Diamond crystal splicing repairing method

Abstract

The invention is applicable to the technical field of diamond crystal splicing, and provides a diamond crystal splicing repairing method, which comprises the following steps of: performing splicing treatment on treated diamond single crystal seed crystals by treating flaws of single crystal diamonds, and then performing precision polishing on the seed crystals on a substrate. And carrying out monocrystal diamond epitaxial growth on the spliced substrate by utilizing a microwave plasma chemical vapor deposition method, so as to obtain the large-size diamond.

Description

Technical Field

[0001] The present invention belongs to the technical field of diamond crystal splicing, and particularly relates to a method for splicing and repairing diamond crystals. Background Art

[0002] CVD diamond, namely chemical vapor deposition diamond, is a synthesis method in which carbon-containing gases (such as methane) and hydrogen are excited and decomposed under high temperature and pressure below standard atmospheric pressure to form plasma carbon atoms, and these carbon atoms are deposited on a substrate and grow interactively into diamond. This technology can synthesize diamond materials with excellent properties.

[0003] Currently, the synthesis of single-crystal diamond is limited by size. Usually, a single natural diamond or a thin slice of artificially synthesized single-crystal diamond is used as a seed crystal, and growth is carried out on its original size. Since large-size single-crystal diamonds are rare and expensive, the synthesized diamond is limited by the size of the seed crystal. Due to more defects and difficult-to-control at the edge of the seed crystal, polycrystalline diamond is likely to grow, resulting in the size of the obtained product not being larger than the size of the original seed crystal. Therefore, large-size single-crystal diamonds cannot be obtained.

[0004] During the growth of CVD diamond, flaws are likely to appear. The flawed area needs to be cut off and regrown. If a larger diamond seed is needed, smaller seeds need to be spliced and then grown, and then cut to obtain a larger seed.

[0005] Therefore, how to provide a method for splicing and repairing diamond crystals is an urgent problem to be solved by those skilled in the art. Summary of the Invention

[0006] The purpose of the present invention is to provide a method for splicing and repairing diamond crystals, aiming to solve the problems mentioned in the background art.

[0007] The present invention is implemented as follows. For the method for splicing and repairing diamond crystals, the flaws of single-crystal diamond are processed, and the processed single-crystal diamond seed crystals are spliced. Subsequently, the seed crystals on the substrate are polished precisely together. Immediately afterwards, single-crystal diamond epitaxial growth is carried out on the spliced substrate by using the microwave plasma chemical vapor deposition method; specifically, it includes the following steps:

[0008] Step 1: Cut single-crystal diamond

[0009] Select single-crystal diamond with flaws during the growth process, cut both sides of the flawed part, and polish the splicing surface of the seed crystal.

[0010] Step 2: Clean the seed crystal and splice it, and bombard the side with argon beam

[0011] Clean the seed crystal and splice it, and then bombard it with Ar+ ion beam;

[0012] Step 3: Depositing a metal film on the seed crystal

[0013] Before bonding, in a coating system, deposit a transition metal / bonding metal layer on the joint surface of the diamond seed crystal at room temperature;

[0014] Step 4: Bonding the seed crystal joints

[0015] After the deposition of the film, take out the seed crystal, in the room-temperature atmosphere, splice the joint surfaces of the seed crystal together and press them tightly to complete the bonding of the substrate, or choose not to deposit the metal film and directly bond the joint surfaces of the diamond seed crystal treated by Ar+ bombardment;

[0016] Step 5: Polishing the substrate

[0017] Place the obtained substrate on the polishing workpiece so that all the substrates formed by splicing the seed crystals can be polished under the same polishing process conditions to ensure that the height difference of the seed crystals on the polished substrate is controlled within 10 μm and the surface roughness is controlled within 0.1 nm;

[0018] Step 6: Epitaxial growth of single-crystal diamond

[0019] After the cleaning is completed, use microwave plasma chemical vapor deposition to achieve large-size epitaxial growth of single-crystal diamond on the surface of the substrate.

