Method for preparing large-area diamond at high temperature through HFCVD method

Abstract

The invention discloses a method for preparing large-area diamond at high temperature by an HFCVD (High Frequency Chemical Vapor Deposition) method. The method comprises the following steps: producing the diamond through a hot filament chemical vapor deposition device; the diameter of the produced diamond is more than or equal to 200mm; the hot filament chemical vapor deposition device is provided with a deposition space, and a hot filament assembly, a deposition base station and a temperature compensation device are arranged in the deposition space. The hot wire assembly comprises a plurality of hot wires which are arranged in parallel; the deposition base station comprises a substrate and a cooling interlayer mechanism; the substrate is placed on the upper surface of the cooling interlayer; the temperature compensation device comprises a substrate compensation device; the hot wire distance D between the parallel hot wires is adjusted, and D is 4-12 mm; adjusting a substrate distance H between the hot filament plane and the substrate through a first formula according to the hot filament distance D; after cooling is completed, hydrogen in the furnace is discharged, the diamond film layer is taken down from the surface of the deposition base body, and diamond is obtained; and the diamond with large area, high quality and few impurities and defects is prepared.

Description

Technical Field

[0001] The invention relates to the field of diamond preparation, and in particular to the field of a method for preparing large-area diamonds by a HFCVD method at high temperature. Background Art

[0002] Diamond is a common macroscopic crystal composed of carbon. It has a series of excellent physical and chemical properties such as high hardness, high thermal conductivity, low thermal expansion coefficient, good optical transmittance, chemical inertness, etc. It has very broad application prospects in the fields of aerospace, military, machinery, electronic information, etc. The limited reserves and small size of natural diamonds have greatly restricted the industrial application of diamonds, so artificial diamond technology has gradually become a research hotspot.

[0003] The most common way to produce artificial diamonds is to use high temperature and high pressure. However, this method can only grow diamond grains or powders. If you want to make them into blocks, you must add a metal binder, which leads to poor performance of the finished diamond products. Chemical vapor deposition can grow high-purity diamond films or diamond sheets.

[0004] The methods of growing diamond films by chemical vapor deposition can be roughly divided into the following four categories: pyrolysis CVD method, including chemical transport reaction method, hot wire method, and oxyacetylene flame method; DC plasma CVD method, including low-voltage DC discharge, medium-voltage DC discharge, hollow cathode discharge, DC arc, and DC plasma jet. RF plasma CVD method, including low-pressure glow discharge and thermal plasma CVD method. Microwave plasma CVD method, including gas pressure 2.45GH2 plasma method and gas pressure 2.45GH2 plasma method, but the production cost is high; DC plasma CVD method and RF plasma CVD method have high large-scale production costs, and cannot produce large-area diamonds. The diameter of the produced diamonds is no more than 150mm; CVD diamonds prepared by the hot wire method have the characteristics of low operating cost, relatively simple equipment, high production efficiency, and large product size; However, CVD diamonds prepared by the hot wire method have the following problems:

[0005] There are many impurity defects in the deposited diamond; it is difficult to ensure a high deposition rate and deposition quality; expanding the deposition area will lead to problems such as difficulty in controlling the thermal field and uneven deposition.

[0006] Therefore, how to prepare large-area, high-quality diamonds with few impurities and defects has become a difficult problem that needs to be solved urgently in this field. Summary of the invention

[0007] In order to solve the above technical problems, a method for preparing large-area diamonds by high temperature using HFCVD method is provided, so as to achieve the preparation of large-area, high-quality diamonds with few impurities and defects.

[0008] According to the present invention, a method for preparing large-area diamond by HFCVD at high temperature is provided, comprising the following steps:

[0009] Produce diamonds by hot wire chemical vapor deposition device; the diameter of the produced diamonds is ≥200mm;

[0010] The hot wire chemical vapor deposition device is provided with a deposition space, wherein the deposition space includes a hot wire assembly, a deposition base, and a temperature compensation device;

[0011] The hot wire assembly comprises a plurality of hot wires arranged in parallel;

[0012] The deposition platform comprises a substrate and a cooling interlayer mechanism; the substrate is placed on the upper surface of the cooling interlayer;

