WO2024125264A1 - 一种复合衬底的制备方法 - Google Patents

一种复合衬底的制备方法 Download PDF

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WO2024125264A1
WO2024125264A1 PCT/CN2023/133943 CN2023133943W WO2024125264A1 WO 2024125264 A1 WO2024125264 A1 WO 2024125264A1 CN 2023133943 W CN2023133943 W CN 2023133943W WO 2024125264 A1 WO2024125264 A1 WO 2024125264A1
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Prior art keywords
substrate
single crystal
crystal layer
composite
laser
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PCT/CN2023/133943
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English (en)
French (fr)
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母凤文
郭超
谭向虎
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青禾晶元(天津)半导体材料有限公司
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Publication of WO2024125264A1 publication Critical patent/WO2024125264A1/zh

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    • C—CHEMISTRY; METALLURGY
    • C30—CRYSTAL GROWTH
    • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
    • C30B33/00—After-treatment of single crystals or homogeneous polycrystalline material with defined structure
    • C30B33/02—Heat treatment
    • C—CHEMISTRY; METALLURGY
    • C30—CRYSTAL GROWTH
    • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
    • C30B33/00—After-treatment of single crystals or homogeneous polycrystalline material with defined structure
    • C30B33/04—After-treatment of single crystals or homogeneous polycrystalline material with defined structure using electric or magnetic fields or particle radiation
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

Definitions

  • the present application relates to the field of semiconductor technology, for example, a method for preparing a composite substrate.
  • Devices made of silicon carbide single crystal substrates have the advantages of high temperature resistance, high voltage resistance, high frequency, high power, radiation resistance, and high efficiency. They have important application value in radio frequency, new energy vehicles and other fields.
  • the conventional manufacturing method of silicon carbide single crystal substrate includes the following process: growing silicon carbide single crystal by physical vapor transport method to obtain a silicon carbide single crystal ingot; processing the periphery of the ingot to obtain the required diameter and surface quality, then slicing the ingot into slices, grinding and polishing the slices to the required thickness and flatness, and obtaining the final silicon carbide single crystal substrate.
  • the physical vapor transport method is very inefficient in growing silicon carbide single crystals, resulting in a high cost for a single silicon carbide single crystal substrate.
  • One solution to reduce the cost of silicon carbide substrates is to use a composite substrate structure: a thin layer of single-crystal silicon carbide is bonded to a lower-priced support substrate.
  • This solution requires processing the surfaces of low-quality substrates and high-quality substrates separately to make their surface quality meet the bonding requirements, and then bonding. High-quality surface processing has certain complexity and difficulty.
  • this solution will form a bonding interface layer, which may have a negative impact on the vertical conductivity of the substrate.
  • CN114746980A discloses a method for manufacturing a composite substrate: using ion implantation to form a pre-buried weakened layer in a high-quality single crystal substrate; using a CVD method to deposit a low-quality crystal layer or a polycrystalline layer on the surface of the single crystal substrate; separating along the weakened layer to obtain a composite substrate.
  • the problem with this method is that due to the high temperature of the CVD process, the pre-buried weakened layer may crack in advance during the CVD process, causing the CVD process to have to be interrupted.
  • CN112701033A discloses a method for preparing a composite substrate, a composite substrate and a composite film.
  • the preparation method of the composite substrate includes: cleaning the single crystal silicon substrate to obtain a single crystal silicon substrate layer with a clean surface; growing polycrystalline silicon on the clean surface of the single crystal silicon substrate layer, and performing a flattening process to form a first polycrystalline silicon layer; focusing the laser on the side of the first polycrystalline silicon layer close to the single crystal silicon substrate layer until a single crystal silicon fusion layer is formed, stopping the laser focusing, and obtaining a composite substrate; wherein the composite substrate includes a single crystal silicon substrate layer, a single crystal silicon fusion layer, and a second polycrystalline silicon layer from bottom to top.
  • the above-mentioned scheme is adopted to accurately control the position, distribution, and size of the single crystal silicon fusion area by adjusting the power, focal length, and position of the laser, so that the bonding force of the target area at the target interface can be improved according to the actual situation of the single crystal silicon substrate layer and the polycrystalline silicon layer, thereby improving the adhesion of the polycrystalline silicon deposited on the silicon substrate.
  • the preparation efficiency of the above-mentioned preparation method is low.
  • the present application provides a method for preparing a composite substrate.
  • a method for preparing a composite substrate By growing a low-quality crystal layer on a high-quality single crystal substrate, the manufacturing efficiency of the composite substrate can be improved, and laser cold cracking cutting treatment is used to obtain a composite substrate with a very thin high-quality single crystal substrate.
  • the composite substrate has high quality and a wide range of applications.
  • the present application provides a method for preparing a composite substrate, the method comprising the following steps:
  • a single crystal substrate is used as a seed crystal, and a crystal layer is grown on one of its surfaces to obtain a composite crystal layer structure consisting of the single crystal substrate and the crystal layer;
  • the single crystal substrate in the preparation method of the composite substrate described in the present application is a high-quality single crystal substrate, which has fewer defects such as micropipes, dislocations, phase changes, and polycrystalline inclusions.
  • the high-quality single crystal substrate is used as the growth basis of the low-quality crystal layer, and a low-quality crystal layer is grown on its Si surface or C surface.
  • the low-quality crystal layer is allowed to contain more micropipes, dislocations, phase changes, polycrystalline inclusions, and other defects, and can be single crystal or polycrystalline; then a laser is used to irradiate the composite crystal layer structure composed of the single crystal substrate and the crystal layer.
  • the laser can be irradiated from the other surface of the single crystal substrate, or from the surface of the low-quality crystal layer of the composite crystal layer structure.
  • a modified surface can be formed inside the single crystal substrate of the composite crystal layer structure, and then the single crystal substrate is disconnected along the modified surface to obtain a composite substrate with a very thin high-quality single crystal substrate and a low-quality crystal layer of a specific thickness.
  • the preparation method described in the present application can improve the manufacturing efficiency and quality of the composite substrate.
  • the preparation method described in the present application is to grow a low-quality crystal layer on a high-quality single crystal substrate, and will not form a bonding interface layer. Therefore, it will not have a negative impact on the vertical conductivity of the high-quality single crystal substrate.
  • the single crystal substrate in step (1) is a silicon carbide substrate.
  • the thickness of the single crystal substrate is 150 to 1000 ⁇ m, for example, 150 ⁇ m, 200 ⁇ m, 400 ⁇ m, 700 ⁇ m, 900 ⁇ m or 1000 ⁇ m, etc., but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.
  • the single crystal substrate has a crystal type of 4H or 6H.
  • the surface of the single crystal substrate on which the crystal layer is grown includes a Si surface or a C surface.
  • the diameter of the single crystal substrate is 2 to 8 inches, for example, 2 inches, 3 inches, 4 inches, 5 inches, 6 inches or 8 inches, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.
  • the ⁇ 0001 ⁇ crystal plane of the single crystal substrate in step (1) and the surface of the single crystal substrate The angle between them is 0° to 8°, for example, it can be 0°, 1°, 1.5°, 2°, 3°, 5° or 8°, but it is not limited to the listed values, and other unlisted values within the numerical range are also applicable.
  • the angle between the ⁇ 0001 ⁇ crystal plane of the single crystal substrate and the surface of the single crystal substrate in the optional step (1) of the present application is 0° to 8° because cracks will be generated in the crystal when the laser is used to irradiate the crystal.
  • the fracture toughness of the ⁇ 1100 ⁇ and ⁇ 1120 ⁇ crystal planes of the crystal is about 1.5 times that of the ⁇ 0001 ⁇ plane, so the cracks tend to extend toward the ⁇ 0001 ⁇ crystal plane. In other words, the above-mentioned modified surface is roughly parallel to the ⁇ 0001 ⁇ crystal plane.
  • the angle between the ⁇ 0001 ⁇ crystal plane of the high-quality single crystal substrate 1 and the substrate surface is ⁇ (i.e., off-axis ⁇ )
  • the angle between the reference plane of the grinding and polishing and the modified surface is adjusted to ⁇ , so that the substrate after grinding and polishing is still off-axis ⁇ , 0° ⁇ 8°.
  • the crystal layer in step (1) comprises single crystal or polycrystal.
  • the thickness of the crystal layer in the composite crystal layer structure is 100 to 1000 ⁇ m, for example, it can be 100 ⁇ m, 300 ⁇ m, 500 ⁇ m, 700 ⁇ m, 900 ⁇ m or 1000 ⁇ m, etc., but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.
  • the growth method of the crystal layer in step (1) includes any one of a physical vapor transport method, a solution method or a high temperature chemical vapor deposition method.
  • the growth rate of the crystal layer is 300 to 5000 ⁇ m/h, for example, it can be 300 ⁇ m/h, 400 ⁇ m/h, 500 ⁇ m/h, 600 ⁇ m/h, 700 ⁇ m/h, 800 ⁇ m/h, 900 ⁇ m/h, 1000 ⁇ m/h, 2000 ⁇ m/h, 3000 ⁇ m/h, 4000 ⁇ m/h, 4500 ⁇ m/h or 5000 ⁇ m/h, etc., but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.
  • the quality of the growing crystal layer decreases as the growth rate increases. Therefore, a high growth rate can be used to grow a low-quality crystal layer, and the crystal is allowed to contain more microtubes, dislocations, phase changes, polycrystalline inclusions and other defects, and even transition from single crystal to polycrystalline.
  • the present application can choose the growth rate of the crystal layer to be 300 to 5000 ⁇ m/h. When the growth rate is low, the preparation time of the composite substrate is long and the preparation efficiency is low. When the growth rate is high, impurities or holes will appear in the crystal layer, and the quality of the obtained composite substrate will be poor.
  • the surface of the composite crystal layer structure to be irradiated with the laser is ground and polished to ensure that the laser can penetrate the surface with as much energy as possible and focus on the modified surface.
