Impact of interface treatment with assisted ion beam on Mo-Si multilayer formation for EUVL mask blanks

To reduce the surface roughness of a substrate for mask blanks for extreme ultraviolet (EUV) lithography, the layers of a Mo-Si multilayer structure being deposited by magnetron sputtering were treated with an assisted ion beam. The effectiveness was analyzed by atomic force microscopy, X-ray reflection diffraction, and EUV reflectivity measurements, which revealed a large improvement in the interface and surface roughness, resulting in a multilayer with better EUV performance than one formed without such treatment.