2 April 2014 Focus control budget analysis for critical layers of flash devices
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As design rule shrinks down, on-product focus control became more important since available depth of focus (DOF) is getting narrower and also required critical dimension uniformity (CDU) becomes tighter. Thus monitoring, control the scanner focus error and reducing the focus control budget of scanner are essential for the production. There are some critical layers which has so narrow DOF margin that hardly be processed on old model scanners. Our study mainly focused on the analysis of the scanner focus control budget of such layers. Among the contributors to the focus budget, inter-field focus uniformity was turned out to be the most dominant. Leveling accuracy and intra-field focus uniformity were also dominant.
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Jong Hoon Jang, Jong Hoon Jang, Tony Park, Tony Park, Kyeong Dong Park, Kyeong Dong Park, Jong Hyun Hwang, Jong Hyun Hwang, Jin Phil Choi, Jin Phil Choi, Young Seog Kang, Young Seog Kang, "Focus control budget analysis for critical layers of flash devices", Proc. SPIE 9050, Metrology, Inspection, and Process Control for Microlithography XXVIII, 90502F (2 April 2014); doi: 10.1117/12.2046235; https://doi.org/10.1117/12.2046235

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