Self-selection lateral growth large-size diamond (110) single crystal and preparation method thereof

Abstract

The invention relates to a self-selection lateral growth large-size diamond (110) single crystal and a preparation method thereof. The preparation method comprises the following steps: selecting X diamond substrates; growing a (110) crystal orientation epitaxial diamond layer on the upper surface of each diamond substrate to obtain X (110) single crystal epitaxial structures; each of the X (110) single crystal epitaxial structures is provided with a (100) crystal orientation side surface and a (111) crystal orientation side surface; dividing the X (110) single crystal epitaxial structures into M groups; performing intra-group first crystal orientation splicing on the N (110) single crystal epitaxial structures in each group of (110) single crystal epitaxial structures, and growing diamond under the growth condition of the first crystal orientation to obtain M first spliced structures; carrying out second crystal orientation splicing on the M first splicing structures, and growing diamond under the growth condition of the second crystal orientation to obtain a second splicing structure; and performing post-treatment on the second splicing structure to obtain the large-size diamond (110) single crystal.

Description

Technical Field

[0001] The invention belongs to the field of microelectronic technology, and in particular relates to a large-size diamond (110) single crystal grown in a self-selected lateral direction and a preparation method thereof. Background Art

[0002] As an ultra-wide bandgap semiconductor, diamond has a high bandgap width (5.45 eV), a high electron saturation drift velocity (2.5×10 7 cm / s), high hole mobility (4500cm 2 / (V·s)), high electron mobility (3800cm 2 / (V·s)), high breakdown electric field (>10MV·cm -1 ), high thermal conductivity (2200W / (m·K)), low thermal expansion coefficient, high mechanical strength, low dielectric constant (5.7) and good radiation resistance, which are superior to other semiconductor materials. Diamond has a wide range of application prospects in high-frequency communications, power amplifiers, radar systems, radiation-resistant devices, chip heat dissipation and other fields due to its excellent performance, and is known as the "ultimate semiconductor material".

[0003] Diamond is widely used in the field of devices. Diamond diodes and hydrogen-terminated diamond MOSFET devices have obvious advantages in the field of high temperature and high pressure. However, the n-type doping of diamond is still a difficult problem to solve. Studies have shown that the (110) crystal orientation is a suitable orientation for diamond n-type phosphorus doping. Under the same conditions, the doping efficiency of the (110) crystal orientation is 3 orders of magnitude higher than that of the (100) crystal orientation. At the same time, in hydrogen-terminated diamond devices, the concentration of two-dimensional hole gas (2DHG) on the surface of hydrogen-terminated diamond with a (110) crystal orientation can reach up to 2.22×10 15 cm -3 , which is greater than the maximum hole concentration of (111) and (100) crystal orientations. The hydrogen-terminated devices made of diamond with (110) crystal orientation have been shown to have better performance than diamond devices made of other oriented substrates. Diamond with (110) crystal orientation has certain advantages in the fields of p-type hydrogen-terminated diamond and n-type phosphorus-doped diamond. Large-size diamond substrates can improve production efficiency, reduce production costs, and promote innovation and development in materials, processes, and equipment in the semiconductor industry.

[0004] In the prior art, diamond with (100) crystal orientation is prepared by high temperature and high pressure method (HTHP), and then cut along a specific crystal orientation by laser to obtain a diamond substrate with (110) crystal orientation. However, the area of ​​the (110) crystal orientation diamond prepared by HTHP is limited, and it is impossible to prepare a high-quality and large-size (110) crystal orientation diamond substrate, which greatly limits the application of (110) crystal orientation diamond materials and (110) crystal orientation diamond electronic devices. Summary of the invention

[0005] In order to solve the above problems existing in the prior art, the present invention provides a large-size diamond (110) single crystal grown by self-selection and a preparation method thereof. The technical problem to be solved by the present invention is achieved by the following technical solutions:

[0006] A first aspect of the present invention provides a method for preparing a large-size diamond (110) single crystal by self-selective lateral growth, comprising the following steps:

[0007] Select X diamond substrates, where X=M×N, M and N are both positive integers greater than 1; the upper surface of the diamond substrate is (110) crystal orientation;

[0008] Growing an epitaxial diamond layer with a (110) crystal orientation on the upper surface of each diamond substrate to obtain X (110) single crystal epitaxial structures; each of the X (110) single crystal epitaxial structures has a side surface with a (100) crystal orientation and a side surface with a (111) crystal orientation;

