c

Lieht orangr o r )r~llcnr to pink 1.54 l1,dl yvllcm- smrn

C;urnution pink

t it:^ appo a q u! mqlr~wbmu! srun~ldsoq~l "11 s ~ ~ ! d a p PIE 111d MOJO SWJ

-y.'!qr .vpo ~IRIIJ s sorv-xpu! q~!t,.w ' ~ 1 . c a~lC?!d U! I M \ O ~ S an! SqnS.II 3 1 1 ~ 'alwl'iqns lla>![!s all1 0111!

tq111.7~ JO 110!1311"J n sc T : I ~ ~ ! I ~ J I ~ ~ . U L I O J mt>qds(tqd 17111 1 ~ 1 d PUP! luud a n .alrlldlttu7 k? UO!IPP!X~ J-)IJY ,lun!qarr sa5nlr!a e

s! pauuoJl.~i xl.m auop dnrrd pur <In durn nqL .pna "'PI* 3.m 01 y ~ s q *~nn!mn,oz- Ir *,%"p tlum qnrnwnql r:pmmXt~y~:rmd~o'du!t1tn$x1 q lr 3.~1101 amnu!~rg,(n IC dn dm= a~lnuu!m-n~ P .ml :m n; .p.vxa! s! ~.,jn?n\ aql uat l .~ n,,~lfi JO ~ J ~ I P J J < ! < ~ ~ O I an,! m: s t , .mrtunj aqr autnsm

dOLS LOld

lNI8d WISIlJJIO

lN3Ma3 w I s n J J x o

JN3hW3 NoISIlJJIO

lN3Ma3 WISnJJIO

l N 3 w 3 WISIIjJIO

l N 3 W 3 3ZIlVILINI

lN3M*)3 31111

Problems 4 59

<lr~rrilr<l :~r \\.rll. Finall? t b r prowss sim~ll:ation a~fhtare pack~ilr Sl:PRE\l \%:a in t r

dtmrl. Tltr wr niSI:PIIE\I. III)\VP\.PT, is not lit~,it(.d t o olridation, and it \till hc r ~ \ i itrcl in sn~lwcqsrnt r l l ; lptcn.

b REFERENCES 1 E 11 srmlli.,n :.nd J R R-. JIOS Plillrin ond Tl.ihnd~lq. \\ilry. Scu. Yo*. 199-2

2 R E m-.,I ,~,,d ,a. s cnnr -C*.n,.rd lirl.,rltmdllp lor thr Thl.rm:II (fitLt1ion aiSllimtn:] .Apld Phys . : ;-,, , ILW>.,

R I D Slrlndl *.r .d . .sO,n~n E p i ~ . , ~ md Oxi&,hun: in F. \'.I" dr \Iirlc.. \I: 1. En!$ and P 0. Jrqwv. FII. . Pnnv owl 1 h 1 r r >f,rb.iln:ifiir In,~orr~rrdC~m,ft Dtv<n. SmrlmR Lr\~lr.rn. 1977~

I .\ s C m r ~ h . , . ~ l , m d EcI,NJ,,~~ ~fsrminmrbrfsr IX.roh-,. \IiL-. S w Yo*. 1%:.

5 R E Lh-11. ~St..niilnll,nl K.minolw lor Oodr Clt3ql. Asw.idwl urlh Th.~rmdl?Oddmd Silic~m" lEEE Twnc El.,nn,.i I,..! irr., ED-27. FJ6 i I'JVI:

6 \V R,-bn .m<t E (:m~r.,ll. .S,,nll,.tnsrnxv Mcnnmation oiThicblrn mncl Rvfr;n.liw Indm ol Tr.~7v.cmr,t b-dr>w. 18JIJ R n D.~,,lhf,, S.43-51 41kW>l,

r s \I,,li.tnd R T.,nI..r Si!am F m n v l ~ / l r r b r \%S1 Ern. larlirr Pn.-. Sl~nu.1 R,.xlm. CA. ZMD.

\ CI'I'PREI1.I I'.rrl Jfonnnl, S l I \ y n l n b m i , t s ~ ~ ~ ~ l . Sonla CX.ICI C.I. 1%;

,I 11 \~.nu~~, l . <: 11s. m,l J ~Iwn~l;~.r !n J rl\ttnnlt.r. Fcl . Conzytrrr ~ul,.d Dtricn oflnacmrrd Cimril ~d. - , . . , ! : ,~ rn..e~t,., $,, \'I..sI n7 :,.,.%, St,u,ior,l ! ' n , , ~ . ~ ~ ~ T v ~ l x ~ , , ~ ~ l R,.pn. S~.,n(or~l, (:%, lcl9-2.

6. A~s!~mr lhal the Ca mncrntmtion in tile SiO: I ny r i s 5 x 10"alosdcrnl' sf1c.r \;llx,r pL.ur dclmrition and ir rnranrnul with atomic dxorption .pramrnrty. Thr Car <r,nccn- 1r;tlion in thr Si I;tvrri< 3 x 111" atom$cn>' uftrr IIF.'l1.0. <lis$olt!lion. Calc?d;!t*. l l l c . %T. . . nql l inn m l t i c i r n t of Cu in SiO/Si Ia)rm.

'7. I\ I u r r ;utcl i~ndopnl < lW> silimn snrnplr is oridiznl for 1 hour at I I(YI"C in d y 0: I 1 i. tllcn mrrrcd mcl hxr the odde n*mo\vd over hall llrr \rafv.r Next, il is w-odrlind in \vet 0, :at I(YNI°C li,r YI rnisatn. Ilsc SI!I'IIE\I lo tlt.ti.nninr the. thicla~err in Lhv t\m nyilln$. IIc,\v h i ~ h are tltf step on lhr rt~rCncv. and lhc. r l rp in tbc. .i!dntcttr5

PROBLEMS ,\,.I~,i'k$ , /C!,C>~<~ dIf l0 , l f ,3",l,l,.,,,<. I. h 12-t\y <IIYl>-aril~nt?c~ \ilmvl wrkr uilll 81 w*i\ti\ily nf 10 Q.cnt i< plirc~,~l in it \I~.I mi-

cl:ttion y ~ t r , l n to Ftnr a fic,lcl odd,. of11 45 pxn r t ln3l-(:. I)c.~,.minr tlr. limn,. n ~ ~ t l i n . ~ l 10

F"". 1I>V ,,rid,..

'2. hflcr 1111. linl ohi<l:llirm ;I\ *vvn in I'nd,l~,ln I. aaindclu. ir opcnlrl in lhr "\idc. to qrm a w t r oridt, at I IWMl ' ( : li,r 211 tnisnxtt.r in cly ~,nd:xti<,n. I'md tla. ~ l ~ i r b t ~ - \ ~ . ~ nfthr g.,tl <~\~dc. tmd lhr tolnl l i r l c l orirh..

3. Shcnv thrt Eq. I 1 tc~!um\ to I' = RI lor lr,n~ tin,?< nncl lo r = UIAil + ri for rhr,rl lirnv\.

4. I>rlrnninr the t l i f l~ t~ ion wr l l i r i rn l D for (13. oddrlion ol<l(Yh.orin~ltr l silimn mtrnpl(.r nl 9\Oe(: :m<I 1 xlm.

Photol i thography

Tl t r iwprt;tnw oFn rlpat~ rwm fnr l i thopphy

Thr moct \tidcly ttscd litIiqctphic ~ ~ t ~ t l ~ ~ I - - o p t i c ~ ~ l l i t h o ~ p I ~ ) ~ ; ~ n d itc WEOI~I- tton ~n l~ :mnn ,cn t tcrhniqitrs . : \<l~~~lt. tztv old lintitations o ~ o t h e r t i l h ~ n p h i r methci!s

b 4.1 OPTICAL LITHOGRAPHY Thr \-at majjorihofl i th~pl~icrq~~ipmrnt for IC fiahrintion is opti<al rclnipment using ~ ~ l t n \ i o b t lieht itrarrlrnflh nr A = O:?-0.4 prni. This section mncidrn t l ~ r r.qnsure twls. mask, rrsisti. and mwl!tlion eshannment techniques u s ~ l for o p t i d lilliogc~pl~): It .a l<r , <nnsigltxs the pattern t r~ns f r r ~mcess . wI>ich sen.es i ~ 1 a basis for other litllocm~hic ,. . \xtt.ws. Tltr scrtinn first bricfly dscuwrs the. clran m n l . I rc ;~esr all l i tho~. tpl~ic pro- mwc* ~nllrt i r prrfomrd in an idtr;acl~nn entirnnmrnt.

4.1.1 The Clean Room

4s IC f;shriration f:lcilih r r q u i m a clrnn prnwssing rmm. especially in the area I L V ~

I;)r pltotolitllc~r.tpl~y. Thr nr .4 for such a clrnn rmn, arises k , a u s r clust pnlticles in the :ur c:ul wttlr nn wmirnnd~tctnr \rxfrrs and litl~ogntpl~ic , n a b mcl can c;msr clrfects in tlw <I~ \ iws . \vhicIt w v l t in circuit Fiailt~rr. For cntrnplr. a <Illst particle on a srmicon- cluaor xnrf:tn. cm dicnapt thc. s incl~~-c~. i t ;~l ~m7o\\il~ of an cpitxrial film. cansins the for- r~,;ation a l dililmtions. :\ <lust particle inrorpontecl into the cate oriclr can resal* '- ~nl, . tnml cnn<lurti\ity md cruse d ~ \ i w f a i l l ~ r ~ ~ I I P to IIW hwa$la\\m wltaw. Thr ! atlon 11. ~ P I I more critiml in thr. litlttqraphirarct. \\Iten dart particlrs adlrvrc tu tltr f . 8 ~ - OF:, phntntn;~&. t l ~ m I r l ~ a r ~ :u nl,;atjur psttmls on thr maql;. and tltpsr nattrtrls . . . Ir. tnn&.rrcd to t l l r undrrhinc Inyr alnns\\ith thr cirr~lit p t t r rns on thr mxrk. Fis I I <licm.i t h n r rlurt yrticlev on :I ph01oni;r~k.' Particle I may rrsult in tltr F<,nnnlio

. ... ;ih!- sur- trill

I Figure 4.1 \:~riouc na)s i n wl>ivln duet parficlrs can it>trrfi.n. \\itln pl~rto~nr\L prtt~.mr

a pinhnlr in the i ~ ~ ~ d e r l ! i ~ ~ g layer Partirle 2 is Iwatnl nrnr a p:tttcnt rdec :lnd in:t?cmrsv n mnstri~iian of<vnr.nt flcnviu a n~rtal ntnnrr Piirtielc.3 cm Ienl to a sltori ~irL7lit irhvren the h w ~%,~al!!clinq regions and r~n(1c.r t l~e circuit i~s r l~ss .

In ;I rl<.:m rwm. thr tot;d nambrr o fd t~s t ir:wticlr.s per unit volt~rnr mttrt In. ticlttl\. cnntroll~~d. ;>long \!it11 llw t r~nprat t t re and ilulllidih Iiimlrr 4.2 zlrmrs tltr p:trticle.-si~~! distrihutiort rtnwrs krr ~ l r ious clsses ofclean rooms. T\r.rr swetns ;are usrtl to ~ C F I I I , . ~ I I P cI;rwes ~Cclean m0111.' In 1 1 1 ~ Enslish ?stml. thr ~ I I I I I P ~ ~ A I d ~ s i ~ i t t i o t ) 01 tl1(. CI:L<S is tnkr~i Frnt~~ line inaximttrrl nllounhlv namllrr of partklrs that nrr 0.5 prn ;~srl l;trgcr l r r nlhic foot ofair, 111 tlte tn~tr ic s>st~m. 111c elms is tnkrn fmm thr lqarithln tl,.lrr 101 01 thr rn:~~imum nllo\vablr nwnhrr nFp:t~tidrs t l ~ ; ~ t nrr 0.5 p n ~ .tnrl 1;trpc.r 1x.r ruhir invtvr For rx;amplr. a cl;as 100rlr;m rmm (E!,elisll n s t r ~ n ) I t s n dust munl OF l1Ml ~~;~r t i r l rdf t '

0.5 p!n or ! ;~rpr . Sincr 100 p~rtirlrdft ' = 35lNl l ~ ; ~ r t i r l ~ s ~ ~ n ' , a c l ~ w 1lKJ in t l r 12tqli~l1 syt,,tn cx~rrcs~mncls 10 ;t ~1;~'s &I 3.5 in thr nwtric s!slrn~.

Hccanrsr the n l ~ m l r r ofclust pmiiclrs incn.;nm ;r$ p;miidr sirr <!<.c'XFL'S,~ mon.strin- grnl mntml of tlrr clp;~n rmtn cn \ in~n>cn t is mqui~vd ~ . I I P I I l h ~ minin~ttn~ F~al!!rv Ic!~etl~' of ICs are r~<lum,d to thp d r r p sul,anirrnn r;nngc. For aor l IC i;ll,ricotiur~ art.;r<. :t ~ 1 ; ~ s I00 cl ra~l r w m is r~qairrd: that is. lhp dwst cntlnt in l~d Ix- rlwnt four urrlrrs of rn;lSni- tude lonrr tl~itr~ tlwt ofordinan. nnw air llo\vrvcr. for tllr litltograpl~y;~n~n. dm.; 111 clr:m nvnn or on,. wit11 a lnapr <l$lst munl is ti.<lltirrd.

EXAMPLE 1

- 001 0 I I to

r . ,n~rh~u~~ lpm!

Figun 4 2 P;ertidr.sirr <licmhution cunv for Engliqh (- - -1 and #r~cttir (-1 dacw1 of

<I,.,,,, m , , , s a

ll,r nu~sl*.r oidlzrt prrticlcs (0.5 jlrn anrl l:~qc!rrl containcd in thc air \wltnme is . S O x 0.512 = lurtirl,.r.

ThcwA,w. i f thcrp are 4IXI IC chip* on thc \\alcr. Ihr partirlr munt amounts to one paltic11 r.lrh of S?T n f l L chip*. Fr,rtnrnlrl!: onlya fraction of thc. particles that lanrl adhere to thew mti:xr. n><l of tbrm.onkn icstiun arc at aciro~it hrati~merilicd enotqh 10 O~IISC il r."ltt~. Ilmw the. elln~l;tlion in<licrt,.r Ihv isqwnmcr oi the clran mm.

4.12 Exposure Tools

TIN. ~ , t t e r n transfer p r o w s i.; arron~plisl~ed h\. urinrr a l i t l lwapt~ic e w m r e tool. ' .~ . perf,;nrtanw o i an r+sun. t m ~ is <~btern)ine;~ in. titree pamnlrten: ~eso~nt ion, rr tr.ttiaa. :tad tllmtndln~~t. Rnohrfion is tltr minitnuln f ra t l~ r r dimrnsion tl~;lt man k In

. . o i h o ~ ~ c ~ ~ l m t e l ? pixttrms on sacw<si\.r mz~rl;~ can IF a l i p r d (or o\.rrlai(l) \rith resl to nrr\iousl\ ~lclinrtl n:tttma 018 tlir aafrr. Tl~rnselmtt! is tlir number o f uafers I - , em Ic r y x ~ s c d V r Itour for a Gym mxk levrl.

Tllvn ;trr l,asinll\ hvn optictl rsposurc rmrthnls: slradow printins and projw prinlinc.'" SI~:~rkn\pri~~ting ta:n- Il:~\.r. tlrc. m;irkan(l\wfrr in dim+ mntaa \\it11 one anol I ;O in n,lltnrl ),"n!ir,~i or in closv prosinlih. I%< in ~nn.irnift, ~,rit~!ir~c). Fimjrr 4.30 sll .. . .. . . :I h:~ric wttip k'r cvnt.~ct printine. in ~vl~iclt a rrsist-mate11 \mfrr is bmngllt into ph)? rrtr81.td \ r i l l$ a in:~<k, :~n(l tllr n.sist is c . \ ~ s r c l ly a nnr l? m l l i a ~ a ~ d beam of ultnl\i

4.1 Oplicel Lithography 80

ligl~t t l irn~~gh the back of the 111a5k lor ;I f i n 1 titne. n~r inti~natp mntila lrrhv<.r.cn r r s i ~ t ~ and m i d l>m\iclc.s n rrmbtion of ;~pprori~nalrly 1 fim. 1lmvrvc.r. mntart printisg r,lf. rers n n~ajor dc~\vhnck n t ~ s a l I)? rlt~st p;~rticlrs. I\ d a ~ t p:~rtielc or a speck orsilinlrl glllrt on tlir \v;~frr aa i In. in~ l r<k ln l into tlrt, ~ ~ t ; a l i u?len tlw ni;~\k m:ikcr mot;a? r r i t l ~ I I I I . ~ ~ ~ ~ ~ . ~ T l ~ r in~lwddr<l particle citltsrs pmliaar.at dsnrnge to lllr mxqk ;o~rl rrwlts it) (11.Fces in thr w f r r aitli each succt.c.di~ig CqWSLLr,..

'ti1 ~niini~ai/e rnilrk damaee. thr prclsiznityeqmsttre metllnl is tnsetl. F i p m 4.31 SII(MT the 11;~cic setup. It is sin1il;ir 10 t l ~ ? mnrlci p r i s t in~ mtsllt~l. cxcept l l~at tlwrr is a small gap (10-50 pnr) bchvren t l ~ e wvafrr and lltr n~:sk d ! t r i s ~ e v r ! ~ r r . nlr. sn~~all gap rc$ults in optical (clillfi~ction at feature rdprs on tbr pl~uton~a<k: tl~at is. Am liql~t p&-.wr tlte edges of on opnqt~r mwk feature. fringes itre fonnrd xnd some light pe11~1rnte into tile sl~n(lo\v rcm$on. As a result. t l ~ c resol~~tion is dcgnderl to tllc 2 to :-par ranee.

In sl~adnw printing, the minima~n linewi(lt11 lor critical dimr~nion (CDI] tlnt n n IF printed is mtrghly

CDE& (1)

wilere h is tlic \ ~ \ ~ I ~ n @ l i of the ~ P O S U T P radiation and g is the gap hrhvecn tile m a k and the ~rmfrr and inclu(les t l ~ r tl~icLmess of the resist. For h = 0.4 pm and g = 50 p n , tlir CD is 4.5 fim. If \\,r rcdl lc~ h to 0.25 pm (n wavrlen$tl~ ranse of 0.2 to 0.3 pnn is in the drr-p U\: spcctnl rrqion) and g to 15 pm. thr CD h m n ~ e s ? pm. Thus, tllrre is an s d ~ ~ m t a g e in rrducing b t l i h and g. Hn\vevrr. for a given distane g. an? cl~~st particlc w;th a diameter larger th;m g potentidly c:m cause mxsk darni~ee.

To avoid tlie mask damagc p roh l~m associated !villi sl~ado\v printing. pmjection- orintine e ,msure tools ha\.e been dewlowd to proiect an i~n;tcn of the mask patterns *. . . , onto a rrsist-coated \vafer many cmtimetrrc aur?\. from the n~cuk. To incrcw rcsol~~tion. only a snldl nortion of the m a 4 is rmosal at a time. n~r mlall inlacc area is s m n n l or ~ ~ ~~~~~

s t c ~ ) ~ d over tlw \ d e r to m r the entire \\,nfer surface. Fiourc 4.47 slxo\n a 1:I xd'rr . . \cat, pmj~ctton s n t r ~ n "- ;\ n.lnou: arc-sl~apt.d itnasr fiekl appruxi~natt.ly 1 8nln it1 ni1\111 seri:,llv tr.~nsfrrs the slit imncr oltl tr ni;lsl; onto tltv x>it,r. T l ~ e unncc srlm on t l ~ r n:afer

4.1 Optical Lithography + 6%

Rwrs 1.4 Imnpl. pmtioninq terhniqucs lor projection printinq. (n) Anau:al-field \\afrr sm). $1, ' I:1 strynnd-rq~:t~. tr) \ I I n~luaion rtt~p-:md.n~pr;lt, id) >t:I nrhaion strp:url.rr~~~." :

Thr st~v.ill i m n s ~ firld can also he stepped ovrr tllc surfacr of the \ a f e r by hrn- dimensional translatiom of ~ I I P \\nfrr only while tlie mark re1n;dns statinnay Mter the rqmsurr of one cleip site. the \taler i~ n~oved to the nest chip site and the process is rrprxtrd. F i ~ l r e s 4.41, anti 4 . 4 ~ rho\\. tht- p~lrtitioning of tlic safer image by sfq,-and- n'j~<wf pn,irrtion uith s ratio of 1:1 o r at a drmapificntins n l io ofill:l 1r.g.. 10:1 for a 10 times rrdudion on the \wfrr). rt.sprctirrl\: Thr dema@ific:ttion ratio is an impor-

lion ?Jtcms. hltl it is tn~ich more dificult to prndliw (Irfrct-free 111rnk.5 at I:I than it ir

at 1 10: 1 or a Z l rlenlapification ratio. Rrrlaction prnjwtion lithovaphy can also print larger \wfrrs withol~t redrripir

thr strpprr lens. ns lono ns t l ~ e liclrl sizr (i.r.. thr eqmsurr a n onto the \v;ifer) of 11 lrnc is 1;iqe rnoush to contain one or more IC cldps. \Vhm the chip s k c exweds 11 firkl sizr ofthe lrns. fiirthcr pnrtitioningof the image on tlir reticle b IICWSW~: In Fig11 .I.&!. t l ~ r imaqr firld on t l ~ r rrticlr. can hr a narrow arc sham for .\l:l step-and-scan pn jrction lithogmplly The strp-and-scan ?stem )ields hvo-dinier~ionai tr,~nslstionsoltI \\afcr a i th SIX~YI 1,. and one-ditncnsional tr;insl;ttion offlte mwk \ri111 a snecrl .\I ti that of thr ~ : d r r .sped.

The rrsolution o f a projection Fsteni is @\.m by

u;llere ii is t l ~ c intlpx of refraction in tltp im:spr ii~rdium 111st1nIIy air. \vlirn. ii = 1). ilnd

Ois thr half-anglr of thr mnr of ligl~t mnvrrgiag to n point image at th? \v;~frr. ar s l m ~ ~ in F i p ~ r r 4.5." Also sho\\ii in 1111. lipn is tltr depllt of fnctts (DOFI, u,lxich cln IF rxprc~'srrd RS

\t,lirrr k, is another prowss-dependent factor. Equation 2 indimtes that resolution a n Iw iinprov~l (i.e.. smdlerl,:) IT either nrduc-

ins t l ~ c n~:a\~Iength or incrcaqing NA or lmtli. tl~nvevt-r, Erl. 4 indicates that tlw DOF ~ l ~ g r a d c s much inore rapidly by incrcacing NA tllan hy drcrrrning A. This explains the trcnd toward shorter-\wvelengtl~ sourecr in optical litliegraplty

The high-presurc mero~ry-arc lamp is tvidelv usrd in cmostlre tools I m u w of its

405 nm. and 365 nm, rrsp~cli\~r!y I-line litl~ogmpliy\+itl~ 5:I step-and-rrpst prnjwtion a n offer a resolution of0.3 pm with rcsol~~tion rnhsncrment techniqt~t-s isw. Sr~t ion 4.l.fi). Ad\nnced e w s u r e tools sucli .~r tlir 248-nrn lithomnpl~ic sn t rm urine a KrF . . . cxcirncr laser. the 193-nm lith<rgrapliic s)strm using an ArF rrci~ncr Im-r. and tltr 13i- nrn litltocctnl~ic m t e n i usinc a F, excitner layer have k e n drvrlonetl for m a s nmluc-

4.1 3 Masks

h.ktsk.5 used for IC manufachlrinc are ~ist~allv reduction reticles. n l e first step in niask t l r a k i n ~ IS to !IS(. : ~ ~ ~ n ~ p ~ ~ t e r - . i t ~ I ~ I i l t~iqn IC:\l>) ?st(.~n in %$IlicI~ dcsiencn mn r%,~nplvtcly ~ lcvn lx . tltc circuit nnttrnls rl~~rtricallv Tlte 0~eil:tl tlat;i protlt~<t.d In thr (>D nxtrnl ~ ~ ~ ~~~ .. thrn driws npnttem grnentor. a'hicl~ is an clrcimn lxmn lilbogmphic?stcn~ (see Swtian 4.2.1) that tmsfe r s t l ~ e patterns directly to clcctrnn-scnsitiwd ni;rsk. The mak m~~s i s t s ofn f~1wd.sili~.1 s u h s t n t ~ co\.ered \sit11 a cl~m~niunl layer, The ~ircuit pattern i? fitst t m s - frrrerl to the elrctrnn-sensitiirrd layer (rlrctrnn resist). \r.hich is tmnsfrrrcd nnrr rnorr

\ I r l l . 1 4 s

DOF

Figure 4.5 Simple in~ngr qscm.'

66 Chapter 4. Photolithography 4.1 Optical Lithography 4 fi7

into tllr undrrl?ing chromiu~n layer for tllr finished rnzck. Tlte details of pattern tra fcr nrr m n s i d ~ r r ~ l in Section 4.1.5.

TIie pilltcnls on a t n ; ~ ~ k rrpresrnt onr lcvrl nf an IC design. Tile composite l ~ ! is brokrn into mack lrvrks that mrrrrpond to the IC p r m s s srqorncc. s!rcl~ 8s tllr lation re$nn on one lrvrl. thr gatr rrsion oe ;tnothcr. nnrl .w on. T>~icnlly, 15 to 20 fcrrnt nliak It-vrls are rrqsirrrl for a mrnplrte IC p r m s s cycle.

The stanrlanl-izr rnz& snl~str,ite is a hrsrrl-silin~ pl;ttr 1.5 x 15 crn .qrlarc. 0.6 cm 01 The size is nttdcd to aixorntnakt(. t l ~ r lcns f i ~ l d sizes for 4: 1 or 5:L optical expsure t i \vI~erras tlw tllicLness is wqrsirr~l to tninitili.,e pattern placemrnt erron doe to suhst clistorlion, I l ~ r fi~rrrl-silic2 plntr is nrrrlrcl fix its low wfificirnt of t l ~ i ~ n n l rrpansiori l~iell tlii~~r!~li.;don : ~ t h o r l r r \r.:nplrnqths. nnrl its n~rchnnic$~l strrnqtlt. F i p r r 4 . i slto!

Ins-

- . nttr I, its rs n

Slink r revs h? t l i l k t ~ l , ~ .

Figure 4.7 :\n it~trgntc.~l cirnait photornak.'

rnarck on a.hic11 pattenls ofprnrnrtric shnpm h;we l w n fonnel. A frw s v c ~ , n r l : ~ d ~ i p sitt.s. IIS<-I~ for pm.ss e\aluatioti. ;trr also inclt~~lrd in tltr nnmk.

One of tile lrtajor m a i r m s about mmks is elrfrct r l r n i h Alak il~fc~cts can lw intro- cl~tred cluri~iji tllr manl~fist~ire of tlte mask or rluring s~I)se~~r~<'nt I i t l ~ ~ ~ ~ ~ ~ ~ l ~ i c pnmssrs. Evrn n s111:tll rntak-dcfrct densih Ilm n profo!tntl eflrct orb tlle final IC .rirlrl. )?clrl is defilled RS 111e lillio of scad cllips prr \vafer to tI1e total nllnlllfr of ch ip prr aafrr (sr.t. Cliapter 10). :Is a lint-order apprnd8n;ttion. the yield l' for r given ni:rskns IrwI ran br mprcsseell is

y z e - C * 151

tvl~rri. D,, is the a\rrnpe nasnlwr of "Lltal" defects lwr onit arc,;,, wd A, is tllr drfect- sensiH\.c arc1 (or "criticnl area") of the IC chip. If D,, rcmnins the saillnc fnr it11 inlzsk It?.-

rls (e.g.. A' = 10 levels). tlleli tlw final !irkl lxwmrs V " 4 Y s r - (fi)

F i p ~ r c 4.S shows tllr nt:~~k li~nit !it4iI for a 10-IewI l i t l z ~ ' ~ p l ~ i c pr<xrss ;IS 21 frloctioa orcllip sire for \clriaas talurs of ilrfrcl dntsitirs. For mnnplt,. fi~r I),, = 0.25 rlrfdcm'. t l ~ e )irld h 10% lorn chip sir*. ofW innr'. ;utd it rlmps to:dn~~t 1% f i~re r.llip si/e of 1 Yl n~m:. Tlsrrfore, ir~spcctiott ~ n r l rlraniop of al;rsks nrr i tnpn i~n t to acl~irvr Iliqll ) i~ lds on inqt* cltips. Of mt~ni,, ;In oltr;slrnr~ pnxrssing ;lrra is rnnndato~?. fol- l i t l ~ ~ ~ p l ~ i r p m s s i ~ ~

4.1.4 Photoresist

I '

$1 0 4 0 RI Y(1 lln 1211 140 If* lu1 2MJ CI,i,> ,i,,. r,,,,,>21

Rgun 4.8 Yivhl fnr .n LO-rnwk lithwr;~pltir pnxr.ss \4lh \nlious drkw rlmsitir~ per lcvrl.

nct rr.ct~lt is l l~at llw p, t t tm~s fontlrtl (:~lso cidlcul in laps) in the p s i t i w r~,sisI are tl r;tntr ;LX tlvo~e on IIIP mask. For , ~ ~ g o / i ~ . r rr*i.s/.~. tlhe eapnsetl regio~ls I~rconlr less 4 Idr. anrl 1111. p:rttrn~s fi>rnled in t11e ncgl t in~ rcsist arr tlw rr\.rrse of t l ~ r mask pattl

Rlritiw. pl~utorcskts cwaist o f t l ~ r c ~ ~ c o m p n e n t ~ : n photosensitive m m p ~ t n d . ;I

resin. ;lnd an org:tnie solvent. Prior to i,ywsltrc. t l ~ e pl~otosmsitivc r n n l p u l ~ d is insol in 111,. ~lvvelo~wr solution, hfter erposurr. thr photon.!~sitiv? c n m p e n d :hsorlls 1:

tinn in thr r\posCd pnttrnl arras. changes its cllelaic~l~ stnlctrtrr. ;and i?econlrs sol in tl~r ~ I ~ ~ v e l ~ q r r solution. ~\fter d ~ v c l o p t ~ ~ r t ~ t . ~ I I C , : \ ~ X ) S L . ~ arc= are ren~owd.

S r ~ ~ ~ t i v r pl~ntnrrcists arc- p l ! ~ n r n cwn~hinrtl \\it11 e photosrnsitive c o n ~ p ~ ~ n d . i

cympon~rc. tlrp pl~oto~rnsiti \~c c o n ~ p u n d ~ h s o r l ~ s the optical e n r r p and cor~verls it c lac~nir~l rnr.rn to initiate a n c ~ l \ ~ n ~ r cross-IinLine reaction. This reactiohl cartsrs I

.".~. ems. haw Ih~blr

into :ma eight arc'is

. . . . ;mrl I m n r r 5 insoluhlr in the dc\.rlnprr mlotion. Aftrr dwlopmpnt , the i ~ n r s p s c d : :~rv rt,~nore.(l. 0t1v zn:~inr rlfi~\r.l~;sk of a nrlrativc nl~otoresist is tl>;it in the d r \ . r l o n n ~ r ~ ~ t .- a

procrss. the \vl,olr resi~t m;ss nvplls I)? al>n,rhing ~Icrr lnprr solvmt. This nvellithg ;stion limits tllr re%nlt~tion of ~legat i \ .~ p l ~ ~ t o r e s i ~ t s .

Fim~n. 4.% s l ~ o \ \ ~ a t\pintl vqmsure respansc clln.c nncl imagc cmss section for a pxitivv resist.' TI,(. rrcpnrccmwr <lrscrilws tile prrwntageolmist reminingaftcr c . p sun. and dr~vrlnpmrnt \.(.nus tIw r \qnwrc m c r p , S o t r that tlw resist I I ; ~ n finite solu. I l i l i h in its c l r w l o ~ r . men uitl~oltt cyu,cnrr to fialiatioa. A% tllr vxpsurernrrQ incre;Ls. t l ~ . *<rltrl>ility er'~<ll~ally incrr;~rr.s llntil st ;I lI~resl~t>ld m e r q El. 1 1 1 ~ resist h c ~ o n ~ e s mm- p l ~ - t r l \ - m l ~ ~ l ~ l ~ . TIw sr.nviti\ih o f a psitivr rcrist is dclinr(l :rs tllr e n e q r e q ~ ~ i r c d to pm- c l r ~ u . c~nnttpl<.tr sollrl>ilily ill t11e ~ . r l n ~ s ~ d n y i u ~ . TIIUS. E, I Y ~ I T ( . ~ ~ I I ~ S to the sensiti\ih I t ) ;~!rlilic,ll la E,, ;I par:ttnvtrr y. tlbr cnnlfi~rt ratio. is clelined to chanctrrizr the rcsisb

4.1 Optical Lithography 89

Smtav w d ~ t

(1,) 61

Rguw 4.9 Eymsrxre rrslxmw eumc and cmsr section of thc rcrirt im;qe akcr dw'~lopmcnt. ( 0 , PodIRl. pl~oloresisl. ( b ) N~pIivc photorcsis~.

\vI~err E, is the energv ohtained hydr;iaing t l ~ e tangent at E, to reach lOO% resist tl>ickness. ILF s11o\w1 ill r io t re 4.90. ,\ l ave ry ihnplirs a lligller soltdlility of the resivt uith an increhnental increase ofc.vposure e n e r p ant1 res:~~~Its ill shaqxr ima~es.

The irnnge cross section in Figure 4.90 ilhlstratrr thr rrlalionslbip i w h ~ ~ e n thr d e e r of photnmack image and the currespontlin~ e(lges of the rrsist imsees dter (levelon- ment. T l ~ e edges of tl!e msist image arf.ggcccdly not at tlleve~ical~projrdrrlpsitions o l tile I I I ~ L ~ c ( l ~ e s because ofrliffrortio:~. T l ~ r edee of tlre resist imttec mrresmnrls to ,, tllc position udlpre thr Intill ahsnrlrd optical r n r F eqanls thr tl~rrsllolrl e n c r p E,

I'iptrr 4.911 sho\n lllr espsnre reslmnsr CIIW anrl inngr emss section fnr ;i n e p - live resist. T l ~ e negatitr resist rrnnains mn~plekI\ ' soluble in the devrloprr solution for . . e.yxstlre energies hnvrr than E, Alxwe E,, nlore of t l ~ e resist film rem:lins aftcr dcvcl- on~ncnt. ~ \ t wnosure rnereies hciw llhe tlhresbold e n e m , tllr reskt lilln txwnlcs e s m - .~~ ti;slly inso l~~l~ le in t l ~ e dr\elopr. 1 1 e s r~a i t i \ i~yofa negati\,~ resist is CICAIIMI as t l ~ e n ~ q rrqt~ired to retain 50% of tl~r ori@n:~l resist Cl~n tl~ich~ess in 111e eqms<.d rrsion. Tlnr parameter y is (IeCnrd similarly to y in Eq. i. except that E, and E, arc- itit~rt.)~nrgrd. T I I ~ itntigecmss section For tlte negttivr rrsist (Fig. 4.91,) is $so inflecnffd I?\. t l l ~ d i f i lion cfkct.

EXAMPLE 2

Find the prctslvtcr y lor I IW phn~orcris~s rhaw in Figm .1.9.

SOLUTION For tllr p,ri!i\v rcsisl. E, = nn,Jlcm'imml E , = 45 slJicm'. a,

70 Chapter 4 Pholol~lhographv 4.1 Optical Lithography 4 71

4.1.5 Panem Transfer

F i g ~ r ~ 4.10 illustnd~s the steps to tnlllsfer 1C patten~s Troln a ~nmk to a silimll \vafer t11;tt h:rc :m instllnting SiO: I:~yer fonned on its snrlhi~~.' Tllp \v;~Tt.r is pl:mwd in a clean

ti\? to \clvt-lrqths greater th;u1 0..5 urn. To ensurr stttisfilctol?~ srlhrsi(r:l of the resi: the stnfncr ~ I I I I S ~ he cl~i~nzed fro111 I~,clropl~ilic to I~ydropl~~~l~ir . This r l~ang, C:III be ma, by tht- application or an scllwsion prolnotc.r. a.hirh ran pmrtlr n cl~r.micall~ mn~patil> surf:^^ for tlw rrsist. TI,? no st inn~tnor~ ndla.sion pronlotcr for silimn ICs is he: rthyl-disil:lz~n~. (II\IDS!. After tlir ;~pplication of tltis all~rsinl~ li~yer. tllv \v&r is on :I V ~ O I I I I I I spindl~. itnd e to 3 cnl' uf li(loi~lo~~s resist is apl)li~l to tlir wnter o! ss;?Ter. Tbr \\;?fcr is thrn mpidl!.;tcrrlrr.ltnl to ;I constant ~1to1i11n:d sprrd. \\.liich is n ktincd fur about 30 seconds. Spin speecl is grncrlly in thr m g o of II1lUJ to 10.000 to mat :L ilsifr,na f i l r l ~ ;dmut 0.5 to 1 ltm tl~ick. as sl~o\\n in Fiymrta 4.llb. The tl~ich oFpllotor~sict is comlaterl with its \iscnsih

,\ftcr the spinnins step. the <wfer is "soft baked" (t!picallyat 90-120°C for 60 seconds! to n,lllo\.e tlte solvent from t l ~ r pl~otor~.sist film slid to incre;at. resist ;ldhesion to thr xnxfpr. Tlw \rafrr is nlipml with respect to tltr nvask in ;ul optical lit11ngr:tphic s)s- term, and the raist is cqmsrd to UV liqltt. a sllo\\m i n Figure 4.101,. If ;I posilivc pho- torrist is i~sed. the exposed resist is dissu1vt.d in the dtvrloper. ;s sllonm on tl~r lrft side of Fig~rc 4.10k. Photorrsisl dr\~lopn~enl is ~ISIIRI$. done I)? flwding tlte n.itfer \\it11 the cleveloprr .wlutios. Tllr \vafer is tlzrn rinsrd ntld drird. i\fter clcvc~lnpmmt. "post hak- in?" at approxinnately IOO°C to ISO'C ma!. he required to incre:ar the> adhesion of the resist to the s~~hstritte. The \vafer is then put i n all ;imbiel~t t11;~t etchrs the exposed i 1:ltion layer bat dw's not attack the resist. its sho\\n in Fi~tr.? -1.10d. Fillally. the res stripped (e.g.. using solvents or plxuna oxidation). le;~\ing bel~iod 211 ins111:1tor imag pattern) tlrst is tht. sa~nr t l~e opitquc i ~ l ~ i t g ~ on tlrr n ~ ; ~ < k (left side of Fig. 4.10c).

For negt~tirr pllotoresist. tl~r. prncrdl~rrs clrscril~rd ;we :\lso npplicablc. excvpt that ~ I I P ~~nr.rposr~l a r m are rm~oved. The final insul;~tor in~agc (right sirlp 111 17ipre 4.10c) is thr rewrsr nrlhr optqur itnagr on tlir inask.

TIIC ios~~ltitor ini~gr can lw ~tsrtl ac a mnck fnr stihsrqtlel~t p r m s i t ~ g . For example. ion irnl~lotllnli~ln (see Cllnpter 7) can i r done to <lope the rxfnspd srtninrnrl~!ctor wgio h111 not llle ;arra co\.crr<l I,? tile insul;ttor. Tlmr <lop:tnt pitttrr~~ is R dttplioite of the dcsil p:tttcnl on tlir pl~otomx<k for a n~gatiw pl~otorc.riqt or is its c o n ~ ~ l r ~ n e r ~ t n ~ p:lttmI 6 ;I positive pl~olorr~ist. T l ~ r conlpletc circuit is f:tl~riixtc<l hy aligning tltr nrst III:LC~ ir 'I

srqee!lry% 111 tllr prr.\iotrs paltrnl and wprating lhr lillto~mpl~ic tr;alrfer pnress. A reI:~t~d pattern trancffar prm.ss is the /ifl<~/r tpcltniqt~c~. sl~ona in Figlrr 4.1

pmilivr rvsisl is ~ ~ s r d to fonrl tla. resist pnttrm on tlw strhstr;ite (Figs. 4.110 nntl.l.1

<a,11- I~elrl f tl1e main-

ns11- ist is r (or

I. A I Ill!.

The film (e.g., nlnlninurnl is depositetl over tll? resist and tlw s1111st~atr (Fig. 4.1 IT!. TIIP CIIII thicknrs must be sn~allrr tlaan tl~nt of thr n.si~t. Tl~ose ~nrtions of tlrr film on tl~c wsist are rc~nloverl I ~ ~ s r l ~ t i v r t ~ d i s s o I ~ i ~ ~ ~ thr mist l;~!rr i n an nppmp";ste liqttirl t,trltant so tllnt tllr overl!irlg filln is lifted offil~mcl TPIIIO\XYI (Fig. 4.1 Id). Tlw l i h ~ ~ l l t ~ l u ~ i q ~ ~ is c:lpnl,lr oTlliSII is isrd rstensively for discntr rlr\in.s stlrll ;r. Iliph-pou.c.r ~ ~ E S F E T ~ , lloucver, it is ; r ~ ~ ~ i l l r l y a l ~ p l i r . l l ~ l ~ ~ Tor ~dtr.ll~rgr-sc~llc i~~c~:r.ltinn. i n \vllicl~ (In rtclling is the prer(!md t e c l ~ ~ ~ i q ~ ~ c .

4.2 Nen-Generation Limographic Methods 4 73

I l l i i r l l - - hl.rrk

Wpi1 k~ ?? P .\t,l,\!r.,:,. i 1

St~l,rmtc

Ic) a~' (dl

figurn 4.11 The liltoff pnxvss for prttt,n, rmnsfcr

4.1.6 Resolution Enhancement Techniques

r ~ l a c i n ~ the navelrn$l~ of tl,c, r\lmslnr? tools and dewloping new wsists. 111 arl~lition, man>- rpsoltation rnhancrn~ent tecltniqoes have bni de\ploped to estrnd the capability of op t id litlio~apl~y to even smaller feahtre lenghs.

:\n itnportnnt rrsol!~tion enli:tnement trcliniqlte is thr phosc-shif?ir~:: tnrrsk (PSbI). Tlr h;wic mncrpt is sl~otrn in Figare 4.1"" Fnra con\mtional mask (Fig. 4.12n). the electric firld b:rx tllr same pl~ilre at even aperture (clrar a m ) . DiVractian and the limital rrsohation of tlw optiml gsteni spread the electric field at the \wfcr. ;rs shoan I)? the dot- tnl1int.s. lnterli-rmcr Iwhwm \ct\?s $Ifractnl i n tltr acfjawnt apmtms rn!~mces the I W ~ V P F ~ the111. Rrca~~se tile intensie 1.1) is proprtional to the square of the electric F it llrmmrs clilficult to seplrate t l ~ r hro imapvs tllat are projected close to one an01 fllr pl~;~<e-dtift l e y that covers adjacrllt apertures rrvrnes thr s i p of the elrctric I".. .... 2 s sltoan in I ; i ~ r e J.I!/>. Dec;~osr the intnlsih at the mask is unclmozcd. the electric firld nf t l ~ r irn:l$rs at tl~r \\aier a n he cancrll~d. Therrfirr. images tllat are projected close to one atlotl~er can lr sepantrd. :\ 180' phase cllnap can IF ohtained hg using a transpcrenf l:~ycr of tl~icknessd = hll'lii - I!, \\.llrrr ii is the refractivr iindes anrl h ir " \\;n.rlrnflh that m\.ers one aperture, it,. sl~o\\n in Fi01rr 4,121,.

. ., I,ili% For rmmplr. n squaw cnrtt;tct llole uitln dinlensions nrnr the resolution limit p"rrt rrr;trly s :a circle. .\lwlifiin~ IIle contact-llolr pattcn~ wit11 atlditioa:~l seonletl the njrners \r i l l l~elp to print 1 IIIOW aecllntr square Ilolr.

PC). ape-

b 4.2 NEXT-GENERATION LITHOGRAPHIC METHODS \t'!iy is optical lilhogmpl~y so \~6delyrtsml .and wl~at makes a sucr~ a pmmislne inattat: I tle remons are Illat it lias hi$h thm~~~hput . g d rcsoh~tion. Imv mst. .md e:we in opeition.

Howrwr. rhre to rlrep-subrr~icmn IC pmcpss rrqrrircrnents. opticd litl,ngrapl~~ ha some li~nitatioes that 1iw.e not yrt been s o l ~ ~ l . Althoo~h ~r can use PS\1 or OPC to estrml its useful span. the m~npledh of mask prwluction and ilinsl; insption cannot be racily resol\.rd. In addition. the mst of mmk is very higl~. Tl~errfore. \e need to li~al nltematives to optic11 litlhogclphy to pmczss deep-sulrlnicmn or nlno!lletrr ICs.

\krio~~s t ) p s ofnemgenrr.~tion litlioppl~ic ~nethmb for IC fi~hrio~tion are ilism~zrrd in 111;s section. Electn,n beanl litl~ogn~l~y, estreme U\' lithocrapll!: a-n? lithopplr): end ion benni litl~o~.iphy are n~si (krrd . as are the d i f f r l m ~ s :lmotig tllrst. n~ctl~<xls.

42.1 Electron Beam Lithography

Electmn kanr (ore-beorn) l i t l ~ q p h y is prini;~rily~~sed to plwlr~cr pl~otomwb. Rrlatitrl? fe\\ t~lols are dcdialtnl to dirrct rrpsure of tlte resist 11). a fw~tsed elwtnn~ hram \\itll- out a mask. Figure 4.13 slio\vs a schrmatic ofan elcrtron Iwam ~ t l , o ~ ~ p l r y ~ s t t ~ n t . ' " T l z r ~lectron g111 is n devicv that can senerate a h a m of rlt.ctmns nitlt :I saitablr current densih! A ttzngsten tl~~nnionic emission cstl~odr or si~lglr-cl?~tal l;antl~:intnnt hrutlwridr (LaB,) is r~sed for the rlectmn gun. Cosrlenser lp~isrs are used to fwus t l~ r rh~1m11 lwit~n to a spot size 10 to 25 nm in (lianirter. Dram-blankins plates. \vhiclt t11n1 tllr clectmn h a m 011 aad off. lrn~ii <lcflec~ion coils are mn~p~tter~nntrollnl :m<l oprn~trrl : ~ t \I112 or ~ , ig~lcr rates to llirrct tllr fWasrd rlrctmn I m n l to any lor;ltiuo in the sral field 011

tlre sulntnle. Dpc;ause the scat1 lichl (t!picallx l cm) is 11111cll s~rlallcr I~I:III 111~. s~~bs tn~ t r diamrtcr, precisioll l~lecl~;a~ie;d stage is usnl to pnritioa t l~ r a~l>str,lte to he pttmln!.

~ 1 , ~ n(l,.a,ltnps of rlectr~n 1,e3n1 lithosc~plly incl~~dr ~ I I C gencriltinn of s~~l~~aicroti resist s~.ometfirs. llis~lly al,tol,yatetl i ~ ~ t ~ l precisely c~~ntrnllrd opccltio~~. srr;ltcr d r~ ) t l~

4.2 Nen-Generation Lilhogrephic Methods 75

f<x.ur t l ~ . o ~ tll;tt .n;iilnhlr rmm optical litl~oq:tply. and dirt,ct pattrrnin< on :I re ~ ~ ~ ~ ~ 1 ~ : ~ t ~ ~ r ,xti,,r \ \ i t Iw~~t sing a r11;1sk. TI!? d i w < l ~ ~ ~ ~ k t g r is t11;tt v l~ctrnn I ,~ : I I I I lit11 r.q>lt! ~n;trhinr< It;n-t* lo\v t ~ ~ r o ~ ~ ~ ~ ~ ~ ~ ~ ~ t - ; ~ ~ ~ ~ ) r o r i ~ ~ r i l l e ~ ~ 10 \lilfrrs per Iiour at less t 11 1; p111 rt,<olt~t,nn. n~i< throls~hp~lt is aclrqu:tte for tllv protluction of photo~llask. s~tu.ttionr t I ~ . t t rr.rluire sfnall ti~lt~bhers of r11210111 rircuits. :tnd for d c s i p vcrificat: Ilr,\v~.\~.r. inr r~l;~&Ic.s'i diwct a-ritinq. 111,. t~lacl~ine nnjst l~;tvr tile l ! i~l~est imss t l ~ m ~ ~ ~ l ~ ~ x ~ t . ~rlrl tl~t.rrli,rr tltr l a r~cs t lw:1111 dia~llrt<,r possil,lc cn~lsistrnt sit11 tlle n iv~unt c l c . \ 1 ~ din,~nlsion~.

TI~rrr. ;tn. I ~ ; ~ ~ i ~ ~ - a l l ~ hvo \\.;r!s to scan tlte firuscrl rlectmo hrarn: ra te r s n n and tt,r 2l:ln. ' ' In :I rnr~crrmn nlitrrn. rrsist ps t t rn~s are ~~~~~~n IIV ~wrt iCnl lvori~nted beat11

,,,-~ ,- llilll

for ion .. 9

t11.1t nlcr\r.c t l r n ~ t ~ h :r rccul:tr m ~ l c . ;L< s1tou.n in F i ~ u r e .I.l.in. The 1x.an1 srans sequcn- ti;nll\ rwvr c.xvn ix,srihlt. Ikwittion 011 t l ~ c ~ n i s k and is blt~nkrd (hlrnetl o m \vlirre no expo- wn. ic n-altlirr~l. .\I1 rr.ittvnlr on tlbr area to IF \r-rittrn niarst hr s~~l>di\ided into in(li\icl1181 . ~ l c l r i i c ~ r . < . i a r ~ l a $V-I pattern tnt~ct lla\.i. :t minimtun incretnr.n(;tl intrmd t11:1t is e n <Ini~ildc In tlw I K - . ~ ~ , : t< ld rv~~ ~ i z r .

In a itrrrsr <con r!-;tvt11. sllonn in Fimjrr 4.l.th. hlr lwam is directrd only to rvqtw<tt'd p.bt1i.m fi.:%t!!re< ;and jut!lpC frortr ir:tture to it,3turr, rnlller tllnn sc;lnning ~ I ~ I I I v rl>ip. :L* i n r.otcr Gem. For nr.toy ellips. tllr aver;tpe r ~ x ~ s r c l r c ~ i o n is only 20! t i l t . chip .hn~+. s? timr is c.~\-rd tr<inc :t vector scan nslrnr.

I ; ic~tr~ -I 1-IC <I1,1\17 SCYC~P.I~ t!ys of rlt-ctron hr:~m< cmployd b,r r - l w a ~ r ~ lit l~o yl t t t l ~ t . (:.w-i.l!~ yxll l r . t n ~ ro~!ntil IK.RIIII. tltr \ilri:lblc-sllapd lmrn. and c~.ll projer- t> , , rn 111 Ill? \:tri.tl,lc--ri,.~pc.rl 1r.m~ c\st<,!n. tllr p;lttvn~ing I ran) 11x5 a r~ctnngrlnr cross w+iw oiv.uri.d>lv %in% .tn,! :~ywct cttin. I t nfTt-m tlw :t<l\:tnt;~~? ofexposing smen~l acl~!res IIIII~ \i~~>illt.ti~<.ota'lv. T l tv r~hn . . t l t v vvctor sc:et r n ~ l l m l usinr! ;I \;tri;ihlr-sl~apcl !wan1

("1

Egum 4.14 (a1 Hwtrr sc;m \m'ting rd>e~nr. Ihl \'cctur r a n wi~ing s h c m c ~ . irl ShaFs o l r l t r t r rm Ix;tm: nntnd. \;lri;nhIt.. :md <*.It pn~jc~tion."

11% h i ~ l w r tbrougllput than ~ I I P rnnventional Gn~tssiao spot heaal. It is dso pssihle to pattern s rnn~plrx gcomrtric sll;lpe in one Pspsurc \\it11 an elearn" br;lor s!5km: this is d1mI rrlI]~mjrrrrion. s11o\w1 in thr far right o r F i p r r 4.14~. Tllr n*ll pmjrrtion twll- nilup'' is p . ~ i c t ~ l a r l s s ~ ~ i t a l ~ l ~ for l~iglrly reptitiw d e s i ~ a . as in hlOS meznonells. s ine srver;ll n l ~ ~ ~ n o r y a ~ l l p:lttenrs s l r l I*. erposrd at oncr. Crll pmjrction 11% not ! ~ t ncllirvrd tltr tllmt!al>put of opticll e\panare twls.

Electron Resist Electron resists are pnl!n~rm. TIw h~l~i l \ ior 01 an ~ lec tmn henm resist is sirniliu to tlli~t of n pl>otoresist: that is. a cl~emicnl or ph!sind clumsy is indl~crd in the resist by imdi- ation. This chlngc dlo\w tile resist lo In? p:tttcrncd. For A positim rlcdmn resist. tile pol!mrr-clrctron intemaion muses cl~rn~ical lmnds to Iw hmkrn (cllail~ sciscionl to fnnn sllortrr molw~rl;~r fngrnents. m s h o ~ n in F i p r e 4.150."1\s a rrsult, tbr molerular\\riel~t is mluced in thr im<li;~trd area. wl~icll mn lw dissnl~wl sr~hsrqt~entlyin a th \v loyr sol~i- tion that attacks tilt* lo\r-l~~olrrul:lr-~vcisI~t materi:ll. Co!llllloll positiw ~fe~.lrLIll resists inclr~dc poly-rnetl~!l m e t l ~ a c ~ l n t ~ (PhIhIA) and p,lyhutcnr-l sr~lfonr (PBS). Posititr elrrlmn resists c m ~ acltirw resol~~tion oi0.1 Hal or Iwttrr.

For a negative e h ~ t r n n resist. tltc imlrliation c:lusrr r.trliation-induml pnhlner link- ing, is sho,,m i n mslm 4.151,. n,? cmss l in l in~r rea t~~s :, rnrnpler thwt*-clit~~erlsio~~:d rtntr-

ttire \\ i t la n ino~ictl~ar ~ ~ ~ e i g l ~ t Iliglit-r Illall t l~I t of ~ I I ? nonimldiatt~l ixll!nlrr. nlr nonirm<liattyl resist e m IH. l l is~oI~ed in I ~ l r r r l o ~ ~ r s o l t ~ t i o n tllnt dues llot attilrk thr I l i ~ I l -

molPclllar-nriSI,t t~~af~ri :d . P~!\"gIyrid~l 111et1~.1~~l~t~-cn-etll!.l-i1cn~i1te ((:OI') is a rnll1- llloll n e g i , t i ~ rlrdm,l COI: like most nro,ativc pl~ohrrvsists, llso nvells durino, developlnrnt, so rrsolution is limitrd t r r almet 1 W.

The Pmximiy Effect In<>pti<d l i t l l q l p l ~ ~ t11e rcarlution is l i m i t c ~ l I ~ c l i K r ; ~ ~ o ~ ~ o f l i g l ~ t . In elmirun lx.anl litl19-

!Ilr reqc,]tltion is not litnite~l I)? <lilTr:~ction (In'cat~se tlw ~ ~ v c I ~ ~ I I $ I I s :~%swi:it<%l

76 c Chapter 4. Photolithography

rcw>t,,,. ~ - v t Y Y Y Y --,

-?- LC," ,.,on '+ I I L R (a)

Figurn 4.15 Sdwlnatir of positi\.c. and twgoti\.v resists nsc~l in elwtmn Ix:anl l i l l a ~ m p b ~ "

\ritIt e l r d m ~ u of a few kr\' and h i ~ l ~ e r pnergies are less than 0.1 nnt) h t ~ t by electron sc~ltterit~g \\hen rl&onr penetntr the resist film a ~ t d ilnderl!itl~ srtbstr.~tr. tbey undergo collisiom. T l ~ ~ s e rnllisiorls lead to e n e w losses and path chatiqrs. TIIIIS. the incident electrons spread out as the? hxwl t h r o u ~ h tlir ,material lilltil either ill1 of their t~llrw is Inst or the? leave thr rnatrrial k c a t ~ s e of hacbcatterin~.

F i p ~ n , 4 . l k sho\s rnrnputctl elrctrna tnjrctnrin of 100el~ctrnns \\ith initid e n e q of 20 kcVind~lent at the ori$n o f a 0.4-ptn P l l J l h film on a thick silicon suhstri~te."Tl~e clectrnn hram is incident :%Ions tlte z-ajs. and :a11 tnjrctories hare Ixen pn~jrcted ontn tl,r.sz pl:me, This figme slto\\s qtnalitati\.rly that tlte electrons are distriboted i n an ohlot~g pear-slmpnl \alemc ~ i t h a tlilimneter on tlre same o ~ l r r of ni:qnitode ;L< thr rlectrnn pen- rttatios drpth (-3.5 pm). Alw, mmyelrvtrnns undrrxo hackcattrrit~gcollicions :~nd tr .1~1 hackwtrd frnrn the silicon stshstnte into t11r P l l J l h resist film and l m \ r tllr oraterid.

Figtre l.lfiJ, sltmr-i tlir nonnalizerl distributions of tltr ft,n\ar~ll-scatterin and hack~c; t t t~r isp~lrdrons at the resist-ntl~stntr intrrhcr. Rrcause ofhackscattering. dec- tmns rffrctirrly c:m irradiate s rve~ l l nmicmrnet~rs a\wy from the wnter of thr e rpsure h rao~ . Sincr the doce ofa resist is @ven t h ~ sun1 ofthe irradiations from all surmunlfing arp;rs. rlprtmn I~;e.,nt imtliation at one lmt ion will affect tllr imliation in nriglllmrin'z lwzhions. This pllenomenon is c;lllcrl t l ~ r proxiraily eJfic1. Tllr proxitnih rffrct pk-3 3

Limit on the mioirnllnl cpacinp I r h v e ~ n pnttrrn f~thtr rs . TORI-~ for the p m d m i h r k t . p;tttcrns are tli\idnl into mmallc.r sremmts. Thr incident clertrnn dosv ill raclt segment k :t~ljustnl so tl~ttt tile i n t e p t r d tlmr fmm all its nr in ,hln~ri~i~wgnt~nts is h ~ r rnrrrct t.mo s u n close. This tppmach ftlrtllcr c l e c r e ~ ~ r s tllc tl~rnt~ohput of thr elrckon hram c). tvc~uu .o f th r arlrlitionxl mrnputrr time rrtluinrl tn r r r i sv tllr suhrli\ided resist patt

stcm ems.

4 Ememe Ultraviolet Lithography

4 Dow

Figure 4.16 ( 0 ) Sirnulalcd trajectories of la) clcermns in PUMA lor i k 20-CVclrrlmn lx.am." ( b ) Don. ~lislribtion h,r f o n \ d mttcring and hark-ttninp at thr n~isl-nnharntr intrrCarr~.

75 . chapter 4 Phocol!thwra~hv 4.2 Nen.Generstion Lithographic Mclhods 4 79

,, q.) ,c.,,,,, tic^ zt,,, :*,, ELT' l i ~ l , , ~ r a ~ ~ l ~ y qste111. t\ l ~ ~ ? r r - p m l ~ ~ w r l ~ I : L $ I I ~ ~ I or yi- , lLn,tn,,, r.,cli.,ti,,n ,.,,,, srnl. .\r the sourct. n l EI:V ha\inq a \!-,~wlcngtli of 10 to 14 nni. n,,. El'\' Gllll.trs,n is n.ILr.tctl hy it 1n;al. Illat is pnw!llnsd I,? p~l t?rni~lg;~n alrsorlwr malr-. n.,l tl<.lndtr.ll t,n ;I maltil:l\rv cnah.cl 11:tt siliron or p1;us-plat? t11:rrk blank. EU\' KI<$~. I:,,,, ,c n ~ ~ l t r - t M l ironl 11,~. ~ ~ n n ~ ~ : ~ t t ~ ~ r n ~ ~ l rt.,$oss ( i . r .. n o n ; t l ~ ~ ~ ~ r h i n ~ rcxin~ls) of the n~xrli tf2,,,,,c~, ', .tx r r ~ ~ , , c ~ i n l , ci,,,,e~t :incl i ~ t ~ a q t ~ l intn a thin l;iyrr nf resist OII tile n-afer.

<,,,cr 11,~. E ~ T \ . r.aliiltiol, ilram is n:knou: the m;rsk lmlst IIP sc i~n~lcd hy tllr k i t m t I l l l l l l l i l l i t t r s thP t.ntirt, ~ ~ ~ b t t , . n ~ lirld tlnt desrrilx.~ thr rircoit inark li~yrr. Also. Tor a 4x lttlnrrr I.P.. t!lC ~ ~ ~ ~ . ~ ~ ~ . i I ~ l l o i d . h ~ ~ ~ - ~ ~ ~ l i ~ ~ m i d . :tnd one-plmc, niirror! rcd~~ct ion c m e n tIII u:afvr mtrct Ix. Yitnta~d ilt one-fotrlIt I I I ? 111:tsk s ~ e d in a dimt ion oppo i t r lo tb nl:hsk nlo$mbt.tlt to r<.pmlurr the itn;,p lirld on $1 cllip sites OII tllc a l f r r s~~rfao?. pnriqion ? d ~ s ~ is nqttirvd t a l*.rfomt tltc cltip-sit,, nlig~nlrnt and to mntrol tllr \$.a& ,t~td lllitsk t i lq. ~ n o v e ~ n t ~ r ~ t s iu~d ~ I I C rxpnsur~ dosr < l u r i ~ ~ g t11c S C ~ I I I I ~ I I ~ p m s s . E [ I ~ Iltllomtphy is clp;lhlc of printing 50-nm fc: t tun~ nit11 Phl \ lh wsist using 13-nl r.ali;ltion. H~nwver. tlw p m \ ~ ~ c t i o n of EU\' eqmsurc tnols lms a numhcr of clzallenge Sinrc EL\. is strnngl? ahsnrlu~rl in all inntt.ri,ils. the l i t l ~ o p p h y pm.s elurt h r pe h n ~ , p d in :I v;tnm,,,. Tltr can~erz ntttst use reflrctivc lens P~I.IIIPIIIS. ;lnd thr rnirron mu h. u . 1 1 ~ 1 n i h ~ ra l~ l t i l ;~ r r cmltinq that prntlurr distrihl~hrl quarlcr-\fi~re Bra:$ r d r c - t ~ o . 111 i~~ldition. tla. 111:~ck h1:11,k rmtst :ilw h r rnl~ltil:~yrr coated to in:L\irnize its rrllrc- ti,,? st i. of 10 lo 14 om.

3 X-Ray Lithography

S-xty l i t l t ~ n p l ~ y ' " (ZHL) is a pnl~ntial c:mdirl~te to succrerl optical l i t l tqr~pit). for tile f:thriration ~i intzq.ltel circuits nt 11x1 n n ~ . Tile s!ncl~rotron storace rinrc is tllr choice of x-r~v sourcr f i ~ r l~igl~-voluane lii;unuf;rhtrinq. It can proride a i n ~ e anioltnt of colli- oiaterlflt~r and can r:~rily arcnmmcxl:ttr 10 to 20 eqmsinrc twls.

S R L wes ;I s l~n~l~nr . printin? tnetllod sitnilar to optic11 prosimity printing. Figlre4.1S slto\\s a scl~rn~nt i r SRL s)stc.ln. Tile x-ray wvav~lengll~ is al.wut 1 nnl. and tI1? printing is t l ~ r o a l ~ l ~ a l x m,lrk in closr prosirnit). (10-40 pmi to thr uafcr. Since x-ray ahsorption

drprnrls on tla. ntolrlir ntrmlrroftla. niateri:~l and ,nost n~ntcrinls I,;,\.,. I(,,,, I ~ , , ~ ~ , ~ . , , ~ ,

at A - I nm. tl~r nl:r~k s~tlfitrntr ternst lr a thin inrml,r:~nc. (1-2 pm lllirkl ,,f I,,,,.. ntrm~ic-number n~t~tcrinl, surlt :a silica" nrhi<lc or silimn. TIIe pnac.m itsrll i< drlinecl ill a thin (-0.5 w n ~ ) . rrl:~li\r,ly I~ ig l~ - ;~ tomic -~~ l~ml~cr m;tlr.ri;d. stacl~ ;a t .n ta l t~t~~. t t ~ n ~ s t r , ~ . gold. o r on? of tlleir alla!s. 8vllir.11 is s ~ ~ p p o n ~ l I,? tllr tliin mmrnhr~n~~.

hlwks are tllc most dimct~lt and critictl elrmcnt of an XRL s!stcm. 1II<. con- stn~ction of an r-GI? ~ n a k is I I I ~ I C ~ I Inore coriiplicalctl tlian t l~ i a t of n pliotonvirqk. To atoirl aha>rption of tllc X - r a y hrt\rren tllr SosrLx. alld in;lck. thr rxlmsure crnrctlly t;,krs l>l:l<~. it1 n l~rlium en\dmnnimt. The x-ray arc pnxlli~cul in vactntlm. \$.luic\t is srpar;ttrd lronn thc llclinnl ])?a tllin\-acllllnl aindow(lls11;1~1y0f Irtyllium). Tltr inark s!thctr;itr \\ill d,sorb 25% to Xi%. of t l ~ e incidnlt flt!x and nmrl thercfori- l r cmlr,l. Aa r-my resist I ptn tl~ick \*ill shsorlr about 10% of the incirlcnt f l ~ ~ r . Tltrre arr no rrflrctions fn,m tl~r stll,antz to crrntr slantling ~clves. so antireflection m:ttings arc unnewsray

\ r e can ~ t s c clrctmn Iwam rpdsts ns x-ray resists Irrcamsr !vI~ea an x-rav is ~I>UI~IHYI I ~ y a n atom. t l ~ e atom gws toan rrcitrd stisteaitlr tlir rlnission of an rlenrr,~~. T l l ~ r r c i t ~ r l atom r r t ~ ~ r n s to its ground stat? 1y enlittirig an x-ray having a difirrrnt \nvelragtl~ t l t a t ~ 111,. incident x-ray. This x-ray is ahsorlwd by anotller atom, and tllr prrr~.ss wpciit.;. Siuw ;!I1 t l ~ r p r m r e s r e s ~ ~ l t in tile emission of elrctmns. a resist liln~ under r-nty irradiation is ~quiunlrnt to onr Iring irradiated I1y a largr n u n l l ~ r of srrnndary electrons frmn any of tllv other pmmssrs. Onw tllr rrsist filrim is imdinted, clvain cross linkittenr d~;ain wis- sion \\ill occur. clrprnrling on tlir hFe of rrsist.

42.4 Ion Beam Lithography

Ion h ~ n m l i t h m p p h ! . ~ ~ ~ i achieve l i i ~ l ~ c r resolution than ~ ~ ~ t ~ ~ c . ~ ~ , &-In?. v, ~ l r c t m n !w:mn liti~o,craphic trcliniq~les because ions IIR\SC it higlwr mi~w :and tl~rrrfore scattrr less tllan elrctrnlts. Tile most in~pnrtar~t application is t l ~ p rrpair of lnasks for o p t i d Iiit~o~r;rpll!: a 1x4 for \r.llicl~ ~ ~ m a i r r c i s l s$ems are a\;iilal)lr.

l i ipnr~ 4.19 s l ~ ~ \ n Ill? mmpl~ter-simtll:ttc(~ trajectories of 50 11' ions implantrrl at 60 ket' into Phl\lr\ 2nd \.:trious substrates." Note that the sprracl of llle ion lr;an at 1 clrp;ll of 0.4 pxn is only 0.1 p111 i r ~ all c;rses (mmpare \vith Fig. .(.I& for el~rlrnssi. I3nrbottterinp is c o m p l ~ t r l ~ ;rlrs~nt for tlw silimn s ~ l h s l ~ ~ t r , and t l~rrc is oal? ;I s~nnll

I I I ow Figura 4.19 ~nj ,~+~", .~ ofr$14r\' 11. inns tr.trr.linS tlnmu~h lf'U\lA into \$I. Si. : s ~ 1 P\I\I:\ '-

4 2 5 Comparison of Various Lithographic Methods

TItr litltoS.l;lpbir inr.tlnc~I< dirctnsst.d c.ialier all l ~ n \ r 100 11111 or Lwtter r r s d ~ ~ t i o ~ l . A COIII-

p~h,t>n 0 1 \;tnous litl~<v:nt~ltic t t ~ l n ~ o l ~ ~ ~ ~ ~ s is sltmtn in Tzhle 4.1. Elo\%~,ver, rttc11 111etI1nrl Il.~r its un\m I~nlit:~tinnc: lllp difl'c~tinrt vITc~ct in o~t ic id litltOgr.lph\: the prosinlit? eNect it) r l t ~ t m n IU..~TII litla<<r;splty 111:1& f;al,rication rn~~~plexi t i rs in r-my litl~o~r:~pl!\: dim- nrlh 11, ~tl.c<k b 1 . d pmcl~trtiot~ Con. IlCV litl~o<ntpl~c ;n~rl s t o c l ~ ~ ~ t i c S ~ I W c l ~ a q r in i IW:IIU Iitl~cwcr~tplty

Fnr I( : f.tlmc:ttios. n,:tav ~n:wk 1rrr.l~ are i~ lwlwd. Ilo\\r\rr. it is not arrexQ1n IXV tlw SI~I IC l i t l ~ o ~ ~ p l ~ i c tnetltwl for ;dl l r ~ ~ l s , :\ III~X-:UI<I-TII:I~CI~ :~pprm~clt WI k k r ; U I \ ~ ~ ~ . t;ly of tlrr imirltw &,,tlun.s of tach lit~lorr;qdrir p m r s s to inlpn)vc, resollltion alld lo Inax- irnin. tl~n,u<lt~,ot. For ~.ctmplr. n-$:I EL'\' metlml w n IF nsed for the r ~ ~ o s t critical mx5k Ivvrlr. n la~n. .~c a 4: I or 5:) a I ) t i d ?strtn ran h~ used for tile rest.

:\nunlinc: to tlw Srmin~ncllcrtur I~ t r ln t s t~ Asswi:ttinn's It~tumotionol T ~ C ~ I I I ( ' Ilcwd,n,~~>.l;)r .Sc.r,,in,r~d~rctnn. IC in:mnlitctt~ring t rv l~no lnp \rill reacll ti#r 50 n m eration ;irn!~n,i 2l)lll." \fit11 rarh nr\r trcllnolop. genr~d ion . l i t ~ m ~ p l l ! ~ h;S 1w1

TABLE 4.1 Comparison 01 Various Lithographic Technologies

Optird S(::\LI'EI. EUV X-ray Ion R< 249 I'KI nm

Fr,'.""". Xr.1

C~winr . I.wr Filrmrnl Lawr plsma S!ncl~mtmn \lullicla: L),t?r.fr.lni.>n lin~itc-d Ye.; S o Ycq k s No (?IN<- Rt,fr.tni\r. Rcfwti\.c Rrlrncliw So optin Fn~ll.ficld

refmcli\r S1t.r rod \c<e Ym Yc- Yvs YPS Slrppcr llinru.rl~pnr of -m 30-35 2twn 30 30

? o ~ l - m n > ~ ' ~ t i ~ m h r >f,,\L l ) ~ ~ ~ n ~ m i f i ~ - . ~ t i ~ ~ ~ ~ 4x 4x I x Ix 4x I i li? So Y?r Yrs So

I.'ml.'tltl,l R.,s!,.ttu-rc l ) , t t l ~ T i n i s i Rdlwtion Tr.msrnirsion Strnril R..,,', \:SI:IS. n\t>lr~l.nt.r ';in<ll- Sin&. Sud:trr Sinxlt. Singlr

i~n.a$s~: I l.*.n~~t:J-inlpl~lililiI Yv\ Ym So Yes No

r)..,.,

F 4.3 PHOTOLITHOGRAPHY SIMULATION AS is t b case \\it11 oxidation (see Cl~nptcr 3). mmpatvr siml~lstion is also .In importmt tool for stud!ing t l ~ r pl~otolitl~oqapl~y prorcss. Tlnr SUPREXI packarc, snfnltun:ttrly, is not cap:lhlr ofp~loto~it~lr~mp~licsinltl~ntio~l. Ilo\\n.r. anolhrr popular tml. I'ROLITII. clops provide this wpahility

I'IIOLITI I is a \Vind(nw-ban1 pmgmm that IIWS a p i t i \ / n q a t i t r photomist opti- ad l i t l ~ c ~ n ~ p l ~ y morlrl originnlly d w e l o ~ l l h Chris 3l;tck.l" PHOLITII simnl;ttes t l ~ c cnm- plrtr on#:- :1nd hvo-dimr~lsional optic:~l lill~ogr:tpl~y procrss from acrid i m s g ~ firrmation tIimr1$11 rrsist cqnstlrr anal cl?vrlopn~?nt. TIle output o f t l ~ e p r o p m is an ;twnmtc prr- dic!ion of l l l r final resist pmlilr, u.llidl is pr~scntrd in :I \vide \ a r i rhof ilnagrs. plots. rr.iphs. ;anrl calculations. In partic~~l;~r, PROL.ITII is able to sitnnnlate tlte follmvining

Fonnatio~l of an inlnge o h I I I ~ I ~ feature by an optictl projection system

Exlnsr~re of pholoresht by this image

DifTtlrion of the imaCr

PROLITH accppts l i t l~mpl~\~informat ion in t l ~ e form ofdata files and input pa.....

. . menu. :After n SIICCPSS~~II license searcl~, the Imaging Tnnl pammrtrn \visclav appears (see Fig. 4.20). ,\s tltc user makes clloices from tlte \'irwmrntt. PROLITII displ;i!s \\in- clo\\s in which parampten may I r entered in orrlrr to \ieat simsl:ation rrsslts. Thesf be obsemcd fronr tlre Cnplrs mene. These idea are illt~stnted in Example 3.

EXAMPLE 3

t'w PtIOI.ITII 1,) d r \ v rlw n.,ist prc,(iiv for lllr nll~ldnr.~l nl.ak f#,.~lttn.in Rmrr 4 ?naftcr. .,.. sttrt. ;m<1 <h.n.lr,pn~rt~l .\ssttnw tllr fijllcn\,nr: pnrr,.\ cn1mrl118<,n$

SOLUTfON ~ 1 1 nfll,,, piwn ,q,ltlcs can lx. cnteml fmln lhr P;~rrslrtrrs nlrnn or I,? cliclill&7 an 1111. appmpriate imns on thr tmlI,.~r lltr rrstlhins rrriqt PrnfiIc is shcn\n in Fiqxrr . l .Zl .

b 4.4 SUMMARY TII, cont in~~pcl gmutl~ of t l ~ e scnl imndudor industr). is a clircct re r l~ l t o f tile cap>hilitY t o t no~s f c r rln;lllcr and smallrr cilruit p :~ t t~ms onto u.n~iconrltrctor uafcrt. C:tarrrt~t$: tlte v a t inajorih of l i t l~oxrapl~ic r q n i p ~ n r o t is optic:~l systc.ms. This chapter mnsi<lrn,rl v;lr- ious exposllw tools. masks. plrotorrsists, and tla. clr:tn mom lor opric:~l l i ~ l ~ ~ m ~ l r ~ rile primary factor l io~it ing resol~rtion in optical Iitliologr;~pl~y is diffniction. Iln\vc~\~rr. hrcnnu ~ ~ f n d n s ~ c r r n r n t s in rxcilner ism. pltotoresist cllrntistry anrl r~:solution en l~ancrmcot t r r l ~ n i q u r s SIICII as PShl and OPC, optic:al l i t l ~ o g r a p l t ~ ~ ~ i l l remain tl~e mainstr<.a~n trcll- ~ ~ o l o y : at lrnsl t o tlle 1 0 11x11 eerier 1' d 1011.

E ~ r r t m ~ r h a m lilho~rnpl~!.is t l ~ r ~ t e c l ~ n n l ~ o f c l ~ o i c e for ITI-k making and aanofab- rication. in \vhich IIMV dr\icc mncepts nre rrplorcd. Otl~er lithomnpl~ic processin< twh- nokr$rs a re EU\! x-ray, and ion b a n i l i t l~ogr .~pl~y A l t l ~ o ~ ~ g l ~ all tllrsr Ilnvr IIW) nnt o r better resolution, eacll process 11;~s its o w lisrit;~tions: pmrimihrfl?c.l in rlrccrnn k m m litl~ogn~ph!: mask blank prc i l t~a ion d i f f i o ~ l t i r i n EU\'lithognpl~): nv~skfabricxtion conr. p l r a ly in x-ray l i t l ~ognp l~y , and s t o c l ~ i ~ ~ t i c space cl~argr in ion l r ~ a n ~ l i t l ~og rap l~ .

At tl~e present time. no o b \ i o ~ ~ s succe so r t o optical l i t l ~ogn~p l~y can be idrntifierl ~~~~nrnhipioasl): I lo\ve\rrr. a inis-and-match approach a n take ;~clrnnta?e of tltc rzniq~w f r a t u r s o f each l i l l~ogr .~pl~yprocrss t o irnpro\.r reso l~~l ion imd to inaxi~nizp t l ~ m t ~ e l ~ p a t .

b REFERENCES I Far a more drl.rilerl cliaar.inn on lilh<lgrrplly w (31 K. .\'ahmum. -Iirhqmpl,y: in C. C Cbq slnd S. 51. S l r . Eds.. l%Sl Twl8ooln~. Sl&r.~iv.llill. S<?~,Yo'ork. 1%. ihl P. R:u.~~nw,Il~urg. I I ~ d h A "f lficnlrh,?~mphy. 3limrrrwcltining. nnrl ~ l lm~r l~~,nmt inr~ . Vol. I , SPIE. \\:ultin@nn. DC. 1'11;. ic , D. A 5IcCill~~. -lill~~.tplny,- in S. 51. S ~ P . I<<!,, \'l*Sl Tccl,n~d~~gt,, 5l&~~v.llill. S<-.vYo?x. I%?

P For a mom drt3ikl d i ~ a ~ i o n on nclminp. nr K J. T. I J I~ . -Elchine: in C. Y Chmqmd S. 51. Sn. Edr L11.Sl x7lt!1o!<*q. >(cC.r*\v-lldl. Sru. Y c r l . IYJCI.

3. J. 51. D,oK?lo md J. R. Slonkm~rki. -Podionlair Cnntrn>imalion md I h i m Frrlom;uw: Sdd Smtr %dand 27.3. Irn(~su~. 4. 11. P. Tsng and R, J w ~ r n . -Clc.:mmom TmlmolnS\:" in C. Y. Cb:mg md S. \I. Sm. Ed,. VIA<! Trrltnolo~y. 5lrCr~~v.llill. S~?vY<,rk. ID*.

