Performance Evaluation of Run-to-Run Control Methods in Semiconductor Processes

Run-to-run (RtR) control plays an important role in semiconductor manufacturing processes. In this paper, RtR control methods are classified and evaluated. The set-valued RtR controllers with ellipsoid approximation are compared with two typical RtR controllers: the exponentially weighted moving average (EWMA) controller and the optimizing adaptive quality controller (OAQC) by simulations according to the following criteria: a good RtR controller should be able to compensate for various disturbances, such as small drifts, step disturbances and model errors; moreover, it should be able to deal with bounds, cost requirement and multiple targets that are often encountered in semiconductor processes. Based on our simulation results, suggestions on selection of a proper RtR controller for a semiconductor process are given as conclusions.