High-speed preparation method of thick diamond film

Abstract

The invention belongs to the technical field of diamond preparation, and discloses a high-speed preparation method of a thick diamond film, which comprises the following steps of: uniformly spreading diamond particles on a substrate by using absolute ethyl alcohol, placing the substrate on a sample table in an MPCVD (Micro-Pressure Chemical Vapor Deposition) system, and introducing hydrogen, slowly heating the interior of the MPCVD system to a preset cleaning temperature so as to perform plasma cleaning on the surface of the substrate, and growing the substrate on the basis of the growth hydrogen flow, the methane gas flow, the growth power, the growth temperature and the growth air pressure through a segmented growth method, promoting the growth of nano-scale diamonds in gaps of the diamond particles on the surface of the substrate to connect the diamond particles to obtain a compact and uniform rough thick diamond film, and polishing the rough thick diamond film to obtain a thick diamond film with a smooth surface; the thick diamond film is grown on the substrate on which a layer of diamond particles are paved by using hydrogen and methane gas through a segmented growth method, so that the high-speed preparation efficiency of the thick diamond film is improved.

Description

Technical Field

[0001] This application relates to the technical field of diamond preparation, and more specifically, to a method for rapidly preparing thick diamond films. Background Art

[0002] With the rapid development of modern semiconductor technology, especially the evolution of power semiconductor devices towards high frequency, high temperature, and high power, traditional silicon-based materials have gradually become difficult to meet the performance requirements. Third-generation semiconductor materials such as gallium nitride (GaN) and aluminum nitride (AlN) exhibit great potential in high-frequency and high-power application fields due to their excellent properties such as wide bandgap, high breakdown electric field, and high electron mobility. However, with the continuous increase in the power density of GaN devices, the heat generated by them increases sharply, and the heat dissipation problem has become a key bottleneck restricting further breakthroughs in their performance. An effective heat dissipation solution is crucial for improving the reliability and power output of GaN devices.

[0003] Diamond, as a material with excellent comprehensive properties such as extremely high thermal conductivity (far exceeding that of metals and traditional semiconductor materials), high hardness, high insulation, and low thermal expansion coefficient, is considered an ideal choice for solving the heat dissipation problem of high-power devices, especially in the heat dissipation management of third-generation semiconductor devices such as GaN, with broad application prospects. By integrating diamond materials with GaN devices, the thermal resistance of the devices can be significantly reduced, thereby improving their power density and operating stability.

[0004] However, the existing diamond material preparation technologies, especially the methods for preparing thick diamond films, still face some challenges. For example, the growth rate of single-crystal diamond is very slow, usually only a few micrometers per hour, and it is difficult to prepare large-size materials, resulting in high preparation costs. Although the preparation of polycrystalline diamond is relatively easy to obtain large sizes, it also faces problems such as slow nucleation rate and relatively slow growth rate (usually a few micrometers to dozens of micrometers per hour). These disadvantages make it difficult to obtain high-quality thick diamond films efficiently and at low cost, thus limiting the widespread application of diamond in the heat dissipation field of high-power semiconductor devices.

[0005] Therefore, in order to solve the technical problems such as the slow diamond growth rate in the existing diamond preparation methods, a method for rapidly preparing thick diamond films is urgently needed. Summary of the Invention

[0006] The purpose of this application is to provide a method for rapidly preparing thick diamond films. By using the segmented growth method and hydrogen and methane gases, a thick diamond film is grown on a substrate covered with a layer of diamond particles, solving the problems such as the slow diamond growth rate in the existing diamond preparation methods. Through the method of pre-setting diamond particles and quickly filling and connecting the gaps between them, the rapid preparation of diamond films is achieved.

[0007] In a first aspect, the present application provides a method for rapidly preparing a thick diamond film, which is used for rapidly preparing a thick diamond film and includes the steps of: Using absolute ethanol to evenly spread diamond particles on a substrate; Placing the substrate covered with diamond particles on a sample stage inside an MPCVD system, introducing hydrogen gas, and slowly heating the inside of the MPCVD system to a preset cleaning temperature to perform plasma cleaning on the surface of the substrate covered with diamond particles; Based on a preset growth hydrogen gas flow rate, a preset methane gas flow rate, a preset growth power, a preset growth temperature, and a preset growth pressure, through a segmented growth method, promoting the growth of nanoscale diamonds between the gaps of the diamond particles on the surface of the substrate covered with diamond particles, so as to connect the diamond particles through the nanoscale diamonds to obtain a dense and uniform rough thick diamond film; Polishing the rough thick diamond film to obtain a thick diamond film with a smooth surface.

