Monocrystalline diamond growth method based on MPCVD micro-descent method

Abstract

The invention is applied to the technical field of material synthesis, and discloses a single crystal diamond growth method based on an MPCVD micro-descent method, and the method comprises the following steps: S1, substrate pretreatment; s2, seed crystal placement; s3, setting the MPCVD equipment; and S4, carrying out post-treatment. According to the single crystal diamond growth method based on the MPCVD micro-descent method, the growth rate is remarkably increased, the growth rate of a traditional technological method is only 8 microns per hour, and the growth rate of the single crystal diamond growth method based on the MPCVD micro-descent method reaches 11 microns per hour in a specific embodiment; the high growth rate means that the thicker single crystal diamond can be obtained within the same time, or the production cycle is greatly shortened under the condition that the requirement for a certain thickness is met, the method has important significance on industrial large-scale production of the single crystal diamond, the production efficiency is effectively improved, and the time cost is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of material synthesis, and in particular to a single crystal diamond growth method based on an MPCVD micro-descent method. Background Art

[0002] In the field of modern materials science, single crystal diamond has become a hot research topic with its unparalleled physical and chemical properties. It has extremely high hardness, excellent thermal conductivity, high chemical stability, wide bandgap width and excellent optical properties. These characteristics make single crystal diamond widely and critically used in many high-end fields. In the field of ultra-precision machining, such as cutting of superhard materials and grinding and polishing of high-precision optical components, single crystal diamond tools and grinding tools can achieve nanometer-level machining accuracy, which is unattainable by other materials. In the electronics industry, with the rapid development of semiconductor technology, the demand for high-performance semiconductor materials is growing. As a kind of wide bandgap semiconductor material with great potential, single crystal diamond has the characteristics of high carrier mobility and high breakdown electric field strength, which provides an ideal material basis for the manufacture of high-frequency, high-power and low-power electronic devices, and is expected to break through the performance limitations of traditional silicon-based semiconductors. In the field of optics, the high transparency from deep ultraviolet to infrared bands makes single crystal diamond a high-quality material for manufacturing high-performance optical windows, lenses and laser optical components.

[0003] However, the synthesis of high-quality single-crystal diamond has always been a challenging problem. Traditional growth methods are faced with many serious problems. On the one hand, the slow growth rate has always been a key factor restricting its large-scale production and application. Due to the complex and inefficient growth process, the production cycle is long and the cost is high, which greatly limits the availability and wide application of single-crystal diamond in the market. On the other hand, the quality of crystals obtained by traditional growth methods is unstable, which is manifested in the presence of a large number of defects inside the crystals, such as dislocations, twins, inclusions, etc. These defects will not only reduce the physical properties of single-crystal diamond, such as hardness and thermal conductivity, but also have a negative impact on its application in electronics and optics, such as increasing the probability of electron scattering in semiconductor devices and reducing device performance. Summary of the invention

[0004] The object of the present invention is to provide a single crystal diamond growth method based on the MPCVD micro-descent method to solve the problems of slow growth rate, high cost and unstable crystal quality of the traditional single crystal diamond growth method mentioned in the above background technology.

[0005] To achieve the above object, the present invention provides the following technical solution: a method for growing single crystal diamond based on MPCVD micro-descent method, comprising the following steps:

[0006] S1. Substrate pretreatment: Select suitable substrate materials, perform ultrasonic cleaning with organic solvents, and perform drying and polishing to ensure that the surface is flat and free of impurities;

[0007] S2. Seed crystal placement: Place the pre-treated seed crystals on the tungsten or molybdenum seed crystal table at equal intervals, with a spacing of 0.2 mm between adjacent seed crystals, ensuring that the seed crystal sheet is in close contact with the seed crystal table;

[0008] S3, MPCVD equipment settings: adjust the microwave power, gas flow, reaction chamber pressure and temperature of the MPCVD equipment to optimize the growth conditions of single crystal diamond, and finally control the temperature gradient through the micro-descent method to achieve constant microwave power, constant plasma temperature, constant reaction chamber pressure, constant single crystal diamond growth rate, and long-term stable growth;

[0009] S4, post-processing: After the growth is completed, continuous annealing is performed without leaving the furnace. After etching, the obtained single crystal diamond is taken out from the reaction chamber for cleaning, cutting and polishing to remove surface impurities and defects and improve the crystal quality.

[0010] Preferably, the substrate material in S1 is one of a single crystal diamond seed wafer and an iridium-coated sapphire wafer.

