Single crystal diamond splicing body and preparation method and application thereof

Abstract

The invention discloses a single-crystal diamond splicing body and a preparation method and application thereof, the preparation method comprises the following steps: (1) taking a single single-crystal diamond seed crystal, vertically and equally cutting along any surface of the single-crystal diamond seed crystal to obtain small single-crystal diamond seed crystals, and cutting the small single-crystal diamond seed crystals according to a cutting sequence, after the upper cutting surfaces of the adjacent single crystal diamond small seed crystals are attached to each other, the upper cutting surfaces of the adjacent single crystal diamond small seed crystals are attached to the lower cutting surface of the next adjacent single crystal diamond small seed crystals to be spliced alternately, and a mosaic seed crystal group substrate is obtained; and (2) the mosaic seed crystal group substrate is placed in microwave plasma chemical vapor deposition equipment, secondary epitaxial growth is carried out, a single crystal diamond splicing body is obtained, and due to the fact that the splicing interface of the mosaic seed crystal group substrate is consistent with the crystallographic orientation height of a growth face, the single crystal diamond splicing body is obtained. Therefore, the single crystal diamond splicing body with excellent crystal quality, optical performance and mechanical strength can be prepared, and the single crystal diamond splicing body can be widely applied to the fields of semiconductor substrates, power device heat dissipation or infrared optical windows.

Description

Technical Field

[0001] This invention belongs to the field of diamond material technology, specifically relating to a single-crystal diamond splice, its preparation method, and its application. Background Technology

[0002] Single-crystal diamond, due to its extremely high hardness, thermal conductivity, carrier mobility, and wide bandgap, is hailed as an ideal material for third-generation semiconductors, possessing irreplaceable application prospects in high-temperature, high-frequency, and high-power electronic devices, quantum information, and high-end optical windows. However, natural diamond is scarce, limited in size, and extremely expensive, making it difficult to meet the demands of industrial applications. Currently, microwave plasma chemical vapor deposition (MPCVD) has become the mainstream technology for preparing high-quality artificial single-crystal diamond, but it is limited by the seed crystal size, making it difficult to economically and efficiently prepare large-size single-crystal diamonds for commercial use.

[0003] In order to overcome the limitations of single-crystal seed size, the industry has gradually developed spliced ​​epitaxial growth technology (MosaicGrowth or Tile Growth), which involves splicing multiple small-sized single-crystal diamond seed crystals into a large-area substrate and then performing epitaxial growth. However, this technology still faces several serious challenges in practice: First, it is difficult to achieve a high degree of consistency in the crystallographic orientation between the seed crystal blocks, and crystal defects such as grain boundaries, dislocations, and stacking faults are easily formed at the splicing interface. These defects become scattering centers and non-radiative recombination centers for charge carriers, significantly degrading the electrical and optical properties of the material. Second, in order to maintain the temporary stability of the splicing structure, some technical solutions use organic or inorganic adhesives. This not only introduces foreign impurities and contaminates the seed crystals, hindering the direct epitaxial merging between the seed crystals, but also generates additional stress due to the mismatch of thermal expansion coefficients during subsequent high-temperature growth, leading to seed crystal warping, cracking, or interface debonding. Furthermore, cutting the epitaxial layer multiple times to make it a new seed crystal substrate also leads to a significant reduction in the thickness of the splicing substrate while increasing its area, which has obvious limitations: it is impossible to balance large area and necessary thickness, and the final product form is monotonous, mostly epitaxial layers on thin substrates, making it difficult to obtain bulk materials with excellent overall integrity, thus limiting its application in fields such as optical windows and high-power heat dissipation substrates.

[0004] Patent application CN115874282A discloses a method for improving the quality of large-area single-crystal diamond splicing growth. This method involves pre-growing samples in an MPCVD (microwave plasma chemical vapor deposition) system, then selecting pre-grown samples with similar step flow growth directions for splicing growth. This improves splicing efficiency, reduces defect density during splicing growth, improves stress distribution at the splice seam, and enhances the crystal quality of the spliced ​​growth. However, the pre-growing process itself introduces varying degrees of stress, dislocations, or microscopic differences in surface morphology into different samples. Even if the macroscopic direction of the step flow is consistent, these microscopic defects may become stress concentration points or dislocation sources during splicing growth, affecting the final quality.

