trigate transistor yeswanth

7/24/2019 Trigate Transistor Yeswanth

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1. INTRODUCTION

1.1 Transistor

A transistor is a semiconductor device used to amplify and switch electronic sinals and

power. It is composed of a semiconductor material with at least three terminals for connection to

an e!ternal circuit. A voltae or current applied to one pair of the transistor"s terminals chanes

the current flowin throuh another pair of terminals. #ecause the controlled $output% power can

&e hiher than the controllin $input% power' a transistor can amplify a sinal.

The transistor is the fundamental &uildin &loc( of modern electronic devices' and is

u&i)uitous in modern electronic systems. *ollowin its development in the early 1+,-s the

transistor revolutionied the field of electronics' and paved the way for smaller and cheaper

radios' calculators' and computers' amon other thins.

The thermionic triode' a vacuum tu&e invented in 1+-/' propelled the electronics ae

forward' ena&lin amplified radio technoloy and lon0distance telephony. The triode' however'

was a fraile device that consumed a lot of power. hysicist 2ulius 3dar 4ilienfeld filed a patent

for a field0effect transistor $*3T% in Canada in 1+5,' which was intended to &e a solid0state

replacement for the triode.

*rom Novem&er 1/' 1+6/ to Decem&er 57' 1+6/' 2ohn #ardeen and 8alter #rattain at

AT9T"s #ell 4a&s in the United :tates' performed e!periments and o&served that when two old

point contacts were applied to a crystal of ermanium' a sinal was produced with the output

power reater than the input. The transistor is the (ey active component in practically all modern

electronics. ;any consider it to &e one of the reatest inventions of the 5-th century.

1.1.1 Advantages

The (ey advantaes that have allowed transistors to replace their vacuum tu&e predecessors in

most applications are

:mall sie and minimal weiht' allowin the development of miniaturied electronic

devices.

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=acuum tu&es create a distortion' the so0called tu&e sound' that some people find to &e

more tolera&le to the ear.

1.2 History

=ery0lare0scale interation $=4:I% is the process of creatin interated circuits &y

com&inin thousands of transistors into a sinle chip. =4:I &ean in the 1+/-s when comple!

semiconductor and communication technoloies were &ein developed.

Durin the 1+5->s' several inventors attempted devices that were intended to control the

current in solid state diodes and convert them into triodes. :uccess' however' had to wait until

after 8orld 8ar II' durin which the attempt to improve silicon and ermanium crystals for use

as radar detectors led to improvements &oth in fa&rication and in the theoretical understandin of

the )uantum mechanical states of carriers in semiconductors and after which the scientists who

had &een diverted to radar development returned to solid state device development. 8ith the

invention of transistors at #ell la&s' in 1+6/' the field of electronics ot a new direction which

shifted from power consumin vacuum tu&es to solid state devices.

Another pro&lem was the sie of the circuits. A comple! circuit' li(e a computer' was

dependent on speed. If the components of the computer were too lare or the wires

interconnectin them too lon' the electric sinals couldn"t travel fast enouh throuh the circuit'

thus ma(in the computer too slow to &e effective.

2ac( ?il&y at Te!as Instruments found a solution to this pro&lem in 1+,@. ?il&y"s idea

was to ma(e all the components and the chip out of the same &loc( $monolith% of semiconductor

material. 8hen the rest of the wor(ers returned from vacation' ?il&y presented his new idea to

his superiors.


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and which led to development in small0scale interation $::I% in the early 1+-s' medium0scale

interation $;:I% in the late 1+-s' and lare0scale interation $4:I% and =4:I in the 1+/-s and

1+@-s with tens of thousands of transistors on a sinle chip $later hundreds of thousands and now

millions%.

1.2.1 Developments

The first semiconductor chips held two transistors each. :u&se)uent advances added

more and more transistors' and' as a conse)uence' more individual functions or systems were

interated over time. The first interated circuits held only a few devices' perhaps as many as ten

diodes' transistors' resistors and capacitors' ma(in it possi&le to fa&ricate one or more loic

ates on a sinle device. Now (nown retrospectively as small0scale interation $::I%'

improvements in techni)ue led to devices with hundreds of loic ates' (nown as medium0scale

interation $;:I%. *urther improvements led to lare0scale interation $4:I%' i.e. systems with at

least a thousand loic ates. Current technoloy has moved far past this mar( and today"smicroprocessors have many millions of ates and &illions of individual transistors

As microprocessors &ecome more comple! due to technoloy scalin microprocessor desiners

have encountered several challenes which force them to thin( &eyond the desin plane' and

loo( ahead to post0siliconB

ower usae


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reachin a tippin point' with many desin houses optin to switch to 3lectronic desin

automation $3DA% tools to automate their desin process.

