A Real-Time Monitoring Framework for Wafer Fabrication Processes With Run-to-Run Variations

Real-time process monitoring is a vital technique to maintain safety and quality in the wafer fabrication processes. Hence, statistical process monitoring methods such as statistical process control chart, principal component analysis have been widely applied in wafer fabrication. However, these methods often suffer from the performance degradation problem caused by run-to-run (R2R) variations such as uneven duration and R2R drifts. In this paper, we propose a real-time monitoring framework for continuous wafer fabrication processes with uneven duration and R2R drifts. In this framework, processes are divided into several phases and further aligned in a real-time manner to solve the uneven duration problem. Then, R2R drifts are compensated by a down-sampling seasonal autoregressive integrated moving average model and a moving window multi-batch forecast strategy. Finally, multiphase multiway principal component analysis models are built on the compensated data to monitoring the processes. The efficiency of this framework is demonstrated by a case study on a plasma etch process. The results indicate that the proposed framework can diminish the influence of R2R variations and improve the monitoring model performance.