Some Open Problems in Semiconductor Manufacturing Control

This presentation will cover different kinds of models used for semiconductor manufacturing control from the device manufacturer aspect. Issue of loop-to-loop variability will be highlighted along with the non-stationary nature of process variation. In order to be successful, any process control application in this environment has to be capable of auto-tuning itself and be easy to set up and sustain. Examples of integral controllers will be presented that allow for this while optimizing different criteria of interest. While these provide a good solution for specific process models, for the general case, one needs to employ alternate estimators for which the solution is not so obvious. In fact, only recently there has been closure on the correctness of solutions surrounding these general models. Obtaining solutions to this and other related problems is of great interest, and the talk will explicitly list these out. It is hoped that this presentation will provide the audience with a flavor of the challenges within an alternate application of control theory.