Integration of run-to-run control schemes and on-line experiment to deal with the changes in semiconducting dynamic processes

Abstract

Recently, detailed investigations of various ‘run-to-run’ (R2R) control schemes for semiconductor manufacturing have been conducted. However, a pure R2R control scheme cannot ensure sufficient control quality when the process suddenly undergoes a larger change (herein, a larger change is defined when the output exceeds 2σε ). In many semiconductor processes, sudden changes in the situation are often generated through the operation of different devices during the same process or changes in the control environment (e.g. process ageing or the influence of chemical concentrations). We propose an integrated R2R control system (IRCS) to alleviate this problem; the system includes an on-line experiment, R2R double exponentially weighted moving average (dEWMA) control, R2R triple EWMA (triEWMA) control and R2R self-tuning control. The IRCS initially employs a warning threshold to evaluate the process changes. When the process is changed, the system then uses the 2k centre points design to amend the process model and selects a suitable R2R control scheme to execute the process control. We used polysilicon gate etching and chemical mechanical planarisation processes as case studies for verifying the proposed method. Based on the analysis results, the IRCS can reduce problems due to process changes. The IRCS is also an improvement in that R2R EWMA-like control does not deal with the problem of process changes in more complicated models.