[0020] Preferably, the cutting angle at the defect of the single-crystal diamond in Step 1 is 90-135°.

[0021] Preferably, the process parameters of the polishing treatment in Step 1 are as follows: load 100-800, time 10-60 min, so that the roughness can be controlled within 10 nm.

[0022] Preferably, the parameters of the Ar+ ion beam bombardment in Step 2 are as follows: bias power supply 40-100 V, chamber pressure: 0.5-5 Pa, time: 5-10 min.

[0023] Preferably, the transition layer metal in Step 3 is Ti / Ta / Cr / W / Mo, and the bonding layer metal is an alloy that meets the growth temperature, oxidation resistance, and oxidation resistance. Deposit the transition metal layer 3-20 nm and deposit the bonding metal layer 50-100 nm.

[0024] Preferably, the seed crystal joint bonding in Step 4 includes two cases. One is to bond the diamond seed crystal after coating, and the other is to directly bond the diamond seed crystal after Ar+ bombardment. In both bonding cases, it is necessary to ensure that the joint surfaces are completely fitted. The bonding pressure is selected to be 10-50 MPa, and the bonding temperature is 100-300 °C.

[0025] Preferably, before the substrate growth in Step Five, to obtain a good surface state of the substrate and a small difference in seed crystal height, the substrate needs to be polished. The parameters of the polishing machine are as follows: load 200 - 800, time 10 - 90 min; fine polishing is achieved during the polishing process, so that the height difference of the seed crystal after polishing is controlled within 10 μm, and the surface roughness is controlled within 0.1 nm.

[0026] Preferably, the growth parameters of the single-crystal diamond epitaxial growth in Step Six are as follows: CH4 (2 - 10%) is introduced therein, the growth power is selected to be 2000 - 3800 W, the pressure is 15 - 25 kPa, the growth temperature is 700 - 1000 °C, and the growth time is 50 - 20.

[0027] Preferably, the bonding metal is precious metals such as Au and Pt.

[0028] Preferably, by using side bonding, multiple seed crystals can be spliced together in advance. One to three single-crystal diamonds with defects can be selected, after treating the defects, they are spliced into a substrate for epitaxial growth to achieve the preparation of large-size single-crystal diamonds.

[0029] Compared with the prior art, the beneficial effects of the present invention are as follows: By using single-crystal diamonds with defects, adverse conditions can be transformed into favorable conditions. On this basis, small-volume diamonds are used as favorable conditions for growing large-size diamonds, effectively improving the utilization rate; Using the single-crystal diamonds after cutting the defects to form a substrate and polishing them together can ensure that the polished seed crystals have similar surface states and height differences, so that the substrate surface is basically maintained on the same plane, solving the problems of difficult control of the height difference of the seed crystals and uneven surface states in the traditional splicing method; Through side bonding, the size of the splicing seam can be controlled to be very small, even reaching the nanoscale, which is beneficial to quickly connecting the splicing seams together; Since the seed crystals are spliced in advance, it is more convenient to operate during the substrate transfer and deposition growth processes, greatly suppressing the phenomenon of seed crystal misalignment caused by external disturbances during this process, reducing the appearance of polycrystals at the edge of the splicing seam, and effectively improving the quality of the grown diamond. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The drawings are used to provide a further understanding of the present invention, and constitute a part of the specification. They are used together with the embodiments of the present invention to explain the present invention, and do not constitute a limitation to the present invention.

[0031] Figure 1 It is a schematic diagram of sputtering coating on a single-crystal diamond seed crystal in the method of the present invention.

[0032] Figure 2 It is a schematic diagram of splicing the coated single-crystal diamond seed crystals in the method of the present invention.

