Deep-submicrometre fully-depleted SOI MOSFET drain current model for digital/analogue circuit simulation

Abstract

A simple, complete, and analytical deep submicrometre SOI MOSFET model for accurate simulation of digital/analogue circuits is presented. The model was developed by using the drift-diffusion equation with a modified mobility formula to account for velocity overshoot, and was based on a quasi-two-dimensional Poisson's equation. It is a charge control model, expressed as a function of inversion charge per unit area. The drain current equation has been successfully applied to model both submicron and deep-submicrometre SOI nMOSFETs with various channel lengths and a good agreement between the modelled and experimental data has been obtained. The model contains the following advanced features: (a) precise description of the subthreshold, near threshold, and above-threshold regions of operation, and I-V and G-V characteristics in the saturation region; (b) single-piece drain current equation smoothly continuous from the linear region to the saturation region; (c) consideration of the source/drain resistance; (d) inclusion of important short channel effects such as velocity overshoot, drain induced barrier lowering and channel length modulation; (e) inclusion of the self-heating effect due to the low thermal conductivity of the buried oxide; and (f) inclusion of the impact-ionization of MOS devices and the parasitic BJT effect associated with drain breakdown. This model uses few fitting parameters and can be employed in a circuit simulator to improve the convergence of simulation and computational efficiency.