In the fabrication of masks for EUVL, a combination of dry and wet etching was used to remove the SiO₂ buffer layer. This technique greatly improves the pattern quality, yielding re-entrant shaped mask patterns with a steep SiO₂ sidewall. Under proper conditions, etching results in the base of the sidewall being recessed around 5 nm from the edge of the Ta pattern. The strength of hydrofluoric acid (HF) solution was set to 3.3 percent to allow good control of the etching rate. A combination of dry and wet etching is an effective way to remove the SiO₂ buffer layer because it can compensate for a variation of as much as 7.6 percent in the thickness of the SiO₂ film before etching.

Date Published: 19 July 2000
PDF: 7 pages
Proc. SPIE 4066, Photomask and Next-Generation Lithography Mask Technology VII, (19 July 2000); doi: 10.1117/12.392050

Published in SPIE Proceedings Vol. 4066:
Photomask and Next-Generation Lithography Mask Technology VII
Hiroaki Morimoto, Editor(s)