Expression of worst case using multivariate analysis in MOSFET model parameters

Device and circuit performance such as drain current and delay time varies stochastically due to uncontrollable factors in the fabrication processes. In this paper, a new method that represents the variation of the performance as worst case parameters in a MOSFET model is proposed. The variation of the performance can be expressed as a linear combination of several process-related parameters of the MOSFET model. Because of this fact, the worst case of parameters which corresponds to the worst case of performance can be directly and uniformly determined. Therefore, the calculation time of worst case parameters can be reduced by this method. The worst case parameter sets calculated by this method enable designers to estimate circuit performance variations accurately and easily. The capability of this method is verified in the variation analysis of drain current.