2. MOORES LAW.

2.1 Predition

In 1+,' Eordon ;oore s(etched out his prediction of the pace of silicon technoloy.

Decades later' ;oore>s 4aw remains true' driven larely &y Intel>s unparalleled silicon e!pertise.

Accordin to ;oore>s 4aw' the num&er of transistors on a chip rouhly dou&les every two years.

As a result the scale ets smaller and smaller. *or decades' Intel has met this formida&le

challene throuh investments in technoloy and manufacturin resultin in the unparalleled

silicon e!pertise that has made ;oore>s 4aw a reality.

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!ig"re 2.1 Moores la#

Nearly 6- years ao' Intel co0founder Eordon ;oore forecasted the rapid pace of technoloy

innovation. s 4aw to in0crease functionality and performance and decrease costs' &rinin

rowth to industries worldwide.

2.2 Present

;oore>s 4aw is not a law of science founded in scientific investiation &ut an uncannily

accurate proHection &ased on o&servation.

The present time' researchers are strulin to (eep ;oore>s 4aw on trac(. rocessor

cloc( rates have stalled' as chip desiners have struled to control enery costs and heat

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dissipation' &ut the industry>s response has &een straihtforward simply increase the num&er

of processor FcoresG on a sinle chip' toether with associated cache memory' so that areate

performance continues to trac( or e!ceed ;oore>s 4aw proHections.

The law states that the comple!ity $i.e.' num&er of transistors per chip% for minimum

component costs has increased at a rate of rouhly a factor of two per year. Certainly over the

short term this rate can &e e!pected to continue' if not to increase. Over the loner term' the rate

of increase is a &it more uncertain' althouh there is no reason to &elieve it will not remain nearly

constant for at least 1- years. That means &y 1+/,' the num&er of components per interated

circuit for minimum cost will &e ,'---.

Anyone wor(in in the computer industry will at some time hear a&out ;oore>s 4aw

&ecause of its a&ility to predict future processor transistor density and thus performance. In 1+,'

Hust four years after the first planar interated circuit was discovered $not microprocessor%' Dr.

Eordon 3. ;oore with Intel had o&served e!ponential rowth in the num&er of transistors that

could &e manufactured on a chip. Dr. ;oore went on to predict this e!ponential rowth would

continue. As it turned out' Intel has &een a&le to manufacture microprocessor chips that at least

dou&led the num&er of transistors over a 150month period or so and yet the cost per transistor has

dropped over time.

;oore>s law says that computer power dou&les for the same cost a&out every two years'

implyin rapidly fallin cost' increased power and proliferation. If this continues' the e)uivalent

price of a J-- ihone would &e J1@./, in 5-5-' J-.,+ in 5-7- and overall power or cost

improvin 1'---'--- times &y 5-,-. s law continuesK

The ta&le &elow shows the proHected relative computin power if ;oore>s 4aw continues at its

current paceB

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$a%le 1.1 Relative omp"ting po#er i& Moores la# ontin"es

If this technoloical proress continues for another forty years' computin hardware in

5-,- will &e more than one million times more powerful than today. And that>s &uildin on a&ase that already seems amainly advanced.

'. $RA(S)S$OR $E*H(OLO+)ES

7.1 1stTransistor 0 Thermionic triode

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!ig"re '.1 t,ermioni triode

A triode is an electronic amplification device havin three active electrodes. The term

most commonly applies to a vacuum tu&e $or valvein #ritish 3nlish% with three elementsB thefilament or cathode' the rid' and the plate or anode. The triode vacuum tu&e was the first

electronic amplification device' which propelled the electronics ae forward' &y ena&lin

amplified radio technoloy and lon0distance telephony. Triodes were widely used in consumer

electronics until the 1+,-s' when &ipolar Hunction transistors replaced them. The word is derived

from the Eree( LMPQ' trodos,from tri-$three% and hodSs $road' way%' oriinally meanin the

place where three roads meet.

The directly0heated cathode $or indirectly &y means of a filament% produces an electron

chare &y thermionic emission. This electron stream is attracted to the positively0chared plate

$anode%' inducin a current. Applyin a neative DC voltae $&ias% to the control rid willrepel some of the electron stream &ac( towards the cathode' thus isolatin the plate from the

cathode full &ias will turn the tu&e off &y &loc(in all current from the cathode. Conversely'

increasin the positive DC voltae on the plate will attract more electrons toward it. As rid &ias

is increased' more of the electron current is repelled' resultin in a smaller current at the plate. If

an AC sinal is superimposed on the rid' that sinal will &e amplified and directed toward the

plate as the neative DC &ias is increased.

