A method for homogeneous splicing of single crystal diamond and low interface stress regulation

Abstract

The present invention discloses a single crystal diamond homogeneous splicing and interface low stress control method, wherein a metal catalysis method is used to generate SiC nanowires at the single crystal diamond seed crystal connection interface, and the metal catalysis-grown SiC nanowires pass through the diamond crystal structure to flexibly connect the single crystal diamond seed crystal; a metal catalysis method is used to generate SiC nanowires at the single crystal diamond seed crystal connection interface to achieve single crystal diamond microscopic flexible connection, and this heterogeneous connection interface is stable and can withstand the high temperature environment of diamond growth, and the SiC nanowires maintain structural integrity throughout the entire process of diamond homoepitaxial growth. The single crystal diamond seed crystals are flexibly connected by SiC nanowires, which will help alleviate the stress accumulation effect during homoepitaxial growth of the single crystal diamond splicing interface, and greatly reduce the growth stress level of the splicing interface.

Description

Technical Field

[0001] The invention relates to the field of single crystal diamond homogeneous splicing, and in particular to a single crystal diamond homogeneous splicing and interface low stress regulation method. Background Art

[0002] At present, there are usually two ways to synthesize single crystal diamond: high temperature and high pressure (HPHT) and chemical vapor deposition (CVD). For HPHT diamond, the transformation of graphite into diamond requires overcoming extremely high pressure and temperature conditions. Due to the size and pressure limit of the growth chamber of the high temperature and high pressure equipment, the size of HPHT diamond is usually around a few millimeters. Large-size products cannot be industrialized with low cost and high repeatability, which makes it difficult to directly apply HPHT diamond to the field of thermal management of power devices. In comparison, the growth of CVD diamond is in a low-pressure and controllable hydrocarbon decomposition atmosphere chamber, and the preparation conditions are milder. This technology has the potential to manufacture large-size inch-level single crystal diamonds. However, the preparation of CVD single crystal diamond mostly uses HPHT diamond substrates as substrate materials, and the growth of diamond is achieved by homoepitaxial growth. Its growth size will be limited by the size of a single seed crystal; in addition, the "edge effect" of the chemical vapor deposition process easily causes polycrystallization around the crystal, resulting in a gradual reduction in the area of ​​the single crystal substrate, making it difficult to achieve the growth of the single crystal substrate to a larger size. In 1995, G. Janssen and LJ Giling first proposed the concept of splicing single crystal diamonds together, and successfully spliced ​​two 2*2*0.5mm single crystal diamonds together using the hot-wire CVD method. Although there were obvious gaps and a lot of stress at the joints, this method undoubtedly pointed out the development direction for the low-cost, high-repeatability and rapid preparation of large-size single crystal diamonds.

[0003] However, the splicing growth of diamond is different from that of conventional crystals. It cannot be carried out by melting and recrystallization of crystals, but can only be achieved by phase change transformation of active carbon atom groups under certain conditions. The existence of connection gaps will significantly affect key growth parameters such as gas pressure, temperature distribution and plasma state, making the quality control of the connection interface extremely difficult, especially the stress regulation of the splicing interface, which has become a difficult-to-overcome technical bottleneck, seriously restricting the large-scale production and industrial application of large-size single crystal diamond. In addition, in the homogeneous splicing of single crystal diamond, there is inevitably a certain degree of lattice mismatch and thermal stress mismatch between seed crystals, which leads to the generation of crystal growth stress. The cumulative effect of stress will lead to diamond lattice distortion, and even lead to the generation and expansion of cracks in severe cases. Therefore, the evaluation of the quality of the homogeneous splicing interface of single crystal diamond is not only reflected in the absence of obvious joints and polycrystalline phenomena at the macro level, but also the internal stress at the joint should be at a low level at the micro level, otherwise it is easy to cause cracks, breakage and other failure problems in subsequent processing applications, making it difficult to obtain practical applications. The generation of interface stress in homogeneous splicing of single crystal diamond is the result of the synergistic effect of many factors such as lattice orientation, thermal mismatch, step flow direction, etc. The existing technology mainly solves the problem of lateral growth of single crystal diamond across the connection interface and realizes the quality growth of single crystal at the connection interface. However, the serious interface stress generated by the synergistic effect of many factors such as lattice orientation, thermal mismatch, step flow direction, etc. still exists widely.