[0008] The method for rapidly preparing a thick diamond film provided by the present application can realize the rapid preparation of a thick diamond film. Through the segmented growth method, using hydrogen gas and methane gas, a thick diamond film is grown on a substrate covered with a layer of diamond particles, solving the problems such as slow diamond growth rate existing in the existing diamond preparation methods. By presetting diamond particles and quickly filling and connecting the gaps between them, the preparation efficiency of the diamond film is improved.

[0009] Optionally, using absolute ethanol to evenly spread diamond particles on a substrate includes: Sequentially placing the diamond particles in absolute ethanol, a mixed solution composed of concentrated sulfuric acid and concentrated nitric acid, and absolute ethanol for ultrasonic cleaning to obtain the cleaned diamond particles; Dispersing the cleaned diamond particles in absolute ethanol; Applying the absolute ethanol containing the cleaned diamond particles to the substrate so that the cleaned diamond particles are evenly spread on the substrate.

[0010] The method for rapidly preparing a thick diamond film provided by the present application can realize the rapid preparation of a thick diamond film. By performing multi-step cleaning and dispersion treatment on the diamond particles, the problems of surface contamination and agglomeration of the diamond particles are solved, thereby realizing the uniform distribution of the particles on the substrate.

[0011] Optionally, the ultrasonic cleaning frequency for ultrasonic cleaning in absolute ethanol is 35 - 60 kHz, the ultrasonic cleaning time is 5 - 15 min, the ultrasonic cleaning temperature is 50 - 70 °C, and the ultrasonic cleaning power is 500 - 700 W.

[0012] Optionally, the mixed solution is prepared by mixing concentrated sulfuric acid and concentrated nitric acid solution in a ratio of 1:1; wherein, the concentration of concentrated sulfuric acid is 98%, and the concentration of concentrated nitric acid is 60%-65%; the ultrasonic cleaning time in the mixed solution is 5-15 min, the ultrasonic cleaning temperature is 50-70 °C, and the ultrasonic cleaning power is 500-700 W.

[0013] Optionally, place the substrate covered with diamond particles on the sample stage inside the MPCVD system, introduce hydrogen, and slowly heat the inside of the MPCVD system to a preset cleaning temperature to perform plasma cleaning on the surface of the substrate covered with diamond particles, including: Wipe the sample stage of the MPCVD system with anhydrous ethanol to prevent the influence of impurities; Place the substrate covered with diamond particles on the wiped sample stage; Based on a preset breakdown pressure, introduce hydrogen with a preset breakdown hydrogen flow rate into the inside of the MPCVD system to initiate breakdown; After breakdown is completed, adjust the MPCVD system to a preset cleaning power, and slowly heat the inside of the MPCVD system to a preset cleaning temperature to perform plasma cleaning on the surface of the substrate covered with diamond particles.

[0014] Optionally, the preset breakdown pressure is 2-6 Torr; the preset breakdown hydrogen flow rate is 30-120 sccm; the preset cleaning power is 500-1000 W; the preset cleaning temperature is 450-500 °C.

[0015] Optionally, the preset methane gas flow rate includes a preset first methane gas flow rate and a preset second methane gas flow rate; the preset growth power includes a preset first growth power, a preset second growth power, and a preset third growth power; the preset growth temperature includes a preset first growth temperature, a preset second growth temperature, and a preset third growth temperature; the preset growth pressure includes a preset first growth pressure, a preset second growth pressure, and a preset third growth pressure.

[0016] Optionally, based on a preset growth hydrogen flow rate, a preset methane gas flow rate, a preset growth power, a preset growth temperature, and a preset growth pressure, by the segmented growth method, promote the growth of nanoscale diamonds between the gaps of the diamond particles on the surface of the substrate covered with diamond particles, so as to connect the diamond particles through the nanoscale diamonds, and obtain a dense and uniform rough thick diamond film, including: Introduce methane gas with the preset first methane gas flow rate into the MPCVD system, and based on the preset first growth power, the preset first growth temperature, and the preset first growth pressure, combined with the preset first growth time, perform a preliminary growth promotion operation to start growing nanoscale diamond between the gaps of each diamond particle on the surface of the substrate covered with diamond particles; Adjust the flow rate of hydrogen to the preset growth hydrogen flow rate, adjust the flow rate of methane gas to the preset second methane gas flow rate, adjust the power inside the MPCVD system to the preset second growth power, adjust the temperature inside the MPCVD system to the preset second growth temperature, and adjust the pressure inside the MPCVD system to the preset second growth pressure to perform a first-stage growth on the substrate for a preset second growth time, so that the nanoscale diamond between the gaps of each diamond particle gradually becomes larger and gradually contacts and connects with each diamond particle during the enlarging process; After the preset second growth time, keep the flow rates of hydrogen and methane gas unchanged, adjust the power inside the MPCVD system to the preset third growth power, adjust the temperature inside the MPCVD system to the preset third growth temperature, and adjust the pressure inside the MPCVD system to the preset third growth pressure to perform a second-stage growth on the substrate for the preset second growth time, so that the nanoscale diamond between the gaps of each diamond particle is tightly connected to each diamond particle and grows together; After completing the second-stage growth, slowly adjust the power inside the MPCVD system to zero. At the same time, slowly reduce the temperature and pressure inside the MPCVD system to room temperature and room pressure respectively. During the temperature reduction process, slowly reduce the flow rates of hydrogen and methane gas to zero. After the substrate covered with diamond particles is adjusted to room temperature, a dense and uniform rough thick diamond film is prepared on the surface of the substrate covered with diamond particles.

