SPICE Modeling of Process Variation Using Location Depth Corner Models

For robust designs, the influence of process variations has to be considered during circuit simulation. We propose a nonparametric statistical method to find sets of simulation parameters that cover the process spread with a minimum number of simulation runs. Process corners are determined from e-test parameter vectors using a location depth algorithm. The e-test corner vectors are then transformed to SPICE parameter vectors by a linear mapping. A special corner extension algorithm makes the resulting simulation setup robust against moderate process shifts while preserving the underlying correlation structure. To be applicable in a production and circuit design environment, the models are integrated into an automated model generation flow for usage within a design-framework. The statistical methods are validated for analog/mixed-signal benchmark circuits.