Method for enhancing CVD diamond heteroepitaxial nucleation through pulse positive bias

Abstract

The invention discloses a method for enhancing CVD diamond heteroepitaxial nucleation through pulse positive bias, and belongs to the technical field of CVD method heteroepitaxial single crystal diamond. Firstly, a molybdenum support bearing a sample is placed on a water cooling table in the center of a CVD cavity, the positive electrode of a direct-current pulse power supply is connected to an antenna of CVD equipment through a wire, and the other electrode of the direct-current pulse power supply is connected to a shell of the CVD cavity through a wire and is grounded; then placing a heterogeneous substrate for epitaxy in the center of the molybdenum support, and vacuumizing; introducing hydrogen, turning on a microwave power supply, gradually increasing power and adjusting air pressure; and methane is introduced, a pulsed bias power supply is turned on, and enhanced nucleation is carried out. According to the invention, the direct-current pulse power supply is used for bombarding the surface of the matrix in a discontinuous pulse mode, so that the thermal balance compensation effect is achieved; meanwhile, pulse positive bias voltage is applied to the base body, the effect of high-density epitaxial nucleation on the insulating heterogeneous substrate is achieved, and the method has important significance on heteroepitaxial growth and application of large-size single crystal diamond.

Description

Technical Field

[0001] The invention relates to a method for pulse positive bias voltage enhanced CVD diamond heteroepitaxial nucleation, belonging to the technical field of CVD method heteroepitaxial single crystal diamond. Background Art

[0002] As a typical ultra-wide bandgap semiconductor, diamond has better thermal and electrical properties than traditional semiconductors. At the same time, due to the absence of grain boundaries, single-crystal diamond has greatly improved carrier mobility and charge collection efficiency. Compared with polycrystalline diamond, it has great potential in the fields of detectors and power devices. Due to breakthroughs in equipment and processes, the size of polycrystalline diamond can reach 200~300 mm, which can basically meet the application requirements in terms of heat sinks, microwave windows, wear-resistant coatings, etc. However, large-sized natural single-crystal diamonds are extremely rare and expensive. The technical problem that single-crystal diamonds need to be urgently solved for semiconductor materials is how to prepare large-sized, high-quality single-crystal diamonds.

[0003] The main ways to prepare large-sized, high-quality single-crystal diamonds include three-dimensional growth, splicing growth, and heteroepitaxial growth. Although the three-dimensional growth method can replicate the crystal structure to obtain a high-quality epitaxial layer, it is limited by the seed size and is difficult to meet the size requirements of semiconductor devices. Splicing growth and heteroepitaxial growth are currently the most commonly used preparation methods. Among them, the splicing method overcomes the limitation of seed size, but there are problems such as interface dislocations, polycrystalline and defects at the splicing seams, which affect the quality of epitaxial single-crystal diamonds and limit the advanced applications of large-sized spliced ​​diamonds in semiconductors. The heteroepitaxial growth process refers to a method of obtaining a large-sized epitaxial single-crystal diamond film by high-density epitaxial nucleation on a non-diamond substrate and controlling the growth process to achieve grain merging and texture growth. This method has greater advantages than three-dimensional growth and splicing growth.

[0004] The most important technical issue of heteroepitaxial process is high-density epitaxial nucleation. The most common process at present is bias-enhanced nucleation method, which applies a certain bias voltage to the heterogeneous substrate. The plasma in the cavity is accelerated to bombard the substrate and interact with each other under the action of the electric field, forming an amorphous carbon film during the carbon dissolution-precipitation process. When the surface carbon concentration is saturated, diamond nuclei will be precipitated along the grain boundaries of the heterogeneous film. Applying a DC negative bias to the CVD equipment is the mainstream method reported so far, which is to connect the positive pole of the bias power supply to the ground of the CVD equipment cavity and the negative pole to the sample holder. However, if the substrate is insulated, this bias application method is basically ineffective.

