Optical element having multilayer film, and exposure apparatus having the optical element

摘要

A catoptric optical element includes a multilayer film for improving a reflectance to a light. The multilayer film includes a first lamination structure including plural basic lamination elements, each basic lamination element having two types of materials in each layer, each of the two types of materials having a constant thickness in each basic lamination element, the first lamination structure having a constant periodic length where one periodic length is defined as a thickness of each basic lamination element, and a second lamination structure alternately layering the two types of materials, wherein each of the two types of materials has a non-constant thickness, or the second lamination structure has a non-constant periodic length.