MULTILAYER FILM REFLECTION MIRROR, PRODUCTION METHOD FOR MULTILAYER FILM REFLECTION MIRROR, AND EXPOSURE SYSTEM

摘要

A multilayer film reflection mirror intended to reduce the dependency of reflectance on an incident angle. A substrate (1) is made of a low-thermal-expansion glass polished until its surface (top surface in the FIG.) has a roughness of up to 0.2 nmRMS. An Ru/Si multilayer film (3) having the large half width of peak reflectance is formed on the surface of the substrate (1), and an Mo/Si multilayer film (5) having a high peak reflectance is formed on this Ru/Si multilayer film (3). Accordingly, a reflectance peak having a higher reflectance than the case with of Ru/Si only and a larger half width than the case with of Mo/Si multilayer film (5) only is obtained. Since Ru provides a larger EUV beam absorption than Mo, a higher reflectance than with the case of a structure in which the Ru/Si multilayer film (3) is formed on the Mo/Si multilayer film (5) is obtained. Since a multilayer film having a larger half width at a spectral reflectance has a smaller dependency of reflectance on an angle, the invention can keep a high imaging performance in a projection optical system.