2011-8 finfet and the concept behind it

7/28/2019 2011-8 FinFET and the Concept Behind It

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FinFET 3D Transistor &the Concept Behind It

Chenming Hu, August 20111

Chenming HuUniv. of Calif. Berkeley

http://www.eecs.berkeley.edu/~hu/


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Intel will use 3D FinFET at 22nm

Most radical change in decades

There is a competing SOItechnology

May 4 2011 NY Times Front Page



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New MOSFET Structures


Cylindrical FET

Ultra Thin Body SOI

3


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Vt, S, Ioff are bad &sensitive to Lg

Dopant fluctuations.

Requiring higher Vt, Vdd, and

power consumption higher design cost

Good Old MOSFET Nearing Limits

Finally painful enough for change.Chenming Hu, August 2011

4

0.0 0.3 0.6 0.910 -11

10 -9

10 -7

10 -5

10 -3

D r a

i n C u r r e n

t , I D

S ( A /

m )

Gate Voltage, VGS (V)

Sizeshrink

Smallersize


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Why V t Variation & Swing are So BadL

GateOxide

Source Drain

Cg

Cd

Gate


0.0 0.3 0.6 0.910 -11

10-9

10 -7

10 -5

10 -3

D r a

i n C u r r e n

t , I D

S ( A / m

)

Gate Voltage, V GS (V)

Size

shrink

Smallersize

MOSFET becomes resistor at verysmall L Drain competes with Gate tocontrol the channel barrier.


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Making Oxide Thin is Not Enough

Gate cannot control theleakage current paths

that are far from the gate .

Gate

Source Drain

Leakage Path


C.Hu,Modern Semicon. Devices for ICs 2010, Pearson


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FinFET- 1999Undoped Body. 30nm etched thin fin.Vt set with gate work-function.

X. Huang et al., IEDM, p. 67, 1999

-0.6

-0.4

-0.2

0.0

0.2

0.4

0.6

0 10 20 30 40 50Lg [nm]

V t [ V ]

Vt at 100 nA/m, Vd = 0.05 V

Fin width: 20 nm



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FinFET Leakage Path

S D

C.Hu,Modern Semicon. Devices for ICs 2010, Pearson

Body thickness is the new scaling parameter.


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Two Improvements to FinFET


Original FinFET had thick oxide on fin top& used SOI for process simplicity.

2002 FinFET with thin oxide on fin top.F.L.Yang et al. (TSMC) 2002 IEDM, p. 225.

2003 FinFET on bulk substrate.

T. Park et al. (Samsung) 2003 VLSI Symp.p. 135.


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STI

Gate

SiSTISTI

Gate

SiSTI

State-of-the-Art FinFET

20nm Hi Perf C.C. Wu et al.,2010 IEDM



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2nd Way to Eliminate Si far from GateUltra-thin-body SOI (UTB-SOI)

No leakage path far from the gate.

1.E-12

1.E-10

1.E-08

1.E-06

1.E-04

1.E-02

0 0.2 0.4 0.6 0.8 1

Gate Voltage [V]

D r a

i n C u r r e n

t [ A / u m

]

Tsi =8nmTsi =6nmTsi =4nm

Y-K. Choi, IEEE EDL, p. 254, 2000

Gate

Source DrainUTBSiO2

Si



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Y-K. Choi et al, VLSI Tech. Symposium, p. 19, 2001

3nm Silicon Body, Raised S/DUTB-SOI



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State-of-the-Art 5nmThin-Body SOI

ETSOI, IBMK. Cheng et al, IEDM, 2009



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Both Thin-Body Transistors Provide

Better swing.S & Vt less sensitive to Lg and Vd.No random dopant fluctuation.

No impurity scattering.Less surface scattering (lower Eeff).

Higher on-current and lower leakageLower Vdd and power consumptionFurther scaling and lower cost



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Similarities between FinFET & UTBSOIDevice Physics

Superior S, scalability and device variations-use body thickness as a new scaling parameter-can use undoped body for high and no RDF

History 1996: UC Berkeley proposed both to DARPAas 25nm Transistors. 1999: demonstrated FinFET

2000: demonstrated UTB-SOI Since 2001: ITRShighlights FinFETand UTBSOI



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Main Differences FinFETbody thickness ~Lg. Investment by fab.

UTBSOIthickness ~1/3 Lg . Investment by Soitec. FinFEThas clearer long term scalability.UTBSOImay be ready sooner than FinFET for

some companies. FinFEThas larger Ion.UTBSOIhas a good back-gate bias option.

STI

STI

Si

Gate 1 Gate 2UTBSOI

FinFETChenming Hu, August 2011 21


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What May Happen

FinFETwill be used at 22nm by Intel andlater by more firms to


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Berkeley S hort-channel IGFET Model 1997: became first industry standard

MOSFET model for IC simulation

BSIM3, BSIM4, BSIM-SOI used byhundreds of companies for design of ICs worth half trill ion dollars

BSIM models of FinFET and UTBSOIare available free

BSIM SPICE Models



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FinFET and UTB-SOI allows lower Vt

and Vdd Lower power. Body thickness is a new scaling

parameter Better short channel

effects to and beyond 10nm. Undoped body Better mobility and

random dopant fluctuation.

BSIM models of FinFET and UTBSOIare available free

Summary

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2011-8 finfet and the concept behind it

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