  • the laser in step (2) is a pulsed laser.
  • the pulsed laser comprises a solid-state laser or a fiber laser.
  • the pulse width of the pulse laser is 100 to 300 fs, for example, 100 fs, 120 fs, 150 fs, 200 fs, 240 fs or 300 fs, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.
  • the pulse width of the pulse laser in the present application can be selected to be 100 to 300 fs.
  • the pulse width is too small, the single crystal substrate cannot be cut well along the modified surface; when the pulse width is too large, cracks will be generated on the modified surface, seriously affecting the quality of the composite substrate.
  • the scanning path of the laser irradiation includes any one of parallel straight lines, concentric circles, curved lines or curves.
  • the scanning path of the laser irradiation in step (2) is: divide the mutually parallel scanning paths from the beginning to the end into a group for every N, assuming that they are divided into M groups, and sequentially scan the first scanning path of the first to M groups, the second scanning path of the first to M groups, the third scanning path of the first to M groups, and so on, until all the paths are scanned.
  • the scanning directions of two consecutive paths can be the same or opposite.
  • the purpose of optimizing the laser scanning path in the present application is to make the internal stress generated in the crystal due to laser irradiation as evenly distributed as possible, so as to prevent or reduce the warping and deformation of the substrate after the modified surface is broken due to excessive stress concentration.
  • the modified surface of the composite substrate obtained in step (2) is ground and polished to achieve a desired surface quality.
  • the remaining portion of the single crystal substrate after being cut along the modified surface is ground and polished and reused as a seed crystal.
  • the thickness of the single crystal substrate therein is 1 to 50 ⁇ m, for example, it can be 1 ⁇ m, 5 ⁇ m, 10 ⁇ m, 20 ⁇ m, 30 ⁇ m, 40 ⁇ m or 50 ⁇ m, etc., but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.
  • the preparation method comprises the following steps:
  • a single crystal substrate is used as a seed crystal, and a crystal layer is grown on one of the surfaces to obtain a composite crystal layer structure consisting of the single crystal substrate and the crystal layer; wherein the thickness of the crystal layer is 100 to 1000 ⁇ m;
  • the single crystal substrate is a silicon carbide substrate with a thickness of 150 to 1000 ⁇ m and a crystal type of 4H or 6H;
  • the surface of the single crystal substrate for growing a crystal layer includes a Si surface or a C surface;
  • the angle between the ⁇ 0001 ⁇ crystal surface of the single crystal substrate and the surface of the single crystal substrate is 0° to 8°;
  • the crystal layer includes single crystal or polycrystal; the growth method of the crystal layer includes any one of physical vapor transport method, solution method or high temperature chemical vapor deposition method; the growth rate of the crystal layer is 300-5000 ⁇ m/h;
  • the composite crystal layer structure After grinding and polishing the surface of the composite crystal layer structure to be irradiated with laser, the composite crystal layer structure is irradiated with laser to form a modified surface inside the single crystal substrate of the composite crystal layer structure; external force is applied to break the single crystal substrate along the modified surface, and after surface grinding and polishing, a composite substrate having a thickness of 1 to 50 ⁇ m of the single crystal substrate is obtained;
  • the laser is a pulsed laser; the pulsed laser includes a solid-state laser or a fiber laser; the pulse width of the pulsed laser is 100 to 300 fs;
  • the scanning path of the laser irradiation includes any one of parallel straight lines, concentric circles, curved lines or curves; the scanning path of the laser irradiation is: divide the mutually parallel scanning paths from the beginning to the end into a group for every N, assuming that they are divided into M groups, and sequentially scan the first scanning path of the first to M groups, the second scanning path of the first to M groups, the third scanning path of the first to M groups... and so on, until all the paths are scanned;
  • the thickness of the single crystal substrate is 1-50 ⁇ m; the remaining portion of the single crystal substrate after being cut along the modified surface is ground and polished and reused as a seed crystal.
  • the preparation method of the composite substrate provided in the present application is simple to operate. A low-quality crystal layer is grown on a high-quality single crystal substrate, and no bonding interface layer is formed, which will not have a negative impact on the vertical conductivity of the high-quality single crystal substrate;
  • the method for preparing a composite substrate provided in the present application can prepare a composite substrate having a very thin high-quality single crystal substrate by removing a high-quality single crystal substrate through laser cutting, and has high preparation efficiency and high quality of the composite substrate.
  • FIG. 1 is a schematic diagram of a method for preparing a composite substrate provided in Example 1.
  • FIG. 2 is a schematic diagram of the modified surface in Example 1.
  • FIG. 3 is a schematic diagram of a scanning path of laser irradiation in Example 1.
  • FIG. 4 is a schematic diagram of a device for growing crystals by induction heating physical vapor transport in Example 1.
  • FIG. 5 is a schematic diagram of a method for preparing a composite substrate provided in Example 2.
  • FIG. 6 is a schematic diagram of a scanning path of laser irradiation in Example 2.
  • FIG. 7 is a schematic diagram of a device for growing crystals by resistance heating physical vapor transport in Example 2.
  • FIG. 8 is a schematic diagram of a scanning path of laser irradiation in Example 3.
  • FIG. 8 is a schematic diagram of a scanning path of laser irradiation in Example 3.
  • FIG. 9 is a schematic diagram of a device for growing crystals by induction heating solution method in Example 3.
  • FIG. 10 is a schematic diagram of a device for growing crystals by resistance heating solution method in Example 4.
  • FIG. 11 is a schematic diagram of a device for growing crystals by induction heating high temperature chemical vapor deposition in Example 5.
  • FIG. 12 is a schematic diagram of a device for growing crystals by resistance heating high temperature chemical vapor deposition in Example 6.
  • 1-single crystal substrate 101-single crystal substrate remaining on the composite substrate; 102-remaining part after breaking along the modified surface; 2-crystal layer; 20-silicon carbide powder; 21-crucible cover; 3-graphite support; 4-seed crystal rod; 40-laser; 5-graphite crucible; 6-crucible support; 7-thermal insulation box; 8-induction heating coil; 9-chamber; 10-reaction chamber; 11-resistance heater.
  • This embodiment provides a method for preparing a composite substrate.
  • the schematic diagram of the method is shown in FIG1 , and includes the following steps:
  • a single crystal substrate 1 is used as a seed crystal, and a crystal layer 2 is grown on one surface thereof to obtain a composite crystal layer structure consisting of the single crystal substrate 1 and the crystal layer 2; wherein the thickness of the crystal layer 2 is 350 ⁇ m;
  • the single crystal substrate 1 is a silicon carbide substrate with a thickness of 500 ⁇ m and a crystal type of 4H; the surface of the single crystal substrate 1 on which the crystal layer 2 is grown is a Si surface; the angle between the ⁇ 0001 ⁇ crystal plane of the single crystal substrate 1 and the surface of the single crystal substrate 1 is 4°, that is, 4° off-axis;
  • the crystal layer 2 is a single crystal; the growth method of the crystal layer 2 is a physical vapor transport method; the growth rate of the crystal layer 2 is 3000 ⁇ m/h;
  • the laser 40 After grinding and polishing the surface to be irradiated with laser in the composite crystal layer structure, the laser 40 irradiates the other surface of the single crystal substrate 1 in the composite crystal layer structure to form a modified surface inside the single crystal substrate 1 of the composite crystal layer structure; a schematic diagram of the modified surface is shown in FIG2 ; an external force is applied to break the single crystal substrate 1 along the modified surface, and after grinding and polishing the modified surface, a composite substrate with a thickness of 2 ⁇ m of the single crystal substrate 101 remaining on the composite substrate is obtained; when grinding and polishing the modified surface, the angle between the reference plane of the grinding and polishing and the modified surface is adjusted to 4°, so that the substrate after grinding and polishing is still off-axis by 4°;
  • the laser 40 is a pulsed laser; the pulsed laser is a solid-state laser; the pulse width of the pulsed laser is 200 fs; the scanning path of the laser irradiation is: divide the mutually parallel scanning paths from the beginning to the end into a group for every N, assuming that they are divided into M groups, and sequentially scan the first scanning path of the 1st to M groups, the second scanning path of the 1st to M groups, the third scanning path of the 1st to M groups... and so on, until all the paths are scanned; specifically, the scanning sequence is: 1-1, 2-1, 3-1, 4-1, 1-2, 2-2, 3-2, 4-2, 1-3, 2-3, 3-3,...; the scanning directions of two consecutive scanning paths are opposite, as shown in FIG3;
  • the remaining portion 102 of the single crystal substrate 1 after being cut along the modified surface is ground and polished and reused as a seed crystal.
  • This embodiment is carried out in an induction heating physical vapor transport method crystal growth device, the structure diagram of which is shown in FIG4, comprising a graphite crucible 5, a single crystal substrate 1, a crucible cover 21, a crucible support 6, a heat insulation box 7, an induction heating coil 8 and a chamber 9; the chamber 9 has at least one exhaust port and at least one
  • the graphite crucible 5 is filled with silicon carbide powder 20.
  • the crucible cover 21 is connected to the single crystal substrate 1, and one surface of the single crystal substrate 1 is opposite to the silicon carbide powder 20.
  • the crucible support 6 supports the graphite crucible 5, driving the graphite crucible 5 to rotate or move in the vertical direction.
  • the outside of the graphite crucible 5 is surrounded by an insulation box 7, and the insulation box 7 is in the chamber 9.
  • the induction heating coil 8 is arranged on the periphery of the chamber 9.
  • the induction heating coil 8 is spiral, the current frequency is 8kHz, the coil is hollow, and can be cooled by water.
  • the energized induction heating coil 8 heats the silicon carbide powder 20 in the crucible, causing the silicon carbide powder 20 to sublime.
  • the crucible support 6 passes through the wall of the chamber 9.
  • This embodiment provides a method for preparing a composite substrate.
