ADI to in-cell overlay stability improvement for DRAM using novel scatterometry and comprehensive process control

Hyunsok Kim; Jaewuk Ju; Ikhyun Jeong; Baikkyu Hong; Sunouk Nam; Changkyu Lee; Kangmin Lee; Sumin Jang; Jaeyoun Lee; Hongcheon Yang; Minho Jeong; Mingyu Kim; Hongpeng Su; Wayne Zhou; Nanglyeom Oh; Dongsub Choi; Tal Yaziv; Hedvi Spielberg; Ohad Bachar; Renan Milo; Rawi Dirawi

doi:10.1117/12.2657632

27 April 2023 ADI to in-cell overlay stability improvement for DRAM using novel scatterometry and comprehensive process control

Hyunsok Kim, Jaewuk Ju, Ikhyun Jeong, Baikkyu Hong, Sunouk Nam, Changkyu Lee, Kangmin Lee, Sumin Jang, Jaeyoun Lee, Hongcheon Yang, Minho Jeong, Mingyu Kim, Hongpeng Su, Wayne Zhou, Nanglyeom Oh, Dongsub Choi, Tal Yaziv, Hedvi Spielberg, Ohad Bachar, Renan Milo, Rawi Dirawi

Author Affiliations +

Proceedings Volume 12496, Metrology, Inspection, and Process Control XXXVII; 124962E (2023) https://doi.org/10.1117/12.2657632
Event: SPIE Advanced Lithography + Patterning, 2023, San Jose, California, United States

Conference Poster

Abstract

As the cell size of memory devices continues to shrink, tighter on-product overlay (OPO) specs require more accurate and robust overlay control. The overlay error budget mainly consists of the reticle, scanner, process, and metrology errors. The metrology budget is generally required to be <10% of the OPO control budget so that the accuracy and robustness of overlay metrology become more crucial as pattern size gets smaller on current 1x nm DRAM nodes. For overlay control in high-volume manufacturing (HVM), the primary optical overlay metrology typically used is Image-Based Overlay (IBO). In many cases, scatterometry overlay (SCOL), using a direct grating-scanning method, was shown to achieve more accurate After Development Inspection (ADI) overlay measurements. Using a tunable source and customized illumination pupil to directly scan within the grating cell, this technology improves accuracy by reducing the contribution of pattern surroundings in the scribe line, resulting in improved OPO control stability. Since the purpose of overlay control is to minimize actual device pattern misregistration, as measured after the etching process (AEI), achieving accurate and stable characterization of the systematic deviation between ADI and AEI overlay known as Non-Zero-Offset (NZO) is critically important. Accurate NZO applied to the scanner via the Advanced-Process-Control (APC) loop enables effective scanner overlay control at the post-lithography ADI step. This paper demonstrates a new scatterometry overlay technology adopted in DRAM use cases that resulted in OPO and NZO stability improvement. In addition, we demonstrate an efficient method to monitor HVM run-to-run overlay performance and NZO stability by comprehensive dataset modeling combining ADI and AEI.

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Hyunsok Kim, Jaewuk Ju, Ikhyun Jeong, Baikkyu Hong, Sunouk Nam, Changkyu Lee, Kangmin Lee, Sumin Jang, Jaeyoun Lee, Hongcheon Yang, Minho Jeong, Mingyu Kim, Hongpeng Su, Wayne Zhou, Nanglyeom Oh, Dongsub Choi, Tal Yaziv, Hedvi Spielberg, Ohad Bachar, Renan Milo, and Rawi Dirawi "ADI to in-cell overlay stability improvement for DRAM using novel scatterometry and comprehensive process control", Proc. SPIE 12496, Metrology, Inspection, and Process Control XXXVII, 124962E (27 April 2023); https://doi.org/10.1117/12.2657632

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