Preparation of composite substrate

Abstract

The present application provides a method for preparing a composite substrate. The preparation method includes the steps of: (1) growing a crystal layer on one surface of a single crystal substrate as a seed crystal to obtain a composite crystal layer structure composed of a single crystal substrate and a crystal layer; and (2) irradiating the composite crystal layer structure with a laser to form a modified surface inside the single crystal substrate of the composite crystal layer structure, and applying an external force to cut the single crystal substrate along the modified surface to obtain a composite substrate. The preparation method of the present application grows a low-quality crystal layer on a high-quality single crystal substrate, and then employs a laser cold cracking cutting process, thereby achieving high preparation efficiency, good quality, and a wide range of application of the composite substrate.

Description

[Technical field]

[0001] The present application relates to the field of semiconductor technology, for example to a method for preparing a composite substrate. [Background technology]

[0002] Devices made on silicon carbide single crystal substrates have advantages such as resistance to high temperatures, high pressures, high frequencies, high power, radiation resistance and high efficiency, and are of great value in applications such as RF and new energy automobiles.

[0003] A typical manufacturing method for silicon carbide single crystal substrate includes the steps of growing silicon carbide single crystal by physical vapor transport to obtain a silicon carbide single crystal ingot, processing the outer circumference of the ingot to obtain the required diameter and surface quality, and then cutting the ingot into slices, grinding and polishing the slices to the required thickness and flatness to obtain the final silicon carbide single crystal substrate. Due to the low efficiency of growing silicon carbide single crystal by physical vapor transport, the cost of a single silicon carbide single crystal substrate is high.

[0004] One of the ways to reduce the cost of silicon carbide substrate is to adopt a composite substrate structure, which bonds one single crystal silicon carbide thin layer to a low-cost support substrate. This requires processing the surfaces of the low-quality substrate and the high-quality substrate respectively so that the surface quality meets the requirements for bonding, and then bonding. There is a certain degree of complexity and difficulty in processing the high-quality surface. In addition, this embodiment will form a bonding interface layer, which may adversely affect the vertical conductivity of the substrate.

[0005] CN114746980A discloses a method for manufacturing a composite substrate, which involves forming a pre-embedded weakened layer in a high-quality single crystal substrate by ion implantation, depositing a low-quality crystalline or polycrystalline layer on the surface of the single crystal substrate by CVD, and then separating the layer along the weakened layer to obtain a composite substrate. However, this method has a problem in that the temperature of the CVD process is high, and the pre-embedded weakened layer may crack early during the CVD process, forcing the CVD process to be interrupted.

[0006] CN112701033A discloses a method for preparing a composite substrate, a composite substrate and a composite thin film, in which the method for preparing the composite substrate includes: cleaning a monocrystalline silicon substrate to obtain a monocrystalline silicon substrate layer with a clean surface; growing polycrystalline silicon on the clean surface of the monocrystalline silicon substrate layer, performing a planarization process to form a first polycrystalline silicon layer; focusing a laser on the side of the first polycrystalline silicon layer close to the monocrystalline silicon substrate layer, and stopping the laser focus when the monocrystalline silicon fusion layer is formed, to obtain a composite substrate, in which the composite substrate sequentially includes a monocrystalline silicon substrate layer, a monocrystalline silicon fusion layer and a second polycrystalline silicon layer from bottom to top. By adopting the above-mentioned embodiment, adjusting the power, focal length and position of the laser, and accurately controlling the position, distribution and size of the monocrystalline silicon fusion region, the bonding force of the target region at the target interface according to the actual situation of the monocrystalline silicon substrate layer and the polycrystalline silicon layer can be improved, and the adhesion of the polycrystalline silicon deposited on the silicon substrate can be improved. However, the preparation efficiency of the above-mentioned preparation method is low.

[0007] Therefore, it is of great significance to develop a new method for preparing the composite substrate to improve the production efficiency and quality of the composite substrate. Summary of the Invention [Problem to be solved by the invention]

[0008] The following is a general summary of the subject matter described in detail in this document. This summary is not intended to limit the scope of the claims.

[0009] In view of the problems in the prior art, the present application provides a method for preparing a composite substrate, which can improve the production efficiency of the composite substrate by growing a low-quality crystal layer on a high-quality single crystal substrate, and further adopts a laser cold cracking cutting process to obtain a composite substrate having a thin and high-quality single crystal substrate, and the composite substrate has high quality and wide application range. [Means for solving the problem]

[0010] The present application, (1) A step of growing a crystal layer on one surface of a single crystal substrate as a seed crystal to obtain a composite crystal layer structure composed of the single crystal substrate and the crystal layer; (2) irradiating the composite crystal layer structure with a laser to form a modified surface inside the single crystal substrate of the composite crystal layer structure, and applying an external force to cut the single crystal substrate along the modified surface to obtain a composite substrate; A method for preparing a composite substrate is provided.

[0011] The single crystal substrate in the preparation method of the composite substrate according to the present application is a high-quality single crystal substrate, which has few defects such as micropipes, dislocations, phase transitions, polycrystalline inclusions, etc., and the high-quality single crystal substrate is allowed to have a low-quality crystal layer grown on its Si face or C face as the basis for the growth of the low-quality crystal layer, and the low-quality crystal layer may have many defects such as micropipes, dislocations, phase transitions, polycrystalline inclusions, etc., and may be single crystal or polycrystalline. Then, the composite crystal layer structure composed of the single crystal substrate and the crystal layer is irradiated with a laser, and the laser may 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, and if the focal depth of the laser is well controlled, a modified surface can be formed inside the single crystal substrate of the composite crystal layer structure, and then the single crystal substrate is cut along the modified surface to obtain a composite substrate having a thin, high-quality single crystal substrate and a low-quality crystal layer of a specific thickness. The preparation method according to the present application can improve the manufacturing efficiency and quality of the composite substrate.

