Method for repairing surface defects of single crystal diamond substrate and single crystal diamond substrate

Abstract

The application discloses a single-crystal diamond substrate surface defect repairing method and a single-crystal diamond substrate. The method comprises the following steps: taking a single-crystal diamond after laser cutting as a substrate, and performing solution cleaning treatment on the substrate; placing the cleaned substrate in an MPCVD device, inputting hydrogen to form a hydrogen plasma, and performing etching activation on the surface of the substrate; inputting a carbon source gas into the MPCVD device, and performing carbon atom pulse deposition on the surface of the etching-activated substrate to repair the surface defects of the substrate. The application realizes effective repair of the surface defects of the single-crystal diamond substrate after laser cutting.

Description

Technical Field

[0001] This application relates to the field of diamond preparation technology, and in particular to a method for repairing surface defects of a single-crystal diamond substrate and a single-crystal diamond substrate. Background Technology

[0002] Microwave plasma chemical vapor deposition (MPCVD) technology has become the mainstream technology for the large-scale preparation of high-quality single-crystal diamond due to its outstanding advantages such as controllable deposition temperature, high diamond crystal purity, stable growth rate, and ability to prepare large-size preforms. In practical applications, the single-crystal diamond preforms prepared by MPCVD need to be cut and shaped to obtain substrates with specific dimensions and geometries that meet the requirements of the application. Laser cutting, as the mainstream processing method, is prone to various defects on the diamond substrate surface due to the instantaneous high-temperature impact, local stress concentration, and plasma sputtering effect generated during the process, such as microcracks, lattice distortion, residual graphite phase impurities, and surface pits. These defects can seriously damage the crystal integrity of single-crystal diamond, significantly reduce its mechanical strength, wear resistance, optical transmittance, and electrical stability, and thus limit its large-scale application in high-end fields such as high-precision instruments, semiconductor devices, high-energy optical windows, and quantum computing chips.

[0003] In existing technologies, surface treatment processes for single-crystal diamond after laser cutting mainly include mechanical polishing, chemical cleaning, and traditional hydrogen etching. Although mechanical polishing can reduce the macroscopic surface roughness, it easily introduces new surface mechanical stress damage and cannot repair microcracks; chemical cleaning can only remove impurities such as oil and metal ions adsorbed on the surface, and has no effect on repairing defects at the crystal lattice level; although traditional hydrogen etching can eliminate graphite phase impurities to a certain extent, it has problems such as poor etching uniformity and easy to cause excessive surface corrosion, making it difficult to achieve precise defect repair.

[0004] Therefore, there is an urgent need to develop a surface defect repair process to effectively repair surface defects on single-crystal diamond substrates, thereby improving the product yield and application value of MPCVD single-crystal diamond. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the purpose of this application is to provide a method for repairing surface defects in single-crystal diamond substrates and a single-crystal diamond substrate, which can effectively repair surface defects in single-crystal diamond substrates, thereby improving the product yield and application value of MPCVD single-crystal diamond.

[0006] To achieve one or more of the above objectives or other objectives, the first aspect of this application provides a method for repairing surface defects on a single-crystal diamond substrate, comprising:

[0007] Using laser-cut single-crystal diamond as a substrate, the substrate is subjected to solution cleaning treatment;

[0008] The cleaned substrate is placed in an MPCVD device, and hydrogen gas is introduced to form hydrogen plasma to etch and activate the substrate surface.

[0009] Carbon source gas is introduced into the MPCVD equipment to perform carbon atom pulse deposition on the etched and activated substrate surface to repair surface defects of the substrate.

[0010] Furthermore, the step of using laser-cut single-crystal diamond as a substrate and performing solution cleaning treatment on the substrate includes:

[0011] Using laser-cut single-crystal diamond as a substrate, the substrate is subjected to gradient cleaning with a solution, wherein the gradient cleaning includes cleaning with organic solvent, cleaning with alkaline solution, cleaning with acidic solution, and ultrasonic cleaning with deionized water.

[0012] The substrate surface is dried using inert gas after cleaning.

[0013] Furthermore, the organic solvent includes at least one of anhydrous ethanol and acetone, the alkaline solution includes potassium hydroxide solution, and the acidic solution includes at least one of sulfuric acid and hydrochloric acid.

[0014] Furthermore, prior to the step of using laser-cut single-crystal diamond as a substrate for solution cleaning, the method further includes:

[0015] The surface of the substrate after laser cutting is polished, and the polishing process includes at least one of particle abrasive polishing and chemical mechanical polishing.

[0016] Furthermore, the particle grinding and polishing includes: using diamond micro powder with a particle size of 0.5~1μm as the grinding medium, controlling the grinding pressure to be 0.1~0.3MPa, the grinding speed to be 300~500r / min, and the grinding time to be 20~40min, to polish the surface of the substrate;

[0017] The chemical mechanical polishing steps include: using silica sol as the polishing liquid, controlling the polishing pressure to be 0.05~0.1MPa, the polishing speed to be 100~200r / min, and the polishing time to be 60~90min, to polish the surface of the substrate.

