CVD diamond film growth device and method

Abstract

The present invention discloses a CVD diamond film growth device and method. The device includes: a reaction chamber, which is a cylindrical cavity with multiple independently controlled gas inlets uniformly arranged along the circumference of the cavity; a mixture of hydrogen and carbon-containing gas, or pure hydrogen, is introduced into the gas inlet; a substrate, which serves as the diamond film growth base, and is fan-shaped and arranged in multiple layers in a ring; a hot wire array, which is composed of multiple hot wire assemblies, the number and shape of which are adapted to the substrate; the hot wire assemblies are fixed above the substrate in the reaction chamber; and a cooling unit, whose upper surface is in contact with the substrate and can be raised and lowered and rotated as a whole, for controlling the substrate temperature during the film growth process. The device and method of the present invention can not only solve the problem of carbon accumulation on the hot wires, but also ensure the uniformity of the temperature field and gas flow field on the substrate surface, effectively improving the quality of the diamond film.

Description

Technical Field

[0001] The present invention relates to the technical field of vacuum coating, and in particular to a CVD diamond film growth device and method. Background Art

[0002] Diamond is an allotrope of carbon with many physical and chemical properties that are unmatched by other materials, such as ultra-high hardness, high thermal conductivity, high optical transmittance and excellent electrical insulation. Therefore, it has many applications in mechanics, thermodynamics, optics and electronics. Research on the artificial preparation of diamond has always been a topic of concern.

[0003] There are many methods for preparing diamond films by chemical vapor deposition (CVD) under low pressure. Among them, hot filament CVD has the advantages of low equipment cost and simple operation. In addition, the growth area can be expanded by increasing the number of filaments. Therefore, it is one of the commonly used CVD methods. Hot filament chemical vapor deposition (HFCVD) is to install a filament made of refractory metal materials such as tungsten, molybdenum, tantalum, etc. horizontally on the upper part of the vacuum reaction chamber, and use a DC or AC power supply to heat the filament to above 2000℃; the substrate for depositing diamond is placed about 10mm below the hot filament, and its temperature is controlled within the range of 650-1200℃; carbon-containing gases such as CH4 and H2 are introduced into the vacuum chamber, and the mixed gas is ensured to flow to the substrate surface through the hot filament, and the pressure of the mixed reaction gas is controlled within 10 1 ~10 4 Within the Pa range, the high temperature of the filament causes the reactant gases to decompose and ionize, producing carbon-containing groups and atomic hydrogen. These interact to form graphite and diamond, with the vast majority of the product being graphite, with diamond accounting for only a small fraction. However, due to the selective etching of graphite by atomic hydrogen (the etching rate of atomic hydrogen on graphite is much higher than that on diamond), although the majority of the product is graphite, what remains is diamond. Diamond films typically grow at a rate of several to tens of microns per hour.

[0004] Existing methods for producing diamond films using hot filaments (especially those producing multi-layer diamond films with varying grain sizes) require the continuous flow of a mixture of carbon-containing gases and hydrogen into the reaction chamber. Furthermore, the carbon source concentration sometimes needs to be varied over time as the diamond film grows. High carbon source concentrations (greater than or equal to 5%) can lead to carbon accumulation on the filament surface, causing carbon poisoning and preventing the effective decomposition of process gases, thus affecting the diamond content in the deposited film. Furthermore, the growth of high-quality diamond films requires a suitable substrate temperature within a certain range, and growing diamond films over large areas requires a highly uniform substrate temperature distribution. Currently, most equipment struggles to maintain uniform temperature and gas flow fields on the substrate surface, significantly impacting the quality and scalability of diamond films.

[0005] Chinese patent CN208201117U discloses a CVD diamond coating device with multiple hot wire devices. The solution includes a cavity device, multiple hot wire devices, a main frame device, a cooling device and a driving device. The main frame device is arranged in the cavity device. The main frame device includes a frame and multiple loading platforms evenly distributed on the frame. The frame is connected to the output end of the driving device. The multiple loading platforms correspond to the multiple hot wire devices respectively, and the multiple loading platforms are all connected to the cooling device. This prior art is to perform diamond coating on products such as cutting tools, and adopts the design of multiple hot wire devices in order to improve the safety factor of the coating process and meet the requirements of different types of coated products in the same batch. However, this solution does not have technical measures to solve the carbon deposition of the filament, and it is difficult to maintain long-term operation.

