Performance Analysis of a MEWMA Controller for MIMO Processes Subject to Metrology Delay

• Activity Number: 254
• Type: Contributed
• Date/Time: Monday, August 1, 2011 : 2:00 PM to 3:50 PM
• Sponsor: Section on Quality and Productivity
• Author(s): Chien-Hua Lin*+
• Companies: Providence University
• Keywords: Run to Run (R2R) Process Control ; MEWMA Controller ; Stability Conditions ; Metrology delay ; Virtual Metrology

Abstract

To maximize the competitiveness of semi-conductor manufacturers, they try to increase wafer sizes and reduce measurement devices. Metrology delay is a natural problem in the implementation of run-to-run process control scheme in semi-conductor manufacturing processes. Wu et al. (2008) demonstrated the influences of metrology delay on both the transient and asymptotic properties of the product quality when the single-input and single-output process is compensated by an exponentially weighted moving average (EWMA) controller. However, many semi-conductor manufacturing processes have multiple-input and multiple-output variables. To overcome this difficulty, Good and Qin (2006) proposed a multivariate EWMA controller to compensate it, and only discussed the stability conditions of a MEWMA controller. In practical applications, an optimal control scheme has more criteria than a stability region of discount matrix. In this talk, based on the criterion of minimizing asymptotic mean squares errors, we show that how to choose the optimal discount factor for various combinations of metrology delay. In addition, we discuss the ability of virtual metrology applied in delay MIMO processes.