Method for preparing large-area diamond at high temperature using hfcvd method

Abstract

Disclosed in the present invention is a method for preparing large-area diamond at a high temperature using a hot-filament chemical vapor deposition (HFCVD) method, comprising the following steps: producing diamond by means of an HFCVD apparatus, wherein the diameter of the produced diamond is greater than or equal to 200 mm, the HFCVD apparatus is provided with a deposition space, a hot-filament assembly, a deposition base, and a temperature compensation apparatus are provided inside the deposition space, the hot-filament assembly comprises a plurality of parallel hot filaments, the deposition base comprises a substrate and a cooling interlayer mechanism, the substrate is placed on the upper surface of the cooling interlayer mechanism, and the temperature compensation apparatus comprises a substrate compensation apparatus; adjusting a hot-filament spacing D between the parallel hot filaments, wherein D is equal to 4-12 mm; on the basis of the hot-filament spacing D, adjusting a substrate spacing H between a hot-filament plane and the substrate by means of a first formula; and after cooling, discharging hydrogen from a furnace, and removing a diamond film layer from the surface of a deposition substrate to obtain diamond, thereby achieving the preparation for large-area and high-quality diamond having few impurities and defects.

Description

A method for high-temperature preparation of large-area diamonds using HFCVD Technical Field

[0001] This invention relates to the field of diamond preparation, and more particularly to a method for high-temperature preparation of large-area diamonds using HFCVD. Background Technology

[0002] Diamond is a common macroscopic crystal composed of carbon. It possesses a range of excellent physicochemical properties, including high hardness, high thermal conductivity, low coefficient of thermal expansion, good optical transmittance, and chemical inertness, making it highly promising for applications in aerospace, military, machinery, and electronics. However, the limited reserves and small size of natural diamonds significantly restrict their industrial applications, leading to a surge in research interest in synthetic diamond technology.

[0003] The most common method for producing synthetic diamonds is high-temperature, high-pressure manufacturing. However, this method can only grow diamond grains or powders; to produce bulk diamonds, a metal binder must be added, which leads to a decrease in the performance of the finished diamond product. Chemical vapor deposition (CVD) can grow high-purity diamond films or diamond sheets.

[0004] Methods for growing diamond thin films by chemical vapor deposition can be broadly classified into four categories: pyrolysis CVD (including chemical transport reaction, hot filament, and oxyacetylene flame methods); DC plasma CVD (including low-voltage DC discharge, medium-voltage DC discharge, hollow cathode discharge, DC arc, and DC plasma jet); radio frequency plasma CVD (including low-voltage glow discharge and thermal plasma CVD); and microwave plasma CVD (including 2.45 GHz plasma methods, but with high production costs); DC plasma CVD and radio frequency plasma CVD have high costs for large-scale production and cannot produce large-area diamonds, with diamond diameters not exceeding 150 mm; CVD diamonds prepared by the hot filament method have advantages such as low operating costs, relatively simple equipment, high production efficiency, and large product size; however, CVD diamonds prepared by the hot filament method have the following problems:

[0005] The deposited diamond contains many impurities and defects; it is difficult to guarantee a high deposition rate and deposition quality; increasing 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 an urgent problem to be solved in this field. Summary of the Invention

[0007] To address the aforementioned technical issues, a method for high-temperature preparation of large-area diamonds using HFCVD is provided, enabling the preparation of large-area, high-quality diamonds with few impurities and defects.

[0008] This invention provides a method for high-temperature preparation of large-area diamond using HFCVD, comprising the following steps:

[0009] Diamonds are produced using a hot-wire chemical vapor deposition apparatus; the produced diamonds have a diameter ≥200mm.

[0010] The hot filament chemical vapor deposition apparatus is provided with a deposition space, which includes a hot filament assembly, a deposition platform, and a temperature compensation device.

[0011] The hot wire assembly includes a plurality of hot wires arranged in parallel.

[0012] The deposition stage includes 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 spacing D between the parallel hot wires, D = 4-12mm;

[0015] The substrate spacing H between the hot wire plane and the substrate is adjusted according to the hot wire spacing D using the first formula.

[0016] Evacuate the deposition space;

[0017] Introduce hydrogen and methane in proportion to the target pressure; turn on the hot wire to heat the upper surface of the deposition substrate to the preset temperature, and start timing;

[0018] Once the deposition time reaches the preset time, the hot wire heating is turned off and cooling begins.

[0019] After cooling is complete, the hydrogen gas inside the furnace is discharged, and the diamond film is removed from the surface of the deposition substrate to obtain diamond.