[0018] Further, the step of placing the cleaned substrate in an MPCVD device and introducing hydrogen gas to form hydrogen plasma to etch and activate the substrate surface includes:

[0019] The cleaned substrate is placed in the reaction chamber of the MPCVD equipment, the reaction chamber is sealed and evacuated to a preset vacuum level;

[0020] Hydrogen gas is introduced into the reaction chamber, and the hydrogen flow rate is controlled at 400~600 sccm / min. The chamber pressure is adjusted to 10~20 kPa.

[0021] Start the microwave generator of the MPCVD equipment, set the microwave power to 8000~10000W, ionize hydrogen to form hydrogen plasma, heat to 800~1000℃, and etch and activate the substrate surface for 10~20 minutes.

[0022] Further, the step of introducing a carbon source gas into the MPCVD equipment to perform carbon atom pulse deposition on the etched and activated substrate surface to repair surface defects of the substrate includes:

[0023] After etching and activation are completed, the process parameters of the MPCVD equipment are adjusted, including a chamber pressure of 5~10 kPa, a temperature of 600~800℃, and a microwave power of 600~800W.

[0024] Under the stated process parameters, pulsed deposition is performed in tens to hundreds of cycles, each cycle comprising:

[0025] A mixture of carbon source gas and hydrogen gas is introduced into the reaction chamber and maintained for 10-20 seconds to allow carbon atoms to be adsorbed on the substrate surface.

[0026] Turn off the carbon source gas and purge the reaction chamber with inert gas for 5-10 seconds to remove unadsorbed carbon source gas.

[0027] Stop the inert gas supply and continue to supply hydrogen gas to activate the carbon atoms adsorbed on the surface through hydrogen plasma for 15-25 seconds.

[0028] Furthermore, the carbon source gas is methane or acetylene, and the volume ratio of the carbon source gas to hydrogen is 1:50 to 1:100.

[0029] Furthermore, after the step of introducing carbon source gas into the MPCVD equipment to perform carbon atom pulse deposition on the etched and activated substrate surface to repair surface defects of the substrate, the method further includes:

[0030] Annealing is carried out under inert gas protection at a temperature of 400-500℃ for 30-60 minutes.

[0031] Vacuum drying at 80~100℃ for 2~4h yields a single-crystal diamond substrate with repaired surface defects.

[0032] The second aspect of this application provides a single-crystal diamond substrate, which is prepared by the above-described method for repairing surface defects in a single-crystal diamond substrate.

[0033] The method for repairing surface defects in single-crystal diamond substrates provided in this application involves cleaning the surface contaminants of the single-crystal diamond substrate with a solution, then activating and eliminating residual graphite phase and oxide layer through hydrogen plasma etching, while simultaneously activating the activity of defect sites. Then, carbon atom pulse deposition is used to deeply fill microcracks and correct lattice distortion through targeted adsorption and lattice reconstruction, effectively eliminating various surface defects introduced by laser cutting, restoring the integrity of the diamond crystal surface, and thus significantly improving the product yield and application value of MPCVD single-crystal diamond. Attached Figure Description

[0034] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0035] in:

[0036] Figure 1 This is a flowchart illustrating a method for repairing surface defects on a single-crystal diamond substrate in one embodiment.

[0037] Figure 2 This is a schematic diagram of a method for repairing surface defects of a substrate by pulse deposition in one embodiment;

[0038] Figure 3 This is a macroscopic comparison image of the surface of a single-crystal diamond substrate before and after repair in one embodiment;

[0039] Figure 4 This is a microscopic comparison of the surface of a single-crystal diamond substrate before and after repair in one embodiment;

[0040] Figure 5 This is an AFM image of a single-crystal diamond substrate surface after repair in one embodiment. Detailed Implementation

[0041] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein in the specification of the application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application; the terms "comprising" and "having," and any variations thereof, in the specification, claims, and foregoing drawings of this application, are intended to cover non-exclusive inclusion. The terms "first," "second," etc., in the specification, claims, or foregoing drawings of this application are used to distinguish different objects, not to describe a particular order.

[0042] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0043] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings.

[0044] Reference Figure 1 The embodiments of this application provide a method for repairing surface defects in a single-crystal diamond substrate, comprising:

[0045] S1: Using laser-cut single-crystal diamond as a substrate, the substrate is subjected to solution cleaning treatment;

[0046] S2: Place the cleaned substrate in the MPCVD equipment, introduce hydrogen gas to form hydrogen plasma, and etch and activate the substrate surface.

[0047] S3: Introduce carbon source gas into the MPCVD equipment to perform carbon atom pulse deposition on the etched and activated substrate surface to repair surface defects of the substrate.

