Diamond composite substrate and preparation method and application thereof

Abstract

The invention relates to a preparation method of a diamond composite substrate. The preparation method comprises the following steps: providing a substrate; ion implantation is conducted on the substrate, the substrate is divided into a substrate body, an ion implantation layer and a stripping layer which are sequentially arranged in a stacked mode, the thickness of the substrate body is h, and h is larger than 0 and smaller than or equal to 100 nm; preparing a carbon-based buffer layer on the surface, deviating from the ion implantation layer, of the substrate; preparing a diamond layer on the carbon-based buffer layer, wherein the elasticity modulus of the carbon-based buffer layer is smaller than that of the diamond layer; and stripping the ion implantation layer and the stripping layer by adopting an electrochemical stripping process to obtain the diamond composite substrate. The invention further provides the diamond composite substrate and application. According to the preparation method, the diamond composite substrate based on the nanoscale ultrathin substrate can be obtained, the comprehensive thermal resistance of the diamond composite substrate is greatly reduced, and large-scale application of the diamond composite substrate in the field of power devices is promoted.

Description

Technical Field

[0001] The present invention relates to the field of microelectronic technology, and in particular to a diamond composite substrate and a preparation method and application thereof. Background Art

[0002] With the continuous changes in microelectronics technology, power devices are developing in the direction of high frequency, high integration and high intelligence. As a result, the power consumption of power devices continues to increase, resulting in higher and higher chip temperatures, which directly affects the service life and reliability of power devices. In order to solve the heat dissipation problem of power devices, the most promising solution is to use high thermal conductivity diamond materials as heat dissipation substrates for power devices, so that the diamond is close enough to the active area of ​​the device to quickly transfer heat out by heat conduction. At present, the commonly used method is to directly epitaxially grow a diamond layer on a substrate to prepare a composite substrate, and then use the composite substrate as a base material to prepare power devices.

[0003] However, since the thinner substrate cannot withstand the high temperature thermal field environment during the diamond growth process and the internal stress caused by lattice mismatch and thermal mismatch, when growing diamond on the substrate, the substrate material must have a certain thickness. For example, when preparing a 2-inch diamond composite substrate, the thickness of the selected substrate must be ≥3mm, and the larger the size of the diamond composite substrate, the thicker the required substrate thickness. Therefore, after epitaxial growth of diamond, the substrate must be thinned. Only when the thickness of the thinned substrate is at the nanometer level can the high thermal conductivity of diamond be fully utilized. At present, the commonly used thinning methods are mechanical grinding and chemical etching. However, both methods can only thin the substrate to between 10μm and 500μm, and during the thinning process, the substrate and the diamond layer are very likely to break. Therefore, the substrate cannot be thinned to the nanometer level, and then the diamond composite substrate based on the nanometer-level substrate cannot be obtained, which seriously hinders the large-scale application of diamond composite substrates in the field of power devices. Summary of the invention

[0004] Based on this, it is necessary to provide a diamond composite substrate and its preparation method and application to address the above problems. The preparation method of the diamond composite substrate can obtain a diamond composite substrate based on a nanoscale ultra-thin substrate, which greatly reduces the comprehensive thermal resistance of the diamond composite substrate, and is conducive to promoting the large-scale application of the diamond composite substrate in the field of power devices.

[0005] A method for preparing a diamond composite substrate comprises the following steps:

[0006] providing a substrate;

[0007] Performing ion implantation on the substrate to separate the substrate into a substrate, an ion implantation layer and a peeling layer stacked in sequence, wherein the thickness of the substrate is h, 0<h≤100nm;

[0008] Preparing a carbon-based buffer layer on a surface of the substrate away from the ion implantation layer;

[0009] Preparing a diamond layer on the carbon-based buffer layer, wherein the elastic modulus of the carbon-based buffer layer is smaller than the elastic modulus of the diamond layer;

[0010] The ion implantation layer and the stripping layer are stripped by an electrochemical stripping process to obtain a diamond composite substrate.

[0011] In one embodiment, 10 nm ≤ h ≤ 100 nm.

[0012] In one embodiment, in the ion implantation step, the implanted ions are selected from hydrogen ions, and the implantation dose is 10 16 cm -2 ~10 17 cm -2 , the injection energy is 10KeV~30KeV;

[0013] And / or, the implanted ions are selected from helium ions, and the implantation dose is 10 17 cm -2 ~10 18 cm -2 , the injection energy is 20KeV~50KeV.

[0014] In one of the embodiments, in the step of preparing the carbon-based buffer layer, the thickness of the carbon-based buffer layer is 1 nm to 3 nm.

[0015] In one embodiment, the carbon-based buffer layer is selected from at least one of a graphene buffer layer, a carbon nanotube buffer layer or a graphite buffer layer.

[0016] In one of the embodiments, a diamond layer is prepared on the carbon-based buffer layer by microwave plasma chemical vapor deposition, wherein the temperature is 600° C. to 750° C. and the time is 48 h to 120 h.

[0017] In one embodiment, the thickness of the diamond layer is 150 μm to 500 μm.

[0018] In one embodiment, in the step of stripping the ion implantation layer and the stripping layer using an electrochemical stripping process, the voltage is 80V to 120V and the current is 300mA to 600mA.

[0019] A diamond composite substrate comprises a substrate, a carbon-based buffer layer and a diamond layer which are stacked in sequence, and the thickness of the substrate is h, 0<h≤100nm.

[0020] An application of the diamond composite substrate in power devices.

[0021] The method for preparing a diamond composite substrate provided by the present invention is based on an intelligent cutting process of ion implantation technology, so that the thickness of the substrate is controlled within 100nm, and a carbon-based buffer layer and a diamond layer are sequentially prepared on the surface of the substrate away from the ion implantation layer, and finally the ion implantation layer and the peeling layer are peeled off by an electrochemical stripping process. Among them, by controlling the elastic modulus of the carbon-based buffer layer to be smaller than the elastic modulus of the diamond layer, and adopting a mild electrochemical stripping process, the internal stress of the nano-scale substrate during the preparation of the diamond layer and the peeling process can be relieved and released, and the substrate is prevented from being broken, which is conducive to thinning the substrate to the nano-scale, and obtaining a diamond composite substrate based on a nano-scale ultra-thin substrate.

[0022] Therefore, the preparation method of the present invention can obtain a high-quality diamond composite substrate based on a nanoscale ultra-thin substrate, give full play to the high thermal conductivity advantage of diamond, greatly reduce the comprehensive thermal resistance of the diamond composite substrate, and is conducive to promoting the large-scale application of diamond composite substrates in the field of power devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0024] Figure 1 It is a schematic diagram of the process of preparing the diamond composite substrate of the present invention.

[0025] In the figure: 1, substrate; 11, underlay; 12, ion implantation layer; 13, stripping layer; 2, carbon-based buffer layer; 3, diamond layer; 100, diamond composite substrate. DETAILED DESCRIPTION

[0026] For ease of understanding of the present invention, the present invention will be described in more detail below. However, it should be understood that the present invention can be implemented in many different forms and is not limited to the embodiments or examples described herein. On the contrary, the purpose of providing these embodiments or examples is to make the understanding of the disclosure of the present invention more thorough and comprehensive.

[0027] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific implementation methods or embodiments, and are not intended to limit the present invention. The optional scope of the term "and / or" used herein includes any one of two or more related listed items, and also includes any and all combinations of related listed items, and the combinations include any two related listed items, any more related listed items, or all related listed items.

[0028] Reference Figure 1 , Figure 1 A schematic flow chart of a method for preparing a diamond composite substrate 100 provided by the present invention is shown, and the method comprises the following steps:

[0029] S1, providing a substrate 1;

[0030] S2, performing ion implantation on the substrate 1 to separate the substrate 1 into a substrate 11, an ion implantation layer 12 and a peeling layer 13 which are stacked in sequence, wherein the thickness of the substrate 11 is h, 0<h≤100nm;

[0031] S3, preparing a carbon-based buffer layer 2 on the surface of the substrate 11 away from the ion implantation layer 12;

[0032] S4, preparing a diamond layer 3 on the carbon-based buffer layer 2, wherein the elastic modulus of the carbon-based buffer layer 2 is smaller than the elastic modulus of the diamond layer 3;

[0033] S5 , stripping the ion implantation layer 12 and the stripping layer 13 using an electrochemical stripping process to obtain a diamond composite substrate 100 .

[0034] In step S1, the material of the substrate 1 can be selected from silicon, silicon carbide, sapphire or SOI, etc., preferably silicon or silicon carbide. The thickness of the substrate 1 is related to the size of the prepared diamond composite substrate 100. The larger the size of the prepared diamond composite substrate 100, the thicker the required thickness of the substrate 1 is, so that it can withstand the high temperature thermal field environment during the diamond growth process and the internal stress caused by lattice mismatch and thermal mismatch. Specifically, the thickness of the substrate 1 can be selected according to the size of the diamond composite substrate 100.

[0035] In step S2, ions are implanted on the surface of the substrate 1 to separate the substrate 1 into a substrate 11, an ion implantation layer 12, and a peeling layer 13 which are stacked in sequence. In this process, it is necessary to control the formed ion implantation layer 12 to be located near the surface of the substrate 1, so as to control the thickness of the substrate 11 to be less than or equal to 100 nm, which is beneficial for subsequently thinning the substrate 1 to the nanometer level, and further beneficial for forming a diamond composite substrate 100 based on a nanometer-level ultra-thin substrate.

[0036] Optionally, by controlling the implantation dose and implantation energy, it is possible to form a nano-scale ultra-thin substrate. Specifically, a high-energy ion implanter can be used to implant ions into the substrate 1, and the implanted ions are preferably hydrogen ions, and the implantation dose is preferably 10 16 cm -2 ~10 17 cm -2 The implantation energy is preferably 10KeV to 30KeV; or, the implanted ions are preferably helium ions, and the implantation dose is preferably 10 17 cm -2 ~10 18 cm -2 The implantation energy is preferably 20KeV to 50KeV.

[0037] Optionally, the thickness of the substrate 11 is preferably 10nm to 100nm, so that the nanoscale ultra-thin substrate 11 can make the chip active area as close as possible to the high thermal conductivity diamond layer 3, realize near-junction heat dissipation of the chip, and give full play to the high thermal conductivity advantage of diamond. In addition, the nanoscale ultra-thin substrate 11 can greatly reduce the interface thermal resistance and improve the heat dissipation effect of the power device.

[0038] The substrate 11 formed in the substrate 1 has a thickness of nanometers, and there is a risk of fragmentation in the subsequent process due to its excessively thin thickness. Therefore, in the subsequent process of growing the diamond layer 3 on the substrate 11, and in the process of stripping the ion implantation layer 12 and the stripping layer 13, it is necessary to avoid the substrate 11 from being fragmented, so that the substrate 1 can be smoothly thinned to the nanometer level, forming a diamond composite substrate 100 based on a high-quality nanometer-level ultra-thin substrate.

[0039] Therefore, in step S3, a carbon-based buffer layer 2 is prepared on the surface of the substrate 11 away from the ion implantation layer 12, which is helpful to relieve the internal stress of the substrate 11 and avoid the fragmentation of the substrate 11 during the subsequent growth of the diamond layer 3 and the stripping process, and further helps to smoothly thin the substrate 1 to the nanometer level.

[0040] Optionally, the thickness of the carbon-based buffer layer 2 is preferably 1 nm to 3 nm, so that the carbon-based buffer layer 2 can further prevent the diamond composite substrate 100 from breaking, and will not affect the heat dissipation performance of diamond.

[0041] The carbon-based buffer layer 2 can provide excellent thermal conductivity, thereby further giving full play to the heat dissipation capability of diamond. The carbon-based buffer layer 2 is preferably at least one of a graphene buffer layer, a carbon nanotube buffer layer or a graphite buffer layer.

[0042] Optionally, the method for preparing the carbon-based buffer layer 2 is not specifically limited, and preferably, the carbon-based buffer layer 2 is prepared by chemical vapor deposition (CVD). Specifically, the reaction gas is preferably methane, the protective gas is preferably argon, and the catalyst is preferably at least one of nano-scale iron powder, nano-scale nickel powder or nano-scale cobalt powder, and different carbon-based buffer layers 2 can be prepared by controlling the reaction process and the catalyst type.

[0043] In step S4, a diamond layer 3 is prepared on the carbon-based buffer layer 2, and the elastic modulus of the carbon-based buffer layer 2 is controlled to be smaller than the elastic modulus of the diamond layer 3, so that during the growth of the diamond layer 3, the carbon-based buffer layer 2 can provide a buffering effect between the diamond layer 3 and the substrate 1, and alleviate the internal stress generated during the diamond growth process, thereby avoiding the substrate 11 from breaking during the diamond growth process; at the same time, during the stripping process, it can also alleviate the internal stress generated by the substrate 11 during the stripping process, further avoiding the breakage of the substrate 11, thereby forming a higher quality substrate 11 during the thinning process of the substrate 1.

[0044] Furthermore, since the carbon-based buffer layer 2 and the diamond layer 3 are made of the same raw material, diamond can grow better on the carbon-based buffer layer 2 .

[0045] Preferably, diamond nucleation treatment is first performed on the carbon-based buffer layer 2, and the method of diamond nucleation treatment is not specifically limited, and then the diamond layer 3 is prepared by microwave plasma chemical vapor deposition (MPCVD), and the diamond growth temperature is controlled at a relatively low temperature to avoid the ion implantation layer 12 of the substrate 1 from cleaving due to thermal expansion during the diamond growth process, causing the substrate 11 to break. Further preferably, the temperature is 600°C to 750°C.

[0046] Optionally, the time is preferably 48 hours to 120 hours, so as to be more conducive to controlling the thickness of the diamond layer 3 growing.

[0047] Optionally, the thickness of the diamond layer 3 is preferably 150 μm to 500 μm, so that the diamond can further transfer the chip heat longitudinally and transversely at the same time, diffuse the chip heat, and thus reduce the heat density of the chip; and further reduce the preparation cost and facilitate the subsequent packaging steps.

[0048] Optionally, after preparing the diamond layer 3, the diamond layer 3 may be polished to reduce the roughness of the diamond surface. During the polishing process, the carbon-based buffer layer 2 can buffer the internal stress of the substrate 11 caused by the polishing process, thereby better preventing the substrate 11 from breaking.

[0049] Preferably, a grinding and polishing machine can be selected to grind and polish the diamond surface. After polishing, the thickness of the diamond layer 3 is reduced by 40 μm to 60 μm.

[0050] In step S5, the ion implantation layer 12 is etched by an electrochemical stripping process, causing the substrate 1 to split at the ion implantation layer 12, thereby stripping the ion implantation layer 12 and the stripping layer 13 to obtain a diamond composite substrate 100 based on a nano-scale ultra-thin substrate.

[0051] Compared with the stripping process performed by high-temperature heat treatment process used in conventional technology, the electrochemical stripping process is relatively mild. Not only will it not introduce thermal stress, but it can also relieve and release the internal stress of the substrate 11, making it easier to thin the substrate 1 to the nanoscale, thereby obtaining a diamond composite substrate 100 based on a high-quality nanoscale ultra-thin substrate.

[0052] Optionally, in the electrochemical stripping process, the composite substrate on which the diamond layer 3 is grown in step S4 is placed in an electrolytic cell filled with electrolyte, and a DC regulated power supply supplies power to the electrodes respectively, the anode is a Pt electrode, and the cathode is a graphite electrode. The ion implantation layer 12 and the stripping layer 13 are stripped off from the substrate 1 by slow electrolytic stripping, so that the thick substrate 1 is split to form the substrate 11.

[0053] Optionally, the electrolyte is preferably a chromic acid solution, the voltage is preferably 80V to 120V, and the current is preferably 300mA to 600mA, so as to achieve a more ideal stripping effect and further avoid the breakage of the diamond composite substrate 100 .

[0054] Optionally, after stripping the ion implantation layer 12 and the stripping layer 13, some hydrogen ions remain on the surface of the substrate 11 near the ion implantation layer 12, and the surface of the substrate 11 can be polished to remove the loss caused by the hydrogen ion implantation and the tiny unevenness formed during the stripping, so that the final diamond composite substrate 100 based on the nanoscale ultra-thin substrate is not doped with hydrogen ions, thereby further forming a higher quality diamond composite substrate 100 based on the nanoscale ultra-thin substrate.

[0055] The present invention also provides a diamond composite substrate 100, comprising a substrate 11, a carbon-based buffer layer 2 and a diamond layer 3 stacked in sequence, wherein the thickness of the substrate 11 is h, 0<h≤100nm. The diamond composite substrate 100 can provide a nano-scale ultra-thin substrate, thereby greatly reducing the comprehensive thermal resistance of the diamond composite substrate 100 based on the nano-scale ultra-thin substrate.

[0056] The present invention also provides an application of the diamond composite substrate in a power device.

[0057] Hereinafter, the diamond composite substrate and its preparation method and application will be further described through the following specific embodiments.

[0058] Example 1

[0059] A 2-inch, 3 mm thick SiC substrate was selected and an ion implanter was used with an implantation dose of 5 × 10 16 cm -2 The SiC substrate was implanted with hydrogen ions at an energy of 15 KeV to separate the substrate into a substrate, an ion implantation layer and a peeling layer stacked in sequence. After testing, the thickness of the substrate was found to be 20 nm.

[0060] Using methane as reaction gas, argon as protective gas and nano-cobalt powder as catalyst, a 2nm graphene buffer layer is grown on the surface of the substrate away from the ion implantation layer through a CVD process.

[0061] First, diamond nucleation treatment was performed on the surface of the graphene buffer layer using a diamond powder ultrasonic seeding method, and then a diamond layer was grown at 700°C for 72 hours using an MPCVD process. The thickness of the diamond layer was 250μm. The diamond surface was ground and polished using a grinding and polishing machine. After grinding and polishing, the thickness of the diamond layer was 200μm.

[0062] Chromic acid is configured as an electrolyte and placed in an electrolytic cell. The substrate on which the diamond layer is grown is placed in the electrolytic cell filled with the electrolyte. Current is applied to the Pt anode and the graphite cathode respectively through a stabilized DC power supply. The voltage is set to 90V. The electrolyte concentration is adjusted to make the current 300mA. The ion implantation layer and the stripping layer are stripped from the substrate through slow electrochemical stripping, so that the thick substrate is split to form an ultra-thin substrate.

[0063] The substrate surface close to the ion implantation layer is precisely polished to remove the loss caused by hydrogen ion implantation and the tiny unevenness caused by peeling, and finally a high-quality diamond composite substrate based on a nano-scale ultra-thin substrate is obtained.

[0064] After testing, the diamond composite substrate obtained in this embodiment has no cracks or warping, and the comprehensive thermal conductivity is 1600 W / mK.

[0065] Example 2

[0066] A 4-inch, 6-mm-thick SiC substrate was selected and an ion implanter was used to implant the SiC substrate with a dose of 1×10 16 cm -2 The SiC substrate was implanted with hydrogen ions at an energy of 20 KeV to separate the substrate into a substrate, an ion implantation layer and a peeling layer stacked in sequence. After testing, the thickness of the substrate was found to be 40 nm.

[0067] Using methane as reaction gas, argon as protection gas and nano nickel powder as catalyst, a 1 nm carbon nanotube buffer layer is grown on the surface of the substrate away from the ion implantation layer through a CVD process.

[0068] First, diamond nucleation treatment was performed on the surface of the carbon nanotube buffer layer using a diamond powder ultrasonic seeding method, and then a diamond layer was grown at 650°C for 48 hours using an MPCVD process. The thickness of the diamond layer was 150μm. The diamond surface was ground and polished using a grinding and polishing machine. After grinding and polishing, the thickness of the diamond film was 100μm.

[0069] Chromic acid is configured as an electrolyte and placed in an electrolytic cell. The substrate on which the diamond layer is grown is placed in the electrolytic cell filled with the electrolyte. Current is applied to the Pt anode and the graphite cathode respectively through a stabilized DC power supply. The voltage is set to 100V. The electrolyte concentration is adjusted to make the current 400mA. The ion implantation layer and the stripping layer are stripped from the substrate through slow electrochemical stripping, so that the thick substrate is split to form an ultra-thin substrate.

[0070] The substrate surface close to the ion implantation layer is precisely polished to remove the loss caused by hydrogen ion implantation and the tiny unevenness caused by peeling, and finally a high-quality diamond composite substrate based on a nano-scale ultra-thin substrate is obtained.

[0071] After testing, the diamond composite substrate obtained in this embodiment has no cracking and warping, and the comprehensive thermal conductivity is 1400 W / mK.

[0072] Example 3

[0073] A 6-inch, 8 mm thick SiC substrate was selected and an ion implanter was used with an implantation dose of 1×10 17 cm -2 The SiC substrate was implanted with hydrogen ions at an energy of 25 KeV to separate the substrate into a substrate, an ion implantation layer and a peeling layer stacked in sequence. After testing, the thickness of the substrate was found to be 70 nm.

[0074] Using methane as reaction gas, argon as protection gas and nano iron powder as catalyst, a 2nm graphite buffer layer is grown on the surface of the substrate away from the ion implantation layer through a CVD process.

[0075] First, diamond nucleation treatment was performed on the surface of the graphite buffer layer using a diamond powder ultrasonic seeding method, and then a diamond layer was grown at 600°C for 60 hours using an MPCVD process. The thickness of the diamond layer was 200 μm. The diamond surface was ground and polished using a grinding and polishing machine, and the thickness of the diamond film after grinding and polishing was 150 μm.

[0076] Chromic acid is configured as an electrolyte and placed in an electrolytic cell. The substrate on which the diamond layer is grown is placed in the electrolytic cell filled with the electrolyte. Current is applied to the Pt anode and the graphite cathode respectively through a stabilized DC power supply. The voltage is set to 110V. The electrolyte concentration is adjusted to make the current 500mA. The ion implantation layer and the stripping layer are stripped from the substrate through slow electrochemical stripping, so that the thick substrate is split to form an ultra-thin substrate.

[0077] The substrate surface close to the ion implantation layer is precisely polished to remove the loss caused by hydrogen ion implantation and the tiny unevenness caused by peeling, and finally a high-quality diamond composite substrate based on a nano-scale ultra-thin substrate is obtained.

[0078] After testing, the diamond composite substrate obtained in this embodiment has no cracking and warping, and the comprehensive thermal conductivity is 1400 W / mK.

[0079] Comparative Example 1

[0080] The difference between Comparative Example 1 and Example 2 is that an ion implanter is used with an implantation dose of 1×10 18 cm -2 The SiC substrate was implanted with hydrogen ions at an energy of 100 KeV to separate the substrate into a substrate, an ion implantation layer and a peeling layer stacked in sequence. After testing, the thickness of the substrate was found to be 200 nm.

[0081] After testing, the comprehensive thermal conductivity of the diamond composite substrate obtained in this comparative example is 720 W / mK.

[0082] Comparative Example 2

[0083] The difference between Comparative Example 2 and Example 2 is that no carbon-based buffer layer is provided.

[0084] After testing, it was found that the diamond composite substrate obtained in this comparative example was broken, and a complete nano-scale ultra-thin SiC-based diamond composite substrate could not be obtained.

[0085] Comparative Example 3

[0086] The difference between Comparative Example 3 and Example 2 is that a 2 nm gold layer is grown on the surface of the substrate away from the ion implantation layer by magnetron sputtering process.

[0087] After testing, cracks appeared in the substrate of the diamond composite substrate obtained in this comparative example. The buffering effect of the gold layer was poor, resulting in excessive stress during the stripping process, which caused cracks in the composite substrate.

[0088] Comparative Example 4

[0089] The difference between Comparative Example 4 and Example 2 is that the substrate with the diamond layer grown thereon is placed in a tubular furnace and subjected to high temperature heat treatment at 1050°C to cause the substrate to be split at the ion implantation layer, and the ion implantation layer and the stripping layer are stripped off from the substrate.

[0090] After testing, it was found that the substrate in the diamond composite substrate obtained in this comparative example was broken. Due to the violent reaction of high-temperature heat treatment, the ion implantation layer was split instantly, resulting in the inability to release the internal stress of the diamond layer, thereby causing the substrate to break.

[0091] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0092] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A method for preparing a diamond composite substrate, characterized in that: The following steps are involved: providing a substrate; Performing ion implantation on the substrate to separate the substrate into a substrate, an ion implantation layer and a peeling layer stacked in sequence, wherein the thickness of the substrate is h, 0<h≤100nm; Preparing a carbon-based buffer layer on a surface of the substrate away from the ion implantation layer; Preparing a diamond layer on the carbon-based buffer layer, wherein the elastic modulus of the carbon-based buffer layer is smaller than the elastic modulus of the diamond layer; The ion implantation layer and the stripping layer are stripped by an electrochemical stripping process to obtain a diamond composite substrate.

2. The method for preparing a diamond composite substrate according to claim 1, characterized in that: 10nm≤h≤100nm.

3. The method for preparing a diamond composite substrate according to claim 1, characterized in that: In the ion implantation step, the implanted ions are selected from hydrogen ions, and the implantation dose is 10 16 cm -2 ~10 17 cm -2 , the injection energy is 10KeV~30KeV; And / or, the implanted ions are selected from helium ions, and the implantation dose is 10 17 cm -2 ~10 18 cm -2 , the injection energy is 20KeV~50KeV.

4. The method for preparing a diamond composite substrate according to claim 1, characterized in that: In the step of preparing the carbon-based buffer layer, the thickness of the carbon-based buffer layer is 1 nm to 3 nm.

5. The method for preparing a diamond composite substrate according to claim 1 or 4, characterized in that: The carbon-based buffer layer is selected from at least one of a graphene buffer layer, a carbon nanotube buffer layer or a graphite buffer layer.

6. The method for preparing a diamond composite substrate according to claim 1, characterized in that: The diamond layer is prepared on the carbon-based buffer layer by using a microwave plasma chemical vapor deposition method, wherein the temperature is 600° C. to 750° C. and the time is 48 h to 120 h.

7. The method for preparing a diamond composite substrate according to claim 1 or 6, characterized in that: The thickness of the diamond layer is 150 μm to 500 μm.

8. The method for preparing a diamond composite substrate according to claim 1, characterized in that: In the step of stripping the ion implantation layer and the stripping layer by using an electrochemical stripping process, the voltage is 80V to 120V and the current is 300mA to 600mA.

9. A diamond composite substrate, characterized in that: The diamond composite substrate is obtained by the preparation method of any one of claims 1 to 8, comprising a substrate, a carbon-based buffer layer and a diamond layer stacked in sequence, wherein the thickness of the substrate is h, 0<h≤100nm.

10. Use of the diamond composite substrate according to claim 9 in a power device.

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