[0013] The temperature compensation device includes a substrate compensation device;

[0014] Adjust the wire spacing D between the parallel wires, D = 4-12mm;

[0015] According to the hot wire spacing D, the substrate spacing H between the hot wire plane and the substrate is adjusted by the first formula;

[0016] evacuating the deposition space;

[0017] Introduce hydrogen and methane in proportion to the target pressure; start heating with the hot wire to make the upper surface of the deposition substrate reach the preset temperature, and start timing;

[0018] When the deposition time reaches the preset time, the hot wire heating is turned off and the temperature starts to drop;

[0019] After the temperature is lowered, the hydrogen in the furnace is exhausted, and the diamond film layer is removed from the surface of the deposition substrate to obtain diamond;

[0020] Preferably, the diameter of the prepared diamond is ≥300 mm; preferably, the surface reflectivity of the temperature compensation device close to the substrate and the cooling sandwich structure is high; preferably, the substrate material is one of silicon, molybdenum, tungsten and graphite.

[0021] Compared with the prior art, the present invention has the following beneficial effects: large-area diamonds are prepared by hot-wire chemical deposition method, and the diameter of the diamonds is ≥200 mm;

[0022] The deposition space includes a temperature compensation device to avoid the tip thermal effect, that is, it is conducive to achieving that the temperature of the center position and the edge position of the substrate are basically consistent during the deposition process, and it is also conducive to avoiding the problem of cracking or damage of large-area crystals due to the different cooling rates of the edge of the substrate and the middle part during the cooling process;

[0023] The control of the dimensionality reduction range of the cooling sandwich mechanism is beneficial to controlling the temperature reduction transfer range of the cooling sandwich mechanism within the contact surface between the cooling sandwich mechanism and the substrate during the deposition process, which is beneficial to avoid the cooling sandwich mechanism affecting the radiation temperature of the hot wire during the deposition process, thereby avoiding the problem of uneven temperature of the hot wire radiated on the upper surface of the substrate;

[0024] This is conducive to achieving the goal of preventing the internal structure of large-area diamonds from being uneven, and is conducive to reducing impurities and defects in large-area diamonds;

[0025] By adjusting the hot wire spacing D between parallel hot wires, D = 4-12mm, it is beneficial to achieve uniform temperature at all places on the upper surface of the substrate, avoiding the problem that the temperature distribution of the substrate in the same direction produces temperature fluctuations corresponding to the position of the hot wires due to the small hot wire spacing and large hot wire distribution discreteness, and avoiding the problem that the temperature difference between the center and the edge of the hot wire influence area increases due to the concentration of heat radiation when the hot wire spacing is large; and the hot wire spacing is conducive to assembly;

[0026] This is further conducive to achieving the goal of preventing the internal structure of the prepared large-area diamond from being uneven, and further conducive to reducing the impurities and defects of the large-area diamond;

[0027] By adjusting the substrate spacing H between the hot wire plane and the substrate through the first formula according to the hot wire spacing D, it is further helpful to eliminate the problem of increased temperature fluctuation on the substrate surface and decreased temperature uniformity caused by the increase in the spacing between the hot wires; that is, the temperature fluctuation caused by the setting of the spacing between the hot wires and the substrate is compensated for the temperature fluctuation on the substrate surface caused by the change in the hot wire spacing; it is further helpful to achieve uniform temperature distribution on the substrate surface during deposition;

[0028] Ultimately, it is possible to produce large-area, high-quality diamonds with few impurities and defects.

[0029] Further, the first formula:

[0030] The beneficial effect of adopting the previous step is that it is conducive to achieving uniform temperature everywhere on the upper surface of the substrate, avoiding the problem that the temperature distribution of the substrate in the same direction produces temperature fluctuations corresponding to the position of the hot wires due to a small hot wire spacing and a large discrete hot wire distribution, and avoiding the problem that the temperature difference between the center and the edge of the hot wire influence area increases due to the concentration of heat radiation when the hot wire spacing is large; and the hot wire spacing is conducive to assembly;

[0031] This helps to prevent the internal structure of large-area diamonds from being uneven, and further helps to reduce impurities and defects in large-area diamonds.

