# US 12,215,419 B2 · Smoothing surface roughness using atomic layer deposition > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 12,215,419 B2 - Document ID: US12215419B2 - Status: Granted - Kind: B2 - Application number: 17/733,575 - Filed: 2022-04-29 - Published: 2023-11-02 - Granted: 2025-02-04 - Earliest claimed: 2022-04-29 - Assignees: Eagle Technology, LLC; University of Colorado Boulder - Applicants: Eagle Technology, LLC; University of Colorado Boulder - Inventors: James Throckmorton; Tyler Myers; Rebecca Borrelli; Malcolm O'Sullivan; Tukaram Hatwar; Steven M. George - Web page: https://patentgrep.com/patent/US12215419B2 ## CPC - C23C 16/45525: {Atomic layer deposition [ALD]} - C23C 16/0254: {Physical treatment to alter the texture of the surface, e.g. scratching or polishing} - C23C 16/345: {Silicon nitride} - C23C 16/402: {Silicon dioxide} - C23C 16/403: {of aluminium, magnesium or beryllium} - C23C 16/405: {of refractory metals or yttrium} - C23C 16/407: {of zinc, germanium, cadmium, indium, tin, thallium or bismuth} - C23C 28/042: {including a refractory ceramic layer, e.g. refractory metal oxides, ZrO2, rare earth oxides} - 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 Methods of producing an optical surface atop an exterior of a substrate that includes smoothing the exterior using an ALD process to sequentially deposit ALD layers to produce one or more ALD films that fill spaces between spaced-apart asperities existing on the exterior, and thereafter depositing a reflective material on the smoothed exterior of the substrate to produce the optical surface. The smoothing resulting from depositing the ALD film on the exterior of the substrate causes the grain size of the reflective material to be reduced in comparison to the grain size that would exists without having deposited the ALD film on the exterior of the substrate. The smoothing is sufficient to cause a reduction in grain size that results in a reduction in plasmon absorption in the optical surface in comparison to the plasmon absorption that would otherwise exist without having reduced the grain size of the reflective material. ## Claims ### Claim 1 A method of producing an optical surface, the method comprising: obtaining a substrate having an exterior above which the optical surface is to reside, the exterior including laterally spaced-apart asperities having peaks which are spaced <1000 nm apart and affect optical performance of the produced optical surface absent a smoothing of the exterior surface; smoothing the exterior of the substrate using an atomic layer deposition process to sequentially deposit a first plurality of ALD layers to produce an ALD film that fills spaces between the laterally spaced-apart asperities existing on the exterior surface; and depositing a reflective material on a surface of the ALD film to produce the optical surface, the smoothing resulting from depositing the ALD film on the exterior of the substrate causing the grain size of the reflective material to be reduced in comparison to the grain size that would otherwise exists without having deposited the ALD film on the exterior of the substrate, the reduction in grain size of the reflective material causing a reduction in plasmon absorption in the optical surface in comparison to the plasmon absorption that would otherwise occur in the optical surface without having reduced the grain size of the reflective material. ### Claim 2 (depends on 1) The method of producing an optical surface according to claim 1, wherein the first plurality of ALD layers are selected from the group consisting of Al2O3 layers, SiO2 layers, TiO2 layers, ZrO2 layers, ZnO and SiNx. ### Claim 3 (depends on 1) The method of producing an optical surface according to claim 1, wherein the first plurality of ALD layers comprises layers of different metals. ### Claim 4 (depends on 3) The method of producing an optical surface according to claim 3, wherein the layers of difference metals are selected from the group consisting of Al2O3 layers, SiO2 layers, TiO2 layers, ZrO2 layers, ZnO and SiNx. ### Claim 5 (depends on 1) The method of producing an optical surface according to claim 1, wherein the reflective material is selected from the group consisting of silver, gold, aluminum, germanium and chromium. ### Claim 6 (depends on 1) The method of producing an optical surface according to claim 1, wherein each of the laterally spaced-apart asperities has a peak, the ALD film having a thickness of no more than one half an average lateral distance between the peaks. ### Claim 7 (depends on 6) The method of producing an optical surface according to claim 6, wherein the ALD film has a thickness of 3 nanometers to 400 nanometers. ### Claim 8 (depends on 1) The method of producing an optical surface according to claim 1, further comprising an additional step of smoothing the exterior of the substrate prior to the depositing of the ALD film, the additional step of smoothing the exterior of the substrate comprising a chemical-mechanical polishing process. ### Claim 9 (depends on 1) The method of producing an optical surface according to claim 1, further comprising an additional step of processing the exterior of the substrate prior to the depositing of the ALD film, the additional step of processing the exterior of the substrate comprising depositing one or more layers of metal on the exterior surface of the substrate using a chemical vapor deposition process. ### Claim 10 (depends on 1) The method of producing an optical surface according to claim 1, further comprising an additional step of processing the exterior of the substrate prior to the depositing of the ALD film, the additional step of processing the exterior of the substrate comprising an ion-beam figuring process. ### Claim 11 (depends on 1) The method of producing an optical surface according to claim 1, further comprising an additional step of processing the exterior of the substrate prior to the depositing of the ALD film, the