CS1: A Two-Dimensional Finite Element Charge-Sheet Model of a Short-Channel MOS Transistor

摘要

A two-dimensional charge-sheet model for short-channel MOS transistors has been developed. The unique feature of the model is that the effect of channel inversion layer charge is included as a nonlinear integral boundary condition on the two-dimensional electrostatic field in the transistor. The average inversion layer charge density and source-drain current are obtained directly from the model rather than from the electron density or electron quasi-Fermi level. The model retains all of the physical detail of more complex two-dimensional models such as sensitivity to source-drain profile shape, channel profile, and oxide field shape. This allows the model to represent the changes in drain current associated with short-channel effects while still allowing simple comparison with long-channel models. For long-channel transistors, the results of this model are identical to Brews' long-channel charge-sheet model. The accuracy of this model is verified by modelling a sequence of transistors with channel lengths between 4.6 and 1.1 micrometers. In short-channel transistors, effects previously attributed to high field mobility are explained by simple two-dimensional electrostatics.