Comparative Study of Uniform Versus Supersteep Retrograde MOSFET Channel Doping and Implications for 6-T SRAM Yield

The benefit of supersteep retrograde (SSR) channel doping for suppressing short-channel effects in planar bulk MOSFET performance is studied via technology computer-aided design simulation of devices with gate length $L_{g}=28~{\rm nm}$ . It is found that drain-induced barrier lowering is reduced by more than 40%, and variation in saturation threshold voltage $(\sigma ~{\rm V}_{T,\rm Sat})$ , caused by random dopant fluctuation, is reduced by ${\sim}{50%}$ , with SSR channel doping. However, degraded drive current is observed for SSR channel doping due to enhanced body effect. Estimations of six-transistor static random access memory (SRAM) cell yield indicate that 33% reduction in the minimum operating voltage $(V_{\rm MIN, SRAM})$ can be achieved with SSR channel doping.