# US 2023/0056416 A1 · Process of transferring of vcsel epi layer onto metal host substrate > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2023/0056416 A1 - Document ID: US20230056416A1 - Status: Published application - Kind: A1 - Application number: 17/408,762 - Filed: 2021-08-23 - Published: 2023-02-23 - Earliest claimed: 2021-08-23 - Assignees: Palo Alto Research Center Incorporated - Applicants: Palo Alto Research Center Incorporated - Inventors: Christopher Chua; Joerg Martini; Mark Teepe; Elif Karatay - Web page: https://patentgrep.com/patent/US20230056416A1 ## CPC - H01S 5/423: {having a vertical cavity} - H01S 5/0217: {Removal of the substrate} - H01S 5/02345: Wire-bonding - H01S 5/02423: {Liquid cooling, e.g. a liquid cools a mount of the laser} - H01S 5/02476: {Heat spreaders, i.e. improving heat flow between laser chip and heat dissipating elements} - H01S 5/04252: {characterised by the material} - H01S 5/06804: {by monitoring an external parameter, e.g. temperature} - H01S 5/04256: {characterised by the configuration} - H01S: DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL ## Abstract A method of transferring a semiconductor epi layer onto a metal host substrate is described. An epi layer of a semiconductor chip (e.g., semiconductor laser array) including a substrate can be mounted onto a planar handle wafer with an adhesive, wherein a backside of the substrate faces upward and away from the epi layer and the planar handle wafer. The backside of the substrate can be treated to substantially remove the substrate, while leaving the epi layer undamaged (e.g., by polishing to where no more than 20 micrometers of the substrate remains). Metal can be formed on the treated backside resulting in a metalized backside. The planar handle wafer can then be removed from the epi layer by dissolving the adhesive with a solvent, wherein a modified semiconductor chip remains. The semiconductor chip can be annealed to form a backside ohmic contact interface. The semiconductor chip can then be attached to a mechanical block by the ohmic contact interface. ## Claims ### Claim 1 A method of transferring a semiconductor epi layer onto a metal host substrate, comprising: mounting an epi layer of a semiconductor chip including a substrate onto a planar handle wafer with an adhesive, wherein a backside of the substrate faces upward and away from the epi layer and the planar handle wafer; treating the backside to substantially remove the substrate, while leaving the epi layer undamaged; forming a metal on the treated backside resulting in a metallized backside; removing the planar handle wafer from the epi layer by dissolving the adhesive with a solvent, wherein a modified semiconductor chip remains; annealing the modified semiconductor chip to form a semiconductor-metal ohmic contact interface on the metallized backside; and attaching the metallized backside to a mechanical block. ### Claim 2 (depends on 1) The method of claim 1, wherein the step of forming a metal on the treated backside comprises depositing a thin film metal to form an electroplating seed, followed by electroforming a bulk metal over the thin film to replace a portion of the substrate that was removed. ### Claim 3 (depends on 2) The method of claim 2, wherein the thin film is deposited by one of sputtering, electron beam evaporation, thermal evaporation, and laser ablation. ### Claim 4 (depends on 3) The method of claim 3 wherein the thin film comprises Ge, Au, Ni, Al, Ti and alloys thereof; and wherein the electroformed bulk metal comprises copper. ### Claim 5 (depends on 1) The method of claim 1, wherein treating the backside comprises selective chemical etching, in which backside substrate removal is accomplished by chemical dissolution and where an etch stop layer within the epi at the substrate interface blocks chemical attack. ### Claim 6 (depends on 5) The method of claim 5 wherein the etch stop layer is one of AlGaAs, InGaAs, InGaAsP, GaP, and GaInP ### Claim 7 (depends on 5) The method of claim 5 wherein a chemical etchant used to accomplish the selective chemical etching comprises NH4OH, H2O2, HNO3, and HCl. ### Claim 8 (depends on 1) The method of claim 1 wherein the adhesive is a thermoplastic polymer or thermal wax ### Claim 9 (depends on 1) The method of claim 1, wherein the solvent is acetone. ### Claim 10 (depends on 1) The method of claim 1, wherein thickness control during the polishing can be maintained by using a mechanical stop. ### Claim 11 (depends on 1) The method of claim 1, wherein the planar handle wafer comprises at least one of glass or silicon. ### Claim 12 (depends on 1) The method of claim 1, wherein the metal block is a 3D mechanical block including at least one embedded channel formed therein and configured to accept cooling liquid therethrough, a first tubular connection for providing cooling liquid to the at least one embedded channel, and a second tubular connection for removing cooling liquid from the at least one embedded channel. ### Claim 13 (depends on 1) The method of claim 1, wherein the semiconductor chip comprises a laser array. ### Claim 14 A method of transferring a semiconductor laser epi layer onto a metal host substrate, comprising: mounting an epi layer of a semiconductor chip including a substrate onto a planar handle wafer with an adhesive, wherein a backside of the substrate faces upward and away from the epi layer and the planar handle wafer; treating the backside to substantially remove the substrate, while leaving the epi layer undamaged; forming a metal on the treated backside resulting in a metalized backside; removing the planar handle wafer from the epi layer by dissolving the adhesive with a solvent, wherein a modified semiconductor chip remains; annealing the semiconductor chip to form a semiconductor-metal ohmic contact interface; and attaching the metallized backside to a mechanical block, wherein the metal block metal block comprises a 3D mechanical block including at least one embedded channel formed therein and configured to accept cooling liquid therethrough, a first tubular connection for providing cooling liquid to the at least one embedded channel, and a second tubular connection for removing cooling liquid from the at least one embedded channel. ### Claim 15 (depends on 14) The method of claim 14, wherein the metallized backside comprises an electroplated metal formed to replace the removed substrate. ### Claim 16 (depends on 15) The method of claim 15, wherein the electroplated metal comprises copper. ### Claim 17 (depends on 14) The method of claim 14, wherein thickness control during the polishing can be maintained by using a mechanical stop. ### Claim 17 (depends on 14) The method of claim 14, wherein the polish is chemically and mechanically executed. ### Claim 18 (depends on 14) The method of claim 14, wherein treating the backside comprises selective chemical etching, in which backside substrate removal is accomplished by chemical dissolution and where an etch stop layer within the epi at the substrate interface blocks chemical attack. ### Claim 20 A method of transferring a semiconductor laser epi layer onto a metal host substrate, comprising: mounting an epi layer of a semiconductor chip including a substrate onto a planar handle wafer with an adhesive, wherein a backside of the substrate faces upward and away from the epi layer and the planar handle wafer; treating the backside to substantially remove the substrate, while leaving the epi layer undamaged, wherein the treating can be done either chemically and mechanically; evaporating a thin film metal on the treated backside electroforming bulk copper resulting in a metalized backside; removing the planar handle wafer from the epi layer by dissolving the adhesive with a solvent, wherein a modified semiconductor chip remains; annealing the semiconductor chip to form a semiconductor-metal ohmic contact interface; and attaching the metallized backside to a mechanical block, wherein the metal block comprises a 3D mechanical block including at least one embedded channel formed therein and configured to accept cooling liquid therethrough, a first tubular connection for providing cooling liquid to the at least one embedded channel, and a second tubular connection for removing cooling liquid from the at least one embedded channel.