# US 7,405,808 B2 · Optical system, in particular illumination system, of a microlithographic projection exposure apparatus > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 7,405,808 B2 - Document ID: US7405808B2 - Status: Granted - Kind: B2 - Application number: 11/014,199 - Filed: 2004-12-16 - Published: 2005-07-14 - Granted: 2008-07-29 - Earliest claimed: 2003-12-19 - Assignees: Carl Zeiss SMT GmbH - Inventors: Toralf Gruner; Michael Totzeck; Damian Fiolka; Wilhelm Ulrich; Gerhard Fuerter - Web page: https://patentgrep.com/patent/US7405808B2 ## CPC - G03F 7/70191: {Optical correction elements, filters or phase plates for controlling intensity, wavelength, polarisation, phase or the like} - G02B 27/286: {for controlling or changing the state of polarisation, e.g. transforming one polarisation state into another (G02B5/3083 takes precedence; light guide coupling means utilising polarising elements G02B6/34)} - G03F 7/70566: {Polarisation control} - G02B 5/04: Prisms - G02B 5/3066: {involving the reflection of light at a particular angle of incidence, e.g. Brewster's angle} - G03F: PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR; (phototypographic composing devices B41B; photosensitive materials or processes for photographic purposes G03C; electrophotography, sensitive layers or processes therefor G03G) - G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS ## Abstract An optical system, particularly an illumination system, of a microlithographic projection exposure apparatus contains at least one plane reflecting surface for folding the beam path. The at least one reflecting surface is arranged with respect to an optical axis of the optical system such that the intensity ratio between two mutually perpendicular polarization directions is at least substantially preserved for an axially parallel light ray deviated by the at least one reflecting surface. In accordance with a second aspect, the at least one reflecting surface is arranged such that a maximum effect on the polarization of the projection light is achieved, so as to be able to compensate for polarization dependencies which occur in other components of the illumination system. ## Claims ### Claim 1 An optical system of a microlithographic projection exposure apparatus, having: a)an optical axis and b)a mirror device that i) deviates the optical axis and ii) comprises at least two plane non-transparent reflecting surfaces that are arranged with respect to the optical axis such that every possible intensity ratio between two mutually perpendicular polarization directions is at least substantially preserved for every light ray that runs parallel to the optical axis. ### Claim 2 (depends on 1) The optical system of claim 1, wherein the normal of the at least one reflecting surface makes an angle of less than 40° with the optical axis. ### Claim 3 (depends on 2) The optical system of claim 2, wherein the normal of the at least one reflecting surface makes an angle of less than 30° with the optical axis. ### Claim 4 (depends on 3) The optical system of claim 3, wherein the normal of the at least one reflecting surface makes an angle of at least substantially 22.5° with the optical axis. ### Claim 5 (depends on 4) The optical system of claim 4, wherein the optical axis is deviated by 90° and the mirror device comprises two plane reflecting surfaces having normals that both make an angle of approximately 22.5° with the optical axis and an angle of approximately 135° between each other. ### Claim 6 (depends on 1) The optical system of claim 1, wherein an angle between the optical axis and each normal of the at least two plane non-transparent reflecting surfaces is the same, and wherein the mirror device further includes an optical element, which exchanges the polarization directions of s-polarized and p-polarized light and is arranged between the at least two plane non-transparent reflecting surfaces. ### Claim 7 (depends on 1) The optical system of claim 1, wherein the mirror device comprises two reflecting surfaces having normals that are arranged with respect to the optical axis such that the incidence planes for coaxial rays are perpendicular to each other. ### Claim 8 (depends on 7) The optical system of claim 7, wherein the optical axis is deviated by 90°, and wherein the normals of the two reflecting surfaces make an angle of approximately 45° with the optical axis and an angle of approximately 60° between each other. ### Claim 9 (depends on 8) The optical system of claim 8, wherein the two reflecting surfaces are the reflecting surfaces of a Nachet prism. ### Claim 10 (depends on 1) The optical system of claim 1, comprising a light source for illuminating a structure. ### Claim 11 (depends on 1) The optical system of claim 1, wherein the mirror device comprises: a) a first plane reflecting surface having, for incidence angles of more than 30°, a reflectivity for light polarized perpendicularly to an incidence plane which is greater than the reflectivity for light polarized parallel to the incidence plane, and b) a second plane reflecting surface having, for incidence angles of more than 30°, a reflectivity for light polarized perpendicularly to an incidence plane which is less than the reflectivity for light polarized parallel to the incidence plane. ### Claim 12 (depends on 1) A microlithographic projection exposure apparatus comprising an optical system of claim 1. ### Claim 13 (depends on 1) A method for the microlithographic production of microstructured components, comprising the following steps: a) providing a support, on which a layer of a photosensitive material is at least partially applied; b) providing a reticle, which contains structures to be projected; c) providing an illumination system for the generation of projection light according to claim 1; d) projecting at least a part of the reticle onto a region on the layer with the aid of a projection lens.