# US 7,407,869 B2 · Method for manufacturing a free-standing substrate made of monocrystalline semiconductor material > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 7,407,869 B2 - Document ID: US7407869B2 - Status: Granted - Kind: B2 - Application number: 11/212,795 - Filed: 2005-08-29 - Published: 2006-02-16 - Granted: 2008-08-05 - Earliest claimed: 2000-11-27 - Assignees: S.O.I.Tec Silicon on Insulator Technologies - Inventors: Bruno Ghyselen; Fabrice Letertre; Carlos Mazure - Web page: https://patentgrep.com/patent/US7407869B2 ## CPC - C30B 29/36: Carbides - H10P 90/1916: {with separation or delamination along an ion implanted layer, e.g. Smart-cut} - H10W 10/181: {Semiconductor-on-insulator [SOI] isolation regions, e.g. buried oxide regions of SOI wafers} - C30B: SINGLE-CRYSTAL GROWTH (by using ultra-high pressure, e.g. for the formation of diamonds, B01J3/06); UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL (zone-refining of metals or alloys C22B); PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE (casting of metals, casting of other substances by the same processes or devices B22D; working of plastics B29; modifying the physical structure of metals or alloys C21D, C22F); SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE (for producing semiconductor devices or parts thereof H10); APPARATUS THEREFOR - H10P: GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10 - H10W: GENERIC PACKAGES, INTERCONNECTIONS, CONNECTORS OR OTHER CONSTRUCTIONAL DETAILS OF DEVICES COVERED BY CLASS H10 ## Abstract A method for manufacturing a free-standing substrate made of a semiconductor material. A first assembly is provided and it includes a relatively thinner nucleation layer of a first material, a support of a second material, and a removable bonding interface defined between facing surfaces of the nucleation layer and support. A substrate of a relatively thicker layer of a third material is grown, by epitaph on the nucleation layer, to form a second assembly with the substrate attaining a sufficient thickness to be free-standing. The third material is preferably a monocrystalline material. Also, the removable character of the bonding interface is preserved with at least the substrate being heated to an epitaxial growth temperature. The coefficients of thermal expansion of the second and third materials are selected to be different from each other by a thermal expansion differential, determined as a function of the epitaxial growth temperature or subsequent application of external mechanical stresses, such that, as the second assembly cools from the epitaxial growth temperature, stresses are induced in the removable bonding interface to facilitate detachment of the nucleation layer from the substrate. ## Claims ### Claim 1 A method for manufacturing a free-standing substrate made of a semiconductor material, which comprises: providing a first assembly by bonding of a nucleation layer of a first material to a support of a second material at a bonding interface being defined and located between facing surfaces of the nucleation layer and the support, wherein the nucleation layer is applied onto the support by direct bonding with molecular adhesion; growing, by epitaxy on the nucleation layer, a substrate of a layer of a third material to form a second assembly with the substrate attaining a sufficient thickness to be free-standing, with at least the substrate being heated to an epitaxial growth temperature, wherein the third material is a wide bandgap material; and selecting the coefficients of thermal expansion of the second and third materials to be different from each other by a thermal expansion differential, determined as a function of the epitaxial growth temperature or subsequent application of external mechanical stresses, such that, as the second assembly cools from the epitaxial growth temperature, stresses are induced in the bonding interface to facilitate detachment of the nucleation layer and the substrate from the support. ### Claim 2 (depends on 1) The method of claim 1, wherein the wide bandgap material is silicon carbide. ### Claim 3 (depends on 1) The method according to claim 1, wherein the coefficients of thermal expansion of the second and third materials are selected to be sufficiently different from each other so that the nucleation layer and substrate become detached as the second assembly cools to ambient from the epitaxial growth temperature. ### Claim 4 (depends on 1) The method according to claim 1, which further comprises applying a thermal treatment to raise stresses at the bonding interface to assist in the detachment of the nucleation layer and the substrate. ### Claim 5 (depends on 1) The method according to claim 1, which further comprises applying an external stress to assist in the detachment of the nucleation layer and the substrate by increasing the stress between the materials at the bonding interface. ### Claim 6 (depends on 1) The method according to claim 1, wherein the substrate is a monocrystalline material deposited at least in part by hydride vapor phase epitaxy (HPVE). ### Claim 7 (depends on 1) The method according to claim 1, wherein removal of the bonding interface is facilitated by effecting a treatment for augmenting the roughness of the facing surface of at least one of the nucleation layer or the support. ### Claim 8 (depends on 7) The method according to claim 7, wherein