Method for repairing and growing surface defects of MPCVD monocrystalline diamond

Abstract

The application discloses a MPCVD monocrystal diamond surface defect repairing and growing method, and aims at the problem that surface defects are difficult to remove and the crystal quality of a growing layer is reduced in the process of growing the MPCVD monocrystal diamond.The defect repairing and growing method comprises the following steps: firstly, laser processing is adopted to cut off the defect area on the surface of a monocrystal diamond seed crystal, so as to form a square pit; secondly, the diamond seed crystal is placed in a tube furnace for high-temperature treatment; thirdly, a mask is adopted to fill the pit with a monocrystal iridium; fourthly, the diamond seed crystal plated with iridium is transferred to a growing device, and a plasma is ignited; fifthly, the growing gas pressure, the temperature of the diamond seed crystal and the content of methane are controlled, and a direct current bias is applied, so as to promote the high-density nucleation growth on the surface of the hetero-epitaxial monocrystal iridium; and sixthly, homo-epitaxial growth of the MPCVD monocrystal diamond is carried out.The monocrystal iridium is plated on the notch area by means of electron beam evaporation, the influence of the original defects is eliminated, and a high-quality monocrystal diamond epitaxial growing layer is obtained.

Description

Technical Field

[0001] This invention belongs to the field of diamond preparation, specifically relating to a method for repairing and growing surface defects in single-crystal diamond by microwave plasma chemical vapor deposition (MPCVD). Background Technology

[0002] Diamond is an allotrope of carbon, existing in its elemental form. It is an allotrope of graphite and carbon nanotubes, but its unique crystal structure gives it superior properties unmatched by other materials. These properties, such as extremely high hardness and chemical stability, extremely high thermal conductivity and good insulation, and a wide electromagnetic wave transmission frequency domain, make diamond, especially single-crystal diamond, an ideal material for applications in precision machining, aerospace, device heat dissipation, and optical windows. Microwave plasma chemical vapor deposition (MPCVD) technology uses hydrogen and methane as raw materials and microwaves as an energy source to rapidly and cleanly deposit and grow high-quality single-crystal diamond materials on diamond seed crystals or other substrates. Depending on the substrate used, MPCVD diamond growth is divided into homoepitaxial and heteroepitaxial growth. In heteroepitaxial single-crystal diamond growth, single-crystal iridium is generally used as the substrate because iridium has a good lattice matching with diamond. In the process of homoepitaxial single-crystal diamond crystal growth using diamond seed crystals, the quality of the seed crystal largely determines the crystal quality of the epitaxial growth layer. Defects such as polycrystalline points, microcracks, and dislocations on the surface of the diamond seed crystal will extend and accumulate into the epitaxial growth layer during growth, severely degrading the quality of the grown layer crystal. Polishing can remove surface polycrystalline points, but it introduces polishing damage layer defects, further reducing growth quality; various etching methods can remove surface dislocations, but they create etching pits, increasing roughness, and the etching efficiency for polycrystalline points is extremely low. Summary of the Invention

[0003] This invention addresses the problem of surface defects being difficult to remove and reducing the crystal quality of the grown layer during MPCVD single-crystal diamond growth. It proposes a method for repairing surface defects in MPCVD single-crystal diamond by combining laser processing and heteroepitaxial growth, thereby completely eliminating the influence of defect areas.

[0004] The MPCVD single-crystal diamond surface defect repair growth method of the present invention is implemented according to the following steps:

[0005] 1. The defective area on the surface of the single crystal diamond seed crystal is removed by laser processing to form a square pit. The four sides of the square pit are along the (100) crystal plane of the single crystal diamond to obtain a diamond seed crystal with a square pit.

[0006] 2. Place the diamond seed crystal with square pits in a tube furnace and heat it at 400-550℃ in an air atmosphere to obtain a diamond seed crystal with graphite removed.

[0007] 3. Place the graphite-removed diamond seed crystal on the sample stage of the electron beam evaporation coating equipment. Using a masking method, fill the pit with a single crystal iridium at 600-800℃ to grow the single crystal iridium higher than the surface of the single crystal diamond, and obtain the iridium-coated diamond seed crystal.

