# US 2021/0341831 A1 · Mask Assembly and Associated Methods > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2021/0341831 A1 - Document ID: US20210341831A1 - Status: Published application - Kind: A1 - Application number: 17/375,283 - Filed: 2021-07-14 - Published: 2021-11-04 - Earliest claimed: 2015-02-03 - Assignees: ASML Netherlands B.V. - Applicants: ASML Netherlands B.V. - Inventors: Derk Servatius Gertruda BROUNS; Dennis DE GRAAF; Robertus Cornelis Martinus DE KRUIF; Paul JANSSEN; Matthias KRUIZINGA; Arnoud Willem NOTENBOOM; Daniel Andrew SMITH; Beatrijs Louise Marie-Josep VERBRUGGE; James Norman WILEY - Web page: https://patentgrep.com/patent/US20210341831A1 ## CPC - G03F 1/62: Pellicles, e.g. pellicle assemblies, e.g. having membrane on support frame; Preparation thereof - G03F 1/38: Masks having auxiliary features, e.g. special coatings or marks for alignment or testing; Preparation thereof - G03F 1/66: Containers specially adapted for masks, mask blanks or pellicles; Preparation thereof - G03F 7/70983: {Optical system protection, e.g. pellicles or removable covers for protection of mask} - G03F 1/22: Masks or mask blanks for imaging by radiation of 100nm or shorter wavelength, e.g. X-ray masks, extreme ultraviolet [EUV] masks; Preparation thereof - G03F 1/42: Alignment or registration features, e.g. alignment marks on the mask substrates - G03F 1/64: characterised by the frames, e.g. structure or material, including bonding means therefor - G03F 1/84: Inspecting - 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) ## Abstract A method comprising the steps of receiving a mask assembly comprising a mask and a removable EUV transparent pellicle held by a pellicle frame, removing the pellicle frame and EUV transparent pellicle from the mask, using an inspection tool to inspect the mask pattern on the mask, and subsequently attaching to the mask an EUV transparent pellicle held by a pellicle frame. The method may also comprise the following steps: after removing the pellicle frame and EUV transparent pellicle from the mask, attaching to the mask an alternative pellicle frame holding an alternative pellicle formed from a material which is substantially transparent to an inspection beam of the inspection tool; and after using an inspection tool to inspect the mask pattern on the mask, removing the alternative pellicle held by the alternative pellicle frame from the mask in order to attach to the mask the EUV transparent pellicle held by the pellicle frame. ## Claims ### Claim 1 A pellicle inspection tool for an EUV transparent pellicle, the pellicle inspection tool comprising: a support structure for supporting: a) a pellicle comprising the EUV transparent pellicle membrane supported by a substrate perimeter that borders the membrane; or b) a pellicle assembly comprising the EUV transparent pellicle membrane and a pellicle frame attached to the substrate perimeter that borders the membrane; or c) a mask assembly comprising the EUV transparent pellicle membrane, a pellicle frame attached to the substrate perimeter that borders the membrane, and a mask attached to the pellicle frame; and a device for measuring a property of the EUV transparent pellicle and monitoring for a change of the property that is associated with an increased risk of pellicle breakage, wherein the EUV transparent pellicle is configured to transmit at least 65% of incident EUV radiation. ### Claim 2 (depends on 1) The pellicle inspection tool of claim 1, wherein the device is arranged to measure a property of the pellicle using one or more measuring technique selected from the group consisting of EUV reflection measurements, EUV transmission measurements, birefringence measurements, ellipsometry, Fourier transform infra-red spectroscopy, Raman spectroscopy, X-ray reflection measurements, microscope inspection, resonance measurements, scanning heat load measurements, measurement of pellicle displacement due to pressure difference, and pellicle deflection during pumpdown or venting. ### Claim 3 (depends on 1) The pellicle inspection tool of claim 1, wherein the device is an infra-red sensor arranged to (i) measure an infra-red radiation emitted by the pellicle with the wavelength of that radiation being linked to the temperature of the of the pellicle, or (ii) monitor for changes of infra-red absorption of the pellicle film in order to detect localized changes of the emissivity of the pellicle. ### Claim 4 (depends on 1) The pellicle inspection tool of claim 1, wherein the device is a sensor arranged to monitor global or localized variations in the EUV reflection of the pellicle. ### Claim 5 (depends on 1) The pellicle inspection tool of claim 1, wherein the device is a sensor arrange to determine the amount of EUV radiation that is transmitted