12 February 1997 Current status of mask CD uniformity as related to e-beam system
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As pattern density is increased, it is difficult for current photolithography technology to meet the required resolution. Therefore, instead of the photolithography e-beam direct writing and x-ray lithography have been considered as next generation technology. However, due to the rapid development in photolithography, it will be employed in manufacturing the first generations of 1 or 4 Gb DRAM. As smaller design rules require tighter controllability of the mask CD uniformity, mask CD uniformity smaller than 20 nm (3 (sigma) ) will be required for next generation devices. This paper reports on evaluation of mask CD error using a raster scan type e-beam system. In our study, CD uniformity (global) is improved by the advanced blank mask and local CD uniformity requires consideration, in order to reach the 20 nm CD uniformity. In particular, the butting error is a major source of CD variation but it is difficult to monitor this in this real mask production. Thus, the MPP (multi phase printing), and voting method are an alternative plan for reducing the butting error. However, we found that the 2X MPP (4 pixel merged) produced some CD skews, between even address pattern and odd address pattern. The voting gave some improving in butting error, but at the expense of loss of writing time. To meet the needs of mask CD uniformity, not only the global CD variation but also the local CD variation requires consideration. These types of mask CD errors were studied herein.
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Sung-Chul Lim, Byung Guk Kim, Seong-Woon Choi, Kyung Hee Lee, Hyun Joon Cho, Yong Hun Yu, Hanku Cho, Jung-Min Sohn, "Current status of mask CD uniformity as related to e-beam system", Proc. SPIE 3236, 17th Annual BACUS Symposium on Photomask Technology and Management, (12 February 1997); doi: 10.1117/12.301202; https://doi.org/10.1117/12.301202

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