A method for preparing a polycrystalline diamond diaphragm

Abstract

The present invention belongs to the field of diamond diaphragm preparation, and discloses a method for preparing a polycrystalline diamond diaphragm. The method comprises the following steps: (1) coating or plating a release agent on a molybdenum table, wherein the release agent is a graphite emulsion solution or a carbon film, and in the graphite emulsion solution, the volume ratio of graphite emulsion to water is 1:3-10; (2) placing the molybdenum table in a deposition chamber of an MPCVD device for diamond diaphragm deposition; (3) after the deposition is completed, cooling and demolding. The present invention improves the molding conditions of the diamond diaphragm by pretreating the upper surface of the growing molybdenum table, adding a transition layer, and using the lubricating and uniform characteristics of the graphite emulsion or the carbon film, thereby overcoming the shortcomings of substrate cracking and inability to demold during the cooling process.

Description

Technical Field

[0001] The present invention belongs to the field of diamond diaphragm preparation, and more specifically, relates to a method for preparing a polycrystalline diamond diaphragm. Background Art

[0002] The advantages of diamond diaphragms include high hardness, low mass, ultra-high frequency response, low distortion, high temperature stability, corrosion resistance and long life, which make them an ideal choice for high-end audio equipment, especially for high-fidelity and high-performance audio applications.

[0003] As we all know, chemical vapor deposition (CVD) has become the mainstream method for preparing diamond diaphragms due to its many advantages. However, there are also many problems in its production process, as follows: The existing technology for preparing diamond diaphragms (CVD method for preparing diamond diaphragms) mostly uses silicon wafers as growth substrates. After the growth is completed, the silicon wafers are dissolved with acid or alkali solution to finally obtain a diamond diaphragm. The production cost is high and pollutants are generated, which is not conducive to industrial production. However, the diamond diaphragm prepared by MPCVD technology has edge effects during the growth process, which leads to uneven thickness of the grown diamond diaphragm, easy cracking of the diamond diaphragm during the substrate cooling process, and low yield rate, which is not conducive to industrial production. Summary of the invention

[0004] In view of the above problems existing in the prior art, the object of the present invention is to provide a method for preparing a polycrystalline diamond diaphragm, which improves the molding conditions of the diamond diaphragm by pretreating the upper surface of the growth molybdenum table and overcomes the shortcomings of cracking and inability to demold during the cooling process of the substrate.

[0005] To achieve the above purpose, the technical solution adopted by the present invention is: A method for preparing a polycrystalline diamond diaphragm comprises the following steps: (1) coating or plating a release agent on a molybdenum table, wherein the release agent is a graphite emulsion solution or a carbon film, and in the graphite emulsion solution, the volume ratio of graphite emulsion to water is 1:3-10; (2) Placing the molybdenum stage in the deposition chamber of the MPCVD equipment to deposit the diamond diaphragm; (3) After deposition is completed, cool down and remove the film.

[0006] Furthermore, in step (1), the film thickness of the graphite latex solution after coating is 5 to 10 μm.

[0007] Further preferably, the graphite emulsion solution is coated on the molybdenum table by a spray gun.

[0008] Furthermore, in step (1), the thickness of the carbon film is 5-10 μm.

[0009] Further preferably, the carbon film is deposited on the molybdenum stage by chemical vapor deposition.

[0010] Further preferably, the parameters of the chemical vapor deposition are: The process gas is hydrogen; The flow rates of methane and hydrogen are 200~400sccm; Volume ratio V 甲烷 / V 氢 8%~20%; The deposition temperature is 500~650℃; The pressure is 8~15kPa; The deposition time is 0.5~2h.

[0011] Furthermore, in step (1), the molybdenum platform is first cleaned and dried for the first time before use; preferably, the molybdenum platform is ultrasonically cleaned with acetone, alcohol, and deionized water in sequence; Further preferably, the first drying temperature is 60-100°C; Further preferably, the release agent is coated or plated on a molybdenum table and dried for a second time.

