A method for improving the quality of large-size single-crystal diamond joints by secondary epitaxy

Abstract

The invention discloses a method for improving the quality of large-size single-crystal diamond seams by secondary epitaxy, wherein a primary epitaxial layer is deposited and grown on a substrate surface by chemical vapor deposition, and then crystal defects at orthogonal intersections of multiple substrates are removed by laser to form rectangular grooves; after removing pollutants on the surface of the primary epitaxial layer of the spliced ​​crystal by conventional cleaning and ion cleaning, a single-crystal diamond secondary epitaxial layer is grown on the surface of the primary epitaxial layer by chemical vapor deposition; after splicing and growth by this method, a large-size single-crystal diamond spliced ​​crystal without crystal defects at orthogonal intersections of multiple substrates of the spliced ​​crystal can be obtained.

Description

Technical Field

[0001] The invention belongs to the technical field of single crystal diamond material preparation, and particularly relates to a method for improving the joint quality of large-size single crystal diamond by secondary epitaxy. Background Art

[0002] Diamond has extremely excellent mechanical, thermal, optical and electrical properties, such as extremely high hardness, high thermal conductivity, wide optical transmission band, large bandgap width and high carrier mobility. It is considered to be the "ultimate semiconductor" material for the preparation of the next generation of high-power, high-frequency, high-temperature and low-power loss electronic devices. There are no grain boundaries inside single-crystal diamond, and it has higher carrier mobility and charge collection efficiency than polycrystalline diamond. Therefore, it has outstanding application effects in cutting-edge scientific and technological fields such as quantum communication / computing, radiation detectors, cold cathode field emission displays, semiconductor lasers, etc.

[0003] Natural diamond and single crystal diamond synthesized by high temperature and high pressure method are small in size and have high impurity content, which is difficult to meet the application requirements of electronic devices. Microwave plasma chemical vapor deposition (MPCVD) technology has the technical characteristics of high plasma density, non-polar discharge, no pollution, and strong epitaxy controllability. It is the preferred method for achieving high-quality single crystal diamond growth. Although the homoepitaxial method can obtain a lower defect density (about 10 4-5 / cm 2 ), but limited by the size of the single crystal substrate, the preparation of large-sized single crystal diamond is usually achieved by splicing and growing multiple single crystal diamonds with consistent crystal orientation. For example, the Yamada team used the "Lift-off" technology to obtain multiple single crystals with consistent crystal orientation characteristics as splicing seeds, realizing the preparation of single crystal diamonds from 20mm×20mm to 2 inches. However, the joints between the seeds are still very obvious, and non-destructive processing is very difficult.

[0004] The technical difficulties of the splicing method are mainly concentrated on the control of the crystal orientation of the substrate and the control of the microscopic gap at the joint. Since it is difficult to achieve seamless arrangement of the interface during the growth process, the substrate is not tightly placed and slightly misaligned, which will lead to the appearance of subgrain boundaries or even gaps at the joints of large-area single-crystal diamonds grown by splicing, resulting in dislocation defects and stress concentration in this area, which seriously affects the quality of the crystal and cannot meet the preparation of large-size electronic-grade diamonds. In order to solve the problem that the microscopic gaps when the substrate is placed are misaligned, resulting in defects such as subgrain boundaries at the joints of spliced ​​single-crystal diamonds, patent CN114032610A designs a mosaic splicing device, which compresses the single-crystal substrate sheets inward uniformly at the same time through the compression spring, so that the contact between the substrate sheets is closer; patent CN104878447A describes an in-situ connection method for seed crystal substrates of homoepitaxially grown single-crystal diamonds, which uses vacuum brazing technology to achieve in-situ connection of single crystals. Although these methods can fix the positions of two seed crystals during chemical vapor deposition, they are still limited to positioning the substrate on a macro scale and it is difficult to solve the crystal defect problem caused by misaligned placement on a micrometer scale. Summary of the invention

[0005] The purpose of the present invention is to provide a method for improving the quality of large-size single-crystal diamond joints by secondary epitaxy in view of the above-mentioned deficiencies in the prior art, wherein a single-crystal diamond secondary epitaxial layer is grown on the surface of a primary epitaxial layer by chemical vapor deposition.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0007] A method for improving the quality of large-size single-crystal diamond seams by secondary epitaxy comprises the following steps:

[0008] (1) Select 4 to 16 single crystal diamonds with (100) orientation on the main surface as substrates, and after ultrasonic cleaning, place the single crystal diamond substrates closely and place them in the sample stage of a microwave plasma device. After evacuation, introduce the reaction gas to chemically vapor deposit and grow a single crystal diamond primary epitaxial layer on the substrate surface;

