Multilayer mirror, method for manufacturing the same, and exposure equipment

摘要

A multilayer mirror aims to reduce incidence angle dependence of reflectivity. A substrate is made of low thermal polished expansion glass with 0.2 nm RMS or less roughness of the surface. On the surface thereof formed is a Ru/Si multilayer having a wide full-width half maximum of peak reflectivity, and on the Ru/Si multilayer formed is a Mo/Si multilayer having a high peak reflectivity value. This enables higher reflectivity than when Ru/Si alone provided and a reflectivity peak having a wider full- width half maximum than when the Mo/Si multilayer alone provided. Since Ru absorbs EUV ray more than Mo does, higher reflectivity is obtainable than that of a structure having the Ru/Si multilayer formed on the Mo/Si multilayer. The multilayer with a wide full-width half maximum has small incidence angle dependence of reflectivity in spectral reflectivity, thereby achieving high imaging performance in projection optical system.