5-axis control ultra-precision machining of complex-shaped mirrors for extreme ultraviolet lithography system

The study deals with the manufacture of novel mirrors, an arc-shaped fly-eye mirror and a rectangular fly-eye one, for an extreme ultraviolet lithography system. Both mirrors have a complex reflective surface consisting of many small spherical mirror elements. A method is proposed to accurately realize such mirrors, using ultra-precision 5-axis control machining. The method enables to manufacture spherical surfaces with any radius, without changing the tool shape. Furthermore, another advantage of the method is that the sphericity of the resulting surfaces is independent of tool shape accuracy. By using this method, two kinds of fly-eye mirror with sixteen mirror elements are successfully fabricated.