# US 7,465,681 B2 · Method for producing smooth, dense optical films > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 7,465,681 B2 - Document ID: US7465681B2 - Status: Granted - Kind: B2 - Application number: 11/510,140 - Filed: 2006-08-25 - Published: 2008-02-28 - Granted: 2008-12-16 - Earliest claimed: 2006-08-25 - Assignees: Corning Incorporated - Inventors: Gary Allen Hart; Robert LeRoy Maier; Jue Wang - Web page: https://patentgrep.com/patent/US7465681B2 ## CPC - G02B 1/10: Optical coatings produced by application to, or surface treatment of, optical elements (G02B1/08 takes precedence) - C23C 14/22: characterised by the process of coating - G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS - C23C: COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL (making metal-coated products by extrusion B21C23/22; covering with metal by connecting pre-existing layers to articles, see the relevant places, e.g. B21D39/00, B23K; metallising of glass C03C; metallising mortars, concrete, artificial stone, ceramics or natural stone C04B41/00; enamelling of, or applying a vitreous layer to, metals C23D; treating metal surfaces or coating of metals by electrolysis or electrophoresis C25D; single-crystal film growth C30B; by metallising textiles D06M11/83; decorating textiles by locally metallising D06Q1/04) ## Abstract The invention is directed to preparing optical elements having a thin, smooth, dense coating or film thereon, and a method for making such coating or film. The coated element has a surface roughness of <1.0 nm rms. The coating materials include hafnium oxide or a mixture of hafnium oxide and another oxide material, for example silicon dioxide. The method includes the use of a reverse mask to deposit the coating or film on a rotating substrate. ## Claims ### Claim 1 A method of depositing a thin film of a selected material on the surface of a substrate using plasma ion assisted deposition, the method having the steps of: providing a vacuum chamber and within said vacuum chamber: providing a substrate on which a coating is to be deposited; providing at least one selected coating material source, or a mixture of coating materials source, and vaporizing said material(s) using an e-beam to provide a coating material vapor flux, said flux passing from said material source through a reversed mask to said substrate; providing plasma ions from a plasma source; rotating said substrate at a selected rotation frequency f; and depositing said coating material on said substrate as a coating film and bombarding said substrate and said film with said plasma ions before and during said material deposition process: wherein said flux is delivered to said substrate at an angle φ that is ≦20°. ### Claim 2 (depends on 1) The method according to claim 1, wherein providing at least one selected coating material source means providing a material selected from the group consisting of Al2O3, SiO2, HfO2, Si3N4, TiO2, Ta2O5, ScO2, Y2O3 and ZrO2, and mixtures thereof. ### Claim 3 (depends on 1) The method according to claim 1, wherein said film is deposited with a columnar microstructure that is formed with an inclination angle ω, said angle ω being between the film normal and vapor flux angle φ. ### Claim 4 (depends on 1) The method according to claim 1, wherein said film is deposited with a columnar microstructure that is formed with an inclination angle ω, said angle ω having a value in the range of 0° to 18°. ### Claim 5 (depends on 1) The method according to claim 1, wherein said rotation frequency f is in the range of 4 to 20 rpm. ### Claim 6 (depends on 1) The method according to claim 1, wherein said plasma ions are formed from a plasma gas, said plasma gas is selected from the Noble gas group and a mixture of a Noble gas with oxygen. ### Claim 7 (depends on 1) The method according to claim 1, wherein said plasma ions are formed from a plasma gas, said plasma gas is selected from the group consisting of argon, xenon, and a mixture of argon or xenon with oxygen. ### Claim 8 (depends on 1) The method according to claim 1, wherein said substrate is selected from the group consisting of silicon (Si), alkaline metal fluoride single crystals including mixed alkaline metal fluoride single crystals, silica (SiO2), fused silica, fluorine doped fused silica, and silica or fused silica doped with at least one substance selected from the group consisting of TiO2, Al2O3, B2O3, and SnO. ### Claim 9 (depends on 8) The method according to claim 8, wherein said substrate is selected from the group consisting of silicon, silica, fused silica, optical glasses, germanium, ZnSe, As2S3, ZnS, fluorine doped fused silica, TiO2 doped silica and TiO2 doped fused silica. ### Claim 10 (depends on 1) The method according to claim 1, wherein said method includes the additional step of bombarding said substrate with said plasma ions prior to deposition of said coating materials to densify and smooth the surface of said substrate, said bombarding being for a time in the range of >0-10 minutes. ### Claim 11 (depends on 10) The method according to claim 10, wherein said plasma ion bombardment is for a time in the range of 1-4 minutes. ### Claim 12 A method for preparing a silica optical element having a coating of a selected material, said method comprising the steps of: providing a vacuum chamber and within said vacuum chamber: providing at least one selected coating material source, or a mixture of coating materials source, and vaporizing said material(s) using an e-beam to provide a coating material vapor flux, said flux passing from said material source through a reversed mask to said substrate; providing plasma ions from a plasma source; rotating said substrate at a selected rotation frequency f; depositing said coating material on said substrate and bombarding said substrate and said deposited materials with said plasma ions before and during said material deposition process; wherein: said rotational frequency f is in the range of 12 to 15 rpm, and said flux is delivered to said substrate at an angle φ that is ≦20°; and the surface of said substrate is bombarded with said plasma ions for a time in the range of 1-4 minutes prior to the deposition of the coating martial(s). ### Claim 13 (depends on 12) The method according to claim 12, wherein said coating material source means providing a material selected from the group consisting of Al2O3, SiO2, HfO2, and a SiO2/HfO2 mixture of any composition. ### Claim 14 (depends on 12) The method according to claim 12, wherein said film is deposited with a columnar microstructure that is formed with an inclination angle ω, said angle ω being between the film normal and vapor flux angle φ. ### Claim 15 (depends on 12) The method according to claim 12, wherein said film is deposited with a columnar microstructure that is formed with an inclination angle ω, said angle ω having a value in the range of 0° to 18°. ### Claim 16 (depends on 12) The method according to claim 12, wherein said plasma ions are formed from a plasma gas, said plasma gas is selected from the group consisting of argon, xenon, and a mixture of argon or xenon with oxygen.