Advanced Process Control Using Partial Least Squares

This paper applies the partial least squares (PLS) technique to the multiple-input multiple-output (MIMO) semiconductor processes under the paradigm of the Advanced Process Control (APC). First, we present a controller called the PLS-MIMO double exponentially weighted moving average (PLS-MEMO DEWMA) controller. It uses the PLS method as the model building/estimation technique to help the EWMA controller to produce more consistent and robust control outputs than purely using the conventional EWMA controller. To cope with metrology delays, the proposed controller uses the pre-process metrology data to build up a Virtual Metrology (VM) system that can provide the estimated process outputs for the PLS-MIMO DEWMA controller. Finally, a Fault Detection (FD) system is added based upon the principal components of PLS, which supplies the process state for VM and the PLS-MIMO DEWMA controller to respond to the system errors.