[0008] 4. Transfer the iridium-plated diamond seed crystal to the sample stage of the MPCVD diamond growth equipment, close the chamber door, draw a vacuum, introduce hydrogen gas, and turn on the microwave to ignite the plasma.

[0009] 5. Control the growth gas pressure to 30-60 mbar, the diamond seed crystal temperature to 750-850℃, the methane content (volume fraction) to 10%-15%, and apply a DC bias voltage of 100-300V to promote high-density nucleation growth on the surface of heteroepitaxial single crystal iridium.

[0010] 6. Turn off the DC bias power supply, control the growth gas pressure to 200-280 mbar, the diamond seed crystal temperature to 900-1100℃, and the methane content to 4%-8%, and carry out MPCVD homoepitaxial growth of single crystal diamond to obtain a high-quality single crystal epitaxial growth layer.

[0011] The MPCVD single-crystal diamond surface defect repair growth method of the present invention first removes the material in the defect area by laser processing, which can quickly and completely remove defects including polycrystalline points, twins, dislocations, etc., and the side of the pit after removal is set as (100) crystal plane to meet the requirements of subsequent single-crystal iridium filling and heteroepitaxial growth; then, the graphite impurities introduced by laser processing are completely eliminated in air at a suitable temperature, which provides favorable conditions for subsequent single-crystal iridium plating; high-quality single-crystal iridium can be prepared by electron beam evaporation, and it is grown into the pit formed by laser processing by masking. Then, nucleation is carried out using suitable heteroepitaxial growth process conditions for high-density nucleation of single-crystal diamond, and finally, the process parameters are changed to promote its vertical epitaxial growth and obtain a complete high-quality single-crystal growth layer.

[0012] The MPCVD single-crystal diamond surface defect repair growth method described in this invention can quickly, accurately, and thoroughly remove the defective areas on the surface of single-crystal diamond and inhibit their extension into the growth layer, thereby preventing a decline in the quality of the prepared crystal. Attached Figure Description

[0013] Figure 1This is a flowchart of the MPCVD single-crystal diamond surface defect repair growth method of the present invention, wherein (a): diamond with defect points on the surface; (b): laser removal of defects; (c): removal of laser ablation residue; (d): plating of iridium metal in the pits; (e): growth to obtain a defect-free surface;

[0014] Figure 2 These are mound-like defects on the surface of diamond seed crystals, which generally correspond to screw dislocations;

[0015] Figure 3 The surface morphology of the diamond single-crystal epitaxial growth layer obtained by the single-crystal diamond surface defect repair growth method in the example (image observed under a 100x optical microscope) shows a good step morphology and no surface defects.

[0016] Figure 4 The surface morphology of a single-crystal diamond seed crystal containing surface defects after growth without treatment is shown. The surface defects accumulate during the growth process, forming enlarged black polycrystalline points. Detailed Implementation

[0017] Specific Implementation Method 1: This implementation method for repairing surface defects in MPCVD single-crystal diamond is carried out according to the following steps:

[0018] 1. The defective area on the surface of the single crystal diamond seed crystal is removed by laser processing to form a square pit. The four sides of the square pit are along the (100) crystal plane of the single crystal diamond to obtain a diamond seed crystal with a square pit.

[0019] 2. Place the diamond seed crystal with square pits in a tube furnace and heat it at 400-550℃ in an air atmosphere to obtain a diamond seed crystal with graphite removed.

[0020] 3. Place the graphite-removed diamond seed crystal on the sample stage of the electron beam evaporation coating equipment. Using a masking method, fill the pit with a single crystal iridium at 600-800℃ to grow the single crystal iridium higher than the surface of the single crystal diamond, and obtain the iridium-coated diamond seed crystal.

[0021] 4. Transfer the iridium-plated diamond seed crystal to the sample stage of the MPCVD diamond growth equipment, close the chamber door, draw a vacuum, introduce hydrogen gas, and turn on the microwave to ignite the plasma.

[0022] 5. Control the growth gas pressure to 30-60 mbar, the diamond seed crystal temperature to 750-850℃, the methane content (volume fraction) to 10%-15%, and apply a DC bias voltage of 100-300V to promote high-density nucleation growth on the surface of heteroepitaxial single crystal iridium.