[0032] Further, the substrate compensation device is a circular ring structure, or the substrate compensation device is composed of 2-5 arc segments assembled into a circular ring;

[0033] The substrate compensation device is flush with the substrate height or slightly lower than the substrate;

[0034] The substrate compensation device is sleeved outside the substrate and contacts the substrate;

[0035] The substrate compensation device is located on the outer upper surface of the cooling sandwich structure;

[0036] The thermal conductivity of the substrate compensation device is less than or equal to the thermal conductivity of the substrate; the material of the substrate compensation device includes one of molybdenum, graphite, tantalum, and silicon carbide ceramics.

[0037] The beneficial effect of adopting the previous step is that it is conducive to avoiding the tip thermal effect, and is conducive to achieving basically consistent temperatures at the center and edge of the substrate during the deposition process. At the same time, it is conducive to avoiding the problem of cracking or damage of large-area crystals caused by the cooling rate at the edge of the substrate being different from that in the middle during the cooling process; thereby, it is conducive to achieving the large-area diamond prepared without the phenomenon of uneven internal structure, which is conducive to reducing impurities and defects in large-area diamonds.

[0038] Furthermore, the temperature compensation device also includes a thermal radiation compensation device;

[0039] The thermal radiation compensation device comprises a first arc-shaped plate and a second arc-shaped plate which are arranged opposite to each other;

[0040] The first curved plate is connected to a first bottom plate which is vertically arranged to the first curved plate;

[0041] The second arc-shaped plate is connected to a second bottom plate which is vertically arranged to the second arc-shaped plate.

[0042] Furthermore, the thermal radiation compensation device is sleeved outside the cooling interlayer mechanism;

[0043] The cooling sandwich mechanism is located between the first curved plate and the second curved plate;

[0044] The first bottom plate and the second bottom plate are located below the cooling sandwich mechanism;

[0045] A spacing is provided between the end of the first arc-shaped plate and the end of the second arc-shaped plate;

[0046] The minimum distance L between the inner curved surface of the first curved plate or the second curved plate and the cooling sandwich structure satisfies Formula 2;

[0047] Formula 2 is: L = 10ε × (20-H);

[0048] ε: thermal reflectivity of the first curved plate or the second curved plate; H: substrate spacing between the hot wire plane and the substrate;

[0049] Preferably, the thermal conductivity of the substrate compensation device is less than or equal to the thermal conductivity of the substrate; the material of the substrate compensation device includes one of molybdenum, graphite, tantalum, and silicon carbide ceramics.

[0050] The beneficial effect of adopting the previous step is that the cooling sandwich mechanism is located between the first curved plate and the second curved plate; the first bottom plate and the second bottom plate are located below the cooling sandwich mechanism; the dimensionality reduction range of the cooling sandwich mechanism is controlled, which is conducive to controlling the temperature reduction transfer range of the cooling sandwich mechanism within the contact surface between the cooling sandwich mechanism and the substrate during the deposition process, which is conducive to avoiding the influence of the cooling sandwich mechanism on the radiation temperature of the hot wire during the deposition process, thereby avoiding the problem of uneven temperature of the hot wire radiated on the upper surface of the substrate;

[0051] This is conducive to achieving the goal of preparing large-area diamonds without the phenomenon of uneven internal structure, and is conducive to reducing impurities and defects in large-area diamonds.

[0052] Furthermore, the heating wires are arranged in a rectangular structure; the four corners of the rectangular structure are not located above the distance between the end of the first arc plate and the end of the second arc plate;

[0053] The thermal radiation compensation device is not in contact with the cooling sandwich structure.

[0054] The beneficial effect of adopting the previous step is that the four corners of the rectangular structure are not located above the distance between the end of the first arc plate and the end of the second arc plate, which is beneficial to avoid the cooling effect of the cooling sandwich structure affecting the four corners of the matrix structure of the hot wire.

[0055] Furthermore, the hydrogen and methane are introduced to a target pressure of 1000-8000Pa.

[0056] Furthermore, the volume ratio of methane to hydrogen is (0.5-8):(92-99.5).

[0057] By adopting the beneficial effect of the previous step, full and uniform contact between hydrogen and methane is achieved, which is conducive to uniform and defect-free diamond deposition.

