Influence of background pressure on the microstructure and optical properties of Mo/Si multilayers fabricated by magnetron sputtering

Abstract

Mo/Si multilayers were fabricated by using magnetron sputtering method at different background pressures: 6×10-5 Torr, 3×10 -5 Torr, and 3×10-6 Torr. The reflectivity of the Mo/Si multilayers increased from 1.93% to 16.63%, and the center wavelength revealed a blue shift to 0.12 nm with the decrease of background pressure. Grazing incident X-ray diffraction (GIXRD) indicated that multilayers fabricated at high background pressure possessed better periodic structure and thinner Mo-on-Si interlayers. Low crystallization degree in (110) preferred the orientation of Mo layers and serious interdiffusion in the Mo/Si multilayers fabricated at low background pressure were observed by transmission electron microscopy (TEM). According to quantitative analysis of microstructural parameters, the Mo layers thickness and thickness ratio Γ of Mo/Si multilayers both decreased and approached the design value gradually by the decrease of background pressure. In addition, the thicknesses of Mo-on-Si and Si-on-Mo interlayers were 1.17 nm and 0.85 nm respectively. It is suggested that the influence of background pressures on the microstructure has a critical role in determining the optical properties of Mo/Si multilayers. © 2013 Science China Press and Springer-Verlag Berlin Heidelberg.