Optimized Extraction of MOS Model Parameters

A common problem faced by designers in simulating MOS circuits is the specification of model parameters. Typical parameter extraction procedures determine parameters sequentially, ignoring many of the interactions between parameters. The resulting fit of the model to measured data may be less than optimum. Furthermore, the usual extraction procedures are specialized to a particular model; considerable effort is required to accommodate improvements in the model. This paper describes the application of general-purpose optimization techniques to the problem of extracting MOS transistor parameters. With this method, all parameters are extracted in a single operation, using the Levenberg-Marquardt algorithm to find a least-squares fit of the model to measured device characteristics. The technique is independent of the MOS model used-new models may be incorporated simply by inserting the model equations into the extraction program. The optimized parameter extraction technique has been implemented and has proven effective. The ease with which the model may be changed makes the program particularly useful for the evaluation of new models.