[0012] The preparation method of the present application grows one low-quality crystal layer on a high-quality single crystal substrate, and does not form a bonding interface layer, which does not adversely affect the vertical conductivity of the high-quality single crystal substrate.

[0013] In one embodiment, the single crystal substrate referred to in step (1) is a silicon carbide substrate.

[0014] In one embodiment, the thickness of the single crystal substrate is 150 to 1000 μm, and may be, for example, 150 μm, 200 μm, 400 μm, 700 μm, 900 μm, or 1000 μm, but is not limited to the recited values, and other unrecited values ​​within the numerical range also apply.

[0015] In one embodiment, the crystal type of the single crystal substrate comprises 4H or 6H.

[0016] In one embodiment, the surface of the single crystal substrate on which a crystal layer is grown includes a Si-face or a C-face.

[0017] In one embodiment, the diameter of the single crystal substrate is 2 to 8 inches, and may be, for example, 2 inches, 3 inches, 4 inches, 5 inches, 6 inches, or 8 inches, but is not limited to the recited values, and other unrecited values ​​within the numerical range also apply.

[0018] In one embodiment, the included angle between the {0001} crystal plane of the single crystal substrate described in step (1) and the surface of the single crystal substrate is 0° to 8°, and may be, for example, 0°, 1°, 1.5°, 2°, 3°, 5°, or 8°, etc., but is not limited to the recited numerical values, and other unrecited numerical values ​​within the numerical range also apply.

[0019] The angle between the {0001} crystal plane of the single crystal substrate and the surface of the single crystal substrate, which is preferred in the present application in step (1), is 0° to 8° because cracks will occur in the crystal when it is irradiated with a laser. The fracture toughness of the {1100} and {1120} crystal planes of the crystal is about 1.5 times that of the {0001} plane, and therefore cracks tend to spread to the {0001} crystal plane. In other words, the modified surface is approximately parallel to the {0001} crystal plane.

[0020] Assuming that the included angle between the {0001} crystal plane of a high-quality single crystal substrate 1 and the substrate surface is θ (i.e., θ away from the axis), when grinding and polishing the modified surface, by adjusting the included angle between the reference plane to be ground and polished and the modified surface to θ, the substrate after grinding and polishing can still be θ0°-8° away from the axis.

[0021] In one embodiment, the crystalline layer described in step (1) comprises a single crystal or a polycrystal.

[0022] In one embodiment, the thickness of the crystal layer in the composite crystal layer structure is 100 to 1000 μm, and may be, for example, 100 μm, 300 μm, 500 μm, 700 μm, 900 μm, or 1000 μm, but is not limited to the recited values, and other unrecited values ​​within the numerical range also apply.

[0023] In one embodiment, the method for growing the crystalline layer described in step (1) includes any one of a physical vapor transport method, a solution method, or a high temperature chemical vapor deposition method.

[0024] In one embodiment, the growth rate of the crystal layer is 300 to 5000 μm / h, and may be, for example, 300 μm / h, 400 μm / h, 500 μm / h, 600 μm / h, 700 μm / h, 800 μm / h, 900 μm / h, 1000 μm / h, 2000 μm / h, 3000 μm / h, 4000 μm / h, 4500 μm / h, or 5000 μm / h, but is not limited to the listed numerical values, and other unlisted numerical values ​​within the numerical range also apply.

[0025] Generally, the quality of the grown crystal layer decreases with increasing growth rate. Therefore, the growth of a low-quality crystal layer can adopt a high growth rate, and the crystal can be allowed to contain many defects such as micropipes, dislocations, phase transitions, polycrystalline inclusions, etc., and can even transition from single crystal to polycrystal. The growth rate of the crystal layer preferred in the present application is 300 to 5000 μm / h. If the growth rate is low, the preparation time of the composite substrate becomes long and the preparation efficiency becomes low. If the growth rate is high, impurities, cavities, etc. appear in the crystal layer, and the quality of the obtained composite substrate is poor.

[0026] In one embodiment, prior to the laser irradiation in step (2), the surface of the composite crystal layer structure to be irradiated with the laser is ground and polished to ensure that the laser transmits as much energy as possible to the surface and focuses it on the modified surface.

[0027] In one embodiment, the laser described in step (2) is a pulsed laser.

[0028] In one embodiment, the pulsed laser comprises a solid-state laser or a fiber laser.

[0029] In one embodiment, the pulse width of the pulsed laser is 100 to 300 fs, and may be, for example, 100 fs, 120 fs, 150 fs, 200 fs, 240 fs, or 300 fs, but is not limited to the recited values, and other unrecited values ​​within the numerical range also apply.

[0030] The pulse width of the pulse laser preferred in the present application is 100 to 300 fs. If the pulse width is too small, the single crystal substrate cannot be cut well along the modified surface, and if the pulse width is too large, cracks will occur on the modified surface, significantly affecting the quality of the composite substrate.

[0031] In one embodiment, the scanning path of the laser irradiation includes any one of parallel straight lines, concentric circles, bent lines, or curved lines.

[0032] In one embodiment, the scanning path of the laser irradiation described in step (2) is assumed to be divided into M groups of N parallel scanning paths from the beginning to the end, and the first scanning path of the first group to the Mth group, the second scanning path of the first group to the Mth group, the third scanning path of the first group to the Mth group, etc. are scanned in sequence until all the paths are scanned. The scanning directions of two consecutive paths may be the same or opposite.

[0033] The purpose of optimizing the laser scanning path in this application is to distribute the internal stress caused by laser irradiation within the crystal as uniformly as possible, and to prevent or reduce warping and deformation of the substrate after cutting the modified surface due to excessive stress concentration.

