Effectiveness of Mo–Au Gibbsian segregating alloys and the surface removal effect on the Gibbsian segregating performance for extreme ultraviolet collector optics

Abstract

Successful implementation of extreme ultraviolet (EUV) lithography depends on minimizing collector optics degradation from intense plasma erosion and debris deposition. Thus, studying the surface of collector optics and its reflectivity degradation processes and then implementing innovative methods to enhance the surface chemistry causing the collector optics to suffer less damage or to be self-healing is crucial for this technology development. A high-quality Mo-Au Gibbsian segregation (GS) alloy is fabricated on silicon using a DC dual-magnetron co-sputtering system, and the subsequent effectiveness is investigated as a result of surface removal, bulk erosion, surface roughness, and reflectivity degradation after exposure in an EUV source. A thin Au segregating layer is maintained through segregation during exposure, even though overall erosion in the Mo-Au film is taking place in the bulk. The reflective material, Mo, underneath the segregating layer is protected by this sacrificial layer, which is lost due to preferential sputtering. The experimental results are presented on the effectiveness of the GS alloys to be used as the potential EUV collector optics material by comparing to the pure Ru and Mo films. The effect of the surface removal rate on the GS performance is also investigated.