[0012] Furthermore, in step (2), the parameters of the diamond diaphragm deposition are set as follows: Hydrogen 300~400SCCM; The volume ratio of CH4 / H2 is 3%~10%; Introduce nitrogen, oxygen and argon, keeping the volume ratio of nitrogen, oxygen and argon to hydrogen as follows: V N2 / V H2 0.1~5%, V O2 / V H2 0.1~1%, V Ar / V H2 0.1~10%; The pressure in the deposition chamber is 15~20kp; Growth temperature is 600~900℃; The deposition time is 10~24h.

[0013] Furthermore, in step (3), the cooling rate during the cooling and demolding process is 10-15°C / min.

[0014] Furthermore, the molybdenum platform includes a base, a circular groove is arranged on the upper surface of the base, a growth cylinder is arranged at the bottom of the circular groove, and the top of the growth cylinder is a convex spherical surface; The growth cylinder comprises a cylindrical section at the bottom and a convex spherical section at the top, the height of the cylindrical section is less than the depth of the circular groove, and the height of the growth cylinder is greater than the depth of the circular groove.

[0015] Further preferably, the upper surface of the base and the side surface of the base are transitioned through a concave arc to form an arc transition surface.

[0016] Further preferably, the diameter of the arc transition surface gradually decreases from bottom to top.

[0017] Further preferably, the bottom of the circular groove is a horizontal plane, and the growth cylinder is vertically arranged at the bottom of the circular groove.

[0018] Further preferably, at least three growth cylinders are provided.

[0019] Further preferably, a plurality of the growth cylinders are evenly distributed at the bottom of the circular groove.

[0020] Further preferably, a plurality of the growth cylinders are arranged in a circular array and evenly distributed at the bottom of the circular groove.

[0021] Furthermore, the base is a cylindrical structure or a truncated cone structure.

[0022] Further preferably, the central axis of the circular groove coincides with the central axis of the base.

[0023] Further preferably, the diameter D of the base is ≤72 mm, and the height h1 of the base is ≤15 mm ≤20 mm.

[0024] Further preferably, the diameter of the circular groove is ≤60 mm, and the depth h2 of the circular groove is 3 mm≤5 mm.

[0025] Further preferably, 10 mm<the diameter d of the cylindrical section of the growth cylinder<25 mm; and the height h3 of the cylindrical section of the growth cylinder=h2-1 mm.

[0026] Further preferably, the diameter of the convex spherical surface at the top of the growth cylinder is 20-30 mm; the sagittal height h3≤3 mm, and the roughness Ra≤1.6 μm. It should be noted that the sagittal height of the convex spherical surface refers to the maximum thickness of the convex spherical surface in the vertical direction.

[0027] Compared with the prior art, the present invention has the following beneficial effects: The preparation method of the polycrystalline diamond diaphragm of the present invention improves the molding conditions of the diamond diaphragm by pre-treating the substrate on the upper surface of the growth molybdenum table, and overcomes the shortcomings of substrate cracking and inability to demold during the cooling process through the lubricity of graphite emulsion and the characteristics of uniform film formation. It also avoids the shortcomings of mechanical grinding and acid washing nucleation inoculation, improves the growth quality of the diamond diaphragm, avoids contamination by impurities, facilitates demolding, and has low cost, providing good prerequisites for the growth of high-quality diamond films.

[0028] The molybdenum platform of the present invention has a simple structure. Through structural setting and further size setting, the edge effect of the diaphragm can be effectively mitigated, so that the thickness of the diaphragm is more uniform within 1 micron, and batch growth of diamond diaphragms can be achieved.

[0029] The molybdenum table structure of the present invention cooperates with the process, which can effectively reduce production costs, ensure a safe production environment to a certain extent, and reduce environmental pollution; it effectively improves the product yield and shortens the growth cycle of the diamond diaphragm.

