A method for producing a single crystal diamond

Abstract

The application belongs to the field of diamond preparation, and discloses a preparation method of single crystal diamond. The method comprises the following steps: selecting highly close seed crystals and performing acid washing treatment; preparing a substrate table, plating a carbon film on the upper surface of the substrate table, the thickness of the carbon film being 5-10 microns, and cleaning and drying after the plating is completed; placing the acid-washed seed crystals into the substrate table after the plating, then placing the substrate table into a deposition cavity, starting to pass in hydrogen after vacuumizing, and starting to open the microwave etching; after the etching is completed, passing in a mixed gas of methane, carbon dioxide, argon and nitrogen, and growing; after the growing is completed, stopping to pass in methane, increasing the temperature by 100-150 DEG C on the basis of the growing temperature, keeping warm, then cooling to room temperature, and obtaining the single crystal diamond. The application greatly improves the temperature distribution on the seed crystals, promotes the flatness of the growing surface, and can mass-produce single crystal diamond with medium-high quality and high flatness.

Description

Technical Field

[0001] This invention belongs to the field of diamond preparation, specifically relating to a method for preparing single-crystal diamond. Background Technology

[0002] Microwave plasma chemical vapor deposition (MPCVD) has become the preferred method for preparing large-size, high-quality diamonds due to its advantages such as high plasma density and no electrode contamination. During MPCVD deposition, the structural characteristics of the substrate and the fabrication method used have a significant impact on the deposition rate and quality of the diamond.

[0003] However, due to the "edge effect" of microwave discharge, the temperature of the seed crystal gradually decreases from the edge to the center during diamond deposition, with temperature differences reaching tens of degrees Celsius. Furthermore, as the height difference between the diamond single crystal growth surface and the substrate increases, the "edge effect" intensifies, ultimately resulting in extremely poor surface smoothness of the prepared diamond. Moreover, during growth, the polycrystalline diamond at the edge gradually extends into the seed crystal, eventually shrinking the single crystal growth area. To obtain a larger single crystal, growth must be stopped after a certain period, resulting in a smaller thickness per growth cycle. Simultaneously, due to varying contact conditions between the bottom of each seed crystal and the substrate during growth, heat dissipation varies, sometimes leading to significant temperature differences between the seed crystals and inconsistent quality of the prepared single crystal diamond.

[0004] Therefore, it is necessary to develop a substrate stage structure for preparing single-crystal diamond and a method for preparing single-crystal diamond that is compatible with this structure. Summary of the Invention

[0005] In view of the problems existing in the prior art, the purpose of the present invention is to provide a method for preparing single crystal diamond. This method promotes the lateral growth of the seed crystal, i.e., diameter expansion growth, in the early stage of growth, inhibits the growth of polycrystalline diamond at the edge of the seed crystal, expands the growth area of ​​single crystal diamond, and can greatly improve the temperature distribution on the seed crystal. Each seed crystal grows a flat single crystal diamond, and the thickness of a single growth is increased.

[0006] To achieve the objectives of this invention, the specific technical solution is as follows:

[0007] A method for preparing single-crystal diamond includes the following steps:

[0008] (1) Select seed crystals with similar heights and perform acid washing treatment;

[0009] (2) Prepare a substrate stage, deposit a carbon film with a thickness of 5~10μm on the upper surface of the substrate stage, and clean and dry it after the film is deposited.

[0010] (3) Put the seed crystal after acid washing in step (1) into the substrate platform after film plating in step (2), and then put the substrate platform into the deposition cavity, vacuumize, start to pass in hydrogen, and start the microwave, and etch for 0.5-2 h at a temperature of 700-1000℃ and a pressure of 17-21 kPa;

[0011] (4) After etching, pass in methane, carbon dioxide, argon, and nitrogen, and grow for 180-200 h in an environment with a pressure of 20-25 kPa and a temperature of 900-1050℃;

[0012] (5) After growth, stop passing in methane, carbon dioxide, argon, and nitrogen, increase the temperature by 100-150℃ on the basis of the growth temperature in step (4), and keep warm for 1-2 h, then reduce the temperature at a gradient of 100-200℃, and keep warm for 1-2 h at each gradient temperature until room temperature, turn off the microwave, and stop passing in hydrogen, to obtain a single crystal diamond.

[0013] Preferably, in step (1), the acid solution in the acid washing treatment is one or more of aqua regia and concentrated sulfuric acid; and the acid washing is performed until no bubbles are generated on the surface of the seed crystal.

[0014] Preferably, in step (1), the highly close seed crystal has a height difference of ≤0.09 mm between different seed crystals.

