Mirror, projection objective with such mirror, and projection exposure apparatus for microlithography with such projection objective

摘要

A mirror (1a; 1a′; 1b; 1b; 1c; 1c′) with a substrate (S) and a layer arrangement configured such that light (32) having a wavelength below 250 nm and incident on the mirror at at least an angle of incidence of between 0° and 30° is reflected with more than 20% of its intensity. The layer arrangement has at least one surface layer system (P′″) having a periodic sequence of at least two periods (P3) of individual layers, wherein the periods (P3) include a high refractive index layer (H′″) and a low refractive index layer (L′″). The layer arrangement has at least one graphene layer. Use of graphene (G, SPL, B) on optical elements reduces surface roughness to below 0.1 nm rms HSFR and/or protects the EUV element against a radiation-induced volume change of more than 1%. Graphene is also employed as a barrier layer to prevent layer interdiffusion.

主权项

1. A mirror comprising:
a substrate; a reflecting layer arrangement; at least one surface protecting layer; and a graphene layer arranged between the reflecting layer arrangement and the at least one substrate protecting layer,
wherein the reflecting layer arrangement is configured such that light having a wavelength of less than 250 nm that is incident on the mirror at at least an angle of incidence of between 0° and 30° is reflected with more than 20% of its intensity, and the layer arrangement comprises at least one surface layer system (P′″) comprising a periodic sequence of at least two periods (P3) of individual layers,wherein the periods (P3) comprise two individual layers composed of different materials providing a high refractive index layer (H′″) and a low refractive index layer (L′″),wherein the graphene layer supports the reflecting layer arrangement on the at least one surface protecting layer and has a surface roughness of less than 0.1 nm rms HSFR (high spatial frequency roughness), andwherein the surface roughness of the graphene layer is less than a surface roughness of the surface protecting layer.