# US 8,540,891 B2 · Etching pastes for silicon surfaces and layers > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 8,540,891 B2 - Document ID: US8540891B2 - Status: Granted - Kind: B2 - Application number: 10/526,497 - Filed: 2003-08-08 - Published: 2005-11-10 - Granted: 2013-09-24 - Earliest claimed: 2002-09-04 - Assignees: Merck Patent GmbH - Applicants: Armin Kübelbeck; Sylke Klein; Werner Stockum - Inventors: Armin Kübelbeck; Sylke Klein; Werner Stockum - Web page: https://patentgrep.com/patent/US8540891B2 ## CPC - H10P 90/126: {by chemical etching} - C09K 13/02: containing an alkali metal hydroxide - H10F 71/121: {The active layers comprising only Group IV materials} - H10P 50/642: {Chemical etching} - Y02E 10/547: Monocrystalline silicon PV cells - Y02P 70/50: Manufacturing or production processes characterised by the final manufactured product - H10P: GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10 - C09K: MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE - H10F: INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION - Y02E: REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION - Y02P: CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS ## Abstract The invention relates to novel etching media in the form of etching pastes for etching selected areas or the entire area of silicon surfaces and layers, in addition to the use of said media. ## Claims ### Claim 1 A process for the selective etching of patterns or lines on silicon surfaces and layers to a depth of 1-3 μm, said process comprising: applying a printable thickened, alkaline liquid etching medium (a) over the entire surface area of said surface or layer, or (b) in accordance with an etch structure mask specifically only to the areas of the surface where etching is desired, and removing said medium after an exposure time of from 30 s to 5 minutes, wherein said etching medium is effective at temperatures from 70 to 150° C. or can be activated by the input of energy, and wherein said etching medium comprises (a) 30-40% by weight of a potassium hydroxide etching component, based on the total amount of an etching medium, (b) from 55-75% by weight, based on the total amount of said etching medium, of a solvent which is a mixture of water and at least one other solvent that is diethylene glycol, dipropylene glycol, polyethylene glycols, 1,2-propanediol, 1,4-butanediol, 1,3-butanediol, glycerol, 1,5 pentanediol, 2-ethyl-1-hexanol, acetophenone, methyl-2-hexanone, 2-octanone, 4-hydroxy-4-methyl-2-pentanone, 1-methyl-2-pyrrolidone, ethylene glycol monobutyl ether, ethylene glycol monomethyl ether, triethylene glycol monomethyl ether, diethylene glycol monobutyl ether, dipropylene glycol monomethyl ether, or a carboxylic acid ester, (c) 1.0-10% by weight of a thickener which is hydroxyalkylguar, xanthan gum, and/or ethyl hydroxypropyl or hydroxyethylcellulose, sodium carboxymethylhydroxyethylcellulose, homopolymers or copolymers based on functionalised vinyl units of acrylic acid, acrylates or alkyl methacrylates (C10-C30), individually or in a mixture, and (d) optionally an additive that is a thixotropic agent, a flow-control agent, a deaerator or an adhesion promoter, and wherein said etching medium selectively etches patterns or lines on said silicon surface or layer to a depth of 1-3 μm. ### Claim 2 (depends on 1) A process according to claim 1, wherein said thickener is sodium carboxymethylhydroxyethylcellulose, homopolymers or copolymers based on functionalised vinyl units of acrylic acid, acrylates or alkyl methacrylates (C10-C30), individually or in a mixture. ### Claim 3 (depends on 2) A process according to claim 2, wherein said thickener is from 1.5-6% by weight, based on the total amount of the etching medium. ### Claim 4 (depends on 1) A process according to claim 1, wherein said additive is a thixotropic agent, a flow-control agent, a deaerator or an adhesion promoter in an amount of from 0 to 2% by weight, based on the total amount. ### Claim 5 (depends on 1) A process according to claim 1, wherein said etching medium is activated by exposure to heat. ### Claim 6 (depends on 5) A process according to claim 5, wherein said source of heat is and IR lamp or a hotplate. ### Claim 7 (depends on 1) A process according to claim 1, wherein said etching medium is applied to the surface to be etched by template, pad, stamp, ink-jet or manual printing process or by a dispensing technique. ### Claim 8 (depends on 1) A process according to claim 1, wherein said etching medium is rinsed off using a solvent or solvent mixture when the etching is complete. ### Claim 9 (depends on 1) A method for etching of silicon surfaces and layers in a process for the production of semiconductor components and circuits thereof comprising applying an etching medium according to claim 1 to the