[0009] (2) Focusing the laser on the orthogonal intersection of multiple single-crystal diamond substrates, and using the laser to etch a rectangular microgroove at the defect position at the intersection;

[0010] (3) Perform routine cleaning on the spliced ​​crystal after laser treatment, and then perform ion cleaning on the surface of the primary epitaxial layer of the spliced ​​crystal to remove contaminants generated by laser ablation;

[0011] (4) The grooved spliced ​​crystal is placed in the cavity of a microwave plasma device, and a single crystal diamond secondary epitaxial layer is grown on the surface of the primary epitaxial layer by chemical vapor deposition, thereby achieving large-scale, high-quality single crystal diamond splicing growth.

[0012] In step (1), the single crystal diamond substrate is synthesized by high temperature and high pressure method or chemical vapor deposition method, has no macroscopic defects and a dislocation density of less than 5000 / cm 2 The single crystal diamond crystal is oriented along the (100) crystal plane with an error of no more than ±1°.

[0013] In step (1), the single crystal diamond substrates are placed orthogonally in an "edge-to-edge" manner, the spacing between adjacent single crystal diamond seed crystals is 50 to 300 μm, and the thickness deviation does not exceed 5 μm.

[0014] In step (1), a single crystal diamond primary epitaxial layer is deposited on the substrate surface by microwave plasma chemical vapor deposition, and the conditions are temperature 800-1000°C, gas pressure 100-140 torr, power 4-6kW, hydrogen flow rate 500-1000sccm, methane flow rate 30-60sccm, nitrogen flow rate 0.1-1sccm, and growth time 10-20h.

[0015] In step (2), the laser power is set to 9-13 W and the laser step length is set to 15-25 mm / s.

[0016] In step (2), the adjacent sides of the rectangular microgroove are respectively parallel to a group of adjacent sides of the square diamond substrate, the length of the short side of the rectangular microgroove is 50 to 200 μm, and the depth of the rectangular microgroove is 20 to 30 μm.

[0017] In step (3), the spliced ​​crystal after the groove processing is placed in acetone, anhydrous ethanol and deionized water for soaking and cleaning in sequence, and the soaking time is 15-30 minutes.

[0018] In step (3), the gas used for ion cleaning is H2 or H2 / O2 mixed gas, the O2 ratio is 0%-4% of the total gas volume, the etching temperature is 700-950°C, and the cleaning time is 30 minutes.

[0019] In step (4), the method for depositing a single crystal diamond secondary epitaxial layer on the substrate surface adopts microwave plasma chemical vapor deposition, and the conditions are temperature 900-1200°C, gas pressure 100-140 torr, power 4-6kW, hydrogen flow rate 500-1000sccm, methane flow rate 30-60sccm, nitrogen flow rate 0.5-1sccm, and growth time 40-80h.

[0020] In step (2), the laser is focused on the orthogonal intersection of the four single crystal diamond substrates.

[0021] The beneficial effects of the present invention are:

[0022] (1) The present invention discloses a method for improving the quality of large-size single-crystal diamond seams by secondary epitaxy, wherein a primary epitaxial layer is deposited and grown on the surface of a substrate by chemical vapor deposition, and then crystal defects at multiple orthogonal intersections of the substrate are removed by laser to form rectangular grooves; after removing contaminants on the surface of the primary epitaxial layer of the spliced ​​crystal by conventional cleaning and ion cleaning, a single-crystal diamond secondary epitaxial layer is grown on the surface of the primary epitaxial layer by chemical vapor deposition; after splicing and growth by this method, there are no crystal defects at multiple orthogonal intersections of the spliced ​​crystal.

[0023] (2) The method of laser etching microgrooves followed by secondary epitaxy can improve the crystal quality at multiple substrate intersections and reduce crystal defects without the need for high-precision processing and positioning of the substrate. The process is simple and more operable, solving the problem of crystal defects caused by misaligned placement at the micrometer scale.

[0024] (3) Laser grooving for targeted defect elimination has the advantages of precise positioning, controllable shape, high processing accuracy, etc. It can accurately etch according to the defect location and size, and the side of the formed microgroove is perpendicular to the main crystal plane, ensuring that no other crystal planes are exposed after grooving, and the crystal plane direction meets the conditions for secondary epitaxial homogeneous connection.

