A method for producing a self-supporting polycrystalline diamond

Abstract

The scheme discloses a self-supporting polycrystalline diamond preparation method, which comprises the following steps: transferring a multilayer graphene film on a growth surface of a traditional diamond growth substrate layer by layer to prepare a growth substrate containing an intermediate layer; growing and preparing a polycrystalline diamond sheet on the surface of the growth substrate containing the intermediate layer; after the polycrystalline diamond sheet is grown, the polycrystalline diamond sheet is taken out by cooling, and the polycrystalline diamond sheet is peeled off by a pure mechanical method; and the growth substrate after the polycrystalline diamond sheet is peeled off can be reused. The method can grow the polycrystalline diamond with high quality, solves the problems of cracks in the polycrystalline diamond growth process, pollution and high cost caused by peeling off the substrate after the growth is completed, many processes, long time, resource waste and the like.

Description

Technical Field

[0001] This invention relates to the field of diamond preparation technology, and in particular to a method for preparing self-supporting polycrystalline diamond. Background Technology

[0002] Diamond is a material that combines many excellent properties, with a hardness of up to 10,000 kg / mm². 2 With a thermal conductivity as high as 2000 W / (m·K) at room temperature and a band gap of 5.47 eV, which is about 5 times higher than that of commonly used semiconductor Si materials, and its transparency across almost the entire wavelength range from ultraviolet (>227 nm) to far infrared, its excellent mechanical, thermal, electrical and optical properties make it a promising material for applications in industries such as machining and protection, heat sinks, optical windows and semiconductors.

[0003] Currently, single-crystal diamond can only be grown using homoepitaxial growth, making it difficult to manufacture large-sized sheets or films. In industrialization, only granular forms can be produced, which is costly and limits its applications. In contrast, polycrystalline diamond can be grown using heteroepitaxial growth, with the substrate being any material other than diamond, including both single-crystal and polycrystalline substrates. This allows for the fabrication of larger sheet and film materials, finding applications in semiconductor packaging, heat sinks, and window materials.

[0004] Current mainstream diamond fabrication methods include high-temperature, high-pressure (HTHP) and chemical vapor deposition (CVD). HTHP can only produce smaller diamonds, while CVD allows for larger deposits and can produce diamond wafers suitable for the semiconductor industry. During the growth of polycrystalline diamond wafers, the internal stress is high, and the difference in thermal expansion coefficients between the polycrystalline and substrate materials can cause cracks or even flaking due to stress during growth, cooling, or polishing. Cracks and flaking render the diamond wafers unusable, severely impacting product quality, production costs, and application promotion.

[0005] Meanwhile, chemical vapor deposition (CVD) requires the epitaxial growth of polycrystalline diamond wafers on a growth substrate. To avoid cracking of the diamond and reduce processing difficulty, the industry currently generally chooses to etch away the substrate using chemical or physical methods after growth to remove the diamond wafer. This method results in the substrate not being reusable, and the etching process typically produces wastewater and other byproducts that easily pollute the environment. This leads to increased costs, longer processing times, and wasted resources. Summary of the Invention

[0006] One objective of this solution is to provide a method for preparing self-supporting polycrystalline diamond, which can grow polycrystalline diamond with high quality and solves the problems of cracks during the growth process, pollution caused by substrate removal after growth, high cost, many processes, long time and waste of resources.

[0007] To achieve the above objectives, the following plan is proposed:

[0008] A method for preparing self-supporting polycrystalline diamond, the method comprising:

[0009] The substrate is separated from the self-supporting polycrystalline diamond grown on the substrate by physical peeling to obtain the self-supporting polycrystalline diamond.

[0010] The self-supporting polycrystalline diamond is in the form of a sheet or a film.

[0011] Preferably, an intermediate layer is provided between the substrate and the self-supporting polycrystalline diamond grown on the substrate; the self-supporting polycrystalline diamond is grown on the surface of the intermediate layer.