[0030] The preparation method of the present invention prepares a transition layer in the early stage of diamond growth. The transition layer can effectively reduce the bonding force between the diamond diaphragm and the molybdenum table, so that the diamond diaphragm can be automatically delaminated during the cooling process. The obtained diamond diaphragm is not easy to crack, and the method of using acid or alkali etching to delaminate is avoided. There is no damage to the molybdenum table, it can be reused, the production cost is reduced, and it is suitable for large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings: Figure 1 It is a process flow chart of the present invention; Figure 2 Schematic diagram of the three-dimensional structure of the molybdenum platform in Example 1; Figure 3 Schematic diagram of the top view of the molybdenum platform in Example 1; Figure 4 Schematic diagram of the cross-sectional structure of the molybdenum platform in Example 1; Figure 5 Schematic diagram of the three-dimensional structure of the molybdenum platform in Comparative Example 1; Figure 6 Schematic diagram of the top view of the molybdenum platform in Comparative Example 1; Figure 7 1 and 1 are Raman characterization spectra of the diamond diaphragms obtained in Example 3 and Comparative Example 3, wherein a is the Raman characterization of the diamond diaphragm of Comparative Example 3, and b is the Raman characterization of the diamond diaphragm of Example 3.

[0032] Figure 8This is a photo of the diaphragm prepared in Example 3.

[0033] Among them: 1—base, 2—upper surface of base, 3—circular groove, 4—growth cylinder, 5—concave arc, 6—convex spherical surface. DETAILED DESCRIPTION

[0034] In order to facilitate the understanding of the present invention, the present invention will be described more comprehensively and meticulously below in conjunction with the accompanying drawings and preferred embodiments of the present invention, but the protection scope of the present invention is not limited to the following specific embodiments.

[0035] Unless otherwise defined, all the professional terms used below have the same meanings as those generally understood by those skilled in the art. The professional terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention.

[0036] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or prepared by existing methods.

[0037] Example 1 like Figures 2~4 As shown, this embodiment provides a molybdenum table for preparing a diamond diaphragm, including a base 1 with a cylindrical structure, a circular groove 3 is arranged on the upper surface 2 of the base, a growth cylinder 4 is arranged at the bottom of the circular groove 3, and the top of the growth cylinder 4 is a convex spherical surface 6.

[0038] In this embodiment, the growth cylinder 4 is divided into a cylindrical section at the bottom and a convex spherical surface 6 at the top. The height of the cylindrical section is less than the depth of the circular groove 3 , and the height of the growth cylinder 4 is greater than the depth of the circular groove 3 .

[0039] In this embodiment, the upper surface 2 of the base and the side surface of the base are transitioned through a concave arc 5 to form an arc transition surface, and as a further preferred embodiment, the diameter of the arc transition surface gradually decreases from bottom to top.

[0040] In this embodiment, the central axis of the circular groove 3 coincides with the central axis of the base 1 .

[0041] In this embodiment, the bottom of the circular groove 3 is a horizontal plane, and the growth column 4 is vertically arranged at the bottom of the circular groove 3 .

[0042] In this embodiment, three growth cylinders 4 are provided, and the three growth cylinders 4 are arranged in a circular array and evenly distributed at the bottom of the circular groove 3 .

[0043] In this embodiment: The base 1 has a diameter D=72 mm and h1=20 mm.

[0044] The diameter of the circular groove 3 is 60 mm, and the depth h2 of the circular groove 3 is 5 mm.

[0045] The diameter d of the cylindrical section of the growth cylinder 4 is 25 mm, and the height h3 of the cylindrical section of the growth cylinder 4 is 4 mm.

[0046] The diameter of the convex spherical surface 6 at the top of the growth cylinder 4 is 25 mm; the arrow height h3 is ≤ 3 mm, and the roughness Ra is ≤ 1.6 μm.

[0047] Example 2 This embodiment provides a method for preparing a polycrystalline diamond diaphragm, using the molybdenum stage of embodiment 1, such as Figure 1 As shown, the following steps are included: (1) Clean the molybdenum platform by ultrasonically cleaning it with acetone, alcohol, and deionized water in sequence, and then dry it; (2) Apply the release agent on the upper surface of the molybdenum table and dry it; (3) Placing the dried molybdenum stage in the deposition chamber of the MPCVD equipment for diamond diaphragm deposition; (4) After deposition is completed, cool down and remove the film; Wherein, the release agent is a graphite emulsion aqueous solution, in which the volume ratio of graphite emulsion to water is 1:3, and the coating thickness is 10 microns.