[0048] In this embodiment, step S1 is used to remove contaminants and some surface impurities adhering to the surface of the single-crystal diamond substrate after laser cutting. During laser cutting, oil stains, cutting auxiliary medium residues, and environmentally adsorbed impurities easily remain on the substrate surface. If these impurities are not removed, they will hinder the contact between hydrogen plasma and the substrate surface, and may also mix into the repair layer during the deposition process, leading to repair defects. Solution cleaning can efficiently remove surface contaminants through physical dissolution and chemical action without damaging the diamond substrate itself.

[0049] Step S2 removes residual oxide layers and graphite phase impurities from the substrate surface, while simultaneously activating carbon atoms at defect sites on the substrate surface to form active sites containing unsaturated dangling bonds, which are then used for targeted adsorption of carbon atoms in subsequent steps. Hydrogen gas is ionized under the microwave energy of the MPCVD equipment to form hydrogen plasma. The high-energy hydrogen atoms in this plasma have strong chemical activity, selectively etching non-diamond phases (such as graphite phases) and oxide layers on the diamond surface. Furthermore, the impact of high-energy hydrogen atoms can break some saturated C-C bonds on the substrate surface, causing unsaturated dangling bonds to form at defect sites (such as microcrack edges and lattice distortion regions), thus enhancing the adsorption selectivity and binding capacity of carbon atoms in these areas.

[0050] Specifically, the substrate cleaned by S1 is placed in the reaction chamber of the MPCVD equipment. After sealing the chamber, it is evacuated to a preset vacuum level to eliminate interference from air and impurity gases inside the chamber. Hydrogen gas is introduced into the sealed reaction chamber to create a stable atmosphere. The microwave generator of the MPCVD equipment is activated to excite the hydrogen gas to ionize and form hydrogen plasma. This hydrogen plasma is then used to etch and activate the surface of the substrate.

[0051] Step S3 uses a pulsed deposition process to directionally fill the defect sites on the substrate surface with carbon atoms, forming stable covalent bonds with the substrate lattice, thus achieving targeted defect repair. The etched and activated substrate surface defect sites have unsaturated dangling bonds, which preferentially adsorb carbon atoms. Pulsed deposition, through an adsorption-purification-activation cycle, avoids excessive growth of non-defect areas caused by continuous deposition, allowing carbon atoms to aggregate directionally at the defect sites. Simultaneously, under the activation effect of hydrogen plasma, the adsorbed carbon atoms can be reconstructed along the lattice arrangement of the substrate, filling microcracks and correcting lattice distortions, thereby repairing surface defects.

[0052] Specifically, after S2 etching and activation, the process parameters of the MPCVD equipment are adjusted to suit the deposition state; a mixture of carbon source gas and hydrogen is introduced into the reaction chamber, so that the mixed gas contacts the substrate surface, and the carbon atoms generated by the dissociation of the carbon source gas are adsorbed at the active sites of the defect sites; then the unadsorbed free carbon source gas in the chamber is removed to prevent it from depositing in non-defect areas; then the carbon atoms adsorbed at the defect sites are activated by hydrogen plasma, which promotes the reconstruction of the carbon atoms with the substrate lattice and the formation of stable covalent bonds; the above pulse cycle process is repeated until the preset stopping conditions are reached, such as reaching the predefined deposition time, to obtain a single-crystal diamond substrate with repaired surface defects.

[0053] This embodiment achieves effective repair of surface defects on single-crystal diamond substrates after laser cutting through the above steps. Surface contaminants are removed by solution cleaning, followed by hydrogen plasma etching to eliminate residual graphite phase and oxide layer, while simultaneously activating defect sites. Then, carbon atom pulse deposition, through targeted adsorption and lattice reconstruction, deeply fills microcracks and corrects lattice distortion, effectively eliminating various surface defects introduced by laser cutting, restoring the integrity of the diamond crystal surface, and thus significantly improving the product yield and application value of MPCVD single-crystal diamond.

[0054] In some embodiments, step S1, which uses laser-cut single-crystal diamond as a substrate and performs solution cleaning on the substrate, includes:

[0055] S101: Using laser-cut single-crystal diamond as a substrate, the substrate is subjected to gradient cleaning with a solution, wherein the gradient cleaning includes cleaning with organic solvent, cleaning with alkaline solution, cleaning with acidic solution and ultrasonic cleaning with deionized water.

[0056] S102: The surface of the substrate after cleaning by blowing with inert gas.

[0057] In this embodiment, step S101 targets different types of contaminants on the substrate surface after laser cutting, such as organic residues, attached impurities, metal ions, and inorganic residues, and removes these contaminants through stepwise gradient cleaning. Different types of contaminants require appropriate cleaning media for removal. For example, organic solvents can dissolve oil stains and organic cutting aid residues; alkaline solutions can peel off stubborn impurities and some oxides attached to the surface; acidic solutions can chemically react with metal ions, converting them into soluble substances, and can also slightly etch away residual graphite fragments on the surface; and deionized water ultrasonic cleaning is used to remove residual cleaning solution and trace amounts of soluble impurities from the substrate surface.

