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This paper presents a novel intelligent run-to-run control strategy for chemical-mechanical polishing (CMP) processes. With the help of the recursive least squares identification method for model building, a real-coded genetic algorithm is applied to adaptively adjust the discount coefficients for double exponentially weighted moving average (EWMA) controller. The online intelligent scheme can effectively prevent the CMP processes from reaching unstable condition and can thus achieve high control performance. To demonstrate the effectiveness and applicability of the proposed intelligent run-to-run control strategy, two typical case studies are worked out in this paper. Extensive simulation comparisons with traditional double EWMA run-to-run control were performed. The simulation results show that the proposed intelligent run-to-run control is able to achieve better control performance than conventional schemes, especially for a process that has nonlinearities, process noise, and extra large metrology delays.
Date of Publication: Feb. 2010