MULTILAYER FILM REFLECTION MIRROR, METHOD OF MANUFACTURING A MULTILAYER FILM REFLECTION MIRROR AND EXPOSURE SYSTEM

摘要

A multilayer mirror aims to reduce the incidence angle dependence of reflectivity. A substrate 1 is made of low thermal polished expansion glass with 0.2 nm RMS or less roughness of the surface (the upper surface in the drawing). On the surface thereof formed is a Ru/Si multilayer 3 having a wide full width at half maximum of peak reflectivity, and on the Ru/Si multilayer 3 formed is a Mo/Si multilayer 5 having a high peak reflectivity value. Therefore, higher reflectivity than when Ru/Si alone provided and a reflectivity peak having a wider full width at half maximum than when the Mo/Si multilayer 5 alone provided are obtainable. Since Ru absorbs EUV ray more than Mo does, a higher reflectivity is obtainable than that of a structure having the Ru/Si multilayer 3 formed on the Mo/Si multilayer 5. Owing to small incidence angle dependence of reflectivity of a multilayer having a wide full width at half maximum in spectral reflectivity, it is possible to keep high imaging performance in a projection optical system according to the present invention.