[0009] Dividing the X (110) single crystal epitaxial structures into M groups, each group of (110) single crystal epitaxial structures including N (110) single crystal epitaxial structures;

[0010] Splicing N (110) single crystal epitaxial structures in each group of (110) single crystal epitaxial structures in a first crystal orientation within the group, and growing diamond under growth conditions in the first crystal orientation to obtain M first spliced ​​structures;

[0011] The M first spliced ​​structures are spliced ​​in a second crystal direction, and diamond is grown under the growth conditions of the second crystal direction to obtain a second spliced ​​structure; the first crystal direction is one of the (100) crystal direction and the (111) crystal direction; the second crystal direction is the other of the (100) crystal direction and the (111) crystal direction;

[0012] The second spliced ​​structure is post-processed to obtain a large-sized diamond (110) single crystal.

[0013] In one achievable manner, the diamond substrate has a side surface with a (100) crystal orientation and a side surface with a (110) crystal orientation.

[0014] In one achievable manner, N (110) single crystal epitaxial structures in each group of (110) single crystal epitaxial structures are spliced ​​in the first crystal direction within the group, including:

[0015] The side surfaces of the N (110) single crystal epitaxial structures in each group of (110) single crystal epitaxial structures in the first crystal direction are in contact with each other and arranged in a straight line.

[0016] In an achievable manner, when the first crystal orientation is (100) and the second crystal orientation is (111), growing diamond under the growth conditions of the first crystal orientation includes:

[0017] Using MPCVD equipment, growing diamond with a (100) crystal orientation under growth conditions of a (100) crystal orientation;

[0018] Growing diamond under the growth conditions of the second crystal direction, comprising:

[0019] Diamond with (111) crystal orientation is grown under the growth conditions of (111) crystal orientation using MPCVD equipment.

[0020] In one achievable manner, the growth conditions of the (100) crystal orientation include:

[0021] The pressure is 140-160 Torr, the power is 4000-4200 W, the temperature is 850-950°C, the H2 flow rate is 300-400 sccm, the CH4 flow rate is 12-18 sccm, and the growth time is 40-60 h.

[0022] In one achievable manner, the growth conditions of the (111) crystal orientation include:

[0023] The pressure is 100-120 Torr, the power is 2000-2300 W, the temperature is 850-950°C, the H2 flow rate is 300-400 sccm, the CH4 flow rate is 2-4 sccm, and the growth time is 40-60 hours.

[0024] In one achievable manner, growing an epitaxial diamond layer with a (110) crystal orientation on the upper surface of each diamond substrate comprises:

[0025] An epitaxial diamond layer with a (110) crystal orientation is grown on the upper surface of each diamond substrate under the growth condition of a (110) crystal orientation using an MPCVD device.

[0026] In one achievable manner, the growth conditions of the (110) crystal orientation include:

[0027] The pressure is 120-140 Torr, the power is 3200-3600 W, the temperature is 850-950°C, the H2 flow rate is 300-400 sccm, the CH4 flow rate is 10-12 sccm, and the growth time is 10-20 hours.

[0028] In an achievable manner, post-processing the second spliced ​​structure includes:

[0029] The edge of the second splicing structure and an upper surface of a preset thickness are removed by laser cutting, and the cut surface is polished.

[0030] The second aspect of the present invention provides a large-sized diamond (110) single crystal that is self-selectively grown laterally, which is prepared by the method for preparing a large-sized diamond (110) single crystal that is self-selectively grown laterally provided by the first aspect of the present invention.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] The method for preparing a large-sized diamond (110) single crystal by self-selective lateral growth provided by the present invention forms a large-sized diamond (110) single crystal by splicing a plurality of diamond substrates through two-step splicing and two-step self-selective lateral growth, thereby solving the long-standing problem that (110) crystal orientation diamond substrates cannot achieve enlarged growth, and realizing a high-quality large-sized (110) single crystal diamond substrate. The large-sized substrate is of great significance for improving the performance of (110) crystal orientation diamond devices. In addition, the preparation method provided by the present invention can be realized by a simple method in the engineering application and scientific research fields of diamond, providing convenience for obtaining a large-sized (110) diamond substrate. At the same time, the diamond single crystal material prepared by the preparation method provided by the present invention has fewer defects and higher quality than the diamond prepared by HTHP. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a flow chart of the steps of a method for preparing a large-size diamond (110) single crystal by self-selective lateral growth provided by an embodiment of the present invention;

