Evaluation of Mo-Based Multilayer EUV Mirrors

The soft x-ray reflectivities and the effects of thermal annealing on both reflectivity and on the layered structures of Mo-based multilayers, such as Mo/Si, Mo/SiC, Mo/C, Mo/B, Mo/BN, Mo/B 4 C, MoSi 2 /Si and Mo 5 Si 3 /Si were evaluated. The Cu-Kα x-ray and soft x-ray reflectivities of the Mo/Si and Mo/B multilayers markedly decrease after annealing above 400°C. On the other hand, the reflectivities of the other Mo-based multilayers decrease only slightly for annealing temperatures up to 700°C. TEM observation reveals markedly less thermally induced deterioration in Mo/SiC, Mo/C, Mo/BN, M0/B 4 C, MoSi 2 /Si and Mo 5 Si 3 /Si multilayers than in Mo/Si multilayers. These results suggests that Mo/SiC, Mo/C, Mo/BN, Mo/B 4 C, MoSi 2 /Si and Mo 5 Si 3 /Si multilayers are superior to Mo/Si multilayers in terms of thermal stability.