5. 54. C. Kin$ -Ptiwiplm of Optid Ufhmr.~pl~):- in S. G Einspn~clt. Dl.. VI.SI lYlrr(mnin. GI. I. Aorlrs~lc. Sos.York. 1981.

fi. J. H . Rruning. *I\ Ttlntid on Opticd Ulltalfinl,hc"in D, h. 1)cunr. r l d.. Dlr . .Cnrtimnrlur(r,r 7.~1~nuloq. Elwtrwhrmiwl Sor. R~nninckm. illY2.

7. R. I(. \\:ills :,nd J. I!. 8noning. -A Rlzirr.ofFinc..Lisr. Utho~r;aphicTt&ni,~u<.s: Prcunt :old Futurr.- %lid smr? Trrl~tm,d., W, s. 119911.

S. \\! C. ? i l l and J. T. h o n . Inc:nmhd Cirnnts. .llotmnlr. k. irrr . nnd Fobrimfi<na. Pn.nticr,-l1:JI. ~ ~ ~ ~ ~ , m l aim. s j . I!+*'.

0. \I. D. L * W I ~ I I . S. S. \ln~:m;~~ll,tll. md I . A. Simpsn. -lmpnnins Rrrrtlslio!8 in Pl~~~tali l l~c~npl? uilh a Pl~zrp.SLifl 5I;~~k: IEEE Tmns FJ~drnra a ~ i c n . ED.29. I'r29 !l!lvYI.

10. 1). p nl., -pmclir.J .+WIT of \lirmfal,~m~inn in (la, lM.nsn R<@yion.'Wirl Stair x~Ic*td. Pi. 2. 12i (199.11.

11. J. A. ~ ~ n o l c l r . -,in ( hx~n io r . o f r .~v~n~ \knk-~~&~ag.'S.Jid Sfott Evlrad. 22. s. $7 119-1.

I?, Y, ,%lt~nlr, r( d.. -Elemn.Rr.lm ci.ll P m j ~ ~ ~ i ~ n Lj~ftofr;~pl~y 11s .Ammo. rnrl 11s nlnwlchpllt: 1. \'or ,W. Evh,zd., Ill2 !6l, XXW il!Tjl). 13, \y, L R~ ,,,, T y,.,,heq,", %I A. \\,,,=V~. -ton k.xm utlwqn~rplty." Wid Slmr Tvhrwl. 91.J. (*'I 19\1''

la. D. S. K~~ , m ~ S. \I: \im;,nal,m. - 510~1~ carlo Simal:,ion ofsps ldh Ihrltihuhut rd&.nny i l l

Eleron.Rlwn> lithop,pl,?:-] !'or. 5". Thnol . 12, I?Ri I l!l:i!

15 Chr&.r C\s~n. rt ad.. .f.\lrrnu, Ul~ntioliolrt U~bogrn~l~~: \\l~itc P n ~ r . Scrnnlrrh. Nm Cencrntion Utl",r~pl,).\\hrWly. Cmlur~loSprisqr. h. 7-10, IVLY.

16 j. 1' sil,.l.nl,.ta. -Pmlrniy S.H3~ Ut1~4~apl1< \\llitv Pnpr, Srrnnuch. Snl Cvm~csion ljllmpph! \\i3rlrrlm1,. Cobr.acb Spnnqc. I><Y. :-Ill, l!KR

IT. I. I;.rnriyti.. rl rl . -lo,, b:tm F.yanln. PmRlrr in P\l\tA.Compatrr Simmdlio~~."]. Vor Sd Techr~d . IS. !%!I il!J?Il,

IS M, rnamnriond nd(ard,q, RRntrlrru~rrjrr Sn,tir~,rrl~,rr~,n. Srmimnd~~rtor In,!. A r w . S:va Jose. CA 2tnl.

19 PROLITII:? h i .\Ionan1 FIS1.E T ~ h n o l ~ ~ r ~ . ,\asin. lS. I%lS.

b PROBLEMS

SECTION 1.1: OFTICAL L1171OGWIIY

I. For I rl:m lLW cleat) nnnl . find thr nnmlx.r oirlurt p;trlirlrs prr rabic mrtcr with p: rlt. sin,< [:mli-lclrl p m v a in o.hiuh thr a\r.r;t~c fxtd J:fcd dcnril mm: k 0.1 lor f i x ~ r luvk. (1'25 kw fintr Ic-\.ls. :and 1.0 lor one lcwl, Tllc chijr wra i c 50 mm~.

3. .An optiml litlnngctphic s!stem lriw an rqwnrre pwrr of 0.0 m\Vlcicl~i:. Thr relnired eqm rurc encqv for :t p,sili\r l>l>otorcsist is 14U mJ/r.m:. md for r ne<ati\u pholorrsirt is 9 mJ/nn'. ~\s ' iw~lin~ n~eliqildr timcs lnr lording ;and ttnlo:tdin< n?fcm. cumpan: the m k r thronqhptlt krr lxniti\r. pl~c,tc,n.sist and nrg:ttivr photow%ist.

4. (n)For ;m ArF c.rci!ner l:tscr 1 m n m optiwl lilhnpaphir. nrlrm \viIh Sf\ = 0.65. k, = 0.60. :m<l k: = 0.50. what up the thron~tinl rcsnhztion nncl rl~ptil of fcxtns h,r this tm,l? (I)) \\hat

I \\r do is pncticp to arljurt SA. k,. and k1 panmrtcs to inlprnw. resolt~tion'? (c) \\hat

pantnrler clws lhe pha~-%hiit nl;r-li (PSXI) techniqt~r clrangr to imprnxc resol!ltian?

5. Ihe plots in Fiaxrc 1.9 arc callcd respurasc nrrxcs in microlithopnphy. (a) \\lvul arc the n<l\nnt.~qes ascl clin<lvantaqcr of urine resists aith h i ~ h y wI~~es'> ( I r l Convcstional resist

SECTION 1.2: SEXT-CEKEIUTIOX LITHOGRAPIIIC 51EniODS

6. (a1 Explain wl~y a shaped heam prnmiser higher throughput than a Gaussian k a m in r-lraln litlt~mphv. (1,) llmv cm aliqmcnt Ix perlonned for e-ham lithopnphy? \\h) . . . .~ i 5 diwtnrnt in r-rav lithm~mhv sn dificult? (c) \\%:$I are the tntential adwntsces of

7. \\hv has thc orrratinc modr ulonticsl lithogranhie mtem.; rrvlved from nnnimily prin , . . . . . ing to 1:l prnjection printing and finally to 5:l projcrtion stcp-and-repeat? (h) Is it pos I,lc. to build a rlvp-sn<l-sr;ln r-ny lithopphic s\stem? \\hy or why not?

Etching

As cliscussed in the previous chapter. litl~ogmplly is tlle p r w r s of transfrrring patterns to photoresist mvering the surface of a semimnductor\~afcr. To pmrlucr circuit lrntares. tllese resist patterns rnlzst hr trassferred into the andrrl\ing lnyws conlprising the de\ice. The pnttenl trc~nsler is acco~~~plishecl in. :in ctching process that rclraivrl!. rraloves ~mmilskcd portions o f a layer.' A hrief dcscription of etching given in Scainn 1.4.2. The present chapter co\,crs the following topics:

Mrchat~isrns for a r t cllen~icnl etching of srmimndnctors. insalatorr. and ntrtal f i l l l l ~

Plasnia-assisted rtct~ing (also cnllrd dyrtching) far Iii$~-fidcli+ pnttrm tnt--'--

b 5.1 WET CHEMICAL ETCHING \Vet cl~emical etching is uscd e~ensively in scrnimndnaor p-ssing. Starting fmn, c,,..- mnductor wafers sliced frnm an ingot (Chapter 2). cllemical ctcllants are trsrcl for lap- ping and polishing h~ @\? an optically flat, clamage-free surface. Prior to tlaemd oddation (Chaptcr3) orepi ta~id p v t h (Cl~apter 8). sr~nic~znluctor~cders arc cl~emidlyclc.?ned to rrmove contamin:itinn that results fmln lvar~dling and storing. \Vet clI?ltlic~l rtdlino, is esprcidly suitable for blanket etchrs (i.e.. over the a~ltole \cnfrr sttrhce) of pol!silim~l. odrle. nitride. mekds, ant1 Ill-\' mmpoencls.

Thr ~nccllsnisms forwrt clirnticxl etcllisg in\ol\r three rssentinl steps. as illnslrateil in Figure 5.1: The rradants are tnnsportrd by dilfusion to t l~e r c c t i g stndnce. cl~emicnl reactions occur i t thr surface. and thr prodacts frn~n lhe sadacc are n~nlo\,cd by clilTt~sinn. Both agitation and the tcmperatarr of the etcllant snlutinn inllr~rnw t l ~ r rtrl~ rile, \vllich is tltr :,rnoant of film removed I>? etching prr unit timc. lo IC p m c i n c . most wct chemic:11 etcltcs pmcrrd IJ? itnmrninp tllr \vafcn in a chrmi~ l l sohltion or hy .spqing tlie \ \ d e n \ritlb the etclmnt mlolt~tion. For imntcrsion etclling. (I,ru%\:lfrr h i m m r w l in the etcll solution, nncl merl~;tnicnl a@tntiot~ is urnally required to P I I S ~ I I ~ ctcli snik~r- ~ility imd n mnsistrnt etclt mtr. Spr.3~ r~ching hils gnidtmlly r ~ p l ; ~ c e ~ l inln11.ni011 etrlli~lg hecause it greatly increases tllc rtrl, n t r and aniforn>ity I I ~ mnstn~~tly stnppl!it~g fresh etchant to thr a d e r surf:^^.

For srmimnductor production lines, hi$tl? ttnifonn r tdl rates arc imlnrln~t. Etch r . ~ t ~ s nlust h r unifonn acrnss ;I unfrr. fmm wlfrr to \\xfcr. fmm nln to nln. itnd lor my \~rintions in fcatorc sizes and pnttcm drnsitirr. Etch r.11~ asilbnaih is $vctl by tllr fill- lowing cqt~:ttinti:

5.1 Wet ChemicalEtching 4 87

EXAMPLE 1

5.1.1 Silicon Etching

For s~nrimnd~tctor inatrrisls. a.rt r11rn~ic.d ctrlline i~st~:~Ily procretls Ily orid:ltion. lowrd I,? tlw ~IL~soItrtion or tlw oxid<, I>! ;I cl,rn~ic;~l rc~:~ctinn. For silicon, the itlost L< manly ~tsrcl r t c l~ ;~nfs a of nitric acid ( I ISO, ) and l ~ ~ l r o f l a o r i c ;sid ( I IFI in \nrtvr or :~cvtic acid iC Sitric acid o~iclirrs silicon to fr~rtn s SiO, I:lyrr.' The oxidation rcartion is

\\:~trr c t t r l r 11s(.d :is aclilucnt for tltis rtcllnnt. Iloa.v\~rr, arctic ;wid is prrfcrrrd hr i t n,ltl(vs tlw rlisoltttinn of tlto nitric acid

Sonr ctcl\;~nt<cli<~<>l\.<~ aSi\.rn r-?~tsl plalrr of singlr-cnstd silimn m11c11 fwte :mr,tll<.r plan^: t l l i q n.sults in o r i m t : ~ t i m ~ l t ~ l r r ~ ~ l ~ n t rtclting.' For ;I silimn lntticr. the (I 111 pl:tnr. Il;a tnorr :nnil;ahlr Ina(l.; 1x.r ilrlit ;trra lllnn t l ~ e ( 110) ;md (IIWI) p lan~s : tllrrrforr. llw c.tcl> r,ttr i < ~ \ ~ r l r d to lw ~l;lawcr for ~ I I C ( I 111 pl:mr. A con~n~only usrtl orirst8tion- ,lt.p.n'lrnt ctdr filr %i!i(~nl mnsists of :B miaturr of KO1 I ill rr,ahr and isopropyl llwI10I.

. - . , ~~~ ... ~)rirn~ltiolr-drpn<Ir~~t vtcl~iny: of < IUO>-O~~O~~IP<I silicon ~ I , T O I B ~ I , a PlttrmP(~ ~ilj.

can di~nxidc nmqk rrr:itrs pnr isr \'-slispnl proo\r.s.' t l ~ r rc~qos ~ ~ i , , ~ [I,(. i I I 1) plsnc5 :,(

:an a n k r of 5.1.7' from t l ~ r (11 I ) s~lrlncc. ns s l~aun at tl,r 11.11 of F i ~ u r r 5.B. 1ftlIc \M,). rln\v in tl~r mask is si~fficiontly I:~rgr or if tllc etchins tin),. is sl~ofl. a U-slt:~pcd grwsr

tri l l l~r fonncd. ns s l~o\r~i :at tl~r r i ~ l ~ t of Fixup 5.41. uidth of thr. Inttnn~ nld:tw. is given hy

\if,, = \\I,> - 61 (4)

u!~rre \I:, is thr wividtl~ oftllc uindo\r on tllr \calrr S E I ~ : I W and I is tllr rtcl~cd depth. If -oriental silimn is IIXY!. crsrnt ia l l~s lmi~ I~ t~~~~a I Id groaps uith s i d c s o ~ ( l l l \ pl:inps c2n 1w fnmlrd. ~LF s l ~ o ~ m in F i q z r ~ 5 . 9 ~ \\i. can usc t l ~ c large orientation dcp-t~clt~nn i n tllr e tc l~ n t r r to fabric~tr d w i n structlrrrs aitl~ sltllnnicron feature Implla.

5.1.2 Silicon Dioxide Etching

Thp wet e t c h i n ~ o f silimn dioxidr is mmnmonly nchirved in a dilute solution of IIF \titlt or a i t l l o ~ ~ t the addition of ammonium fll~oride (SII,Fl. A(ldin~ Sll ,F creates u.l~nt is

f l b l

Figure 52 Orirnfdion-dcveln>t c,tchiag_' (ni IhrnugI~ \vindm\. pltrrnr ott <Irn~-t,rirnl~d ~ilima. rb) nlmllgll \ t i z ~ l , ~ ~ p;altcms on < 1 lO>.orir!~tcrl rilimn.

5.13 Silicon Nitride and Polysilicon Etching

Silwm nitn<lr. f i l n l ~ :mrv r t r l r .~ l~ l r :11 nx,r~~ tt~!nIn~fiattrn. ill conn.ntr;~trtl A F or baf iml I I F .ln<l in i t hoiliuc I1 PO, wl~itintt. Sclcctivr r t r l ~ i t ~ e o f nitridr to ori<lr is donr w i t l~ hi4 Il.,PO, at I U I C ix.r.~~~.;r t l lh vll!ltion R ~ ~ R P ~ C 'ilimn dioridc v ? y s l ~ ~ ~ v l ~ The r.*tv is h~ icd l l y 111 nrn1~nin for s i l i m r ~ t ~ ~ t r i ( l ~ . I v ~ t l eu ~IILIII I ntr~'111i11 ihr silimn dim I Im\r.\rr. pl,oton-ist ;i<ll,esion pndvlt-111s a r re rwn t rm .d \ v l~m r t c l ~ i n ~ nitrirlc \\it11 l in= 11.1'0, *rrlution. Rt.ttrr pitttmlirle cxn hr itrllic~vr~<l l)y rlvpnsitillg a tlliri oxide I; on top o f the nitridr fi lm Ix.fi~n. n.si.;t <w:~tine. T l ~ r rt.sist p:tttcnl i s tr.lnsfvrrcd to the o v i d ~ I;I~v. w l ~ t c l ~ t11~t1 ;acts :LS ;t r~xtsk for % ~ ~ h s r q ~ ~ r n t nitr i~lc < ~ t c l t i t ~ ~ .

Etrltinq prl \r i l ime i s similar to ctcliinc sinel<.-mst;tl silirrm. Iln\r~.\rr. tl lr etch cite is ~ ~ ~ n s i ~ l ~ r . ~ I ~ l v l:~stf,r I ~ I I S P of tl~e? qfi~in lm1111,1:1rirs. T lw v tc l~ sn111ti<~11 i s usuallv mwl- i f i n l to rnwn- t11.1t i t dws not attilck tlte ilnd~rl!inc p t c odd^. I>op;~nt conirntrnh and tmmprr.tt81rr mil\- : a l f ~ i the etch r ~ t p o f p o l ~ ~ i l i r o ~ ~ .

. . .. ions

5.1.4 Aluminum Etching

.Unminom mcl :dllrnin11111 alloy films arv gmer.aIl? ~ t c l > ~ l i t ) I ~ ~ n t v d snl~~tiuns o f phor- pltorir acid. nitric arid. :Iwtic acid. and Dl wxtrr. TI,? t!pic:ll rtrl~:tnt is asoltttion o f i s% I I PO,. 4 7 I l S 0 , . 3.5% CII,C001-I. and 19.57 DI v.atcr itt 30-C to MI'C. l l l r w t ekh- inq of ~ l n t m i ~ ~ t ~ n ~ prcrcrds follo\r~: 11x0, o\-iclin%s al~nrlinum. itnd 11,1'0, t l ~cn dis- ~ I \ P P tl~r orirlir~.d al~~ni inum. Tltr ctclt rat? drpm<ls on ctcllant mncrzitntion. tempPr.ittlrc. amtatinn nf tI1r aafrrs. mtl irnpt~ritic.c or ;tllq- in t l ~ r ;dutninatn film. For vr;tlnplc. tlip t-trll n t e is r rdunr l \vllrn mppr r i s ;aldrtl to t l x nlaminunt.

1G.t efrhincol ins8tl;btinq snrl metal film< i s i~su:ally~Ionc r \ i t l ~ sintilar r l~e~i i icals tltnt cli~solrc thrzc tnntrri;ds in hulk form and invuln. t l ~ r i r mnvrrsioa into solr~blr salts or m ~ n p l e r ~ % . Ccnrdl!: film mntrrinls tri l l lu. t*tcllrcl more rnpidl? t lnn tltrir hulk mun- t tvpr t r . i\lso. tibe vteh rates arr lliehrr for films that l~a\,r a p m r tnicrostmctnrc. bn in stresq. or clcpzlltnrr from stoie1t1o1n~t~\: or that Ilia\.r hrvn irr.~cliikt~~I. Some us< ~ t th .~n ts for in<nll.rtinqa!~d mcfitl films :err. l i ~ t ~ l in Tahlr 5.1.

lilt- !.r,,l

5.1.5 Gallium Anenide Etching

4 aide %nr i r lynfrbhw h:tw htvn ilar?tie.lC~l for callitlm 3wnVIr: I~rnv~vc~r, fc.\vof 11: .>v trttl, isotrnpir " This i s l n ~ a t t s ~ ~ t11c st~rfitw acti\itit,< of tlw I I I I Ga and 11 I I 1 (.LC..\ ikn, v v y tlifl;,rrttt. \lost c,tcl,c% g i v ~ :I p l i s l l r d st!rF;~cv 0 1 ) the ars~nic fnw. 11111 e.alln~m f.acv. trmclq tn rlto\v mst ; t l l~ r :~p l r i c r l r f f ~ t r nnrl r.tellrs more slmr.ly lllr 11

r m*rnrvnnnlv OUSNI ctcl,ants :trr t l ~ t ~ l l ~ S ~ l ~ - l l ~ O , - l l ~ ~ > :and l l , P O ~ - l l ~ O ~ - l l ~ O ?strrr~s.

an ctcl~nnt nit11 an 8:1:1 \nhtme nt ia of H,SO,:H,O,:A,O. f l i r etrlt rate is 0.8 Ndmin for t l ~ r Ca faw ;md 1.5 pndmio for ;dl o t l~ r r bws. F o r m rtrl~;mt \\<ill) n 3:1:50 \olt~nle n t i u of II,P0,:HIO,:H,O, hlr etch n t c i s 0.4 pndmin for tl~r <I1 I > Ca faw and 0.6 pm for ;dl otllrr Clilrrs.

5.2 Dry Etching 4

TABLE 5.1 H e l m lw Insulmn and &dueton

\ I . t t c ~ r h l ICtrleut ( : ~ rn~n~~ t i , , ~ Efrl, I l r t v Innr~min~ SiO: I'l 1111 I IF

170 trnl l l F U~>fi,n,~l I IF I I t X l 113pS11,F

15 rnl I IF lo ml IlZIO, P i.tcl, t 12 DlXl ml l l:0

Si,Xt n a l l r ~ d IIF 11 i

A1 II,PO. Ill

4 ml IINO, 3.5 ml C11~COO11 I 311 i 3 rill II,PO, 19.5 ml 11?0

,At, 4 g KI lo(

b 5.2 DRY ETCHING In psttrrn tmnr r r opmtions. a mist pattern i s dcfiard l>yn lithogn~pl~ir p m x s tosew a? a mxsk for e t c l ~ i n ~ o f its o~ldrrl!ins I ; iy~r (Fig. i.3nI:' hlost n f t l~v I;l!vr mnlcrials (ex. . SiO,. Si,N,. and drps i t rd mrtals) an, ~rnoq,l~atts or p o l y ~ ~ ~ t a l l i n r thin filtns. I f tbry are etcltrd in a upt r.l~rmiral r t r l ~ ~ n t . t l ~ r etclt mtp i s ~cr~rr . l l ly isotmpic (i.c., thr in tc~d anll \rrtinl rtclk rates ;lrr tltr san~r). ;rs illustn~tcd in F i p m 5.3,. ll hi i q the tl~iehcss oftlle rnntrrid alrl I tlrr l a t r d rlistaney rtcllrvl t ~ t~demr r t l ~ tlw rwist nvsk. ul. c.m &fine the d~prrr rrf ;~nisotrnpy (A,) 13.

]I!'> 40 ml Ilp

Zlo 5 ml II,PO, 2 ml IISO, .l ,,,I CII,C0011 1sn II!O

XK

I ml 11x0, Pt i rrnl Itl:I 1 50

4 ,"I 11,O

31 g KlI:PO, \V 13.4 p KO11 t IMP

.33 p K,FrlCS), II:O to makc I litrr

90 c Chapter 5. Etching

\vhere t is timc and R, and R~ are thr lateral md \~rtic;ll etcll mtes, rr.qxcti~~rly. For isotropic etchine. R, = R and A, = 0. ,, . .

Tllc major dis~rl\~nnta~c ofwet d ~ c m i a l ~rtcbing in pattern transfer is tile undrrcotting of the li~wr ~ ~ n d ~ r n e i ~ t l i tlar ninsk. rcsrlltine in s loss of resolt~tion in t l ~ r c t c l ~ e ~ l nattem. m practice. for ivotropic rtcllise, the film tlt ich~rss sltoltl<l be ;thoot onr-tliirrl or lrss of the resolution rcquirr.~l. I f pnth.rns arr rrquirrd \\it11 rrsol~~tions mtlcll sm;~llcr than the film tltickiless. anisotronic ctclline (i.e.. I 5 ,\, > 01 must I><, t~sed. I n nr;lcticc. tile \allle , . ofA,is chos~n to b r close to unity Fim~re 5.Rr sl~o\rss tlrr lin~itingc:tsr ,vlterr A, = I , cwr- respon(Iiag to 1 = O (or R, = 0).

To acl,ie\.e n 11igl1-fidrlity trnnsfcr o f t l ~ e wrist p;tttems rrquirrd for altrala~e.scde integration prncrssiog. d n etching mr,tl~ods ha\:s hrm drvelopetl. Dry etching is 9n- on!?oot~s ~ ~ i l ~ ~ p / ~ ~ r ~ m - n . % ~ i . ~ ! n / d c ~ ~ i ~ ~ & \dlieh dcnotrs se\.c.~id t r c l ~ n i p ~ r s that tar? pislna in t l ~ r form o f low-prcsrurr disrhnrgrs. D n r t r l ~ n l r t l ~ ~ l s incllzdr plas~rra etching. rracti\.c ion r tc l~ ing (RIE). sputlrr rtclling. mnpnctically cnlutnccrl RlE (X f ERIE). rrnctive ion be;tm rtchinp. and l> ig I~ -~ I~ns i l y pli~qtnit ( l lDP1 rtrhing.

5.21 Plasma Fundamentals

A plasma is a ftllly or partially ionized RLS cnn~pas~d of eqilal nt irnhm of positive and negatit* cllargrs and :I differrnt nolnl>rr of rnnionizrtl ~ao l r c~~ l r s . A plasma is proilt~wrl

5.2 Dry Etching 4 $11

uhen an electric field of suficient mngnit~ldc is applitxl to r ga~, cau5in~t~,,. mx tar break clown and hcn~nle ioniml. The planla i s initiated I>? f n r clcc+rons t~,;,t art. rclr;wd h\. some meanc, slrcl~ s firld emission from a ncp:fiti\.?ly I,iasrd ~ lmr rx le . .n,r iree r.lrc- tronc gin idnrticencre\. from llle clcctric fic.lrl. In tlte munr of thpir trmpl tlaronsol, t1,e gas. t l ~ r electrons rn l l i~ le~+i tb gxs moluo~les and lo<? tI~<+ir c n r w nrrr.nrrqttr;la~i,.rred in thr callisinn canrrs thr gnz molccc~lrs lo h. ionized 1i.r. .. to frc:~ ~I~rlr , lns>. n , ~ Ire,: clrctrnnr g i n kinr t icenrrq from tltc field. and tltr prow<\ mntinaes. nr.n.forr. ulrcn tllc applied voltaw i s laxer than tile hrrakdmm patentid, a sllrl;dn~l plasma i s form,-l t h r n ~ ! ~ ~ ~ o l r t t l l r rrnction cha~n l r r

l'l~r ~ l rc t rnn concvntrations in the plasma ford? etrllinss arc- rclarivdy lrnv. (?pi. c*lly on the ordcr of 10'' to 10" cm-'. At a prrssrtrc of I Tom. the rnncrntrations of :,a rnr,irculrr are 10' to 10' timrs l~ieltrr than thr rlrctron mnw~r.ntr:ttionr. n t i r rr.aclts in an a\?ra?r gas trpmprr.ltulre in ti,? nnge of 50°C to IMIC. Tliersforc. pl;~cmn.a~<istd c!r? etchin? is n lmv-cmpnt t~ rp prccsx.

EXAMPLE 2

'Illr vllrtmn dm\itim in RIE md III>P ?>tr-rns mnet. fntm 11,' lo 111' r m ' a:r l II~' in In" .... . r L ~ ~ p c a i v ~ ~ l . :\wun,inq ~IIV HIE cbrrnlx~r prr -v~n I. ZlM) rnTc>n ;and llDP cbrrn!r.r pn-.lin: is

5 111Torr. c.llckrl~lr tIw iosi,:nlion vflicirny ill RIE n..lrlcm ;m<1 IIDI' n~ielor; :tt nxmra 1 k . m ~ r . i -

tun.. TIIC ikmir.ntir,n r,R<ir.n<? cr Iln. r.,iio uf tlbr vlrc7mn ilensih. tn tlic dvn\ih 14 nir;!:ntlo

SOLUTION

s.lrcnc Pis Il,r prcrwrr in aim i t at") = IFnSYxl rnTont. 1'ir the wlttmv in litrn. n I < ibr "11

Ixv of zsnlw. n i~ 11~. qx- mn-l.ml I I I IRZ lilvr-itn~'m~~l.li1. rncl Ti' ila. r l ~ u l l l ~ t v ~crnp.r.~:~~r~, K. rc,*pl.rli\r.l!:

For lhv HIE r>~lenm.

= PIRT = ~ ? w ~ ~ m , i m ~ ~ ~ ~ n o v ? x ,MI = 1.1% x IOF ~,,;oI I,tt.,

= 1 1 6 . ~ l O ~ ~ ' x f i l ~ 2 x l f l ' - l lml

; hO\x 10".r.n,

lnniz~lion elTicil.no.= :IN'- IlP'iJ fix\ x 10 '',

= 1 5 6 x l t ! ~ - - 1 . 56~ Ill"'

I l~~rr lon. . 111)1, inn' 11111111 Ili<l~er ioni,.~tion c4Tidr.an ih.111 HIE.

Etch Mechanism, Plasma Diagnostics, and End-Point Control

pl:Lsrll;l f.~elki,,g is l~rwy.ss in w l ~ i c l ~ :t solid film i s r c ~ n n \ t ~ l :L c lwn~ i c~ l w.tctin~l vi th

mollml.sr;l~r ,,r rsritr,l.st;btc n,.lltr.d slnil~s. I ' l:n~n;~c.trl~i~~~i.;nfll~~~ cttla.ut<~xl or i n< l ! l<~~ i

R.2 L Chapter 5 Etching

tn t.lx..tyvt~r iota c e ~ ~ e m t ~ ~ l in a g..amtls discl~arge. T l ~ r basic etch med~anisrn. p l ; ~ a ! t , ,~~o~t~cw. :,nl(l cr~tl-~x>i~bt m111tro1 are intnuh~c'i~d l>rivfly i11 this section.

Etch \techanism I'l.~~tr~.t rtclunc pmrr(b in Rvi. steps. ;L< illustfi~td in F i g ~ r e 5.4 First. lhr r t c h n ~ ~ t speck3 I , Ernt~r.xtcyl 11 , tlar. pll~stni~. Thr n.:lctant is then t n ~ o s ~ , r t r d by c l i l ~ t ~ s i o ~ ~ t l ~ r n ~ ~ g h a sbo.

c,Lc I,, tIlC Nt.yt. t11r r ~ i ~ r t a n t is adsorlrtl 01) the s ~ ~ r l i ~ c c . I\ cltemi, n.,,ction (z,j,,,l; nit!, pll~sic:~l rl'tiyts such :u ion l)ot~~lx~rrIn~t,ntj f n l l o ~ tn form vol:tt i ' ~ ~ ~ ~ ~ ~ ) o t ~ n r k . F i ~ ~ i d l ~ I I I V C U I I I ~ ~ ~ ~ ~ S are d e s ~ ~ ~ I m I fmm the s11rf.m'. difins~d into the 1,)

.h

cnl ile

C,R 3tnd l > ~ t ~ n l ~ < l out I,? the \-~tcrnnm S!T~PIII.' F>I .~SI I~ ,~ rtcl~inc is l>:r~ed on thr gr:ler.~tion ofplmma i s ;I gns :,u;t lo\v prcssnrr. T\\n bn

b v * of tnrthmL\ an. IIXYI: PII\T~c.J I I I C ~ ~ I I ( X I S and rllr~rrlial m ~ t l ~ m b . The forrll(lr incltli yl~tttcr etrltil~~. :In11 tht 1.1ttc.r inchlclrs purr clrrnlir:~l etch is^. In ph!~icd etrl~ing. P( t ~ \ , . ions lmmlrar~l the sorf:tc~. at IliSIt spiv.d: snn;dl a~nollnts of nepti\r. ions k~nned in t l ~ p l i s ~ ~ ~ a cannot rwrh the \$afkr st~rf:t~t. and lll~refore PI:?\. no t l iwt mle in pl:~~nlaetcl~- i~tq. I n chrrnicll e t c l ~ i n ~ . 11e11tn11 reactive s l ~ i ~ , s s c * ~ ~ r r a t ~ d by thr pl:~sm;~ intenct Nit11 1 1 1 ~ nr,ltrn;~l s u t i ~ v to k1m1 \ulatile pmhxdr. Cl~enlinil ;ual p11)sid etch mecl~illlis~ns I I \ V dil&nwt rl~;~r.+a#~ristin. Chrlnic:ll etching ed~il,its a lti$ rtrh mtc allrl g~rx l s r l r r t i ~ i h (i.e.. tlw ntio of rtch r.ttt.s for diffrwnt rnatrri;lls) and pnxlt~ces low ion In~nbanlrnc~~t-inc111crd cl;tmn<r, hut !iclrlc isotrnpic pmfiles. l'lt!sic;ll stching r;m !ield ;misotmpic p1~r6lc.s. but is :n\rri;rt~l \\it11 Lnv etch scl~%ai\it\.;urd hicl, Ix ,~~~banlt~~est- induml ilarniqe. (i.n~hinatinnc of chrtnical and pl~!sicnl etcltine give ;misotropic rtch profiles, r ra<~~n:i l , l~ g w d srl' ti\i% and muli,n~tr ho!~ll~lK!lnrlll-in<I11~1~<l iLll;u~~;lge. h n e .umpl~ is the RII? pnrPss, n.11 nsrs a ph!sic;tl method to msist cl~enliod elchins or clrntrs reactive Ions to particip in cltrmicd etrllinc.

ec- ich ate

5.2 Dry Etching 4 93

Plnsmn Dingnostics 5lost prwrrsing pl:~s~n;is emit rtiiliatio~r in the nnxe frnm isfmrrd to itltnnialt~t. A ~ i m . plr ;in:ll!lil~ll t~v~hnilIar is to nlorrllrr the intensih of tllrse rlnisrions ~ ~ N I I ~ \ \ ~ : ~ ~ I P ~ ~ @ ~ ~ with thc ;lid of optir;tl cn~issinn sprdrnscop) (OKs). U~insob.;m.r<l spctn,l lualiX. i t is ~rrtmlly lnssihlr to ~ L ~ t e n n i ~ ~ r thr pnwncr afncutnd and ionic \~x.cir< I)! cnrrr.l:,tinC tllr.us rmis~ions nit11 pn?ioasl? d ~ t r n n i ~ ~ c ~ l ywtfid urirs. R~latirr! mscmtnlk)ns nftllr rprcics can in. ohtailad I?).corr~~l;ltil~~c!~anges i s iatensity\ritl~ lhr pl:em;~paranleters. TI~t.rrrli$- sion s i p ~ d ilc.rivvd f m ~ n tile pritn;tr). ~tclulnt or l ~ y p ~ x l ~ ~ c t hrfie.; to ria. or f:dl :tt t l ~ p r r ~ d ot'thr P ~ L ' I I y d ~ .

End-Point Contrnl L)I? rtc11i11g differs fro111 wet cllemicnl r t c l ~ i ~ ~ g in that dr).etching bas lrss etcll wlwti\.- it? to the ilndrrl!i~~g layer. Tl~errfore. the plaima reactor must lr ~ ( 1 1 1 i p p 1 \,it11 a mc~n- itor that i~~dicatc.s w l ~ e ~ ~ the r,tching p m s s is to ix. terminrtnl (i.e.. an ,,,ar17,0irl, i/d&iOn :::drrn). L w r intrrfrrolnrtv of thr wafer surfaw is esrd to mnt in t to~~s l~ n~onitor etch r.ltrs alld to drtermine the end point. Duril~getcliing, the intensity oflnsrr light reflmrrl oK a t11i11 film s~trface oscill;ltes. This oscillation wcurs kuausp of the pllase interfer- cncr hrtween the l i ,~ l~ t reflected from t l ~ r o~lter and inner intrdxws of the etchinc la!rr. ?-l~i.; l:l?rr must thercforr In? optically t m p a r c n t or rcmitrn~lsparent to o l~s~rve tho owil. Istion. Figure 5.5 sl~o\rr a t)pical si,qal frnm a silici~lrJplycnstaIIi~~~ Si <ate rtcl~. Thr period of the oscillation is related to the change in film tllichlers I)?

& I = 1 / 26 (fil

~ s h r l r h I is the change i s Rlm thickness for one wriml of reflected liel~t. h is the \r-a\.e- Iengtl~ oftlle 1.2Ferliglrt. and ,? is the refnctirieiti~r~oftllcla~cr hing~tched . Forex;~m- rile. &I for rml\silimn is 80 nm. ~ne,lrarecl In. usine a hc.liam-neon lmrr source for wl~irh

52.3 Reactive Plasma Etching Techniques and Equipment

Placnra reactor techno lo^ in the IC industv has ellaneed dc+nlaticaIly since the fimt application of ph.snla processing to photoresist stripping. :.I rractor for pla5111a etrhing c~ln- tnins a clcuum clraelber, pump systi*n~. paver snpply genrntors. pressure senurn. ps flow control l~nits. and end-point rlrtrctor. Table 5.2 slm\rs the similaritic.s;asl differrnrrs

Elcl~ llmr (arl,ilnn: tlnilcl

Figure 5.5 TIlr n,lolivc reflectmw of lhc rtrhing r!~rfao. of n m!nyostlr altnll<:,lwl!.>! e!vr T ~ , C m,i p o l rtrll is indic~ted I)? tlnr c~.s<rtinn of thr n.flcr.t;t!xv ~cill.di0~8.

5.2 Dry Etching 95

TABLE 52 Etch M.chsnim and R n u n Ranges of Plasma Rsscmn

t-!Lll l i W l ( ' ~ ~ ~ ~ l i ~ t r . ~ t i ~ ~ ~ ~ ICIvlt >l~~~l~:anis!~b I3rcss!!w I3:trty (T,,-h . . .

il, the bpps ~ f ~ t ~ l , i ~ ~ ~ ~ ~ ~ ~ ~ i p ~ ~ ~ ~ ~ t that i t r ~ m~n~nrrrially;~\~;tilablc~. I\ cornpsrison nf sllw opr;,ting m s c s and ion rnrrgirs fi,r diffrrent h p r s of r~actnrs is slai\m in F 5.6 E;trln rtclt t rnl is < l c ~ i ~ j r d e ~ n ~ i r i c ~ i i l l ~ nnrl uscs ap:ntict~l:tr r n n ~ b i ~ ~ a t i o ~ ~ ofprrs t4wtml r mnfimlr:tlion 2nd t \ p . and sour<%. freqttrnr? to control tllr hvo pliltlar) rnwI~;~~tisrn~-cl,~-~~~ic:J :tnd ~ l i ! s i a ~ . l l i ~ l l r r rtch r.rtcs and tml al!tom:~tion trr rrtl for nlnct C ~ C ~ I C ~ T I I Z P ~ in ~~lal t l l~l(~l l l r i l l~ .

Reactivc Ion Etching RIE 11:~s k c . <.\trnsivt~IY used in the rnicrorlectronics industn In a p:~r.~llel-plnte I

nxtcsn. ;I nirlio f r < . q o ~ n ~ mpncitivrly corlpletl lmtiorn rlwlmdt. I~r,lrl.; I!!? urafer. illo\rs t h ~ cmund~rl ? l c ~ t r ~ l z lo have $1 si:aifinntly largrr area h.crusr I! is. in file rl~ntnbrr itsclf. Tltr i a ~ e r qrouncl~l are;) cnrnhined \sit11 the lower oprnting pre I<irK) tnTorr) causrs tllr u;lfers to l,c sol,jected to a Item? Imn,banlm~nt o i rnel ions iron1 t 1 ~ pl;r<n,n s a result of the large negative self-bia at the n.afcr surface.

Tlw etch svI~ct i \ ih of tllis ?strnl is rcl:lli\rly low mmparc~d ~ i t l l 1r.alitional han etch ?strtns l rca~rse of siron< ph!ninl spnttrrinS. Hrnvwrr. s r l~ct i%ity ran ire illlpro\

I - I 10 100 Inn

l ' r t ~ ~ ~ ~ ~ r c . {n~l'nnl

Fipvrs 56 Cltmpiri'nm nf ion m e v and i>pCCatin< prrrrurr ranceri for clifirent h F s of ,"L*.lI.L v.<1r ,n .

I,? choosing the pmpcr etch cIi~.nlistry for rwn~ple. ~ > y pnl!~neridnq tllr ~ i l i ~ , , ~,,rl;,~~, \\it11 flllnrnc.lrlmn pnl!.mrn looblnin wkcli\ihof SiO,m,?r silimn. i\~lernativcly a trinlc. mnfip~nl ion RIE etch. :rs s l ~ m w ~ in F i p m 5.i. can scpante pl:lrmn prnrr.rtion fmrrt ion tmnrlmrt. Inn cnerpy is mntrnllrd tl~rnt~sl, r separate h i x o r ~ lllr \\afrr clwrmlr. tl.rrI,y ~ l l i ~ ~ i ~ ~ ~ i l j l ~ ~ t l ~ e 101s of srkr t i \ ih and 111~ ion I x ~ n ~ l ~ w l n n , t - i ~ ~ ~ I ~ ~ m ~ c l r l n n ; ~ ~ ~ obrmrrl in most lnrlitionnl lllE sylen~s.

Electron Cyclotron Resonnnn Plnsmn Etching hfost panllcl-platr p lml* elellen. e~cep t lriodc RIE, do ,lot p m ~ i d e the al,iliv to mn. lro! pl i~nln pxnslet rn such a rlrdmn enerk;. plnrnla density and m e a n t densityiwde. vn( l rnt ly As a result, ion I~nml~anlment-~~ICIIICPII damage l m ~ ~ l r s a seriolls prol,Imm. Tlrr (,lrcfrorl n/c/[~frnll TpPnllflnr~ 1ECR) m e t o r mn~l~ ines micro\%wrr p v r r nith a static o ~ ; ~ g ~ r l i c firkl to forcr clrdrons to circulate around t l ~ c mapetic licld line at m NISI,- lar f r rq~~rnc) : \\IIPII this frequesq eq~ialr the applird micm~~'il~,c freqsmc?: a rpsons mupling occlzrs I~ehveen thc ~ lec t ro~ l mrrg . and the applied r l ~ a r i c field that ws in ;t I L ~ S I I degree ofdissoci:ttion n~lrl ioni7atio~; (10-'for ECH rnnl~prs l uilh 10"' fi,r RI F i p n j .8 sho\vs an ECR reaction cl~anlber configurntion. \licrowave paver is cuey thrn~tgl~ a nlicrowvavr %\indo\r. into the ECR so~irce rcgion. Tltc magnetic field is s p l i d fmm the magnetic mils. ECR planla s)stenls ran also In. ased in Illin film (lr sitinn. High eflicienq in exciting thc reactants in ECR plamns allmr.s the clepnsitio~ films at room trrnperaturc \vitllout the nred fnr tbrrmd 8iclivation.

O t h e r High-Density Plasmn Etchers As icatnre sires for ULSI continue to drcrense. tllc limits of t l ~ e mnvcntional RIE s:x- tern are k i n g appmached. In addition to the ECR system. otl~er hpps of high-d~nsih plasma sources, sucll as the inducti\.el\f mt~plerl plania (ICP) soitrcr. the tmsfonner- . . . &upled plusma (TCP) source. m d surface \r-dve-mopled plnsma (S\VP) sourc~s. llaw been (le\.rlnnrd. Thrse etchers have hie11 nlanla densih (10"-10'' ern-') md lo\r. Dm- .~. . cessing pressltre ( 8 0 rnTorr). In addition, they allo\r~thr \~vf?rplrt?n to k p r r v r l inde- pmdcntIyof the source, pm~i(lingsipifirant demnpling iwhvwn the ion e n e p (\?xfer bias) and the ion flu (plsmn densit!; prinlarily driven I,! source pmver), Tl~c priman

Figum 5.7 ~ ~ ~ , ~ ~ ~ ~ i ~ ~ ~ ~ ~ t i , ~ l ~ waetiw ion ctch ne to r Thr ion m r q is scpan~tpl!. mu tmllc.d 1,). ;, l,ia5 ,x,~nse on t l ~ lntton> rlcctmlr. rl. radio fwclttrnrs

9% b Chapter 5. Etching

TABLE w ~ n h Chsnittries of DiNewm Etch Processes

\I.,tr.ri.J B..ln$ Etvir,d I?trhins Chrnlirtn

I k ~ p Si tn,nrl> IIBr/SFJOJS12,, ~i , ,~l lou 53 tm>ch lll3ri<:l~O: l',,l$ 5 ) IIUr!Cl.JO;. HBrlO,. RCIJ(:I,, SF,

.\I Bc;lp:I2. SiCljCI2. Illld(.:ll

.~lSiCu I3CI JCl.m, \v SF,, onh: SF./CI, l i ly SF,, onk \\'Si> liSi:, CvSi: CC:I:F.JXF,. CFJC:I> Clfi'jC'Jc,F,

SiO: CF)CllFJAr.C,F, C,F,. C,FJCO.C.,F,.CII,F: S i r , (:llI.'JO,. CII:F:. CIItCIIF:

of a DH,\\I crll. This snrfaw nrra can he reduwd I)? etclring trencllrs into the silimn s ~ l k t m b and fillin? the111 nit11 suit~ble tlielwtric or conrhctiw materials. Ileep trenclien, usu:~Il? \ \ i t l t ;I ilc,ptll greater tlrsn 5 pm, an. used mainly for forming s t o c l g capacitors. ~ l ~ a l l o \ r trrnclss. usu:illy with :I depth less than 1 pal, are often ~ l s r d for isol:itioli.

Clllorinc-l>asrd ;md l>rosline-l,;ls~d cllrmistries 11avr a lliglr silicon rtcll nltr and lliglr etclt s ~ I ~ c t i \ i h to the silicon ilioxi<h~ ~nnsk. Tlrr cornhination of llBr + KF, + SF, + O2 g ~ q n ~ i ~ t n r c r is used to k ~ n n n trench cnp;lcitor uith il depth of approsimnt,:ly 7 p ~ n . This urmlrin:ttio~i is nLw used fnr shallo\r trench isolation ctdling. &~ect mtio~l.;.~:~~~(lent etdz- i r ~ z ti.?.. wriation in r t c l ~ ntt , \~itlr aspect ratio) is often ohscn.c.d in cleep silicon trench etching. <x;llrsrrl bylinlitrd ion and nrrltrnl tr ,msprt witliin the trencli. F:~:ure5.11 s ~ O ~ T

tla. ~ l r l r n d ~ n c r of ;i\-cra~e silicon tr(?ncll etch rate on :&spect ratio. Trpnrlirs aitli la aspect n t i o ~ are etcl~r<l more slo\vll!. ttlrtin trencl~es with small aspea ratios.

Polysilicon and Po1,Tidc Gate Etching Pol,~ilicx,n or pnlycidr (i.c.. lo\\.-rcsisf.ln~~ metal silicides ovrr pnlpi~imnl is usu~llly used ;L< a <.ale s1atrri;il for SIOS deticvs. r\nisolropic ctcl~ing and l~iglr etch srlrcti\ity to the

Rguw 5.11 Dvpendmw of a~rrase rilimn trench rtch ntlr on a y d mtio.'

Kate orid? tllp 1110st i~nprtant r rqu i re~ l~~nts for Eat(! c t c l ~ i n ~ . F~~ prarnplr, tile srlp ti+. reriuirecl ill 1 6 IIRAhl is more tlran 150 (i .~.. the ntio of C~CI ,

for polyedr and gate mid? is 150:l). hrl~ic\ing lligl~ srlrc~i\it).nn(I etch a n i ~ ~ t m p y a( I),,. is diffictllt for nlosl ion-cnl~nnc~.r.d ~tclling prrxrssrs. nlercfore, lnllltjctrp pror~rsing is arrrl, i s ufhiclr diffrrrnt r t c l ~ strps itr the prMrss are optinbtd for rtrlt anirr!tmpy and srlccti\ih: On tlie otl~cr lranrl. t l ~ e trmd in p1.lrt.a t e c h ~ t o l o ~ f r ~ r w i ~ o t r ~ ~ ~ i c r t r h i n ~ ; ~ ~ d I1iq11 st>leaidty ic to utilbr ;I lm%.-press~~re. I~ igl~-~le~,si t ) .~ la~m;~ #sing s rcl:~tiwly Imr, pwt.r. l f r l~ l rl~lorine-haw1 and l~rominc-Imwd cl~r.niktries m ir uuvl forgate rtrhinS tn acliirqr. tile rr-cluircd ctcll anisotropy and scl(,didt!:

Dielectric Etching TI,? pnttcming of dielectrics, especially silicon dioxjdr and silicon nitride, is a kc,. prr,. cess i n the man~~farlurcof mcilrrn semimnrltxctor rlr\ices. BPC;~IISP of t l~ ( ! i r l l ig~~~r im~d- inp cncrgirs. dielectric etching requires agressive ion-mllanced, flttorine-b:aell rl~emistn. \krtical profiles are ncl~ierrd 11). sicle\rall pvsitstion, t!pically by intrwl~~cing n :;~rlmn-containing flolorine species to the plx~rna ie.g.. CF,. CIIF;. C,F,l. Htd, ion- homl~nrrlmrnt energies are required to rrlnovr this pl!mer layer from tlw ndde, ;o ~ r l l .AS to illis the rcaaivr species into tlie onillr st~rfarr to form SiF, pruducts.

h lowv-prcsrllre, higll-densit). pliama is advantnpous for a~prct rati~leprndent etclt. i~:r;. Ila\cevrr, the RDi' generates 11i~h-temperature electrons snrl snl)serlt~r:stl! gcnrr- atrs a ltigl~ dcgrccof rliss<xi;ttion of ions and mdicals. It genentrs far rnorr:~ctive mclids :~ntl ions Illan HIE or LIERIE plasrnns. In pnrtic~~lar. a high F mnwntmtion \\onens the 5% iectivity to silicon. \'ariu~~s mrthods Iiave h e n tried to cnhann tlir sel~cti\itin in tllr 1t:~lr-rlensity placma. Fint, a pawnt gasuith ahis11 C/F ratio. such as C,F,,. C,F,.or C,F,. U:L< attempted. Other metl~ods to scavrnge F radials h:~ve also h e n rlrwloped~

Interconnect Metal Etching Etclrinrr of a met:illi7~tion laver is a very iniwrtant step in IC hhricttion. Altrrninln . . , . mpper. and tungtrn are the most ppular mslrrials arerl for intrrronn~iion.Tllpre mat rials ~isrtallv re,l~rire anisotronic etcltine. The reaction uf darninurn uith flt~orine res!zlts . , in nonvolatile AIF,. \vIiicli has a w p r pressure of on!\. 1 Torr at l%ObC. Chlorine-bxs~rl clie~nistty (e.g.. a CIJBCl, nii~ture) I~as I m n \\idply used for aluminum etchisq. Cl~lorinr I l is a v e n I~iglr cl~e~nical dcll rate n4tb altrminom and tends to prdrrw an usdrrcnt during rtcl~ing. Carlws-containing gas (e.g.. CHF,) or Xi is a d d ~ d to Tom) sidntall p m - \ntion cltiring aluminum etclring to obtain anisotropic ctclling.

Exposurr to flip ambient is mother prohlern in ahnninum rtchin~. Residual dllo- rine on Ill? alunlinltln side~~~;LII and the p11otore~ist tends to read aith atmospilrric a , e r to fonn IICI. \r,lricll m m l r s nluminual. An in sitrr rxpsure of the sxfer to a CF, dis- cllnrgr to exchange CI \ritli F and then lo an o q e n discl~arge to rrlnow the wsist. follo\\?d by imnlediate im!nrnion in ileionizrd \cltrr. cm rliminlW danlinlial mmrcion. F i p r e 5.12 s l l o \ ~ ~ 0.35-pin TiS/,\IITi lines an11 spaces on a \wfer m:~int;lind at anlbi- ent for i2 Itours. S o mrmnion is present cvrn after l~mlongnl r \ p S U N ' to the :ambient.

copper Ilas dn,,a nl~rcl~ attention as a s ra r ~iict:tllbi~tios niatcnd in ULSI cirnlits

becallsr of its low rcsisti\ity (-1.7 R-ail) and suprrinr rrsistancr to e l ~ ~ m m i ~ i t i o n mln- pared ,,(th or ,\I dl~!~. ~ o , ~ ~ , v r . h a r e of th r low \nlstililyof mpprr l~:didrs. pl;uma etcl,ins at nmm temperatllrr is di~Xadt. P m s s teinperat~irrs l~iplrrr thaa ~ ~ " C req,,ir(.rl to rtell rapper f i ~ , ~ , ~ . ~ l , ~ ~ e k ~ r r . tIier/rrnrn.vcrn~. p r w s s is O S ~ to foml QI illtisr- mn,,rrlio,l ,,jtlloltl ( ~ ~ , ~ t ~ l , i ~ ~ . D ~ ~ ; L W C pmrning intnl\rs tl~r emtion of i n f r m l l n ~ t litles I,\. fint rtel,ing a trench or cxu1al in ;t pl;rnar iliclrclric In!rr.ud then fill ill^ tll;lt t~"lr1'

,,jtll n;rtnl, sllcll ;Is al,,,nint,nl orcoplwr. 191 dnal dmn;ae*~rr pmssi l lg (Fig. 5.13). a set'

onrl lc,cl is in\.o~yetl , , . I , ~ ~ ;, srrin; ~fItolc.s (i.r,.. mnrarls or an. ptcllnl :md fill^'

in .~d<litinn to fltr trrnclt. hftrr fill in^. l l ~ r mr ld and dirlcctrir :ire pl;tn:trixed hycli i,.ol ,,~,.cbo,zi,ul ,,olrrhirz:: iC\IP. rrv C11:lptrr hl. TIw n i h s n t ; ~ c ~ ~ o F d : i ~ ~ ~ . ~ ~ w n r prm i iqi< tlt.tr it ~litnttutw lhc, n ~ d fir ilwkdrtrh. This kan in\prt;alt c.011~~~nl :s t h ~ inti1 n8rnt.s imrn :d!trnlirtttn> 10 mppr r int<~~m!ln<.Ctiorl~.

5.3 Etch Simulation 101

, l i Y 1h:tdc.r I.,,...

L*,\v-prms~~r(. C\'D (LPCI'D) tangslm (I!') lax I r e s niilcl? I I W ~ for fillirtemnt:trt I~olvs a ~ ~ i l first-lwr! nlrt;dli/ation 11rcausr nf its rxwllrnt drlx,rition c~nfonn:,l,ilit?. Rotll Il~~orirlr- ;mil d~loriar-haqrrl chrn~irlncs etch \\'ar~<l fom~ \nl:*tilr r.tc11 pmlt~n5. ,\rt intpor- tilnt tmtnsst?n rfc11 p r w s s is t11(~ l~litnk<!t \\. et~lll>ilck to fimn ;i \V plup. TI,? l,lallk<*t l.l'(:\'D I\. is d(.posited on top of a E N banicr l:?\pr. as sl~rnw~ i n Fistre 5.1.1. A ta.0- strp p r m s s is ilso:~lly I I S P ~ . First. 90% of t l l ~ \\'is e t c l ~ ~ i l itt a Iti~11 vtclt rate. :md tllet~ 1\11. i.1~11 rate is r ~ ( h ~ r r c l m rrnmovc. llrc mrnnini!~~ I!' nitlb an ~tvllnsl that b:u a lticl~ \\.-to-TiS selrcti\ih

t 5.3 ETCH SIMULATION

- ~ ~

rnantl. ,rhicl~ .~llo\vs tltc user to r t c l ~ all or part of ;tny $vm I;t?rr at tllr top of tlnr cur- renl slnlPtore. If the rnntrrial at t l ~ c lop of tile stnzrturr is not the inntmial slx.rili~cl. tltrn no ctclting talirs pl;mm. If tllr alnount to lr rtcl~rd is not s p i l i ~ d . t l ~ r r ~ tllr cotire I:I\.P~ il: rcmowil.

EXAMPLE 3

SOLU?lON SIIPRI:\I i~>ptst listing is a< folln\+

TITLE COYHENl INITIALIZE

COUlENl DIFFUSION

C M E N l DIFFUSlW CWENT DIFFUSION

COHIENl DIFFUSIOH C W E N l DIFFUSION

Etch ing Example Initialize r l l l c o n r u b r t r n t c

<100, S i l l c o n Phosphor Concentration-1.16 amp furnace up t o 1180 C over 19 n i o u r e l i n N Time-18 Tmperaturc-980 Nitropen T.rate-20

Or i d i ze the wafers for I n i n v t c r a t 11W C i n cry ur Time-5 Tempcrarure.ll0e Or@2

Ox id lze t h e wafers fo r 120 minuter a t 1180 C i n r t 02 ~ i w - 1 1 0 ~pnperarurc-1180 Wet02 o x i d i z e the wafers for 5 minute. at 1000 C i n d r y 02 7inc.S ~ m p c n t u r e - 1 1 8 0 OlyO1 R~~~ furnace d m t o 980 c over 10 n i nu t c r i n N2

T~.C-IO ~enp~ra turc-1108 Nl t ropcn T.rate--z@

I I U - Chmter 5 EtcLI,19

,~l.c-n. , I , is 111,. ~r,?t~vtktr*tio#l of F atoms i"m"I. T the tt~8nprahtw iK1. :mrl E. m d H tl,,. .,,<,,~dtt,,rt t.nt.v $ 2 45 k~- .~ Ihn~~ l~ ~~ncl *L, m>tt-k~t (1,997 e:d.KI, ms~xvliv~~ly. l f n r i ; I . ~ , ~ l ' . ~ ~ l . ~ t ~ . tllr rwln mtr ofSi rt nwun le~npcnhtn..

;. .;to: rtlti.d I n F rtwns ntt~ld itlw lx. cq>n.rrrd

~ t ~ t , ,, ,mllnin, = o.61.1 x iO~",a,.x l'"'rxpl-E)Rn

,,hqn. n, ;, 3 ,,.,,, - ? E. is 3.76 k~;tlItn~~l. C;ilo~l;~lr the ~ t c h ralt. of SiO: ;and .tch r..l.+-ti,it~ ol'sio? orrr Si ;at nxrnl trs~lwnltl!n-.

S, \ ,,,,,ltiplt..,l,,p e tC~I l)nlT,ss i- rrqlliml for rwlninl: s polpilims gatr s i lh thin g;ttr oddr. ~ l ~ . , d,, !,,,, <),3irm Rn ,.trlt pnwTr thxt 1v.a r x r micr0m;okin~. b;rs :tn anisolmpic ctrh ,,mfi~,., as,^ i, ,r.~rctiv* to thin q~tc. o ~ i d c ' ~

9, ~i.4 tl,c ,.tch u.l,cli,i~ nrl,,inyl to ctcll a . I i n -~~m pol\silimn 1;hyc.r \\itla>al remming T7t<,ry I I ~ . ~ ~ I nrn ,,K its ~ ~ r ~ ~ l ~ r l ~ ~ n c $:+tc midc, ;tsstntnine th:3t the l w ~ ~ ! ~ i ~ i ~ ~ l ~ is ctc11<~1 ~ 4 t h 8

rmx..*' l,.b,i2,c :, 105 t~t'~l~.c~tt~ ttnifi>r8rnit,

10, ,\ I . ~ , , ~ film is d,.ln,utlrl :, flat field oxide rrgion :and l x ~ t t ~ m ~ . d nith photo~~sist. ,he. tllr.~,Ll is thrn rtc.lllrl uith ;, in~irtan, o l RCI:Cl, lyaws at a tenrpvralt~rr ol i i l°C in a I ~ ~ I , ~ , , , c,lrl,cr nu. a.l,rti\ity "K:\l <,rrr phrrtansirl is m;tint;~it~ccl :kt 3. :Asntminu r 306 o,.,.mtcl,, ,,hat is tl,,. n8irli~7nstn p l ~ ~ ~ t ~ ~ r e s i s t thicko~c~s rcqt~iw<I to erl\urc t h ~ t the tap mrt:tl ~ a d a c v is not ; t t t . ~ r k ~ l ~

11. 1. .,n E<:n Irl:~rte~. :L st.~lic m:pclic lirld R k,mr dcxtrons to circalare ,xnrulrl tine m a r n,.tir l;cl,l linc.s ;tt m artpll;s inrinene!: a?. llnnt is girrn

o = qRhn.

\ rhm y i\ thr rlran,nic chaw 2nd na. the rlrctrnn sn:r\s. If tlrr micrwr.nr ircqamcy is ? 4.5 (:llz what is the rrquin.d magnetic nckl'?

I?. \\llrt :ur thr itl:ajor d~rtinaions luhveen trnditionnl rcactirr ion rtrhinc m d l~ich-d~nrih pl.lmmn elchin< IICCR. ICP. r tc -P

13. ~ x ~ t i l ~ . lanv to ~ [ i m i n a t ~ the mrmsion iwlrrr in i\l linrr after etchins\sith chlorine- ~ S L Y I pIsnn:a.

Diffusion

Impurity doping is the ilttmluction ofc~etmllc~laamounborim~uri~do~ants intorem,. m n r l ~ s t o n . The pnctical 11% oolinip~rrity doping mainly hxs h e m to d ~ : t s ~ * x tllp elrari- cd pmpett irs of the s e~ t i iwnr l~~c ton . Diffttsion anrl ion impl:xr>tation are tllr hbr, kc? tnrt!~ocls o f impurity duping. Botb dilllsion and ion iniplantation are ltsetl for lablicit. ing d i s c r r ~ e rlevicrs and ititegrnted circuits l ~ n u s r t l ~ r s r p r w s w s gencnllv complr. ~ n r r ~ t r i s l ~ otller." For rxamplr. diffusion is t ~ s r d to form a drcp junction (c',g.. a h,in well i:t CMOS). \vherrac ion implantation. \vhicl~ is discusse<l in Clvapter i, is uretl to form .I sl~nllnw junction (e.g.. a sourcrl~lnin junction of a hlOSFET).

Until t l~cear ly 1970s. in lpur ihdoping\w dose mainly I)ydi&~sion at e l rva t~d Irm- p r a l a r r s . ;LC sho\vn in F i q r c fi.1. In t l~ is inetl~ml the dopant atolns nreplacwlnoaor near t l ~ps t~ r f ace oft l teuxfer b)dcposition from the garpliwr ofthe dop:mt o r l y u s i n g d ~ ~ r l oxid? sources. The dopins mticentration decrrares monotonically frotn the sa&rcr. ;md tlte profile o f the dopant distribution is detrnnit~ed mainly II? tlte t rmpmta rc and diffusion time.

6.1 Basic Diffusion Process 107

i f ) I I I C c u tnktur~,. [:or <liililsi,,,~ it1 i l imn. lu,n,n is tllr amst popular dop:~nt for i n t r o < l ~ ~ c i ~ ~ g a ))-t!.pc

imp,,rih: ,vl,t.r,-;ls .,nrtlir pl>aspltoms ;ire I I S V ~ crt~.nrivt.ly :IT 11-hp? dopants. Tllrsc tlnr,~. r l~,n~t ,ntr an. I,iSI~I\- snl~~lrlr i l l ~ilintn: tla.? IPXP snl~~l~iliti(-s : ~ l ~ v e 5 x 10"etn-~ in tl,,. ,lifiaion t~.lnpr.ltllri. olt,<t.. TI~PSP (Inpants <:in l r in tmlun~d in sevrr.d \\;ns. includ- I I B ~ soli~l courcr7r ,r.:.. RX for I n ~ r ~ n . .AslO, Tor i m ~ n i c , and P _ 0 7 lin I > ~ l < ) ~ [ l ~ l ~ n l ~ ) . liq- Itid SU,IRY>F iRBr,. .\s(:I.. s ~ l POCI;I. :ind C:L<I.OIIS soIIrcrs (R,li,,. hsll .. and PllJ. I lmnvc\-t.r. liqll icl scntrcrs are tnwt <01111110111? ~ ( . d . A scI~r!n:ltir <!~:LET:IIII of ~ I I C r t~maw :lncl e:ls fin^ . ~ r n t r ~ ~ ~ . ~ t w t l t h r a liltlid soarw is s l lo \ \~~ in Fi3trr fi.2. This arnngemnlt ic sin~ilar to tlnt w ~ u l for tl>~nrtal o\i<l:~tioa. ;\n ralnplv o f t l ~ r d ~ e n ~ i c . ~ l reaction inr ~IIOS-

f i t - P.O. forms 3 cl:~~r-on-silicon u ~ f r r ~ n d is t l~en rrduced to p l ~ o s ~ l ~ ~ ~ n ~ s I)!. silicon.

?P,O; + 5Si -t 4P + 5Si0, i?l

T1w phoVhmn~~ is rele:~rrcl and diNuses into the silicon. an11 CI1 is vented. Fnlr <liNitsion in g:allinrn nrsrniclr. tlw hie11 \-:ipnr presslnrr or arsrnic r c ( ~ ~ i r ~ s SF-

<in1 mcth<xls to prweut tlte loss o i a n m i c h ~ r l ~ r n n ~ ~ m s i t i o e or e\?lpnr.ition.'Tl~pse meth- 1x1s incl.ln<lr ilifhtsinn in 5r.rlnl ampules \\it\, an nvctycs$ure oF ammic a11d riihsion in ;in oIx.n-ti~lw~ frlmacp \\itlt a <loTKrl ~ x i d e capping layer (e.e.. silicon nitride). hlost of tile sttldivr on p-t\pr <liNr~<ion lravr h v n uonfizad to the {IW oiiinc in the fnnns ~TZII-GR-.~S

6.1.1 Diffusion Equation

DiNtlsion in a ser~~i(nnrltlctor can lr \ir~~ali;.*.rl as the atotnic tllove,,lp,,t orlllp difl,ls:,,,t (c!npollt :ltom~) in tl1e cqr;t:tl latticr I?.\ac~a.andcsor iaterrti(ials. ~ : i ~ , ~ ~ h . ~ dro,,r tl,r hvo I>:r5ic atomic di%~sh>n nlrxlols in ;I solicl.' 'Tllcapcn circlc5 rcl,ww,rt tllr. host ~ , t n m s Im,.

p!ing the ~quilil)rinm htticc pnsitions. l l ~ e solkl dots rcprrsrnt imporit\. :,tomr.

vntrd trnlpr~lttlrrs. the lnlticc atoms vilrate aro~lnrl tile cluililrriulll l;ltiicy. ~ 1 , ~ ~ ~ is ;i linitr probability that a lmst atom will nnluire suficipt~t cnrrw to lc;lr.~. tllP lattilv sitc an11 I r m ~ r l e an intrntitial atorn, tl1rrel~~cre:ttin~a\3*im~.\\la.~,:~~ei~l~k,ri~~i,~~,,. rihatom ~ n i ~ l t e s to tllr \;iculqsitc. a illastmtnl in Figtrr6.k. tltc mcTltanisrrr is ctllNl c m ~ t c y d$fit.sios. Ifan intentitid atom mows fron~ one plaw to ;,notCr uitIlaut WW,.

p)ing a lattice site (Fig. 6.31). the rnrcl~nnisn~ is infen.rifin1 rlifit.~ion. ,\n ator11 smallrr tll;trl tllr h o t aton1 oftrn moves i~ltentitiallr

Tile hz ic difi~sion pmcessofimpuri~~tonrsissimilar totl~at ofchnrercnien idPe- trolls an11 l~olrs). 1% d~fi11c a fllu F rrs t l~e nanlb~r ofdopmt :~ton~s p;~rsing t l t r n \ ~ ~ l ~ a unit area inn unit tinle allrl C as the dopant macentration p r unit wlll~ne. \Vt. tltrn ltave

\vl~err l l ~ e propnrtionalih constant D is tl~r ~/ifi~.~ion roflcienr or di/li,.siciry Notc that tllr h u i c rlridng fort? of the diffusion process is the concmtntion gradient XI&. Tlte f lux 3 proprt iood to the mnccntration gradient. an11 the clopant aklms $\ill move (dii- 111s~) au.:iy from a Iiigb-concentr.~tion region tnwrd a lowrr-concentration region.

I f \ v ~ s u h d i t ~ ~ t e Eq. 3 into the one-dimmsional mntitllrih equation nndrr thc mndition th;tt no n1:lterials are fom~ed or mns~lnlrd i n tllr host sr~~nirnndl~dar. we o11t;lin

\Vl~m tllr mnccntmtion ofthc dopant atoms is lorr t l ~ e diNusion menidrnt cnn I]? mn- sidrred to be independent of doping mnnntntion. nnd Eq. 4 lxcnrncs

Equation 5 is often referred to XY Fickk dilfirsior~ rilrrofiort or Firki 101

(0) (h)

Figurn 6.3 n,ml,:,nisn,r for 8 htn-dimm\-ionnl latticx.' ' in' V;ccan'r in(%'Il:l

n i \ ~ n . (h ) Incrstitial ~tr.rl~imis~n.

6.1 Basic Dinusion Process < 109

nl,rrr D is tb,. ~Iiff~~sion ~rf l ic ient in cm'fs c~tr.~pol:~trd to infinite t e r i ~ p n ~ t ~ ~ r e , and . ~. ~~ ~~

E, is tlbr ;arti\ation mPq- ill r , or tllr intPn.tjti.J clitTtsiorl eludrl. E, & n-l i~t~l to the rnc@rs qll ired to Inow dowt

stoms fnlll, intmtiti.,l to anntlter. Thr \;dnrs of E, nu? fonlld to lrhveen 0.5 2 ,.\.in hot), rilicy,rn ;rnrl c:Jlitaa~ mrnide. For the \;~nno.clifiaioa nlmlel. Ed is related

to hot), tile rnrrojrs of lnotinn ;and tile v~tergies of fonll:ition of \ncancics. Tbns. E, for \ar.mn. ~ l i f i ~ s i ~ ~ ~ is I;lrqer III:~II tlnt for intrmtitii~l diff~rsion. ~~su:dl! brhv?rn 3 and 5 e\!

IWT IR-'I I W T IT')

In) ib)

figun 6.4 Difl!aion cnellkient idw called difieivityl as a function of the reciprocal or tcm- prantrr for i,~i dim" nnd (hl ~xlliwn awnirlp.' '

Fr,r h q t cliff~~sants, sltcl~ ia Cu in Si aecl GOAS. sho\~m in ~ I I P ttpprrprti~r) of Fip~rcr 6.40 and 1,. tltr mnwurrd activation cnrrpir.s :lrr. Ips? t l~i~il 2 (.\: ibncl illt(.rslilial alc)n~ir rncnc~r~ent is 1I1f. ~lo~nillant rliffmrion inwl~;t!~isn~. For sln\v rliNt~s;t~~ts. sna.ln :IT A% i l l Si aid GaAs. s!ln\%m ill lllr Icnvcr plrtioll of i7iplres fi.4n allcl h. C. is 1:trgcr tlanl, 3 P\: nsrl ~ l c a t l q ~~iffllsiol~ is I ~ I C I ~ O I ! ~ ~ I I : ~ I I I rnecl~;~nis~l~.

5.12 Diffusion Profiles

Tbr dilTurion prnfib. ofthe dopant atoms is dependent on t l~e initial and hottntlat?. rrm- clitions. This slllxrdion rnnsiclrrs hw ianpnrtilnt cmrs, nanlclx mnst;111t stdrl:tct. con. centration diff~~sion alal mnstant total d o p l ~ ~ t ~lifitsian. In tllu fitst ca%r, itnpllrity:ltotes :ire transported from s mpnr soltrcrt o ~ ~ t o t l~e s ~ ~ ~ n i ~ v ~ ~ ~ d t t c t o r sttrF~r(. and diN,lrrc\ intr, tile rerni~~)nl~llctor unfrn. Tllr \apor murrr m;lint:~ins a ronstiirlt 1cvt.I of s~trfa~v mn- centration during tlie rntirr dilTusion prriml. In t la . srmnd cse. a fired ;tnto~st of<lop;tnt is drposit~d ontn the srn~imn<l~~ctor s~~rfztrr and is s~~l ,s r~~~irnt ly ~lif i~srd into t l ~ r \v:dr.rs.

Constant Surface Concentralion The initial condition at 1 I 0 is

\v11icl1 states that t l~e dopant mncrntn~tion in the ilost srmimnd~~ctor is initi~llv TA,W. Tl~p boantln~?. conditions are

and

rip atonis. T l ~ r sol~rtion of Fick's diffi~sion eq~~i~tion illat satisfies the initial and b o t ~ n d a ~ mn-

ditions is given h!!'

svl~ew erfc is tile mmplen~entav rrrnr function and \/i;; is tlie diNusion lrn$ll. Tllr definition off rfc and some prnlxrties of tile function nrr su~nniariz~d in TaI)le 6.1. T l ~ r clifi~sioa profile for tllr constant s~~rfacc wnceotration mndition is sllo\n~ in Fiplre 6,:xi. \vl~icl~ plots, 011 hotl~ linrar (upper) ;lncl logarithmic (lower) sc:d~s. thr norn~:tli;.wl mn- cc~ltration as a fnnctiori of deptli for tllrw valucs of tllr difitzsion lrngh mrrt,sponrli~~g to tllrcr collseclltivc dilfusion tirlles ;lnd a f~xrd L) for a given dimlsion trnIlwr~t!!n.. Sol,. that :a time pmpssrs , l l ~ e 11opnnt prnetrxtrs drrprr into tlw sr~~~irnad~~ctor .

The total IIIIIIIIIP~ of (Iopat~t atoms per unit nr1.a of the s~~tnicr,ndnctor is Sivc~n 1)y

Sullstitnting Eq. 9 into Eq. IOjieIcL?

6.1 Basic Diffusion Process 4 1

This c.rprrssion ctan hr i~a~rpre t r r l a< follous. Tlar q~~ant i ly Q( t ) reprrsrr,ls the area under nnr of tlat- difli~sion pmf i l~s of the linear plot in Figure fi.51. Tllesr prnfilcs can be appma-

imatwl hy trinnelrs nillr hriglrt C. and bmr 2 f i . This lrnds to Q(t i z c,*. wlaicla is clmr to llw rxart rrstslt ol~t:u~~rrI fro111 Eq. 11.

;\ rrldttd quanlih is l l ~ e gradirnt of t l ~ r (lifftrsion profile Kt&. TI,? r(mc1ient can b ohtaincd I,! dilli.n.otiating Eq. 9:

EXAMPLE 1

Fur tx,mn ilifitsi<,n in rilio,n at l(WsC. thr s~tf iaw m,ncrntmtir,n is maint:~inrd at 10"'cm.' .kncI tllr <lifi~-icm time is I hour Find Q(f1 snd the gndivnt at r = 0 and at Imxtion \\.hew thr 111p:ant er>ncr.ntr;~tinn rrwhrr l0'"crn.

SOL(ITI0N Thr clifT!mion awlliricnl of h m n at IiKKIDC. as ohtainc~l fmnn Fiqarr 6.4. ir alnllt 2 u I l l ' rm':s. sn lhr clil>-!z~inn I m ~ t b ir

.. lo '

0.1 pm

0 1 2 3 4

Figurn 6.5 DiKusiota pmlilrs. (a) Normali;.cd mmplmtcnt~n ermr htnetion \mnu clirtmw for s~rc~~:~s iv r dini~sinn times. (b ) Sormrliml C.anssian bnctim vcmu rlirtmre.

\\l,rn C ; LO" cm". the mrresparlding distmcr r, is piw'n 11s Eq. 9.01

= 2fi(2.75) = 4.66 x 10.' crn = 0 4mpr

Conrlnnt Tolnl Dopn For tl~is cacr, n fixed (or mnstant) nmol~nt oldopant is rlrporitnl onto the sc!nlmnrlt tor rurf:acr in ;I thin I;t!rr. and the dop;ant ~ ~ ~ l ~ s r ~ ~ ~ e ~ ~ t l ~ d i f l ( ~ s r into 111r scnaimnduct Tl~e ia~itial conditioaa is the sanir ;N in Eq. 7. The. Ixntnd:~n m~lditiote aw

6.1 Basic Dinusion Process 1 I:

6.1.3 Evaluation of Diffused Layen

Ftsln. 6..% slmts tltr clolrult lm,lil~ for a Gntr\\imi rbstrihr~tion un \rluirl! the nornldii.nl ~ ~ , u c r . ~ ~ t l t ~ t i ~ r n ,C/SI is plc>ttt~l ;ci ;t finnetion oi t lw dist;lncx~ ior t l tn .~ iu>crrai~ug diNt~sion Icn$llr. Sot? llrr r r~ lua icn of t l s . s~)rl.rrr mncvntr:,th>~> . ~ c llrr <\ilfitsioa timv i~rrc:~ws. TIII Lx7.alirwt of thv clifliwion prr,file i.i ubk~inrd I,! dilT~.r.n.nti;utin: Eq 1.4 and is

TIIP qa7rtll&t lor slope\ is z rm rt x = 0 and ;kt r = -. and thp mxYiu~?om !zrarlicnt oc~11 I = \ I n .

111 intcsr.stt.d circllit p m s s i ~ ~ q . ;* h\r,-stvp <lilTitsinn prrrcss is mnumonly use \r.lrirl, a pn~~/c,,r,~iti,r~t difft~srd l;yer is f i ~ t i o m ~ r d nrudc.r thc rnntant n~rft~cr m r tmtion cnnditinrt, Tl~is step is i o l l n ~ v ~ ~ l I,! a ,l"rc-irt cIiff\t.iim~ i;tlso rallwl n,di.vtril>~ ~IiKucinn) undrr x mestsrut trrtal dop:uut couu<lition. For ,nost pr.lctic:il eaqes. thr I

siw) Ikng l~ \ Grr tlw prp<le.lmsitintl ~I iN~~sinn is I ~ I I I C I I s n ~ n l l ~ r 111:111 ~ I I P diNnrinn lr for t 1 ~ . (lri~r-in diffi~~ion. T l ~ m f n r c . tla. pn.dcposition profilr can h r rr~nricIc~rt.d n htndioll ;lt tltc sllrfitcc. lnrl tbr cxtrnt oitltt. penrtr:ltinn oillle prrt!qx,silinn profill Iw nyiunlrrl to I,? ~ttylizihly S I I ~ I I mmp;arrd \rill) Illat oftlw~ find prolil(. t11:it rrstllts .. ~

tlw ,lrivc.-itu stt%p.

EXAMPLE 2

SOLUTION

TI?.. u,ltllion lo ibis rrl~x;dicm mn I*. <lrlmninr*l hy 1Lt. m,<r p i n t nf cq!lslinn $ = I 11": = I l l l r l r - \%ill ll>rn.forr, I = I I'XI stwad<. or rpprnd~tlalvlr LO rninutcr.

TI)? rrs!~lts oiza diff~lrinn pmwss n n nv r~ l l~ ln t r r l Ily Ilarer ~ n r : ~ n ~ r r ~ n c r ~ t s : Ill? jl~nctinn < I ~ p t l ~ , 111~. sltcrt rcsistanw. :~nd tlie ~lnpa~ut pmfilc of tlw dilfuw~l Iayrr. lit,. jnjt,~iio,, rlr,pll~ can i r drlinrnlc~d Ily cl1tling:l grnovr it110 1111. srtsiconclt~ctor :arl ctc.l~ine 11)t. stir.

f ;ac \r . i t I~ a soln~tint~ (r.g.. 1IW) cnl' Ill: ; s ~ d n fiw drops of IISO, for silicnni tls;tt stuns tl,r p - 1 1 ~ re,gion d:~rker ll~;a! t l ~ c 11-hpr reginn. :rr illustratrcl in Figntrr 6.h. If ! I , , i.i tla. r.ldit~s of tluc tucrl ~isrtl to fonn the CmWC. tl1(.11 tl~r junction <lrpIll x, is given IT

,r, = ,- - ,@2 (171

\\.l~en. o and IJ are indici~tcd in 111" f igur~. In aldition. if 4, is xn~trl\ lsrgur than o rnd I t l r n

Tllr jllndioa rlcptl~ x,. z? illustrated in Figure G.rh, is the position wlwre tlur dopa, concrrltt-ation rqodr tllr subrtratc concentralion C,,. or

C(x,) = C, (1%

Thus. if tllrjullction drptll and C, are kno\vn, tile m&tceronrt.ntration C, ant! tlnc isnpqr- riy clistrib~~tion can he ~Jcn la t rd . prnvidrcl tlue dillusion pmfilr iollo\n one or the otller simple equation drrivrd in Section 6.1.2.