[0058] In some specific embodiments, the organic solvent includes at least one of anhydrous ethanol and acetone, the alkaline solution includes potassium hydroxide solution, and the acidic solution includes at least one of sulfuric acid and hydrochloric acid. In one specific embodiment, the organic solvent is a 1:1 volume ratio mixture of anhydrous ethanol and acetone, and the acidic solution is a 1:3 volume ratio mixture of hydrogen peroxide and sulfuric acid or a 5% to 10% dilute hydrochloric acid solution.

[0059] In some specific embodiments, gradient cleaning is performed sequentially in the following order:

[0060] Organic solvent cleaning: The substrate is placed in an organic solvent and surface oil and organic residues are removed by soaking, rinsing or gentle stirring to remove the oil film covering the substrate surface.

[0061] Alkaline solution cleaning: The substrate, after being cleaned with organic solvent, is transferred to an alkaline solution to remove stubborn impurities and part of the oxide layer adhering to the surface;

[0062] Acidic solution cleaning: After the substrate is removed from the alkaline solution, it is placed in an acidic solution to remove residual metal ions and trace amounts of graphite phase impurities on the surface through a chemical reaction.

[0063] Deionized water ultrasonic cleaning: The substrate after acid and alkali cleaning is placed in deionized water, and the ultrasonic equipment is started to remove residual acid and alkali solutions, reaction products and trace suspended impurities.

[0064] Step S102 is used to quickly remove the moisture adhering to the surface of the substrate after gradient cleaning. The cleaned substrate is taken out and placed in a clean and dry environment. High-purity inert gas is introduced into the surface of the substrate, and the blowing direction is moved evenly from the edge of the substrate to the center to ensure that the blowing covers the entire surface of the substrate until there are no visible water droplets on the surface of the substrate and no traces of moisture residue, so as to obtain a dry and clean substrate to be etched.

[0065] In some embodiments, before step S1 of solution cleaning treatment of the single-crystal diamond after laser cutting as the substrate, the method further includes:

[0066] S01: Polishing the surface of the substrate after laser cutting, wherein the polishing process includes at least one of particle abrasive polishing and chemical mechanical polishing.

[0067] In this embodiment, pre-leveling is performed on larger physical defects on the surface of the substrate after laser cutting to improve the overall flatness of the substrate surface. Specifically, particle abrasive polishing removes cutting burrs, large protrusions, and loose surface layers from the substrate surface through the physical grinding action of abrasive particles; chemical mechanical polishing further smooths the surface by combining chemical etching with micro-scale physical grinding. In some embodiments, one of the two processes can be used alone to adapt to different substrates; in other embodiments, the two processes are used in combination to achieve substrate surface polishing.

[0068] In some embodiments, the particle grinding and polishing includes: using diamond micro powder with a particle size of 0.5~1μm as the grinding medium, controlling the grinding pressure to be 0.1~0.3MPa, the grinding speed to be 300~500r / min, and the grinding time to be 20~40min to polish the surface of the substrate. Specifically, diamond micro powder with a particle size of 0.5~1μm is selected as the grinding medium, and the grinding medium is uniformly coated between the grinding disc and the surface of the substrate to be polished; the grinding process parameters are adjusted, the grinding pressure is set to 0.1~0.3MPa, the grinding disc speed is set to 300~500r / min, and grinding is continued for 20~40min. For example, the particle size of the diamond microparticles is 0.5μm, 0.6μm, 0.7μm, 0.8μm, 0.9μm, 1μm, etc.; the grinding pressure is 0.1MPa, 0.2MPa, 0.3MPa, etc.; the grinding speed is 300r / min, 400r / min, 500r / min, etc.; and the grinding time is 20min, 30min, 40min, etc. Through the physical grinding action of the diamond microparticles, burrs, flash, shallow loose damage layers, and macroscopic unevenness defects generated by laser cutting on the substrate surface are efficiently removed, completing the initial leveling of the substrate surface.

[0069] In some embodiments, the chemical mechanical polishing step includes: using silica sol as the polishing fluid, controlling the polishing pressure to be 0.05~0.1MPa, the polishing speed to be 100~200r / min, and the polishing time to be 60~90min, to polish the surface of the substrate. Specifically, using silica sol as the polishing fluid, the polishing fluid is continuously and uniformly supplied to the polishing pad during the polishing process to ensure the lubrication and reaction stability of the polishing interface; adjusting the fine polishing process parameters, setting the polishing pressure to 0.05~0.1MPa, the polishing speed to 100~200r / min, and continuously polishing for 60~90min. For example, the polishing pressure is set to 0.05MPa, 0.06MPa, 0.07MPa, 0.08MPa, 0.09MPa, 0.1MPa, etc.; the polishing speed is set to 100r / min, 150r / min, 200r / min, etc.; and the polishing time is set to 60min, 70min, 80min, 90min, etc. The low-pressure, low-speed process parameters reduce mechanical stress input, further optimize the surface smoothness of the substrate, and avoid excessive polishing that could damage the substrate material.

