17 October 2008 Simulation analysis of backside defects printability in 193nm photolithography
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Backside defects a few micrometers in size are serious concern in lithography because they can degrade the image quality on a wafer. It was known that defects attached on the backside affected the printing images on a wafer by locally altering the partial coherence (σ) and the transmitted intensity of the illumination. The ability to detect and to simulate their impact of defects on the backside is one of the key components in ensuring quality of photomask. The purpose of this study is to determine the minimum size of defects on the backside which would be affected printability in 193nm photolithography. It was investigated to the influence of wafer critical dimension (CD) variation according to illumination and NA, that of refraction according to defect size. For this study, a reticle was designed to include line and space patterns, contact patterns and isolated patterns on the front side. And the type of defects attached on the backside was made of chrome to investigate the relation between transmittance of backside defects and its printability. The correlation of measurements made with UV and DUV-based inspection system; simulation performed with a 193nm aerial image measurement system. Besides the allowable size of backside defects was determined using the criterion of a maximum intensity variation of 10%.
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Jisun Ryu, Jisun Ryu, Dongwook Lee, Dongwook Lee, Jinho Ryu, Jinho Ryu, Sookyeong Jeong, Sookyeong Jeong, SangPyo Kim, SangPyo Kim, Changyeol Kim, Changyeol Kim, "Simulation analysis of backside defects printability in 193nm photolithography", Proc. SPIE 7122, Photomask Technology 2008, 712218 (17 October 2008); doi: 10.1117/12.801437; https://doi.org/10.1117/12.801437


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