[0011] Preferably, the microwave power of the MPCVD equipment in S3 is 6KW.

[0012] Preferably, the gas flow rates of the MPCVD equipment in S3 are: 400 sccm of hydrogen, 40 sccm of methane, 15 sccm of carbon dioxide and 1.5 sccm of nitrogen.

[0013] Preferably, the reaction chamber pressure of the MPCVD equipment in S3 is 150 Torr and the temperature is 880°C.

[0014] Preferably, in the substrate pretreatment cleaning step, the organic solvent immersion time before cleaning is 20-30 minutes, and the ultrasonic cleaning frequency is 30-50kHz. After cleaning, it is rinsed with deionized water for 3-5 times, and each rinse time is 5-10 minutes to ensure that the organic pollutants and water-soluble impurities on the substrate surface are completely removed.

[0015] Preferably, during the seed crystal placement process, the grain size of the sandpaper used for grinding the contact surface between the seed crystal table and the seed crystal is 800-1200 mesh, and the roughness of the contact surface is less than 0.2 μm, so as to ensure close contact between the two and the flatness of the contact interface, which is beneficial to heat transfer and seed crystal fixation.

[0016] Preferably, the microwave power fluctuation in the MPCVD equipment is set to be less than ±0.1 KW to maintain a stable plasma state, ensure a stable supply of active substances during the growth process, and avoid uneven growth or crystal defects caused by power fluctuations.

[0017] Preferably, the gas flow fluctuation in the MPCVD equipment is set to be less than ±1 sccm, and before the gas enters the reaction chamber, it needs to undergo a gas purification process to remove trace impurities that may be contained therein, such as oxygen, water vapor, etc., to prevent the impurities from having an adverse effect on diamond growth.

[0018] Preferably, in the continuous annealing process in the post-treatment, the cooling rate is 3-7°C / h, and in the etching process, the flow rate of the etching gas is 0.1-0.3sccm / cm according to the surface area of ​​the crystal. 2 The ratio is adjusted to ensure the uniformity of the etching effect.

[0019] Compared with the prior art, the invention has the following beneficial effects: the single crystal diamond growth method based on the MPCVD micro-descent method:

[0020] 1. The single crystal diamond growth method based on the MPCVD micro-decline method of the present invention achieves a significant increase in growth rate. The growth rate of the traditional process method is only 8 μm per hour, while the present invention reaches 11 μm per hour in a specific embodiment. This higher growth rate means that thicker single crystal diamonds can be obtained in the same time, or the production cycle can be greatly shortened under the condition of meeting certain thickness requirements. This is of great significance for industrial large-scale production of single crystal diamonds, effectively improves production efficiency, reduces time costs, and enables the output of single crystal diamonds to better meet market demand, especially in industrial processing fields such as cutting, grinding, polishing, etc., which have a large demand for single crystal diamonds, as well as high-tech fields such as semiconductors;

[0021] 2. Through the precise setting of MPCVD equipment parameters and the effective control of temperature gradient by micro-descent method, the present invention realizes long-term stable growth of single crystal diamond with constant microwave power, constant plasma temperature, constant reaction chamber pressure and constant growth rate. Compared with the problems of uneven growth and growth interruption caused by various factors such as temperature and pressure fluctuations and unstable gas flow in traditional growth methods, the present invention can ensure that single crystal diamond grows continuously at a stable rate and quality during the entire growth process, and can continuously and stably produce high-quality single crystal diamond within the set growth time. The traditional process has a simple growth time of about 150 hours and poor stability, which greatly reduces the material waste caused by growth failure or unstable quality and reduces production costs;

[0022] 3. The present invention creates ideal conditions for the growth of single crystal diamond by precisely controlling the concentration, temperature, pressure and microwave power of the reaction gas and other MPCVD equipment parameters. This precise control enables carbon atoms to be deposited in an orderly manner on the surface of the seed crystal, reducing crystal defects such as dislocations and twins caused by unreasonable growth conditions. At the same time, in the post-processing step after the growth is completed, continuous annealing and etching treatment can be performed without leaving the furnace to further eliminate the internal stress and surface impurities generated during the growth process, thereby improving the structural integrity and purity of the crystal;

[0023] 4. The method of the present invention has good process applicability and operability. In the substrate pretreatment, single crystal diamond seed wafers or iridium-plated sapphire wafers can be selected as substrate materials, and the substrate quality is ensured through clear cleaning, drying and polishing steps. The seed crystal placement steps are clear and easy to operate, ensuring close contact between the seed crystal and the seed crystal table. The parameters and steps in the entire MPCVD growth process and post-processing process are detailed and controllable, which is convenient for researchers and production personnel to master and implement, which is conducive to the promotion and application of this technology and further promotes the development of the single crystal diamond industry. DETAILED DESCRIPTION

[0024] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0025] The present invention provides a technical solution: a method for growing single crystal diamond based on the MPCVD micro-descent method.

