A method of repairing defects in a single crystal diamond

Abstract

This invention discloses a method for repairing defects in single-crystal diamond, comprising removing the defective portion to form a pit and preparing a defect-free patch. After cleaning, the patch is filled into the pit, ensuring that the crystal orientation of the patch is consistent with that of the diamond surrounding the pit. The single-crystal diamond with the patch then is fed into a growth system for growth to obtain a single-crystal diamond with the defect repaired. Compared with existing technologies, this invention not only has high repair efficiency but can also effectively repair defects with a side length of 2.0 mm or more.

Description

Technical Field

[0001] This invention relates to the field of diamond preparation, specifically to a method for repairing defects in single-crystal diamond. Background Technology

[0002] Diamond, with its high thermal conductivity, high breakdown electric field, and high carrier mobility, has become one of the most promising semiconductor materials. However, compared with other semiconductor materials (such as Si, SiC, and GaN), the biggest obstacle to the application of diamond is the lack of high-quality, inch-scale single-crystal wafers. To obtain high-quality, large-size diamond single-crystal wafers, various methods for artificially synthesizing diamond have been developed, such as high-temperature high-pressure methods and hot-filament chemical vapor deposition. Among them, the MPCVD (Microwave Plasma Chemical Vapor Deposition) method, theoretically, can synthesize high-quality, large-area diamonds without the introduction of impurities, and is currently the most commonly used method for diamond production.

[0003] The quality of synthetic diamond is related to many factors. Currently, the mainstream approach is to select higher-quality diamonds as seed crystals, but this is extremely expensive and still cannot completely eliminate surface defects. As the diamond area increases, defects (polycrystalline, twinned, non-diamond carbon phases, microcracks, etc.) inevitably appear within the single-crystal diamond during growth. Besides optimizing (cavity optimization, microwave field optimization, process optimization) to control the environment during MPCVD growth and avoid defects, repair methods can be used to restore the quality of subsequent diamond replication growth from defective diamonds, preventing the situation where a defective diamond seed crystal cannot continue to replicate diamonds.

[0004] Currently, the primary method for repairing and restoring defective diamonds is the pit-cutting repair method. This involves using laser processing or similar techniques to remove the defective area from the surface of the single-crystal diamond seed crystal, creating a pit. After treating the pit, the diamond seed crystal is transferred to a diamond growth device for homogeneous growth, thereby eliminating the influence of the original defect. Examples include Chinese patent applications such as "202111603967.5 A method for repairing surface defects in MPCVD single-crystal diamond," "200910210558.1 A method for homogeneous epitaxial repair and homogeneous epitaxial growth of single-crystal diamond," and "202310104712.7 A method for preparing high-quality single-crystal diamond by removing polycrystalline defects." However, these methods still have shortcomings: 1. Low repair efficiency, and the larger the defect area (or the larger the pit area), the longer the repair time. 2. For defects with excessively large areas, such as pits with a side length greater than 2.0 mm, the repair growth stage requires too much time. In addition, due to the tip effect, the closer the repair area is to the center of the plasma sphere, the more easily the pit attracts the plasma sphere, resulting in an excessively fast growth rate in the repair area. Moreover, defects such as polycrystalline and twinned crystals are prone to occur, making these methods difficult to repair. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to propose a method for repairing defects in single crystal diamond with high defect repair efficiency and effective repair of defects with a side length of 2.0 mm or more, in light of the above-mentioned technical status.

[0006] The technical solution adopted by the present invention to solve the above-mentioned technical problems is as follows: The method for repairing defects with single-crystal diamond of the present invention includes the following steps:

[0007] 1) Defect removal and patch preparation: Use a laser to remove the defective part at the defective part of the single crystal diamond, with a removal depth greater than 0.25mm, to form a pit; take a diamond block with a size that matches the pit from the defect-free part of the same single crystal diamond as a patch.

[0008] 2) Clean the pitted single-crystal diamond and patches;

[0009] 3) Fill the pit with the patch and ensure that the crystal orientation of the patch is consistent with that of the diamond around the pit. Then send the single crystal diamond with the patch in it into the growth system for growth.

[0010] 4) After the growth is completed, a single crystal diamond with repaired defects is obtained.