[0034] Figure 2 is a schematic diagram of the crystal orientation of a diamond substrate provided by an embodiment of the present invention;

[0035] Figure 3 is a schematic diagram of the morphology and crystal orientation of a (110) single crystal epitaxial structure provided by an embodiment of the present invention;

[0036] Figure 4 It is a growth environment characterization diagram of the (111) crystal orientation, the (110) crystal orientation and the (100) crystal orientation provided by an embodiment of the present invention;

[0037] Figure 5 SEM image of (110) crystal orientation diamond provided by an embodiment of the present invention.

[0038] Figure 6a to Figure 6b This is a schematic diagram of a method for preparing a large-size diamond (110) single crystal by self-selective lateral growth provided by an embodiment of the present invention;

[0039] Figure 7a to Figure 7c This is a step structure diagram of a method for preparing a large-size diamond (110) single crystal by self-selective lateral growth provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0040] The present invention is further described in detail below with reference to specific embodiments, but the embodiments of the present invention are not limited thereto.

[0041] Embodiment 1

[0042] See also Figure 1 , Figure 1 The present invention provides a flowchart of the steps of a method for preparing a large-size diamond (110) single crystal by self-selective lateral growth according to an embodiment of the present invention.

[0043] This embodiment provides a method for preparing a large-size diamond (110) single crystal by self-selective lateral growth, comprising the following steps:

[0044] Step 1: Select X diamond substrates, where X=M×N, M and N are both positive integers greater than 1; the upper surface of the diamond substrate has a (110) crystal orientation.

[0045] Specifically, X (110) single crystal diamond substrates prepared by HTHP method are selected, and the diamond substrates have a side surface with a (100) crystal orientation and a side surface with a (110) crystal orientation. Figure 2 As shown, Figure 2 Schematic diagram of the crystal orientation of the diamond substrate provided by the embodiment of the present invention. The upper surface of the diamond substrate is in the (110) crystal orientation, the two opposite side surfaces are in the (110) crystal orientation, and the other two opposite side surfaces are in the (100) crystal orientation.

[0046] Step 2: growing an epitaxial diamond layer with a (110) crystal orientation on the upper surface of each diamond substrate to obtain X (110) single crystal epitaxial structures; each of the X (110) single crystal epitaxial structures has a side surface with a (100) crystal orientation and a side surface with a (111) crystal orientation.

[0047] Specifically, growing an epitaxial diamond layer with a (110) crystal orientation on the upper surfaces of X diamond substrates comprises:

[0048] Using plasma chemical vapor deposition (MPCVD) equipment, under the growth condition of (110) crystal orientation, epitaxial diamond layers with (110) crystal orientation are grown on the upper surfaces of X diamond substrates.

[0049] In this embodiment, the growth conditions of the (110) crystal orientation include:

[0050] The pressure is 120-140 Torr, the power is 3200-3600 W, the temperature is 850-950 ° C, the H2 flow rate is 300-400 sccm, the CH4 flow rate is 10-12 sccm, and the growth time is 10-20 hours. Under the above conditions of medium power, medium pressure and medium methane concentration, high-quality (110) crystal-oriented diamond can be grown by MPCVD process.

[0051] See also Figure 3 , Figure 3 It is a schematic diagram of the morphology and crystal orientation of the (110) single crystal epitaxial structure provided by an embodiment of the present invention. When a single crystal diamond is grown under the growth conditions of the (110) crystal orientation by the MPCVD process, as the thickness increases, the upper surface area of ​​the epitaxial structure will gradually decrease, and the epitaxial structure as a whole will be a prism. Therefore, a large-area (110) crystal orientation epitaxial diamond structure cannot be directly obtained by the MPCVD process. As the (110) crystal orientation epitaxial diamond grows in the vertical direction, the upper surface of the epitaxial diamond still maintains the (110) crystal orientation, while the side surface of the (110) crystal orientation of the original diamond substrate will expose the (100) crystal orientation, and the angle between the (100) crystal orientation and the (110) crystal orientation is 45°; while the side surface of the (100) crystal orientation of the original diamond substrate will expose the (111) crystal orientation, and the angle between the (111) crystal orientation and the (110) crystal orientation is 39.23°. After step 2, we can get X Figure 3 The prism-shaped (110) single crystal epitaxial structure shown has an upper surface with a (110) crystal orientation, which is grown from the (110) crystal orientation of the original diamond substrate; a pair of opposite side surfaces of the (110) single crystal epitaxial structure have a (100) crystal orientation, which are located on the same side as the (110) crystal orientation of the original diamond substrate; another pair of opposite side surfaces of the (110) single crystal epitaxial structure have a (111) crystal orientation, which are located on the same side as the (100) crystal orientation of the original diamond substrate.

