19 May 2006 Method for measuring the granite surface topography of wafer stage with laser interferometer
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Topography of a granite surface has an effect on the vertical positioning of a wafer table in a lithographic tool, when the wafer table moves on the granite. The inaccurate measurement of the topography results in a bad leveling and focusing performance. In this paper, a method to measure the topography of a granite surface with high accuracy is presented. In this method, a double frequency laser interferometer is used to measure the tilts of the wafer table in the X and Y direction. From the tilts information, the height of every point on the surface can be obtained by a special algorithm. Then, according to the height information, a high order polynomial is fitted to express the topography of the granite surface with high accuracy. Experiment results shows that the measurement reproducibility of the method is better than 10 nm.
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Le He, Le He, Xiangzhao Wang, Xiangzhao Wang, Weijie Shi, Weijie Shi, Jianming Hu, Jianming Hu, } "Method for measuring the granite surface topography of wafer stage with laser interferometer", Proc. SPIE 6150, 2nd International Symposium on Advanced Optical Manufacturing and Testing Technologies: Optical Test and Measurement Technology and Equipment, 615008 (19 May 2006); doi: 10.1117/12.676906; https://doi.org/10.1117/12.676906

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