REFLECTIVE PROJECTION LENS FOR EUV-PHOTOLITHOGRAPHY

摘要

PROBLEM TO BE SOLVED: To provide an extreme ultraviolet (EUV) projection lens that is operable at high numerical aperture and capable of substantially correcting distortion errors along all the image directions.;SOLUTION: A projection lens is for imaging a pattern arranged on an object plane onto an image plane, by using electromagnetic radiation from an extreme ultraviolet (EUV) spectral region. The projection lens comprises a plurality of imaging mirrors, each of which has a reflective coating, which define the optical axis of the projection lens and which are arranged between the object plane and the image plane, wherein the plurality of mirrors are mutually disposed, such that each is irradiated over a range of incidence angles characteristic of the mirror, wherein at least the mirror having the largest range of incidence angles has an acentric, graded reflective coating having film thickness gradient which is rotationally symmetric with respect to a coating axis, and wherein the coating axis substantially coincides with the optical axis of the projection lens.;COPYRIGHT: (C)2009,JPO&INPIT