[0011] Because placing the patch within the recess can prevent the diamond seed crystal and patch from bonding tightly due to machining precision issues, the patch may overheat in this area due to heat dissipation problems (e.g., unevenness within the recess can create a gaseous insulating layer on the bottom wall of the recess and the bottom surface of the patch, hindering heat dissipation and causing excessively high temperatures during patch growth). This can lead to inconsistent growth rates between the seed crystal and the patch, resulting in polycrystalline phenomena. Therefore, excessively high patch temperatures reduce diamond quality, for example: 1. Significant local temperature differences may cause thermal stress within the material; 2. Excessive temperatures may lead to more defects in the diamond structure, such as grain boundaries, vacancies, and non-diamond carbon phases. To solve the heat dissipation problem of the patch during the growth process within the growth system, this invention employs one of the following four methods:

[0012] 1) The pit is a completely penetrating pit, and the single crystal diamond and the patch filling the pit are both placed on the molybdenum support and sent into the growth system for growth; because both are placed on the molybdenum support, they can dissipate heat together, so the temperature consistency is good and the scheme is simple.

[0013] 2) Ion implantation is performed on the defective side of the single-crystal diamond at a depth of 20nm to 2μm from the top surface, followed by annealing. Laser cutting frames are then performed at the defective and defect-free areas, and the diamond within the frames is electrochemically removed to obtain the pits and patches. After cleaning, the patches are filled into the pits and sent to the growth system for growth. This method is more complex than the aforementioned method 1), but this method only electrolyzes the ion-implanted area, while other areas are not electrolyzed and remain connected, which can effectively ensure the temperature consistency of the area during ion implantation.

[0014] 3) After using laser to remove the defective part to form a pit, the pit is finely polished by ion beam, and the patch is ground and polished to form a good contact surface between the two. After cleaning, the patch is filled into the pit and then sent into the growth system for growth.

[0015] 4) After cleaning, a layer of metal with a melting point higher than the diamond growth temperature (such as MPCVD growth temperature, which is generally 850-1150℃) is deposited on the bottom wall of the pit and the bottom surface of the patch by magnetron sputtering. The patch is then placed in the pit and bonded to the metal on the bottom surface of the patch with the metal on the bottom wall of the pit through a vacuum high-temperature environment (3×10^3 Pa to 1×10^-1 Pa, 800-1200℃). After bonding, the metal in the seam where the pit sidewall and the patch meet is removed. After cleaning again, the patch is filled into the pit and sent into the growth system for growth.

[0016] To ensure the quality and efficiency of the finished product, it is preferable that the distance between the upper surface of the patch and the upper surface of the single crystal diamond is 5 to 300 micrometers, and the gap width between the pit sidewall and the patch is ≤117 micrometers.

[0017] In addition, since the thickness of single-crystal diamond itself may vary in different places, and thus the thickness of the patch may also vary in different places, in order to ensure the quality of the finished product, the preferred single-crystal diamond should meet the requirement of a height difference ≤ 40 micrometers and a patch height difference ≤ 40 micrometers.

[0018] The specific procedure for cleaning the pitted single-crystal diamond and patch in step 2) is as follows: The single-crystal diamond and patch are ultrasonically cleaned successively with acetone and anhydrous ethanol for 10–30 minutes; then, they are ultrasonically cleaned with ultrapure water for 10–30 minutes, and finally, residual water droplets are blown away with high-purity nitrogen (99.999% or higher) for 5–10 minutes. This cleaning process effectively removes inorganic ions, organic impurities, and cutting residue from the diamond surface.

[0019] The growth system is supplied with 4%–8% methane, 0.1%–1% nitrogen, and the remainder hydrogen; the microwave power is 1000–6000 W, the gas pressure is 100–200 torr, the growth temperature is controlled at 850℃–1150℃, and the diamond growth layer is at least 0.5 mm thick.

[0020] The shape of the pit can vary, but it is best if it is easy to process and easy to determine the direction. It can be triangular, trapezoidal, square, etc.

[0021] The elements selected for ion implantation include Ar, H, C, B, N, P, and He. Preferably, the element implanted in this invention is carbon, which forms a graphite layer after high-temperature annealing. The process conditions for carbon ion implantation are: an implantation angle of 0-60 degrees and a dose of 1×10^12~1×10^17 atom / cm². 2 Energy 10-400KV, injected into one layer.

[0022] After ion implantation, the diamond is cleaned and then placed in a growth system for 1-2 hours to thicken before laser rigging and electrochemical stripping. Electrochemical stripping involves placing two electrodes at a certain interval in an electrolyte solution, placing a single-crystal diamond with a graphite layer between the electrodes, and applying a DC voltage to the electrodes to etch away the graphite layer. Once the graphite layer is etched away, the diamond and patch in the pit can be separated from the single-crystal diamond. Because the ion implantation depth is usually shallow, the diamond is allowed to grow thicker after ion implantation before subsequent operations to prevent the upper layer from being too thin, which would make pit excavation and patch removal difficult.