[0058] Furthermore, the preset temperature of the upper surface of the substrate is 800-1000°C.

[0059] The beneficial effect of adopting the previous step is that it helps to avoid the occurrence of graphite phases or defects during the diamond film deposition process.

[0060] Furthermore, the cooling interlayer mechanism is provided with a liquid inlet and a liquid outlet, and the liquid inlet is connected to a cold source;

[0061] The cooling medium in the cooling sandwich mechanism is water, and the outlet water temperature of the cooling medium is 40-60°C;

[0062] The interface temperature of the precipitation and cooling sandwich mechanism is 190-260°C.

[0063] The beneficial effect of the above step is that the cooling medium in the cooling interlayer mechanism is water, and the outlet water temperature of the cooling medium is 40-60° C., that is, the deposition substrate is cooled uniformly, which is conducive to avoiding the problem of uneven temperature of various parts of the substrate caused by excessive cooling; thereby, it is conducive to avoiding the problem of defects in the diamond growth process;

[0064] The interface temperature of the precipitation and cooling sandwich structure is 190-260°C, which is helpful to avoid the problem of deformation of the substrate caused by long-term high temperature due to too slow cooling. BRIEF DESCRIPTION OF THE DRAWINGS

[0065] Figure 1 This is a schematic diagram of the structure of the hot wire assembly, deposition base, and temperature compensation device of Example 1;

[0066] Figure 2 A three-dimensional diagram of the hot wire assembly, deposition base, and temperature compensation device of Example 1;

[0067] Figure 3 A top view of the hot wire assembly, deposition base, and temperature compensation device of Example 1;

[0068] As shown in the figure:

[0069] 1. Hot wire assembly, 2. Substrate, 3. Substrate compensation device, 4. Cooling interlayer mechanism, 5. First arc plate, 6. First bottom plate, 7. Thermal radiation compensation device, 8. Second arc plate, 9. Second bottom plate. DETAILED DESCRIPTION

[0070] In order to better understand the technical solution of the present invention, the present invention is further described below in conjunction with the accompanying drawings and specific embodiments.

[0071] Embodiment 1:

[0072] This embodiment provides a method for preparing large-area diamond by HFCVD at high temperature, comprising the following steps:

[0073] Diamonds are produced by hot wire chemical vapor deposition equipment; the diameter of the produced diamonds is 300 mm;

[0074] The hot wire chemical vapor deposition device is provided with a deposition space, wherein the deposition space includes a hot wire assembly 1, a deposition base, and a temperature compensation device;

[0075] The hot wire assembly 1 comprises a plurality of hot wires arranged in parallel;

[0076] The deposition platform comprises a substrate 2 and a cooling interlayer mechanism 4; the substrate 2 is placed on the upper surface of the cooling interlayer; the substrate 2 is made of molybdenum;

[0077] The temperature compensation device includes a substrate compensation device 3 and a thermal radiation compensation device 7; the substrate compensation device 3 and the thermal radiation compensation device 7 are made of molybdenum, and the surface reflectivity of the temperature compensation device close to the substrate 2 and the cooling sandwich structure is high;

[0078] The substrate compensation device 3 is a circular ring structure, and the substrate compensation device 3 is flush with the substrate 2;

[0079] The substrate compensation device 3 is sleeved outside the substrate 2 and contacts the substrate 2;

[0080] The substrate compensation device 3 is located on the outer upper surface of the cooling sandwich structure;

[0081] The thermal radiation compensation device 7 comprises a first curved plate 5 and a second curved plate 8 which are arranged opposite to each other;

[0082] The first curved plate 5 is connected to a first bottom plate 6 which is vertically arranged to the first curved plate 5;

[0083] The second arc-shaped plate 8 is connected to a second bottom plate 9 which is vertically arranged to the second arc-shaped plate 8 .

[0084] The thermal radiation compensation device 7 is sleeved on the outside of the cooling sandwich mechanism 4;

[0085] The cooling sandwich mechanism 4 is located between the first curved plate 5 and the second curved plate 8;

[0086] The first bottom plate 6 and the second bottom plate 9 are located below the cooling sandwich mechanism 4;

[0087] The hot wires are arranged in a rectangular structure; the four corners of the rectangular structure are not located above the distance between the end of the first curved plate 5 and the end of the second curved plate 8;

[0088] The thermal radiation compensation device 7 is not in contact with the cooling sandwich structure.