[0026] Embodiment 1

[0027] Substrate pretreatment

[0028] A single crystal diamond seed wafer was selected as the substrate material, and the seed wafer was placed in an ultrasonic cleaning tank filled with acetone and soaked for 25 minutes. The ultrasonic cleaning frequency was set to 40kHz, so that the organic solvent was fully in contact with the substrate surface to remove organic impurities such as oil stains, and then rinsed with deionized water for 4 times, each rinsing time was 8 minutes, to completely remove the residual organic solvent and possible water-soluble impurities;

[0029] The cleaned substrate was placed in a vacuum drying oven at a temperature of 85°C and a vacuum degree of 5×10 -3 Pa for 2.5 hours, and then polish the substrate on a high-precision polishing machine using diamond polishing powder with a particle size of 0.3 μm for 2.5 hours until the surface flatness of the substrate reaches the atomic level and no impurities remain after detection;

[0030] Seed placement

[0031] The contact surface between the tungsten seed crystal table and the pretreated seed crystal was polished with 1000-grit sandpaper. The force should be evenly maintained during the polishing process to ensure that the contact surface is flat. The polished contact surface was carefully wiped with an alcohol cotton ball. The roughness of the contact surface was measured by a roughness detection instrument and was less than 0.15 μm.

[0032] Place the seed crystal on the seed crystal table according to a specific pattern, use a small pressure device to apply 60N of pressure and maintain it for 12 seconds, and double-check with an optical microscope and an electron microscope to ensure that the seed crystal is in close contact with the seed crystal table without any gap visible to the naked eye or at the microscopic level;

[0033] MPCVD Equipment Setup

[0034] The microwave power of the MPCVD equipment was accurately adjusted to 6KW, and a high-precision power monitoring instrument was used to ensure that the power fluctuation range was within ±0.05KW. The gas flow controller was set to make the hydrogen flow rate 400sccm, the methane flow rate 40sccm, the carbon dioxide flow rate 15sccm, and the nitrogen flow rate 1.5sccm. The control accuracy of the gas flow was maintained within ±0.5sccm. Before the gas entered the reaction chamber, it was allowed to pass through a gas purification device consisting of an activated carbon adsorption column, a molecular sieve drying tower, and a low-temperature condensation trap in sequence to remove trace oxygen, water vapor, and other impurities that may be contained therein;

[0035] The pressure of the reaction chamber was adjusted to 150 Torr through a vacuum pump and a high-precision pressure sensor, and the temperature of the reaction chamber was raised and stabilized at 880°C with a temperature control accuracy of ±1°C. The micro-down temperature control system was started. During the entire growth process, the temperature gradient at different positions in the reaction chamber was accurately monitored and adjusted in real time, so that the microwave power, plasma temperature, reaction chamber pressure and single crystal diamond growth rate were all kept highly constant. The growth time was set to 800 hours to achieve continuous and stable growth.

[0036] Post-processing

[0037] After the growth is completed, the temperature is maintained in the reaction chamber for continuous annealing. The annealing temperature is reduced from 880°C to 650°C at a rate of 4°C / hour, and then cooled naturally. During the annealing process, a thermal stress monitoring device is used to monitor the stress changes inside the crystal in real time to ensure that the stress is fully released.

[0038] After annealing, a mixture of chlorine and oxygen (volume ratio of 3:1) was introduced to etch the crystal surface at 620°C for 1.2 hours. The etching gas flow rate was 0.2 sccm / cm according to the crystal surface area. 2The ratio of was precisely adjusted, and then the obtained single crystal diamond was taken out from the reaction chamber, and chemically cleaned by immersing it in a mixed solution of aqua regia and hydrofluoric acid (volume ratio of 5:1) for 40 minutes, and then rinsed with deionized water for 4 times, and then physically cleaned by ultrasonic cleaning with pure water in an ultrasonic cleaning machine for 25 minutes;

[0039] After cleaning, the single crystal diamond is cut into predetermined sizes using laser cutting equipment at a cutting speed of 8 mm / minute and a cutting depth of 0.8 mm each time. Finally, chemical mechanical polishing equipment is used in conjunction with polishing liquid and polishing pads to polish the cut single crystal diamond for 3.5 hours, so that the surface roughness reaches the nanometer level and the crystal quality is improved.