[0017] The method for rapidly preparing a thick diamond film provided by this application can realize the rapid preparation of a thick diamond film. Through the segmented growth method, the growth process of diamond in the particle gaps is effectively controlled, the effective connection between nanoscale diamond and initial diamond particles is realized, and finally a diamond film with the required density and uniformity is obtained, improving the preparation efficiency of the diamond film.

[0018] Optionally, the preset hydrogen flow rate for growth is 300 - 500 sccm; the preset first methane gas flow rate is 0.9 sccm - 6 sccm; the preset second methane gas flow rate is 9 - 15 sccm; the preset first growth power is 3000 - 5000 W; the preset second growth power is 4000 - 7000 W; the preset third growth power is 5000 - 8000 W; the preset first growth temperature is 400 - 600 °C; the preset second growth temperature is 700 - 800 °C; the preset third growth temperature is 800 - 950 °C; the preset first growth pressure is 60 - 80 Torr; the preset second growth pressure is 80 - 120 Torr; the preset third growth pressure is 90 - 130 Torr; the preset first growth time is 1.5 - 2.5 h; the preset second growth time is 4 h.

[0019] Optionally, polishing the rough thick diamond film to obtain a thick diamond film with a smooth surface, including: Using laser polishing technology to perform primary polishing on the rough thick diamond film to obtain a thick diamond film after primary polishing; Using mechanical polishing technology to perform fine polishing on the thick diamond film after primary polishing to obtain a thick diamond film with a smooth surface.

[0020] Beneficial effects: The high-speed preparation method of the thick diamond film provided by this application uses a segmented growth method, utilizes hydrogen and methane gases, and grows a thick diamond film on a substrate covered with a layer of diamond particles, solving the problems such as slow diamond growth rate in existing diamond preparation methods. By means of pre-set diamond particles and quickly filling and connecting the gaps between them, the preparation efficiency of the diamond film is improved. Description of the Drawings

[0021] Figure 1 It is a flowchart of the high-speed preparation method of the thick diamond film provided by the embodiment of this application. Detailed Embodiments

[0022] Next, the technical solutions in the embodiments of this application will be clearly and completely described in conjunction with the drawings in the embodiments of this application. Obviously, the described embodiments are only a part of the embodiments of this application, rather than all the embodiments. Usually, the components of the embodiments of this application described and shown in the drawings here can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of this application provided in the drawings is not intended to limit the scope of the claimed application, but only represents the selected embodiments of this application. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative efforts fall within the protection scope of this application.

[0023] It should be noted that similar reference numerals and letters denote similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings. At the same time, in the description of the present application, terms such as "first" and "second" are only used for distinguishing descriptions and cannot be construed as indicating or implying relative importance.

[0024] Please refer to Figure 1 , Figure 1 which is a method for rapidly preparing a thick diamond film in some embodiments of the present application, used for rapidly preparing a thick diamond film, and includes: Step S1, uniformly covering diamond particles on a substrate with absolute ethanol; Step S2, placing the substrate covered with diamond particles on a sample stage inside an MPCVD system, introducing hydrogen gas, and slowly heating the inside of the MPCVD system to a preset cleaning temperature to perform plasma cleaning on the surface of the substrate covered with diamond particles; Step S3, based on a preset growth hydrogen gas flow rate, a preset methane gas flow rate, a preset growth power, a preset growth temperature, and a preset growth air pressure, by means of segmented growth, promoting the growth of nanoscale diamonds between the gaps of each diamond particle on the surface of the substrate covered with diamond particles, so as to connect each diamond particle through the nanoscale diamonds to obtain a dense and uniform rough thick diamond film; Step S4, polishing the rough thick diamond film to obtain a thick diamond film with a smooth surface.

[0025] This method for rapidly preparing a thick diamond film grows a thick diamond film on a substrate covered with a layer of diamond particles by means of segmented growth, using hydrogen gas and methane gas, solving the problems such as slow diamond growth rate existing in the existing diamond preparation methods, and improving the preparation efficiency of the diamond film by means of presetting diamond particles and quickly filling and connecting the gaps between them.