surface of said silicon or layer in a process for the production of a semiconductor component and circuit thereof. ### Claim 10 (depends on 1) A method for etching of silicon surfaces and layers in a process for the production of components in high-performance electronics comprising applying an etching medium according to claim 1 to the surface of said silicon or a layer in a process for the production of a component in high-performance electronics. ### Claim 11 (depends on 1) A process according to claim 1, wherein said carboxylic acid ester is [2,2-butoxy(ethoxy)]ethyl acetate or propylene carbonate. ### Claim 12 (depends on 1) A process according to claim 1, wherein said additive is an antifoaming agent, a flow-control agent, a deaerator or an adhesion promoter. ### Claim 13 (depends on 1) A process according to claim 1, wherein said etching medium comprises a. 55-75% by weight of at least one solvent b. from 1.5-6% by weight of a thickener and optionally c. additives and wherein said medium forms a paste that is activated by the input of energy, and said etching paste is printable. ### Claim 14 A method for the selective etching of patterns or lines on silicon surfaces and layers for isolation of the pn transition in solar cells comprising: applying a printable thickened, alkaline liquid etching medium to the surface of said silicon or a layer for isolation of the pn transition in a solar cell, wherein said etching medium comprises (a) 30-40% by weight of a potassium hydroxide etching component, based on the total amount of an etching medium, and (b) from 55-75% by weight, based on the total amount of said etching medium, of a solvent which is a mixture of water and at least one other solvent that is diethylene glycol, dipropylene glycol, polyethylene glycols, 1,2-propanediol, 1,4-butanediol, 1,3-butanediol, glycerol, 1,5 pentanediol, 2-ethyl-1-hexanol, acetophenone, methyl- 2-hexanone, 2-octanone, 4-hydroxy-4-methyl-2-pentanone, 1-methyl-2-pyrrolidone, ethylene glycol monobutyl ether, ethylene glycol monomethyl ether, triethylene glycol monomethyl ether, diethylene glycol monobutyl ether, dipropylene glycol monomethyl ether, or a carboxylic acid ester, and (c) 1.0-10% by weight of a thickener which is hydroxyalkylguar, xanthan gum, and/or ethyl hydroxypropyl or hydroxyethylcellulose, sodium carboxymethylhydroxyethylcellulose, homopolymers or copolymers based on functionalised vinyl units of acrylic acid, acrylates or alkyl methacrylates (C10-C30), individually or in a mixture, and wherein said etching medium selectively etches patterns or lines on said silicon surface or layer for isolation of the pn transition in of a solar cell to a depth of 1-3 μm. ### Claim 15 A process for the selective etching of patterns and lines on silicon surfaces and layers to a depth of 1-3 μm, comprising: applying a printable thickened, alkaline liquid etching medium over the entire surface area of said surface or layer or in accordance with an etch structure mask specifically only to the areas of the surface where etching is desired, activating said medium by exposing to temperatures of from 70 to 150° C, and removing said medium after an exposure time of from 30 s to 5 minutes, wherein said etching medium comprises (a) 30-40% by weight of a potassium hydroxide etching component, based on the total amount of an etching medium, (b) from 55-75% by weight, based on the total amount of said etching medium, of a solvent which is a mixture of water and at least one other solvent that is diethylene glycol, dipropylene glycol, polyethylene glycols, 1,2-propanediol, 1,4-butanediol, 1,3-butanediol, glycerol, 1,5 pentanediol, 2-ethyl-1-hexanol, acetophenone, methyl-2-hexanone, 2-octanone, 4-hydroxy-4-methyl-2-pentanone, 1-methyl-2-pyrrolidone, ethylene glycol monobutyl ether, ethylene glycol monomethyl ether, triethylene glycol monomethyl ether, diethylene glycol monobutyl ether, dipropylene glycol monomethyl ether, or a carboxylic acid ester, and c) from 1.5-6% by weight of a thickener which is hydroxyalkylguar, xanthan gum, and/or ethyl hydroxypropyl or hydroxyethylcellulose, sodium carboxymethylhydroxyethylcellulose, homopolymers or copolymers based on functionalised vinyl units of acrylic acid, acrylates or alkyl methacrylates (C10-C30), individually or in a mixture, and wherein said etching medium selectively etches patterns and lines on said silicon surface or layer to a depth of 1-3 μm. ### Claim 16 (depends on 15) A process according to claim 15 wherein said etching medium comprises a) from 30 to 40% by weight of a potassium hydroxide etching component, based on the total amount of said etching medium b) from 55-75% by weight of a solvent mixture c) from 1.5 to 6% by weight of a thickener that is a sodium carboxymethylhydroxyethylcellulose and/or a crosslinked acrylic acid homopolymer.