[0023] Compared with existing technologies, the method of this invention, because it fills the pit with a homologous and identically oriented patch, only needs to fill the gap between the pit and the patch during the growth process while simultaneously increasing the diamond thickness upwards. Theoretically, this gap can be very small, therefore defects of any size can be repaired using this method. Furthermore, because the gap is small, the repair time is shorter, resulting in high repair efficiency. Moreover, by reducing the transverse and longitudinal epitaxial distance of the diamond, the probability of polycrystalline and twinned defects during diamond epitaxy is effectively reduced, which helps improve the quality and success rate of the repaired product. Attached Figure Description

[0024] Figure 1 A schematic diagram of a defective single-crystal diamond seed crystal;

[0025] Figure 2 A schematic diagram of the seed crystal for proper orientation and slitting markings;

[0026] Figure 3 This is a schematic diagram showing the removal of defects to form a pit on one piece after slicing, and the removal of a patch from the other piece.

[0027] Figure 4 This is a diagram showing the diamond after the patch has been filled into the depression.

[0028] Figure 5 A schematic diagram of a diamond after restoration following growth.

[0029] Figure 6 This is a schematic diagram showing carbon ion implantation at a certain distance from the top surface on the defective side of a diamond seed crystal.

[0030] Figure 7 for Figure 6 A magnified view of a portion of the diamond shown.

[0031] Figure 8 for Figure 6 The diagram shows a diamond after 1 hour of growth.

[0032] Figure 9 In order to be in Figure 8 The diagram shows two identical and parallel frames cut out using a laser from the defective and defect-free areas of the diamond.

[0033] Figure 10 for Figure 9 The diagram shows the removal of defective parts from a diamond after electrochemical peeling and the filling of the pit with a patch.

[0034] Figure 11 A schematic diagram showing how to cut a cutting frame of a certain depth at a defective part of a diamond seed crystal, and how to cut a patch cutting frame at a depth less than the aforementioned cutting frame at a defect-free part;

[0035] Figure 12 To be Figure 11 The diagram shows a diamond being cut along the cutting depth of the patch cutting frame.

[0036] Figure 13 To be Figure 11 The diagram shows the lower layer of diamonds after the diamond is cut along the cutting depth of the patch cutting frame;

[0037] Figure 14 To be Figure 11 The diagram shows the upper layer diamond after the defective part has been removed, obtained after the diamond is cut along the depth of the patch cutting frame.

[0038] Figure 15 To be Figure 14 Fill in the middle block Figure 13 A schematic diagram of the diamond behind the central pit;

[0039] Figure 16 The image shows a magnified microscopic view of two 3.1mm x 3.1mm recesses cut into a diamond seed crystal, with the left recess not filled with a patch and the right recess filled with a patch.

[0040] Figure 17 for Figure 16 The image shown is a magnified microscope image of the diamond grown in the growth system (a filter was added when taking the picture for clarity). Detailed Implementation

[0041] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0042] All embodiments of the present invention satisfy the following conditions:

[0043] The distance between the upper surface of the patch and the upper surface of the single crystal diamond is 5 to 300 micrometers, the gap width between the pit sidewall and the patch is ≤117 micrometers, the height difference of the single crystal diamond is ≤40 micrometers, and the height difference of the patch is ≤40 micrometers.

[0044] like Figure 16 , 17 For comparison, the two pits are identical in size, with side lengths of 3.1mm × 3.1mm, after the defects were repaired using the method of this invention. Figure 16 The left-hand depression was not filled with a patch, while the right-hand depression was filled with a patch. Figure 17 As shown in the figure, the pit on the left side was not successfully repaired, while the pit on the right side was successfully repaired because a patch was filled in. This fully demonstrates that the method of the present invention can effectively repair single-crystal diamonds with defects of 2.0 mm or more.

[0045] Example 1

[0046] like Figures 1-5 The image shows a preferred embodiment of the method for repairing defects with single-crystal diamond according to the present invention.