[0005] Patent application CN113529175A discloses a substrate, a method for splicing the substrate, and a method for preparing single-crystal diamond. The method for splicing the substrate includes the following steps: providing a single-crystal diamond seed crystal, the single-crystal diamond seed crystal having a bottom surface and a top surface opposite to the bottom surface; the single-crystal diamond seed crystal having a first height from the bottom surface to the top surface; cutting the single-crystal diamond seed crystal along the bisectors of the first height, so that the single-crystal diamond seed crystal is cut into multiple seed crystals with the same second height; splicing the multiple seed crystals along a direction perpendicular to the second height, ensuring that the crystal orientations of the spliced ​​seed crystals are the same, thereby obtaining a substrate. While this application solves the crystal orientation consistency problem to some extent, since the bonding interface and growth surface are often not the same primary crystal plane, it is difficult to strictly achieve uniform orientation without deviation between different primary crystal planes. Therefore, to ensure strict uniform orientation... <100> It is very difficult to achieve a consensus on orientation.

[0006] Therefore, developing a high-quality single-crystal diamond orientation splicing technology that can ensure high consistency of seed crystal orientation, eliminate the need for external adhesives, and effectively suppress the formation of interface defects is of great significance for promoting the large-scale application of large-size single-crystal diamond materials in the semiconductor and optical fields, and has become a key technical bottleneck that urgently needs to be overcome in this field. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the first aspect of this invention provides a method for preparing single-crystal diamond splices, which can produce single-crystal diamond splices with good interface crystallization, high optical transmittance and uniformity, and high structural strength.

[0008] This invention provides a method for preparing a single-crystal diamond splice, comprising: (1) Take a single single-crystal diamond seed crystal and cut it vertically and equally along any surface of the single-crystal diamond seed crystal to obtain a single-crystal diamond seed crystal. Then, according to the cutting order, the upper cut surfaces of adjacent single-crystal diamond seed crystals are attached to each other, and then attached to the lower cut surface of the next adjacent single-crystal diamond seed crystal. The two are spliced ​​alternately to obtain a mosaic seed crystal group substrate. (2) The mosaic seed crystal group substrate is placed in a microwave plasma chemical vapor deposition (MPCVD) device for secondary epitaxial growth to obtain a single crystal diamond splice.

[0009] This invention involves vertically and equally dividing any surface of the single-crystal diamond seed crystal, and then, according to the cutting sequence, bonding the upper cut surfaces of adjacent single-crystal diamond seed crystals together, and then bonding them together with the lower cut surfaces of the next adjacent single-crystal diamond seed crystal, alternatingly splicing them together to obtain a mosaic seed crystal group substrate. The upper cut surface and the lower cut surface are respectively the upper end surface and the lower end surface of the single-crystal diamond seed crystal in the cutting direction.

[0010] The inventors made an unexpected discovery: by using the above-mentioned bonding and splicing method, two adjacent cut surfaces are bonded together, so that all contact surfaces involved in the splicing and the growth surface of the mosaic seed crystal group substrate originate from the same primary crystal face of the same seed crystal, and the crystallographic orientation is completely consistent. The defect density at the splicing interface is significantly reduced. The growth surface is the side surface of the single-crystal diamond seed crystal, that is, the upper surface of the mosaic seed crystal group substrate.

[0011] When epitaxial growth is performed on the mosaic seed crystal cluster substrate, the deposited diamond atoms can achieve epitaxial growth on the growth surface with consistent orientation, cross the initial splicing boundary between single crystal diamond seed crystals, achieve seamless splicing and continuous growth, and simultaneously expand the single crystal area and volume of diamond, thereby completing the preparation of high-quality, large-size single crystal diamond splice.

[0012] Meanwhile, since no organic or inorganic adhesives are used throughout the process, the splicing interface and the interior of the single-crystal diamond splice have very few impurities and defects, giving the single-crystal diamond splice high and uniform optical transmittance. In terms of mechanical strength, the high-quality splicing interface enables the material to effectively bear thermal and mechanical stress as a whole, avoiding the risk of cracking due to weak interface bonding, thus ensuring its reliability in harsh environments.

[0013] Preferably, the single-crystal diamond seed crystal is a cuboid or cube, with all six faces being... <100> Orientation: The specifications of the single-crystal diamond seed crystal are as follows: length 10~20 mm (tolerance ±0.1 mm), width 5~10 mm (tolerance ±0.1 mm), and thickness 500~600 µm (tolerance ±10 µm).