[0006] Therefore, there is an urgent need for a CVD diamond film growth device and method that can not only solve the problem of carbon deposition on the hot wire, but also ensure the uniformity of the temperature field and air flow field on the substrate surface, effectively improve the quality of the diamond film and increase the size of the diamond film.

[0007] The information disclosed in this background technology section is only intended to enhance understanding of the overall background of the invention and should not be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art. Summary of the Invention

[0008] The purpose of the present invention is to provide a CVD diamond film growth device and method, which can not only solve the problem of carbon deposition on the hot wire, but also ensure the uniformity of the temperature field and air flow field on the substrate surface, and effectively improve the quality of the diamond film.

[0009] To achieve the above-mentioned objectives, according to a first aspect of the present invention, a CVD diamond film growth device is provided, comprising: a reaction chamber, which is a cylindrical cavity and has a plurality of independently controlled gas inlets uniformly arranged along the circumference of the cavity; a mixture of hydrogen and carbon-containing gas, or pure hydrogen, is introduced into the gas inlet; a substrate, which serves as a diamond film growth substrate, and the substrate is fan-shaped and is arranged in multiple shapes in a ring; a hot wire array, which is composed of a plurality of hot wire assemblies, and the number and shape of the hot wire assemblies are adapted to the substrate; the hot wire assembly is fixed above the substrate in the reaction chamber; and a cooling unit, the upper surface of which is in contact with the substrate and can be raised and lowered and rotated as a whole, for controlling the temperature of the substrate during the film growth process.

[0010] Furthermore, in the above technical solution, the reaction chamber can be provided with an even number of partitions greater than 2, each partition being separated by a gas distribution plate and corresponding to a gas inlet; during the continuous rotation of the cooling unit, within a preset period of time, the gas inlet of a certain partition and the opposite partition is switched from introducing a mixture of hydrogen and carbon-containing gas to introducing pure hydrogen.

[0011] Furthermore, in the above technical solution, when the number of even-numbered partitions is 8, the preset time can be 0.5 to 2 hours.

[0012] Furthermore, in the above technical solution, the hot wire assembly may include: an electrode, which is vertically arranged and fixed in the reaction chamber with the upper end exposed; a wire rack, which is a rectangular frame structure and is in contact with and fixed to the lower end of the electrode, and the wire rack is horizontally arranged and located above the substrate and spaced a certain distance apart; a hot wire, which is arranged parallel to the wire rack and is in a stretched state.

[0013] Furthermore, in the above technical solution, the heating wire may be a tantalum wire, a tungsten wire or a rhenium wire.

[0014] Furthermore, in the above technical solution, the end of the hot wire can be fixed to the wire rack by a straightening spring.

[0015] Furthermore, in the above technical solution, the cooling unit may include: a cold water workbench, which is an annular hollow cylindrical structure, into which circulating cooling water can be introduced; a substrate attached to the upper surface of the cold water workbench; a lifting rod, which is arranged at the bottom of the cooling workbench and is a hollow structure, in which a water inlet and outlet channel for cooling water is provided; the lifting rod is dynamically sealed to the reaction chamber; and a lifting and rotating mechanism, which drives the lifting rod and drives the cold water workbench to rotate or lift.

[0016] Furthermore, in the above technical solution, a spiral baffle is provided in the annular hollow columnar structure of the cold water workbench, and the cooling water flows in along the lower part of the cold water workbench on the water inlet pipe side, and flows out along the upper part of the cold water workbench on the water outlet pipe side through the spiral baffle.

[0017] Furthermore, in the above technical solution, the rotation speed provided by the lifting and rotating mechanism can be 0.1 to 5 rpm, and the lifting height provided can be 0 to 200 mm.

[0018] Furthermore, in the above technical solution, the distance between the hot wire and the inner wall of the upper cover of the reaction chamber can be greater than 50 mm, and the distance between the hot wire and the surface to be deposited of the substrate can be within 30 mm.

[0019] According to a second aspect of the present invention, the present invention provides a method for applying the aforementioned device, comprising the following steps: A. hydrogen and carbon-containing gas are mixed and then enter the reaction chamber through the gas inlet of each partition, and a fixed gas channel is formed through the fan-shaped space surrounded by the gas distribution plate, the substrate surface and the upper cover of the reaction chamber; B. In the fan-shaped space of each partition, the mixed gas is decomposed and dissociated under the high temperature of the hot wire at the corresponding position to generate carbon-containing groups and atomic hydrogen; C. Diamonds are deposited on the cyclically cooled and continuously rotating substrate through the interaction between the carbon-containing groups and atomic hydrogen; D. During the continuous rotation process, within a preset period of time, the gas inlets of a certain partition and the opposite partition are switched from passing a mixture of hydrogen and carbon-containing gas to passing pure hydrogen.

