Patent ID: 11360293

Abstract:
A catadioptric projection lens images a pattern of a mask in an effective object field of the projection lens into an effective image field of the projection lens with electromagnetic radiation with an operating wavelength λ<260 nm. The projection lens includes a multiplicity of lens elements and a multiplicity of mirrors including at least one concave mirror. The lens elements and mirrors define a projection beam path that extends from the object plane to the image plane and contains at least one pupil plane. The mirrors include a first mirror having a first mirror surface in the projection beam path between the object and pupil planes in the optical vicinity of a first field plane optically conjugate to the object plane. The mirrors also include a second mirror having a second mirror surface in the projection beam path between the pupil and image planes in the optical vicinity of a second field plane that is optically conjugate to the first field plane. The first mirror surface and/or the second mirror surface is a freeform surface.