[0026] Specifically, in Step S1, uniformly covering diamond particles on a substrate with absolute ethanol includes: Sequentially placing the diamond particles in absolute ethanol, a mixed solution composed of concentrated sulfuric acid and concentrated nitric acid, and absolute ethanol for ultrasonic cleaning to obtain the cleaned diamond particles; Dispersing the cleaned diamond particles in absolute ethanol; Applying the absolute ethanol containing the cleaned diamond particles to the substrate so that the cleaned diamond particles are uniformly covered on the substrate.

[0027] In step S1, the diamond particles are ultrasonically cleaned successively in anhydrous ethanol, a mixed solution composed of concentrated sulfuric acid and concentrated nitric acid, and anhydrous ethanol to remove the contaminants on the particle surface and reduce the van der Waals force between the particles, thereby reducing the possibility of particle agglomeration. The cleaned particles are dispersed in anhydrous ethanol, and the dispersion effect of the liquid is utilized to maintain the dispersed state of the particles. The anhydrous ethanol containing the dispersed particles is applied to the substrate. As the ethanol volatilizes, the particles are uniformly deposited on the substrate surface. Thus, a uniformly distributed diamond seed layer is formed on the substrate, providing uniform nucleation sites for the subsequent growth of the diamond film, promoting the dense and uniform growth of the diamond film, and avoiding film layer defects and performance degradation caused by uneven seed distribution. Among them, the substrate includes a nitride substrate (such as gallium nitride or aluminum nitride) or a molybdenum substrate.

[0028] Among them, when ultrasonically cleaning the diamond particles with anhydrous ethanol, the ultrasonic cleaning frequency for ultrasonic cleaning in anhydrous ethanol is 35 - 60 kHz, the ultrasonic cleaning time is 5 - 15 min, the ultrasonic cleaning temperature is 50 - 70 °C, and the ultrasonic cleaning power is 500 - 700 W.

[0029] When ultrasonically cleaning the diamond particles with the mixed solution, the mixed solution is prepared by mixing concentrated sulfuric acid and concentrated nitric acid solution in a ratio of 1:1; among them, the concentration of concentrated sulfuric acid is 98%, and the concentration of concentrated nitric acid is 60% - 65%; the ultrasonic cleaning time for ultrasonic cleaning in the mixed solution is 5 - 15 min, the ultrasonic cleaning temperature is 50 - 70 °C, and the ultrasonic cleaning power is 500 - 700 W.

[0030] Specifically, in step S2, the substrate covered with diamond particles is placed on the sample stage inside the MPCVD system, hydrogen is introduced, and the inside of the MPCVD system is slowly heated to a preset cleaning temperature to perform plasma cleaning on the surface of the substrate covered with diamond particles, including: Wipe the sample stage of the MPCVD system with anhydrous ethanol to prevent the influence of impurities; Place the substrate covered with diamond particles on the wiped sample stage; Based on the preset breakdown gas pressure, introduce hydrogen with a preset breakdown hydrogen flow rate into the MPCVD system to initiate breakdown; After breakdown is completed, adjust the MPCVD system to a preset cleaning power, and slowly heat the inside of the MPCVD system to a preset cleaning temperature to perform plasma cleaning on the surface of the substrate covered with diamond particles.

[0031] In step S2, wipe the sample stage with anhydrous ethanol to remove impurities on the sample stage and prevent these impurities from affecting the cleanliness of the substrate or diamond particles during the cleaning process. Place the substrate covered with diamond particles accurately on the clean sample stage. Introduce hydrogen gas into the MPCVD system and control the gas pressure (preset glow discharge pressure) and hydrogen gas flow rate (preset glow discharge hydrogen gas flow rate) inside the MPCVD system chamber to reach the preset glow discharge conditions, prompting the hydrogen gas to undergo glow discharge to form plasma. After the plasma is successfully ignited, by adjusting the applied power (preset cleaning power), maintain the intensity of the plasma discharge and control the temperature inside the MPCVD system to slowly rise to the preset cleaning temperature. At the preset cleaning temperature, the highly reactive particles in the hydrogen plasma can effectively react with the organic substances, oxides and other impurities on the substrate surface and diamond particles, convert them into gaseous substances or strip them off through physical sputtering, thereby achieving the purification of the substrate and diamond particle surfaces. Slowly heating up helps the substrate to be heated evenly and reduces thermal stress. By controlling the cleaning power and cleaning temperature, while effectively removing impurities, damage to the diamond particles or substrate can be avoided, providing a clean surface for subsequent diamond growth. Among them, the purity of the introduced hydrogen gas is not less than 7N.

[0032] Among them, the preset glow discharge pressure is 2 - 6 Torr; the preset glow discharge hydrogen gas flow rate is 30 - 120 sccm; the preset cleaning power is 500 - 1000 W; the preset cleaning temperature is 450 - 500 °C.