[0034] In one embodiment, the modified surface of the composite substrate obtained in step (2) is ground and polished to a required surface quality.

[0035] In one embodiment, the remaining portion of the single crystal substrate after cutting along the modified surface is reused as a seed crystal after the surface is ground and polished.

[0036] In one embodiment, after the composite substrate described in step (2) is ground and polished, the thickness of the single crystal substrate therein is 1 to 50 μm, and may be, for example, 1 μm, 5 μm, 10 μm, 20 μm, 30 μm, 40 μm, or 50 μm, but is not limited to the recited values, and other unrecited values ​​within the numerical range also apply.

[0037] As a preferred technical solution of the present application, the preparation method includes: A step (1) of growing a crystal layer having a thickness of 100 to 1000 μm on one surface of a single crystal substrate as a seed crystal to obtain a composite crystal layer structure composed of the single crystal substrate and the crystal layer, the single crystal substrate is a silicon carbide substrate, having a thickness of 150 to 1000 μm and a crystal type including 4H or 6H, a surface of the single crystal substrate for growing a crystal layer includes a Si-face or a C-face, and an included angle between a {0001} crystal plane of the single crystal substrate and a surface of the single crystal substrate is 0° to 8°; Step (1), in which the crystal layer includes a single crystal or a polycrystal, the growth method of the crystal layer includes any one of a physical vapor transport method, a solution method, and a high-temperature chemical vapor deposition method, and the growth rate of the crystal layer is 300 to 5000 μm / h; (2) grinding and polishing a surface of the composite crystal layer structure to be irradiated with a laser, irradiating the composite crystal layer structure with a laser to form a modified surface inside the single crystal substrate of the composite crystal layer structure, applying an external force to cut the single crystal substrate along the modified surface, and grinding and polishing the surface to obtain a composite substrate having a single crystal substrate thickness of 1 to 50 μm; The laser is a pulsed laser, the pulsed laser includes a solid-state laser or a fiber laser, and 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, bent lines, and curves, and the scanning path of the laser irradiation is assumed to be divided into M groups, with N parallel scanning paths being divided into groups from the beginning to the end, and the first scanning path of the first group to the Mth group, the second scanning path of the first group to the Mth group, the third scanning path of the first group to the Mth group, ... are scanned in sequence by analogy until all paths are scanned, The composite substrate is ground and polished, and the thickness of the single crystal substrate therein is 1 to 50 μm. The single crystal substrate is cut along the modified surface, and the remaining portion is ground and polished to reuse it as a seed crystal. Effect of the Invention

[0038] Compared with the related art, the present application has at least the following beneficial effects:

[0039] (1) The preparation method of the composite substrate according to the present application is simple in operation, and allows a low-quality crystal layer to be grown on a high-quality single crystal substrate, without forming a bonding interface layer, and without adversely affecting the vertical conductivity of the high-quality single crystal substrate.

[0040] (2) The method for preparing a composite substrate according to the present application can remove a high-quality single crystal substrate by laser cutting, and prepare a composite substrate having a thin and high-quality single crystal substrate, with high preparation efficiency and high quality of the composite substrate.

[0041] Other aspects may be understood upon reading and understanding the drawings and detailed description. [Brief description of the drawings]

[0042] The drawings are intended to provide a further understanding of the technical solution of the present application, constitute a part of the specification, and are used to interpret the technical solution of the present application together with the embodiments of the present application, and are not intended to limit the technical solution of the present application.

[0043] [Figure 1] 1 is a schematic diagram showing a method for preparing a composite substrate according to Example 1. FIG. [Diagram 2] FIG. 2 is a schematic diagram of a modified surface in Example 1. [Diagram 3] 3 is a schematic diagram of a scanning path of laser irradiation in Example 1. FIG. [Figure 4] FIG. 1 is a schematic diagram of an apparatus for growing crystals by an induction heating physical vapor transport method in Example 1. [Diagram 5] 5 is a schematic diagram showing a method for preparing a composite substrate according to Example 2. FIG. [Figure 6] FIG. 11 is a schematic diagram of a scanning path of laser irradiation in Example 2. [Figure 7] FIG. 1 is a schematic diagram of an apparatus for growing crystals by a resistive heating physical vapor transport method in Example 2. [Figure 8] FIG. 11 is a schematic diagram of a scanning path of laser irradiation in Example 3. [Figure 9] FIG. 11 is a schematic diagram of an apparatus for growing crystals by an induction heating solution method in Example 3. [Figure 10] FIG. 1 is a schematic diagram of an apparatus for growing crystals by a resistive heating solution method in Example 4. [Figure 11] FIG. 13 is a schematic diagram of an apparatus for growing crystals by induction heating high-temperature chemical vapor deposition in Example 5. [Figure 12] FIG. 13 is a schematic diagram of an apparatus for growing crystals by resistance heating high-temperature chemical vapor deposition in Example 6. [Explanation of symbols]

[0044] 1...single crystal substrate; 101...single crystal substrate remaining on composite substrate; 102...remaining portion after cutting along the modified surface; 2...crystal layer; 20...silicon carbide powder; 21...crucible lid; 3...graphite support; 4...seed crystal rod; 40...laser; 5...graphite crucible; 6...crucible support; 7...insulating box; 8...induction heating coil; 9...chamber; 10...reaction chamber; 11...resistance heater. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0045] The technical solution of the present application is further described below with reference to the drawings and specific embodiments.

[0046] The present application will be described in more detail below. The following examples are merely illustrative of the present application, and do not represent or limit the scope of the claims of the present application, and the scope of protection of the present application is based on the claims. EXAMPLES

[0047] This embodiment provides a method for preparing a composite substrate, the schematic diagram of which is shown in FIG. 1, including the following steps:

[0048] (1) Using a single crystal substrate 1 as a seed crystal, a crystal layer 2 having a thickness of 350 μm was grown on one surface of the single crystal substrate 1, thereby obtaining a composite crystal layer structure consisting of the single crystal substrate 1 and the crystal layer 2.