[0089] Adjust the wire spacing D between the parallel wires, D = 4-12mm;

[0090] According to the hot wire distance D, the substrate 2 distance H between the hot wire plane and the substrate 2 is adjusted by the first formula;

[0091] First formula:

[0092] There is a gap between the end of the first curved plate 5 and the end of the second curved plate 8;

[0093] The minimum distance L between the inner arc surface of the first arc plate 5 or the second arc plate 8 and the cooling sandwich structure satisfies Formula 2;

[0094] Formula 2 is: L = 10ε × (20-H);

[0095] ε: thermal reflectivity of the first curved plate 5 or the second curved plate 8; H: substrate distance between the hot wire plane and the substrate 2.

[0096] evacuating the deposition space;

[0097] Hydrogen and methane are introduced in proportion to the target pressure; the hot wire heating is turned on to make the upper surface of the deposition substrate reach a preset temperature, and the timing is started; the hydrogen and methane are introduced to a target pressure of 4500 Pa; the volume ratio of methane to hydrogen is 4.3:95.7; the preset temperature of the upper surface of the substrate 2 is 900°C;

[0098] The cooling medium in the cooling sandwich mechanism 4 is water, and the outlet water temperature of the cooling medium is 50°C;

[0099] The interface temperature of the precipitation and cooling sandwich mechanism 4 is 225°C.

[0100] When the deposition time reaches the preset time, the hot wire heating is turned off and the temperature starts to drop;

[0101] After the temperature is lowered, the hydrogen in the furnace is exhausted, and the diamond film layer is removed from the surface of the deposition substrate to obtain diamond.

[0102] Embodiment 2:

[0103] The same contents as those in Example 1 are not described in detail here. The differences between this embodiment and Example 1 are as follows: This embodiment provides a method for preparing large-area diamond by high temperature using a HFCVD method, comprising the following steps:

[0104] The diameter of the produced diamond is 350mm; the substrate 2 is made of silicon; the substrate compensation device 3 and the thermal radiation compensation device 7 are both made of graphite; the substrate compensation device 3 is composed of 2-5 arc segments assembled into a circular ring; the height of the substrate compensation device 3 is slightly lower than the height of the substrate 2;

[0105] The target pressure of hydrogen and methane is 4000 Pa; the volume ratio of methane to hydrogen is 3:97; the preset temperature of the upper surface of the substrate 2 is 850°C;

[0106] The cooling medium in the cooling sandwich mechanism 4 is water, and the outlet water temperature of the cooling medium is 45°C;

[0107] The interface temperature of the precipitation and cooling sandwich mechanism 4 is 200°C.

[0108] Embodiment 3:

[0109] The same contents as those in Example 1 are not described in detail here. The differences between this embodiment and Example 1 are as follows: This embodiment provides a method for preparing large-area diamond by high temperature using a HFCVD method, comprising the following steps:

[0110] The diameter of the produced diamond is 400 mm; the substrate compensation device 3 and the thermal radiation compensation device 7 are both made of silicon carbide;

[0111] The target pressure of hydrogen and methane is 7500 Pa; the volume ratio of methane to hydrogen is 7.7:92.5; the preset temperature of the upper surface of the substrate 2 is 980°C;

[0112] The cooling medium in the cooling sandwich mechanism 4 is water, and the outlet water temperature of the cooling medium is 58°C;

[0113] The interface temperature of the precipitation and cooling sandwich mechanism 4 is 255°C.

[0114] Those skilled in the art should understand that the scope of the invention involved in this application is not limited to the technical solutions formed by a specific combination of the above technical features, but should also cover other technical solutions formed by any combination of the above technical features or their equivalent features without departing from the inventive concept. For example, the above features are replaced with (but not limited to) technical features with similar functions disclosed in this application.