[0033] Figure 3 Another perspective schematic diagram Figure 2 for

[0034] Figure 4 This is a schematic diagram of realizing microwave plasma chemical vapor deposition growth of single crystal diamond on the spliced coating single crystal diamond seed crystal in the method of the present invention

[0035] Figure 5 This is a schematic diagram of the transition metal layer and the bonding metal layer in the method of the present invention

[0036] In the drawings: 1 - single crystal diamond seed crystal; 2 - flaw; 3 - transition metal layer; 4 - bonding metal layer; 5 - large-sized diamond grown epitaxially Specific embodiments

[0037] In order to make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below with reference to the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention

[0038] The following describes in detail the specific implementation of the present invention with reference to specific embodiments

[0039] The present invention processes the flaws of single crystal diamond, splices the processed diamond single crystal seed crystals, then polishes all the seed crystals on the substrate precisely, and then uses the microwave plasma chemical vapor deposition (MPCVD) method to grow single crystal diamond epitaxially on the spliced substrate

[0040] Example 1

[0041] As Figure 1 shown, first, a single crystal diamond with flaws is selected, and it is cut into a regular cuboid according to its shape using a laser cutting machine, and then the two sides of the flaw are cut, with an angle of 135°. After cutting, the two cut surfaces of the seed crystals are polished so that the contact degree of the two seed crystals can reach 100%, and the surface roughness of the cut surface is controlled at 7 nm. The polished seed crystals are ultrasonically cleaned with acetone, ethanol and deionized water

[0042] As Figure 2 、 Figure 3As shown, the cutting surfaces of two seed crystals are bombarded with an Ar+ ion beam at a bias voltage of 50 V, a chamber pressure of 3.5 Pa, and a bombardment duration of 5 min. Subsequently, a Ti / Au film is deposited on the seed crystal cutting surfaces by magnetron sputtering, and the film thickness is controlled at 5 / 52 nm. After taking out the seed crystals, the cutting surfaces of the seed crystals are spliced and pressed at 250 °C, and the bonding pressure is 10 MPa. The substrate produced after splicing is polished. This treatment process places the substrate composed of seed crystals on the polishing workpiece and polishes them together under the same process conditions to ensure that the seed crystals have similar height differences and surface states after surface polishing. First, a load of 200 is used for 10 min, then the load is increased to 500 and polished for 15 min, and finally a load of 300 is used for 10 min. After polishing, the height difference is 5 μm and the surface roughness is 0.3 nm. Then, the samples are ultrasonically cleaned with acetone and absolute ethanol for 10 min;

[0043] As Figure 4 As shown, the processed single-crystal diamond substrate is placed in the chamber of a microwave plasma device, 300 sccm of hydrogen and 2% methane are introduced, the growth power is 3800 W, the pressure is 23 KPa, and the growth temperature is controlled at about 750 °C. Under this process, a single-crystal diamond splicing growth experiment is carried out, and the growth time is 100 h; after the growth is completed, a large-size diamond with the same length, width, height, and substrate surface area is obtained.

[0044] It should be noted that in Example 1, Example 2, and Example 3, the cutting surfaces of the seed crystals and the sides to be spliced can be collectively referred to as the splicing surfaces.

[0045] Example 2

[0046] First, two single-crystal diamonds with defects are selected and cut into regular cuboids using a laser cutter according to their shapes. Then, the two sides of the defects of the two single-crystal diamonds are cut at an angle of 100°. After cutting, the four seed crystal splicing surfaces are polished so that the contact degree of the four seed crystals can reach 100%. The roughness of the splicing surface is controlled at 7 nm. The four polished seed crystals are ultrasonically cleaned with acetone, ethanol, and deionized water;

[0047] As Figure 5As shown in the figure, the cutting surfaces of four seed crystals and the side surfaces of two of them were bombarded with Ar+ ion beam at a bias voltage of 60 V, a chamber pressure of 1.5 Pa, and a bombardment duration of 5 min. Subsequently, a Ti / Au film was deposited on the side surfaces of the seed crystals by magnetron sputtering, and the film thickness was controlled at 15 / 100 nm. After taking out the seed crystals, the splicing surfaces of the seed crystals were spliced and pressed at 200 °C, and the bonding pressure was 12 MPa. The substrate produced after splicing was polished. This processing technology was to place the substrate composed of all seed crystals on the polishing workpiece and polish them together under the same process conditions to ensure that the seed crystals had similar height differences and surface states after surface polishing; first, a load of 200 was used for 10 min, then the load was increased to 700 and polished for 20 min, and finally a load of 200 was used for polishing for 10 min. After polishing, the height difference was 4 μm and the surface roughness was 0.2 nm; then the samples were ultrasonically cleaned with acetone and absolute ethanol for 10 min respectively;