[0048] As one of the preferred solutions of this embodiment, in step (2), the coating method is: spraying with a spray gun. In this embodiment, spraying with a spray gun can make the graphite emulsion more uniformly adsorbed on the molybdenum platform.

[0049] As one of the preferred solutions of this embodiment, in step (1), the drying temperature is 100° C. In this embodiment, the coated molybdenum platform needs to be dried. If there is too much water, the surface formed by the spraying will be uneven during the transfer of the molybdenum platform.

[0050] As one of the preferred solutions of this embodiment, in step (3), during the diamond film deposition process, 400 sccm of hydrogen and 12 sccm of methane are introduced.

[0051] As one of the preferred solutions of this embodiment, nitrogen, oxygen and argon are also introduced, and the volume ratio of nitrogen, oxygen and argon to hydrogen is V, V and V respectively. 氮气 / V 氢气 =0.1%, V 氧气 / V 氢气 =0.1%, V 氩气 / V 氢气 =0.1%.

[0052] As one of the preferred solutions of this embodiment, the pressure in the deposition chamber is maintained at 15 kPa.

[0053] As one of the preferred solutions of this embodiment, the growth temperature in the deposition chamber is maintained at 600°C.

[0054] As one of the preferred solutions of this embodiment, the deposition time is 24 hours.

[0055] As one of the preferred solutions of this embodiment, in step (4), the cooling rate during the cooling and demolding process is 10°C / min.

[0056] The diamond diaphragm obtained in this embodiment can fall off naturally on the molybdenum table.

[0057] Example 3 This embodiment provides a method for preparing a polycrystalline diamond diaphragm, using the molybdenum stage of embodiment 1, such as Figure 1 As shown, the following steps are included: (1) Clean the molybdenum platform by ultrasonically cleaning it with acetone, alcohol, and deionized water in sequence, and then dry it; (2) Plating a release agent on the upper surface of the molybdenum table; (3) Placing the dried molybdenum stage in the deposition chamber of the MPCVD equipment for diamond diaphragm deposition; (4) After deposition is completed, cool down and remove the film; As one of the preferred schemes of this embodiment, chemical vapor deposition (CVD) is used to deposit a uniform carbon film on the surface of the growth molybdenum table: the process gas is hydrogen and methane, the hydrogen flow rate is 400sccm, the deposition temperature is 650°C, the pressure is 15kPa, the deposition time is 2h, and the carbon film thickness is 10 microns.

[0058] As one of the preferred solutions of this embodiment, in step (1), the drying temperature is 100°C.

[0059] As one of the preferred solutions of this embodiment, in step (3), during the diamond film deposition process, 400 sccm of hydrogen and 12 sccm of methane are introduced.

[0060] As one of the preferred solutions of this embodiment, nitrogen, oxygen and argon are introduced, and the volume ratio of nitrogen, oxygen and argon to hydrogen is V 氮气 / V 氢气 =0.1%, V 氧气 / V 氢气 =0.1%, V 氩气 / V 氢气 =0.1%.

[0061] As one of the preferred solutions of this embodiment, the pressure in the deposition chamber is maintained at 15 kPa.

[0062] As one of the preferred solutions of this embodiment, the growth temperature in the deposition chamber is maintained at 600°C.

[0063] As one of the preferred solutions of this embodiment, the deposition time is 24 hours.

[0064] As one of the preferred solutions of this embodiment, in step (4), the cooling rate during the cooling and demolding process is 10°C / min.

[0065] The diamond diaphragm obtained in this embodiment can fall off naturally on the molybdenum table.

[0066] Figure 8 This is a photo of the diaphragm prepared in Example 3. Figure 7 This is the Raman characterization of Example 3, where a is the Raman characterization of the edge of the diamond diaphragm, and b is the Raman characterization of the center of the diamond diaphragm. It can be seen that the half-width and fluorescence peak values ​​of the diamond indicate that the growth quality of the obtained diamond diaphragm is good.

