MOSFET effective channel length, threshold voltage, and series resistance determination by robust optimization

Abstract

MOSFET parameters, such as effective channel length, series resistance, and channel mobility, are important for process control and device design. These parameters are typically obtained from intercepts and slopes of plots of intermediate quantities, such as peak transconductance, derived from I-V data. Commonly, the intercept of a plot is found by extrapolation. However, the extrapolation process is sensitive to measurement errors. In addition, the plots often show nonlinear behavior, hence slopes and intercepts cannot be determined accurately. It is shown how these problems can be overcome by using a nonlinear optimization procedure to determine those MOSFET parameters, by explicitly identifying them as the parameters of a simple, widely used MOSFET model that is a good approximation in the triode region of operation. The results of five tests of robustness and accuracy that show that the method is significantly more accurate and robust than a number of other methods are presented. >