[0048] Finally, the processed single-crystal diamond substrate was placed in the chamber of a microwave plasma device, 300 sccm of hydrogen and 5% methane were introduced, the growth power was 3000 W, the pressure was 20 kPa, and the growth temperature was controlled at about 800 °C. Under this process, a single-crystal diamond splicing growth experiment was carried out, and the growth time was 150 h; after the growth was completed, a large-size diamond with the same length, width, height and substrate surface area was obtained.

[0049] Example 3

[0050] First, three single-crystal diamonds with defects were selected and cut into regular cuboids according to their shapes by a laser cutting machine. Then, the two sides of the defective parts were cut at an angle of 90°. After cutting, the six splicing surfaces of the cut seed crystals were polished so that the contact degree of the six seed crystal splices could reach 100%, and the roughness of the splicing surface was controlled at 5 nm. The polished seed crystals were ultrasonically cleaned with acetone, ethanol and deionized water;

[0051] Next, the bonding surfaces of the six seed crystals were bombarded with an Ar+ ion beam at a bias voltage of 80 V, a chamber pressure of 4.0 Pa, and a bombardment duration of 5 min. Subsequently, a Ti / Pt / Au film was deposited on the bonding surfaces of the seed crystals by magnetron sputtering, with the film thickness controlled at 5 / 15 / 100 nm. After removing the seed crystals, the bonding surfaces of the seed crystals were spliced and pressed at 300 °C. The bonding pressure was 20 MPa. The substrate produced after splicing was polished. This treatment process involved placing the substrate composed of all the seed crystals on the polishing workpiece and polishing them together under the same process conditions to ensure that the seed crystals had similar height differences and surface states after surface polishing. First, a load of 300 was applied for 5 min, then the load was increased to 800 and polished for 20 min, and finally, a load of 300 was applied and polished for 10 min. After polishing, the height difference was 5 μm, and the surface roughness was 0.6 nm. Then, the specimens were ultrasonically cleaned with acetone and absolute ethanol for 10 min respectively;

[0052] Finally, the processed single-crystal diamond substrate was placed in the chamber of a microwave plasma device, and 300 sccm of hydrogen and 5% methane were introduced. The growth power was 2700 W, the pressure was 19 KPa, and the growth temperature was controlled at about 800 °C. A single-crystal diamond splicing growth experiment was carried out under this process, and the growth time was 200 h; after the growth was completed, large-sized diamonds with the same length, width, height, and substrate surface area were obtained.

[0053] The key points in the implementation process of the present invention are:

[0054] 1. To ensure good bonding between the metal layer and the diamond, the side surface roughness needs to be controlled within 10 nm; this can not only ensure a high enough bonding strength but also not affect diamond growth. The control of roughness can be achieved by changing the diamond particle size of the polishing disc and increasing the rotation speed of the polishing disc.

[0055] 2. Argon beam bombardment can not only play a cleaning role but also change the roughness, enabling the metal film to have better adhesion. If only considering the removal of the surface contamination layer, the influence of surface damage caused by high-energy Ar+ bombardment can be ignored. However, to ensure good quality of the subsequent diamond substrate, serious surface damage to the diamond and excessive changes in surface physical and chemical properties need to be avoided, that is, to perform a safe cleaning on the diamond surface. The applied bias voltage should not be too high. Clean for 5 - 10 min under the conditions of a bias voltage of 40 - 100 V and a chamber pressure of 0.5 - 5 Pa.