[0005] In the above-mentioned technology of applying a DC negative bias to the CVD equipment, in order to solve the problem of substrate insulation, Chinese patent CN112695382A discloses a method for providing uniformity of diamond heteroepitaxial nucleation based on a grid structure electrode, but this technology does not fundamentally solve the problem of non-conductivity of the heterogeneous substrate, causing the charge in the plasma field to accumulate on the substrate surface, causing the substrate temperature to be too high, thereby destroying the template effect of the heterogeneous substrate. Other scholars have proposed depositing a metal film on the bottom and around the heterogeneous substrate (CN114134566A, CN113430642A), or designing auxiliary devices (CN112813497A). Although these operating methods can solve some problems, the DC negative bias can easily cause the substrate temperature to be too high, resulting in uneven temperature and substrate warping, which greatly limits the bias nucleation effect. Summary of the invention

[0006] In order to solve the problem of high-density epitaxial nucleation and maintain the uniformity of nucleation, the present invention aims to provide a method for pulsed positive bias enhanced CVD diamond heteroepitaxial nucleation.

[0007] The present invention uses a DC pulse power supply to bombard the substrate surface in a discontinuous pulse manner, changing the temperature gradient between the inside and the surface of the substrate, achieving a thermal equilibrium compensation effect, reducing thermal damage to the substrate, and effectively avoiding the peeling of the iridium film on the surface of the heterogeneous substrate or the cracking of the heterogeneous substrate, and better achieving the epitaxial integrity of large-size single-crystal diamonds; on the other hand, applying a pulsed positive bias to the substrate avoids the inability of the DC bias to effectively apply a bias to the insulating heterogeneous substrate, and relatively easily achieves the effect of high-density epitaxial nucleation on the insulating heterogeneous substrate, which is of great significance to the field of heteroepitaxial single-crystal diamond. The present invention connects the CVD equipment antenna to the positive pole of the DC pulse power supply, applies an electric field above the plasma, and makes the C in the plasma x H y + Under the action of the electric field, the ions migrate to the molybdenum support and the heterogeneous substrate on the surface for epitaxy. At the same time, under the action of the additional electric field, the plasma is compressed and forms a sheath layer on the surface of the heterogeneous substrate for epitaxy, avoiding the serious weakening of the electric field due to the poor conductivity of the heterogeneous substrate, greatly improving the uniformity and efficiency of nucleation.

[0008] The invention provides a method for pulse positive bias enhanced CVD diamond heteroepitaxial nucleation, wherein a molybdenum holder carrying a sample is placed on a water-cooled table in the center of a CVD cavity, a positive electrode of a direct current pulse power supply is connected to an antenna of a CVD device through a wire, and a polytetrafluoroethylene (PVC) insulating ring is used to insulate it from the cavity, and another electrode of the direct current pulse power supply is connected to a CVD cavity shell through a wire and is grounded; then a heterogeneous substrate for epitaxy is placed at the center of the molybdenum holder, and vacuum is evacuated; then hydrogen is introduced, a microwave power supply is turned on, the power is gradually increased, and the gas pressure is adjusted until the temperature reaches 600-800°C; finally, the methane concentration is controlled, the pulse bias power supply is turned on, and the bias process parameters are set to enhance the nucleation, thereby obtaining a heterogeneous substrate for high-density epitaxial nucleation.

