A high-speed preparation method for thick diamond films

Abstract

The present application belongs to the technical field of diamond preparation and discloses a method for high-speed preparation of thick diamond films. The method comprises: using anhydrous ethanol to evenly spread diamond particles on a substrate, placing the substrate on a sample stage inside an MPCVD system, introducing hydrogen and slowly heating the MPCVD system to a preset cleaning temperature to perform plasma cleaning on the surface of the substrate; based on the growth hydrogen flow rate, methane gas flow rate, growth power, growth temperature and growth gas pressure, a segmented growth method is used to promote the growth of nano-scale diamonds between the gaps between the diamond particles on the surface of the substrate to connect the diamond particles, thereby 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; and a thick diamond film is grown on the substrate covered with a layer of diamond particles using hydrogen and methane gases through the segmented growth method, thereby improving the efficiency of high-speed preparation of thick diamond films.

Description

Technical Field

[0001] The present application relates to the technical field of diamond preparation, and in particular to a method for high-speed preparation of thick diamond films. Background Art

[0002] With the rapid development of modern semiconductor technology, especially the evolution of power semiconductor devices toward high frequency, high temperature, and high power, traditional silicon-based materials have gradually become unable to meet performance requirements. Third-generation semiconductor materials such as gallium nitride (GaN) and aluminum nitride (AlN) have shown great potential in high-frequency and high-power applications due to their excellent properties such as wide bandgap, high breakdown electric field, and high electron mobility. However, as the power density of GaN devices continues to increase, the heat they generate increases dramatically, and heat dissipation has become a key bottleneck limiting further performance breakthroughs. Effective heat dissipation solutions are crucial to improving the reliability and power output of GaN devices.

[0003] Diamond, a material with exceptionally high thermal conductivity (far exceeding that of metals and traditional semiconductor materials), high hardness, high insulation, and a low coefficient of thermal expansion, is considered an ideal choice for solving the heat dissipation problems of high-power devices. It holds particular promise for thermal management in third-generation semiconductor devices, such as GaN. Integrating diamond with GaN devices significantly reduces the device's thermal resistance, thereby improving its power density and operational stability.

[0004] However, existing diamond material preparation technologies, particularly those used to produce thick diamond films, still face several challenges. For example, the growth rate of single-crystal diamond is very slow, typically only a few microns per hour, and large-scale production is difficult, resulting in high production costs. While polycrystalline diamond is relatively easy to produce in large sizes, it also faces challenges such as slow nucleation rates and relatively slow growth rates (typically a few to tens of microns per hour). These shortcomings make it difficult to efficiently and cost-effectively produce high-quality thick diamond films, thus limiting the widespread application of diamond in the heat dissipation of high-power semiconductor devices.

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

[0006] The purpose of this application is to provide a high-speed preparation method for thick diamond films. Through a segmented growth method, hydrogen and methane gases are used to grow a thick diamond film on a substrate covered with a layer of diamond particles, thereby solving the problems of slow diamond growth rate in existing diamond preparation methods. The rapid preparation of diamond films is achieved by pre-setting diamond particles and quickly filling and connecting the gaps between them.

[0007] In a first aspect, the present application provides a method for rapidly preparing a thick diamond film at high speed, comprising the steps of:

[0008] Use anhydrous ethanol to evenly spread the diamond particles on the substrate;

[0009] Placing the substrate covered with diamond particles on a sample stage inside the MPCVD system, introducing hydrogen gas, and slowly heating the MPCVD system to a preset cleaning temperature to perform plasma cleaning on the surface of the substrate covered with diamond particles;

[0010] 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 gas pressure, a segmented growth method is used to promote the growth of nano-diamonds between the diamond particles on the surface of the substrate covered with diamond particles, so as to connect the diamond particles through the nano-diamonds to obtain a dense and uniform rough thick diamond film;

[0011] The rough thick diamond film is polished to obtain a thick diamond film with a smooth surface.

[0012] The high-speed preparation method for thick diamond films provided in the present application can realize the rapid preparation of thick diamond films. Through the segmented growth method, hydrogen and methane gases are used to grow a thick diamond film on a substrate covered with a layer of diamond particles, thereby solving the problems of slow diamond growth rate in existing diamond preparation methods. The preparation efficiency of diamond films is improved by pre-setting diamond particles and quickly filling and connecting the gaps between them.