  • the schematic diagram of the method is shown in FIG5 , and includes the following steps:
  • a single crystal substrate 1 is used as a seed crystal, and a crystal layer 2 is grown on one surface thereof to obtain a composite crystal layer structure consisting of the single crystal substrate 1 and the crystal layer 2; wherein the thickness of the crystal layer 2 is 200 ⁇ m;
  • the single crystal substrate 1 is a silicon carbide substrate with a thickness of 200 ⁇ m and a crystal type of 6H; the surface of the single crystal substrate 1 on which the crystal layer 2 is grown is a C surface; the angle between the ⁇ 0001 ⁇ crystal plane of the single crystal substrate 1 and the surface of the single crystal substrate 1 is 8°, that is, 8° off-axis;
  • the crystal layer 2 is polycrystalline; the growth method of the crystal layer 2 is physical vapor transport method; the growth rate of the crystal layer 2 is 300 ⁇ m/h;
  • the laser 40 is a pulse laser; the pulse laser is a fiber laser; the pulse width of the pulse laser is 100 fs; the scanning path of the laser irradiation is a series of parallel straight lines, and the spacing between adjacent paths remains unchanged; the scanning direction of each path is opposite, and the scanning path is to scan each path in turn from top to bottom, as shown in FIG6 ;
  • the remaining portion 102 of the single crystal substrate 1 after being cut along the modified surface is ground and polished and reused as a seed crystal.
  • This embodiment is carried out in a device for growing crystals by resistance heating physical vapor transport method, the structure schematic diagram of which is shown in FIG7 , and includes a graphite crucible 5, a single crystal substrate 1, a crucible cover 21, a crucible support 6, a heat insulation box 7, a resistance heater 11 and a chamber 9; the chamber 9 has at least one exhaust port and at least one air inlet.
  • the graphite crucible 5 is filled with silicon carbide powder 20.
  • the crucible cover 21 is connected to the single crystal substrate 1, and one surface of the single crystal substrate 1 is opposite to the silicon carbide powder 20.
  • the crucible holder 6 supports the graphite crucible 5, driving the graphite crucible 5 to rotate or move in the vertical direction.
  • the outside of the graphite crucible 5 is surrounded by a resistance heater 11, which is surrounded by a heat insulation box 7.
  • the resistance heater 11 is a graphite heater, and the energized graphite heater heats the silicon carbide powder 20 in the graphite crucible 5, so that the silicon carbide powder 20 sublimates.
  • the crucible holder 6 passes through the wall of the chamber 9.
  • This embodiment provides a method for preparing a composite substrate, the method comprising the following steps:
  • a single crystal substrate 1 is used as a seed crystal, and a crystal layer 2 is grown on one surface thereof to obtain a composite crystal layer structure consisting of the single crystal substrate 1 and the crystal layer 2; wherein the thickness of the crystal layer 2 is 100 ⁇ m;
  • the single crystal substrate 1 is a silicon carbide substrate with a thickness of 1000 ⁇ m and a crystal type of 4H; the surface of the single crystal substrate 1 on which the crystal layer 2 is grown is a C surface; the angle between the ⁇ 0001 ⁇ crystal plane of the single crystal substrate 1 and the surface of the single crystal substrate 1 is 0°, that is, the eccentricity is 0°;
  • the crystal layer 2 is polycrystalline; the growth method of the crystal layer 2 is a solution method; the crystal layer 2 The growth rate is 5000 ⁇ m/h;
  • the composite crystal layer structure After grinding and polishing the surface of the composite crystal layer structure to be irradiated with laser, the composite crystal layer structure is irradiated with laser to form a modified surface inside the single crystal substrate 1 of the composite crystal layer structure; external force is applied to break the single crystal substrate 1 along the modified surface, and the modified surface is ground and polished to obtain a composite substrate with a thickness of 46 ⁇ m of the single crystal substrate 101 remaining on the composite substrate; when grinding and polishing the modified surface, the angle between the reference plane of the grinding and polishing and the modified surface is adjusted to 0°, so that the substrate after grinding and polishing is still off-axis by 0°;
  • the laser is a pulsed laser; the pulsed laser is a solid-state laser; the pulse width of the pulsed laser is 300 fs; the scanning path of the laser irradiation is a series of straight lines parallel to each other, and the spacing between adjacent paths remains unchanged; the scanning direction of each path is the same, and the scanning path is to scan each path in turn from top to bottom, as shown in FIG8 ;
  • the remaining portion 102 of the single crystal substrate 1 after being cut along the modified surface is ground and polished and reused as a seed crystal.
  • This embodiment is carried out in a device for growing crystals by induction heating solution method, the structure schematic diagram of which is shown in FIG9 , including a graphite crucible 5, a seed crystal rod 4, a graphite holder 3, a single crystal substrate 1, a crucible holder 6, a heat insulation box 7, an induction heating coil 8, and a chamber 9.
  • the chamber 9 has at least one exhaust port and at least one air inlet.
  • the graphite crucible 5 contains a co-solvent solution.
  • the seed crystal rod 4 is connected to the graphite holder 3, and the bottom of the graphite holder 3 can be connected to the composite seed crystal.
  • the seed crystal rod 4 can rotate and move in the vertical direction.
  • the crucible holder 6 supports the graphite crucible 5, and can drive the graphite crucible 5 to rotate and move in the vertical direction.
  • the outside of the graphite crucible 5 is surrounded by an insulation box 7, and an induction heating coil 8 is arranged on the outer periphery of the insulation box 7.
  • the induction heating coil 8 is spiral, the current frequency is 3kHz, the coil is hollow, and can be cooled by water.
  • the energized induction heating coil 8 heats and melts the flux in the graphite crucible 5.
  • the chamber 9 provides an atmosphere environment for crystal growth.
  • the seed crystal rod 4 and the crucible holder 6 pass through the wall of the chamber 9.
  • This embodiment provides a method for preparing a composite substrate, the method comprising the following steps:
  • a single crystal substrate 1 is used as a seed crystal, and a crystal layer 2 is grown on one surface thereof to obtain a composite crystal layer structure consisting of the single crystal substrate 1 and the crystal layer 2; wherein the thickness of the crystal layer 2 is 100 ⁇ m;
  • the single crystal substrate 1 is a silicon carbide substrate with a thickness of 150 ⁇ m and a crystal type of 4H; the surface of the single crystal substrate 1 on which the crystal layer 2 is grown is a Si surface; the angle between the ⁇ 0001 ⁇ crystal plane of the single crystal substrate 1 and the surface of the single crystal substrate 1 is 3°, that is, 3° off-axis;
  • the crystal layer 2 is a single crystal; the growth method of the crystal layer 2 is a solution method; the growth rate of the crystal layer 2 is 2400 ⁇ m/h;
  • the composite crystal layer structure After grinding and polishing the surface to be irradiated with laser in the composite crystal layer structure, the composite crystal layer structure is irradiated with laser to form a modified surface inside the single crystal substrate 1 of the composite crystal layer structure; external force is applied to break the single crystal substrate 1 along the modified surface, and the modified surface is ground and polished to obtain a composite substrate with a thickness of 1 ⁇ m of the single crystal substrate 101 remaining on the composite substrate; when grinding and polishing the modified surface, the angle between the reference plane of the grinding and polishing and the modified surface is adjusted to 3°, so that the substrate after grinding and polishing is still 3° off-axis;
  • the laser is a pulse laser; the pulse laser is a fiber laser; the pulse width of the pulse laser is 160fs; the scanning path of the laser irradiation is a series of parallel straight lines, and the spacing between adjacent paths remains unchanged; the scanning direction of each path is the same; its scanning path is to scan each path in turn from top to bottom;
  • the remaining portion 102 of the single crystal substrate 1 after being cut along the modified surface is ground and polished and reused as a seed crystal.
  • This embodiment is carried out in a device for growing crystals by a resistance heating solution method.
  • the device is shown in FIG10 , and includes a graphite crucible 5, a seed crystal rod 4, a graphite holder 3, a single crystal substrate 1, a crucible holder 6, The heat-insulating box 7, the resistance heater 11, and the chamber 9.
  • the chamber 9 has at least one gas extraction port and at least one gas inlet port.
  • the graphite crucible 5 contains a solvent solution.
  • the seed crystal rod 4 is connected to the graphite holder 3, and the bottom of the graphite holder 3 can be connected to the composite seed crystal.
  • the seed crystal rod 4 can rotate and move in the vertical direction.
  • the crucible holder 6 supports the graphite crucible 5, and can drive the graphite crucible 5 to rotate and move in the vertical direction.
  • the outside of the graphite crucible 5 is surrounded by a resistance heater 11 and surrounded by a heat insulation box 7.
  • the resistance heater 11 is a graphite heater.
  • the energized graphite heater heats and melts the flux in the graphite crucible 5.
  • the chamber 9 provides an atmosphere environment for crystal growth.
  • the seed crystal rod 4 and the crucible holder 6 pass through the wall of the chamber 9.
  • This embodiment provides a method for preparing a composite substrate, the method comprising the following steps:
  • a single crystal substrate 1 is used as a seed crystal, and a crystal layer 2 is grown on one surface thereof to obtain a composite crystal layer structure consisting of the single crystal substrate 1 and the crystal layer 2; wherein the thickness of the crystal layer 2 is 750 ⁇ m;
  • the single crystal substrate 1 is a silicon carbide substrate with a thickness of 630 ⁇ m and a crystal type of 6H; the surface of the single crystal substrate 1 on which the crystal layer 2 is grown is a Si surface; the angle between the ⁇ 0001 ⁇ crystal plane of the single crystal substrate 1 and the surface of the single crystal substrate 1 is 5°, that is, 5° off-axis;
  • the crystal layer 2 is polycrystalline; the growth method of the crystal layer 2 is high temperature chemical vapor deposition; the growth rate of the crystal layer 2 is 500 ⁇ m/h;
  • the composite crystal layer structure After grinding and polishing the surface to be irradiated with laser in the composite crystal layer structure, the composite crystal layer structure is irradiated with laser to form a modified surface inside the single crystal substrate 1 of the composite crystal layer structure; external force is applied to break the single crystal substrate 1 along the modified surface, and the modified surface is ground and polished to obtain a composite substrate with a thickness of 24 ⁇ m of the single crystal substrate 101 remaining on the composite substrate; when grinding and polishing the modified surface, the angle between the reference plane of the grinding and polishing and the modified surface is adjusted to 5°, so that the substrate after grinding and polishing is still 5° off-axis;
  • the laser is a pulsed laser; the pulsed laser is a solid-state laser; the pulse width of the pulsed laser is The scanning path of the laser irradiation is a series of parallel straight lines, and the spacing between adjacent paths remains unchanged; the scanning direction of each path is opposite; and the scanning path is to scan each path in sequence from top to bottom;
  • the remaining portion 102 of the single crystal substrate 1 after being cut along the modified surface is ground and polished and reused as a seed crystal.