[0070] In some embodiments, step S2, which involves placing the cleaned substrate in an MPCVD device and introducing hydrogen gas to form hydrogen plasma for etching and activation of the substrate surface, includes:

[0071] S201: Place the cleaned substrate into the reaction chamber of the MPCVD equipment, seal the reaction chamber and evacuate it to a preset vacuum level;

[0072] S202: Introduce hydrogen into the reaction chamber, control the hydrogen flow rate to 400~600 sccm / min, and adjust the chamber pressure to 10~20 kPa;

[0073] S203: Start the microwave generator of the MPCVD equipment, set the microwave power to 8000~10000W, ionize hydrogen to form hydrogen plasma, heat to 800~1000℃, and etch and activate the substrate surface for 10~20 minutes.

[0074] In this embodiment, the cleaned and dried single-crystal diamond substrate is placed on the sample stage of the MPCVD equipment reaction chamber. The chamber door is closed and sealed, and the vacuum pumping system is activated. After reaching the set vacuum level, the vacuum state is maintained for 2-3 minutes to ensure that impurity gases inside the chamber are fully discharged. High-energy hydrogen plasma is formed by ionizing hydrogen gas using microwave energy, achieving selective etching of the graphite phase and oxide layer on the substrate surface. Simultaneously, carbon atoms at defect sites are activated to form unsaturated dangling bonds. Exemplarily, the hydrogen flow rate is set to 400 sccm / min, 500 sccm / min, 600 sccm / min, etc.; the chamber pressure is set to 10 kPa, 15 kPa, 20 kPa, etc.; the microwave power is set to 8000 W, 9000 W, 10000 W, etc.; the temperature is set to 800℃, 900℃, 1000℃, etc.; and the etching time is set to 10 min, 15 min, 20 min, etc.

[0075] In some embodiments, step S3, which involves introducing a carbon source gas into the MPCVD equipment to perform carbon atom pulse deposition on the etched and activated substrate surface to repair surface defects of the substrate, includes:

[0076] S301: After etching and activation are completed, adjust the process parameters of the MPCVD equipment, wherein the process parameters include a chamber pressure of 5~10 kPa, a temperature of 600~800℃, and a microwave power of 600~800W.

[0077] S302: Under the stated process parameters, pulse deposition is performed in tens to hundreds of cycles, each cycle including:

[0078] S3021: A mixture of carbon source gas and hydrogen is introduced into the reaction chamber and maintained for 10-20 seconds to allow carbon atoms to be adsorbed on the substrate surface; in some specific embodiments, the carbon source gas is methane or acetylene, and the volume ratio of the carbon source gas to hydrogen is 1:50 to 1:100.

[0079] S3022: Turn off the carbon source gas and purge the reaction chamber with inert gas for 5-10 seconds to remove unadsorbed carbon source gas.

[0080] S3023: Stop the inert gas supply and continuously supply hydrogen gas to activate the carbon atoms adsorbed on the surface through hydrogen plasma for 15~25s.

[0081] In this embodiment, step S301 switches from the high-temperature, high-pressure, and high-power process state of etching activation to process parameters adapted to carbon atom pulse deposition. After etching activation is completed, the reaction chamber is kept sealed and hydrogen is continuously supplied. The temperature of the substrate surface is reduced from 800~1000℃ to 600~800℃ and stabilized using a temperature control module. The chamber pressure is adjusted from 10~20kPa to 5~10kPa. The microwave power is reduced from 8000~10000W to 600~800W. After all parameters reach the set values, the stable state is maintained for 3~5 minutes.

[0082] In step S302, refer to Figure 2 Through multiple cycles, atomic-level layer-by-layer deposition is achieved to effectively fill microcracks, avoiding excessively thick repair layers or incomplete defect filling caused by single deposition. In pulse deposition, each cycle forms an atomic-layer-scale carbon adsorption layer on the substrate surface, which binds to the substrate after activation; after tens to hundreds of cycles, defects of different sizes can be filled, while avoiding over-deposition.

[0083] Specifically, in step S3021, carbon atoms generated by the dissociation of the carbon source gas are preferentially adsorbed onto the etched and activated defect active sites, achieving targeted deposition. The carbon source gas (methane / acetylene) can dissociate into active carbon atoms under microwave plasma conditions. The unsaturated dangling bonds at the defect sites exhibit strong adsorption selectivity for active carbon atoms. The aforementioned carbon source-hydrogen volume ratio of 1:50 to 1:100 ensures a sufficient supply of carbon atoms, while hydrogen dilution prevents excessive carbon source aggregation leading to graphitization. Specifically, a dual-channel mass flow controller introduces high-purity carbon source gas and hydrogen, where the carbon source gas is methane or acetylene, with a volume ratio controlled at 1:50 to 1:100. This mixed gas is then introduced into the reaction chamber. The mixed gas continues to circulate for 10-20 seconds. During this period, the carbon source gas undergoes slight dissociation under the microwave field, and the generated active carbon atoms are directionally adsorbed onto the defect active sites on the substrate surface, forming a monolayer adsorption film. The unadsorbed carbon source gas remains suspended in the chamber. For example, the volume ratio of carbon source gas to hydrogen is 1:50, 1:60, 1:70, 1:80, 1:90, 1:100, etc.