[0052] Step 3: Divide the X (110) single crystal epitaxial structures into M groups, each group of (110) single crystal epitaxial structures includes N (110) single crystal epitaxial structures.

[0053] Step 4: Splice the N (110) single crystal epitaxial structures in each group of (110) single crystal epitaxial structures in the first crystal orientation within the group, and grow diamond under the growth conditions of the first crystal orientation to obtain M first spliced ​​structures; the first crystal orientation is one of the (100) crystal orientation and the (111) crystal orientation.

[0054] In this embodiment, the side surfaces of the first crystal direction of N (110) single crystal epitaxial structures in each group of (110) single crystal epitaxial structures are contacted with each other and arranged in a straight line. Diamonds of the first crystal direction are grown using MPCVD equipment under growth conditions of the first crystal direction to obtain M first spliced ​​structures.

[0055] Specifically, the angle of the crystal direction can be measured by an atomic force microscope (AFM) and a confocal fiberscope. The angle between each crystal direction and the (110) crystal direction is a constant value. Therefore, by measuring the crystal direction angle of the side surface of the (110) single crystal epitaxial structure, the crystal direction of the side surface of the (110) single crystal epitaxial structure can be determined; or, by observing the side surface morphology of the (110) single crystal epitaxial structure through a microscope, the crystal direction of the side surface of the (110) single crystal epitaxial structure can also be directly determined according to the morphological characteristics of different crystal directions. After determining the crystal direction of the side surface of the (110) single crystal epitaxial structure, the side surfaces of the first crystal direction of the N (110) single crystal epitaxial structures in each group are contacted with each other and arranged in a straight line along the same direction. Under the growth conditions of the first crystal direction, diamond will grow along the first crystal direction, that is, grow at the contact point of each two (110) single crystal epitaxial structures, so that the N (110) single crystal epitaxial structures in each group are connected together to form M first splicing structures.

[0056] Step 5: Splice the M first spliced ​​structures in a second crystal direction, and grow diamond under the growth conditions of the second crystal direction to obtain a second spliced ​​structure; the second crystal direction is the other of the (100) crystal direction and the (111) crystal direction.

[0057] In this embodiment, the side surfaces of the second crystal direction of M first splicing structures are contacted with each other and arranged in a straight line, and diamond of the second crystal direction is grown under the growth conditions of the second crystal direction using MPCVD equipment to obtain a second splicing structure.

[0058] Specifically, under the growth conditions of the second crystal direction, diamond will grow along the second crystal direction, that is, grow at the contact point between every two first splicing structures, thereby connecting the M first splicing structures together to form a second splicing structure.

[0059] When the first crystal direction is the (100) crystal direction and the second crystal direction is the (111) crystal direction, accordingly, the growth conditions of the first crystal direction in step 4 are the growth conditions of the (100) crystal direction, and the growth conditions of the second crystal direction in step 5 are the growth conditions of the (111) crystal direction; when the first crystal direction is the (111) crystal direction and the second crystal direction is the (100) crystal direction, accordingly, the growth conditions of the first crystal direction in step 4 are the growth conditions of the (111) crystal direction, and the growth conditions of the second crystal direction in step 5 are the growth conditions of the (100) crystal direction.

[0060] In this embodiment, the growth conditions of the (100) crystal orientation include:

[0061] The pressure is 140-160 Torr, the power is 4000-4200 W, the temperature is 850-950°C, the H2 flow rate is 300-400 sccm, the CH4 flow rate is 12-18 sccm, and the growth time is 40-60 hours. Under the above conditions of high power, high pressure and high methane concentration, high-quality (100) crystal-oriented diamond can be grown by MPCVD process.

