Analysis of the gate-voltage-dependent series resistance of MOSFET's

Abstract

The intrinsic parasitic series resistance that occurs near the channel end of a MOSFET is analyzed. This new model includes the effects due to the unavoidable doping gradient near the metallurgical junction. It is assumed that current first conducts through the accumulation layer before spreading into the bulk region, and thus the spreading (injection) resistance and the accumulation layer resistance have to be considered in series and both are gate-voltage dependent. More importantly, they are shown to be a strong function of the steepness of the doping profile. The model quantitatively predicts these resistance components for a given process, and it emphasizes the necessity for a steep junction profile in order to minimize the series resistance of MOSFET's.