[0009] The above-mentioned pulsed positive bias enhanced CVD diamond heteroepitaxial nucleation method specifically comprises the following steps: (1) The molybdenum tray carrying the sample is placed on the water-cooled table in the center of the CVD chamber. The positive electrode of the DC pulse power supply is connected to the CVD equipment antenna through a wire and insulated from the chamber by polytetrafluoroethylene. The other electrode of the DC pulse power supply is connected to the CVD chamber shell through a wire and grounded. (2) Place the heterogeneous substrate for epitaxy at the center of the molybdenum tray, close the CVD chamber, open the vacuum pump and the gas valve to start evacuating the chamber until the background vacuum is 1×10 -4 ~5×10 -4 Pa; (3) Introducing hydrogen and controlling its flow rate and the gas pressure in the CVD chamber. When a certain gas pressure is reached, the microwave generator is started to activate the plasma; (4) Adjust the hydrogen flow rate and gas valve to gradually and steadily increase the gas pressure in the CVD chamber, the microwave power, and the temperature of the epitaxial substrate; (5) Continuously measure the surface temperature of the epitaxial substrate with a temperature measuring gun, and stop the microwave generator when the surface temperature reaches 600-800°C; (6) Introduce 0-500 sccm of methane gas and adjust the gas valve to balance the gas pressure at 3-4 kPa; (7) After the substrate surface temperature is stabilized for 5 to 15 minutes, turn on the DC pulse bias power supply, set the process parameters such as constant voltage mode, voltage, duty cycle and bias time, and then start the power supply for bias enhanced nucleation; the DC pulse setting parameters are: pulse voltage is 100 to 1000 V, preferably 400 to 900 V, pulse duty cycle is 10% to 85%, and bias time is 10 to 60 minutes.

[0010] (8) After the bias-enhanced nucleation is completed, the DC pulse bias power supply and the equipment are turned off, and the sample is taken out, completing the method of enhancing the CVD diamond heteroepitaxial nucleation by applying a positive bias based on a DC pulse power supply.

[0011] In the above method, in step (1), the thickness of the molybdenum tray carrying the sample is 1-5 mm, so that the temperature of the epitaxial substrate can meet the requirements under low power and low pressure.

[0012] In the above method, in step (2), the substrate used for epitaxy is Si, c-BN, SiC or Ir-based composite substrate.

[0013] In the above method, in step (3), the hydrogen flow rate is 50-600 sccm, and the cavity pressure when the microwave generator is started is 0.4-0.8 kPa.

[0014] In the above method, in step (4), the rate of pressure increase is 0.1~0.5 kPa / min, the rate of power increase is 50~200 W / min, and the rate of temperature increase is 30~70℃ / min; the temperature of the epitaxial substrate is 600~800℃, the pressure in the cavity is 3~4 kPa, and the microwave power is 1500~2000 W.

[0015] In the above method, in step (6), the flow rate of methane (CH4 / H2) is 0-500 sccm, and the volume fraction of methane is 1%-5%.

[0016] Beneficial effects of the present invention: (1) The present invention uses a DC pulse power supply to bombard the substrate surface in a discontinuous pulse manner, thereby changing the temperature gradient between the inside and the surface of the substrate, achieving a thermal equilibrium compensation effect, and reducing thermal damage to the substrate; (2) The present invention simultaneously applies a pulse bias to the substrate to avoid the inability of a DC bias to effectively apply a bias to the insulating heterogeneous substrate, thereby achieving the effect of high-density epitaxial nucleation on the insulating heterogeneous substrate; (3) The present invention applies a positive bias voltage on the MPCVD device, avoiding the design of a more complicated sample base, while achieving uniform temperature and uniform nucleation, which is of great significance for the heteroepitaxial growth and application of large-sized single crystal diamond. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic diagram of the structure of an MPCVD device connected to a DC pulse bias power supply; Figure 2 It is a schematic diagram of DC pulse bias mode; Figure 3 This is the SEM morphology of the pulsed positive bias nucleation on the SiC substrate surface in Example 1; Figure 4 This is the SEM morphology of pulsed positive bias nucleation on the surface of the Ir-based composite substrate in Example 2; Figure 5 This is the SEM morphology of pulsed positive bias nucleation on the surface of the Ir-based composite substrate in Example 3; In the figure: 1. Molybdenum support; 2. Water cooling table; 3. DC pulse power supply; 4. Microwave antenna; 5. Cavity; 6. Heterogeneous substrate; 7. Vacuum pump; 8. Gas path valve; 9. Microwave generator; 10. Plasma. DETAILED DESCRIPTION

[0018] The method for pulsed positive bias enhanced CVD diamond heteroepitaxial nucleation provided by the present invention specifically comprises the following steps: (1) Place the sample-carrying molybdenum holder 1 on the water-cooled table 2 in the center of the CVD chamber. Connect the positive electrode of the DC pulse power supply 3 to the CVD equipment antenna 4 through a wire, and use a polytetrafluoroethylene insulating ring to cover the antenna to insulate it from the chamber 5. The other electrode of the DC pulse power supply is connected to the CVD chamber shell through a wire and grounded. In this step, the thickness of the sample-carrying molybdenum holder is 1-5 mm.

