Abstract
Exponentially weighted moving average (EWMA) controller has been widely used in semiconductor manufacturing processes. In the literatures, several papers addressed the efforts of long-term stability and short-term performance of EWMA control scheme. However, all the existing models are only valid when focusing on single-product and single-tool production style. In practical applications, multiple-product and multiple-tool production style is common for the practical implementation of run to run (R2R) control scheme. Recently, product-based approach and tool-based approach have been proposed to handle this mixed-run production problem. Although these control schemes will eventually bring the process output to the desired targets; they may suffer from a larger rework rate (RR) due to larger process variations. To overcome this difficulty, we propose a modified single EWMA controller to tackle this problem. We first address the stability conditions of the proposed controller. The result demonstrates that the stability conditions of the proposed controller will be held under some specific assumptions. Furthermore, we also use simulation study to investigate the performance of the proposed controller via total mean square error (TMSE) and RR criterion. The results demonstrate proposed controller outperforms existing models.