[0040] Embodiment 2

[0041] Substrate pretreatment

[0042] Iridium-plated sapphire wafers were selected as substrate materials and placed in an ultrasonic cleaning tank containing a mixed solution of ethanol and acetone (volume ratio of 1:1) for 30 minutes at an ultrasonic cleaning frequency of 35kHz. After the soaking, the wafers were rinsed with deionized water for 5 times, each time for 7 minutes, to ensure that the oil and impurities on the substrate surface were completely removed;

[0043] The cleaned substrate was placed in a vacuum drying oven at a temperature of 82°C and a vacuum degree of 8×10 -3 Pa for 3 hours, and polish the substrate on a polishing machine using diamond polishing powder with a particle size of 0.4 μm for 3 hours, so that the surface of the substrate reaches atomic-level flatness without any impurities remaining, and the surface roughness is less than 0.05 μm after detection;

[0044] Seed placement

[0045] For the contact surface between the molybdenum seed crystal table and the pretreated seed crystal, use 1100 mesh sandpaper to gently polish it, and then wipe it clean with an alcohol cotton ball. The roughness of the contact surface is less than 0.18μm after testing. Place the seed crystal on the seed crystal table in the predetermined direction and position, use a press to apply a pressure of 55N and hold it for 15 seconds, and observe it under a high-resolution optical microscope to ensure that the seed crystal sheet is in close contact with the seed crystal table without any gap;

[0046] MPCVD Equipment Setup

[0047] The microwave power of the MPCVD equipment was adjusted to 6KW, and the power fluctuation was controlled within ±0.08KW. The gas flow controller was set to make the hydrogen flow rate 400sccm, the methane flow rate 40sccm, the carbon dioxide flow rate 15sccm, and the nitrogen flow rate 1.5sccm. The gas flow fluctuation was kept within ±0.8sccm. Before entering the reaction chamber, the gas passed through a purification device equipped with activated alumina and silica gel to remove trace impurities therein;

[0048] The reaction chamber pressure was adjusted to 150 Torr through a vacuum pump and a pressure sensor, the reaction chamber temperature was raised and stabilized at 880°C, the temperature control accuracy was ±1.5°C, and the micro-down temperature control system was started to maintain constant microwave power, constant plasma temperature, constant reaction chamber pressure, and constant single crystal diamond growth rate during the entire growth process, and the growth time was set to 900 hours;

[0049] Post-processing

[0050] After the growth is completed, continuous annealing treatment is carried out in the reaction chamber. The annealing temperature is reduced from 880°C to 620°C at a rate of 6°C / hour, and then naturally cooled. After the annealing is completed, oxygen is introduced to etch the crystal surface at 630°C for 1.5 hours. The etching gas flow rate is 0.25sccm / cm according to the surface area of ​​the crystal. 2 After that, the obtained single crystal diamond was taken out from the reaction chamber, and chemically cleaned by immersing it in a mixed solution of nitric acid and hydrochloric acid (volume ratio of 3:2) for 35 minutes, then rinsed with deionized water for 5 times, and then physically cleaned by ultrasonic cleaning with pure water in an ultrasonic cleaning machine for 30 minutes;

[0051] After cleaning, high-precision cutting equipment is used to cut the single crystal diamond according to the designed size, with a cutting speed of 9mm / minute and a cutting depth of 0.9mm each time. Finally, chemical mechanical polishing equipment is used with polishing liquid and polishing pad to polish the cut single crystal diamond for 4 hours, so that the surface roughness reaches the nanometer level, further improving the crystal quality;

[0052] The following are the test data of the single crystal diamond growth method based on the MPCVD micro-descent method in different embodiments of the present invention:

[0053] Example 1 Detection Data

[0054] 1. Growth parameters and size and weight changes

[0055] When entering the furnace, the seed crystal size was 15mm×15mm×0.5mm and the weight was 4Ct. After 800 hours of growth, the crystal size out of the furnace reached 15mm×15mm×9.3mm and the weight was 73Ct. The calculated crystal growth rate was about 11μm per hour.