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The triode is very similar in operation to the n0channel 2*3T it is normally on' and

proressively switched off as the ridate is pulled increasinly neative of the sourcecathode.

'.2 1stSemiond"tor $ransistor - Point ontat transistor

!ig"re '.2 point ontat transistor

A point0contact transistor was the first type of solid0state electronic transistor ever

constructed. It was made &y researchers 2ohn #ardeen and 8alter


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effects in solid state materials' with the aim of replacin vacuum tu&es with a smaller' less

power0consumin device.

The critical e!periment' carried out on Decem&er 1' 1+6/' consisted of a &loc( of

ermanium' a semiconductor' with two very closely spaced old contacts held aainst it &y a

sprin. #rattain attached a small strip of old foil over the point of a plastic trianle a

confiuration which is essentially a point0contact diode.


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!ig"re '.' planar transistor

In 1+,+' Dawon ?ahn and ;artin ;. $2ohn% Atalla at #ell 4a&s invented the metalo!ide

semiconductor field0effect transistor $;O:*3T% as an offshoot to the patented *3T desin.

Operationally and structurally different from the &ipolar Hunction transistor' the ;O:*3T was

made &y puttin an insulatin layer on the surface of the semiconductor and then placin a

metallic ate electrode on that. It used crystalline silicon for the semiconductor and a thermally

o!idied layer of silicon dio!ide for the insulator.

The metalo!idesemiconductor field0effect transistor $;O:*3T' ;O:0*3T' or ;O: *3T%

is a transistor used for amplifyin or switchin electronic sinals. Althouh the ;O:*3T is a

four0terminal device with source $:%' ate $E%' drain $D%' and &ody $#% terminals' the &ody $or

su&strate% of the ;O:*3T often is connected to the source terminal' ma(in it a three0terminaldevice li(e other field0effect transistors. 8hen two terminals are connected to each other $short0

circuited% only three terminals appear in electrical diarams. The ;O:*3T is &y far the most

common transistor in &oth diital and analo circuits' thouh the &ipolar Hunction transistor was

at one time much more common.

The ;O:*3T is used in diital complementary metalo!idesemiconductor $C;O:% loic'

which uses p0 and n0channel ;O:*3Ts as &uildin &loc(s. Overheatin is a maHor concern in

interated circuits since ever more transistors are pac(ed into ever smaller chips. C;O: loicreduces power consumption &ecause no current flows $ideally%' and thus no power is consumed'

e!cept when the inputs to loic ates are &ein switched. C;O: accomplishes this current

reduction &y complementin every n;O:*3T with a p;O:*3T and connectin &oth ates and

&oth drains toether. A hih voltae on the ates will cause the n;O:*3T to conduct and the

p;O:*3T not to conduct and a low voltae on the ates causes the reverse. Durin the

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switchin time as the voltae oes from one state to another' &oth ;O:*3Ts will conduct

&riefly. This arranement reatly reduces power consumption and heat eneration.

Di&&i"lties arising d"e to MOS!E$ sie red"tion

roducin ;O:*3Ts with channel lenths much smaller than a micrometer is a challene' and

the difficulties of semiconductor device fa&rication are always a limitin factor in advancin

interated circuit technoloy. In recent years' the small sie of the ;O:*3T' &elow a few tens of

nanometers' has created operational pro&lems.

Hig,er s"% t,res,old ond"tion

As ;O:*3T eometries shrin(' the voltae that can &e applied to the ate must &e

reduced to maintain relia&ility. To maintain performance' the threshold voltae of the ;O:*3T

has to &e reduced as well. As threshold voltae is reduced' the transistor cannot &e switched from

complete turn0off to complete turn0on with the limited voltae swin availa&le the circuit desin

is a compromise &etween stron current in the on case and low current in the off case' and

the application determines whether to favor one over the other. :u& threshold lea(ae $includin

su& threshold conduction' ate0o!ide lea(ae and reverse0&iased Hunction lea(ae%' which was

inored in the past' now can consume upwards of half of the total power consumption of modern

hih0performance =4:I chips.

)nreased gate/o0ide leaage

The ate o!ide' which serves as insulator &etween the ate and channel' should &e made

as thin as possi&le to increase the channel conductivity and performance when the transistor is on

and to reduce su& threshold lea(ae when the transistor is off.