[0004] Therefore, a method for homogeneous splicing of single crystal diamonds and low interface stress regulation is needed to overcome the technical difficulties in regulating interface stress of homogeneous splicing of single crystal diamonds. Summary of the invention

[0005] In view of this, the purpose of the present invention is to provide a method for homogeneous splicing of single crystal diamond and low interface stress regulation, so that the diamond can grow laterally across the interface on the surface of the seed crystal, thereby realizing low-stress homogeneous connection of the interface of the single crystal diamond, and the heterogeneous connection interface is stable and can withstand the high temperature of diamond growth, providing technical support for the growth and preparation of large-size single crystal diamond.

[0006] The single crystal diamond homogeneous splicing and interface low stress control method of the present invention uses a metal catalysis method to generate SiC nanowires at the single crystal diamond seed crystal connection interface, and the metal catalytically grown SiC nanowires pass through the diamond crystal structure to flexibly connect the single crystal diamond seed crystal;

[0007] Further, the following steps are included:

[0008] s 1 , surface cleaning and roughness treatment of diamond seed crystal;

[0009] s 2 , Plating of solid precursor film on the connection surface of diamond seed crystal;

[0010] s 3 , the diamond seed crystals are heat treated so that the diamond seed crystals are interconnected;

[0011] s 4 , remove the metal Ni impurities at the interface of the diamond seed crystal and then clean it;

[0012] s 5 , removing amorphous carbon impurities from the surface of diamond seed crystals and then performing homoepitaxial growth;

[0013] Further, step s 1 In the process, HPHT diamond is used as a diamond seed crystal, and the surface treatment of HPHT diamond is performed, including the following steps:

[0014] First, the roughness of all surfaces of HPHT diamond is reduced by chemical mechanical polishing, so that the roughness of all surfaces is less than 5nm; then, HPHT diamond seed crystals with smooth surfaces are obtained after aqua regia pickling and multiple deionized water ultrasonic cleaning; finally, acetone, alcohol and deionized water are used as solvents for ultrasonic cleaning respectively, to obtain HPHT diamond seed crystals with clean surfaces and extremely low roughness;

[0015] Further, step s 2 In the process, silicon film and nickel film are uniformly coated on the connecting surface of diamond seed crystal by magnetron sputtering;

[0016] Further, step s 2 wherein the thickness of the silicon film and the nickel film are both 1-10 nm;

[0017] Further, step s 3 In the process, the diamond surfaces coated with silicon film and nickel film are firstly butted and fixed by a metal molybdenum fixture, and then placed in a tube furnace for heat treatment under argon protection, wherein the heat treatment temperature is 700-1000° C. and the treatment time is 1-30 minutes;

[0018] Further, step s 4 In the process, the heterogeneously connected diamonds were placed in dilute hydrochloric acid for pickling to remove the metal Ni impurities at the connection interface; the pickled samples were then cleaned 2-3 times with deionized water, acetone, and alcohol, respectively, and finally washed with N 2 Blow dry;

[0019] Further, step s 5 In the process, hydrogen plasma etching is used to remove amorphous carbon impurities on the surface of diamond seed crystals. The hydrogen plasma generator uses 99.99% pure hydrogen as the gas source, microwave power 1000-3000W, microwave frequency 2.45GHz, H 2Flow rate 180-200sccm, gas pressure 120-200mbar, substrate temperature 500-1000℃, etching time 1-5 minutes;

[0020] Further, step s 5 The microwave power for homoepitaxial growth on the surface of diamond seed crystal is 3000-5000W, the microwave frequency is 2.45GHz, and the H 2 Flow rate 180-200sccm, CH 4 Flow rate 2-20sccm, gas pressure 150-200mbar, substrate temperature 700-1000℃, growth time 1 hour or more.

[0021] The beneficial effects of the present invention are as follows: the single crystal diamond homogeneous splicing and interface low stress control method disclosed by the present invention uses a metal catalysis method to generate SiC nanowires at the single crystal diamond seed crystal connection interface to achieve single crystal diamond micro flexible connection. This heterogeneous connection interface is stable and can withstand the high temperature (700-1000°C) environment of diamond growth. The SiC nanowires grown by metal catalysis pass through the diamond crystal structure to connect the seed crystals, and the SiC nanowires maintain the integrity of the structure throughout the diamond homoepitaxial growth process. The flexible connection of single crystal diamond seed crystals by SiC nanowires will help alleviate the stress accumulation effect during homoepitaxial growth of the single crystal diamond splicing interface, greatly reduce the growth stress level of the splicing interface, achieve low stress homogeneous splicing of the single crystal diamond interface, and provide technical support for the growth and preparation of large-size single crystal diamonds. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The present invention will be further described below in conjunction with the accompanying drawings and embodiments:

[0023] Figure 1 It is the technical roadmap for low-stress homogeneous splicing of single crystal diamond interfaces.

