Study of Sn removal by surface wave plasma for source cleaning

Gianluca Panici; Dren Qerimi; David N. Ruzic

doi:10.1117/12.2258065

24 March 2017 Study of Sn removal by surface wave plasma for source cleaning

Gianluca Panici, Dren Qerimi, David N. Ruzic

Proceedings Volume 10143, Extreme Ultraviolet (EUV) Lithography VIII; 101432I (2017) https://doi.org/10.1117/12.2258065
Event: SPIE Advanced Lithography, 2017, San Jose, California, United States

Abstract

A hydrogen plasma cleaning technique to clean Sn off of EUV sources is studied in detail. The cleaning process uses hydrogen radicals (formed in the hydrogen plasma) to interact with Sn-coated surfaces, forming SnH₄ and being pumped away. This technique has been used to clean a 300mm-diameter stainless steel dummy collector optic, and EUV reflectivity of multilayer mirror samples was restored after cleaning Sn from them, validating the potential of this technology. A concern for plasma based methods is the implantation of high energy hydrogen ions into the MLM, reducing reflectivity and possibly blistering. With a surface wave plasma (SWP) this concern is alleviated somewhat because of lower ion energies. Surface wave plasmas have lower electron temperatures than conventional sources in the range of 1 to 3 eV. In addition, SWP sources result in plasma densities on the order of 10^11-12cm^-3, allowing for greater utilization of ion etch enhancement. Experiments measuring radical density and etch rate profiles have been conducted and the results from these measurements are presented. These will help demonstrate scalability of SWP cleaning techniques for use in EUV sources.

Citation Download Citation

Gianluca Panici, Dren Qerimi, and David N. Ruzic "Study of Sn removal by surface wave plasma for source cleaning", Proc. SPIE 10143, Extreme Ultraviolet (EUV) Lithography VIII, 101432I (24 March 2017); https://doi.org/10.1117/12.2258065

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