# US 11,307,505 B2 · Method for operating an optical apparatus, and optical apparatus > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,307,505 B2 - Document ID: US11307505B2 - Status: Granted - Kind: B2 - Application number: 16/790,107 - Filed: 2020-02-13 - Published: 2020-06-11 - Granted: 2022-04-19 - Earliest claimed: 2017-08-15 - Assignees: Carl Zeiss SMT GmbH - Applicants: Carl Zeiss SMT GmbH - Inventors: Moritz Becker; Stefan-Wolfgang Schmidt - Web page: https://patentgrep.com/patent/US11307505B2 ## CPC - G03F 7/70883: {of optical system} - G01N 29/022: {Fluid sensors based on microsensors, e.g. quartz crystal-microbalance [QCM], surface acoustic wave [SAW] devices, tuning forks, cantilevers, flexural plate wave [FPW] devices (microdevices per se B81B)} - G01N 29/2443: {Quartz crystal probes} - G03F 7/7085: {Detection arrangement, e.g. detectors of apparatus alignment possibly mounted on wafers, exposure dose, photo-cleaning flux, stray light, thermal load} - G03F 7/70908: {Hygiene, e.g. preventing apparatus pollution, mitigating effect of pollution or removing pollutants from apparatus} - G03F 7/70983: {Optical system protection, e.g. pellicles or removable covers for protection of mask} - G01N 27/12: of a solid body in dependence upon absorption of a fluid; of a solid body in dependence upon reaction with a fluid {, for detecting components in the fluid} - G01N 2291/0256: Adsorption, desorption, surface mass change, e.g. on biosensors - 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) - G01N: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES (measuring or testing apparatus or processes other than immunoassay, involving enzymes or microorganisms C12M, C12Q) ## Abstract A method for operating an optical apparatus (100A, 100B, 200), having a structural element (201) which is arranged in a residual gas atmosphere (RGA) of the apparatus and which is formed at least partly from an element material subjected to a chemical reduction process and/or an etching process with a plasma component (PK) present in the residual gas atmosphere includes: feeding (S2) a gas component (GK) that at least partly suppresses the reduction process depending on a detected suppression extent (UM) for a suppression of the etching process and/or reduction process by the suppressing gas component in the residual gas atmosphere; and detecting (S1) the suppression extent with a sensor unit (208) arranged in the residual gas atmosphere. The sensor unit includes a sensor material section (211) composed of a sensor material and exhibiting a sensor section property that is measurable under the influence of the suppressing gas component. ## Claims ### Claim 1 Method for operating an optical apparatus, comprising: arranging a structural element in a residual gas atmosphere of the optical apparatus, which is formed at least partly from an element material which is subjected to a chemical reduction process and/or an etching process with a plasma component present in the residual gas atmosphere; feeding a suppressing gas component that at least partly suppresses the reduction process and/or the etching process depending on a detected suppression extent for suppressing the reduction process and/or the etching process by the suppressing gas component in the residual gas atmosphere; detecting the suppression extent with a sensor unit arranged in the residual gas atmosphere, wherein the detecting is based on a sensor section property of a sensor material of a sensor material section of the sensor unit that is measurable under influence of the suppressing gas component; and effecting a material removal or a material supplementation such that the sensor material is etched, reduced or oxidized under the influence of the plasma component and the suppressing gas component in the sensor material section. ### Claim 2 (depends on 1) Method according to claim 1, wherein the sensor section property is an electrical conductivity of the sensor material section, a thickness of the sensor material section on a substrate, an optical reflection and/or a transmission coefficient and/or a mass of the sensor material section. ### Claim 3 (depends on 1) Method according to claim 1, further comprising: measuring the sensor section property; and determining a substance amount to be fed of the suppressing gas component in the residual gas atmosphere depending on the measured sensor section property for detecting the suppression extent. ### Claim 4 (depends on 1) Method according to claim 1, wherein the suppression extent is detected as a ratio of proportions of the plasma component and the suppressing gas component in the residual gas atmosphere. ### Claim 5 (depends on 1) Method according to claim 1, further comprising: measuring the sensor section property; mapping the measured sensor property with a) a mapping specification, b) a reaction model for the influence of the suppressing gas component and/or the plasma component on the sensor material and/or the element material, c) a heuristic model for the influence of the suppressing gas component and/or the plasma component on the sensor material and/or the element material and/or d) a table onto the suppression extent. ### Claim 6 (depends on 1) Method according to claim 1, wherein feeding the suppressing gas component comprises determining that the detected suppression extent lies within a predefined range during operation of the optical apparatus. ### Claim 7 (depends on 6) Method according to claim 6, wherein the predefined range is selected to at least partly prevent an etching process of the element material reduced on account of the reduction process. ### Claim 8 (depends on 1) Method according to claim 1, wherein the optical apparatus comprises at least one optical element having a mirror surface, wherein the suppressing gas component is an oxidant, and wherein feeding the suppressing gas component comprises depositing element material oxidized by the suppressing gas component and previously reduced by the plasma component to an extent smaller than a predefined extent. ### Claim 9 (depends on 1) Method according to claim 1, wherein the optical apparatus is a lithography apparatus which comprises an illumination device for generating ultraviolet (UV) light, a reticle device for a photomask with lithographic information, and a projection device for imaging the lithographic information onto a wafer, and wherein the sensor unit is arranged in the