the treatment for augmenting surface roughness is carried out by chemical attack or etching. ### Claim 9 (depends on 1) The method according to claim 1, wherein removal of the bonding interface is facilitated by effecting a treatment for decreasing hydrophilicity of the facing surface of at least one of the nucleation layer or the support. ### Claim 10 (depends on 1) The method according to claim 1, wherein the epitaxial growing of the second material includes initially providing a fine nucleation layer on the nucleation layer in order to improve the crystal quality of the deposited third material of the substrate. ### Claim 11 (depends on 10) The method according to claim 10, wherein the tine nucleation layer is provided by metal organic chemical vapor deposition (MOCVD) epitaxy or by molecular beam (MBE) epitaxy. ### Claim 12 (depends on 1) The method according to claim 1, which further comprises eliminating the nucleation layer after detachment so that the substrate becomes a free-standing structure. ### Claim 13 (depends on 1) The method according to claim 1, which further comprises, prior to bonding the nucleation layer onto the support, forming the nucleation layer by implantation of an atomic species into a source substrate to a defined depth to form an embrittled zone that defines a boundary of the nucleation layer in the source substrate. ### Claim 14 (depends on 13) The method according to claim 13, wherein the source substrate comprises a monocrystalline or polycrystalline wide bandgap material. ### Claim 15 (depends on 14) The method according to claim 14, wherein the wide bandgap material of the source substrate is gallium nitride (GaN) or aluminum nitride (AIN). ### Claim 16 (depends on 1) The method according to claim 1, which further comprises detaching the nucleation layer and the substrate from the support. ### Claim 17 (depends on 16) The method according to claim 16, which further comprises eliminating the nucleation layer after detachment so that the substrate becomes a free-standing structure. ### Claim 18 A method for manufacturing a free-standing substrate made of a semiconductor material, which comprises: providing a first assembly by bonding of a nucleation layer of a first material to at least one intermediate bonding layer present on a support of a second material at a bonding interface being defined and located between facing surfaces of the nucleation layer and the intermediate bonding layer of the support, wherein the nucleation layer is applied onto the intermediate bonding layer of the support by direct bonding with molecular adhesion; growing, by epitaxy on the nucleation layer, a substrate of a layer of a third material to form a second assembly with the substrate attaining a sufficient thickness to be free-standing, with at least the substrate being heated to an epitaxial growth temperature, wherein the third material is a wide bandgap material; and selecting the coefficients of thermal expansion of the second and third materials to be different from each other by a thermal expansion differential, determined as a function of the epitaxial growth temperature or subsequent application of external mechanical stresses, such that, as the second assembly cools from the epitaxial growth temperature, stresses are induced in the bonding interface to facilitate detachment of the nucleation layer and the substrate from the intermediate bonding layer and the support. ### Claim 19 (depends on 18) The method according to claim 18, wherein the intermediate bonding layer is positioned adjacent the nucleation layer and a second intermediate bonding layer is positioned adjacent the support. ### Claim 20 (depends on 19) The method according to claim 19, wherein at least one of the intermediate bonding layers is a layer of silicon oxide or silicon nitride. ### Claim 21 A method for manufacturing a free-standing substrate made of a semiconductor material, which comprises: forming a nucleation layer by implantation of an atomic species into a source substrate to a defined depth to form an embrittled zone that defines a boundary of the nucleation layer from a remainder of the source substrate; providing a first assembly by bonding the nucleation layer of a first material to a support of a second material, at a bonding interface being defined and located between facing surfaces of the nucleation layer and the support; detaching the nucleation layer at the embrittled zone to remove the remainder of the source substrate and provide the nucleation layer bonded to the support; growing, by epitaxy on the nucleation layer, a substrate of a layer of a third material to form a second assembly with the substrate attaining a sufficient thickness to be free-standing, with at least the substrate being heated to an epitaxial growth temperature; and selecting the coefficients of thermal expansion of the second and third materials to be different from each other by a thermal expansion differential, determined as a function of the epitaxial growth temperature or subsequent application of external mechanical stresses, such that, as the second assembly cools from the epitaxial growth temperature, stresses are induced in the bonding interface to facilitate detachment of the nucleation layer and the substrate from the support. ### Claim 22 (depends on 21) The method according to claim 21, wherein the third material has a band gap value above 1.5 eV.