A simple method of source optimization for advanced NAND FLASH process

Yi-Shiang Chang; Satoshi Ogasawara; Koichi Fujii; Shigeru Hirukawa; Motokatsu Imai; Wan-Lin Kuo; Chia-Chi Lin

doi:10.1117/12.878887

22 March 2011 A simple method of source optimization for advanced NAND FLASH process

Yi-Shiang Chang, Satoshi Ogasawara, Koichi Fujii, Shigeru Hirukawa, Motokatsu Imai, Wan-Lin Kuo, Chia-Chi Lin

Proceedings Volume 7973, Optical Microlithography XXIV; 79731Z (2011) https://doi.org/10.1117/12.878887
Event: SPIE Advanced Lithography, 2011, San Jose, California, United States

Abstract

We have developed a very simple source optimization (SO) method for L/S and C/H critical layers patterning of advanced NAND FLASH. Starting from the strong off-axis illumination shape which is optimized for the finest structure of the mask pattern, a systematic procedure is performed to extract the optimum parameters of additional assist sources to balance the imaging performance (DOF, contrast and optical proximity effect, etc.) of dense/sparse/rough patterns. Performance equations (linear optimization) with performance map (sensitivity) are utilized to search the best combination of intensity for each assist source. For C/H pattern, the optimization procedure is modified to solve the non-linearity and non-continuity problems on the relationship between assist source intensity and each imaging performance. Finally, optimized source shapes have been successfully demonstrated and verified on 40 nm node NAND FLASH L/S and C/H critical patterns despite the simplicity of the optimization method, without utilizing SO dedicated software.

Citation Download Citation

Yi-Shiang Chang, Satoshi Ogasawara, Koichi Fujii, Shigeru Hirukawa, Motokatsu Imai, Wan-Lin Kuo, and Chia-Chi Lin "A simple method of source optimization for advanced NAND FLASH process", Proc. SPIE 7973, Optical Microlithography XXIV, 79731Z (22 March 2011); https://doi.org/10.1117/12.878887

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