projection device. ### Claim 10 (depends on 1) Method according to claim 1, wherein the optical apparatus is a mask inspection apparatus which comprises an illumination device for generating UV light, a reticle device for a photomask with lithographic information, and a projection device for imaging and for inspecting the lithographic information, and wherein the sensor unit is arranged in the projection device. ### Claim 11 (depends on 1) Method according to claim 1, wherein the structural element is an optical element, a mirror body, a mirror coating, a reticle mount and/or a carrying element. ### Claim 12 (depends on 1) Method according to claim 1, wherein the element material is selected from the group consisting of: an oxide material, a glass material, a ULE material, a zinc oxide, amorphous or crystalline silicon and a silicon carbide. ### Claim 13 (depends on 1) Method according to claim 1, wherein the plasma component comprises hydrogen. ### Claim 14 (depends on 1) Method according to claim 1, wherein the gas component that suppresses the etching and/or the reduction process comprises oxygen and/or water. ### Claim 15 Optical apparatus comprising: a housing closing off a residual gas atmosphere; a structural element which is arranged in the residual gas atmosphere and which is formed at least partly from an element material which is subjected to a chemical reduction process and/or an etching process with a plasma component present in the residual gas atmosphere; a feed unit arranged to feed a suppressing gas component that at least partly suppresses the reduction process and/or the etching process into the residual gas atmosphere; and a sensor unit arranged in the residual gas atmosphere and comprising a sensor material section composed of a sensor material, wherein the sensor material section has a measurable sensor section property that varies under influence of the suppressing gas component, and wherein the sensor material is configured to be etched, reduced or oxidized under the influence of the plasma component and the suppressing gas component in the sensor material section. ### Claim 16 (depends on 15) Optical apparatus according to claim 15, further comprising a control unit configured to control the feed unit. ### Claim 17 (depends on 15) Optical apparatus according to claim 15, wherein the sensor unit comprises a variable-resistance nanowire fabricated from the sensor material as the sensor material section and a measuring unit for measuring an electrical resistance of the nanowire as the sensor section property, wherein the sensor material is configured to be oxidized by the suppressing gas component to form a sensor material oxide. ### Claim 18 (depends on 17) Optical apparatus according to claim 17, wherein the nanowire is configured such that the sensor material oxide is stripped from the sensor material. ### Claim 19 (depends on 15) Optical apparatus according to claim 15, wherein the sensor unit comprises a variable-resistance thin layer fabricated from the sensor material and arranged on a substrate as the sensor material section and a measuring unit for measuring an electrical resistance of the thin layer as the sensor section property, wherein the sensor material is configured to be oxidized by the suppressing gas component to form a sensor material oxide. ### Claim 20 (depends on 15) Optical apparatus according to claim 15, wherein the sensor unit comprises a film fabricated from the sensor material as the sensor material section and a measuring unit for measuring an optical property as the sensor section property. ### Claim 21 (depends on 20) Optical apparatus according to claim 20, wherein the sensor material is configured to be oxidized by the suppressing gas component to form a sensor material oxide. ### Claim 22 (depends on 20) Optical apparatus according to claim 20, wherein the sensor material is configured to be reduced under the influence of the plasma component. ### Claim 23 (depends on 20) Optical apparatus according to claim 20, wherein the sensor unit is configured to determine ellipsometric parameters for a surface of the film as the sensor section property and/or to measure an optical transmission property of the film as the sensor section property. ### Claim 24 (depends on 15) Optical apparatus according to claim 15, wherein the sensor unit comprises a quartz crystal microbalance for measuring a sensor material removal from or supplementation to the sensor section under the influence of the suppressing gas component and/or the plasma component on the sensor material. ### Claim 25 (depends on 24) Optical apparatus according to claim 24, wherein the quartz crystal microbalance comprises a ruthenium, palladium, platinum or rhodium layer coated with silicon oxide. ### Claim 26 (depends on 24) Optical apparatus according to claim 24, wherein the residual gas atmosphere has a pressure of between 10−4 and 5 mbar. ### Claim 27 (depends on 15) Optical apparatus according to claim 15, wherein a partial pressure of the suppressing gas component is between 10−10 and 10−7 mbar. ### Claim 28 (depends on 15) Optical apparatus according to claim 15, further comprising a projection device configured to image lithographic information with extreme ultraviolet (EUV) radiation. ### Claim 29 Optical apparatus comprising: a housing closing off a residual gas atmosphere; a structural element which is arranged in the residual gas atmosphere and which is formed at least partly from an element material which is subjected to a chemical reduction process and/or an etching process with a plasma component present in the residual gas atmosphere; a feed unit arranged to feed a suppressing gas component that at least partly suppresses the reduction process and/or the etching process into the residual gas atmosphere; and a sensor unit arranged in the residual gas atmosphere and comprising a sensor material section composed of a sensor material, wherein the sensor material section has a measurable sensor section property that varies under influence of the suppressing gas component, wherein the sensor unit comprises a variable-resistance nanowire fabricated from the element material as the sensor material as the sensor material section and a measuring unit arranged to measure an electrical resistance of the nanowire as the sensor section property, wherein the sensor material is configured to be reduced under the influence of the plasma component.