18 December 2012 In situ aberration measurement technique based on quadratic Zernike model
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A novel technique (AMAI-Quad) for aberration extraction of lithographic projection based on quadratic relationship model between aerial-image intensity distribution and Zernike coefficients is proposed. Zernike coefficients in this case represent the imaging quality of lithographic projection lens in a semiconductor wafer exposure scanner. The proposed method uses principal component analysis and multivariate linear regression analysis for model generation. This quadratic model is then used to extract Zernike coefficients by nonlinear least-squares. Compared with earlier techniques, based on a linear relationship between Zernike coefficients and aerial images, proposed by Duan, the new method can extend the types of aberrations measured. The application of AMAI-Quad to computed images of lithography simulators PROLITH and Dr.LiTHO for randomly varied wavefront aberrations within a range of 50mλ demonstrated an accuracy improvement of 30%.
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Jishuo Yang, Jishuo Yang, Xiangzhao Wang, Xiangzhao Wang, Sikun Li, Sikun Li, Lifeng Duan, Lifeng Duan, Guanyong Yan, Guanyong Yan, Dongbo Xu, Dongbo Xu, Anatoly Y. Bourov, Anatoly Y. Bourov, Andreas Erdmann, Andreas Erdmann, "In situ aberration measurement technique based on quadratic Zernike model", Proc. SPIE 8550, Optical Systems Design 2012, 85503O (18 December 2012); doi: 10.1117/12.981328; https://doi.org/10.1117/12.981328

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