Approach to Patterning of Extreme Ultraviolet Lithography Masks using Ru Buffer Layer

The properties of Ru film were examined to determine its suitability as a repair buffer layer for the patterning of extreme ultraviolet lithography (EUVL) masks, Ru is etched more slowly than a conventional SiO2 buffer layer by a focused ion beam (FIB) for mask repair, which makes it more suitable as a sacrificial layer during repair. When etched in an O-2/Cl-2 gas mixture with a high Cl-2 content at a low total gas flow rate, Ru exhibited a high etching selectivity with respect to Si, the top layer of a Mo/Si multilayer reflector. This could enable use of a simpler mask patterning process without any damage to the multilayer. In addition, the use of Ru rather than SiO2 for the buffer layer improved the deep ultraviolet (DUV) inspection contrast before and after buffer layer etching. The patterning of a mask with a TaN absorber layer and a Ru buffer layer was demonstrated.