Claims

1. A method for preparing large-area diamond by high-temperature HFCVD, characterized in that: The following steps are involved: Produce diamonds by hot wire chemical vapor deposition device; the diameter of the produced diamonds is ≥200mm; The hot wire chemical vapor deposition device is provided with a deposition space, wherein the deposition space includes a hot wire assembly, a deposition base, and a temperature compensation device; The hot wire assembly comprises a plurality of hot wires arranged in parallel; The deposition platform comprises a substrate and a cooling interlayer mechanism; the substrate is placed on the upper surface of the cooling interlayer; The temperature compensation device includes a substrate compensation device; Adjust the wire spacing D between the parallel wires, D = 4-12mm; According to the hot wire spacing D, the substrate spacing H between the hot wire plane and the substrate is adjusted by the first formula; evacuating the deposition space; Introduce hydrogen and methane in proportion to the target pressure; start heating with the hot wire to make the upper surface of the deposition substrate reach the preset temperature, and start timing; When the deposition time reaches the preset time, the hot wire heating is turned off and the temperature starts to drop; After the temperature is lowered, the hydrogen in the furnace is exhausted, and the diamond film layer is removed from the surface of the deposition substrate to obtain diamond.

2. The method for preparing large-area diamond by HFCVD at high temperature according to claim 1, characterized in that: The first formula is:

3. The method for preparing large-area diamond by HFCVD at high temperature according to claim 1, characterized in that: The substrate compensation device is a circular ring structure, or the substrate compensation device is composed of 2-5 arc segments assembled into a circular ring; The substrate compensation device is flush with the substrate height or slightly lower than the substrate; The substrate compensation device is sleeved outside the substrate and contacts the substrate; The substrate compensation device is located on the outer upper surface of the cooling sandwich structure; The thermal conductivity of the substrate compensation device is less than or equal to the thermal conductivity of the substrate; the material of the substrate compensation device includes one of molybdenum, graphite, tantalum, and silicon carbide ceramics.

4. The method for preparing large-area diamond by HFCVD at high temperature according to claim 1, characterized in that: The temperature compensation device also includes a thermal radiation compensation device; The thermal radiation compensation device comprises a first arc-shaped plate and a second arc-shaped plate which are arranged opposite to each other; The first curved plate is connected to a first bottom plate which is vertically arranged to the first curved plate; The second arc-shaped plate is connected to a second bottom plate which is vertically arranged to the second arc-shaped plate.

5. The method for preparing large-area diamond by HFCVD at high temperature according to claim 4, characterized in that: The thermal radiation compensation device is sleeved on the outside of the cooling interlayer mechanism; The cooling sandwich mechanism is located between the first curved plate and the second curved plate; The first bottom plate and the second bottom plate are located below the cooling sandwich mechanism; A spacing is provided between the end of the first arc-shaped plate and the end of the second arc-shaped plate; The minimum distance L between the inner curved surface of the first curved plate or the second curved plate and the cooling sandwich structure satisfies Formula 2; Formula 2 is: L = 10ε × (20-H); ε: thermal reflectivity of the first curved plate or the second curved plate; H: substrate spacing between the hot wire plane and the substrate.

6. The method for preparing large-area diamond by HFCVD at high temperature according to claim 5, characterized in that: The heating wires are arranged in a rectangular structure; the four corners of the rectangular structure are not located above the distance between the end of the first arc plate and the end of the second arc plate; The thermal radiation compensation device is not in contact with the cooling sandwich structure.

7. The method for preparing large-area diamond by HFCVD at high temperature according to claim 1, characterized in that: The hydrogen and methane are introduced to a target pressure of 1000-8000Pa.

8. The method for preparing large-area diamond by HFCVD at high temperature according to claim 1, characterized in that: The volume ratio of methane to hydrogen is (0.5-8):(92-99.5).

9. The method for preparing large-area diamond by HFCVD at high temperature according to claim 1, characterized in that: The preset temperature of the upper surface of the substrate is 800-1000°C.

10. The method for preparing large-area diamond by HFCVD at high temperature according to claim 1, wherein the cooling interlayer mechanism is provided with a liquid inlet and a liquid outlet, and the liquid inlet is connected to a cooling source; The cooling medium in the cooling sandwich mechanism is water, and the outlet water temperature of the cooling medium is 40-60°C; The interface temperature of the precipitation and cooling sandwich mechanism is 190-260°C.

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