[0020] Furthermore, in the above technical solution, the carbon-containing gas may be methane, ethane, propane, butane, ethylene or acetylene, or methanol, ethanol or acetone in a vapor state.

[0021] Furthermore, in the above technical solution, the current passing through the hot wire can be 600A to 1500A; and the surface temperature of the hot wire can be controlled to be 2300°C to 2900°C.

[0022] Furthermore, in the above technical solution, the substrate temperature can be controlled between 650° C. and 1200° C. by circulating cooling water and adjusting the distance between the substrate surface and the hot wire.

[0023] Furthermore, in the above technical solution, the deposited diamond film layer can be two layers with different grain sizes that are grown sequentially and repeatedly.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] 1) The present invention uses multiple hot wire assemblies to form an annular array, which corresponds to the annular structure formed by the sector-shaped substrate. The substrate can rotate relative to the hot wire assemblies, so that the growth surface of the diamond substrate is heated more evenly. It is particularly suitable for the uniform thermal field requirements of industrial large-scale diamond production.

[0026] 2) The gas inlets are evenly arranged along the circumference of the reaction chamber and symmetrically distributed along the formation axis, which is conducive to uniform flow field and uniform gas concentration distribution;

[0027] 3) The uniform separation of the gas distribution plate forms relatively independent gas channels, which can make the concentration field and temperature field of the independent space of each hot wire assembly different, which is conducive to the combined application of different deposition processes and can adapt to the changes of deposition processes to the greatest extent. At the same time, it can also effectively increase the growth rate of the diamond film on the substrate surface and improve the gas utilization rate;

[0028] 4) By switching the gas inlet of a certain partition and the opposite partition from a mixture of hydrogen and carbon-containing gas to pure hydrogen within a preset period of time, and so on, the carbon deposits on the hot wire in different partitions can be etched sequentially without stopping during the diamond growth process, effectively ensuring the long-term operation of the equipment, and simultaneously removing the graphite and non-diamond phase carbon produced in the metastable diamond growth process, making the diamond film crystallization purer.

[0029] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention and to implement it according to the contents of the specification, and to make the above and other purposes, technical features and advantages of the present invention easier to understand, one or more preferred embodiments are listed below and described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a cross-sectional view of the CVD diamond film growth apparatus of the present invention.

[0031] Figure 2 It is a top view of the CVD diamond film growth apparatus of the present invention.

[0032] Figure 3 Schematic diagram of carbon deposition on the hot wire in Example 3 of the present invention.

[0033] Figure 4 Schematic diagram of carbon deposition on the hot wire of a comparative example of embodiment 3 of the present invention.

[0034] Figure 5 This is a Raman spectrum analysis diagram of Example 3 of the present invention.

[0035] Figure 6 This is a Raman spectrum analysis chart of the comparative example of Example 3 of the present invention.

[0036] Figure 7 This is the SEM surface morphology of Example 3 of the present invention.

[0037] Figure 8 This is a SEM surface morphology image of a comparative example of Example 3 of the present invention.

[0038] Description of main reference numerals:

[0039] 1-reaction chamber, 11-gas inlet, 12-gas distribution plate, 13-gas outlet pipe;

[0040] 2-cold water workbench, 20-connecting plate, 21-water inlet pipe, 22-water outlet pipe, 23-spiral baffle;

[0041] 3-substrate;

[0042] 4-lifting and rotating mechanism, 41-lifting rod;

[0043] 5-hot wire assembly, 51-electrode, 52-hot wire, 53-wire rack. DETAILED DESCRIPTION

[0044] The specific embodiments of the present invention are described in detail below with reference to the accompanying drawings, but it should be understood that the protection scope of the present invention is not limited by the specific embodiments.

[0045] Unless expressly stated otherwise, throughout the specification and claims, the term “comprise” or variations such as “include” or “comprising” will be understood to include the stated elements or components but not to exclude other elements or components.

[0046] In this document, for ease of description, spatially relative terms such as "below," "beneath," "down," "above," "above," etc. may be used to describe the relationship of one element or feature to another element or feature in the accompanying drawings. It should be understood that the spatially relative terms are intended to encompass different orientations of an object in use or operation in addition to the orientation depicted in the drawings. For example, if the object in the figure is turned over, the element described as being "below" or "below" other elements or features will be oriented "above" the element or feature. Therefore, the exemplary term "below" can include both below and above directions. Objects may also have other orientations (rotated 90 degrees or other orientations) and the spatially relative terms used herein should be interpreted accordingly.