[0024] Figure 2 This is a SEM image of SiC nanowires grown on the interface of a single crystal diamond seed crystal. DETAILED DESCRIPTION

[0025] Embodiment 1

[0026] s 1: Selection of diamond seed crystals and their surface treatment: Single crystal diamonds synthesized under high temperature and high pressure (HPHT) were selected as splicing seed crystals. The original size of the single crystal diamond sheet was 5 mm long × 5 mm wide × 1 mm thick. The HPHT diamond was surface treated. First, the roughness of all surfaces of the HPHT diamond was reduced by chemical mechanical polishing to a roughness of about 1 nm on all surfaces. Then, HPHT diamond seed crystals with smooth surfaces were obtained after pickling with aqua regia and multiple ultrasonic cleanings with deionized water. Finally, acetone, alcohol and deionized water were used as solvents for ultrasonic cleaning respectively to obtain HPHT diamond seed crystals with clean surfaces and extremely low roughness.

[0027] s 2 :Deposition of solid precursor film on the connection surface of diamond seed crystal: A layer of silicon (Si) and a layer of nickel (Ni) are respectively plated on the connection surface of diamond seed crystal by magnetron sputtering. The specific method is as follows:

[0028] Place the diamond sheet treated in step 1 on the stage of the magnetron sputtering coating system, with the surface of the diamond used for connection facing upwards; first, evacuate the equipment to a high vacuum so that the pressure in the reaction chamber is about 1×10 -6 Pa, after high-purity argon gas is introduced, the surface of the diamond sample is cleaned with a remote plasma source for 3 minutes; then, Si film and Ni film are uniformly plated respectively with certain sputtering parameters, so that the thickness of the Si film is about 5nm, and the thickness of the Ni film is about 2nm, thereby completing the plating of the precursor on the surface of the diamond seed crystal.

[0029] s 3 :Low stress heterogeneous connection of diamond seed crystals: First, the diamond surfaces coated with the precursor are contacted and connected with each other, and clamped and fixed by a metal molybdenum fixture; then the fixed diamond and the molybdenum fixture are placed in a tube furnace for heat treatment under argon protection atmosphere, the treatment temperature is 900℃, the treatment time is 10 minutes, and the heating power is turned off after the heat treatment. The sample is naturally cooled to room temperature in the argon protection atmosphere. Take out the sample, at this time, the diamond seed crystals are connected to each other.

[0030] s 4 : The heterogeneously connected diamonds were placed in dilute hydrochloric acid for pickling to remove the metal Ni impurities at the connection interface; the pickled samples were then statically cleaned three times with deionized water, acetone, and alcohol, respectively, and finally rinsed with N 2 Blow dry.

[0031] s 5 :S 4The treated samples were placed on a molybdenum tray on the stage of the microwave plasma chemical vapor deposition system. First, hydrogen plasma etching was used to remove amorphous carbon impurities on the sample surface and the heterogeneous connection interface. The hydrogen plasma generator used high-purity (99.99%) hydrogen as the gas source. The specific process was microwave power 2500W, microwave frequency 2.45GHz, H 2 The flow rate was 200 sccm, the pressure was 135 mbar, the substrate temperature was 600 °C, and the etching time was 3 minutes. Subsequently, homoepitaxial growth was carried out on the surface of the diamond seed crystal. The specific process was microwave power 3800 W, microwave frequency 2.45 GHz, H 2 Flow rate 196sccm, CH 4 The flow rate is 4 sccm, the gas pressure is 165 mbar, the substrate temperature is 850°C, and the growth time is 6 hours.

[0032] Embodiment 2

[0033] S 1 :Selection of diamond seed crystal and its surface treatment. Single crystal diamond synthesized by high temperature and high pressure (HPHT) was selected as the splicing seed crystal. The original size of the single crystal diamond sheet was 10mm long × 10mm wide × 1mm thick. The surface of the HPHT diamond was treated. First, the roughness of all surfaces of the HPHT diamond was reduced by chemical mechanical polishing to about 2nm. Then, after aqua regia pickling and multiple deionized water ultrasonic cleaning, a smooth HPHT diamond seed crystal was obtained. Finally, acetone, alcohol and deionized water were used as solvents for ultrasonic cleaning respectively to obtain a HPHT diamond seed crystal with a clean surface and extremely low roughness.

