# US 2002/0153595 A1 · Semiconductor substrate and thin-film semiconductive member, and method for making thereof > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2002/0153595 A1 - Document ID: US20020153595A1 - Status: Published application - Kind: A1 - Application number: 10/067,486 - Filed: 2002-02-04 - Published: 2002-10-24 - Earliest claimed: 1997-12-26 - Assignees: Sony Corporation - Inventors: Hiroshi Tayanaka - Web page: https://patentgrep.com/patent/US20020153595A1 ## CPC - C30B 25/18: characterised by the substrate - H10D 62/83: being Group IV materials, e.g. B-doped Si or undoped Ge - H10D 62/85: being Group III-V materials, e.g. GaAs - H10P 14/6309: {of silicon in uncombined form, i.e. pure silicon} - H10P 14/6324: {Formation by anodic treatments, e.g. anodic oxidation} - H10P 14/6529: {by exposure to a gas or vapour} - H10P 14/6544: {to change the morphology of the insulating materials, e.g. transformation of an amorphous layer into a crystalline layer} - H10P 14/665: {Porous materials} - H10P 14/6922: {the material containing Si, O and at least one of H, N, C, F or other non-metal elements, e.g. SiOC, SiOC:H or SiONC} - H10P 90/1924: {with separation/delamination along a porous layer} - H10W 10/181: {Semiconductor-on-insulator [SOI] isolation regions, e.g. buried oxide regions of SOI wafers} - H10P 14/24: using chemical vapour deposition [CVD] - H10P 14/2905: {Silicon, silicon germanium or germanium} - H10P 14/3248: {consisting of two layers} - H10P 14/3256: {Microstructure} - H10P 14/3411: {Silicon, silicon germanium or germanium} - 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 - H10D: INORGANIC ELECTRIC SEMICONDUCTOR DEVICES - 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 semiconductor substrate comprises a porous semiconductor having a porous layer with an impurity concentration distribution varying in the depth direction. Alternatively, the semiconductor substrate comprises a porous layer comprising a porous semiconductor containing an impurity with a content of 1×1018 cm−3 or more, or comprises a porous layer provided by pore formation in an epitaxial growth layer. A thin-film semiconductive member is formed on one surface of a supporting substrate with a porous layer provided having the above-mentioned configuration therebetween, and separated from the supporting substrate by cleavage in the porous layer. In a method for making a semiconductor substrate, a variant impurity layer with an impurity concentration varying in the depth direction is formed on one surface of a supporting substrate. Next, the variant impurity layer is converted into a porous layer having a variant porosity in the depth direction. In a method for making thin-film semiconductive member, a semiconductive thin film is formed and is separated from the supporting substrate by cleavage in the porous phase, in addition to the method for making the semiconductor substrate. ## Claims ### Claim 1 A semiconductor substrate comprising a porous semiconductor having a porous layer with an impurity concentration distribution varying in the depth direction. ### Claim 2 (depends on 1) A semiconductor substrate according to claim 1, wherein said porous layer comprises a semiconductor selected from the group consisting of a semiconductor containing at least one of silicon and germanium, a semiconductor containing gallium and arsenic, and a semiconductor containing gallium and phosphorus, and a semiconductor containing gallium and nitrogen. ### Claim 3 (depends on 1) A semiconductor substrate according to claim 1, wherein said porous layer comprises at least two sublayers having different impurity concentrations. ### Claim 4 (depends on 3) A semiconductor substrate according to claim 3, wherein said porous layer is formed on one surface of a supporting substrate, and comprises a high-porosity sublayer having a low impurity concentration and a high porosity and at least one low-porosity sublayer having a high impurity concentration and a low porosity, and said high-porosity sublayer is provided on the surface, at the side of said supporting substrate, of at least one low-porosity sublayer. ### Claim 5 (depends on 4) A semiconductor substrate according to claim 4, wherein said supporting substrate and said porous layer each comprise p-type silicon containing a p-type impurity, the low-porosity sublayer has a p-type impurity concentration of 1×1019 cm−3 or more, and the high-porosity sublayer has a p-type impurity concentration of less than 1×1019 cm−3. ### Claim 6 (depends on 1) A semiconductor substrate according to claim 1, further comprising a semiconductive thin film provided on one face of said porous layer. ### Claim 7 (depends on 6) A semiconductor substrate according to claim 6, wherein said semiconductive thin film comprises a semiconductor selected from the group consisting of a semiconductor containing at least one of silicon and germanium, a semiconductor containing gallium and arsenic, and a semiconductor containing gallium and phosphorus, and a semiconductor containing gallium and nitrogen. ### Claim 8 (depends on 6) A semiconductor substrate according to claim 6, wherein said semiconductive thin film comprises a single crystal. ### Claim 9 (depends on 1) A semiconductor substrate according to claim 1, wherein said porous layer has unevenness. ### Claim 10 A semiconductor substrate comprising a porous layer comprising a porous semiconductor containing an impurity with a content of 1×1018 cm−3 or more. ### Claim 11 A semiconductor substrate comprising a porous layer provided by pore formation in an epitaxial growth layer. ### Claim 12 A thin-film semiconductive member formed on one surface of a supporting substrate with a porous layer provided therebetween, and separated from said supporting substrate by cleavage in said porous layer, said porous layer comprising a porous semiconductor having an impurity concentration varying in the depth direction. ### Claim 13 (depends on 12) A thin-film semiconductive member according to claim 12, wherein said porous layer comprises a semiconductor selected from the group consisting of a semiconductor containing at least one of silicon and germanium, a semiconductor containing gallium and arsenic, and a semiconductor containing gallium and phosphorus, and a semiconductor containing gallium and nitrogen. ### Claim 14 (depends on 12) A thin-film semiconductive member according to claim 12, comprising a single crystal. ### Claim 15 (depends on 12) A thin-film semiconductive member according to claim 12, having unevenness. ### Claim 