Effective parameter extraction using multiple-objective function for VLSI circuits

Abstract

Effective parameter extraction is a crucial step in accurate simulation of microelectronic circuits and systems. A parameter extraction program, which is based on a global optimization algorithm, uses a single objective function that minimizes the drain current error between the predicted and measured data. Parameter sets extracted on this basis are adequate for the purpose of digital circuit simulation, but fall short of simulation requirements for analog circuits. The use of a multiple-objective function is proposed, which simultaneously optimizes several critical electrical quantities including the drain current, output conductance, and transconductance. Experimental results with the multiple-objective function are presented, to show the improvement in extracted parameters. The recently developed BSIM_plus MOS transistor model for sub-half-micron integrated circuits uses a compact set of parameters, which greatly enhances the ability to accurately extract parameter values. This model was implemented into the parameter extraction program and some extraction results are presented. The parameter space has several local minima within which a gradient descent method may be trapped. Simulated annealing techniques can be applied to find near-optimal solutions of problems containing multiple local minima in their solution spaces. Experimental results showing the optimization of drain current error using simulation annealing techniques are presented. © 1994 Kluwer Academic Publishers.