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24 March 2008 Alignment system and process optimization for improvement of double patterning overlay
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As a design rule shrink down aggressively, various RETs (Resolution Enhancement Technology) have been developed to extend the resolution limits of lithography. Until now, next generation lithography has been focused on EUV technology. But no one can assure when EUV will be implemented. So, we must develop new technology with current immersion tool to catch up with aggressive design rule. One of those is DPT (Double Patterning Technology), however there are also many challenges to overcome such as patterning, overlay, hard mask etch and so on. The most critical issue would be overlay, because it affects CD (Critical dimension) uniformity directly. Therefore, overlay control is very important between 1st DP layer and 2nd DP layer. We utilized ArF immersion scanners for this experiment. In this paper, DP process flow, hard mask film dependency, align method dependency, efforts of new align key design and direct align analysis in DP overlay will be reported to understand and get better overlay accuracy than tool specification. It is needed to be verified that how much they take an effect on improving the DP overlay. Continuously we can conclude that most efforts in DPT should be focused on overlay control issue.
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Won-kwang Ma, Jung-hyun Kang, Chang-moon Lim, HyeongSoo Kim, Seung-chan Moon, Sanjay Lalbahadoersing, and Seung-chul Oh "Alignment system and process optimization for improvement of double patterning overlay", Proc. SPIE 6922, Metrology, Inspection, and Process Control for Microlithography XXII, 69222T (24 March 2008); doi: 10.1117/12.772474;

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