16 A thin-film semiconductive member formed on one surface of a supporting substrate with a porous layer provided therebetween, and separated from said supporting substrate by cleavage in said porous layer, said porous layer comprising a porous semiconductor having an impurity concentration of 1×1018 cm−3 or more. ### Claim 17 A thin-film semiconductive member formed on one surface of a supporting substrate with a porous layer provided therebetween, and separated from said supporting substrate by cleavage in said porous layer, said porous layer being provided by pore formation in an epitaxial growth layer. ### Claim 18 A method for making a semiconductor substrate comprising: a variant layer forming step for forming a variant impurity layer with an impurity concentration varying in the depth direction on one surface of a supporting substrate; and a porous layer forming step for forming a porous layer by providing pores in the variant impurity layer by anodic oxidation so that the porosity in the porous layer varies in the depth direction. ### Claim 19 (depends on 18) A method for making a semiconductor substrate according to claim 18, wherein a variant impurity layer including at least two sublayers having different impurity concentrations is formed in said variant layer forming step, and a porous layer including at least two sublayers having different porosities is formed in said porous layer forming step. ### Claim 20 (depends on 19) A method for making a semiconductor substrate according to claim 19, wherein at least two sublayers having different impurity concentrations is formed on one surface of the supporting substrate in said variant layer forming step. ### Claim 21 (depends on 19) A method for making a semiconductor substrate according to claim 19, wherein, in said variant layer forming step, a growth layer is deposited on one surface of the supporting substrate, and then an impurity is diffused into the growth layer so as to form at least two sublayers having different impurity concentrations. ### Claim 22 (depends on 18) A method for making a semiconductor substrate according to claim 18, wherein, in said variant layer forming step, said variant impurity layer comprises a semiconductor selected from the group consisting of a semiconductor containing at least one of silicon and germanium, a semiconductor containing gallium and arsenic, and a semiconductor containing gallium and phosphorus, and a semiconductor containing gallium and nitrogen. ### Claim 23 (depends on 18) A method for making a semiconductor substrate according to claim 18, wherein, in said variant layer forming step, a low-impurity sublayer comprising a semiconductor having a low impurity concentration is formed and a high-impurity sublayer comprising a semiconductor having a high impurity concentration is formed on the surface, away from the supporting substrate, of the low-impurity sublayer. ### Claim 24 (depends on 23) A method for making a semiconductor substrate according to claim 23, wherein, in said variant layer forming step, each of said supporting substrate and said variant impurity layer comprises p-type silicon containing a p-type impurity, the low-impurity sublayer has a p-type impurity concentration of 1×109 cm−3 or more, and the high-impurity sublayer has a p-type impurity concentration of less than 1×1019 cm−3. ### Claim 25 (depends on 18) A method for making a semiconductor substrate according to claim 18, wherein said one surface of the supporting substrate is uneven. ### Claim 26 (depends on 18) A method for making a semiconductor substrate according to claim 18, further comprising a step for forming a semiconductive thin film on the surface, away from the supporting substrate, of the porous layer. ### Claim 27 (depends on 26) A method for making a semiconductor substrate according to claim 26, wherein said semiconductive thin film is formed of a single crystal provided by epitaxial growth. ### Claim 28 (depends on 26) A method for making a semiconductor substrate according to claim 26, said semiconductive thin film comprises a semiconductor selected from the group consisting of a semiconductor containing at least one of silicon and germanium, a semiconductor containing gallium and arsenic, and a semiconductor containing gallium and phosphorus, and a semiconductor containing gallium and nitrogen. ### Claim 29 (depends on 18) A method for making a semiconductor substrate according to claim 18, further comprising a heating step of heating the porous layer for recrystallization. ### Claim 30 A method for making a semiconductor substrate comprising: a high-impurity layer forming step for forming a high-impurity layer comprising a semiconductor having an impurity concentration of 1×1018 cm−3 or more on one surface of a supporting substrate; and a porous layer forming step for forming pores in the high-impurity layer by anodic oxidation to form a porous layer having different porosities in the depth direction. ### Claim 31 (depends on 30) A method for making a semiconductor substrate according to claim 30, wherein in said high-impurity layer forming step, the high-impurity layer is formed by epitaxial growth. ### Claim 32 A method for making a thin-film semiconductive member comprising: a variant layer forming step for forming a variant impurity layer with an impurity concentration varying in the depth direction on one surface of a supporting substrate; a porous layer forming step for forming a porous layer by providing pores in the variant impurity layer by anodic oxidation so that the porosity in the porous layer varies in the depth direction; a step for forming a semiconductive thin film on the surface, away from the supporting substrate, of the porous layer; and a separation step for separating the semiconductive thin film from the supporting substrate by cleavage in the porous phase. ### Claim 33 A method for making a thin-film semiconductive member comprising: a high-impurity layer forming step for forming a high-impurity layer comprising a semiconductor having an impurity concentration of 1×1018 cm−3 or more on one surface of a supporting substrate; a porous layer forming step for forming pores in the high-impurity layer by anodic oxidation to form a porous layer having different porosities in the depth direction; a step for forming a semiconductive thin film on the surface, away from the supporting substrate, of the porous layer; and a separation step for separating the semiconductive thin film from the supporting substrate by cleavage in the porous phase.