[0014] This invention controls the geometry and crystallographic orientation of the single-crystal diamond seed crystal, as well as the specifications of the single-crystal diamond seed crystal obtained after cutting, and strictly controls the processing precision of the single-crystal diamond seed crystal. This ensures that the specifications of the cut single-crystal diamond seed crystals are consistent, and achieves tight bonding of the interface during splicing, eliminating the process instability caused by the quality differences between multiple seed crystals during the splicing process.

[0015] Preferably, the mosaic seed crystal group substrate is cleaned and etched to remove impurities or contaminants from the surface of the mosaic seed crystal group substrate.

[0016] More preferably, the cleaning process involves cleaning the mosaic seed crystal substrate with a piranha solution for 90-120 minutes at a temperature of 50-80°C, followed by ultrasonic cleaning with acetone or ethanol for 10-30 minutes.

[0017] This invention cleans the mosaic seed crystal substrate. Appropriate cleaning parameters can remove organic residues and carbon impurities from the surface of the single-crystal diamond seed crystal, further improving the splicing quality of the single-crystal diamond seed crystal and promoting high-quality epitaxial growth.

[0018] More preferably, the etching is performed using an MPCVD device, and the etching parameters are: hydrogen flow rate of 200~2000 sccm, etching temperature of 500~800 ℃, etching pressure of 8~10 kPa, and etching time of 30~60 min.

[0019] This invention involves etching the cleaned mosaic seed crystal cluster substrate to further remove impurities from its surface. A suitable etching temperature can effectively remove the non-diamond carbon phase from the surface of the mosaic seed crystal cluster substrate without damaging the substrate itself; a suitable etching time can shorten the etching time and improve process efficiency while ensuring sufficient impurity removal.

[0020] Preferably, the parameters for the first epitaxial growth are: growth temperature of 800~1000 ℃, growth gas pressure of 8~13 kPa, growth time of 100~200 h, hydrogen flow rate of 400~5000 sccm, methane flow rate of 1%~3% of hydrogen flow rate, and nitrogen flow rate of 10~200 ppm of the total flow rate of hydrogen and methane.

[0021] By controlling the parameters of the first epitaxial growth, this invention can ensure high-quality epitaxial growth of the mosaic seed crystal cluster substrate after splicing. The appropriate time for the first epitaxial growth can ensure that the mosaic seed crystal cluster substrate achieves a strong and low-defect effective bond during the epitaxial growth process, providing a stable foundation for the subsequent second epitaxial growth.

[0022] Preferably, the parameters for the second epitaxial growth are: growth temperature of 800~1000 ℃, growth gas pressure of 8~13 kPa, growth time of 300~500 h, hydrogen flow rate of 400~5000 sccm, methane flow rate of 1%~3%, and nitrogen flow rate of 10~200 ppm of the total flow rate of hydrogen and methane.

[0023] This invention aims to ensure a thicker, higher-quality epitaxial layer by appropriately extending the time of the second epitaxial growth, thereby obtaining a single-crystal diamond splice with large size, high crystal quality, and excellent optical and mechanical properties.

[0024] Preferably, the epitaxial layer obtained after the first epitaxial growth and the single-crystal diamond splice obtained after the second epitaxial growth are subjected to laser milling, grinding and polishing, and cleaning. The laser milling power is 10~40 W, the scanning speed is 5~15 mm / s, and the time is 1~5 h. The grinding and polishing medium is a grinding disc made of silicon carbide or polyurethane / diamond composite material, the grinding speed is 2000~5000 r / min, and the grinding time is 20~200 h.

[0025] This invention performs post-processing on the epitaxial layer obtained after the first epitaxial growth. The parameters described above ensure that the surface of the epitaxial layer is smoother, laying the foundation for a subsequent high-quality second epitaxial growth. The post-processing on the single-crystal diamond splice obtained after the second epitaxial growth optimizes the surface state of the single-crystal diamond splice, meeting the application scenarios in semiconductor chip substrates, power device heat dissipation, and infrared optical windows.

[0026] On the other hand, the present invention provides a single-crystal diamond splice prepared by the preparation method of the single-crystal diamond splice.

[0027] Preferably, the Raman full width at half maximum (FWHM) of the single-crystal diamond splice at the interface is 2-3 cm. -1 The average optical transmittance in the 8~12 µm band is ≥70%, and the optical transmittance non-uniformity is <1%.

[0028] More preferably, the three-point bending strength of the single-crystal diamond splice is >480 MPa.

