Two-dimensional semi-analytical model of subthreshold surface potential and drain current for double-doping polysilicon gate MOSFET

摘要

A semi-analytical subthreshold surface potential model for double-doping polysilicon gate (DDPG) MOSFETs is presented. By introducing two rectangular sources located in the gate insulator and the channel-depleted region, the two-dimensional (2D) Poisson equations are solved using a semi-analytical method combined with an eigenfunction expansion method. Expressions for the potentials are obtained as special functions of infinite series expressions. A subthreshold drain current is proposed on the basis of the potential profile, and it accounts for the carriers' drift diffusion and thermionic emission theory. The advantage of this work is that the two-dimensional treatment of the gate insulator region has resulted in physical consistency across a dielectric boundary. The proposed model not only offers physical insight into device physics but also provides the basic designing guideline for DDPG MOSFETs, enabling the designer to optimize the device in accordance with the application. Very good agreement for both the subthreshold surface potential and drain current is observed between the model calculations and the simulated results. (C) 2015 The Japan Society of Applied Physics