[0023] 6. Turn off the DC bias power supply, control the growth gas pressure to 200-280 mbar, the diamond seed crystal temperature to 900-1100℃, and the methane content to 4%-8%, and carry out MPCVD homoepitaxial growth of single crystal diamond to obtain a high-quality single crystal epitaxial growth layer.

[0024] This embodiment thoroughly removes the defective area through laser processing, and deposits single-crystal iridium in the removed notched area by electron beam evaporation. Then, single-crystal diamond is grown on the treated seed crystal to eliminate the influence of the original defects and obtain a high-quality single-crystal diamond epitaxial growth layer.

[0025] Specific Implementation Method Two: This implementation method differs from Specific Implementation Method One in that the depth of the square pit described in step one is 50-200 micrometers.

[0026] Specific Implementation Method 3: This implementation method differs from Specific Implementation Method 1 or 2 in that the heat preservation time in step 2 is 1-4 hours.

[0027] The purpose of maintaining the temperature at 400-550°C in air in this embodiment is to remove the graphite generated on the sidewalls and bottom of the pit due to laser processing.

[0028] Specific Implementation Method Four: This implementation method differs from one of the specific implementation methods one to three in that in step three, the iridium crystal is 10-50 micrometers higher than the surface of the single crystal diamond.

[0029] In the early stages of growth, diamond seed crystals coated with iridium exhibit both heteroepitaxial growth on the iridium surface and homoepitaxial growth on the diamond surface. Heteroepitaxial growth on iridium involves two processes: nucleation and growth. The nucleation process is slower, but once the iridium surface has formed a film through nucleation, it enters the same growth stage as homoepitaxial growth. Therefore, in step five of this invention, the iridium surface nucleates and forms a film. Under these conditions, the diamond growth thickness of the homoepitaxial portion is 10-50 micrometers. By setting the iridium-coated portion to be 10-50 micrometers higher than the original diamond seed crystal, the surface height of the homoepitaxial portion after nucleation is the same as the height of the iridium-coated nucleated portion. Finally, step six, homoepitaxial growth, is performed.

[0030] Specific Implementation Method Five: This implementation method differs from Specific Implementation Methods One through Four in that step four involves closing the hatch and evacuating the vacuum to a degree of 5 × 10⁻⁶. -5 Below mbar.

[0031] Specific Implementation Method Six: This implementation method differs from Specific Implementation Methods One to Five in that 50-100 sccm of hydrogen gas is introduced in step four.

[0032] Specific Implementation Method Seven: This implementation method differs from Specific Implementation Methods One to Six in that the high-density nucleation growth time in step five is 1-4 hours.

[0033] Specific Implementation Method Eight: This implementation method differs from Specific Implementation Methods One to Seven in that step five controls the growth gas pressure to be 50-60 mbar, the diamond seed crystal temperature to be 750-850℃, the methane content (volume fraction) to be 10%-14%, and applies a DC bias voltage of 150-250V.

[0034] Specific Implementation Method Nine: This implementation method differs from Specific Implementation Methods One to Eight in that in step six, the growth gas pressure is controlled at 200-250 mbar, the diamond seed crystal temperature is 950-1000℃, and the methane content is 4%-6%.

[0035] Specific Implementation Method 10: This implementation method differs from Specific Implementation Methods 1 to 9 in that the thickness of the single crystal epitaxial growth layer in step 6 is 0.5-2.5 mm.

[0036] Example: This example demonstrates an MPCVD single-crystal diamond surface defect repair growth method implemented according to the following steps:

[0037] 1. The defective area on the surface of the single crystal diamond seed crystal is removed by laser processing to form a square pit. The four sides of the square pit are along the (100) crystal plane of the single crystal diamond to obtain a diamond seed crystal with a square pit.

[0038] 2. Place the diamond seed crystal with square pits in a tube furnace and heat it at 480°C for 2 hours in an air atmosphere to obtain a diamond seed crystal with graphite removed.

