Chemical durability studies of Ru-capped EUV mask blanks

Takeya Shimomura; Ted Liang

doi:10.1117/12.803065

17 October 2008 Chemical durability studies of Ru-capped EUV mask blanks

Takeya Shimomura, Ted Liang

Proceedings Volume 7122, Photomask Technology 2008; 712226 (2008) https://doi.org/10.1117/12.803065
Event: SPIE Photomask Technology, 2008, Monterey, California, United States

Abstract

Surface cleaning has become one of the most critical processes in photomask manufacturing in the last few years because of the demands for high cleaning efficiency with no film loss and no damage to fragile patterns. The requirement is getting tighter as the feature-size shrinks. In addition, EUV masks pose further unique challenges in the cleaning process, because of the reflective multilayer (ML) mask structure, which is sensitive to surface damage, and a more frequent cleaning requirement due to the lack of pellicle protection during handing and usage. To address the challenge of ML surface damage from EUV mask cleaning processes, this paper presents the chemical durability of Ru-capped ML blanks against two types of chemistries: a mixture of sulfuric acid and hydrogen peroxide (SPM) and ozonated water (DIO3). The authors found that SPM slightly oxidized the Ru capping layer, but with minimal effect to EUV reflectivity. It was observed that DIO3 damaged the Ru capping layer and resulted in a significant EUV reflectivity drop. An alloyed Ru-capping layer showed improved durability against DIO3 damage. The changes to the Ru-surface were characterized with atomic force microscopy (AFM) and X-ray photo electron spectroscopy (XPS).

Citation Download Citation

Takeya Shimomura and Ted Liang "Chemical durability studies of Ru-capped EUV mask blanks", Proc. SPIE 7122, Photomask Technology 2008, 712226 (17 October 2008); https://doi.org/10.1117/12.803065

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