[0033] For example, place the substrate covered with diamond particles on the MPCVD system sample stage, introduce hydrogen gas into the MPCVD system, set the glow discharge pressure to 4 Torr, set the glow discharge hydrogen gas flow rate to 80 sccm, and conduct glow discharge. After the glow discharge is completed, set the cleaning power to 750 W, and at the same time slowly heat up the inside of the system to 480 °C to perform plasma cleaning on the substrate surface.

[0034] Specifically, the preset methane gas flow rate includes a preset first methane gas flow rate and a preset second methane gas flow rate; the preset growth power includes a preset first growth power, a preset second growth power, and a preset third growth power; the preset growth temperature includes a preset first growth temperature, a preset second growth temperature, and a preset third growth temperature; the preset growth pressure includes a preset first growth pressure, a preset second growth pressure, and a preset third growth pressure.

[0035] Specifically, in step S3, based on a preset growth hydrogen flow rate, a preset methane gas flow rate, a preset growth power, a preset growth temperature, and a preset growth pressure, through a segmented growth method, the growth of nanoscale diamond is promoted between the gaps of each diamond particle on the surface of the substrate covered with diamond particles, so as to connect each diamond particle through the nanoscale diamond, and a dense and uniform rough thick diamond film is obtained, including: Introduce methane gas with a preset first methane gas flow rate into the MPCVD system, and based on a preset first growth power, a preset first growth temperature, and a preset first growth pressure, combined with a preset first growth time, perform a preliminary growth promotion operation to start the growth of nanoscale diamond between the gaps of each diamond particle on the surface of the substrate covered with diamond particles; Adjust the hydrogen flow rate to the preset growth hydrogen flow rate, adjust the methane gas flow rate to the preset second methane gas flow rate, adjust the power inside the MPCVD system to the preset second growth power, adjust the temperature inside the MPCVD system to the preset second growth temperature, and adjust the pressure inside the MPCVD system to the preset second growth pressure, so as to perform a first-stage growth on the substrate for a preset second growth time, and make the nanoscale diamond between the gaps of each diamond particle gradually become larger and gradually contact and connect with each diamond particle during the enlargement process; After the preset second growth time, keep the flow rates of hydrogen and methane gas unchanged, adjust the power inside the MPCVD system to the preset third growth power, adjust the temperature inside the MPCVD system to the preset third growth temperature, and adjust the pressure inside the MPCVD system to the preset third growth pressure, so as to perform a second-stage growth on the substrate for a preset second growth time, and make the nanoscale diamond between the gaps of each diamond particle tightly connect with each diamond particle and grow together; After the second-stage growth is completed, slowly adjust the power inside the MPCVD system to zero. At the same time, slowly reduce the temperature and pressure inside the MPCVD system to room temperature and room pressure respectively, and during the cooling process, slowly reduce the flow rates of hydrogen and methane gas to zero. After the substrate covered with diamond particles is adjusted to room temperature, a dense and uniform rough thick diamond film is prepared on the surface of the substrate covered with diamond particles.

[0036] In step S3, by controlling the process parameters of the MPCVD system in stages, the precise regulation of the growth process of nanoscale diamond in the gaps between diamond particles is achieved. First, in the preliminary growth promotion stage, a lower methane gas flow rate (the purity of methane gas is not less than 6N) and specific growth parameters (i.e., methane gas with a preset first methane gas flow rate, a preset first growth power, a preset first growth temperature, a preset first growth pressure, and a preset first growth time) are adopted to induce preferential nucleation and initiate the growth of nanoscale diamond in the tiny gaps between diamond particles. The key in this stage is to control the nucleation density and the initial growth rate, laying a foundation for subsequent filling and connection. Then, entering the first-stage growth, by adjusting the hydrogen and methane gas flow rates (i.e., a preset growth hydrogen flow rate and a preset second methane gas flow rate) and the power, temperature, and pressure of the MPCVD system (i.e., a preset second growth power, a preset second growth temperature, and a preset second growth pressure), the growth rate is increased, promoting the rapid growth of nanoscale diamond to fill the gaps between particles and start contacting adjacent diamond particles. The parameter adjustment aims to optimize the growth direction and morphology of nanoscale diamond so that it can effectively bridge the particles. Subsequently, in the second-stage growth, the power, temperature, and pressure of the MPCVD system are further adjusted (i.e., a preset third growth power, a preset third growth temperature, and a preset third growth pressure). While keeping the gas flow rate unchanged, a more favorable growth environment is provided to strengthen the connection strength between nanoscale diamond and diamond particles and promote their co-growth to form a continuous and dense diamond film structure. After completing the second-stage growth, by slowly reducing the system parameters (power, temperature, and pressure) and the gas flow rate, the cooling process is achieved, reducing the internal stress of the film layer and avoiding defects such as cracks in the diamond layer on the substrate surface due to thermal stress, which may affect the quality. Finally, a dense and uniform rough thick diamond film is obtained. Through this segmented growth strategy, the problem of being difficult to simultaneously optimize nucleation, filling, and connection under a single growth condition is overcome, improving the denseness and uniformity of the film layer.