[0049] The single crystal substrate 1 is a silicon carbide substrate, has a thickness of 500 μm, and is of 4H crystal type. The surface of the single crystal substrate 1 on which the crystal layer 2 is grown is a Si surface. The included angle between the {0001} crystal plane of the single crystal substrate 1 and the surface of the single crystal substrate 1 is 4°, i.e., 4° off the axis.

[0050] The crystal layer 2 was a single crystal, the method for growing the crystal layer 2 was a physical vapor transport method, and the growth rate of the crystal layer 2 was 3000 μm / h.

[0051] (2) After the surface in the composite crystal layer structure to be irradiated with the laser is ground and polished, the other surface of the single crystal substrate 1 in the composite crystal layer structure is irradiated with a laser 40 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 as shown in FIG. 2. An external force is applied to cut the single crystal substrate 1 along the modified surface. After the modified surface is ground and polished, a composite substrate is obtained in which the single crystal substrate 101 remaining on the composite substrate has a thickness of 2 μm. When the modified surface is ground and polished, the angle between the reference plane to be ground and polished and the modified surface is adjusted to 4°, so that the substrate after grinding and polishing is still 4° away from the axis.

[0052] 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, and the scanning path of the laser irradiation is assumed to be divided into M groups of N parallel scanning paths from the beginning to the end, and the first scanning path of the first group to the Mth group, the second scanning path of the first group to the Mth group, the third scanning path of the first group to the Mth group, ... are scanned in sequence until all the paths are scanned, and specifically, the scanning order 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, and a schematic diagram is as shown in FIG. 3.

[0053] The remaining portion 102 of the single crystal substrate 1 after cutting along the modified surface is ground and polished, and then reused as a seed crystal.

[0054] This example was carried out in an apparatus for growing crystals by induction heating physical vapor transport, and the structural schematic diagram of the apparatus is shown in Fig. 4, which includes a graphite crucible 5, a single crystal substrate 1, a crucible cover 21, a crucible support 6, a heat insulating box 7, an induction heating coil 8, and a chamber 9, and the chamber 9 has at least one air extraction port and at least one air supply port. Silicon carbide powder 20 was placed in the graphite crucible 5.

[0055] The crucible lid 21 was connected to the single crystal substrate 1, and one surface of the single crystal substrate 1 faced the silicon carbide powder material 20. The crucible support 6 received the graphite crucible 5 and drove the graphite crucible 5 to rotate or move in a vertical direction. The outside of the graphite crucible 5 was surrounded by a heat insulating box 7, which was in a chamber 9, and an induction heating coil 8 was provided on the outer periphery of the chamber 9. The induction heating coil 8 was spiral, had a current frequency of 8 kHz, was hollow, and could be cooled by passing water through it. The induction heating coil 8, when energized, heated the silicon carbide powder material 20 in the crucible, causing the silicon carbide powder material 20 to sublimate. The crucible support 6 penetrated the wall of the chamber 9. EXAMPLES

[0056] This embodiment provides a method for preparing a composite substrate, the schematic diagram of which is shown in FIG. 5, including the following steps:

[0057] (1) Using a single crystal substrate 1 as a seed crystal, a crystal layer 2 having a thickness of 200 μm was grown on one surface of the single crystal substrate 1, thereby obtaining a composite crystal layer structure consisting of the single crystal substrate 1 and the crystal layer 2.

[0058] The single crystal substrate 1 is a silicon carbide substrate, has a thickness of 200 μm, is of 6H crystal type, the surface of the single crystal substrate 1 on which the crystal layer 2 is grown is the C-plane, and the included angle between the {0001} crystal plane of the single crystal substrate 1 and the surface of the single crystal substrate 1 is 8°, i.e., 8° off the axis.

[0059] The crystal layer 2 was polycrystalline, the method for growing the crystal layer 2 was a physical vapor transport method, and the growth rate of the crystal layer 2 was 300 μm / h.

[0060] (2) After the surface in the composite crystal layer structure to be irradiated with the laser is ground and polished, a laser 40 is irradiated onto the surface of crystal layer 2 in the composite crystal layer structure to form a modified surface inside single crystal substrate 1 of the composite crystal layer structure, an external force is applied to cut single crystal substrate 1 along the modified surface, and after the modified surface is ground and polished, a composite substrate having a thickness of 10 μm is obtained, and when the modified surface is ground and polished, the angle between the reference plane to be ground and polished and the modified surface is adjusted to 8°, so that the substrate after grinding and polishing is still 8° away from the axis.

[0061] The laser 40 is a pulsed laser, the pulsed laser is a fiber laser, the pulse width of the pulsed laser is 100 fs, the scanning path of the laser irradiation is a series of parallel straight lines, the pitch between adjacent paths is constant, the scanning direction of each path is opposite, and the scanning path scans each path sequentially from top to bottom, and the schematic diagram is as shown in FIG. 6.

[0062] The remaining portion 102 of the single crystal substrate 1 after cutting along the modified surface is ground and polished, and then reused as a seed crystal.

[0063] This example was carried out in an apparatus for growing crystals by resistance heating physical vapor transport, and the structural schematic diagram of the apparatus is shown in Fig. 7, which includes a graphite crucible 5, a single crystal substrate 1, a crucible cover 21, a crucible support 6, a heat insulating box 7, a resistance heater 11, and a chamber 9, and the chamber 9 has at least one air extraction port and at least one air supply port. Silicon carbide powder 20 was placed in the graphite crucible 5.