[0029] On the other hand, the present invention provides an application of the single-crystal diamond splice in the fields of semiconductor substrates, power device heat dissipation, or infrared optical windows.

[0030] This invention successfully fabricates large-size, high-quality single-crystal diamond splices using the aforementioned method. These splices exhibit excellent and consistent performance in terms of crystal quality, optical properties, and mechanical strength, and have broad application prospects in semiconductor chip substrates, power device heat dissipation, or infrared optical windows.

[0031] Compared with the prior art, the present invention has the following beneficial effects: This invention involves vertically and equally dicing any surface of a single-crystal diamond seed crystal. Following the dicing sequence, the upper diced surfaces of adjacent single-crystal diamond seed crystals are joined together, and then joined together with the lower diced surface of the next adjacent single-crystal diamond seed crystal. This process is repeated alternately. Since all diced surfaces and growth surfaces originate from the same crystal plane of the same seed crystal, this invention successfully obtains a mosaic seed crystal group substrate with highly consistent crystal orientation at the diced interface and the growth surface. During epitaxial growth on the mosaic seed crystal group substrate, seamless continuous growth can be achieved. The Raman full width at half maximum (FWHM) value at the diced interface is low, with fewer lattice defects and higher crystal quality, enabling the formation of high-quality, large-size single-crystal diamond splices.

[0032] Moreover, since no adhesive is used, impurities and defects are greatly reduced, giving the single-crystal diamond splice high and uniform optical transmittance. In addition, the splice interface has high bonding strength and can withstand mechanical stress and external impact, making it widely used in semiconductor substrates, power device heat dissipation, or infrared optical windows. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the preparation method of the single-crystal diamond splice provided in Embodiment 1 of the present invention.

[0034] Figure 2 The optical transmittance is the single-crystal diamond splice prepared in Examples 1-3 and Comparative Example 1 of this invention.

[0035] Figure 3 The crystallographic orientation of the single-crystal diamond splices prepared in Examples 1-3 and Comparative Example 1 of this invention is compared in the X-axis and Y-axis directions. Detailed Implementation

[0036] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0037] Example 1 (1) Take a single single-crystal diamond seed crystal, which is commercially available (manufacturer: Hubei Carbon Six Technology Co., Ltd.), with a rectangular shape and the following specifications: length 10±0.05 mm, width 5±0.04 mm, thickness 3±0.03 mm, and all six faces are... <100> Orientation. For example... Figure 1 As shown, the upper and lower surfaces of a single-crystal diamond seed crystal are marked as surface E and surface F, the left and right sides as surface B and surface A, and the front and rear surfaces as surface D and surface C. Then, perpendicular to surfaces E and F, the single-crystal diamond seed crystal is equally divided from surface E to obtain 6 small single-crystal diamond seed crystals. The specifications of the 6 small single-crystal diamond seed crystals are: length 10±0.05 mm, width 5±0.04 mm, and thickness 500±5 µm.

[0038] Following the cutting sequence, the six single-crystal diamond seed crystals are sequentially labeled A-1, A-2, A-3, A-4, A-5, and A-6. The upper surface of each single-crystal diamond seed crystal is the upper cutting face (E-face) in the cutting direction, and the lower surface is the lower cutting face (F-face) in the cutting direction. Then, following the cutting sequence, the F-face of A-1 is bonded to the F-face of A-2, and the E-face of A-2 is bonded to the E-face of A-3, making face A of A-1 and face B of A-2 the growth faces. Subsequently, A-3 to A-6 are joined by bonding the upper cutting faces of adjacent single-crystal diamond seed crystals together, and then bonding them to the lower cutting faces of the next adjacent single-crystal diamond seed crystal, alternating in this manner to ultimately form a mosaic seed crystal cluster substrate.

[0039] Next, the mosaic seed crystal cluster substrate was cleaned and etched to remove surface impurities or contaminants. The cleaning process was as follows: the mosaic seed crystal cluster substrate was cleaned at 80 °C for 90 min using commercially available piranha solution (a mixture of sulfuric acid and hydrogen peroxide prepared at a volume ratio of 7:3), followed by ultrasonic cleaning with acetone for 10 min. The etching process was performed using an MPCVD device with the following parameters: hydrogen flow rate 200 sccm, temperature 800 °C, gas pressure 10 kPa, and etching time 30 min.