[0013] Optionally, the diamond particles are evenly spread on the substrate using anhydrous ethanol, comprising:

[0014] placing the diamond particles in anhydrous ethanol, a mixture of concentrated sulfuric acid and concentrated nitric acid, and anhydrous ethanol in sequence for ultrasonic cleaning to obtain cleaned diamond particles;

[0015] Dispersing the cleaned diamond particles in anhydrous ethanol;

[0016] The anhydrous ethanol containing the cleaned diamond particles is applied on the substrate so that the cleaned diamond particles are evenly spread on the substrate.

[0017] The high-speed preparation method for thick diamond films provided in this application can realize the rapid preparation of thick diamond films. By performing multi-step cleaning and dispersion treatment on diamond particles, the problems of surface contamination and agglomeration of diamond particles are solved, thereby achieving uniform distribution of particles on the substrate.

[0018] Optionally, the ultrasonic cleaning frequency 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.

[0019] Optionally, the mixed solution is prepared by mixing concentrated sulfuric acid and concentrated nitric acid solutions 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 minutes, the ultrasonic cleaning temperature is 50-70°C, and the ultrasonic cleaning power is 500-700W.

[0020] Optionally, placing a substrate covered with diamond particles on a sample stage inside an MPCVD system, introducing hydrogen gas, and slowly heating the MPCVD system to a preset cleaning temperature to perform plasma cleaning on the surface of the substrate covered with diamond particles, comprising:

[0021] Use anhydrous ethanol to wipe the sample stage of the MPCVD system to prevent the influence of impurities;

[0022] Place the substrate covered with diamond particles on the wiped sample stage;

[0023] Based on a preset ignition gas pressure, introducing a preset ignition hydrogen flow rate of hydrogen into the MPCVD system to perform ignition;

[0024] After ignition is completed, the MPCVD system is adjusted to a preset cleaning power, 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.

[0025] Optionally, the preset ignition gas pressure is 2-6 Torr; the preset ignition hydrogen flow rate is 30-120 sccm; the preset cleaning power is 500-1000 W; and the preset cleaning temperature is 450-500° C.

[0026] 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.

[0027] 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 gas pressure, a segmented growth method is used to promote the growth of nano-scale diamonds 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 nano-scale diamonds to obtain a dense and uniform rough thick diamond film, comprising:

[0028] introducing methane gas at a preset first methane gas flow rate into the MPCVD system, and performing a preliminary growth promotion operation based on the preset first growth power, the preset first growth temperature, and the preset first growth pressure, in combination with a preset first growth time, so that nano-diamonds begin to grow between the gaps between the diamond particles on the surface of the substrate covered with diamond particles;

[0029] adjusting the flow rate of hydrogen to a preset growth hydrogen flow rate, adjusting the flow rate of methane gas to the preset second methane gas flow rate, adjusting the power within the MPCVD system to the preset second growth power, adjusting the temperature within the MPCVD system to the preset second growth temperature, and adjusting the gas pressure within the MPCVD system to the preset second growth pressure, so as to perform a phased growth on the substrate during a preset second growth time, causing the nano-diamonds between the gaps between the diamond particles to gradually grow and gradually contact and connect with the diamond particles during the growth process;

[0030] After the preset second growth time, the flow rates of hydrogen and methane gases are maintained unchanged, the power within the MPCVD system is adjusted to the preset third growth power, the temperature within the MPCVD system is adjusted to the preset third growth temperature, and the gas pressure within the MPCVD system is adjusted to the preset third growth pressure, so as to perform two-stage growth on the substrate during the preset second growth time, so that the nano-diamonds between the gaps between the diamond particles are tightly connected with the diamond particles and grow together;

[0031] After completing the second-stage growth, the power inside the MPCVD system is slowly adjusted to zero. At the same time, the temperature and air pressure inside the MPCVD system are slowly lowered to room temperature and room pressure, respectively. During the cooling process, the flow rates of hydrogen and methane gases are slowly reduced 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.

[0032] The high-speed preparation method for thick diamond films provided in this application can realize the rapid preparation of thick diamond films. Through the segmented growth method, the growth process of diamond in the gaps between particles is effectively controlled, and the effective connection between nano-scale diamonds and initial diamond particles is achieved, and finally a diamond film with the required density and uniformity is obtained, thereby improving the preparation efficiency of the diamond film.