[0012] The intermediate layer is a graphene layer;

[0013] The graphene layer comprises two or more graphene films.

[0014] The graphene layer is transferred to the substrate surface by a layer-by-layer transfer method;

[0015] The self-supporting polycrystalline diamond is grown on the surface of the graphene layer.

[0016] In this application, a graphene layer is introduced as an intermediate layer, and diamond is grown on the graphene. As a two-dimensional material, graphene has low interlayer forces and is prone to interlayer slip. Therefore, using a multilayer graphene film as an intermediate layer to grow diamond can avoid cracks caused by the mismatch of thermal expansion coefficients between diamond and the substrate. Also, the mismatch of thermal expansion coefficients and the relatively weak bonding force between graphene layers make it easier to peel diamond off from the substrate, avoiding the method of corroding the substrate.

[0017] Furthermore, since diamond growth on graphene is a homogeneous growth process with high lattice matching, it facilitates high-quality growth. As graphene is an allotrope of carbon, it allows for better nucleation and growth of diamond. Due to the high lattice matching, the diamond growth quality is also better, with lower internal stress, which further reduces the probability of crack formation.

[0018] In one embodiment of this solution, the substrate material includes one or a composite material formed from silicon carbide, silicon, sapphire, quartz, glass, and metal.

[0019] In one embodiment of this scheme, self-supporting polycrystalline diamond is grown on the substrate by chemical vapor deposition (CVD).

[0020] In this solution, the different coefficients of thermal expansion between diamond and the substrate are utilized to assist in diamond peeling through interlayer slippage of graphene during cooling. It can even achieve automatic peeling of diamond sheets during cooling, which greatly reduces the difficulty of peeling and avoids peeling by corroding the substrate.

[0021] In one embodiment of this solution, the substrate is separated from the self-supporting polycrystalline diamond grown on the substrate by manual operation and / or a fixture to obtain the self-supporting polycrystalline diamond.

[0022] or

[0023] Self-supporting polycrystalline diamond is obtained by separating the substrate from the self-supporting polycrystalline diamond grown on the substrate during the cooling process.

[0024] Separation by physical peeling may also include separating the substrate from the self-supporting polycrystalline diamond grown on the substrate by vibration, thereby obtaining self-supporting polycrystalline diamond; or

[0025] By applying suction, the substrate is separated from the self-supporting polycrystalline diamond grown on the substrate to obtain self-supporting polycrystalline diamond.

[0026] To prevent graphene from being etched away during diamond growth and to ensure effective interlayer slip, this approach employs multilayer graphene, rather than in-situ graphene growth on a substrate. The preferred method is to transfer the multilayer graphene to the substrate layer by layer, which increases the interlayer spacing, further reduces interlayer forces, and improves the overall performance.

[0027] For the graphene layer transferred onto the substrate, in this scheme, the graphene layer preferably comprises multiple graphene films; the thickness of the graphene layer is 2 to 100 carbon atom layers; preferably, the thickness of the graphene layer is 5 to 20 carbon atom layers.

[0028] When preparing self-supporting polycrystalline diamond by chemical vapor deposition, the gas in the deposition chamber preferably contains hydrogen and methane; it also contains one or more of argon, nitrogen, oxygen, carbon dioxide, carbon monoxide and water vapor.

[0029] The environmental pressure inside the deposition chamber is 100 Pa to 100,000 Pa;

[0030] The growth temperature inside the deposition chamber is 700℃~1300℃.

[0031] In this solution, the substrate can be reused after simple processing after being separated from the self-supporting polycrystalline diamond grown on the substrate, which greatly reduces resource waste and lowers production costs.

[0032] The beneficial effects of this plan are as follows:

[0033] This solution introduces a multilayer graphene layer that is transferred layer by layer between the substrate and the polycrystalline diamond. Due to the low interaction force between the graphene layers, interlayer slip is easily formed, which solves the problem of cracking and fragmentation caused by the inconsistency of the thermal expansion coefficients between the diamond and the substrate during diamond growth.