Tlur rpsi<tanre o i a difirswl layer can he rnrasuml hytlle fosr-,,oitlt p m b ~ tedtnirpse sl~own in Fiparr 6.7. Tllr prohcs nrr rqrially spam.rl, I\ srnxll currr~,t I from n msslant- n ~ r r r n t sntnrcc is pxwrd tl~rno~lu t l ~ r outer tunpmlrs, andawltap Viq rne;a~~mlhrh\wn tllc inner h$n pmlrs . For n tluin srrniconductor sample \vitl! 1lrirLness \\ 'tl~nt is mn~cb sm:iIlrr titan t l ~ r sample dinmrter d . tltr rmi~ticify ( p ) is @vcn hy

\\.llrre C F is known :LS tlur corrrction L3etor. The mmcrlion fi~dor rlrlvntlc on tltr ratio ofrlls. n.lurre s is the p m l r spacing. \Vluen dL$ > 20. tllr eorrrction kctor epproaclurs 4..%.

p.Si I I I I3 lbl

~i~~~ 6.6 jllnrtion.dcpth mc;L,,,n:tnmt. (01 CnminS and staining. ib) Pwition in ~ ~ ~ ~ i ~ ~ l l

<lc~p;%st :rind ~ ,~ l~s tmw c(,ncl.ntr.lli(lns an. e.r]!l:d.

114 + ~hrmr 6 D!fhrrion 6.2 Extrinsic Diffusion 4 I 1s

f i p a 67 Slr.~rtmw~r~rt~t of n..iismity usins :t lot~r-pint prohr.'

The shn,f mi.vmnre lR , ) is relatnl to thrjuection depth (x,). the. carrirr mnhilil >vllirll i< a ftlndion of the tohJ impl~rin mnwntr.~tion). and tile irllporih distribstion hv thr follm\in< e\~rrssioIl:

ly (1. I Cir!

For :I @WII diffusion pmfilr. thr a\.entge resistibih (P = R,r,) is nniquel? related to the ssrf.lw mnwntmtion (C,) iind thr sul>str.tte doping mnwntration for an a r s r~~ned dil- CInsion pnlfile. Desiml clxmes nlatine C. and P 11w.r been calculated for simple ~kNusion

sUclz ik* the erfc or Gausrian rlistribution.' To use t h e s ~ cnwcs mrrectly, we must he sure thnt thr dilfusion agrre uith the a..sumrd pmfilrs. R > r low conwntra. tion and clcrp diN~~cions. the diN~~sion profiles generally can IE representerl I>? the afore- mentioned simple CInnctions. Ilowrwr. as ~liscussed in the n p a srction, for h i ~ h mnn.ntr.~tinn ;u~rl shdlmrr diNnsiom. the diNusion pmfiles nnno t In- reprrsented hyt11e.s~ silnplc functions.

Tile dilli~cion pmfile cnn h= mea~lnz l l~cing a n@t;mm-\altage tc~frhnique. The ma* i h n n i e r pmfile (ni . $vhich is equal to tile ilnpllrih pmfilr if ilnpllrities are ful!\. i n n i d . GUI l r cletrnninrrl I? mr;\surinz tllr rrrrm-hi= (ilp~citanw o f a p - n junction or a Scl~dtLy lx~rrier d i ~ l e :u a hxnction of the applirrl roltage. 31 i s is due to tlle r~lationsllip"

rvhrrr q is th r charg- of an electron. E. is the prnni t t i \ ih of the semicond~~ctnr. n ~ l c i t ~ s n ~ p r r unit arra o l the sample. and V' is tile applied voltap.

:\ more ~li~hOr.ate n1rthn11 is 111~. secnnd:~ryion mass s p ~ t r o s m l > i c (SJMS) trcllniql~e. rvhich me:lrl!rrs thr total inlporih profilr. In the SIhlS trchniqllr, an ion beam splltten n ~ a t c r i ~ l off t h r s ~ ~ r f a c r of a sen~icnnductor. ant\ t l ~ c ion cnmp,nent is detected anrl mas analynl . This t ~ h n i < ~ t r r ha.$ hie11 msi l i \ i ly to many elrmcnts. sllch a.< boron m d a r and is an ideal I M ~ for p rn \ id i~~< the pr~cision ne rdn l for prnfile s ~ r a t r r e ~ n e n t s in mnc-ntration o r shallmv-jc~nction diffusions."'

W 6.2 EXTRINSIC DIFFUSION Thr rlimlrion profiles d e s c r i k l in Srction 6.1 are for constant difi~si\ities. nlrrp Prcr file5 n n l r 4 t - n thr dopin< mnwntratinn is l m v r than the intrinsic clrrier mncnl lm

lion (11,) ;It tllc clifilsion trtnprral~~rr. For cam~plr, at T = I ~ " c . ,,, rr,,,n15 5 10" rm Tor ilimll and f, x LO" rl!li' lor ~ i ~ l l i a ~ n a~st.nid<.. .fllr difl,ni,ity ;,t lnr cq,,wntrafi,,,,r

is ofil'n nbfrm.ll to as tllr itlfrinrir difir.,icily. IJnping profilc.~ tllat evnn.,,frati,,,,, Irss than II,(T) tirr in 111~ intrinsic diff~lsion region. as indic;ltnl i n t l l r lrrt siclr. of ~ i , , , , ~ 6.8. In this rcpion. thv r c s ~ ~ l l i ~ ~ g clnpnot prnfil~s olsrqv~rn~tinl or sis,llt;lllm,,r di(r,,,ions of n- and p-t!lx. i~npllritips GIII Iw ~ I v t c n n i ~ ~ ~ d by sulrrposition: tlint is, tllc llifl'~,rioas can hr trratrcl ieiirlx~i~drntl. Iloprvr,r. !VIII.II 111~. in~p~~Tihwnwntmtion, inclllclinS lnt l l thr slll~.;tnltr nllrl the lh1p:lnt. is Rrratrr th:ln n,O, tllr scmimnrl!tdor lmn,rs r.rtritt- sir. and the difi~si\ily is mnsidrrr~l to hc extrinsic. In tho extrinsic <liN(tsion rvpion. tllr diN~tsi\it? I ~ m r ~ n e s mnwntr.ttion drprn~lmt." In tl~r cxtrinsic 11iNt1rion repion. tlae dil- fnsinn pmfilrs arc more mmplicated, and there nrr intelilctinns and cmpr.ativc clkr<r amollg tllr srqllenti~d o r silllu~t;llleola rliff~lsions.

Concenhation-Dependent Diffusiviv

As ~nrlrtioned prmiorls\y, \vI1e11 n llost atom .acquires sufficient e n c q fmvn tla lattiw \il>mtion to ] raw its latticc sitr, a \acnnr) is created. D r p c o ~ l i a ~ on tllc cllar~cs &?mi- ;ttrc! nit11 a u:lonc): \rte can haw a neotnl vamr) . l"'. an acceptor \;tcanc? l'-. ;I dot~l,lr:- c l ~ a r p l a w p t o r ~ a m ~ ~ c y l " - , iidonor \IIC~IIC?.B.. andso k~rth. \Ve cqwct t11:tt the\aw,~r) d ~ i l s i h of a giwn charge state (i.r.. the nunlber ol\;~mncies per unit voLmr. C,) ha5 n tmipra to rc drpendencl? similar to that of the a n i e r density that is.

\ i , h~re C, is the intrinsicvnc.mcydensity, E , is thc Fermi le\rl. m d E , is t l ~ c intrinsic Fenni lewl.

f i ' thr dopant difi~sion is dominated Ily the \ a n o r ) mechanism. the cliNtlrion mrf- ficirnt is e ~ y c c t d to i r prnprtional to thr \?mnc).densi~. At lluv~lopinl:cnnc~ntntior~s

0.1 J o o ~ n.1 t o 10 100

,,I,~, (n

Figvn 6 1 Donor impurity difi,ri\it? \t*rslzs plwtmn mnrr~nfr.ttion rllmsin~ r rgon~ of inlrin%ir ancl rrtrinsiu cliNt~sion."

6.2 Enrinric Diffusion 117

,r.l~<.rt~ C, i< tlas s-~rF:t<v m m r ~ w t n t i o ~ ~ . 11, is t l ~ e rliNusion mrfir ient at 1111. s~~rfimcv y i~ ; a paran,r,tvr to drscrilr tltr mnc~~ntnttinn d~pnclc~nm.. linr supl~ a C:LFP. tvc can El1 4 .n< 21, ~,rcli,l.t~ rliff<.r~.nti:jl rtpv.~ti,,n rnld solvr it nnmrric;tlly

F I ~ I ~ . 6!1 sI~xr5 thf. ~nltttions" fur R111S1;1111 ~ ~ ~ r f i ~ ~ ~ e c ~ ) r l c r . t ~ t c t t i o n diN~~sinr~ \tit11 difft~r,.nt \,LIIII., 1 tC y For y = 0. \vr Iti~vv 111,' c i~ic of c~~ts t imt difftwivity 311d Ill? profile is tllp r:tmr .L\ th;h sl,cnvn in I ' i q ~ r ~ 6.k . For y > 0. tlw diffusi\ih d c ~ w ; ~ r r s :IS t l ~ . con- wntmtion ~ l t ~ c r c , ~ ~ t ~ , ~lnd i~tcrc;Ciin~Iy s twp trncl lnxl ik~ c x m c ~ ~ r ~ t r a ~ i ~ u ~ p n ~ f i l ~ s result for inrrt,;~\ine y Tlrrn.li~rc. Iliql~b ;thn~pt j ~ l t ~ c t i o ~ ~ s arc fonnld n.lt<.n dill;t<ioi~r are I

intu 3 l~tckqronnrl oC an olyxxitr impnrit? t\pp. Tllr :rhn~ptnrss of t!~r (loping p~ r,-qtcltnwuttxti~~n. 111.11 t l ~ v jomction i k p t l ~ !<re Fiz. 6.91 is given II?

x, = 0 . 8 7 6 for D - C' ( y = 3,

In tllc raw of y= -t tltc <Iiff~si\it). i n c r ~ ~ u n \\it11 d ~ r r r r n i n ~ ~nnn*ntr~tina. \r?tlct~ tp;,r!5

to :I concaw profile, m nppsrt l to tllc convex profilrs for a t l~ r r car.s.

622 Diflusion Profiles

Dimusion in Silicon Tllc inr:~surrd (lilhtsion cocficirntsof lmron and arsenic ill silkmn ilave, .,,,,,..,,,,.,,,,,, (li,pllrlenc~' -it11 Y 2 1. Their mncmtc~tios profiles arr abnlpt, as drpic(p,l i n o,n.p of Fisnru 6.9. For gold and platinum diffusio~t i n silimn. yis close to-" ,a,lrl tllrircon. ~u.ntr:ltion prnfilrs llst'c the cuncave s h ; p sl,m\n in mllv,. d of Fiparr 6.9.

'rl~t. ~lifi~sion of pl~ospl~on~s in sili(n11 is :usncintcrl \sit11 tl,r ~ l o l ~ l , l ~ cllarwcl a m p - tur vwanc). \"-, a ~ n l t l~ rd i f f~s ion coefficient at l~igll cnnwntntinn \arirs .zr c:. \\i.uall~d cxpl-t that the diN~~sion profile of pl~ospl~orus mem\,les that sl~o\m in cunp b oi Figure fi.9. Hmvewr. l ~ r c ~ n ~ s r ofa dissociation elTcd. tile diffusion pmfilc edlibits nnolsa lom l~el~iwior.

F i g ~ ~ r e 6.10 sl~o\rs pl~osphorus diNusion profiles for vidrimts surface concentrations aRrr rliffttsion into silicon for 1 hour at 1000'C."\\ltet1 t l ~ r surpaw concentration is lo\v, c o r r e ~ m r l i n g to t l ~ e intrinsic diffusion rrgion, the dilTusinn pmfilr is given hy an r d c ( c u n r a) . A5 the concentration increi~ws. t h e prufile h @ n s to dmiate from the simple eslxession i n t n r s h and c). At w n high concrntmtion (c~ twr dl. tllr profile nc:u the surl:~rr is indeed similar to tl~nt sllo\m in c u m 6 of F ig~re 6.9. Ilm\r,rr. st mnrrntr.1- tiun ,I,.. s kink occurs and is follo\val hy a rapid diff~~silsion in tlw tail region. Thr mnrcn- tr.ttio~~ 11+ corrrspnds to a Fcmii lrvrl0.11 r\ 'hln\r d ~ r condt~ction b;mrl. At tllis e s r r p Irvel. tl~r couplrd in~p~lrityvacnncy pair (P'V2-) rlissociates to P'. 1'-. and at1 clrccmn. Tln~s. t11e dissociation generates o l ace namlxr of sinxIy c l i a ~ c d amptor \aorncies V-. \\,llich in tlnnl rnllat~ms tlre rliNusion in tlre tail reginn of the profile. T l ~ r difilsirih i n thr toil repion is over 10." ~111~1s. \vl>icJ~ is about n w orcIrrs of ina~nihldr lilr<~r than tlle intrinsic (IiNtlshity at lWOODC. Rrca~tre of its higl~ diflusivit)r phmpl~on~s is cominonl? I I S P ~ to forn~ deep jotlctions, sucl~ ;LS the a-tubs i n CIIOS.

Zinc DifTusion in Gallium Arsenidc \\i, fb.qwct diNtrsion in gallit~m nnmidr to ir nlorr~ mmpliatnl tl~an tlwt ill silicon l m u w thr diffilsion of impttritirs ~r~; tyin\nReato~~~ic mo!rmmts on lntll l l ~ c pllitnrn and xrrrnic suhlnttiws. \'aca~~cies play I ~Iolominant role in diffusion pmcrsrrs in pllium imenbk hrcnl~sr Iw,tl~ p- and )I-hpr in~pllrities must inltimittdy reside in lnttiw sitrs. Hmvevcr. tlle c l l a ~ e slntes of the \i~canci~.s lvavc not Iwen est~blisI~Cd.

Zirrc is t l ~ c most edrnsivrly studied rliNusant in ~xlliam arsrnide. Its diN~ainncwf- ficip~lt is fotmd t o \ a ~ a s C'. Tl~rwfow. 111,- difitsion prnfiles an. strrp. sshrnrn in li iyw 6.1 1,":md r r s e ~ n b l ~ ctlrvel, of Fipnw 6.9. Sot? that even for tlw casr oltlw br\vst sur- facv mnwntntion, t l ~ r diflusion is in the extrinsic dilTusion reson. IW~IISC n. Cur C d s at IOOO0C is less than 10" em' . As sprn in F i p ~ r e 6.11. t l ~ strrliacv ~ ~ n ( ~ n t m t i O n I i i ~ % a

pmfo!tnd rN?ct on tl~ejttnctior~ drpth. The difilsitity varirs linmrl?\ritl~ tl~r ptrlkd prt.r- sltrr of the lint \.npor. and the snrfaw concctllration is prnpi~rtiold to thr scpccN. rlxrt of tltr p:~rti;~l pressarrr. Tltrrrforr. fmm Eq. 55, thr j~~l~ctii>n ilrptl~ is linrarl? pmpllr-

.I son. tionnl to tlw S I I ~ ~ . I ~ P c ~ n c ~ n t r 1'

I 1s L chepnt 6 DMuslOn 6 3 Lateral Oiusion 4 119

Figurs 6.10 Phosphonu difiaion pmfiles" for \ariour atrface mnwntratiun, .%her <lifiasiol ink, rll!c~,n for I hour at IO(Y)'C.

b 6.3 LATERAL DIFFUSION The onc-dimensional Glliiion quation disnisss~l pre\iouslycan dncrihr the dillit~sion m s mtisfac~oril\: exmpt at the ~ l q e of tlbc ma5k \\+ndrnv. Mere the inlpurities \till dil

P'D mlrc iond

9.-

kr rn t initial and h u n d a y contlitions. Fimrrr fi. 19 shrnr5 the mntoun ofmnstant doping concentration for a mnstant sur-

face mnwntntion rliff~ision mndition. asuming that the diNusi\ih iq i n d e p d r n t of cnn- cmtralion.!'At the fiir r i~ l l t o f t h r fim~re. tl~e\.sriation o f t l ~ e dopant conc~ntration i 0.5 C. to lo-' C. i \vl~rrr (:, is tloc surfacr concentration) corresponds to the rrfc d h ~ ~ t i o n @\?n hy Eq. 9. The m n t o i ~ n ;xrc in rffrct a map oftlle lrxation of the jund crrntnl 11: (IifTt~sino, into \anoms I ~ a c k p n n d mncvntrations. For exxlnple. at CfC. = li.r.. tl~r hnrkgrr1111~11 [Inpine is 10' titnps lrnver than tlie surface m n r ~ n t n ~ t i o n ) . \VI

fnml tliis mnrtnnt mnwntratinn cun.r t l~at tllr vertical peertntinn is ahout 2.8 ~ v 1 a . r ~ ~ ~ the Iatrral p w r t a ~ t i o ! ~ is almut 2.3 Mm 1i.e.. t l ~ r penrtralion d o n g the d im ~ ~ ~ : ~ ~ k \ m ~ i c n n < l ~ i c t o r interfarr). n l r r r fo r r , the lateral ptnrtratinn is ahout sW% 0: ..--

Figurn 6.11 DitTurion pm~les" of Ant in GaAs after annealing at lWODC for 2.7 hours. Ihr dilfL.w;i! nnrfaw mnastmtionr arc 01,t;linmI by ,vndntaininp: thc Zn msrny. at trmprmt~~rrs in tl,v r.11xe :PT I,, Snn"C.

penrtration in the \.ertical direction for mnmntrations three or more ordcm of mapi- tircle Below tlie surface cnncentmtion. Similar rest~lts obtained for a mnstant total dopant dilliwsion mntlition. The ratio of lateral to v e r t i d pnetration is about 75%. For mncmtmtion-dependrnt dilliurivities. tlw rxtio is found to hr redoced sliqhtly, to about fiSCr' to 70%.

b 6.4 DIFFUSION SIMULATION nl? \arionr mn~pl ic~l iom that arise in the ronrpnlation of diffieioll prnfik-q (s81ch a con. ~ntnt ioa<! , .~n<I?~bt difitsi!ih) tellct lo preclllde the use of allal!tical hnnlcst nnmplrs. Fottunntrl\: the SUPREM sofh\rue p:sh$c intm111ml in C:ltrpt*r 3 dso inch~dcs mmpkte m ~ l r l s for difft~si(r~~. SUPRE!! citr~ s in~ol i~tr one- or nwdinrmrion;d ililh~sion p d l ~ s . This is a m ~ n p l i s l ~ c d usins llle DIFFUSIOol command. The o ~ ! p u t of th(. [)nqr.llIl is t!pic.llly the chm~irnl. cimrrirr. end \ a m n o ; :lr.~Plltntiolls .~r fwrtinns of drpth into the wmi<vnduc*or suhstrdtr.

:lII ddTtaion pnmssirnolaton. inrlilclir~g SL!PHE!I, are had upon tltrrr bacicqua- tions." TIw lint rq<~ation is lor the flus I]). \vlticl~ in one dime~~sion is %$'en ly

w h ~ w Z, is the chaqe state. # is the mohilih of the impurity and E is the electric field. The ~st~bscript i indicatm t l ~ c SUPREhI girl location. The second relationship is the mn- tinuih rrluiltinn. \vhirb is $wn hy

\vl:rre G, is tile genentionlrrmmhination rate of the impurih The fi~ral key relationship is Poinons equation. which in one dinlensinn is given by

wlierr E, is the pennitti\ih: n and p arr the electron ant1 hole concentrations. and h'l; and S; are the (oncentntions of ionizer1 donors and a m p t o n . respectively. SUPREM solves Eqs. 26 to 25 s i rnul tan~nt~sl~ over a one-dimenrional grid specified hv the user. The diffosi\ih \allies 11sed hy SUPREXI are bawd on t11r varanc). ~ n ~ l r l of Fair." The talues of E* and D, for 8. Sh. ant1 As are inclllclcd in a look-up table. E ~ ~ ~ p i r i c a l models nrr 11sm1 to aml ln t for field-aided. oxidation-enlmnmd. and oddation-whded diffusion.

EXAMPLE 3

Sl3pp-e w *ant la simulate lhc pnrlcposition olhomn intn an n-hpe clM> silicon wafer a1 8501C h,r l i minnt-. lfthcsilimn nllntntr i-clnpnl ~ i t h phrnpllnnaat r l o ~ l o f 10''.cm-'. ttu: SUPREXI lo dcltmttin*. the h m n dopinc: pn~filr and thr junnirtar drpth.

SOLUTION The SIIPREXI input listing ir nq follm\rn:

6.5 Summary r 121

TLE Predeposit ion Example COYMENT I n i t i a l i z e s i l i c o n substrate IN IT IALIZE <100, S i l i c o n Phosphor Concentration.lel6 COWENT Dif fuse boron DIFFUSION Time-15 Temperature-850 8oron so l idso l PRINT Layers Chemical Concentration Phosphorus Boron ~ e t PLOT A c t i v e Net Onin- lel5 STOP End predeposit ion example

Sot<- ~ l ~ . t t rt~rfacr e,nrmtmtion of thc lnmn is qr.1 to lhe did soltlhilil? limit hy ih? Sol idso l pazan~rlrr in thr DIFFUSION rnmmmd, ARvr prcdrposition i* mmplrtr. \rr. print rind plot the Ix~n,ri n~ntl~stmlion a a fi~naionofdep~h into the rilimn atb*nte.n~<. rrrultr a n rl l rnln is liimln. 6.13. :vhich indi~2tes n junction rh.ptl> 010.05% ~ O T B . 4

b 6.5 SUMMARY Diffusion is a key method of impnrity doping. This chapter fint considerctl the baicdif- fusion rqustion for constant difi~nivit): T l ~ e ~nmplemrntar).emr function (edc) and the Ga,;-rian function \\,ere obtainctl for the constant surface concentration case and Nln- stant total dopant cares. respecti\rly. T l ~ e res~tltr o f a diffusion p r w s s can l r r\.aluatrd by mea-~lrements of tile junction deptl~, the sheet resistance. ant1 tile clopant prnfile.

- .~ . . .-~.s~, --.,.- ...~T- .~ - - . . 7 . . . ~. reEep. zn Data from twOOiS3

Boron l f c rn j ) , . Phosphorus l / c

3 .. Ne: Wping (/cm3)

0 0.1 0.6 0 . 1 1 1.2 1. ~lstancr . l lo~g limn

Figure 6.13 Pht of.lx,rnu ~ ~ , n c l . n t ~ ~ t i o ~ ~ a itlscticnn of <lrptl~ ih,tn tltc siliom a~l,strdv. nri

st:l'liE\t.

15: r Chapter 6. Dittusion

\ \ l l n l t l ~ ,Itpins r ~ > n w n t n ~ t i o n is Iti$wr than tl le intrinsic carrier conmntmtion !I, ,t

tl,,. c l i lh~don tetn[rntttmb. t l ~ r dilfi~ri\.iiy l m r n e s r n n c r n t n ~ t i o ~ l depnr lcnt . This clepcn. ~l,.,~~,~ 1,;ks ;I pmfot~ncl r f f w t 08, t h r rrsull i l lg rlopillg profile. For rralnple. arsenic and

l*,rnn di i l i t r i \ i ty i n silirnn \.al? linearly wi th t l r ~ imp~t r i ty rn~lcetttr.~tion. Their dopinq

rmlilfi ;In murl t nlun- d jn tp t tllall t l t r r d c pmlile. P l l o s p l l o r ~ d i f i l s i \ i h in si l imn \ari& ;a tllr xlnn;rrr o f r n n c m l r a t i o ~ ~ . This (Ielwnclr~lcr ilnd :I d i s ~ o c i n t i ~ l l r v e c t $\T rise l o a P~,tK,,l,c,n,s di@,,si,<(? t\lat is 100 ti,,,es i nqe r tb:~n its iacriasic ciiffiai\ity.

Lt tcml rli&aioll at t l w rtlcc. of;, mask and imp t l r i h rt:distriblltion dllring ofidation

nw hvo pmccs~es i n \vllicll difiaion mn h;lw an i~rl lmrtnnt impilC+ on device perfonsnnce. fonll~~rr.lll srlhs~ntiall,y rellllm the brrnl;do\m vol tap. ilnd l l te l i l l ter \\ill i ~ ~ f l t ~ e n ~

tile tl l~slloLl \ultasp ;LS well as tlbc cantact resistanw.

P REFERENCES I. s XI. sa. &I.. 1 . ~ ~ 1 ~ ~ c I I ~ I , ~ ~ ~ C ~ ~ . ?nd Ed.. \I&n\v.llill. Zc1v York. 19%. Ch. 7.8.

? s I;. C1,rnclhi. l'1.Sr ~ ~ l ~ t i r o t i . , ~ Pti,,til~lrr. 2nd Eel. \\ilry. Say York. 1941. CL. '1.6.

3. 11.. R. Aun9n aed I;. E. k u 8 . Sonin,sdt,nor Inhgmtd Cimrif I ' r n r ~ ~ i r ~ g T r d t n d ~ ~ . ~ddia~- \ \ ' c '

Rtitnn. I%nI, Cb. 5.

4. It. C. Clqv mcl G. L Rarun. 'Dimorion in Srmimndacton.~ in J. It. Cn\donl and L \.I. SliMn. F i r n r Drfid, ,n Cdidr. <,I. 2. Plt,ntom. S r n Ynrk. 1975.

5. J. P. Jt71y. -Xlrl;dlic Contamination of Silimn \I jSn." > l i m l m m n En& 40. $55 (190'1).

6. .%. S. Cmw Ryr inn~~dPr l~nu ln~yo j&mi r r~nr la r l r~ r l h h. \\$I<? ?..~1-.vYorl\. I!K.

7 ASTZI XIrtbal F374-9. - n r r \IctJwl ior Shed Rrsirm~te ofSilimn Epilsu'd. Dillusd. md 108,. lmpllntcrl I.X)%~ U r i n ~ 3 ColPnm Four-Pmlr Amy," V10.1.19 ilLJ93!.

9. J. C. Inin. ̂ El;llualicm of Difilurl L)Y.PI in Sili~>n.- BrN Sysl TwI~.J.. 41.2 11W2).

9. S. 51. Sa.. Srmi<4~md~nrlor h i r ,~ : PI8yric~ and P c I ~ n ~ ~ o ~ , 2nd Ed.. \\itr): Sea Yo*. PIKIL. CIt. i.

10. STXI XII.thd EIUYJtl. -Standm1 Cuicle for >Iwntinq\I'idth olltnlcd+<~,r.r ir. Sputter Drpth Pn,fili,,e UsilleSIXIS.- \Ill. JiE 11*'111.

1 1 R. R. Fair ~Cotmwnlnlion Pmfilmaf Diflttsr~l Dqmnrs.'in F. F Y. \\'ylg, Ed., lrnlanry Doping Fnr,s.r, Sdirr,n. Sunl,-llol1:md. .\mncnhm. IOsl

12. L R. \Vci%lxq and I. Blanc. -Dilhssion ~ 4 t h lntrnticial-Sub~tin~tion~l Eqailihnilrn. Zinc in CaAr.' rf,!,~. urn., 1st. 1515 ~IWI.

13. F . 4 Ct~nnrll md C. It. Cmh.-Difi~rion ofzinc in Calliam Arrnidc:J P ly . C b r n ~ Sdid, 15. I27 1 l!xI). I4 D P Kl~nnrcb:ind R. R. ORticn. ",4nd\sir of tllr In>puti? Atom Dirlr i t~~~tina Sear lhc Diffitrion Yn for:, P1.1n:nrrp.n J!mninn.- lR>IJ. R,Y. D F X . 9. I79 ,IW>j,.

1.5 S. .A. C:m!phc~ll. The .%iew#ond E n ~ i n ~ ~ n ' n g ~ j A l i r m r l ~ d m n i c ~ & r ( ~ r l n n . 2nd ~ d . . Orford Unir rrc.r-. S",,.Yoioir. 21nt. CI,. 3

PROBLEMS :\<fcrirkv dcnarr difioal( pmlrlrtn?

S E C n O S 6.1: BASIC DlFFVSlOS PROCESS

Problems 4 I23

....~..... . - .,, atonericm'. itnrl the m r m m l junaion depth is I pm at a rshstr;ttr mnrcntmtion ,,i I x 10". Cdculale thc dillinion time. ;md the total dnmnt in the ,limlrrrl I;,,,.,

~

'4. To ntnid \n~ lc r warp d~~~~ to P sud<len rnlmiion in tcmperntrtrc. thr temperatllrr in a <lifil. sion lum;mw is decrm.asrd lillrrrly from IrKXPC in .YX)'C in 20 mint,tr.. \lhnt is tllr tivc diNstrion lime at tbr initial diNusi<m t r m p m t ~ ~ r c fur r phospl>nn~s dilltlrion in rilicnn?

'5. For a l o ~ ~ ~ - r ~ ~ s r r . ~ 1 t r a t i ~ ~ 8 ~ phosphon~s drivc-in diflusion in silicon at IMO'l:. Rnrl the ~rrcentasc. change o l r a d m cortcentmtion for 1% wriatian in diNnuion time anll t r rnynt l l r r .

6. I f :arrenic is difitscd into a thick slim of silieon doped \%+tl> 10" I nmn atomston' at a

trmperatt,rc of IIOn'C for 3 hours. \vh;tl i s the final clirltibution of if the ~ ~ i d a c ~ ~ ~ ~ n r m t n t i o n is held f i r r l at 4 x 10"ntornr/cm'? \!hat arc the difhrrios lcnmh ;ual j~mr. tian rlrpth?

SECI70216.2: EXTRINSIC DIFFUSION

7. IF;wvnir.;wl.nir. is difilsd into a thick slice of rilimn doped \>ith 10" h m n atomx/emlat a

tcnipcraturc of 900'C lor 3 hrnm. abal is the find distrilrtrtion oiarrcnir i f the r7rrl.d'~

cuncvntrntion is held firrd at 4 X 10"1lomslcm'? \\Inat is tltc jundion depthaAs~t~me the follm\ing:

8. Exyl:~i,lain thr meaning of irl~rinsiic difi~riora and dnrrinsic cf!fir.~ion.

SECTION 6.4: DIFFUSION SlhlUWTION

9. Use SUPREAI 11) p for rn a drive-in step lor 6 hortrr at I l i5 'C lolimmng tne prearpoa- tion desuri1n.d in Example 3. Plot the h m n profile and gi\r thc nnv junction depth.

'10. After thc lmmn drive-in step in Pml,lcm 9. suppre pllorpl~on~r is n~hrrquentl? prede- posited anrl dt iwn in. Tltr phosphorus prrdeposition occurs at SjO0C lor 34 minuter. and the drive-in oecttrr at LW'C for 30 minetrs. Use SUPREM lo plot the phosphons and Iwmn impari* profiles. anrl determine the junction depthls).

I. Ctlr t~latr the jrlnctinn drpth and th* total amount ofdop:tnt intrmlttcrd ;trier h m n I di.lxniti<m ~ d o r m e c l at <l5O0C for X) minutrr is a neutral amhient. Asstjrnr thc sill,. <tr;alc i v n-hpe rilic~,n \rill, S, = I.$ x 10''. cm.' and lhc tnron srnrlace concentralion C, = 1.9 x I I P ' c m ~

2. I l t h . wnp l r in Pmhlem I is nnl,jedcd to a n ~ u t n l drive-in at laiO°C for M) minute! calct~lrte thc. difi~ricln profile and the jenc~ion depth.

7.1 Rsngs of lmplented Ions 4 IPS

F 7.1 RANGE OF IMPLANTED IONS

Ion Implantat ion

&sctlsHl is Chnptrr 6. difi~siou and ion inlplantntion are tile hvo kc). ~ l ~ e t l ~ o t k of imporit\- Ilr,ping. Sinw tht. early 1970s. ~I~II!. doping operations have heen performed hy ion i~nplantatius. :u sltmvn is Fi,pre 7.1. I n this p rmss t l ~ ~ d o p a n t ions m i ~ n ~ l a ~ ~ t m l ,,,to tllr s,.,,,imn~luctor hr. means of an ion l n l n ~ . The doping ~~scent ra t ion IIXS a pak

clist~l,lltioll iesi<lc tlw srn~icvaductor, and tltr p r o l i l ~ of t l ~ r dopant distrihl~tion is deter. nrirttyl in;lil~l~ I,! t l ~ e ion mnrs and the in,plantt~l.ioz~ energy This cllapter rliscusses the fnl lmria~ topics: . nlr prows an11 admnta~er of ion impl;mtntion

r Ion distributions in thr cnstnl lattirr aral IIO\V to rrnlove lattice rl:~ma$e CRI '

by ion implflntrtinn

ImpIant~tion-re1~tPd pmsses. sllc!~ a$ n la~kng. higll-~nerQ'i~:lplantation. Id<lwurmnt implantation

I l~ r simttlstion of ion implantation using SUPREh.I

(hl

fipun1.1 Cos>pri.nn oclo\ diff~sinn and IL) ion-implantation technirlvnt.s hr the s ~ l r d !olr-xlttc+ion cd dnpants ihtu the wmimndunor s~~hrtmtr..

usett

and

Ion implant;ltion is i n t r d ~ ~ c t i o n of cn~rgetic. chargerl particles into a S , , I , S ~ ~ ~ ~ s,lcl, as siliwn. Jnlplank~tion ene@~s itre hehwcn I kr\l ;,rid I hlP\: rcs,lltinR in ion ,list". butions \vitll ilvernglo [leptla canping from 10 nm to 10 pm. Ion limes ,al? fmln 10'2 io~lslutn' for tllresllokl s.oltage arlj~~stmrnt to 10" ionslcn~: klr tllo fonllation of [,,,ried insalatinji i;~)rrs. Note t l~at f l ~ e (lose i s exprrswd a5 tl,r. nunl\rr of ions in,pl;ultNl into

1 cm' of tllc srmicondtlctor surlicv arm. Tlw main acl~anta~rs ion ilnplanta,jon arc its more precise control and reprotl~~cibility of impuriq dopings and its I r n n ~ ~ ~ pn~vss- ing tempcrahre mnlparetl \%it11 tl~osr o f the difilrioo p r w r s .

Figure 7.2 schrmatidly slrmr?; a n~cdil~rn-mewion implantor.' n,* ionroitrcc a heatrd filamrnt to break up source g a r s such as BF, or Asl I., into cltaqetl ions ( R . or As'). An extraction voltagr, aronnd 40 kV, caltses the chargrtl inns to n i v e 0.1 of the ion-source chamlwr into n mncs anaI!i.fr. The lnagnrtic fir111 nft l te itnnlFr is r l ~os r t~ slzcl~ t l~at o111y ions \%it11 thr desircrl n~ass-to-claargc ratio c:tn t w e l tl>n>u$t it aitllnllt br ing filtered. T l ~ e srlectrd ions then enter the amvlemtion tube. \vlwre tllW nrr accf.l- eratr.rI to the impbntation r l l c r o as thry move from 11igIn voltage to ground ~ p r f ~ ~ r e s ensure that the ion beam is well collimated. TI)* presstlrc i n t l ~ e inlplantor i s kppt IrIw 10-' to ~ninimizr ion scattering hy giu molrcules. Tile ion Ixatn is then scanned over tllc tr.alc,r surface llsing electrostatic dcflrction platrs and is invplant~l into the srn~i- w n ~ l i i -tor s~~l,strate.

n ~ e mergetic ions lose energy t l~mugll collisions \\it11 electrons and nuclei i n the substrate and finally came to rest at some depth uithin the lattice. The average depth cm 1% contmllrd by adjustingthe awlerntion rnergy. TII~ dopant dosenn bemntrolltri by rnortitoring tile ion current during implantatio!~. The principle sidr e(Tect is disntp- tion cr dntnagc oftlle ~micon~ luc to r lattice due to ion collisiom. n~erpfom. a sul~setloent annerling treatment is needed to remove this damage.

7.1.1 Ion Distribution

The total distance that an ion travels i n coming to m a is called its rongc (8) and is illla- t r a t ~ d in Figure 7.30,'Tlle projection o f t l~ is distance along thp axis ofinridenw i s c . ~ l l ~ l tlrc l~rnjccit,~l range (8,). Because the n u t n l ~ r ofcollisions p r ~ m i t distanrv anrl the energv lost per mllision ;ire random \~riahles, there $\ill hc a spatid cfistribotion of ions lr;nin< t l ~ e same mass and the same initial enerp, n ~ e statistical flnactr~ations i n the p r o j ~ x i ~ l range am called the pmjrcte(l sbtm#lc (up). There i s also ;I statisticttl fluctuation along an :L"S prpendictdar to t l ~ e axis oflicidence. whicl~ is called t l ~ r lolrrol.~btrn~/~! (0,t).

Figure 72 Sehmtrtir of n mcdittnl-nrmnt ion implantor

1 ~ 6 . Ch*mr 7. Ion Implantation

(h)

Rplns13 (ol Schematic nfthe ion range R and projected range Rr. (b ) T,\rrd~n~ensional distri. I,~~tgon of the irnpl:mltxl ions '

F i p m 7.31 sho\ss the ion dhtribrition. Along the *~ of incidence, the implanted ilnpurihprofile can he approsimated hya Gaussian distribution function:

wlierc S is the ion dose p r unit area, n i i s equation is similar to Eq. 14 in Chapter 6 for mnstant total dopant ~lifiusion. except that tlie rluantih 4Dt is replnced by 2-3; and the clistribation is shift& dang tlie I-nus by R,. 'Illus. for diffusion. tlie maximum concfn- tmtion is at x = 0. \r.!~erear for ion implantation the ma"rnnm concentration is at tile p m jrctnl range. The ion cnnwntmtion is rcqluced by 40% lmm its peak \slue at (x -R,) = to,. h? on. drcatlr at t70F hy hvo decadrs at *3a,. and hy R\T d ~ n c l e s at i4.8Up.

.4lon~: the ii*s prlpnclinrlar to the aus of incidcnrr, the distribution is dso a Gaussian h~nrtion of the form eqn-,:/2ail. R e n u w of this distrihntinn. t h ~ r c \\ill he some roil implnnmtion: Ho\r.ev?r. the lateral pnetrntion from tile mwk edee (on the oApr nf 0.1 i\ cnnsidrnbly smaller than that from the t11enn;ll dillinion prowss ~liscussedin Seuqion fi.3.

7.1 Range of Implanted Ions 121

7.12 Ion Stopping

T1a.n. arr hvo stripping ~ i ~ ~ ~ c l ~ a ~ i i s ~ n s I]? u.hiclt on cnrrgt~tic ion, 011 cntcrine ;a semirvm. d~tctor st~bstrntr (;~lso r;~llril tla! tnrgf,f I, ran 1%- lbm~lxlit to n,st. TIIP lint i* 11) trilllsfr.r-

ring its c i l r w to tlw t:~rge:rl n ~ ~ r l r i . This caltsrs drfl<.ctins of t l ~ inri<lrllt ion ;,ITrl clislnrlxrs man) t a x r t nllclri fro181 tbrir original latticr sLrs. I f E is t l ~ e cr lcrpoft l lc ins at clay point x nlnnl: its piith. I ~ T can d d h :t nuclr:ir stopping pmrer. $,(El = ( d ~ / , / ~ ) . , to cl~;~r.st?rize tllis process. TIIF second stoppingm~cl~nrlis~n is 11). tl,c istr,r.laiorn of 1 1 ~ ~ . incident ion with lhr clolld o f ~ ~ ~ r ~ l r n n s alrmllnding tllr. t .qct i alolns. 1 1 ~ e ion lm,s n ~ r q in collisions \nth I~IPCI~OIIS tllro~lpl~ Coulond~ic int(lr.icIiol>. Thr clrctn,ns c t l r l r r rc i t~~<l to higl~rr e n e r p I r ~ e l s (rscitatin~n), or tllry can l ~ l ejwtrd frnni t l ~ c atom (ioniattior~l. \\i. cnn tl?finr ;m eIectmnic stoppill$ pmver. S,(I.:) E (dFJtlx(. to c l ~ a m a r ~ e tl1i.i pnxrw.

Thr avrr:tg?er rate of ~ n r r e loss \\it11 dist;mce is @\.en Iq. a supqmrition of tlw. hv,, stnppitll: ~ilrc~~:misrns:

If t l ~ e totll distsnc* travelrcl l y t l ~ c ion hefare coining to rcst is R. th,

\r.here E,, is t11r initial ion cnerg. The qunntihn hm k n droned prmiotrdym tlte r.mge. Mi. can \isualize the nrlclcar stopping process I)? mosiclerin~ tb? ~Iml ic mllision

behwen an inmniinglianl sphere ( c n ~ r p E , , and m a s dl,) anda target hiir~l sphere (initial m e r p zero and iiinss ,If2). 2% illartrated in F i ~ u r e 7.4. \\11en il,e splrerrs mllirlr. momrntnm is transferretl along tlir wntrrs of 111~ spllercs. Tile cleflcaiot~ angle (81 and the s~lucities, v, :ual v? can IF olitfiin~l from the requimmenk for clmsrn2tion of motnrn- hlm ;ind energy The riiatimlnrn e n e r g loss is in a h~ad-on collision. For tl~is msc, tlw e n e r g Ins3 by the incirlel~t parlicle M,. or the e n c r p ttnnsferrrd tn AJ?, is

rr. f

7.1 Range ol Implanted Ions 4 129

t[,.~t i q , I.,V;~Y crBtq loss p?r tmit di%t~l~lc~-. n,,. ,.lt.amnir stoppine p v c r is fc~tnd to IF prnportion:d to t11~. \ r , l c r i h oftltr inr

t!,,. o*,fieirnt k , is a rrlativrl? wcxk ltinction o l ato~nic rn;lr~ iind xton~ic nu ln l~r . TI,? ,:,lur ,,fq is ; , l ~ p m r i m a t ~ I y 1 ( i ir\'l1 'fc111 fur sil ic~n a1111 3 X 10' (e\!)' '1~111 for gal- l i l l l l , :InL.llill,. TI,(. PltCtrc,llie ~ t o p ~ i y e p\vt,r in silimll is plottccl in F i p r r i.5 (dottrd ltnt. i , .\Iqo sl,c,,,,l ill ti,,. fiOlm. :trr t 1 1 ~ crossover ~ n r @ s . at n.hicli S,!F) = S , ( E ) . For lwmn, ,,.l,irl, lIcLr ;I n.l;,tir.,.ly Imv inn niasc rnnlparcd \\it11 tlle t s y r t silimn atom. llle cn,5.0,cr r.,,erS\- is 10 lie\', This means thnt owr most of th r irnp1:mtntian mew r.,,l,,,. I k.\. t,] 1 )I,.\: th,. 1n:tin <znrr,p loss mwl~anisnl is due to rlcrtrnnic stoppino,. On t!,,. othrr ilarld. far .,rsroir. $4tl1 i t wlativrly I l i ~ i l ioll n1;lss. tllr rroszover e s e q is 71x1 kc\: lltt~s. n~trlmr stoppine dornir~:+tes o\-r most of thr p n r w met,. For pl~os~llonl-t.

Figurn 7.5 St!cb.;a 5tnppin.: p v c r . S7Ei . ;md rlwtrnnic s1oppinepnnsr.r. SLEI. (or As. P. 2

H III Si. Thv p i n t s oFintt,rua~,n o l t lw r,rnm c ~ ~ n ~ s p m d in I ~ I P m c q at a.ltirl~ nuclear a r.lc<i*>n!c \tr>,>plrl.: :trr ,.<]8,:,1 '

tllr rmssn\rr m r w is 130 kc3\! ].'or an F:,, IC.;.; tlmn IUO kr\: rlllrlrar s t n l , p in~ ,,ill rln,,,. inittv: h r i l i~l l r r r!argit.s. clrrtrnriir stoppinp,,$ll b,kc <,ver.

Once S,,O:) 91E) are bloun. ar, out cnln~l;ttr the mnse ir,,,,, q. 3. ?inis in t l lm ?in SjW 1l.i llll'pmj('(*rni mns(.ztn11 pnl jwI~~d stnq$cuitl~ 1I1e I,vlpaftl~r imntr ~r~nntions:'

F i p ~ r r 7 . h sl~o\>% tile projwted range (RJ, tlie prnjedrrl stngele fa,.). anrl tllp 131-

cml 1r;rq:le (0,) for rmnic . Imron. and pl~ospllon~s in silimn.' ,%$ r . ' p ~ n l , t l ~ e i;lvcr thr escrr?loss. thesmaller the rmge. Also, thc ~)rojw+Cd r.tngrmdstmqI~? incrr.awaitll ion mcrS\: For a ,@\en rlcment 111 a sprcific iriri~lrnt enrrp, a, and al ;Ire mmpn~l l~ lc and ~~wvally \\ithin +20%. Figure 7.Ch sllow t11r m m r p n t l i s g \dues i,,r I~\rlnqrn. hnc. ;lnrl tr,lluriom in p~lli11111 ars(wide.' Iltvc mmpare Figures 7 . k :)rid b. \I.?'SCP tltat tnost o l tltr p o p ~ ~ l n r dopants ( r n r p t I~ydrogen) bave 1:irgcr projwterl r a n ~ e s in silimn than t l ~ r y I!avc= in ~a!li11r11 anenide.

Figure 7.11 5lnh.l fix a diamond rtrurtlrre. \ic\\t.d illosg a <LIO> ads.'

1.1 6) id

Figure 7.9 >linimiljn< clt;~nnrlinz. (a ) 1mpl;mtrtion tl,nnlgh m nmorphr,ur r~ridr layer. ~h \liuwivntatinn "i the l w ~ m dineion to dl r3stal axrr ic) Pn-d:gma~r an t l ~ . rpmtal n~rfam.

Tltp tree of disorder for l i ~ h t ions is quite ~IiTTrrrnt front that for Irma\y ions. h111cl1 of t l ~ r e n r v l m c for lieltt ions ie.g.. "R. in silicon) ic dale to rlwtronicmllisions (SLY Fig. 7.5). ulliclt rlo not wusr lntticr daznagr. nrc ions lose their r n ~ q i r r m thry p m c l n t r ll(*per into IIIV s u h ~ t n t e . E\-vnhlall!: tlbr ion e n r q is rcqlund b ~ l o u . tllr missover ~tV&?.V (10 kc\' for lmranl ahere n~lrlpar stoppine l r n m ~ c dominant. Tllrrrforr, most of thr 181-

tin3 ~lisorrlrr occixus near tlw finit1 ion psition. This is illustrated in Fig11re ;.I&. \I.c>otn cstin~;tte tllr dam:qr h y c ~ , n s i ~ l r r i ~ ~ ~ a 1(X)-k~\'Imrnn ion. Its pro.iectrd nlnkr

is 0.31 pnr (Fit. hi, and it3 initi:~] nnrlcar m r r p loss is only 3 eV1:i (Fig. 7.5). Sinw 111e spncinc: Iw.hr.,rln I;tltin. planes in silimrt is nllout 2.5 A. this mrans tllat the h r o n ion \till loqc 7.5 e\' at rarlr !attic? p l ~ n r h c t a s r of nurlrnr stopping. Tilr c n e r u r e q u i d

7.2 Implant Damage and Annealing 4 130

J-- S~rnlamdltnor .udj,o.

in)

(h) Figure 7.10 Implantation disorder cause11 by (a) light ions and (1,) Ilea\? i~,,,.

to dijplacr n silicon atom from its lnttiw position is ahout I 5 c\: ~ ~ ~ ~ ~ r ~ ~ ~ . tllc inri(lrst honm ion does not rrlezwr rnollgh c l t r rq frnm nuclear stoppinji to d i s p l i ~ ~ ~ Bsilimn \!,Ian i t f i s t enten tlie sil ic~n s~tlislntc. \\'hen the ion e n e y is redecn~ to al,o,,t 50 kc\' !st a de~t11 of 1500 ,i), the rnrrp. loss due to nuclear stopping ittcrears to 15 for r x l l lattice plaoc (i.e.. 6 e\'/i\). st~mcient to create a lt~ttirc ~lisonler r\ssttming 11~:~t 1 aton1 is displac~d prr lattice pl:me k>r tllr rrmaininpion rang.ur l>a\r 600 L7ttice atolns rlispiacr~l (i.r.. 1500 rb2.5 ,\I. If eacl~ displaced atiton1 nto\.er r o ~ g l l l ~ 25 ;\ fmitt its arig- ivni position. tllp ~lantaer \ah!me is given l ry \',, E n(25,i)'(l500:il = 3 x 10-"cnl'~. mlc dani;lpe clensity is 600A',, s 2 X 10." cni', a.lricl~ is olllY 0.-1% of the atoms. Tl~nzs. v r ~ Iliql~ (loses of ligl~t ions are needrcl to create an amorplious layer.

For I1r:t.a3. ions. the energ\. l o s is primarily due to narlearmlli~ons: tltrreforv. \\T. CT,XC+

s~~lrstantial da rn :~~r . Considrr a 100-k\' amrnic ion witl~ ;I pmjwted ran?'. of 0.M pm. or 60 nm. Tlte nwr.tge auclrar energy loss over t11e entire c n e w zmgc is alxn!t 1320 eV/nm (Fip. 7.51, This mmms t h t tI1e ausenic inn lows alwl~t 300 eV lor ct~cli lrttiw plane on tlw avcntgr, hlost of t l ~ r energ) is ~ ~ \ T I I 111 one prima? silimn atom. E : s l ~ pritsen aton1 \\ill stll)srqaentlyc;esc22displ:~crd t;lrget atoms (i.~.. 330r\'/lJeV). Tl~r tnt.11 n ~ ~ ~ n h r r ofdip- placrd atorils is 5280. Assnnting a nnge of 2.5 nm for thr dicplawd ~11on1s. tltr dan~ng~~vol- tlmr is VD I ~ ( 2 . 5 nm)' (60 IIIII) = IO-"c~il.'. The ( h ~ ~ i a ~ c densit). is t11r11 52W4',, 2 5 x 10'' an". or alxr~lt 10% o i tllr total nuntlrr of atoms in I;, r\s a rrsnlt of tl~r 11ca\y-ion implantation. tlir ntaterial lwmtnes rssmtidly amorpl~nus. F i p ~ r r 7.lOl1 illustnt~s t l ~ p sit- !lation in \vl~icll tllr dai t ta~~: fontis a d i so~bred rluslrr over lllr ealirr pmjtaml ctngr.

To cstirnatr tllr dnsr r~qts i rs l to convrrt a cnstallittr rt~atrriitl to all ;anorphons i;,ni~. \r.r can use the rriterios t l~st tllr e n r r p drnisih is 01 ~ I I C s:t1t1c1 ~ n l r r of i i ~ i t q ~ i t ~ ~ ( I e a< tltat llrellc~ll for mrlting the illaterial (i.e.. 10" krV/cm'l. For 100-krV arsrnir iut~s. tlhr dosr requirrd to innkr :tniorphot~s silicwn is tlrr~r

( 1 0 ~ ' I C ~ I ~ ' ) R ~ S = =6x 10'' io~alczr ' IS)

EL,

Chsptcr 7. Ion Implantahon

F~~ Itx,.b.\. i011s. tlir dose r ~ ~ l t i r e d is 3 X 10'' iolldvln' Ircilllsr np for Immn is

I;,,. li,,,,.~ fi,r:mn~ir.. Ilnsr.vcr. in pnlcticr. Iligllcr doses (> 10'" ionslcm') arr

n,ll,,r,yl f,,rlx,rnn in~pl:rn(itlio~~ inln :I Lsr~et ;st m l n t r l ~ ~ p n l t l l n i r ~ l l l s r of tllr nonIlni. h,",, , ~ , ~ t r i l , , , ~ i ~ , ~ ~ of tltc ,laln:tev ;dnng ~ I I I io~a petl~.

7 2 2 Annealing

&r;l,,v. of tl,,. dtnmwd ".$on ;in11 1I1r disordrr cl~lstcr that wsldt fmm inla irnplanta. ti,r,,. u.,,,imd,slor lr,clm,.trn S,KII ntnbilih anrl lifetinrc arr srvcrrl\. degradal. 1" nclclilion. ,,lo5t oftloe irvtls .%c ilrq,l;artcrl ;are not lwated i l l sll~~stiteliolls~ sites. Tn ;sti\atr tl,v impl.,,,t,.d ions to wston. inohility.uld otl~?r ~anll.rial pa ra~nr t rn , ~ l l t~s t anneal

l~, , . ~r , , , i c r , r , ,~ , , r~or a,l i,ppmprint~. mnalri~~alios of limr alad tenIpn*ture. (:onv,~ll~,os;tl ;,,,np.&q lacs an npr.n-t~!lx.. lratcl~ furnace s!strln simiklr to that used

Glr tlwznn:d ou~litticn~. This p m ~ , s s rrquirrs it long time a1111 big11 trmpcratnrv to remove 11,- ilnpl:lst cl:,lll.tn.. H o ~ r r v ~ r . ~x~n\~rntinn;tl ~11nr:tling toay cnllsc~ slll>sklntial dopant dif. htcion ;,ml c:,nnclt inwt w q u i r c ~ n r ~ ~ t s for sl,ello\v jonctio~~s and ~~:arro\~~~lo~~ingpmfile~. Bopid ihrntrnl ,j,,r,mlir~c I IiTA) is ;an arltlrnlirlg proccss tll:lt enlplnys a \arirh of m e v sorrm nit11 :I wrlr m n c ~ of ti1nr.s. frn~tt 100 semn~ls down to nasosrmntlr-all s l~on mlopxrrd uitlr cun\.rntional annealing. RT,\ call ; s t i \a t r dopants lu11y wit11 minimal rrdirtribution.

Conventional Annealing of R o m n a n d Phosphomr :\nnraIin~rh:mctrristics ~lcprnd or, t l ~ r doplnt t)pr ;~nd the dose invo!vrd. F i p r e 7.11 s~,,~us t l ~ ;alnmling lwlv;l\ior; of lx,ron ;and pl,usphoms i~nplnntation into silimn sub- stntcr.' Thr s t t h ~ t r i d ~ is Ilrld at room ternpcmttlrr (T,) dllring implnnl3tion. At a @!vn ion <lose. tllr asnrnling tn~apent t l r r is drlinrcl ;a the trlnpernture sl n.hicl~ 90% of the

7.2 Implant Damage and Annealing 4 105

irnpla1ltr3l ions arc, ;~ctivatrd 11). a 30-minute itnnralinc in con,.Pntionnl anntqlinp; filr. sac.,. F~lrIw~roll i~lplia~tntion. I ~ i d r r annc;dinrtrn~~!l;~t~~~~~ an: ,,r.rrlKl for ~,i,.~,~~d,,~~, Flrrpllospllonls at l c f i < r r ( l ~ s . lI~~~:r~lnralingIx~l,rnior ir ~ i rn i ln r t~~r \~ ;~ t in, I ~ ~ , , . [{m,,,.,pr,

\vlirn tllr rlc)sr is sn.*tcrtl~nn 10" CIIIP. t l ~ r annealing tcmprmtIlrc drops to f i ~ ( ~ a ~

Tllis pl~rllolnrnoll is rcl:*trcl to thc solid-pllme epitnx).procrss (ser (:llaptc.r %). ,,I,(~. pl~nnls (losrs grratrr than fix 10" era-', t l ~ silima surf:tc.. In,cr )xunmes amorpbo,n, Tllc s inglccn~tnl semiconductor andcme:ttb tlrr amorpl~our layrr w n ~ s ar :t r<.r.<Iinl: arra fix rec~t.1Ili7~1tion of t l ~ c a ~ n o r p l ~ o ~ ~ s l;!!vr. .flw qit:rdal fnn\ilr mtr alonC tllu < I(x), clirwtion is 10 nln/nrin at 550°C and 50 nmlmin at fiflO"C. \\iihh an acli\:btion ( .new at 2.4 c\: l l~e r r fo r r . a 100- to 500-nm amorphous layer can he r~c~stnl l izpd it1 a Tc.\r. ,,,in. ~rtrs. During tllr solid-pl~asc rpitadd process. tltr impurih (lopant atoms arc i n c r , ~ z~ tc t l into tl~r lattice sites along\rith tllc l~ost :atoms. Thus, full acti\ation can he ohtninnl at rrlalirely low tumprratares.

Rapid Tbennnl Annealing Tht. ~ t ~ n c l d ~ a for RTA uith tnmsient lampi~c~dingissha\m in Figure 7.l?,n1e trrnprattlw tllr-:uurnl f m n ~ tllc l~eatnl \clfrr is us~lally fmm C4XlW)'C to 1 100"C.'A\r%II~r is lneatnl q~licklkly r~ndcr atmospl~eric conditions o r at l~nv prrsswr ~tnrlrr isotltemal wnrlitions. Typinl I m n p in nn IiTA s)xtcm are lllngstrn filamrnts or arc lamps. The procvssinC c11amlrr.r is nrnrlc ~f ~ i t l l e r qa~:aTtZ. silicon carbide. sk~inless steel, or nluminna~ and ilm qlrarti: ain- d o ~ ~ throoclt \vlticl~ t l ~ r optical ndintion p a w s to illunlinate tl~r\vafrr The uafrr b l d r r is o!?n n ~ a l r of rleanz and contacts tlte n%lfer in a minilnun, nllmlrr of places. A mea- st~rcment s>strm is plarrd in a mntml loop to set \taler temperaturv. The RTA ?*ern interraws -4th a gas-lrandling ?stem and a mmputer that cnntmls qxtern oprntioa. T!picnlly. \r:~fer tr~nperdturv in an RTA ss)ztem is meaca~red \vitl~ a noncontaci optical p!n,tnv.;cr tlrat detrnnines tempmtorr from radiated infnred enelp?:

X ~ b l e 7 . l mmparcs con\,entional furnace .and RTA l e c l ~ n o l ~ . To achimr short processing ti~nes using RTA, trade-offs must IIC made in tempemture and pmcrss (mifor- oaity. :empentun= nleacuw~nrnt and control. and\\~.IFerstress m d t l ~ m u g l l ~ ~ ~ t . I s nd~lition. there am cvncems ahout the in tdac t ion of rlectrically activr nafer defects d u r i n ~ the

rmE 1.1 Tuhaolonv Eomwriron

I . . . .,.,,.,,,,

,,.,-,f,lsf i IiW-.YK) "C's) thmrt:al tr;ansi~nts. Rlpid hentillg \\it11 trlllprr.ltllrr pr.ldirnts in ;lIP a-:lfvn c:u~ cttosr \\:ah d:tniiqr in IIIC fnnn of slip ilislorxtio~ls i a d ~ ~ w c l I>!. tllcr. ,,,,I r(n.cs. 0,) (I,,. ~ t l , ~ r hand, ~~,nr, .~,tiosal l i ~ n t x ~ pnx'csrins c;nlsrs si<~nifivant pmh.

sttcl~ :LS lxtriiclr ~ e t ~ v ~ t t i o ~ t rr(>~n tlw !tot wdls, Ii~ttitrd :xvcl!~ic~tt cnzlt~'ol it1 an op=n nxtrm. ;sal 2 1 . 1 ~ . tht~nnal m;~ss that wstrirts rnntrnllcd l~r ; t l i11~ limps lo tcns of min- atl,.i. In (x i . rrc]llin-l!lcnts on coot~tnitlittion. p m 5 S ~vlltro!. llld met or lllilnllfacl~r- in? llmr c p ~ v I>:ivt, n.sttlte,l in a pnr,aliet~r sl~iit to tltr RT;\ p m s s .

7.3 IMPLANTATION-RELATED PROCESSES

n~i.; wction cmnsirlen :I fmr. i~npl;mtathrn-wlntnl prcersrs. xtsll ;u nri~ltxp!? implantation. ~ l ~ . n b n ~ . t ~ l t - ; u ~ e l ~ impl:a~tation. l i ~ l ~ c n r r p io~pl;mt;~tioo. and hiehi.~tc:-:~t implantation.

7.3.1 Multiple Implantation and Masking

In man!. applications. dopins profilrs other tlian the simplr C A I I S F ~ : ~ rli~trilrution arc nTt~ircvi. ~ n v srcrlt mv is tlte preimplnntation of silicon \\it11 an invn ion to n r a h the s i l i~l l i rnrL~w regon i~rnorphotls. This techniqor allo\r~ close m~ntrol n!llu.claping profile and pc.rnlits r~r;trly 1M'i dopant nrtimtion nt low trniprralllrrs. &? rliscussr(l prcvi- ntrsl!: In slnclt a cmr. a d e ~ p atnurpltous r r ~ o n may be req~~irrcl. Tn ol>t:lilt t l~is t)pe ol rt-zinn. rw mtut mak? a S C ~ V S of implants at banins inn mrrqirs and doscs.

.\lultipl~ impl;,ntation a n d w l r tard to fomr a flat dopingpmfilc.. ;L- sbn\m in Fipln :.I:l. Ilm.. Imrr inmn impl;mts into silimn arv usrd to prn\irlt. ;L cornlxlritr doping prn- filr.." The n i ~ x ~ r r n l mrrirr onwntrat i r~n and that prrrlict<rl itsin? G I I I S ~ t11von arr slimn in t h r f i ~ ~ r c . Olllrr rlnpineprolilrc. una~ailnhlr fmm <liff~~sion technirlut-3, ran IE ohainrd L t ins i~ te~ar io~~s ~nmhirutiom of impnrihdnw and implantntiori v n c r v l l ~ ~ l t i p l e implanh h w r IXYYI tlscd to pn,sr t i r stoichinn~rtn durin? the implnz~t:ition and annealine,of CaA<. Tl~i% :~pproacl~. \vhcrcl>y cqnal;~mtntnt.; of gallilliltln md ;I!, n - h y dopant (or arsenic and a p-t!p. clnp;lnti a w impl;mtcrl prinr a, wnc.;tline. has rrs?tltrd in hiehrr n r r i r r arti\ation.

To fonr>Inl jllnccions in wdrc t~d ; t r~a% of th~srmim,nrln~ror ~~lhstra te . an appmnri- :It? n1:~4 rl~oold 1w ~ ~ x r r l for the implnntation. RCYXUW implantation is a low-trmper p m m s . :I I:I~?P \=rip? of tllr in;trkinq m:ttmals can lx. ~ ~ a v l . mininlttn~ tl~icl Oflllr ma.;liin~ nl:ltrri;ll rrqtlir~ll to stop n mvr.11 perwntrqe of incirlrnt ions ran rll;llt.rl fro111 111~ clner pnctrnctrrs for inns. Tlrr insrt of F i p r r 7.14 shous u pmfrre- us an i~npl;tnt in a nl .~ \hu t ir!;ltv":rl. Tlw do<? implantrd in tlle rrqjon hrPlld n deptll i,lunrrb \Iradrdi is ~ w n hy intr~r . t ion of Eq. I i ~ r

,,,!Z

0 11.1 I t 4 0 6 0 8 I 0

Di'trnm. ipml

Figure 7.13 O>mp,silc dopine prnAlr urinq m~dtiplr implants*

140 r Chepler I . ton Implantation 7.5 Summary 4 141

~ i g u ~ 7.16 T~~. . I ,OI , I \o~tagc- ;wljt~qtnlmt w i n < Lamr~ ion implantation."

illralntfll from tlte s~lhstr.~te by implanting o q ~ e s . creating an i n t m e n i ~ l g layer ofsil. . 011mn-on. imn dlo\idr. Tl~is sq,orntioe by itrq~lfl~~tnlior~ o f n x y ~ c ~ ~ (SlhlOS) is a b! .' ' insnlator (SO11 trcl~nolap'.

nlr SI>IOS p m s c uws n I~igh-enere 0. Iwa~n. typidly in thr 150- to 200-ke~' r.,,,z,.. xl tllat tllr o q r n ions Ilnw projected l a n p of 100 to 200 nm. Additiosall~. a hc.a,?r?. dew. 1 to 2 x ]ol' iondcn~'. is used lo produce an iiosulating !n!Vr of SiO, that is ~ i y to ino nnl tllick. Tlie use of SIXIOX iixiterial leads to a sipifivallt wd~~ct ion of cotlmf~Ir.lin apacitances in 310s de\ices. \lormver, it reduces m l ~ p l i ~ r ~ Iwhwen debires

thus Illm\s tizl~ter packing \rithout the problem of latcliup. As a rrsult. it is \\idely propnwd .ls the i~~;ltcrid of clloice for ad\ancctl. Iligh-speerl CXIOS circaits.

+ 7.4 ION IMPLANTATION SIMULATION SUPRE11 nm. be used to si~llulate ion implantation prnRI~s. Sirnulatccl profiles can be impl;mted nncl activated using the IMPLANT mmmand. anrl subsequen!!:\ driven in using t l ~ c DIFFUSION mn~mand. SUPREXI contains the implant pardnieters h r most mmmon ~ l o ~ ~ n t s . hut also allows the trser to input mnge and s tragle data for u ~ ~ r ~ s a a l iniplantrd materials. SUPRE>[ a n also simulate implants tbrnu$l 111oltiple l a p .

EXAMPLE 3

Supprne u m t to simt~latc thc implinntation of a 2 x 1O"cm~'dorr of lxlmn at 30 kc\' il

r 8 . h ~ cIIYi> rilimn xafrr Tile impl;ant is thcn follo\\rd by a d~ive-in at 950°C Tor 60 minu thr <limn n~hrtr.hte is doped \<ith pllmphan~r at r level of 10"ern-'. use SUPREM to det? thr lnmn dopine pmfilr and the janaion depth.

SOLUTION The SUPREY input listing is ilr follmo1-i:

TITLE C O W E N INITIALIZE COwrENl I'IPLAM C W E N DIFFUSION PRINT PLOT STOP

Implantation Exmple I n i t i a l i z e r l l l c o n substrate <10bSfl ican Phosphor Concentration-lel5 Implant boron bran Energy-30 Dose->el3 Dlffurc boron T i n - 6 9 Tmperature-950 Layers Chemical Concentration Pkorphorur Boron Ner Active Wet b i n - l e 1 4 End laplantat ion example

w 7.5 SUMMARY

Ion iniplantation isake~methud for impurity doping. Tltr kqpanmeten fclr iiol imp13n. tation llle pruJrctr.11 range in,) and its stantl;ml debiation (o,,), (dlell pl.o- jccted s tnmlr . T ~ P ilnplank~tion profilr cxn hr apprnximatd ijy a ~~~~~i~ clist~h,,tion wit11 i t p:lh located at R p from tllr surface of tl~r s r m i c ~ n < I ~ a o r su~,rtr;ttc. TI,? arlr:,n. tages oftllc ion inlplantation process arc olore prrcise control ortllr anlot,nt ofrlop;,nt, a tilore rcpral~~cible rloping prnfile. and l o w r p w s s i n g tempr . t t~~re cornFred with the dillr~sion nrar,ss.

The cllapter cnnsidcml R, and 0, for barinus elementr i n silimn and gdliuln aw,,icle an11 clisc~~ssed the cl~anneling eNmt and urays to niisirni;.r t l ~ k ellea. HoIewr. impla". tation may callre severe c!:lnlngr to tllc cnstal lattice. To remow tlrc implant damage md to restore niol~ility and otllcr device paramrters, the semimndanor n~r~s t be r n n d e l l at an apprnpriatr mnibination of time and temperatare. Currmtly rapid tllemal mncd- ing (KC:\ I i% prefcrrerl to mn\rntinnd furnace annealins b u r r RTA mn ren~we implznt d a ~ n : i ~ ~ . aitl~out t l~enl ld broade11in.g of tlre dopine profile.

loll i~iiplantation 11s rid^ applications for a t h a n d wmimnductor dr\ires. Thne inclt~dr (1) ~nttltiple implantation to fonn novel clistrih~~tions. (b) selection of making

Figure 7.17 1'1~1t ,,11n,n,,, r~,~~rc.t,trntir,r~ ;I\ .I ilt~rtion oS<lrlltl l i ~ l t c r tllr rilicrm ,nl*lr.~tt.. ,mine S~. ' l ' l~E>I,

b REFERENCES I I b,~,,.~,,j~ J \tllrm: ~ , , f , , . h , ! f ~ ~ i m ~ d ~ r i ~ ~ f i n ~ . Flmum. S-VYC:I,A. Iw?

(::I.$ nm. -1 ,,,, ~,,,plmartinn." in S P D.Ilvr. Ed . tl~~,,Nx*~k con Sc?nimndarlnn. \bl 3. Sonh. ll,>!L".l, ,\,,,.,,.nI3,,,, ICL%l

1 5 ~~~h ,~ - , , 11 \ ~ ~ t ~ , , , , ~ ~ , . m,l 11 I~bm-~m. 7l~mnl!cd (:unsidrr.,lion 0 1 1 ira.ml Sprrd of l",pl~n,,,l l,,n,.-Jlm 1 ..l,,~>l rh",, I t . 1st llq72'

I 8 5.,th. 1,- lr.t~lnntans~~ &ncr Dnra /.,r Srl~on osid Csrnloale~n~ Dniw F~i!nd,,Sirr, Rrwanrlt .~t,~t,... F.,W cnn~.. I I R . I*7

5 K 3 kk.,, lt,:pLmomr, in Slbmlt: in H. \I.df,,. Ed.. .(l,$ird Wid Srorr Wrnrr. \."I 5, A d m i r

Fn-<. Slu b r k . 1'475

6 I. F . ~ ~ ~ l i n ~ ml H t l ~ n ~ ~ m l . r h ~ ~ . 4 r l ~ ~ ~ ~ ~ 1 n ~ , ~ f ~ f ~ J m r l ~ . Fmman, Ssn Fca!t'?w, IT3

7 L) h do.^. .R,.,,LI C ~ , ~ t n h ~ t i ~ ~ ~ to lun lml~L~stnlior~ E l t r p ?-petion Dinnhutlon.'] Ap,~I. PItyr, 46. 2 i 8 lu7i3

F c Y chlillc .w,[ s $1. Slv. EA. I'LSl Zdznch,~!,. \IrCr.~.nr..Ilill, Sew Ibrl. IYXi. (:It I .

8 D H Lrr a a l J \I. Llr\rr, ~llm-llllplmlnl Semkmndudur h-icn.. Pns. IEEE. 62. 12-11 (19741.

I0 G I)r.mldly, .I. Im Inqd~dNlon. Sonb.llalLud. Arn~lrrdrm. 1973.

11 \I. c. oldham. 7)~. Fdhncation of $l~mxwt,~.r(msir Cirn~it: in, .!fimrbnmnln. F~cvmrn. SXII F.:,"L,*". 1"-

b PROBLEMS .%nmrl' r l c ~ ~ n r ~ ~ difimh pnhlms.

SECnOS i.1: WYCE OF IMPL4hTED IOSS

1. .k~s,~n,~ that ;a l(r)-mm diam~trr Ga*? uafer is ixnifi,rndg impl;inl~~d \\it11 1(W-kc\'nnc ions for 5 mintttrs \lith 2 cl,nsmt ion k r m currcnt of ill w\. \\I>:xt arc th, ion dose p r unit nn.3 md thc pl..tk ion mncrntratinn?

2. -4 rilimn p-n junction i s f o m d I)? implantins lmnm ions at 54 key thmuch :s aindm in an oxirlr. I f the h m n clmr is 2 x 10" r m ~ ' ;and thr n - h ~ snb.itr;ntv mmcvntratina is 10" o71.'. find thr lrxation of the mr~;il lt~n$c~l jttnetion.

3. A thre<hc,l<l tnltaee a<ljlstm~nt implantation is mrdr through a 25-nm ratr oddc. The suhxtntr is a < Irni>-oncntrd p - ~ J W rilimn uith ;I rcsisti\ity of 10 Q-crri. I f thr inmmen- ud thrt-hold mltirce dtw to a 411-kc\' llonrn implantstion i s I \:what i s 1111 tol;d implmt~.cl rlo.;c p r irnil area? Evlirnatr the lkr.;lti<rn r,ftlntr pak Ixlmn mnmntntion.

'4. For the alhstmte in Pmblem 3, ullat prwntace of thc tnt;d dosr is in thr rilimn?

SECnOS 7.2: I \ IPU\T D.41L4CE A 3 D ASSEALISC

5. I f a 3-kc! 'hmn ion i s irnplantrvl into the silir~m v,)ntr;tte. cllo~latc t l r d;amace densiN .\ss\~mr stlimn itom drnrih i~ 5.02 x 10" alon,stcm". thr! siliwn rlisp1;tr~rnrnI m c r p ir 15 1.t: thr rmxc is 2 5 om. and thr r pdnq irhvecn qllimn l:,tticr pl;ancs i s 0.25 nm.

6. ErpINn u*? hiel~-tempntulp RT.4 i~ pwfcnhlr to low-trmpnt~ln. RT,\ for dt,frd-fme ~h:,l!cnr-junctiort form;aion.

SECIIOS 77.: IhIPIAXTATION-REWTED PROCESSES

8. \\1. \%xlllld hkc 10 hlnrn 0.1-pm 11r.t.p. Ibcntily dnwd jllndi,m~ hlr tha. %otnnr ancl dr,.,, r r ~ o n r c,f :I suhmirnrn !dOSFIX: (:otnp;sr 111- optic,!>\ th;it m. ;~r - r i l~ l~ l~ to intrrxltlCv and arti\ate dopnnt for tl~is ~nppliotion. \ \ l l i d~ nptir,tl s\~>otld )1>11 m~)rvttli~.n<l i t t t < l ~ ~ l , ~ . ,

9. \\lr.n an irrwmic inlpl:mt at 1W kr\. is u s d and thc ph~,ton~rirt thirha.r\ is *MI nmr, find tltr t f l r r l i \ rnr~s~ of lhr rcdst m:r,k in pnwcnling lhr tr.tosnl,~\ion of ik,,n (% . 11 6 )I,,,. ov = 11.2 pn~!. I f thy rc<i%t thicknc~s i 5 CIWIXL~~I I<) I )I">. c~lcn~l;at<. !It<, ~ u ~ s k i r , ~ cfi~i,.,,'~.

10. Uith rrf<.rcnrr lo Example 2. a.hat thirknrrs of SiO: is nrplired to m:ak yll<M)Ci rtf tlr in~plantrd ions''

SECI10S 7.4: IOS I>IPL&hTA'ITON SIhlVUTIOS

I I. ,\ <lW> phosphoms~l~~pd silicon r!~hrtrate aith a dopin~mnrcnlr.~linn nf 111" ml' is

impl*ntccl uith Ixbmn. Thr implant cnerp i s 34 keV\\ith r <I<w or lo" mt:. I:u. SIPREXI to plot Ihr lx>n,n profile. \111;11 arc. ia! Ihr dvpth of thr p;ik of lhr irnplrntnl pwfile. il,l thv lloron mmvxntmtion at the pak drpth. imd icl tltr jtxsr<ion rh~ t l t '

'12. Cre SUPREhl to design an implantation strp that @\,ri th. same rlopinq pmfilc as thr. dlllnnion Examplr 3 in Chapter fi.

Film Deposi t ion

T,, f,,hrimtF discrete ~ l r \ i e s mrl i ~ l t e q ~ t e d cirroits, w e use many different knrL nftllin filllls. \\i. GUI rl;rcqih- t l~ in films into fi%r groapr: thermal nkidrs, clirlrctric la!rn, mi.

I:nm. pl!mst;dlinc silirnn. anrl metal fihns. The p \ \ i h of tl~cnnal oxides rliw2s& in CII:q,trr :3. This elt;tpter dr:ds with v~rinrts otlar t rc l~niq~~ps for depns thin lilnlr.

~~s;,\i l l mn,ill i~ ~ l ~ h ~ . l i ~ t ~ l to t l ~ r cnstal p s t h mnmpb c l i x l ~ q d in Chap

in,.rll\r,9 itlr mo,,tll ~ i s ~ l r - c ~ s t i d srniimnd~~clnr ia!m on x sill~Ie-cnstd s

mntl,,rtor s,llwtmtr. The uanl ipifo.ry is deri\.rrl from the Greek \wrds bnra

-nn.! :,,,d ,n,r:,ning ";lrr.ln3rlnr~t"l. Thr epit;~<al la!rr and t l lr suhstmte m;; ;& ,,,:,)- 1". tllr u,nr. tin^ r i s r to l,os~nq,itn.ry. For example, an 11-hpt. silirnn a

epitx<dlYun 31) r ~ ' - silirnn substmtr. On the other 11;1nd. i f tlw t%pit;tnd l a p tllr stllwtr.lte :<re cl,rtnidly ;mrl often c~~tal lopapl~ical ly differmt. \\.r hnvr heten fay. < t l r l ~ ;IS the rpitx<al ?~m\ri l l of AI.Cn,,As on Gds .

Dil,lt*ric I a y ~ n ~ n d i a silicon &oxide ancl silirnn nitride aw ure4 for insul, bh t ren rnndudilq la*. for diffnsion and inn implimtatioo mwhx for capping ds films to p m n t the loss of dop;mls. m d for passiv;ttion. Poly~nstnllinr siliron, us rpfcrrwl to x polll.~ilicnn. is urerl :IS a gate elcctmlr material in \ I C E de\icer. a duaiw mzterid for rnultilrvel olet;dliution, anrl s mntact material Cur dericrs\ritl~ Inu. jttndions. JIrtal films s~,cl~ ac alttminurn and silicides are used to form low-resi~t intrrcr,nnrrrinns. ohniic mntans. and rectioing met;tl-semimnd~~ctnr h:tnien.

This chapter mvcn the follo\tine topics:

Rasic techniques of rp i tay that is. gro\<inS a sinslecr)stal la)rr or1 a sin~le. cvstal s~~hstrate

Structures and de fas of lattice-matched and strained-layer epit.zrial gro\vfl.