[0033] Optionally, the preset growth hydrogen flow rate is 300~500sccm; the preset first methane gas flow rate is 0.9sccm~6sccm; the preset second methane gas flow rate is 9~15sccm; the preset first growth power is 3000-5000W; the preset second growth power is 4000~7000W; the preset third growth power is 5000~8000W; the preset first growth temperature is 400~600℃; the preset second growth temperature is 700~800℃; the preset third growth temperature is 800~950℃; the preset first growth pressure is 60~80Torr; the preset second growth pressure is 80~120Torr; the preset third growth pressure is 90~130Torr; the preset first growth time is 1.5~2.5h; the preset second growth time is 4h.

[0034] Optionally, polishing the rough thick diamond film to obtain a thick diamond film with a smooth surface comprises:

[0035] Performing preliminary polishing on the rough thick diamond film using a laser polishing technique to obtain a preliminary polished thick diamond film;

[0036] The thick diamond film after the initial polishing is finely polished by using a mechanical polishing technology to obtain a thick diamond film with a smooth surface.

[0037] Beneficial effects: The high-speed preparation method for thick diamond films provided in the present application uses hydrogen and methane gases through a segmented growth method to grow a thick diamond film on a substrate covered with a layer of diamond particles, thereby solving the problems of slow diamond growth rate in existing diamond preparation methods. The preparation efficiency of the diamond film is improved by pre-setting diamond particles and quickly filling and connecting the gaps between them. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 Flowchart of the high-speed preparation method of thick diamond film provided in an embodiment of the present application. DETAILED DESCRIPTION

[0039] The technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all of the embodiments. The components of the embodiments of the present application generally 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 the present application provided in the drawings is not intended to limit the scope of the application for protection, but merely represents the selected embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without making creative work fall within the scope of protection of the present application.

[0040] It should be noted that similar reference numerals and letters represent similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined or explained in subsequent drawings. At the same time, in the description of this application, the terms "first", "second", etc. are only used to distinguish the description and should not be understood as indicating or implying relative importance.

[0041] Please refer to Figure 1 , Figure 1 A high-speed method for preparing a thick diamond film in some embodiments of the present application is provided, which is used to quickly prepare a thick diamond film, comprising:

[0042] Step S1, using anhydrous ethanol to evenly spread diamond particles on the substrate;

[0043] Step S2, placing the substrate covered with diamond particles on a sample stage inside the MPCVD system, introducing hydrogen gas, and slowly heating the MPCVD system to a preset cleaning temperature to perform plasma cleaning on the surface of the substrate covered with diamond particles;

[0044] 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, promoting the growth of nano-diamonds in the gaps between the diamond particles on the surface of the substrate covered with diamond particles by a segmented growth method, so as to connect the diamond particles through the nano-diamonds to obtain a dense and uniform rough thick diamond film;

[0045] Step S4, polishing the rough thick diamond film to obtain a thick diamond film with a smooth surface.

[0046] This high-speed method for preparing thick diamond films uses a segmented growth method, utilizing hydrogen and methane gases, to grow a thick diamond film on a substrate covered with a layer of diamond particles. This method addresses the shortcomings of existing diamond preparation methods, such as slow diamond growth rate, and improves the efficiency of diamond film preparation by pre-setting diamond particles and quickly filling and connecting their gaps.

[0047] Specifically, in step S1, diamond particles are evenly spread on the substrate using anhydrous ethanol, including:

[0048] placing the diamond particles in anhydrous ethanol, a mixture of concentrated sulfuric acid and concentrated nitric acid, and anhydrous ethanol in sequence for ultrasonic cleaning to obtain cleaned diamond particles;

[0049] The cleaned diamond particles are dispersed in anhydrous ethanol;

[0050] Anhydrous ethanol containing cleaned diamond particles is applied to the substrate so that the cleaned diamond particles are evenly spread on the substrate.

