Linear versus saturated drive current: tradeoffs in super steep retrograde well engineering

Abstract

Compared to uniform well doping profiles the use of super steep retrograde well (SSRW) doping can significantly improve short channel effects permitting operation at smaller device sizes. However, the use of a SSRW does not significantly increase saturated drive current for these devices due to reduced drain saturation voltages (V/sub DSAT/). The reduction in V/sub DSAT/ occurs because the SSRW increases the depletion bulk charge and threshold voltage near the drain at high drain biases (body effect). It is shown for the first time that unlike the saturated drive current, the linear drive current exhibits a large increase for minimum size devices resulting in significantly improved inverter switching times. Improvements in gate delay of more than 10% are reported for SSRW devices.