The characteristics of Ru film were examined to determine its suitability as a buffer layer for EUV mask patterning. When etched in an O₂/Cl₂ gas mixture with a high Cl₂ content at a low total gas flow rate, Ru exhibited a high etching selectivity with respect to a-Si, the otp layer of a Mo/Si multilayer mirror. This could enable use of a simpler mask patterning process without any damage to the multilayer. The patterning of a mask with a TaN absorber layer and a Ru buffer layer was demonstrated. Etching the TaN with an Ar/Cl₂ gas mixture yielded a high etching selectivity with respect to Ru of over 30:1. In addition, the use of Ru rather than SiO₂ for the buffer layer improved the DUV inspection contrast of TaN mask patterns before and after buffer layer etching. Finally, Ru is etched more slowly than SiO₂ by a focused ion beam, which makes it more suitable as a sacrificial layer during repair.

Date Published: 20 August 2001
PDF: 8 pages
Proc. SPIE 4343, Emerging Lithographic Technologies V, (20 August 2001); doi: 10.1117/12.436699

Published in SPIE Proceedings Vol. 4343:
Emerging Lithographic Technologies V
Elizabeth A. Dobisz, Editor(s)