Internal model control approach to run-to-run control for semiconductor manufacturing

This paper presents the design of Run to Run (RtR) controllers using the Internal Model Control (IMC) structure. In RtR control the input recipe for a run is determined using the in-situ and ex-situ measurements of the previous runs; RtR controllers designed based on linear Response Surface Models (RSM) are considered. The RtR controllers should be robust to modelling errors and account for measurement delays. The RtR-IMC filter design is modified to compensate for process drifts, and to account for the additional unit measurement delay that exists for Run to Run control. Robustness conditions are developed for specific cases, to facilitate controller tuning. Simulations show that the developed RtR controllers are able to control the process output even in the presence of sudden disturbances, measurement delays and aging of the reactors. Simulations also show that they perform better than exponentially weighted moving average controllers and RtR-IMC controllers based on a double exponential filter. Since for many processes in semiconductor manufacturing the RtR controllers used are often based on linear RSM models, the current approach has wide applicability.