FinFET 3D Transistor & the Concept Behind It

1 FinFET 3D Transistor & the Concept Behind ItChenming Hu, August 2011 1 Chenming HuUniv. of Calif. ~hu/ 2 Intel will use 3D FinFET at 22nm Most radical change in decades There is a competing SOI technologyMay 4 2011 NY Times Front PageChenming Hu, August 2011 23 New MOSFET StructuresChenming Hu, August 2011 Cylindrical FETU ltra Thin Body SOI34 Vt, S, Ioff are bad & sensitive to Lg Dopant higher Vt, Vdd, and power consumption higher design costGood Old MOSFET Nearing LimitsFinally painful enough for Hu, August 2011 Drain Current, IDS (A/ m)Gate Voltage, VGS (V)Size shrinkSmaller sizeWhy VtVariation & Swing are So BadLGateOxideSourceDrainCgCdGateChenming Hu, August 2011 Drain Current, IDS (A/ m)Gate Voltage, VGS (V)Size shrinkSmaller sizeMOSFET becomes resistor at very small L Drain competes with Gate to control the channel Oxide Thin is Not EnoughGate cannot controltheleakage current paths that are far from the PathChenming Hu, August 2011 , Modern Semicon.

2 Devices for ICs 2010, Pearson One Way to Eliminate Si far from GateGateGateSourceDrainFinFET body is a thin finN. Lindert et al., DRC paper , 2001 SourceDrainFin WidthFin HeightGate Length Chenming Hu, August 2011 7A thinbody controlled by gate from more than one side. FinFET - 1999 UndopedBody. 30nm etched thin fin. Vtset with gate Huang et al., IEDM, p. 67, [nm] Vt [V]Vt at 100 nA/ m, Vd = VFin width: 20 nmChenming Hu, August 2011 8 Chenming Hu, August 2011 9 FinFETis Easy to ScaleLeakage is well suppressed if Fin thickness =or< Lg Thin fin and gate can be made with the same lithography and etching Hu, August 2011 Lg = 5 nm5nm Lg TSMC2004 VLSI Symp10nm Lg AMD2002 IEDM3nm Lg KAIST2006 VLSI Symp10 Chenming Hu, August 2011 11 FinFET Leakage , Modern Semicon.

3 Devices for ICs 2010, Pearson Body thickness is the new scaling Improvements to FinFETC henming Hu, August 2011 12 Original FinFET had thick oxide on fin top & used SOI for process simplicity. 2002 FinFET with thin oxide on fin et al. (TSMC) 2002 IEDM, p. 225. 2003 FinFET on bulk Park et al. (Samsung) 2003 VLSI Symp. p. FinFET20nm Hi Wu et al., 2010 IEDMC henming Hu, August 2011 132nd Way to Eliminate Si far from GateUltra-thin-body SOI (UTB-SOI) No leakage path far from the gate. Voltage [V]Drain Current [A/um]Tsi=8nmTsi=6nmTsi=4nmY-K. Choi, IEEE EDL, p. 254, 2000 GateSourceDrainUTBSiO2 SiChenming Hu, August 2011 14 Most Leakage Flows >5nm Below SurfaceY-K. Choi et al., IEEE electron Device Letters, p. 254, 2000 Chenming Hu, August 2011 15 Silicon Body Needs to be <Lg/3 For good swing and device variation Y-K.

4 Choi et al., IEEE electron Device Letters, p. 254, 2000 Chenming Hu, August 2011 16Y-K. Choi et al, VLSI Tech. Symposium, p. 19, 20013nm Silicon Body, Raised S/DUTB-SOIC henming Hu, August 2011 17 State-of-the-Art 5nm Thin-Body SOI ETSOI, IBM K. Cheng et al, IEDM, 2009 Chenming Hu, August 2011 18 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 leakage Lower Vdd and power consumption Further scaling and lower costChenming Hu, August 2011 19 Similarities between FinFET & UTBSOID evice Physics Superior S, scalability and device variations -use body thickness as a new scaling parameter-can use undoped body for high and no RDFH istory 1996: UC Berkeley proposed both to DARPA as 25nm Transistors.

5 1999: demonstrated FinFET2000: demonstrated UTB-SOI Since 2001: ITRS highlights FinFETand UTBSOIC henming Hu, August 2011 20 Main Differences FinFET body thickness ~Lg. Investment by ~1/3 Lg. Investment by Soitec. FinFET has clearer long term scalability. UTBSOImay be ready sooner than FinFET for some companies. FinFET has larger Ion. UTBSOIhas a good back-gate bias 1 Gate 2 UTBSOIFinFETC henming Hu, August 2011 21 What May Happen FinFET will be used at 22nm by Intel and later by more firms to <10nm. Some firms may useUTBSOI to gain market from regular CMOS at 20/18 so, competition between FinFETand UTBSOI will bring out the best of both. Chenming Hu, August 2011 2223 Berkeley Short-channel IGFET Model 1997: became first industrystandard MOSFET model for IC simulation BSIM3, BSIM4, BSIM-SOI used by hundreds of companies for design of ICs worth half trillion dollars BSIM models of FinFET and UTBSOI are available free BSIM SPICE ModelsChenming Hu, August 2011 23 Chenming Hu, August 2011 24 Chenming Hu, August 2011 25 Chenming Hu, August 2011 26 Chenming Hu, August 2011 2728 FinFET and UTB-SOI allows lower Vtand Vdd Lowerpower.

6 Body thickness is a new scaling parameter Better short channel effects to and beyond 10nm. Undopedbody Better mobility and random dopantfluctuation. BSIM models of FinFET and UTBSOI are available free SummaryChenming Hu, August 2011 28