[0067] Example 4 This embodiment is basically the same as Embodiment 3, except that the process parameters of chemical vapor deposition are set as follows: Hydrogen 400 sccm; CH4 / H2 volume ratio is 10%; The volume ratios of nitrogen, oxygen, argon and hydrogen are respectively, keeping V 氮气 / V 氢气 =5%, V 氧气 / V 氢气 =1%, V 氩气 / V 氢气 =10%; Maintain the pressure in the deposition chamber at 20 kPa; Maintain the growth temperature in the deposition chamber at 900°C; The deposition time was 10 h.

[0068] Example 5 This embodiment is basically the same as embodiment 4, except that: V 氧气 / V 氢气 =0.5%.

[0069] Example 6 This embodiment is basically the same as Embodiment 4, except that the growth gas pressure (pressure inside the deposition chamber) is 15 kp.

[0070] Example 7 This embodiment is basically the same as embodiment 4, except that: V 甲烷 / V 氢气 =6.5%.

[0071] Comparative Example 1 This comparative example is basically the same as Example 2, except that the growth molybdenum platform of this comparative example is not provided with a circular groove.

[0072] like Figure 5 and 6 As shown, this comparative example provides a molybdenum platform, including a base with a cylindrical structure, a growth cylinder is arranged on the top of the base, and the top of the growth cylinder is a convex spherical surface.

[0073] In this comparative example, the growth cylinder is divided into a cylindrical section at the bottom and a convex spherical surface at the top.

[0074] In this comparative example, the upper surface of the base and the side surface of the base are transitioned through a concave arc to form an arc transition surface, and as a further preferred embodiment, the diameter of the arc transition surface gradually decreases from bottom to top.

[0075] In this comparative example, the top of the base is a horizontal plane, and the growth column is vertically arranged on the top of the base.

[0076] In this comparative example, three growth cylinders are provided, and the three growth cylinders are arranged in a circular array and evenly distributed on the top of the base.

[0077] In this comparative example: The diameter of the base is D=72 mm, and h1=20 mm.

[0078] The diameter of the cylindrical section of the growth cylinder is d=25 mm, and the height of the cylindrical section of the growth cylinder is h3=4 mm.

[0079] The diameter of the convex spherical surface at the top of the growth cylinder is 25 mm; the arrow height h3≤3 mm, and the roughness Ra≤1.6 μm.

[0080] Comparative Example 2 This comparative example is basically the same as Example 4, except that: there is no step (2), and no carbon film is deposited, that is, the thickness of the carbon film is 0.

[0081] Comparative Example 3 This comparative example is basically the same as Example 4, except that the growth temperature is 500°C.

[0082] Comparative Example 4 This comparative example is basically the same as Example 4, except that: V 甲烷 / V 氢气 =15%.

[0083] Comparative Example 5 This comparative example is basically the same as Example 4, except that the cavity pressure is 10 kPa.

[0084] Comparative Example 6 This comparative example is basically the same as Example 4, except that: V 氧气 / V 氢气 =1.5%.

[0085] Comparative Example 7 This comparative example is basically the same as Example 4, except that: V 甲烷 / V 氢气 =1%.

[0086] Table 1 Table 1 shows the experimental parameters of Examples 2 to 7 and Comparative Examples 2 to 7 and the growth rate of the diaphragm during the experiment.

[0087] It can be seen from Comparative Example 1 and Example 2 that the edge structure can significantly mitigate the edge effect, promote uniform distribution of plasma on the molybdenum platform, grow a uniform diaphragm thickness, and have high product performance.

[0088] As can be seen from Examples 2-7, the present application improves the molding conditions of the diamond diaphragm and overcomes the shortcomings of cracking and inability to demold during the cooling process of the substrate. Changing some parameters will speed up the diamond growth rate, but will also lead to a decrease in the elastic modulus and a decrease in the overall performance, but the performance is still very excellent and can meet the use requirements.

[0089] Compared with other examples, in Comparative Example 2, a complete diamond diaphragm can be obtained after pre-treatment of the upper surface of the growth molybdenum platform, while the surface without surface pre-treatment will break during the cooling process.

[0090] It can be seen from Examples 2 to 7 and Comparative Examples 3 to 7 that the present application improves the growth quality of the diaphragm, has a high elastic modulus, and improves product performance.

