Robustness Analysis of Mixed Product Run-to-Run Control for Semiconductor Process Based on ODOB Control Structure

Abstract

In this paper, we propose a unified framework for the mixed-product run-to-run (RtR) controller, which is called the output disturbance observer (ODOB) structure. Many mixed-product RtR controllers, such as product-based exponentially weighted moving average (PB-EWMA) threaded predictor corrector controller (t-PCC), cycle forecasting EWMA (CF-EWMA), and combined product and tool disturbance estimator (CPTDE), can fit in this framework. The relations of the above-mentioned controllers and the ODOB controller are discussed. Furthermore, based on the ODOB structure, we analyze the robust stable conditions and provide a systematic method for obtaining the optimal parameters that guarantee the optimal nominal performance under the robust stability. The simulation cases show that the output performances of PB-EWMA, t-PCC, CF-EWMA, and CPTDE controllers are improved by using the optimal weights obtained from the proposed approach.