Choosing Optimal Control Structure for Run-to-Run Control - A Thin Film Example

This paper presents a case study for determining the optimal structure of the run-to-run control algorithm for thin film processes. Specifically, the expected process disturbance characteristics are used to determine the nature of the control strategy. Two examples of thin film processes are considered $(i) one involving a simple one-step deposition, and (ii) the other involving two deposition steps, with feedback only possible at the end of both the steps. This paper shows that a unified control structure is capable of handling multiple process types, which traditionally have used different controllers (in terms of their structure), especially in the presence of process shifts and drifts. Furthermore, the paper will also touch upon how the choice of the controller structure depends on the number of context dependent free parameters in the model