[0040] (2) The cleaned and etched mosaic seed crystal cluster substrate was placed in an MPCVD device for the first epitaxial growth. The parameters for the first epitaxial growth were: temperature 800 ℃, gas pressure 8 kPa, hydrogen flow rate 400 sccm, methane flow rate 3% of hydrogen, nitrogen flow rate 10 ppm of the total flow rate of hydrogen and methane, and growth time 200 h. Then, the surface of the obtained epitaxial layer was laser milled to make the surface flat, and then ground, polished and cleaned. The laser milling parameters were: power 10 W, scanning speed 15 mm / s, time 2 h; the grinding and polishing parameters were: grinding medium was a silicon carbide grinding disk, rotation speed 5000 r / min, time 20 h; the cleaning parameters were the same as in step (1).

[0041] The epitaxial layer was then placed in an MPCVD machine for a second epitaxial growth. The two surfaces of the resulting epitaxial layer were laser-milled to flatten them, followed by grinding, polishing, and cleaning to obtain a single-crystal diamond assembly, labeled S1. The growth time for the second epitaxial growth was 500 hours, with all other parameters remaining the same as the first epitaxial growth.

[0042] The average Raman full width at half maximum (FWHM) of the obtained S1 sample was 2.82 cm. –1 The average optical transmittance in the 8-12 µm band is 71.3%, and the optical transmittance non-uniformity is 0.5%; the three-point bending strength is 485 MPa.

[0043] Example 2 (1) Take a single single-crystal diamond seed crystal, which is commercially available (manufacturer: Foshan Yaoshi New Materials Co., Ltd.). It is rectangular in shape with the following specifications: length 16±0.07 mm, width 7±0.07 mm, thickness 3.85±0.04 mm, and all six faces are... <100> Orientation was performed, and the top and bottom surfaces of the single-crystal diamond seed crystal were marked as plane E and plane F, the left and right sides as plane B and plane A, and the front and rear surfaces as plane D and plane C. Then, perpendicular to planes E and F, the single-crystal diamond seed crystal was equally divided from plane E, yielding 7 small single-crystal diamond seed crystals. The specifications of the obtained small single-crystal diamond seed crystals were: length 16±0.07mm, width 7±0.07mm, and thickness 550±6µm.

[0044] Seven single-crystal diamond seed crystals were sequentially labeled A-1 to A-7 according to the cutting order. The upper surface of each single-crystal diamond seed crystal was the upper cutting face (E face) in the cutting direction, and the lower surface was the lower cutting face (F face) in the cutting direction. Then, following the cutting order, the F face of A-1 was bonded to the F face of A-2, and the E face of A-2 was bonded to the E face of A-3, so that face A of A-1 and face B of A-2 became the growth faces. Subsequently, A-3 to A-7 were joined by bonding the upper cutting faces of adjacent single-crystal diamond seed crystals together, and then bonding them to the lower cutting faces of the next adjacent single-crystal diamond seed crystals, in an alternating splicing manner, ultimately forming a mosaic seed crystal group substrate.

[0045] Next, the mosaic seed crystal cluster substrate was cleaned and etched. The cleaning process was as follows: the mosaic seed crystal cluster substrate was cleaned with commercially available piranha solution at 60 ℃ for 90 min, followed by ultrasonic cleaning with ethanol for 15 min. The etching process was as follows: etching was performed using an MPCVD device with the following parameters: hydrogen flow rate 1000 sccm, temperature 600 ℃, gas pressure 8.5 kPa, and etching time 40 min.

[0046] (2) The cleaned and etched mosaic seed crystal cluster substrate was placed in an MPCVD device for the first epitaxial growth. The parameters for the first epitaxial growth were: temperature 900 ℃, gas pressure 11 kPa, hydrogen flow rate 1000 sccm, methane flow rate 1% of hydrogen, nitrogen flow rate 105 ppm of the total flow rate of hydrogen and methane, and growth time 160 h. Then, the surface of the obtained epitaxial layer was subjected to laser milling, grinding and polishing, and cleaning. The laser milling parameters were: power 20 W, scanning speed 10 mm / s, and time 1 h; the grinding and polishing parameters were: grinding media was a silicon carbide grinding disk, rotation speed 2000 r / min, and time 120 h; the cleaning parameters were the same as in step (1).

[0047] The epitaxial layer was then placed in an MPCVD machine for a second epitaxial growth. The resulting epitaxial layer was then subjected to laser milling, grinding, polishing, and cleaning on both surfaces to obtain a single-crystal diamond assembly, designated S2. The second epitaxial growth took 430 hours, with all other parameters remaining the same as the first epitaxial growth.