[0025] (4) Before the secondary epitaxial growth, multiple substrates are connected into a whole through a primary epitaxial growth process, which greatly reduces the temperature difference between different substrates, makes all substrates under similar growth conditions, and achieves better homogeneous growth effect, thereby improving the crystallization quality of diamond at the interface. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 are different stages of an embodiment of the present invention;

[0027] Figure 2 It is 4 pieces of 9×9mm 2 Optical microscope image of single crystal diamond arranged orthogonally in an "edge-to-edge" manner;

[0028] Figure 3 It is 4 pieces of 9×9mm 2 Optical microscope image of the center point of the single crystal diamond after a chemical vapor deposition growth;

[0029] Figure 4 yes Figure 3 A partial enlarged schematic diagram of the middle rectangular area;

[0030] Figure 5 It is 4 pieces of 9×9mm 2 Optical microscope image of the center point of the splicing after secondary chemical vapor deposition growth of single crystal diamond. DETAILED DESCRIPTION

[0031] The following is a description of the implementation of the present invention by means of specific embodiments. Those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification.

[0032] The present invention provides a method for improving the quality of large-size single crystal diamond joints by secondary epitaxy, such as Figures 1 to 5 shown.

[0033] Example 1

[0034] A method for improving the quality of large-size single-crystal diamond seams by secondary epitaxy comprises the following steps:

[0035] (1) Select 4 to 16 single crystal diamonds with (100) orientation on the main surface as substrates, and after ultrasonic cleaning, place the single crystal diamond substrates closely and place them in the sample stage of a microwave plasma device. After evacuation, introduce the reaction gas to chemically vapor deposit and grow a single crystal diamond primary epitaxial layer on the substrate surface;

[0036] (2) Focus the laser on the orthogonal intersection of four single crystal diamond substrates and use the laser to etch a rectangular microgroove at the defect location at the intersection;

[0037] (3) Perform routine cleaning on the spliced ​​crystal after laser treatment, and then perform ion cleaning on the surface of the primary epitaxial layer of the spliced ​​crystal to remove contaminants generated by laser ablation;

[0038] (4) The grooved spliced ​​crystal is placed in the cavity of a microwave plasma device, and a single crystal diamond secondary epitaxial layer is grown on the surface of the primary epitaxial layer by chemical vapor deposition, thereby achieving large-scale, high-quality single crystal diamond splicing growth.

[0039] The details are as follows:

[0040] Four pieces of 9×9×0.25mm 3 Single crystal diamond is used as substrate, the substrate thickness deviation is 5μm, there is no macro defect on the growth surface, and the dislocation density is less than 5000 / cm 2 .

[0041] The substrates were ultrasonically cleaned with acetone, anhydrous ethanol and deionized water, and the substrates were placed closely in the cavity of the microwave plasma equipment. Figure 2 As shown, there is a placement gap of 100-200 μm at the vertices of the four substrates.

[0042] A single crystal diamond primary epitaxial layer was chemically vapor deposited on the substrate growth surface by microwave plasma chemical vapor deposition. The deposition conditions were: temperature 870°C, pressure 110 torr, power 5.5 kW, hydrogen flow rate 700 sccm, methane flow rate 30 sccm, nitrogen flow rate 0.2 sccm, and deposition time 12 h. Figure 3 As shown, there are non-(100) crystal planes and crystal defects at the orthogonal intersections of the substrate on the primary epitaxial layer.

[0043] A green laser cutting machine was used to etch a rectangular microgroove at the defect position at the orthogonal intersection of the substrate on the primary epitaxial layer. The laser power was 9.5W, the laser step length was 20mm / s, and the size of the rectangular microgroove was 0.2×0.8mm. 2 , depth is 0.03mm.

[0044] The spliced ​​crystal was cleaned in acetone, anhydrous ethanol and deionized water in turn, each time for 20 minutes; then the surface of the epitaxial layer of the spliced ​​crystal was ion cleaned using a H2 / O2 mixed gas with an O2 ratio of 4% of the total gas volume, an etching temperature of 850°C, and a cleaning time of 30 minutes.

[0045] The grooved spliced ​​crystal is placed in the cavity of a microwave plasma device, and a single crystal diamond secondary epitaxial layer is grown on the surface of the primary epitaxial layer by chemical vapor deposition. The microwave plasma chemical vapor deposition method is used, and the deposition conditions are: temperature 950°C, gas pressure 110 torr, power 5.5kW, hydrogen flow rate 700sccm, methane flow rate 30sccm, nitrogen flow rate 0.5sccm, and deposition time 48h.

[0046] like Figure 4 As shown, there are no defects at the orthogonal intersections of the substrate after the secondary epitaxial growth, and the crystal quality at the splicing interface is good.

[0047] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for explaining the principles of the present invention. The present invention may be subject to various changes and improvements without departing from the spirit and scope of the present invention. These changes and improvements fall within the scope of the invention claimed for protection. The scope of protection claimed for the present invention is defined by the attached claims and their equivalents.