[0062] In this embodiment, the growth conditions of the (111) crystal orientation include:

[0063] The pressure is 100-120 Torr, the power is 2000-2300 W, the temperature is 850-950 ° C, the H2 flow rate is 300-400 sccm, the CH4 flow rate is 2-4 sccm, and the growth time is 40-60 hours. Under the conditions of low power, low pressure and low methane concentration, high-quality (111) crystal-oriented diamond can be grown through the MPCVD process.

[0064] Step 6: Post-process the second spliced ​​structure to obtain a large-sized diamond (110) single crystal.

[0065] In this embodiment, the edge of the second splicing structure and the upper surface of a preset thickness are removed by laser cutting, and the cut surface is polished to obtain a large-sized diamond (110) single crystal.

[0066] Figure 4 1 is a characterization diagram of the growth environment of the (111) crystal orientation, the (110) crystal orientation and the (100) crystal orientation provided by the embodiments of the present invention, wherein (a) is a characterization diagram of the environment in the chamber at 2000w, 100Torr, and CH4 / H2=0.5%, (b) is a characterization diagram of the environment in the chamber at 3600w, 120Torr, and CH4 / H2=4%, and (c) is a characterization diagram of the environment in the chamber at 4300w, 140Torr, and CH4 / H2=6%; Figure 5The SEM image of the (110) crystal orientation diamond provided by the embodiment of the present invention, wherein (b) is a partial enlarged image of (a). When growing diamond by MPCVD, the C1 group (C, CH, CH2, CH3) and the C2 group (C2H2, C2H4, C2H5, C2H6) are the main groups involved in the reaction, and the concentration of the C1 group and the C2 group determines the crystal orientation of the diamond growth. The C1 group and the C2 group can be converted into each other, and the reaction process that occurs is as follows:

[0067]

[0068] like Figure 4 As shown in (a), under the conditions of low power, low pressure and low methane concentration, the C1 group in the equipment cavity tends to transform into the C2 group. The concentration of the C2 group in the cavity is relatively high, and the C2 group is the main reactive group for growing diamond with (111) crystal orientation. At this time, the grown diamond has (111) crystal orientation. Figure 4 As shown in (c) in the figure, under the conditions of high power, high pressure and high methane concentration, the C2 group tends to transform into the C1 group. The C1 group in the cavity occupies a dominant position, and the C1 group is the main group participating in the reaction of growing the (100) crystal orientation. Under this condition, the C1 group has reached the level of fast growing diamond with a (100) crystal orientation. At this time, the grown diamond is in the (100) crystal orientation. There are two growth mechanisms inside the diamond with a (110) crystal orientation, such as Figure 5 As shown in the figure, during the growth of diamond, the crystal will grow in layers along the (100) and (111) directions. As the growth trends along the (100) and (111) directions approach equilibrium, high-quality diamond with the (110) direction can be grown. Figure 4 As shown in (b), under the conditions of medium power, medium pressure and medium methane concentration, the strength of the C1 group and the C2 group is in a certain equilibrium state, and the tendency of the crystal to grow along the (100) and (111) directions is balanced, and high-quality (110) crystal direction diamond can be grown. The optimal growth condition for diamond is 900°C, but the power, pressure and methane concentration will affect the number of plasma C2 groups and C1 groups in the chamber. By controlling the power, pressure and methane concentration of MPCVD, the conversion between the C2 group and the C1 group is regulated, the strength of the group is regulated, the specific crystal direction required is grown, and the growth of other crystal directions is inhibited, so that diamonds with different crystal directions can be self-selected and grown at different steps.

[0069] Furthermore, taking the case where the first crystal direction is (100) and the second crystal direction is (111) as an example, the method for preparing a large-size diamond (110) single crystal by self-selective lateral growth provided in this embodiment is further described. Figure 6a to Figure 6b , Figure 6a to Figure 6b Schematic diagram of a method for preparing a large-size diamond (110) single crystal by self-selective lateral growth provided by an embodiment of the present invention. Figure 6a As shown, the (110) single crystal epitaxial structures are divided into groups in the steps, and the side surfaces of the (100) crystal orientation of the (110) single crystal epitaxial structures in each group are in contact with each other. Since a pair of opposite side surfaces of the (110) single crystal epitaxial structures are in the (100) crystal orientation, and another pair of opposite side surfaces are in the (111) crystal orientation, the side surfaces of the (100) crystal orientation of the (110) single crystal epitaxial structures in each group are in contact with each other to form an array of M N×1 epitaxial structures. When diamonds are grown on the M N×1 epitaxial structure arrays under high power, high pressure and high methane concentration conditions by MPCVD, the epitaxial structures are arranged along the <100> The (100) crystal orientation diamond grows in the direction of the (100) crystal orientation, while the growth of the (111) crystal orientation diamond is suppressed. Therefore, the (100) crystal orientation exposed on the side will grow sideways, so that the side surfaces of the (100) crystal orientation of two adjacent (110) single crystal epitaxial structures are connected together, realizing the splicing of N×1 rectangular structures, and obtaining a first splicing structure of M N×1 rectangles. In addition, the (110) crystal orientation diamond will generate a certain tensile stress during the growth process due to the reduction of the upper surface area, while the (100) crystal orientation and (111) crystal orientation diamond will generate a certain compressive stress when growing sideways. The compressive stress and tensile stress will offset each other, making the grown diamond higher in quality.