[0034] By taking advantage of the different coefficients of thermal expansion between diamond and the substrate, as well as the relatively weak bonding force between graphene layers, diamond can be peeled off by sliding between graphene layers during cooling, which reduces the difficulty of peeling and avoids the method of corroding the substrate.

[0035] The stripped growth substrate can be reused after simple processing, which greatly reduces resource waste and lowers production costs. Attached Figure Description

[0036] To more clearly illustrate the implementation of this solution, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this solution. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0037] Figure 1 This is a schematic diagram of the structure of a self-supporting polycrystalline diamond before peeling after growth.

[0038] Wherein, 1-diamond; 2-graphene layer; 3-substrate. Detailed Implementation

[0039] The implementation methods of this solution will be described in further detail below. Obviously, the described embodiments are only a part of the embodiments of this solution, and not an exhaustive list of all embodiments. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of this solution can be combined with each other.

[0040] The terms “first,” “second,” etc. (if applicable) in the specification and claims are used to distinguish similar objects and are not necessarily used to describe a particular order or sequence. It should be understood that such data used in this way can be interchanged where appropriate so that the embodiments described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms “comprising” and “having,” and any variations thereof, are intended to cover a non-exclusive inclusion, such as a process, method, system, product, or apparatus that comprises a series of steps or units, not necessarily limited to those explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0041] It should be understood that the term "and / or" used in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. Additionally, the character " / " in this article generally indicates that the preceding and following related objects have an "or" relationship.

[0042] Currently, chemical vapor deposition (CVD) allows for easier fabrication of large-sized sheets or films, making it a common method for producing diamond wafers that meet the requirements of the semiconductor industry. Since polycrystalline diamond can be grown via heteroepitaxial growth, the substrate can be any material other than diamond, including both single-crystal and polycrystalline substrates. Therefore, polycrystalline diamond can be fabricated into larger sheet or film forms and applied in semiconductor packaging, heat sinks, and window materials.

[0043] However, during the growth of polycrystalline diamond wafers, the internal stress is relatively high, and there is a difference in the coefficient of thermal expansion between the wafer and the growth substrate. This stress can cause cracks or even flaking of the diamond wafer during growth, cooling, or polishing. Cracks and flaking will render the diamond wafer unusable, seriously affecting product quality, production costs, and application promotion.

[0044] In view of the above problems, the inventors of this application provide a method for preparing self-supporting polycrystalline diamond. This method introduces a graphene layer as an intermediate layer, on which diamond is grown. Graphene, as a two-dimensional material, has low interlayer forces, making it very easy to form interlayer slip. The mismatch in thermal expansion coefficients between the diamond and the substrate makes it easier to peel the diamond off from the substrate. By using multiple layers of graphene as intermediate layers and growing diamond on these intermediate layers, the methods solve the problems of how to grow high-quality polycrystalline diamond sheets, the presence of cracks during polycrystalline diamond growth, pollution and high costs caused by peeling off the substrate after production, and the problems of numerous processes, long time, and resource waste.

[0045] A method for preparing self-supporting polycrystalline diamond includes the following steps:

[0046] 1. A graphene film is transferred onto the growth surface of a substrate used for growing diamond to prepare a substrate containing an intermediate layer;

[0047] 2. Polycrystalline diamond wafers are grown on the surface of a substrate containing an intermediate layer;

[0048] 3. After the polycrystalline diamond wafer is grown, it is cooled and removed. The diamond wafer and the substrate are separated by physical peeling. The substrate after the diamond is peeled off can be reused.

[0049] In one embodiment, the substrate material includes one of silicon carbide, silicon, sapphire, quartz, glass, and metal, or a composite material formed from several of these.

