Effect of Process Gradients and Process Parameter Correlation on Mismatch Modeling for Analog IC Design

The effect of across-wafer process gradients on pair mismatch is generally considered to add an additional, normally distributed, stochastic component. We analyze radial process parameter distributions, which, wafer maps show, are predominant and prove that they give rise to a semi-elliptical, not normal, distribution. Additionally, we discuss different approaches to modeling parameter correlations and the geometry dependence of mismatch and present data that show how the correlation in key mismatch parameters has changed over technology generations.