[0037] Among them, the preset hydrogen flow rate for growth is 300 - 500 sccm; the preset first methane gas flow rate is 0.9 sccm - 6 sccm (specifically 3% - 5% of the preset hydrogen flow rate for plasma ignition); the preset second methane gas flow rate is 9 - 15 sccm; the preset first growth power is 3000 - 5000 W; the preset second growth power is 4000 - 7000 W; the preset third growth power is 5000 - 8000 W; the preset first growth temperature is 400 - 600 °C; the preset second growth temperature is 700 - 800 °C; the preset third growth temperature is 800 - 950 °C; the preset first growth pressure is 60 - 80 Torr; the preset second growth pressure is 80 - 120 Torr; the preset third growth pressure is 90 - 130 Torr; the preset first growth time is 1.5 - 2.5 h; the preset second growth time is 4 h.

[0038] For example, a preset growth hydrogen flow rate (300 - 500 sccm) is introduced into the MPCVD system to maintain the atomic hydrogen concentration in the plasma. The growth process is divided into three stages. In the first stage, a preset first methane gas flow rate (3% - 5% of the preset hydrogen flow rate for plasma ignition, specifically 0.9 sccm - 6 sccm) is introduced. Based on the preset first growth power (3000 - 5000 W), the preset first growth temperature (400 - 600 °C), and the preset first growth pressure (60 - 80 Torr), combined with the preset first growth time (1.5 - 2.5 h), a preliminary growth promotion operation is carried out. The lower methane flow rate, power, temperature, and pressure are conducive to initiating the nucleation and preliminary growth of nanoscale diamond in the gaps between diamond particles. In the second stage, the methane gas flow rate is adjusted to the preset second methane gas flow rate (9 - 15 sccm), the power is adjusted to the preset second growth power (4000 - 7000 W), the temperature is adjusted to the preset second growth temperature (700 - 800 °C), and the pressure is adjusted to the preset second growth pressure (80 - 120 Torr) to grow the substrate for a preset second growth time (4 h). The increased methane flow rate, power, temperature, and pressure accelerate the growth of nanoscale diamond, making it gradually larger and contacting and connecting with diamond particles. In the third stage, the hydrogen and methane gas flow rates are kept unchanged, the power is adjusted to the preset third growth power (5000 - 8000 W), the temperature is adjusted to the preset third growth temperature (800 - 950 °C), and the pressure is adjusted to the preset third growth pressure (90 - 130 Torr) to grow the substrate for a preset second growth time (4 h). The further increased power, temperature, and pressure enable the nanoscale diamond to be tightly connected to the diamond particles and grow together, forming a dense and uniform rough thick diamond film. Thus, by optimizing the gas flow rate, power, temperature, and pressure parameters in stages, rapid filling and connection of the gaps between diamond particles are achieved, a dense and uniform rough thick diamond film is prepared, and the preparation speed is improved.

[0039] Specifically, in step S4, the rough thick diamond film is polished to obtain a thick diamond film with a smooth surface, including: Using laser polishing technology, the rough thick diamond film is initially polished to obtain a thick diamond film after initial polishing; Using mechanical polishing technology, the thick diamond film after initial polishing is finely polished to obtain a thick diamond film with a smooth surface.

[0040] In step S4, the rough thick diamond film is initially polished using laser polishing technology. Laser polishing achieves material removal by interacting with the material through a high-energy laser beam, and is suitable for removing surface unevenness or flattening the surface. This step can reduce the surface roughness of the film and lay the foundation for subsequent polishing. As a non-contact processing method, laser polishing avoids the influence of mechanical stress on the film structure. For diamond materials, laser polishing has advantages in removal efficiency. If ultraviolet laser polishing technology is used for polishing, an ultraviolet laser with a wavelength of 248nm can be used, the laser energy is 200mJ~400mJ, the laser power is 100~500W, and the laser action time is 1~5μs. The surface of the rough thick diamond film is scanned with an ultraviolet laser to remove the macroscopic unevenness of the surface of the rough thick diamond film.

