The dEWMA fault tolerant approach for mixed product run-to-run control

Semiconductor manufacturing is an industry with high cost. Improvement of production efficiency is always an important goal for manufacturers. Run-to-run control has been widely used in batch manufacturing processes to reduce variations. Threaded EWMA run-to-run control is an important stable control scheme. In this paper mixed products are manufactured in cycles. However, the process outputs will oscillate greatly in the first runs of every cycle if the disturbance follows IMA(1,1) series with deterministic linear drift and the break length of a certain product is large enough. A double EWMA controller is adopted to handle the disturbance and the drift. Furthermore, how to deal with process fault is also considered in this paper. Two kinds of fault - the step and ramp fault are discussed for fault tolerant approach which can reduce the large deviation of output from the target. Simulation study showed that the proposed approaches are effective.