[0084] In step S3022, unadsorbed free carbon source gas and trace amounts of dissociation byproducts are removed from the cavity by purging. Inert gas, such as high-purity argon, can be used to quickly remove free substances from the cavity space. Specifically, the carbon source gas flow controller is turned off, while hydrogen is continuously supplied to maintain the basic atmosphere of the cavity; the inert gas (high-purity argon) supply system is activated, and argon is introduced into the cavity for purging for 5-10 seconds; during the purging process, the cavity pressure is maintained at 5-10 kPa to remove unadsorbed carbon source gas and byproducts.

[0085] In step S3023, the carbon atoms adsorbed at the defect sites are activated, causing them to interact with the substrate substrate. 3 Stable covalent bonds are formed in the crystal lattice, completing defect filling. Specifically, the inert gas supply is stopped, while the microwave power, cavity pressure, temperature, and hydrogen supply status remain constant, allowing the hydrogen to form a uniform hydrogen plasma under the action of the microwave field. This hydrogen plasma is then used to activate the carbon atoms adsorbed on the substrate surface for 15-25 seconds. During activation, the adsorbed carbon atoms gain energy and combine with the dangling bonds at the defect sites, filling the microcrack voids and forming splines integrated with the substrate. 3 A hybrid carbon layer completes a single deposition cycle.

[0086] Repeat the pulse cycle of S3031 to S3023 above for a set number of times to achieve effective repair of defects on the substrate surface.

[0087] In some embodiments, after step S3 of introducing carbon source gas into the MPCVD equipment to perform carbon atom pulse deposition on the etched and activated substrate surface to repair surface defects of the substrate, the method further includes:

[0088] S4: Annealing is carried out under inert gas protection at a temperature of 400~500℃ for 30~60 minutes.

[0089] S5: Vacuum dry at 80~100℃ for 2~4h to obtain a single crystal diamond substrate with repaired surface defects.

[0090] This embodiment is used to release trace residual stress generated at the interface between the repair layer and the substrate during pulse deposition, promoting the further formation of stable covalent bonds between incompletely bonded carbon atoms and the substrate lattice. The inert gas used is argon, and the annealing temperatures are 400℃, 450℃, and 500℃, with annealing times of 30 min, 40 min, 50 min, and 60 min, respectively. Vacuum drying removes any trace moisture and volatile impurities that may have been adsorbed on the substrate surface after annealing, ensuring a dry and clean substrate surface and preventing residual impurities from affecting its subsequent application performance.

[0091] This application also provides a single-crystal diamond substrate, which is prepared by the single-crystal diamond substrate surface defect repair method of any of the foregoing embodiments.

[0092] The single-crystal diamond substrate of this embodiment is prepared by the process described in the previous embodiment. The obvious damage and contaminants on the surface are removed by polishing and gradient cleaning. Then, the graphite phase is eliminated and the defect sites are activated by hydrogen plasma etching. Then, the microcracks are closed by pulse deposition to form a repair layer integrated with the substrate. Finally, the residual stress is released by annealing and the surface is purified by vacuum drying. The resulting single-crystal diamond substrate with effectively repaired surface defects has a clean surface with no impurities, low roughness, no obvious unevenness or etching marks, and presents a uniform and flat crystal surface state. This meets the application requirements of high-end fields such as chips and broadens the application prospects of MPCVD single-crystal diamond.

[0093] Example 1

[0094] Take a laser-cut MPCVD single-crystal diamond substrate with dimensions of 9mm × 9mm × 1mm, and repair defects according to the following steps:

[0095] Step 1: Using diamond micro powder with a particle size of 0.8μm as the grinding medium, the grinding pressure was set to 0.2MPa and the grinding speed to 400r / min. The substrate surface was rough polished for 30 minutes to remove cutting burrs and shallow loose damage layers. Then, silica sol was used as the polishing liquid, and the polishing pressure was adjusted to 0.08MPa and the polishing speed to 150r / min. Chemical mechanical polishing was performed for 75 minutes. After polishing, the surface roughness Ra of the substrate was 42nm.

[0096] Step 2: Place the polished substrate in a mixture of anhydrous ethanol and acetone of equal volume and ultrasonically clean it at 70°C for 18 minutes; then transfer it to an 8wt% potassium hydroxide solution and soak it at 90°C for 25 minutes; then place it in a 6wt% hydrochloric acid solution and soak it at room temperature for 12 minutes; finally, ultrasonically clean it three times with 50°C ultrapure water for 12 minutes each time; use high-purity nitrogen to evenly blow along the surface of the substrate until there is no moisture residue on the surface.