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

[0021] Compared with the prior art, the advantages of this invention are: large-area diamonds are prepared by hot filament chemical deposition, and the diameter of the diamonds is ≥200mm;

[0022] The deposition space includes a temperature compensation device to avoid tip thermal effects. This helps to ensure that the temperature at the center and edge of the substrate is basically the same during the deposition process. At the same time, it helps to avoid problems such as cracking or damage to large-area crystals caused by different cooling rates at the edge and center of the substrate during the cooling process.

[0023] Controlling the dimensionality reduction range of the cooling interlayer mechanism is beneficial to controlling the temperature transfer range of the cooling interlayer mechanism within the contact surface between the cooling interlayer mechanism and the substrate during the deposition process. This helps to avoid the cooling interlayer mechanism affecting the radiation temperature of the hot wire during the deposition process, thereby avoiding the problem of uneven temperature radiation from the hot wire on the substrate surface.

[0024] This helps to ensure that the prepared large-area diamond does not have uneven internal structure, and helps to reduce the impurities and defects in the large-area diamond.

[0025] By adjusting the spacing D between parallel hot wires, where D = 4-12 mm, it is beneficial to achieve uniform temperature across the substrate surface. This avoids the problem of temperature fluctuations in the same direction corresponding to the hot wire position caused by a small hot wire spacing and large dispersion of hot wire distribution. It also avoids the problem of increased temperature difference between the center and edge of the hot wire-affected area due to concentrated heat radiation when the hot wire spacing is large. Furthermore, the hot wire spacing facilitates assembly.

[0026] This further facilitates the preparation of large-area diamonds without internal structural inhomogeneity, and further helps to reduce impurities and defects in large-area diamonds.

[0027] By adjusting the substrate spacing H between the hot wire plane and the substrate according to the hot wire spacing D using the first formula, it is further beneficial to eliminate the problem of increased substrate surface temperature fluctuation 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 wire and the substrate is compensated for the temperature fluctuation of the substrate surface caused by the change in the hot wire spacing; it is further beneficial to achieve uniform temperature distribution during deposition on the upper surface of the substrate.

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

[0029] Furthermore, the first formula:

[0030] The advantages of the previous step are that it helps to achieve uniform temperature across the substrate surface, avoids the problem of temperature fluctuations in the same direction of the substrate due to small hot wire spacing and large hot wire distribution dispersion, and avoids the problem of increased temperature difference between the center and edge of the hot wire-affected area due to concentrated heat radiation when the hot wire spacing is large; and the hot wire spacing is also beneficial for assembly.

[0031] This helps ensure that the prepared large-area diamond does not have uneven internal structure, and further helps to reduce impurities and defects in the large-area diamond.

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

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

[0034] The substrate compensation device is sleeved on the outside of the substrate and in contact with 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 advantages of the previous step are that it helps to avoid tip thermal effects, helps to ensure that the temperature of the substrate center and edge is basically the same during the deposition process, and helps to avoid problems such as cracking or damage to large-area crystals caused by different cooling rates at the substrate edge and center during the cooling process. Therefore, it helps to ensure that the prepared large-area diamond does not have uneven internal structure and helps to reduce impurities and defects in large-area diamond.

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

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

[0040] The first arc-shaped plate is connected to a first base plate that is perpendicular to the first arc-shaped plate;

[0041] The second arc-shaped plate is connected to a second base plate that is perpendicular to the second arc-shaped plate.

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

[0043] The cooling interlayer mechanism is located between the first arc-shaped plate and the second arc-shaped plate;

[0044] The first base plate and the second base plate are located below the cooling interlayer mechanism;

[0045] The ends of the first arc-shaped plate and the ends of the second arc-shaped plate are spaced apart;

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

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

[0048] ε: Thermal reflectivity of the first or second arc-shaped plate; H: Substrate spacing between the hot filament 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 the previous step is that, with the cooling interlayer mechanism located between the first arc-shaped plate and the second arc-shaped plate, and the first base plate and the second base plate located below the cooling interlayer mechanism, the dimensionality reduction range of the cooling interlayer mechanism can be controlled. This is beneficial for controlling the temperature transfer range of the cooling interlayer mechanism within the contact surface between the cooling interlayer mechanism and the substrate during the deposition process. It also helps to avoid the cooling interlayer mechanism affecting the radiation temperature of the hot wire during the deposition process, thereby avoiding the problem of uneven temperature on the upper surface of the substrate caused by the hot wire radiation.

[0051] This helps to ensure that the prepared large-area diamond does not have uneven internal structure, and helps to reduce impurities and defects in the large-area diamond.

[0052] Furthermore, the heating filaments are arranged in a rectangular structure; the four corners of the rectangular structure are not located above the distance between the ends of the first arc-shaped plate and the ends of the second arc-shaped plate.

[0053] The thermal radiation compensation device does not come into contact with the cooling interlayer structure.

[0054] The advantage of the previous step is that the four corners of the rectangular structure are not located above the distance between the ends of the first arc plate and the ends of the second arc plate, which helps 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 1000-8000 Pa.

