Abstract
Exponentially weighted moving average (EWMA) feedback controller has been widely used in semiconductor manufacturing processes. The long-term stability and short-term performance of EWMA control scheme have been addressed by several studies in the literatures. Most of the controllers emphasize on the case of a single-tool with single-product production situation. However, in advanced manufacturing, multiple-product production situations are common for the practical implementation of run-to-run (R2R) control scheme. Recently, tool-based (TB), product-based (PB), cycle resetting (CR) and modified tool-based (MTB) controllers have been proposed to handle the mixed-run R2R control problem. These controllers are developed under the scenarios of non-drifted processes. For drifted-processes, these control schemes may suffer from a larger total sum square error (TSSE). The drifted-version MTB (DMTB) controller partially solves this problem, leading to a smaller TSSE (of output) but still having a non-ignorable bias during the same product production run. To overcome this issue, this thesis propose a modified DMTB with an extra controller to compensate for drift, called MTB-dEWMA. The stability conditions of MTB-dEWMA controller under the assumption that the process disturbance follows general time series are discussed. Furthermore, a simulation is conducted to examine the performance of MTB-dEWMA controller with existing competitors, including DMTB, MTB and CR. The results show that MTB-dEWMA controller outperforms other competitors in terms of TSSE criterion.