[0097] Step 3: Place the cleaned and dried substrate on the sample stage of the MPCVD equipment reaction chamber, seal the chamber and evacuate; introduce high-purity hydrogen gas, control the flow rate to 500 sccm / min, and adjust the chamber pressure to 18 kPa; start the microwave generator, set the power to 9000W, heat to 850℃, and etch and activate the substrate surface for 10 minutes.

[0098] Step 4: Set microwave power to 700W, cavity pressure to 8kPa, and temperature to 700℃; use methane as the carbon source gas and introduce it into the cavity with hydrogen at a volume ratio of 1:80, start the pulse deposition program, set the number of cycles to 80, and each cycle process is as follows: introduce methane-hydrogen mixed gas for 15s, then purge with high-purity argon for 8s, and then activate with hydrogen plasma for 20s;

[0099] Step 5: After deposition, high-purity argon gas is introduced, and the mixture is annealed at 450℃ for 45 minutes to release residual stress at the interface; then it is placed in a vacuum drying oven and evacuated to 10℃. -3 Pa, dry at 90℃ for 3 hours to remove trace amounts of surface moisture and volatile impurities.

[0100] Depend on Figure 3 and Figure 4 It can be seen that the repaired single-crystal diamond substrate surface has no residual impurities, and the crystal integrity is significantly better than before repair. The surface roughness of the diamond substrate was detected by AFM (Atomic Force Microscope). After repair, the surface roughness Ra of the substrate was 3.2 nm, and the surface microcracks were closed. The point defect density was 60~80 points / cm². 2 Among them, point defects refer to visible point defects such as pits, micropores, pits, and impurity particles with a size ≥0.5 μm; the point defect density is calculated by scanning the substrate surface with an optical microscope (×1000), counting the number of point defects under the microscope per unit scanning area, and taking this value as the point defect density.

[0101] Example 2

[0102] Take a laser-cut MPCVD single-crystal diamond substrate with dimensions of 15mm × 15mm × 1.5mm, and repair defects according to the following steps:

[0103] Step 1: Using diamond micro powder with a particle size of 1μm as the grinding medium, the grinding pressure was set to 0.3MPa and the grinding speed to 500r / min. The substrate surface was rough polished for 40 minutes to remove cutting burrs and shallow loose damage layers. Then, silica sol was used as the polishing liquid, and the polishing pressure was adjusted to 0.1MPa and the polishing speed to 200r / min. Chemical mechanical polishing was performed for 90 minutes. After polishing, the surface roughness Ra of the substrate was 38nm.

[0104] Step 2: Place the polished substrate in a mixture of equal volumes of anhydrous ethanol and acetone, and ultrasonically clean it at 80°C for 20 minutes; then transfer it to a 10wt% potassium hydroxide solution and soak it at 100°C for 30 minutes; then place it in an 8wt% hydrochloric acid solution and soak it at room temperature for 15 minutes; finally, ultrasonically clean it three times with 60°C ultrapure water for 15 minutes each time; use high-purity nitrogen to evenly blow along the surface of the substrate until there is no moisture residue on the surface.

[0105] Step 3: Place the cleaned and dried substrate on the sample stage of the MPCVD equipment reaction chamber, seal the chamber and evacuate; introduce high-purity hydrogen gas, control the flow rate to 500 sccm / min, and adjust the chamber pressure to 20 kPa; start the microwave generator, set the power to 9000W, heat to 900℃, and etch and activate the substrate surface for 20 min.

[0106] Step 4: Set microwave power to 800W, cavity pressure to 10kPa, and temperature to 800℃; use acetylene as the carbon source gas and introduce it into the cavity with hydrogen at a volume ratio of 1:100; start the pulse deposition program; set the number of cycles to 100; each cycle consists of: introducing the acetylene-hydrogen mixed gas for 20s, then purging with high-purity argon for 10s, and then activating with hydrogen plasma for 25s;

[0107] Step 5: After deposition, high-purity argon gas is introduced, and the mixture is annealed at 500℃ for 60 minutes to release residual stress at the interface; then it is placed in a vacuum drying oven and evacuated to 10℃. -4 Pa, dried at 100℃ for 4 hours to remove trace amounts of surface moisture and volatile impurities.

[0108] like Figure 5 As shown, after repair, the surface roughness Ra of the substrate was 2.8 nm, the surface microcracks were closed, and the point defect density was 60~80 points / cm. 2 There were no impurities remaining on the surface, and the crystal integrity was significantly better than before the repair.

[0109] Obviously, the embodiments described above are only some embodiments of this application, not all embodiments. The accompanying drawings show preferred embodiments of this application, but do not limit the patent scope of this application. This application can be implemented in many different forms; rather, these embodiments are provided to provide a more thorough and comprehensive understanding of the disclosure of this application. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing specific embodiments, or make equivalent substitutions for some of the technical features. Any equivalent structures made using the content of this application's specification and drawings, directly or indirectly applied to other related technical fields, are similarly within the scope of patent protection of this application.

