7 May 2013 High-order aberration measurement technique based on a quadratic Zernike model with optimized source
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Optical Engineering, 52(5), 053603 (2013). doi:10.1117/1.OE.52.5.053603
Abstract
In this paper, we propose an aberration metrology (AM) of a lithographic projection lens based on aerial images (AI) by using a quadratic relationship model (Quad) between the aerial-image intensity distribution and the Zernike coefficients. The proposed method (AMAI-Quad) uses principal component analysis and multiple linear regression analyses for model generation. The quadratic model is, then, used to extract Zernike coefficients by a nonlinear least-squares minimizing technique. The best linear constrain condition is estimated by optimizing the illumination settings. Compared with earlier techniques, based on a linear relationship between Zernike coefficients and AIs, the new method can extend the orders of Zernike coefficients measured. The application of AMAI-Quad to AIs, computed by lithography simulators PROLITH and Dr.LiTHO, demonstrated an extension of measurement range to 90mλ and an enhancement of measurement accuracy by more than 30 percent.
© 2013 Society of Photo-Optical Instrumentation Engineers (SPIE)
Jishuo Yang, Xiangzhao Wang, Sikun Li, Lifeng Duan, Guanyong Yan, Dongbo Xu, Anatoly Y. Bourov, Andreas Erdmann, "High-order aberration measurement technique based on a quadratic Zernike model with optimized source," Optical Engineering 52(5), 053603 (7 May 2013). http://dx.doi.org/10.1117/1.OE.52.5.053603
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KEYWORDS
Photomasks

Lithography

Artificial intelligence

Principal component analysis

Optical engineering

Process modeling

Monochromatic aberrations

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