  • This embodiment is carried out in a device for growing crystals by induction heating high temperature chemical vapor deposition, the structure schematic diagram of which is shown in FIG11 , and includes a seed crystal rod 4, a graphite holder 3, a single crystal substrate 1, a reaction chamber 10, a heat insulation box 7, an induction heating coil 8, and a chamber 9.
  • the chamber 9 has at least one exhaust port and at least one air inlet.
  • the seed crystal rod 4 is connected to the graphite holder 3, and the bottom of the graphite holder 3 can be connected to the composite seed crystal.
  • the seed crystal rod 4 can rotate and move in the vertical direction.
  • the reaction chamber 10 is made of graphite and is surrounded by a heat insulation box 7 on the outside.
  • the heat insulation box 7 is in the chamber 9, and an induction heating coil 8 is arranged on the periphery of the chamber 9.
  • the induction heating coil 8 is spiral, the current frequency is 20kHz, the coil is hollow, and can be cooled by water.
  • the seed crystal rod 4 passes through the wall of the chamber 9.
  • the energized induction heating coil 8 heats the reaction chamber 10 to the temperature for crystal growth.
  • the gas inlet of the chamber 9 is filled with reaction gas, and the reaction gas includes silicon source gas and carbon source gas.
  • the silicon source gas is silane
  • the carbon source gas is propane.
  • This embodiment provides a method for preparing a composite substrate, the method comprising the following steps:
  • a single crystal substrate 1 is used as a seed crystal, and a crystal layer 2 is grown on one surface thereof to obtain a composite crystal layer structure consisting of the single crystal substrate 1 and the crystal layer 2; wherein the thickness of the crystal layer 2 is 330 ⁇ m;
  • the single crystal substrate 1 is a silicon carbide substrate with a thickness of 670 ⁇ m and a crystal type of 4H; the surface of the single crystal substrate 1 on which the crystal layer 2 is grown is a Si surface; the angle between the ⁇ 0001 ⁇ crystal plane of the single crystal substrate 1 and the surface of the single crystal substrate 1 is 7°, that is, 7° off-axis;
  • the crystal layer 2 is a single crystal; the growth method of the crystal layer 2 is a high temperature chemical vapor deposition method; the growth rate of the crystal layer 2 is 800 ⁇ m/h;
  • the composite crystal layer structure After grinding and polishing the surface of the composite crystal layer structure to be irradiated with laser, the composite crystal layer structure is irradiated with laser to form a modified surface inside the single crystal substrate 1 of the composite crystal layer structure; external force is applied to break the single crystal substrate 1 along the modified surface, and the modified surface is ground and polished to obtain a composite substrate with a thickness of 41 ⁇ m of the single crystal substrate 101 remaining on the composite substrate; when grinding and polishing the modified surface, the angle between the reference plane of the grinding and polishing and the modified surface is adjusted to 7°, so that the substrate after grinding and polishing is still off-axis by 7°;
  • the laser is a pulsed laser; the pulsed laser is a solid-state laser; the pulse width of the pulsed laser is 140 fs; the scanning path of the laser irradiation is: divide the mutually parallel scanning paths from the beginning to the end into a group for every N, assuming that they are divided into M groups, and sequentially scan the first scanning path of the 1st to M groups, the second scanning path of the 1st to M groups, the third scanning path of the 1st to M groups... and so on, until all the paths are scanned; specifically, the scanning sequence is: 1-1, 2-1, 3-1, 4-1, 1-2, 2-2, 3-2, 4-2, 1-3, 2-3, 3-3,...; the scanning directions of two consecutive scanning paths are opposite;
  • the remaining portion 102 of the single crystal substrate 1 after being cut along the modified surface is ground and polished and reused as a seed crystal.
  • This embodiment is carried out in a device for growing crystals by resistance heating high temperature chemical vapor deposition, the structure schematic diagram of which is shown in FIG12, and includes a seed crystal rod 4, a graphite holder 3, a single crystal substrate 1, a reaction chamber 10, a heat insulation box 7, a resistance heater 11, and a chamber 9.
  • the chamber 9 has at least one exhaust port and at least one air inlet.
  • the seed crystal rod 4 is connected to the graphite holder 3, the bottom of the graphite holder 3 can be connected to the composite seed crystal, and the seed crystal rod 4 can rotate and move in the vertical direction.
  • the reaction chamber 10 is made of graphite, and a resistance heater 11 is arranged on the outside.
  • the resistance heater 11 is in the heat insulation box 7, and the heat insulation box 7 is in the chamber 9.
  • the seed crystal rod 4 passes through the wall of the chamber 9.
  • the resistance heater 11 is a graphite heater, and the graphite heater, when powered, heats the reaction chamber 10 to a temperature for crystal growth.
  • the gas inlet of the chamber 9 is filled with reaction gas, and the reaction gas includes silicon source gas and carbon source gas.
  • the silicon source gas is silane
  • the carbon source gas is propane.
  • This embodiment provides a method for preparing a composite substrate.
  • the preparation method is the same as that of Embodiment 1 except that the growth rate of the crystal layer is replaced from 3000 ⁇ m/h to 150 ⁇ m/h.
  • This embodiment provides a method for preparing a composite substrate.
  • the preparation method is the same as that of Embodiment 1 except that the growth rate of the crystal layer is replaced from 3000 ⁇ m/h to 5500 ⁇ m/h.
  • This embodiment provides a method for preparing a composite substrate.
  • the preparation method is the same as that of Embodiment 1 except that the pulse width of the pulse laser is replaced from 200 fs to 50 fs.
  • the pulse width of the pulse laser is only 50 fs, the single crystal substrate cannot be cut along the modified surface, so a composite substrate cannot be obtained.
  • This embodiment provides a method for preparing a composite substrate.
  • the preparation method is the same as that of Embodiment 1 except that the pulse width of the pulse laser is replaced from 200 fs to 350 fs.
  • This embodiment provides a method for preparing a composite substrate, which is the same as Embodiment 1 except that the scanning path of laser irradiation is a series of parallel straight lines, the spacing between adjacent paths remains unchanged, and the scanning direction of each path is the same.
  • This comparative example provides a method for preparing a composite substrate, comprising the following steps:
  • the single crystal substrate and the crystal layer are respectively manufactured by physical vapor transport method, the crystal type is 4H, and the thickness is 350 ⁇ m; the angle between the ⁇ 0001 ⁇ crystal plane of the single crystal substrate and the surface of the single crystal substrate is 4°;
  • Ion implantation or laser irradiation is performed on one surface of the single crystal substrate to form a pre-buried weakened layer at a depth of about 2 ⁇ m from the surface;
  • the composite substrate is heat treated so that the single crystal substrate is broken along the pre-buried weakened layer.
  • the thickness of the single crystal substrate of the obtained composite substrate is 2 ⁇ m.
  • the resistance values of the composite substrates obtained in the above embodiments and comparative examples were measured by forming a back electrode on the surface of the crystal layer of the composite silicon carbide substrate and a circular surface electrode with a diameter of 0.3 mm on the surface of the single crystal substrate. A voltage V was applied between the surface electrode and the back electrode, and the corresponding current I was recorded to obtain a V-I curve and calculate the resistance value.
  • Example 1 Combining Example 1 and Comparative Example 1, it can be seen that the resistance value of Example 1 is 3.7 ⁇ , and the resistance value of Comparative Example 1 is higher, reaching 4.0 ⁇ , due to the negative impact of the vertical conductivity of the composite substrate on the existence of the bonding interface layer.
  • the composite substrate prepared by the method for preparing the composite substrate provided in the present application has high quality and better vertical conductivity;
  • Example 7 since the growth rate of the crystal layer is only 150 ⁇ m/h, the quality of the prepared composite substrate is high and the resistance value is 3.6 ⁇ , but the preparation time of the composite substrate is long and the preparation efficiency is low; in Example 8, since the growth rate of the crystal layer is too high, impurities or holes will appear in the crystal layer, and the quality of the obtained composite substrate is poor, and the resistance value is 3.9 ⁇ ;
  • Example 9 since the pulse width of the pulsed laser is only 50 fs, the single crystal substrate cannot be broken along the modified surface, so a composite substrate cannot be obtained. In Example 10, since the pulse width of the pulsed laser is 350 fs, cracks are generated on the modified surface, which seriously affects the quality of the composite substrate.
  • Example 1 (4) Combining Example 1 and Example 11, it can be seen that the scanning path of the laser irradiation in Example 1 is: divide the mutually parallel scanning paths from the beginning to the end into a group for every N, assuming that they are divided into M groups, and scan the first scanning path of the first to M groups, the second scanning path of the first to M groups, the third scanning path of the first to M groups, and so on, in sequence, until all the paths are scanned; specifically, the scanning sequence is: 1-1, 2-1, 3-1, 4-1, 1-2, 2-2, 3-2, 4-2, 1-3, 2-3, 3-3, ...; the scanning directions of two consecutive scanning paths are opposite; the modified surface formed inside the single crystal substrate of the composite crystal layer structure after cutting does not warp or deforms very little, and the warpage WARP is only 16 ⁇ m; while the scanning path of the laser irradiation in Example 11 is a series of mutually parallel straight lines, and the spacing between adjacent paths remains unchanged; the scanning direction of each path is the same, and the modified surface
  • the preparation method of the composite substrate provided in the present application is simple to operate.