[0048] In the description of the present invention, it is necessary to understand that the terms "front", "rear", "left", "right", "center", etc. indicate directions or positional relationships based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as a limitation on the protection content of the present invention.

Claims

1. A method for improving the quality of large-size single-crystal diamond joints by secondary epitaxy, characterized in that: The following steps are involved: (1) Select 4 to 16 single crystal diamonds with (100) orientation on the main surface as substrates, and after ultrasonic cleaning, place the single crystal diamond substrates closely and place them in the sample stage of a microwave plasma device. After evacuation, introduce the reaction gas to chemically vapor deposit and grow a single crystal diamond primary epitaxial layer on the substrate surface; (2) focusing the laser on the orthogonal intersections of multiple single crystal diamond substrates, and using the laser to etch rectangular microgrooves at the defect locations at the orthogonal intersections of the primary epitaxial layer substrate; (3) Perform routine cleaning on the spliced ​​crystal after laser treatment, and then perform ion cleaning on the surface of the primary epitaxial layer of the spliced ​​crystal to remove contaminants generated by laser ablation; (4) The grooved spliced ​​crystal is placed in the cavity of a microwave plasma device, and a single crystal diamond secondary epitaxial layer is grown on the surface of the primary epitaxial layer by chemical vapor deposition, thereby achieving large-scale, high-quality single crystal diamond splicing growth.

2. The method for improving the quality of large-size single crystal diamond joints by secondary epitaxy according to claim 1, characterized in that: In step (1), the single crystal diamond substrate is synthesized by high temperature and high pressure method or chemical vapor deposition method, has no macroscopic defects and a dislocation density of less than 5000 / cm 2 The single crystal diamond crystal is oriented along the (100) crystal plane with an error of no more than ±1°.

3. The method for improving the quality of large-size single crystal diamond joints by secondary epitaxy according to claim 1, characterized in that: In step (1), the single crystal diamond substrates are placed orthogonally in an "edge-to-edge" manner, the spacing between adjacent single crystal diamond seed crystals is 50 to 300 μm, and the thickness deviation does not exceed 5 μm.

4. The method for improving the quality of large-size single crystal diamond joints by secondary epitaxy according to claim 1, characterized in that: In step (1), a single crystal diamond primary epitaxial layer is deposited on the substrate surface by microwave plasma chemical vapor deposition, and the conditions are temperature 800-1000°C, gas pressure 100-140 torr, power 4-6kW, hydrogen flow rate 500-1000sccm, methane flow rate 30-60sccm, nitrogen flow rate 0.1-1sccm, and growth time 10-20h.

5. The method for improving the quality of large-size single crystal diamond joints by secondary epitaxy according to claim 1, characterized in that: In step (2), the laser power is set to 9-13 W and the laser step length is set to 15-25 mm / s.

6. The method for improving the quality of large-size single crystal diamond joints by secondary epitaxy according to claim 1, characterized in that: In step (2), the adjacent sides of the rectangular microgroove are respectively parallel to a group of adjacent sides of the square diamond substrate, the length of the short side of the rectangular microgroove is 50 to 200 μm, and the depth of the rectangular microgroove is 20 to 30 μm.

7. The method for improving the quality of large-size single crystal diamond joints by secondary epitaxy according to claim 1, characterized in that: In step (3), the laser-treated spliced ​​crystal is sequentially placed in acetone, anhydrous ethanol and deionized water for immersion and cleaning, with the immersion time being 15-30 minutes.

8. The method for improving the quality of large-size single crystal diamond joints by secondary epitaxy according to claim 1, characterized in that: In step (3), the gas used for ion cleaning is H2 or a mixed gas of H2 and O2, the proportion of O2 is 0%-4% of the total gas volume, the etching temperature is 700-950°C, and the cleaning time is 30 minutes.

9. The method for improving the quality of large-size single crystal diamond joints by secondary epitaxy according to claim 1, characterized in that: In step (4), the method for depositing a single crystal diamond secondary epitaxial layer on the substrate surface adopts microwave plasma chemical vapor deposition, and the conditions are temperature 900-1200°C, gas pressure 100-140 torr, power 4-6kW, hydrogen flow rate 500-1000sccm, methane flow rate 30-60sccm, nitrogen flow rate 0.5-1sccm, and growth time 40-80h.

10. The method for improving the quality of large-size single crystal diamond joints by secondary epitaxy according to claim 1, characterized in that: In step (2), the laser is focused on the orthogonal intersection of the four single crystal diamond substrates.

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