Analysis and Modeling of Lateral Non-Uniform Doping in High-Voltage MOSFETs

This paper reports on the impact and modeling of lateral doping gradient present in the intrinsic MOS channel of high voltage MOSFETs e.g. VDMOS and LDMOS. It is shown that the conventional MOSFET models using uniform lateral doping can never correctly model the capacitance behavior of these devices. A new charge-based analytical compact model for lateral non-uniformly doped MOSFET is reported. The model is validated on the measured characteristics of VDMOS and LDMOS transistors. The model shows good results in DC and, most importantly in AC regime, especially in simulating the peaks in C_GD, C_GS and C_GG capacitances. This new model improves the accuracy of high voltage MOS models, especially output characteristics and during transient response (i.e. amplitude and position of peaks as well as slope of capacitances)