13 November 2014 A high-accuracy subaperture stitching system for nonflatness measurement of wafer stage mirror
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Abstract
Nonflatness of stage mirror surface affects the position accuracy of the wafer stage in lithography tool. Precise surface flatness measurement is needed for the computer controlled polishing of stage mirror. A subaperture stitching system using a commercial 4-inch Fizeau interferometer was presented in this paper. Absolute test was used to calibrate the surface figure of the reference mirror with the accuracy better than λ/100 PV (λ = 632.8nm). Subaperture stitching was used to extend the measurement aperture larger than 450×50mm. Stitching measurements were carried out for stage mirrors during surface polishing. Comparison tests were also made with a 24-inch interferometer. The results show that the stitching system has the advantages of larger dynamic range, higher spatial resolution, and better measurement accuracy in local area.
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Yunjun Lu, Feng Tang, Xiangzhao Wang, Yong Li, Xiulong Wan, Fudong Guo, Fengzhao Dai, "A high-accuracy subaperture stitching system for nonflatness measurement of wafer stage mirror", Proc. SPIE 9276, Optical Metrology and Inspection for Industrial Applications III, 927617 (13 November 2014); doi: 10.1117/12.2071824; https://doi.org/10.1117/12.2071824
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