[0050] In one embodiment, the graphene layer is a multilayer graphene film, and the thickness of the graphene layer is 2 to 100 carbon atom layers, such as 2, 7, 12, 17, 22, 27, 32, 37, 42, 47, 52, 57, 62, 67, 72, 77, 82, 87, 92, 97, or 100 carbon atom layers; preferably, the thickness of the graphene layer is 5 to 20 carbon atom layers, such as 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 carbon atom layers.

[0051] In one embodiment, the graphene film is transferred to the substrate surface by a transfer method.

[0052] In one embodiment, chemical vapor deposition (CVD) includes methods such as hot filament CVD, microwave plasma CVD, DC arc plasma jet CVD, hot cathode plasma CVD, laser-induced plasma CVD, combustion flame deposition, electron cyclotron resonance microwave plasma CVD, radio frequency plasma CVD, electron-assisted hot filament CVD, biased microwave plasma CVD, radio frequency-assisted hot filament CVD, hot filament-assisted laser-induced plasma CVD, radio frequency-assisted microwave plasma CVD, or arc discharge plasma CVD; preferably, hot filament CVD, microwave plasma CVD, or DC arc plasma jet CVD.

[0053] In one embodiment, when growing self-supporting polycrystalline diamond on a substrate using chemical vapor deposition, the gas constituting the growth atmosphere in the deposition chamber must contain hydrogen and methane, and may or may not contain one or more of argon, nitrogen, oxygen, carbon dioxide, carbon monoxide, and water vapor.

[0054] In one embodiment, the ambient pressure of the gas constituting the growth atmosphere in the deposition chamber is 100 Pa to 100,000 Pa, such as 100 Pa, 500 Pa, 1000 Pa, 1500 Pa, 2000 Pa, 2500 Pa, 3000 Pa, 3500 Pa, 4000 Pa, 4500 Pa, 5000 Pa, 5500 Pa, 6000 Pa, 6500 Pa, 7000 Pa, 7500 Pa, 8000 Pa, 8500 Pa, 9000 Pa, 9500 Pa, 10000 Pa, 20000 Pa, 30000 Pa, 40000 Pa, 50000 Pa, 60000 Pa, 70000 Pa, 80000 Pa, 90000 Pa, or 100000 Pa;

[0055] The growth temperature in the deposition chamber is 700℃~1300℃, such as 700℃, 750℃, 800℃, 850℃, 900℃, 950℃, 1000℃, 1050℃, 1100℃, 1150℃, 1200℃, 1250℃ or 1300℃.

[0056] In one embodiment, the diamond sheet and the substrate are separated by physical peeling. This can be achieved by placing the substrate with self-supporting polycrystalline diamond grown on it around a vibration source and separating the substrate and polycrystalline diamond through vibration. In another embodiment, the substrate with self-supporting polycrystalline diamond grown on it can be placed in an electric or magnetic field, and the substrate and polycrystalline diamond can be separated by electric or magnetic attraction. In yet another embodiment, the substrate and polycrystalline diamond can be separated by manual operation or with the help of some auxiliary separation jigs. Alternatively, during the cooling process after preparation, the polycrystalline diamond and the substrate may separate due to the different thermal expansion coefficients of the polycrystalline diamond, graphene, and the substrate.

[0057] The present application will be further described below through specific embodiments.

[0058] Example 1

[0059] Ten layers of graphene film were transferred onto the surface of a 3-inch single-crystal silicon substrate using a layer-by-layer transfer method to ensure complete coverage. The silicon wafer was then placed in an MPCVD device, through which hydrogen and methane were introduced in a volume ratio of 50:1, at an ambient pressure of 1000 Pa. Under microwave excitation at 6 kW and 2.45 GHz, the silicon wafer was kept at 950 °C to carry out the diamond growth reaction.

