The application of high-reflectance Mo/Si multilayers in extreme ultraviolet (EUV) lithography does not only require high normal-incidence reflectivity but also long lifetime. In this paper, the microstructure of multilayers has been studied by means of X-ray reflectivity, X-ray diffraction, atomic force microscopy, and transmission electron microscopy. The interface width of Mo/Si multilayers is strongly influenced by the deposition rate. The interface width increases with the deposition rate. Thereafter the reflectivity decreases and bandwidth narrows down. Lower deposition rate is required to fabricate high quality Mo/Si multilayers according to our results. Our findings are beneficial to improve the reflectivity of Mo/Si multilayer mirrors by reducing the interface width with proper deposition rate. (C) 2015 Elsevier B.V. All rights reserved.