[0064] The crucible lid 21 was connected to the single crystal substrate 1, and one surface of the single crystal substrate 1 faced the silicon carbide powder 20. The crucible support 6 received the graphite crucible 5 and drove the graphite crucible 5 to rotate or move vertically. The outside of the graphite crucible 5 was surrounded by a resistance heater 11, which was surrounded by an insulating box 7. The resistance heater 11 was a graphite heater, and when energized, the graphite heater heated the silicon carbide powder 20 in the graphite crucible 5, thereby sublimating the silicon carbide powder 20. The crucible support 6 penetrated the wall of the chamber 9. EXAMPLES

[0065] This embodiment provides a method for preparing a composite substrate, which includes the following steps:

[0066] (1) Using a single crystal substrate 1 as a seed crystal, a crystal layer 2 having a thickness of 100 μm was grown on one surface of the single crystal substrate 1, thereby obtaining a composite crystal layer structure consisting of the single crystal substrate 1 and the crystal layer 2.

[0067] The single crystal substrate 1 is a silicon carbide substrate, has a thickness of 1000 μm, is of 4H crystal type, the surface of the single crystal substrate 1 on which the crystal layer 2 is grown is the C-plane, and the included angle between the {0001} crystal plane of the single crystal substrate 1 and the surface of the single crystal substrate 1 is 0°, i.e., 0° off the axis.

[0068] The crystal layer 2 was polycrystalline, the method for growing the crystal layer 2 was a solution method, and the growth rate of the crystal layer 2 was 5000 μm / h.

[0069] (2) After the surface to be irradiated with the laser in the composite crystal layer structure is ground and polished, the composite crystal layer structure is irradiated with a laser to form a modified surface inside the single crystal substrate 1 of the composite crystal layer structure, an external force is applied to cut the single crystal substrate 1 along the modified surface, and after the modified surface is ground and polished, a composite substrate having a thickness of 46 μm is obtained in which the single crystal substrate 101 remaining on the composite substrate is obtained. When the modified surface is ground and polished, the angle between the reference plane to be ground and polished and the modified surface is adjusted to 0°, so that the substrate after grinding and polishing is still 0° away from the axis.

[0070] 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 parallel straight lines, the pitch between adjacent paths is constant, the scanning direction of each path is the same, and the scanning path scans each path sequentially from top to bottom, and the schematic diagram is as shown in FIG. 8.

[0071] The remaining portion 102 of the single crystal substrate 1 after cutting along the modified surface is ground and polished, and then reused as a seed crystal.

[0072] This example was carried out in an apparatus for growing crystals by the induction heating solution method, and the structural schematic diagram of the apparatus is shown in Figure 9, which includes a graphite crucible 5, a seed crystal rod 4, a graphite support 3, a single crystal substrate 1, a crucible support 6, a heat insulating box 7, an induction heating coil 8, and a chamber 9. The chamber 9 has at least one air extraction port and at least one air supply port. A co-solvent solution was contained in the graphite crucible 5.

[0073] The seed crystal rod 4 was connected to the graphite support 3, the bottom of which could be connected to the composite seed crystal, and the seed crystal rod 4 was rotatable and vertically movable. The crucible support 6 received the graphite crucible 5 and could drive the graphite crucible 5 to rotate and move vertically. The outside of the graphite crucible 5 was surrounded by an insulating box 7, and an induction heating coil 8 was provided on the outer periphery of the insulating box 7. The induction heating coil 8 was spiral, had a current frequency of 3 kHz, was hollow, and could be cooled by passing water through it. The energized induction heating coil 8 heated and melted the cosolvent in the graphite crucible 5. The chamber 9 provided an atmospheric environment for crystal growth. The seed crystal rod 4 and the crucible support 6 penetrated the wall of the chamber 9. EXAMPLES

[0074] This embodiment provides a method for preparing a composite substrate, which includes the following steps:

[0075] (1) Using a single crystal substrate 1 as a seed crystal, a crystal layer 2 having a thickness of 100 μm was grown on one surface of the single crystal substrate 1, thereby obtaining a composite crystal layer structure consisting of the single crystal substrate 1 and the crystal layer 2.

[0076] The single crystal substrate 1 is a silicon carbide substrate, has a thickness of 150 μm, and is of 4H crystal type. The surface of the single crystal substrate 1 on which the crystal layer 2 is grown is a Si surface. The included angle between the {0001} crystal plane of the single crystal substrate 1 and the surface of the single crystal substrate 1 is 3°, i.e., 3° ​​off the axis.

[0077] The crystal layer 2 was a single crystal, the growth method of the crystal layer 2 was a solution method, and the growth rate of the crystal layer 2 was 2400 μm / h.

[0078] (2) After the surface in the composite crystal layer structure to be irradiated with a laser is ground and polished, the composite crystal layer structure is irradiated with a laser to form a modified surface inside the single crystal substrate 1 of the composite crystal layer structure, an external force is applied to cut the single crystal substrate 1 along the modified surface, and after the modified surface is ground and polished, a composite substrate with a thickness of 1 μm is obtained in which the single crystal substrate 101 remaining on the composite substrate is obtained. When the modified surface is ground and polished, the angle between the reference plane to be ground and polished and the modified surface is adjusted to 3°, so that the substrate after grinding and polishing is still 3° away from the axis.

[0079] The laser was a pulsed laser, the pulsed laser was a fiber laser, the pulse width of the pulsed laser was 160 fs, the scanning path of the laser irradiation was a series of parallel straight lines, the pitch between adjacent paths was constant, the scanning direction of each path was the same, and the scanning path scanned each path sequentially from top to bottom.

[0080] The remaining portion 102 of the single crystal substrate 1 after cutting along the modified surface is ground and polished, and then reused as a seed crystal.