[0015] Preferably, in step (2), the substrate platform comprises a substrate platform body in a cylindrical structure or a circular platform structure, the upper surface of the substrate platform body is provided with a circular groove, and the bottom of the circular groove is provided with a plurality of grid grooves for accommodating seed crystals.

[0016] The width of the grid groove is 0.15-0.5 mm larger than the width of the seed crystal, the depth of the grid groove is 0.05-0.15 mm smaller than the thickness of the seed crystal, and the limiting step width between two grids is 0.9-1.5 mm; the diameter of the circular groove is 1-3 mm smaller than the diameter of the upper surface of the substrate platform, and the depth of the circular groove is 0.5-1 mm larger than the difference between the thickness of the seed crystal and the depth of the grid groove.

[0017] The carbon film is arranged on the upper surface of the substrate platform body, the surface of the circular groove, and the surface of the grid groove.

[0018] Further preferably, the center of the circular groove coincides with the center of the surface of the substrate platform body.

[0019] Further preferably, the seed crystal is in a square columnar structure, and the grid groove is in a square columnar hollow structure.

[0020] Further preferably, the grid grooves are uniformly arranged on the upper surface of the substrate table body; the grid grooves are arranged in any one of the following array modes on the upper surface of the substrate table body: a plurality of linear arrays, a plurality of circumferential arrays, and a plurality of rectangular arrays.

[0021] Further preferably, the distance between adjacent grid grooves is 0.9-1.5 mm; the adjacent grid grooves are in communication with each other.

[0022] Preferably, in steps (3)-(5), the flow rate of the hydrogen is 400-500 sccm; in step (4), the flow rate of the methane is 8-75 sccm, the flow rate of the carbon dioxide is 0.5-3 sccm, the flow rate of the argon is 1-10 sccm, and the flow rate of the nitrogen is 0.05-0.1 sccm.

[0023] Preferably, in steps (3)-(5), the heating rate is 5-20 ℃ / min; in step (5), the cooling rate is 1-2 ℃ / min.

[0024] The square columnar (hollow) structure mentioned in the application is a cuboid (hollow) structure with equal length and width.

[0025] Compared with the prior art, the application has the following advantages:

[0026] (1) The preparation method of the application makes the lateral growth trend of the diamond very obvious in the early growth stage, expands the growth area of the single crystal diamond, suppresses the growth of the polycrystalline diamond at the edge of the seed crystal, and improves the thickness of single growth.

[0027] (2) The preparation method of the application can mass-produce single crystal diamonds with medium-high quality and high flatness, and the circular grooves and grids arranged on the upper surface of the substrate table provide sufficient growth space for the lateral growth of the diamond. The edge effect of the seed crystal is transferred to the edge of the substrate table by lowering the seed crystal surface below the edge of the substrate table, which greatly improves the temperature distribution on the seed crystal, is conducive to suppressing the growth of the polycrystalline diamond at the edge, and promotes the flatness of the growth surface.

[0028] (3) The carbon film is creatively arranged on the substrate table of the application. Due to the existence of the carbon film on the substrate table, the temperature difference of each seed crystal in the early stage is small, and the quality of the single crystal diamond grown is uniform.

[0029] (4) The substrate table of the application has a simple structure and is easy to produce and manufacture, can mass-produce single crystal diamonds with high quality and high flatness, reduces the production cost, and has good industrial application prospect. BRIEF DESCRIPTION OF DRAWINGS

[0030] The accompanying drawings are included to provide a further understanding of the application, and are incorporated in and constitute a part of the specification, illustrate embodiments of the application, and are used to explain the present application, but are not intended to limit the present application.

[0031] In the drawings:

[0032] Figure 1 A top view of a substrate table for growing single crystal diamond according to the present application;

[0033] Figure 2 A sectional view of a substrate table for growing single crystal diamond according to the present application;

[0034] Figure 3 A Figure 2 Partial enlarged view;

[0035] Figure 4 Process flow chart of the present application. DETAILED DESCRIPTION

[0036] In order to facilitate the understanding of the present application, the following will be combined with the drawings and the preferred embodiments to make a more comprehensive and detailed description of the present application, but the protection scope of the present application is not limited to the following specific embodiments.

[0037] Unless otherwise defined, all the professional terms used in the following are the same as the meanings commonly understood by those skilled in the art. The professional terms used in the present application are only for the purpose of describing the specific embodiments, and are not intended to limit the protection scope of the present application.

[0038] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present application can be purchased from the market or can be prepared by existing methods.

[0039] Example 1

[0040] As Figures 1-3 shown, the present embodiment provides a substrate table for growing single crystal diamond, which includes a circular table-shaped substrate table body 1, and the substrate table body 1 is a circular table-shaped structure with a top surface diameter of 53 mm. It should be noted that the top surface and the side surface of the substrate table body 1 are circularly arc transitioned, and a circular groove 2 is arranged on the upper surface of the substrate table body 1, the diameter of the circular groove 2 is 52 mm, and the depth of the circular groove 2 is 0.65 mm.