[0056] 2. Crystal quality inspection

[0057] Surface morphology: Scanning electron microscopy (SEM) observation shows that the crystal surface is smooth, without obvious macroscopic defects such as protrusions, depressions or scratches. Under high-magnification SEM, it can be seen that the surface microstructure is uniform and the atoms are neatly arranged, indicating that the growth process is stable and of high quality;

[0058] Crystal structure: X-ray diffraction (XRD) analysis shows sharp diffraction peaks, and the peak positions completely match the diffraction peaks of standard single crystal diamonds. No impurity peaks appear, indicating that the crystal structure is complete and there are no impurities of other phases. At the same time, the lattice constant calculated based on the XRD data is consistent with the theoretical value, and the deviation is within the allowable range (less than 0.05%), indicating that the lattice arrangement inside the crystal is regular;

[0059] Internal defect detection: The transmission electron microscope (TEM) was used to observe the interior of the crystal and found that the dislocation density was low, about 10 per square centimeter. 2 -10 3 This is much lower than the single crystal diamond grown by traditional technology (about 10 per square centimeter). 4 -10 5 ), and no other serious internal defects such as twins and inclusions were detected, which is conducive to improving the application performance of single crystal diamond in the fields of electronics and optics;

[0060] Impurity content analysis: Through secondary ion mass spectrometry (SIMS) detection, it was found that the content of impurities such as nitrogen and oxygen was extremely low, among which the nitrogen content was 10 16 -10 17 atoms / cm 3 In the range of 10 15 -10 16 atoms / cm 3 Within this range, the impurity content of single crystal diamond grown by traditional methods is significantly reduced, which helps to improve the electrical and optical properties of the crystal;

[0061] 3. Performance Testing

[0062] Hardness test: Using a Vickers hardness tester to measure, the hardness value is about 100-105GPa, which is close to the theoretical value, and the hardness is evenly distributed on the entire crystal surface, reflecting the superhard characteristics of high-quality single crystal diamond;

[0063] Thermal conductivity test: The thermal conductivity is measured by laser flash method. The thermal conductivity reaches 2000-2200W / (m·K) at room temperature. The high thermal conductivity indicates that the crystal is of good quality and can be used in electronic devices with high heat dissipation requirements.

[0064] Optical performance test: The optical transmittance test was carried out in the UV-Vis-NIR spectrum range. The results showed that in the 220nm-2500nm band, the average transmittance was as high as over 90%, and the transmittance curve was smooth without obvious absorption peaks, indicating that the single crystal diamond has good application prospects in the optical field.

[0065] Example 2 Test data

[0066] 1. Growth parameters and size and weight changes

[0067] When the seed crystal enters the furnace, the size is 15mm×15mm×0.5mm and the weight is 4Ct. After 900 hours of growth, the size of the crystal out of the furnace reaches 15mm×15mm×10.2mm and the weight is 83Ct. The crystal growth rate is about 11.9μm per hour.

[0068] 2. Crystal quality inspection

[0069] Surface morphology: Scanning electron microscopy shows that the crystal surface is smooth and has no visible defects. High-resolution SEM images show that the microstructure is uniform and the surface atoms are arranged in a regular and orderly manner, reflecting good growth quality.

[0070] Crystal structure: The X-ray diffraction pattern shows clear and sharp diffraction peaks, which are consistent with the standard single crystal diamond diffraction peaks, without additional impurity peaks, proving that the crystal structure is complete. The deviation between the calculated lattice constant and the theoretical value is extremely small (less than 0.03%), further confirming the high order of the lattice inside the crystal;

[0071] Internal defect detection: Transmission electron microscopy observation found that the dislocation density was as low as about 5×10 per square centimeter. 2 -10 3 No defects such as twins and inclusions were found, which is crucial to improving the performance of crystals in electronic and optical devices;

[0072] Impurity content analysis: Secondary ion mass spectrometry results show that the nitrogen content is 5×10 15 -10 16 atoms / cm 3 In the range of 8×10 14 -10 15 atoms / cm 3 Within this range, the impurity content is at an extremely low level, which helps to improve the electrical and optical properties of the crystal;

[0073] 3. Performance Testing

[0074] Hardness test: The hardness value measured by the Vickers hardness tester is about 102-107GPa. The hardness distribution is uniform and close to the theoretical hardness value, showing the excellent mechanical properties of single crystal diamond;

[0075] Thermal conductivity test: The room temperature thermal conductivity measured by the laser flash method is between 2100-2300 W / (m·K). High thermal conductivity values ​​indicate high quality crystals suitable for heat dissipation related electronic applications.

