Coma measurement using a PSM and transmission image sensor |
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Authors: | Fan Wang Xiangzhao Wang Mingying Ma Dongqing Zhang Weijie Shi Jianming Hu |
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Institution: | aInformation Optics Laboratory, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800, China;bGraduate School of the Chinese Academy of Sciences, Beijing 100039, China |
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Abstract: | As feature size decreases, especially with the use of resolution enhancement technique, requirements for the coma aberrations in the projection lenses of the lithographic tools have become extremely severe. So, fast and accurate in situ measurement of coma is necessary. In the present paper, we present a new method for characterizing the coma aberrations in the projection lens using a phase-shifting mask and a transmission image sensor. By measuring the image positions at multiple NA and partial coherence settings, we are able to extract the coma aberration. The simulation results show that the accuracy of coma measurement increases approximately 20% compared to the previous straightforward measurement technique. |
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Keywords: | Optical lithography Aberrations Projection lens Image quality Zernike coefficients |
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