[0041] The circular groove 2 is uniformly provided with 23 square columnar hollow structure grid grooves 3 for accommodating and limiting the seed crystal, which are arranged in a linear array in a layered manner, and the length, width and height parameters of the seed crystal to be accommodated are 5 mm x 5 mm x 0.3 mm, the width of each grid groove 3 is 5.2 mm, and the depth of each grid groove 3 is 0.15 mm.

[0042] In this embodiment, the distance between adjacent grid grooves 3 is 0.9 mm. And the adjacent grid grooves 3 are interconnected, which in this embodiment is specifically manifested as that the adjacent grid grooves 3 are interconnected at the connecting top corners, further reducing the temperature difference of each point of the whole substrate table and the temperature difference of each seed crystal.

[0043] Embodiment 2

[0044] This embodiment is basically the same as embodiment 1, the difference is that the depth of the circular groove is 1.15 mm, and the distance between adjacent grid grooves is 1.5 mm.

[0045] Embodiment 3

[0046] The embodiment provides a preparation method of single crystal diamond, comprising the following steps:

[0047] (1) Select seed crystals (5mm×5mm×0.3mm) with a height close to each other, and the height difference is less than or equal to 0.09mm. Observe the morphology of the growth surface of the seed crystal in a microscope, and remove unqualified seed crystals. Clean the qualified seed crystals with deionized water for 10 minutes, and finally put them into aqua regia for acid washing until no bubbles are generated on the surface of the seed crystal;

[0048] (2) Ultrasonic clean the substrate table in embodiment 1 for 5-10 minutes, then coat a layer of carbon film with a thickness of 10μm on the surface of the substrate table body, the surface of the circular groove and the surface of the grid groove, ultrasonic clean for 3-5 minutes after coating the film, and dry with dry air;

[0049] (3) Ultrasonic clean the seed crystal after acid washing in step (1) with deionized water, acetone and anhydrous ethanol for 10 minutes, and dry with dry nitrogen. Place the seed crystals in the grid grooves of the substrate table after coating the film in step (2) according to the number, and then put the substrate table into the deposition cavity. The cavity pressure is extracted to below 0.8Pa, the hydrogen valve is opened, the hydrogen flow value is set to 400sccm, when the pressure rises to 1kPa, the microwave is turned on, the microwave power is set to 600W, the temperature rising speed is set to 10℃ / min, the pressure rises to 17KPa, and etching is performed for 30 minutes;

[0050] (4) After etching, introduce methane, carbon dioxide, argon and nitrogen, set the methane flow value to 32sccm, the carbon dioxide flow value to 2sccm, the argon flow value to 10sccm, the nitrogen flow value to 0.1sccm, set the pressure to 20kPa, keep the temperature at 950℃, and grow for 180 hours;

[0051] (5) After the growth is completed, stop the supply of the methane, carbon dioxide, argon, and nitrogen, set the temperature increase rate to 5°C / min, increase the temperature to 1300°C, and keep the temperature for 1 hour. Then, decrease the temperature at a gradient of 200°C at a rate of 2°C / min, keep the temperature for 1 hour at each gradient, and decrease the temperature to room temperature. Then, stop the supply of the hydrogen, and obtain the single crystal diamond.

[0052] Example 4

[0053] This example is basically the same as Example 3, except that the single crystal diamond growth substrate table in Example 2 is used.

[0054] Example 5

[0055] This example is basically the same as Example 3, except that in step (2), the thickness of the carbon film is 5 μm, the carbon dioxide flow rate is 0.5 sccm, the argon flow rate is 1 sccm, and the nitrogen flow rate is 0.05 sccm.

[0056] Example 6

[0057] This example is basically the same as Example 3, except that in step (4), the pressure during the growth is 24 kPa, and the temperature is 1050°C.

[0058] Comparative Example 1

[0059] This example is basically the same as Example 3, except that the substrate table does not have a circular groove.

[0060] Comparative Example 2

[0061] This example is basically the same as Example 4, except that the depth of the circular groove of the substrate table in the example is 2 mm.

[0062] Comparative Example 3

[0063] This example is basically the same as Example 3, except that step (2) is omitted.

[0064] Comparative Example 4

[0065] This example is basically the same as Example 3, except that in step (4), the carbon dioxide flow rate is 4 sccm, the argon flow rate is 10 sccm, and the nitrogen flow rate is 0.1 sccm.