[0076] Optical performance test: The optical transmittance test in the spectral range of 200nm-2500nm shows that the average transmittance is above 92%, and the transmittance curve is smooth without abnormal absorption peaks, showing the good application potential of this single crystal diamond in the field of optics;

[0077] These test data fully prove that the single crystal diamond growth method based on MPCVD micro-descent method of the present invention can produce high-quality and high-performance single crystal diamond, which is superior to traditional growth methods.

[0078] The above specific embodiments further illustrate the purpose, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above are only specific embodiments of the present invention and do not limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention are included in the protection scope of the present invention.

Claims

1. A method for growing single crystal diamond based on MPCVD micro-descent method, characterized in that: The following steps are involved: S1. Substrate pretreatment: Select suitable substrate materials, perform ultrasonic cleaning with organic solvents, and perform drying and polishing to ensure that the surface is flat and free of impurities; S2. Seed crystal placement: Place the pre-treated seed crystals on the tungsten or molybdenum seed crystal table at equal intervals, with a spacing of 0.2 mm between adjacent seed crystals, ensuring that the seed crystal sheet is in close contact with the seed crystal table; S3, MPCVD equipment settings: adjust the microwave power, gas flow, reaction chamber pressure and temperature of the MPCVD equipment to optimize the growth conditions of single crystal diamond, and finally control the temperature gradient through the micro-descent method to achieve constant microwave power, constant plasma temperature, constant reaction chamber pressure, constant single crystal diamond growth rate, and long-term stable growth; S4, post-processing: After the growth is completed, continuous annealing is performed without leaving the furnace. After etching, the obtained single crystal diamond is taken out from the reaction chamber for cleaning, cutting and polishing to remove surface impurities and defects and improve the crystal quality.

2. The method for growing single crystal diamond based on MPCVD micro-descent method according to claim 1, characterized in that: The substrate material in S1 is one of a single crystal diamond seed wafer and an iridium-coated sapphire wafer.

3. The method for growing single crystal diamond based on MPCVD micro-descent method according to claim 1, characterized in that: The microwave power of the MPCVD equipment in S3 is 6KW.

4. The method for growing single crystal diamond based on MPCVD micro-descent method according to claim 1, characterized in that: The gas flow rates of the MPCVD equipment in S3 are: 400 sccm of hydrogen, 40 sccm of methane, 15 sccm of carbon dioxide and 1.5 sccm of nitrogen.

5. The method for growing single crystal diamond based on MPCVD micro-descent method according to claim 1, characterized in that: The reaction chamber pressure of the MPCVD equipment in S3 is 150 Torr and the temperature is 880°C.

6. The method for growing single crystal diamond based on MPCVD micro-descent method according to claim 1, characterized in that: In the substrate pretreatment cleaning step, the organic solvent immersion time before cleaning is 20-30 minutes, and the ultrasonic cleaning frequency is 30-50kHz. After cleaning, it is rinsed with deionized water, and the number of rinses is 3-5 times, and each rinse time is 5-10 minutes to ensure that the organic pollutants and water-soluble impurities on the substrate surface are completely removed.

7. The method for growing single crystal diamond based on MPCVD micro-descent method according to claim 1, characterized in that: During the seed crystal placement process, the grinding sandpaper particle size of the seed crystal table and the seed crystal contact surface is 800-1200 mesh, and the roughness of the contact surface is less than 0.2 μm, so as to ensure close contact between the two and the flatness of the contact interface, which is conducive to heat transfer and seed crystal fixation.

8. The method for growing single crystal diamond based on MPCVD micro-descent method according to claim 1, characterized in that: The microwave power fluctuation in the MPCVD equipment is set to be less than ±0.1KW to maintain a stable plasma state, ensure a stable supply of active substances during the growth process, and avoid uneven growth or crystal defects caused by power fluctuations.

9. The method for growing single crystal diamond based on MPCVD micro-descent method according to claim 1, characterized in that: The gas flow fluctuation in the MPCVD equipment setting is less than ±1 sccm, and before the gas enters the reaction chamber, it needs to undergo a gas purification process to remove trace impurities that may be contained therein, such as oxygen, water vapor, etc., to prevent the impurities from having an adverse effect on diamond growth.

10. The method for growing single crystal diamond based on MPCVD micro-descent method according to claim 1, characterized in that: The continuous annealing process in the post-treatment has a cooling rate of 3-7°C / h. During the etching process, the flow rate of the etching gas is 0.1-0.3sccm / cm according to the surface area of ​​the crystal. 2 The ratio is adjusted to ensure the uniformity of the etching effect.