[0019] (2) Place the heterogeneous substrate 6 for epitaxy at the center of the molybdenum tray, close the CVD chamber, open the vacuum pump 7 and the gas valve 8 to start evacuation until the background vacuum is 1×10 -4 ~5×10 -4 In this step, the heterogeneous substrate used for epitaxy is Si, c-BN, SiC or Ir-based composite substrate.

[0020] (3) Hydrogen is introduced, and its flow rate and the gas pressure in the CVD chamber are controlled. When a certain gas pressure is reached, the microwave generator 9 is started to activate the plasma 10. In the step (3), the hydrogen flow rate is 50-600 sccm, and the cavity pressure when the microwave generator is started is 0.4-0.8 kPa.

[0021] (4) Adjust the hydrogen flow rate and the gas valve to gradually and steadily increase the gas pressure in the CVD chamber, the microwave power, and the temperature of the epitaxial substrate. In step (4), the rate of increasing the gas pressure is 0.1-0.5 kPa / min, the rate of increasing the power is 50-200 W / min, the rate of increasing the temperature is 30-70°C / min, the temperature of the epitaxial substrate is 600-800°C, the gas pressure in the chamber is 3-4 kPa, and the microwave power is 1500-2000 W.

[0022] (5) Continuously measure the surface temperature of the epitaxial substrate using a temperature measuring gun. When the surface temperature reaches 600-800°C, stop applying microwave power.

[0023] (6) Introduce 0-500 sccm of methane gas, and adjust the gas valve to balance the gas pressure at 3-4 kPa. In step (6), the flow rate of methane (CH4 / H2) is 0-500 sccm, and the volume fraction of methane is 1%-5%.

[0024] (7) After the substrate surface temperature is stabilized for 5 to 15 minutes, turn on the DC pulse bias power supply, set the constant voltage mode, voltage, duty cycle, bias time and other process parameters, and start the power supply to perform bias enhanced nucleation. In step (7), the pulse voltage is 100 to 1000 V, the pulse duty cycle is 10% to 85%, and the bias time is 10 to 60 minutes.

[0025] (8) After the bias-enhanced nucleation is completed, the DC pulse bias power supply and the equipment are turned off, and the sample is taken out, completing the method of enhancing the CVD diamond heteroepitaxial nucleation by applying a positive bias based on a DC pulse power supply.

[0026] The present invention is further illustrated by the following examples, but is not limited to the following examples. Example 1

[0027] This embodiment provides a method for pulsed positive bias enhanced CVD diamond heteroepitaxial nucleation, the operation steps of which are as follows: (1) Place the 1 mm molybdenum tray carrying the sample on the water-cooled table in the center of the CVD chamber. Connect the positive electrode of the DC pulse power supply to the CVD equipment antenna through a wire and insulate it from the chamber using a polytetrafluoroethylene insulating ring. Connect the other electrode of the DC pulse power supply to the CVD chamber shell through a wire and ground it. Figure 1 shown.

[0028] (2) Place the SiC substrate for epitaxy at the center of the molybdenum tray, close the CVD chamber, open the vacuum pump and the gas valve to start evacuating the chamber until the background vacuum is 1×10 -4 Pa.

[0029] (3) Hydrogen gas was introduced and its flow rate was controlled to 200 sccm. The gas pressure in the CVD chamber was controlled. When the gas pressure reached 0.4 kPa, the microwave generator (microwave power was 600 W) was started to activate the plasma.