[0047] In this document, the terms "first", "second", etc. are used to distinguish two different elements or parts, and are not used to limit specific positions or relative relationships. In other words, in some embodiments, the terms "first", "second", etc. can also be interchangeable with each other.

[0048] Example 1

[0049] like Figure 1 、 2As shown, this embodiment provides a CVD diamond film growth device, which includes a reaction chamber 1, a substrate 3, a hot wire array, and a cooling unit. The reaction chamber 1 is a cylindrical cavity and a plurality of independently controlled gas inlets 11 are evenly arranged along the circumference of the cavity. Specifically, a gas distribution plate 12 extending radially is arranged at each gas inlet position. The gas distribution plate 12 divides the reaction chamber 1 into an even number of partitions greater than 2. In this embodiment, the partitions are divided into 8 partitions from I to VIII (see Figure 2 ), the gas in each zone is independently controlled to ensure a relatively balanced flow of gas into the reaction chamber 1, resulting in a uniform and controllable concentration and flow field of the incoming gas. The gas inlet 11 can be fed with a mixture of hydrogen and carbon-containing gas, or it can be fed with only pure hydrogen by closing the valve for the carbon-containing gas. Therefore, independent control allows one zone to flow a mixed gas while another zone flows only pure hydrogen, more effectively eliminating carbon deposits on the hot wire.

[0050] In addition to the gas inlet 11 and the gas distribution plate 12, the reaction chamber 1 in this embodiment is also provided with a gas outlet pipe 13. The gas inlet 11 independently controls the introduction of process gases such as hydrogen and carbon-containing gas. The gas outlet pipe is connected to the vacuum system to discharge waste gas in order to maintain the pressure of the reaction chamber. The gas outlet pipe 13 is located at the center of the upper cover of the reaction chamber 1. The gas distribution plate 12 divides the reaction chamber 1 into multiple independent areas (i.e. Figure 2 The fan-shaped space shown in FIG) forms a gas channel from the gas inlet 11 on the side wall of the reaction chamber to the central gas outlet pipe 13 (as shown in FIG). Figure 1 The process gases are hydrogen, nitrogen, argon, and a carbon source such as methane, ethane, propane, butane, ethylene, or acetylene, or a volatile carbon-containing organic liquid such as methanol, ethanol, or acetone (which can be used in a vapor state). In this embodiment, methane is used as the carbon-containing gas. A certain flow rate of each process gas is mixed and then introduced into reaction chamber 1. Within the gas channel, the hydrogen and methane are decomposed and ionized at the high temperature of the hot filament, producing carbon-containing radicals and atomic hydrogen, ultimately depositing diamond on substrate 3.

[0051] Further Figure 1 、 2As shown, substrate 3, serving as the diamond film growth substrate, can be made of materials such as Si, Mo, Ta, Ti, W, WC, SiO2, or Al2O3. However, W and Mo are most commonly used for depositing self-supporting thick diamond films. This substrate is fan-shaped and arranged in a ring. Specifically, multiple fan-shaped substrates 3 are placed on the annular upper surface of the cold water table 2, with the substrates 3 arranged in a circular ring. In this embodiment, a molybdenum substrate is used. Substrate 3 is attached to the upper surface of the cold water table 2 of the cooling unit. The substrate 3 and cold water table 2 can be raised, lowered, and rotated as a whole. The cold water table 2 is used to control the substrate temperature during film growth. Specifically, in addition to the cold water table 2, the cooling unit also includes a lifting and rotating mechanism 4 and a lifting rod 41. The cold water table 2 is an annular hollow cylindrical structure, through which circulating cooling water is passed. The ratio of the outer diameter D1 to the inner diameter D2 of the cold water table 2 is preferably 2 to 5; its height is preferably 0.4 (D1-D2) to 1.0 (D1-D2). Such a size design can ensure the cooling effect while making the fan-shaped shape of the substrate 3 more rectangular, so that it can better match the rectangular wire rack of the hot wire assembly 5 during the film growth process. The cold water workbench 2 is arranged on the top of the lifting rod 41 and is sealed by the support connecting plate 20. The lifting rod 41 is driven by the lifting and rotating mechanism 4 to achieve lifting and rotation. The lifting and rotating mechanism 4 can provide a rotation speed of 0.1 to 5 rpm and a lifting height of 0 to 200 mm. The control of the rotation speed can make the growth of the substrate 3 film more uniform, and the control of the lifting height can further control the temperature of the substrate by adjusting the distance between the substrate and the hot wire while the cooling water has a cooling effect. A dynamic sealing device is provided between the reaction chamber 1 and the lifting rod 41. The lifting rod 41 is a hollow structure, and a water inlet and outlet channel for cooling water is provided in the hollow structure. The cooling water enters the annular space of the cold water workbench 2 to cool the substrate 3 and adjust the substrate temperature. Preferably, but not restrictively, a spiral baffle 23 ( Figure 1 (For illustration only), cooling water flows into the lower annular space of the cold water table 2 from the water inlet pipe 21, spirals upward along the annular space, and flows out from the upper annular space of the cold water table 2 from the water outlet pipe 22 under the action of spiral baffles 23. The provision of spiral baffles 23 effectively enhances heat transfer.