[0051] In step S1, diamond particles are ultrasonically cleaned in anhydrous ethanol, a mixture of concentrated sulfuric acid and concentrated nitric acid, and anhydrous ethanol, sequentially, to remove contaminants from the particle surface, reduce van der Waals forces between the particles, and thereby reduce the possibility of particle agglomeration. The cleaned particles are dispersed in anhydrous ethanol, and the dispersion of the particles is maintained by the dispersing effect of the liquid. The anhydrous ethanol containing the dispersed particles is applied to a substrate. As the ethanol evaporates, the particles are evenly deposited on the substrate surface. This forms a uniformly distributed diamond seed layer on the substrate, providing uniform nucleation sites for subsequent diamond film growth, promoting dense and uniform growth of the diamond film, and avoiding film defects and performance degradation caused by uneven seed distribution. The substrate may comprise a nitride substrate (such as gallium nitride or aluminum nitride) or a molybdenum substrate.

[0052] Among them, when using anhydrous ethanol to ultrasonically clean diamond particles, the ultrasonic cleaning frequency of the ultrasonic cleaning in anhydrous ethanol is 35~60kHz, the ultrasonic cleaning time is 5~15min, the ultrasonic cleaning temperature is 50~70℃, and the ultrasonic cleaning power is 500~700W.

[0053] When using a mixed liquid to ultrasonically clean diamond particles, the mixed liquid is prepared by mixing concentrated sulfuric acid and concentrated nitric acid solutions 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 liquid is 5-15 minutes, the ultrasonic cleaning temperature is 50-70°C, and the ultrasonic cleaning power is 500-700W.

[0054] Specifically, in step S2, a substrate covered with diamond particles is placed on a sample stage inside the 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, including:

[0055] Use anhydrous ethanol to wipe the sample stage of the MPCVD system to prevent the influence of impurities;

[0056] Place the substrate covered with diamond particles on the wiped sample stage;

[0057] Based on the preset ignition gas pressure, hydrogen gas with a preset ignition hydrogen flow rate is introduced into the MPCVD system to perform ignition;

[0058] After ignition is completed, the MPCVD system is adjusted to a preset cleaning power, 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.

[0059] In step S2, the sample stage is wiped with anhydrous ethanol to remove impurities on the stage to prevent them from affecting the cleanliness of the substrate or diamond particles during the cleaning process. The substrate covered with diamond particles is accurately placed on the clean sample stage. Hydrogen gas is introduced into the MPCVD system, and the gas pressure (preset ignition pressure) and hydrogen flow (preset ignition hydrogen flow) within the MPCVD system chamber are controlled to achieve preset ignition conditions, promoting a glow discharge of the hydrogen gas and forming a plasma. After successful ignition of the plasma, the applied power (preset cleaning power) is adjusted to maintain the plasma discharge intensity, and the temperature within the MPCVD system is slowly increased to a preset cleaning temperature. At the preset cleaning temperature, the highly active particles in the hydrogen plasma effectively react with impurities such as organic matter and oxides on the substrate surface and diamond particles, converting them into gaseous species or stripping them through physical sputtering, thereby cleaning the substrate and diamond particle surfaces. Slowly increasing the temperature helps evenly heat the substrate and reduces thermal stress. By controlling the cleaning power and temperature, impurities can be effectively removed while avoiding damage to the diamond particles or substrate, providing a clean surface for subsequent diamond growth. The purity of the hydrogen gas introduced must be no less than 7N.

[0060] Among them, the preset ignition gas pressure is 2~6Torr; the preset ignition hydrogen flow rate is 30~120sccm; the preset cleaning power is 500~1000W; and the preset cleaning temperature is 450~500℃.

[0061] For example, a substrate covered with diamond particles is placed on the sample stage of the MPCVD system. Hydrogen gas is introduced into the MPCVD system, and the ignition pressure and hydrogen flow rate are set to 4 Torr and 80 sccm, respectively. After ignition, the cleaning power is set to 750W, and the system temperature is slowly raised to 480°C to perform plasma cleaning on the substrate surface.

[0062] 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.