[0048] The average Raman full width at half maximum (FWHM) of the obtained S2 sample was 2.76 cm. –1 The average optical transmittance in the 8-12 µm band is 71.5%, and the optical transmittance non-uniformity is 0.6%; the three-point bending strength is 498 MPa.

[0049] Example 3 (1) Take a single monocrystalline diamond seed crystal, which is commercially available (manufacturer: Ningbo Crystal Diamond Technology Co., Ltd.). It is rectangular in shape with the following specifications: length 20±0.1 mm, width 10±0.1 mm, thickness 4.8±0.08 mm, and all six faces are... <100> Orientation. The upper and lower surfaces of the single-crystal diamond seed crystal are marked as E-plane and F-plane, the left and right sides as B-plane and A-plane, and the front and rear surfaces as D-plane and C-plane. Then, the single-crystal diamond seed crystal is equally divided from the E-plane in a direction perpendicular to the E-plane and F-plane to obtain 8 small single-crystal diamond seed crystals. The preferred specifications of the 8 small single-crystal diamond seed crystals are: length 20±0.1 mm, width 10±0.1 mm, and thickness 600±10 µm.

[0050] Eight single-crystal diamond seed crystals were sequentially labeled A-1 to A-8 according to the cutting order. The upper surface of each seed crystal was the upper cut surface (E surface) in the cutting direction, and the lower surface was the lower cut surface (F surface) in the cutting direction. Then, following the cutting order, the F surface of A-1 was bonded to the F surface of A-2, and the E surface of A-2 was bonded to the E surface of A-3, making surface A of A-1 and surface B of A-2 the growth surfaces. Subsequently, from A-3 to A-8, adjacent single-crystal diamond seed crystals were bonded together by first bonding their upper cut surfaces, and then to the lower cut surface of the next adjacent seed crystal, in an alternating bonding manner to ultimately form a mosaic seed crystal cluster substrate.

[0051] Next, the mosaic seed crystal cluster substrate was cleaned and etched. The cleaning process was as follows: the mosaic seed crystal cluster substrate was cleaned with commercially available piranha solution at 50 ℃ for 120 min, followed by ultrasonic cleaning with ethanol for 30 min; the etching process was as follows: etching was performed using an MPCVD device with the following parameters: hydrogen flow rate 2000 sccm, temperature 500 ℃, gas pressure 8 kPa, and etching time 60 min.

[0052] (2) The cleaned and etched mosaic seed crystal cluster substrate was placed in an MPCVD device for the first epitaxial growth. The parameters for the first epitaxial growth were: temperature 1000 ℃, gas pressure 13 kPa, hydrogen flow rate 5000 sccm, methane flow rate 2% of hydrogen, nitrogen flow rate 200 ppm of the total flow rate of hydrogen and methane, and growth time 100 h. Then, the surface of the epitaxial layer was subjected to laser milling, grinding and polishing and cleaning. The laser milling parameters were: power 40 W, scanning speed 7 mm / s, time 5 h; the grinding and polishing parameters were: grinding medium was a polyurethane / diamond composite grinding disk, rotation speed 4500 r / min, time 200 h; the cleaning parameters were the same as in step (1).

[0053] The epitaxial layer was then placed in an MPCVD machine for a second epitaxial growth. The resulting epitaxial layer was then laser-milled, ground, polished, and cleaned on both surfaces to obtain a single-crystal diamond assembly, designated S3. The second epitaxial growth took 300 hours, with all other parameters remaining the same as the first epitaxial growth.

[0054] The average Raman full width at half maximum (FWHM) value of the obtained S3 sample was 2.56 cm. –1 The average optical transmittance in the 8-12 µm band is 70.9%, and the optical transmittance non-uniformity is 0.9%; the three-point bending strength is 554 MPa.

[0055] Comparative Example 1 The only difference from Example 1 is that, in Comparative Example 1 of the present invention, during the splicing process, the F surface of A-1 is bonded to the E surface of A-2, and then the E surface of A-2 is bonded to the F surface of A-3, so that the A surface of A-1 and the A surface of A-2 are growth surfaces. Subsequently, A-3 to A-6 are spliced ​​by bonding the upper cutting surface with the lower cutting surface of the adjacent single crystal diamond seed crystal, and finally forming a mosaic seed crystal group substrate. Then, it is placed in an MPCVD device for secondary epitaxial growth to obtain a single crystal diamond splice, labeled as D1.

