Phase shift improvement in ArF/KrF haze-free mask cleaning

Cathy Liu; Shirley Zhao; Eric Guo; Shinichi Hasegawa; Keiichi Nemoto; Tsuneaki Kuwajima

doi:10.1117/12.801439

17 October 2008 Phase shift improvement in ArF/KrF haze-free mask cleaning

Cathy Liu, Shirley Zhao, Eric Guo, Shinichi Hasegawa, Keiichi Nemoto, Tsuneaki Kuwajima

Proceedings Volume 7122, Photomask Technology 2008; 712212 (2008) https://doi.org/10.1117/12.801439
Event: SPIE Photomask Technology, 2008, Monterey, California, United States

Abstract

The continuous evolution of LSI design rules has created an increased demand for the use of KrF and ArF phase-shift photomasks (EPSMs). One of the critical issues in the use of those photomasks, especially ArF half-tone photomasks, has been the generation of optical hazes known as (NH4)2SO4. The other critical issue has been a relatively large phase shift of those ArF and KrF photomasks caused by so-called haze-free mask cleaning.. In the present study we used an SPM integrated clean (as a reference) consisting of heated SPM, diluted SC-1 and heated UPW (widely known for rinsing), and a haze-free integrated mask clean consisting of Ozonated-water with a simultaneous 222nm Excimer UV irradiation, diluted SC-1 and heated UPW. We found that both Ozonated-water with a simultaneous 222nm Excimer UV irradiation and the diluted SC-1 (the components of the haze-free integrated clean) caused a sizable phase shift during the mask clean. We also found that the other component of the haze-free integrated clean, the heated UPW developed a relatively large phase shift in those photomasks. We have confirmed that the more we repeat the use of the 172nm Excimer UV light irradiation treatment before the clean, the less (more improved) phase shift has been realized in the haze-free clean. We found that the haze-free integrated clean also developed the CD shifts of the above photomasks and that those CD shifts could be recovered (reduced) drastically by the use of the 172nm Excimer UV light irradiation before the clean.

Citation Download Citation

Cathy Liu, Shirley Zhao, Eric Guo, Shinichi Hasegawa, Keiichi Nemoto, and Tsuneaki Kuwajima "Phase shift improvement in ArF/KrF haze-free mask cleaning", Proc. SPIE 7122, Photomask Technology 2008, 712212 (17 October 2008); https://doi.org/10.1117/12.801439

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