[0034] S 2 : Plating of solid precursor film on the connection surface of diamond seed crystal: A layer of silicon (Si) and a layer of nickel (Ni) are respectively plated on the connection surface of diamond seed crystal by magnetron sputtering. The specific method is as follows:

[0035] Place the diamond sheet treated in step 1 on the stage of the magnetron sputtering coating system, with the surface of the diamond used for connection facing upwards; first, evacuate the equipment to a high vacuum, so that the pressure in the reaction chamber is about 2×10 -6 Pa, after high-purity argon gas is introduced, the surface of the diamond sample is cleaned with a remote plasma source for 5 minutes; then, Si film and Ni film are uniformly plated respectively with certain sputtering parameters, so that the thickness of the Si film is about 5nm, and the thickness of the Ni film is about 2nm, thereby completing the plating of the precursor on the surface of the diamond seed crystal.

[0036] S 3:Low stress heterogeneous connection of diamond seed crystals: First, the diamond surfaces coated with the precursor are contacted and docked with each other, and clamped and fixed by a metal molybdenum fixture; then the fixed diamond and the molybdenum fixture are placed in a tube furnace for heat treatment under argon protection atmosphere, the treatment temperature is 850℃, the treatment time is 15 minutes, and the heating power is turned off after the heat treatment. The sample is naturally cooled to room temperature in the argon protection atmosphere. Take out the sample, at this time, the diamond seed crystals are connected to each other.

[0037] S 4 : The heterogeneously connected diamonds were placed in dilute hydrochloric acid for pickling to remove the metal Ni impurities at the connection interface; the pickled samples were then statically cleaned twice with deionized water, acetone, and alcohol, respectively, and finally rinsed with N 2 Blow dry.

[0038] s 5 :The sample processed in step 4 is placed on the molybdenum tray of the stage of the microwave plasma chemical vapor deposition system. First, the hydrogen plasma etching method is used to remove the amorphous carbon impurities on the sample surface and the heterogeneous connection interface. The hydrogen plasma generator uses high-purity (99.99%) hydrogen as the gas source. The specific process is microwave power 2500W, microwave frequency 2.45GHz, H 2 The flow rate was 200 sccm, the gas pressure was 140 mbar, the substrate temperature was 650 °C, and the etching time was 2 minutes. Subsequently, homoepitaxial growth was carried out on the surface of the diamond seed crystal. The specific process was microwave power 3800 W, microwave frequency 2.45 GHz, H 2 Flow rate 192sccm, CH 4 The flow rate is 8 sccm, the gas pressure is 180 mbar, the substrate temperature is 900°C, and the growth time is 5 hours.

[0039] Embodiment 3

[0040] s 1 :Selection of diamond seed crystal and its surface treatment. Single crystal diamond synthesized by high temperature and high pressure (HPHT) was selected as the splicing seed crystal. The original size of the single crystal diamond sheet was 15mm long × 15mm wide × 2mm thick. The surface of the HPHT diamond was treated. First, the roughness of all surfaces of the HPHT diamond was reduced by chemical mechanical polishing to about 1.5nm. Then, after acid washing with aqua regia and ultrasonic cleaning with deionized water for multiple times, a smooth HPHT diamond seed crystal was obtained. Finally, acetone, alcohol and deionized water were used as solvents for ultrasonic cleaning respectively to obtain a HPHT diamond seed crystal with a clean surface and extremely low roughness.

[0041] s 2: Plating of solid precursor film on the connection surface of diamond seed crystal: A layer of silicon (Si) and a layer of nickel (Ni) are respectively plated on the connection surface of diamond seed crystal by magnetron sputtering. The specific method is as follows:

[0042] Place the diamond sheet treated in step 1 on the stage of the magnetron sputtering coating system, with the surface of the diamond used for connection facing upwards; first, evacuate the equipment to a high vacuum, so that the pressure in the reaction chamber is about 3×10 -6 Pa, after high-purity argon gas is introduced, the surface of the diamond sample is cleaned with a remote plasma source for 5 minutes; then, Si film and Ni film are uniformly plated respectively with certain sputtering parameters, so that the thickness of the Si film is about 6nm, and the thickness of the Ni film is about 3nm, thereby completing the plating of the precursor on the surface of the diamond seed crystal.

[0043] s 3 :Low stress heterogeneous connection of diamond seed crystals: First, the diamond surfaces coated with the precursor are contacted and connected with each other, and clamped and fixed by a metal molybdenum fixture; then the fixed diamond and the molybdenum fixture are placed in a tube furnace for heat treatment under argon protection atmosphere, the treatment temperature is 800℃, the treatment time is 20 minutes, and the heating power is turned off after the heat treatment. The sample is naturally cooled to room temperature in the argon protection atmosphere. Take out the sample, at this time, the diamond seed crystals are connected to each other.