[0056] The average Raman full width at half maximum (FWHM) value of the obtained D1 sample was 3.22 cm. –1 The average optical transmittance in the 8-12 µm band is 68.5%, and the optical transmittance non-uniformity is 2.2%; the three-point bending strength is 341 MPa.

[0057] Performance Analysis The Raman full width at half maximum (FWHM) was measured according to the national standard GB / T 33252-2016. To eliminate testing errors, five test points were randomly selected at the splicing interface of each single-crystal diamond splice prepared in Examples 1-3 and Comparative Example 1, and six test points were randomly selected in the internal region of the single-crystal diamond splice at the non-splicing interface.

[0058] The average optical transmittance test in the 8~12 µm band was performed in accordance with the national standard GB / T 36403-2018. Optical transmittance non-uniformity test method: On each single-crystal diamond splice in Examples 1-3 and Comparative Example 1, three test points were randomly selected at the splice interface and the non-interface internal region, and the average optical transmittance was measured. The optical transmittance non-uniformity was characterized by the difference between the maximum and minimum values ​​of the average optical transmittance among all test points.

[0059] The three-point bending strength test adopts the three-point bending method and is performed in accordance with the method of the national standard GB / T 6569-2006.

[0060] The optical transmittance of the single-crystal diamond splices prepared in Examples 1-3 and Comparative Example 1 of this invention is as follows: Figure 2 As shown. Because Comparative Example 1 did not use the splicing method described in this invention, its splicing interface originated from different primary crystal planes, making it difficult for the crystal orientation of the bonding interface to be completely consistent, thus affecting the optical performance.

[0061] Figure 3 (a) and (b) show a comparison of the crystallographic orientations of the single-crystal diamond splices (taking A-1 and A-2 as examples) prepared in Examples 1-3 of this invention along the X and Y axes. The colors of the two are very similar, indicating a high degree of consistency in crystallographic orientation. However, in Comparative Example 1, as... Figure 3 As shown in (c) and (d), there is a significant difference in color between A-1 and A-2, reflecting an inconsistency in crystallographic orientation at the joint and poor splicing quality.

[0062] Table 1 shows the orientation angle deviations in the X and Y axes of the single-crystal diamond splices (taking A-1 and A-2 as examples) prepared in Examples 1-3 and Comparative Example 1 of the present invention.

[0063] Table 1. Orientation angle deviations in the X and Y axes of the single-crystal diamond splices (taking A-1 and A-2 as examples) prepared in Examples 1-3 and Comparative Example 1 of the present invention.

[0064] It can be seen that the orientation angle deviations of the single-crystal diamond splices obtained in Examples 1-3 of this invention are all less than 1° in both directions; while the deviation in Comparative Example 1 is significantly increased, exceeding 10°. This indicates that the splicing method of this invention can obtain single-crystal diamond splices with highly consistent crystallographic orientation at the splicing interface.

[0065] Table 2 shows the Raman full width at half maximum (FWHM) values ​​at the splicing interface and non-splicing interface of the single-crystal diamond splice bodies prepared in Examples 1-3 and Comparative Example 1 of this invention.

[0066] Table 2. Raman full width at half maximum (FWHM) values ​​of the single-crystal diamond splices prepared in Examples 1-3 and Comparative Example 1 at the splicing interface and non-splicing interface.

[0067] Analysis of crystal quality at the interface: The full width at half maximum (FWHM) of the Raman spectrum is the core indicator for evaluating the quality of single-crystal diamond crystal splices. The lower the FWHM, the fewer the lattice defects and the higher the crystal quality.

[0068] The FWHM values ​​of all samples in the embodiments of this invention were stable at 3 cm. -1Within this range, the FWHM value (>3.5 cm) at the splicing interface of Comparative Example 1 is lower. -1 This indicates that the present invention successfully achieved high consistency in crystal orientation and low defect density at the splicing interface, solving a core challenge in splicing growth. In contrast, the crystal quality at the non-splicing interface (i.e., the internal region of the seed crystal) showed no significant difference, indicating that the preparation method described in this invention has a significant impact on the interface bonding quality.

[0069] The non-uniformity of optical transmittance of the single-crystal diamond splices prepared in Examples 1-3 and Comparative Example 1 of this invention is shown in Table 3.

[0070] Table 3. Optical transmittance non-uniformity of single-crystal diamond splices prepared in Examples 1-3 and Comparative Example 1 of the present invention.