Depndtion techniques to form lo\\.-diel~tricconstant and hi~h-dielectric- mnstant films. ac ~ ~ 1 1 xs pol!silimn films

Deposition t r c l ~ n i ~ ~ r r to form daminl~ln and mpprr intemmnneaions. a a xs t h ~ r ~ l l t w l ~loh;tl plmarimtion p r m r

Charadrristim of these thin films and their compatibility \\it11 i n t e p t r d cir p m s i n z

b 8.1 EPITAXIAL GROWTH TECHNIQUES In an rpitxiial p m s . the suhstratr safer act- the swrl crytall. Epit;~*id pmC :Ire difT<,renti.~tcd from the mr l t -pmih procrsser dewrihrd in Chapter 2 in that tla L~tiaI I,~ypr can lr $m\\11 at R ternprahlrr st~hstanti;dl? b l n w tile melting point, hp

In w rand !wpi-

slid- 'anw

8.1.1 Chemical Vapor Deposition

1,~iflIre S.1 SII~VS l l~rer (nlntnntb st~s<~,ptom for ipit;Lyi;ll grm,*),. s,,t,, tlBZkl tl,,, ce,l. ~nelric rllnpcof lllr snlscr,ptor pro\idcs t l ~ r t);n!nr. lor t l ~ n.;,anr: I t ~ r i ~ r , ~ ~ t ~ l , penclb.. ;~v,rl

I,am,l. All tnalr frotn graphite blocks. Slrvwpto~ in ,.pitjui;,l n.,~.tnm ;,rr :,ssllq,,,,T to rnlcihlrs in t11~- cnstd zr",\itlz ft~nraws. Not tntl? do tltt.? ~n t * l~ : ta i c~~ l l~ r,lppr,rt II,,..

\v;~fcr, IIIJ~ in i n ~ l ~ ~ c t i ~ ~ t ~ ~ l ~ ~ ~ ~ t r ~ ! reactors, tllc? 31-o wwc t l ~ v S~IN~RT ~I,,.~i,;,l , . tbPrq~ for tllr rrarlinn. Tllr lnrr~lilllisln of C\'I> ill\alves a nllallx.r o l \trp? 1;ll tltc ~.~r. t ; ,nt~ (qxsrr an11 dopants) are trs~nsprrtccl to t l t r ruhrtratr rrcion: (1,) ~IIc? an. tranrlcnr,rl I,, thv s~~hst ra t~~ s~lrface. where tllvyarr aclsorlml: (ci :I cl~c~nicl l rr;tciion ncr,ln. odal\-,A*ll at thr snlrfa~r. folln\w.d II~ grout11 of tllc cpifiuinl l a y : ( c l ! the X:,unllr pnxl,,ns ;an.',lcp. orhvd into the main prs strrarn: and (el t l ~ r rvletiun prorlnas :tn. tra!nmrl<.d 0111 OI IIIP

C\'D for Si l imn Four bilirnn so~tn~,S have b r r r~ u w l for \'PE gnnv111. Thr,yarrsilicr,n tctr.ldtL,tidr (SiCI,,. dicltlorn-ila~~~* (Sil l!Cl:l, tricl~lomsilane (SiIlCl,), and sil:~n<, (Sil l,). Silicvn t ~ t ~ ~ c l t l o ~ ~ l r h;~r I x ~ n ct1alL.d thr nlost and 11;s thc \\iid?a ind1.1sirid itu., n l e hpiotl n;l<.iion 1~1111*.~\11~n. i s 121Tlfi'C. Olllrr dlirr~n sources arr ilsrd ix.car~sr of 1knx.r rr:rction tnt,Frat,~n.r. Tl~r

146 I Chapmr 8. film Deposition

s,l),.titlltinn of .I In!dn~q.~~ inlorn for e ~ c l t cl~lorinr i ~ t o ~ n fmnl silicon tetr.rcl~lorirlt, pmnits .,lrl,,t .I ;o 'C nqAzc(inrc in tlzr n.;nclion terlr lwntl~~r~~.. The o~r.mll n.;lction of sililun trtn. cl,)t,n,{<. !l,.,t r,7sultq in tlw v\vll~ nl'si~imll !a?c~n is

s i ~ I , ( ~ a r ) + PII,(?;LS\ H Si (solid) + 4IIC1 (en$)

;\n ;lddition:tl rn~~qr.t ing rc;stion lakes pl:~n. ;tlo~rgwilh tbat @vm i n Eq. I:

..b a rrntlt. i f tll,. silinm tetn~dllnridr mn rn~ tn~ t i on is tm hi~lt, etclring. ~ t l l p r tl1n11 Rm,il, ,,ir,licyl1,, ,,ill t:,ke plnry.. Fimlrc 5.2 slto\$r l lw efli.ct o f t l l r collcentnltion ofsilicon tern. rllltlridr. ill llnr n:s o ! ~ tl~r, rt>;tction. tvltrrr tlrr molt fc~ction is dcfintul the cltio oft),e

ntjrlll*,r "f a~ok.rttlr.s 0f:1 ~ i v r n spccirs to the to ld n u m b r o f l l lo~ecll~rs.' Sote thnt ini. tlrll\- tI1? g o ~ i l ~ r.t t~ ~~cR.,Is(.s Ii~lritrI? \\it11 all illcrrming mncrl l tnt ion of silicon tetra. rlllori~lr. \s thv mn(vntntlion of silico~l t r t c ~ c l ~ l o r i d ~ is incwnsrd. a mtr~ilnllm p u i h r;tt,. i s rr:lrla.cl. Rr!ond tl~at. t l l r f l<rnl l~ n t r stilrts to clrcrmse. and e,r.ntn~lI!. ctcllinS oftll,* ~ i l ~ ( ~ ~ t r ( k i l l um-ur. Si l i t~m i s 11sllid1~ gro\\n in the ~ o ~ ~ ~ - m l l n l t e l t i o n n?$os. ;LT in&. ctted in F i p w 3.2.

llnr n.;~ction of Eu. 1 is rr\miblr: t l~at is. i t n n take place in eitllcr rlirertion. I c tn i r r g;a cotering r l ! ~ n~;ac(or ~III~~UIIS it!rlrocl~loric ;~cicl. remov;d or rtcll ing ,s i l l l~l.~cy~. :\rts.tll\: thix rtrl~in:open~tion h used for in situ clrnninl:of the silicon \ d e r la t,pil;i\i:J cro\\i l~.

n,,. clupnt is intrrxlumd at t l l r s;unr time :u the silimn t r t n c l ~ l o r i d ~ daring el t.16;d hmwil~ i Fie. 3.10). Gr~mus rlilx)nne (B,II,) is used as tile p-t)pc dc~pnnt, u,licw pltospl~inv I I'H , I and aninr i;\sR ,) are ltsed ;I.. rl-hpr dopalrts. InLxtures are on n.~rih i1.ic.d \\it11 I l \ ~ l r w m ns t l l r d i l ~ ~ r n t to allo\v rensonahlr control nf Ilnw eltes for t1 <lt.<irtrl [loping rnn~~~ntcatioo. The dnp;mt r l l r n ~ i s t ~ fur anine is i1l11stratt.d in Figure 5.3. ul,irli sllrnn :~F in r l r c i n ~ nrlsorkd on tlrp s ~ ~ r f ~ t ~ ~ . drcnmposin~. and h r i n ~ inmrponted

l thp t ab prior

8.1 Epitaxial Grorvlh Techniques 147

into t l ~ r prowing 1;tyr. F i p r r 8.3 also sl~ons tlre p v ~ t l ~ rnr~ehanisrns nt tlic surfncc.\,,llich are )Y~PII on tile s11dace ndsorptioll of 110st atoms (silicon) :L< \vc!l s tlte rlopant :tton,r ir.g.. arsenic) and tile rnowrrlertt of thrcf! atoms torsa~l t l ~ r ledw sites.: TO $re tiICIP adrorlwd iltonls sltfficicnt mobil ih for fillcling their proper positions within tltr c?stnl latticr. r p i k ~ ~ i a l grllrvtll reqllircs relati\r$. 1ligI1 tmlpemtnres.

CVD for Gulliurn Arsenide For e:l!lil~m anrnidr. the l>wic sehlp i s sinrilar to that shmvt~ in Fiqlrt. 3.1". Rmusr gallium orscnidr drcomposes into gnllionl and arsenic 11po11 rnponation. its direct t n w - port in tllc u p o r pllase i s not possible. One approncll is thc use of hs , for t l ~ r nnrnir m m p ~ ~ n r n t and gsllir~m cl~loricle iGaCI,\ for t l ~ c g d l i ~ ~ r n mlnponrnt. The ovrrall reae- tion 1t~;riinp to epift~xinl ~ o \ \ i l ~ of g11li11m anmidr i s

As, + 4GaCI, + 511, + JGa& + I?HCI i3)

4Ast1, + As, + 611,

and the ~o l l imn cl~hnide i s genen~led I)!. tl lr rcaclion

h l e tn l o rp~n i c m'D Xlrt;~lorg;t~rir C\'Il (\IOC\'I)) is ;llso a \'lJE p m s s I,nsrrl on pyml!iic irartiollc. Llalilir con\.r~~tional C\W. AIOCVD i s i l istit~g~isl,rd try tile r l ~ e ~ n i ~ d t~ntt~rt, of tl lr prrcntnor. I t is important for tllosr r lrmrnts t1,;1t (In not fnr~rr st:tl,!e Il!rlri<lvs or imlidrs. hut tllnt (10 form sti~lde n~~lalorg;~:alric cotnpO~mds \sit11 rrnson:ddt. \.,lp,r prr,sltrr. \IOC\.D lr.~c

hh>m rstensiwly ;~pplic~l i n tllc l~ct r rorp i ta~i ;~ l FMIII of Ill-\' ant1 11-I'I ~I~I~~IIIII~.

148 b Chapter 8. film Deposition 8.1 Epitaxial G r M Techniques 4 141

PO\II G;~\S. are a n use tnet;dozpnic compoan~h sucll as trimetl~ylgnl [ c a ( ~ ~ l ,),I for tilr pl~~iu, l l component m ~ l aninr (ASH,) for the ancllic a m p n c n t . cllPmio,~s mn ir tr;msported in \;tpor foml into the reactor. The ovcmll rrnction is

ASH, + Ga(CH,!, 4 Guts + 3CH, (4)

F~~ ,\j-mnt.~iains mmpounds. sucll as AIAs. t r i ~ n e t l ~ ~ l n l ~ ~ n ~ i n u ~ n [AI(CH,),I can be ~ u t i n ~ ppiti~\?: the Ga t s is dopl 11,y i n t r ~ l ~ t c i n g dopants in \-.llmr fonn. Dieth)' [z~(c,I I,):] and dietl~~lr~~lmiu111 [CII(C:N,I~I are t!~ic;llp-hp dopants. nnd silnne (:

;ln ,,.t\p dopant for Ill.\' compounds. The i?\rlridrs ofsulf~rr nnd selenium or I metll!ltin m ;also uxrl f o r n - h p dopa~~ts, an11 chrnai~l cl~lorido is nsnl to clope chml into GU\S to form scn~iinsttl;~ting layers. Sincp these mn~pounds are higl1ly poiso and of tm mntaneously inflanl~nahlr in air, rigomlrs safeh precnutions arc necesr; 111~ \10c\:D pmcess.

F i p r e S.4 slto\n a schen~atic of an hlOCM) reactor.'T!picall!: the metalorl compound is t ra~~s~mrted to the quam reaction vessel I?\. Ilylmsen carrier g a . \ ~ I I , i p miv-l with ,\rII, in the meofG:As gro\vill. The c h e m i d rrlction is indllced by ~~~ ~

ins th? gases to 6 k ' C to SOOT aho\,e a sal~stmte pl:lcrd on a prapllite suscpptor I radio frequency Ilealing. A p!~ol!tic reaclion forms the GaAs layer. Tile a(hrantae usins n~et i~loqanin are that tlley are volatile at mOifemte$. low telnpmtures ant there are no trnublesoll~e liqui~l G ~ I or In sources in the reactor.

8.12 Molecular Beam Epitaxy

\iBE is an rpitaeal p m s s io\,olving the reaction of one or more t l~ern~xl beams ofa or molrcules wit11 a cr)stalline surface uz~der elh.al~ish-\acuum conditions (-lo-'

ere it heat. using :es of

~tonc( Pal!

hlnE c%n aelliew precise mntrol of hntll cliemiml mmpasitions m l ~ l[aping pmfilrr Single-cr)ltnl. lnultilnyer stnictures \\it11 dimensions on tllc OKI,!~ n~a ton , i r . r2,, Iw grown Itsing hl BE. Thus. t l ~ c XlBE n~rthml enitbl~s tlte prrcisc f:,1,ric2tion &semi. mndtstor 11ctrmstnlctll~~ harinx thin 1:iyelr from a fra11ion ofa !nicrn,, elm,,, to a m,,no. 1;t)~r. In genenll. a l n E grntvth ratcs arc quite imv. For cab. for e.umplr, a of 1 wndlr is lyp id . . .

8.5 sham ascllenlaticofan > l B E . ~ t e t n orgallium al,rl r,.~8tM~ III.\Z compoe~lds. sllcll as AI,Gn,.,,\s. T l ~ c s)rtrm represents the ,,ltimate in film llrposition mntrol. clcanlincss. and in sit11 clvmiml cl~nractcri~~tion n,p;d,ility separatr cfi,sion ovens ma& 0fp)~ol)tic boron nitri(le are used for Ga. AT, and the dopants. AII tllr. (.&I-

sion o m s are l~oused in an oltrahigh-vacaom chamber (-10.' P;iI. Tile trmpcntllr of eacl~ oven is adjusted to give the drrircrl evaponltion rate. T l ~ c ruhstmte ILoklrr rotates mntinuo~ssly to achieve unifonn epittud 1n)m (e.g., +l% in dopinxvariations ;md +n..j% in thickness variations).

To gro\sr Garb, an overpressure of As is maintined. since tllr ~tickin~meficient or Ga to GaAs is unity. wl~ereas that for AT is zero. ~lnless there is .I pre\iousl? depositr(l GR Iy r r . For a silicon XIBE s)stem. an electrol~ gun is nscrl to evaporate silimn. Onc or rnoreefli~sion ovens are used for thedopants. ENusionov~ncirl~ave like rm;~ll-nrrasoenw and exllilrit a cos8 emission. \\,ltert, 0 is the angle khveen the direction of tile sourcc and tltr nornlal to the srlbstmte s~~r f i ce .

MBE uses an evaporation ~netlloil in s \acaum system. An import;!nt panmar r Tor vacuum technologv is the molecular impinsement mte: that is. I~mv man)- molrc~~les impinge on a unit a n o f t h e sobstrxtr pcr unit time. The impinsenlent rate ( 0 ) ic a func- tior, of the molecular weigl~t. t n ~ ~ p c r a t ~ ~ r e . and pressure. T l ~ r rat? is deri\rcl in :\ppcncli~ H and cnn he expressed as '

9 = P(Zmnk7

- Chapter 8. film Oeposilion

,,.llpyp p is the pressm- in Pa. rn is the in;L?s of^ molecole in kg. k is Boltzmann's con. stant in J K . T is the trn~perature in degnrs Keltin, and is the ~ n o l e c ~ ~ l a r wejdlt,

TllerPfore. at 3 M i; and 10' Pa pressltr~, lhr impingement nlte is 2.7 x jOlr n~oleculrdc~~~'-s for oxTgen (>I = 32).

EXAMPLE 1

.it MI R. thr molenllnr di.mrkr ofonyen is 3.64 A. md thr numbrr of molmles per unit areax is 7% x Find ihr t i m ~ reqttin~l to lorn, a rnor>olnyer o f q . ~ c n at prcsuws d l . 10'. and 10" I'a.

SOLUTION The time rrquimd to film a monnl;a>er (asurning I N % slicking) is obtained lhr impln~cmmt r;llu:

To innid mntaminntion orthe epitaiial layer. it is o fpa r~mo~~nt importance to rnxintain ultrahigh. wonurn mnditions (-10.' Pal for the .\IRE p m s s . 4

During molecular motion. molen~les \ d l collide wit11 one anotber. The average dist; t m w e d by all the ~nolecules h h v e e n successive collisions \\it11 each otller is deP as the rnmn f rc~ path. It can be derived from a simple collision theon: A ~nolecule ins a diameter d and a velocity vnill move a distance vSt in the time St. The mole sr~ffen a collision with another molecule if its center is an)~vllerr \tithin the distan o f t l ~ e center of another molecule. Tllerefore. it s\treps out (\rithout mllision) a c: der of diameter 2d. The volume of the cylinder is

mee ined Lav- cule

Since there are n molecoles/cm3, ttl~evoltlme awociated wit11 one molecule is on the a age VII cm'. \\hen the w l ~ l m r 6V is equal to 1/11. it must contain on the average on o t l~e r molecule. Tl~es. a mllision wo~lld 11at.r occurred. Setting 7= 61 ~s the ;nfenge tim h h v e r n collisions.

The mean free pat11 (A) is tben

8.1 Epitaxial Growth Techniguel 4 1:

A more rigorollr df.riwtion give5

and

for air molen~les ( rqu idea t molecl1lardinmcterof3.i A) at morn t rmpenhw, nlerrfore. at a systrm pressurr of 10.' Pa. A \r,o~~ld be C i O km.

EXAMPLE 2

Asamc :tn efi~sion oven geometry ofawsA = 5 an' :md a dirtanw I, lx.hrren tllc tap ofthe mr.n and lhc callilrm amnide ~~bs l ra tc of 10 cm. Cnlorlatr the Y R E vmmth ctte for tile i.fftlSi,ln 611r<l uitlt galli?nrn mmidr at W'C. Thc ra&%w dcnsit). of ealli~ln, atoms i- 6 r 1t1" rnn-;. and the svcr:xec tltich~ess of ;I monulaycr is 2.8 ;\.

SOLUTION On heating galli~nn ancnidc. the \vlatile itrvnic~aporizrs fint. Ira\inca ~rlli~rm-n~b rolutiarl. ll~crefon,. only 1hv pressures inarkcd"Ca-rich* in Fiplrr 2.1 I arr olintrre<t. nlv pr<+ sure st 'XK)'C is 5.5 x 10r' I'a krrplliatn tmd 1.1 Pa fi,r arwnic (:k:i. Tile arrird mtr can l r clb~ur from thr inq e (Eq. 51) I I ~ multipl\in~ it hy ,Vnl.::

The moletulnr \wight (.!I) is 69.i2 for Ga and 2.92 x 2 for .k2- Substitutinq V ~ I I ~ S of r. JI. a,,,, Til l73 Kl into tlw almveeqnrstion giver

Tha p ~ i h rate of~alliurn menidc is gm~rnn l I)? the arri,al rate olpdlium. Thr kmnmnth ntc i s

Notr that the pm\rih rate is rrlstively lcnvmmpamd with that of\

Tllerc are t\m r,wys to clean a surfitce in sit" for MBE. Iligh-trmp~nture b:&ne can deco~npose t l ~ r nati\,e oxide and remove otlar akorlwd sln.ries I,? r\.i~p>ration or diff~~sion into the wafer. Anotl~er appm;lcl~ is to use a low-earrp ion lwam of ;m inert zas to sp~~tter-clean the sl~rfnce. folln\\wd In. a lo\v-ten~wr.~tore annmling to reonlrr tltr slld?ce lattice structure.

hlBE can use a \\icle variety of clopnnts kwnparcd \tit11 C\'D and hIOCVD). itnd the doping profile r.in be exactly contmllecl. Ilo\ve\rr. t l ~ c doping p m s is similar to the \:rpor-pl~ase gm\\ l l~ pmcess: I\ f l t ~ x of r\apon~te(l dopant atoms ani\.rs at a fi~\nraIllr lattice site and is i n c o l p n t e d alonfi the p w i n g interfi~ee. Finr mntml of t11r (lopine profile is achieved 13. atljusting the d0p;lllt flux rr1;ltive lo the flux of silicon iltolllr Ifor silicon epitarial lil~ns) o r gnlliu~n atolns (for palliutn ln rn id r epik~xkd filn~s). It ic xlro possible to c l o p t l ~ r epit;r\i:d film using n lo,\.-c!lrrent. Imv-ellcrp ion ir;lnl to ilnpl: i l ~ e dopant (s& ~ h a ~ i r r 7).

TIlr ~ ~ ~ b ~ t r . l l r trznlwrnttarrs for hII1E r;lng? fmlll 4W'C to 9W'C. nlld thr gm,*g c,I,,< r.i!~;,- fron~ 0.~h31 to 11.3 )ln!ltnin I3t'r:n~s~~ of ~ ~ ~ ~ v - t c ~ l l ~ ~ ~ t t l r ~ prW~*ssil~g ancI I , ~ V Lm,,,q~h r,~tr. rn;aly ~tnique eloping prnlilvs :lnd mnipositi(>ns 1101 obtnini~hl~ rmln ~ ~ ~ ~ t ~ , . ~ ~ t i ~ ~ ~ : ~ l <:\'l> r:itn Ink l ) m ~ l t ~ e ~ l in \!11E. Xlany novf.1 s tnr turrs ~ : I W hecn ,,x,c]c ILC~ZIC \!BE. T1ll.sc itslad,. tltr *rprr/nlfi~r~. n.ltirh is a priollir stnlrtllre mnsistisS of .dte-n~;atinc 18ltcltliin I:~y,.n !\it11 3 I w r i ~ l ~CSS lllilll the elrrtmll lllrnll free pi11l1 (P,R,, ( : 1 ( S . \,itll i.:sll l;nrr 10 n m or 1k.s~ in thickness). ;lnd hrlemjllnclion fiel,l.

x . -. c f l i ~ t t~.tnsi<tom.

.\ l i~dllrr <lt.\rlopn~rt~t in 5IBE i ~ m rrpl:lcetl t l ~ e p u p Ill rlelnrntal S~I IKVS hyma. :,loyrnnic mtnpouncb surll as t ~ i m r t h y l ~ n l l i ~ ~ ~ ~ ~ (ThIG) or trietl~ylg:~llitl~n (TEG). This :tppn,;tclb is crllrrl s ~ r l n l ~ ~ r ~ r r ~ i ~ . , ra~l~nt lor .h .ot~~ q>ifn.vy (5IOhIUE) ;lnd iS also referred to ;R ,./,crni,al l)<.ne~ t7riIory (CUE:]. Altllolr~lt cIosr1y nklted to lIOC\'I). i t is cnnsid. I , I n f I . T I n t : i are st~llicienlly wlatilr tllat tlwY a n

* 8.2 STRUCTURES AND DEFECTS IN EPITAXIAL LAYERS 8 2 1 Lattice-Matched and Strained-Layer Epitaxy

For cnnv~ntiond la,~noc~ilxxi.d qo\rth, n singlecnstal selnimndtstor layer is gmnn on ;I sin~lc*-cnst;al srnlicvnductor sttbstratr. T l ~ e srrnimndnctor I~tyrr :~nd t!~c st~bstrate are tl~r sntnt. rnntcrial I~n\ing tile s:amr Intticv mnshnt. Thrrefore. homnepit:~y is, by defi. nition. n 1nttic~-tnatclred rnitaxi.11 nrocess. The l>omuenitaxi;~l nrocrss offen one imnor. a

t;int IIIP:LIB of mntmll in~ the duping profilrs so that &\ice and cirr~rii pcrformane nn Ix. opti~nizt~l. Fnr rxmnplc. an r t - h ~ e silicvn layer \\it11 a relntivrly low doping conen- tratinn cxn hr gm\\n epitxially on an 11' silimu s~tbstratc. This stn!c!<~rr s!~bsta~~ticall~ redt~(rs the s r r i ~ s msistanrr ;usminted ,\it11 the sabstrate.

Fnr Itetrrorpita~y. the epitnkal layer and t l ~ r sr~bstrate are hvo r1;;TPrent sernimn- ~lurton. and the epiti~xial layrr lrntst he qoroan in s!lcll a \rc?\. that :m idr.:t!ized interfacial stntcture is in:lintainr<l. This implies thxt atomic lmnrlins across the intrrfacr must k mrrtinao~ls. Therefort.. t l ~ r hvo sca>imncInctors must ritlrer have tile r;tnir lnttice spar- in: or IF nhlr n~ drforrn to adopt a common spacing. Tllrse h o cases Arc referred to s . . Iolfirc-rnnlcltrrl q~ilnxy m d sfroinefl-layer q)itoxy. rrspcti\.ely

Fimlrr 4 . k sl~o\w a lattice-rnatchrd enit:Lw \r.llrrr the stlhstratr and tile film I~ave z .

the Nllllt' littticv llllStRnt. An inlportant exnnlple is the epitaxial grouih rlfAI,Ga,Js on :I Gm\s si~h<trate\vl~rrr foranyx hchvern 0nnd 1. 111~ latticrmnstant ofAI,Gn,~ibdif- f r n from tli;rt of Cajjs by less t11i1n 0.13%.

For t l ~ r latticr-rnisn~atrl~rd c a e . if tllr rpitaual layer Iias ;I 1;lrprr lattice constant and iq flerihlr. it \rill h~ mmpresscrl in the plane of rro\tih to mnfornl to the sr~bstrate

8.2 Structures snd Defects in Ephaxial Layers 4 153

1 . 1 1 1 1 ~ . I I I~ I< I I IYI ?trancrl .-.. Cl*.... . . . . . . . . . .l L'numnnl

C.......... . . . . . . +. ... .+.... ,..

Figure 8.6 Srhcn~ntic iilnrtmlion of in) latti~~.matchrd. (bl strrinrd." md icl ~.IXYLTI hrtrrwpi. t.nill rln,rt?m~%. Ilnrntrpil~r~? i r sln~durd~ll!. idantical lo llse l a l t i ~ ~ - m a t c l . ) l c r l l ~ r l c r ~ i t ~

Tlw critic;tl I;?\.e-r t!~ic!arsses for hvo aterid rid ?stems are shmtn in F i p r r 4.i.'Tlle upper cume is for the strained-lnyer epita\? o l a Gr,Si,., layer 011 1 silimn s11\\~tratr. and tllr lower curve is for a G;~,.,ln,i\s layer on a C;u\ sahstr.~tr. For er;tn~plr. for Ce,, ,Si,, 011 silimn. the s~;r\imun~ r p i t a d tl~icknrss is ;tlnal 70 net. For thicker Tiltns. rdsr dis- lue:llicns \rill occur.

.A rrlattrl hetcrnepik~rial stnlrttlre is tllr s f r o i r ~ c d - l ~ t ~ r r . w r ~ ~ ~ r / n l l i r ~ ~ (SLS). i\ super- lattice iir :III artificit~l oi~r-dimnaion,d periodic stntcturr constituted by cdiifc:rcnt material nit11 a neriotl of nlxlut 10 nm. Fim~rr 3.8 s l ~ o w ' an SLS i~a\inc hvosmiimn<lt~cton uith rliffrrrnt eq~~il ibr iun~ lattice co~~st;u~ts a , > n,. groun inn stntctttrr \ r i t l r I common inpl:$ne latticc c~j~~stal l t b. u.llrrr n, > b > o, For sufirirntly thin l;~yen. tile lnttice n~is- matcl~ i.; s rn~mn~rx l i~ t rd lq. t ~ ~ ~ i f o n n strains i n the lyrrs. Ut~rlpr t l ~ r s ~ m n d i t i o ~ ~ s . no mis- fit rlislncatio~a are gt,n~nrted ; ~ t t l ~ r intrrfimcx-s. so h i ~ l ~ q u n l i ~ cr\stallinc materids can be oht:~inr~l. Tl~esr nrtifiri;dly stntchlred in:tterids can hr ~ r n \ \ n hy XIRE. Tltrs? materials pro\irlr a ne\v arra i n s rn~ico~~doctor rrsrarcl~ and Iwrnlit nr\v solirl-statr de\icrs. especially for l~i~l~-spercl and pbotonic applic:~tions.

~. spacing. Elir~tic forces then compel it to dilatr in s dirwtion prpenclic~tlar to the inter- LIW. Tl~is hpr o f s ~ n ~ c h ~ r r is ~ I I I v I I stnined-layer rpit:n~;md is ilh~strntetl in Figure (I.&.' 822 Defects in Epitaxial Layers On tht. clt1a.r hand. iftlte rpitaxial 1;ryer ha< a srn:~llprhtticr ronstant. i t t r i l l Iw dilated in t l ~ r plane of $n)\r?li and ror~lprrssed in a direction prpmdicular to tlw intrrfaw. In t l ~ r cilxr r. strained-Iayrr vpit:L\?. zs I I I~ . str.linrd-li~yr tllickn(.ss increars. tile total nllm- Iwr o f : ~ t o n ~ r t ~ s ~ l r r stnin of the rlistortrd atomic tmntLv grows. and at sonw point. mi<- fi t ~lislocxtinns arr nnrlmtr(l to rrliew tlw l~orno~eneotts strain e n e p This tl"cLnrss is rrfrrrrcl to ;u tllr crilir~nlin~,rr fhirknr .~.~ Tor tl~r wstrrn. F im~rr 3.1% sItn\vs ~ I I P c a e in

Defects in rpikainl l:~yrn \rill r l ~ p t l r rlevice pmpertirs. For er:enplr. defects can n511lt in re.CdtlwcI i~~ohility or incrci~srrl lritka~e ctarrent. T l ~ r drfeds in c p i t a d la!vn can in3 categorizrd into fiw groups:

1. D~fic/.s~finel tho ,s~rhs/rolrr. Tllrsr dcfcrts n1;ty prolx~ptv fmtn the n~l~stnl t r into tla, cpit;r\i:~l I;npr. To ;n.oi<I tllrsr drk~rts. ~lirl~;llion-frt.r s r n ~ i m ~ a h ~ r t o r

?

u.l~ivll tlirrr are NIc(, d i s l ~ ~ i ~ t i o n s at the. interfcacr. substratrs ;trr r r q ~ ~ i r r d .

1% b Chapter 8. Film Deposition Dielectric Oaporirion 4 15

G o r in Inecmn. I

F i p m 8.7 Erprrirnentally detprminrd critical la!cr thickness for drfm-free, str~incd-lap rl~tqolCd,Si:., on Si. and Ga,,iqAson G A S . -

2. D + n . ~ / m n ~ the interfnce Odde precipitates or any mnta~~~ir~; t t ion at the interface of the epitaual layer and ruhstnte may cause tlie formation ofmir- or ient4 cIustt.rs or nuclei mntaining stacking faults. Tllese c h t ~ t e n and stacking farrltc may malrrce with nom~al n ~ ~ c l r i and gmw into tlip film in the shnpr of an inwrtrd pyramid. To avoid these defects. the surface of the s u b stmte must hr thomaebly cleaned. In addition. an in sihr etchhack may he usrd. sncli s the rmmable reaction of Eq. 1.

3. P~~cipitnlei or dirlncotior~ Imps. Their formation is due to s~~prmtura t ion of implrritiw or dopants. Epitaxial l a ) m mntair~ing rPn high intentional or t~nin- tcntionnl dopants or impurih. mncentntions are suicrptihlr h~ s t ~ c l ~ defects.

~ ~

4. Dnr~onole groin bmmrlorifi~ nnd /IL.~IIS. Any misorient~d arrac of an cpitaud film dorincpo\rih may mert and mnlesce to fonn tlnc,sc defects.

5. & l ~ ~ ~ d ~ s l m ' n t i n n ~ . These arc hxrned in the h r t r m p i t a y of hm lattice- mi~mntcllrd sen~imnducton. If hoth lattices are rigid. they uill retain their f l l l i l~an~~ll td Illtic.? spncina. and the intrrface \\ill mntain rows of mis- h n d r d :,toms ~lvscrihrd a< nlklit or edge dislnations. Tl~r edge dislocationr ctn :+lw form in ;i s t ~ u n r d 1 : y r \vl~rn t l ~ r I a y r thickness Im, lnes lnrger tllm tlw critic11 ILtwr thickness.

' , * ! - L . LL/-. ~-..,-.~.-L.-!J~

I Cndnl laver

t Sulntnte

Figure 8.8 illustration of the rlmmntr ant1 formation of a rtminnl-la!r*r ~ u ~ r l a ~ t i m . ' :\mn\r slarr tl~e direction ofthr str.zin.

b 8.3 DIELECTRIC DEPOSITION Depositrd dielectric films arc i s r ~ l mainly for insttlation and lxssi\:~tinn ofdiscrrt~ d ~ \ i w , and i n t r p t n l circuits. Thew arc time commonly used depl,sition ~tletl~cib: idrn~~pl!eric- prcssorv O'D, low-prrsst~rc O ' D (LPC\'D). and pl:~cmn-rnhanml cl~e~nicd wpor rlcpn- sition (PI:C\'D, or placnla deposition). PECVD is an rarrgwihnncr<l CVD nirtl~~wl ia \\.l~icl~ pl;~wna m e r v is ad~lrd to thr thrrnlal c n e r p of a mnvcntiond 0 '1) S!T~CIII. Considc.rations in x.l<rtingadrposition pmcrss am the s t~bstc~tr tr111prr.itum. l l ~ r dspo- sitinn n t r and film itniforn~ih tllr n~or~l~ologv, the rlectri~ll lnr! mrchnnicll ppmprr-

~ ~~ ~~~~~ ~~

ercrpt that diNrrc.nt gxsr:il~. l l s~c l at tlw inlet. In ;I Itot-\$:dl. rd~irrd-prrs- t~rr mar- tor like the one sl~o\\qi i n F i g ~ m s.&. tlie q~~i~rtz-lllhr is he:dnl hy a tlrms-znnr Iilnl;lm. and fix- is intmllrml at nnr rnd ; a ~ d punnprrl out at t l ~ r oppocitr end. T l ~ r rr~~~irnnrlnnor \ r a f m ;*re ht-Id \ ~ ~ r t i ~ a I l ~ in a slottrd qunrtz Inat.' Tltr rluitr?~-It~lw \(.:III is 1101 ~ W O I ~ I S F

it is aclji~c.?nt to the f t~n~~c .? . in mntr:r<t ton mld-xxll rrarlnr sac11 ;o 111,. I~orizontal ?pi- t ;~~inl n.:stor tl~:~t usrs rildio l i rquenq (rfl he:~ting.

I S 6 r Chapter 8. Film Deposition 8.3 Dieleclfic Daporition 4 1.j

Deposition hlcthods

Altorninarn rhc(nxl~1

,-:I -1

t 1 I rs 1 hnmp ca i"I..l inlt.1

Ilr~tlrl

I Om >b llO!dCT

(b)

Figun 8.9 Schematic d i a w r of chemiml vapor depnsitinn reacton. (a ) Ilot-\\dl. r e d t r d - pn,rmw reactor ~ h l Pamllr~l.platr pl;~mm ddcposition reactor. ri. radio freqlxene),

The padel-plate. radial-flmv PEC\'D reactor shm\n in F i p ~ r e Y.9b consists ofa qlin- dncd g l s s or a l ~ ~ s ~ i n u m chanlber sealed wit11 a l ~ ~ m i n l ~ ~ l ~ endplater. l n ~ i d e are hvo par. allel nl!~n~inr~m electmles. An rf wltage is applird to the upper electiudr. \rtllereas the Irnsrr elcerodr is grorinded. Tllr rf\olta:e causes a plasma discharp, bchrren the elrc- trmlrs. \\:If?n are pl;~ced on the lower e lec t r~ le . \vhich is l~eated i r h w r n 100°C and 4006C bs resistwm heaters. The reaction gixes flo\rf throagh the d i sc l~nrp f ron~ outlets locatrd along the rircunlfrrence of the 1rnrr.r e l e c t r ~ l e . Thr main ad~xntaxe ofthis reactor is its lmv deptlsition temperature. Ilmvr\vr. its capacih is limited. esprcially for large. clian~eter \vafrrr. and the aafers may Lwrnme rnntan1in:lted if Iwsely adl~rring deposits fall on thenl.

8.3.1 Silicon Dioxide

CYD silimn dioxide cannot replace thermallyrn\tn oxides. bec;~use t l ~ r hest electrical prnperti~s are obtained u i t l ~ thrrn~dly grown films. C\'D oxides are ased instead to mu). plement thermal o d d ~ s . A l a ) ~ r of a o d o p d silirnn diodde is u s ~ d to insttlate m~!ltile\?I m~tnllb.?tion. to mask ion implantation an11 diihlsion, and to inc rea r t l ~ r t l l iche '

tlrrr~n;illy gm\m fir111 oxides. Pl~osphonzs~loppd silirnn dioxi~le is used both as an i lator i rhvren metd la)vn and ;IS a final passivation layer oIpr de\ic-s. Oxides doped p l ~ m p l ~ o n ~ s . ttni.nic. o r boron are ~tsed wxasionally as rliKusion soorws.

Silio~n dirl\irll. fillns ~ I I I In. d r p s i t r ~ ~ 1,s srwral ~ P ~ I I W L S . R,, ~(,,~.t,.,,. , , ,I,.,~,. sitinn (31~)-5(YI'(:I. thr fil~ns;*rc k,nnrtl I,? n~;~ein~si l ; ,~a . . ,lnplnt. ;.,, I ical reactions f i r phrtcpllon~s-clo,d arid,.s an.

Sill, +O,+S~O: +ZH, i l l )

Jpll , +X):-~P:O, +611, 1121

Tllr drposition prmws cln Iw prrfunnc.11 rithrr at atmospIlrric PrmxIIrc ill ;, C\,D rr:L(.. tor or ;It redllc~rl p r c s ~ l r r in an LPC\'D renczor (Fix. f i . ~ , , ) . l ' l l r lo,v prmtltrr of llrr silane-oygm rmctisn nukes it a suital-l,lr pr,rpr5 , ~ l , , . , ~ fi1,,,, ,ll,lsl I,+ rlrpositcd ovrr a l;iyrr of nlun~inlnm.

For inl~~rrnrtli:ltr-te~ny~~lurr. drpsilion ( :M0"CI . silirxrn clio\irlc c;l,, forlllr,l I? drmmlmsinx trtc~etllyh~rtls,nilintr. SiiOC,II,),. i s ;in I.PC\'I> n.;lr(or la. rnnlpllsrI. ~ i I ~ h r t ~ \ i a t ~ ~ I TEOS. is \:tporizrd lronn a liqnid sourer. l ~ r TEOS mnp,tjncl c l ~ < ~ ~ ~ ~ ~ ~ ~ a< f<>!l<>!~~:

S~(OC,FI,), SiO, + lq.-products (131

furnminl: both SiO2 ant1 a rni~tllre of organic and oreanosilicon byprrxltrcts, hlll,onnlb tllc hiol i~r t r m p r r t t ~ ~ r r require11 for t l ~ c rr~tctios pwwnts its ttw ovrr nhls~inrn~n. it is suit- a l h for pol)si!icon gates rrqnirinq n unifunrt insal:ttin~ Iayrr uilli qml step mrrm~.. 1 ' 1 ~ . srmd step m\.eraSe is a rrstllt ofrnh;unced surface i~>ohility at Ilirrllrr trlnyc~turrc. Tllr oridrs can hr dnpnl l q a d d i ~ ~ g stnall anlotlnts of thr clopiint hyrllirlvs (pl~ncphinrs. nninp. or diborane), similar to thr pmcess in epitaxial grmvtlt.

i'lle deposition n t e as n function o f t r n l p r r ; ~ l ~ ~ r r \:,rirs rv(-E,/kTI. \vllmnx E , k tllc :;rti\alisn r n r r p , The E, ofthe silancb-oqyrn rraction is qnitc lokr.: dmut 0.6 d' for ~ledo;x.<lnddrs :u~Ialn~ostzmrn for ph l ,vho~~- r l~pe<l nxirle. Inmntnct. E , for ~IIcTEOS renct;,>o is ~ n t ~ c l ~ higher: almr~t 1.9 P\' filr i~ndopr.d oxide and 1.4 eY \r,hpn pltosplton~r cloplnr: compounds arc. prrsmt. The d r p ~ ~ d r o c r of the delnsitinn ratr nn TEOS pi~r- tin1 prr<sor? is to (I-P*'). \vhere I' is t l ~ r TEOS partial pressure ;~nrl I:, ir itl~vtt GO Pa. At low TEOS partial presstwrs. the dqmsitioe rntr is dr tcn~~inrr l by the rille of tlrr sllrfacr rraction. :\t high p;trtinl prrsst!res. 111e SIIT~.I<P hrmlll('s 11~arIy S l t l l -

ratrd \till) ndsorbed TEOS. and thr dcymsition cite lwcomes r ~ s r ~ ~ t i : d l ~ il~dr(u.ndrnt of TEOS press~~w.'

Iirun~tly, at~nospl~eric-prrssttrc and low-tr~aper;~htre C\'D pmcl%ws using TEOS and w o n r 10,) Il;w Iuen nrnrx,rrtl,"as sl~o\\n in F i g ~ r r S.lO. l 1 i 9 CYI) tcrltnolq'prnilws . . oridr filnls \tit11 l ~ i JI confon1l;llih and leu tiw,.;ih tinder low rh.prition tt'~np,ntun.. Thr slninkaSr ofosirlc f i ln~ durin$ ansmling is :iho a h~nction ofmonc conc~ ,~~t r~ t ion . CL~

slbo\\n in Figlrr 8.1 1. HPCYI~ISP of their pnrosih 0,-TEOS C\I) oddrs arc oFtcn arrnlll- panird I>? l~l:~~am-msistorl odrles to p n i t plannli7i1tio11 in ULSl pnrrssine.

For l i ,~ll . tenrpnl~llrr drpnsition (90°C) . silicnn rlioiidr is fnnt~rtl hy rt~:slillo ~lid~lorosil;lne. SiCI2kl1. \tit11 nitmlls oxiclr at r rdt~wtl prrsslirt,:

Properties of Silicon Dioxide ~ ; ~ l , l ~ 8.1 lists (lrpositioa ,,,,~tl,ntls :11ld prnpcrtirs of silicon clioddr fillns.' In x+~~a.r.~I. t ~ , , . ~ ~ is (lirrct mrr,,~:ltion ~ , ~ ~ \ ~ r r ~ rlrpo~ition trnllwraturr and film cl~~:ilit!.. :it I I I S ~ ~ , ~

.- .- It. 3 .'"I s, , , , t , ~ t r d t , ~ . ~ . , ~ ~ ~ c o ~ ~ ~ ~ h ~ t ~ k ~ ~ l

TABLE 8.1 Rownies of Silicon Dioxide F i l m

l l ~ t ~ n ~ ~ . ~ l l v <:rown S i l l , + 0: TEOS ~ , t l l w ~ l ~ < ; :,t 4.wc a1 7lXI"C

- SiO, SiO, Il l1 SiO, ., ., - - 2.1 0 9

I - I6 1.4.1 1.46 > l ( l 5 I0

8.3 Dielectric Deporitioo 181

, , . J , ~ ~ I is tIIe tlist:~~tc~ fmrn tlw top S I I ~ N Y and \\'is the \ridtl~ of tbe o p r ~ ~ i n g . This hl*. ofqtpp mrrAer is tl,ill ;Jung the v r ~ i c d ~ ~ ~ t l l s . 1~it11 :a l ~ ~ ~ s i b k . cmck i ~ t the l r ~ t t ~ , " ,,r the c,,,s.d I? w I i . ~ h : ~ r l ~ r d n ~ .

slllcne dn,o,lc. ionnrtl I,? TI-OS r l m n ~ p s i t i o l ~ at rrtluwd pressure gives n srarl\. ~n,,f,,n,,.d m\rr.ter dsc to ntpi~l sllrlllrr inigmtioa. Si~nilnrl!: thr I~i~h-tr!rtprrnh,;~ ,~iclll,,nlril.+r~t~-nilmus odclc re:adioll dso r ~ ~ ~ ~ l t s in rullionnnl co\'cngr. Ho\wver, dar illg r,l.,n.-nnyrt~ . ~ <lr.pnsition. no s a r f . m nlitnttion t.dcs p l a c ~ . a!ld tllr step rovrmgp iq rb.t,,m,innl h ill? :tm\:d ;tl!~h.. llnct r$apc t t~ l arcpottcm! m;lteri;ll. l~:tvc:~ stcpmv. r.r;tg+ <trnnlar to 1I1;et in F io tn 9.1%.

P-Glnss Flow .* sr~l(x,tlt topnmplr? is itrtt:tlly r q u i n d for the drpnsitrd silimn clioxidr nsrd :u an insu. I.ttar lx,hnrn rnclnl I:tyvn. I i l l ~ r o u ~ l ~ used to m w r tile h v r r rnrt;~] layer is mnGlve, rirorit (.lil#trr m:i\ r~r!rlt imnl an o p n i n g that nl:iy m u r in the lrpprr nletitl !:rw=rdur. irk? dt- mit ti an. Recxtrw ~ b o ~ p h ~ ~ ~ - I h l r w d sitimn dinxld? (P-E~:L%S~ drmsited at low tern.

- ~, F i v m 5.13 <h~n\s lour rmss sections o f ~ c s n ~ ~ i n ? c l ~ t m n I I I ~ ~ ~ O X I I ) ~ ~ photopphs

nip-<I.sr m\rrin< a pol!~ilirnn strp.' 'h l l mslplrs arr I~eated in strnlrl at 1lW"C for20 n~inutcs. Fiprr h. I.% sl~o\ts :I sample ofsla5s that c n l ~ t ; u ~ ~ s a n e c l i q ~ ~ l y s l ~ ~ a l l amount of pl~nc~llorus :tntl tlnrs not flu\<,. SOIL. tt~r conmtih o f l b r filnl and tllat thr correspond. ins :mglr i t l I i% nln-rt 120". Fimlres 9.121, c. and d sllo\v snmplcr of P-rl;as will) pro. w~~~i~t~lyhighrrpl~ocpl~on~s cnntrnts. up to 7.2 at? iuright prrcrnt'. I n t l ~ ~ s c s~n~ples , the i l t~rrmine rtep angles oi thr P-o,l:fis l:+vr indicatr ho\v flmr incrriocr wit11 plmsphnnnr mnc~ntr;ttiorn. P-elzu fl~m. drprndc on annealing tirnp, trrnprcttllrr, pttnct>llon~s n crntnlion. and 1111. ;tnnrding ;rmf,irnf."'

Tltc anslr 6':~s a itlnction oi\rright prrcent ofphozphoms m s l ~ o a ~ ~ in F i p w 8 cdn br appmximat~d h\-

l f a r nant :an nnzlr rrnnllrr than 4.5". wr rrqllirr a pl ro~phon~s roswntmtion l aqer 111 6 \riC. klmvr.vrr at mnrmtnt ions ahorp l, nt4. tltr nlrtnl film 1r.g.. nll~minum) n. LW m~rnxh.rl the :led p n ~ l ~ l c b fonnrcl dt~rine the rr;taion l rhvrcn 1111. pl~mphol in 1 1 1 ~ n~iclr i~nd i~t ln~~pIi?r ic nloistum. Thrrrfore. the P-clil~s flmv prmvss IIS,S plu p t ~ n n ~ s concvnlntionr o r 6 to k ul?

8.32 Silicon Ni i ide

h is rlilfi<?~lt In L ! V silimn nitrirlr by t h ~ n n a l nitridation (e.g.. uith amn~onia. XH,) ~ I I I ~ C . nf 1t.i h r . m i l l c ~ t r :mrl hiell cm\\ih tr~apcattircs, tIo\~e\.t.~. silicon nitride

lilnlr ran h. ~lrpnsitrd Iry an i a t r ~ r r l i a t ~ - t e n ~ ~ r n t t ~ r ~ (7jODCI L P O V pnxrcx or a lmv- tr!rrprmtllrr (300'C) plxsma-:l~ristrd C\7) p n m ~ s ~ . " '' T I I ~ LPCVII I;l!ns ;XI. nl stoi- chinmrhic cu~llpcition (Si ,N,lv<tlt his11 tlrnsih (29-3.1 gIcn1'1. Tllra, films can I r urn1 to 1) :~~~ir ; l t r d r d c ~ s lrc;tost. tlley s ~ w r ns gw~cl 1,anirn to thr diftifilrion of n:ltrr :t!d

smli!trn. Thr fil~rls also ran lv tlsrtl :a nl:nk i i r tlw srlrclivc odrl:,tinn ofsilimn ln%:a~w, silic~m nitride o\ i r l i z~~sa~t?~s Io~v l~ ;a~d pn,\vnts tl~r ,~mlcr l~i~lcs i l icn~~ rn>r~l o\idirinc. Thr. filrns llrlnsitrd \I? p~ssn~a-x~sistrd CVII are TMII s t ~ ~ i c ~ ~ i o ! ~ ~ t ~ t n c :111d h:lvc ;I hnwr d ? t l ~ i t ~ (2 .k2 ,S ~ c t l l ' l , I3rc11~sc ~ ) f t l w low dc~pnsitio~~ t r n ~ p r ~ ~ t o t r e , silimn~ ttitril!t. l?!tlts c:tn drpl,<itr(l ovrr l:d)ricatrd drdccr and sm.<.;rc thpir finel p;~rsi\-.ltin~t. l ' la~ma-drp)~itnI nitrid? I,m\jll~s prLrllrllt scriltcll pmlrrtion, s m . 5 ;rs 3 nloisttlrt. I,:lnif.r. illlil prt.\l'rlt\ sndiu~n difi>sion.

111 t l ~ c LI'C\'I> prtrx,ss, diclllomril;m~ ;and ;~mmonin r r x t ;at n.dtirr.d pwssun. In drp,sit $ilicon llitridc at t r m p r c ~ t t ~ r r s lu*t\vwn 7Oo'C and Nil'C. Ila. n . r r t~o~i i.;

83 Dielectric Deposition < 163

. , , , , ~ ~ ~ ~ ~ t ~ i ; ~ ~ t ~ ~ ~ i i c l ~ 1 o m s i 1 . ~ ~ t ~ ~ cttio. s,limn nl tnc~r cIt.p,riterl I,! LPCVI) is nt a n ~ o v l ~ o u dirlr*~*ric n>ntnining up to

\ nlo,,nr irm.,, 1 i ~ , ~ ~ l ~ ~ , . n . Tltr rtdr natr in h~~ni-nvl H F is ~ C S S Illan 1 n k ~ , , , ~ ~ . ~ h ~ . fill,, I,;,% ;, \.PI?. l l tell tmsilt- stlrss oieppn~ri~t~:~tr ly 10"' d!nrdc~n'. \vhich is near^? 10 tilnts tllnt ~ , f ~ ~ . : O s . ~ l ~ ~ ~ s i t ~ ~ l SiO:. Filttls thirkrr than 200 n n ~ el:,? crack htcnllsco~ 1 1 , ~ ,ml"d, \I-%. rill. n,qi~ti,ih.oi~ilimo nitri~lr :it m,nl trn?prmtllreb a1n11t 101'12. l t r ,l,rl~Tr.lnr mn.il;l,,t is ;. ;,nd its Jirb~ctrir s t rengl~ is 10- \'/c111.

I,, t l l r pl.ulll;l.;arirkd C\'I) pnxx.ss. silicvn nitride is hnncd citllrr I?\. reaciingsil :,,,d ;,,,t,~s,o,:, in ;an ;trgon pl.mnt;t or I,! rrilctiltg sil:~lte ill il n i t m ~ r n rlischnye. Tlw m.,.~

~ h , - pnxluas drprnd stronely on depsitiol~ mnditions. Tllr radial-llml: p ~ n l l r l - ~ l a t ~ rrarlnr (Fin. 9'3111 is used to drpnsit t l ~ e filtns. T l ~ r drposition nltr $*ncr.llly incrrasn uitlt i n c n . ~ i n ~ trnmpr~~turr. p n w r input. a11rl reactant g s prrssllrt~.

~ , r g ~ wnn.ntrations of I~\rln~rprn are mntaincd in p l sma-d~podtcd films. The pls lnn nitride tdso n-irrrrrl to ;L< SiSl used in srmimndr~ctnr pmcrscinggenrrally mn. tmn\ 20 to 25 ;~tPr h y r l r ~ e n . Filnls \\it11 lo\v tmsilr stress (-2 x 10 ' <l!n?dcnt'l can L+ prrlllwl hv plasma ilrp>sition. Film resisti\ities range iron1 LO' to 10" Q-cm. depend. ine on silimn-to-nilrne?n ratio. \vl~rreas rlielectlic strenglts a r r iwla.r?n 1 x 10' and ti x In' \ '/cn~.

8.3.3 Low-Dielectric-Constant Materials

.4sdmirrsizes mntinur tosltrink dmw to the d e p submicron region. tlwy rrquireamal. t ikPI intcrmnnection ard~itec+ure to minimize tlte time delay IIIIP top:mritic resistam (R! and capnritnnrr IC), ntr gain in dmiw speed at tlte gate lrvrl ir ir!!irt by the prop. nc;ttion drl;~? at tltr mrtal intcrmnnrcts lxc:iuse of the incrrsed RC lime constant, ar sl~o\\n in Figtrr 9.1-I. For es~mplr , in d n i r r s \\it11 p t e len$lt of231 nm o r b s . up to .%)Or oftltr time drlay is rltw to t h ~ RC <IPI;?\. of Ions intrrm~~nwtior~s."Therefore. the r h \ i c p intrnonnrrtinn nrhmrk hrmrnn a limiting factnr in determining cllip perfomlanu tttrtrim stir11 as dmiw speed. cmss tillli and po\!rSr consllnrption I$ ULSI circ~rits.

Rrd~lcing thr RC time mnstant of ULSI circuits requires intrrmnnection nnaterids ~ i t h ln\r rrshti\ihand interlayer films uitlt lmv capacitance. Note that C = E,N(I. where E, is the d i r l ~ d r i c prrmitti\ity A is tltr arra. and d is the tl~icknrss of the dielwMc film. R q m l i n c tla. Imvapacitancp issue. it b not ray to lower tlte pan-itic capacitance by inc r~ . l r in~ rl~icb~ess of the interln!rr dielectric (x.l~icll makes rap filling more dificulll or dwrr:~qine \\irine I~r ic l~ t and area (\vhicIt rrsults in t l ~ r incr~.;rsr. of intrrmnnrct psis- ~ A I I C Y ) . Tl~rrrfnn-. n~aten.ds\\itl~ lo\vdirlrctricmnstant (Imvkl;trc wquired. Tl~edidee- tric pcmtilti\ihis M ~ I I ~ I I to tl~r pmluci ofk anrl ~.a.ltew k and ~ , N P t l ~ diel&ricmnstNI~ and pt.rnlilti\ih o i lrw .qxtw. r n p ~ ~ i v ( . l ~

n ~ . p m p l t i c s o i t l ~ r intrrlayr d i r l ~ i r i c film and IIW it is fornled h a w to meet thr f r~I l~n~inc rrq~~irrrnrnts: Im\. (lirlrciric mnstant. Imv residttal stress. l~iglr planari7atinn

Figum 8.14 CalnLted gat* and inlrrmnnpd delay vcrrur t r c h n o l ~ Kenention. Tllr dirlc~tric ~ , n > ! r n t for thr ImvB material is 2.0. Rotb ,\I and Cu intprcr,nnntt m.0.5 prn thick and 13 lrm

long.

car:.l>ilit).. 1tiqlt capabilih. for gap filling. low depmition trmpenlurr. simplicit). o f p m cvv. ;sal rase of intepntion. A suhrt.u)ti:d nuntkr o i l m 4 matrkds ltaw I r r l t ~ m t l m L . r d for tlw intrrmrtal < l i ~ l e c ~ c in L'LSI circuits. Somr artltr prnmising lo\\.-k mntcrialr arc s h r * ~ in X~hlr S.2. Tltese ~natcnals GIII b e i t l s r inopnicororpanicandcan lr~(lrpmitnl by ,.ither CVU or spin-on trcl~niqups."

TABLE 8.2 Low-&Materials

EXAMPLE 3

~.~i,,~.,t,. 1hr ; , ,~ , i l l s i c RC of l a x , pnmllrl :\I s.irrs 11.5 icln x (1.5 Llln ill cnnr a.ninl,, 1 ,, ,,, I*.,,*I,. ;,,,c~ ,,.l,,,r:,~,Tl I,? :, l ~ , ~ ~ + , , , i c ~ c ( k - 2.71 ~lie~lcctri~~ I :y r tl,:tl i- 0..5 p!n tI>ick TI,,, ti\rh .d I i\ 2.7 vCl.css.

8.3.4 High-Dielectric-Constant Materials

I litrl,.(. tnnt~ri;~ls aw also q n i r r d k ~ r ULSl circuits. esprcially for ll?nvnall~ic nndonl arrcsr In,.gnoF I I)It:\.\II cixr~its. TIII. s l o r . ~ < ~ ~ c:tpacitor in a DRAXI 11;s to maintain a certain ,: , I , I~ of c;ap;tcit:tncv for propcr opmt ioo (r.g.. 40 IF). For a @\.en capacitance. a ,in!. rnutn d is t ~ a l . t l l ~ srlectr~l to inprt tllc "illlllitions of lllr nl;~Umuln nllo\vell leakage current and t l ~ . I I I ~ I I ~ T I I I I I I I rrqr,ired lrrrakdoun \r,ltagr. T l ~ e area of the capacitor can lx inmn*,we~I IK usins starkrd or trenclt stnlctures. These stnlct1rrt.s are considerel in Cl1aptc.r 9. Hmvmr. for ;I planar stnlctarcv. ;ma is rcr lu~~,d uitll iner?:LSins DRAM den. siv. ~Itcn>forr.. tllr ~lielrrtric mest;~nt n i t l ~ e film r n ~ ~ s t be incrr:ard.

Sc$rr.d I~idl-k rnatrri:ds h;nr invn pmlmsecl. sucl! as lh?riuln stnmtiuln titanate (BST] and Irirrl rjm,nitlm titanatr (P%TI. T l ~ r s e materials are s l lo\n in Tahlc 8.3. In a ~ l d i f i ~ ~ , there arc tikbn;~trs doprtl t r i t l ~ one or inore ;~ccrptors, S I I ~ ~ I as alkaline earth metals, or rlovcl ail11 nnr or nlorr donors. suc l~ ns Elre eatill elrmrnts. T:tntidtll:~ oxide (Ta:0.)11~ a ,liclrr+ric mnstant in t l ~ e r;Ingc of 20 to 30. As a refrrrncr. the dirlrctric mnsta Si ,S, is in d ~ r n n ~ c o f 6 to 7. and that for SiO, is c.9. A 'l':1:0; filln ,7111 be deposit1 ;I CVD p m ~ . s s sine <;~<cons T;tCI, and Oi a? the starting inatrrinls.

TABLE 8.3 High-k Materials

hl~tmialr IicIect~c Con

nin;tr\. TazO; 25 TO, 40 Y:O, 17 Si.S, -

l'amrlwtric ,wnn4itc SrTiO, ISTO! 140

( h . , S r , ! TiO,fUSTl 3M-5M B;I~T~,,Z~,!O,(D%TI .UYI

( P h , . , h , l ~ Z r , ~ ~ T ,~o,~I'L~TI SIW)-IMO P l ~ ! > l c , - , S l ~ ~ . ~ l O , i ~ ~ l X ~ 11m-2OM

F t ~ m l r r l r i ~ ,wrmsLitc PI , 'Z~ ,,,. 1; ,,., ~ ~ j r f l ) >IOMI

8.4 Pohlsilicon Deposition 4 165

wMPLE 4

t 8.4 POLYSlLlCON DEPOSITION Usin$ polvsilicon ns the gate electrode in hl0S daices is a sipilicant de\,cloprnent in X10S technnlogv. One important r eaon is that polysilimn s n ~ , u r e s aluminum for elec- tmrlc rrliahilit): Figure 8.15 sbo!a the maurnurn time to hreakdmn for capncitors with both plysilicon and alrtrninum eleamdcs." Pol!~ilicnn is clearly superior. especially for

- - - l rr l - -

4 - -

l a - - - - .- - - C E - .. 8 - 4.

10' -

d(nm1

Figurn 8.15 hla~imarn time to brcnkdm\n wmrr oddc tl~icknc%s b ~ r a lml!.iilimn r l t d d r md all aluminom rlrrlnxlc."

C h a ~ n r 8 Flm Deoositlon 8.5 Metallization 4 1 ~ 7

,,,, at., c,,lr. TI,? i,,h.rior t i m ~ to h n ~ ; ~ L d o \ \ ~ of ;al~llllilllflll elcctnxlrs is d,,, lo

,I,.. ,,,,O.,l, ,,,,, , , f i l ~ l l l l ~ i l l , l ~ ~ ~ i ~ t ( t ~ t ~ s into tilt. thin odde t~ntlrr ;III (,L.dric:ll field. Pnl!sili( 1,,,

,, .,I.<, ,,rc,{ :,, ;, ,lin;,,i,,,, sollnr I,, ~ n s ~ t t ~ sI~:tllcnv j ~ ~ e r l i a t ~ s a11d 10 tlrls!lrc o l ~ t l i ~ m,l.

c .n , r . ,~~ i , ,~ ,iltCr,,,. ,i,l,lition;~l !trvs invludv tllr ~llilllll~~l~*(ln'~~~~~ll~l~l~tom zind lliS~,_

"(t~,,. h,n ,,,o~t mrnnlorl Imnv.pre<~t~re p m s s r s . one op'nltes at a pn7ssilre of 25 to 1 : ~ I:, ,,sit,q ItwIPr sil.a,p. a.ll<,n.;~x tlw a t l ~ r r intr,ln.s n rlillllrll midllrr of 20% to ri].,r,r ,n nitnr:,.t~ :,I t l l r s;ttap tr,t:\l presslln.. Rat11 p n w r s r can deposit pl!silimn on 1 ,,,,,, {,& ,,f,,-,,ft.m Fr n,,, ~ i t h x ~ ~ x l unifom~ity (i.e., t~~ ic~ l l esses \ ~ i t ~ l i l l 5 5%).

F , ~ , ~ . \.I(; \lanrs tllr d~qwsitiorn mtr at frrur drpavilion trmprnll!ln's. At Ina~silane F'*,J I,R.wt,w, t l ~ . ~l,.lwl~iti~rj~ r.11~ is prnlx,rtiotl;d to tllr sil:lnr prrs-lire.' At highersiliInp ~.,,,~,.,,tn,~,,n~r. a t ~ r , ~ t ~ , r t ofthv dqn,~ition nh. uccua. I)c'posililnl :It n'dllcrrl pressore i' rcI)CP.lll~ I c ! l l i t ~ l to t,~r~lpcrntt~n's 1~.1\$1%.11 64lI)'C rind fiWec. 111 this tPlnprr.th!re mye, tllr ,{i.ms,tjnrt c,tr- v:uie< ;rv espi-f:/kT). tvhc.rt> E. is 1.7 P\'. \\JlicIl is (~ssentii\lly inrle. ptntl,.i'lt c,itlar tnt;d l)rc,sstm in tla. rt.artor. At higllrr tmlprnlllres. gx5-phisr reactions th;tt ~ ~ , , l t in a mnqh. I<nu.l! ncUtwing d r p s i t Ix~cn~ne sienilia~rt. and sil:me drpletion M T U ~ , c3t1sine ixwr i~nilbm~it!: At tc.lnlwntsrcs tnurh loa.rr than filI)*C. tlw cleposi. tiott fill? i< t ~ n slmv to IP pncticd.

Pnrrss ~ I C I ~ C ~ P ~ Y th:tt : t f f ~ i the pnl!si~imn s tmdunSare depsi t ion temperahzn?, ~ l o ~ ~ n t x . and tltr lw;it ?rle npplirtl fr,lhmin~ t l ~ e deposition step. h mltllnnar s t n s n u ~ r r \ l t l t \ u.ltpn pnl!-ilimn is clrlx,site<l at a t e ~ n p n h r r r of fiOODC to 6JODC. This StruQllw mnsi.;tr of pnl!rnstallinr grain rancin< in rim from 0.m to 0.3 pzn at ;I preferred a cnt.rtinn o f , 1 I O ~ . \ilx.n pl~nsplionts is <liffusrcl at 95fl°C. the stnrctorr chanses to cr trllitt.. ianrl qfiutl s i r i n c r r m ~ . ~ to a size Irhveen 0.5 and 1.0 pm. \\Iten t r rnpn tum inrrr.xwcl to IlE4c(: ~lt~rinearidation. tile g c u ~ ~ s reach a fin;\! rim of I to 3 pnl. ~ l t h o u tlw initidly drpoqitecl film apppaa a rno~hot l s rvhm drpositins ayun hrlmv pm\%ili rllnfi~ctrristin similar k, tile p,l!c?+t;tIlinc-pn~ir~ cnl!!n~o,r strurturc ; ohstm'rd itftrr rlopinq and itr:ttin~.

5" 'C. Ire

Pol!silimn Mn 1~ clopcl I,? rlifFf~sio~~. inn implmtntion. or tl,,. ;,,ldition ,I,,,,:,,,~ gwes 'Illrills drppitioe. r ~ f i ~ m . ( l to in i t l a d,ry,f~,c. nlr irnplilntatin,, nr,.tl,orl ir n,mt rn~rllnonl? ( 1 ~ ~ 1 lrclllsr ofits lo\\rr prnrsxio~tc~mprnt~~res . F~v,,,. x . I ; ~ ~ , ~ , ~ tllp d,,.cl rrristimn of sins!?-cnstal silimn osd of.UHI-nn~ lx,lpilirnn +,.,l ,,ill, pl,,npl,on,r ;,,,,l sntilnnny IIS~IIC ion i~npl;~nt:~tios."~ Tlr. inn inlpl:tnt;,tir,n Pr,KIls ,(CL5 n,,,xi,lPr(.,) i n

(:ll;nptrr 7. Inlplant d(>st.. annrltling tcmpctntlln., ;anrl :alncalil,s tim,. il,flllrsn t~,,. shprt rrsist:mw of inlpllnt(.d prl!silimn. Canirr tr;lps : ~ t the Fmin Imtlsd;lnr< c7esP a

v r y I I ~ S I I resist:inw in the lisl~tly i~rlplat~teel pIvsilicon. AS ~ i q , , ~ 8.1; i l~ , ,~ t~ ; , t ,~ . N+.

t:lnw drops nlpidl!: a p p m ~ r l ~ i l ~ s tllat of implantr.ci sincle-c&td silio,n. ; ~ r tlle mnirr t n p s in*mmc sattlntrd \ritll rlnpa~tts.

F 8.5 METALLIZATION 8.5.1 Physical Vapor Deposition

Tllr most canlmon metllocls ofph).riral \upor deposition (WD) of tact;<ls .... tion. r - l r am r\npontion. p~:uma spray drpmition, ant1 spultrrin~. \let& and inPt.l mm- por1nd5 SIICII a? Ti. Al. CIS. TiN, and Tax can l r deposited Ity P\'I). Ev:tponttion m l n \r.llvn ;I soarw mat-rid is Isnted above its mpltinx p i n t in m e\aorated nlr e n q w ~ ~ t r r l atonls then travel at l ~ i g l ~ vclocih in stmisht-line trajjprtarir$. TI,,, soure ran IK. ~nrltcd I n reshtanw heating. In &heating. or\rith a fmtrecl cltrlm!~ lram. E ~ ~ n t i o ~ and r - l r am evaporation s e r e used es te t~si \~Iy in earlier generations of intrqratrrl rir. cu i t~ . but tlrey haye i r e n rcplac~d hy sputtering for ULSl circuits.

In ion l r a m spotterillg. ;I snllrce of ions is >lcuelrnted to%;vrl llte larget a d impinem on its sc~rfacr. Figure 8.1% sho\w a standard sptlltrrinq ?sten,, T I I ~ sputtvrcd matrrid depocits on a w f r r that is placed facing the target. T l ~ e ion current and e n e p can l r indt.lrerlr~~tly acljratetl. Sinw the target and \rafc.r are p b e d in ac l l ;~mhr tllnt h.x< lmwr p resx l~r~ , more target material and less mnta~nination are tnns f rmd to tllr unfer.

ultr n~ethod to incrcae the ion density and. llcnw. the sp~~tter-tlrpsition ntte is to use a tllird el&r(~le that pm\ides Inare elwtmns for ioni7->tion. Another mell~ml is to IIX

loll d m (em-'1

figure 8.17 S I , ~ ~ rcsistnn'.~ rrnw ion dtxr into 5M-nm lnl~silirnn .I! XI kc\:"

164 . Chaptar8. Rlm Oeposltion 8.5 Metalli>atian 4 Is!

CVD Tunnsten

,, firld, sl,rl, ;,< p / ~ m , l cYrlr,,tmn naotlnrzcr (ECR). to c:lphlrc and spin1 e

tmm, ill~~xvi~~~tlleirioni;.ing~~llirin~c~ in the\icinihof tile spl~nering tarset. Tl~is 1, n,fmr,l to :a ,n,le,r.,tmrl v,strm",~g. ha$ ~ > ~ I I I I I \ridespread spplic;rtinns for

drpoPitian of;J,,zsi,l,,nl a111 its allrqs at a rate that -In ap~m:lcll 1 Jllllflnill. ~no.t~lmx.sp,,t trring isanother tcclrniqur used t o c o ~ ~ t m l the anp11lar distribu~

\.IS, i l o t ~ s a Iung-t~~m\v sputtrring s!steni. III stancLud sputtcrins m n l i g ~ n t i tl,rrr are hro p,j,nar? rp.uons for :I nide ; lsplar distribation of incirlrnt flux ; ~ t the f;lw: the lrse of a stnnll ti~rget-to-suhstnte s~paration. 4.: and sc:%ttrriog of the flu tl leuarkne as tll? flllx 1mwLs from the tilrget to the substrate. Tllesz hvo filcton l i n k ~ I I,&& a s~nallrl, is n m l d to acltirve gmil tl~mngl~put, unifomlih and film p erties a.llm thmre is rubstnntial gas scattering. I\ sol~~t ion to this probleli~ is to sputta vel? Imr pressures. n apahi l ih tllat Itas bern r!e\rloprll rlsillg a rariet). of s)r;tems n n sustain the rt~:r,petron pl:uma under more nrefird conditions. T l ~ r s r s!rtems a for spattrrinqat working pressures of less than 0.1 Pa. At these pressurcr, g:s scatte is less important. and ~ J I P targ~-t-to-s~thstrate distanw can be greatly incre;~sed. Fmm silnnlr eeonletrical arCarnent. this dlo~vs the angular distribution to he arratly narm\~~ed.

>,IT-

x 11). i are

m P ?rat tllat 11mv ring

.... ~.~~ ~ .- . s o n r r i n e r \ m b nt tsr the top oprnin$nftlle iiolr to seal h r b r e apprrci;#l>k' m:lteria ~lepmitnl on its floor. This pmhlrm n n hr overconre hy m l l i ~ n ; ~ t i ~ ~ c tlir sputtered at hy placins an arm!. of mllimntin~ tnlws jr~st alwre the a d e r to restrict the depositing lo nomjial 5". Spnttrrin~ with it mllimator is sl~mvn in F i p r e K.1Xr. Aton~s \vl~ose rm- j m o ~ is lnorr tllan 5" from normal arc ~lcpositrr~ on the inner sufiac'~'~ ortllc mllinlaton.

8.52 Chemical Vapor Deposition

C\'D is ntt~ictive for metalliwtion lwcaasr i t nflen coatings that are mnfr~rmnl. has g m l step mvrra:e. and mn mat a l a ~ e nnmlwr of \vxfen at a time. Tlrr h;~sic C\'U setup is 111" &?me a? tllat use11 for rlrpocition of dirlrctrin and pl!silicon lsre Fis. S.90). h \ v - pnlnnre C\'D is cgpablr of pnx luc in~w~~formal step coverage ovcr a \\irlr range of top* mphical profiles, often \r i l l ) imver electricat resistitit) tllarl tllat fronl !'\ID.

Onr of tllr n~ajor nmv spplintions of C\W metal deposition for integrated cirruit prah~ction i q in the arra nf rrfrxcton. mrtal deposition. For example, tungstm's l o \ t r ~ l ~ - trim1 rrsisti\ih /5:3 @-c1n) irr~cl r(.'fractory nahlrc. makc it a rlesirahlr tn~.tal for OW in inlr~ml<vl circalit fahrintion.

- T~tngst'n is llscll imtb as a mrrtsrt plug and nc a l i r r t - l ~ ~ l

can 1,. clrpositrd 11). wing \s'F,, as the mlrrrr, gm. since it is a liluirl that h i l s ;,t rmlll tplll. prn~turc . \VF, ~ ; I I I he r e ~ l a c ~ d by silicon. l~ydrogm. or sil:,nr. Tllr b:~rir cltrmistv lor C\:D \V is as follo\vs:

\\'F,, + 311: + \t' + 611F (Ily~lmgcn redttclinn) (2.01

2\W, + 3Si + 2\1' + 3SiF, (silimn rnlttction) ("11

2\\'F. + RSill, + 2\V + DSiF, + 6Hl lsilane reduction) (2.2) --

On a Si WnhCt, tile s~Iecti\.e process starts from a silimn reducticln pmss. n,is pmN'SS pm'ides a llucleation 1;lyrof \ V ~ n v n on Si hut not on Sir4 n,r l , , ~ l ~ ~ , : ~ mlur. tinn p r m s s can deposit \\'rapidly nn the nlrcleation layer. fonnirlp tlrr .rI,r ilr.tlrr,. gen reduction pmcess pro\i<l*s excellent confom~al covcra<e of tltr tnp,lSraplb): Tliis process. bo\\,e\rr. d w s not haw p e r f ( ~ t selecti\ity and the HF ss I>y-prc,dt~d of tllr

re;~ction is responsible for the encmachment of the oxide. well .lr fir tlip mtzgh surfaw of depositerl I\' films.

Tile silane reduction p m s gives a high depsition rate and much smdler\P grnin size than that ohtaincd \at11 the hy~lrng~n rrductinn p m s r . In addition. tllp pmlrlems of encmachment and a mrlgl~ I\' surfiiw .w elirninnted b m r ~ s e thew is no 1IF hy-pm~lud generation. Usually, a silane rerluction process is used as the first step in blanket \Vdcpo- sitinn to serve a3 a n~~cleation layer and to redlice junction damage. After the silanr mlur- tion. 11)rlmgen reduction is used to grow the blanket \\'layer,

CITY EN TiN is \\idely usedas adilfr~sion barrier metd layer in n~etalliwtion a n d n n he rleposit.%. by sputtering fmm acornpound target or hy C\Q. O D TiN n n prnikle hetter rtrpmv- em;: than P\'D methmls in deep si~hmicron t w l ~ n o l w C\'D TiS be depnsitcrl"" usir,? TiCI, \\it11 NH,. H JN,. or NHJH?:

6TiC1, + RNH, + 6 E N + 24HCI + i\': 123) Z'TiCl, + S, + 4H: + 2TN + 8HC1 1%)

2TiC1, + 2NH, + H, -+ 2 TiS + RHCI ('5)

The deposition t e m ~ m t u r r is ahout 400°C to iOO0C for NH, redl~ction and is hiqher t l ~ : ~ ~ 700'C for the NJI1, reaction. The higher the drposition temprmturt,. thr hmer tlrp E N film. and the less CI incorpmted in TiN (-5%).

8.5.3 Aluminum Metallization

Alt~rniult~ll :lnd its i i l ln)~ an. urn1 r~lcnsi\.rly for nlet.?lli?-,tlon III intcmtrd clrrllitr - ,\I filn~ C;~II 11,. d r ~ m ~ ~ i l ~ d lrr P\'D or (:\'I). Since altmlint~m ialrcl it< .d11ns 11:t\1. lo!(. rw\ . tivities (2.7 PO-CIII for Al and up 103.5 pQ-cn~ for its alln!?il. Illex n~etals s:rtizfy tlw lo\.- resistance req~~irements. Aluminum also adlleres u.ell to silimn di~io~ide. Iloav\.c.r. t11e

allimlioo a ~ l d their SO!II~~OIIS

Junction Spiking Figure 8.19 slr~~\\.s the pl~sse diagram of the AI-Si s)5ten1 211 1 atni."' T ~ P plr:~%r rli81m.lrn relates tllese hvo m~npnnents as a function of teolpwhlre. T l a AI-Si ?slrsi r\l~ihits

4,Xl I

0 1 0 '31 30 40 .X fdl 70 50 'XI IIRI

mmir 'F "limn

Figure8.19 Pl*zw rliaprn o l ~ h r d~m,inurmilimn nstrm."'

nrte,iir elonr;nirristic~: tlmt is. tlt~;slrlition o f r i t h r r m m p n c n t lo\vrrs tllr y - t r m i r ittq p i n t lr lou. 1h;h of e i t l ~ ~ r m6st;d. I l r r r . t l ~ r minimum n i r l t i n ~ trnlpecttare. c;

rvrrrctic roaq,+.mfr,rr. is .5;7'C. mnrcpondine to n 11.356 Si and N'I.7C6 ,\I m m p s i Tlac 111r1tin~ p i n t % of pure altlrninurn anrl pure silicon are 6Ml"C ;tnd 1-112LC. ws tiv~l!: RCCIIIW of IIIP r~~tPCt ic r l~ ;mcir r i s t ic~ . luring a l a~minun~ d r p ~ i t i t ~ n tltr tern n t n n on t l ~ e silimn s~dlstrate lnllst lw limited to Irss than 5 7 7 C .

The i n v t i d F i ~ r r r 5 . 1 9 shoas tllr solid ml~thil ihofsi l icon in : Jn rn in~~m. F o r e pl?. thr. urlllhilih ofsilicmn in nlttmintlm is 0.25 ~ i ? at 4IWl"C. 0.5 n i C $ a t 450-C. O.\ at? : ~ t .-fl)'C. ni?r r for r . U.!IP~P\C~ ;~l!~!ninum contavts silimn. 111,. silic~m \till solve. intn tllr .~ln~nin~x!n ~ l t ~ n n e ;~nnralin<. Tltr amount o f silimn d i s s o l v ~ ~ ~ l xill clrl not only nn t l ~ r snlt th~lih at l l ~ r ,innenline tcrnper:~tnrc. hut :tlso on the vnlurnr of ntinllm to 1%. c l t umt r~ l u i t h rilimn. Consider n l o n r . a l ~ ~ m i n ~ ~ s ~ n1et;J lint. in ntntact :MI :arc:* Zl, of siliwr~. :* d m w l in F ip r t - 3.20. .Alter ;an :+nnealinc tinn~r f , 111" silimn - r l i f i ~ r r ; ~ <list:mcr. nfappr ,~umntr l \ VUf d r m c the ~ l u m i n t ~ m line fro111 tltc rdcf 01 ~511t.1ct . wl~vrt, 1) is the (lifi~qic~n cwffirirnt c i v ~ r ~ hy 4 x 10.: <.vi4)32!kT) for sil

LIIP<l

lion.