  • a low-quality crystal layer is grown on a high-quality single crystal substrate, and no bonding interface layer is formed.
  • the high-quality single crystal substrate is then removed by laser cutting, and a composite substrate with a very thin high-quality single crystal substrate can be prepared.
  • the preparation efficiency is high and the quality of the composite substrate is high.

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Abstract

本申请提供一种复合衬底的制备方法，所述制备方法包括如下步骤：（1）单晶衬底作为籽晶，在其中一个表面生长晶体层，得到单晶衬底与晶体层组成的复合晶体层结构；（2）激光照射所述复合晶体层结构，在所述复合晶体层结构的单晶衬底内部形成改质面；施加外力，将单晶衬底沿着改质面断开，得到复合衬底。本申请所述制备方法通过在高质量单晶衬底上生长低质量晶体层，之后采用激光冷裂切割处理，复合衬底的制备效率高且质量好，应用范围广。

Description

一种复合衬底的制备方法 技术领域
本申请涉及半导体技术领域，例如一种复合衬底的制备方法。
背景技术
碳化硅单晶衬底制作的器件具有耐高温、耐高压、高频、大功率、抗辐射、效率高等优势，在射频、新能源汽车等领域具有重要的应用价值。
碳化硅单晶衬底的常规制造方法包括以下流程：利用物理气相传输法生长碳化硅单晶，得到碳化硅单晶的晶锭；加工晶锭的外周，得到所需要的直径和表面质量，再将晶锭切成薄片，将薄片研磨、抛光至所需要的厚度和平整度，得到最终的碳化硅单晶衬底。物理气相传输方法生长碳化硅单晶效率很低，导致单一碳化硅单晶衬底成本很高。
一种降低碳化硅衬底的成本的方案是采用复合衬底结构：在价格较低的支撑衬底上键合一单晶碳化硅薄层。该方案需要分别加工低质量衬底和高质量衬底的表面使其表面质量满足键合的要求，然后进行键合。高质量的表面加工存在一定的复杂度和难度。另外，该方案会形成键合界面层，键合界面层可能会对衬底的垂直导电产生负面影响。
CN114746980A公开了一种复合衬底的制造方法：利用离子注入在高质量单晶衬底中形成预埋的弱化层；利用CVD方法在单晶衬底表面沉积低质量晶体层或者多晶层；沿着弱化层分离从而得到复合衬底。该方法存在的问题是：由于CVD工艺温度较高，预埋的弱化层可能会在CVD的工艺过程中就提前裂开，造成CVD过程不得不中断。
CN112701033A公开了一种复合衬底的制备方法、复合衬底及复合薄膜，其 中复合衬底的制备方法包括：对单晶硅衬底进行清洗，获得具有洁净表面的单晶硅衬底层；在单晶硅衬底层的洁净表面上生长多晶硅，并执行平坦化工艺，形成第一多晶硅层；将激光聚焦在第一多晶硅层靠近单晶硅衬底层的侧面上，直至形成单晶硅融合层，停止激光聚焦，得到复合衬底；其中，复合衬底从下至上依次包括单晶硅衬底层、单晶硅融合层以及第二多晶硅层。采用前述的方案，通过调整激光的功率、焦距以及位置，准确的控制单晶硅融合区域的位置、分布和大小，从而可根据单晶硅衬底层和多晶硅层的实际情况对目标界面处的目标区域的键合力进行改善，提高多晶硅在硅衬底上沉积的粘附性。但上述制备方法的制备效率较低。
因此，开发一种新的复合衬底的制备方法，提高复合衬底的制造效率和质量具有重要意义。
发明内容
以下是对本文详细描述的主题的概述。本概述并非是为了限制权利要求的保护范围。
鉴于现有技术中存在的问题，本申请提供一种复合衬底的制备方法，通过在高质量单晶衬底上生长低质量晶体层，可提高复合衬底的制造效率，而且采用激光冷裂切割处理，得到了具有很薄的高质量单晶衬底的复合衬底，所述复合衬底质量高，应用范围广。
本申请提供一种复合衬底的制备方法，所述制备方法包括如下步骤：
(1)单晶衬底作为籽晶，在其中一个表面生长晶体层，得到单晶衬底与晶体层组成的复合晶体层结构；
(2)激光照射所述复合晶体层结构，在所述复合晶体层结构的单晶衬底内 部形成改质面；施加外力，将单晶衬底沿着改质面断开，得到复合衬底。
本申请所述的复合衬底的制备方法中的单晶衬底是高质量单晶衬底，其中有较少的微管、位错、相变、多晶夹杂等缺陷，该高质量单晶衬底作为低质量晶体层的生长基础，在其Si面或者C面上生长一层低质量晶体层，该低质量晶体层中允许含有较多的微管、位错、相变、多晶夹杂等缺陷，而且可以是单晶或多晶；之后采用激光照射单晶衬底与晶体层组成的复合晶体层结构，激光可以从单晶衬底的另一个表面照射，也可以从复合晶体层结构的低质量晶体层的表面照射，只要控制好激光聚焦深度，即可在所述复合晶体层结构的单晶衬底内部形成改质面，之后沿着改质面将单晶衬底断开，得到具有很薄的高质量单晶衬底和特定厚度的低质量晶体层的复合衬底。本申请所述制备方法可以提高复合衬底的制造效率和质量。
本申请所述制备方法是在高质量单晶衬底上生长一层低质量晶体层，不会形成键合界面层，因此，不会对高质量单晶衬底的垂直导电产生负面影响。
在一实施方式中，步骤(1)所述单晶衬底为碳化硅衬底。
在一实施方式中，所述单晶衬底的厚度为150～1000μm，例如可以是150μm、200μm、400μm、700μm、900μm或1000μm等，但并不仅限于所列举的数值，该数值范围内其他未列举的数值同样适用。
在一实施方式中，所述单晶衬底的晶型包括4H或6H。
在一实施方式中，所述单晶衬底生长晶体层的面包括Si面或C面。
在一实施方式中，所述单晶衬底的直径为2～8寸，例如可以是2寸、3寸、4寸、5寸、6寸或8寸等，但并不仅限于所列举的数值，该数值范围内其他未列举的数值同样适用。
在一实施方式中，步骤(1)所述单晶衬底的{0001}晶面和单晶衬底的表面 之间的夹角为0°～8°，例如可以是0°、1°、1.5°、2°、3°、5°或8°等，但并不仅限于所列举的数值，该数值范围内其他未列举的数值同样适用。
本申请可选步骤(1)所述单晶衬底的{0001}晶面和单晶衬底的表面之间的夹角为0°～8°，是因为利用激光照射晶体时，会在其中产生裂纹。晶体的{1100}、{1120}晶面的断裂韧性约为{0001}面的1.5倍，因此，裂纹呈现向{0001}晶面扩展的趋势。也就是说，上述改质面大致平行于{0001}晶面。
假设高质量单晶衬底1的{0001}晶面和衬底表面的夹角是θ(即偏轴θ)，在对改质面研磨抛光时，调整研磨抛光的基准平面和改质面的夹角为θ，可使得研磨抛光后的衬底仍然是偏轴θ，0°～8°。
在一实施方式中，步骤(1)所述晶体层包括单晶或多晶。
在一实施方式中，所述复合晶体层结构中晶体层的厚度为100～1000μm，例如可以是100μm、300μm、500μm、700μm、900μm或1000μm等，但并不仅限于所列举的数值，该数值范围内其他未列举的数值同样适用。
在一实施方式中，步骤(1)所述晶体层的生长方法包括物理气相传输法、溶液法或高温化学气相沉积法中的任意一种。
在一实施方式中，所述晶体层的生长速率为300～5000μm/h，例如可以是300μm/h、400μm/h、500μm/h、600μm/h、700μm/h、800μm/h、900μm/h、1000μm/h、2000μm/h、3000μm/h、4000μm/h、4500μm/h或5000μm/h等，但并不仅限于所列举的数值，该数值范围内其他未列举的数值同样适用。
一般而言，生长晶体层的质量随着生长速率的提高而降低。因此，低质量晶体层生长可采用较高的生长速度，晶体中允许含有较多的微管、位错、相变、多晶夹杂等缺陷，甚至可以从单晶过渡为多晶。本申请可选所述晶体层的生长速率为300～5000μm/h，当生长速率较低，所述复合衬底的制备时间长，制备效 率低；当生长速率较高，晶体层中会出现杂质或孔洞等，得到的复合衬底质量差。
在一实施方式中，步骤(2)所述激光照射之前，对复合晶体层结构中要进行激光照射的表面进行研磨抛光，以保证激光能够将尽可能多的能量穿透该表面，聚焦于改质面。
在一实施方式中，步骤(2)所述激光为脉冲激光。
在一实施方式中，所述脉冲激光包括固态激光或光纤激光。
在一实施方式中，所述脉冲激光的脉冲宽度为100～300fs，例如可以是100fs、120fs、150fs、200fs、240fs或300fs等，但并不仅限于所列举的数值，该数值范围内其他未列举的数值同样适用。
