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The importance of substrate doping engineering for extremely thin SOI MOSFETs with ultra-thin buried oxide(ES-UB-MOSFETs) is demonstrated by simulation.A new substrate/backgate doping engineering,lateral non-uniform dopant distributions(LNDD) is investigated in ES-UB-MOSFETs.The effects of LNDD on device performance,V t-roll-off,channel mobility and random dopant fluctuation(RDF) are studied and optimized.Fixing the long channel threshold voltage(V t) at 0.3V,ES-UB-MOSFETs with lateral uniform doping in the substrate and forward back bias can scale only to 35nm,meanwhile LNDD enables ES-UB-MOSFETs to scale to a 20nm gate length,which is 43% smaller.The LNDD degradation is 10% of the carrier mobility both for n MOS and p MOS,but it is canceled out by a good short channel effect controlled by the LNDD.Fixing V t at 0.3V,in long channel devices,due to more channel doping concentration for the LNDD technique,the RDF in LNDD controlled ES-UB-MOSFETs is worse than in back-bias controlled ES-UB-MOSFETs,but in the short channel,the RDF for LNDD controlled ES-UB-MOSFET is better due to its self-adaption of substrate doping engineering by using a fixed thickness inner-spacer.A novel process flow to form LNDD is proposed and simulated.
The importance of substrate doping engineering for extremely thin SOI MOSFETs with ultra-thin buried oxide (ES-UB-MOSFETs) is demonstrated by simulation. A new substrate / backgate doping engineering, lateral non-uniform dopant distributions (LNDD) is investigated in ES The effects of LNDD on device performance, V t-roll-off, channel mobility and random dopant fluctuation (RDF) are studied and optimized. Fixing the long channel threshold voltage (V t) at 0.3 V, ES- UB-MOSFETs with lateral uniform doping in the substrate and forward back bias can scale only to 35 nm, whilewhile LNDD enables ES-UB-MOSFETs to scale to a 20 nm gate length, which is 43% smaller. The LNDD degradation is 10% of the carrier mobility both for n MOS and p MOS, but it is canceled out by a good short channel effect controlled by the LNDD. Fixing V at at 0.3V, in long channel devices, due to more channel doping concentration for the LNDD technique, the RDF in LNDD controlled ES-UB-MOSFETs is worse than in back-bias controlled ES- UB-MOSFETs, but in the short channel, the RDF for LNDD controlled ES-UB-MOSFET is better due to its self-adaption of substrate doping engineering by using a fixed thickness inner-spacer. A novel process flow to form LNDD is proposed and simulated.