# US 10,483,111 B2 · Metal-metal direct bonding method > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,483,111 B2 - Document ID: US10483111B2 - Status: Granted - Kind: B2 - Application number: 15/650,175 - Filed: 2017-07-14 - Published: 2018-01-18 - Granted: 2019-11-19 - Earliest claimed: 2016-07-18 - Assignees: Commissariat A L'energie Atomique Et Aux Energies Alternatives - Applicants: Commissariat A L'energie Atomique Et Aux Energies Alternatives - Inventors: Paul Gondcharton; Bruno Imbert; Hubert Moriceau - Web page: https://patentgrep.com/patent/US10483111B2 ## CPC - H10P 10/128: {by direct semiconductor to semiconductor bonding} - B23K 20/002: {specially adapted for particular articles or work (B23K20/129 takes precedence)} - B23K 20/24: Preliminary treatment - B23K 31/02: relating to soldering or welding - H10H 20/018: {Bonding of wafers} - H10P 10/12: {Bonding of semiconductor wafers or semiconductor substrates to semiconductor wafers or semiconductor substrates (preparing SOI wafers using bonding H10P90/1914)} - H10W 72/952: {comprising metals or metalloids, e.g. PbSn, Ag or Cu} - H10W 72/957: {Multiple bond pads having different materials} - H10W 80/102: {Controlling the environment during the bonding, e.g. the temperature or pressure} - H10W 80/312: {characterised by the direct bonding of electrically conductive pads} - H10P: GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10 - B23K: SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM - H10H: INORGANIC LIGHT-EMITTING SEMICONDUCTOR DEVICES HAVING POTENTIAL BARRIERS - H10W: GENERIC PACKAGES, INTERCONNECTIONS, CONNECTORS OR OTHER CONSTRUCTIONAL DETAILS OF DEVICES COVERED BY CLASS H10 ## Abstract A method for assembling a first substrate and a second substrate by metal-metal direct bonding, includes providing a first layer of a metal at the surface of the first substrate and a second layer of the metal at the surface of the second substrate, the first and second metal layers having a tensile stress (σi) between 30% and 100% of the tensile yield strength (σe) of the metal; assembling the first and second substrates at a bonding interface by directly contacting the first and second tensile stressed metal layers; and subjecting the assembly of the first and second substrates to a stabilization annealing at a temperature lower than or equal to a temperature threshold beyond which the first and second tensile stressed metal layers are plastically compressively deformed. ## Claims ### Claim 1 A method for assembling a first substrate and a second substrate by a metal-metal direct bonding, comprising: providing a first layer of a metal at a surface of the first substrate and a second layer of said metal at a surface of the second substrate, the first and second metal layers having a tensile stress comprised between 30% and 100% of the tensile yield strength of said metal thereby forming a first tensile stressed metal layer at the surface of the first substrate and a second tensile stressed metal layer at the surface of the second substrate; bonding the first substrate with the second substrates at a bonding interface by directly contacting the first and second tensile stressed metal layers; after said bonding, subjecting first and second substrates to a stabilization annealing at a temperature lower than or equal to a temperature threshold, wherein the temperature threshold is such that the first and second tensile stressed metal layers are plastically compressively deformed above the temperature threshold. ### Claim 2 (depends on 1) The method according to claim 1, comprising determining said temperature threshold from the tensile stress of the first and second metal layers and the thermo-elastic coefficient of said metal. ### Claim 3 (depends on 1) The method according to claim 1, wherein the providing comprises depositing the first metal layer onto a face of the first substrate and the second metal layer onto a face of the second substrate. ### Claim 4 (depends on 3) The method according to claim 3, wherein the tensile stress of the first and second metal layers is obtained during the depositing. ### Claim 5 (depends on 1) The method according to claim 1, wherein the tensile stress of the first and second metal layers is obtained after deposition of the first metal layer onto a face of the first substrate and of the second metal layer onto a face of the second metal layer during a stress adaptation step. ### Claim 6 (depends on 5) The method according to claim 5, wherein the stress adaptation step is a step of plasma treatment or ion bombardment. ### Claim 7 (depends on 5) The method according to claim 5, wherein the stress adaptation step comprises a heat treatment followed by a cooling, the heat treatment being performed at a temperature lower than or equal to a temperature limit beyond which the first and second metal layers are plastically tensile deformed by cooling, and wherein the temperature of the heat treatment sets the temperature threshold of the stabilization annealing. ### Claim 8 (depends on 7) The method according to claim 7, wherein the cooling is performed down to an ambient temperature. ### Claim 9 (depends on 7) The method according to claim 7, wherein the temperature of the stabilization annealing is equal to the temperature of the heat treatment. ### Claim 10 (depends on 1) The method according to claim 1, wherein the bonding of the first substrate with the second substrates is performed under ambient air. ### Claim 11 (depends on 1) The method according to claim 1, wherein the first and second substrates are comprised of identical materials. ### Claim 12 (depends on 1) The method according to claim 1, wherein the first and second substrates are made of silicon and the first and second metal layers are made of copper. ### Claim 13 (depends on 1) The method according to claim 1, wherein the first and second metal layers have a thickness comprised between 10 nm and 5 μm. ### Claim 14 (depends on 1) The method according to claim 1, further comprising, before bonding the first substrate with the second substrates, preparing the surface of the first and second metal layers. ### Claim 15 (depends on 1) The method according to claim 1, wherein the first substrate comprises a first barrier layer and the second substrate comprises a second barrier layer such that the first metal layer is formed on the first barrier layer and the second metal layer is formed on the second barrier layer. ### Claim 16 (depends on 1) The method according to claim 1, wherein each of the first and second barrier layers is a titanium nitride layer.