PROJECTION LENS FOR EUV MICROLITHOGRAPHY, FILM ELEMENT AND METHOD FOR PRODUCING A PROJECTION LENS COMPRISING A FILM ELEMENT

摘要

A Projection lens (PO) for imaging a pattern arranged in an object plane (OS) of the projection lens into an image plane (IS) of the projection lens by means of electromagnetic radiation having a working wavelength lambda from the extreme ultraviolet range (EUV) comprises a multiplicity of mirrors (M1 - M6) having mirror surfaces which are arranged in a projection beam path between the object plane and the image plane in such a way that a pattern arranged in the object plane can be imaged into the image plane by means of the mirrors. An assigned wavefront correction device (WFC) comprises a film element (FE) having a film which is arranged in the projection beam path in an operating mode of the wavefront correction device and at the working wavelength lambda transmits a predominant proportion of the EUV radiation impinging in an optical used region. The film element comprises a first layer, which consists of a first layer material having a first complex refractive index n1 = (1-delta1) + ibeta1 and has a first optical layer thickness, which varies locally over the used region in accordance with a first layer thickness profile, and a second layer, which consists of a second layer material having a second complex refractive index n2 = (1-delta2) + ibeta2 and has a second optical layer thickness, which varies locally over the used region in accordance with a second layer thickness profile, wherein the first layer thickness profile and the second layer thickness profile are different. The deviation delta1 of the real part of the first refractive index from 1 is large relative to the absorption coefficient beta1 of the first layer material and the deviation delta2 of the real part of the second refractive index from 1 is small relative to the absorption coefficient beta2 of the second layer material.