[0056] 3. The bonding process can be divided into two types: direct bonding of diamond itself and coated film bonding. There is a need for good bonding force between diamond seeds. If the bonding of the single metal layer alone cannot meet the requirement of bonding force, coated film bonding is selected. At this time, a transition metal layer is introduced, with a thickness of 3 - 20 nm, and the bonding metal layer has a thickness of 50 - 100 nm, to ensure that the seeds can have good bonding force while having a very small splicing gap.

[0057] 4. Considering that the bonding metal should be easy to bond and can also achieve issues such as non-cracking, low stress, and oxidation resistance at the diamond deposition temperature, the bonding metal is usually a noble metal such as Au, Pt, etc. On this basis, it can also be an alloy coating that adjusts the melting point of the bonding metal.

[0058] 5. During the substrate splicing process, the fitting of the seed crystal sides should be completed quickly to reduce the attachment of impurities. To ensure a large bonding force of the bonding layer during the subsequent polishing process, the bonding pressure is selected as 10 - 50 MPa, and the bonding temperature is 100 - 300 °C.

[0059] 6. During the substrate splicing process, the splicing area of the seed crystals affects the stability of the substrate. To ensure the stability of the substrate, the cutting angle of the single crystal diamond at the defective part is selected as 90 - 135°.

[0060] 7. During the substrate polishing process, to obtain a good substrate surface, the surface roughness of the substrate is usually controlled within 0.1 nm, and the height difference of the seed crystals is controlled within 10 μm. The seed crystals that make up the substrate need to be polished simultaneously. During this process, the substrate may break during polishing due to insufficient bonding force and insecure splicing at the splicing part. Therefore, first, a lower load and slow speed are selected for trial polishing, and then the load is gradually increased and the rotation speed is increased. The load parameter of the polishing machine is usually selected as 200 - 800, and the polishing time is 10 - 90 min. Pay attention to the polishing process and carry it out in the order of "low load and slow speed - high load and slow speed - low load and high speed" to achieve fine polishing.

[0061] 8. During the growth process, temperature has a significant impact on the growth of CVD single-crystal diamond. As the temperature increases, the corresponding growth rate increases. However, too high a temperature will lead to an increase in the defect density. To ensure the growth of high-quality diamond crystals at a relatively high speed, the growth temperature range is selected to be 700 - 1000 °C. Under the same temperature conditions, a high chamber pressure will significantly increase the growth rate, and the pressure is selected to be 15 - 25 kPa. The influence of microwave power on the growth process is mainly related to the ionization rate of the carbon source. A high power can obtain a high ionization rate of carbon atoms, and it is easier to arrange and epitaxially grow in the sp3 form during the deposition process. Moreover, a high power increases the concentration of atomic H, enhancing the etching effect on the amorphous carbon phase in the sp2 form. However, too high an energy input will cause the seed substrate to overheat and affect the crystal quality. Therefore, the power selection range is 2000 - 3800 W. The increase in the carbon source concentration can effectively increase the growth rate, but the quality of the grown crystal will also be affected accordingly. To ensure a relatively high-quality CVD growth layer during the growth process while obtaining a relatively large growth rate, the CH4 concentration introduced is selected to be 2 - 10%.

[0062] In summary, the growth process parameters are as follows: the cutting angle of the single-crystal diamond at the defect is selected to be 90 - 135°, the growth power is selected to be 2000 - 5000 W for the introduced CH4 (2 - 10%), the pressure is 15 - 25 kPa, the growth temperature is 700 - 1000 °C, and the growth time is 50 - 200 h.