Claims

1. A method for repairing surface defects in a single-crystal diamond substrate, characterized in that, include: Using laser-cut single-crystal diamond as a substrate, the substrate is subjected to solution cleaning treatment; The cleaned substrate is placed in an MPCVD device, and hydrogen gas is introduced to form hydrogen plasma to etch and activate the substrate surface. Carbon source gas is introduced into the MPCVD equipment to perform carbon atom pulse deposition on the etched and activated substrate surface to repair surface defects of the substrate.

2. The method for repairing surface defects on a single-crystal diamond substrate as described in claim 1, characterized in that, The step of using laser-cut single-crystal diamond as a substrate and performing solution cleaning treatment on the substrate includes: Using laser-cut single-crystal diamond as a substrate, the substrate is subjected to gradient cleaning with a solution, wherein the gradient cleaning includes cleaning with organic solvent, cleaning with alkaline solution, cleaning with acidic solution, and ultrasonic cleaning with deionized water. The substrate surface is dried using inert gas after cleaning.

3. The method for repairing surface defects on a single-crystal diamond substrate as described in claim 2, characterized in that, The organic solvent includes at least one of anhydrous ethanol and acetone, the alkaline solution includes potassium hydroxide solution, and the acidic solution includes at least one of sulfuric acid and hydrochloric acid.

4. The method for repairing surface defects on a single-crystal diamond substrate as described in claim 1, characterized in that, Before the step of using laser-cut single-crystal diamond as a substrate for solution cleaning, the method further includes: The surface of the substrate after laser cutting is polished, and the polishing process includes at least one of particle abrasive polishing and chemical mechanical polishing.

5. The method for repairing surface defects on a single-crystal diamond substrate as described in claim 4, characterized in that, The particle grinding and polishing includes: using diamond micro powder with a particle size of 0.5~1μm as the grinding medium, controlling the grinding pressure to be 0.1~0.3MPa, the grinding speed to be 300~500r / min, and the grinding time to be 20~40min, to polish the surface of the substrate; The chemical mechanical polishing steps include: using silica sol as the polishing liquid, controlling the polishing pressure to be 0.05~0.1MPa, the polishing speed to be 100~200r / min, and the polishing time to be 60~90min, to polish the surface of the substrate.

6. The method for repairing surface defects in a single-crystal diamond substrate as described in claim 1, characterized in that, The step of placing the cleaned substrate in an MPCVD device, introducing hydrogen gas to form hydrogen plasma, and etching and activating the substrate surface includes: The cleaned substrate is placed in the reaction chamber of the MPCVD equipment, the reaction chamber is sealed and evacuated to a preset vacuum level; Hydrogen gas is introduced into the reaction chamber, and the hydrogen flow rate is controlled at 400~600 sccm / min. The chamber pressure is adjusted to 10~20 kPa. Start the microwave generator of the MPCVD equipment, set the microwave power to 8000~10000W, ionize hydrogen to form hydrogen plasma, heat to 800~1000℃, and etch and activate the substrate surface for 10~20 minutes.

7. The method for repairing surface defects in a single-crystal diamond substrate as described in claim 1, characterized in that, The step of introducing carbon source gas into the MPCVD equipment to perform carbon atom pulse deposition on the etched and activated substrate surface to repair surface defects of the substrate includes: After etching and activation are completed, the process parameters of the MPCVD equipment are adjusted, including a chamber pressure of 5~10 kPa, a temperature of 600~800℃, and a microwave power of 600~800W. Under the stated process parameters, pulsed deposition is performed in tens to hundreds of cycles, each cycle comprising: A mixture of carbon source gas and hydrogen gas is introduced into the reaction chamber and maintained for 10-20 seconds to allow carbon atoms to be adsorbed on the substrate surface. Turn off the carbon source gas and purge the reaction chamber with inert gas for 5-10 seconds to remove unadsorbed carbon source gas. Stop the inert gas supply and continue to supply hydrogen gas to activate the carbon atoms adsorbed on the surface through hydrogen plasma for 15-25 seconds.

8. The method for repairing surface defects of a single-crystal diamond substrate as described in claim 7, characterized in that, The carbon source gas is methane or acetylene, and the volume ratio of the carbon source gas to hydrogen is 1:50 to 1:

100.

9. The method for repairing surface defects in a single-crystal diamond substrate as described in claim 1, characterized in that, After the step of introducing carbon source gas into the MPCVD equipment to perform carbon atom pulse deposition on the etched and activated substrate surface to repair surface defects of the substrate, the method further includes: Annealing is carried out under inert gas protection at a temperature of 400-500℃ for 30-60 minutes. Vacuum drying at 80~100℃ for 2~4h yields a single-crystal diamond substrate with repaired surface defects.

10. A single-crystal diamond substrate, characterized in that, It is prepared by the method for repairing surface defects of single-crystal diamond substrate as described in any one of claims 1-9.

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