# US 11,439,959 B2 · Porous flat deformation-resistant membrane > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,439,959 B2 - Document ID: US11439959B2 - Status: Granted - Kind: B2 - Application number: 16/842,402 - Filed: 2020-04-07 - Published: 2021-10-07 - Granted: 2022-09-13 - Earliest claimed: 2020-04-07 - Assignees: Global Life Sciences Solutions USA LLC - Applicants: Global Life Sciences Solutions USA LLC - Inventors: William A Hennessy; Douglas Albagli - Web page: https://patentgrep.com/patent/US11439959B2 ## CPC - B01D 71/643: {Polyether-imides} - B01D 67/0034: {by micromachining techniques, e.g. using masking and etching steps, photolithography} - B01D 69/06: Flat membranes - B01D 69/108: {Inorganic support material} - G03F 7/00: Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor (using photoresist structures for special production processes, see the relevant places, e.g. B44C, H10P76/00, H05K) - B01D 2325/0283: Pore size - B01D 2325/08: Patterned membranes - B01D: SEPARATION (separating solids from solids by wet methods B03B, B03D; by pneumatic jigs or tables B03B; by other dry methods B07; magnetic or electrostatic separation of solid materials from solid materials or fluids, separation by high-voltage electric fields B03C; centrifuges, vortex apparatus B04; presses per se for squeezing-out liquid from liquid-containing material B30B9/02; treatment of water C02F, e.g. softening by ion-exchange C02F1/42; {arrangements of air intake cleaners in gas turbine plants F02C7/05} ; arrangements or mounting of filters in air-conditioning, air-humidification or ventilation F24F13/28) - 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 Porous membranes are provided according to the invention having desirable coefficient of thermal expansion and large surface area, for example at least about 4,000 mm2. These porous membranes may be made according to an exemplary process employing lithographic patterning of a photoresist followed by development of the photoresist and etching. In one aspect, the etch barrier layer is chosen from a material that does not react with or incorporate metal or other contaminants into the membrane layer. ## Claims ### Claim 1 A method for making a liquid-filtering porous membrane comprising: a) depositing a photoresist layer on the top surface of a substrate, the substrate comprising a support layer, a polymer layer, and a hard mask layer, wherein the polymer layer has a thickness of between 5 to 25 microns and the polymer layer being of polyimide having a matched coefficient of thermal expansion that is within ±25% relative to the support layer; b) exposing the photoresist to a pattern of light; c) developing the photoresist layer to provide a first pattern of openings in the photoresist layer that expose portion of the hard mask layer; d) etching the exposed portions of the hard mask layer to provide a second pattern of openings in the hard mask layer that expose portions of the underlying polymer layer; e) removing the photoresist; f) etching the polymer layer through the openings in the hard mask layer thereby providing a third pattern of openings in the polymer layer; g) removing the hard mask layer; and h) releasing the polymer layer from the support layer, thereby providing the porous membrane, wherein the pore dimensions of the porous membrane are defined by the pattern of light and membrane has a surface area of at least 4,000 mm2, wherein the hard mask layer comprises hydrogenated amorphous SiN (SiN:H) or hydrogenated amorphous SiO (SiO:H). ### Claim 2 (depends on 1) The method of claim 1, wherein the matched coefficients of thermal expansion are within ±15% relative to each other. ### Claim 3 (depends on 1) The method of claim 1, wherein the matched coefficients of thermal expansion are within ±10% relative to each other. ### Claim 4 (depends on 1) The method of claim 1, wherein the membrane has a surface area of at least 0.1 m2. ### Claim 5 (depends on 1) The method of claim 1, wherein the membrane has a level of residual hard mask material that is at most 0.15 μg/cm2. ### Claim 6 (depends on 1) The method of claim 1, wherein the pores have an aspect ratio of 0.5:1 to 20:1. ### Claim 7 (depends on 1) The method of claim 1, wherein the support layer is a glass support layer. ### Claim 8 A method for making a liquid-filtering porous membrane comprising: a) depositing a photoresist layer on the top surface of a glass substrate, the substrate comprising a support layer, a polymer layer, and a hard mask layer, wherein the polymer layer has a thickness of between 5 to 25 microns and the polymer layer being of polyimide having a matched coefficient of thermal expansion that is within ±25% relative to the glass substrate, the hard mask layer comprising hydrogenated amorphous SiN (SiN:H) or hydrogenated amorphous SiO (SiO:H); b) exposing the photoresist to a pattern of light; c) developing the photoresist layer to provide a first pattern of openings in the photoresist layer that expose portion of the hard mask layer; d) etching the exposed portions of the hard mask layer to provide a second pattern of openings in the hard mask layer that expose portions of the underlying polymer layer; e) removing the photoresist; f) etching the polymer layer through the openings in the hard mask layer thereby providing a third pattern of openings in the polymer layer; g) removing the hard mask layer; and h) releasing the polymer layer from the support layer, thereby providing the porous membrane, wherein the pore dimensions of the porous membrane are defined by the pattern of light and membrane has a surface area of at least 4,000 mm2. ### Claim 9 (depends on 8) The method of claim 8, wherein the matched coefficients of thermal expansion are within ±15% relative to each other. ### Claim 10 (depends on 8) The method of claim 8, wherein the matched coefficients of thermal expansion are within ±10% relative to each other. ### Claim 11 (depends on 8) The method of claim 8, wherein the membrane has a surface area of at least 0.1 m2. ### Claim 12 (depends on 8) The method of claim 8, wherein the membrane has a level of residual hard mask material that is at most 0.15 μg/cm2. ### Claim 13 (depends on 8) The method of claim 8, wherein the pores have an aspect ratio of 0.5:1 to 20:1.