F" l p r -

(am- and dis-

Rgun 1120 Dimtsion of silieon in nl~rminum metdliration.~

diffusion in d e p s i t e d aluminum films. Assuminq that this lend11 of aom,sum is mm. plrtely saturated with silimn. the volume of silicon m n s u m ~ I is tllen

(26)

a41ere p,, andp,, are the densities ofaluminum and silicon, r e w t i v r l y . and S b the ral- ubil ih o f silimtl in aluminunl at the annealin!: tempmturc." If th? consumption t&es plitc? u n i k ~ r m l y w r r the mntact area)\ (\vhereA = ZL for uniform diwlutiani. the depth to s.l~irh silimn \\auld be mnsumed is

EXAMPLE 5

Let T = YN)"C. t = 30 min. ZL = 16 pm'. Z = 5 pm. and H = I pm. Find the dcpth 6. arrumi ttnifwrn disulltttion.

SOLUflON - The dilh~sionmlficirnt ofsilimn in alttminum st5M'Cis abu t 4 x 10-'cm'lr: thtra. V I l l i.i fill pm. Thr drnsity nlio is ?.in33 = 1.16. At ,W"C. S is 0.8 r\i%. Fmm Eq. 27. u.e haw

Aluminum \\ill fill a depth n fb = 0.35 pm from which rilimn is mnn~mnl. llat thr contari point thrn. is a rhallmv jnnction whose drpth is less than b. thc difhsion of rilimn into alumintnm cm short-circuit thr junction. 4

In ap rac t i n l situation. the dissolution of silimn does not take plaw imilonnb but rather at only a fmvp in t s . I l l? effwtiw area in Eq. 2 i ic l e n than thr aciual mntnrt arric I~cncr. b is inttch larger. F i p r e 8.21 illustmtes the actual sitlnatioll in the #I-n j ~ ~ n l i i o n :Ire3 of d u n ~ i n u m penetratinp the silimn at only the le\vpoints \vhew rpikes are fnnnvrl. One uay to minimize alrlminum spikne is to arld silicon to the alulnint~m by co-r.va~nntinn

until ll,p l,,,,,l,,lt ,,f 9ilicll, ~lll,kti,i,y~ hy tItc ~ 1 1 0 ~ sltisfics t l ~ r solt~bility v\ t i re lnml, r,,,tl,t,r ,n..~l,,nl is lo i r l t m l , ~ ~ y . :a Ib;trrirr nlet:d I t ~ y ~ r Irhtm.11 thr il~lllllill~~nl and the ~(1 . im,, s,,ln~crt,. I I?;<. 'r 221. Tllis hrrripr mvtd 1;nrr n111s1 mrrt tl~r fi~llo\\ing i r q ~ ~ i r r r n ~ ~ : 11 ,,,,,< ion,, I<,,,. cont:,~t n.siska!~m~ N ~ I I I siIi&n. i t n111st not react \\it11 d111trintt111, al,<l its , j r l ~ s i t i o t ~ .II,LI (i)nni~tio~l l~itjst IW comp:ltil~l~ \\it11 the orrmll p n w s s . Barrier m ~ t . nlq surll .,< tit:ulilll,l ~~ i t r idc Il'iS) I I :~vI~ 1wen P \ : I I I I R I ~ :II)II fo1111d to IIP stithlr for mn. r.,rt . m n c ~ t l i l t ~ ~ , . , , ~ ~ r . , t t t w s nf up t a ,55O0C fi,r 30 ininatrs.

ti,,,, rrirn to lhr t m l w r t of m;r~r 1.i.p.. ~ t o t n s ) in 111rtalc ilndrr tllr i~llluc~~ice ofalrrent. I t ~ t t n hy thr tnnsirr of t s o n ~ e n t ~ ~ ~ a frorrl the rleTtrons to tllr psiti \ .r metal ions. \\I,?" ;t lligh wrn.nt p;~rscs thrnugl~ llbirl rr~rt;d condrlc'tors in intrr, l tell circllits. metal inltr in sonv. rqions \\ill pilc up. ;inel voicls \rill for111 in otlrcr reeion<. Tlds pileup can sl~or+.circt~it :acIpwnt c v n d ! ~ c t o ~ . ~vherr ;~? the \nids c3n rt-sttlt in an uprn circttit. nw nzrar, t ,r,u.~o foiltin. 1 XlTFI ol'acnn<l~~c.tor due f o r l < c t r n m i ~ t i o ~ t cim he related

to thr o jn rn t rlt.nsih I]) and thr acti\atioa r n r q I?

Eywrim~nt;Jly a \ a l u ~ of E, I 0.5 P\' is obtitinrrl for deps i t ed dsniinum. 'This indi- c:rtpr t1t:fit Lm.-trmpmturr min-ir)rreclan llilli~sion is thr pr iman \.clsiclr of olsterinl transport. since an I.:, s 1.4 r.V \vo1111l elraractrrizr the self-difirsitm of sieqle-cnstal ala- minunl. lllr e l ~ c i r o m i ~ ~ ~ t i o n resistance of alt~lniettrn r n n d ~ ~ c t o n =in In. incrc;rrrd I)?

Figun 8 2 Cm%~-w<in!rl \in\ '4 ;I \IOSFET nilb $8 I?arnrr mrtd h,hvc.cn ihr alurninxtm and ':lh.,n .find .8 rrampn>tr tit., vl.ctn.L. of s i l r ~ i ~ l r and p l ~ ~ i l i m n .

g,5.4 Copper Metallization

11 is \vcll kno,\n t1111t Imth li icI~-mnlIuei~iy uirir~g ~ m , . . , l i ~ l ~ ~ " ~ . ~ ~ ~ ~ ~ , ~ ~ t o n :rrr r r q l l i ~ t l to lo\vpr the RC time drlny of titr intrrmnncd ,lr.tlv~,rk. i5 (I,,, ob\'iolls clloiue for ;I nm' illtcr~nnnrclioe mPtalli~;ltinn lxc~or[, it llas I,iSlllr c,,s,l,,ct,,.. it? and iliehrr r l r c l r l ~ n l i p ~ t i o ~ ~ rosist;~ncr than ; r l t t a ~ i n ~ ~ . copprr c;lll ,\rpwilpr) I,, PVD. C\'I). and olrctmcl~rrnical ~nrtl~rxls. IImvowr. tile ,,w o~c , , ;,,, altcn,;rti\.,. ,,,;, tr. rial to AI in ULSl circllils ha$ dr~i\vhi~cks. such xs its t r n d e n ~ to mnrrlr ilrldc,r rt;lnd;ml chip m~ti~ifnc~l l r ing conrlitions. its 1;1& o f a fr;~ril,lc. dn. rtcllinp mrllanl or a stal,ll ,,.I(. pi~ssi\.atinl:o\iclr sitnilar tnAL,O, on Al. :rnd its p m r adllrsirrn to rlit,lcnrip m;lteri;41s. n,rh ac SiO: :mrl low-k pol!mcn. This s r c t i o ~ ~ disorsul y p r in<.tallirntiol~ itxllchni<lllr.s.

S m r n l difirrrnt trchniql~es for f>~l>rication olmaltilrvrl CII intrr<ntinc~iq I ~ : ~ v P lmn mpnrte<l." ' The first metlaxl is ;I convrntio~lal mctlad to pattern the lllrtd linrs. fol. lo\vrd hy dirlcctric clrposilion. Tllr s m n d ~netl~rxl is to patten) tltr dirltylric I;t?rr first and fi l l mppr r metal intn trencl~es. l l ~ i s step is fi)llmvrul I? rlavmirol rrtrcltnrjtrnl ,x,l. ishing. d i s n a s d later. to n n o v e thr rrcess nietal on tlir top SUK:+LY of the dirlq.ririr and lrave CII matrrial in tlrr lrolcs and trenches. This methal k also ho\\n a a ,laln,,~o- sc r t~c pmcrss.

Dnmnscene Technology Thr approach for bhria~tinp, a mpperAou.4 dirlrctric intermnnn? stnlchrrr is hy tlte dan~rnct .~~r o r dual dam:ucr~re procrss. F i ~ t r e 8.23 sho~vs tlw 1111al dam:rwnu srqurnce for an arl\anwd 0 1 il~termnnfftion stnlatlrr. For a hpid <hm;lrrmr stnzar~re. tn~sclws lor metid lines are de f ind ;l~lrl etched in tllr intrrlayerdirl~<ric (ILIII, follor~wl I)? lartd drpocition ofTaNICu. TllcTaN layer sewer a% a difTnsion barrier I?r.r and pn-r-cxrts mp p r from penetrating the lmv-k clielerMc. Thr r r m s m p p r mrtnl on tlrr S I I K . ~ . is removed to ohtain a planar structorr \r i t l r metal inl:i\s in lltr dielectric.

Vur tlre <III;II I I . I I I I , L ~ ~ ~ ~ > p w r s s . 1 1 ~ . \I;>? ;lnd trt~nclteq tn tlw ,li,,lrcl"c :an. clefit~t,tl

usinc 1 n . c ~ l i t l~om~nln.an~l n'.~ctivv ion rtchine IRIE t 5tms lu-inrr clr~vxili~lc tljr (:I, I . 7 .. . . -

(Fits. 3.Zk-c). Then a Co cllemiral mcclranical p l i s h i n ~ pmcrss is 1ts.d to reo~orr metal on tlrr top surface. lrwing tlie planariretl \ \ inns and \ia imh.d~lcd in thr in tor:" One sprrial h l ~ e f i t of t l ~ e d u d il:tm.rcwnr t rc l tniq~~r is tllat dw \ia pl~lg is nt tlie sntnr m;ttcrial ;L% the i n ~ a l line and tllc riskofxia e l ~ l r o n l i p t i o ~ ~ L~illlre is m l n m l

EXAMPLE 6

If\w mplan. Al \~\\th Cu\\ire~srri;hd\\i t l> romr lmv-k diclwtric 11 s 2 Tr\ inrtnd of r Sin, I;pvr. what p e m l a p r of rc<ltlaion in tltr RC tirnr mnstant uill lr i ~ c h i ~ ~ ~ ~ l ? I l ~ r rt.ri\li\il).of Al i, ? I pR-cm. and t h ~ n,sisti\lr). of CII is 1.7 pRcm.

SOLUTION

Chemical hfeehanicd Polishing I s r e n t ?ran. tlre den.lopmrnt ofclrr~tricnl mccl~rnicnl plisl~inp: (CXII'I 11:~s Ixmmr incrc:~sinf$~ important for in l~l t i l r \~! istrm)nneCfio~l hralrnr it i v tll? only t<clllln!lT?

ChspCer 8 film Deposition 8.5 Metallization 4 175

'E,Y

(dl

Figurn 8.23 P-s s c q u r n ~ 1 ~ x 1 to fahricatr a Cu line-stud stnlcturc r~rin:: dud dam- i o Ilcsi<t stencil npplitvl. ( b ) Reactiw ion rlrhinr: diclcdrir and resirt ptten:ine. ( r ) Trcneh \ in drlinition. (dl Ca dcpitiosr follmwd by rhcrniral rn~h; tnia l plirlnine.

sits,

ne. and

that d l m n ~ loha l plwariwtion (i e.. makes a flat sllrface across the \\holr wafer). It oi m.m\.ad\xntaees ovrr other h w s of technoloeies, incll~dine h r t t r r ellbal danari7ation

Diclwitic Dlr!dnr

- , . k. ~. over l a w or small structures. rnl l~ced drfect dens ih and the avoid:i~lcr of plz~smadarn- ase. Three CMP appruncl~~s are s u 1 n a ~ a r i 7 ~ ~ l in Table 5.1.

The C l I P process mnsists of moxing the san~ple surface against a pad that carrier s111rn hrhvrrn th? sample s~lrface and thr pad. i\hrasiw particles in tllr s l n m caaa mmllanical damncr on the san~ple surf;tw. loosening the nvaterial for enhanced cllemi- r;d attack or fracttlrin~ off the pieces of sllrf;rce into :I s l u m \vllew tile? (lissolve or a n n w p t R I ~ . Thc p r m s s is tailnrrd to provide an enhanced material removal rate from hioh points on surfac~s. t h w ztffrctin~ the planari7iition Iwai tsr most c l~e~nic ;~ l aetions arc iu~tmpir. \lechmical pillding done may tltm~+icnl!\. a c h i c ~ r the dr.sirrd planaiz~tion.

, r.. I Si,S,

Cu linr -~

TABLE 8.4 Three Mhods d Chemical Mechanical Polishino (CMPI

Slrthrrl \Y;*lvr F,icin< Pialcn Slo>vr.m,.nt S l u ~ Feeding

R"l;m. CSIP Lh%n Rolar). ap;ainst ml;ltin< uafer otrrirr Drippin< lo pat1 rudm Orhilnl (:SIP Dmrn Orhital n~ainrt mlalin~ \vafcr carrier n l r o n ~ h the pad n~rfaw linr.:cr CMP Dmw Lint-ar aqdn.it mlatin~ wafer carrier Dripping to p d ntrfaw

I,ut is not desirahlr &.IU olrxtmsiw x < s ~ + a t n l r~amaCr to tl,c ,,,alerid s,,rfacm, n,crr arc tl~re* mnill parts oftllp prne-IS: ( i n ) ~ I I P ~ t ~ r l : ~ ' ~ ~ 1" I". po~is~,ccl: (1,) tl,e ,,-,I. ,rl,icl, is t l ~ e key 11lcdi~lll ennl~lins tltr tr:mslrr of m~cllanical aclios to tltr. s,,rfaw lu.illK lw,lid,p,l: and (c) llle s l u q \vllicll pm\ides in t l l cll~miad nud mcchaniml cfl~rtr. Fig,. $2.1 sl,mn,, tllr C \ IP srt11p.~'

IIw odd? rcmor.d n te and thr rerno\ltl m e olil lit!~r , ~ n l l , . ~ ~ t l , the. &,I,. ir;di,.d a stq, >are I r and 0.11: n ~ s p ~ t i v c l ~ . To remove I prn ofoxidr ancl a n.nl wm stnp I;:rr. r l , ~ lOt:,i r<.rnc,,nl tin~c is 5..5 ~nim~I<.h. Find Il tc o~iclc rt~mwal mte.

8.5.5 Silicide

Silimn fonns many stnble metallic and semimnducting mmpounas \ \ q t l ~ metals. spvcral metal silicides s l~o\ \~ lo\$. resiskity and high thermal stability making tllrrn suitable for ULSI :ipplication. Silicidrs such ;is TiSii and CoSii 11;lve ~ n c o n a h l ~ Im\- resisti\itips ant1 arr nenecdly mnlpatihle uith it~tegratcrl circuit processing. Silicirlrs lmqmc important mrt:dlization materials as de\ices l r m ~ n e snldler. One inlportant applimtion oisilici~le is fur the SIOSFETpte eledmle. either done or\rith d o p l pnl!silimn (~x>lycidr) aimy tllr gate oxide. Tnhle 5.5 sliaus a mnlparison of titasiunt silicidr and mhalt silicide.

hletal silicidrs have heen ~ ~ s e d to reduce the wntaet r~r is tanw of thr source and drain, tl~r gate e l rc t rdes , and intermnncctions. Sdf-nliqell metal silicidr trchsoloq

Figure 820 Scl~ernatic of a ChIP pdi-her

TABLE 8.5 A Comparison of TiSi, and CoSi, Films

Pnrlxrlics XSi, CnSi:

I S 1 6 .=-?$ l~csisli~ity Siliridc*!mct.l mtia 2.37 0.56 SilicilrtSi mtiu 1.IU n5):

Il?ncti\x. to native ondr YCS Y ~ D

Silirklatinrl tcmpmlarc ('C) SIXLW 53L~XWI

Film strcqs l~hnc!cm?) I 5 x Ill lo 1.2 x 10'"

176 r Chapter8 hlm Deposition I

~- ~ ~

sl,;,Ri,,c t l l r ~ ; , t r to t l l r <nu& ;tnd ,Inin during l l ~ r siliriclntian pmces. h metal la\? ritl,rr .fi or c:<,. is l,l:,~~k,~t-sp~~ttc~rr~l or1 thr. rntirc. stnlctllrr. fullcnr.rd I)? siliridr sinic ins Siliri,lr is fiInec~l. ill prinriplr. or~ly$vllrrr tll? nlebd is in mntilct \tit11 Si, i \ \ $ ~ t CJ

ir,ll s:ucl, tIIC.~t rinr(.s ull tllr unn~ndcd 111r1al. I P ; L \ ~ I I ~ o111y the silicide. This krhll elinlin:4~er t l ~ t - t ~ p n l to pitttrm the nrntlx,sitc iwl!ridr satr stntcturi. and :trlds siliri, tl,,, arm 10 ~CYIIILY the c~~nt:ict r~~sisblnff.

Sillci~ll.s an. pmn,isi!!$ ~natrliats k,r ULSl circllits iwcilusr of their lo\\. resisl ~ ~ ( ~ ~ l l ~ ~ n t t1b#~nn:d st;~I?ilih. Colxdt siticidcs 1 1 ; ~ ~ heell WidcI? i1~vrsti~;ltPl~ ~ G I I L !

its 1 , ~ n.<ivti\ih;tnrl l~ i~ l~- t~~!n lwmture tl,rr~oal rt;d>ilit) Ilo\vr\.rr. ml,slt is sensitir native oritlvr m a.vII ;IS :In apern-cont;lininS rn\ironlllcnl. and :I hug. :Ilnollnt of sil.,,,, i~c mnioni,xl rll~linc silicid;~tio~l.

SOLUnON nlr rrriqti\i?\. is rr~llsl to the pnxluct ol the rhrrl , ~ $ a ; , ~ ~ n,,rl nl,,, tt,ichr,,:

p = R , x r

Thcn

. 8.6 DEPOSITION SIMULATION SUPREhl may be used to sin~alntc the depsition pracrrr. Like etch simrlation. depo sition olmleting is ,,el). stmiglltfonvartl. Sinlulation is cxec~ted wing the D E M S m O N mm mand. u.lric11 deposits a piwn amollnt of user-sprcifiwl material on top of tlrc nlrren stmctorr. Tlte matorial deposited may be either , d o p e d or uniformly doped. irrinSIe- cqstal siliwn is deposited. t l~en the cnstal orientation must :Jso be specified. If plp i l . imn is dcpositrd. the tcnipernhmre must l r qwificd for SUPREM todeteminethepraprr p o l y i i ~ i m grain size.

L~pp>se \\T. \*ant to simulate the deposition o l a ~ ) A CVD silimn nitlidc on top nla d~ o t i h lqvr appmdmitlrly 4 ~ : \ thick. If the p-hv silimn suhtrnte is doped nith lam" at a lnul of 1O1'cm-'.

Sl!PRELI to detenninr lhc final oddc and nitridc l q e r thichnrr. m \\rll a- the lnnn d q in: profile in tho oxide and nitride la!urr.

SOLUTION The SUPIiEM input listing is a follmrs:

TITLE COWENT INITIALIZE C N E N T DIFFUSION C M E N T DEPOSITION

PRINT PLOT STOP

Deposition Example I n i t i a l i z e s i l icon substrate <lee> Si l icon 8oron Concentratla-lclS Grow 488A oxide Time-PO Temperature-1090 Or! Deparit 800A CVD n i t r i d e N i t r i d e Thickness-0.08 Layers Chemical Boron Net End Departtion Example

Aftrr simulstion is rnmpletr. the rert~lts are rhmm in Figurr 8.?6.\~1cn mn~narr ;In:d osidc md nitride l:tver thiclnesrs ol3i9 vncl li00:\, rrsFti\uly and drpicts thr lnmn inc",rpor.~tion in thr oridr lnvr 4

b 8.7 SUMMARY

blmlern selnimndllctor device falr~ication requires the use of thin filnls. In the epik~da1 ~ \ S I I I process, tile substnte d e r is tltc s m l . Higll-quality. sinslrcnstd films Gill l p Fm,,.,n at a tempmtaw 30% 1 ~ 5 0 % I(nn:r than thr lnrltin~poillt. T l ~ r mmtnon t ( ~ l l n i q ~ ~ ~ . i fi,r Ppibnjnl p,I~l, ~IwmimI wpor dep<i t io~~ . mrtalarymuc C\'ll. and molwtll:tr ~ ~ ~ l n l

Chapter 9. Process Integration 4

Process In teg ra t ion

\licm%:t\r. photosic. ; u ~ l ix,\\rr applintions grnrnllh. P I I I ~ ~ O - (liscrete dr\iws. For P ) L ~ .

; a t I\IP:\m diwlr i t~sml ;w i~ inirmaaw grnr~ltor. ;III injwtion lmer as an optid solnn~.. i l t lcl :t th!%stor s a i~i~I~-pn\vt'r nvitch. tlo~vrwr. lll~lst c~l+.tn~nic?5tenIs arc 1, on t h r in,t.cmtrrl rirnrir. \vllicll is :in rnsr~~nl~lc, of lmth :~c t iv~ (r.g.. transistor) and sitv t r .~ . . n,cistor. c;~p:~ritnr. ;tml inductor) dc.dct.s fonncd on and \ \ i t l ~ i n a sioglr.cn? srnmimndttctor suhstmtr : t n ~ l ititrrconnrctrd hy :I mrtnlli;r;ttioo pnttrm.' ICs l~a\.e & IW,IIS :~,I,i~nt;qrs mrr disewtr ilmices c o n n r d ~ l b\.\viirr lxrn~linp. nrr ad\antages it~cll ;:I) mltjrtion of tllc i~itcrc~,nnection panritics, brc;~osc an IC ail11 niultilrvrl n~etalli tion mn a~hct:lntiall~ wduw thp o\rr;dl wiring irngtI1: (b) ft11I utili;.ation of a semi0 clltctor u;ifrr's :m'. Irnllu. rlr\im n n Ir clost.lyp:rltrd\\itl~it~ an IC: chip: a~ld (e) dm mluction ia prI~t.~~ingtVSt. Ixatlse u i r ~ bonding is a ti~ne-coosun~ing :tnd error-p~ oprcltioa.

This 41;ipter rlisn~sers cornhinations of tllc buic pmvssrs drscril~rtl in the pn our elr:uptrm to f;Bricate activr sn~l p:ssi\se mlnponrnts in an 1C. Ren~use t l ~ r keyele. ~ r ~ ~ n t O ~ ~ I I I IC is t11e transistor, sprcific pmcrssi~lg seqnenn!s arr drvt,lnprd to optimkr its prfinn~~ancr. T l~c chapter considms t11rt.r in;Ijor IC techaolopies ;~<sociatrd wit11 the tllrrr t~tnsi~tor families: tllr hipolar transistor, tllr 1IOSFET. an11 tllr \II?SFET. In a<ltk. tion. it ~~iscussc.s thr fnbrirxtion of micrnr1ectrornrcllanir;rl s!+trrlls I,? lnicromacllin: lrcl~niq~~rs. Spzcificdl!: it mvrrs the follo\\ing topics:

Tlr rlrsi~.ll and fabrication of IC resicton. capacitors. and indtlctors The prnc~s~ing sequc.nce for standnnl bipolar tr~nsistor and ad\iincrd bipolar rlcticc.s

Tllr prowssine sequence for XIOSFETs. \\it11 sprcid empl~xsis on CXIOS and mtSrnor\. <lt.\im,s

n ~ e pmcrssing seqllrnce for I1igI1-performance XIESFETs and ~nonolithic n~icro\ra\.r ICs

T l ~ r lllaior challengrs for fuhlre microelectronics. inclndin~ ultr.~~l~allo\vjunc- lion. ~~ltrathin ovidc.. ne\v intrrmnnrction materials. low powrr dissipation. and isolation

Xlicmrlrctro~nrcl~anical systrms fonnrd hy orientation-drpende~t etching. sac- rifici;~l r t c l ~ i ! ~ ~ . or LlGA i l i t l ~ o w . ~ ~ l ~ ~ rlrctrnplatine. and molding) pmcesses Tl~r. sinl~~lntion of IC f:~l)rication pmcpssrs using SUPREXI

F i ~ r r 9.1 ill11str81tr< thr intrrrclationsl~i~ i rhvrm thr major process steps ~~ser l I-. IC f;~hrimtion. I'olisl~rtl aafrrs aith a sprcific resistidty an11 orirntntion arr llsed thr \t;trtinc m:~trri:d. Thr filrr~ formation strps inclutle tItrrmdl!.(7o\\n oxirlr films (Clr~pter3) : I I I ~ c l q x w i t r d pnl!~ilimn. dielectric. and metal fi1111s (C11:iptc.r 8). Film fnrn~ation is oftrll

Figurn 9.1 Schematic llm\, dingr;~s~ of integrated C ~ V U O ~ ravn~dclun.

follo\ved by l i t l~npphy (Chapter 4 ) or impurity doping (Chapters 6 and i). Lithograpll? is generally follo\ved by etching (Chapter 5). \v11icI1 in tum is often followed by anotller impurity doping or lihn fonnation. The final IC is made by sequentially transferring d ~ e pattens fmn~ each mask, le\.el by lewl. onto the surface of the semiconductor wafer.

After pmcrssing. each wifer mntainr h a n d d c of identical redanplarcbips (or (lice). hp'cal$. behrren 1 and 20 nlln on each side. as sho\\n in Figure 9.20. The chips are srp. aratrd bysa\\ingor laser cutting: Figure 9.31 sllmvs asepnntedchip. Schematic top\ir\r.r of a single XIOSFETand a single bipolar transistorare sho\w~ in Figure 9 . 2 to gi\r some persp?cti\.r of the relative ssiz*. of a component in an IC chip. Prior to chip scpmtion. eacti ellip is electrically tested (see Chapter 10). Defrctive chips are usnally marked \sit11

-50 10 IMQrLipr IU' 1" loq

I to to prn

Bipolar

Collaor

(0.5 to 0.i55 nnlm thick) B.w 1:mitIcr

(4 (h) k) Figurn 92 5i.m mnlparison of a \wfvr to individual mmponcnts. lo) Scmimndudnr uxtrr. (hl Chip. (c) MOSFET anrl hipolar transistor.

ISI C h l a e r 9 Process Integration

t;ulls o\-t.; 3 billion mn,ponrnls

9.1 PASSIVE COMPONENTS 9.1.1 The Integrated Circuit Resistor

r0 fi,nrl .,,I IC n~sistor. m r am drlx,sit a resistive Ia!rr on a silicon s~lbstmte. then pat. tcm tllr I:lwr by pl~otolitltom;q~l~~ eocl rtcliin~. \\i. call also define a n i ~ ~ r l n \ v in a silicoll dio\iclr h \ ~ r qmw tla.nrt;tll! on a silim~t s~zI>stmte i ~ n d tllcn i l ~ l p l ~ n t (or iliN11se) imp,,. r i t i~ .~ nftllr oppnsitr mndtlcti\ih t!p? into tile r\?lli'r. Fiplre 9.3 s l lo\ \~ tllta top and cross. s,r(lonzl \ie-us of h$n rpshton f o r n ~ < ~ I 11:. thr latter appm:ic1l: One 11s x meander shape, ;and the- otltrr 11% n hiir sl~apr.

I 1. ~ \, A

1 dr R - R m , , ~ union

Agum 9 3 lstrernkd cirruit n t i r tnn . :\I1 n a m v lines in thr lar~t. s<plarr itmi* haw the ral \\?,!tl,, \\: avK1 ;,I1 <.3nt:rt< .,w tl,,. 5.,,,,<. ~i,l..

a)esi<lcr 111~ l > a r - d m d resistor lint. rile dillrrential mndudpnw ,,fa titin la)vr

of the 1 1 - h v ~ mat~rial tlli~t is of tl~icknrss rlx p;illcl to tllr s,,rfacr .ul,l dPPtl, , jilq sl~o\\n by tile H-R cross srction) is

\vhrrr IV is t l ~ r uicltll of the bar, L is t l ~ r lend11 of tltr har (\$,,. neClm tile cnnk,d aress for thr time lrinx). P,, is IIIP roohilit). of a 1101% and p i x ) is t l , ~ doping or,ncrntra. tion. The total rnncl~~ctancr of tllr entirr imp1nntr.d repion oftlle bar is ~ i r c n I,\.

\vhrrr 5 is the junction depth. If the \due of y, (wlrich is a hlnction of tllr llolc mn. centc~tion). and the distrih~~tion of l~ix) are known. tlte total mndl~aanee can ile e\.a~,r. ated fmm Eq. 2. \\'r can \\.rite

wherr g 7 lor' yp(r)fl.r is tllr conductance of a square resistor pattern: that is. c = g

when L = \I! Tlic resistance is tl~ereforc given hy

\vl~ere 1Ig nsndly is defined by the symbol Rz and is callrrl the slleet mistanw. T I I ~ sl~eet resistann has itnib of ollmns hilt is co~i\cntiondh.Mfied in units ofal~mcm.r s~11;m (MI). . . . .

!.lc~ny resiston in an intemted circuit are fahricatrd sinil~ltanenusly hy def ia i~ ,~ different crotnetricnattenls in the n~.zck. sucl~ as tl~ose sho\\n in Fimtrr9.3. Sisw the srrnnr - ~~ ~

prncrssine cycle is used for all these rrsiston. it is convenient to srnanttr tlw resistancv ~. iotu bvo parts: t l ~ e sheet resistnnw R-. rlrtrrminrrl h? the i~nplantatinn (or diffilrion) p m wrs: :md t l ~ ~ ratio LnV. determinedl\. the nattrm dimensions. Onw tlw \;~lur of H - . is , . kno\\n. the resistance is @\.en I)? tlie ratio Lnr'. or the numbrr of sqn~res (cnch square b :~ . an area of \%'x I{') in the resistor pattern. The end mntan a r e s \\ill intmcluce additional resistance to the IC resiston. For tile h~ sho\\n in Fiptrr 9.3. vrcl~ m d mntaci correrpnflz to appmkirnately O.Gisqtlnre~. For the meandrr.sl~;~pr mistor. the rlrctlic- fielcl lines at the l rnds are not spaced uniforn~ly acms. t l ~ p \\l\idtl~ ortllr resistor hut ;ur crnwv~led toward tllr inside corner. h squarr at t11r Iwnd dars not m~~tribulte rlinctly 1 square. hut n t h r r 0.65 squares.

EXAMPLE 1

Find the t.;<lttr of a resistor 90 pnn lone md 10 pm uidr. s~r r l~ i s tl,r irwd~ayd nvirtor in Fiosn 9.3, The sheet rcsist;mc~ is 1 kn5.

9.12 The Integrated Circuit Capacitor

Raically. hm types ofcapaciton arc used in intrStatrtl cirntits: NOS clpcih,n and )'+I

jllnctions. Tlir hlOS capacitor can Iw fabrintrd by tlsins u I~cavily chrlrd n.@on isllcll

:hapnr 9. Process Integration

an r,,,itt,.r ,,.rionl plate. t l ~ r top metal r l e t d r as the other plate. and th, ,ntm,.,,inS ,,,jrl,, I , , , ~ ~ iLr tlre divlcrtric. TIN, top ;111rl cross-swtional \ ~ R \ T ofn JIOS (a PC-

arr slar,,,, ill ~ i ~ , ~ ~ 9.h. T,, form n \lOS r;~p;silnr, il thick o.ide la:rr is tltrnna{lv m,,,l on s i~i ("~ sil~r~tr.,tc. ~ r s t . a v+ndow is litl~o~n~pl~imlly clrfined and etched

orid?. ninilciotl or ion impli~ntatian is used to for111 I 11' rrgio~r in ~ I I P \\indn\v ;lrea.

,,l,,.m:ls tllP 511mlllldinx tl,icI. side S C W ~ S as a nl;uk. A thin o.tide la\.pr is tllrn tiler. ,,,,,l[, Lm,s i t , ~ 1 , ~ ,,inllo,~ \.lrea. k>I,llo\\rd hy n ~~rctnllizntiorl step. nplcitnncp pr

unit art..) is Ciwa I,?

1 SOLUTION

I (a1 \' @=s-xAx- rl

9.1 Passive Cornpanems r 187

.nn- tl1e ate.

,,.llPrr <,. is tile &Lirlmric prnnittivih. of silimn dio6dr (the didrctric constant E,& is

3.9) d is tile 06,1e tl,icbtes. TO inCrcav tile T.~pncitil~lm h~rtl~er. insulaton uitll

clic)arir mnstnnts arc Iring sturli~l, sue11 ;L$ Si,K, and $0,. \vllicll h:l\te dielectric, of 7 and 2% r q w t i r c h : T l ~ r 310s ca[,acitnnce is essentiall! i~~de~x.ndest of

am, l id I m u s r tllc lotver pl:~te of t l ~ c cap~citor is 111mle orllra\il! dopd n1 rial. ~ l , i < also ,duces 1111. ;~roci:~ted srries resistance.

:\p+tjunctio~ is sonr~times osrd a s capacitor in an inteprated circuit. Tile top alld cmss.a~ional ,it?,* oin!~ )I.-JI junctio~t ctpwitor are s11o\vn in Figure 9.41~ The cletailn1 fabrimtion p m s s ir m~uidrretl i n Section 9.0, brcause this stnlcture forms part ofa hipollr tmncirtor :k :a npacitor. tlrr de\ice is usrt;rllyre\mc biased: that is, tile p rep;," h rr\vma binwl\\itln rps~xd to t l ~ r n. rpgjon. The capitcitnnce is not amnstant, but v; a ( \k + \;.I-~:, wI~.-re 1'- is t l ~ c appliml rrrprsr ,nlt:~ge and 16 is t l ~ r l,uilt-in p te l of the junction. The series resist.lKv is con~idrnl r l~ I~io,Iler tl~an that of a XIOS c a ~ tar lur:~nsr tllr 1, region 11;s higher resisti\ity tl~an dors the p' regjoa.

'-.. uin otial lad.

EXAMPLE 2

\that iq the s t a d ehsqe and the numbc.r of elmirons on s \lOS capadlor uith an area of4 pm: few n dirlrarir of la ) 10-nrn thick SiO, and (I,) 5-nrn thick T+O,? Thr ;tpplicd \vltasc is 5 \' for Imlh cscs.

SiOi SiO,

(b) figun 9,4 lo1 intqalcd UOS c.lp;~de>r ihl Intul(r;~trrl p-n junction capiritnr.

I 5v =3.9xR.RSxIO " I ' 1 ~ ~ x 4 ~ 1 0 \ , , , : x-

i I0 ' nn =6,9xlO~"C

i NIIIIIIW~O~ cIccirnns= 6 . 9 ~ I O . ~ ' C , ~ = 4,jX10'

I (b) Chanens fhr dil+ctric cnnstant from 3.9 to 25 m , ~ llrr t ~ , i ~ h ~ ~ ~ fro,,, lo ,,,,,, ,,.

ohtnin 0. ; 8 S5 x 10"' (:. nnd t~lt!nlrr of ,.lwtmls = s,&j I O I (:,, = zi3 r

i 9.1.3 The Integrated Circuit Inductor

1C inductors llave brnl \rirlrly usrcl in III-\~-IX,SP~I ,nonolit~~ie ,r,icm,,.;,\l. illtPeratcd circ~tits (hlXllC:s).'tIFtl~ tl~r increr fsilicon clr\icrs and nch.anwmmt ill ,,,,,I. tilrvrl irltrrconllectio~~ t ec l~no lo~ rs iraw started to rcci.i.i\.r lnore anrl ,nor? attention in silimn-had radio fre,l,zc,lL> ..,,u I r i ~ I ~ - f r r q ~ ~ c n ~ ~ ~ ~ ~ i ~ ~ i ~ ~ ~ , \la,,? kin,ls of inrluctors can be lal)ricated using IC processrs. TIM. Innst popl,lar ,nell,rxl is tl,r tl~in-film spirnl ind~etor. Figores 9.70 as11 b shots, the top tie,r.a,,(l tlle sr,<ia,l a silicon-h:~vd, hvo-level-~netnl spiral ind~lctor. To fonn ;I spiral itillduetor. a tlliek n.;idr is th~mal ly groun or clepnsited on a silicnn substrate. The first mrtal is tlrrtl depositPll and defir~rrl as one earl of the isductor. Sest, motller dielrctric is deposited onto lnrtal I. A via l~ole is dcfinerl litl~ograpl~icall!. and etcl~etl in the oxkle. \letale is rlepritcd alld

the \ia llole is filled. Tlrr spiral pattern can ba defincad and ctcl~ed on irtetal 2 :u tllc second cnd of the inductor.

To ev;iluate the indnctor, an important fiptre of merit is the quality Laor. Q. \vl~iclt is defined a5 L d R , wl~ere L. R. and wi~re tl~r ind~rctnncr, rrsist;urcr. ;~nd fwqarnry rcspwtiwb: The 11i:Ilrr the Q \.doe. the lo\wr tile loss from reskt,uncr.. and l e s w the htt;.r tlre performann. Figure 9.52 slro\\s the equi\dent cimit rn~ le l for an IC intltr- tor 3, is the inllerent resisti\ity of the oletnl. C,., an11 Cr, are t11r mnpling capacitances heh~cen 11ne nnrtnl lines aarl the s~rl,stnte. n~rcl an11 Re,,, are tlre rmistances of tlte silicon s~lbstmte asociated \vitIr the rnet:tl lines. respectiwly. The Q \.:rl!lc inrrF;ser lie- early \\it11 f r e q ~ ~ ~ n c y initially atid then drops at lti~lrcr lreqomcies k.ausr of ptc~~it ic resistallccs and cap:sitancrs.

Sonle appro:~rl~es exist lor inrpro~ing t l~e Q talue. Tire first is to tlsr lo\\,-dirlrrtric- corlsta~it materials (< 3.9) to reduce C,,. Tllc otlrcr is to use a tliick-fill11 tnet:~I or 10)\v- resisti\ih nretsls (r,p,. CII. Ae to replace hl) to rrdun R,. The thinl ;~ppro:lcl~ rlscs all insl~lsti~l< suhstrnte (e.p,, silicon on sapphire. silicon on plnss. or ql~artxl to r r d ~ ~ n * H,,,,.

Tool~t;in ~ I I P cx;cc< ,-aloe of;, h~in-film iarl~rctnr. ~ r a ~ l i c i ~ t e d si~~it~lation tmls itnat 1xa e 1 n p l o ~ d for llotl~ circuit sior~~lation and inductor optimimtion. TI\(. IIIMIVI fnr t11ia-fiI111 illdncton 111ust take into acrount IIIP w s i s t n ~ ~ ~ of t l~c 111rtd. the c~~piacikltlce of tl~t. UUIIP.

I line-to-line apacitancv. 111e rrsist~~mcc of tire s~tbstmte. t l ~ r a~p;sit;s~cx. to tlrr n~hstn~tr. and tile inductanc? l ~ ~ ~ i t ~ ~ ; ~ l iraluct;~nn. o f l l ~ r rnrt.4 lines. Ilrnns. it is man. dilficlllt to c.l~ol~ate tile intwltr~l iadudance t l , : ~ ~ to nlcl~latr i s t r p t ~ d raptrcir:t~lff or r&tall(*. 11~,,.,-\.~~, sillll,lr cclllatio~~ to estin~ate tllr squaw plm~ar spir.11 illdllclrlr 1% ~WPII :lqi

L - fl,,~t'r c 1 . 2 ~ 10"n'r ifi)

\,.llere ,," is tll(. I,erlllnlbilit). i n vaclll~ln (471 x 10-' kll~n). I. is in ilmrir.s, 11 is tl*. 1111111-

her of trims. and r is t l ~ r r.111ius of tlle spirt11 ill 1111'tPn.

Iss * Chaoler9 Process lntepration 9.2 Bipolar Technalaw 4 189

1 cr,

n...!.: ln~., , r> *

(cl

Figun 9.5 ~ n l Srhrmatic \in\, of n rp id intluctor on s silimn substrate. ( b j ?+.rsprctive \ i~w nlno? :\-.\'. Ir.1 An cqttC.dent cirntit mulrl for a88 intrpnted inrlltclor.

EXAMPLE 3

For an in1emte-11 indwior\\ith an inductance of 10 nll. what is the w(1111rwI radius ifthe num. I r r of tunlr i~ 203

SOLUTION :\rmnlinc tn Eq. 6.

9.2 BIPOLAR TECHNOLOGY

For IC :~pplic;~tions. ~ . y v i a l l y for \ 2 S I and ULSI. the size of hipolar transistors ~nllst Ir n ~ l ~ l c r r l to lltrPt llicl> dvnsity rt~quircmmts. F i y r r 9.fi illustrntes tlie redaction ill

~ I I P size u f t l ~ r hipolar tr,msictor in rrcrnt !ears.'Tl~e main differrncrs in a bipolar tmnsi\tor in ;In IC. wmparccl \\it11 e discrete transistor. are tl~nt :dl rlrctrocle mntacfs a n

("1 Ibl (cl (d

Figun 9.6 I1~dacti<m nf the hnrimntal atd wrtir.al dilnensions of a l>ip,lnr transistor in I ]#lnr.ti<m ikol:tti~m. (bl Osiclc iw,lation. lr and dl Sdwl oxitlc iad:gtirm4

loc,ttrtl on t l i ~ top s~trface or lbe IC \\%~frr. and eacl~ transistor mtlst Iw ~lrctr ical l~ iso- latrrl to pre\.e~it interactio~ls behveen dc,irrs. Prior to 1970. hot11 th? lat<.ral and \.erti- c . l . . ~ .I ) > . I ntno~ls . \$*ere pmbidrd hy p-?~ jttnctions (Fig. 9.b). and the l a te~ t lp isolation r e o n \ws ;!lu.:i!.s reverse bksetl \\it11 r e s ~ c t to the 1 1 - h p collcaar. In 1971. thrrrnal oddr \<a* tlsrcl for latrnl isol;~tion, restrlting in a sd~stanfiil rrr(luclion in dr \ iw size (Fix. 9.%) hcet tsr tlie base an11 cnllector contacts a l i ~ ~ t tllr isolation region. 111 tltr n~id-IY;Os. the emitter e\trnded to the \valls of tllr oside. rrsldting in an a~lditionrtl rctludion in area (Fig. 9 .k) . :\t t l ~ r present tinie, all lateral and wrticnl dinlewioiis I ~ a \ r hern scaled dam. ;tnd entitter stripe wvidtbs 11;tve rlimmsions in the snhrnicrnn r@on (Fig. 9.full.

' 92.1 The Basic Fabrication Process

Tile n~ajority of bipolar tr~nsiston usrd in ICs are ortllc ~I-~>-II h~ I m u r r the l~iclter nlobilih of minority carrirm (electmns) in tllr h u e region rcsslts in I ~ i ~ l ~ e r - s p d p r - fonr~atice than can be ob t in rd \\it11 1>-#1-j> bps. Figure 9.7 sl~o\\s a prrsprctivr \irw oran 11-11-II hipolar transistor, in \vhich lateral isolation is prn\icled I?\. oxid" w-.dIs :in< tic:d isolation is prodded 1,). the "'-1) junction. TIIP lateral odd? isnlation :tpprn:tcIt not on$. the dr\icp size, but also the pamitic c;~pacitmlw lrc.a!lsr of thr rnlalkr d lric const;lnt of silitnn cbodde (3.9. cr~lnpared uith 11.9 for silimn). This srdion nov s id rn the 811;ljor prowss steps tltat :Ire iisrd to &lbrici~t~ tllc d r \ i ~ v s11m\11 in Fiwr

For an tt-l)-n bipolar tmnsistor. the startin? material is a p - t ! ~ . li?Iltl!. < (-10'' ctn-'), c I l l > - or <100>-orieaterl, polislird silimn \tafrr. Rw:a~~sc tile jlia are fonnrd insidc the sen~ico~idnctor, t l ~ r dloiw of cnstal nrientnlio~l is 1101 i ~ i c a for hIOS devices (src Section 9.3). Tllp lint step is to f o m ~ a li~~riwl la!rr. T l a pl~rpoce of this 1:lyrr is to n~inin~izc dlr sc.rirs redsla~lcr of t l ~ r collrctor. A thick iO..%l pla) is thmnallY g r n w ~ on the uabr . and ;I \\inrlo\v is tbrn oprnrrl in t l ~ r A pmisrlycontroll~~l ;umumt of Io\\*cnrqv anniic ions (-33 lid! -10"' olii? b i111pxaan~c7~ into tllc \\illdotv rrgior~ to serve as pn,deposit (Fig, 9 . a ~ ) . Xest. t I ~ i g l ~ - t e ~ n ~ r . ~ t u r r ( - 1 1 ~ " ~ ) &iW.ia strl, fi,nlls tile 11. borird l;~y~=r. \vIticll 11;u :I t>pical slirrt n:xirla~lw orapprosin~atrly 2 1 R D .

,r 9.7. loped clions "tical

190 chapter 9. ~ m c s s s Integration 1

(d)

Figun 9.0 Cms-vdonal \ia\.i nfbipnlar transistor hhricntion. (oi Buried-layer implantat i b ~ Epilxial Ia!vr. (ci Pl~otomsist ma+. (dl Chanstop implant.

ion.

Tile seinnd step is to deposit an u-hpe r p i t a d layer. Tile oxidr is removed and the wxfvr iq plawd in an epitaxial reactor Tor epitaxial gro\\th. The thichn~ss a11d the dopine mnwntmtion oft l~e epita\ii~I Ia!w mdetern~inml by t l~e ~~ltimate ltse of the clevice. Amlm d n ~ ~ i t s init11 tllrir l~ ie l~rr voltaxes for amplification) require thicker layers (-10 lrml Imvcr dopings ( -5 x IO" cm-'i, ~ h ~ r r x r dietal circuits (\rith tlrrir lo\\:r\.olt:tges forw in<) rrquiw tllinllerLi!?rs (-3pm) and hiqI>~rdopingS (-2 x 10'hcm~'). Figlre 9.N) SI

a crnss-srctionnl \ic*v of the dc\icr after thr rpit:Mnl prrrrss. Sot<. tltat tlier,. is wmr ontdiff~lsiall fronl tllc bllripd I;lycr into l l ~ r rpi1;aial i;1!.r.r. To mininti7r otltclifftaion, a lo \~ , . tm~~mt~~reepi tadd pmsssho~~lr l I r relployd, anrl lmwl i f l t~s i \ iy imp~~r i t i~~ ic.~., ,\I) sl>oolrl Iw l a ~ d i n 1 1 1 ~ b~~ticcl lii\,rr.

111e tl~inl step is to Cnm~ tl~a latcr~l oxirle isolation region. h tlrin oddc pad 1-50 "rn) is thenr~nlly g m w ~ on tll?rpit:~~id I:t)rr. Collm~rrlIy:~~limn-nitriducl~ition (-IMnm). If nitrirlr is ~lrp~siteddirectl~onto the silimn \b~tltout the thin oxide pxl, tlte nitriclr may cmse damage 10 tile silimn surl.tcr dtlringsuhwq~~rnt higl~-trrnpent~~rr step. SC.~. tl,r nitride-oxide l:~ycrs and a b u t llalf of tlle epikuinl layer arc etchnl lain< a phalorrdst ~s mask (Figs. 9 .k and (1). Boron ions are t l m i~nplwtrd into tllc rxpose<l silicon antar (Fig. 9 .W.

The pl~otomist is removed. and tltr wafer is placed in an oxidation furn;icv. Sinw the nitride layer has avely lo\r.oridation rate, thick oxid~s uill be gram onlgin the areas not pmtrcted 1>ytl1e nitride layer. The isolation oxide is ss~tz~llp xro\n, toa t l~ichee suclt tlv~t the top of the oxide \rmmes rnplallar with thc oriend silimn slnrfac~ to ininimiz tllr surface topoppl~): This oxide isolation p r w s is callrll local mi,!otion of .silicon (LOCOS). Fi~ore 9.90 sl~o\vs tlic cmss section of the isolation odde after the rr:maal of tlw nitride layrr. Because of segregation eflectc, 111ost of tile implanted horon ions arc pt~sl~ed underneath the isolation oxide to form a 11' layer. This is calld t l~e p' clmnriel .S~O,I (or clmn.vto~?) because tlte big11 cu)ncentnlion n ip -Qr semimnd~~ctor \\ill prevent

fa)

Bomn bast. implant

(4 Anmic impla81

(dl

Figurn 9.9 ~ ~ ~ ~ ~ . ~ ~ d i ~ ~ ~ l ,ir,,~ ofbipolar tnnristor fabric~lion. lo) Chid? iu3lalion. IWl H w i n ~ ~ , l ~ ~ t . (c) R ~ ~ O V I ~ I of thin oxide. id! Emitter and collcvtor itnplant-

:,,,, cT,ll,d8,r, :,s ~ 1 ~ 0 ~ ~ ~ ~ in I:im~rc 9 7 . I,, I , ; , ~ , ~ hiF,l:lr p n K ~ r s . tllc.rr arc six filnl fonnntion opemtiolls, sir litbomPllir

oF,ti 4,,,.., ica, ,lllpl;,,lt;,tion~. ; ~ n d itntr etcl~ingoprr.~tions. Eacli oprralion nrust lx pnv,sr~,. m,,lmll,ql m , ~ , , ~ ~ , n i t c ~ r ~ ~ I . F:&iltlrr of RII? one 01 (llr opr . l l ion~ generally \till ;<.,,,I,.~ t h ~ wxfc-r t~srlt~ss.

TI,,. clol,inc pn,tilt.~ of tlrr c o m p l r t ~ l t~msislor along a modinate perpendicular to ll,c, s,,rl:,cu .,,,<I p:rssint tlmrn,,ch tlrr i~ntittrr. IV,LCC. an11 ~ ~ l l t v t ~ r ~ r r ~110\\11 in F i q r e Y.1n. mlr Pmitt,.r pmfilc, is ; , ~ , ~ , ~ t im:~use ol'tle rnnccnh;t(io~t-<kpn~k~~t ~ l i f i l s i \ i h o f a ~ ~ i ~ TI>,. Ikw dopin? prnlilr lrnl.ntll tllr rt~rittrr n n be approenlatt~l I)!. a Calrssi:m distri. h,,tion fnr ill,llt,.ll sotlrn. dilh~sion. Tltr cnllcctor doping is pivm 1)). the epitaeal doping ( 1 , I , I (or3 n.prrwtt(;ttirr svitclting tr;~n~istor. Jlo\vc\rr. st larger depths, 1 1 , ~ mllrr+or llnpine n ~ e ~ ~ n t r , ~ l i o n ilrc~.zws brcatlse nfoatdifilsion fmrn the buried I:?\rr

922 Dielsctric Isolation

In ,Iv. inhtian sclwlne described pre\iously for t l ~ bipolar tnnsistor. the dmice is iw. I.ltnl fn>nz otllrr (!P%~<M 111. t l r odd^ lilxer arnund ib pr iphe? and is ia~lated from its rnmnnn atlntmte l y a n' ,t junciion lbnrird la)~rl . 111 Ir i~~-~ol t ; i?e applications. adifferent

i~ppmncll. (7llh.d (Ilt~l,r.crlr 1.~0lnfion. is itsod B, fomr inatI:itin< tul,~ to is,,l:,l,. s,,,,,)wr oflxx.kcts of sit1~11~-c1?staJ s r s n i m r ~ d t ~ c t ~ ~ ~ . In (Itis ~ppm.~clt. tl>r deriw is ~ ~ l . ~ t r . < l [n,,,,

llotlt its C ~ I ~ I I I ~ I I s~~l>str:~tr. ;wd its rtlm,lnndine nviKlnlnn I,,. a <lit.l,.r.ttir 1:tlr.r . . . . . . . . . . . . . , ,

I\ prcm,sx srquc.trn. for il id<dric isolation is \ l t r , u . ~ t i s ' f inLr r 9.1 I . A;, oriel,. I.,\,.~ is fon1w.d ilaidc :I <llW)>-orirntccl )I.I?x- silir.orl r8!lslr:$t~ t s i n ~ l ~ i ~ l ~ n ~ r ~ ~ r,qqt.rp inn impl:u~t;~liotr (1%. 9.1 In). h'~.xt, t l ~ r \v;lfc.r an<lcrpwv a I~i$,-tc~n~,r;~ttlrr annrxl~r,e pr,,. n.ss x, Illat lhv i ! ! lp l~~~t rd ii*).g<!n \$ill wtcl \\ill) silirnn to inmr IItt. ~,riclc l:\vt.r. TIIv d;,lt,. zgc r c ~ ~ l ~ t i n g f m n ~ i ~ l l ~ ) ~ : ~ l l t : ~ t i i ~ ~ ~ is also :innv:tI(d otnt in tliis prwvss i ~ i ~ . ' 9 . 1 l1>1, :\ftvr tlris. \\r ol~lilin an 11 silic~m i;t!.er lllal i? hnlly isnlatc.d on an ori<lc In ;~!n~l~ . x r i l i < ~ , ~ r - ~ ~ ~ . instdator, or SOT. I:?\.vr). Tllis p r w a is r:dlt.d SIhIOX (wp.r;itian h? itnplant,*l o y c c n ~ .

Sinw t l l r top silimn is so t l ~ i t r . thr isolnlir,r~ n.giorl is m a i l s forna,d 1111. I.OCOS pm. wcs i l l~~s tc~ tcd in I'iq~rt. 9.* or Iyc.td~ing;~ trencl~ (Fit. 8.1 1rl and refillinSit witlt oyi<lr (Fig. 9.1 Id). T l ~ r othrr p r w s s r s arr ;tl!1~o5t tllr. ~ ~ 1 1 1 1 . zs tltose in i:iplrr5 !).* ll~rotn~ln 9.9 to fornr tllr 11-hlu. hxsr. II. emittrr. and n collr.ctor . ..

Tlnr main nd\mtagr ofthis f ~ c l i r ~ i ~ ~ u c is its lticll l>rc.ak(l~l\n volliagc IYI\VP(.II the ~ t t ~ i t .

t ~ r and t l ~ r cnllc~*or. \ v l ~ i d ~ C~III lr in PXWSS of S~V(.KLI hundred snits. This t~rl~niqn,,- i~ also mmpatil~l* with mwlern CVOS intcgr.rth,n (Swtion 9.33). Tl~ir C\ IOSmoqr~t i l~ l~ prcxrqs is w n 11wfnl 61r n~ix<.d I~igI~->nlt:#sc :p:uncl l>iel>-clcnsit? ICs.

Self-Aligned Double-Polysilicon Bipolar Structures

I l i e p m v a slro\\n in Figlrc 9%- n r n k anotllcr l i t l~mpl r ic step to ~ b f i n r an oxide +on to s rpan t r tlrr base and cnrittrr mnlact r?*ons. Tliis civrs risr to alarcr inactive clr\irt. awn \vithin the isolated boundary wl~icl~ inrrmmrs not only tlw pzmitic rapncit:src~,c. but :xlqo the resistance tlrat d e p d e s tmnsi$tor priormancp. Tlte most r.fftr.tivv \ ~ t y to reducr tlrese rffmcts is by using a rcrf-olig~stl stn~ctttre.

19( . O . ~ I C ~ Y Process Integration

n,,. ,,id,.l\. uuyl s r~ i - ;~~iCnt~ l stntcture is the rlot~ble-pl!silim~l stn~cture ,,jth ,-I ,;,,,cyq 1 i~,,],,tio,, l,tT,,itlt~l I)! 2, tn.nrlt rvfille~l wit11 pn l~~i l i~nn . ' SIIO\\?I in Fi,ww 9.19 -. ,.- ,, ,I ,,,,,? tl,,. c~c,t,,i~cvl s w l , ~ ~ ~ t ~ t ~ . ~ , i s t t ~ p ~ for the scl i~:~l iw~~~cl ~ ~ ~ t ~ l ~ l ~ ~ ~ ~ l ! s i l i w n

\tn~'<tnrt~ ' I~Iw tr:~n<istor is 1t11iIt on a111 1 1 - h ~ ~,pit:~~ill! I:t>~r. A twncl, ,,,n,y,,,,:, t,,l, 5 . f ~ p , ~ ,n cl,71~tlt is c , tc tzd n,:t~+ive ion etc~lillC ~ ~ 1 ~ ~ ~ ~ ~ ~ 1 the 11. suIxn).

I , ~ ~ ~ , ~ r,.3q,,l iatll IIIC,, n~I)rtr.ttr R ~ ~ O I I . A thin i:t~vroftI1en11:11 o ~ i d r i ~ I I P I I gnN71 ;lnd ,,, !I,,. wnrl, lor thr cln;tnnvl stop itr~plallt of h r o l l ill Ill? imttom of^,^

tnncl,, n,,, tW,,,.l, is tl,,.,, f i l l t ~ l a i t l ~ ttnrlnlx,l pl~siliws and rapp-I I!\. 21 thick pI;a,,, fi,.lrl odd?.

lint pol\silimn I;t)rr is drpositcd nntl Iten\iIib. d u d \rill1 homn. The p. p~l!~il. ,<,,I, ,c:,~~,.c{ ,,,,I,. I ,ti11 1%; t,sel : a soli<I-plt;~w 11iN11sio11 source to hrtn t11~ ~ s t r i n ~ i ~ I, , ,~. n*,,,, I),,- e r l t ~ n ~ I ~ . This lityc,r is m\vr?d \%it11 a rbemic:~l \ a p r deposi. ti<,,, ou,lc ;rn<l llitnrlr {Fiq. I).I:L,I. Thr t-ntitlcr nl;rvk is used topattcni tlte emitter resinns, a,,,f ,, (In- ,.tell pnKrcc IS ~ v ~ l to ~ K ~ I X I L Y . ;an nprninx in t11e CYD usidt* and pi,l\. 1 ,pie 9 I:$,. 4 ~ l ~ ~ . n r ~ ; ~ l ,bride is tlacn q \ % m o w r the ~tcIt?d StnlctllrP. nnrl a relati\:elv !ltlVk t3vicle ~:ll~pm%rt~:~tt~ly 0.14.4 pntl is y o \ \ i ~ on the v<,rtioil sidm\dls of tltr I t m & , ~ ~ , ~ ~ d ,,,,I,. TI,.. thicl-rrr~s ufthir oxide d r t r m ~ i n ~ s the sparing behwrn the e d p s oft],; Ir.,>.. :,rlcl t,lrtiltq,r mst:rcs. Tla. rxtrinsir p. I,;r~r rreons arr alco forr~trd cltlrin~ the tllrr. n,.,~ c,xicl,. Srq,\\il~ > I P ~ :c; :l r~sttlt o f t l ~ e o u t d i ~ t ~ s i n t ~ ofhomn f m ~ n the p)ly 1 into the all,rtr.,t,. i Ftc. 9 1 3 I. RPCXUX. Iwmn <liRtns<? I:at~~r;dl~ ar a r l l .zc \rrtictlly. the extrinsic

nqot t ail1 In. ahlt- to n1;ll;r mnt:tct uitlt the intrimic bmr meion tl~:~t is f o n a ~ l n r d , ~nntler 1 1 ~ ~ ~ rmittpr mnllrt .

Fnllowin~ tltr oddc step. the intnnsicb;~u~re@on is form& tningion implan. riltintr 01 lamn I Fie. 'J.I;+I1. This a n P s to self-;dim lllc intrinsicnnd mtrindc ha* yionc. \ f t r r t11e mntiwt is c l v w d In rtSnto\r an). o d e ln!pr. tlre seml~li pol\.jilimn la!~r is <lqxxitrrl and implilntr~l nit11 As o r F! Tllr rr' pnl~silicvs 1 d l ~ I p>ly 2' is ~jser! as a solid- pl,;~u. ~ l i~ l i s ic~ t w u n r to fnnn the emitter region ;utd t l a emittrr e l r c t d e . :\ ~ b d l ~ ~ e m i t - tr.r rt+nn ir tlten b m ~ r r l tltrnr~elt dopant o~~tdifftlsion from p l y 2. ;\rapid tl~ern~alanned for t la. I n w and emitter ot~t,lifi~sion steps I.icilitat~s the fom~iition olhdlmvemitter-lwe and ml!wtor-h:~rr junrtioss. Finall!: Pt All11 is rlcyositrd and sintered to fomi PtSi over tht. n. Inl!~ilimn rmittrr:~nd tl,r p' pol!silimn lhue mnt:tct (Fit. !ilk).

T l l i < wlllaliymd slntd?ln. nllms the fal~rication of emitter r q o n s smaller than the rninimtlnt l i t h m p h i c dimension. \tl~rn tlte sirlo\<dl-spner osi<lt. is <ro\rm. it fills the c~,ntort llolr to u>rnr d ~ q r ~ e ~*C . IOSP tltr themla1 oxide m u p i e s a l a p r volume than tlw ori*nal wltlmr o r p,l!rilimn. TIIIIS. an openine 0.8 ptn a ide will sl~rink to a b u t 0.4 pnn ~f sidr<tall oddp 0.2 pm tlrick is p \ \ 7 l on each siclr.

,. . m,nsun,ptinn ol';all I(: trrl~sol%?.

~ j ~ , ~ ~ g1.c sllO\\5 t I~c redt,dion i n the size oftl~t' XIOSFET in rrccnt years. ln tlw Pnrk I+,;o~, 1 1 , ~ s,;lcr lcllpll ,v;u 7.5 pnl and the m n r s p o ~ l d i ~ ~ g dexiff m a \\% a b u t MYXI ,,,,,'. .+s t l l r <lt.\icv is sc:~Irrl down. tllpn- is a dnutic r~.duc.tion in the dcbicr area F,~,~ ~IOSI:ET,,~~I, 3 gatr 1~n.911 of 0.5 pin. t l ~ r (Irvicv arm s l ~ r i n k to Ivss tliali 1% of tllr arlv hIOSFET Dcviw ni i~~iat~trb~l t iol~ is e x ~ c t r r l to ~ l l t i n i l r . TIIF p t r lengtll sill pm),a~liyd,Tn.xq,. to lp.;s tl~an 0.10 p n ~ in t1w mrly h\voh-first cx*ntrtl?: TI)* futurr trnllv of ~ O S F E T <lr,iws arc, mnsidprrrl hrirfly in S~.ction 9.7.

The Basic Fabrication Process

r i g r e 9.15 sho~: e p q w c t i r r riew of an n-cl~annrl MOSFET prior to final i~~rtalliz~. t i o n . - n r top la\pr is a pl~osl)l~ona-dope(l silimn diodde (PQ:L~s) t l ~ ~ t is 11se(1 w an insll. lator h t \ twn 11,- pol!siIimr~ gatr ;ual tlie git~ e1etnlli7;1tion nnd also iu a xettering !ayer

nlo[,i]r ions. Conlp;lre Fipl~re 9.15 \\it11 Fi~gure 9.7 for the hipolar tnulsistor and note tllnt a .\(OSFET is m,nsidenl,l? sin~pler in its bwic stnlctllre. Altlloil~h lboth de~ices use

Figure 9.14 Rrrltta!on i n the an? of the MOSFET :r< thp gate leneth lrniniln~~n~ ft-:ntt~rc lt.~x?h I I\ n d t ~ m ~ l

9.3 MOSm Technology lo?

P-*a,,

latrr.ll odde isolation. t l~cre is no need for vertic2l bolation in flit S I O S F ~ , , , . I , ~ ~ ~ a

Iluried-l;iyer n'-;'junction is required in the bipolar tmnsirtor nlr dnpillg profile in a hlOSFET is not Xs cnnlplicxted as tll;~t in a bipolar transistor. and mntrol uftllr dnpmt distribntion is also less criticalnl. Tltis sec+ion nmv mnsi(I,-rs t l ~ c lnajor pmcerr arr esrd to fabricate the do ice in F i p r e 9.13.

To process an n-cllannel hlOSFET INJIOS). the st.zrtinprnntrri4 is ap- t )F. liKl,tly (loped I-10"cmn~'). <lCO>-orirnte~l. polisl~al silim~lu;~frr.Tlbe <1C1)> arirntation ispw. frrred over cll l> because it 1i.u an i n t r r L ~ v tmp density dlat is almut one-tmth that of . Thr first step is to form tllr oxide isolation region using LOCOS t w l ~ r t o l ~ . Tlir p r m s s sequence Tor this step is sin~ilar to that Tor the hipolar transistor, ,\ thin F?d o d d r (-3.5 nm) is thermally grnm follo\ved L?\. a silimn nitridr (-1% tin!) deposition (Fig. 9.1Fn).'Tlie actiw dmicv area is defisnl I): a photorrsist mxsk m ~ d a lnron dvanstop I:tyvr and is then i~nplnntrd t l ~ r o ~ ~ ~ l l t l ~ r maipnsite nitridcoridr layer IFiz. 9.lfd>),) Thc nitride l:~yer nnt covered hy the pbotorrsist m:uk is sahsrqi~cntly rrrnovrd I)! rtclting. Aiter stripping the pl~otoresist. tlte \nfer is placrd in an odrlntion furnacr to grnw an usillc [ c ~ l l n l tl~ejirlrloxicl~). \vllere the nitridr layer is rrmo\.nl. :mcl to drive in thc lnrnn inlpl:~nt. The t l~ icb~css of tlir field oddr is h~>ic;dl?0.5 to 1 pm.

The second step is to p r v the sate oxide arid to a<ljitst t l ~ r tl~resl~old wltnp. The mlnpositr nitridr+ddr layrrowr tlle :~cti\.r dr\iccare;l is rrn~mprl. mida tl~io ne cddr l;iyer (less tllan 10 nni) is growll. For ;in rnhanwrnent-mode ~~-cI~ant i r l clrdcc. lnmn i<rrlsarei~n~lanted i s ll~r c l~mnr l region. ;is dlo\\n in Fi,q1re9.lt?. to incrrm the thrrsh- lrlcl \nltepc to a predctmninrrl \slur (c.g.. r0.5 \;I. For a deplrtion-omxlc i i c l~ ;ua~d iloicl.. anenic ions arc ilnnlaated in tile rllannrl re-cion to dt.cre;c\e the thrrsllohl vnlklee 1c.g.. -0.5 \I).

The tliird stcbp is lo lomi thr gale. h pol!silimn is dcpoitnl and is iirail, doped by cliiftision or itnplaotation of pl~ospllonls to a h-pirwd s ter t rrsistanff of 20 to 91 RI2. This resistance is adcqliatr for hlOSFETs \sit11 ptr lr~i$l~s larger t l i : ~ ~ 3 11111. For SIII:LIIP~ dedms. pol!cidr (a c~r~nposite I;tvrr of nlrtal silicidr anrl [nl!silim~ri. s1s.11 as \Lpnl?cidr) c;in br used ;LS the gate 111steri;ll to r rduw tllr sllrrt rrsiskinw to :~lmi~t 1 WO.

n ~ e fol~iib stel) is to fonn tlw sourm wddmin. :\fter t l r s ~ t r b l*?nmiml IFi&9.1Ml. it s e w s ns a III;L+ iortlir arrrnicinipl:aat;~fion (-30 lie\! -5 x 10" cni'! to Timl 1\11. so~lrc?

dr.lill (Fig. 9,lioin). \vl~icl~ are sdF-aligicd nit11 rrsppct to t11r RI~I..' At this rkiec.. I ~ I C '

only ovrrlnpl~iep or tllp gate is (Itlt- to latvml s tn~~c l ing of tbr ilnplantnl ion.; (for J)-krV AS, 0, is o,IIy ,j ~ f ~ ~ ~ ~ ~ . t ~ ~ ~ ~ ~ ~ t ~ r e p m s s r s art. i!.;c~! for sn~~snpl rn t steps to mill- imkc l:ltmll r ~ i ~ , l s i O l l . tllC p ~ m ~ t i c g i t c - ~ l r : l i ~ ~ and gate-so-~w c o ~ ~ p l i n e c ; ~ ~ x i c i k ~ ~ ~ ~ . t ~ s ~ * l l he ~ I I I C I I s111allrr Illan the g:ite.rl~nnncl c;~pacikuln~.

19* * F a I r l r r g Process lntsgraf*on

4;- - :: ,- ,--- --s?- 1 2 .

I

Tlw l i ~ t S I ~ I is n ~ ~ t ; ~ l l i z ~ t i n n . A p l ~ ~ p l t o n ~ ~ ~ l ~ ~ d n\jdr 1P-glass! is drpositrd over t11r ~ r ~ l i n . wlfvr :IIIII is flm.c(I I?\. l ~ r a t i n ~ 1111. \vakr to Rib.? :I srnno!ll r!lrfa<c topoprapll!. \Fie. 9.l71,I. (.:unlact ai~r(lmts re rlrfinvd :tnd rtcl~rcl in tlr. P-elarc, r\ n l ~ t a l layer, sur11

:tlt~min~tns. i.; t11r.11 ilvpxile<l :tnd p:tltt.rn~d. :\ cmw-sc.ction.tl * i m . of tllr rn~nplc~t~d \10S17ET i.c shmln in Fie~zrv !). 17r. ;ul<l tllr corr~spot~rliee, top \ic.u. is sl~mvm in F i p w 9. I:,/. 'rllv $itIc c ~ n s t ; c t is I I S U : ~ ! ~ ~ rnndc. orllsi(lt. 1111. :stivr rlr\iw i1rr.a 10 ;t\aid pssiblr <!:+rn:ler t c ~ t l ~ c * ftltin g:ttr oriclt..

Nh:tf i' ill,. nl;ninlllrr, <;~lr..trwmrn \r>ll;ty~ that .* \IOSFET \\irilh n 5-ntn c:+tc clridr can uifh- -1.lnd' .\~llntv 111:1I lllr. tlucll. hn.;,L% clcntm .a1 6 \I\'i<.rn ilnd llvaf llnc rtnl,sfmtc. vfrll;ter is 7rm.

I--+ I,?,

(dl

Figure 9.17 NJ10S fabticllinn aqt!~nc~, . . (01 Si>ttnr md clr~in, ihi P.~la<r clrywtion. lr! (:urn r<r iirarr r,f t h . .\IOSFI':T ( d ) Top \ir-vof thr \IOS17ET

9.32 Memory Devices

hl<.~norics are (lc.\icvs tlr;~t can store diqitnl infom~ation !or dnfa) in tcrnts olhl!v !l>io;kr). clieitci. h r i o o s aicnlor). chips II;~VP hrrn d r s i ~ ~ l r d ;lntl f:~l,ricstrcl tnsin~ S\ lOS tr~rbnnl- om: For most larpr slt~mories. t l ~ r raa<lnnl :icww nlernrtn- (II:\\Il orf:aaintion i.; pn,- Fr.rrr<!. In ;i Rhhl. toernor). n4ls art- onr:~aizrtl i11 a iu;ltria sln~rturt-, and ilnla GI,, i r at.n.scc<l (i.c., rtornl, rrtrir\r.cl, or rr.lsc.,l) in nndom nrttrr. inrh.pntlral or ils pIl!sic.l! lon,tilrn. I\ st;llir r:tll~lom :Icrrss nlrnlr,? (SH:\\li ran r~tnirl stoml <l;rt;l irl(k.litrit<+ :a lonS np tllr pl,\\rbr stlpply is OII. TIIC SRA>I is Irnir;rlly :I llip-llnp cirruif th;if rztll sloW or~p !>it o f i ~ l ~ ~ n l ~ ~ l i ~ ~ ~ l . ,\,I SR,\%l crll II;L< four ~ ~ ~ I ~ ~ : ~ ~ I ~ v I I ~ ~ ~ I I ~ - I ~ I I u ~ ~ \lOSFlCTs : I I I<~ fw> drph~tirlll-lllo~l~ \IOSFETs. Tlw drplrlio~~-tn<xk hlOSFF(Is ran lr n3pt:~ccd I!!' rrci7- ton f ~ ~ ~ ( n r l ill undopc.(l pnl!silimn lo lr~i!linli~c pu.r,r n~llslllrlplina.'

T,, rr<{,,cy. 1flp cy.ll : I~ ,>~I a ~ ~ ~ l ~~~~~r wnstn~nption, 111~ d\n:i~!lir cln~~n111 :ICYY.<S l l l ~ ~ l ~ l -

,,? ( ~ l t \ h l ) has I ~ P , ~ L~P\.~I,,PCd. ~ i p , n . 9.1% sslto\\~ tll? rirrllit d i ; ~ q c ~ n ~ of lllr ntu.-

tnnsistor 1 ) ~ h h f (y.ll, i n wl,icll lllr (r.lltrislors,,n.rs ;lz an\itrl$ ;~~lc~ol t r isit ofillblml~ltioll

- Figura9m \ : , . I I 'I:\\I ,',.,: ,,,,.,.,,, i\iIII I: 1.11111111 & 1 1 ! 1 I I . . i ! . i I ! . I ! . , :...:.ill# i i . , , ,1 , . . \ 01

I l < \ ! ,:, , <.,, \ ,".,1, 1):i:I.: l i l t ~ < 1 1 1 1 1 \t.ttc. (:111.111t 1:11111rn.111.~'

7 ':."" C: f

(I, &

Smtrrr. -- I Drcin

,& ss,,t,tr,,t,.

(rl

figure 92( Zonrnlat~l~~ nle,wr,~ <It.ria~. In' FIc~,tinp~alc. nonvolatile mcmon 1 1 2 ) xIV?S \.7!,1!#l,. rr,v?nrnn , r - * I~~l~!i\nlvnt rirout i>fcitltt.r hpc. nomalatil,. s~rs~,y

I 9.3 MOSFElTochnology 4 203

$;~trslnlctlln'. illu*tr.ltf,ll io Pip~n.!J.?lr:n~.cl~;~rg,. ~ t ~ ~ , . , l i e I),,. mp, , torI~,) r-,,,v- sl~ifl it1 t111- t !~r~~sl~c~l( l \~o~t:tc~-. :~ I IC! tlw <I,*viw r~,t>1:,i11~ t!,,. [ , i , ,~ ,~.~ t1,~,.<\,~)1(\ v,,ltz,cc

state. ilr>fir 1). Rlr ~\vrll-i l*\im~~gI 1111.11103.d~ti<t~. tl1v c l ~ : ~ ~ . n.t(lllti,)n tilne. c;,,, I,,. o,.,.r

I I N I yntrq. 'ti1 crc~<t. t 1 1 ~ !nwIun li.<~,., t110 stored c ln ;# r<~~ ;,n,l rctt,n, 11," ,I,.,,~~ tc, ;, I ~ , . , , ~ tl1n41oI(I voltas(. statr ( l ~ ~ i c 0 ) . a gate vnlt;~q(. or o t l ~ r r irlr.;ttir (nlrll :a tlltnt\inlet l i r l l l i can lw. 13srd.

I Sor~\.ol:~til(. s . ; c ~ n i a ~ ~ ~ d ~ a t o r I I I ~ I I I O ~ ) . (l'\'SSI) II;IS I r c n c r t ~ . n ~ i ~ ~ ~ ~ ,,u.,l ill prt;,l,lc <~lrctmlliCs c)strllls, sllrll :I5 cTllltlnr pllollrs m d rlipitnl csmmm%. A ~ I O ~ I , P ~ i n t r n ~ ~ t i ~ ~ ~ ; ~ p ~ l i . c;~tion is t111. chip c:~r(l, also c:*llc~l 111~ 1C c%ar<l. TIM. pl~oto i r b F ip~r , , 9.22 is ;,I, 11: c:,c,l, T l ~ c rliapraln at Ole imttonl or I ' i p~re $1.22 ilh~rtnitm llw non\.ol:ttilr i s r t ~ 1 n ~ dr\icy* tI,:,t stores I l l? d:ltil. \vllidl call Ix. r?ild and \ \ n t t ~ ~ 1 1 t l l ro~z~!~ lllr lluf to :a n.ntr;d prw!,,srit~$ unit (CI'U). I I I mntr:ut t c ~ t11~~li111iterl vulnmr (1 k R i ittsidcnmr~\.~~ntinn;J m;i~~t,tict;ip. atrd. t l ~ r r im O ~ I I I P no~~w~lat i [e 111e1110ry~111 IK. increacrd to IC,lil>. M kB, a r r.vm l;trcrr ~ l c ~ n c l i n ~ on tl~r applie.?tios (e.p.. orlr collld ston. p~nos: l l pl~oto$ or finct*q~riritq. Tllrwlel~ tl~r IC cxrtl rt.:rl/\witc t ~ ~ ~ ~ c h i a c s . tile data c2n I* nlrr.cl in nunlrmmlr appl~cn- tions. inrllldit~g tc~L.cntnrn~~niwtir,s ic~rr l t r~l~phonr . mohilr ndioi. pa!mrnt tculr;~ction< ( ~ I ~ ~ c t m n i c ~ I I R P . credit c ~ n l ) . trl?\isior~. triIrIymT1 i~lrctrnnic tick~t. p1111Iic 11;2119-

pi), 11t~:dtIl a r e 1p;htirrlt-data cardi. arid :lecess c,~lltm!. TI),, IC cilrd \s-i!I likrly p1,ay a

crlltml role in tllr ~lol,;ll i11fonrl;ttiun and senicv mjrh or lllr flllllrr.'"