[0070] like Figure 6b As shown, by bringing the side surfaces of the (111) crystal orientation of M first splicing structures into contact with each other and arranging them in sequence, an M×N epitaxial structure array can be obtained. Under low power, low pressure and low methane concentration conditions, the (111) crystal orientation is selectively grown, the growth of the (100) crystal orientation is suppressed, and the (111) crystal orientation exposed on the side grows laterally, so that the longer side edges of the spliced ​​M N×1 rectangular first splicing structures are connected together to achieve mosaic splicing, thereby obtaining an M×N second splicing structure. Since there are still diamonds with (100) crystal orientation and diamonds with (111) crystal orientation on the edge of the second splicing structure, and the height of the diamonds grown at the connection between the (110) single crystal epitaxial structures is less than the height of the epitaxial growth in step 2 during the two splicing processes, and the connection between the (110) single crystal epitaxial structures is in a "V" shape, the edge and upper surface of the second splicing structure are laser cut and polished to remove the polycrystalline and uneven areas at the edge of the second splicing structure, and obtain a large-sized diamond (110) single crystal. In an achievable manner, a thickness of 1 mm is cut along the cross section of the second splicing structure.

[0071] The second aspect of this embodiment further provides a large-sized diamond (110) single crystal grown by self-selective lateral growth, which is prepared by the method for preparing a large-sized diamond (110) single crystal grown by self-selective lateral growth provided by the first aspect of this embodiment.

[0072] Embodiment 2

[0073] Based on the first embodiment, this embodiment provides a method for preparing a large-size diamond (110) single crystal by self-selective lateral growth. Figure 7a to Figure 7c , Figure 7a to Figure 7c This is a step structure diagram of a method for preparing a large-size diamond (110) single crystal by self-selective lateral growth provided by an embodiment of the present invention.

[0074] This embodiment provides a method for preparing a large-size diamond (110) single crystal by self-selective lateral growth, comprising the following steps:

[0075] Step 1: Select 9 diamond substrates with (110) crystal orientation on the upper surface, and the size of each diamond substrate is 5mm×5mm×0.5mm. In this embodiment, M and N are both 3. During the selection process, X-ray diffraction is performed on the diamond substrate to ensure that the deflection angle of the upper surface of the diamond substrate is less than 0.5°, and the thickness difference between different diamond substrates is less than 50μm, so as to ensure the interface lattice matching between different substrates at the joint and no twinning. The selected diamond substrates are ultrasonically cleaned for 15 minutes using acetone, ethanol and water respectively to ensure that no impurities are introduced during the growth process of diamond. Furthermore, a crystal orientation meter is used to determine the crystal orientation of the four sides of the diamond substrate and mark them.

[0076] Step 2: Use Shanghai Boshiguang's MPCVD equipment to perform diamond homoepitaxial growth on a diamond substrate. Specifically, a diamond substrate is placed in an MPCVD device, and the cavity pressure is evacuated to 0.001 Torr or less; H2 is introduced into the MPCVD device, and the H2 flow rate is 300 sccm; when the cavity pressure is increased to 15 Torr, a microwave source is turned on and ignited, so that the cavity pressure is increased to 120 Torr, the power is 3200 W, and the substrate surface temperature is 900°C; before growth, the diamond surface is etched for 10 minutes using H plasma, and after the etching is completed, CH4 and O2 are introduced to start growth, with a CH4 flow rate of 12 sccm and an O2 flow rate of 1.5 sccm. The growth is carried out for 20 hours, and a 0.5 mm thick (110) crystal orientation diamond is grown, and at the same time, a pair of opposite side surfaces of the (110) crystal orientation expose the (100) crystal orientation, and another pair of opposite side surfaces expose the (111) crystal orientation, with an overall prism-shaped morphology, to obtain 9 (110) single crystal epitaxial structures. The microwave input frequency of the MPCVD equipment used in this embodiment is 2.45 GHz.

