A method for producing a gallium nitride single crystal wafer material using a silicon carbide single crystal substrate

Abstract

The application discloses a method for preparing a gallium nitride single crystal wafer material by using a silicon carbide single crystal substrate, and belongs to the technical field of semiconductor materials. In the material preparation process, a magnetron sputtering process is first adopted to sequentially deposit an aluminum nitride single crystal thin film template layer, a first ultrathin zinc oxide single crystal thin film layer, an ultrathin magnesium single crystal thin film layer, a second ultrathin zinc oxide single crystal thin film layer and an aluminum nitride single crystal thin film nucleation layer on the silicon carbide single crystal substrate. Then, a high-temperature and high-vacuum in-situ annealing is performed to form an ultrathin porous amorphous magnesium-zinc-oxygen weak bonding decoupling layer in the middle. Then, a crack-free low-stress gallium nitride single crystal thin film template layer is obtained through sputtering deposition. Finally, a gallium nitride single crystal thick film epitaxial layer is prepared by using a hydride vapor phase epitaxy, and a self-supporting gallium nitride single crystal wafer material is obtained after cutting, grinding and polishing.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor materials technology, specifically relating to a method for preparing gallium nitride single-crystal wafers using a silicon carbide single-crystal substrate. Background Technology

[0002] Group III gallium nitride (GaN) has a wide bandgap (E g (3.39eV), high breakdown field strength (E) C 3-5 MVcm -1 ), high saturated electron drift rate ( υ sat 2.2×10 7 cms -1 High electron mobility (µ) r Up to 1000-2000 cm tall 2 V -1 s -1 Its excellent properties, such as strong spontaneous polarization and piezoelectric polarization effect, make it very suitable for developing high-performance, high-frequency, high-power electronic devices.

[0003] However, the fabrication of self-supporting gallium nitride (GaN) single-crystal wafers using conventional sapphire (or silicon) single-crystal substrates and hydride vapor phase epitaxy (HVPE) processes requires overcoming the large mismatch heteroepitaxial growth problem, resulting in low material yields and hindering large-scale production. Furthermore, the warping and residual stress in the fabricated GaN single-crystal materials make it difficult to improve the performance of devices fabricated using GaN single-crystal materials as homogeneous substrates. This is the main reason why the use of existing large-size GaN single-crystal wafers as homogeneous substrates for the fabrication of various high-end GaN devices is limited by production capacity and performance constraints, preventing widespread application and promotion.

[0004] Compared to commonly used sapphire and silicon substrates, silicon carbide substrates have more similar in-plane lattice constants and coefficients of thermal expansion to gallium nitride (GaN). However, large-size silicon carbide single-crystal substrates remain expensive, and it is difficult to effectively coordinate large lattice mismatch stresses and thermal mismatch stresses. Furthermore, it is challenging to achieve warp-free, low-stress fabrication of self-supporting GaN single-crystal thick-film materials using the HVPE process, making it difficult to improve the quality and yield of GaN single-crystal materials. To achieve warp-free, low-stress, high-crystal quality, and low-cost fabrication of self-supporting GaN single-crystal thick-film materials, it is necessary to design and fabricate suitable GaN large mismatch stress control structures on silicon carbide substrates, and to develop new methods for achieving complete self-peeling and reuse of silicon carbide substrates. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing gallium nitride (GaN) single-crystal wafers using a silicon carbide single-crystal substrate, thereby addressing the problems of warpage, residual stress, and difficulty in improving material yield and achieving large-scale production in self-supporting GaN single-crystal thick-film materials prepared by the aforementioned HVPE process. The GaN single-crystal wafers prepared by this invention have the advantages of being crack-free, warpage-free, low-stress, and having low dislocation density.

[0006] To achieve the above objectives, the first aspect of the present invention provides a method for preparing gallium nitride single-crystal wafers using a silicon carbide single-crystal substrate, comprising the following steps:

[0007] S1. Place the silicon carbide single crystal substrate, high-purity aluminum metal target, high-purity zinc metal target, high-purity magnesium metal target, and high-purity liquid gallium metal target into the growth chamber of the magnetron sputtering equipment, and evacuate to a pressure not exceeding 5 × 10⁻⁶. -5 Pa;

[0008] S2. Heat the substrate to 1100-1200℃ and bake the surface of the silicon carbide single crystal substrate in a hydrogen atmosphere of 5-50Pa to completely remove the residual oxide layer and adsorbed impurities on the surface.