9.3.3 CMOS Technology

F ~ q ~ r r 9.2% sI~o\vs a CXIOS invrrter The sate n l tl~r 1rppr.r PMOS dr \ iw is cannruird to .la? gate of t l ~ c l o w ~ r NMOS device. Both doices are rn l~ancern~~~t -mtn l r HOSFETs

20.1 c Chaoler 9. Process Integration I

Rgun 923 CornpIcnwn~a~ JIOS (CXIOSI in\rtirr. (01 Circuit dinram. (hi Circuit laynut i , . (:nns &ion ;donq clottrd I\-:\' line of ib).

ned

\,it11 tile thrrsholrl tnltaee lrTV I? than zero for the P\IOS de\ict, and ITTn p a t e r t E m for tllr S\IOS dr\icr (hTlc;llly the tllresllold wltasc is ab111 I14 I1,,l. \Illen tile inplnt \.ohage (V,) is at g o ~ ~ n r l or at small positive \.dues, t l ~ r P\IOS d ~ t i c e is turned on (the gatr-to-pund potential of I'>IOS is -I;,,. \r.liicl~ is more nr~at i \ .e than I\ ), and tllr SJIOS dmice is oK Ilrncr. tllc output wltage (1') is ver). cloir to V,,, ( 1 4 c I). \\lien thr input h at I;,,. the P\IOS (aitlt I::, = 0) is t ~ ~ r n e d om, and (11r h'\iOS is ~ I I I

on (V, = 17,, > I' 7- ) ' Thrrefore. V,, eqrtnls zero (logic 0). The C\IOS inverter I t= a unique feature: In ritller logic star?. one device in

series path frr~m I$,, to groa~ntl is nonmodtstiw. Tllr current that iln\w in eitl~er st1 state is ;a small lrakaee cllrrent. ;md onlya.llen hotll d e \ i c ~ s are 011 d r ~ r i ~ ~ s s \ i t c l ~ i n g ~ a sipificant alrrrnt flo\r tllrouoh thr CMOS inverter. Tl~as. the n-:rr:~~cr power diss tion is small. on thr order of n;~nnrmtts. i\s the n ~ ~ o ~ l x ~ r o f m m p o n ~ ~ ~ ~ t s p.r ellip incre; poiver dissipation ix.cnnles a major limiting factor. Low po\\rr mnsu~nption is the I I I U ~ L

itttr.stive feat~rrr oftllc CMOS circuit. Fieurr I):23 sl~o\\s a Ia\n~!t of the CXiOS inverter. m d Figire 9.- sho\\s the rlolniw

the lllv ices iipa- Ices. ..-.,

cmss section alone, tllc ,\-:I' linr. In the prmssing. a p tub ii~lso called a 1, rcell) is fist inlplantrd an11 sohscquenlly driven into the 11 s~rbstmtc~. The J J - h ~ r dopant COnRntIa. tion l~lust I r Itich enouch to o\.ermn~pensate t l ~ r bnckgrotzntl clopil~g of the n s~~hstnte . Thr s ~ ~ b s r r ~ ~ r r n t p m , s s r s for tllr ,~-cllsnnrl XIOSFET in tile 1) tub a r r identical to t l 1 0 ~

rlc~scrilwd prr\io~rsl!.. For tbr p c l ~ m n r l \IOSFET. "B. or "'(BF;)' ions are implanted -. into t I~e n suhstratr to form tllr s o u r e ancl drain re@ons. A cl~annrl implant of "As' ions m:ay hr itcod to at l j~~st t l ~ r tl~rrshold voltage. and an 11. cl~anstop is fonnecl ~~~ldrrnralh t11r hrld odd? ;~munrI thepchannel dr t im~. BW,IIISP oftlle 1) tul) an11 the additional StepI

9.3 MOSFEITechnoloqV 4 en!

nrpdcd to n ~ n k ~ t l i ~ p-cl~annrl XIOSFET. t l ~ r nllmlvr of strps to ~,~:,k,. :, (:\IOS drt.,,, is rss?nlinlly clo~~blr 111:rt to m:lkc ;In NMOS circuit. n n ~ s . ~ l n c ~ r is n tndc-ofll,r.t\wr,, tllr rnmplcxily of pmcmsing nllrl 1111 rnlti~.tios in p \ w r r o n s ~ ~ ~ ~ ~ ~ t i ~ ~ .

1nstr;ld of111~ p tub just drscriln.11. an altemltc appmacll is to IISC an ,I t,,l, i,,,mlr,l in )~-t?pP ndi'Sll"l1c. as ~I10~111 i l l liipllre 9.2rkr. In Ilti5 CLV., 11,~. ".hF ~lr,p:,nr cT,,,eTn. tn~tion nus st IF hidl rnoclel~ to o\.crcnmprnsxtr for tllr l~ack~ro~ind;lo~in~~ftl~~ ,, r,,h. str.~tr (i.r.. A', > S,l. In 11oll1 tile JI-II~I , ;and the n-lul, nppro:sl~, tlnr cll;arnrl ,nohilily will lr d r ~ c ~ d r c l h r ~ n a s e inobilit). is dctrnninrd by tltc ~o t ;~ l clopant c~,nrr.nt~;,~i~,, is, + A',). An approacl~ using hvo srpnntrrl tubs inlplantrrl inlo a liSlltly rlnFd suhrtr.,tr. is

sho\\m in Fic11rc 9.2411. 'Illis slntrlurf. is cal l~d :I twin frrb.' H~cit!t<<. 110 o \ . c ~ ~ ~ , , ~ ~ ~ ~ ~ . tion is nepdrrl in cithcr nflllr !\uin tubs, llielter cl!mnrl inohility cm hf. obtninr<l.

hll C>!OS circ~~its hwte thr pote~~tial for a trol~blesome pmhlmm c3llnl lntdt,rlr tllat is zssociatrl1 \\it11 p:lr.\5itic hipolar tmsistors. Thcs? panr%itic ile\io.% consist af ,Ilc ,,-,,-,, tnnsistor li,nnrcl by tllr ShlOS n ~ ~ ~ r w k l r a i n regions, p 11th. and r t - h p r s~~l~str:,t~.. m,,rll as tllr p-n-JJ tr:~osistor fonnrtl I)!. tllr PlIOS so~rrcvf~lr~io n.gionr. n - 1 ) ~ ~ . seI,lr.lte. :tsd IJ tub. Undrr appropriatr <nnditio~a, llle colleclornftl~r p-WJ, dc\ice supplies hwe atr- rent to thr n-11-n. :IIKI \iw \.erm in a positive ierrlback arnngernent. This I;ttrl,,~p current cxn h;~\.e s r r i o ~ ~ s neeativ? rrprrn~ssior~s in a CJIOS circuit.

An effective prorrssing tecl~nir~ue 11) eliminntc tllp I;~lehup proMcm is to ILW dwp- hpnclr isolation. a$ shmvn in Fiplurr 9:&." In tlnk trclmip~r. atrend1 nidt ;tdeptl~clnlx~r than the u.t.11 is formed in tllr silicon 1)). :lnisotmpic reacli\,r sputtrr etclling. n oxid? I;lYrr is thermally gmum on t l ~ e lmtto~n and \r.dls of tllr trrncl~. \%,l~icl~ is tllrlt rcfillrd hy (lrposited polysilirnn or silicon riioxidr. This trcllniq~a can elin~inntc latellup Iwiarsr tllr rt-channel and ~~-ch;mnel dedn.s are p11)~inlly isol:ttrd hy thr rcfillrrl trclsl~. TIIP 11~tailcd steps for trencl~ iwl:~tion anrl sonle related CJIOS pmcesses nrr rlircuss~d n~xt .

\r'ell Formation Technolo!?? ,.,, , , . I , 0 , , I n i s l e I . a I 1 1 1 1 h i . ! ,,vll pnxvss rxl,il,ils so,llr disad,701tilg~.~. !:or rrralsplr. it needs 1li~ll-tempmh1r1- pm , rrsri,,s ,;,luxr l l , j t l ~ ~ ~ il,,c[ :, lolls lliift~sio~t tinlr (lonpr tllall S Ilolln) to achirvr tile ..,.... ;,I ,v.. 11 ,~,.,,~l, to 3 uln I,, tl~is p m s s , t11r dopills ~nmlltrntion is 11iglas~ 1 ,1,1 ,.... .. . . . , . . ~ ~ tl,c r,,r&,cy. 2iln,l rlwn.i~srs nar'rtoto~~icaill? \\ i t l l (lrptll.

To n,d,,rr l,rO(Ps tPIl,per4t,I~ and tizllc3. l ~ i $ b - e ~ l e ~ irnplnnlation is ~ ~ s e d (i.e,,

i,llpl;,ntine ion to t l lp desin.d dpI)tll inrtr;ld ofdil'iusinn the sorf:lm). Since tile <lrptl, ~,,tl,n,linrll I,! t l~c i~r~~>Iantittio~~ r n r w . ,?:w can desi~n tllc \\,eII depth witll~lif. rrrrllt i,npla,,llt;on mlrlR: TIIP l>rnlilr of t l~c \wII in tl~is can Imave a peak nt a wr. tain rl<,ptl, in silim,l s~~l,stfi>tr. This is called :I rrfmgrofl" ccfll. Fisure 925 shotvs a

n,,,,pafiwn i n l p o r i t ~ l ~ ~ ~ i l r s i n tile rrtrognde \\fell and the mn\.rntional tllenn;dlV

<lifiLud urll.l: TI^,. r,lcw k,r tllr ,I- ;mdp-l)p re t rgndr \\'rlls is nrolllld i O O ke\rmb JIWl kc.\: n,sPLdi,P~\: r11ention14 Prr~io~~I!: tile adssntagr of iligll-cnew in~p la t~ .

is t)IHt i t fon',l dIP ,,1'~~ t ~ n d ~ r lo\v-tr~nprmtuw it~ld s l~or t - t i~n~ mnditinns. firnW, i

it rm rPdllw tl lr IItefiJ diN~rsion and iacwasr the device densih: The r e t r w d e url[ olfi.n ;Ir]rlitina$ ;rl\ant;~qes over tllr coovention:ll \!*ell: (:I) Ber~tase ofl~igb dopine ncia tllP JmttoII1. tllP \\l.II rr$isli\iy is loarr Illan that of tile mll\~lltiollnl \veII. md (he latcllup pmhlrln CUB be tnini~r~izetl: (b) the ellanstop n n he fonnccl at tllc sanlc time a tilr rptruFr.alr WFII i~r~plnntstio~~. redncing processing steps and time: a1111 (c) Iligher\Spll &,pine ill tllr lmttorn r . u ~ rnluce t l ~ e c l ~ a ~ ~ c r o f ~ u r ~ c l ~ t l ~ m ~ l g l ~ from tll?drdin l o t l ~ e s o ~ ~ ~ .

i #

Advanced Isolation Tcehnolnev ." .flip mn\rlltional isolation procvss (Section 9.3.1) has ~ir;lrlcanlaS,.s lnakr it ~llls~lital~l(' for cll-p-sllbnlirmn 10.25 pm fr;tturcs nnrl smaller) fn[,ricalion. ~ 1 ~ ~ . llipl,. tcmpcfiltllrp oxidation of silicon nnd long oci<Ltion timp res,,lt i n tllr r.ncrnad,mcnl of

Ill? ellenstop i~~~pl;n~t;llinn (~lsually lwrnn for N5loS) to tl,,? nctiw an,] I,, shift. Tllp nrr;t III*. :tcti\.e region is r~d t~c rd IX.C~UIP of tlle letcml 1" adrli. tinn. thr firld-oxide tl~icLx~rsc in s~rl~rnicron isnlntion spacings is ~ i q ~ i f i ~ : , ~ t l ~ lSs tllm I),,. tl~icknrss of firld oridc grouil in uidcr spacings. Trr.nrl~ isolation tr.cltaolw cn,~ avoi<~

t l~rsr problcms nod 11:rc I>~comr tllr mainstrc:tm tpr l ,nn~nn . tnr ;r-l+:-.. . ~ . . . . . . . . . . . ..I. .."" ..., , .",

Figure 9.26 sl~o\ss tllr prurss sequrnre Fnr i o m i n ~ n dmp (lnrprr [Ilan 3 pm) ),,,I narros. ilrss tllall ?. pm) trenc!~ isobtion stn8ctore. Thert. arc foer st,+: pattcming tile arra: trencll etcl~ing and oxirlr gro\~rih: refilling wit11 dirlectric materikIs. stlch a$ mi,~e or nnrloped pol)rrilicon: and planarimtion. Tl~is drrp-trmcl, isolation can k used in lntll a d c ~ n c ~ d ChlOS and l~ipular rl~\ices and for the trencl~-t:p DIth\f. Sir><? tl~e isoln- tion material is drpusitrtl by C\'I), it clws not z~cnl a long time or ;t higI,-trmpemtnlrr prmss , and it elin~inates liitcntl oxidation and lx,ron mcroacl,mmt nmhlrms

1~~~~ Anotller exa~lrplr is sllidlo\v-trencll (llrptll less tllan I pm) isolntk,n for ChIOS, s l ~ a \ , ~ in Figure 9.2i. After patt~ming (Fig. 9.270). the trrncll area is etched (Fig. 9:2;11) and tllrn refilled \vith wide (Fig. 9.2%). Rrforr refilling. a ehanstop implantation can he per. iorrned. Since tile mide luu overfilled t l~e trrnch. the oxide on the nitride sl~oul~l he rr~llo\~ed. Cl~elnicnl lnrcl~aninl pulislling. \vl~ich \\;rc discussed in Srction 8.5.4, is used to remove tlle oxide on the nitride aid to gel a flat sarfnec (Fig. 9.2idl. Bec;~usp of its lliell rrsistallce to polislling. tllr nitridr acts a a stop layer for the CLIP p m s s . After

mq r Chapmr 9. Process integration

Chemsinp

i I (c) (dl

~ ~ ~ ~ $ 2 7 Sfl;Jl,nv.~n.,lrh ikr,lalion firr CSIOS. ( a ) P.1t1erning with p!s*on.sisl 0. nilrid~/,,~d~ (ill,,q I . ~n ctrhinl: rind ch2a,r1ol, irnplimt~tior~. (r) C:l~rmiml \ymr drprsitinn (0'0) o-irlc to wfill I$I planar wrf.~cv ahcr rl,rxsicd nwcl~rnicll polidli!l<.

thr polishing. tltlr nitride laxer anrl tllr ohid? i;?\?r can h remowd h? H ,PO, and HF. rpcprr(irrh: This initial pli~nnrkation step is brlpful for the subsrqnrnt pol!3ilirnn pat. tc~n~inq and plnoarimtions of the multilevrl intenonnwtion pmcr..;ws.

Gate Enencering Technology l f u r use r t . poI!silimn for lmtlr PXIOS and NMOS gates. the tl~rrsholil \r~ltage for P ~ I O S {I;? z -0.3 to -1.0 VI ltns to lx. acljustc4 by tmmn i,npI;xntation. T l~ i r >n;rkes t l ~ c cl~annrl of the P\IOS a btnriml hpe. as sllo\~n in Ficure 9.2%. TIte buecd-hp? P\IOS suNen wrioos s l ~ o n c h a n ~ l effrcts as t l ~ r l rdm size shrink helmv 0.25 ltni Thr most notice. a h b phmo~nrna for sltort-chitnnrl effects arc the 1; roll-ON. drain- ind~tnd Oxnier lmv. mint (DIRL). and the large lealilcr current at thc ofC statr, so lll:!t even with t l ~ e gate \nlt.s<r ;,I rrm. InLcc nlrn,nt fllnrr l l t r n ~ t ~ l ~ wunr and dnUn Tu .illv\i:~t#. t l>i< pml* l r n ~ o n c c ~ n cl~.,ncv r: r r th~!l lm~l tot,' l n h v l ~ m n for P \ l O S DIIV 10 llteunrk funnmo ,- , . 7 . .

rljlfprrnm i 1.0 r.V fmrn 1,' top. pol!silimnl. onr can obtain a d : m ~ p - h ~ x ~ c l r a r t n e l ~ I o ~ witltout the h r o n 1; a~ljljllrtmrnt inlplantation. Henm. a3 t l ~ r twl111~11p s l ~ r i n k to 0.3 p n ~ mtl less. <br;rl-~atr stnwtlrm arc requirrrl:p' po!,Tjlimn gaB for P.\IOS. and n' pl>ril. icon for ShIOS 1 F i ~ . 9.2%). .A comparison of \; for the serf;~cr cl~antlrl and the halied rhnnnel is shntn in Finlrr 9.29. Sole that the 1% of the s~~rl;?cls clt;u~nrl rolls off Inow sln\vly in the deep-suhmicmn r@me than in the hnried-cl~annrl dv\ice. This nukes tl~e s~~fi;aw-cl~annrl r l ~ \ i w \\it11 11' pnl\silirun snitahle for d r r p - r ~ t l ~ r n i r r o ~ ~ i.lr\ice opention.

To f o m ~ tlir p' pl!silirnn gat(.. ion implantation of RFI is mm~nonl!~usrrl. Ilm\.r\rr. h m n penrt-cltrs earily fmm thr pol!rilir~m t l ~ r o r ~ g l ~ t11r oxidr into the silimn suhstmte at hiel! ternpcnilorps. r r s~~l t inq in it 1; sltift. This pmrtration is r-nliancwl in the pres. e n n nf an F atom. I l ~ e r ~ arc n l ~ t h d ~ to r r d ~ ~ m this effect: rnsc of rapid tl~ermal :inned- ins to ndsm dtr t i~ue a t hiell t<7rnprmtur~s and. c~nsrqst-ntI\: tlir rlifitsion of hornn: IISP of n i l r i d ~ l od~lr to s11ppr<.s5 1111. boron pmetmtion, s inw Imrnl~ n n ra~il!.mmbin~ \rifh n i t n w n ; m ~ l I m r n r s Irss mohilp: anrl thr n ~ n k i n ~ of a rnultil;l!vr ofpol\silimn to trt1' t l ~ v lr,mn :ltnnlr at the intrrfnt~. of t l ~ r hto ln\.rn.

Figure 928 !ol A mn\~cnfiunal lonpd~nsnel CMOS an,rt~lre w ~ n a nnew p,~).iltlmn CAI,. in.). (b , .\dinnml C\IOS rtnnctttrrs \rill) dual polyili<~m gate..

"10 . chapter9 Process Integration - 93 MOSFETTechnology 21 I

F , ~ ~ ~ ~ 9.31) rll,,,,s ;, I l~irrn~~nnvssor cltip (Pmtilim 4) 1Il:tI I~:L* an ansib of

"01, cr,nl;linr 41 ,nillion ,wtnpc,n~nts. This UISI diip is Ll>ri=ltrd u s i ~ ~ g O . l ' i . ~ ~ C\lOs I,.(.I,,,,,I,,$\. ~ i t l , :I siy.llv,.l :~lttntinttr~~ ~nrtzl l imti~~l .

~ . .

H~(:\IOS is t t y ~ ~ , n o ~ ~ tllat m, , l~, in~s lxltll ChlOS and bipolar c lo r i~ . stn~ctrlres in s,,,clr 1 ~ . TI,,. w:sOII tOnllllllin~ IIIPSL' h$n difkrr11t IPCIIIIOII*(.S is 10 Create an IC cllip

I,;,- tllr ;al,n,l:,Srs ,,I' hlltll C\IOS iind bilnlitr ilr\i<r.s. (:\IOS caliibits advantnxcs i,, pcn,,.r ilissipjtin~t, !nois<. n~sip$n, ant1 I X I C ~ I I ~ clc,~isity. \vlirw:s 11i1mI:ir t < v l ~ n o l ~ S I , ~ , ~ ad,.,,,,tag,.s j,, ~,itCl,inl:sFrrl. c n m n t clriw r;qxtl,ilit!'. :aid :ulalog~~:lpabilih hs n rrslllt. fi,r ei\.,.n rL.5isl RiC\IOS c m Ilavc a 11i~lt1.r slx~,d 111~1 CMOS. lwltrr perfor.

,,, ~l,,;,~rv2cin.,lit~ tl,:,,, (:~Ios. ;I I o \ \ ~ r pcrwer dissipntion tllnlr 1)ilmlnr. ;uidn hiSllrr n,tnlr,,tmt d<.ll'iiy tlr.an l,ilnlar. Figlrr 9.31 mnip:trer ii HiCMOS :ttlcl a CXlOS logic Catr. F~~ ;, (:\I(>S invvtter thc. rurnmt to driw (or to c l ~ a v r ) t l ~ c neat load. C , , is tllr ,Ir.",, n t m n l I,,, For $1 RiCXIOS in\.rrtrr. Ilxr cllrrnlt is h,,.l,,,. \vllcn. h , is the ci,rrent c.ti,l tIIP hiIx>litr tmnsistor :an11 I , , , is tlte lwsc cttrrent of the bipolar tcinsistor 2nd is ~ c l l l l l to tilr clr.lin n~rrt>nt of ,!I, i s tl~r C\IOS. S i n e h,, is rnucll i n v r r l11:m 1. the speed

TIw initi:tI t~iateri:~l is :I j J - t>~c ~iliwtn s~~l~str:fit~-. ,\,I i,,,",.,~ I ;3,Tr is tl ,(.,, f 1 lo rrdllw m i k t o r resi~tRII(~~. TIIC Ij11riwl~1 liyrr i5 fonll~<! I>\. io~, illlpl~tntilli,lll 10 inCmLY1

thr dnpi~lc lc\.r.l to prrvt3a( p ~ ~ r ~ c h t l ~ n ~ ~ ~ ~ l ~ . I\ liqlttl!. ~l<,~n.li byCr is no,,o on tl,r \rnfrr. i~nd :I t\~i~i-\r.rll prwv\s for t l ~ r C\IOS is pcrr,,nnt.d. 'L,aclti~.vc l,i$, prrfnnnanlr f o r t l ~ r l>ilmlar tn~nsistor, ~ C J I I ~ addition:~l tn;~sk:$rc n ~ ~ ~ I ~ ~ l . Tit?!. :trc t l , ~ I,,,ri,.<l,,~ l,,:,sk, tltr cr)llr~dor clc~,p a' ~llosk, tllr. I).lrr p lnwk. and llbr pc8lycrnitt<.r ma&. 11, otlrr pr,,. rcssi~~fi strps. rhr p' region h r h:~rc concart car) iw kjrrnr.cl \ r i l l , tile 11. i~npl:tnt in thr sn~~rcc*I<lr;lin inlplnnk~lion of tlw PMOS. and the :I' rznittvr can lu. fonnrd \t+tl, tile sn~~rtr/(lr:lin impli~nlntion ortllr XUOS. Tllrr athlilinnd ~n:rsk* asfl lnnCvr p m s d n q tin,,. comp:~rrtl \\it11 s rl:~nrl:sd CMOS arc tltr wain iln\vl,acli\ of HiCJIOS. TIIV :alrlitinr~:tl cost s l ~ o ~ ~ l d I)? justihc.d hy t l ~ r c ~ i l ~ ; ~ n r ~ ~ d prlonnarsc.

(a) Ibl

Figure 9.31 ("1 ChlOS lc*c ptr. Ibl Bipolar ChIOS iRi<:JIOSI lo$c gate.

9.5.1 Bulk Micromachining

Is hnlk ~~ricromk~cl~ining. 1131. d r \ i w ( t . . ~ . . x msor rrr ;m fic*,lalorj is sl,alw.cl by ,.lcl,inS a large sillsh.-cl)stal suh5tr;ltr*. TIII. films ;arr p ; ~ t t ~ m r d on tllc l,,,lk s,,~,slr.,ta to ,lrfin,. ,I,,, isol:~tioxl ;aid tmlabrcvr filnctir,~a. Orieat~~t ion-#lr~: t~~l~nt svct chla.miml rtcllisS trchnilllcc pro\ i~lr I~ik~-rr.sol~~tir,t~ r t c l~ nnrl tisl\t ilin~ensio!r;d mntrnl. Often. :a I,lllk-microls;s~Iil,rI~ rlr\in. llscs Wo-sidrd pnnYc*.ssing. crrali!,e st srlf-isf>l:ltr.ll stnrctllrr \\,itll one ridr. rvutd to tlw i i ~ r i ~ ~ ~ ~ r e d wriablrs. S I I ~ I as ~nerl~;tnic:al or clt~nriotl rivals. \vttil~ tltc otller sirIr is ~nclosrd in n c1r.11 packimp. T\vo-ri~lr.~l slnacturer an, vc.3. n,l,>lst for oprration i s cmi. rn~~nients liostil~~ to ~rricnx~l~vtrnttia dc.\im-q. Simplo rnerln;tr>inl daxicrs sllrll as <liaplmrgm presnlre srllam. ~ncnrhr:inrs. and clntil~rr.r-Iran, pi<,mresisti\.c amlclrr;rtion spnsan ;are fiihricat~d cn~litncrcidly 11). tl~is trcltni~lur. Figurc 9 . 5 ill~xstr~trs a f:thrica-

I I tion p m ~ . s s of ;I dnlplr. silicon? n111lx.r rnernhr.~ne.''

1 9.52 Surface Micromachining St~rfncc-a~icromacl~ined rlr\ices arc cnnsln~ded entirely from tliin films. TIrun. an. w. era1 (di&.rrncrs nnd tndr-ofls hchvffn stnstt8res rnnrlr imm 11ulk awl Illin filni mntrri- 01s. T \ p i d dimensio~is for I)t~lk-~nicro~~~acl~in~~l sensors ilrr in t l ~ r tnillimrtpr xinp. hut sa&~~rr-nticrornacIii~~vd dr.\icps arc of micronetrr dinlrsrions. Surfnw nncnm:icl,ining prnnits tllc fahricatio~i of stn~durnll\. co~nnlrr de \ i c~s In. stacltine ar~d natternine Iav~m

~ ~ .- . .- . or "l,t~ilcling blockc" of Illin films. \r.l&rrs~iultil;tyered hulk devices ;ire dilficult toms- struct. Free-standing anid movnblr ptrts can be Ethricalnl insins s:~crificial 1aycs. Fimrr 9.36 ilhatr.ites l~o\v sacrifick~l rtchine t~cliniuurs can l r usrd to create an ?lrdrort;ttic

I 1 95.3 LlGA Process 1 LIG.4 is n Crrznan ncrnn!m for lilhogrnl~hic. gnlm,rq{onnntttg. ol$>nn~#ng." It consists

of llirrr l).lcicprocvssi~lSsteps: l i t l~o$~ipl~y, elec~roplating. and inolding.Tl~r LLCA prw ccss is basr~l on .;-my ndi:ttion frnm a s!ncllrotron. Tla! pmcess can pra111rr micrnslwc- h ~ r r s wit11 lntrral dinnensions in tlir nricromctrr m s e and stntanr.d I~f'isIrts of S\ -I?T~

l~nn<lwd micronirters fro111 a \ar ieh of nlatrrinls. Its potential applic3lioss w r micm-

i rlrctronics, srnmrs. nlicrooptin, micromeclt~iaics, ;md biotecl~nolom:

i 10) (dl

9.35 ~,~,ric;,tio,, prm.s* S ~ I ~ ~ I V rilin~tr nl1,lx.r nac!nl~r.~ne. la) Sitride drlxail~~

plllrmir,k (h) );of1 ,,td,inL. silio,nr n l l l ~ r r ~piu msting. ~ d ) Si~ridr w~no\:d on 1r.d

An exanlple or the LlGA p m s s i s sl~mm in Figure 9.37 A" x-nv resin. mzing Imm 300 ltln Inore than pm in tl~icknrss. is depsitrd on s s,,h5tritr ,,.itla an ,.lee. tncnlly cnnrll~ctive srarf;*cr. Litl~ofli~pl~ic plttrrrbing is rlonr>\.itlt extmrled CTS,~~,. fmm

I,isl~l~collimnted x-ray mdialion tl~rnn~ll at, x-ray ~~i&%li. EIIW FiprC Q.R;n. :! flmvrr. sltapcd trencl~ stn~ctr~rc is lonard i s thr thick wrist a l t c r d c v ~ l o ~ r tnzttment I Fi:. :.,,D;I,!.

2 1 s , Chaoler 9 Process Integration 1

I J l r l , ~ i, tllm , . l , . , ~ ~ ~ l ~ t ~ d the pqmsed ln,ttonl m~alacti\r surfilrr. filling the trrncll

m,rli,,e lllr s,lrfntl.oftl,r. wrist (Fig. 9.37~). Thr nlrt;ll stnldun? is formed

n~,,lmi,ls tl,,. n.sist (Fig. !J.:37rll. This stnrvtllw r;ln ht- llr13rl relw;ltrdl!. % a nlold filr i,ri,r,,c,,l ,ll,,l,~illq to f i rm r ~ ~ t t l t i p l ~ plx%ti~. w p l i ~ ~ q clftlle ~ri.$llal plating b;ue

, F,., !),:):,.,,, TI,<. Il:~.e r ~ ~ ~ l i c ~ . ~ . in t l~nl . ciln Iw 11si.d ~. to . ( l I ~ l r ~ ~ l ? l i d c ~llan). mctnl - t l l r i,,;,1 pr t r l~~rts . cLr sI~o\\n in Fiwln>s 9.37 and E.

~ 1 , ~ llisti,,(, 3~h.iDltlSI. ,,fthc L1CA p m s s is tl~r ill>ilit!.to ( . w a t ~ tbr*e-dinlensional stn,&,lrr< iLs thick m b~r lk . r~~icme~~cl~ i~ ,c(~ drrircs. \vl~ilr rl~tninine tllr sanlc degree of (lesio, f l ~ . ~ ~ , i l i t ~ is s,,rf;,cv r ~ ~ i c r o ~ t ~ ; ~ c l ~ i ~ ~ i n g . llo\\?vcr, t11e illitkll s~7lc~lrntmn racliation nm-rs i? wn. cnstl\- step, and t l ~ r mold s r p a ~ ~ t i n n steps I I I : ~ ~ rr~11lt in clrgradntion of ihr o r i ~ n a l alol(l insrrt

c 9.6 PROCESS SIMULATION SUPRE11 can I? edrrtnr!!. ~ l r r f t ~ l fnr the si~ntllation of x cnllbplrt~ IC filbrintion s p c , 1 1 ~ 1 1 ~ ~ :is an ~~am~lr . :"n,nsi , l r r a si~n,llntioa of thr S.\lOS pt3i\xili,:on gate prncrss d ~ ~ ~ l i l ~ d in Slrtion !~.:3.1. TIIP cmss sertiorr of the d r \ i r r to I,<. ~ i ! t~ t~ la t r t l \cis shm!n iaiti:~Il\- in Fim~rr 9 . 1 7 ~ snrl is n , p c n t ~ l hrrc in F i g ~ ~ n . 9R'i. T l ~ n , r \.rrtir:ll rrlions of thr d p \ j ~ ~ . ~ l ( ~ ~ ~ o t , . d In. clrt lint-s A-:\: B-B', nnrl C X ' , ar r sirnn~l.~tc,il. TI~c.sr t11rr.r sinlala- tinns repwwnt 11,;. crntrr of the. drticr. tla. so~r rc r l~ lc~ ia ns~fion. ;lr,,i the lirld refion. rrcprrti\c4!

Tls. Elnlchlrr is simttlnterl minq a tnkd of 1k.r SUPRE\I inp~tt drcks. Tllr lint clcck sinlt~l;ltv% prncrsring in 111~. adivo rt.$on nf tllr de\ i ( r . Ilp to tllc p l i l l t 31 \~.llidl 1 1 1 ~ pW w w crtltlencr divt*rqrs for t l a ~ gztfr. ;~rtd cotcrcr/rlmin rt.giotts. TI>,, %!.(.~,nr! and thin1 deck <l.~rt u i l l ~ tltc result'i fnnn 1Iw I>nt drck an11 wl~,pl,.t(. ~ T I H . I . S \ / ~ ~ : rnr t11r pntr md s ~ u n ~ ! a l ~ " n rroinns. r r c p c f i v ~ l ~ . This is nrxnmpli~l~c~~l hy t ~ c i ~ t c t lh . SAVEFILE rtntrmcnl ;at lllr rnd nf t l l r fint clwh in SRVP t h ~ . s t n t c t ~ ~ r r itnd S I I ~ I S ( . ~ I I ~ ~ I ~ I I ~ t~sirne th r sawd StnK- hlrr in tllr. INITIALIZE rtatrmratr in 1111. srcnnt! :trld tlfirt! <lw.kc. TJrr ir,vlrtJl cl<u.k is ""* 1I;br tn t l ~ t . f h t . mivpt tli,tt i t si111111,ttrs tlw prw+winq in tI\t. firld rvqinn. Tile fiftl r n m p l r t * ~ ~ iit.lrl rtyion pnmssi lq.

T l ~ r onrnplrtv p r w x s s c ~ l ~ l r ~ n c r is a5 f O l l ~ 5 ~ :

1. D ~ s n \\it11 a bigll-wsirtibih <110, ,).hpe ~ i l i ~ , ~ s , l ~ t n t r ,

2. Crow a 400.A SiO, pad layr.

3. Deposit an 800-A silicon nitride layer on top 01 t l ,~ pad orillr..

4. Strip nitridr from a r e a o ~ ~ t s i d r ofthe aeiw 5. Implant lmmn into t l ~ ~ firlrl rcqions.

6. 0yi1li;rfl t11e lid11 rrfiio~~s Cor 3 1lo1,n at I(KXI-C in oP 7. Etch dm\n to tllc silimn in tlw active repion.

8. Ilnplant h m n to sct the tl~reshold voltage of t l l r J I O S F ~

9. Crow a 400-A gate oxide.

10. Deposit 0.5 prn ofpol!silimn. 11. Dopr the pnl)silimn \\it11 phosphonts usins POCI,.

14. Etch the pol!lilicon in the arras outsirle the gate rP@o".

13. I~nplant aneoic to lonn the so~ire/clrain reeons. 14. Drive in tllr so~~rceIclrain 11s implant for 10 n~inl~trs at 1000'C in dl?. 0:.

15. O p n mntact holes in the gate. sotzrce. and drain w@ons.

16. Deposit p l ~ o s p h o n ~ s - ~ ~ o p r ~ l SiOi (P-glas! over the \ctfir sari:~rr.

17. Reflo\v the P-glass at IOOO'C for 30 nlinutcs.

18. Rmpcn thr contact holcs, and deposit al~rminl~tn.

Plots of thr doping pmlilrs in the pate (section A-A'). sourceI(lrain (section B-8'1. :tnd nrlrl (section C-C'! regions are sIlo\\~l in F i p w s 9.39.9.40. end 9.41. rrsprcii\vl!-. Tile SUPHEhl input listinp is a5 follo\n:

TITLE NMOS Polysilicon Gate-Deck 1 COM'IENT Active device region i n i t i a l processing COMMENT I n i t i a l i z e s i l icon substrate INITIALIZE <lo@> Silicon Boron Concentration-lelS COMMENT Grw 400A pad oxide DIFFUSION Time.40 Temperature-1000 Dry02 COMMENT Deposit 800A CVD nitr ide DEPOSITION Nitride Thickness-8.08 CWYENT Grow f i e l d oxide OIFFUSI~ Timed80 Temperature-lBBO Wet02 CWYENr Etch t o s i l icon surface ETCH Oxide a l l ETCH Nitride a l l

SO , Chapter 9. Process Integration

ETCH COmENT IYPIANT CMENT DIFFUSION CWENT DEPOSITION CWEKT DIFFUSION PRINT PLOT WEFILE STOP

TITLE CDmENT COIHENT INITIALIZE COrrrENT IMPLANT CWENT DIFFUSION CWENT ETCH CWENT DEPOSITION CWYENT ETCH COmENT DEPOSITION PRINT PLOT STOP

TITLE CWENT CWENT INITIALIZE COWENT ETCH ETCH CWYENT IMPLANT COuYENT DIFFUSION COuYENT ETCH CWYENT DEPOSITION CWUENT DIFFUSION

Oxide a l l mplant boron t o s h i f t threshold voltage Boron Oose-4el1 Energy-50 ~ r ~ l r gate oxide Time.30 ~em~erature-10S0 Dry02 HC'&3 Deposit polys i l icon po lys i l i con Thickness-@. 5 Temperature-600 mpe the p l y s i l i c o n using WC13 Time.25 ~~ rn~e ra tu re - l 000 Phosphorus so l idso l Layers chemical Boron Phosphor Net structur ~i1~name.nmosactiveinit.Str

End Deck 1

NWS polys i l icon Gate-Deck 2 Gate region I n i t i a l i z e s i l i con substrate structur-nmosactiveinit.str implant arsenic for source/drain regions Arsenic Dose-5elS Energy-150 Drive-in arsenic and re-oxidize source/drain regions Time.30 Temperature-1000 Dry02 ~ t c h contact holes t o gate, source, and d ra i n regions Oxide Deposit phosphorus-doped Si02 using CVD Oxide Thickness-0.75 C.phosphor-le21 Reopen contact holes Oxide Deposi t Aluminum ~luminum Thickness-1.2 Layers Chemical Boron Arsenic Phosphor Net End Deck 2

ws Polys i l icon Gate-Deck 3 Source/drain regions I n i t i a l i z e s i l i c o n substrate Structur-nmosactiveinit.str ~ t c h po lys i l i con and oxide over source/drain regions Polys i l icon Oxide Implant arsenic for source/drain regions Arsenic Dose-5elS Energy-150 I Drive-in arsenic and re-oxidize sourcc!drain regions Time-30 Temperature-1000 DryO2 Etch contact holes t o gate. source, and d ra i n regions Oxide Deposit phosphorus-doped Si02 using CVD Oxide Thickness-0.75 C.phosphor-le21 Reflow glass t o smooth surface and dope contact holes Time-30 Temoerature-1000

COmENT ETCH CMENT DEPOSITION PRINT PLOT STOP

TITLE CMENT COWENT INITIALIZE COYYENT DIFFUSION COMHENT IMPLANT COYYENT DIFFUSION COYYENT IMPLANT COYYENT DIFFUSION CWYENT DEPOSITION CWENT DIFFUSION PRINT PLOT SAVEFILE STOP

TITLE COMYENT CO'IYENT INITIALIZE CWENT ETCH ETCH COYMENT IMPLANT CrnYENT DIFFUSION COWENT DEPOSITION CONVENT DIFFUSION COYMENT DEPOSITION PRINT PLOT STOP

9.6 Process Simulation 4 421

ReoDen contact holes Oxide Deposit Aluminum Aluminum Thickness-1.2 Layers chemical Boron Arsenic ~hosphor Net End Deck 3

NMOS Polysi l icon ate-~eck 4 Iso la t ion region i n i t t a l processing I n i t i a l i z e s i l i con substrate 400> S i l i con Boron Concenrratim-le15 Grow 400A pad oxide Time-40 Temperature-I000 Dry02 Implant boron t o increase f i e l d doping Boron Dose-lel3 Energy-150 Grow f i e l d oxide Time-180 Temperature-1000 Wet02 Implant boron t o s h i f t threshold voltage Boron Dose-4ell Energy-50 Grow gate oxide Time-30 Temperature-1050 Dry02 HC1)6-3 Deposit p l y s i l i c o n Pol ys i l i con Thickness-0. 5 Temperature-600 Dope the polys i l icon using POC13 Time-25 Temperature-1000 Phosphorus solids01 Layers Chemical Boron Phosphor Net Structur Filename-nmosfieldinit.str End Deck 4

NMOS Polys i l icon Gate-Deck 5 I so la t i on region f ina l processing I n i t i a l i z e s i l i con substrate Structur=nmosfieldini t . s t r Etch polys i l icon and oxide over source/drain regions Pol ys i l i con Oxide Thickness-0.07 Implant arsenic for source/drain regions Arsenic DosemSelS Energy-150 Dr ive- in arsenic and re-oxidize source/drain regions Time-30 Temperature=1000 Dry02 Deposit phosphorus-doped SiO2 using n/D Oxide Thickness-0.75 C.phosphor-le21 Reflow glass t o smooth surface and dope contact holes Time-30 Temperature-1000 Deposit A1 umi num Aluminum Thickness-1.2 Layers Chemical Boron Arsenic Phosphor Net End Deck 5

Relerences 4 123

Figure 9.39 I'!,>t , p i !lit. ~I~[)iol: i ) ~ r l R i , . 11, 111,. <;,tv n.(.11111

Figure 9.40 I'!UI ul t l j t . c I , , j ~ l > l : I ~ ~ I I I I I , . 11: ti,,. ,1311rrI. ,Ir.,ili r~.ri,,li

, b 9.7 SUMMARY

" FET. ;md tile hIESFET wcrc dkcasse~l in (letail. It iippcars tllnt the IIOSFET \\ill he the dominant technolop at least until 2014 I)ecluse of its stlpriur prrforrnanw ma)- pared witl~ tile bipolar tmsistor. For 100-nm ChlOS t rc l lnoln~: a goo11 ca111li&1r is the ro!nbitlatiotl oran SO1 sul,slr.tle \vilb itltcrmllnedions using (:u and lmv-k matrr ia~.

XIELIS is still :in enlrrging liel(l. \,lE\IS llns ;l~lopt~.d tltr l i t l~o~mpl~ic and etching trcl~nologirs from IC fal,ric;~tiu~~. Specinlir~arl etcl~ing tt,cl~niques Ilave alw Invn drvcl- oped for MEBIS: balk n~icmn,achinin~ ilsit~g NI oricntation-depend(~nt etchitlg pnxrss. surf;lce micro~Il:lc~li~ri~~g usin$ sncrific;d I;l!'!.rr;. and tllr LIGI\ pnmss l t s in~r-r : i~ litlloe- r;lplly n"tl~ 11igI1Iy collimstr~l nllialion.

REFERENCES I. For r dcldlrd di<cas$inn on IC i,nn.~$ inlcfntiol,. rer C. Y Liu .v~tl\\: Y. Lv. Tmn,. I n l q h , n . - in C. Y. Cbmp S. M. Sn. Ed\.. t.l.SI T,<!2nologg. \Idm~v-llill. Smv York. I M .

2 . ~ ~ ~ l , i t :,,,-, -bqrn,f,l! mml ~ ~ ~ k ; ~ @ ~ ~ g . - in C. Y, Cllan<.url S. St. Srr. Ed'.. ('!.Sf Zrhlldq. Mdr*w- Itill, S ~ ~ ~ ~ ~ Y ~ ~ r k . I%,.

3. T H. llv, TI,< i)rqlca n J C ~ ~ ~ ~ l{n,li~r-Frrrpn~"l bllrer,i!nl Cimtllr. Camhndgr Uni\r,~tn Fn-. Ctrnbti~Ip~.. I1.K.. IW5. CII 2

J D, h., -lsol,[mrr.~ sllrr IL,,,~, for S C ~ V Ilri~lttr i s P$.rlnnamol,: f l 'dn~ni*. 33. I37 ilmJJI 5, 7 c ~l,,, , , , ;,I., s,,bs,ierus,,.er l ~ i ~ h . h . ~ b , ~ ~ ~ ; , ~ n r Ripl.aTtci~~~~deR:'lEEE fl'rmw arir IA.!,,, IO!Sl, X,l (1!199l.

29.1 Chapter 9. Process lntegrarian

(: p 1 ,.( ,,I , .\,, ,,h.,,my~ ~ ~ i d , . p ~ ~ ~ i ~ ~ ~ ~ ~ ~ ~ l ~ r . ~n.srl#-ln,lrlc~I S r l C ~ l i q > c . ~ ! Bipol.,r Tccl~nulr~: rn3,,\ 1:1;,7nm, lk~t,.,.~, 3.1, i01. 5241;(l!lS7s.

7 \y 1~,,~.1,.. 1 1. TS.,~, .,,,,I II 1) Plt3,q21p,+.r, &I. , <h,ick R~fin'eaw .\loftr~nl f i ~ Sc8tti,?888<lt8ec?r

T , , ~ , , ~ , ~ , , ~ , \llB,,. Sc.r Yt>&. 19%

Y R \V ~ \ ~ ~ ~ n t ~ ~ ~ "?<ip~ ;and TWh8~"k-: ih! \I 1. !1<>>~3 ,&!LC! 1). \'. \f0"!:3!3, Ed,., hO!* of^

{,,!,.<",!,,,,,. \G! ,.,, X,%V f i ,rk, l!l%l

9 \ K ~ l , ~ ~ . , . S.,n8~l,,lrl~tm>r \b.nl,rir.-Tiubn,.I~~~y. 7?sfing. on,$ Ilrllnl~ilil~~. ICW. Scu. So&, 1597.

(7 I(~,,,,,,,,,, -(:hip ~:,,c5-nl,~ .\pl~tl~tinn R~~"l~ttion." 1f:EE l i rb Dig. In1 flcrrmrr l>n.irrr I; i'rl:

11 R II ~ , n f It. \Iclnru., rtal Y. Y:qdxtho. "Dwp Tn.ttcIc I\ulation CMOS Dr\lrrr: IEEE Tcclt. Dig. l rz l fll.*-lnn l h a,.r \I..,., . ),. 2; 1 I!&V?'.

I2 I, \I Hnm. \I l:llt~7Ja. ;at61 1. 51. I'tilsl?l~~y, Tnmb in .<l\;lnnrl CZlOS I'nrcrs Xrlall,lq: I'm ICEE 13 lM6 lcl%:.

I3 11 t ~ ~ ~ ~ ~ t ~ i . 1.1 I)\.. - P ~ l ( o n > ~ ~ u ~ ~ ~ Slnx?~>n. n i S ~ : ~ l ~ ~ d . I , ~ ~ ~ Uilnl>r Ih.\i<r.\ \<rqr \\rllt

(:\IO:FETI.- IECE z.<h D,: I,~I F J ~ . ~ ~ w a.,.irer .~f...-i. 1,. 611.1 I I!IU)

I4 \I. .I II~IICS 83r*,1 II ;\ >ttwpI>y, - l l ~ ~ ~ n t ~ ~ ~ t ~ ~ v ~ t o ~ ~ i ~ ~ l ~ l - E f i ~ t Tcttwist<>m," in S. \!. Sw, 131.. fligft.Spcp,i S . , , ~ C C ~ ~ J , , , ~ , ~ ~ n., I,~,. \V,I,?, SC-V snrL, I!FNI

IS 11. F slnclt. rr d . -<:.L\S LIn,. R w r Inltc-w,ttnl Cin.aitr hrr r tlidn SIX-l 1)icitd Sign:>l PR~\.s<oc' IFEE Tronmr t:b.nnm f v c . Bfi. 3 0 i I!lS9l.

I 6 C. 11 l.,rtr~nqrlo .md I\'. C. T.a~g. -Srs~iuln~cB~ror & ~ ~ r o r TwllnoloS\:'in S. \( Srr. . Ell . .~~~,io~,,,l,,~,~r S<!,<#3r,, \ \ i l t~ , snv Yo&, I W .

I: 1. S F . ~ I . S 1: T:Y. . l l tq l R. S. \ttslli.r -1C-Pn~r~r~r l Elcen,sk~lic \ l i r m n ~ o t o ~ . ~ in ITET lr!r flcornn fA,?P.*' JIP,~,. p w> lllY\'.

I S S ,:me, r t :,I . -4 \IE\lS Silic~,s<, Rlrblx,r \lrmhnnr \:Ilvr..- Soi i Ar.rnntz,rr. AM. ldI l'm

19. 11' Ebrf-lcl. 1.1 .)I -F.mhri<>tion of \licmrtnlRam V~inq lhr L I C Prmrr.-Pnu IEEC .!her R<zlnts nnA Z.lo,lr.mo,n \l;tr*cL~~,. Ii!:mni~. \I:\. Sov. I!>%

3 Y)C P 110, md 5 Il;m*~n. Sl'PRE.\I Ill L'r.r'v .\bnnnl. S~mbnl l!sivcnih 1957.

P PROBLEMS .Asrr.nrk~ rlmntr ,l;filjffinrlt prnblnrr~

I. For a rhrcl rwirtancr of I k Q E . find the tn;r~imltn, rrristnnw thal nkn lu, fifibrintcul on n 2.5 x 2.5 mm chip using 2-prn linm \\ill> ;r 4 p m pitch kc.. dirtanw Irhvvvn tlnc wnten of l h ~ p:tridL.l linrrl.

2. Drriwl n m;ak s r l for. S.pF \IOS r;lpacilr,r. llre oxide ll~irlmerr i s 30 nm. :A~s~tnrc that thr rvtinimtml uindmv s i x i< 2 x 10 ptn i d tbr n~:rvirnnm irsistration crmn arr 2 pm.

3. lInn\v ;I mmplctr slrp-llyslpp s r l of mavks for tlw spiral inrlo~clor \ \ i t l t thrre ltzrnr un a sllllltn,tc.

.5. IJctw t l ~ c cirwit ~ l b ~ ~ r : t m ZLIKI <I<-iw crow wctinn of 2 cl;amp~d tcanslstor,

6. 1tlvnti& thr potrpnsr of the li,ll<n<inc 5tt.p~ in srlf-nlism.mrd dc,~~l,lt~-[xllpilirnn hilx,lar stntc- tun,: i . t i it!irlnpnl [wll>~ilimn in trr.nclt in Fi$lrc9.I:kt. (h l 1111. pol? I in F i ~ l n , 9.131,. and i c i tb+,prtl!2 In Fi~n1n.!l.I3rl.

-.

'7. I n NMOS pmcr.ssins. t l ~ r sh8r(in): mateliitl i s ap-t!p. 111 n . ~ ~ <l~n,.,,ri,.~t~d <ilinln \wfcr. Thr sour<". ;and <lr;tin an. lirrmrd lq nnvnic itnplzmtati~rn o i 111~' iiosr/cln: at 70 ke\' tl~n>ugln it gate oddc ill Zj nm. (:,I Eslisl;btc. the i l tn4~ol< l vcnltrKe r h a n ~ , ~ r,ithr C\rcr.. (Ir) Dr;nv thr doping profill along :I monlinalr p(.wza!lcldnr 11, tbr ntrf;tcr. nnrl pa-ring t l~mtqh thr cla:~nnc.l n,eion or thr saarrr. rvrio~,.

8. (a) \t%"s cl(m> ~~rirntati<,n pwh,rn,d it, SXIOS f:,hricati,,,,? (1,l \\I,~~ ;,m diw~,%,,. bscs i r t m thin a liclrl ~xide. i- usnl in S\IOS ,hicv.? I?) \\h:,t p,t,l,lcmr ,xyl,r pol?ili~*n g:gtc is urcd for p ~ t c len~ths Irrs tlratl R pm? can anotl,,.r ,,,at,.r~ I", n,l,vli. ttlfrd b r pl!xil in~n? (d\ l low is a w\f.;di~ni plc ~ h v ~ i ~ ~ d . and iLs .rl,anl;,gc,? (t.1 \Illat ~ I I ~ ~ I V does P.gl;~r r c m ~ ?

'9. Far a flnrting-~ate non\nlatilc mrmory thc lmrrr innllator hm dirlrcttic mnstar,t .I mcl i s 10 nm thick. The issttl:tk,r alx~vc the flontir~~ p t c ha% , ~ i ~ l ~ ~ ~ ~ ~ ~ ~ , ~ ~ ,,( 10 and i s 11Y) thick. I f the, ommcnt dendty J in thr 1cnrr.r insulaton is )?I = ,,E, ,vl,rw 0. 10'' S/cnl. and 1111 LTlmnt is l l t r otbcr inrnlalur is n~yli~lllysmall, fin,! the tllm~f,,,~d

vnlt:~ee shift of thr rlc-ire cncrrwl hya r~l l taw of 10 \: applircl 10 thr. unntnll gate br o 25 W, and (1,) a suficiaraly long time that1 ill tltc 1onil.r insul:ttnr lrrvrnrr ne+*bI? small.

10. Draw a rnmpl?to step-hystrp s r l of ma& for the CYOS in\.crter shmtn in F i ~ l r e 9.23. I'ny p;-rticul;nr nttmtinn to the cmrr spcfion sl><n\m in F iprc 9.B for )nlnr xdo.

'11. A 0.5-pm digital C;hlOS t r d l n o l ~ has S.pm-\,iidc tmnrhton. l lnu n,inimum air', \\idth i s 1 pnl. and tlw n~rlalli,.?tion I:tycr mn~i$ls of I-pm-hick alamintlm. ~\snmntc that w. is 400 cm2N.s. r l i s 10 nm. \',,,,is 3.3 \! and thc tltn~rholcl toltagc i s 0.6 \: Fin:dIy, a e m r that the nlwi~num voltage 'Imp thnt ran lw tolrr;ttnl is 0.1 Vtvhrn n I pm' cms scctitm aluminam wire is n m i n g lhc madmttm cttnrnl that can lr nnpplinl h? thc S\lOS transistor Ilo\\~long a air? can lr nllm\rd? Usc a simple qnair-la\r: Ions-channrl mdel to predict the ,\lOS cttmcnt dri \r (rcristivity of daminam i s 2.7 x 1W' n-em).

12. Plot the cmss-swtinnal \~CWS of a hv in- lh ChIOS structttn. of the follmviinq stager of pmcc.;sinq (a) ,t-lld, ilnplnnt. (h l p-l!th implant. (cl h4n-tnb drive-in, (dl nonsrlre(ivc 1)' soum/clr:iin impla~t. (cl selective n' xnnrce/cIr~iraia in\plant usins phot~rvrist s nwk. and (0 P.glirss <lqmsilion.

13. \\I,). do \<T ore a 13' polysilimn gntc for PhlOS?

14. \\hat is the h r n n lmetntion pmhlrm in p' [xll!dliron PMOS? Ilmvar~eld !nu cliniinatt, it?

15. To ol~tuin a g~ml inlrrfacial prolrrty a haNerrrl I;?,y>r i s l~nm11~ d c p ~ r i t ~ l irh\ru.n the

Il igll l m;ttrtirl and ro~bstratc. Cnlctllale tlw eNrcti\r oxidr thickness i i thc rtsckrrl gate dirlrr.tric stn~cturr i s (;I) a balli.n~l nilridr of 0.5 nm and (hl n T:L:O, of 10 nm.

16. Drcrilw tl lr diradvimtrgcs of I.OCOS t e c l ~ n d w nnrl the ;~~l~;rnfa<~s of s h ~ ~ l l m ~ ~ t ~ ~ ~ d t isolation t ~ c l ~ n o l o ~ .

SECTION 9.4: JIESFET TECIIXOLOGY

17. \\llal i s the purpsc oftlte ln,l!imirlc l e d in F iwr r 9.Mf

18. \~l,~l is tile R.asol, ~I,;,I it is d i ~ l i n ~ l t 10 makc bipllar transistors wcl 1IOSFns in G:L~ '

SECTION 9.6: PROCESS S I M U U T l O K

-19 . use SU~HE\I simulrtr tllr l,ip,lnr p rows descrilml in Swlion 92.1. Plot the d<Vine

l,rnfilcs lllc follu\,ing ,rvlic.d cmsr srdiow: (a1 fmnl lhr top of the ~~~~ ~ ~ n t ' ~ ~ ~ .

(1,) [,,,,,, ,,ft~,~ r s i ~ t ~ r m n t i ) ~ ~ . and (c ) fmm thv top o ~ t l ~ c mllrrtor N'ntM.

-20, use SUPREXI lo sin,t,~atr thr C~IOS p m r s ilrscrilnl In. I'ig~w 1)s. Plot ~ 1 1 c d ~ V i l l ~ pmfilc,r ;,lclng ll,r fi,ll,,,,ing \..rtinl rnns srctions: (it) t l~rn!~d) tlw PJIOS sollm.'(lfilin rc *,,,, $, (1,) tl,m,,S), ll,r P\IOS s.,~p w@on. ("1 tltn,tngh lhc SJIOS mllm,!Jr.un nqrmr. .?,,(I (dl tlln,,,<Il IIII. S\IOS p t r rc.sior~.

IC Manufacturing

\I.,,,,,f.,~+~ri i q ,ll.finwl :rs lllr p n n w I?? rvllirh mu. 111ntrri:lls 1w (nn \ .e r t~ I into fin. i,l,..,l pn~lol~~, As 411twt~~tvd iu Fiturt- lll.1, ;I n~:~nct~,~cturing o p ~ l t i o n can he ~ i e ~ w l cr,l~l~l~..,ll~ ,AS ;, , ~ ~ t r n t n ~ t l t ntu t~t:atvrials ;~IKI sttppli~s srninq :IS its inputs :ln<I f i n i s l ~ ~ l ,l~T~,l~~f~r~~~,31 l ~ m l t ~ c i < s v m i r ~ c ; ~ ~ o ~ ~ t ~ ~ ~ ~ l ~ . I!) intmttcxl c i r t l i l ! t ~ ~ ~ r l l ~ f ~ ~ ~ < ~ ~ r i r l g , inptlt mate. ".,I, i ~ ~ c l t ~ l q . ~v,nicl>t,d+~ctnr \u:~fvm. insol:\tt)rs. ~IO~X~II~S. itnd i t~~ f i t l s . TIIC nu lp~~ ts arc- tllP I<. , II,.~~IL.~~IV~~ Tltv qx.<oipnx~~sst.s tIt:tt arise in I(; rna!~!~&~~turinc, ~ ~ l ~ i c l t l ~ i i v ~ ~ lm,, t l ~ s~~lplrr ir ol pn.\x,ta\ r l ~ a p t ~ n in tllis tvxt. incltidr oxidation an11 drpsi t ion pm~sses.

~ ~

cia1 cll.~rmnic n.itvrns .m~l pnxlurts isttch ;cr mtnpelm. wlllrlar pllonrs. 3niI t[i@t;d cam. ~.r.ni. a ~ r c t l ot l t t~r kt? pnr l~ssr~ tnt~st t.&r p lnc~ . Thrsr irbrlndr vlectri, .,I kstiog wd p~.L.t@n?. li.*tin< is ne~r.s\.ty In ! i ~ I d 1tigI1-qo;dih pr<xlllcts. Ou:llih :c,v!iir?r mnfor- m.ww 01 ;all pnulltcq* to :I s1.1 of slx~cifi~:~tiuns a d th r n311uction o f ;my !a: .;xllilih in tile a,;hntll:tci,!rinq pmv$<. \I;tintnining iui~lih oftrn invoIve4 t l l ~ O S P ofst i~l lc. l l p m s s mntml. :\ <lt,rvpnl t.ywrirn~nt is ;an c r t r~ rnr ly ~ r s r l i ~ l tool for clism\.~.no:: k1.1. variables tl,:lt ~n f l t ~ rn r r tI~t.Jihr.l~;tctc(~~ristin. Statistirxl r \ ~ r r i o l m t d clesiq is a l;c1ac :-I!;I appm?cli Inr n~ t rn r .~h r ;~ l l \ \aninn mntrrrllnhlr p r m s s mn(lition% ;urd dr t rn i . i~ inp11eir impact nu noi t l~ l l [xbr.~rnf~t~rs t11:at tnrasurv q!t;dit!:

.\ k ~ . ~nvtrir. tlt;tt ~ t n lw msrtl 11, <?;da~atc any o~;rnul~tburin< p n ) r ~ s ~ IS mst. and mst i G diwrtl? imp;stml b??irl,i Yidd r d e n to t l l r prnpnrtio~l o i ~n:tn.ci-ict,~n~tl pml- ItC+s tl1:it p r f o rm :I< nqu iwd hv a set 01 specifimtior~s. Yield i s in\rrjcl$ [>rnpr~rtionnl to tltc tnt.11 n~.tnt#fxa!xing m5t: T l ~ r lliqhrr t l l r !iel~l. the lo\vrr t l ~ r cost. Ftn;?lI!, compater- i ! t t tm lw l rn;mtrfxitl"n? i s ;timnl st optimidnq tlnr [nrt-rffeciivcness ofcli.rlmnin inan. t l~u l l lnn? hv llrille the l:%tc.cf ilrzr,b,pmrnts in mmpltter i1anla;tre and svfhsarr t p c l m o l ~ 1,) <.n!~:u>cv c\~r.nsivr~ m:muhrturi~i? otetllods.

Tilt< cllilp18.r c!vsrtilu~% r:~rll n i l l l r c r mnwpts. Sp i f i ca l l y i t clircussrs tile follmv- inq topics:

Elrctricnl mrzsurrmPn1C p r f ~ ~ r n a v l nn test stnlcturrs are ;I ra:tjor mrrl,:anistn &,r ;lcw*.

inq intecr;rtr,l eirnlit ! i r . l~ l ism* Sectinn 10.5). w \vrll ;tr ot1tc.r italir;+tum c,f l>nul!~d pr h,rn~;tnc~,. S~lclt ~nc-nl~r<~nlents arc pvrfonnrd Ix>tlt ilwiatg ;m<l itt t l ~ r cntlrln~rion 01, tII,.

fnhriration prmss. 111 :alllitil>n. clrctriczal t rs t in~< l f t i l r final prrrluct i s cntri;rl lo rnslrrr <luxlit\. T11rsr cnncrpts arr disc~~s.ir~l in omn. dct:til in tltr fr,llmvine rubsrninr~s.

10.1.1 Test Structures

. . ticlrs. mntaminittion, or at l~cr soltrcrs. spcinlly drsigned trst rlnlcturrr a n oerl. Tltrsr ctnlchlrcs. also lino%\ii :rs I>mrrw mtllml trlorlifon (PC>lsl. includr. sinolp tnnristnn. single linrs of mnd~~ct ing material. hlOS ctpacitors. :and i n t r n n n n ~ i irnaniton. l'mhla \v;tfcrs hpical? mlifaill se\.rral PC114 distribated acrms tltr s~lrl.se. c i t h ~ r in clir sitr.s or in thr scrilx. lines behv?rn dic (SCP Fig. 10:~.'

I'rmss qunlih r:ol be d ~ ~ c k ~ d at \nriol!s sta~es of rnannlhtc%!rin~ tlsrouel~ in-linc !ne:~<t!renlrnts on PCXI stnwti1res. T l ~ r w hpid inlermn~iect test stn~cll!rvs :are s11mti1 111 Fizorc ln.3.' Usinr! s n r l ~ t(*st stnxtltrrs. ~ n r : ~ t ~ r ( ~ m r o t s arr prrfnnnrd to avsrss t11r pwsrncr of drfrcts. \vhich can lr i n f r r r ~ d I,? tllc prrsrnw of short rirc~iits aroprn circuits usins rinlnlr resistilntr inr;r<t~n,mrnts. For i.r;amnle. t11(. mealder stntrtun fnril- n a

ii.tt<bs t l i r detcc.tion of ope11 circuits throtlglt incre;rse~l end-to-el111 rrsistalm. nf tltp

Figure 10.2 I :ktnfim~rd1inn 01 pnxl~tcts ;!n<l lT:>l, c w i* t,y>ir.tI sctvim>r><lttctr~r ~-*it.r.'

10.12 Final Test

ft~tlai,,,J h.$linS;tt t l , ~ mn~~~ l~ . t i < ,~ , of n~;~nttf;trtt~rinji i s t l l r final arl,itrr ufpmcrss qtm1. it?. and ! i i . l c l . TIt,, p t ~ l p w ni fin;tl lrsting is to pnsllrc Ihsl ill1 prmluct\ p.rl'onl~ to tile ~ p ~ i t " , ~ . , r , ~ , , ~ ~ (or ul,iclt tl~c,, t,r.n. ~ lvs i~nr t l . For in tegr :~ t~~I virct~its. 1111. tw t p-ss rl,-lx.rr,l< .I p a t <h.d on a.lwtlwr thr cltip tvstr<l is a heir or m ~ ~ n o n rlc-.icy. I n either c.r~c.. . t l~lon~.tt t~I trxt q t ~ i p ~ n r z ~ t i.\TG i\ I ~ S V ~ 10 apply :I ntr;lsurrvnrnt \ti~nolus lo the clup .tnd n.rrr>nl lllr nw~lts. Tlw tnitjor f i~~l r t ions u r t l l r ,\TI' iirr inpltt p;tttenl Kenen, t i~m. psttvm .tpplt~~ittiou. : ~ r i < l otntput r r s ~ m ~ ~ s c d~trct ior~. '

I > u r i n ~ r : r l ~ h~r~rfioa;cl tr,cl c\rlr.. inl1111 v<~c t~ ts arc. sent IIBNIISII the rhip by the ATE in .I timt.11 st.qut~~~m~. Om~tput rt-sponsrs ;arc rrad nnd m~nparrr l ui t l t c~~ywr t rd results. This n~lt~a,nm. i, npcatrtl k,r c.trl~ inptlt p ~ l t e n ~ . I t is often n w s s : t n ~ I I p r k ~ r m stsh tr.?t? at \.rious ntppl! vnltnwc aurl o[w!r.,tinc trmpr:r~tnrr5 to cnrntn. cl..\icc opemtion at 311 ~x~tvn t i ;~ l rt7ci!8w,<. Tlw n181nlvr :and srqI!6*ncf~ of kult~res iu 111~ o~atpt~t sip:$tttre ;an in,lir.~livc. of irl.inafncit~"no pr<Krss hnltc.

X.4 r,<t!lts III'~?IW wprmstd in :t \:t"<.hof~t?i:s.'Xt~~ ex:!~n~plcs arc dno\m in Fiq1n.s 10.4 :and I1l. i . Fimsn. 10.4 s l l o a ~ it b~n-clir~tr.~<ion;d plot cn l l ~d ;I ~l,r,cnt, ,,lot for a I~!.po- thr~ic:rl hipn1.n prorluct. I n n 411ncm plot, tlte u t ~ t l i n ~ d s l ~ i r d ~ ~ ~ l n.,@ort i~ \ r l ~c r r t l l r ~ l v \ i w Lq i n t ~ ~ r ~ ~ l ~ ~ l t o o p m t ~ . ~ v ~ t i ~ ~ ~ Ill? I>lank arr;, ouIsid<~ rt~prcscl l t~ t l ~ v IhiIt~re rr$on. Anoll~rr

h l ~ ~ ~ l tr.it o u t p ~ ~ t i q llv wll ~n.\pslm\n in F im~n 10 5. in:tps ;In. v r n uscf~d in iden- I t l i \ inc nnrl isnl;tlin? <lr\ict. hil18r<.s. p:8rtirul;1rlv in nrr!rbnr?. nrr;t!r. I n ;trl<litio~l. t l ~ e p t - tvm. ~<'nr.rat<vI in 111~ n.11 tllitp illity 1 ~ . m~npilerl. catalog!cd. and later n,mpnred \\ith ;I I ~ h r a n o f v ~ i c t i n ~ clrfcct h y q . tlt,.rr*h? nidioS i r l tl~,. ~li.cma,sis of l i u l~s .

* 10.2 PACKAGING h w l \ clc.fined. t i ~ r t r nn parkoyirr~ rr&n tn the srt of t r c l , nd~@p~ :lnd pnKI.SSPS that ov~nn-t IC\ sit], elcrlronic \n-tt.ntq. \ ~ r r ~ h ~ l :midoc.? is to cr,lvi<lcr an vlr.ctr(mic prod- l!rl :L< t ltr !~IIIII:*II h~!! 1.ikc tltr I d ? . tlwu. prwlnvtq \>:>YP "Inii~,s: \vItivlt :IF ando- wwr lo IC*. Elvdmnic p.a.br@~~c l>m\ i< l~~\ tIw "nrnr,~ls s\.rtem" :rs w<.II ;L< t h ~ "skrlrtal ~ \~ t rn ! , " 'n iv packac~. is r t ~ s r ~ n ~ i l ~ l c h~ r i n t ~ ~ r < ~ ~ n n ( ~ t i n t ~ pn\~r in< . molil)<. ;tnrl pnrtrdine 1 I . TI,,, ,,~,,iv.pt is illtt,tr,,lc~<l it, l:ip,r,* 10.6.

n.,rc. (,,,I ,a,,.

l),*i<..<,prdir,<

1:.

2

I -.. .~ ,' -__--- ~A-

I 2 .I

I*,,

Figure 10.4 Cv;tn>pl<. of t ~ v ~ ~ - ~ l i r ~ ~ ~ ~ n ~ i c ~ n ~ l \nl!~~v 511rncm 1,101 zoc a r~~lx,~;ar 1,-

Figure 10.5 C:cll map rhmving roa~npl~~r of C?iltxn, p;tltmms rnrl dc,fcn h ~ s . '

10.2 Packaging 4 23

1021 Die Separation

\trntt.. T!,t* I\ t..;~c.nti:all$ 111~. lirsl strp in tltc pil~kil@lll: pm(CSP. I n m l l ~ n ~ o n nrtllo t l ,~ ! I,A< IW,V t ~ s t ~ l l,tr rn:tr~\!r:tm, tlhc st~l>st~~tc, nxi<,r is tnot1111?d on :I l~oldcr andscrilw in h,tI1 tI1r r .and !I i l iwrt ira~r tlsin: a ~li;trnon<l swilK.. This is done id~lng t r i l w lmnlpl -- , 7 rr, 331 pm in aiclll8 t l j . t l .tn. for!t!rtl :lrn>llld tllc pripllc~?'of thr diw during f;~l,"~,. tion Tls.ct, l n n l r ~ n .rm ;~ligwrl \\itln the y3 l ;d pl.slvr of the s l~hs tc~ t t~ i f pssi l l l r . :\fter ~ n l > i r q . tltr. a:&r i c r.-r~cr\c.cl fn,n~ tltr l~n ld r r end p l nc~d i~psidc-<lo\m on :t soft sup- port .\ ~ , l l t ~ r i\ tlwrt 1 t w 1 ibppl, ~>ressurt-. i c i c t~~ i i ns the \!:~li-r alntiq Ill? s c r i l ~ lines. n1i.i must In. arcc,mpli~l~nl vitl, inininl;d datl>i~qv to t l ~ e indi\idu:J dic.

\Ion. r~urlvnt clic %vp.tr.ttion prrx.t.<srq llsc a r!ianlond saw r;rthrr tllnn s diaalond rrrilxs. 111 tl ln pn~w lun . . t l l r \r:tfvr i s altacl~ed to :I,) adhrsive sI~v<~t o f irylnr film. TIle ua. is tlwn n m l to r i thrr rrr ihr tlnr n:tfer or cut rurnplrtrls t h ro~n~h it. :\fter sepa. c3tion. tlw d im are r ~ t n o v c ~ l from t l ~ r t~~ylnr. The sept~mtml <lice t i ~ ~ n rea(ly to pl.tm~l into p r k a g c ~ .

1022 Package Types

Tl,rw ow a numhrr ofaPpro:rclirs to tlw pacL l@n~ o f sinel? ICr. I l j e d~tol ir1-1ine pack. o:r. or 1)IP IFic. I0.S). IS t ltr p~ckaer no st p o p l r rrnixion \I.IIPII t l ~ v y think ofinte- mrld riwt~its. T l ~ r DIP u : ~ ~ l ~ % c l r ~ p . ~ l in t l ~ ? I<Xinc. quickly I w a ~ n e lltc p r i r , ~ a ~ packqe ior ICs. :mrl II:LC Inn< r lomin:~t~d 1111. rlrttmnics packa@nx inarkrt. Tlat. I)Il'rnn I* lnarlp

of pl;atic or wmmic. \viilll t l l r latter called tlle CrrVlP VIP CrrDlP consists of a DIP mnstn~ctcrl of hm piccvs nf s s ~ r l ~ ~ ~ c l ~ e d wcunic \r,itlb lends pratntding from hrhVl.rn thr (?x~tnic pl;ttrs.

I n tile 1~1iOs ;mrl IBXOs. .571rj%fncc emstlf packogrr* \r.n. devclop~l in rr%pnnsr t on nerd for l~ ig l~cr -dms ih int~rcnnnvct than the DIP apprnacl~ rnltld prmClr. I n contnst to 1lIPs. 1111 lc.a<lr ofn rorf:tcr-~nount~l package donot pnptratc t l a p~ in tn l cirolit lm~! (PCRI upirn wliich it is monnted. This rltezms that the packaw can In. mountpd un l m t l ~ sirlrs of the Iward, t l~rreby allowing l ~ i p l ~ r r dmsit?. On? cuznplr o l such ;t lx~ckaqc i s

tile q ~ ~ a r l flatpack or QFP i F i ~ . 10.91. \vl~ielt ltas lrarlr on ;dl fnur sirlr5 to furthrr incrr.rcr thr, nomlwr o f inp~~Wonlpnt (110) connrctions.

\lore recently, the need for grcnter and gwater n~~mhers ofU0cnnnec(ions 11- lerl to 11~~~ r l r~c l op rn~n t ofpin @<lam). (PCA) and hall $rid array(BGAI p t c k ~ ~ n iFig5.10.10 and 10.11, rrspertiv~lyl. iJCi\s Ilave an I/O drnsity of about Mn. and HCAs c in hstr densities grcator t l~an 1000. uc mmp;~rred \villi i lmut 200 for QFPs. RGAs nn lx. irlen- tifietl I,? the solrlrr h ~ ~ ~ n p s on the 1)ottom of t l i r p?ckage. \\it11 QFPs, rn t l ~ r sp:tcing IIehvwn Ira& Imvmcs tidlter. tltp ~nilllufac*lirin< )irld [ I ~ c m r r s r ~ p i d l ~ TIIP RGA dhnrs itizher dmsity anrl takes up less space than thr QFP, but its ~nant~E~dt~r ing p r w w i s i n l ~~ ren t l y Inore rrpenriw.

Figure 10.9 QII:~,~ tl~ttpack.'

Figure 10.10 1,111 cnql ilm\.p-cka~r ' Figun 10.11 Rnll @<I arr.,v p.nl.net. '

nbr n,n i w r n t d rwbpmmt ill p~rl t ;~@ng is t l ~ r chip rcllr pnrkngr ICSP). wl,ieh ,, ,hmn in F I ~ I W 11). 12. [:St'<, d ~ f i n ~ l .n piwki~qcs 110 111rger tl~iln 20% ~ r c a t r r tllall tllC ,,re. < X I tla. IC: ~lir itcpli. oitr.n takr tltr h,nu of ininint~iriz<.cl h;dl grid :1m!5. TIlo .l,.inrtyl I,, 11. I l t lwl~ip i s o ~ ~ n t c ~ l (se* Srctian 10.1.:11 cui~+!mnn-ntio!~i~l rguipn~mt and w,!?!,.~ n t l ~ n v C:\PV :~r,. hpir;dl, ~n:tnuf:nrtn~rr<l in ;I pnn,ss t l ~ t CT~ . I I~PS rxtcrnal A,,,[ .,p,,! I 0 <~,,tt:,cts ; IS~ , I en~.ipsnl:~tcs t11c firti-Iird silic~~n cIits prim to ~ l i c i n ~ the ~ ~ ~ . ~ , r ~ . , l ! \ : CSI'S l,nniclr ;m intmnntartion fr.~n~rx.ork fnr ICs so t l ~ ~ t hri<,rr ~ l i ~ i , ~ ~ ,

,I:,- I;,<* ,111 ti,,. i~tr~?ions (r.g.. t~xtc~n~id rkiric.11 m~lt~lcts. r n e ~ p s ~ ~ I ; ~ t i c > ~ ~ of tlte fir,. ~ , l ~ ~ r l .,llcrln) oian,n\-rntiuznel f t i l lyp?ck~g~l IC. Xvo rrst.~ltinl fca t~~n~sof t l i i s appmacl, ;tn rl,.,! t l l r lr.tdc ant1 intrqwsrr I;l!x.r (:<n added 1;ty.r on tla. IC used to p m i d e tncJ f,illc<inrrJin. and n>trlt.u~intl st;>l,ilityl ;lrc fleiihlr rnouglt sn that the p7ck1gnl rle\iw is ~ w ~ ~ ~ p l i ~ ~ l t I I W t r q t ti~tttn. for islll tcs t ingi~~rl l ,~~m-in. and t l ~ r pack;~gc ctn a ~ ~ ~ ~ . ~ n t n h t t . thr rrrtlwl nonpl.u,:tri~ ilnrl tla.nnd i,.vtnsion and mntnctioll oi the I I I I ~ ~ ~ ~ , . .

[ ~ n n t t ~ l ornuit lxunl <luting ;~rsen,hl, :tud opmtion.

102.3 Attachment Methodologies

.\n IC elwt hc inountt~l nntl bondnl to i~ pnchee.. and tll;it p ~ c k ~ g e murt he attaclld tn n printnl cirnlit hn:~nl ht-forr thr IC r;ln In. used in an ~I<*mnic ?stem. M r t h d ofatt:lrlt~nc ICr .vr r e i r m l h~ iu L r c l 1 pnckneir~e. Tlir tecl~eique nsrd to lnnd a hap <lie to a pcktcr 11:s a vi~nificmt rffrct on t l ~ r ulti~nate el&rid. ri~rchanical. and tiler- m:d p m ~ r t i r , < nfthe ~It,ctronic s!sbn~ k i n g ~n:tn~~f:~ciulwl. Cl~ip-t+p:~ck:a;ler intrrmn. nmmn iq ccnerdly a m u r ~ ~ ~ l i s l m l I,? r i t l~cr ,%in. Ix>edin~. tape-:a~ton~ntt>rl Imnding, or f l ipr l~ip hnncling srv Fig. IO.I:~1.

\\ire Bonding \ \ iw k,ndin. is the oLIrst attacl~ment metl~ocl and is still the dominant technique for rllip uitlv i;wv t l ~ m 100 110 connections. \\'ire hndinq IrquireT mnnruiing gold or duminttm eirm hchrven chip bonding park and eontad points on the pachgc. ICs are fint an;arhnl to the suhctntr urine a t h r r n ~ . d ~ m n d ~ ~ c t i v r adhesiw. !t?til t l~ r i r bonding

)nl~l. ,r lull Elrh.lrr,,.

pa& facing up\nld. The Au or Al \\ires are then attached hehveen the pads and sub stntr usinc ~ l l t w n i c . tllmnosonic. or tl~ennommpmcion inn(Iing.'Altlion~l~ ;a~tomatnl. tlsi.; p m s s is still time-miauming since each <\ire must l r attached indi\idl~ally

In t l ~ r rA~nnocn,~~prc.ssio,, technique (Fig. 10.14). a fine \\ire (15-75 pnl (liameter) is frrd from a spool t l~roagl~ a l~eatetl capillary A slnall h!rlmgen torch or elrcirie spnrk tlwn indts the end of tlw \\ire. forming n ball. The 11;tIl is tllrn positionrd ovrr the chip :,:.n~lin$ p;lcl, the capillary is lmveretl. and the hall deforms into a"nai1 head" due to prrs- s:!rc ant! heat lront tlir c~pillary. (Tlw sobstx~tr is maintained at a t en~pc t tu r r of 1SliC h> .'O(l0C. and tile bonding interface tempratare ranges frnm %O0C to :lWIC). Sed . the. c~pillary is raised. and \\ire is frd fmm the spool itnd positionex1 ovrr thr p~ckage substratr. The bond to the pacbge is a rvcllge Inn11 p m l t ~ c l I)? drfonnine 1111- \sire uith tlir r d p of 111r capilla3 T l ~ r capillar?. is tllrn raisrtl mid thr \ r i p is irmkrn near till. edge of tile Innd.

Oxidation of Al at 11igI1 trnlprratnrrs makes it ~lilficult to form :I god l d l at t l a rnll of tllr \!ire: in addition. many ppnirs mnnnl \\itl~stan<l thr trmpr.1hlrrs necdrd in thl2r- mc~m~npression Innding. Cltm.~ortic Ix,n~ling rrprrsentr a lo~vrr-trtepmturr xltrrnati\r that relics on a mznl,ination of prcssurr n~lcl mpirl rneclmnnic;~l \ibr.~tion to form lu)nds (Fig. 10.15). In tllis :~ppronch, tlte wirp is fed frotn a spool t l ~ r n ~ ~ g l ~ a llnlr in thr imntl- ins twl. a.llich is tltrrl lo\wrrd into position . l ~ an i~ltfiw~~nic \ihrxtion at 20 to M k l l ~ cntrses the 111rtal to drk)rm :mrl f l~~t r . (r\m at mom t rn~pemt~~rc) . As the tml is cuwd aRrr tllc lnnd to t l ~ r package is forn~rd. a clamp pulls an11 l)n,aks 1I1e \sin..