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

[0057] The benefits of the previous step are achieved by ensuring full and uniform contact between hydrogen and methane, 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℃.

[0059] The advantage of using the previous step is that it helps to avoid the formation of graphite phases or defects during the diamond film deposition process.

[0060] Furthermore, the cooling jacket 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 interlayer mechanism is water, and the outlet water temperature of the cooling medium is 40-60℃.

[0062] The interface temperature of the precipitation and cooling interlayer mechanism is 190-260℃.

[0063] The advantage of the previous step is that, since the cooling medium in the cooling interlayer mechanism is water and the outlet temperature of the cooling medium is 40-60℃, the deposition substrate is cooled uniformly, which helps to avoid the problem of uneven temperature in different parts of the substrate caused by excessively rapid cooling; thus, it helps to avoid the problem of defects in the diamond growth process.

[0064] The interface temperature between the precipitation and cooling sandwich structure is 190-260℃, which helps to avoid the problem of substrate deformation caused by prolonged high temperature due to slow cooling. Attached Figure Description

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

[0066] Figure 2 is a perspective view of the hot wire assembly, deposition substrate, and temperature compensation device of Example 1;

[0067] Figure 3 is a top view of the hot filament assembly, deposition substrate, and temperature compensation device in Example 1;

[0068] The figure shows: 1. Hot wire assembly, 2. Substrate, 3. Substrate compensation device, 4. Cooling interlayer mechanism, 5. First arc plate, 6. First base plate, 7. Thermal radiation compensation device, 8. Second arc plate, 9. Second base plate. Detailed Implementation

[0069] To better understand the technical solution of the present invention, the present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0070] Example 1:

[0071] This embodiment provides a method for high-temperature preparation of large-area diamond using HFCVD, comprising the following steps:

[0072] Diamonds were produced using a hot-wire chemical vapor deposition apparatus; the produced diamonds had a diameter of 300 mm.

[0073] The hot filament chemical vapor deposition apparatus is provided with a deposition space, which includes a hot filament assembly 1, a deposition platform, and a temperature compensation device.

[0074] The hot wire assembly 1 includes a plurality of hot wires arranged in parallel.

[0075] The deposition stage includes 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;

[0076] The temperature compensation device includes a substrate compensation device 3 and a thermal radiation compensation device 7; both the substrate compensation device 3 and the thermal radiation compensation device 7 are made of molybdenum, and the surface of the temperature compensation device near the substrate 2 and the cooling sandwich structure has high surface reflectivity.

[0077] The substrate compensation device 3 has a circular structure and is flush with the substrate 2.

[0078] The substrate compensation device 3 is sleeved on the outside of the substrate 2 and is in contact with the substrate 2;

[0079] The substrate compensation device 3 is located on the outer upper surface of the cooling sandwich structure;

[0080] The thermal radiation compensation device 7 includes a first arc-shaped plate 5 and a second arc-shaped plate 8 arranged opposite to each other;

[0081] The first arc-shaped plate 5 is connected to a first base plate 6 that is perpendicular to the first arc-shaped plate 5;

[0082] The second arc-shaped plate 8 is connected to a second base plate 9 which is perpendicular to the second arc-shaped plate 8.

[0083] The thermal radiation compensation device 7 is fitted outside the cooling interlayer mechanism 4;

[0084] The cooling interlayer mechanism 4 is located between the first arc-shaped plate 5 and the second arc-shaped plate 8;

[0085] The first base plate 6 and the second base plate 9 are located below the cooling interlayer mechanism 4;

[0086] 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 arc plate 5 and the end of the second arc plate 8.

[0087] The thermal radiation compensation device 7 does not come into contact with the cooling interlayer structure.

[0088] Adjust the spacing D between the parallel hot wires, D = 4-12mm;

[0089] The substrate spacing H between the hot wire plane and the substrate 2 is adjusted according to the hot wire spacing D using the first formula.

[0090] First formula:

[0091] The end of the first arc-shaped plate 5 and the end of the second arc-shaped plate 8 are provided with a gap;

[0092] 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;

[0093] Formula 2 is: L = 10e × (20 - H);

[0094] ε: Thermal reflectivity of the first arc plate 5 or the second arc plate 8; H: Substrate spacing between the hot wire plane and the substrate 2.

[0095] Evacuate the deposition space;

[0096] Hydrogen and methane are introduced in proportion to reach the target pressure; the hot wire is turned on to heat the upper surface of the deposition substrate to reach the preset temperature, and the timing is started; the target pressure of hydrogen and methane is 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℃;

[0097] The cooling medium in the cooling interlayer mechanism 4 is water, and the outlet temperature of the cooling medium is 50°C.

