# US 10,481,500 B2 · Imaging optical system and projection exposure installation for microlithography with an imaging optical system of this type > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,481,500 B2 - Document ID: US10481500B2 - Status: Granted - Kind: B2 - Application number: 13/197,065 - Filed: 2011-08-03 - Published: 2012-03-22 - Granted: 2019-11-19 - Earliest claimed: 2009-02-12 - Assignees: Carl Zeiss SMT GmbH - Applicants: Hans-Juergen Mann; Wilhelm Ulrich; Erik Loopstra; David R. Shafer - Inventors: Hans-Juergen Mann; Wilhelm Ulrich; Erik Loopstra; David R. Shafer - Web page: https://patentgrep.com/patent/US10481500B2 ## CPC - G03F 7/70233: {Optical aspects of catoptric systems, i.e. comprising only reflective elements, e.g. extreme ultraviolet [EUV] projection systems} - G02B 17/0647: {using more than three curved mirrors (G02B17/0668, G02B17/0694 take precedence)} - G02B 17/0663: {off-axis or unobscured systems in which not all of the mirrors share a common axis of rotational symmetry, e.g. at least one of the mirrors is warped, tilted or decentered with respect to the other elements} - G03F 7/7015: {Details of optical elements} - G03F 7/7025: {Size or form of projection system aperture, e.g. aperture stops, diaphragms or pupil obscuration; Control thereof} - G02B 17/0652: {on-axis systems with at least one of the mirrors having a central aperture} - 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 imaging optical system has a plurality of mirrors which image an object field in an object plane in an image field in an image plane. The imaging optical system has a pupil obscuration. The last mirror in the beam path of the imaging light between the object field and the image field has a through-opening for the passage of the imaging light. A penultimate mirror of the imaging optical system in the beam path of the imaging light between the object field and the image field has no through-opening for the passage of the imaging light. The result is an imaging optical system that provides a combination of small imaging errors, manageable production and a good throughput for the imaging light. ## Claims ### Claim 1 An imaging optical system, comprising: a plurality of mirrors configured to image an object field in an object plane into an image field in an image plane along a beam path of imaging light, wherein: the last mirror in the beam path of the imaging light between the object field and the image field has a through-opening to pass the imaging light; the penultimate mirror in the beam path of the imaging light between the object field and the image field is outside an imaging light bundle in front of the imaging field; and a reflective face of the penultimate mirror within an optically used region of the penultimate mirror has no through-opening to pass the imaging light. ### Claim 2 (depends on 1) The imaging optical system of claim 1, wherein a working spacing of the penultimate mirror in the beam path of the imaging light between the object field and the image field of the imaging light is at least 20 mm. ### Claim 3 (depends on 1) The imaging optical system of claim 1, wherein an angle of incidence of the imaging light on the penultimate mirror is at most 35°. ### Claim 4 (depends on 1) The imaging optical system of claim 1, comprising an imaging beam path section between a third to last mirror in the beam path of the imaging light between the object field and the image field and the penultimate mirror in the beam path of the imaging light between the object field and the image field, wherein a portion of the imaging beam path in front of the imaging beam path section and an imaging light bundle in a region of the image field are guided on opposing sides of the imaging beam path section, respectively. ### Claim 5 (depends on 1) The imaging optical system of claim 1, comprising an imaging beam path section between a third to last mirror in the beam path of the imaging light between the object field and the image field and the penultimate mirror in the beam path of the imaging light between the object field and the image field, wherein a portion of the imaging beam path in front of the imaging beam path section and an imaging light bundle in a region of the image field are guided on the same side of the imaging beam path section. ### Claim 6 (depends on 1) The imaging optical system of claim 1, wherein a third to last mirror in the beam path of the imaging light between the object field and the image field and a sixth to last mirror in the beam path between the object field and the image field are arranged back to back. ### Claim 7 (depends on 1) The imaging optical system of claim 1, comprising an intermediate image in the beam path of the imaging light between the object field and the image field. ### Claim 8 (depends on 1) The imaging optical system of claim 1, comprising an intersection region between imaging beam path sections. ### Claim 9 (depends on 1) The imaging optical system of claim 1, wherein the imaging optical system has a numerical aperture of at least 0.3. ### Claim 10 (depends on 1) The imaging optical system of claim 1, wherein the image field is a rectangular field. ### Claim 11 (depends on 1) The imaging optical system of claim 1, wherein the imaging optical system is a microlithography projection optical system. ### Claim 12 (depends on 1) A projection exposure installation, comprising: an illumination system; and a projection optical system comprising the imaging optical system of claim 1, wherein the projection exposure apparatus is a microlithography projection exposure apparatus. ### Claim 13 (depends on 1) A method, comprising: providing a microlithography projection exposure comprising: an illumination system; and a projection optical system comprising the imaging optical system of claim 1; and using the projection exposure installation to project a structure on a reticle onto a light-sensitive layer of the wafer. ### Claim 14 (depends on 1) The imaging optical system of claim 1, wherein only the last mirror in the beam path of the imaging light between the object field and the image field has a reflective surface that surrounds a through-opening to pass the imaging light.