Time Exposure Performance of Mo-Au Gibbsian Segregating Alloys for Extreme Ultraviolet Collector Optics

Appl. Opt. 47, 2443-2451 (2008).

Qiu, H., Srivastava, S. N., Thompson, K. C., Neumann, M. J., Ruzic, D. N.

Successful implementation of extreme ultraviolet (EUV) lithography depends on research and progress toward minimizing collector optics degradation from intense plasma erosion and debris deposition. Thus studying the surface degradation process and implementing innovative methods, which could enhance the surface chemistry causing the mirrors to suffer less damage, is crucial for this technology development. A Mo-Au Gibbsian segregation (GS) alloy is deposited on Si using a dc dual-magnetron cosputtering system and the damage is investigated as a result of time dependent exposure in an EUV source. A thin Au segregating layer is maintained through segregation during exposure, even though overall erosion in the Mo-Au sample 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. In addition to theoretical work, experimental results are presented on the effectiveness of the GS alloys to be used as potential EUV collector optics material.