[0081] This example was carried out in an apparatus for growing crystals by the resistance heating solution method, and the structural schematic diagram of the apparatus is shown in Figure 10, which includes a graphite crucible 5, a seed crystal rod 4, a graphite support 3, a single crystal substrate 1, a crucible support 6, a heat insulating box 7, a resistance heater 11, and a chamber 9. The chamber 9 has at least one air extraction port and at least one air supply port. A co-solvent solution was contained in the graphite crucible 5.

[0082] The seed crystal rod 4 was connected to the graphite support 3, the bottom of which could be connected to the composite seed crystal, and the seed crystal rod 4 was rotatable and vertically movable. The crucible support 6 received the graphite crucible 5 and could drive the graphite crucible 5 to rotate and move vertically. The outside of the graphite crucible 5 was surrounded by a resistance heater 11 and surrounded by an insulating box 7. The resistance heater 11 was a graphite heater, and the energized graphite heater heated and melted the co-solvent in the graphite crucible 5. The chamber 9 provided an atmospheric environment for the crystal growth. The seed crystal rod 4 and the crucible support 6 penetrated the wall of the chamber 9. EXAMPLES

[0083] This embodiment provides a method for preparing a composite substrate, which includes the following steps:

[0084] (1) Using a single crystal substrate 1 as a seed crystal, a crystal layer 2 having a thickness of 750 μm was grown on one surface of the single crystal substrate 1, thereby obtaining a composite crystal layer structure consisting of the single crystal substrate 1 and the crystal layer 2.

[0085] The single crystal substrate 1 is a silicon carbide substrate, has a thickness of 630 μm, and is of 6H crystal type. The surface of the single crystal substrate 1 on which the crystal layer 2 is grown is a Si surface. The included angle between the {0001} crystal plane of the single crystal substrate 1 and the surface of the single crystal substrate 1 is 5°, i.e., 5° off the axis.

[0086] The crystal layer 2 was polycrystalline, the method for growing the crystal layer 2 was high-temperature chemical vapor deposition, and the growth rate of the crystal layer 2 was 500 μm / h.

[0087] (2) After the surface to be irradiated with the laser in the composite crystal layer structure is ground and polished, the composite crystal layer structure is irradiated with a laser to form a modified surface inside the single crystal substrate 1 of the composite crystal layer structure, an external force is applied to cut the single crystal substrate 1 along the modified surface, and after the modified surface is ground and polished, a composite substrate having a thickness of 24 μm is obtained in which the single crystal substrate 101 remaining on the composite substrate is obtained. When the modified surface is ground and polished, the angle between the reference plane to be ground and polished and the modified surface is adjusted to 5°, so that the substrate after grinding and polishing is still 5° away from the axis.

[0088] The laser was a pulsed laser, the pulsed laser was a solid-state laser, the pulse width of the pulsed laser was 160 fs, the scanning path of the laser irradiation was a series of parallel straight lines, the pitch between adjacent paths was constant, the scanning direction of each path was reversed, and the scanning path was scanned from top to bottom sequentially.

[0089] The remaining portion 102 of the single crystal substrate 1 after cutting along the modified surface is ground and polished, and then reused as a seed crystal.

[0090] This example was carried out in an apparatus for growing crystals by induction heating high-temperature chemical vapor deposition, and the structural schematic diagram of the apparatus is shown in Figure 11, and it was equipped with a seed crystal rod 4, a graphite support 3, a single crystal substrate 1, a reaction chamber 10, a heat insulating box 7, an induction heating coil 8, and a chamber 9. The chamber 9 has at least one air extraction port and at least one air supply port.

[0091] The seed crystal rod 4 was connected to a graphite support 3, the bottom of which could be connected to a composite seed crystal, and the seed crystal rod 4 was rotatable and vertically movable. The reaction chamber 10 was made of graphite, surrounded on the outside by an insulating box 7, which was in a chamber 9, and an induction heating coil 8 was provided on the outer periphery of the chamber 9. The induction heating coil 8 was spiral, had a current frequency of 20 kHz, was hollow, and could be cooled by passing water through it. The seed crystal rod 4 penetrated the wall of the chamber 9. The current-carrying induction heating coil 8 heated the reaction chamber 10 to a temperature for crystal growth.

[0092] A reaction gas was filled from the inlet of the chamber 9, and the reaction gas contained a silicon source gas and a carbon source gas, where the silicon source gas was silane and the carbon source gas was propane. EXAMPLES

[0093] This embodiment provides a method for preparing a composite substrate, which includes the following steps:

[0094] (1) Using a single crystal substrate 1 as a seed crystal, a crystal layer 2 having a thickness of 330 μm was grown on one surface of the single crystal substrate 1, thereby obtaining a composite crystal layer structure consisting of the single crystal substrate 1 and the crystal layer 2.

[0095] The single crystal substrate 1 is a silicon carbide substrate, has a thickness of 670 μm, and is of 4H crystal type. The surface of the single crystal substrate 1 on which the crystal layer 2 is grown is a Si surface. The included angle between the {0001} crystal plane of the single crystal substrate 1 and the surface of the single crystal substrate 1 is 7°, i.e., 7° off the axis.

[0096] The crystal layer 2 was a single crystal, the method for growing the crystal layer 2 was high-temperature chemical vapor deposition, and the growth rate of the crystal layer 2 was 800 μm / h.

[0097] (2) After the surface in the composite crystal layer structure to be irradiated with a laser is ground and polished, the composite crystal layer structure is irradiated with a laser to form a modified surface inside the single crystal substrate 1 of the composite crystal layer structure, an external force is applied to cut the single crystal substrate 1 along the modified surface, and after the modified surface is ground and polished, a composite substrate having a thickness of 41 μm is obtained in which the single crystal substrate 101 remaining on the composite substrate has a thickness of 41 μm. When the modified surface is ground and polished, the angle between the reference plane to be ground and polished and the modified surface is adjusted to 7°, so that the substrate after grinding and polishing is still 7° away from the axis.

