Mirror element for extreme UV projection exposure system, has mirror surfaces comprising smooth surface with quadratic roughness of specific value and micro-structure with specific period length and specific amplitude

摘要

The element has curved mirror surfaces (3) comprising a smooth surface with a quadratic roughness of smaller than or equal to 0.2 to nanometer root mean square in a period length range of smaller than or equal to 10 micrometer. The mirror surfaces comprise a micro-structure with a period length (4) of 10 micrometer to 100 micrometer and amplitude (5) of 0.5 nanometer to 10 nanometer. The micro-structure is even or irregular. The mirror surfaces are comprised of a reflectance coating with a set of layers e.g. molybdenum/beryllium layers or molybdenum/silicon layers. The mirror element comprises a mirror body, which is made of metal, silicon glass, quartz glasses, Zerodur(RTM: lithium aluminosilicate glass-ceramic) or ULE(RTM: ultra low expansion titanium silicate glass). An independent claim is also included for a method for manufacturing a mirror element with scattering function.