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Increasin the dielectric constant of the ate dielectric allows a thic(er layer while maintainin a

hih capacitance $capacitance is proportional to dielectric constant and inversely proportional to

dielectric thic(ness%. All else e)ual' a hiher dielectric thic(ness reduces the )uantum tunnelin

current throuh the dielectric &etween the ate and the channel. On the other hand' the &arrier

heiht of the new ate insulator is an important consideration the difference in conduction &and

enery &etween the semiconductor and the dielectric $and the correspondin difference in

valence &and enery% also affects lea(ae current level. *or the traditional ate o!ide' silicon

dio!ide' the former &arrier is appro!imately @ e=. *or many alternative dielectrics the value is

sinificantly lower' tendin to increase the tunnelin current' somewhat neatin the advantae

of hiher dielectric constant.

)nreased "ntion leaage

To ma(e devices smaller' Hunction desin has &ecome more comple!' leadin to hiher

dopin levels' shallower Hunctions' halo dopin and so forth' all to decrease drain0induced

&arrier lowerin $see the section on Hunction desin%. To (eep these comple! Hunctions in place'

the annealin steps formerly used to remove damae and electrically active defects must &e

curtailed increasin Hunction lea(ae.


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Lo#er transond"tane

The transconductance of the ;O:*3T decides its ain and is proportional to hole or

electron mo&ility $dependin on device type%' at least for low drain voltaes. As ;O:*3T sie is

reduced' the fields in the channel increase and the dopant impurity levels increase. #oth chanesreduce the carrier mo&ility' and hence the transconductance. As channel lenths are reduced

without proportional reduction in drain voltae' raisin the electric field in the channel' the result

is velocity saturation of the carriers' limitin the current and the transconductance.

)nteronnet apaitane

Traditionally' switchin time was rouhly proportional to the ate capacitance of ates.


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&ecomes more challenin as well. In addition' microscopic variations in structure due simply to

the pro&a&ilistic nature of atomic processes re)uire statistical $not Hust deterministic% predictions.

These factors com&ine to ma(e ade)uate simulation and riht the first time manufacture

difficult.

'.'.2 3allisti $ransistor

!ig"re '.4 3allisti $ransistor

#allistic deflection transistors are electronic devices &ein developed for very hih0speed

interated circuits. Instead of switchin the flow of several electrons usin ates' as it is done in

field0effect transistors' they manipulate the course of sinle electrons usin electromanetic

forces. *ree flowin electrons are forced around a wede0shaped o&stacle $the "deflector"% on one

of two paths' correspondin to a loical "1" or "-". Initially impelled &y the circuits electric field'

electrons proceed on their respective paths via this electromanetic deflection. The "&allistic" title

was chosen to reflect the property of an individual electron traversin the transistor materialB a

two0dimensional electron as' actin as a thin sheet semiconductor.

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The #allistic Deflection Transistor $#DT% should produce far less heat and run far faster

than standard transistors &ecause it does not start and stop the flow of its electrons the way

conventional desins do. It resem&les a roadway intersection' e!cept in the middle of the

intersection sits a trianular &loc(. *rom the south an electron is fired' as it approaches the

crossroads' it passes throuh an electrical field that pushes the electron slihtly east or west.

8hen the electron reaches the middle of the intersection' it &ounces off one side of the trianle

&loc( and is deflected straiht alon either the east or west roads. In this way' if the electron

current travels alon the east road' it may &e counted as a ero' and as a one if it travels down the

west road.

A traditional transistor reisters a one as a collection of electrons on a capacitor' and a

ero when those electrons are removed. ;ovin electrons on and off the capacitor is a(in tofillin and emptyin a &uc(et of water. The draw&ac( to this method is that it ta(es time to fill

and empty that &uc(et. That refill time limits the speed of the transistorthe transistors in

today"s laptops run at perhaps two iahert' meanin two &illion refills every second. A second

draw&ac( is that these transistors produce immense amounts of heat when that enery is emptied.

The #DT desin should also &e a&le to resist much of the electrical noise present in all

electronic devices &ecause the noise would only &e present in the electrical steerin field' and

calculations show the variations of the noise would cancel themselves out as the electron passes

throuh.

The #DT is &allistic &ecause it is made from a sheet of semiconductor material called a

5D electron as' which allows the electrons to travel without hittin impurities' which would

impede the transistor"s performance.