[0047] This embodiment

[0048] Select a single-crystal diamond seed crystal 2 with defects 1 and a thickness greater than 0.5 mm, such as... Figure 1 As shown. Figure 2 As shown, orientation mark 3 and slitting mark 4 are made on the sidewall of the seed crystal. Figure 3 As shown, the seed crystal is cleaved into two pieces of equal thickness, upper and lower, along the cleaving mark 4 using a laser. On one piece, the defect 1 portion is removed to form a through-hole square pit 6. On the other piece without defects, a patch 7 of the same size as the pit is cut, with the four sides of the patch 7 parallel to the four sides of the pit 6. Directional marks 8 are made on the patch 7. Then, the pitted diamond and the patch are cleaned. The specific operation method is as follows: the single-crystal diamond and the patch are ultrasonically cleaned first with acetone and then with anhydrous ethanol for 10–30 minutes; then ultrasonically cleaned with ultrapure water for 10–30 minutes; and finally, residual water droplets are blown off the surface with high-purity nitrogen (5N and above) for 5–10 minutes. This cleaning operation effectively removes inorganic ions, organic impurities, and cutting residue from the diamond surface. Figure 4 As shown, the cleaned patch was moved into the cleaned diamond pit in its original orientation, and both were placed on a molybdenum support and fed into the growth system for growth. After growth, the result was as shown. Figure 5 As shown in the figure, the seed crystals grown on the single-crystal diamond are defect-free.

[0049] The process conditions in the growth system are as follows: the proportion of methane introduced is 4% to 8%, the proportion of nitrogen is 0.1% to 1%, and the remainder is hydrogen; the microwave power is 1000 to 6000 W, the gas pressure is 100 to 140 torr, the growth temperature is controlled at 850℃ to 1150℃, and the diamond growth layer is at least 0.5 mm thick.

[0050] Example 2

[0051] like Figures 6-10 And refer to Figure 1 , Figure 5 This is a preferred embodiment of the method for repairing defects with single-crystal diamond according to the present invention.

[0052] The cleaning method and diamond growth process in this embodiment are the same as in Embodiment 1.

[0053] See Figure 1 Select a defective single-crystal diamond seed crystal 2. For example... Figure 6 , 7As shown, on the side with defect 1, a layer of carbon is ion-implanted at a depth of 300 nm from the upper surface, and after high-temperature annealing, a graphite layer 9 (also known as the damaged layer) is formed. Figure 8 As shown, the diamond, after being cleaned following the aforementioned treatment, was fed into a growth system for 1 hour, resulting in a thickening of the portion above the graphite layer. Figure 9 As shown, two identical parallel squares are cut into the diamond surface using a laser, with the cut depth reaching the graphite layer; one square surrounds the defective area, and the other square is the defect-free area, with directional markings made on the diamond within the square using a marker.

[0054] The ion implantation conditions are as follows: implantation angle of 7 degrees, dose of 5×10^15 atom / cm2, energy of 350KV, and implantation of one layer.

[0055] like Figure 10 As shown, after electrochemical stripping, both frames are peeled off, removing the defective areas to form pits, while the defect-free parts are separated as patch 7. After cleaning, the patch is filled into the pits in its original orientation. Because the roughness of the peeled surface is within 10nm, a polishing effect is achieved, resulting in a tight bond and good heat dissipation.

[0056] The electrochemical stripping process involves placing two electrodes at a certain interval in an electrolyte solution, placing a single-crystal diamond with a graphite layer between the electrodes in the electrolyte solution, and applying a DC voltage to the electrodes to etch away the graphite layer. After the graphite layer is etched away, the diamond and patch in the pit can be separated from the single-crystal diamond.

[0057] Then it is fed into a growth system to grow at least 0.5 mm. After growth, a single-crystal diamond is obtained. See [link to documentation]. Figure 5 It can be seen that the seed crystals grown on it are without defects.

[0058] Example 3

[0059] like Figures 11-15 And refer to Figure 1 , Figure 5 This is a preferred embodiment of the method for repairing defects with single-crystal diamond according to the present invention.

[0060] The cleaning method and diamond growth process in this embodiment are the same as in Embodiment 1.

[0061] See Figure 1 Select a defective single-crystal diamond seed crystal 2. For example... Figure 11As shown, a laser is used to remove a section of material downwards from the defect, with a depth > 0.25 mm. The length and width dimensions are unlimited and depend on the processing capability, forming a square recess 6. A square cutting frame 10, with the same size as the recess, is then cut out from the defect-free area using the laser. The depth of this square cutting frame 10 should be less than the depth of the defect removal, and the four sides of the cutting frame should be parallel to the four sides of the recess 6. Figure 12 As shown, the diamond is diced along the depth of the cutting frame (the dicing point should ensure that the diamond within the square cutting frame can be separated from the seed crystal), resulting in the following: Figure 13 The lower diamond 11 shown and as Figure 14 As shown in the figure, the upper diamond 12 and patch 7 have a pit 6 formed at the defect in the lower diamond 11, which is then polished using an ion beam. After slitting, the patch 7 can be removed. The slitting surface of the removed patch can be reduced by laser milling / grinding to minimize height differences, ensure close contact between the heat dissipation surfaces, improve heat dissipation efficiency, and guarantee temperature consistency. After cleaning the lower diamond and patch, as shown... Figure 15 As shown, the patch is moved along its original direction and filled into the depression, then fed into the growth system for growth. After growth, a single-crystal diamond is obtained. See [link to documentation]. Figure 5 It can be seen that the seed crystals grown on it are without defects.