[0052] Further Figure 1 、 2As shown, a hot wire array is also disposed within the reaction chamber 1. The hot wire array comprises multiple hot wire assemblies 5. This embodiment employs eight hot wire assemblies 5, corresponding to the eight partitions. The number and shape of the hot wire assemblies are adapted to the substrate 3; the hot wire assemblies 5 are fixed within the reaction chamber and positioned above the rotatable substrate 3. Specifically, the hot wire assemblies 5 are arranged in a circular array along the circumference of the reaction chamber. The hot wire assembly 5 comprises an electrode 51, a hot wire 52, and a wire holder 53. The electrode 51 is vertically disposed and fixed within the reaction chamber (it may be fixed to the reaction chamber cover), with its upper end exposed. The wire holder 53 is a rectangular frame structure that contacts and secures the lower end of the electrode 51. The wire holder 53 is horizontally disposed above the substrate 3 and spaced a certain distance from the substrate. The hot wire 52 is arranged parallel to the wire holder and is in a stretched state. The present invention installs multiple hot wire assemblies within a single reaction chamber, significantly increasing substrate loading capacity and improving production efficiency. Electrode 51 is electrically connected to a power source via a cable. Wire holder 53 is connected to electrode 51 at both ends, allowing current to flow through the hot wire. Preferably, but not limiting, a wire straightening spring can be installed at the end of wire holder 53 to prevent the hot wire from bending and affecting diamond growth. A hot wire assembly consisting of multiple hot wires is positioned on the annular surface of the cold water workbench 2. Each gas channel formed by the gas distribution plate 12 corresponds to a group of hot wire assemblies, and the current of each hot wire assembly can be independently controlled. Preferably, but not limiting, the hot wire can be made of tantalum, tungsten, or rhenium. The distance between the hot wire and the inner wall of the upper cover plate of the reaction chamber 1 is greater than 50 mm, and the distance between the hot wire and the substrate surface to be deposited is within 30 mm.

[0053] During the continuous rotation of the cold water table 2, the CVD diamond film growing device of this embodiment can, within a preset period of time, select a partition (for example, Figure 2 I partition in the ) and the contralateral partition (e.g. Figure 2 The gas inlet of the second partition in the process is switched from the gas inlet of hydrogen and carbon-containing gas to the gas inlet of pure hydrogen. When the number of partitions is 8, the preset time can be set to 0.5 to 2 hours. That is, during the continuous operation of film growth, within the first preset time (for example, 1 hour), only pure hydrogen is introduced into the first and second partitions, while the other partitions are introduced into the process gases such as the mixture of hydrogen and carbon-containing gas. While the diamond film is prepared in the other partitions, the carbon deposits on the hot wires in the first and second partitions can be removed. In the second hour, only pure hydrogen is introduced into the third and fourth partitions, while the other partitions are introduced into the process gases such as the mixture of hydrogen and carbon-containing gas, and so on. In this way, the carbon deposits on the hot wires in each partition can be effectively removed.

[0054] Example 2

[0055] This embodiment is a method for applying the CVD diamond film device of embodiment 1, and the method includes the following steps:

[0056] In step S101, hydrogen and a carbon-containing gas are mixed and introduced into the reaction chamber through the gas inlet of each zone. A fixed gas channel is formed through the fan-shaped space enclosed by the gas distribution plate, the substrate surface, and the reaction chamber cover. Specifically, the carbon-containing gas can be methane, ethane, propane, butane, ethylene, or acetylene, or vapor-state methanol, ethanol, or acetone.