[0066] Comparative Example 5

[0067] This example is basically the same as Example 3, except that in step (4), the carbon dioxide flow rate is 2 sccm, the argon flow rate is 0.1 sccm, and the nitrogen flow rate is 0 sccm.

[0068] Comparative Example 6

[0069] This example is basically identical with example 3, except that in step (4), the pressure during growth is 15 kPa.

[0070] Comparative example 7

[0071] This example is basically identical with example 3, except that in step (4), the growth temperature is 1100°C.

[0072] The growth process of the single crystal diamond of examples 3-6 and comparative examples 1-7 was detected, and the results are shown in Table 1. From the experimental data table, it is not difficult to see that the thicker the carbon film, the smaller the temperature difference between the seeds. The greater the depth of the circular groove, the relatively flat the growth surface, the more obvious the lateral growth, but the slower the growth rate, and the temperature and pressure have a certain influence on the lateral growth.

[0073] Table 1

[0074]

[0075] The above only is the preferred embodiment of the present application, and is not used to limit the present application, for the person skilled in the art, the present application can have various changes and variations. Any modification, equivalent replacement, improvement, etc. within the spirit and principle of the present application should be included in the scope of the present application.

Claims

1. A method of producing a single crystal diamond, characterized by, The method comprises the following steps: (1) selecting highly close seed crystals and performing acid washing treatment; (2) preparing a substrate table, wherein the substrate table comprises a cylindrical or circular table-shaped substrate table body, a circular groove is arranged on the upper surface of the substrate table body, a plurality of grid grooves for accommodating seed crystals are arranged at the bottom of the circular groove, the center of the circular groove is coincident with the center of the surface of the substrate table body, the grid grooves are uniformly arranged on the upper surface of the substrate table body, the grid grooves are arranged in any one of the following modes: a plurality of linear arrays, a plurality of circular peripheral arrays, and a plurality of rectangular arrays on the upper surface of the substrate table body, a carbon film with a thickness of 5-10 μm is plated on the upper surface of the substrate table body, and the substrate table body is cleaned and dried after the plating is completed; (3) placing the seed crystals subjected to the acid washing in step (1) into the substrate table obtained in step (2) after the plating, and then placing the substrate table into a deposition cavity, vacuumizing the cavity, and then starting to input hydrogen, and starting to turn on a microwave, and etching for 0.5-2 h at a temperature of 700-1000 ℃ and a pressure of 17-21 kPa; (4) after the etching is completed, inputting methane, carbon dioxide, argon and nitrogen in an environment with a pressure of 20-25 kPa and a temperature of 900-1050 ℃, and growing for 180-200 h; wherein the flow value of the methane is 8-75 sccm, the flow value of the carbon dioxide is 0.5-3 sccm, the flow value of the argon is 1-10 sccm, and the flow value of the nitrogen is 0.05-0.1 sccm; (5) after the growing is completed, stopping the input of the methane, the carbon dioxide, the argon and the nitrogen, increasing the temperature by 100-150 ℃ on the basis of the growing temperature in step (4), and then performing temperature reduction with a gradient of 100-200 ℃, and keeping the temperature at each gradient for 1-2 h until the temperature reaches room temperature, and then turning off the microwave and stopping the input of the hydrogen, and obtaining a single crystal diamond.

2. The production method according to claim 1, wherein In step (1), the acid liquid in the acid washing treatment is one or more of aqua regia and concentrated sulfuric acid, and the acid washing is performed until no bubbles are generated on the surface of the seed crystals.

3. The production method according to claim 1, wherein In step (1), the highly close seed crystals are specifically seed crystals with a height difference of ≤0.09 mm between different seed crystals.

4. The production method according to claim 1, wherein In step (2), the width of the grid groove is 0.15-0.5 mm larger than the width of the seed crystal, the depth of the grid groove is 0.05-0.15 mm smaller than the thickness of the seed crystal, the limiting step width between two grid grooves is 0.9-1.5 mm, the diameter of the circular groove is 1-3 mm smaller than the diameter of the upper surface of the substrate table, and the depth of the circular groove is 0.5-1 mm larger than the difference between the thickness of the seed crystal and the depth of the grid groove.

5. The production method according to claim 4, wherein The seed crystal is a square columnar structure, and the grid groove is a square columnar hollow structure.

6. The production method according to claim 4, wherein The distance between adjacent grid grooves is 0.9-1.5 mm, and the adjacent grid grooves are in communication with each other.

7. The production method according to claim 1, wherein In steps (3)-(5), the flow of the input hydrogen is 400-500 sccm.

8. The production method according to claim 1, wherein In steps (3)-(5), the temperature increasing rate is 5-20 ℃ / min, and in step (5), the temperature decreasing rate is 1-2 ℃ / min.

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