[0009] S3. Adjust the substrate heating temperature to 750-850℃, use a high-purity aluminum metal target as the target material, high-purity nitrogen as the reaction gas, and high-purity argon as the sputtering gas to sputter and deposit a 100-300nm thick aluminum nitride single crystal thin film template layer on a silicon carbide single crystal substrate.

[0010] S4. Adjust the substrate heating temperature to 500-600℃, use high-purity zinc metal as the target material, high-purity oxygen as the reaction gas, and high-purity argon as the sputtering gas, and sputter deposit a first ultrathin zinc oxide single crystal thin film layer with a thickness of 10-20nm and a single C-axis preferred orientation on the aluminum nitride single crystal thin film template layer.

[0011] S5. Adjust the substrate heating temperature to 500-600℃, use high-purity magnesium metal as the target material and high-purity argon gas as the sputtering gas, and sputter to deposit an ultra-thin magnesium metal single crystal thin film layer with a thickness of 10-40nm and a single C-axis preferred orientation on the first ultra-thin zinc oxide single crystal thin film layer.

[0012] S6. Adjust the substrate heating temperature to 500-600℃, use high-purity zinc metal as the target material, high-purity oxygen as the reaction gas, and high-purity argon as the sputtering gas, and sputter deposit a second ultrathin zinc oxide single crystal thin film layer with a thickness of 10-20nm and a single C-axis preferred orientation on the ultrathin magnesium single crystal thin film layer.

[0013] S7. Adjust the substrate heating temperature to 500-600℃, use a high-purity aluminum target as the target material, high-purity nitrogen as the reaction gas, and high-purity argon as the sputtering gas, and sputter deposit a 100-300nm thick aluminum nitride single crystal thin film nucleation layer with a single C-axis preferred orientation on the second ultrathin zinc oxide single crystal thin film layer.

[0014] S8. Heat the substrate to 700-900℃ and anneal it in a hydrogen atmosphere of 10-100Pa for 0.5-5 hours.

[0015] During the initial heating process, when the heating temperature exceeds the melting point of metallic magnesium, the ultrathin metallic magnesium single crystal film layer melts, and the first and second ultrathin zinc oxide single crystal film layers undergo thermal decomposition. The generated zinc and oxygen atoms diffuse into the middle ultrathin metallic magnesium single crystal film layer. The molten metallic magnesium decomposes into the upper and lower first and second ultrathin zinc oxide single crystal film layers to form nanopores for diffusion. Finally, an ultrathin porous amorphous magnesium-zinc-oxygen weak bond decoupling layer with a magnesium composition that first increases and then decreases is formed, thereby achieving partial weak bond decoupling between the bottom aluminum nitride single crystal film template layer and the top aluminum nitride single crystal film nucleation layer.

[0016] S9. Heat the substrate to 1100-1200℃ and anneal it for 1-10 hours in an ammonia atmosphere at 10-100Pa to fuse and recrystallize the grains in the nucleation layer of the aluminum nitride single crystal film to form a dislocation density not exceeding 1×10⁻⁶. 8 cm -2 Furthermore, a high-quality aluminum nitride single-crystal thin film nucleation layer with a surface flatness of no more than 1.0 nm;

[0017] S10. Adjust the substrate heating temperature to 700-900℃, using high-purity liquid gallium metal as the target, high-purity nitrogen as the reaction gas, and high-purity argon as the sputtering gas, to sputter and deposit a 1000-5000 nm thick layer with a dislocation density not exceeding 5×10⁻⁶ on a high-quality aluminum nitride single-crystal thin film nucleation layer. 8 cm -2 A gallium nitride single-crystal thin film template layer with a surface flatness of no more than 1.0 nm;

[0018] S11. Cool down rapidly to room temperature according to the preset first cooling rate. The thermal mismatch tensile stress generated during the cooling process of the silicon carbide single crystal substrate and gallium nitride single crystal thin film template layer is first transferred to the magnesium composition gradient ultrathin porous amorphous magnesium zinc oxygen weak bond decoupling layer containing nanopores in the middle, and partially released in the high magnesium composition region in the middle. Cool down and take it out to obtain a crack-free low stress gallium nitride single crystal thin film template layer that is partially weakly decoupled from the silicon carbide single crystal substrate.

