Run-to-run control of CMP process considering aging effects of pad and disc

CMP processes are known to be erratic and unstable. A simple control strategy is to predict the run-to-run process removal rate and then adjust the processing time based on the prediction. EWMA and PCC techniques are two most often used prediction techniques. In this work, we revise the PCC design to take into account the ages of the abrasive pad and conditioning disc. It is shown that the proposed age-based technique can significantly improve the prediction capability and, thus, the control efficiency over conventional techniques.