[0077] Step 3: Divide the 9 (110) single crystal epitaxial structures into 3 groups, each group of (110) single crystal epitaxial structures includes 3 (110) single crystal epitaxial structures.

[0078] Step 4: Place the diamond substrate into the MPCVD device so that the side surfaces of the (100) crystal orientation of the three (110) single crystal epitaxial structures in each group are in contact with each other and the side orientations are consistent, such as Figure 7a As shown. The chamber pressure was pumped down to 0.001 Torr or less, and H2 was introduced into the MPCVD device at a flow rate of 300 sccm, raising the chamber pressure to 140 Torr. The power was 4200 W, and the substrate surface temperature was 900°C. CH4 was introduced to start growth, with a CH4 flow rate of 15 sccm, and the growth lasted for 50 hours. Under this condition, the CH group in the MPCVD device occupies a dominant position. The CH group is the main group involved in the reaction during the growth of the (100) crystal direction. At this time, the (100) crystal direction grows sideways. Since the (110) and (100) crystal directions are 45 degrees, the (100) crystal direction grows along <100> While growing vertically in the direction, the (110) crystal orientation joints of two adjacent (110) single crystal epitaxial structures are connected together to obtain three first spliced ​​structures. The unmerged portions on the upper surface of the first spliced ​​structure and the polycrystalline generated by the unjoined edges are removed by laser cutting to avoid the influence of the polycrystalline on the subsequent growth process.

[0079] Step 5: Place the three first spliced ​​structures into the MPCVD device so that the side surfaces of the three first spliced ​​structures in the (111) crystal orientation contact each other, as shown in FIG. Figure 7b As shown. Pump the chamber pressure to 0.001Torr or less, introduce H2 into the MPCVD device with a flow rate of 300sccm, raise the chamber pressure to 100Torr, power to 2500W, substrate surface temperature to 900℃, introduce CH4 to start growth with a flow rate of 1.5sccm, and grow for 50h. In this step, the C2 group in the MPCVD device occupies a dominant position. The C2 group is the main group involved in the reaction during the growth of the (111) crystal direction. At this time, the (111) crystal direction grows sideways. Since the (110) crystal direction is 39.23 degrees from the (111) crystal direction, the (111) crystal direction grows along <111> While the (110) crystal orientation of the first splicing structure grows vertically, the splicing parts of the first splicing structure will be connected together, thereby connecting the three first splicing structures together to form a second splicing structure, such as Figure 7c shown.

[0080] Step 6: The obtained second spliced ​​structure is firstly laser cut to remove the prisms on the surface due to different growth rates, and then cut along the cross section of the (110) crystal direction and finely polished to obtain a large-size diamond (110) single crystal of 15 mm×15 mm.

[0081] Furthermore, by using the large-sized diamond (110) single crystal obtained in step six as the diamond substrate in step one and repeating steps one to six, a larger-sized diamond (110) single crystal can be obtained.

[0082] The method for preparing a large-sized diamond (110) single crystal by self-selective lateral growth provided in this embodiment, through two-step splicing and two-step self-selective lateral growth, splices multiple diamond substrates to form a large-sized diamond (110) single crystal, solves the long-standing problem that (110) crystal orientation diamond substrates cannot achieve enlarged growth, and realizes a high-quality large-sized (110) single crystal diamond substrate. The large-sized substrate is of great significance to improving the performance of (110) crystal orientation diamond devices. In addition, the preparation method provided in this embodiment can be implemented by a simple method in the engineering application and scientific research field of diamond, which provides convenience for obtaining a large-sized (110) diamond substrate. At the same time, the diamond single crystal material prepared by the preparation method provided in this embodiment has fewer defects and higher quality than the diamond prepared by HTHP.

[0083] The above contents are further detailed descriptions of the present invention in combination with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the concept of the present invention, which should be regarded as falling within the protection scope of the present invention.