[0030] (4) The hydrogen flow rate and the gas valve were adjusted to gradually and steadily increase the gas pressure in the CVD chamber, the microwave power, and the temperature of the epitaxial substrate. The rate of pressure increase was 0.1 kPa / min, the rate of power increase was 50 W / min, and the rate of temperature increase was 30°C / min.

[0031] (5) The surface temperature of the epitaxial substrate is continuously measured by a temperature measuring gun. When the surface temperature reaches 650°C, the microwave power is stopped. At this time, the microwave power is 1500 W and the pressure in the cavity is 3 kPa.

[0032] (6) Pass methane gas with a flow rate of 50 sccm and a volume fraction (CH4 / H2) of 1%, and adjust the gas line valve to balance the gas pressure at 3 kPa.

[0033] (7) After the substrate surface temperature has stabilized for 5 min, turn on the DC pulse bias power supply, set the constant voltage mode, set the pulse voltage to 800 V, and the duty cycle to 30%, then start the power supply to perform bias enhanced nucleation for 20 min. Figure 2 shown.

[0034] (8) After the bias-enhanced nucleation is completed, the DC pulse bias power supply and the equipment are turned off, and the sample is taken out, completing the method of enhancing the CVD diamond heteroepitaxial nucleation by applying a positive bias based on a DC pulse power supply. The SEM morphology of the nucleation on the substrate surface is as follows: Figure 3 shown. Example 2

[0035] This embodiment provides a method for pulsed positive bias enhanced CVD diamond heteroepitaxial nucleation, the operation steps of which are as follows: (1) Place the 3 mm molybdenum tray carrying the sample on the water-cooled table in the center of the CVD chamber. Connect the positive electrode of the DC pulse power supply to the CVD equipment antenna through a wire and insulate it from the chamber using a polytetrafluoroethylene insulating ring. Connect the other electrode of the DC pulse power supply to the CVD chamber shell through a wire and ground it. Figure 1 shown.

[0036] (2) Place the Ir-based composite substrate for epitaxy at the center of the molybdenum tray, close the CVD chamber, open the vacuum pump and the gas valve to start evacuating the chamber until the background vacuum is 1×10 -4 Pa.

[0037] (3) Hydrogen gas was introduced and its flow rate was controlled to 300 sccm. The gas pressure in the CVD chamber was also controlled. When the gas pressure reached 0.6 kPa, the microwave generator was started to activate the plasma.

[0038] (4) The hydrogen flow rate and the gas valve were adjusted to gradually and steadily increase the gas pressure in the CVD chamber, the microwave power, and the temperature of the epitaxial substrate. The rate of increasing the gas pressure was 0.15 kPa / min, the rate of increasing the power was 100 W / min, and the rate of increasing the temperature was 50°C / min.

[0039] (5) The surface temperature of the epitaxial substrate is continuously measured by a temperature measuring gun. When the surface temperature reaches 700°C, the microwave power is stopped. At this time, the microwave power is 1800 W and the pressure in the cavity is 3.5 kPa.

[0040] (6) Methane gas with a flow rate of 200 sccm and a volume fraction (CH4 / H2) of 3% was introduced, and the gas line valve was adjusted to balance the gas pressure at 3.5 kPa.

[0041] (7) After the substrate surface temperature has been stable for 10 min, turn on the DC pulse bias power supply and set the constant voltage mode. At the same time, the pulse voltage is 500 V and the duty cycle is 50%. Then start the power supply to perform bias enhanced nucleation for 40 min.