[0057] In step S102, in each sector, the mixed gas is decomposed and ionized by the high temperature of the hot wire at the corresponding position, generating carbon-containing radicals and atomic hydrogen. In this embodiment, the current passing through the hot wire can be 600A to 1500A; the surface temperature of the hot wire can be controlled to be between 2300°C and 2900°C.

[0058] In step S103, diamond is deposited on the circulated, cooled, and continuously rotating substrate through the interaction between the carbon-containing groups and atomic hydrogen in step S102. This embodiment controls the substrate temperature between 650°C and 1200°C by circulating cooling water and adjusting the distance between the substrate surface and the heating filament. During the diamond film growth process, the exhaust gas from the reaction is discharged from the exhaust pipe through a vacuum system to maintain the required deposition pressure within the reaction chamber.

[0059] Step S104: During the continuous rotation of the substrate and the cold water workbench, the gas inlet of a certain partition and the opposite partition is switched from a mixture of hydrogen and carbon-containing gas to pure hydrogen within a preset time. Figure 2 I partition in the ) and the contralateral partition (e.g. Figure 2 The gas inlet of the second partition in the process is switched from the gas inlet of hydrogen and carbon-containing gas to the gas inlet of pure hydrogen. When the number of partitions is 8, the preset time can be set to 0.5 to 2 hours. That is, during the continuous operation of film growth, within the first preset time (for example, 1 hour), only pure hydrogen is introduced into the first and second partitions, while the other partitions are introduced into the process gases such as the mixture of hydrogen and carbon-containing gas. While the diamond film is prepared in the other partitions, the carbon deposits on the hot wires in the first and second partitions can be removed. In the second hour, only pure hydrogen is introduced into the third and fourth partitions, while the other partitions are introduced into the process gases such as the mixture of hydrogen and carbon-containing gas, and so on. In this way, the carbon deposits on the hot wires in each partition can be effectively removed.

[0060] Using the method of this embodiment, process gas enters the reaction chamber simultaneously from multiple gas inlets arranged circumferentially around the chamber, passing through the fan-shaped space enclosed by the gas distribution plate, the substrate surface, and the reaction chamber cover to the axial gas outlet pipe at the center of the reaction chamber cover. Each gas inlet forms a fixed gas channel corresponding to the fan-shaped space, and the process gas composition of each gas channel can be individually controlled. This allows for systematic control of a specific gas channel to be entirely hydrogen-filled to remove carbon deposits from the hot wire. When the hot wire surface temperature is between 2300°C and 2900°C, the hydrogen gas decomposes and removes carbon deposits on the hot wire. Experimental research by the inventors has found that carbon deposits on the hot wire are closely related to the hot wire temperature and methane concentration. Specifically, as the methane concentration increases, carbon deposits are more likely to form on the surface, while as the temperature decreases, carbon deposits also form on the surface. At a methane concentration of 1%, the minimum temperature of the hot wire should be above 1900°C; at a methane concentration of 5%, the minimum temperature of the hot wire should be above 2850°C. Multiple hot wire assemblies are arranged in a circular array atop a sector-shaped substrate. Process gas is decomposed by the hot wires within the sector-shaped space, depositing a diamond film on the substrate surface. Exhaust gas then flows into an exhaust pipe and is extracted by a vacuum system. The vacuum system's exhaust volume controls the deposition pressure within the reaction chamber. As the substrate rotates, the hot wires remain stationary, continuously decomposing the process gas and depositing the diamond film on the substrate in a repetitive cycle.

[0061] Preferably, but not limiting, the diamond film deposited by the process method of this embodiment can be two layers of different grain sizes grown sequentially and repeatedly on the substrate.

[0062] Example 3

[0063] This embodiment is a specific example of embodiment 2, and two diamond film layers with different grain sizes can be grown on a substrate sequentially and repeatedly:

[0064] The hot wire used in this embodiment is a tantalum wire with a diameter of 0.4 mm, and the temperature of the tantalum wire is measured using an E1RH-F2-V-0-0 two-color high-temperature infrared thermometer. The tantalum wire in the reaction chamber is evenly arranged on a rectangular wire rack. The tension spring at the end of the wire rack makes the tantalum wire uniformly stressed as a whole. The effective heating area of ​​the hot wire is 300 mm × 200 mm. The substrate substrate uses 16 fan-shaped molybdenum substrates with a thickness of 20 mm. These 16 fan-shaped molybdenum substrates are combined into a ring, placed and attached to the surface of a cold water workbench with an outer diameter of 960 mm and an inner diameter of 600 mm. Before the reaction, the substrate is first ground with diamond micropowder with a diameter of 0.5 μm for about 1 hour, and then placed in an acetone solution for ultrasonic treatment for 10 minutes. The device in Example 1 of the present invention is used to grow a thick diamond film. The working gases are hydrogen and methane. The 8 relatively independent hot wire deposition areas are marked as I to VIII respectively. The process conditions for the independent hot wire deposition areas are shown in Table 1:

