13 March 2018 Quantitative approach for optimizing e-beam condition of photoresist inspection and measurement
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Severe process margin in advanced technology node of semiconductor device is controlled by e-beam metrology system and e-beam inspection system with scanning electron microscopy (SEM) image. By using SEM, larger area image with higher image quality is required to collect massive amount of data for metrology and to detect defect in a large area for inspection. Although photoresist is the one of the critical process in semiconductor device manufacturing, observing photoresist pattern by SEM image is crucial and troublesome especially in the case of large image. The charging effect by e-beam irradiation on photoresist pattern causes deterioration of image quality, and it affect CD variation on metrology system and causes difficulties to continue defect inspection in a long time for a large area. In this study, we established a quantitative approach for optimizing e-beam condition with “Die to Database” algorithm of NGR3500 on photoresist pattern to minimize charging effect. And we enhanced the performance of measurement and inspection on photoresist pattern by using optimized e-beam condition. NGR3500 is the geometry verification system based on “Die to Database” algorithm which compares SEM image with design data [1]. By comparing SEM image and design data, key performance indicator (KPI) of SEM image such as "Sharpness", "S/N", "Gray level variation in FOV", "Image shift" can be retrieved. These KPIs were analyzed with different e-beam conditions which consist of “Landing Energy”, “Probe Current”, “Scanning Speed” and “Scanning Method”, and the best e-beam condition could be achieved with maximum image quality, maximum scanning speed and minimum image shift. On this quantitative approach of optimizing e-beam condition, we could observe dependency of SEM condition on photoresist charging. By using optimized e-beam condition, measurement could be continued on photoresist pattern over 24 hours stably. KPIs of SEM image proved image quality during measurement and inspection was stabled enough.
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Chia-Jen Lin, Chia-Jen Lin, Chia-Hao Teng, Chia-Hao Teng, Po-Chung Cheng, Po-Chung Cheng, Yoshishige Sato, Yoshishige Sato, Shang-Chieh Huang, Shang-Chieh Huang, Chu-En Chen, Chu-En Chen, Kotaro Maruyama, Kotaro Maruyama, Yuichiro Yamazaki, Yuichiro Yamazaki, } "Quantitative approach for optimizing e-beam condition of photoresist inspection and measurement", Proc. SPIE 10585, Metrology, Inspection, and Process Control for Microlithography XXXII, 105852W (13 March 2018); doi: 10.1117/12.2297384; https://doi.org/10.1117/12.2297384

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