[0063] 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 gas pressure, a segmented growth method is used to promote the growth of nano-diamonds between 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 nano-diamonds to obtain a dense and uniform rough thick diamond film, including:

[0064] introducing methane gas at a preset first methane gas flow rate into the MPCVD system, and performing a preliminary growth promotion operation based on a preset first growth power, a preset first growth temperature, and a preset first growth pressure, in combination with a preset first growth time, so that nano-diamonds begin to grow between the gaps between the diamond particles on the surface of the substrate covered with diamond particles;

[0065] adjusting the flow rate of hydrogen gas to a preset growth hydrogen flow rate, adjusting the flow rate of methane gas to a preset second methane gas flow rate, adjusting the power within the MPCVD system to a preset second growth power, adjusting the temperature within the MPCVD system to a preset second growth temperature, and adjusting the gas pressure within the MPCVD system to a preset second growth pressure, so as to perform a first-stage growth on the substrate during a preset second growth time, causing the nano-diamonds between the gaps between the diamond particles to gradually grow and gradually contact and connect with the diamond particles during the growth process;

[0066] After the preset second growth time, the flow rates of hydrogen and methane gases are maintained unchanged, the power within the MPCVD system is adjusted to a preset third growth power, the temperature within the MPCVD system is adjusted to a preset third growth temperature, and the gas pressure within the MPCVD system is adjusted to a preset third growth pressure, so as to perform a two-stage growth on the substrate during the preset second growth time, so that the nano-diamonds between the gaps between the diamond particles are tightly connected to the diamond particles and grow together;

[0067] After completing the second-stage growth, the power inside the MPCVD system is slowly adjusted to zero. At the same time, the temperature and air pressure inside the MPCVD system are slowly lowered to room temperature and room pressure respectively. During the cooling process, the flow rates of hydrogen and methane gases are slowly reduced 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.

[0068] In step S3, the process parameters of the MPCVD system are controlled in stages to precisely control the growth of nanodiamonds within the interstices between diamond particles. First, in the initial growth promotion stage, a low methane gas flow rate (methane purity not less than 6N) and specific growth parameters (i.e., 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 used to induce preferential nucleation and initial growth of nanodiamonds within the tiny interstices between diamond particles. The key to this stage is controlling the nucleation density and initial growth rate, laying the foundation for subsequent filling and bonding. Next, the first growth stage begins. 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), as well as the MPCVD system power, temperature, and pressure (i.e., a preset second growth power, a preset second growth temperature, and a preset second growth pressure), the growth rate is increased, prompting the rapid growth of nanodiamonds, filling the interstices between the particles and initiating contact with adjacent diamond particles. Parameter adjustments are designed to optimize the growth direction and morphology of the nanodiamonds, enabling them to effectively bridge the grains. Subsequently, during the second growth stage, the MPCVD system's power, temperature, and pressure (i.e., the preset third growth power, temperature, and pressure) are further adjusted while maintaining the gas flow rate to provide a more favorable growth environment. This strengthens the bond between the nanodiamonds and the diamond grains, promoting their coordinated growth and forming a continuous, dense diamond film structure. After the second growth stage, the system parameters (power, temperature, and pressure) and gas flow rate are gradually reduced to achieve a cooling process, reducing internal stress in the film and preventing defects such as cracks in the diamond layer on the substrate surface due to thermal stress, which could affect quality. Ultimately, a dense, uniform, and rough, thick diamond film is obtained. This segmented growth strategy overcomes the difficulty of simultaneously optimizing nucleation, filling, and bonding under a single growth condition, thereby improving the density and uniformity of the film.

[0069] Among them, the preset growth hydrogen flow rate is 300~500sccm; the preset first methane gas flow rate is 0.9sccm~6sccm (specifically 3%~5% of the preset ignition hydrogen flow rate); the preset second methane gas flow rate is 9~15sccm; the preset first growth power is 3000-5000W; the preset second growth power is 4000~7000W; the preset third growth power is 5000~8000W; the preset first growth temperature is 400~600℃; the preset second growth temperature is 700~800℃; the preset third growth temperature is 800~950℃; the preset first growth pressure is 60~80Torr; the preset second growth pressure is 80~120Torr; the preset third growth pressure is 90~130Torr; the preset first growth time is 1.5~2.5h; the preset second growth time is 4h.

