Double EWMA controller for semiconductor manufacturing processes with time-varying metrology delay

Double Exponentially weighted moving average (dEWMA) is a typical Run-to-run (RtR) control in the semiconductor manufacturing process. The performance of dEWMA is determined by the measurement of process output real-time. However, it is impossible to obtain the output online owing to restriction of measurement tool and cost. Based on the logical relationship among the wafer quality, actually measured time-delay, estimated time-delay and the drift of process, a estimated algorithm for time-varying metrology delay is proposed by using the Bayesian statistical analysis. The simulated example demonstrates the performance of the presented algorithm.