[0098] The laser was a pulsed laser, the pulsed laser was a solid-state laser, the pulse width of the pulsed laser was 140 fs, and the scanning path of the laser irradiation was assumed to be divided into M groups of N parallel scanning paths from the beginning to the end, and the first scanning path of the 1st group to the Mth group, the second scanning path of the 1st group to the Mth group, the third scanning path of the 1st group to the Mth group, ... were scanned in sequence until all paths were scanned, and specifically, the scanning order was 1-1, 2-1, 3-1, 4-1, 1-2, 2-2, 3-2, 4-2, 1-3, 2-3, 3-3, ..., and the scanning directions of two consecutive scanning paths were opposite.

[0099] The remaining portion 102 of the single crystal substrate 1 after cutting along the modified surface is ground and polished, and then reused as a seed crystal.

[0100] This example was carried out in an apparatus for growing crystals by resistance heating high-temperature chemical vapor deposition, and the structural schematic diagram of the apparatus is shown in Fig. 12, which includes a seed crystal rod 4, a graphite support 3, a single crystal substrate 1, a reaction chamber 10, a heat insulating box 7, a resistance heater 11, and a chamber 9. The chamber 9 has at least one air extraction port and at least one air intake port.

[0101] The seed crystal rod 4 was connected to a graphite cradle 3, the bottom of which could be connected to a composite seed crystal, and the seed crystal rod 4 was rotatable and vertically movable. The material of the reaction chamber 10 was graphite, and a resistance heater 11 was provided on the outside, which was in an insulating box 7, which was in a chamber 9. The seed crystal rod 4 penetrated the wall of the chamber 9. The resistance heater 11 was a graphite heater, and the electrically-powered graphite heater heated the reaction chamber 10 to a temperature for crystal growth.

[0102] A reaction gas was filled from the inlet of the chamber 9, and the reaction gas contained a silicon source gas and a carbon source gas, where the silicon source gas was silane and the carbon source gas was propane. EXAMPLES

[0103] This embodiment provides a method for preparing a composite substrate, which is the same as that in Example 1 except that the growth rate of the crystal layer is changed from 3000 μm / h to 150 μm / h. EXAMPLES

[0104] This embodiment provides a method for preparing a composite substrate, which is the same as that in Example 1 except that the growth rate of the crystal layer is changed from 3000 μm / h to 5500 μm / h. EXAMPLES

[0105] This embodiment provides a method for preparing a composite substrate, which is the same as that in Example 1 except that the pulse width of the pulse laser is replaced by 50 fs instead of 200 fs.

[0106] In this example, since the pulse width of the pulse laser was only 50 fs, the single crystal substrate could not be cut along the modified surface, and therefore a composite substrate could not be obtained. EXAMPLES

[0107] This embodiment provides a method for preparing a composite substrate, which is the same as that in Example 1 except that the pulse width of the pulse laser is replaced by 350 fs instead of 200 fs. EXAMPLES

[0108] This example provides a method for preparing a composite substrate, in which the scanning paths of the laser irradiation are a series of parallel straight lines, the pitch between adjacent paths is constant, and the scanning direction of each path is the same, and the rest of the preparation method is the same as that of Example 1.

[0109] This comparative example provides a method for preparing a composite substrate, which includes the following steps:

[0110] The single crystal substrate and the crystal layer were each produced using a physical vapor transport method, and all had a crystal type of 4H, a thickness of 350 μm, and an included angle between the {0001} crystal plane of the single crystal substrate and the surface of the single crystal substrate was 4°. One surface of the single crystal substrate was subjected to ion implantation or laser irradiation to form a pre-buried weakened layer at a depth of about 2 μm from the surface. The ion-implanted or laser-irradiated surface of the single crystal substrate was bonded to one surface of the crystal layer to obtain a composite substrate including the single crystal substrate, the crystal layer, and a bonding interface layer therebetween. The composite substrate was subjected to a heat treatment to cut the single crystal substrate along the weakened layer that had been embedded in advance, and the thickness of the single crystal substrate of the obtained composite substrate was 2 μm.

[0111] The resistance value of the composite substrate obtained in the above examples and comparative examples was measured, and the measurement method was as follows. A back electrode was formed on the surface of the crystal layer of the composite silicon carbide substrate, and a circular front electrode with a diameter of 0.3 mm was formed on the surface of the single crystal substrate. A voltage V was applied between the front electrode and the back electrode, the corresponding current I was recorded, a VI curve was obtained, and the resistance value was calculated.

[0112] (1) As can be seen from Example 1 and Comparative Example 1, the resistance value of Example 1 is 3.7Ω, and the resistance value of Comparative Example 1 is higher, reaching 4.0Ω, due to the existence of the bonding interface layer, which adversely affects the vertical conductivity of the composite substrate. The composite substrate obtained by the composite substrate preparation method of the present application has high quality and better vertical conductive performance.

[0113] (2) As can be seen from Examples 1 and 7 to 8, in Example 7, the growth rate of the crystal layer was only 150 μm / h, so the prepared composite substrate was of high quality and had a resistance value of 3.6 Ω; however, the preparation time of the composite substrate was long and the preparation efficiency was low; in Example 8, the growth rate of the crystal layer was too high, so impurities and cavities appeared in the crystal layer, and the obtained composite substrate was of poor quality and had a resistance value of 3.9 Ω.

[0114] (3) As can be seen from a summary of Example 1 and Examples 9 to 10, in Example 9, the pulse width of the pulse laser was only 50 fs, so the single crystal substrate could not be cut along the modified surface, and therefore a composite substrate could not be obtained. In Example 10, the pulse width of the pulse laser was 350 fs, so cracks occurred on the modified surface, which significantly affected the quality of the composite substrate.

