Abstract: A method for producing a reflective mask blank, includes: forming a reflective multilayer film on or above a substrate by using an ion beam sputtering apparatus and a process gas, the ion beam sputtering apparatus accelerating an ion generated by applying a voltage to a grid, and causing the ion to collide with a target to perform sputtering, the process gas including at least one inert gas selected from He, Ne, Ar, Kr, Xe, Rn, and N2 as an ion source, in which a product of an effective area (cm2) of the grid and a flow rate (sccm) of the process gas supplied to the ion beam sputtering apparatus during film formation is 3600 (cm2·sccm) or less.

Abstract: A reflective mask blank includes a substrate; a multilayer reflective film that reflects EUV light; a protection film that protects the multilayer reflective film; and an absorption film that absorbs the EUV light, in this order. The protection film contains 50 at % or more of Rh. When a band-shaped gray scale image parallel to an interface between the protection film and the multilayer reflective film is obtained by imaging a cross section of the protection film with a transmission electron microscope (TEM) and a luminance profile of the gray scale image in a longitudinal direction of the gray scale image is created, a number of peaks of the luminance profile per 100 nm in the longitudinal direction of the gray scale image is 50 or more.