Performance and quality analysis of Mo-Si multilayers deposited by ion beam sputtering and magnetron sputtering

Ion beam sputtering and magnetron sputtering were used to grow Mo-Si multilayer structures to investigate which is more suitable for the fabrication of mask blanks for extreme ultraviolet (EUV) lithography. For ion beam sputtering, the difference between using Ar and Xe as the sputtering gas was also examined. For ion beam sputtering, the peak EUV reflectivity of 40 Mo-Si bilayers was measured to be about 62% at wavelengths in the range of 12-15 nm; while for magnetron sputtering, the value was 65%. A transmission electron microscopy analysis of multilayers deposited by ion beam sputtering revealed an interface layer between the two materials: It had a thickness of 1.5 +/- 0.2 nm when Mo was deposited on Si, and a thickness of 0.7 +/- 0.2 nm when Si was deposited on Mo. These interface layers were 30-50% thicker than those formed during magnetron sputtering. The mechanism by which interface layers form is discussed based on an ion implantation model.