T14cn~loso,~ic bortrli~~g is ;L cnnll,ination of t11t. ntl~er two tecl~niques. Tlir s~~hstr .~te tmlper.lt,,rr is m;unt;linetl :lt : ,hl~t l5(l9C:. ntal ultfiuonic\ihr.~tiot~ and prcssuw are lid to c;l,lse tllr lnctal to no,v un~Irrprcssllrc to Cnnn a\rrld. Tl~rnnosoniv Imndrrs arc w i t e f;r5t-tlley are ~.,~,al,le of p~xlucing 5 tn I0 Innds p r srn)lld.

10.2 Packaging 4 2'

(el (0

Figure 10.14 Thcrmcmn~~n~ssion Imndinr: pnxvrs.' (nl C~,ld \\ice ins mpillnr? : l j l Ball forma. ~i<,rl. iw Ik>ntlin~ idl \!in. lhrlp and MI<<, Imliins. (rl \\ire Irmh,s at irl*zc. 10 i;rornrtryof l~,,ll-,v~"l<,. l">,,~l.

L . - 1 111 Ihl 1cI

Id1 (el

Figure 10.15 liltr;a\onir ix,nditcq l>nxrs<.' ini F u r l mtirlrs uirr to thc pnrka~c. 1R! I'rcr.urc and rlltr.twn~r pnvrm lorn, l*,n~I. tr ;and d ' Xx~l fi..'ds u ~ r t l ;mrl rcprnitions nlmvr thr IC. ic) \\'irr I>nd..n .d l x ~ ~ l

Tape-Autornntcd Rondlng ' lhpe-a~lto~n;~tr~! lmn<lin): iT,\B) was d~wlr>prd in 11,. lgios is oflrr, bolld packegrs to printvd rirct~it hnnr~ls. In TAB. clbip$ ;trc fin1 mountr.rl on a flprihlp pol!mtsr tapt. iust~:illy lmlyi~nhlr) uontnininc, n.pr:ttrd mpprr intcmmnraion patterns (Fiz. 10.l(il. T l ~ r N l p p r ii.atis arc drfinrll litl~ognphs oarl i.tching. and t l ~ lend pat- tent n n ro11t:iin h ~ m ~ l r r d s of mnnrctionr. hft~.r alicsing tl?e 1C pads lo metal inlrrmnnrction stripes on l l ~ r lap(., i~l lncl~m(.~~t tnkr*s plaw I,? tlirrmomnrprc~ssion (Fig. IO.L~I. Gnld bsmps are fonnnl on rilhrr sirlr of l l ~ c tlic or t a p anti :are ~ s n l to lmnd the dic to tltc lends on thr tapc.

A ltrnrfit of T,\I% is that all b o n d arc formed sim~~ltanenusly, \\,l\ich rignificnntly inxpro\.rs mnnufact~~ring t l ~ r o u g l ~ p ~ ~ t . Ilowerer, unlpss all thr leads are coplanar. rrlia- hility pwhloms c.m rcst~lt. TAB also require? mtdtilayrr solder bumps wit11 mmplcr met- a l l l~qy Crnmdly Illerr i~llrnps ~ ~ s r g o l d o r copper xs tlieprimn~cnr~stiturnt.\\ill~ tit.ulium or turrgstm s r n i n s . 2 ~ a rliif~~sion hamvr to prrvrnt ;tllo)inq. I n atldition, apanicular tapr can only be usrtl for a chip nt~d package Illat matcl~cs its intcrconntvl p t t cm. t l a r r b rrnrlrring TI\B an rrtrrmoly a~stomizc.(l procrss for \vhicll thr bonding crptipmrnt is rrl- atively erpensivr.

Flip-Chip Ronding I;lil>.d,iP bonrling is :I direct interconnection xppmach in wvldch the IC is mountcd upside- do%m onto a modulr. or printed circuit lmarrl. Elrctrinl mnnections are madr \ia sol- (1i.r brrn~ps (or soldrrless n~aterials such as epories or c n n d ~ ~ a i v r adl~rsi\,es) lwatrtl m r t l ~ r st~rface of the chip. Since humps mn lx located an)~\,l~ere on thc chip. flip-chip lnnd- i:y rnsurcs that the intrrconnect distance behveen the chip and package is m i n i m i ~ d . The 110 tlensity is limited only 13. the inininiunl distancr brhvmn adjacent hond pads.

l o flip-chip procrssing. chips are placed face do\m on the module substrate so that I>:lds on t l ~ e chip are aligner1 wit11 those on the substntr (Fig. 10.13). h sokler reflow

plocrss is then osed to siw~tltaneously fortn all the required connections. thrreby d m - (;, ..i I \ . . ~mpro\ing tl~mughput cnmpared \\,tl~ mire bonding. However. tbe bump fal,ric;l- tirq, procrss itself is fairly complex and capital illtmsi\'e.

~ ~ l ~ l ~ ~ l ~ ~ ~ flip-chip technolop involves stencil printing of an organic polyller onto ,:,> IC. ~ ~ : , , i ~ g t ~ ~ ~ ~W,ICI pads anmatrd. A bi~l~-conducti\ih.orgnnicpol)~ner p:-tp is then ,!i.,lcjlerl tile lmnd pads to inn11 the solderlrss bumps. \vhich are tllcn cured. The <i,,ilr o ~ a n i c pol!q,ler is stcnciled onto tlre lmnd pads of the sul)stmte. Al i~ l lm~nt is t1l-n nrLnnlplislle(~, a l n ~ tile final bond is formrd I>y appl!ing pressurr and heat to tilt. hllnl~s.

Ourrr 1ba1 lx>ml

I l'l>l,l1,l.r (:111,1

Figure 10.16 Tnpntnlomatnl lnndink'

10.3 Statistical Process Control 4 23

c l l c a t e d ulndinq tool w

- I>>,. 17, ,,,.a,*,

(4

Figurs 10.17 T,\B ppmcecltnrr.' ( a ) Leads lmvered into position ;and aligntrl ehwr lmnding pi ih Tml desmnds and pedorms hnds. (c) Tml and film ;,re nised so a 13 .:v I!;? c:m 'Jc. mow into position.

Strlnlntr

Figurn 10.18 Flip-chip hondinq.'

b 10.3 STATISTICAL PROCESS CONTROL

IC ~nanufacturing processes must IK. stable, repeatable. and ofhigl, qualiy to )qeld praf. ucts \sit11 ;lcrrptahle pcrforma~ice. This i~nplicr that all intli\iduals inWlvetl in ,nar,,,fac- tllrinf :an IC (incllldinl: opentors, engineers. and manage:elncnt) must mntinuously srck to ilnpro\,e nisnufactl~ring process otttput and rrduuc v>rriaBility. \iarial,ilit) reduainn is ;~cn~lplistlecl in large p:lrt by strict process control. TILLS seaion focltscs on sfolisriml proresy ci~ntml (Sl'C) techniques a ..n means to acltieve hi~li-qualiy prmlllas.

SPC refers to a p v e r f ~ l l collection olprd)lcm-solring tools ilsed to acllieve p m s stabiliy and reduce wiriahility. Perl~aps tlbe primary and most tecl~nically sopllistimted of t l~esc twls is t l ~ e control cllnrt. Tlie control cl~art\mv developedby Dr. \Valter S I t c \ ~ l ~ ~ r t of Brll Telcpho~~e Liboc~tories in tllc 1920s."For this reaon. control chart^ are ;dsaoftcn referrecl to as Slterchnrt corllml cl~ortr.

A control chart is an online SPC tecl~niqee that is userl to detect tllc mt t r rmce of shifts in process performance so that investigation and corrective action may 1)e under- taken to bring at1 incorrectly heliari~~g~nanuf~ctaringpr~ss hack under control. A h ~ - ical n~n t ro l cllart is sllorvn in Figurc 10.19. This chart is a g m p l ~ i d display of s quality cl~ziracteristic that l ~ a heen meacurrd from a sample \.enus the wmple number or time. T l ~ r chart consists of (a) a cenler l i ~ ~ s . \rfliicl~ represents the mean value of the characteristic correspondins to an in-control state: (11) im 1r11l)erconlr~l limit (UCLI: and (c) a / 0 1 ~ ~ # - ~ 0 ! l t / i t n i l (LCL). Tile control limits are selededsucl~ that iftlie pronss is under statistical control. nearly all the sample points w i l l plot beh\'een Illem. If the \;lriance oftlie ~lualitycharacteristic is d and the standard de\iation of tliecliaracterictic iso. t l~en tile control limits are hpically set at +30 from tlie rrnter line. Points that plot outside o F t l l ~ control limits are interpreted as e\idence that the process is out of control.

103.1 Control Charts for Atlributes

Solne quality cltancteristics cannot he ensily represented numerid!\: For erample. we ~!iay I)? conmrned with \vl~etlier or not a \\$re imnd is defective. In this case, the bond is dassified RS either defecti\.e or nondefmti\.e (or equi\:ilently, confonninc or nonwn- lom~ing). md tllere is no nunierical \alne associated\vitli tl~eqoality of the lwnd. Quality cl~ac~cteristics of this hv are referred to as nttril~trtrs.

Upper mntml limit .- - 'C I&--

109 Statinical Process Contml 239

T,,,, comtnrnonl? usnl contml cl~lrts for attribr~trs are the drfrcf cl~nri (or cdmn) till. r l 4 y - t d,n.\-it,, clinri (or t,-cl~,,n). \\lien n syw.cifintion is not sntislipd in a ~ ~ 1 .

,,ct, ,, dpl;u.t or nnn(~nfonaity nr.,? result. In sl~ch c ; s r S , it is possibtr to rlrwlop mu. tml vll;trts rort.itla,r tJw total ~ ~ ~ ~ n i l w r o f d ~ f ~ ~ t s or t l~e dried ~dlenrih Tl~rsr dlnrts xqucne tl1:,t t l l r prescn(v of rlrfects in santplcs ofconstaat size is appmprintel? modrlpd h!. the p, , ,~.~, , , r/,,rtril,t,,i~,r.'. ill \rhich tllr prnl>ability of a rlrfrct wcllrrillg is $c~\.PI~ hy

,<hrre is tile. ,,tl,n[rr of drfeuts md r is a constant grcnter tl~un zero. For the Poisson ,listriblltjor1, r is lntll tltr alean and tarinnut.. TI~~rrfore. the ccl~nrt wit11 i3o control limits i e Ejrrn hs

ucL=c+3& Centerline = c (2) L C L = C - ~ &

;~s,,mine that c is LSIO\tn. iA70t,-: if these calculations yield a negatk'e \due for the LCL, the stnnrlanl pnciicv is lo set the LCL equal to 0). I f c is not known. it I I I S I ~ be rstimated fmm an ohsend ivrraze nl~~nlwr of defects in R satnple (5.). In this c s e , the control clrart 1nwn1c-s

U C L = ? + ~ &

Center line = T; (3 ) L C L = ? - ~ , ~

EXAMPLE 1

s u w the in.qwc%on of25 rilimn traferr !ields 37 defects. Set up a c-ch.:? ior this situatil

SOLUnON \\i. ntimale c ttsin-g

This ir the enter line for the c-ehnrt. lhr upper and Icnver mntml limits ran l>r foltnrl fmm Eq. 3 L5 fi,llm\s:

~ ~ ~ = F + 3 f i = 5 . 1 3

~ ~ ~ = ~ - 3 f i = - 2 . 1 7

Sin* -2.17 < 0. \ r ~ set the LCL equal to 0 in this care. - Suppose \rr would like to set up a mntml chart for the nvmngr n ~ ~ m h e r of clefects

over a sample size of n prcilocts. I f there \\.ere c total defrcts amon? t l ~ r 11 samples. thrn tile m.efil<r n l~mlrr of (lefrcts per sample is

Tl,e plramrtrrs of a .lo dried densiv chart iu-chart) are then @en by

IKL=ii-3 - t \vllere r is ~ I I P avenge nr~nlher of defrcts owr m gmaps of sample sir*. n.

EXAMPLE 2

S u p p t an IC rn;muC&ddc(l~rcr wnls ln cstahlish a dcfcd denrih chart. Tsvnty clillrrrnt s,.,mplc3 of s i 7 ~ *I = .5\clrcm am inspec?r<l. and r total of183 defec(s rrr k,lmd. Sr i ulp ihc u<lrrrt firr thi% s i t ~ l i ~ t i ~ n .

Thir is thc entrr line for the u-clvwt. The rapper md lr~\vvr control limits a n l r fotlnd from Eq s r,,llm~5:

10.3.2 Control Cham for Variables

lu many caws. quality cl~aracteristics are expressd as specific nnlneric n~eas~trraicnts. r.~tlier tl1:111 messing the probability of presencr of defrcts. For rumple. tllr thickness of a film is an important characteristic to Be measured and mntmlled. Contml cllarts fur continuous \fariables sucl~ s this can pro~ide more infomation reg~nling rn;u~nlkrtur- ing process performance than sttri1)utr contml cllarts like tbr c- and rt-cllarts.

\\lien attempting to mntml continuous variables, it is important to mntml hot11 the mean and \~ariance of tlie oualiW cl~nracferistic. This is tnte hecarrsr shirts or drifts in , , either of tl~esr parameters can result in sipificant mirpmssing. Cantrol of the me.m is acl~iew(l using an i-chart. and vnriancv can be nlonitod using t l~e s tmd~nl clmin- tion as in an s-chart. The names of these hta charts orieaate fronl the an~npl? rrlrnn if) and .samplr vorinr~ce (s'). \\,l~icl~. respec(ivelr: are S i r r n Iry

whew x,. x:, .... x,, are obsen2tions in a sample of size 11. The square mot of tltr sarsplr vari:mce is ino\\n as the .sflrnl~/o sfn~~r!flr(/ (/c.~~iolinn (8).

Suppow na vmmles of rim 11 :rn=mllt~Ied. Iff,, f,.....?. - a r r the s:lnlple mcnns, 1 1 , ~ h.a Nomator for thv true mean (pl is thr ~ m n d n t r m C p (i ). >r,l~irlt is @vrn I,?

sinm. F rstiatates p, it is usrd KS the N.ntrr line of the?-chnrt. It can nlso b shown" th:,t if A qlldih d l a ~ ~ c i r l i r t i c is i ~ o m ~ d l ~ < h s t ~ i h o t ~ u l \\lth a hlo\vn nlenn p imcl standad ck.,i.ltiorl a. th.n F ix :3ro aonna l lyd i sMI~~~t~<l uith n~e:u~ and stnndnnl dr\iatioa on/;; Thta. thr wntpr line and mntrnl lilnits for the Echart srr

- Center line = .T (9)

Sin* a b ianlinomm. it must also he estimatnl by analyzing pmt data. Calltion must he ; ~ ~ p l i n l in doinc so s i r w s itself cannot be used directly ~s the estimate lwcause s is not an vnhiad estirnntor o f o . (The tenn tr~tbio.~rd referr to tile s ihlaf i~n in a.hich tile eqmvrd \:due of the estimator isequal to the pmtee te r Iwingestimatrd.! Insteads a&l- all\-cstitnatrr r,s. \vherr r, is a statistical paramrter that is dependent on th r a ~ n ~ p l e siw iuv T ~ h l c 10.11. For ,n s2mples ofsize 11, the avemse sample staadsr~l deviation is

It turn? out that the statistic Z l c , is. in fact. an unbiased estimator of o. In addition. the standard daiation o f r is 06. Using this information, the con.

tml Iilnitc for the s-chart can be set up as follous:

Center line = 3

L C L = ~ - ~ A G C.

\\'hen.i/c, is uwd to &mate a. the limits on the conecpondingf-chart may be defined as

33 UCL=T+- c, &

C m t ~ r line =

EXAMPLE 3

Stqqmw i- and reharts aw to hr -tahli<hd to nmhnl linm\idth for a lith-ph! pmorss. Tivent).- fnr. ~IiITcrcnt samples of size n = 5 lincviclth an mrzurcd. S l l p p thc p n d awlage for the 125 lrnn is 101 vnl. If; = 0.09 mm. what are thr mntml limits for thc r-ch:trt'

103 Statistical Proeers Comrol 4 ~1

TABLE 10.1 c, Panlnmr lor ,Char(

Sample Siw ( 1 1 1 Ct

2 0.7979 3 o'iqh?

4 0 . ~ 2 1 3 5 0.9.llX) 6 0.51515 -

0.9591 fi n.wm 9 0.%93 10 n.51i2i 11 0.9i.Q 12 0.9ii6 13 0.9794 14 O.YSIO 15 O.YLi23 16 095.3 l i 0.9'445 18 0.95.54 19 09%2 20 09569 21 0.9476 22 0.miS2 ?3 0.9USi 24 0.999? 25 0.94%

SOLUTION The salur forc, for n = 5 (found in Tahle 10.1) is 0.94. The o p p r and lmvcr control linnits fix E can be found fmm Eq. 12 ss follo~s:

31 U C L = ~ + J=4.14pr

c4 " - 35

LCL=,T--~=3.88 p n ~

ttppcr lmver mnlrol limits for s can ir found fmm Eq. I I % flolmn:

:\L- . CL=.?+3- I c: =019vm C.

c 10.4 STATISTICAL EXPERIMENTAL DESIGN ~,~,,,,,,, , , .~~t~ ;dPnr. it~\rstic;ttr,rs to determine the ~ f l j c t s of srvrr.~l \rrinblcs on a pivrn I,n%'.,, ,,, pmluct. .i rlr~i<nc,l c..ty.",rrvtI is a lest o r series Of trSts t11;lt involve p,,r. P M . ~ I ~ I L . l , , , ~ ) ~ ~ . ~ 10 tl~est. \.~Tii!l~l~~s in cbnlrr to obsrn-r tllr rNwt of the c l~;m~t%s os t ~ , ~ ~ I,nKv.,s ,,' ,,m,,lt,rt. Smti,vrir.nlt~.~~n'nu.riloIrl~.~i~t~ is an ~ f i c i e n t a ~ p n l l c h for qf elg;ll. ,,i,llr t ~ , ~ ~ , . ~ ~ ~ t n ~ l l ; ~ l ~ l ~ pnxx.s \i~rii~l>lrs and i~ l t i~n;~tc lyc lc~tt~r~t~inin~ thc.ir ilnpnrt ,,,, pnx,.,x ,,r pnxluat qu:dit!: or Iw,th. This :ipprn:~rl~ is 1 a c 4 t I fur r o m p a r i z ~ ~ mrtllwls, ,bvl l r r in~ ~ l r F ~ r l r n r i r ~ . ;tud crratiltg in$xlrls to pndir t rfliu.1~.

st.,ti,+ictl pnxr<s wntn,l ;aal crlurinlrntal dc,sip~ an, closely intrrrrlatnl. Rot11 trrll. ctll I*. l~s l r l to rcdttrr, \nri:rh~lih. Ilo\r.rvrr. S I T is I p:\ssiw approach in tvllicl,

pnxy.cs k n~onitonrl ; u ~ l m,ILrtrul. \vl~rn.irr e.xprrin~~t~lnl clesip w q t ~ i n ~ s active intrr. ,r,tt~on in pedonnino, tvrts on tla. pRKVS 11ndt.r rliEcsn~nt condition. Exprinlrnld desim ';ul ;also hr 1r.ncliri.d in i ~ ~ ~ p l r z ~ ~ r ~ ~ t i ~ ~ q S I T . since dc~sipa.d exprimmts nlnyl~elp to ill&,. tiiv 1 1 , ~ tnwt infltwntid p m s ntriahlrs. is arll ;a their optilnam settings.

(h.<.mIl. cqwrirn<.ntal rlrsiw is a pnrrriul er~gin<willf tool fnr inlpnairg a man,,. I.tct8mnq prrx~.qs. Applicittioa of ?.qwrilllelltal dc-sip1 trchlliqnes can ie:lrl to impmpd \it.Ll. r<~lr ,<rd vwi:thility n.d~mri ~ P Y P ~ I ~ I I I F I I ~ ti~ne. and r r ( l ~ ~ r v d cost. Ultimatclv, thp n w l t is rr~h.tn<x~l t t ~ ; ~ r ~ ~ ~ f a r t ~ ~ n h i l i h perlbnn:mw. and p n x l t ~ d rrli:lhilih The folio,,.. in^ wt ions illmrtnte tltv use n l ~ ~ x ~ r i n ~ e r ~ t ; ~ l d e s i p ~ i net hods in IC fabrication.

10.4.1 Comparing Distributions

Cnnrid~r tla\ield data in T h l e 10.?obtaind fmnl an IC man~i la r tu r ingpnwr~ in t\.l~ich hm lr;itr.ltc*s of 10 \r:d<.rs were Grbrirat~l llsingnstandnrd methml (.\lrtltod A) and a nld . i f i d mrthnl ( \ l e t l ~ n l RI. Ill? qa?stion to he anmvrred f m ~ n the e q ~ ~ i ~ n ~ r n t is\~Ilat eti. d r a w cii any\ dnrs t l ~ r d;~t;i cvllecird prn\idr tllat hlell~wl B is rcali? Iwtter than >lt.thnl :\'?

To mnwr thk qlrestion. \ve examine the avenge yields for rach p n ~ w s . The mod. ifinl tnctllocl !\lrtllml R) save an nvenge !irld th;tt \vas 1.30% hither than the standard n~etlml. Hn\vr.nrr, tn thr considen~hlp \ariabilihin tllr indi\idu:d t-t reslllts, it might not he comyt to imn~nl int~ly mnclude that %lethod B is snperior to Xletlwxl A. In r~a.

TA8LE 102 Yield Data Imm a Hypothetical IC Manufacturing P r o e m

\\:tit., \t,.thnl A SI~ thn l B Ylvlcl ('TI Yirlrl l%l

it is mntriv:~lrlr t l s t t l ~ r rliNc~rc~~rr obsewcd w l ~ l d IK* d11e to ~ w r i r n ( l ~ ~ t ~ l emor. ator errnr. o r r\.?!l nuna chancr.

~ ~

Thr proper ;lpprn;~ch to d r t eminr \vhethrr tlbr rlifirrrnn lwhvwn tlte nvo mancg. f i~c t~ i r i t~s procrssc-s is simifi<xnt is 7, /~y j~n t l~vs i~ I(,.Y/. A statistic~il l ~ ~ ~ ~ t l t ~ s i ~ is ;a stat?. mrnt i~lmt~t t11c \.id~res nit11c piknm~ter\ nf ;) l>rol>ahility rlistril>tttioe. A IqFtllr5is trrt is ntl c\nltn:~tion of tile \xlidityof the l~!vtl~esis ttcmnllrtg t,, some criterion. I i!ythwr arc rrpr~.ssr(l in the Fn lh~ ing Inannrr:

11": p = p,, 11,:p*p<, (I:,,

\vl~ere the statentcmt !I,,: p = pm is c~ l l cd thr ttsll hypofli~.vi~. and 11,: p +&, is cnlled t l~e okcn~n/it:r I~!ll~o/hmir. Tn i r r funn ;I l ~ y p t l ~ r s i s test. wv wlrct a random xtn,plr from a populalio~~. co~npule an appropriatr test slatistic. ;and l l ~ r n ~ i t h r r a m p 1 or rejrct tlnr. nldl I~!potllrsis. For thr )ield c.xpvriment, h ~ r I~!pothrsis tmt GIII lw rrprrsentc<l :u

H,,: M, = P, I ~ , : P , * P S (14)

\\,here p, and M,, reprrsent t l ~ r mean yields for thr. hrv rncthmk. To evaltlntc this 11)'pt~lrsis. a IY(./ .stflli.~lic is reqlliwd. q l r nppropriate test slatis

in this caw is"

where c., and y, are the sample means of the ) i e lk for each method, n, and ?I,, are the nllmlx.r of trials in e;sh satnple (LO each in this caw), and

\vltich is rerered to is the /IOO/IV/ ~.~tirn(t/~. O / I ~ I C C O ~ ~ P ~ O U wriot tc~ of the t1t.o procesws. The drmoninntor of Eq. 16 is calletl th(. number oirlrgrrrr offwr(Ion1 for the h!pnth- esis test. The \.alnes of the sample variances are calcalatt'il using Eq. 7: r, = 2.90 :in11 s,, = 3.65. Using Eqs. 16 and 15 then giws \~d.llncs o f s = 3.30 m d I.. = 0 . S . resvctiwl!:

\\i, uun use i\ppr~xbx I; to detenninr the prnl>a&litY of colnpntting a piws statistic vi lh a wrixin nrrrnlrr of degrers or frc.rclo~~l. Thi$ prob:bbilih ir rrpresrntd hy the s l~adrd region in the l i p r e in tllv : l p ~ n d i s . Int~qwlatinp front Appm~lis R.\w find tl~at thr likelilrwd of mlnputing a I statistic \\it11 91, + PI,, - ? = 1 s d q r r r s of frrnlom rq11al to 0.84 is 0.195. The v:d~le 0.195 is t l ~ e . s l o l i . ~ / i r n l s i ~ ~ ~ i f i ~ ~ ~ ~ ~ ~ of t l r I l ! ' p ~ b ~ l i ~ trst. This me:llls tllat there is only n 19.J"c chnnrr Illat the o h s m l ~ d c l i f l r r r n ~ ~ I)rt\\,ren the Inran )irlds is due to pure c l ~ m ~ c r . in ot l~cr aanls. tvr can Iw 30.56 a>nfidrot t h ~ t !drtl~ml R is renlIys~~~(.rior to Mrthod A.

10.4.2 Analysis of Variance

The previous e ~ ~ n l p l c sho\vs IIO\V we migl~t uw h~'pthesis trstitlg to m m p n . hro (lis- tril>utions. Ilmvcver, it is aften importlnt in IC nlanufi~ct~~ring i~pplic:+tio~~s to hr ahlr to mlnparr w,.ml distribl,tions. hlorm\rr. NV might illso IF intercsta~d in ~ l ~ t r n n i n i ~ ~ ~ a . l ~ i d l pmcrss con&tilms in pnrtical;lr haw a siplilicsnt impact on pmct.ss qaalih A!~ol!~vi.\ 11f unm,lw (AX()\;\) is :I,I pscrllent teclmi~lt~r lor:tcmmplishing t l ~ e s ~ oh~rdi\.es. ;iSO\':\

10.4 Statistical Experimental Dasign 4 215

. .. ~ , m,,s,,l,.r i,, T . , I ,~~ 1 0 . ~ . , ~ l , i ~ l , n~pn~st~ntsl~~lntl~rti~xl drfect dpnsitirs n ~ e x % u ~ ~ ( i ,," ,v.,j,.n f;,l,,.ic+tcyl tlrillS firer clinisnvlt sets of pnr rss n - r ips (I:IIVIP~ 1 t l l r n l ~ ~ l ~ .I), n,m,,cl, tltc ,L<cs ,,(.&NoV;\. \\ill ,l<*tt,nninr ~ v l ~ ~ ~ t l o r r t l ~ r &scw[~~#~cies / m ' t r ~ ~ v n twips ,.?, tn..,tlllrl,tr) is trill? , p a t r r tllu!~ thr \-.triation nf tltr \ia rliat~~rtcrr a!i/hi~i t l ~ r in&.

,jd,,:,l Cn,ul,s of\i;ts pramwrl uitlt tlrr s?111(' liPri[w. b.1 k Ir tllP n s ~ n l h r of tw;ttnlrnts ( k = 4 i n this case). Note that the srunplc sin! (,I)

forrrlt tmatrl)rnt \>lric.s (tr, = J. rt2 = n , = 6. i ~ z d ,I, = 8). T11r treatinPnt I ~ P O I I S (in m1-2) .w ;rc fr,llmn,~: 5, = 61. ij, = I%. q, = 6.5. and ij, - = 61. The total I I I I ~ I ~ W ~ nf san~ples (s) is 2-1. and t l lp m .u~l nwr.yr <of itll 24 s;~nrplrs is = f4 em-'.

Sums of Squarer T,, Ixfiom .\SO\:4. sr\rr;tl kry plr.enrtm must in' mmplltrd. n l r s? panm?tm. cnlld arnrv ,,f rr7rmn~.s. sm.1- to quitntify clr\i;tti<)ns \\%tliin and hehvrell diffilrc~~t treatme~lts. I r t y,, wpnrmt the lth obs~rnttion for the lth twatlnent. Thr sum of squiues~~%thin tllr ttll tn.;rlnlrnnt is ,*vtv~ h\

r ~ ~ w n, is the ~ r n p l e size for the trrat!nent in question and IJ, is the treatment mean. The ~t~ithin-rm/,,te~~zt atr11 of sqrmres for all trentalents is

To qtlmtic the deviations of t l ~ e treatment averages from the p a n d 3vemqc. \vc use the I ~ t n z ~ e - / r ~ n t m w / nrta o/.~qrorps. wldoh is given hy

Finally the total sum of squares for all the data alnut the p n d sv,-mxr is

TABLE 10.3 Hypothetical Dded Densities [in em-'I lor Four Different Process Recines

Each slim ofsqblores l~ns an mnci:~trtl nnm1n.r of d r m c ~ % ~ of frwdoln n~rl,lirrcl for its co~np~ttatioe. Thr <lrlprres of frcrdon~ fnr 1 1 1 ~ ~\itl~i~t-tr~atm(.nt. I ~ ~ . t ~ v v c ~ ~ . t n ~ a t ~ ~ ~ r n t . nnd tot:tl stlnlr of sqllnr~~s. n~s~c t iv r ly . an,

v, = N - l ;

v , = k - I (21) v,, = A' - l

Rnal quantity needed to cany out anal!sis of tarinn(* is thc pmlrvl rstim:ttc of the varinncc quantified bycacl~ s u ~ n of vl~lares. Thir quantity. hm\n :IS tltr m,-o,t .iq,tnrr.

is the ratio of the sum ofsqualrs to its iusociatc~l nulnlrr ~ ) f d ~ q r e e r of irccdnm. n~r uithin-trmtmcnt. tvhs,ren-trrato~unt. and topal nlrnn squnrrs arc tb~rrforr

ANOVA Tahle Oow thr panmeterr just d rsc r ik l havr heen computed, it is c s s t o m a ~ to arrange them in a tal,nlar format mllrllrcl an AA'Ol'A toblr. Thr g e n r l fonn of the ANO\':\ tahllr is rlrpictnl in T n h l ~ 10.4. Thr ANO\',\ tahlr that cvrrrspontls to the defrct densit\. d;tt,~ in Talrle 10.3 is sho\\n in T:ihle 10.5. Note that in lntll the Sum of Squaws and llryx-rs of Frrrdonl colnmns, tile values for iwhverll and \b%lliin treatnrents add up to give tllp cor- n.sl'onding total d u e . This ad&ti\.e pmpr ty of tllr sutn ofsquarrs nrisrs frunl tllr ake- hn ic identity

L " ii~.-~' = ~ n , ( y , - ~ ) ' + ~ ~ ( y . , - ~ , ~ ,., 8 I , I . , , . I

or rqtthslently.

S,, = S , + S,

Tllc mnlpletr ANO\',\ tahlr pmvidrs a medinnim~ for testins thr h!-ptla~sis that all of thv trrptniont rne;lns ;,re erlsal. Thr JIIIII l ? \~n th~s i s ill illis GLW iS tllll~

TABLE10.1 General Fornutof lhe ANOVA hbls

s,,,,, nf Drmrrr of \lwn Squaw

10.4 Stalinical Experimental Oesipn 4 147

nuu 18s AIMVI Tabla tor Via Diemeter Dam (illlll ~~1 I),.FY.- of \Iran sqtn.~n~ F Ilrti,,

. ~ ~ , n r of V m ~ t i u s &IU.Q"'Y Fn.adors - *mw,, tre.,l,3><'!lt> s, . ?2* ,,, = 3 s; - ifi.0 $4 = 13.6 \ \: ,h,c, lrr.*t,~~l,t. 5,- 111 ,; . 20 9; = 5.fi

%>,.,I s,, . $10 I,,, = z3 s;,. 1.1.8

nllll b,F>lhesis \vt*re tnle. the ntin .r+; uwuld follmv t l ~ r F distribution \citl, ", ,.e <lW& of f m l ~ ~ t ~ . Int~qwI:$ting fn~rn App?n(~s L. 111e .siz!~$rfl~~c~ Imt-I (LC,,,

,I,,. f in r s,,t,scnpt of the F \idt~t-s in thv 1:1blrs) for 1 1 1 ~ 011scn.ed F ratio of 13.6 tvitl, 3 :UI dpSnys ,,irrn~lo!t~ is O.NWMl(i. This nirans tllat there is eel!. it O.(KU(i% c 1 1 ~ ~ ~ ~

tll.tt tllc ntr.ms :ur in f.r< N~II:L!. iutd IIir n111l I ~ > ~ ~ ) t l ~ e s i s is discwlited. 111 other aa&, ,,.,.r.l, k 9 9 . ~ 3 ~ sure that real ilini.mcrs exist aolonp t l ~ e rot~r different processa in our ewmplr.

10.49 Factorial Designs

EFrimentd clesim is an n ~ i i m l r n r t l d ofcnnductingeywrimenh to extract the m . s -

imtlm mount oiinforn~;ttion irnm a l i rni t~l n~~mhrofe .qxr iments . E x ~ r i n i ~ n f a l d e s tecllniqrnrs ;*re ?mplo!rcl in mmufac<uring lo s)strnlatically and efficirntl!. e.xplore rlf<es afa srr ofinput \ari;~hles, orjndnn (such as pmcessioS tempen~tore). on respon (njc l~ ;w !iekl). Tltr unif!inq feature in statistimlly desipetl e.ywrinirnts is that all I ton a v \~r imI sintt~ltmmus!\: a opposed to the more tratlitiond "one-\:~risl>Ir-at-a-tin trcllnique. A pmprly d r s i q ~ l e x ~ r i m e n t mn minimize the n u ~ n l x r of experimer runs tlast \auld otl~rntkw l r required if this approncl~ o r m d o m s m ~ p l i n s u r r e usc

F:eorial r ~ r i m r n t a l dpsips ;ire of great p m c t i d impoltnncr for IC irLm~~factnr applic~tions. To p r f o r n ~ a factorial e.yrilnent. an investisator selects a Inred numl of l<r.cIr for each of numher of \nriahles (facton) and nrns e q x r i n ~ c l ~ c i all possi: rnmhinationr of l l r iewls. Tuv of tlw most iniportant issues in factorid rxpprime~l ~lrsi.m< are cllomine the set of facton lo he trricd in 1l1e exyriment an11 cpecifvirlg t l ~ e n n w s o\vr a.l~irlt \:%riation \rill take placp. TIP choicv of t11r n~lrnlxr of fiavton directly ;~ffccts the nomhrr of erperin~ental nlns (an0 tl~erefore the mst of the esperinleot).

ac- ne" llal !(I. ing wr hlc llal

Two-Lmel Factorials TIP mges of tllr pm variables invcrti,ptnl in kctorial experiments c m he discreti7~d into minimum. nl;r-6mum. and "c~nter" ievels. In a frrn-/m/ fndorinl (lc.vlgfl, llle minimum snd n~aumom l r r rk ofrach hctor (nonnalizrd to take on \nlocs -I ;tnd +I. respec- tivrly) are ustvl tosrthrr in clry possihlr mmhination. Tl~us, a full hvo-le\.rl factorial e p e r i l m s t with 11 Lwtorr requires 2" rxprrimentnl nzns. The \mioes factor level mm- binatinns of ;I tl~rre-factor eqxrinient c ln be represented pictorially a5 the vertices of a c u l r , is shorn in F i p r r 10.20.

Tirhlr 10.6 s h a ~ r a 2' fia?nrial eqxrilnent for a CVD p r m s s . The three facton arr tpmprellorr (TI. prfAssllrr (Pi. and ~a flow n t r ( F ) . The response k i n g mras~tred is t l~e drpositinn rate iD) in snestroms per minute. Tlie l ~ i ~ l i r s t and loucst lrvrls of r a c l ~ lactor :In. rrprrwnted b!- f l ~ r + and - siyms. rrsprc+i\.t.ly T11r 11ispl;y of lewls c l r p i c t ~ l in 1I1ca fin1 t l ~ r e r cn l t~n~ns of this tahle is mllml :i,/c.$ip~ ~nof"~.

TABLE 10.6 Two-Lavel Factorial Exnarimam

\\%at can we detennine fmm this factorial desip? Furtl~ermore. a,l~at rloes llle data mllrcted tell us ahout thc effect of pressure on deposition ratr?The e h t of an) single mriahlc: on the response is called s lnoin #~d. The m c t h d used to m r n p ~ ~ t e such a main effrct is to find tllr difference behveen ilrr averase deposition rate \,,hen the pressllre is Iligll (i.e.. nrns 2. 4, 6. 8) and the awrage dcposilios n ~ t c w l ~ m thr prrssrlre is IOW (ntas 1.3.5. ;ind i). hIatl~eniatieall!: this is rx-ressed

p = dn, - d,- = ~ w [ ( d , + d, + d, + rl,) - (d, + d., + (1, + 101 = 40.S6 (24'

,\.llere p is tile main evrct for pressure. (1,. is the a\rrage deposition rntewhpn the pres- sl,m is lligll, md d i.; ,Ile ;,wvape deposition mle \ ~ - I ~ P I I tlie presum is lour. \\'e inter- pret tllis rrslllt s sLo;\ins that the werage evert of incrr:nins pressup frnm its lo3wst to its lligllest leWI is lo increil(e tile drpositio~i mte by40.56 Jbnlin. Tllrotller eflPds for tclllperalure nllcl flo,,. ~ ~ t e are m m p t ~ t n l in a siniilar nlsnner. In grnerd. 111aill

for cacll variable i n htv.lm.el Ls to r i~~ l eqxr immt is 111~ dirfermee kh\ . f fn the

145 01.g~ 10 IC ManufacNnnQ

\\; .,Isn iltt,~n-st~%l i n qnt;tntiT\i~r$ Ilmv htn or nlore facton inlrmcl. For cmm.

,,!'., tl,.,t rl,.. pn.ss12rt, , . k t is tnocl~ p a l e r i?t iligll 1~111pr.lllln~s than it is a t : ,% ~, . , , , lx .~ , t~~m.~ . :I ~tat..Lstln, of this int~rilclio~i is p m \ ~ l c ~ l I,? 11s. clilli.renrn iwh,%-rn I I ~ , . .n,.r.,cv lpns~,,n. rltlrt \,itl, tc.rnpmit~~n. l~igll and tllr il\r.ragc prc'ssllre clli.ct wjtl, I , . , , , ~ ~ ! , , v Ihne 1 % ~ rnnv~~ntion. I ~ ~ ~ ~ o l ' t l ~ i r rliffen.ncr is ~ d k l t ~ t e ~ ~ n ? - ~ ~ n ~ - h ~ ~ f ~ r ~ ~ x ~ r n t , , ~ ,,,!..,,,~~r.7r~, tlr mrtholir.dl\: tllr P x T intrrilution. This intmrtion niny ailm Iw tlronsllt

.<< oi,,..l~;klitllr c~&.lrn& in tlnr avrrilge t~~~nlx~ntt t t re cfli~cls ;It lllc h!Tl levels of pk.s. WR. \l,~tl~~~tr~:ctic:dl~~. thi< is

p x T = 1 , - d m = / d + + d + d - d d + 1 + 1 = 6.89 (26)

n,? P ~ ; ~ , d TxFintpfi~~tions are ohtined in a sin~ilw f.asl~ion. Find?: \%%- nright a h o h il,trw*ttd it) lire inrer.ntiot8 o f d tllm. hcton. ~Ienotrd is t ~ l e ~ ~ n : c ~ l t r - b ~ - f - f t ? l : l ~ ~ ~ r n l t ~ ~ ~ ~ p,*l- d,. or II,.-P X T X F i,,trmciion. nlk intcndion defines tl~ea\vr.l~~differrnrc hrh,.een .ul\. hrx,.(,le(or in led ion :it lltr l t i~h and imv Imrb of tlie tl~inl Lactor. It is @cn

PxTxF=(ImF, - d m = S . B S (27)

It is in~porktnt to note 111;tt tlre !nail1 effect ofany kctor can be individudly interpreted onlv if t1,t.w is no mi<lencv tlnt t l ~ k t o r inCr.\cts \\itb other facton.

'Ihc i'ptes Algorithm It c:u~ lr- trcli<nur to calculate the e&ts and interactions for h\~-level factorial eqxri. ments usin: tltr methixi just described. particularly if tlrere are more than tllree 1x1 ia\nh.rrl. Fortun;ttrh: tlw Ynfc.q nlgnritha~ prndllrs n quicker m r t l i ~ l ofm~npr~tat io~l t h ; d o wl;iti\ply c-:~<ily pmfr..unn~e<l sia mnlputer Tn implement this algoritl~n~. the e q inin~td ilcsign rnatm k tint arran~ed in !vll;rt is c a ~ ~ ~ ~ r f f l r l d n r d o r r :\ 2* fitctorid drs is in sran~L,rd onlrr ahen the first column of the drsign mntrix consists of alternnt minnrc 2nd plus siyms. thr srmntl mlrlfnn mnsists of st~cwrsive pain ofrninus and r sicns. the tl~inl mlumn consists of four minus sims follotrd h\. follr phis sims. and

'on hat r r - i- "a,

ing lltls l so

~ . mnt;<ns thc deposition rates for ratcl~ nrn. These are c o n s i d e d in s ~ ~ n e s - i w pain, Tlte lint f o ~ ~ r cntrirs in column (1) are obtained h\.addinc tlrr pain tocetl~er. anrl tlie ned t'ottr .trr al,t.~inrrl 13 -t~l,rr.,ciitte tlw top n t~~nlwr from t l ~ o lxlrtnnt nulnhcr of t.:,ch p (:ol!~nin Z l 8s <,l,t;unnl from wlttrnn 11 in tlir <anIe W.IV. and col~nnv> !31 ns ol~ta~r -

fmm rnlumn (21 To ohla~n the eyxrimrntd effrcts. one need on], ~ I I \ T I ~ P tlie mlu

air. lrd mn

TABLE 10.7 Illustration of ma Valet Alaorithm ~ ~~ - ~~

P T F y ( I t 121 (31 Di\isor Eflwt ID

- - - 91'1 20i.X 675.i0 1543.0 H 192.97 A w

10.4 Statinical Experimental Design 4 2.49

(3) rntrics hy tllr Divisor rnl~s~nn rntrirs. IT, ~enr.raI, tllr f is t di,hor ,,ill lr T, and wm:tilliog~li\iron \\ill he 2'~'. The first rlr,mvnrt in tlir ldmtific:t;ion ( ID) coll,,rln i5 ,llc grand nvvmgc ofall of t l ~ ~ al~sm.ati~tns. ;md tlrh n,~nainintg irlcntificntion\ ;Ire dC.rivc<l hy InL';llillg Ill? pills s i p s in tla* d?sifl.n inntrix.

hl l l~o~~elz tl~r i:~tes algorill~~n pro\idt.s at rrlati\r.ly atrni~lltfon\~anl mr~tl~wlolow for m m p ~ l t i n ~ i.sp~rimrntal cffects. it sl~ol~ld I,? pointrd out tltat modrm and!sis of statis. tical rxprin~vtlts is ;~cco~nplisl~rtl :dmnrt urrln1si\.,4y hy mtnsterci;llly a\aild,lr s~tisti . cal soft\v:~re p;skagcs. A k.\v of hir morv conllrrorl packacc,s incllr<lc RSII. SAS. ;,"d \linitid>. T i les psckages mlnp!rtely ;lllrrist? the ntwssity ofprrfonning my terliona band c;llc~d:~tions.

Fractional Factoriat Desigms A disarlvantagr of tlrr two-lr\.el factorisl desipi is that tla~. number of erpcrirnrntnl runs incrrmm eqmncntiallly wit11 t l ~ e number of fitcton. To alleviate thi5 mnwrn,jro~ionnl Jnrforiol designs are mnstn~cted I)? systrrnatirnlly eliminating sorne oi the NIBS i s n hill fistorinl drsipl. For exa~nple. ;i 11:Jf frnction;tl design n<tlt r , fndolr requires only 2.-' ntlis. Full or fractional hr,o-level f:~;ldori;d designscan be used to rstitnate thr main ellrrts nfintli\illlial facton a5 \%'ell ns tllr interaction ?ff&s iwh~w?n factors. Hmvever. t h q cannot Iw used tomtiniatr quadratic or l~igliernnler rffms. Tlris is not aserior~r shortmming. since l~iglier-order effects and interactions tend to lr smaller d ~ a n lo\vnr~ler cffrcts (ie.. nlain efiects tend to he larger tl~an hro-factor interactions. alridi tend to he laxer tlzan three-factor inteiactions, etc.). Ignoring Iriki-onlrr rffccts is mnceptudly similar to ignoring l~igl~er-onler tcrms in ;I Taylor series expansion.

To illnstiate the nse of fractionnl factorial desi,gns, let n = 5 and considpr a 2' factorial desip. n i e ftd1 fadorid iimplcmentation of this <I?sip \vo~~I<l require 32 eqxrimental rims. Horve\.er. a zi' fractional C?clorial design only requips 16 runs. This 2" d r s i p is gmeclted h!.first \witingtllr design nlatrix for ;I 2' roll factorial design in stantlad order. Tlwn pltts and ininus s i p s in t l ~ r four columns of the 0' desitp matrix are racli "multi- ,'\ied" together to fom) a fifth mluinn.

For esa~nplr. let? take ;ulotlrer look at our CVD erpcrimcnt. Suppose ur only hare tlic time or resottrces .a\.:"lablr to perfomi four deposition eqxrin~ents. rather t11.m the eiql1t required for a 2' htll fiictorial d r s i p . This cnlls for a I*' fractional factorial alter- n;rtive. This new design could be genentedby\\nting the 11111 2'desiq lor tlrr pressure

t c r ~ ~ p r n t u w variables, and thrn moltipl!ing those mlumns to obtain a tl~inl mlu~nn for flout rate. Tllis is illestrated in T a l h 10.8. The only dr.l%vl>ack in 11SinS tllis I,mclure is tllat s i l l c e , ~ bnve r~sed the FT relation to rlefine m l ~ ~ n l n F. \tr: om no lonscr r ~ ~ s t i , l ~ l i s ~ l h ~ h $ . ~ ~ ~ ~ tile effpets ofthc P X T interactiot~ ;ind t l ~ r F inain rffmt. \\l~ell tlbis ,murs. tile two effects are s:iirl to be conJo1~11~11~11.

TABLE 10.0 Illustration of ??' Fractional Factorial Dssian for CVO Example

2.w . chip, 10. IC Manufacturing

F 10.5 YIELD ,.,,n,,l,,lih- in IC t,lnlltf;lr(uring proccssrs can irad to de~fonllntiolls or llonn)nfnrnlities

fi,,l.i!,,.d pnx~,,r(s. sllrh p m s (listerhancrr ofim rr~l l l t i l ~ f n l ~ ~ l s ~ o r uninrmtional c, ,l,,zc.rl ll,p IX.rfOrnlill~~~rmelunsmrr o f r l ~ l m n i c p d u c t s . T111' pwsenrc ~ f ~ , , ~ ~ ,.,,,ll, q,,.antif;Nl I,! tllr tn.u~t~r:tc(uri~~<!i~.I~L 1'icl(l is cldfifilml ;a t l ~ r prmntngr of~~r,,im or r,rnlils tl,;,t ,,,-,t nominal p r i u r ~ n l l l w sprcifi~ltioll.

yipl~l r.,n 1". c$,tqc,li.,~l iu ~ ~ i ~ l ~ r r j r r ~ c f i o r ~ ~ t l orj,flmrra.lrir. F~~nctinnnl yield is deter. I,,. tllr pmpoltlou oilidly litt~ctior~al (lmlucts. Oitrrl rcf<.rrrd to:^ 11;1nl !ielrl. tllp

f,,,,lt,o,,~ ,ield "i ICZ is usually cl~:~r.~rtrrirrd In. opct~ c i r r~~ i t s o r short circuits nued h\. pl,pica clt.&.& rci p:~rticles). I n sotlle cxws. ho\te\rr. 1 ft1Ily ftllldional prwl. ,,A srill E,ik to 1nn.t pdorn~:utrr slx~ilications fur onror mow paranlrtcn (sucl~ noiqr. lrtP1, pmwr mnsttmptio~~l. Tla.s~, situations cbscrihed I)!. p:munetric !irlel tor soit !irldl.

10.E.1 Functional Yield

ncdnrlnpmmt ofn~mlels toestimate the hmction:ll!ield of ICs is h~ndamrntal to mm. Itf,,dunne. :\ nlcvlel ~II;II pm\irlcs atctzcite estimates orm:u~r~C~cturing >ield n n lirlp ere. did p ~ l t j r ( m t . cl~lrnl~inroptimnnl cquipmellt l~ti~w!tioli. or he used a ;I nlehicaping ,vl,iclt actad memtlrllrtrl m:+~~ufis t t~l isg>ir l~k can IF? e \nl~~ated. Yield rnc~lc~ls are also c,jt. i d to s l lppr t d ~ c i ~ i o i ~ 1 inwl\ing sew trclinolo$es and tlie idrntificittion ofpmbl ;,tic p d t t c l s or pm-sses.

:\s prr\iously mrntioned. functional yield is sipificnntly aWected by the prese o f d c f ~ ? s . Defrcts n n wsult f m n ~ many random sourws. including mnt:rmination f quipmrnt. p m s s r s or l~andling. Inark imperfrctionc, and airlmrnc particlrs. Pl~!sicatl~ tllcx. drf&s inrlrtde shorts, opens. misalipn~ent. pl~oloresist splatters and flakes, pill. holrs. seratcber. and c~?stnllo,ppl~ic fla\\s. This is illustrated h!. F i w r e 10.21.

l'icld mnrlrls are t ~ s ~ ~ a l l y presented as a hlnction of t l ~ e avrragc. n u r n l ~ r of defects p r unit arm ID,,) and ~ I I P rrilirfll orrn (Ac) of thr electmnic q s t r ~ n . 111 o t l~e r words,

em.

'rice

rom

mnk

Kpvn 102l \:brious In which dust partirlr~ can interfere with intcrmnnce mxsk pane

wherc 1' is tllr fillrc1ion;~l !irhl. critical arm is tllr aria in a dcfrn mc,,rring )I%% a high pmlclhilily of nrultinl: in ;r klrtlt. For cx:tn~plu. ifpartielr 3 ill Figllrr 10.21 is large rnaug11 and conrlnctiv~!. it llns fallrn inlo an area in wlticb it catlsrs a sltort Ileh\.ccn 1 1 1 ~ hvo nlrtnl lines it l~ridgcs. The rrlationsltip bchwcn tllr. virld. rlrfol.t dpn.i;h. .,,.I

, . ~ ~ . . ~ ~ critical anra is mmplrx. I t ilrpencls on lhr circuit gromrt~?;. 111~. <lcr,silv of photoli~llo. ~ m p l ~ i c patterns. I I I ? number of pbotolitl~oprapl~y stppr usrd in tlle tnm~tl:actt~rin~ pro. cess. ;nn<l otllcr f;~cton. A ic*rraf t l ~ c rnow crmrnos n~wlrlr that ;tttcmpt to qa;mtifv tlti5

r<~lationsl~ip are dcscrihcd next.

Poisson Model Tllr Poisson )irld m d c l a5sumes tliat defects arc uniformly distribatrd acmT a snlwtnlc. and tliat ear11 defect results in a fzult. P inda de Cywz pm~i<lrs an emllcnt drniation of this model.' Let C he the numlwr of circuits on a snhstratr (i.e.. tlrr nt8mlx.r o l ICr). and let .\I be the n~rmher oflmssihlc drlrct ilprs. Untlrr tllrse wnditions. tllerc arc C" n n i q ~ ~ e \cryr in \vl,icl~ the XI drfrcts can he dist~ibt~tecl on the C circuits. Far r.umplr, if tllcre ;trr three circuits (Cl. C2. . u~d C3) and time dcfwt bps (such a5 511 = mrtal opm. b12 = metal sl~ott. ant1 h13 = ~rletal I to 111?tal2 short, forenmplcl. tlitw Illerr arr

C" = 3' = 2: (29)

possible wa!s in \vl~icl~ tllese t l~ree defects can he distrihnterl o\.rr tllrre chips. nlpsp conrbinations are illtatrated in Table 10.9.

I fone circuit is removed (i.e.. is round to contain no defeffs!. the nun~lxr ofn<ijs to distribute the M defects among the remaining circuits is

Tlius. the prohahilit). that a circuit will contain zero defects of an? tp

TABLE 10.9 TMh Table for Unique raulr orn no ma ti om

Coml,inibtion C l ce C? Combination CL C? C3

%5? Chwer 10 IC Manufacturing

Slllmttttinr! Jf = C:\,D,.. tl~c !irkl is the nanllwr of circllits \titll 7rm clef<~ts, or

F,,~ J' rirclli~s a) ltarr i r rn defects, tl~is lwmnles

y= e.v(-A,Da,)' = e.qd-A7ArD,,) (3'3)

ne poi.wn ,n~odxlcl S simple iutd relatiwly e;rry to derive. It pmbides a re;rronahly of!ield \r,)~pn tlw critiod awn is srn;ill. Ifo\vrver. if I], , is callcalated b;Swl

~ ~ ~ x l l . ~ r r ; t rircrrits. ~rnins tllr mmr D,, fnr l a r g e - a n !ielll computations res~~l t s in a ,irbl e5tifnate tl~at is overly 1x-ssin~istic mmpnrrcl \\it11 a c t ~ ~ n l ineirr~~red data.

~urphy's Neld Integral R . r \f,,rpllY lint pmlmscd t h ~ t the \n l l~ r of thc defect densih ( D ) should not be mn. stmt.' ~nstr:ad. Ilr re:sanrd that D ,nust Lr s ~ t m n ~ e d over dl circuits and substmtes using a n o r n ~ d i ~ r l prnl~xhilih dcnsih h~~~ct ion. j?D). TIke !iel~l ciln then be calc~tlatrcl using

the in tcyd - Y = Je-""f(D)dD (34)

0

Various forms of/iDl lorm the basis for the dilferencrs behveen snarly analytic4 )if malels. TI,? Poisson modd ;asumes that/iD) is a deltn fu~lction, that is.

\I+IPTP D,$ is the a\vmge defect density a7 before (see Fig. 10.22). Using this density rune. tion. the !ieLl is drtrnnined f m n ~ Eq. 34 to Lr

(c) (d)

Awn 1 0 Z Pn,habilihdrnsih functions for lo) the Poisson rnnlel. (1,) the uniform hluvhy nlsxlel. ir .1 thr t r i an~ la r hfwph? model. 2nd (dl the crponentid Srdv modrl.'

h l ~ ~ r p l ~ y initiall!.invvstigabd n usilorn, drnsity function, z sl~mvn in Fipnrr 10.W lltr rval~~stion of t l ~ c )iclrl intcgrnl for tl~r itnifnrm dmsity hmctior, @vrs

h111rphy lntrr hrliwrtl tlint a G;i~rssi:~n di.;trihu~tion \rouId k a lwttrr rrflrction of tl~r. tnw dercct ~lrnsity distrihntio~~ tl~tm tlie delta htnction. Ilmve~cr. sincr i,r \\:is isnablc to integrnt? the )ictrl ietrgntl with I C.;IIISS~AII htndirrn std~stituted for/cDJ. hc sppm.ri- mated it using thr triang~~lar function sl~mvn in Fierrc! 10.2Z-. This h ~ t ~ c t i o ~ ~ rcs~tltr in the !$rI(l rxTrcssion

The triang~lar hlnrphy )ield model is ~ ~ i ~ l r l y use11 t d ~ y in indnrstly to rletermine the effi.ct of manufacturing prowss defect clensit\,.

. . . ,. . . big11 rnorlpl~ to nu% faults) a a l a slnnll propoltion olhi$~ defrrt dpnsities ii.e.. II~<II enolqi~ to cause f.aults). Me thereforr propred t l ~ r ~qnnen t ia l drnsiy function given by

and shown in Fipl~re 10.221. This function implies that the probability ofobsening a lo\\, defect densih is significantly higher than that of o h s e n i ~ ~ g a higll defrct clensity Sobstituting this eqnnentinl finetion in t l ~ c Murphy integral and i ~ l t r p t i n s ) i r l~L~

.%lthouJ~ the Seeds mwlel is sia~ple, its yield predictions for 1;~rgc-area sabstrntrs arc tno optirnistic. Therefore. this isodcl has not h e m niclely used.

Okabe, h'a,qtn. and Shin~ada remg\ized the p h g i n l nature of delect distriln~tions and prnposetl the gamma prohahilit). drnsity fnnction.'" Stapprr Itas likm~ise derrk~prd and ap1)lied !ield n11xlels esizlg the gamnls dezlsih function." TIlr ganllna distribution is @\.en hy

f ( o ) = [r(=)p.]-' D ~ - ~ , - " ' ~ (41)

\\,here a and p a r e h\a panmr ten of the distrilnttios. and r i a ) is tllr garnm:) function. The s11 ;1~ of r i a ) is SIIO\\TI for several \slues o f a in F i p r c 10.23. In this tlistrib~~tio~l. t l r ave&e drfect densih is D,, = ap .

~l~~ ) ie l~l ,,~odcl derived hY sn~hstitatitlg Eq. 41 into h111rpllyP intcv.ll is

AD, " y w,,,,.,

n l i s ,nodel is mmmollly r r f e m d to i s tile t~egntirx bino~ninl mulrl. The p?nnleter a nlllst tlt drtemlinecl. 11 is gcnenlly calle~l the cluster pnm~~leter hc~cnsc it increases ,,itll llecwsing rarianw in the distriht~tion of defects. If a is ili.e11. t l l~l l the ,.arial,iliy of defects is loat (little dt~stering). Ilnrler thew msditions. the $111iora rl~nsit! r,,,,cti,,n annrl,:lcllrs a l ~ ~ ~ t n hlnction. i ~ n ~ l the ~~rg l t ivo 1)inonli.d m d r l n d r l r ~ s to tllp .~~~~~~ . , p[,isso~~ naxlrl. hlothcn~alically this nlrarls

]fa is iOII: the o t I ~ e r I ~ : ~ ~ d . the tilriabilih ofdrfrrts a c m s the wafer is si~~iificant (nl,rll rltlstmrin). ;mil tltr ptmnia inmlel wrluc~.s to t l ~ e Seeds espnential ~ n m k l , or

1ftIlr cr i t id area and defect d m i h are known (or can he .lCCnf'atel!. n l e a < ~ ~ r ~ l ) . the nq;,ti,,. hinoa,ial ~nodrl is :in excellrnt gened-purpose )ielcl predictor that m s he used for ;t nrieh.of IC rnanafactllrill< proceSS?S.

10.52 Parametric Yield

Ewn in a dcfrrt-free mm~ifncturingenrimnment. randonl procrssie:variations can lead to \*?in< levels of ?stem perfr,rmance. These v;lriations result from the fluct~tation of nunlrmtjs pl~!sinl and endmnmcntal parameters (linetvidtlis. film thichesses. ambient humirlih, rtr.), ,vl~icl~ in turn manifest t~lemselver as variations in filial ?stern per. fonr~.ulcy (such as speed or noise level). Tl~eseperfomance variations lr;al to "soft" fat~lts m d i re cllarnctrrirtl by the ~ ~ n r n m ~ i r i c yidd of tile manufacturing pr<x.ess. Parametric \ield is a mesure of tlrc qoalih of fitnctioning ?stems. \rzllereas lilnctiond yield mea- surrs the proportion of functioning tlnits pmduced by the lna~ilrfactllri:~$ process.

A comnloo methml USHI to evaluate paranietric)ield is Bf~>rtlr Cnrlo sin~slalion. In 111r Monte Carlo approach. a large nulnber of psetl~lo-nndoni sets of \ J I U C S for circnit or systcnl pmannetcrs arc $enrratwI acmrding to an assumed pmbahiliv clistribution (usu- al!\ ~ I I P normal distribution) b;rsetlon sample nieans and stsndnrd d~\i :~t ions earacted fmm incasar~l data For rach set o f p l c ~ m e t ~ n . asimrllation is p r fonnrd toohtsn inror. n~ation iho~lt the predictrtl l ~ b a d o r of a circuit or ?.stem. Tllc ovrmll perfonnanw <!is- tribatios is then rxtnctecl fron~ t l ~ r a t of sim~~lation results.

To ill~~stratr tllr Monte Carlo t c c l ~ n i q ~ ~ r , conskler as a performance mrtric the d r iv currrnt ofan nrllannrl .\IOSFET in satr~ration (I,). It can he shown that"

\vl~la,rr j! is the \si~ltli of tlie dedcr. I, is its length. p,, is t11e elearon mobility in tile clian- nrl. C,, is tl~r oe~l t . capacitance prr unit area. 1:: is the applied gate \,olt;~ge. and V, is

the tl~reshold voltnge of t l ~ e tnmsistor. In tltis equation. C,, is a fimnion of tllr tl,ickn,.<r of tlw oxide (11). and If., is f t ~ n r t i n ~ ~ of t l~p oriclr tllicknrss ;D w.II .~r tla. doping in thc channrl. nr I , , =.flC,, IfT). Rotl~ of tlnesr di~nr~,<ions itrr sul,jra to rna~\ufn<zt~ritig prowss \.;tri:ttions. l111*? n n tl111s hc r l~arac te+~~d :r~ vnqinq ncror<liling to nonnal distnhtl- tions \\itll melms p,~ and #,and shtlrlanl rir~iations a, :xnd a, rt~slx-cti\~rlv (srtc Fie. 10.21).

~. rcSer hy uon~puting the \.:~IIIP nf rIL, for r v r n ~mssil)I~: wtnbiniltion OF (;,;and 1;. n,e result of t l ~ r s r mnrpl~tations is :I final perforrnanw ~Iistribution like the one rltm\m in Fignrr lo.%/,. This probalrility density function can tl~rrt hC use11 to mmptttr tltr pmpn~lion of hns i s tna having ;I fi\,rs nngr of drive arrrc,ntr. For rmmplp, if we \,qintnl to rne~plltr tlw p e r c ~ n t n p of hlOSFElS msn~~fac*lnr~.d that \\aald I~avr a n l u e of I,,,, hch\vrn ho limits n and 1,. !ltr \\.oll!d ~ \ ~ l w a t e the intrpnl

~(XIOSFETS wi th o < I , , < h) = J ~ ( ~ ) d ~ (.ifi)

Tina, once the o v e ~ ~ l l ~lislril~ation of a even o~nlput metric is loimm, it is possible

the znanufnct~ring process to facilitate and ?ncouragr design lor t ivan~~fncta~~hilih

(b)

figure 10.~4 ( n ) Normal prol~~hil i t~ dvnrity ft~nctir,ns fnr C,, md \', (Irl O\mll pndx311ility dvnsity ftnnction fin I,,,.

2 s . Chapter 10. IC Manufacturing References 4 257

w 10.6 COMPUTER-INTEGRATED MANUFACTURING

,lit. ,:<* nLlk,rii, . . nfquas t ik~ t i~ cviduation of lC 111ilnef~lril ls p w b w s is a r m ~ n ~ l i i ~ ~ ~ ,i, mmp,,f,.rJ r,,tl,er tl,;,,, h\- hitnil mlntlatio~u. Xot only is Illis !son. eficient. hut in tm~lvi Nn,,,,,,,y i t ~ ,.rsr-ntittl. F.tbric;~tion of intc*gmtr(l circuits can bv q ~ ~ i t e e,qwnlsive, in hd, tilr i.<?t dKildr XVI! rlrctrunin n~nn~ifistaring iw.mlnr so c*lpihll i n l r n s i ~ ~ tllat s m . ~ ~ mn,pw,ies ofi,.,l find i t t o cnpensi\r to slipport lllrir Cl%wl n l l o l ~ l f i s t ~ ~ r i ~ ~ ~

,* ,,,,iC~ aatrof.tltr-stt i~ i~I~- \ r r luo~r m n n l ~ h ~ i u r i ~ ~ g fi~cilit). t ~ l : l y msts wtrcd ,,i ,nlmit,,l~t. nlore than it mmp:mlblr f.~cilit\. 20 ?:In go. This Ilm led to tllc rise -. .....-.. laqr Lntr.,d manuf.a.h~rir~g it~d~rstn.

A, :, r,-sldt of rising msts. tltr rl~sllrngr berow n~anufaduren tmliiy is to offset s,,eh . ... .. . . . ~~~~ ~~.., I;w r.lpit.zl in\rstn~rnt \\it11 a grratrr ;anoullt or 1wl111olo$cd ilmo\atio11 in the bb".

in ~ t I ,~ . r \rnrrls. 1I1e olqrctive ow is to make us? of llle latest dr,'PIOp mp,,rs ill m,no,nter 1tanla;lrr auld sulh\are t~c~ loo lnp ' to enhlnce ll l~l~lufi~c~lurin~ sletllorlq

T l ~ r lo\<,rr le\-r! of Illis hvo-lwcl arcl~ilr~ctarc includrr ~ l n h r ~ l d ~ d mntmlldn tl,nt t ide real-time mntml ant1 snnl!sis of fabrication rqunipnacrlt. nlrsc mntroll,.r, oftr.,, mn. sist ofprnonal compulrn and llle nrsoci:itr<l mntnd software drtlicttcrl to <,arl~ indi,idtld pic% o f r q ~ ~ i p n l ~ n t . T l ~ c srmnd lcvrl of tllis IC-CI\l arcl~itectlnrc ir cnlnpsrd or;, di<- tri1111ted incd area nrhsork of mlllputcr \rorkst:~ti~~ss and filr sma.rs link<.<l 11). a eom- Inon distril>ated clatabaw. E q l ~ i p ~ n ~ n t cnm~nunication ~ i t h l~ost mmplntvn is f ; ~ ~ l i t ; ~ t ~ l 11)' an electronics mallof:actllring slandarll c!allrtl thc. Crnerir ~*c/!,lpn,n,l moclrl ((;I.:XI). T l ~ r CE\ l slanllanl is lad in Iwth xnlicnnd!~rtor alanllf:~~h!rin~~ln(~prist~~Icir~~il lxrLrrl a s c a ~ b l y Tllis strndnml is l~nscrl on thr .sen~ico~tdrrdor r</~llripa~rrzt cornrntrairnli<>ns scnzl- </or(/ (SECS) protocol.

This hp of IC-CIA! srcl~itecture II;L$ great flcribilit): ;dlo\\ing ert~nsion and adap- tation to meet cunstantly cllanging reqeirrment. Over tlar p u t s ~ v c n l )ran, po\vcrhtl. fle\ible. and mst-effectix information 9r t rms b;wrl on mwlels sttell as t l ~ h I,n\.c hrmnle an i n t e p l palt o f t l ~ e IC rnanuf;tctaringmlerprie.

,,,,,,,,rfnmr"nc ofilt&ptnl circr~ils (IC-Clhl) is ;UIIIN~ at optimi7ing Illr r n ~ t - e T T c c t i , ~ ~ ~ orrl,emnin nlanubct t~r in~ia tlw s m ~ r mmner in ~ v l ~ i c l ~ n ~ ~ ~ ~ ~ ~ ~ ~ l ~ ~ r - o l ~ l d d ~ , s i ~ t ~ (CADI b 10.7 SUMMARY I,= dr.ln~~ttic~illly a f i ~ t r d t l ~ r emnomics of circuit d~si@l.

cndrr 11,r o \ ~ w l l lttqnding of mlucieg nla~ufi~clur i~~, : mst. sekrral suhtaqks !lave bn iclpstilinl. ntnc incladr incrcming fabrintion !irld, n:(lucisg prwlllcl q r l c t i a ~ r , main. t;u,un~ mnsirtent I t ~ r h of prwluct quality and prrionnence. and imprn\ing the rrliabil. ihof p m s i n e g t~ ipn l rn t . Since fabricntion processrs often consist of 111jndrelL of .&pcntiid stqis. !ield Ion may ptmtidl! o r m r at e w n step. Consrq~lrntl!: maintainin: prrxlud q u d i h in an clectmrlin man~tbct~tring filcilih reqllires the strict mntrnl of liter. dl? hnnrl r~ls or men tltotuanch of pmccss \~lriables. The interdcpr~ldmt iuoes ofllidl \it.ld. lliell qnalih: and lmv o ~ I e tinlr c in Iw addressed In. the clrvelopt~~ent of smeml ~ r i t . . . . ~ ~ . . icd ctpthilitirs in a sta~e-of-the-art IC-CI.\l ??itern: jrork-in-procczs (\ZlP) monitoring. gtlipmnlt mntmunicition. data acquisition and stonge. pmsdrqu ip rncn t modeling, anll w.d-time p m mntml. to w n e a f w . Tile e~llpllacic ofeach of these acti:itin is to in'-. t l ~ r n u ~ l l p ~ ~ ~ ;md rerl~~re!icld lws bypre\rntingpntcntial o~isprornsin~.!iut each presents sipifir;mf rn$neerin$ challenges in its effective impleme~~tation anrl d rp lo~n~en t .

:\ I,lock ~ l i a v t m o f & hpickd rndern IC-CIkI system is sho\\n in F i ~ u r e 10.25. n1is d a m m outlines manyoftllr key features requiml forefident r n m ~ f a b u r i n ~ o p e n t i o ~ . "

n ~ i s cl~apterprn\idnl an a c n i m v o f t l ~ e relrnvmt irsr~er m K, manulmunng. I sa I~CI \BUMI

a description of elrctricnl testing anrl I~asic packa$ng p m ~ s s e s , a$ \ r l l as a prrscnta- tinn ofstatistical p r m s s mntrnl, statistid experimental design, and yield n~mlcling. Tlw chapter concl~ldwl \\it11 a brief intrmluction to IC-CIM ?sterns. In IC manuf.cturing. prm-ss and equipment reliability d i m l y infl~lence tl~rougl~pul. )ield, and ultimatelymst. O w r the nest s f2wnl yean. significant enhancerncnt of rnanufadt~ring oprnltions \rill l~ required to reaclt projected tzugcts for future genrrntions of tnicroelectrnnic dr\iws, packagrs. and syxtrms.

b REFERENCES ! PinmL? &. C ~ V L md D. Pmlhnn. Inl~~mtcd Cimdl 3fant,fnr(umd~ilny. 1F.EE Pn*?. Pi(~~lam=y, SJ,

2. A Lurlzk,rg, 3fimGdmnirr r\lnn~,f&,n'n~ Din~~mlicr Iln,ullx*rl. \bn Smtrmd Rlinllold. S m Ycnk, lm3.

3. H. xlmmul.. ~ d . . F N ~ ~ ~ ~ ~ ~ ~ I ~ I ~ ~ ~ ~ I ~ ~ ~ ~ ~ I ~ . rn~k.cin~ Y~CW-II~II , SRI.YO.~~J(. 2 ~ 1 .

.I. \\'. Bmn. Ed.. ,\dmnod Flrdmnk Pncknpinn IEEE P m . Sw Yo&. 1W.

5. R, jnqvr, lnlmrltmion m .llimI~~trnnic Fol,:ol,ncnrrm. 2nd Ed.. Ptestiw-llall. llplvr Sadtilt. Rixcr. SJ. 2m2.

6. D. >fost~vn>r~. I n l ~ l ~ ~ d l o n lo Stnlislicnl ptnlil!; Conrnrl. \ l i l ~ , S~.rr. Yo&. I(LF5.

7 . J. Rnnlr dc Cyrr nml V. b l l l m . Inlr~mlrd Cim~il . ! l o n t ~ f ~ ~ ~ d ~ i l i ~ ~ . 1I:EE Pms. Xov Yak. 1W

8. R. !.fuq~h?, -Con-Slm Optima oiSlonol~ll~ir Intrgr.>tnl Cirnbilr.' rnx. IEEE. 52.l12). 153-1515 OSIl.

9. R. S<drdr. Trld and Co.1 Annlyh olRilaliir Ul.- IEEE In1 Elmmn Dnim Ilrd. \V.~%langton. IX:. Mo1x.r 1x7.

10. T. Okidx. \I. Sagala. md S. Sbimacl.. -Ansd>sir olYicld ol l n t ~ l n l Cimrirr and 3 St-v Eqmsion lor thr Yi<.lcl.' in C. Shhplxr. Ed . Ikfm nnd Fnulr Xrlrrnrtrr i,r I'LSI Sydrzr~<. \ id 1. Pleeum I'm<-, Sc-x, Ywk, pp. 47s ) . IWI.

I I . c. slaplrr. -F.CI t m c ~ vir(ion i,, nrld ~ ~ ~ ~ , . ~ i ~ ~ . - . ~ f i ~ ~ l r ~ ~ ~ ~ ~ i ~ t ~ . LIO.I?~-151 11sw1. 12. 5. SIA~. Srrnimmrl~mor DT.ICCS: rlbyr(n nnd r ~ ~ l , ~ , o l ~ ~ , . ?nd Ed.. \\',I.,: St-\- Ywk. IIWY

13. D. llulger, L Row.. itnd C. Slnnm. -Conlpaler l~~tcnltml h ~ n n o l ~ i ~ ~ ~ r ~ ~ o f \ I S l ~ Pmmdille~ tLc. 1111, IEt:FJCII\4T Intmn;ntbnll Elteruniw Y r ~ a ~ l t l r ~ t t n n e x ~ I ~ n ~ ~ I ~ ~ S~mpl,Va~n. S<~pcaih.r lcJW. pp. 1 3 .

r PROBLEMS tr?..n\l\ ,L.ruvr ,l,findk j,nll,ltvm

S E W O X 10.3: STATlSnCAL PROCESS C O h ' O L

I. c:<,ntml rllarts fiw f :as(l s are to Iw nuint:~intrl for tlnr thrrrhnld \nltngr of sholt-chnnnrl \I()';VET, ra,,,plr ri71y ~ f n = 111. It is kncmm 1I1;tt thr pmhrr iv ~~onnallydie- ~,,!,,,~,~l ,,,tl, p = 0.75 v ,,,,,I 0 = 11.10 \! l:in<l tlw w n t c ~ li~lc and a~ntrol timils fix each nitht-~. (.(>r>tm>I rlnarl.

2. R~~~ pml,lrln I 8,~s,,mi,rC that p and a;mw t~~>brnrn and tlniat nr. hn\r n>llcctnl M ,,ln,.;ltjom ofw,,,p]t. 10. Thrsr rampler !icldml a p n d awrasc of 11.73.1 \'and an

:,\,.clg@, *, of 11.125 \:

S E C ~ O S 10.~: sT~nSTICM. EXPYPERI\IEhT.AL DESIGN

3. n , ~ folbminq 2' Ixrtoriid rqwriment \\w latrl to annl!m a ph~,ttolitla~ntphv p m c s . .Att,l\-,r lhc tywrinlrnval rcs~rlts using tltc Xttcs itlsoritbrn.

'4. Consider thr thmtrqhptts fie.. wafers pmcersrd per hour) ollivr diITercn? nnnn~tfacttuin~ pm<w< (Iahrllnl A to E in thr follm%i!~g tahlr). For ~:;tch Imrm!r. c!.tta u;r: mlleetnl on thrrc rli%.n.st <l;ttrs. Perform an an;d!sis of wrianw to drtennine a.hc:h~r the prurrwr md p m s i n q datcr arc ripifinntlydiffcrcnt.

SECllOS 10.5: n E L D

5. Ara~rninp: a Pnicmn model. cnlorlate thc maximlsrn defwt density nllcn\,;thle on 100.000 SSlOS transistors in order to nchiwv a hmctional !icLl of 952. :kame the gate of each <lr\iw i' I0 pm \>ide ;md I pm lonq.

6. Use Murphy's )irLl int-l to de"\r Eqr. 3i. 38. nnd 40.

7. Supporr tile pmhability drnsity h~ncticm orthe defect density fi,r a flvcs intrKvnncd m;m~!hr+urinq pnrrrr b gi\.rn hy

lfthr oitinl iirca h ~ r this intrnnnneet is 100 ern?. mlodatc the functional )ichl \r can c x p ~ l k>r the p m ' w over thr nmqr of drfwt <lmrities from O.05 to 0.1 nn-'.

Futu re T rends and Cha l lenges

I Sinr? the Iwginning of the int~grated circuit era in 1959, thr rninim~~m d e d w dimension. also called tlla s~ini~nav~/co~tcrrle~~@h, l~ns l m n mlecrd at an annttnl rateofahr,t

I 13% (i.e.. $1 r~d~lc t ion of 30% on). 3 years). According to tlte prrdieion by tlle Infcn~nlior~ol Tccl~~tnlogy Rnnrl!~urp~?>r Srrnicondttctors.' thc minimum feature. len@h\%ill sllrink from 130 nm (0.13 Urn) in the year 2002 to 35 ntn (0.035 vm) ;lroantl 2014. ;S

sl~o\vn in Table 11.1. Also s l ~ o \ n in Tahle 11.1 is D M M size. Tile DRAhl hsr increared its lrlemory cell capacity rottr limes every 3 years, and 64-Gbit DRA\I is erpcted to Iw av:ilnhle in 2fl11 ming .%-nm drsipl mles. The table dw sl)o\rm that u-&rsi;.r krill i n c m to450 inn1 (18 in. dinmrter) in 2014. In addition to the feature s i x retloaion. clrallen~es

I rornr frnm the &\ice lewl. material lewl, and system lcvrl, as disn~sscd in the follo~v- in: sections.

t 11.1 CHALLENGES FOR INTEGRATION I

F i p n . 11.1 slrows tlre trends ofporver supply mltage ((Bn,,), threshold toltage (1:). and p::lc oxide thicLi~ess (d) V ~ I I S channel lenfitll for CMOS l@c lecl~nolopv.' From this fit- . . urc,, onr c;ul see that the gate oxide tllich~ess will soon apl,road~ the tunnelingcumnt liniit of 2 nra. V,),, scaling nil1 slo\r. do\\~r h m a s e or the nonsnlable V, (is. . to a mini- nlnm IfT of about 0.3 \' ~ I I P to s~tbtl~resl~old Iraklfe and circuit noise immanity). Some clrallenges of the 180-nm t r c h n o l o ~ and be!nnd are shoan in Fi,pre 11.2.' The most stringent requirenrmts are detailed in the follmving sahseaions.