[0041] Mechanical polishing technology is used to fine-polish the thick diamond film after laser initial polishing. Mechanical polishing usually uses abrasives and polishing pads to remove tiny protrusions on the material surface through mechanical grinding and friction to obtain a high surface finish. On the basis of reducing the roughness by laser initial polishing, mechanical polishing can trim the film surface, eliminate the microtexture or heat-affected area that may be left by laser polishing, and achieve the surface smoothness requirement. In the early stage of mechanical polishing, larger particle size polishing powders of W28 or W40 can be used to quickly remove the rough parts of the surface. As the polished surface gradually becomes smooth, it should be gradually transitioned to small particle size polishing powders in the range of W0.5 to W1 to ensure that the surface roughness is further reduced without introducing new scratches.

[0042] By combining the processing capabilities of laser polishing and mechanical polishing, a rough thick diamond film can be transformed into a thick diamond film with a smooth surface, meeting the surface quality requirements of the diamond film.

[0043] As can be seen from the above, in the method for rapidly preparing a thick diamond film, diamond particles are evenly spread on a substrate by using absolute ethanol. The substrate covered with diamond particles is placed on a sample stage inside an MPCVD system. Hydrogen is introduced and the temperature inside the MPCVD system is slowly raised to a preset cleaning temperature to perform plasma cleaning on the surface of the substrate covered with diamond particles. Based on a preset growth hydrogen flow rate, a preset methane gas flow rate, a preset growth power, a preset growth temperature, and a preset growth pressure, through a segmented growth method, the growth of nanoscale diamonds is promoted in the gaps between the diamond particles on the surface of the substrate covered with diamond particles, so as to connect the diamond particles through the nanoscale diamonds, obtaining a dense and uniform rough thick diamond film. The rough thick diamond film is polished to obtain a thick diamond film with a smooth surface. Thus, through the segmented growth method, using hydrogen and methane gas, a thick diamond film is grown on a substrate covered with a layer of diamond particles, solving the problems such as slow diamond growth rate existing in the existing diamond preparation methods, and improving the preparation efficiency of the diamond film by means of presetting diamond particles and rapidly filling and connecting in their gaps.

[0044] In this document, relational terms such as first and second are used solely to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations.

[0045] The above description is only for the embodiments of the present application and is not intended to limit the protection scope of the present application. For those skilled in the art, various changes and modifications can be made to the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included within the protection scope of the present application.

Claims

1. A method for rapidly preparing a thick diamond film, which is used for rapidly preparing a thick diamond film, and is characterized in that Including the steps: Uniformly cover diamond particles on a substrate with absolute ethanol; Place the substrate covered with diamond particles on a sample stage inside an MPCVD system, introduce hydrogen, and slowly heat the inside of the MPCVD system to a preset cleaning temperature to perform plasma cleaning on the surface of the substrate covered with diamond particles; Based on a preset growth hydrogen flow rate, a preset methane gas flow rate, a preset growth power, a preset growth temperature, and a preset growth pressure, promote the growth of nanoscale diamond between the gaps of the diamond particles on the surface of the substrate covered with diamond particles by means of segmented growth, so as to connect the diamond particles through the nanoscale diamond and obtain a dense and uniform rough thick diamond film; Polish the rough thick diamond film to obtain a thick diamond film with a smooth surface.

2. The high-speed preparation method of thick diamond film according to claim 1, characterized in that Uniformly covering diamond particles on a substrate with absolute ethanol includes: Place the diamond particles in absolute ethanol, a mixed solution composed of concentrated sulfuric acid and concentrated nitric acid, and absolute ethanol in sequence for ultrasonic cleaning to obtain the cleaned diamond particles; Disperse the cleaned diamond particles in absolute ethanol; Apply the absolute ethanol containing the cleaned diamond particles on the substrate so that the cleaned diamond particles are uniformly covered on the substrate.

3. The high-speed preparation method of thick diamond film according to claim 2, characterized in that, The ultrasonic cleaning frequency for ultrasonic cleaning in absolute ethanol is 35 - 60 kHz, the ultrasonic cleaning time is 5 - 15 min, the ultrasonic cleaning temperature is 50 - 70 °C, and the ultrasonic cleaning power is 500 - 700 W.

4. The high-speed preparation method of thick diamond film according to claim 2, wherein, The mixed solution is prepared by mixing concentrated sulfuric acid and concentrated nitric acid solution in a ratio of 1:1; wherein, the concentration of concentrated sulfuric acid is 98%, and the concentration of concentrated nitric acid is 60% - 65%; the ultrasonic cleaning time for ultrasonic cleaning in the mixed solution is 5 - 15 min, the ultrasonic cleaning temperature is 50 - 70 °C, and the ultrasonic cleaning power is 500 - 700 W.