[0060] Under the above conditions, after 72 hours of uninterrupted growth, microwave input and gas supply were stopped, a vacuum was maintained, and the temperature was lowered to room temperature. Then, the vacuum was broken, and the silicon wafer with the grown diamond was removed. Figure 1As shown, the self-supporting polycrystalline diamond 1 grown on the substrate 3 and graphene layer 2 is removed after cooling. The removed product is then gently peeled off from the substrate and diamond by manual operation or with the assistance of a jig to obtain sheet-like self-supporting polycrystalline diamond.

[0061] Example 2

[0062] Fifteen layers of graphene film were transferred onto a 2.5-inch molybdenum substrate using a layer-by-layer transfer method to ensure complete coverage. The molybdenum wafer was then placed in an MPCVD apparatus, through which hydrogen and methane were introduced in a volume ratio of 80:1, at an ambient pressure of 1000 Pa. Under microwave excitation at 6 kW and 2.45 GHz, the silicon wafer was kept at 950 °C to carry out the diamond growth reaction.

[0063] Under the above conditions, after 96 hours of continuous growth, microwave input and gas supply were stopped, a vacuum was maintained, and the temperature was lowered to room temperature. Subsequently, the vacuum was broken and the molybdenum sheet with grown diamond was removed. Due to the difference in thermal expansion coefficients, the removed molybdenum sheet and diamond sheet had already separated significantly. The substrate and diamond could be directly peeled off manually to obtain sheet-like self-supporting polycrystalline diamond.

[0064] Example 3

[0065] Ten layers of graphene film were transferred onto the surface of a 4-inch silicon nitride substrate using a layer-by-layer transfer method to ensure complete coverage. The silicon wafer was then placed in an MPCVD instrument, and hydrogen, methane, and nitrogen were introduced in a volume ratio of 60:1:5. The ambient pressure was 2000 Pa, and the silicon nitride wafer was kept at 1000°C under microwave excitation at 30 kW and 915 MHz to carry out the diamond growth reaction.

[0066] Under the above conditions, after continuous growth for 96 hours, microwave input and gas supply are stopped, vacuum is maintained, and the temperature is lowered to room temperature. Then, the vacuum is broken and the silicon nitride wafer with grown diamond is removed. After removal, the substrate and diamond are gently peeled off by manual operation or with the assistance of a jig to obtain sheet-like self-supporting polycrystalline diamond.

[0067] Example 4

[0068] On a 5-inch single-crystal silicon substrate, 20 layers of graphene film were transferred layer by layer to ensure complete coverage. The silicon wafer was then placed in a DC arc plasma jet CVD equipment, through which hydrogen, methane, and argon gases were introduced in a volume ratio of 1000:1:1000, at an ambient pressure of 5000 Pa, and under the excitation of a 15 kW power supply, the silicon wafer was kept at 900 °C to carry out the diamond growth reaction.

[0069] Under the above conditions, after continuous growth for 72 hours, the power supply and gas supply are stopped, the vacuum is maintained, and the temperature is lowered to room temperature. Then, the vacuum is broken and the silicon wafer with grown diamond is removed. After removal, the substrate and diamond are gently peeled off by manual operation or with the assistance of a jig to obtain a sheet-like self-supporting polycrystalline diamond.

[0070] By repeating the above preparation method as needed, a film-like self-supporting polycrystalline diamond can also be obtained.

[0071] In the embodiments of this application, a graphene layer is introduced as an intermediate layer, and diamond is grown on the graphene. As a two-dimensional material, graphene has low interlayer forces and is prone to interlayer slip. Therefore, using multilayer graphene as an intermediate layer to grow diamond avoids cracks caused by the mismatch in thermal expansion coefficients between the diamond and the substrate. Furthermore, the mismatch in thermal expansion coefficients facilitates easier peeling between the diamond and the substrate, avoiding the need for substrate corrosion. Moreover, the growth of diamond on graphene is a homogeneous growth process with high lattice matching, enabling high-quality growth.

