Age-based double EWMA controller and its application to CMP processes

• Published in: IEEE transactions on semiconductor manufacturing Vol. 14; no. 1; pp. 11 - 19
• Main Authors: Chen, A., Ruey-Shan Guo
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01.02.2001; Institute of Electrical and Electronics Engineers; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Adjustment; Applied sciences; Argon; Chemical-mechanical polishing; Control systems; Deviation; Drift; Electronics; Electronics industry; Estimates; Exact sciences and technology; Formulations; Helium; Input variables; Microelectronic fabrication (materials and surfaces technology); Optimal control; Process control; Refining; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices; Semiconductor process modeling; Semiconductors; Statistics; Predictor corrector method; Microelectronic fabrication; Planarization; Mechanical polishing; Statistical analysis; Moving average; Process control; Ageing; Chemical polishing
• ISSN: 0894-6507; 1558-2345
• DOI: 10.1109/66.909650

In the originally proposed run-by-run control scheme, the EWMA statistic is used as an estimate of the process deviation from its target. However, the controller based on the EWMA statistic is not sufficient for controlling a wearing out process. The PCC controller has been thus proposed to enhance the run-by-run controller capability. In this paper, we first reexamine the fundamentals of the PCC formulations and propose an adjustment that is advantageous in controlling processes subject to both random shifts and drifts. The adjusted PCC controller is then further refined to take into account the process age. This age-based double EWMA scheme is then applied to the CMP process, which is known in the semiconductor industry to be rather unstable.