[0070] 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 ignition hydrogen flow rate, specifically 0.9 sccm-6 sccm) is introduced. Based on the preset first growth power (3000-5000W), the preset first growth temperature (400-600°C) and the preset first growth pressure (60-80 Torr), combined with the preset first growth time (1.5-2.5h), a preliminary growth promotion operation is performed. Lower methane flow rate, power, temperature and pressure are conducive to initiating the nucleation and initial growth of nano-diamonds in the gaps between diamond particles. In the second stage, the methane gas flow rate is adjusted to a preset second methane gas flow rate (9-15 sccm), the power is adjusted to a preset second growth power (4000-7000 W), the temperature is adjusted to a preset second growth temperature (700-800°C), and the pressure is adjusted to a preset second growth pressure (80-120 Torr) to grow on the substrate for a preset second growth time (4 hours). The increased methane flow rate, power, temperature, and pressure accelerate the growth of nano-diamonds, causing them to gradually grow larger and contact and connect with the diamond particles. In the third stage, the hydrogen and methane gas flow rates are maintained unchanged, the power is adjusted to a preset third growth power (5000-8000 W), the temperature is adjusted to a preset third growth temperature (800-950°C), and the pressure is adjusted to a preset third growth pressure (90-130 Torr) to grow on the substrate for a preset second growth time (4 hours). Further increased power, temperature, and pressure cause the nano-diamonds to closely connect with the diamond particles and grow together, forming a dense and uniform rough thick diamond film. Therefore, by optimizing the gas flow, power, temperature and pressure parameters in stages, the gaps between diamond particles can be quickly filled and connected, and a dense and uniform rough thick diamond film can be prepared, thereby improving the preparation speed.

[0071] Specifically, in step S4, the rough thick diamond film is polished to obtain a thick diamond film with a smooth surface, comprising:

[0072] The rough thick diamond film is initially polished by using laser polishing technology to obtain a thick diamond film after initial polishing;

[0073] The thick diamond film after initial polishing is finely polished by using mechanical polishing technology to obtain a thick diamond film with a smooth surface.

[0074] In step S4, the rough thick diamond film is initially polished using laser polishing technology. Laser polishing achieves material removal through the interaction of a high-energy laser beam with the material, 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 on the surface of the rough thick diamond film.

[0075] Mechanical polishing technology is used to fine-polish the thick diamond film after the initial laser polishing. Mechanical polishing usually uses abrasives in combination with polishing pads to remove tiny bumps on the material surface through mechanical grinding and friction to achieve a high surface finish. Based on the roughness reduction achieved by the initial laser polishing, mechanical polishing can trim the film surface, eliminate the micro-textures or heat-affected areas that may be left by the laser polishing, and achieve the required surface smoothness. In the initial stage of mechanical polishing, larger particle size polishing powders such as W28 or W40 can be used to quickly remove rough parts of the surface. As the polished surface gradually becomes smooth, a gradual transition should be made to smaller 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.

[0076] 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.

[0077] As can be seen from the above, the high-speed preparation method of the thick diamond film is to uniformly spread diamond particles on the substrate by using anhydrous ethanol, place the substrate covered with diamond particles on the sample stage inside the MPCVD system, introduce hydrogen and slowly heat the MPCVD system to a preset cleaning temperature to perform plasma cleaning on the surface of the substrate covered with diamond particles, and promote the growth of each metal on the surface of the substrate covered with diamond particles through a segmented growth method 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. Nano-scale diamonds are grown between the gaps between diamond particles, and the diamond particles are connected by the nano-scale diamonds to obtain 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, a thick diamond film is grown on a substrate covered with a layer of diamond particles by a segmented growth method using hydrogen and methane gases, thereby solving the problem of slow diamond growth rate in existing diamond preparation methods. The preparation efficiency of the diamond film is improved by pre-setting diamond particles and quickly filling and connecting the gaps between them.

[0078] In this document, relational terms such as first and second, etc. are used merely to distinguish one entity or operation from another entity or operation, but do not necessarily require or imply any actual relationship or order between these entities or operations.

[0079] The above description is merely an embodiment of the present application and is not intended to limit the scope of protection of the present application. For those skilled in the art, various modifications and variations of the present application are possible. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present application shall be included in the scope of protection of the present application.