[0042] (8) After the bias-enhanced nucleation is completed, the DC pulse bias power supply and the equipment are turned off, and the sample is taken out, completing the method of enhancing the CVD diamond heteroepitaxial nucleation by applying a positive bias based on a DC pulse power supply. The SEM morphology of the nucleation on the substrate surface is as follows: Figure 4 shown. Example 3

[0043] This embodiment provides a method for pulsed positive bias enhanced CVD diamond heteroepitaxial nucleation, the operation steps of which are as follows: (1) Place the 5 mm molybdenum tray carrying the sample on the water-cooled table in the center of the CVD chamber. Connect the positive electrode of the DC pulse power supply to the CVD equipment antenna through a wire and insulate it from the chamber using a polytetrafluoroethylene insulating ring. Connect the other electrode of the DC pulse power supply to the CVD chamber shell through a wire and ground it. Figure 1 shown.

[0044] (2) Place the Ir-based composite substrate for epitaxy at the center of the molybdenum tray, close the CVD chamber, open the vacuum pump and the gas valve to start evacuating the chamber until the background vacuum is 1×10 -4 Pa.

[0045] (3) Hydrogen gas was introduced and its flow rate was controlled to be 500 sccm. The gas pressure in the CVD chamber was also controlled. When the gas pressure reached 0.8 kPa, the microwave generator was started to activate the plasma.

[0046] (4) Adjust the hydrogen flow rate and gas valve to gradually and steadily increase the gas pressure in the CVD chamber, the microwave power, and the temperature of the epitaxial substrate. The rate of increasing the gas pressure is 0.2 kPa / min, the rate of increasing the power is 150 W / min, and the rate of increasing the temperature is 70 °C / min.

[0047] (5) The surface temperature of the epitaxial substrate is continuously measured by a temperature measuring gun. When the surface temperature reaches 750°C, the microwave power is stopped. At this time, the microwave power is 2000 W and the pressure in the cavity is 4 kPa.

[0048] (6) Introduce methane gas with a flow rate of 500 sccm and a volume fraction (CH4 / H2) of 5%, and adjust the gas line valve to balance the gas pressure at 4 kPa.

[0049] (7) After the substrate surface temperature has been stable for 15 min, turn on the DC pulse bias power supply and set the constant voltage mode. At the same time, the pulse voltage is 200 V and the duty cycle is 70%. Then start the power supply to perform bias enhanced nucleation for 60 min.

[0050] (8) After the bias-enhanced nucleation is completed, the DC pulse bias power supply and the equipment are turned off, and the sample is taken out, completing the method of enhancing the CVD diamond heteroepitaxial nucleation by applying a positive bias based on a DC pulse power supply. The SEM morphology of the nucleation on the substrate surface is as follows: Figure 5 shown.

[0051] Through SEM morphology observation of the surface after nucleation, the density of CVD diamond heteroepitaxial nuclei on the surface of SiC substrate in Example 1 is about 5*10 9 cm -2 The CVD diamond heteroepitaxial nuclei density on the surface of the Ir-based composite substrate in Example 2 and Example 3 are about 8*10 10 cm -2 and 6*10 10 cm -2 , both at 10 9 ~10 11 cm -2 The range meets the requirements of subsequent CVD diamond heteroepitaxial growth. Therefore, the DC pulse positive bias has a significant effect on enhancing the nucleation effect. Compared with DC negative bias nucleation or other auxiliary negative bias nucleation, pulse positive bias nucleation not only avoids substrate damage, but also significantly improves the nucleation density.

[0052] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that there are many practical solutions that can be adopted in the preparation method, and any equivalent modifications or substitutions made in accordance with the claims of the present invention and the essence of the corresponding technical solutions belong to the scope of the present invention.

Claims

1. A method for pulsed positive bias enhanced CVD diamond heteroepitaxial nucleation, characterized in that The method comprises the following steps: firstly, placing a molybdenum tray carrying a sample on a water-cooled platform in the center of a CVD chamber, connecting the positive electrode of a direct current pulse power supply to an antenna of a CVD device through a wire, and connecting the other electrode of the direct current pulse power supply to an outer shell of a CVD chamber through a wire and grounding; then placing a heterogeneous substrate for epitaxy at the center of the molybdenum tray and evacuating the vacuum; then introducing hydrogen, turning on a microwave power supply, gradually increasing the power and adjusting the gas pressure until the temperature reaches 600-800°C; finally, controlling the methane concentration, turning on a pulse bias power supply for enhanced nucleation, and setting the bias parameters as follows: a pulse voltage of 100-1000 V, and a pulse duty cycle of 10%-85%, thereby obtaining a heterogeneous substrate for high-density epitaxial nucleation.

