On the choice of basis functions in FIR feed-forward design for wafer stages

B.M.H. van Hal, H. Nijmeijer (Supervisor), M.F. Heertjes (Supervisor)

Research output: Book/ReportReportAcademic

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Abstract

In view of the increasing demands on scanning resolution and wafer throughput, control perfor- mance in the presence of disturbances is considered important for lithograpic systems. These sys- tems consist of various positioning modules that need to be synchronized at nano-scale accuracy while being exposed to large acceleration forces. The goal of this project was to establish this nano- scale accuracy by optimizing the coefficients in a Finite Impulse Response (FIR) filter feed-forward structure. The gradients used in the optimization are reconstructed via basis functions. Two types of basis functions are compared throughout this report, namely time delay and time derivative ba- sis functions. The time delay function is a more steady function gives a reasonable estimation of the gradient of the error at a low number of coefficients, but also at a high number of coefficients. Contrarily, the time derivative function, which is not constant over the considered interval of co- efficients, gives a better result at a low number of coefficients, but a worse result at a high number of coefficients. The choice therefore is dependent on the number of coefficients. This is one of the main conclusions of this work.
Original languageEnglish
Place of PublicationEindhoven
PublisherEindhoven University of Technology
Number of pages32
Publication statusPublished - 2013

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