additional step of processing the exterior of the substrate comprising depositing one or more layers of metal on the exterior surface of the substrate using a physical vapor deposition process. ### Claim 12 (depends on 11) The method of producing an optical surface according to claim 11, wherein the metal is selected from the group consisting of silver, gold, aluminum, germanium and chromium. ### Claim 13 (depends on 9) The method of producing an optical surface according to claim 9, wherein the metal is selected from the group consisting of silver, gold, aluminum, germanium and chromium. ### Claim 14 (depends on 1) The method of producing an optical surface according to claim 1, further comprising: a first step of determining the power spectral density of a surface topography of the exterior of the substrate that includes the ALD film surface as a function of spatial frequency after the smoothing of the exterior of the substrate using the atomic layer deposition process; and a second step comprising comparing the power spectral density determined in the first step to a predetermined target power spectral density at one or more spatial frequencies, the predetermined target power spectral density at the one or more spatial frequencies corresponding to a target roughness of the exterior of the substrate before the step of depositing the reflective material. ### Claim 15 (depends on 14) The method of producing an optical surface according to claim 14, wherein upon a determining that the exterior of the substrate that includes the ALD film surface has a roughness greater than the target roughness, smoothing the exterior of the substrate that includes the ALD film surface using the atomic layer deposition process to sequentially deposit a second plurality of ALD layers onto the exterior of the substrate that includes the ALD film surface prior to depositing the reflective material. ### Claim 16 (depends on 14) The method of producing an optical surface according to claim 14, wherein the power spectral density at the one or more spatial frequencies is determined using atomic force microscopy. ### Claim 17 A method of producing an optical surface, the method comprising: obtaining a substrate having an exterior above which the optical surface is to reside, the exterior including laterally spaced-apart asperities; smoothing the exterior of the substrate using an atomic layer deposition process to sequentially deposit a first plurality of ALD layers to produce an ALD film that fills spaces between the laterally spaced-apart asperities existing on the exterior surface; a first step of determining the power spectral density of a surface topography of the exterior of the substrate that includes the ALD film surface as a function of spatial frequency after the smoothing of the exterior of the substrate using the atomic layer deposition process; a second step comparing the power spectral density determined in the first step to a predetermined target power spectral density at one or more of the spatial frequencies, the predetermined target power spectral density at one or more spatial frequencies corresponding to a target roughness of the exterior of the substrate that includes the ALD film surface; and only upon a determining that the exterior of the substrate that includes the ALD film surface has a roughness equal to or less than the target roughness, depositing a reflective material on the smoothed exterior of the substrate that includes the ALD film surface to produce the optical surface. ### Claim 18 (depends on 17) The method of producing an optical surface according to claim 17, wherein upon a determining that the exterior of the substrate that includes the ALD film surface has a roughness greater than the target roughness, smoothing the exterior of the substrate that includes the ALD film surface using the atomic layer deposition process to sequentially deposit a second plurality of ALD layers onto the exterior of the substrate that includes the ALD film surface. ### Claim 19 (depends on 17) The method of producing an optical surface according to claim 17, wherein the smoothing resulting from depositing the ALD film on the exterior of the substrate results in the grain size of the reflective material to be reduced in comparison to the grain size that would otherwise exists without having deposited the ALD film on the exterior of the substrate, the reduction in grain size of the reflective material causing a reduction in plasmon absorption in the optical surface in comparison to the plasmon absorption that would otherwise occur in the optical surface without having reduced the grain size of the reflective material. ### Claim 20 A method of producing an optical surface, the method comprising: obtaining a substrate having an exterior on which the optical surface is to reside, the exterior including laterally spaced-apart asperities having peaks which are spaced <1000 nm apart and affect optical performance of the produced optical surface absent a smoothing of the exterior surface; processing the exterior of the substrate using an atomic layer deposition process to sequentially deposit a first plurality of ALD layers to produce a first ALD film that fills spaces between the laterally spaced-apart asperities existing on the exterior surface; depositing one or more layers of a metal onto a surface of the first ALD film using a physical vapor deposition process to form a metal film over the surface of the first ALD film; smoothing a surface of the metal film using an atomic layer deposition process to sequentially deposit a second plurality of ALD layers to produce a second ALD film over the metal film; and depositing a reflective material on a surface of the second ALD film to produce the optical surface. ### Claim 21 (depends on 20) The method of producing an optical surface according to claim 20, wherein the metal film comprises a metal selected from the group consisting of silver, gold, aluminum, germanium and chromium.