5. The high-speed preparation method of thick diamond film according to claim 1, characterized in that Placing the substrate covered with diamond particles on a sample stage inside an MPCVD system, introducing hydrogen, and slowly heating the inside of the MPCVD system to a preset cleaning temperature to perform plasma cleaning on the surface of the substrate covered with diamond particles includes: Wipe the sample stage of the MPCVD system with absolute ethanol to prevent the influence of impurities; Place the substrate covered with diamond particles on the wiped sample stage; Based on a preset breakdown pressure, introduce hydrogen with a preset breakdown hydrogen flow rate into the MPCVD system to perform breakdown; After breakdown is completed, adjust the MPCVD system to a preset cleaning power, and slowly heat the inside of the MPCVD system to a preset cleaning temperature to perform plasma cleaning on the surface of the substrate covered with diamond particles.

6. The high-speed preparation method of thick diamond film according to claim 5, characterized in that The preset breakdown pressure is 2 - 6 Torr; the preset breakdown hydrogen flow rate is 30 - 120 sccm; the preset cleaning power is 500 - 1000 W; the preset cleaning temperature is 450 - 500 °C.

7. The high-speed preparation method of thick diamond film according to claim 1, characterized in that, The preset methane gas flow rate includes a preset first methane gas flow rate and a preset second methane gas flow rate; the preset growth power includes a preset first growth power, a preset second growth power, and a preset third growth power; the preset growth temperature includes a preset first growth temperature, a preset second growth temperature, and a preset third growth temperature; the preset growth pressure includes a preset first growth pressure, a preset second growth pressure, and a preset third growth pressure.

8. The high-speed preparation method of thick diamond film according to claim 7, characterized in that, Based on the preset growth hydrogen gas flow rate, the preset methane gas flow rate, the preset growth power, the preset growth temperature, and the preset growth pressure, through a segmented growth method, promote the growth of nanoscale diamond between the gaps of each of the diamond particles on the surface of the substrate covered with diamond particles, so as to connect each of the diamond particles through the nanoscale diamond, and obtain a dense and uniform rough thick diamond film, including: Introduce methane gas with the preset first methane gas flow rate into the MPCVD system, and based on the preset first growth power, the preset first growth temperature, and the preset first growth pressure, combined with a preset first growth time, perform a preliminary promotion growth operation to start the growth of nanoscale diamond between the gaps of each of the diamond particles on the surface of the substrate covered with diamond particles; Adjust the flow rate of hydrogen gas to the preset growth hydrogen gas flow rate, adjust the flow rate of methane gas to the preset second methane gas flow rate, adjust the power inside the MPCVD system to the preset second growth power, adjust the temperature inside the MPCVD system to the preset second growth temperature, and adjust the pressure inside the MPCVD system to the preset second growth pressure, so as to perform a first-stage growth on the substrate for a preset second growth time, so that the nanoscale diamond between the gaps of each of the diamond particles gradually becomes larger and gradually contacts and connects with each of the diamond particles during the enlargement process; After the preset second growth time, keep the flow rates of hydrogen gas and methane gas unchanged, adjust the power inside the MPCVD system to the preset third growth power, adjust the temperature inside the MPCVD system to the preset third growth temperature, and adjust the pressure inside the MPCVD system to the preset third growth pressure, so as to perform a second-stage growth on the substrate for the preset second growth time, so that the nanoscale diamond between the gaps of each of the diamond particles is tightly connected to and co-grows with each of the diamond particles; After the second-stage growth is completed, slowly adjust the power inside the MPCVD system to zero. At the same time, slowly reduce the temperature and pressure inside the MPCVD system to room temperature and room pressure respectively, and during the temperature reduction process, slowly reduce the flow rates of hydrogen gas and methane gas to zero. After the substrate covered with diamond particles is adjusted to room temperature, a dense and uniform rough thick diamond film is prepared on the surface of the substrate covered with diamond particles.

9. The high-speed preparation method of thick diamond film according to claim 8, characterized in that, The preset hydrogen growth flow rate is 300 - 500 sccm; the preset first methane gas flow rate is 0.9 sccm - 6 sccm; the preset second methane gas flow rate is 9 - 15 sccm; the preset first growth power is 3000 - 5000 W; the preset second growth power is 4000 - 7000 W; the preset third growth power is 5000 - 8000 W; the preset first growth temperature is 400 - 600 °C; the preset second growth temperature is 700 - 800 °C; the preset third growth temperature is 800 - 950 °C; the preset first growth pressure is 60 - 80 Torr; the preset second growth pressure is 80 - 120 Torr; the preset third growth pressure is 90 - 130 Torr; the preset first growth time is 1.5 - 2.5 h; the preset second growth time is 4 h.

10. The high-speed preparation method of thick diamond film according to claim 1, characterized in that, Polish the rough thick diamond film to obtain a thick diamond film with a smooth surface, including: Use laser polishing technology to perform primary polishing on the rough thick diamond film to obtain a thick diamond film after primary polishing; Use mechanical polishing technology to perform fine polishing on the thick diamond film after primary polishing to obtain a thick diamond film with a smooth surface.

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