[0071] Average optical transmittance and analysis of optical transmittance non-uniformity: In the 8–12 µm infrared atmospheric window band, the average optical transmittance of the three samples was higher than 70.5%. Table 3 shows that the optical transmittance non-uniformity of the single-crystal diamond splice prepared by the method of the present invention is less than 1%. This value is close to the theoretical transmittance of single-crystal diamond, proving that there are very few impurities and light scattering defects at the splicing interface, and no obvious "dark lines" or optical distortions are formed. This high and uniform transmittance performance enables it to meet the stringent requirements of components for extreme environment applications such as precision infrared optical systems (e.g., high-speed aircraft fairings, infrared windows).

[0072] The three-point bending strength of the single-crystal diamond splices prepared in Examples 1-3 and Comparative Example 1 of this invention is shown in Table 4.

[0073] Table 4. Three-point bending strength of single-crystal diamond splices prepared in Examples 1-3 and Comparative Example 1 of the present invention.

[0074] Interface bonding strength analysis: The three-point bending strength data tested by the three-point bending method show that the three-point bending strength of the single-crystal diamond splice prepared in Examples 1-3 of this invention is higher than that of Comparative Example 1. This indicates that the bonding quality at the splice interface is good, and that the single-crystal diamond splice can effectively bear thermal and mechanical stress as a whole, avoiding the risk of cracking at the joint and ensuring the reliability of the device in harsh environments.

[0075] In summary, the method for preparing single-crystal diamond splices provided by this invention successfully unifies large-size fabrication with high-quality performance. The prepared single-crystal diamond splices exhibit excellent and consistent performance in terms of crystal quality, optical properties, and mechanical strength, fully demonstrating the advanced nature, reliability, and industrial application potential of this invention.

Claims

1. A method for preparing a single-crystal diamond splice, characterized in that, include: (1) Take a single single-crystal diamond seed crystal and cut it vertically and equally along any surface of the single-crystal diamond seed crystal to obtain a single-crystal diamond seed crystal. Then, according to the cutting order, the upper cut surfaces of adjacent single-crystal diamond seed crystals are attached to each other, and then attached to the lower cut surface of the next adjacent single-crystal diamond seed crystal. The two are spliced ​​alternately to obtain a mosaic seed crystal group substrate. (2) The mosaic seed crystal group substrate is placed in a microwave plasma chemical vapor deposition equipment for secondary epitaxial growth to obtain a single crystal diamond splice.

2. The method for preparing a single-crystal diamond splice according to claim 1, characterized in that, The single-crystal diamond seed crystal is a cuboid or cube, with all six faces being... <100> Orientation: The specifications of the single-crystal diamond seed crystal are as follows: length 10~20 mm, width 5~10 mm, and thickness 500~600 µm.

3. The method for preparing a single-crystal diamond splice according to claim 1, characterized in that, The mosaic seed crystal group substrate is cleaned and etched.

4. The method for preparing a single-crystal diamond splice according to claim 3, characterized in that, The cleaning process involves cleaning the mosaic seed crystal substrate with a piranha solution for 90-120 minutes at a temperature of 50-80°C, followed by ultrasonic cleaning with acetone or ethanol for 10-30 minutes.

5. The method for preparing a single-crystal diamond splice according to claim 3, characterized in that, The etching is performed using an MPCVD device, and the etching parameters are: hydrogen flow rate of 200~2000 sccm, etching temperature of 500~800℃, etching pressure of 8~10 kPa, and etching time of 30~60 min.

6. The method for preparing a single-crystal diamond splice according to claim 1, characterized in that, The parameters for the first epitaxial growth were: growth temperature of 800~1000 ℃, growth pressure of 8~13 kPa, and growth time of 100~200 h.

7. The method for preparing a single-crystal diamond splice according to claim 1, characterized in that, The parameters for the second epitaxial growth were: growth temperature of 800~1000 ℃, growth pressure of 8~13 kPa, and growth time of 300~500 h.

8. A single-crystal diamond splice prepared by the method of any one of claims 1-7.

9. The single-crystal diamond splice according to claim 8, characterized in that, The Raman full width at half maximum (FWHM) of the single-crystal diamond splice at the interface is 2-3 cm. -1 The average optical transmittance in the 8~12 µm band is ≥70%, and the optical transmittance non-uniformity is <1%.

10. An application of a single-crystal diamond splice according to claim 8 or 9 in the fields of semiconductor substrates, power device heat dissipation, or infrared optical windows.

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