Characterization of striae in ULE for EUVL optics and masks

William Rosch; Lorrie Beall; John Maxon; Robert Sabia; Robert Sell

doi:10.1117/12.656355

23 March 2006 Characterization of striae in ULE for EUVL optics and masks

William Rosch, Lorrie Beall, John Maxon, Robert Sabia, Robert Sell

Proceedings Volume 6151, Emerging Lithographic Technologies X; 615122 (2006) https://doi.org/10.1117/12.656355
Event: SPIE 31st International Symposium on Advanced Lithography, 2006, San Jose, California, United States

Abstract

Compositional striations in Corning's Ultra Low Expansion (ULE^®) glass are thought to affect the surface roughness when the glass is polished. For EUV Lithography photomask blanks, it is important for the polished surface to be as smooth as possible. Therefore, since the compositional striations may impact photomask polishing, Corning has undertaken an effort to better characterize the striae and its impact on surface roughness, improve the fundamental understanding of its origin during boule formation, and develop methods and procedures to reduce its potential impact on polishing. This work has verified that striae can vary quite a bit throughout a single ULE glass boule. Characterization has shown that there are two main types of striae. These can be described as high frequency (secondary) striae and lower frequency (primary) striae. Due to the new understanding of the striae origin, two methods have recently been identified and used to greatly reduce or eliminate the high frequency striae component. Currently, new modeling efforts have helped identify potential process changes that may reduce the impact of the primary striae frequency. Experiments are in process to determine their effectiveness.

Citation Download Citation

William Rosch, Lorrie Beall, John Maxon, Robert Sabia, and Robert Sell "Characterization of striae in ULE for EUVL optics and masks", Proc. SPIE 6151, Emerging Lithographic Technologies X, 615122 (23 March 2006); https://doi.org/10.1117/12.656355

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