Robust run-to-run control for semiconductor manufacturing: an internal model control approach

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 past runs. RtR controllers utilizing linear response surface models are considered. The RtR controllers are designed to be robust with respect to modeling error and incorporate measurement delays. The RtR IMC filter design is modified to compensate for process drifts, and to account for the inherent unit measurement delay that exists for RtR control. A detailed robustness analysis is presented to obtain good stability and performance. These conditions are used to a priori predict achievable process performance. Simulations show that the developed RtR controllers are able to control the process even in the presence of sudden disturbances, measurement delays and reactor aging. Simulations also show that they perform better than exponentially weighted moving average controllers.