Control Performance Monitoring of RtR Controllers Based on Improved KL Divergence in Semiconductor Manufacturing Processes

Exponential weighted moving average (EWMA) run-to-run (RtR) controller is a widely used controller in semiconductor manufacturing process. Machine aging, model-plant mismatch and other factors lead to system performance degradation of EWMA RtR control system, wafer yield reduction, and even the safety of the manufacturing pr ocess degradation. A performance monitoring method for EWMA RtR control system is proposed based on improved KL divergence. First, a novel control performance index (CPI) is constructed based on improved KL divergence only requiring routine operation data. Then, the control limit of the proposed CPI is obtained by kernel density estimation (KDE) method. Next, the control performance online monitoring method is provided to monitor the performance of EWMA RtR control system. Finally, numerical simulations of chemical mechanical polishing (CMP) process are given to illustrate the efficiency of the proposed method.