Claims

1. A high-speed preparation method for thick diamond films, for rapidly preparing thick diamond films, characterized in that: Including steps: Use anhydrous ethanol to evenly spread the diamond particles on the substrate; Placing the substrate covered with diamond particles on a sample stage inside the MPCVD system, introducing hydrogen gas, and slowly heating 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 gas pressure, a segmented growth method is used to promote the growth of nano-diamonds between the diamond particles on the surface of the substrate covered with diamond particles, so as to connect the diamond particles through the nano-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; 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; 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 gas pressure, a segmented growth method is used to promote the growth of nano-scale diamonds 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 nano-scale diamonds to obtain a dense and uniform rough thick diamond film, comprising: introducing methane gas at a preset first methane gas flow rate into the MPCVD system, and performing a preliminary growth promotion operation based on the preset first growth power, the preset first growth temperature, and the preset first growth pressure, in combination with a preset first growth time, so that nano-diamonds begin to grow between the gaps between the diamond particles on the surface of the substrate covered with diamond particles; adjusting the flow rate of hydrogen to a preset growth hydrogen flow rate, adjusting the flow rate of methane gas to the preset second methane gas flow rate, adjusting the power within the MPCVD system to the preset second growth power, adjusting the temperature within the MPCVD system to the preset second growth temperature, and adjusting the gas pressure within the MPCVD system to the preset second growth pressure, so as to perform a phased growth on the substrate during a preset second growth time, causing the nano-diamonds between the gaps between the diamond particles to gradually grow and gradually contact and connect with the diamond particles during the growth process; After the preset second growth time, the flow rates of hydrogen and methane gases are maintained unchanged, the power within the MPCVD system is adjusted to the preset third growth power, the temperature within the MPCVD system is adjusted to the preset third growth temperature, and the gas pressure within the MPCVD system is adjusted to the preset third growth pressure, so as to perform two-stage growth on the substrate during the preset second growth time, so that the nano-diamonds between the gaps between the diamond particles are tightly connected with the diamond particles and grow together; After completing the second-stage growth, the power inside the MPCVD system is slowly adjusted to zero. At the same time, the temperature and air pressure inside the MPCVD system are slowly lowered to room temperature and room pressure, respectively. During the cooling process, the flow rates of hydrogen and methane gases are slowly reduced 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.

2. The method for high-speed preparation of thick diamond films according to claim 1, wherein: Using anhydrous ethanol to evenly spread diamond particles on the substrate, including: placing the diamond particles in anhydrous ethanol, a mixture of concentrated sulfuric acid and concentrated nitric acid, and anhydrous ethanol in sequence for ultrasonic cleaning to obtain cleaned diamond particles; Dispersing the cleaned diamond particles in anhydrous ethanol; The anhydrous ethanol containing the cleaned diamond particles is applied on the substrate so that the cleaned diamond particles are evenly spread 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 anhydrous ethanol is 35~60kHz, the ultrasonic cleaning time is 5~15min, the ultrasonic cleaning temperature is 50~70℃, and the ultrasonic cleaning power is 500~700W.

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

5. The method for high-speed preparation of thick diamond films according to claim 1, wherein: Placing a substrate covered with diamond particles on a sample stage inside an MPCVD system, introducing hydrogen gas, and slowly heating the MPCVD system to a preset cleaning temperature to perform plasma cleaning on the surface of the substrate covered with diamond particles, including: Use anhydrous ethanol to wipe the sample stage of the MPCVD system to prevent the influence of impurities; Place the substrate covered with diamond particles on the wiped sample stage; Based on a preset ignition gas pressure, introducing a preset ignition hydrogen flow rate of hydrogen into the MPCVD system to perform ignition; After ignition is completed, the MPCVD system is adjusted to a preset cleaning power, 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.

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

7. The method for high-speed preparation of thick diamond films according to claim 1, wherein: The preset growth hydrogen flow rate is 300~500sccm; the preset first methane gas flow rate is 0.9sccm~6sccm; the preset second methane gas flow rate is 9~15sccm; the preset first growth power is 3000-5000W; the preset second growth power is 4000~7000W; the preset third growth power is 5000~8000W; the preset first growth temperature is 400~600℃; the preset second growth temperature is 700~800℃; the preset third growth temperature is 800~950℃; the preset first growth pressure is 60~80Torr; the preset second growth pressure is 80~120Torr; the preset third growth pressure is 90~130Torr; the preset first growth time is 1.5~2.5h; the preset second growth time is 4h.

8. The method for high-speed preparation of thick diamond films according to claim 1, wherein: Polishing the rough thick diamond film to obtain a thick diamond film with a smooth surface, comprising: Performing preliminary polishing on the rough thick diamond film using a laser polishing technique to obtain a preliminary polished thick diamond film; The thick diamond film after the initial polishing is finely polished by using a mechanical polishing technology to obtain a thick diamond film with a smooth surface.

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