[0062] Example 4

[0063] The cleaning method and diamond growth process in this embodiment are the same as in Embodiment 1.

[0064] After cleaning, a layer of nickel with a melting point higher than the diamond growth temperature is deposited on the bottom wall of the pit and the bottom surface of the patch by magnetron sputtering. The patch is then placed in the pit and the metal on the bottom surface of the patch is bonded to the metal on the bottom wall of the pit under a vacuum, high pressure and high temperature environment. After bonding, the metal in the seam where the pit sidewall and the patch meet is removed. After cleaning again, the patch is filled into the pit and sent into the growth system for growth.

Claims

1. A method for repairing defects in single-crystal diamond, comprising the following steps: 1) Defect removal and patch preparation: Use a laser to remove the defective part at the defective part of the single crystal diamond, with a removal depth greater than 0.25mm, to form a pit; take a diamond block with a size that matches the pit from the defect-free part of the same single crystal diamond as a patch. 2) Clean the pitted single-crystal diamond and patches; 3) Fill the pit with the patch and ensure that the crystal orientation of the patch is consistent with that of the diamond around the pit. Then send the single crystal diamond with the patch in it into the growth system for growth. 4) After the growth is completed, a single crystal diamond with repaired defects is obtained.

2. The method according to claim 1, characterized in that, To address the heat dissipation issue during the growth of the patch within the growth system, one of the following four methods was employed: 1) The pit is a completely penetrating pit, and the single crystal diamond and the patch filling the pit are placed on the molybdenum support and sent into the growth system for growth. 2) Ion implantation is performed on the defective side of the single crystal diamond at a depth of 20nm to 2μm from the upper surface, followed by annealing. Then, laser cutting frames are performed at the defective and defect-free areas, and the diamond within the frames is electrochemically stripped to obtain the pits and patches. After cleaning, the patches are filled into the pits and then sent to the growth system for growth. 3) After using laser to remove the defective part to form a pit, the pit is finely polished by ion beam, and the patch is ground and polished to form a good contact surface between the two. After cleaning, the patch is filled into the pit and then sent into the growth system for growth. 4) After cleaning, a layer of metal with a melting point higher than the diamond growth temperature is deposited on the bottom wall of the pit and the bottom surface of the patch by magnetron sputtering. The patch is placed in the pit and the metal on the bottom surface of the patch is bonded to the metal on the bottom wall of the pit through a vacuum high-temperature environment. After bonding, the metal in the seam where the pit sidewall and the patch meet is removed. After cleaning again, the patch is filled into the pit and sent into the growth system for growth.

3. The method according to claim 1 or 2, characterized in that... The distance between the upper surface of the patch and the upper surface of the single-crystal diamond is 5 to 300 micrometers; the gap width between the pit sidewall and the patch is ≤117 micrometers.

4. The method according to claim 1 or 2, characterized in that... The height difference of the patch is ≤40 micrometers, and the height difference of the single crystal diamond is ≤40 micrometers.

5. The method according to claim 1 or 2, characterized in that... The specific operation method for cleaning the pitted single crystal diamond and patch in step 2) is as follows: use acetone and anhydrous ethanol to perform ultrasonic cleaning on the single crystal diamond and patch, and the ultrasonic cleaning time is 10-30 min; then use ultrapure water to perform ultrasonic cleaning, and the cleaning time is 10-30 min; and blow away the residual water droplets on the surface with high-purity nitrogen gas, and the blowing time is 5-10 min.

6. The method according to claim 1 or 2, characterized in that... The growth system is supplied with 4%–8% methane, 0.1%–1% nitrogen, and the remainder hydrogen; the microwave power is 1000–6000 W, the gas pressure is 100–140 torr, the growth temperature is controlled at 850℃–1150℃, and the diamond growth layer is at least 0.5 mm thick.

7. The method according to claim 1 or 2, characterized in that... The recess is square.

8. The method according to claim 2, characterized in that The ion implanted element is carbon, which forms a graphite layer after high-temperature annealing.

9. The method according to claim 8, characterized in that... The ion implantation has an implantation angle of 0-60 degrees, a dose of 1x10^12-1x10^17 atom / cm 2 , an energy of 10-400KV, and one layer is implanted.

10. The method according to claim 2, characterized in that... After ion implantation, the tissue is first placed in a growth system to grow and thicken for 1-2 hours, and then laser cutting and electrochemical stripping are performed.

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