EWMA Controller with Concurrent Adjustment for a High-Mixed Production Process
Keywords:EWMA, run-to-run, feedback controller, high-mixed production process, concurrent adjustment
The exponentially weighted moving average (EWMA) feedback controller is a very popular run-to-run (RtR) process control scheme in the semiconductor industry. Traditionally, the manufacturing environment was simplified as a single product and single tool process. In the feedback control, the adjustment of the recipe for the next run is related to the deviation of the current output against the desired target. However, in a commercial foundry, every tool always works for many products. It is called a multiple products and single tool (MPST) process. The challenge of this process is how to adjust the recipes among different products in a production row.
In this study, a modified threaded EWMA feedback controller, the EWMA with concurrent adjustment, is proposed to deal with the issue of multiple products in a tool. When the process disturbances follow an IMA(1,1) time series model, the stability of the proposed method will be proven. The optimum discount factors of the proposed EWMA controller will be investigated by several simulations in terms of the number of multiple products, their distribution and the scheduling of the process. Moreover, according to results of the performance comparisons with threaded EWMA, the proposed controller is advantage in the large number of multiple products and in low-frequency products .
A. Ingolfsson A and E. Sachs, “Stability and sensitivity of an EWMA controller,” Journal of Quality Technology, vol. 25, pp. 271-287, 1993.
E. Sachs, A. Hu, and E. Ingolfsson, “Run by run process control: combining SPC and feedback control,” IEEE Transactions Semiconductor Manufacturing, vol. 8, pp. 26-43, 1995.
A. V. Prabhu and T. F. Edgar, “A new state estimation method for high-mix semiconductor manufacturing processes,” Journal of Process Control, vol. 19, pp. 1149-1161, 2009.
M. D. Ma, C. C. Chang, D. S. H. Wong, and S. S. Jang, “Threaded EWMA controller tuning and performance evaluation in a high-mixed system,” IEEE Transactions Semiconductor Manufacturing, vol. 22, pp. 1-5, 2009.
A. J. Pasadyn and T. F. Edga, “Observability and state estimation for multiple product control in semiconductor manufacturing,” IEEE Transactions Semiconductor Manufacturing, vol. 18, pp. 592-604, 2005.
S. P. Lee, D. S. H. Wong, C. I. Sun, W. H. Chen, and S. S. Jang, “Integrated statistical process control and engineering process control for a manufacturing process with multiple tools and multiple products,” Journal of Industrial and Production Engineering, vol. 32, no. 3, pp. 174-185, 2015.
How to Cite
Submission of a manuscript implies: that the work described has not been published before that it is not under consideration for publication elsewhere; that if and when the manuscript is accepted for publication. Authors can retain copyright in their articles with no restrictions. is accepted for publication. Authors can retain copyright of their article with no restrictions.
Since Jan. 01, 2019, AITI will publish new articles with Creative Commons Attribution Non-Commercial License, under The Creative Commons Attribution Non-Commercial 4.0 International (CC BY-NC 4.0) License.
The Creative Commons Attribution Non-Commercial (CC-BY-NC) License permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes.