Single crystal diamond, preparation method thereof and chip

Abstract

The invention discloses a single crystal diamond, a preparation method thereof and a chip, and relates to the technical field of semiconductors, and the preparation method of the single crystal diamond comprises the following steps: cutting a splicing side surface of a first diamond substrate and a splicing side surface of a second diamond substrate, the splicing side face of the first diamond substrate and the splicing side face of the second diamond substrate are both in a sawtooth shape. And splicing the sawtooth-shaped splicing side surface of the first diamond substrate with the sawtooth-shaped splicing side surface of the second diamond substrate to form the diamond substrate. An epitaxial layer is formed on the diamond substrate. The invention aims to realize seamless splicing of single crystal diamonds on splicing side surfaces of a crystal face (110). The single crystal diamond can be used as a substrate of a semiconductor device.

Description

Technical Field

[0001] This application belongs to the field of semiconductor technology, and particularly relates to a single-crystal diamond, a preparation method thereof, and a chip. Background Art

[0002] Diamond mosaic splicing is a technology that combines multiple small-sized single-crystal diamonds to form a large-sized single-crystal diamond structure. Its principle is based on the crystal structure and epitaxial growth characteristics of diamond. During the splicing process, by precisely controlling the position and orientation of small single-crystal diamonds, methods such as chemical vapor deposition (CVD) are used to enable diamond to grow epitaxially at the splicing joints, thereby fusing multiple small single-crystals into a large-sized single-crystal structure. Currently, single-crystal diamonds with a growth plane of (100) crystal plane and a splicing side face also of (100) crystal plane are often used for splicing. The reason is that for diamonds with a (100) plane, the surface atoms are arranged relatively closely, the number of covalent bonds per unit area is large, the binding force between atoms is strong, and the growth rate is fast, providing a relatively stable basis for epitaxial growth. However, for large-sized single-crystal diamond seed wafers (≥15*15 mm), those with a splicing side face of (110) crystal plane are also more common. If such seed crystals are cut into those with a splicing side face of (100) crystal plane, the size and epitaxial growth area will be reduced by 1 / 2, which is not worth the loss for obtaining large-sized single-crystal diamonds through splicing. Summary of the Invention

[0003] An embodiment of this application provides a preparation method of a single-crystal diamond, aiming to achieve seamless splicing of single-crystal diamonds with a splicing side face of (110) crystal plane.

[0004] An embodiment of this application provides a preparation method of a single-crystal diamond, including cutting the splicing side face of a first diamond substrate and the splicing side face of a second diamond substrate, so that the splicing side face of the first diamond substrate and the splicing side face of the second diamond substrate are both serrated. Splice the serrated splicing side face of the first diamond substrate with the serrated splicing side face of the second diamond substrate to form a diamond substrate. Form an epitaxial layer on the diamond substrate.

[0005] In some embodiments, the splicing side face of the first diamond substrate and the splicing side face of the second diamond substrate both include a plurality of serrations, and the shape of the serrations is an isosceles right triangle. The splicing side face of the first diamond substrate and the splicing side face of the second diamond substrate both include a plurality of serrations, and the width of the serrations along a first direction is less than or equal to 1 mm;

[0006] The first direction is perpendicular to the splicing side face of the first diamond substrate and perpendicular to the splicing side face of the second diamond substrate.

[0007] The distance between the tips of two adjacent sawteeth is twice the width of the sawteeth in the first direction.

[0008] In some embodiments, before forming the diamond substrate, the preparation method further includes:

[0009] Cleaning the cut first diamond substrate and the second diamond substrate.

[0010] In some embodiments, a laser cutting process is used to cut the splicing sides of the first diamond substrate and the splicing sides of the second diamond substrate;

[0011] Before forming the epitaxial layer on the diamond substrate, the preparation method further includes:

[0012] Performing plasma etching on the diamond substrate.

[0013] In some embodiments, the etching gas for the plasma etching is hydrogen, the amount of hydrogen is 200 sccm to 400 sccm, the reaction pressure is 1.5 Kpa to 3 Kpa, the microwave power is 3400 W to 5000 W, and the etching duration is 25 minutes to 35 minutes.

[0014] In some embodiments, forming the epitaxial layer on the diamond substrate includes:

[0015] Using a microwave chemical vapor deposition process to form the epitaxial layer on the diamond substrate;

[0016] The carbon source ratio of the microwave chemical vapor deposition process is 5% to 8%, the deposition pressure is 1.5 Kpa to 3 Kpa, the microwave power is 3400 W to 5000 W, and the deposition duration is greater than or equal to 24 hours.

[0017] In some embodiments, the splicing sides of the first diamond substrate and the splicing sides of the second diamond substrate both include a plurality of sawteeth, the width of the sawteeth in the first direction is 1 mm; the first direction is perpendicular to the splicing side of the first diamond substrate and perpendicular to the splicing side of the second diamond substrate;

[0018] Using a microwave chemical vapor deposition process to form the epitaxial layer, the carbon source ratio of the microwave chemical vapor deposition process is 7%, the deposition pressure is 1.8 Kpa, the microwave power is 3600 W, and the deposition duration is 24 hours.

[0019] In some embodiments, the splicing sides of the first diamond substrate and the splicing sides of the second diamond substrate both include a plurality of sawteeth, and the width of the sawteeth in the first direction is 0.5 mm; the first direction is perpendicular to the splicing side of the first diamond substrate and perpendicular to the splicing side of the second diamond substrate;

[0020] The above epitaxial layer is formed by a microwave chemical vapor deposition process. The carbon source ratio of the microwave chemical vapor deposition process is 7%, the deposition pressure is 1.8 Kpa, the microwave power is 3800 W, and the deposition duration is 100 hours.

[0021] A method for preparing a single crystal diamond provided by an embodiment of the present application includes cutting the splicing sides of a first diamond substrate and a second diamond substrate so that the splicing sides of the first diamond substrate and the second diamond substrate are both serrated. The serrated splicing side of the first diamond substrate is spliced with the serrated splicing side of the second diamond substrate to form a diamond substrate. An epitaxial layer is formed on the diamond substrate. The present invention processes a single crystal diamond substrate with a growth surface of (100) crystal plane and a splicing side of (110) crystal plane, and processes the splicing side of the (110) crystal plane to be spliced into a serrated splicing side of the (100) crystal plane. For diamond with a (100) crystal plane, the arrangement of surface atoms is relatively dense, the number of covalent bonds per unit area is large, the binding force between atoms is strong, and the growth rate is fast. At the same time, during the longitudinal growth process, lateral epitaxial growth will occur, which is beneficial to the seam connection at the splicing position. This makes the loss of the growth surface size smaller and is suitable for mosaic splicing of single crystal diamonds.

[0022] In some embodiments, a single crystal diamond can be prepared by the preparation method of any of the above embodiments.

[0023] On the other hand, an embodiment of the present application also provides a chip, including the single crystal diamond described in the above embodiment and components disposed on the single crystal diamond. Description of the Drawings

[0024] The above and / or additional aspects and advantages of the present application will become apparent and easy to understand from the description of the embodiments in conjunction with the following drawings, where:

[0025] Figure 1 It is a schematic flow chart of a method for preparing a single crystal diamond provided by an embodiment of the present application;

[0026] Figures 2 to 3 It is a specific flow chart of a method for preparing a single crystal diamond provided by an embodiment of the present application;

[0027] Figures 4 to 6 It is a diagram of each step for preparing a single crystal diamond provided by an embodiment of the present application;

[0028] Figure 7 This is the optical microscope morphology diagram of the splicing seam of the diamond substrate in the first embodiment of the present application;

[0029] Figure 8 This is the optical microscope morphology diagram of the splicing seam of the diamond substrate in the second embodiment of the present application. Detailed implementation manners

[0030] Next, in combination with the accompanying drawings, the technical solutions in some embodiments of the present application will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments provided by the present application, all other embodiments obtained by those of ordinary skill in the art belong to the scope of protection of the present application.

[0031] Unless otherwise required by the context, throughout the specification and claims, the term "comprising" is interpreted in an open, inclusive sense, that is, "including, but not limited to".

[0032] Hereinafter, the terms "first" and "second" are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the embodiments of the present application, unless otherwise stated, the meaning of "a plurality" is two or more.

[0033] When describing some embodiments, the expression "connected" and its derivatives may be used. The term "connected" should be understood in a broad sense. For example, "connected" can be a fixed connection, a detachable connection, or integrated; it can be directly connected, or indirectly connected through an intermediate medium. For example, when describing some embodiments, the term "connected" may be used to indicate that two or more components have direct physical contact or electrical contact with each other.

[0034] In addition, the use of "based on" means open and inclusive, because a process, step, calculation, or other action "based on" one or more of the stated conditions or values may in practice be based on additional conditions or values beyond the stated ones.

[0035] It should be understood that when a layer or element is referred to as being on another layer or substrate, it can be that the layer or element is directly on the other layer or substrate, or there may be an intermediate layer between the layer or element and the other layer or substrate.

[0036] Exemplary embodiments are described with reference to cross-sectional views as idealized exemplary drawings. In the drawings, the thickness of layers and the area of regions are exaggerated for clarity. Thus, variations in the shape relative to the drawings due to, for example, manufacturing techniques and / or tolerances are contemplated. Accordingly, the exemplary embodiments should not be construed as limited to the shapes of the regions shown herein, but include shape deviations caused by, for example, manufacturing. Thus, the regions shown in the drawings are schematic in nature, and their shapes are not intended to show the actual shape of the regions of the device and are not intended to limit the scope of the exemplary embodiments.

[0037] Examples of the embodiments are shown in the drawings, where like or similar reference numerals designate like or similar elements or elements having the same or similar functions throughout. The embodiments described below by referring to the drawings are exemplary and are only for explaining the present application and should not be construed as limiting the present application.

[0038] Diamond has a series of excellent physical properties such as high thermal conductivity, high carrier mobility, high saturation drift velocity, and ultra-wide bandgap, and shows great application potential in many high-tech fields, especially in the semiconductor industry, and is known as the "ultimate semiconductor material". However, it is difficult to prepare large-size high-quality single-crystal diamond, which greatly limits its wide application in fields such as large-scale integrated circuits and high-power electronic devices. The diamond mosaic splicing technology emerges precisely to solve this problem.

[0039] The prior art basically uses single-crystal diamond with a growth surface of (100) crystal plane and a splicing side surface also of (100) crystal plane for splicing. For diamond with (100) plane, the surface atoms are arranged relatively closely, the number of covalent bonds per unit area is relatively large, the binding force between atoms is strong, and the growth rate is fast. At the same time, during the longitudinal growth process, lateral epitaxial growth will occur, which is beneficial to the seam connection at the splicing part. For single-crystal diamond with a splicing side surface of (110) crystal plane, the atomic arrangement of the (110) crystal plane is relatively sparse, the number of covalent bonds per unit area is small, the binding force between atoms is relatively weak, the interplanar spacing is larger, and the interaction between atomic layers is relatively weak, which is not conducive to the orderly arrangement of atoms on this plane and lateral epitaxial growth during epitaxial growth. For single-crystal diamond with a splicing side surface of (110) crystal plane, currently it is cut into (100) crystal plane at a 45° inward angle along the (110) side surface for splicing, which greatly reduces the size of the growth surface to 1 / 2, and the loss is too large, and it is not suitable for single-crystal diamond mosaic splicing.

[0040] In view of the above problems, the embodiments of the present application provide a method for preparing single-crystal diamond. Figure 1 It is a schematic flow chart of a method for preparing single-crystal diamond provided by the embodiments of the present application. Figure 2 、 Figure 3Schematic diagram of the specific process of a method for preparing single-crystal diamond provided by an embodiment of the present application. Figures 4 to 6 Each step diagram for preparing single-crystal diamond provided by an embodiment of the present application.

[0041] As Figure 1 shown, the preparation method includes the following steps S10 to step S30:

[0042] Step S10: As Figure 4 shown, cut the splicing side surface 106 of the first diamond substrate 101 and the splicing side surface 106 of the second diamond substrate 102, so that the splicing side surface 106 of the first diamond substrate 101 and the splicing side surface 106 of the second diamond substrate 102 are both serrated.

[0043] Exemplarily, using a laser cutting process, process the first diamond substrate 101 and the second diamond substrate 102 with the growth surface 107 being the (100) crystal plane and the splicing side surface 106 being the (110) crystal plane, so that a plurality of saw teeth 105 are formed on the splicing side surface 106 of the first diamond substrate 101 and the splicing side surface 106 of the second diamond substrate 102. After processing, the shape of the protruding saw teeth 105 is an isosceles right triangle.

[0044] It can be understood that the (100) crystal plane of diamond and the (110) crystal plane form a 45° deflection angle. The splicing side surfaces 106 of the above-mentioned first diamond substrate 101 and the second diamond substrate 102 are both (110) crystal planes. Therefore, it is necessary to cut the splicing side surface 106 of the diamond substrate at a 45° angle to obtain the splicing side surface 106 of the (100) crystal plane.

[0045] That is, the two base angles of the saw teeth 105 are 45°, and the apex angle of the tooth tip is 90°. The shape of the saw teeth 105 is an isosceles right triangle.

[0046] Exemplarily, the width of the saw teeth 105 along the first direction X is less than or equal to 1 mm. The first direction X is perpendicular to the splicing side surface 106 of the first diamond substrate 101 and the splicing side surface 106 of the second diamond substrate 102. For example, the width of the saw teeth 105 along the first direction X is 1 mm, 0.9 mm, 0.8 mm, 0.7 mm, 0.6 mm or 0.5 mm.

[0047] Exemplarily, as Figure 4 shown, the tooth tip spacing between two adjacent saw teeth 105 is twice the width of the saw teeth 105 along the first direction X. When the width of the saw teeth 105 along the first direction X is less than or equal to 1 mm, the tooth tip spacing between two adjacent saw teeth 105 is less than or equal to 2 mm.

[0048] Step S20: As Figure 5As shown, the serrated splicing side surface 106 of the first diamond substrate 101 is spliced with the serrated splicing side surface 106 of the second diamond substrate 102 to form a diamond substrate 103.

[0049] Exemplarily, as Figure 5 shown, the first diamond substrate 101 and the second diamond substrate 102 are placed. The first diamond substrate 101 and the second diamond substrate 102 with the same crystal orientation are placed in parallel. The splicing side surface 106 of both is the (100) crystal plane, and the splicing side surfaces 106 of both are spliced together. Since the splicing side surface 106 is serrated, the recess between the protruding serrations 105 of the splicing side surface 106 of the first diamond substrate 101 and the serrations 105 of the splicing side surface 106 of the second diamond substrate 102 fits, and the entire splicing part is tightly connected to form a diamond substrate 103.

[0050] Step S30: As Figure 6 shown, an epitaxial layer 104 is formed on the diamond substrate 103.

[0051] A method for preparing single-crystal diamond provided by an embodiment of the present application includes cutting the splicing side surface 106 of the first diamond substrate 101 and the splicing side surface 106 of the second diamond substrate 102, so that the splicing side surface 106 of the first diamond substrate 101 and the splicing side surface 106 of the second diamond substrate 102 are both serrated. The serrated splicing side surface 106 of the first diamond substrate 101 is spliced with the serrated splicing side surface 106 of the second diamond substrate 102 to form a diamond substrate 103. An epitaxial layer 104 is formed on the diamond substrate 103. The present invention processes a single-crystal diamond substrate with a growth surface of (100) crystal plane and a splicing side surface of (110) crystal plane, and processes the splicing side surface 106 of the (110) crystal plane to be spliced into a serrated splicing side surface 106 of the (100) crystal plane. For diamond with a (100) crystal plane, the arrangement of surface atoms is relatively dense, the number of covalent bonds per unit area is large, the binding force between atoms is strong, and the growth rate is fast. At the same time, during the longitudinal growth process, lateral epitaxial growth will occur, which is beneficial to the seam connection at the splicing part. This makes the loss of the growth surface size smaller and is suitable for mosaic splicing of single-crystal diamond.

[0052] In some embodiments, as Figure 2 shown, between the above step S10 and step S20, there is also a step S11: cleaning the cut first diamond substrate 101 and the second diamond substrate 102.

[0053] Exemplarily, the processed first diamond substrate 101 and the second diamond substrate 102 are placed in absolute ethanol, ultrasonically cleaned in an ultrasonic machine for 30 minutes, and dried with nitrogen to remove surface impurities. The purpose of this step is to clean the pollutants generated during the processing of the diamond substrate.

[0054] In some embodiments, as Figure 2 shown, between the above step S20 and step S30, there is also included step S21: performing plasma etching on the diamond substrate 103.

[0055] Exemplarily, the diamond substrate 103 is placed in a microwave plasma chemical vapor deposition (MPCVD) device to first perform hydrogen plasma etching. Hydrogen with a flow rate of 200 sccm to 400 sccm is introduced, the reaction pressure is 1.5 Kpa to 3 Kpa, the microwave power is 3400 W to 5000 W, and the etching time is 25 minutes to 60 minutes. The purpose of this step is to use hydrogen plasma etching to remove the graphite and amorphous carbon generated at the laser processing splicing joints by etching the non-diamond phase carbon.

[0056] In some embodiments, as Figure 3 shown, the above step S30 includes the following step 300:

[0057] S300: As Figure 6 shown, using the microwave chemical vapor deposition process, an epitaxial layer 104 is formed on the diamond substrate 103. In the MPCVD device, the carbon source ratio is set to 5% to 8%, the deposition pressure is 1.5 Kpa to 3 Kpa, the microwave power is 3400 W to 5000 W, and the deposition time is more than 24 h. A large-sized single-crystal diamond with seamless mosaic splicing of a (100) crystal plane on the growth surface and a (110) crystal plane on the splicing side is obtained.

[0058] The beneficial effects are further described below in combination with specific embodiments, and at the same time, the feasibility of the solution of the present invention is proved.

[0059] The preparation method of Example 1 includes the following steps S201 to step S205:

[0060] S201: Using the laser cutting process, process the first diamond substrate and the second diamond substrate with the growth surface being the (100) crystal plane and the splicing side surface being the (110) crystal plane, so that multiple sawteeth are formed on the splicing side surfaces of the first diamond substrate and the second diamond substrate. Since the (100) crystal plane and the (110) crystal plane of diamond form a 45° deviation angle, the shape of the protruding sawteeth after processing is an isosceles right triangle. The tip spacing between two adjacent sawteeth 105 is twice the width of the sawteeth 105 along the first direction X. Among them, the width of the sawteeth along the first direction is equal to 1 mm, and the first direction X is perpendicular to the splicing side surfaces of the first diamond substrate and the second diamond substrate.

[0061] S202: Put the processed first diamond substrate and the second diamond substrate into absolute ethanol, ultrasonically clean them in an ultrasonic machine for 30 minutes, and dry them with nitrogen to remove surface impurities.

[0062] S203: Place the first diamond substrate and the second diamond substrate after cleaning. Place the first diamond substrate and the second diamond substrate with the same crystal orientation parallel to each other, and then splice their splicing side surfaces together. The splicing side surfaces are serrated, and the recesses between the protruding sawteeth of the splicing side surface of the first diamond substrate and the sawteeth of the splicing side surface of the second diamond substrate are fitted together, and the entire splicing part is tightly connected to form a diamond substrate. S204: Put the placed diamond substrate into an (MPCVD) device and first perform hydrogen plasma etching. Introduce 300 sccm of hydrogen, the reaction pressure is 2 Kpa, the microwave power is 3600 W, and the etching time is about 30 minutes.

[0063] S205: After the hydrogen plasma etching is completed, set the carbon source ratio to 7% in the MPCVD device, the deposition pressure is 1.8 Kpa, the microwave power is 3600 W, and the deposition time is 24 h. Obtain a single-crystal diamond seamlessly spliced by the mosaic method with the growth surface being the (100) crystal plane and the splicing side surface being the (110) crystal plane.

[0064] The preparation method of Example 2 includes the following steps S301 to S305:

[0065] S301: Using the laser cutting process, process the first diamond substrate and the second diamond substrate with the growth surface being the (100) crystal plane and the splicing side being the (110) crystal plane, so that multiple sawteeth are formed on the splicing sides of both the first diamond substrate and the second diamond substrate. Since the (100) crystal plane and the (110) crystal plane of diamond form a 45° deflection angle, the shape of the protruding sawteeth after processing is an isosceles right triangle. The tip spacing between two adjacent sawteeth 105 is twice the width of the sawteeth 105 along the first direction X. Among them, the width of the sawteeth along the first direction is equal to 0.5 mm, and the first direction X is perpendicular to the splicing sides of the first diamond substrate and the second diamond substrate.

[0066] S302: Put the processed first diamond substrate and the second diamond substrate into absolute ethanol, ultrasonically clean them in an ultrasonic machine for 30 minutes, and dry them with nitrogen to remove surface impurities.

[0067] S303: Place the first diamond substrate and the second diamond substrate after cleaning. Place the first diamond substrate and the second diamond substrate with the same crystal orientation parallel to each other, and then splice their splicing sides together. The splicing sides are serrated, and the depressions between the protruding sawteeth on the splicing side of the first diamond substrate and the sawteeth on the splicing side of the second diamond substrate fit together, and the entire splicing part is tightly connected to form a diamond substrate.

[0068] S304: Put the placed diamond substrate into an (MPCVD) device for hydrogen plasma etching first. Introduce 300 sccm of hydrogen, the reaction pressure is 2 Kpa, the microwave power is 3600 W, and the etching time is about 30 minutes.

[0069] S305: After the hydrogen plasma etching is completed, set the carbon source ratio to 7% in the MPCVD device, the deposition pressure is 1.8 Kpa, the microwave power is 3800 W, and the deposition time is 100 h. Obtain a single crystal diamond with seamless mosaic splicing of the single crystal diamond with the growth surface being the (100) crystal plane and the splicing side being the (110) crystal plane.

[0070] The optical microscope is the simplest and most direct way to characterize the surface morphology of materials. By observing the surface growth morphology and the growth step morphology at the splicing seam, the splicing quality at the splicing part can be seen. For perfect seamless mosaic splicing, after splicing is completed, it will be joined into a large-sized single crystal, and the surface growth morphology has the same-direction growth steps like a single crystal. It can be seen from the morphology diagrams of the splicing seams of the diamond substrates in Example 1 and Example 2 that: as Figure 7As shown, in some areas at the splicing seam of the diamond substrate in the first embodiment, the connection has been completed, and the same growth step morphology is obvious at the connection, indicating that the splicing has been seamlessly connected into an integral body and become the same single crystal. In addition, some areas have not been connected due to the interruption of the growth time. As Figure 8 shown, in the second embodiment, the splicing seam of the diamond substrate has been completely connected, and the growth steps and morphology have been unified into an integral body, indicating the high-quality seamless splicing of the single-crystal diamond on the splicing side of the (110) crystal plane.

[0071] In some embodiments, a single-crystal diamond can be prepared by the preparation method of any of the above embodiments.

[0072] On the other hand, the embodiments of the present application further provide a chip, including the single-crystal diamond described in the above embodiments, and components disposed on the single-crystal diamond. The chip can be an optical chip and is applied to the field of optical windows. The chip can also be an electrical chip and is applied to fields such as integrated circuits and high-power electronic devices.

[0073] As described above, the above is only the specific implementation manner of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art within the technical scope disclosed in the present application, thinking of changes or substitutions, should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A method for preparing single crystal diamond, characterized in that: include: Cutting the splicing side surface of the first diamond substrate and the splicing side surface of the second diamond substrate so that the splicing side surface of the first diamond substrate and the splicing side surface of the second diamond substrate are both serrated; splicing the jagged splicing side surface of the first diamond substrate with the jagged splicing side surface of the second diamond substrate to form a diamond base; An epitaxial layer is formed on the diamond substrate.

2. The preparation method according to claim 1, characterized in that: The splicing side surface of the first diamond substrate and the splicing side surface of the second diamond substrate both include a plurality of saw teeth, and the saw teeth are in the shape of an isosceles right triangle; The splicing side surface of the first diamond substrate and the splicing side surface of the second diamond substrate both include a plurality of saw teeth, and the width of the saw teeth along a first direction is less than or equal to 1 mm; the first direction is perpendicular to the splicing side surface of the first diamond substrate and perpendicular to the splicing side surface of the second diamond substrate; The distance between the tooth tips of two adjacent saw teeth is twice the width of the saw teeth along the first direction.

3. The preparation method according to claim 1, characterized in that: Before forming the diamond substrate, the preparation method further comprises: The cut first diamond substrate and the second diamond substrate are cleaned.

4. The preparation method according to claim 1, characterized in that: Using a laser cutting process to cut the spliced ​​side surface of the first diamond substrate and the spliced ​​side surface of the second diamond substrate; Before forming the epitaxial layer on the diamond substrate, the preparation method further comprises: The diamond substrate is plasma etched.

5. The preparation method according to claim 4, characterized in that: The etching gas of the plasma etching is hydrogen, the amount of hydrogen is 200 sccm to 400 sccm, the reaction pressure is 1.5 Kpa to 3 Kpa, the microwave power is 3400 W to 5000 W, and the etching time is 25 minutes to 60 minutes.

6. The preparation method according to claim 1, characterized in that: Forming an epitaxial layer on the diamond substrate, comprising: Forming the epitaxial layer on the diamond substrate by using a microwave chemical vapor deposition process; The carbon source ratio of the microwave chemical vapor deposition process is 5% to 8%, the deposition pressure is 1.5Kpa to 3Kpa, the microwave power is 3400W to 5000W, and the deposition time is greater than or equal to 24 hours.

7. The preparation method according to claim 1, characterized in that: The splicing side surface of the first diamond substrate and the splicing side surface of the second diamond substrate both include a plurality of saw teeth, and the width of the saw teeth along the first direction is 1 mm; the first direction is perpendicular to the splicing side surface of the first diamond substrate and perpendicular to the splicing side surface of the second diamond substrate; The epitaxial layer is formed by a microwave chemical vapor deposition process, wherein the carbon source ratio of the microwave chemical vapor deposition process is 7%, the deposition pressure is 1.8 Kpa, the microwave power is 3600 W, and the deposition time is 24 hours.

8. The preparation method according to claim 1, characterized in that: The splicing side surface of the first diamond substrate and the splicing side surface of the second diamond substrate both include a plurality of saw teeth, and the width of the saw teeth along the first direction is 0.5 mm; the first direction is perpendicular to the splicing side surface of the first diamond substrate and perpendicular to the splicing side surface of the second diamond substrate; The epitaxial layer is formed by a microwave chemical vapor deposition process, in which the carbon source ratio of the microwave chemical vapor deposition process is 7%, the deposition pressure is 1.8 Kpa, the microwave power is 3800 W, and the deposition time is 100 hours.

9. A single crystal diamond, characterized in that: The method is prepared according to any one of claims 1 to 8.

10. A chip, characterized in that: It comprises the single crystal diamond as claimed in claim 9, and components arranged on the single crystal diamond.

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