[0091] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the scope of the present invention.

Claims

1. A method for preparing a polycrystalline diamond diaphragm, characterized in that: The following steps are involved: (1) coating or plating a release agent on a molybdenum table, wherein the release agent is a graphite emulsion solution or a carbon film, and in the graphite emulsion solution, the volume ratio of graphite emulsion to water is 1:3-10; (2) Placing the molybdenum stage in the deposition chamber of the MPCVD equipment to deposit the diamond diaphragm; (3) After deposition is completed, cool down and remove the film.

2. The method for preparing a polycrystalline diamond diaphragm according to claim 1, characterized in that: In step (1), the film thickness of the graphite latex solution after coating is 5-10 μm; Preferably, the graphite latex solution is coated on the molybdenum table by spraying.

3. The method for preparing a polycrystalline diamond diaphragm according to claim 1, characterized in that: In step (1), the thickness of the carbon film is 5-10 μm; Preferably, the carbon film is deposited on the molybdenum platform by chemical vapor deposition; Preferably, the parameters of the chemical vapor deposition are: The process gas is hydrogen; The flow rates of methane and hydrogen are 200~400sccm; Volume ratio V 甲烷 / V 氢 8%~20%; The deposition temperature is 500~650℃; The pressure is 8~15kPa; The deposition time is 0.5~2h.

4. The method for preparing a polycrystalline diamond diaphragm according to claim 1, characterized in that: In step (1), the molybdenum platform is first cleaned and dried for the first time before use; preferably, the molybdenum platform is ultrasonically cleaned with acetone, alcohol, and deionized water in sequence; preferably, the first drying temperature is 60-100°C; Preferably, the release agent is coated or plated on a molybdenum table and dried for a second time.

5. The method for preparing a polycrystalline diamond diaphragm according to claim 1, characterized in that: In step (2), the parameters for diamond film deposition are set as follows: The hydrogen flow rate is 300~400sccm; The volume ratio of CH4 / H2 is 3%~10%; Keep the volume ratio of nitrogen, oxygen and argon to hydrogen respectively: V N2 / V H2 0.1~5%, V O2 / V H2 0.1~1%, V Ar / V H2 0.1~10%; The pressure in the deposition chamber is 15~20kPa; Growth temperature is 600~900℃; The deposition time is 10~24h.

6. The method for preparing a polycrystalline diamond diaphragm according to claim 1, characterized in that: In step (3), the cooling rate during the cooling and demolding process is 10-15°C / min.

7. The method for preparing a polycrystalline diamond diaphragm according to any one of claims 1 to 6, characterized in that: The molybdenum platform comprises a base, a circular groove is arranged on the upper surface of the base, and a growth column is arranged at the bottom of the circular groove; The growth cylinder comprises a cylinder section and a convex spherical surface located on the upper part of the cylinder section. The height of the cylinder section is less than the depth of the circular groove, and the height of the growth cylinder is greater than the depth of the circular groove.

8. The method for preparing a polycrystalline diamond diaphragm according to claim 7, characterized in that: The upper surface of the base and the side surface of the base are transitioned through a concave arc to form an annular arc transition surface; Preferably, the diameter of the arc transition surface decreases from bottom to top; Preferably, the bottom of the circular groove is a horizontal plane, and the growth column is vertically arranged at the bottom of the circular groove; Preferably, a plurality of said growth cylinders are evenly distributed at the bottom of the circular groove; Preferably, the base is a cylindrical structure or a truncated cone structure; Preferably, the central axis of the circular groove coincides with the central axis of the base; Preferably, the diameter of the base D≤72mm, and the height of the base h1≤20mm; Preferably, the diameter of the circular groove is ≤60mm, and the depth h2 of the circular groove is ≤3mm≤5mm; Preferably, 10 mm < diameter d of the cylindrical section of the growth cylinder < 25 mm, and the height h3 of the cylindrical section of the growth cylinder = h2 - 1 mm; Preferably, the diameter of the convex spherical surface at the top of the growth cylinder is 20-40 mm; the arrow height h3 is ≤3 mm; and the roughness Ra is ≤1.6 μm.

Images