[0098] The interface temperature of the precipitation and cooling interlayer mechanism 4 is 225°C.

[0099] Once the deposition time reaches the preset time, the hot wire heating is turned off and cooling begins.

[0100] After cooling is complete, the hydrogen gas inside the furnace is discharged, and the diamond film is removed from the surface of the deposition substrate to obtain diamond.

[0101] Example 2:

[0102] The content that is the same as in Example 1 will not be repeated here; the differences between this example and Example 1 are as follows: This example provides a method for high-temperature preparation of large-area diamond using HFCVD, including the following steps:

[0103] The produced diamond has a diameter of 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 ring; the height of the substrate compensation device 3 is slightly lower than the height of the substrate 2;

[0104] The hydrogen and methane are introduced to a target pressure of 4000 Pa; the volume ratio of methane to hydrogen is 3:97; and the preset temperature of the upper surface of the substrate 2 is 850°C.

[0105] The cooling medium in the cooling interlayer mechanism 4 is water, and the outlet water temperature of the cooling medium is 45°C.

[0106] The interface temperature of the precipitation and cooling interlayer mechanism 4 is 200℃.

[0107] Example 3:

[0108] The content that is the same as in Example 1 will not be repeated here; the differences between this example and Example 1 are as follows: This example provides a method for high-temperature preparation of large-area diamond using HFCVD, including the following steps:

[0109] The produced diamond has a diameter of 400mm; the substrate compensation device 3 and the thermal radiation compensation device 7 are both made of silicon carbide.

[0110] The hydrogen and methane are introduced to a target pressure of 7500 Pa; the volume ratio of methane to hydrogen is 7.7:92.5; and the preset temperature of the upper surface of the substrate 2 is 980°C.

[0111] The cooling medium in the cooling interlayer mechanism 4 is water, and the outlet temperature of the cooling medium is 58°C.

[0112] The interface temperature of the precipitation and cooling interlayer mechanism 4 is 255°C.

[0113] Those skilled in the art should understand that the scope of the invention involved in this application is not limited to technical solutions formed by specific combinations of the above-mentioned technical features, but should also cover other technical solutions formed by arbitrary combinations of the above-mentioned technical features or their equivalent features without departing from the inventive concept. For example, technical solutions formed by substituting the above-mentioned features with technical features disclosed in this application (but not limited to) that have similar functions.

Claims

1. A method for high-temperature preparation of large-area diamond using HFCVD, characterized in that, Includes the following steps: Diamonds are produced using a hot-wire chemical vapor deposition apparatus; the produced diamonds have a diameter ≥200mm. The hot filament chemical vapor deposition apparatus is provided with a deposition space, which includes a hot filament assembly, a deposition platform, and a temperature compensation device. The hot wire assembly includes a plurality of hot wires arranged in parallel. The deposition stage includes 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 spacing D between the parallel hot wires, D = 4-12mm; The substrate spacing H between the hot wire plane and the substrate is adjusted according to the hot wire spacing D using the first formula. Evacuate the deposition space; Introduce hydrogen and methane in proportion to the target pressure; turn on the hot wire to heat the upper surface of the deposition substrate to the preset temperature, and start timing; Once the deposition time reaches the preset time, the hot wire heating is turned off and cooling begins. After cooling is complete, the hydrogen gas inside the furnace is discharged, and the diamond film is removed from the surface of the deposition substrate to obtain diamond.

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

3. The method for high-temperature preparation of large-area diamond using HFCVD according to claim 1, characterized in that, The substrate compensation device is a ring structure, or the substrate compensation device is composed of 2-5 arc segments assembled into a ring; The substrate compensation device is flush with or slightly lower than the substrate height; The substrate compensation device is sleeved on the outside of the substrate and in contact with 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 high-temperature preparation of large-area diamond using HFCVD according to claim 1, characterized in that, The temperature compensation device also includes a thermal radiation compensation device. The thermal radiation compensation device includes a first arc-shaped plate and a second arc-shaped plate arranged opposite to each other; The first arc-shaped plate is connected to a first base plate that is perpendicular to the first arc-shaped plate; The second arc-shaped plate is connected to a second base plate that is perpendicular to the second arc-shaped plate.

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

6. The method for high-temperature preparation of large-area diamond using HFCVD 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 ends of the first arc-shaped plate and the ends of the second arc-shaped plate. The thermal radiation compensation device does not come into contact with the cooling interlayer structure.

7. The method for high-temperature preparation of large-area diamond using HFCVD according to claim 1, characterized in that, The hydrogen and methane are introduced to the target pressure of 1000-8000 Pa.

8. The method for high-temperature preparation of large-area diamond using HFCVD 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 high-temperature preparation of large-area diamond using HFCVD according to claim 1, characterized in that, The preset temperature of the upper surface of the substrate is 800-1000℃.

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

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