Claims

1. A method for preparing a large-size diamond (110) single crystal by self-selective lateral growth, characterized in that: The following steps are involved: Selecting X diamond substrates, wherein X=M×N, M and N are both positive integers greater than 1; the upper surface of the diamond substrate is (110) crystal orientation; Growing an epitaxial diamond layer with a (110) crystal orientation on the upper surface of each diamond substrate to obtain X (110) single crystal epitaxial structures; each of the X (110) single crystal epitaxial structures has a side surface with a (100) crystal orientation and a side surface with a (111) crystal orientation; Dividing the X (110) single crystal epitaxial structures into M groups, each group of (110) single crystal epitaxial structures including N (110) single crystal epitaxial structures; Splicing N (110) single crystal epitaxial structures in each group of (110) single crystal epitaxial structures in a first crystal orientation within the group, and growing diamond under growth conditions in the first crystal orientation to obtain M first spliced ​​structures; The M first spliced ​​structures are spliced ​​in a second crystal direction, and diamond is grown under the growth conditions of the second crystal direction to obtain a second spliced ​​structure; the first crystal direction is one of the (100) crystal direction and the (111) crystal direction; the second crystal direction is the other of the (100) crystal direction and the (111) crystal direction; The second spliced ​​structure is post-processed to obtain a large-sized diamond (110) single crystal.

2. The method for preparing a large-size diamond (110) single crystal by self-selective lateral growth according to claim 1, characterized in that: The diamond substrate has a side surface with a (100) crystal orientation and a side surface with a (110) crystal orientation.

3. The method for preparing a large-size diamond (110) single crystal by self-selective lateral growth according to claim 1, characterized in that: The N (110) single crystal epitaxial structures in each group of (110) single crystal epitaxial structures are spliced ​​in the first crystal direction within the group, including: The side surfaces of the N (110) single crystal epitaxial structures in each group of (110) single crystal epitaxial structures in the first crystal direction are in contact with each other and arranged in a straight line.

4. The method for preparing a large-size diamond (110) single crystal by self-selective lateral growth according to claim 1, characterized in that: When the first crystal orientation is (100) and the second crystal orientation is (111), growing diamond under the growth conditions of the first crystal orientation comprises: Using MPCVD equipment, growing diamond with a (100) crystal orientation under growth conditions of a (100) crystal orientation; Growing diamond under the growth conditions of the second crystal direction, comprising: Diamond with (111) crystal orientation is grown under the growth conditions of (111) crystal orientation using MPCVD equipment.

5. The method for preparing a large-size diamond (110) single crystal by self-selective lateral growth according to claim 4, characterized in that: The growth conditions for the (100) orientation include: The pressure is 140-160 Torr, the power is 4000-4200 W, the temperature is 850-950°C, the H2 flow rate is 300-400 sccm, the CH4 flow rate is 12-18 sccm, and the growth time is 40-60 h.

6. The method for preparing a large-size diamond (110) single crystal by self-selective lateral growth according to claim 4, characterized in that: The growth conditions for the (111) orientation include: The pressure is 100-120 Torr, the power is 2000-2300 W, the temperature is 850-950°C, the H2 flow rate is 300-400 sccm, the CH4 flow rate is 2-4 sccm, and the growth time is 40-60 hours.

7. The method for preparing a large-size diamond (110) single crystal by self-selective lateral growth according to claim 1, characterized in that: An epitaxial diamond layer with a (110) crystal orientation is grown on the upper surface of each diamond substrate, comprising: An epitaxial diamond layer with a (110) crystal orientation is grown on the upper surface of each diamond substrate under the growth condition of a (110) crystal orientation using an MPCVD device.

8. The method for preparing a large-size diamond (110) single crystal by self-selective lateral growth according to claim 7, characterized in that: The growth conditions of the (110) crystal orientation include: The pressure is 120-140 Torr, the power is 3200-3600 W, the temperature is 850-950°C, the H2 flow rate is 300-400 sccm, the CH4 flow rate is 10-12 sccm, and the growth time is 10-20 hours.

9. The method for preparing a large-size diamond (110) single crystal by self-selective lateral growth according to claim 1, characterized in that: Post-processing the second spliced ​​structure includes: The edge of the second splicing structure and an upper surface of a preset thickness are removed by laser cutting, and the cut surface is polished.

10. A large-size diamond (110) single crystal grown by self-selective lateral growth, characterized in that: The large-sized diamond (110) single crystal is prepared by the method for preparing the self-selective lateral growth as described in any one of claims 1 to 9.

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