Details

Autor(en) / Beteiligte

• Elg, Daniel T.
• Panici, Gianluca A.
• Liu, Sumeng
• Girolami, Gregory
• Srivastava, Shailendra N.
• Ruzic, David N.

Titel

Removal of Tin from Extreme Ultraviolet Collector Optics by In-Situ Hydrogen Plasma Etching

Ist Teil von

• Plasma chemistry and plasma processing, 2018-01, Vol.38 (1), p.223-245

Ort / Verlag

New York: Springer US

Erscheinungsjahr

2018

Quelle

Alma/SFX Local Collection

Beschreibungen/Notizen

• Extreme ultraviolet (EUV) lithography produces 13.5 nm light by irradiating a droplet of molten Sn with a laser, creating a dense, hot laser-produced plasma and ionizing the Sn to the + 8 through + 12 states. An unwanted by-product is deposition of Sn debris on the collector optic, which focuses the EUV light emitting from the plasma. Consequently, collector reflectivity is degraded. Reflectivity restoration can be accomplished by means of Sn etching by hydrogen radicals, which can be produced by an H 2 plasma and etch the Sn as SnH 4 . It has previously been shown that plasma cleaning can successfully create radicals and restore EUV reflectivity but that the Sn removal rate is not necessarily limited by the radical density. Additionally, while Sn etching by hydrogen radicals has been shown by multiple investigators, quantification of the mechanisms behind Sn removal has never been undertaken. This paper explores the processes behind Sn removal. Experiments and modeling show that, within the parameter space explored, the limiting factor in Sn etching is not radical flux or SnH 4 decomposition, but ion energy flux. Thus the removal is akin to reactive ion etching.