TABLE 11.1 TheTechnology Generation horn 1997 to 2M4

Ywr ofthc Orst I !Wi 1YB 2 2 0 0 ? 2 l l O j 2Mri 2011 2014 pmdttct shipment

Fralttrc rim (nw) 2% IS0 130 100 70 50 35 I)R:\\I rim (bit) 256IRhl 1 C: - 8 C - Tr(C - \\!tfcr (mnd 230 300 300 .XO X K I 330 4511 Cat? orhlr (nm) .U 1.9-2.5 1.3-1.7 0.Y-1.1 < I 0 - -

11.1.1 Ultrashallow Junction Formation

IIOSFETrhmnc.1 lrngtll (pmt

Figurn 11.1 Twnrh olprnver ruppl? \nlvr$c V,,,. threshold r.olta~t. jr,. nnd rate o\ide thickness (1 vc~nur chsnnrl Im*h lor CXIOS l@e lrrLnnlnc6cs. Points arc mlltr.ttd horn <lafa pul,lished ",,Y m n t >*an.-

Figurn 11.2 (:hdlcnp<- hrr IVLnnl rind mmxllvr YOSFETs.'

So.called short.cha~lnc~ effects happen ;r? the cltwnel lcnfll, is reducrd. This prohlc~,, hrconres critical ;ri t11e dr\icr rlimension is sc:drrl ~lotm to t rn nm. To ishieve an altra- sltallou. jlmclion \ritlt lo\\. shwl resistance. lo\v-cnrrg). Kc.. less than 1 ke\'1 implantation t w h n ~ d ~ a i t h lug11 dosage nlost IE cmplo~wl. TaI>l,le 11.1 shou-s the required jenciicm clvptl~ versus the tl~chrlnlogy ).enenention. Tile rcquiremrnts i r l l l ~ e junction for 1M n arr drpths aronnd 20 to 13 nm n \ i l L n doping conm!ntntion of 1 x tol'/rm'.

11.12 Ultrathin Oxide

As the gatc length shrink belrnv 130 nm, the oxide eqoi\alent tliickness oftlre gatedielc.- tric mast IE redacrd around 2 nm to maintain perlonnance. Ilo\rrver, ifonly SiO? (with a dielectric mnstiult of3.9) is used, the leakage tl~rougl~ tlic gate I m m e s w r y h i ~ h lxxaur or direct tunneling. For this reams. thickrr 11igh.k dielrctric materials tli;tt l,aw lmver Ieltage n>rrent ar? needed. CandirL~tes for thesl~ort tenn are silicon nitride (\\itl~ a~lilielce- tric runstant of 7). T Q , (27). md TO, (&l(lOl.

111.3 Silicide Formation

Silicide-related technolow Irm hecome an inteeral Dart of submicron devices for reduc- <" ~. . inc the pamitic resistance to improve dexiw and circuit perfonnancr. Tlrr conventional

- in 1M-nm ChlOS applicntions and beyond. COSI, or Nisi processes will replaceTSii for t e r l t o o l a ~ l q o n d LIH) am.

11.1.4 New Materials for Interconnection

'To acltiwe high-sped opention, the nC time d e l y of the intermnnPction must IE mlacprl. F i ~ l r e 8.14 showrtl the delay a fundion of lenture size.' It is oh\ious that gate rlelay decre;scs as the d~anne l length decreases. Meamvhile. the delay r~sttlting from inter- [annect increases significantly N the size decretses. This causes the total dcl:iy time to incretse as the dimension of tllr de\ iw si72 scales down to 2% nm. C ~ n s e ~ ~ ~ e n t l y . hoth h i g h - m n r l t ~ c i i metals, sncl) as Cu. and lot\~..-di~lectric-conskrnt (lo\v-lil inst~ixton, such zs organic (polyinrirle) or inorganic (F-doped odd?) materials. offcr major perfonnallw p ins . Cu exllihits superior perfonnnnw t ~ c a u s e ofits high cnnducti\iy (1.7 pR-on mm- pxred wit11 2.7 pR-cm for All lnd is 10 to 100 times more refistant to d r d m m i p t i o n . T l ~ r delay using Co and the lotv-k material sho\vs a significant drcrease compared ,vith that orcon\.entiot~al Al and oxide. Ilmce. C s nith the low-k material is essmti:rl in mul- tilevel intermnnection for future deep-submicron trchnolop.

11.1.5 Power Limitations

Tile p \ w r reqeired merely to charge and d i s d ~ a ~ e circuit nodes in an IC is pmprtion;~l to tlte a t~mhrr of gates tlntl the frequency at \vl~icl~ d ~ e y are s \ \ i t ch~ l (clock freqursc?'~. TIle power can lw e ~ ~ r e s s e d . 1 ~ P - l / .ZC~~~lf . \vlllpre C is the mpacifatlw prr dc\irr. I' b tlte applied voltn$e, 18 is the numlrr of de\icrs per chip. ;md f is the clnck fmlu<.ncc Tll? tempcnttlre rise c:lased I,? this lmnvr dissipatio~~ in an IC pncbgc, is limitnl hy tlw tlar- I ~ I ~ I con<lllcti\ity of tlw packaKe matcri.ll, unlrss alrxilhp liq11id or ps mmlling ia I I S P ~ . TIIC mrnia~am al lo~~ablr~ ternprr.lt~rnw rise is limited I,? tltr l>sndpp nf tlir svnrimnd~tc(or

. chapter 11. Fmre Trends and Challenpes 11.2 Synarn.on-a.Chip 4 21

11.1.6 Sol Integration srtion 9.22 ,r,pntiollnl 11,- iwlation of SO1 \\%ifen. Rmnll!: SO1 teclln'Jlq3 1 1 ~ recpiv

ll,.2d ofanrntion. Thr aclc~ntnges of SO1 intcgr.ltiotl h rnrne s i~~i l i can t as the frattlrr lcn,$, appm;tchcs 100 nm. Fmnl s p r m s s point of !icrv. SO1 does

,,wd tl lr mnll,lrr arll stnlchnre and isolation p m s s e s . In addition. sl~allow junc. tions dirt.& obtainnl thmugl~ tlw SO1 film thickness. There is no risk of nonani. fonll inlm~i~fil;on ofsilimn nnrl ,\I i n t h ~ contact mgio~~s hcaltse ofosidr. isolation at

lattoln of tllr junction. Hrncr, the rnntitd harrier is not nPwssaF 17mm a rlctice Of,ie\r: tllp mmlem bulk silimn &\ice needs l ~ i g l ~ dopitg i t t l ~ r dcun and %,b.

strate to rlinlin;ltt. sl~ortcl,;~nnrl cfi~cts m d panclitl~m~rgl~. This Iligh r lop i r~~ results in 1,iSl, r;,pcitmw,,.lree the j~ndion is rrwrsc. bix.erl. On tl~eotlirr hand. in SO]. the may. inlltln otpcitancc bhvr rn t l ~ r jt~ndion and subdmte is the capcitancc of t l ~ e burid insnlrtor. ,rhosr dirlrciric mnskmt is tltrre tines solsller than that ofsilimn (3.9 \ynns 11.9, nsed on rinSoscillntorprrf~)nnan~, 130-11111 SO1 ChlOS Iec~lsoloQ'c~n achieve

h ~ t e r spWls or rrqt~ire 54% less power rntnpared a i t l ~ a similar h~rlk tecllnolog):' SR,\hf. I)RA\!. CPU. and rfChIOS ha\? d l l w s snmssh~llyf:~bric~~trrl using SO1 terll. noloq. n le r for r . SO1 b :t keyr.lntLl;tte for the fi~tsre s>str~n-on-n-chip terlinolep, mn. sidcr14 i n t l ~ c ~ folloaillg sedion.

EXAMPLE 1

For ;m rqui\-dcn~ ~ d d e thielnexv of 1.5 nm. &at \\ill be the ph!sicnl thickness wlren the hixh.k m:~trri;als ~nitriclr (c,ic. = 7 ) . T@, 12.51. or Ti0: (60) are tlwl?

SOLUTION For nittidr.

Using thr same wlcalation. \\r obtain 9.62 nm for Tq.0, md l0 .F nm for TiO? 4

11.2 SYSTEM-ON-A-CHIP Increasd component densih and impmcd fahrintion trcllnolng?. hnvr ltelped the real- ii..ltion ofthe syqfrm-on-o-cltip (SOC). that is. an IC chip that cant:iins :, corr~plete elec- tmnuc s?strrn. Drsi,pen mn build all the circuitry n m l n l fora rr,mplctr r l ~ t r o n i c s\stem. surl~ m nn~nlel;~. nalio, t~lnirioe. or p ~ n a l computer (PC), on asinde chip. Figrlre 11.3 S ~ < I R Y an SOC application for 1 PCh motl~rrhonnl. Components ( I I chips in this case) I)II(V btmd on lwqnl\ I z m n s \irtu.tl cwlponvnts CHI 1111. c l ip ;at 1111. rieltl.'

Thvrr m* h~n4dlsldclrs In 1111. rr.d~?.~t!on of tllv SO(: Tllr lint ir 1 1 ~ I I I I C V cl~~ndr.: - of the rlpsiml. Sil~n. Ila. component lw;~r(l is prrscntly dcsiymnl 11y diffrrrnt compan

i h ies

NYS - :m1dWn~ix4 s lpn l ASIC: - rppla.lllon.~pcllir IC CI'U - <".rdr.d pnn.<ci , ,x ,,,,I, l7t.l> . p"~r.~!n?#,:tt~l~. ic>c,c < I < ~ w

using tlillerent desig: lools. it is clifTiicl~It to intcpate tlle mrnponents into one chip. Anotller dilliculty Ii?s in fabrication. In general, tlbc f;ibrication pr~msscs of a DR,\hl are significantly differat from those of logic ICs (c.g.. CPUs). Speed is the first p r i o r i ~ for the logic. nl lerea leakage of the storetl charge is the priority for menlot?: Tl~rrefore. mul- tilrvel inlrrmnnrction scliemes using live to six levels of metal ire rssentinl for logic ICs to ilnpm\.r the spretl. Ho\rrver. DMXl circuits need only hvn to t l~rre lr\~els. In addition. to incrcilce the speed, a silicide p w s s must be used to reducr the series rrsistanw. and ultmthin gate oxide is needrd to increase the driw current in l@c circ~tits. These rrquirernrnts arr not critical for memory

To acl~irve the SOC goal. an emlxdded DRAM trchnoloq llac been intmluml to mrrgr. logic ;md DRAhl into a single chip wit11 compatible processes. Figure 11.4 s h m ~ s :t <r.l~ematir c m srction ofan rmlmltlrd DRAhl. including the DUX1 cells and the logic ChlOS clrviws,'So~nr pmcessing steps arc rndified ;u a mmpmmise. The trrnch-hpe

Dtrp twnch p.stth.tnrr

Figure 11.4 Schemntie cms section ofthe cml*rlrL.d DRAkI inclarling DR.\\! rdls md l ~ i r . hlt)SPPTs. Tltrrr is no hciSht dillewn(~, in thc trrneh npcitor wII l r c r ~ ~ r r of thr UIIAXI wll sln~cturc. 311 I n .\f5 an, rnrtid inlrnnnn<~tionr. and \'I 10 \:I ;~rc \i:l h0lr.r..

r Chapter I t . FutureTrendr and Chellengss

b 11.3 SUMMARY RCC;IIISP 01111r nq,id wduclion i n k; l t t l r r Itxrl$ll. 1C l t ~ r l l n o ~ ~ l p ' u i l l s n l rr:lclt its pnc. tir.;il lilslt :rs t l l r rhxnor l Ir.n$ln is n ~ I u r r r l t o alm111 3) 11111. \!'II:I~ ICs \\ill IIC hr\on(l (:\IOS is n kc, quwtioa I r i t t ~ ;rsl;~I I I ~ r ~ w a m l l srirntists. Jl:~iur c:..mdidnt~s incl!tdr i ~ l ~ ~ . \:ativr <lc\iry.< l,.~w11 oo q11111111111 l l l r ~ ! l : t ~ i ~ d c f k l s . ~ ~ ~ 1 1 1 9 ~ ~.IIPII t h r IRIPKII (Iinlpn. r ion ie r n l t ~ r r t l l o l,t.lorv IOU n n i . r l ~ ~ t r ~ n ~ i r stntcl~!rPs \\ill rsl t i l l i t ilonrlnssical hcllnrior

<l,.I~r~dirl< on tltl* rn:~tc"itls and tltc t c a ~ l w r . ~ l ~ ~ l r o f opr f i~ l ion . T l ~ r o p ~ : ~ t i o n of sllcl, dr.,,cr.s \\ill IN. on tltt. sc;~lv o f s i n~ l r - c l r c l r nn tr.los]mrt. This oppro.,clt 1):s brm drrnon.

s t n t r t l t l ~ r sil~qIt.-rlt.ctro~~ rnclrlo? rrll. T l t r n.:t l i i)~tio~~ o l s ~ t r l ~ s!strms nit11 trillionr

ofmrttlx,nrnt\ \rill lw :I nt:tjor c l~a l l r ng r h r y s c l ChIOS.'

b REFERENCES I. Intmu;fnrurJ T . ~ l ~ , ~ d ~ y , , RxuJrly,lnr .Cnn;mndz~~~~f i . %.ir>imn<lu'inr 1ndrnln.A~u~ctia~~. Sw Jim. 1%.

2. s T.lllr rllll E J . Yrnc~ l . -C\fOS Dc+iur,< Ix~ltnr.0.l MI: I l~n\, Ilidn \\ill Iscr (~ . r~ t l~~r . i~ CO? IEEE %dl. 0: I,>, u,..,nm n.,c,.< Jf",,. 19. 215 :1917'.

7 L p,.tm, -IS 11,~- OI$ pn, scxlc ~ ~ ~ r t ;r noxkl,lr ,~tmiciion? Scvi;,-,x~l I r a , . 22 -11; r IUm

4 21 T hl,r -Intrmnntrt s ~ d i ~ ~ - T l , ~ Red U,nifvr lo l l id l Pcdormancr 0151.' IEEE Twh. 0: 6 1 . fJfimnt D . ~ i m \led. p. 2-11 llviil

5 F Il~ldr,n.lrlrle. c.! d.. 'Srdnl>ilitv ofSOI X.rlmulyv twroO 10 vnl I ? V i:\10S G.n!,ntlon.' IEEE In,. E!,*rn~ Dm#<,< \fa.d, p .tlX3 [lsEtYl.

fi R. Zlrrt,rt. 'l<lmrnnir l>ssiq~ ,\atu!srtion: lEEE Sprs-rr. 3fi. 61 ilm

7 11. I d ~ c h r . <l .d.. -l'mhdd<rl D U \ l T,~l~nob~ti~-.- JEEE Tmh Di? In1 Fi..m!rf fi*,ir(.s .lJrrf.. p. 31 11W78.

\ S Lv~4. J. Xu. md .\ ZL~I ;* \~~, &I$., Fr,fvrm TnvtrJ> ;PI > I i ~ r n ~ l ~ ~ c ~ n ~ ~ ~ ~ ~ ~ , \Vilcy. Xm: Sork, Ism.

b PROBLEMS 1. ia l Calo~latc. ~ h r RC tirnr m,ns~;u~t o i m aln>mitn~m ntnner 0.5 urn thick fnrnlrd on a

thermallY crmtn SiO: 0.5 pnr tllick. T ~ P len@ll 2nd aidth of t l ~ r runnrr an. 1 nn rncl I urn. n~rprr.ti\cIy. Thr rr.ri~ti\i? of lhc. nlnnrr i< 10 ' R-crn (1,l \\11:tI \rill IK. lit<% RC tinir cnnxt.,nt for a p,lpi l iwn nlnnrr ( R , = :I0 Wl,I of idmlicul <li~nvnric,n?

2. \!I>? do \rc nw.cl multiple o~ic l r ~hirlnr.;~cs hr a ?stvrn-on-e-chip?

3. Sormdly we nerd r InlNcrcrl Ia:t-r pl;mmd iwhvrrn n h i ~ h - k X1O, and lbc silicon sub. stntv C:tlc>~lxtr 11w cG-ctivc ~ x i d c tl~irkncss !li_OTj wlivn IIBC s~itrh~.d s ~ t e dirlrclric is 'I'a:O; ik = 5 aith a thidnc<* of 75 .i <rn n btlG.n.d nitridr ls!rr lk = 7 and n tl~icl;cn nf 10 i ; \ l w nlcnnlntc E 0 T lor a bnfft-rd ourlv l;ycr ik = 3'1 and n tbirl;l~c..i of 5 :\I.

List of Symbols

S!lnld Dvwription Unit

I Llt i r r . mnslant A .. c S p e d of li&t in \3murn o n ' s C C~psritanrr F D 1)iflhrion ml f id rn t on%

E Kncrp e\'

i Elraric licld \'/ern

f Frcqurnc). Ilrfcppr) h Plrnck mnstant J.s

1 0,rr""l A

I Current dmvity .Ucm: k Bollmlann nrnstant JIR 1. L*,nflb crn or prn

ltl,, E l ~ ~ r l m n rest mas - kg Ilcfri idi\r index

Dmrity of frcc elertronr "".; '1, Intrinsic carrier mnmntmtion

"".' I' Dmsiv of lrce hnlcr m-' P Prrsrurc P3

'1 l laglitude oiclramnic rhrrge C Q,, Intcrfarr imppnl charge charecskrn'

II llcristrnrr R t Tim<. I

T ;\ha,latc trrnprnhlrc R

c Crnirr \,clwit\. cm'c \' \'"Itage

Cm 1'~~rnli l t i~ity is ~;mluln Flcm

c, Scntir~~ndtetar p-nnitti\ity Flcsl

F.. 1sntl.alor ~r rmi t l i \ i t y Flmi

EJG, Or E,.&, Dirlrdrir <vnrtanl

1. \Vatrlcngh pn, or nm

v Yrcqla.ncy of light I l r

I ' vn~~~ .a l i l i l ~ in \;mlanl ll:csl P" Elmimu mohilih c~:?:.. P. l lolc mobility cm::Y s

/I,,

P Ilrristi~il). R-nv

n Ohm n

International System of Units (SI uni ts)

Quantity Unit Sbmbol Dimensions

Lmslb' Meler m Slars Kilogram kg Time Snnnd Tenlperaturr Kelvin K Ulnt.nt Ampen A Light intmsity Cimdel; Cd A n ~ l e Radian ncl Frvqueny Ilem. l iz Fom N\'mior S Prrssure Pawal Pa Eocrp.' Joule J i'mvcr \\'at1 \\' Electric dlrrge Coulomn C Palmlid \'dl \' Concluclmce Siemens S Rerirtnnw Ohm R Cnpacit;tnee F m d F >l;tgnelic flux \Vclw \!% hlagnrtic indudion Tesla T lndrtctanm Ilenw I1

Unit Pref ixes*

exa peta ten

$%a mega kilo

lrecto d e h drri rrnli rnilli micro nano pirn fc..n,to

10.;. alto a

- .qrlopfrd I? lntrrnrtionrl Cotnrnlttcr on \\'rights and Y<an~m. iCornpound pmtxm sl~mld nal k ilwl. P g.. "at pp bill p.)

Greek Alphabet

Ln~nvnxv. Uppn-rw

Alpha CI

Rcrr (hmnlr

Ik.ll;n Elmilon 71.1.1

Physical Constants

Proper t ies o f S i a n d GaAs a t 300 K

Z \ I O ~ ~ ~ I C ~ ' .i.o2 x 10' 4.42 x IIP ~\tc>mic ~ ~ ~ ~ i ~ l ~ l W.C?) '44.67 I % n ~ ~ h l ~ n ~ n l i r l c l i\'/cm) -3 x 10' .I x Ill' C~?rl.cl rtn~cturr Diamond !inebh:nrlc Ucnrih (~Icrn'l 2.3% i.31: Dic~lcdtic ar,rlnnl 11.9 ~2.4 ET(ec1ive dcmsit? of "$6 x 10'" 4.7 x 10':

\li*tcs in condtnaion l,i,t,,l, S< lc,,,-')

EfTw<ive drnsity of 2.66 x 10'" 7.0 x 10" <tales in tdmm l>rn<I, s, (cnn-?

ENwliw n ; t s s (mnrludi\ilyl Elrc+.(mnr ltn.,/tn,,) 0:26 ').Mi3 I I"l,T (rttv/,8,"l OW 0 5;

Elrrtrrm :tOinit> x(\'l 4.05 4.n;

E n r y gap (cVl 1.12 1 . a 1ndr.r of n,fnr(ion 3.42 3.3 Illlrinsir cwrirr 9.66 x lV8 2.5 x I@

msn~#~lr.rlionlen~-') Intrinsic mrisliuit). (R.cml 3.3 x 10' 2.9 x 10'

Lallicv c*nst:all (A1 5.43102 %iii325 Linrar nx-ffirirsl of 5.59 x 104 5.75 x in*

11,rnnal r\~:knsins. ArlLxT (*(:-'I

>lrlting poirll (OC) 1412 1140 >+intwiIy<amivr I i ~ e t i m ~ ($1 3 x 10.' -10-" Slol,ilil? (crn2A'.s)

fl. (c~~rctrons) ISY) 9200

/+, (hnlrsl 5115 320

S ~ c i R c lrral (J& -'C) 0.7 0.X5 Thvnnal mndtcli\ih(\\'lrrn.l;) 1.31 0.45

\':tpor prrsnm, (Pal I a1 ITSO'C 1M a1 1050"(. LO' nl W'C I ;,I %Yl'C

Some Properties of t h e Error F u n c t i o n

$3 . ~ ~ p ~ n d b G Some Properties of !he Error Function Appendix G. Some Propenies of the Error Function 4 279

,.,q?,.:,'<.</ crf rr : 11' edirr.1

I 5 0 8-3 3 4 1.74 0 9 W 1% I 3) t l $11 -!-I 1.75 11 956 672 I :%I 114i1111Y 1.76 0.!J57 L.?I 0 !I.X IN,; 7 0'~976!Jl I $2 0!47\ 1x5 1 . 3 O.$ISS rdl I . O!Hlr111.5 1.~11 09s!l @I1 t 0!411914 1'1 09 \9 525 I .li 0 '10 7e? 1.S2 0 9 \ 9 91.3 IV, n w i m 1,s; OWN.:

1.:;: O<J-IT312 1 . 9 05WO 7:4i 8 0!U9lJl6 1 \5 119!l1 111

1.931 673 I Ui ll.!#ll 472 I!>?? 2 5 1.57 0.991 $21 I !I53 '52 I.$$ 0VY2 1%

,..: ,l!Jii 376 1 % OJXJ2 479 1 43 0 9.56 5 7 1%) iI.RI? 781 1.44 O M I ? Y 7 1.91 05fiL3 (MI

I 0914695 1.92 OW3375 I 4 6 OY61 1131 1.91 0.W3 6% 1.47 0Y6? 373 1.9.1 0.'&3 928 I 45 0 l W l l 6 3 1.a; RMl1 179 1.49 O W \9Y 1.96 O . W 426 13 nm I ( I ~ 1.9: OYJ-~ r61 1.51 t I Y 6 7 2 7 1.99 0.994 892 I..?? OW5 413 1.99 O.%J.i 111 I ii OY69516 ?.W OW5322 1 . 3 0.970 5% 2.01 O.<XA5.%25 I .55 11971 623 2.02 0.995 719 IS n.9:~ e - 5 2.01 n .s j IXY,

1.57 0.973 64x3 2.61 0 9 % 056 1.54 0.974 547 2.115 0 . ~ ~ 6 ?.is 1.59 0.975 462 2 i f f i 09% 423 1.60 0.976 315 2.07 0.W ,592 1.61 0 9 T ; 207 2.04 0.GSii 731 1 .62&974 (US 2.09 I).!+% $54 I.% 0.975 %3 2.10 lKFJ7 V21 1.64 0.979 622 2.11 0 .37 1 ~ 5 1.65 0 9 W 0 7 6 2.12 0 . 3 7 2 W I I% 0.951 IIL~ 2.13 05rn74n7 6 0.951 510 2.14 0997525 1.65 0.892 493 2.15 O W 7 639 l 69 0 9 U I53 2.l f i 0997747 1.71 O.Y\3 7 W 2 . l i (I,W7 351 I :I n.<JYI 4117 2.15 n.w:951

72 09\5 01J7 2.19 f I . B S M 6 1.73 i1.9\5 573 2.20 0.YJY 137

3.14 O.%N 991 03 3.15 O%FJ W 1 C*l 3.16 0 . 0 9 3 2 1.l 3.17 ll.!MJ !W2 C-4 3.18 0 l H J 9 J 3 l l 3.19 O . O W 5 6 3 2 0 n . ~ m 99397 3.21 0 . M 994 36 3.22 O.!fiM $N4 i 3 3.23 0 . W 3 5 0 i 3.24 0.9%) !+I540 3.15 O.!FfiJ !FlJ 70 3.2fi 0.%19 <A5 99 3 .2 i 0.W9 9% W 3.213 0.999 'Wi 49 3.29 05999 72 3.341 0.999 0 6 91 3.31 0.999 M l i IS 3.32 0.999 3 7 .% 3.33 0.W9 997 51 3.34 0.999 3 7 &5 3.35 O.9J9 'Bi 839

Bas i c K ine t ic Theory o f Gases

T l ~ c ideal g s law states that

PV = RT = h',kT

athere P is the prmrllre. V is the \alsme of I mole of gils. E I I, & t # r K,,, ~cutn,ritnt~ t 1.95 adfmol-K. or a?. ntm-cm.'/mol-K). Tis thr absolute tenlprrature in K. .?',is the Avgadm mnstant (fi.02 x LO'" mdectdedmolr). nedk is the Bolbn~nnnmnstant (1.3-Sx 10-', JK. or 1.37 x 10-"atmcm2K). Sinw rrd g s e s hrl~ave more and more like the icled gaq as the presstnrr is lnwer~d. Eq. 1 is d i d Tor most wcuanl processes. \Vc can use Eq. 1 to calct~latr tltr molec~tlar mnwntration 11 (tllc nlrmlxr o l~no l~-c~~les per tanit vdumrl:

\vl~cre P is in Pa. The dcnsih pd of a gas is given 1,). the pm111ct of its molecular \vcigI~t and its <vnwntl;ltion:

p,, = >lolernlar\veiglitx($]

TI>? gaq molenrles are in mnstant motion and their vt.locitics are tenipcnture r l c p - dent. TIP distril,ution of vclocitics is described by the Xla\~\~ll-Bolt~mann distribution li~\v. \r,ltirh statrs tl~:it for a given spced ti.

where ni is t l ~ r m a s of a molecule. This equation states that if there are n rnoleculcs ill tlir \nlomr. thrrr \\ill In! (/,I mmolecl~les having n hqwcd hehwen 1, and ti + dti. The ax7,r- ace sprrd is ohtiiinal>lp f m n ~ Eq. 4:

282. c H. Bsric Kinetic Theory of Gases

,ln i,,,pO*;,nt paT.LII1et~.r for VRC~IUII I t~d~nologvis tile i~lol~~~tlari)~l/linEc:c))lrnf rnfc. ll,.,t is, I,,,,\. ,,, ll,olrr,,~r i l l lp i l l~r on R init area per unit time. To obhlill (Ilis par:lm-

rtrr, tint rnrahlrr dist~~,,,tintr (,,nctios/;. for tllr vrlocitics ofmolectllrs ill tllrr direc-

tion. f,,,,ction ca, IX. ,c . r l ,~~si~d I,? an erllmtian similar to E l . 4:

tz dv, 2kT

Svtbstitutinrdn. frnm Eq. G ;mrl intrsntins gives

nlr rclatio,,sl,ip~hrrcn tile impinpcmo~~ rote 311,nd the ps pprna~re is ol)tainrd by using Eq. S:

@ = P ( z ~ ~ I P T ) - " (9)

\ Appendix I

SUPREM Commands

Tlw Stsnfonl Uni\.rrsity P r w s s Engineering hlod~ling (SUPREhI) program is n simu. !atinn pnckagc thnt illlo\rs a user to m d e l \sriaos procrss steps USHI in tllr fabrication of intrgmtrd circuits. SUPREM can prctlid the rcsalts ofo~rlation.delx,sition.etchin~. rlilfnsion. epituinl growth. and ion implantation processrs. SUPRE51 Ill mrwlels the clinngcs to tile se~nicontl~~ctor stmchlrr t l~at result from tllesr procesw in one dimen- sirm. Thc priman results are the tl~ic!-mrsses of\arious layers and the rlirtrihution of imp,!. rities within tllose layers. Tlte progc~m can also determine certain material prnpertin. suclt a5 t l ~ e shret resistance of rlilfased regions in silicon layers.

To run SUPHEXI. an input clrck must lw pro\irlrd. This filr contains aseries ofstatc- ments and comm~nts. Tllr rleck begins wit11 a T I T L E statrineat. wI\.~lich is merely a mm- ment repeated on each pigr of the p r p ~ n outpol. T l ~ e next command. INITIALIZE. is a mntrol statement that scts t l ~ e alhstnttr >ye. orientation. and (loping. n ~ i s command ran :also bv oscd to specify thp tl~ickness o f t l~e region to 11r simnlatc<l and establish a@. hfirr tllc sr~l~str;ste ;isd nlaterids arr estnhlisl~ed. a series of statemants is ised to r p c i f j thr srclurnw of process steps 2s 111~y ocvur Finnlly. the outpnt oftlte simulation ~?n k printmi or plattrd llsina PRINT or PLOT rtalementr, reswti\~cly. Simulation ends \\it\\ a

1.1. T11i.q fob/<, i s by an rnenno con~plrfr!. To d)tain t l ~ c complete SUPRE51 rofh\:~re pack- ape i~nd its assnciatctl docl~mentntion, mntact

Silv;~m Data Systems. Inc.

4701 P.ltncli Ilrn~?.Drivc

R~rildirlg 2

S:knta Clilc~. Ch 9.5051

Plto~lr: 409-Cirl-.1372

Fm: 400-727-3297

t~w?v.sil\~aco.mn~

SlIPREhl is a tclde~nark of thr Board of Trustees of Stanford U n i r ~ n i k

Appendix I. SUPAEM Commands 285 . ~ ~ ~ ~ ~ d i i I . SUPREM Commands

TABLE 1.1 Connon SUPREM Cornand.

Ik.cmplnln I$;r5ic S>nt;a I)pical F l ap :and S.<aw. l';nn>m~~tt.m

r r v r u r Olxtll~nts chsnkcl~r st ti!^^ tc CCmENT < t C x b Nanr - .

lllvl m input srclavsn M ~ I T I ~ . it^ ryrili,~l ,n.tctiilI DEPOSITION 4 r e r i n R Aluminum

<,,, top o[c.,m.nt stnlaurc Thickness-<* Tenmrature-<- N l f r i d e Oxldc P o l y s i l i c D n S l l l c o n C.Phorphor (en,.') C.Arsenic (ctn-') c .~oron (cm-') m i c k n e r r (pm) Temperature ('C)

OIFFUSIW Slalrls hi~h-lrmpr;tlurc DIFFUSIc*l The-<* A r ren l c

d;fi,.ion i,, irddi/jr~g and ~ n p e r a r u r e - < r n <mPanh Boron nano\idinac srnhirnts & b i c n D OryO2

N l t r ogen Phosphorus YetO2 S o l i d r o l HCIX (%) T.Rate ('Urnin) Temperature ('Cj Time (rninulcs)

ETCH Etchn qxrifi<d materid ETCH & a t e r i a l > Th ickncr r -em A11 fmm thv top of eamnt Aluminum

~InlClllw N i t r i d e Oxide P o l y s i l i ~ ~ n S l l i c o n Th ickner r (pml

IMPUVr Simulates ion implanlltion I H P M <mpann Dose-<n, Arsenic of i!npr!rilirs Energy-<* Boron

Phosphorus Dose ( r m ~ ? Energy (ke\')

INITIALIZE Sets up initid nrmcients INITIALIZE d r r u c t u r o c S v b r t r a t n <lee, and slnrdl~w to k tncd in <Dopanb Conccnt ra t lon-<m <11b the ~imulittion 411,

INITIALIZE S t ruc tu re -< f i l ename S i l i c o n

A rscn l c Boron Phospho r~s Concent ra t ion (cm-

(ronlinarrl.

. . I'ammtlrm

PLOT Syvilics that impurity PLOT <parameters Act lve mnn~ntmlians or rcrtllL. #,r C M X . ~ ~

clrpth into thc rubrtntr an. to l r plultol

acrm Chemical Net P h o r p h o ~ r Cnln ienn.'l &ax Ic!n-'I

PRINT Olltputs information about PRINT <paranetern Arsenic

lhr rtnlnurc. tlring simcdatcd Boron and ~~n f i c i tm t s ored

C h n l c a l Concent ra t~on LIYCIS Net Phosphoru~

SAVEFILE Si)\'c~ the L.LImcnt StnlLItlrC SAVEFILE <Fea tu re F l l c n a a e - < T e r ~ structYIC

Ir in2 pmr~,sscxl, thc meficirnlr l,c3inp, awd. or h>th

STOP Terminates sirnn~lalion S ~ P < ~ e x o Sonc r n L E lnptnts n character string to TITLE < ~ e r b None

lnlrl thc follmbinq input

Running PROLITH

~~~~. ~ ~-

optic21 litl!ogr;q)ll) proccss from acrid image fr,nnatioa t l ~ r n n ~ ~ I ~ rwist cpponlrc and dmpl. O~IIIII 'II~. T l ~ r n11lp111 of t l~e pWl~n is annnn~c~trpmlirtion ofthe final nsirt pmfile.\\hic\, is prrsrntctl in ;I \ridr \arirh.orinl:tees. plots. gmpl~s. and mlnilntiom.

r 8 . , hftcr tile sofhvare II~LC IWPII iostallcd, a usvr can nln PROLITH by simply clickins on thr PROLITH i h n from t l ~ e \\Tn(lo\~+ Start mcntl. After a s~tcccssf~~l linnsr sc:~rcll. ~ I I P lrnaenc Tool para~nctrrs windo\\, :tpwars (FCC Fie. 4.20). Refore nlnniae a sie\d:ttion. . .. . . the llsrr must choase the simulation options and mter a wt of input pmnnPtrn. This is accornnlisl!ed I)!, selectine Ootions from thp File menu to onen tltr Ootions di$o~. Tltc .- , 7

srttines in this dinloe lms are ucpd to e5tnblisl1 hasic simulation options. snrll C L ~ ~ I I I C . Imace

. boxes or option bt~ttons, enter ineial~~es in t r x t boses. s c l ~ * i n ~ f i l r s or othrr val~a.s from lists. arid so forth. hlany parameter windo\\s, sucl~ as t l ~ e Resist paranleten \\inclmv, for c.xnnlnlr. nro\ide instant m.lollic:ll \imr.s of tile infonnstion cntrred.

L . . v ,

After input paranlcSte~.; Ila\r l e n cnteml. PROLITI I <li.spl;?\s cinlol;ition results rmrn t11c Cclpl~s menu. PROLITH mn p.l.lpl~s simnl:~ting forn~;~tion nf a m;ak fc:~- lure by ;in optical projection .ystem. eqwsure of pllotorrsist alsillg Illis inlnge. or clrvrl- optnent of tllr evsc.d photoresist. The follor\in~ options from thr Gr.~pl~s mrnu ior mrrrspnclinp tmll~ar btnttons) ar? :l\ailal,lo to displ;~!. s11r11 simtllatinns: . Amin/ Ismgn: The relative intcnsihof tltr i r n a s ~ IU P It~nction of psition

Inlnge in R ~ i s i : rile i m n ~ e prnjrctd into thr pllotonsisl at tllr start of expSltn

Exi>o.~r,/ I ~ f r n f Itnngr: The Intent image 1)rfon post-c\posuw hskr (PER) r PEB I n t n ~ l In~ngc: The 1:alent imasc ;Art pust.rxp%urr bake

Dccc/ol> Tinrc Co,lc,rrrs: Contours of mnsklnt clmrlop time ;LT a ~ I I I I ~ ~ O I I of positioll in the resist Herkt PmJilr,: T\\a-di l t~e~~sio~~aI photon~sist profile :tftrr dc\.elop~nrnt

ezp c &pmdlr J Running PROLlTH

ni< m p n , r \ , . a r p ~ ~ ~ l ~ ~ ~ ntpaI,iIitier is I>? so nlelns rr,~nplrt<~. TO obtain tltc run,. ,,I,.~,, p R O ~ 1 ~ ~ 1 wh,nrr p7dt,gr its ;ssocintnl doctr~~~ent~ttion. cwntrct

FISLE Twhnol@n. InC.

PO. Box 162714

,tttstin. lX 79716

P l ~ o n ~ : 5143?73751

Fax: 514327-1510

Percen tage Points o f t h e t D is t r ibu t ion

Z90 . ~ ~ ~ 8 , ~ K ~ ~ , ~ e n ~ a g e ~oents olths r Distribution

Percen tage Points o f t h e F Dis t r ibu t ion

= 5 - .- - i

'4 b - 2 - . , - 2. z .$ ... '~

a - .-

4 . , - 2. - - - i - = . -

c rn

- w ?. - t 7 '7 - T s - .- .- - 5 " . .2

2 - c * < .- E

Append* L Psrcentnge Points of me FOintibut~on . 293 r A ~ ~ ~ ~ ~ x L Percentage Points of the FDinribution

8

-

4

= c ,

- - ._ = - - = - - 2 - 2 - - - c - - - - *

srcg 5 , y p s ~ fs4?% S X R ~ X SRRGS %Sf33 32925 __,,., ----- ----- ----- ----- ----- ----- . . - ,-,-, ,-,lrrs- =go-- 7T-= r , . e l - L * -.,TIC fi%;1~2 3 3 5 % r;ws~:? -4aS:s ----- ----- ----- ----- ----- ----- - .

nanuzat E S ~ ? z;ess s;T$~ snsaa aaqqw 53GL;s %--- _ _ _ _ _ _ _ _ _ ----- -dm-- ----- ----- - .

z-sg ~~~e~~ ;$F$= g!- js~;~ RSsa3 @845S E$Ss? =-"-, ----- ----- ----- ----- ----- ----- " 3 ~ 6 - . S:?~SX 3 7 7 7 BA!-j$4 S$s%z Z4935 %33%% 2-Q,F> ----- ----- ----- ----- ----- ----- s-ns szsz? ZmqsF =gpgx aam? g ~ s S 3 ?@?a: ?,., ----- ----- ----- ---- - ----- ----- %$S+ ssgzs sesqq ~ 4 ~ ~ f i 3 ~ 3 x 9 as%?? ssaqs --**, ----- ----- --L.-- ----- -----

--r.m* C,-,--N 2255 FE$g$ ZBS!?; ?q?Wq fifiSg3 ++a<- - 5 " " ~ SC^,r , ----- ----- ----- ----- ----- ----- =zsg $[:grs zz$%Y $3==4 %$sgx Ws%f$ fj;;WZz _^.,^, _ _ _ _ _ -_--- ----- ----- ----- ----- -. .

,,,, ,"?T% qN-'" Lo---- C55ZX Ct-CCC S??$,W ^r-= <,,;L.. L.,c*j- - - - -9 - -F~; , <-*-a , - " , - i ----- ---- - ----- ----- ----- ----- sszz I^mm ----- $ ~ s g : ----- 8qzq? ----- ==Rz$ ----- 4!5$!53 ----- Rf;ZJG

"7VTC 8-L-N-f 3r - r 3*3rq qC-OT -<-=, ,,-,:+L, ,;<",-- % q p q ?=?=$ -fie-- -e.***j ----- ----- ----- ----- - ---- 02"X 3230- a--0 cO-.n* m - c - n -.;-: Y,l,7;rg gE$z: $-F?I/(L! 9---- -e?3511 <ii i*. i ^^",* __-__ ___-- ----- -_--- ----- ---A_ $=2$ ZFFZ; g3g;q FqFy; 774?' =Ss4= gCPx %""N ----- ----- ----- ----- ----- car-,- 3s--ca -en- 5 x t - e ~ sn---c mew-- -5,-93 ZN-= 2%4L,L? y---- ----- . . . . . ----- . . -<"- . ., P'00 ----- ----- ----- ----- -;--- fq"1- ""NP'/ 51-92? F^^iCI- I-CDlh- -3000 CIOSI-2 a c c c 7 z,:,-,L+ ,?L?L.,B ...., **+-- --7-- ----- -7-..,<... ,̂ el?, ----- ----- ----- ----- ----- -;---

-. - P

-

:

3?2? EYGZi? %$s%% ??:%?? ZZ!;:~Z :;%~cq ~ ~ ~ : ~ , ,73"?" r r r c , ,,,, c , - - - - ----- ---- ----- ----- .izzz y ? z % ? , P $ p ~ Cl.y!& 5gz.g:; sz2,:2z ~~>~~~ r;?on- r c ~ r w r e i cncl--- ----- ---- ----- -_--- L

5,-,0* ,---,: ;if;?;. =)%SF ca=tnel= esa.8- - I -=~I - " - t - c - r - CC-G,Y *.%CI,I :- tt--r.c,

FI* ,Srn I"l?lrlr, C,'1--- ---.-._. __--_ _ _ _ _ _ ----- c

2 5 ~ 4 y a s q s g ~ s ? B ? ~ ? C p e 5 8 ~ :;;3sq e131.̂ - - * I F , O , ? , FI* l - - - ----- ----- ----- ----- c

WP'+P SPqqQ FZZ3$ g?;?E, ;??36 pszzg Z X % I f e l z i m m DOI-IFI-I - I ~ ~ F I - - ----- ----- ----- ----- .L

89;s szZq4 ZZZ8S 893;: f;ccEE Z.%SZ$ 2:;~Fs -- . . cl31m- *.?,^,elel eieir,-.- ----- ----- ----- ----- , 7733 aFq?q 5 3 2 5 43g33 CEE;~ b ~ ~ g z , s,za=q z3,1r: -c,+,cro, c,e,o>^,- ----- ----- ----- ----- C < - < , z GIN=,- ;;%$Ff ?'+E3Z %35%% ?%%;+ ::gczF ?;sg:!q -i-,*-̂ e r , o , e l c , 'INelrl*, ----- ----- ----- ----- C

?=:I% & ~ ~ 3 q ~ ~ 5 3 5 z % $ q z:??.~ r:F%z:? z""l ""'*""' c.'"""'"' "---- ----- ----- ----- SlaCC, - - 3 - 0 3 - r?? i? ze,:*- %KE;Z zzgsg ssg95 %$$Z? FgF$z. $sL0- or>*o,n, El'jl*,Clei FlOlr l - - ----- ----- ----- =*-.. <-** ?%?!%$ q:i;J;(S: 8283s SZ345 ?F'&%~ -̂ .?,or? CCIN'IC, OITICICIC, CIFlelFI- ----- ----- ----- lr

::gg csz,sr rasse svssa sszsz. z % r . ~ g zizi,.l oclcrrle, e,cro,a,c, NIlolND, * I - - - - ----- ----- I ^

:.. --I

- :

:

i - - -

= - i

a N

- <% - - - - -

x 2 = - - - . c

i! = :; , $ - , ..- - z

7 - = - A

i

;= 2 i -

,

-

% . ~ ~ ~ ~ ~ d i ~ L percentage Points of the FOMributian

8 :i- t- s Y ) o * q %*--' "92"' m"mYm - 1 -$SF? SF367 ~ ~ q ~ N ---- --.h?k + . .?+ i:CL?a'.C

= / -_r,> D I N N N ~ d ~ i e i c ~ ~ ----- s- L % 3 ~ ~ ~ ~ E S P ~ $%s=F ?=$IS 283sP 3?8%?

--,, -7-CC, ~ i ~ , e i ~ i & ?i&fie i& NFI--- ----- ----- 3

- 2s - L -

s= zz;?~ xzars 8338$ 889% PCgG? ,,,, -ccnor a N C r r r r l N C l e l C l N

N0IF IC) - ----- ----- -- ->

,+$$ gzzrz p ~ z y g gsgn: r-czpg tp$pz 8311SG ,:,,-. ,arcc. ci"erc,N N C l N C l N F l F l C l C l C l El---- ----- n

e - .- ,-,,- P N N r ~ =%-+c O ~ Y ) O - CIP 2 =*l-m!- ,-.r e=nc!= ,:+,e- . "---- 80-5, -3al:e ,,,, ~ ~ ~ l ~ c . 2 N a ~ e l N C I N e 3 N C I NOIC1OICI me--- - - 4

b ~ " ~ e -"a?C $Nz-- W3732 W Y ) O N C 9?-01Ca3 f - - ,,,, ,-,,-, ar;%+fi ~..,+q *"- ----- -E+%l: . NN'IC,N ~ i 0 l C l N F l NCI+IC,CI F I F , F I N C I ? I C I - - - -- 2 c ,

. .: - - .*-

.z = - i- I - - Z ,L.

( * 5

,

- 0

8

- 8

?%?f &=$?? 8!3zTk2 32454 95X44 $g3$q ;??%$, c;.=e ----r, 0crercrci N n l e l c r c l EIN(i lNC3 F I N C I N F ) N C I N - - , --

- - I - m t C C o D I - &5?5 F2s;q q z F g Sg?;? zq=ss *qqo!e) o!--=?. T S T C --O-(? O E l C l C l C l C I O l c l n l N E l N N N N E lC lC lF lN C1EICI-8- - - +)

:;?$% 2 ~ 3 2 ~ Tszqa a??=? ?%zwq aarez I

e - 1 ~ ~ --n--. o - c l c l c r omelcanr c t c n c r r r n t ~ c r m e n ~ m m r l c : r < -- 5,

085s sasqs qss~z ,:,??3e sGsaa p%77 qzs53 z z C % -Tar-: C i O a O l c l CICICIF!C~ F ~ O ~ E I C ~ E I C ~ N C I F I F ~ CICIC191N

?,

*,-3- ,s5: ?W",2 r.g==r; 3S'SiZK;i F%@":?$'Y;3 &-c!c! =5?C .^T*^r) COC???FI ^ICIFIEIC, FICI*,',N E l C l C l C l F , C I C I ~ I ^ I C , - - r>

*32$ zqq22 ?3%z= s:%s% gzg3c ??$??? $Z3'+.3 - 3 1 1 5 r^---* 5 0 7 e C ) COFlelrl F l O l C l F l F l CICIC1NFI Cl.72CI"I')I -1 - q t

cs5z =cqgq Fag=? qxgss ssszis e$gsg $3?sg ,751-T ,?--TI ~ o T . C ? 1^1100 c ~ o - ~ c : C I ~ I ~ ~ ~ I N C ~ C ~ C ~ ~ I -- - 8

-2yz ""TWiC 0 2 m " -.;-. i:-tr-p! -7C<~: 23g3: SS843 23ygE .- s p s e nr--- ~ = - a * P - - ~ ~ &+&a- oconn ooooc -. - :,

:\rlv:inn4 isol:hli<ln tcrht~<,lop, 207-204 ,\I!trni!wr~~. 14.1

rtcl,ing. 83 ~n~.tallimtion. 169-173

A m n i n ~ ~ i ~ ~ n ~ fluori,lc (Xl1,F). S i A r n o ~ l ~ o t ~ s silicyt. 43 As;d!si< of vnrianw (hNO\J,\)

lid>l~. 2JT+%I6 tc.chniqt~r. %.>%@

Annraling Imrnn ;tnd pl~ocpl~ams. 134 ctpid t l~er~ t~ :~ l , 135136

ANO\':\. n. An;,l!~is of \.nriancr (,\NO\'A) .Anisotropic ctcln prnllles. 92 APC\'I), i\trnosplleric pwsswe C\'D

(,\Pc\'r)) hrca drfcct .% Aspect ra t ic~lepmdcnt rtclling, 99 ATE. sn. r\otornsterl test rquip~nent (t\TE) At~nospl~eric prt.ssl!rr C\'I> (APCVD). I45 :\tt"bt~trs, L3i hutomnted test equipmrllt (r\TE). 2%S :\t~totrrohilr iedrlst? 1

B:111 grid Array (BG,\), B l R;firi,lnt strnntillrll titnnntc (BST). 164 IK:,\. .vrr B:ill grid army (B(:,\) I3iCSIOS t<.cltnolo& 210-21 I Hilx,l;~r tcu.l,aolop, ISS-195 Bipjl.~r tr:t!idstor. 5. IS9 111:tnkct rtclles. 85 !?oron. ewn\.entional anniealing of. 134-135 h,m: :3? I5rirlern;tn tccltniq~a. 6. 30-31 BST s m B:trioal strootiem titanate (RST) 13ofk,rt-d I IF soltrtion (RHF). S* 1311fft~e1l oxid? etch (BOE). srs R I I N C ~ P ~

IIFsolution (BII17) Bulk ~nirroalacl~ini~~g. 215

C:\D, srr Computer.:lided +sign (CADI C:lpacitan~~,. I@?. 186, 201 C ~ ~ ~ t ~ c i k t ~ ~ c c ~ - ~ x ~ l t : ~ g ~ ~ t(vltniqc~e, 114 CAR, src Cl~emic~l-;unplifiecl resist (CAR) Clrlmn conwntntion. 36

I

< - .: 2

- z %

L-

pw . hwl~,i. L percent.~s Points of the FDirtribution

'3s;~ i j ~ ? ; ; ~ $N;;z S C S 2 3.9SA5 : - - - - - _ _ _ _ _ _ _ r _ - ..,mI.Ic I~ C a r a ~ l * l C I N F I C I * I ^ I *I---- . - ' ' -. -

-? - - -<*- - ----+ *2.-,,-,p,T2 c,..a.., ?,C8 c8*3c>cac8 ?aw-- - '..?- - -

- zrrg s E ~ ~ ~ i z x ~ g g g ~ b ~ ~$,?93 Wl3SR Z23FS ? '. ̂- . -- - , . . - I -- __^,^,?, N,.,Flrl*I F l F l F l C I F l C I + I - - -

- - .:;- -

- - - rCc,cln ~ n - a n ~ e a cael-rxel -*I--- ,>?:- '2

- , la3z? 33es3 ~5393 ,?@$?4 5%?1 %88%? I = - - - r-F-can ? 8 ? a ~ l l y C I C 8 C I F I N P I EI^ICI-- ..-- , - -

??!%= ==%g$ %3$%$ RI-NW %W8S($ FgZZ? x-cL.G ---- - C-CC- FC--C C ~ ~ E I C ~ C I elclol^lcl

31-r-t-FI $Z$S5 Fg$;? ??%&'$ 3 T e - e

, - - =I-il-,7 --'-- -C?^F -*?-c c----. -2-ocar8.r - - - ,..--,- - .7 - -

1 ji.5z -,.., -?,. =,> L-L?--- %$YE.? l,?ii~l ---- i-ici;g ??---- l P 3 E I *--_-?? q ? I I V i O - - T l - 4

(CRE). .we CIl~lllicaI Iwiinl c.pi(iw (CRE) CCI). arr Cl~ar~~~-cnopln l d v \ i c c . ' i ~ ~ ~ > ~ C-cl~;irt. see. I)~r,.a eltan iC-d,:,rt) CD. riw Critical tlitncnsion (CI)) Crll prujc.rtion. ii Ceat~ l l prwvssinq onit (CPU). 8.203 CF. s ~ o CnrTMli~z~ FdCtor iCF) Chanstop. sre p+ channel stop C11:qe-cnaplcd drdcv (CCI)). 5 Cl~r~nird-:cmplilicd rrsiqt iChR). 70 Cl~en>icd br;t!n rpitiry (CUE). 15.2 Cl~enniral rtc.l,ant$. %5 Cl~ernicnl etcltinq. 92 Cl~crninl inar11:kicll polidling ((:\IP). 3.

100. 17.2-175 Chrrnic;d \.npnr rlrpsition (CVD). 14. 50.

RS. 14.5, I63 for g:<llium nrsmide. I. mrkllargailnic. 147-144 for silicwn, 14.5-147

,

-

silinn oxides ;tnd diosidc, 156 XN. 169

I-5r4- - 4-

=~,3:3 ~ ~ s 2 2 zqeso ~ 7 3 ~ s:%zz W F ~ C Fax58 _,,,? ,,,.,, ,,,,,- ----- ----- F - l C r s ??-C-r - , . .- ,:~sg Zsyen 367~5 eF!iaq ?fi+Zl Zz=ks g???: r-r,- -=,- cc ?,? ----- --.?-- --;- -*---: -1 5 -,- -

1 5

tungstm. I69 Chip sc:~le package (CSP). %?2 Clear1 rnnm. ilnportancr for lithngrap'

w i 2 Closr proximity printing. 62 Cl~~stcrctl plwna p m r s r i n ~ 07 CLIOS. scr Coniplcmrntan 3lOSFET

(CJIOS) C3IE src Cl~nnical nirrh;mid lmlid~ing

iC3IP) Col,alt siliridr. 176 Con~b-~ncatidrr-n,mb stnlartrc. 228 C ~ ~ ~ n p l r r n r n t ; ~ n \IOSFF.T iC>IOSl.

1% techtiolnq, 20:3-205 \<,all of. ?I16

Coznl>utrr-aided design (CADI. K5, 5 6 Cumpulrr-inleqtrd msnllf.lrturitt,: '4

integr;itrcl circt~its (IC-CIhO. 2jw257

Conc~ntr.~tion-d~-~)rn(I~nt cliNt~sititv.

=?*s scqzg t?:!g;r% q*3-gs gz???! zzo:;;; ;;;;5-;'-?:: rz:.z ?,srr.; er,rlc,. ,:r?,r,̂ r? ----- ----- -r--?,1 _ _ 7 , - - -*- ,-ex"- ,E-Z ?,,dpg szggq %?=;? 2Eyeg 6 ~ m 3 2 %?Srs

; ; z z S 5 " C C ,.,'"" C.*"C,' """"" ,t"LIL*,S -up---

- ,$%ss s:?sws a2o5r e$swx ngqs: ~:;gzz ~ 5 ~ 7 2 .LC*,-= c--c.2 zrr lr) . T C I-,.,. ,.,-,-,-I- r - 1 - , - C.- I :>ss;; ----- - - , - %?(S,-*J ^-el??- ,?.*,-1Ca , G,-r- '>" ----- ----- ZZEI3.7 2,,0,,1;i z-ts - 2

i'm ,o1n,,,,.,,,.y, >ql,", ,anp..uj p, ea.uP1.7"

IISII;. 114 Coofonnnl step m v e c ~ ~ r , 159-lffl

:9F c l d a r

c.,,,,,t.,,,t S,IFI& mt~wntn~tinn. 1 ~ 1 1 1 , ll+ll!i

C6bn<t.+nt t<!t.d <~01h7111. 11 1-112 (..-,,,t.,rt pnv~tinc. +?a c ,.s,, ,,,,,, ,,,s.,,y,,l, , .LT~> p w r , 5 ~ - ~ , , ~ t n d clt:arts, 237

I;,r :,tt"I,utci. 237-39 ~ , ~ ~ , ~ l ~ l ~ ~ s . S'W24I

c o p c,y P ~ , I Y . ~ I ~ C ~ ~ I ~ I ~ I ~ ~ ~ I I : I C ~ ~ ~ I I ~ ~ ~ - ctll!I.;arnI.~t~ (COP)

C0pp.r ,Ce' . IlSJ. 161 il,t,~r<nl,lllYi. s ~twt:illk,.~tion. 1 3

f i ~ r r r c t i ~ ~ ~ (.~ctor (CFl, 113 ~ p t ; , .$,.,. Crntnl p m ~ i n g txnil (CPL'! Critic11 divnmsionl ICD'. 63 (:ritic.al I . y r t l~irknrs. 1.72 C n ~ t ; ~ l drfwts. 5-15 Cnst.J p ' \ i h

Tit;~u:d pv\mailb and. 14-1 twhniquw. 30-31

C p ~ t d p~~ller. 1% cSP $0. (:hip scde p c b e ~ (CSPI C\-I>. rcc Cltcrnicnl \ a p r (leposition

(CVl>l Czoclm~lsk technique. 1 4 . 3 W 1

D;~rn:~wne t f f h n a l q 99-100. 173 Dwp-lrencli isolation. 207 Drfrcl rl~art iC-ch;trtl. 239 Defrct dpnsih cl~art (IT-chalt). 23.9 Dc4r.ct.fwr zone. .we Denuded zone Drmm of frrrdom. 243 Denuded zone. 3 7 4 9 Dr~x>cition

C,tIS, If35 sintsl;ttion. 177

Depth of f m n (DOF). &5 D ~ s i g ~ d c.yriment. 242 Drsi?? matrix. 24fi DIRL, scc Drain-induced harrier low'ering

IDIRL) Dicldomcil;me (Si Il&12). 145 D i r l ~ i r i c (lepsition. 15%165 Di~lrctric rtrhine. 99 D i e l ~ t r i c isolation. 192-193 Diclvctric I : t y . 41. 144, I f iSl63 Ilir qrpnration. 230 Difhction. fig Dilll~vrl layers. oaluatioe of. 113-114 l),!'l'!,.C~l ,v"II, 206

mnstant. 51 equ:ttion. 107-IWJ e~trinsic. 114-1 L i intmltldory llole. 1 6 1 0 6 ion itnplantation and. I4 la1cr;d. 1 IS-I20 p m s s . 106-1 14 pmfilrs. 109-112. 114. 117 in silimn. 117 sin~tali~tion. 120-121 theory fi

I)illitsi\it): see DilTosion, copflicient DIP. srv IIII:II in-line packace (DIP1 . . Dislomtion. SLT Line defect Dis1oc;ition bps. I,% I>OF. src Depth of foctzs (DOF) Donor \:IGIIIC): I15 Dopant

~lirtribution of. 19-21 impurities rrdistrihation, 50-51 profile of the dillrzsed lnyer. 113-1 14 se,qreption copflicient. 3 0 3 1

DOIIIIIP d~arpcd a m p t o r \FIcRnC\C 115 Doal~lecoml~ stn~ctt!rr. 22s Doabl~-p$silicon stnlcttlre. self-aliped.

19.3-195 Dmin. 197, 200.206 Dmin-induml barrier lo\rering (DIBLI.

2ns DRAJI. see Dynamic randoor acxvss

memory (DHA.\ll Drive-in dillusion, 112 D n etching. 71. 89-90 D n oddation. 12 D I ~ I in-linr package (DIP). 270-231 D>namic random amcss inevnun.

(DRAJII. 8. 11. 164. 199-200. 2&'2rA

E-beam lithopplly. .st!<, Electron heam litlinqraplty

ECR. sce Electron c?clotron rrsonilnce (ECR)

Edge dislocation. 23. 151 ECS. spc Polycnstalline silicon (EGS) Elrctrical testinp of integrated circ~lits.

""--"2rj -- Electroluminescence phenomenon. 2 EIectromigr;ltioa. 172-173

Elrctmn ilr:lnn litlqrapltK 73-76 Elvctron c?clotron n.s~r,~,lcc (I:CR)

~I~L$, ,u, etcI,ins, 95 Elcctro~~ics in~I\~slry, I Elrctron resist. 75 Ellipron~ctry 54 Emiltrr. 192. 194 Encl-pint control. 93 Epikuinl gmvi l~ techniqurs. 144-152 Epitmid la!ra. 1.44. 145

tt-hlw, L9O&L91 stnlcttlr?s and dofccts in. 1.52-1.54

Epilminl process. i. 144-145 E p i t q 7. 144 Equililrriurn segregation mefliricnt.

19-21.30 Erfe dirttihution. 118 Etdl

mecllaaism. 91-92 rxtcs, sinlulation. 101-102

Etcltnnts cl>emical. 85 cummonly used. 8 i

Etcltrs. Illaaket. kj

Etching alnminum. 89 ;aspect r a t i d r p d e n t . 98 cltcmical. 92 ~lirlectric. 99 dry i l . 89-90 vquipnlent. 93-94 gallitln~ ;~nenidc. 8S-89 intrrconncct metal. 9S101 orientcttion-rlrpndmt. 8fi. 87 pl~c~tolitl~ogc~pl~y tmd. 13-14 pllysical. 92 plum;^. 91-92 I~olycide gate, 9%99 pnlysilimn. 88. 95-99 silicon, XT-37 silimn dioxide. 8 7 4 9 silicon nitride. 58 silicon treacll. 97-95 single-cnstal si~imn. W , . , \\.rt. 88 x r t cltrmical. 8-9

Etching, pol!rilicon. srfj Pol!silimn, e t c l ~ i ~ ~ g

Etchin< sin~le-cqstnl silicon. sec Single-

Elcl! late i~~~i formi t~ . 85 Etch-reri-tan1 plymen. 6 Et~trciir tempt:ratun.. l i0 EUV lilhwnqlll): rrc Extreme ultraviol~t

(euv) Experimentnl drsiqn. stati<ticnl. 242 Exp,suw tools. FZ-6; Extrc~ne i~ltra\iolr~t iEU\') litlrqr.tphy.

7%78 Extrinsic p* bzse rruonr. 194 Extrinsic ~IiK~tsion, 114-117 Edrinric st:ackise litult. .%I5

Fnhric~tion steps. i~ltcplated circuit. 19f~19S

Factorial rqwrimrnlal drsims. 246 Fenni Ievd. I I6 F i c k rlill~lrion equation. 10i Field osidr. 41. 197 Filrn ~lcpasition

dielcdric, IZ5-165 epiti~xial gro\\zl> twhniqurs. 14&152 ~nrt.dliutiun. 167-lii pol!siliron. 165-167 simal;~tioa. 177 stn,ctar?s. 152-1.54

Filna. 144 Rats. 31 Flip-chip bonding. 23.5 Floatins-gate nonvolatile menlon 201-202 Float-.zone p-ss. 94-33 Four-point pmlw lecllnique. 35-36, 113 Fractional factorial drsim~s. 24-19 Frenkel d r l t e . :X Ftmctional testin$. 238 Function;~l !ielrl. ?jB-El

Gallium anenidr (GaAs). 2. IWJ chemical \ a p r rlrposition iL17)) for.

I47 cpstal p w t h tccl~niqaes. 2 f d l e t c l ~ i n ~ . S3-$9 ST. silicon. 32. 212 zinc dillitsion in. I l i

GII~C oxide. 64 oxide I L I ) ~ . 41

Gate c ~ ~ @ n ~ e r i n q t~chnolo~\ ; ?0>210 Gatassian distrihntio~~. 114 Gennanittrn ICP). 3 Gelterin$. 37

HI)P us. tli~h<irndhpl:snla IHDP) l l ~ t ~ ~ m ~ p i t . ~ ~ ~ . 1.14. 132 ~ , . t , . r n p t ~ ~ ~ ~ ~ ~ m hipo1.u tmlsistor. 2 l l , . t c ~ ~ ~ . t n ~ ~ t ~ ~ r t ~ l.~scr, 4 l l ~ . ~ . ~ n ~ ~ ~ t l ~ ~ l . ~ l i ~ i l : ~ ~ r ~ e (IIhlDS! 70 IIF ,,.,. H\clrnfluwir. acid (HF' flrrll~lc.r~$ih l,l.rrmn (IlDP' ctchem. 'a.

Y>97. !i?l Ilid~-dtt~l.anr-n~~~sI;~nl nntrrids.

I M l f i i H ~ S ~ C I I I . ~ ~ md lki$hcumnt

inbpl.tntatio~n. 13!&140 H-line. 65 II\!L>S. .wc Heamrt l l \ i -d i~ i l ;~~ne

!HSlI>SI Ilomorpi1:y 144. 152 Hprlrntlaorir acid IHF). Sfi tl\pnthrsir lrst. ?A?

IC-CIS!. .sqr Computer-intrpted n ~ ; ~ n ~ ~ f n c h ~ r i n ~ of intrqmtrd circuits (IC-CISII

IC msnttf:tch~ring t rchnolq. 80-31 ICP snalrrr. s w lndnrtivel~ mupled

pl.lrm;i i.lCP1 s n ~ t r c ~ ILD. ur lntrrl;+!er cliclrctric (ILD) I-line. 65 Irnacr n.itrm. simple. Mi ISII'.\?T diode. 5. 15.7 In~plimt dan~ape. 131-134 In~ptrrin. ~listribution. 113 Ilnpllrihdnpinq. IU5 Impurih rrclistrihstion during oridation.

,-xi4 1 Ind~rctivel? couplrd plzmn iICP) sosrce.

I)i

In sit18 doping. 167 In tqn ted circuit (IC)manufacturin~

mmpot~r-intrp.aC.d. 2-%277 elcr.tricll testinq. E i -22s ptckqing. 229-Bfi s ta t i~ t~cd rxprritnentation drs ip .

242-249 statidicd p r w s s cwntml. 237-241 \ i d . 2-+275

Intr~.r.ltPcl circuits (ICr). I. 7, 192

nplcitnr. IS5-187 intlltctnr. ISi-ISS ~nonulitl~ic. i p;tttmt lr.tnsfer, iO-il ~.sist<,r. 1st-IS5

lotrnnnnrciions. 1.1 Intercvnnrct ~nrtill clchisp. 99-101 Intrrfim. drfrcts, 15-1 Interlayer ~lirlrctrir (Ill>). 173 Inrrntntiorml fir./tno/og!l Ron~/~t~o)~/or

S~~,,rin,nrlttcf~~n. (.'A. 1999. SO. 259 llltrnlitial dilTtaion. 107. 108 Intrinsic Ixwr rcS@<ion. 194 Intrinsic c:trrier mnrrntration. 114-1 I5 lnlrit~sic difi~si\ity. 1 IS Intrissic stacking fault. M 5 loll

clmnneling. 13&131 ~listrihotior~. 125126 stopping. 127-130

Ion Iwam l i thoqphy i9-90 sputteri~lg. 167

Ion implantfitinn. 'iO dalnagr and anncalitlg. 1:31-136 arid difi~sion. 14 nrlge of, 125-131 related processes. 136-140 sin~~~lation. 140-131

Isolation trcllnolo*; advanwd. 207-209

Jonciion deptl~. 113. I l i Jt~nction spikins. Ifi9-I72

Kinetics of gro\!.th. 42-19

Lqe-w.de intrpt iol t (LS!!. 1.54 h e r dirxles. 4 L w r interfrrometn: 93 L?tcl,"p. 20.5 Lltrral (IiNusion. 11,%120 Lateral oxidp isolation. 191 Lateral s t n , q l r (a,). 125 Lqtticc disorcler. 131 Lzttiw-matcl,t.d epit?, 152-153 LCL. scr Lower ~ , n t m l limit (LC[.) Ira11 zircimium titanat" (PLT). I 6 4 k w l 1 packqing. 232 Liftoff trclrnique. 7fJ-il LIGA. .XP Litl~ognphic. galv:nofomit~ng.

ahforrn~rr~q (LIGA)

Litltngr;q,ltic ml~rllocls <",l,,p:,ri5o,l ol. SO-'il nest-gl.m.ntion. 7.3-80

Iltltngrnpl~y prwcss. 5. 6 LiftolTtvrhniqttr. 70-71 ILBC:~~ oxid:ttior~ of silicvn (LOCOS), 191.

I97 LOCOS. Local oxirlntinn of silirns

(LOCOS) Long-tllro\v spultr.ring. 163 Lov-angle gmin hn~ts~laries. 1.W Lo\\.-di<.lrcllic-ci~nstnnt (10\\.4) insul;tlon.

26 l Lr~%v-~lit~lertric-(11r1sti1nt mnlerinls. IR>LM ln\t.rr cx,ntml litnil (LCL.!. '277 Lou. pwss~tre rhrn~iml u p o r ~lrlmsilion

(LI'CVl>), 101. l4,5, l,55, 102 LPC\'D. scr Lo\\, pressure chrtnical vapor

~lrpositinn (LI'C\'D) LSI. spc L;irg(..-scr!lr integration (LSI)

hlapeticllls ~n l~ancr ( l rr.adive ion etching (hIEHIE). 00

S l a p ~ t r n n spottrrinx. IF$ Matin rffrct, 247 \l;~qk-lx,;sr, ~\s tcrn. 80 Sla.;k <lnrnacr. C? hl;rslting

~ ! d t i ~ l ~ inl~lttntation itnd. IOC+IRS o~idc . i prnlwrtirc of silicon dioxicle. 51-52

\l;~sks. &i&i. 79 \ I H I . , wc Slolec~~l:~r hr;trn rpita\y (hlRE) hlp;oalc.r .;tn~r.t!~rt.. 2.27-??R SII.;,~~ ire,. p;ltll. 1.50 \!<.art square. 24.15 \lc:m tin,. to F;iilarc (SITF). 17.7 S l e t I i n e ~ - m ~ r p ion in~plantor. 1% Slrdiilnn swlr intrgration (XISI). 1% >lelnor\. dr\.irzs. 1%)9-20:1 SIEhIS, WF \licr<>t.lrdn,tllrcl~;lnical

s)strlns (h1ESIS) hlEHI E. rcc \laqnrtically enllancrd

rr;sliw ion clrltins (hlEl<lK) hlESFET. .st,,. >lrt;~l-s~~znicnm~~I~~ct~~r fivlll-

~ITrr t transi*tor (\ll?SFlYr)

hlrlal.~,vi~l~~-s~~nimn~I~te~r fieldcNrct tnnsislnr (SIOSFET), 4, IS2

I P C I I B O I O ~ 01. 196 hlrhl-o~idr..remi~~~r~rI~~ctor (SIOS)

capacitors. I'ii-186 clr\irrs. 53.9s

hlrlal-srmicond~~ctor firldcNce tnnsistor (hlESFETL 5.3i . IS2

hlrtal silicirlcs. 175176 hlicrn~~cdromer~lit~~ical \)*lrms (hlEhlS).

21'2-014 tecl~noloq 213-214

\licromacl,ining. ssrlace and hulk. 215 hlinimum d ~ \ i c r dim~nsion. 250 hlinirntt!~~ feature lrngtl~. .see hlinimum

cle\irr clitnrnrion SlhllCs. x r Slnnolill~ic micro\bave

intcpmtrd circuits IhlXIICs) hli\'OS. st.c Slrtal-nitride-o.;irIr-

semicondt~cior !SINOS) 14ohik ionic d ~ a r ~ r s . 54 SIOC\W. rn Sletdorpanic chemical \ a p r

clrposition OIOCVD) SlOC\'D rcactor. 14% SIODFET. srt, M~lulation-dopd field-

p a c t tnnsistor (SIODFET) ~ lmlu la t ion-do~d field-efirct transiqlor

(SIODFET). 5 Slolrcular I r a n rpit;r\? (SIREI. 8. 145.

14S1.52 hlOhlHE. see hlelnlorqanir molrcular

brmn epitm? (XIOSII3E) \lonolithir IC, i ~~ooolitll ic e~icm\r;~vc intepr~trd circnits

(SlSilCs~, ,5, ISi, 212 hlonte Carlo sin~elalion. 2% ~ I O S F E T . srr hI~ta~-odc~r-~~mim111~uc*o1

field-effrct tnnsistor (1IOSFETl h1Sl. .SPO \ lc~l i~lm smle intr~.ltilln ISIS11 SITE as,, \lean lilnr to ~ . ~ i ~ l l r e i\!TF) \lldtiplr innplanlation alld lll:~kill

13C+I:33 \ f~~rp l~y ' s !ic,lcl inte<r;iI, 5 2 - 5 4

OES. rw Optinll pmi'rion SpN'tfnSmp? !OES.

Oltmir mnt:ld. 14. 144 Or(: r w Opticd pnxitnih mrrect io~~

( O K I Optical r~nission sprctmunpy IOES). 93 *tictl litltomtphic pttprn tnnsfcr

pnrrs*. 7IL7I 0ptir.d lithomaphy 60-73.79 C\'ticrl prndmin mrrprtion I'OPC). 72 Onrntat~on-rlrlx.ndrllr ctcltinq. Sfi. 37 Orrill.~tion. 93 O\i<l.ttinn

i!nlNlrih n.distribation during. 50-51 in planar p m s r . 11-12 sin~uI:ttic>n. .3, 56-57 wfiic;al. 50

Od<h. ~ \ t l s itltin). 4%50 ILtyr. 7 rn:~43n<, 7 cIvdih. .XL%l thich~rw cl1anctrri7~1tion. 5-4 t n p p r l c l r~qcr . 54

P;shein<. i n t e p l d circuit I<,\l.L\ or. ECBO hpx or. Zill-2.32

~&lx,!ic rati. mnstalt. 46. J i Pacrmrtnc i r l d . ?-ill. 254-355 P.tttrn! tr.loslc,r. 1n t r~~t t t .d cirn~it. i0-71 PUS. r w P o ~ - l ~ t ~ l e n ~ ~ - l sn~lfone iPBSI

l,-channrI >IDSFIT (P\IOSl. 1%. 197. 20,%2(15, 20s

ch;ant~rl stop. 191-192 ['C\ls, n,,. I'nnvss mlltml lnollitors

i l 'C>l~> PECVII. ar. Pl;ulnit-mhnncid chrmic;tl

wpor clqnsition (1'EC:VI)) pG,\, av An grid ;~rnt!. (I'CA) P.pl:rss flow pnxrs*. 1W. 196 Pll;~s<., 2r-27 Pltitsr di : lpm. 27 Il~;a~~.shiSting ~niak (PSXI), 72 Plnnspl~ants

mnwntionsl annrali~~gof. 131-135 <liffttsion profil~s. 117. 1 IS

Pl totol i tho~r.~pl~~ clrBnrd. 60 rtclting ;tnrl. 13-14 simul;ltion. 81-72

Pltotom;uk. 60.69.73 Phutoresist. 13. GO. fii-70. 192. rrc nl.qo

Etcll-wsisfnnt pol!nren nept iw. 6 ' 9 . 7.5 positive, 6 7 4 s . 75

PI~!si~itl etching. 92 Pl~>sic;d vapor deposition (PVll). 14.

167- 167 Pin g i d :trcty IPCA). 231 Plan;~r process, i. 11-14 Plasma

tliapostin. 93 f~tnrlamcntals of. 90-91

Planla-:s<istrd etching, m. DI?. ! ' r l~ing I'lxsms-enl>anmd clle~l~ical vap,r

(lepnsifion (PECVD). 42. 1.55. 156 Pl;lm~a etchin: a process. 91-92 rractoa. 9 S 9 4

P>I>IA. sre Pol!-mrtllyl mrtlt;!~ n l ; ~ t r iP\IhlA)

PhlOS. srr 1,-cl~annel MOSFET (PhlOS) p-n j~mction. 7. 14 Point defect. .% Poisson clistrihotion. ?RS Poisson !irl<l moclrl. 251-352 PnIy 1. rrr p+ p o l d i m n Pol! 2. srr a + pol>silimn Pol?-hutmr-l sttlfonr (PRS). 75 Polycid~ gale rtclting. 9'LW Pol!rillc p r tx rs . 175

P<l!>r.nstallinc i l imn (EGS). 18, 41, 1.l~ .wc olrr, I'ol!rilin,~~

Polygl!ridyl ~nct l~ : t c~ ln tr -cn-~ t I~~ l . ;*c,,I;,t? (<:ol)), 75

P n l ~ ~ ~ ~ ~ ~ r s , 6%. 7.5 I'nly-mctl~yl mctl~ncrylatr ( P \ l \ l ~ ) . is. 79 PnI!silimn. 14.I

c:hp2ritor, 2111 chpsition. lli5-16i ~.l<~clr,,ll,., 201 rtclrin~. !)%99 silimn nitride mtl. 84

Posilivr, photorrsisl. 6i49. 75 I'm\ser limit:~tionr. 261-262 Po\vrr s11pl)l! vnltngt~, 25'3-260 I)+ pnl>silicon. l!I.l

gatr. 209 Pr~cil>itid~s. 1.54 I'rrllcposition difftns~! I w r , 112 Prrssur~-b~-trrn~~ri~t~~r~-~~~-flo~v rate. 248 Prrss~xrc-hy-trn~~rntt~r~ intrractiun. Z18 Prirn;~ry flat. 31 Prwrs cnntrol monifnn (PCM). 22i Prw.r.ss sio~olntion. 21X-222 I'rnlilometty 5-4 Pmjrctrd nngc (Rr ) 125 Projected str~gqlc (aF). 1% PROLITkI. SI Prnxilsip effect. 75-76 PS\I, set, I'l>;ar-sltifting mask (PSM) p t q h . 204-205 l~-t!p- intporily, I06 ,'-h~r silimn sllhstnttr. 211 1, \vt41, s~ 1, tub PZT. srr Lead zinnnium titannte (FZT)

Rapid tl~vnn;il anncilling (RTA). 134. IS% I :I6

Rastrar s n n c)atcm. 74-75 H~nrtivr ion hram rtcllil~g. 90 Hr;tcti\r ion <.lcl~ing (I<II:), 90. 94-95. I i 3 Hr:stivr pl:tsma rtcl~ing

al,plic;~tions, 9i-101 terl~niqnes. 93-94

Rracti\,r rr.lrtor trrlisnloS\, 93 Reactor. !):I Rl.<'tir!i~~g 1n~1;~1.r~~~ni~nncI11ctor h;,mcn,

11.1 Rrrlistrih~~tion diffurion, ace i>riv,:.in

diffwion Rr.lil!rd tw!tcl!. 205 Rr$stration. 62 Hcsislanrr-11c;ltrd oridation hmmxc+, Hrri~titity, 113. 114 R~!si~lors. 1% Rc.u,lution

dvfinrd. 62 cnhnrrmrnt twhniq~rrs, 72

Reson:tnt tnnnr.lin~ diode (WD). 5 Rrtrngrnclr urll. .we Twin u.rll RIE. srt. Rmctive ion etching (RIEI R,. see Projected m g e i R p ) RTA. .SPP R:tpirl thermal ;~nnraling (RTA) RTD. src Hr~osant t,~nnr!inqdiale [RTDI

Salicicle. 176 Smnning focused-heam ystcni, 80 Sdlottl\v banier diode. 114 Scmv dislnc;~tion. a3 Second:ary flat. 31 Secnnclary mass rpcdrosmpic (SI\IS)

trcl,niq~re. 36. 11.1 Segrcs:;ltion cwlficicnt

rffwtive. 22-23 equilihriam. 30. 50

Self-ixlig~rd stnictuw. 19S195 SESIC. .v<r Sinsle-~lcctron mcmol). e l l

iSE\lCl SEhll. srr Semimndactor E q ~ ~ i p ~ n r n t imd

hlaterinls Institutc (SE\lI) Scmimnd~~dor

cIe,iws, 2-5 ind~~rtries. 1 niatm:ils. 2 p w s s trc11noIc)gin. ,

Semimtaluctor Equiplnrnt :xnd \l:rtrrinLq lnstita!tr (SEhII). 3'2

Sepantiar~ I)! in~pInntrdo\?yrn (SIhIOS). 140.193

Sl~ado\v printing. 6243. i s Sl~allo\r. twncll isolation. 207 Sllcrt rcsistancr. 11:3-114 SI~pwhart control d~;trts. .XT Control rllnrts sl111loo plot. s w Xsn-din~rssiot~nl plot

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