Quantifying CD-SEM contact hole roughness and shape combined with machine learning-based pattern fidelity scores for process optimization and monitoring

Hyosung Lee; Seonho Lee; Hyungju Rah; Iksun Park; Jaeil Lee; Jaewoong Sohn; Yongchan Kim; Christoph Ehrlich; Philip Groeger; Sven Boese; Enrico Bellmann; Stefan Buhl; Seop Kim; Kang-san Lee

doi:10.1117/12.2657679

27 April 2023 Quantifying CD-SEM contact hole roughness and shape combined with machine learning-based pattern fidelity scores for process optimization and monitoring

Hyosung Lee, Seonho Lee, Hyungju Rah, Iksun Park, Jaeil Lee, Jaewoong Sohn, Yongchan Kim, Christoph Ehrlich, Philip Groeger, Sven Boese, Enrico Bellmann, Stefan Buhl, Seop Kim, Kang-san Lee

Author Affiliations +

Proceedings Volume 12496, Metrology, Inspection, and Process Control XXXVII; 124961P (2023) https://doi.org/10.1117/12.2657679
Event: SPIE Advanced Lithography + Patterning, 2023, San Jose, California, United States

Abstract

Process window qualification using focus-exposure wafers is an essential step in lithography and a key use case for CD-SEM metrology. An automated analysis using the correlation between CD and focus/dose is easily possible but rarely done due to missing safety checks. Pattern fidelity that is analyzed by eye and problematic focus/dose conditions that may cause pattern degradation are excluded by hand. Specifically, when EUV lithography is utilized for exposing the most critical layers, roughness estimation becomes much more important, as it will restrict the process window further. We develop and describe unbiased and stable roughness estimates for contact hole patterns and integrate them into the process window analysis pipeline and inline monitoring routine. The analysis goes beyond simple roughness values and can detect a variety of possible CD-SEM measurement problems and shape deviations as well. Furthermore, we introduce a novel image-based machine-learning approach to detect outliers and quantify defective or abnormal patterns. Notably, the underlying model does not require knowledge of the types of CD features or design information for which outliers should be detected. We demonstrate that the approach can reliably detect local defects and a variety of other pattern anomalies. Using the generated visualizations, images with anomalous features can be flagged automatically and the locations of the defects or deviations are pinpointed. The approach yields not only the final missing piece in automated process window qualification, but also new opportunities to monitor pattern fidelity in lithographical semi-conductor processes.

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Hyosung Lee, Seonho Lee, Hyungju Rah, Iksun Park, Jaeil Lee, Jaewoong Sohn, Yongchan Kim, Christoph Ehrlich, Philip Groeger, Sven Boese, Enrico Bellmann, Stefan Buhl, Seop Kim, and Kang-san Lee "Quantifying CD-SEM contact hole roughness and shape combined with machine learning-based pattern fidelity scores for process optimization and monitoring", Proc. SPIE 12496, Metrology, Inspection, and Process Control XXXVII, 124961P (27 April 2023); https://doi.org/10.1117/12.2657679

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