[0044] s 4 : The heterogeneously connected diamonds were placed in dilute hydrochloric acid for pickling to remove the metal Ni impurities at the connection interface; the pickled samples were then statically cleaned three times with deionized water, acetone, and alcohol, respectively, and finally rinsed with N 2 Blow dry.

[0045] s 5 :The sample processed in step 4 is placed on the molybdenum tray of the stage of the microwave plasma chemical vapor deposition system. First, the hydrogen plasma etching method is used to remove the amorphous carbon impurities on the sample surface and the heterogeneous connection interface. The hydrogen plasma generator uses high-purity (99.99%) hydrogen as the gas source. The specific process is microwave power 3000W, microwave frequency 2.45GHz, H 2 The flow rate was 200 sccm, the pressure was 145 mbar, the substrate temperature was 650 °C, and the etching time was 2 minutes. Subsequently, homoepitaxial growth was carried out on the surface of the diamond seed crystal. The specific process was microwave power 4500 W, microwave frequency 2.45 GHz, H 2 Flow rate 194sccm, CH 4 The flow rate was 6 sccm, the gas pressure was 180 mbar, the substrate temperature was 900°C, and the growth time was 10 hours.

[0046] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution of the present invention, which should be included in the scope of the claims of the present invention.

Claims

1. A method for homogeneous splicing of single crystal diamond and low interface stress regulation, characterized in that: A metal catalysis method is used to generate SiC nanowires at the connection interface of a single crystal diamond seed crystal, and the SiC nanowires grown by metal catalysis pass through the diamond crystal structure to flexibly connect the single crystal diamond seed crystal; the steps include: s1, cleaning and roughening the surface of diamond seed crystal; s2, plating of solid precursor film on the diamond seed crystal connection surface; s3, heat treating the diamond seed crystals so that the diamond seed crystals are interconnected; s4, removing the metal Ni impurities at the interface of the diamond seed crystal and then cleaning; s5, removing amorphous carbon impurities on the surface of the diamond seed crystal, and then performing homoepitaxial growth; In step s2, silicon film and nickel film are uniformly plated on the connecting surface of the diamond seed crystal by magnetron sputtering, and the thickness of the silicon film and the nickel film are both 1-10nm; in step s3, the diamond surface plated with silicon film and nickel film is first docked and clamped by a metal molybdenum clamp, and then placed in a tubular furnace for heat treatment under argon protection, the heat treatment temperature is 700-1000°C, and the treatment time is 1-30 minutes.

2. The method for homogeneous splicing of single crystal diamond and low interface stress control according to claim 1, characterized in that: In step s1, HPHT diamond is used as a diamond seed crystal, and the surface treatment of the HPHT diamond is performed, including the following steps: First, the roughness of all surfaces of HPHT diamond is reduced by chemical mechanical polishing, so that the roughness of all surfaces is less than 5nm; then, after aqua regia pickling and multiple deionized water ultrasonic cleaning, HPHT diamond seed crystals with smooth surfaces are obtained; finally, ultrasonic cleaning is carried out using acetone, alcohol and deionized water as solvents respectively to obtain HPHT diamond seed crystals with clean surfaces and extremely low roughness.

3. The method for homogeneous splicing of single crystal diamond and low interface stress control according to claim 1, characterized in that: In step s4, the heterogeneously connected diamond is placed in dilute hydrochloric acid for pickling to remove metal Ni impurities at its connection interface; then the pickled sample is statically cleaned 2-3 times using deionized water, acetone and alcohol respectively, and finally blown dry with N2.

4. The method for homogeneous splicing of single crystal diamond and low interface stress control according to claim 1, characterized in that: In step s5, hydrogen plasma etching is used to remove amorphous carbon impurities on the surface of the diamond seed crystal. The hydrogen plasma generator uses 99.99% pure hydrogen as the gas source, microwave power 1000-3000W, microwave frequency 2.45GHz, H2 flow rate 180-200sccm, gas pressure 120-200mbar, substrate temperature 500-1000℃, and etching time is 1-5 minutes.

5. The method for homogeneous splicing of single crystal diamond and low interface stress control according to claim 4, characterized in that: In step s5, the microwave power for homoepitaxial growth on the surface of the diamond seed crystal is 3000-5000 W, the microwave frequency is 2.45 GHz, the H2 flow rate is 180-200 sccm, the CH4 flow rate is 2-20 sccm, the gas pressure is 150-200 mbar, the substrate temperature is 700-1000°C, and the growth time is 1 hour or more.

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