[0115] (4) As can be seen from Example 1 and Example 11 together, the scanning path of the laser irradiation in Example 1 is assumed to be divided into M groups, with N parallel scanning paths being divided into one group from the beginning to the end, and the first scanning path of the first group to the Mth group, the second scanning path of the first group to the Mth group, the third scanning path of the first group to the Mth group, ... are scanned in sequence until all the paths are scanned. Specifically, the scanning order 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, and the modified surface formed inside the single crystal substrate with the composite crystal layer structure after cutting does not warp or has a small deformation amount, and the warp amount WARP is only 16 μm, while the scanning path of the laser irradiation in Example 11 is a series of parallel straight lines, the pitch between adjacent paths is constant, and the scanning direction of each path is the same, and the modified surface formed inside the single crystal substrate with the composite crystal layer structure after cutting has warp deformation, and the warp amount WARP is 29 μm. In summary, the preparation method of the composite substrate according to the present application is simple to operate, grows one low-quality crystal layer on a high-quality single crystal substrate, does not form a bonding interface layer, and then removes the high-quality single crystal substrate by laser cutting, and can prepare a composite substrate with a thin and high-quality single crystal substrate, and the preparation efficiency is high and the quality of the composite substrate is high.

[0116] The above description is merely a specific embodiment of the present application, but the scope of protection of the present application is not limited thereto. The applicant declares that any modifications or replacements that can be easily conceived by any person skilled in the art within the technical scope set forth in the present application as understood by those skilled in the art are all included in the scope of protection and disclosure of the present application.

Claims

1. (1) A single crystal substrate is used as a seed crystal, and a crystal layer is grown on one surface of the seed crystal to obtain a composite crystal layer structure composed of the single crystal substrate and the crystal layer; (2) irradiating the composite crystal layer structure with a laser to form a modified surface inside the single crystal substrate of the composite crystal layer structure; and applying an external force to cut the single crystal substrate along the modified surface to obtain a composite substrate. Method for preparing composite substrates.

2. The single crystal substrate described in step (1) is a silicon carbide substrate; The thickness of the single crystal substrate is 150 to 1000 μm; the crystal type of the single crystal substrate includes 4H or 6H; The surface of the single crystal substrate on which the crystal layer is grown includes a Si-face or a C-face.

2. The method of claim 1.

3. The angle between the {0001} crystal plane of the single crystal substrate and the surface of the single crystal substrate described in step (1) is 0° to 8°; 2. The method of claim 1.

4. The crystalline layer according to step (1) comprises a single crystal or a polycrystal; The thickness of the crystal layer in the composite crystal layer structure is 100 to 1000 μm; 2. The method of claim 1.

5. The method for growing the crystal layer according to step (1) includes any one of physical vapor transport, solution deposition, and high temperature chemical vapor deposition; The growth rate of the crystal layer is 300 to 5000 μm / h.

2. The method of claim 1.

6. Prior to the laser irradiation described in step (2), the surface of the composite crystal layer structure to be irradiated with the laser is ground and polished; 2. The method of claim 1.

7. The laser described in step (2) 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.

2. The method of claim 1.

8. The scanning path of the laser irradiation described in step (2) includes any one of parallel straight lines, concentric circles, bent lines, and curved lines; The scanning path of the laser irradiation is assumed to be divided into M groups, with N parallel scanning paths being divided into groups from the beginning to the end, and the first scanning path of the first group to the Mth group, the second scanning path of the first group to the Mth group, the third scanning path of the first group to the Mth group, ... are scanned in sequence by analogy until all paths are scanned.

2. The method of claim 1.

9. After the composite substrate described in step (2) is ground and polished, the thickness of the single crystal substrate therein is 1 to 50 μm; The remaining portion of the single crystal substrate after cutting along the modified surface is ground and polished, and then reused as a seed crystal.

2. The method of claim 1.

10. A step (1) of growing a crystal layer having a thickness of 100 to 1000 μm on one surface of a single crystal substrate as a seed crystal to obtain a composite crystal layer structure composed of the single crystal substrate and the crystal layer, the single crystal substrate is a silicon carbide substrate, having a thickness of 150 to 1000 μm, a crystal type including 4H or 6H, a surface of the single crystal substrate on which a crystal layer is grown includes a Si-face or a C-face, and an included angle between a {0001} crystal plane of the single crystal substrate and a surface of the single crystal substrate is 0° to 8°; Step (1), in which the crystal layer includes a single crystal or a polycrystal, the growth method of the crystal layer includes any one of a physical vapor transport method, a solution method, and a high-temperature chemical vapor deposition method, and the growth rate of the crystal layer is 300 to 5000 μm / h; (2) grinding and polishing a surface of the composite crystal layer structure to be irradiated with a laser, irradiating the composite crystal layer structure with a laser to form a modified surface inside the single crystal substrate of the composite crystal layer structure, and applying an external force to cut the single crystal substrate along the modified surface to obtain a composite substrate, The laser is a pulsed laser, the pulsed laser including a solid-state laser or a fiber laser, and 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, bent curves, and curves, and the scanning path of the laser irradiation is assumed to be divided into M groups of N parallel scanning paths from the beginning to the end, and the first scanning path of the first group to the Mth group, the second scanning path of the first group to the Mth group, the third scanning path of the first group to the Mth group, ... are scanned in sequence by analogy until all paths are scanned, (2) after the composite substrate is ground and polished, the thickness of the single crystal substrate therein is 1 to 50 μm, and the remaining part after cutting the single crystal substrate along the modified surface is ground and polished to reuse as a seed crystal; The preparation method according to any one of claims 1 to 9.

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