[0065] Table 1 - Process conditions for independent hot filament deposition areas

[0066]

[0067]

[0068] When the diamond film starts to grow, the process conditions of the first and second layers are repeated (i.e., the total growth time of the two layers is 14 hours). Within the first hour, the methane gas is turned off in the deposition areas of the I and II hot wires, and only hydrogen is passed through. Within the second hour, the methane gas is turned off in the deposition areas of the III and IV hot wires, and only hydrogen is passed through. This process is repeated in this way, and hydrogen is used to etch the carbon deposits on the hot wires to prevent carbon deposits from forming. Figure 3 This is the carbon deposition condition of the hot wires of multiple hot wire CVD diamond coating equipment in this embodiment. Figure 3 As shown, using the method of this embodiment, after a total growth time of 240 hours, the carbon deposition length L of the hot wire is only 1.5 cm.

[0069] Comparative Example

[0070] This comparative example is a comparative example of Example 3: This comparative example adopts conventional technology. In H2-CH4 gas, the diamond coating can be deposited into microcrystals, nanocrystals or multi-layer composite materials. In order to make the structural layers of different grain sizes grow in sequence on the surface of the substrate, it is achieved by changing the carbon source concentration. The nano layer is grown by increasing the carbon source concentration, and then the micron layer is grown by reducing the carbon source concentration. The first layer growth parameters (growth parameters for forming the micron layer) are: hydrogen flow rate 1000sccm, methane flow rate 40sccm, hot wire temperature 2500℃, substrate temperature 850℃. After growing for 2 hours, the carbon source concentration is increased. The second layer growth parameters (growth parameters for forming the nano layer) are: hydrogen flow rate 1000sccm, methane flow rate 100sccm, hot wire temperature 2200℃, substrate temperature 750℃. After maintaining for 20 minutes, the normal growth parameters are restored. After 2 hours, the carbon source concentration is increased again. This cycle is repeated. After 240 hours of growth, a diamond film with a total thickness of about 1mm is obtained. Figure 4 This is the carbon deposition condition of the hot wire in this comparative example. Figure 4 As shown, the carbon deposition length L of the hot wire is 24.8 cm. Using the process of this comparative example, the constant change of carbon source concentration exacerbates the carbon deposition poisoning process of the hot wire, causing the effective length of the hot wire to continuously shorten and the power to decrease, making it difficult for the diamond growth process to continue for a long time.

[0071] Further Figure 5 (Characteristic peak diagram of Example 3) and Figure 6 As shown in the characteristic peak diagram of the comparative example, the peak at 1332 cm -1The sharp peak at corresponds to SP 3 Hybrid diamond characteristic peak (D peak), 1580cm -1 The peak corresponds to SP 2 Hybrid graphite characteristic peak (G peak), combined with Figure 5 and Figure 6 It can be seen that the D peak of Example 3 of the present invention is sharper than that of the comparative example, indicating that the diamond has higher crystallinity, greater strength and better purity. Figure 7 and Figure 8 From the comparison, it can be seen that Example 3 of the present invention can obtain a better CVD diamond thick film structure than the comparative example.

[0072] The foregoing descriptions of specific exemplary embodiments of the present invention are for purposes of illustration and description. These descriptions are not intended to limit the invention to the precise form disclosed, and it is apparent that many changes and variations are possible in light of the foregoing teachings. The exemplary embodiments are selected and described for the purpose of explaining the specific principles of the invention and their practical application, thereby enabling those skilled in the art to realize and utilize a variety of exemplary embodiments of the invention and various options and variations. Any simple modifications, equivalent variations, and modifications made to the exemplary embodiments described above are intended to fall within the scope of protection of the present invention.