2. The method for pulsed positive bias enhanced CVD diamond heteroepitaxial nucleation according to claim 1, characterized in that The following steps are involved: (1) The molybdenum tray carrying the sample is placed on the water-cooled table in the center of the CVD chamber. The positive electrode of the DC pulse power supply is connected to the CVD equipment antenna through a wire and insulated from the chamber by a polytetrafluoroethylene insulating ring. The other electrode of the DC pulse power supply is connected to the CVD chamber shell through a wire and grounded. (2) Place the heterogeneous substrate for epitaxy at the center of the molybdenum tray, close the CVD chamber, open the vacuum pump and the gas valve to start evacuating the chamber until the background vacuum is 1×10 -4 ~5×10 -4 Pa; (3) Introducing hydrogen and controlling its flow rate and the gas pressure in the CVD chamber. When a certain gas pressure is reached, the microwave generator is started to activate the plasma; (4) Adjust the hydrogen flow rate and gas valve to gradually and steadily increase the gas pressure in the CVD chamber, the microwave power, and the temperature of the epitaxial substrate; (5) Continuously measure the surface temperature of the epitaxial substrate with a temperature measuring gun, and stop applying microwave power when the surface temperature reaches 600-800°C; (6) Introduce 0-500 sccm of methane gas and adjust the gas valve to balance the gas pressure at 3-4 kPa; (7) After the substrate surface temperature stabilizes for a period of time, turn on the DC pulse bias power supply, set the constant voltage mode, voltage, duty cycle, and bias time, and start the power supply to perform bias enhanced nucleation; The DC pulse setting parameters are: pulse voltage 400~900V, pulse duty cycle 10%~85%, bias time 10~60 min; (8) After the bias-enhanced nucleation is completed, the DC pulse bias power supply and the equipment are turned off, and the sample is taken out, completing the method of enhancing the CVD diamond heteroepitaxial nucleation by applying a positive bias based on a DC pulse power supply.

3. The method for pulsed positive bias enhanced CVD diamond heteroepitaxial nucleation according to claim 2, characterized in that: In the step (1), the thickness of the molybdenum support that carries the sample is 1 to 5 mm.

4. The method for pulsed positive bias enhanced CVD diamond heteroepitaxial nucleation according to claim 2, characterized in that: In the step (2), the heterogeneous substrate used for epitaxy is Si, c-BN, SiC or Ir-based composite substrate.

5. The method for pulsed positive bias enhanced CVD diamond heteroepitaxial nucleation according to claim 2, characterized in that: In the step (3), the hydrogen flow rate is 50-600 sccm, and the cavity pressure when the microwave generator is started is 0.4-0.8 kPa.

6. The method for pulsed positive bias enhanced CVD diamond heteroepitaxial nucleation according to claim 2, characterized in that: In the step (4), the temperature of the epitaxial substrate is 600-800°C, the pressure in the cavity is 3-4 kPa, and the microwave power is 1500-2000 W.

7. The method for pulsed positive bias enhanced CVD diamond heteroepitaxial nucleation according to claim 6, characterized in that: The pressure increase rate is 0.1~0.5 kPa / min, the power increase rate is 50~200 W / min, and the temperature increase rate is 30~70℃ / min.

8. The method for pulsed positive bias enhanced CVD diamond heteroepitaxial nucleation according to claim 2, characterized in that: In the step (6), the methane flow rate is 0-500 sccm and the volume fraction is 1%-5%.

9. The method for pulsed positive bias enhanced CVD diamond heteroepitaxial nucleation according to claim 2, characterized in that: In the step (7), the temperature stabilization time before starting the bias mode is 5 to 15 minutes.

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