[0039] 3. Place the graphite-removed diamond seed crystal on the sample stage of the electron beam evaporation coating equipment. Using a masking method, fill the pit with a single crystal iridium at 700°C to grow the single crystal iridium 30 micrometers above the surface of the single crystal diamond to obtain an iridium-coated diamond seed crystal.

[0040] 4. Transfer the iridium-plated diamond seed crystal to the sample stage of the MPCVD diamond growth equipment. Ground the positive terminal of the DC bias power supply and connect the negative terminal of the DC bias power supply to the sample stage. After closing the chamber door, evacuate the vacuum and introduce hydrogen gas to start the microwave to ignite the plasma.

[0041] 5. Control the growth gas pressure to 55 mbar, the diamond seed crystal temperature to 800℃, the methane content to 12%, and apply a 200V DC bias voltage to promote high-density nucleation growth on the surface of the heteroepitaxial single crystal iridium, and obtain the nucleated diamond seed crystal. At this time, the thickness of the diamond grown in the homoepitaxial part is the same as the height of the iridium-plated nucleated part.

[0042] 6. Turn off the DC bias power supply, control the growth gas pressure to 230 mbar, the diamond seed crystal temperature to 960℃, and the methane content to 5%, and perform MPCVD homoepitaxial growth of single crystal diamond to obtain a high-quality single crystal epitaxial growth layer.

[0043] pass Figure 3 and Figure 4 The comparison shows that the black polycrystalline point defects generated by the homogeneous epitaxial growth of the defect area on the surface of the single crystal diamond seed crystal are removed. However, after the growth is treated by the MPCVD single crystal diamond surface defect repair growth method in this embodiment, good growth steps appear on the diamond surface, indicating that the growth quality is good and there are no surface defects.

Claims

1. A method for repairing surface defects in single-crystal diamond using MPCVD, characterized in that... The MPCVD single-crystal diamond surface defect repair growth method is implemented according to the following steps:

1. The defective area on the surface of the single crystal diamond seed crystal is removed by laser processing to form a square pit. The four sides of the square pit are along the (100) crystal plane of the single crystal diamond to obtain a diamond seed crystal with a square pit.

2. Place the diamond seed crystal with square pits in a tube furnace and heat it at 400-550℃ in an air atmosphere to obtain a diamond seed crystal with graphite removed.

3. Place the graphite-removed diamond seed crystal on the sample stage of the electron beam evaporation coating equipment. Using a masking method, fill the pit with a single crystal iridium at 600-800℃ to grow the single crystal iridium 10-50 micrometers above the surface of the single crystal diamond to obtain an iridium-coated diamond seed crystal.

4. Transfer the iridium-plated diamond seed crystal to the sample stage of the MPCVD diamond growth equipment, close the chamber door, draw a vacuum, introduce hydrogen gas, and turn on the microwave to ignite the plasma.

5. Control the growth gas pressure to 50-60 mbar, the diamond seed crystal temperature to 750-850℃, the methane content to 10%-14%, and apply a DC bias voltage of 150-250V to promote high-density nucleation growth on the surface of heteroepitaxial single crystal iridium.

6. Turn off the DC bias power supply, control the growth gas pressure to 200-250 mbar, the diamond seed crystal temperature to 950-1000℃, and the methane content to 4%-6%, and perform MPCVD homoepitaxial growth of single crystal diamond to obtain a high-quality single crystal epitaxial growth layer with a thickness of 0.5-2.5 mm.

2. The MPCVD single-crystal diamond surface defect repair growth method according to claim 1, characterized in that... The depth of the square pit mentioned in step one is 50-200 micrometers.

3. The MPCVD single-crystal diamond surface defect repair growth method according to claim 1, characterized in that... The heat preservation treatment time in step two is 1-4 hours.

4. The MPCVD single-crystal diamond surface defect repair growth method according to claim 1, characterized in that... In step four, close the hatch and evacuate to a vacuum level of 5×10⁻⁶. -5 Below mbar.

5. The MPCVD single-crystal diamond surface defect repair growth method according to claim 1, characterized in that... In step four, introduce hydrogen gas at a rate of 50-100 sccm.

6. The MPCVD single-crystal diamond surface defect repair growth method according to claim 1, characterized in that... In step five, the high-density nucleation growth time is 1-4 hours.

Images