[0072] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. For those skilled in the art, other variations or modifications can be made based on the above description. It is impossible to exhaustively list all the implementation methods here. All obvious variations or modifications derived from the technical solutions of the present invention are still within the protection scope of the present invention.

Claims

1. A method of making a self-supporting polycrystalline diamond, characterized by, The method comprises: separating the substrate from the self-supporting polycrystalline diamond grown on the substrate in a physical peeling manner to obtain the self-supporting polycrystalline diamond; wherein the physical peeling occurs during a cooling process after the growth of the self-supporting polycrystalline diamond is completed or after the self-supporting polycrystalline diamond is taken out, and the self-supporting polycrystalline diamond is in a sheet or film shape; an intermediate layer is provided between the substrate and the self-supporting polycrystalline diamond grown on the substrate, and the self-supporting polycrystalline diamond is grown on the surface of the intermediate layer; the intermediate layer is a graphene layer; the graphene layer comprises two or more graphene films; the graphene layer is transferred onto the surface of the substrate in a layer-by-layer transfer manner; the self-supporting polycrystalline diamond is grown on the surface of the graphene layer; the material of the substrate comprises one or a composite material formed by one or more of silicon carbide, silicon, sapphire, quartz, glass and metal.

2. The self-supporting polycrystalline diamond production method of claim 1, wherein, The self-supporting polycrystalline diamond grown on the substrate is grown on the substrate by a chemical vapor deposition method.

3. The method of claim 1, wherein the self-supporting polycrystalline diamond is formed by a method comprising: The step of separating the substrate from the self-supporting polycrystalline diamond grown on the substrate in a physical peeling manner to obtain the self-supporting polycrystalline diamond comprises: separating the substrate from the self-supporting polycrystalline diamond grown on the substrate in a shaking manner to obtain the self-supporting polycrystalline diamond.

4. The method of claim 1, wherein the self-supporting polycrystalline diamond is formed by a method comprising: The step of separating the substrate from the self-supporting polycrystalline diamond grown on the substrate in a physical peeling manner to obtain the self-supporting polycrystalline diamond comprises: separating the substrate from the self-supporting polycrystalline diamond grown on the substrate in a manner of applying a suction force to obtain the self-supporting polycrystalline diamond.

5. The self-supporting polycrystalline diamond production method of claim 1, wherein, The step of separating the substrate from the self-supporting polycrystalline diamond grown on the substrate in a physical peeling manner to obtain the self-supporting polycrystalline diamond comprises: separating the substrate from the self-supporting polycrystalline diamond grown on the substrate by manual operation and / or a jig to obtain the self-supporting polycrystalline diamond.

6. The self-supporting polycrystalline diamond production method of claim 1, wherein, The step of separating the substrate from the self-supporting polycrystalline diamond grown on the substrate in a physical peeling manner to obtain the self-supporting polycrystalline diamond comprises: obtaining the self-supporting polycrystalline diamond by separating the substrate from the self-supporting polycrystalline diamond grown on the substrate during a cooling process.

7. The method of claim 1, wherein the self-supporting polycrystalline diamond is formed by a method comprising: providing a substrate; forming a diamond layer on the substrate; and forming a metal layer on the diamond layer. The graphene layer is a multi-layer graphene film, and the thickness of the graphene layer is 2-100 carbon atom layers.

8. The self-supporting polycrystalline diamond production method of claim 1, wherein, The thickness of the graphene layer is 5-20 carbon atom layers.

9. The method of claim 2, wherein the self-supporting polycrystalline diamond is formed by a method comprising: The self-supporting polycrystalline diamond is grown on the substrate in a deposition cavity by a chemical vapor deposition method, and the gas in the deposition cavity comprises hydrogen and methane; and one or more of argon, nitrogen, oxygen, carbon dioxide, carbon monoxide and water vapor. The environmental pressure in the deposition cavity is 100 Pa-100,000 Pa. The growth temperature in the deposition cavity is 700-1,300 ℃.

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