本申请可选所述脉冲激光的脉冲宽度为100～300fs，当脉冲宽度过小，不能将单晶衬底沿着改质面很好地切割下来；当脉冲宽度过大，会导致改质面上产生裂纹，严重影响到复合衬底的质量。
在一实施方式中，所述激光照射的扫描路径包括平行直线、同心圆、弯折线或曲线中的任意一种。
在一实施方式中，步骤(2)所述激光照射的扫描路径为：将相互平行的扫描路径从头至尾每N个分为一组，假设分成M组，依次扫描第1至M组的第1个扫描路径、第1至M组的第2个扫描路径、第1至M组的第3个扫描路径……依次类推，直至所有路径都被扫描。连续的两个路径的扫描方向可以相同，也可以相反。
本申请优化激光扫描路径的目的是，使得晶体内由于激光照射产生的内应力尽量均匀分布，防止或减少应力过于集中造成的改质面断开后的衬底翘曲、变形。
在一实施方式中，对步骤(2)所得复合衬底的改质面进行研磨抛光，以达到所需要的表面质量。
在一实施方式中，所述单晶衬底沿着改质面断开后的剩余部分，经表面研磨抛光后，重新作为籽晶使用。
在一实施方式中，步骤(2)所述复合衬底经过研磨抛光后，其中的单晶衬底的厚度为1～50μm，例如可以是1μm、5μm、10μm、20μm、30μm、40μm或50μm等，但并不仅限于所列举的数值，该数值范围内其他未列举的数值同样适用。
作为本申请可选的技术方案，所述制备方法包括如下步骤：
(1)单晶衬底作为籽晶，在其中一个表面生长晶体层，得到单晶衬底与晶体层组成的复合晶体层结构；其中，晶体层的厚度为100～1000μm；
所述单晶衬底为碳化硅衬底，厚度为150～1000μm，晶型包括4H或6H；所述单晶衬底生长晶体层的面包括Si面或C面；所述单晶衬底的{0001}晶面和单晶衬底的表面之间的夹角为0°～8°；
所述晶体层包括单晶或多晶；所述晶体层的生长方法包括物理气相传输法、溶液法或高温化学气相沉积法中的任意一种；所述晶体层的生长速率为300～5000μm/h；
(2)对复合晶体层结构中要进行激光照射的表面进行研磨抛光后，激光照射所述复合晶体层结构，在所述复合晶体层结构的单晶衬底内部形成改质面；施加外力，将单晶衬底沿着改质面断开，经过表面研磨抛光后，得到单晶衬底的厚度为1～50μm的复合衬底；
所述激光为脉冲激光；所述脉冲激光包括固态激光或光纤激光；所述脉冲激光的脉冲宽度为100～300fs；
所述激光照射的扫描路径包括平行直线、同心圆、弯折线或曲线中的任意一种；所述激光照射的扫描路径为：将相互平行的扫描路径从头至尾每N个分为一组，假设分成M组，依次扫描第1至M组的第1个扫描路径、第1至M组的第2个扫描路径、第1至M组的第3个扫描路径……依次类推，直至所有路径都被扫描；
所述复合衬底经过研磨抛光后，其中单晶衬底的厚度为1～50μm；所述单晶衬底沿着改质面断开后的剩余部分，经表面研磨抛光后，重新作为籽晶使用。
与相关技术相比，本申请至少具有以下有益效果：
(1)本申请提供的复合衬底的制备方法操作简单，在高质量单晶衬底上生长一层低质量晶体层，不会形成键合界面层，不会对高质量单晶衬底的垂直导电产生负面影响；
(2)本申请提供的复合衬底的制备方法通过激光切割去除高质量单晶衬底，可以制备得到具有很薄的高质量单晶衬底的复合衬底，制备效率高且复合衬底的质量高。
在阅读并理解了附图和详细描述后，可以明白其他方面。
附图说明
附图用来提供对本文技术方案的进一步理解，并且构成说明书的一部分，与本申请的实施例一起用于解释本文的技术方案，并不构成对本文技术方案的限制。
图1是实施例1提供的复合衬底的制备方法的示意图。
图2是实施例1中改质面示意图。
图3是实施例1中激光照射的扫描路径的示意图。
图4是实施例1中感应加热物理气相传输法生长晶体的装置示意图。
图5是实施例2提供的复合衬底的制备方法的示意图。
图6是实施例2中激光照射的扫描路径的示意图。
图7是实施例2中电阻加热物理气相传输法生长晶体的装置示意图。
图8是实施例3中激光照射的扫描路径的示意图。
图9是实施例3中感应加热溶液法生长晶体的装置示意图。
图10是实施例4中电阻加热溶液法生长晶体的装置示意图。
图11是实施例5中感应加热高温化学气相沉积法生长晶体的装置示意图。
图12是实施例6中电阻加热高温化学气相沉积法生长晶体的装置示意图。
图中：1-单晶衬底；101-留在复合衬底上的单晶衬底；102-沿着改质面断开后的剩余部分；2-晶体层；20-碳化硅粉料；21-坩埚盖；3-石墨托；4-籽晶杆；40-激光；5-石墨坩埚；6-坩埚托；7-隔热箱；8-感应加热线圈；9-腔室；10-反应室；11-电阻加热器。
具体实施方式
下面结合附图并通过具体实施方式来进一步说明本申请的技术方案。
下面对本申请进一步详细说明。但下述的实例仅仅是本申请的简易例子，并不代表或限制本申请的权利保护范围，本申请的保护范围以权利要求书为准。
实施例1
本实施例提供一种复合衬底的制备方法，所述制备方法的示意图如图1所示，包括如下步骤：
(1)单晶衬底1作为籽晶，在其中一个表面生长晶体层2，得到单晶衬底1与晶体层2组成的复合晶体层结构；其中，晶体层2的厚度为350μm；
所述单晶衬底1为碳化硅衬底，厚度为500μm，晶型为4H；所述单晶衬底1生长晶体层2的面为Si面；所述单晶衬底1的{0001}晶面和单晶衬底1的表面之间的夹角为4°，即偏轴4°；
所述晶体层2为单晶；所述晶体层2的生长方法为物理气相传输法；所述晶体层2的生长速率为3000μm/h；
(2)对复合晶体层结构中要进行激光照射的表面进行研磨抛光后，激光40照射所述复合晶体层结构中单晶衬底1的另一个表面，在所述复合晶体层结构的单晶衬底1内部形成改质面；改质面示意图如图2所示；施加外力，将单晶衬底1沿着改质面断开，并对改质面进行研磨抛光后，得到留在复合衬底上的单晶衬底101的厚度为2μm的复合衬底；在对改质面研磨抛光时，调整研磨抛光的基准平面和改质面的夹角为4°，使得研磨抛光后的衬底仍然偏轴4°；
所述激光40为脉冲激光；所述脉冲激光为固态激光；所述脉冲激光的脉冲宽度为200fs；所述激光照射的扫描路径为：将相互平行的扫描路径从头至尾每N个分为一组，假设分成M组，依次扫描第1至M组的第1个扫描路径、第1至M组的第2个扫描路径、第1至M组的第3个扫描路径……依次类推，直至所有路径都被扫描；具体而言，其扫描顺序为：1-1、2-1、3-1、4-1、1-2、2-2、3-2、4-2、1-3、2-3、3-3、……；连续的两个扫描路径的扫描方向相反，示意图如图3所示；
所述单晶衬底1沿着改质面断开后的剩余部分102，经表面研磨抛光后，重新作为籽晶使用。
本实施例在感应加热物理气相传输法生长晶体的装置内进行，所述装置的结构示意图如图4所示，包括石墨坩埚5、单晶衬底1、坩埚盖21、坩埚托6、隔热箱7、感应加热线圈8和腔室9；所述腔室9具有至少一个抽气口和至少一 个进气口。所述石墨坩埚5内装有碳化硅粉料20。
坩埚盖21和单晶衬底1连接，单晶衬底1其中一个表面和碳化硅粉料20相对。坩埚托6承托着石墨坩埚5，带动石墨坩埚5旋转或在竖直方向上运动。石墨坩埚5外侧包围有隔热箱7，隔热箱7在腔室9中，腔室9外周设置有感应加热线圈8。感应加热线圈8是螺旋状的，电流频率为8kHz，线圈是中空的，可通水冷却。通电的感应加热线圈8加热坩埚中的碳化硅粉料20，使得碳化硅粉料20升华。坩埚托6穿过腔室9的壁。
实施例2
本实施例提供一种复合衬底的制备方法，所述制备方法的示意图如图5所示，包括如下步骤：
(1)单晶衬底1作为籽晶，在其中一个表面生长晶体层2，得到单晶衬底1与晶体层2组成的复合晶体层结构；其中，晶体层2的厚度为200μm；
所述单晶衬底1为碳化硅衬底，厚度为200μm，晶型为6H；所述单晶衬底1生长晶体层2的面为C面；所述单晶衬底1的{0001}晶面和单晶衬底1的表面之间的夹角为8°，即偏轴8°；
所述晶体层2为多晶；所述晶体层2的生长方法为物理气相传输法；所述晶体层2的生长速率为300μm/h；
(2)对复合晶体层结构中要进行激光照射的表面进行研磨抛光后，40激光照射所述复合晶体层结构中晶体层2的表面，在所述复合晶体层结构的单晶衬底1内部形成改质面；施加外力，将单晶衬底1沿着改质面断开，并对改质面进行研磨抛光后，得到留在复合衬底上的单晶衬底101的厚度为10μm的复合衬底；在对改质面研磨抛光时，调整研磨抛光的基准平面和改质面的夹角为8°，使得研磨抛光后的衬底仍然偏轴8°；
所述激光40为脉冲激光；所述脉冲激光为光纤激光；所述脉冲激光的脉冲宽度为100fs；所述激光照射的扫描路径是一系列相互平行的直线，相邻路径之间的间距保持不变；每个路径的扫描方向是相反的，其扫描路径是从上至下依次扫描每条路径，示意图如图6所示；
所述单晶衬底1沿着改质面断开后的剩余部分102，经表面研磨抛光后，重新作为籽晶使用。
