CASTAM: A process variation analysis simulator for MOS LSI´s

A simulator named CASTAM, which includes both process and device models, has been developed to predict MOS process variations through the analysis of variations in electrical characteristics of fabricated MOS devices using the Monte Carlo method. Analysis accuracy using the simulator is examined. Investigation shows that process parameter variations can be estimated with an error of less than 10 percent if an appropriate set of device characteristic items is chosen. Wafer inspection data for a CMOS pilot line can be analyzed with this simulator, and the main cause of threshold voltage variation pinpointed. Predictions derived from the analyzed results have been confirmed using experimental data. This shows that analysis using CASTAM is sufficiently reliable.