史密斯預測器與預測干擾觀測器架構應用於半導體製程的量測延遲

Abstract

在半導體製程中，晶圓完成每道製程後需要送至量測儀器，檢測晶圓的誤差值，但每片晶圓送入量測儀器所消耗的時間不一定相同，當時間延遲過長就會使批次控制器(Run-to-Run Controller)無法即時修正製程配方，使製程結果偏離目標值，進而影響生產的良率。本文應用預測干擾觀測器(Predictive Disturbance Observer，PDOB)作為內迴路架構，用其對干擾有預測能力的優點，使用最佳預測(Optimal Prediction)設計一套對於隨機干擾(Stochastic disturbance)有預測能力的預測控制器，利用干擾的現在值與過去值來求得未來的干擾，進而達到削弱時間延遲對系統輸出的影響；並使用史密斯預測器(Smith predictor)作為外迴路，用以減少當系統模型誤差過大時所引發震盪的影響。

In semiconductor manufacturing, after finishing every process, wafer should be sent to the metrology equipment to measure the accuracy of production. It will consume different time to send the wafer to metrology equipment. If measurement delay is too long, it will cause Run-to-Run Controller to be unable to update the recipe immediately. This will then lower the accuracy of the process outcome and affects the yield rate. In this thesis, we use optimal prediction to design PDOB as inner loop, which can predict future stochastic disturbance by using past and current data values to improve the effect of time delay to the system. And we use Smith predictor as outer loop, which can reduce the oscillation caused by model mismatch.