本实施例在电阻加热物理气相传输法生长晶体的装置内进行，所述装置的结构示意图如图7所示，包括石墨坩埚5、单晶衬底1、坩埚盖21、坩埚托6、隔热箱7、电阻加热器11和腔室9；所述腔室9具有至少一个抽气口和至少一个进气口。所述石墨坩埚5内装有碳化硅粉料20。
坩埚盖21和单晶衬底1连接，单晶衬底1其中一个表面和碳化硅粉料20相对。坩埚托6承托着石墨坩埚5，带动石墨坩埚5旋转或在竖直方向上运动。石墨坩埚5外侧包围有电阻加热器11，被隔热箱7包围。电阻加热器11是石墨加热器，通电的石墨加热器加热石墨坩埚5中的碳化硅粉料20，使得碳化硅粉料20升华。坩埚托6穿过腔室9的壁。
实施例3
本实施例提供一种复合衬底的制备方法，所述制备方法包括如下步骤：
(1)单晶衬底1作为籽晶，在其中一个表面生长晶体层2，得到单晶衬底1与晶体层2组成的复合晶体层结构；其中，晶体层2的厚度为100μm；
所述单晶衬底1为碳化硅衬底，厚度为1000μm，晶型为4H；所述单晶衬底1生长晶体层2的面为C面；所述单晶衬底1的{0001}晶面和单晶衬底1的表面之间的夹角为0°，即偏轴0°；
所述晶体层2为多晶；所述晶体层2的生长方法为溶液法；所述晶体层2 的生长速率为5000μm/h；
(2)对复合晶体层结构中要进行激光照射的表面进行研磨抛光后，激光照射所述复合晶体层结构，在所述复合晶体层结构的单晶衬底1内部形成改质面；施加外力，将单晶衬底1沿着改质面断开，并对改质面进行研磨抛光后，得到留在复合衬底上的单晶衬底101的厚度为46μm的复合衬底；在对改质面研磨抛光时，调整研磨抛光的基准平面和改质面的夹角为0°，使得研磨抛光后的衬底仍然偏轴0°；
所述激光为脉冲激光；所述脉冲激光为固态激光；所述脉冲激光的脉冲宽度为300fs；所述激光照射的扫描路径是一系列相互平行的直线，相邻路径之间的间距保持不变；每个路径的扫描方向是相同的，其扫描路径是从上至下依次扫描每条路径，示意图如图8所示；
所述单晶衬底1沿着改质面断开后的剩余部分102，经表面研磨抛光后，重新作为籽晶使用。
本实施例在感应加热溶液法生长晶体的装置内进行，所述装置的结构示意图如图9所示，包括石墨坩埚5、籽晶杆4、石墨托3、单晶衬底1、坩埚托6、隔热箱7、感应加热线圈8、腔室9。腔室9具有至少一个抽气口和至少一个进气口。石墨坩埚5内容纳助溶剂溶液。
籽晶杆4和石墨托3连接，石墨托3底部可以连接复合籽晶，籽晶杆4可旋转和在竖直方向上运动。坩埚托6承托着石墨坩埚5，可带动石墨坩埚5旋转和在竖直方向上运动。石墨坩埚5外侧包围有隔热箱7，隔热箱7外周设置有感应加热线圈8。感应加热线圈8是螺旋状的，电流频率为3kHz，线圈是中空的，可通水冷却。通电的感应加热线圈8将石墨坩埚5中的助熔剂加热熔化。腔室9为晶体生长提供气氛环境。籽晶杆4、坩埚托6穿过腔室9的壁。
实施例4
本实施例提供一种复合衬底的制备方法，所述制备方法包括如下步骤：
(1)单晶衬底1作为籽晶，在其中一个表面生长晶体层2，得到单晶衬底1与晶体层2组成的复合晶体层结构；其中，晶体层2的厚度为100μm；
所述单晶衬底1为碳化硅衬底，厚度为150μm，晶型为4H；所述单晶衬底1生长晶体层2的面为Si面；所述单晶衬底1的{0001}晶面和单晶衬底1的表面之间的夹角为3°，即偏轴3°；
所述晶体层2为单晶；所述晶体层2的生长方法为溶液法；所述晶体层2的生长速率为2400μm/h；
(2)对复合晶体层结构中要进行激光照射的表面进行研磨抛光后，激光照射所述复合晶体层结构，在所述复合晶体层结构的单晶衬底1内部形成改质面；施加外力，将单晶衬底1沿着改质面断开，并对改质面进行研磨抛光后，得到留在复合衬底上的单晶衬底101的厚度为1μm的复合衬底；在对改质面研磨抛光时，调整研磨抛光的基准平面和改质面的夹角为3°，使得研磨抛光后的衬底仍然偏轴3°；
所述激光为脉冲激光；所述脉冲激光为光纤激光；所述脉冲激光的脉冲宽度为160fs；所述激光照射的扫描路径是一系列相互平行的直线，相邻路径之间的间距保持不变；每个路径的扫描方向是相同的；其扫描路径是从上至下依次扫描每条路径；
所述单晶衬底1沿着改质面断开后的剩余部分102，经表面研磨抛光后，重新作为籽晶使用。
本实施例在电阻加热溶液法生长晶体的装置内进行，所述装置的结构示意图如图10所示，包括石墨坩埚5、籽晶杆4、石墨托3、单晶衬底1、坩埚托6、 隔热箱7、电阻加热器11、腔室9。腔室9具有至少一个抽气口和至少一个进气口。石墨坩埚5内容纳助溶剂溶液。
籽晶杆4和石墨托3连接，石墨托3底部可以连接复合籽晶，籽晶杆4可旋转和在竖直方向上运动。坩埚托6承托着石墨坩埚5，可带动石墨坩埚5旋转和在竖直方向上运动。石墨坩埚5外侧包围有电阻加热器11，被隔热箱7包围。电阻加热器11是石墨加热器，通电的石墨加热器将石墨坩埚5中的助熔剂加热熔化。腔室9为晶体生长提供气氛环境。籽晶杆4、坩埚托6穿过腔室9的壁。
实施例5
本实施例提供一种复合衬底的制备方法，所述制备方法包括如下步骤：
(1)单晶衬底1作为籽晶，在其中一个表面生长晶体层2，得到单晶衬底1与晶体层2组成的复合晶体层结构；其中，晶体层2的厚度为750μm；
所述单晶衬底1为碳化硅衬底，厚度为630μm，晶型为6H；所述单晶衬底1生长晶体层2的面为Si面；所述单晶衬底1的{0001}晶面和单晶衬底1的表面之间的夹角为5°，即偏轴5°；
所述晶体层2为多晶；所述晶体层2的生长方法为高温化学气相沉积法；所述晶体层2的生长速率为500μm/h；
(2)对复合晶体层结构中要进行激光照射的表面进行研磨抛光后，激光照射所述复合晶体层结构，在所述复合晶体层结构的单晶衬底1内部形成改质面；施加外力，将单晶衬底1沿着改质面断开，并对改质面进行研磨抛光后，得到留在复合衬底上的单晶衬底101的厚度为24μm的复合衬底；在对改质面研磨抛光时，调整研磨抛光的基准平面和改质面的夹角为5°，使得研磨抛光后的衬底仍然偏轴5°；
所述激光为脉冲激光；所述脉冲激光为固态激光；所述脉冲激光的脉冲宽 度为160fs；所述激光照射的扫描路径是一系列相互平行的直线，相邻路径之间的间距保持不变；每个路径的扫描方向是相反的；其扫描路径是从上至下依次扫描每条路径；
所述单晶衬底1沿着改质面断开后的剩余部分102，经表面研磨抛光后，重新作为籽晶使用。
本实施例在感应加热高温化学气相沉积法生长晶体的装置内进行，所述装置的结构示意图如图11所示，包括籽晶杆4、石墨托3、单晶衬底1、反应室10、隔热箱7、感应加热线圈8、腔室9。腔室9具有至少一个抽气口和至少一个进气口。
籽晶杆4和石墨托3连接，石墨托3底部可以连接复合籽晶，籽晶杆4可旋转和在竖直方向上运动。反应室10材料为石墨，外侧包围有隔热箱7，隔热箱7在腔室9中，腔室9外周设置有感应加热线圈8。感应加热线圈8是螺旋状的，电流频率为20kHz，线圈是中空的，可通水冷却。籽晶杆4穿过腔室9的壁。通电的感应加热线圈8将反应室10加热至晶体生长的温度。
腔室9进气口充入反应气体，反应气体包括硅源气体和碳源气体，硅源气体是硅烷，碳源气体是丙烷。
实施例6
本实施例提供一种复合衬底的制备方法，所述制备方法包括如下步骤：
(1)单晶衬底1作为籽晶，在其中一个表面生长晶体层2，得到单晶衬底1与晶体层2组成的复合晶体层结构；其中，晶体层2的厚度为330μm；
所述单晶衬底1为碳化硅衬底，厚度为670μm，晶型为4H；所述单晶衬底1生长晶体层2的面为Si面；所述单晶衬底1的{0001}晶面和单晶衬底1的表面之间的夹角为7°，即偏轴7°；
所述晶体层2为单晶；所述晶体层2的生长方法为高温化学气相沉积法；所述晶体层2的生长速率为800μm/h；
(2)对复合晶体层结构中要进行激光照射的表面进行研磨抛光后，激光照射所述复合晶体层结构，在所述复合晶体层结构的单晶衬底1内部形成改质面；施加外力，将单晶衬底1沿着改质面断开，并对改质面进行研磨抛光后，得到留在复合衬底上的单晶衬底101的厚度为41μm的复合衬底；在对改质面研磨抛光时，调整研磨抛光的基准平面和改质面的夹角为7°，使得研磨抛光后的衬底仍然偏轴7°；
所述激光为脉冲激光；所述脉冲激光为固态激光；所述脉冲激光的脉冲宽度为140fs；所述激光照射的扫描路径为：将相互平行的扫描路径从头至尾每N个分为一组，假设分成M组，依次扫描第1至M组的第1个扫描路径、第1至M组的第2个扫描路径、第1至M组的第3个扫描路径……依次类推，直至所有路径都被扫描；具体而言，其扫描顺序为：1-1、2-1、3-1、4-1、1-2、2-2、3-2、4-2、1-3、2-3、3-3、……；连续的两个扫描路径的扫描方向相反；
所述单晶衬底1沿着改质面断开后的剩余部分102，经表面研磨抛光后，重新作为籽晶使用。