[0063] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A diamond crystal splicing and repairing method, characterized in that: By treating the defects of single crystal diamond, the treated diamond single crystal seed crystals are spliced, and then the seed crystals on the substrate are precisely polished together, and then single crystal diamond epitaxial growth is performed on the spliced ​​substrate by microwave plasma chemical vapor deposition method; specifically, the following steps are included: Step 1: Cutting single crystal diamond Selecting a single crystal diamond with defects during the growth process, cutting both sides of the defect, and polishing the joint surface of the seed crystal; Step 2: Seed crystal cleaning and splicing, side argon beam bombardment The seed crystals were cleaned and spliced, and then bombarded with Ar+ ion beams; Step 3: Seed crystal deposition metal film Prior to bonding, a transition metal / bonding metal layer is deposited on the mating surface of the diamond seed crystal in a coating system at room temperature; Step 4: Seed crystal splicing and bonding After the deposition of the film, the seed crystal is taken out, and the seed crystal joint faces are spliced ​​together in the room temperature atmosphere and pressed to complete the bonding of the substrate, or the deposition of the metal film is chosen not to be performed, and the diamond seed crystal treated by Ar+ bombardment is directly used for joint face bonding; Step 5: Substrate polishing Placing the obtained substrate on a polishing workpiece so that the substrates formed by splicing all the seed crystals can be polished under the same polishing process conditions to ensure that the height difference of the substrate seed crystals after polishing is controlled within 10 μm and the surface roughness is controlled within 0.1 nm; Step 6: Single crystal diamond epitaxial growth After cleaning, microwave plasma chemical vapor deposition is used to achieve large-scale epitaxial growth of single crystal diamond on the substrate surface.

2. The diamond crystal splicing and repairing method according to claim 1, characterized in that: The cutting angle at the single crystal diamond defect in step 1 is 90 to 135 degrees.

3. The diamond crystal splicing and repairing method according to claim 1, characterized in that: The process parameters of the polishing treatment in step 1 are as follows: load 100-800, time 10-60 min, so that the roughness can be controlled within 10 nm.

4. The diamond crystal splicing and repairing method according to claim 1, characterized in that: The parameters of the Ar+ ion beam bombardment in step 2 are as follows: bias power supply 40-100 V, chamber pressure: 0.5-5 Pa, time: 5-10 min.

5. The diamond crystal splicing and repairing method according to claim 1, characterized in that: In step three, the transition layer metal is Ti / Ta / Cr / W / Mo, and the bonding layer metal is an alloy that meets the growth temperature, oxidation resistance, and oxidation resistance. The transition metal layer is deposited at 3 to 20 nm, and the bonding metal layer is deposited at 50 to 100 nm.

6. The diamond crystal splicing and repairing method according to claim 1, characterized in that: The seed crystal splicing and bonding described in step 4 includes two situations. One is bonding the diamond seed crystal after coating, and the other is directly bonding the diamond seed crystal after Ar+ bombardment. Both bonding situations need to ensure that the splicing surfaces are completely fitted, the bonding pressure is selected to be 10-50MPa, and the bonding temperature is 100-300℃.

7. The diamond crystal splicing and repairing method according to claim 1, characterized in that: The substrate polishing described in step 5 is performed before substrate growth in order to obtain a good surface state of the substrate and a smaller seed crystal height difference. The parameters used by the polishing machine are as follows: load 200-800, time 10-90min; the polishing process achieves fine polishing, so that the height difference of the substrate seed crystal after polishing is controlled within 10μm and the surface roughness is controlled within 0.1nm.

8. The diamond crystal splicing and repairing method according to claim 1, characterized in that: Step 6: The growth parameters of the single crystal diamond epitaxial growth are as follows: introduce CH4 (2-10%), select the growth power of 2000-3800 W, the pressure of 15-25 kPa, the growth temperature of 700-1000° C., and the growth time of 50-20.

9. The diamond crystal splicing and repairing method according to claim 5, characterized in that: The bonding metal is Au or Pt noble metal.

10. The diamond crystal splicing and repairing method according to any one of claims 1 to 9, characterized in that: By utilizing side bonding, multiple seed crystals are spliced ​​together in advance, and 1 to 3 single crystal diamonds with defects can be selected, the defects treated, and spliced ​​as substrates for epitaxial growth, thereby realizing the preparation of large-size single crystal diamonds.

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