Development of novel focus spot detection methods for high-volume manufacturing

Syed Naime Mohammad; Chao-Jen Tsou; Afu Chiu; Norman Birnstein; Erick deGouw; Clemens Utzny; Philip Groeger; Stefan Buhl; W. H. Wang; C. H. Huang; Elvis Yang; T. H. Yang; K. C. Chen

doi:10.1117/12.2657965

28 April 2023 Development of novel focus spot detection methods for high-volume manufacturing

Syed Naime Mohammad, Chao-Jen Tsou, Afu Chiu, Norman Birnstein, Erick deGouw, Clemens Utzny, Philip Groeger, Stefan Buhl, W. H. Wang, C. H. Huang, Elvis Yang, T. H. Yang, K. C. Chen

Author Affiliations +

Proceedings Volume 12494, Optical and EUV Nanolithography XXXVI; 1249415 (2023) https://doi.org/10.1117/12.2657965
Event: SPIE Advanced Lithography + Patterning, 2023, San Jose, California, United States

Conference Poster

Abstract

In advanced technology nodes, the focus window becomes tighter to achieve smaller CD features while maintaining or improving product yields. During the past decades, focus spot monitoring (FSM) has been a critical topic in high-volume manufacturing, not only for minimizing the contamination impact on focus performance but also for scanner productivity concerns if wafer table cleaning needs to be executed. Although there is a dedicated FSM option combined with automatic wafer table cleaning from the exposure tools, the users often need to be careful to design the threshold and monitor the area by different products and layers, to prevent false positive alarmsthat impact the productivity of scanners. In some cases, a small focus spot threshold can cause more false positive alarms at the wafer edge area due to the edge roll-off effect on the wafer table and steep wafer topography, which brings difficulty to detecting small focus spots due to contamination. In our study, we compare the classic FSM provided by exposure tools to a newly developed automated FSM mechanism. There are several mathematical steps and approaches implemented into our new type of FSM to reduce false positive focus spot alarms. For comparison, we evaluated the performance of classic and new FSM methods on different layers, which showed special topography, edge roll-off effect, or strong intra-field signature. Finally, a new robust and user-friendly FSM method has been demonstrated and proven that even with a tight threshold, the false positive alarm especially around the wafer edge area can be fully eliminated.

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Syed Naime Mohammad, Chao-Jen Tsou, Afu Chiu, Norman Birnstein, Erick deGouw, Clemens Utzny, Philip Groeger, Stefan Buhl, W. H. Wang, C. H. Huang, Elvis Yang, T. H. Yang, and K. C. Chen "Development of novel focus spot detection methods for high-volume manufacturing", Proc. SPIE 12494, Optical and EUV Nanolithography XXXVI, 1249415 (28 April 2023); https://doi.org/10.1117/12.2657965

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