本实施例在电阻加热高温化学气相沉积法生长晶体的装置内进行，所述装置的结构示意图如图12所示，包括籽晶杆4、石墨托3、单晶衬底1、反应室10、隔热箱7、电阻加热器11、腔室9。腔室9具有至少一个抽气口和至少一个进气口。
籽晶杆4和石墨托3连接，石墨托3底部可以连接复合籽晶，籽晶杆4可旋转和在竖直方向上运动。反应室10材料为石墨，外侧设置有电阻加热器11，电阻加热器11在隔热箱7中，隔热箱7在腔室9中。籽晶杆4穿过腔室9的壁。 电阻加热器11是石墨加热器，通电的石墨加热器将将反应室10加热至晶体生长的温度。
腔室9进气口充入反应气体，反应气体包括硅源气体和碳源气体，硅源气体是硅烷，碳源气体是丙烷。
实施例7
本实施例提供一种复合衬底的制备方法，所述制备方法除了将晶体层的生长速率3000μm/h替换为150μm/h外，其余均与实施例1相同。
实施例8
本实施例提供一种复合衬底的制备方法，所述制备方法除了将晶体层的生长速率3000μm/h替换为5500μm/h外，其余均与实施例1相同。
实施例9
本实施例提供一种复合衬底的制备方法，所述制备方法除了将脉冲激光的脉冲宽度为200fs替换为50fs外，其余均与实施例1相同。
本实施例由于脉冲激光的脉冲宽度仅为50fs，无法将单晶衬底沿着改质面断开，故不能得到复合衬底。
实施例10
本实施例提供一种复合衬底的制备方法，所述制备方法除了将脉冲激光的脉冲宽度为200fs替换为350fs外，其余均与实施例1相同。
实施例11
本实施例提供一种复合衬底的制备方法，所述制备方法除了激光照射的扫描路径是一系列相互平行的直线，相邻路径之间的间距保持不变；每个路径的扫描方向是相同的外，其余均与实施例1相同。
对比例1
本对比例提供一种复合衬底的制备方法，包括如下步骤：
利用物理气相传输法分别制造单晶衬底和晶体层，晶型均为4H，厚度均为350μm；单晶衬底的{0001}晶面和单晶衬底的表面之间的夹角为4°；
对单晶衬底的一个表面进行离子注入或激光照射，在距离该表面距离约2μm的深度形成预埋的弱化层；
将上述单晶衬底的离子注入或激光照射面与晶体层的一个表面进行键合，得到包括单晶衬底、晶体层、两者之间的键合界面层的复合衬底；
对上述复合衬底进行热处理，使得单晶衬底沿着预埋的弱化层断开，得到的复合衬底的单晶衬底的厚度为2μm。
测定以上实施例和对比例得到的复合衬底的电阻值，测量方法为：在复合碳化硅衬底的晶体层的表面形成背面电极，单晶衬底的表面形成直径为0.3mm的圆形表面电极。在表面电极和背面电极之间施加电压V，记录相应的电流I，得到V-I曲线，计算出电阻值。
(1)综合实施例1与对比例1可以看出，实施例1的电阻值为3.7Ω，对比例1由于键合界面层的存在对复合衬底的垂直导电产生负面影响，电阻值更高，达4.0Ω。本申请提供的复合衬底的制备方法得到的复合衬底的质量高，垂直导电性能更好；
(2)综合实施例1与实施例7～8可以看出，实施例7由于晶体层的生长速率仅为150μm/h，制备得到的复合衬底的质量高，电阻值为3.6Ω，但所述复合衬底的制备时间长，制备效率低；实施例8由于晶体层的生长速率过高，晶体层中会出现杂质或孔洞等，得到的复合衬底质量差，电阻值为3.9Ω；
(3)综合实施例1与实施例9～10可以看出，实施例9由于脉冲激光的脉冲宽度仅为50fs，无法将单晶衬底沿着改质面断开，故不能得到复合衬底；实 施例10由于脉冲激光的脉冲宽度为350fs，导致改质面上产生裂纹，严重影响到复合衬底的质量；
(4)综合实施例1与实施例11可以看出，实施例1中所述激光照射的扫描路径为：将相互平行的扫描路径从头至尾每N个分为一组，假设分成M组，依次扫描第1至M组的第1个扫描路径、第1至M组的第2个扫描路径、第1至M组的第3个扫描路径……依次类推，直至所有路径都被扫描；具体而言，其扫描顺序为：1-1、2-1、3-1、4-1、1-2、2-2、3-2、4-2、1-3、2-3、3-3、……；连续的两个扫描路径的扫描方向相反；切割后复合晶体层结构的单晶衬底内部形成的改质面不发生翘曲变形或变形量很小，翘曲度WARP仅为16μm；而实施例11中激光照射的扫描路径是一系列相互平行的直线，相邻路径之间的间距保持不变；每个路径的扫描方向是相同的，切割后所述复合晶体层结构的单晶衬底内部形成的改质面发生翘曲变形，翘曲度WARP为29μm。综上所述，本申请提供的复合衬底的制备方法操作简单，在高质量单晶衬底上生长一层低质量晶体层，不会形成键合界面层；之后通过激光切割去除高质量单晶衬底，可以制备得到具有很薄的高质量单晶衬底的复合衬底，制备效率高且复合衬底的质量高。
申请人声明，以上所述仅为本申请的具体实施方式，但本申请的保护范围并不局限于此，所属技术领域的技术人员应该明了，任何属于本技术领域的技术人员在本申请揭露的技术范围内，可轻易想到的变化或替换，均落在本申请的保护范围和公开范围之内。

Claims (10)

  1. 一种复合衬底的制备方法，其法包括如下步骤：
    (1)单晶衬底作为籽晶，在其中一个表面生长晶体层，得到单晶衬底与晶体层组成的复合晶体层结构；
    (2)激光照射所述复合晶体层结构，在所述复合晶体层结构的单晶衬底内部形成改质面；施加外力，将单晶衬底沿着改质面断开，得到复合衬底。
  2. 根据权利要求1所述的制备方法，其中，步骤(1)所述单晶衬底为碳化硅衬底；
    所述单晶衬底的厚度为150～1000μm；
    所述单晶衬底的晶型包括4H或6H；
    所述单晶衬底生长晶体层的面包括Si面或C面。
  3. 根据权利要求1所述的制备方法，其中，步骤(1)所述单晶衬底的{0001}晶面和单晶衬底的表面之间的夹角为0°～8°。
  4. 根据权利要求1所述的制备方法，其中，步骤(1)所述晶体层包括单晶或多晶；
    所述复合晶体层结构中晶体层的厚度为100～1000μm。
  5. 根据权利要求1所述的制备方法，其中，步骤(1)所述晶体层的生长方法包括物理气相传输法、溶液法或高温化学气相沉积法中的任意一种；
    所述晶体层的生长速率为300～5000μm/h。
  6. 根据权利要求1所述的制备方法，其中，步骤(2)所述激光照射之前，对复合晶体层结构中要进行激光照射的表面进行研磨抛光。
  7. 根据权利要求1所述的制备方法，其中，步骤(2)所述激光为脉冲激光；
    所述脉冲激光包括固态激光或光纤激光；
    所述脉冲激光的脉冲宽度为100～300fs。
  8. 根据权利要求1所述的制备方法，其中，步骤(2)所述激光照射的扫描路径包括平行直线、同心圆、弯折线或曲线中的任意一种；
    所述激光照射的扫描路径为：将相互平行的扫描路径从头至尾每N个分为一组，假设分成M组，依次扫描第1至M组的第1个扫描路径、第1至M组的第2个扫描路径、第1至M组的第3个扫描路径……依次类推，直至所有路径都被扫描。
  9. 根据权利要求1所述的制备方法，其中，步骤(2)所述复合衬底经过研磨抛光后，其中单晶衬底的厚度为1～50μm；
    所述单晶衬底沿着改质面断开后的剩余部分，经表面研磨抛光后，重新作为籽晶使用。
  10. 根据权利要求1～9任一项所述的制备方法，其包括如下步骤：
    (1)单晶衬底作为籽晶，在其中一个表面生长晶体层，得到单晶衬底与晶体层组成的复合晶体层结构；其中，晶体层的厚度为100～1000μm；
    所述单晶衬底为碳化硅衬底，厚度为150～1000μm，晶型包括4H或6H；所述单晶衬底生长晶体层的面包括Si面或C面；所述单晶衬底的{0001}晶面和单晶衬底的表面之间的夹角为0°～8°；
    所述晶体层包括单晶或多晶；所述晶体层的生长方法包括物理气相传输法、溶液法或高温化学气相沉积法中的任意一种；所述晶体层的生长速率为300～5000μm/h；
    (2)对复合晶体层结构中要进行激光照射的表面进行研磨抛光后，激光照射所述复合晶体层结构，在所述复合晶体层结构的单晶衬底内部形成改质面；施加外力，将单晶衬底沿着改质面断开，得到复合衬底；
    所述激光为脉冲激光；所述脉冲激光包括固态激光或光纤激光；所述脉冲激光的脉冲宽度为100～300fs；
    所述激光照射的扫描路径包括平行直线、同心圆、弯折线或曲线中的任意一种；所述激光照射的扫描路径为：将相互平行的扫描路径从头至尾每N个分为一组，假设分成M组，依次扫描第1至M组的第1个扫描路径、第1至M组的第2个扫描路径、第1至M组的第3个扫描路径……依次类推，直至所有路径都被扫描；
    所述复合衬底经过研磨抛光后，其中单晶衬底的厚度为1～50μm；所述单晶衬底沿着改质面断开后的剩余部分，经表面研磨抛光后，重新作为籽晶使用。
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