'.'.' *ar%on (anot"%e !E$

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A car&on nanotu&e field0effect transistor $CNT*3T% refers to a field0effect transistor that

utilies a sinle car&on nanotu&e or an array of car&on nanotu&es as the channel material instead

of &ul( silicon in the traditional ;O:*3T structure. *irst demonstrated in 1++@' there have &een

maHor developments in CNT*3Ts

!ig"re '.5 *ar%on (anot"%e !E$

Accordin to ;oore"s law' the dimensions of individual devices in an interated circuit

have &een decreased &y a factor of appro!imately two every two years. This scalin down of

devices has &een the drivin force in technoloical advances since late 5-th century.


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6ey Advantages

#etter Control over channel formation.#etter threshold voltae.#etter su& threshold slope.


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4. TRI EAT3 TRAN:I:TOR

Tri0ate or 70D are the terms used &y Intel Corporation to descri&e their non0planar

transistor architecture planned for use in future microprocessors. These transistors employ a

sinle ate stac(ed on top of two vertical ates allowin for essentially three times the surface

area for electrons to travel. Intel reports that their tri0ate transistors reduce lea(ae and consume

far less power than current transistors. This allows up to 7/W hiher speed' and a power

consumption at under ,-W of the previous type of transistors used &y Intel.

Intel e!plains' The additional control ena&les as much transistor current flowin as

possi&le when the transistor is in the "on" state $for performance%' and as close to ero as possi&le

when it is in the "off" state $to minimie power%' and ena&les the transistor to switch very )uic(ly

&etween the two states $aain' for performance%.

The world>s first demonstration of a 55nm microprocessor 00code0named Ivy #ride

00that will &e the first hih0volume chip to use 70D Tri0Eate transistors. *urther to increase the

drive strenth for increased performance' multiple fins are used. !ig"re 2.ashows such a desin

with Hust a sinle fin while that of &ig"re 2.%and &ig"re 2.show desins with two and three finsrespectively.

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!ig"re 4.1 22nm tri/gate transistor #it, single &in

!ig"re4.1 22nm tri/gate transistor #it, t#o &ins

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!ig"re4.1 22nm tri/gate transistor #it, t,ree &ins

4.1 PER!ORMA(*E $ES$ RES7L$S

The performance tests were done &y Intel with other planar devices of different

technoloies and the test results are o&tained for Eate voltae versus Channel current shown in

fiure 7 8&ig '.a and &ig '.%9and Operatin =oltae versus Transistor Eate Delay shown in

fiure6 $fi6.a0 fi6.d%.

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!ig"re 4.4Comparison of lanar and Tri0Eate

!ig"re '.%comparison of lanar and Tri0Eate with and without reduced threshold voltae

4.2 $ransistor gate delay

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!ig.4.:. Operatin voltae =s Eate delay !ig. 4.:.% operatin voltae =s Eate delay

!ig. 4.:. operatin voltae =s Eate delay !ig. 4.:.d operatin voltae =s Eate delay

5. *O(*L7S)O(

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As transistors et smaller' parasitic lea(ae currents and power dissipation &ecome

sinificant issues. #y interatin the novel three0dimensional desin of the tri0ate transistor

with advanced semiconductor technoloy such as strain enineerin and hih0(metal ate stac('

Intel has developed an innovative approach toward addressin the current lea(ae pro&lem while

continuin to improve device performance.

#ecause tri0ate transistors reatly improve performance and enery efficiency' they

ena&le to e!tend the scalin of silicon transistors. Intel e!pects that the tri0ate transistors could

&ecome the &asic &uildin &loc( for microprocessors in future technoloy nodes. The technoloy

can &e interated into an economical' hih0volume manufacturinprocess' leadin to hih0

performance and low0power products.

:. RE!ERE(*ES

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1%httpBwww.intel.comtechnoloymooreslaw

5%httpBen.wi(ipedia.orwi(i;ultiateXdevice

7%httpBwww.intel.com$Ypdf% files downloadedBa%TriateXpressX&riefinX-- &% IntelXTransistorX#ac(roundeR c% 55nm0DetailsXresentation d%55nm0AnnouncementXresentation

6% =aidhyanadhan :u&ramanian0 ;ultiple ate field effect transistior for future C;O:

technoloies0 httpB www.tr.ieiteHournals.or

,% 2ac( ?avalieros' #rian Doyle' :uman Datta' Eil&ert Dewey' ;ar( Docy' #en 2in' Dan4ion&erer' ;atthew ;et' 8illy Rachmady' ;ar(o RadosavlHevic' Uday :hah' Nancy Zelic(

and Ro&ert Chau0 Tri0Eate Transistor Architecture with


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