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1 April 2010 Application of model-based library approach to photoresist pattern shape measurement in advanced lithography
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The model-based library (MBL) matching technique was applied to measurements of photoresist patterns exposed with a leading-edge ArF immersion lithography tool. This technique estimates the dimensions and shape of a target pattern by comparing a measured SEM image profile to a library of simulated line scans. In this study, a double trapezoid model was introduced into MBL library, which was suitable for precise approximation of a photoresist profile. To evaluate variously-shaped patterns, focus-exposure matrix wafers were exposed under three-illuminations. The geometric parameters such as bottom critical dimension (CD), top and bottom sidewall angles were estimated by MBL matching. Lithography simulation results were employed as a reference data in this evaluation. As a result, the trends of the estimated sidewall angles are consistent with the litho-simulation results. MBL bottom CD and threshold method 50% CD are also in a very good agreement. MBL detected wide-SWA variation in a focus series which were determined as in a process window by CD values. The trend of SWA variation, which is potentiality to undergo CD shift at later-etch step, agreed with litho-simulation results. These results suggest that MBL approach can achieve the efficient measurements for process development and control in advanced lithography.
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Naoki Yasui, Miki Isawa, Toru Ishimoto, Kohei Sekiguchi, Maki Tanaka, Mayuka Osaki, Chie Shishido, Norio Hasegawa, and Shaunee Cheng "Application of model-based library approach to photoresist pattern shape measurement in advanced lithography", Proc. SPIE 7638, Metrology, Inspection, and Process Control for Microlithography XXIV, 76382O (1 April 2010);

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