by the pellicle. ### Claim 6 (depends on 1) The pellicle inspection tool of claim 1, wherein the device is arranged to measure changes in the reflection of the pellicle over a range of wavelengths, wherein the measured changes are indicative of changes in material properties of the pellicle. ### Claim 7 (depends on 1) The pellicle inspection tool of claim 1, wherein the device is arranged to measure changes in the polarization of the radiation beam to determine global or local changes in the stress of the pellicle. ### Claim 8 (depends on 1) The pellicle inspection tool of claim 1, wherein the device is arranged to measure an intensity of a specular reflection of x-rays from the pellicle. ### Claim 9 (depends on 8) The pellicle inspection tool of claim 8, further comprising a source of X-ray beam arranged to direct the beam of X-ray onto the pellicle at a grazing incidence angle. ### Claim 10 (depends on 1) The pellicle inspection tool of claim 1, wherein the device is arranged to measure a variation in a resonant frequency of the pellicle assembly or the mask assembly. ### Claim 11 (depends on 1) The pellicle inspection tool of claim 1, wherein the device is a sensor arranged to measure a degree of deflection of the pellicle due to a pressure difference. ### Claim 12 (depends on 1) The pellicle inspection tool according to claim 1, wherein the device is arranged to measure a position of wrinkles in the pellicle and/or a change in the position of the wrinkles. ### Claim 13 A lithographic apparatus comprising a pellicle inspection tool for an EUV transparent pellicle, the pellicle inspection tool comprising: a support structure for supporting: a) a pellicle comprising the EUV transparent pellicle membrane supported by a substrate perimeter that borders the membrane; or b) a pellicle assembly comprising the EUV transparent pellicle membrane and a pellicle frame attached to the substrate perimeter that borders the membrane; or c) a mask assembly comprising the EUV transparent pellicle membrane, a pellicle frame attached to the substrate perimeter that borders the membrane, and a mask attached to the pellicle frame; and a device for measuring a property of the EUV transparent pellicle and monitoring for a change of the property that is associated with an increased risk of pellicle breakage, wherein the EUV transparent pellicle is configured to transmit at least 65% of incident EUV radiation. ### Claim 14 A method of monitoring a pellicle of a mask assembly, the mask assembly comprising a pellicle assembly and a mask, the method comprising: measuring a property of the pellicle, and monitoring for a change of the property that is associated with an increased risk of pellicle breakage, and when such a change is determined, removing the pellicle assembly from the mask and replacing it with a new pellicle assembly. ### Claim 15 (depends on 14) The method of claim 14, wherein the measuring comprises measuring the property of the pellicle when the mask assembly is in situ in the lithographic apparatus. ### Claim 16 (depends on 15) The method of claim 15, wherein the measuring comprises measuring infra-red emission of the pellicle and/or deflection of the pellicle during scanning movement of the mask assembly. ### Claim 17 (depends on 14) The method of claim 14, further comprising transferring the mask assembly to a mask assembly inspection tool and measuring the property of the pellicle using the mask assembly inspection tool. ### Claim 18 (depends on 17) The method of claim 17, wherein one or more of the following measurement techniques are used to measure one or more properties of the pellicle: EUV reflection measurements, EUV transmission measurements, ellipsometry, Raman spectroscopy, X-ray reflection measurements, microscope inspection, resonance measurements, scanning heat load measurements, or pellicle deflection during pumpdown or venting. ### Claim 19 (depends on 14) The method of claim 14, further comprising removing the pellicle assembly from the mask, transferring the pellicle assembly to a pellicle assembly inspection tool, and measuring the property of the pellicle using the pellicle assembly inspection tool. ### Claim 20 (depends on 19) The method of claim 19, wherein one or more of the following measurement techniques are used to measure one or more properties of the pellicle: EUV transmission measurements (pellicle assembly removed from mask), EUV reflection measurements, birefringence measurements, ellipsometry, Fourier transform infra-red spectroscopy, Raman spectroscopy, X-ray reflection measurements, microscope inspection, resonance measurements, measurement of pellicle displacement due to pressure difference, deflection during pumpdown or venting, scanning heat load measurements, or frame deformation measurements.