Claims

1. A CVD diamond film growth device, characterized in that: include: The reaction chamber is a cylindrical cavity with a plurality of independently controlled gas inlets uniformly arranged along the circumference of the cavity; a mixture of hydrogen and carbon-containing gas, or pure hydrogen, is introduced into the gas inlet; the reaction chamber is provided with an even number of partitions greater than two, each partition being separated by a gas distribution plate and corresponding to a gas inlet; during the continuous rotation of the cooling unit, within a preset period of time, the gas inlets of a certain partition and the opposite partition are switched from introducing a mixture of hydrogen and carbon-containing gas to introducing pure hydrogen; A substrate, which serves as a base for growing the diamond film, wherein the base is fan-shaped and is arranged in a plurality of rings; A hot wire array, which is composed of a plurality of hot wire assemblies, the number and shape of which are adapted to the substrate; the hot wire assemblies are fixed above the substrate in the reaction chamber; A cooling unit, the upper surface of which is in contact with the substrate and can be raised and lowered and rotated as a whole, for controlling the temperature of the substrate during film growth; The diamond film layer deposited by the device is two layers with different grain sizes that grow sequentially and repeatedly.

2. The CVD diamond film growth apparatus according to claim 1, wherein: When the number of the even-numbered partitions is 8, the preset time is 0.5 to 2 hours.

3. The CVD diamond film growth apparatus according to claim 1, wherein: The hot wire assembly comprises: an electrode, which is vertically arranged and fixed in the reaction chamber with its upper end exposed; A wire rack having a rectangular frame structure and fixed to the lower end of the electrode, the wire rack being horizontally arranged and located above the substrate at a certain distance; The hot wire is arranged parallel to the wire rack and is in a stretched state.

4. The CVD diamond film growth apparatus according to claim 3, wherein: The heating wire is a tantalum wire, a tungsten wire or a rhenium wire.

5. The CVD diamond film growth apparatus according to claim 3, wherein: The end of the hot wire is fixed on the wire rack through a straightening spring.

6. The CVD diamond film growth apparatus according to claim 1, wherein: The cooling unit comprises: A cold water workbench, which is an annular hollow cylindrical structure, into which circulating cooling water is passed; the substrate is attached to the upper surface of the cold water workbench; A lifting rod is provided at the bottom of the cold water workbench and is a hollow structure, wherein a water inlet and outlet channel for cooling water is provided; the lifting rod is connected to the reaction chamber in a dynamic sealing manner; The lifting and rotating mechanism drives the lifting rod and drives the cold water workbench to rotate or lift.

7. The CVD diamond film growing apparatus according to claim 6, wherein: A spiral baffle is provided in the annular hollow columnar structure of the cold water workbench. Cooling water flows in along the lower part of the cold water workbench on the water inlet pipe side and flows out along the upper part of the cold water workbench on the water outlet pipe side through the spiral baffle.

8. The CVD diamond film growing apparatus according to claim 6, wherein: The lifting and rotating mechanism provides a rotation speed of 0.1 to 5 rpm and a lifting height of 0 to 200 mm.

9. The CVD diamond film growing apparatus according to claim 3, wherein: The distance between the hot wire and the inner wall of the upper cover plate of the reaction chamber is greater than 50 mm, and the distance between the hot wire and the surface to be deposited of the substrate is within 30 mm.

10. A method of using the device according to any one of claims 1 to 9, characterized in that: The steps include: A. The hydrogen and carbon-containing gases are mixed and then enter the reaction chamber through the gas inlet of each partition, and form a fixed gas channel through the fan-shaped space surrounded by the gas distribution plate, the substrate surface and the upper cover of the reaction chamber; B. In the fan-shaped space of each partition, the mixed gas is decomposed and ionized under the high temperature of the hot wire at the corresponding position to generate carbon-containing groups and atomic hydrogen; C. depositing diamond on a cyclically cooled and continuously rotating substrate through the interaction between the carbon-containing groups and atomic hydrogen; D. During the continuous rotation, within a preset period of time, the gas inlet of a certain partition and the opposite partition is switched from feeding a mixture of hydrogen and carbon-containing gas to feeding pure hydrogen.

11. The method according to claim 10, characterized in that The carbon-containing gas is methane, ethane, propane, butane, ethylene or acetylene, or methanol, ethanol or acetone in a steam state.

12. The method according to claim 10, characterized in that The current passing through the hot wire is 600A to 1500A; the surface temperature of the hot wire is controlled at 2300°C to 2900°C.

13. The method according to claim 10, characterized in that The substrate temperature is controlled between 650° C. and 1200° C. by circulating cooling water and adjusting the distance between the substrate surface and the hot wire.

14. The method according to claim 10, characterized in that The deposited diamond film layer is two layers with different grain sizes that grow sequentially and repeatedly.

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