[0019] S12. A crack-free, low-stress gallium nitride single crystal thin film template layer, which is weakly bonded and decoupled from the silicon carbide single crystal substrate, is placed in the reaction chamber of a hydride vapor phase epitaxy equipment as a gallium nitride homogeneous epitaxial substrate. A gallium nitride single crystal thick film epitaxial layer material with a thickness of 300-3000µm is rapidly epitaxially grown at a growth temperature of 1000-1100℃ using a near-atmospheric pressure hydride vapor phase epitaxy process.

[0020] S13. Cool down rapidly to room temperature according to the preset second cooling rate. The thermal mismatch tensile stress generated during the cooling process of the silicon carbide single crystal substrate and the gallium nitride single crystal thick film epitaxial layer material is first transferred to the magnesium composition gradient ultrathin porous amorphous magnesium zinc oxygen weak bond decoupling layer containing nanopores in the middle, and completely released in the high magnesium composition region in the middle. After cooling, the material is taken out to obtain a crack-free, warp-free, low-stress self-supporting gallium nitride single crystal thick film material that is completely decoupled and self-peeled from the silicon carbide single crystal substrate.

[0021] S14. Crack-free, warp-free, low-stress, self-supporting gallium nitride single-crystal thick film material is cut, ground, and polished to remove the magnesium composition-gradient ultrathin porous amorphous magnesium-zinc-oxygen weak bonding decoupling layer containing nanopores on the back side, the aluminum nitride single-crystal thin film nucleation layer, and the gallium nitride single-crystal thin film epitaxial layer with high defect density, as well as part of the gallium nitride single-crystal thick film epitaxial layer material, to obtain multiple wafers with a thickness of not less than 200µm and a dislocation density of not more than 1×10⁻⁶. 6 cm -2 A crack-free, warp-free, low-stress, self-supporting gallium nitride single-crystal material with a surface roughness of no more than 0.5 nm;

[0022] S15. After rinsing the self-peeled silicon carbide single crystal substrate in a dilute hydrofluoric acid solution or baking it in a high-temperature, high-vacuum baking furnace with hydrogen chloride or chlorine gas to completely remove the residual magnesium component on the surface, the gradient ultrathin porous amorphous magnesium zinc oxygen weak bond decoupling layer is placed in the growth chamber of the magnetron sputtering equipment, and steps S3 to S14 are repeated to realize the reuse of silicon carbide single crystal substrate and the preparation of self-supporting gallium nitride single crystal wafer material.

[0023] Conventional gallium nitride (GaN) single-crystal thick films prepared using sapphire substrates and hydride vapor phase epitaxy processes suffer from defects such as warpage and high stress in GaN single-crystal wafers obtained by cutting, grinding, and polishing sapphire substrates. Compared to the conventional simple silicon carbide substrate GaN large mismatch stress control structure, which only prepares a single aluminum nitride single-crystal thin film strongly bonded to a silicon carbide single-crystal substrate as a nucleation layer, buffer layer, template layer, and stress covariance layer, the GaN large mismatch stress control structure designed and prepared in this invention includes upper and lower aluminum nitride single-crystal thin film nucleation layers and an aluminum nitride single-crystal thin film template layer, with an intermediate ultrathin porous amorphous magnesium-zinc-oxygen weakly bonded decoupling layer containing nanopores and exhibiting a magnesium composition that first increases and then decreases. Because the upper weakly bonded decoupled aluminum nitride single-crystal thin film nucleation layer undergoes high-temperature, high-vacuum annealing, it has higher crystal quality, which is more conducive to reducing the large lattice mismatch stress and dislocation density of the GaN single-crystal thin film or GaN single-crystal thick film prepared on it.

[0024] Furthermore, the in-plane thermal expansion coefficient of zinc oxide (C-plane) is 6.5 × 10⁻⁶. -6 K -1 The coefficient of thermal expansion of magnesium oxide is 9.84 × 10⁻⁶. -6 K -1 The coefficient of thermal expansion of the magnesium zinc oxide film is between the two, compared to the silicon carbide single crystal substrate (4.3×10⁻⁶). -6 K -1 ) and gallium nitride epitaxial layer (5.59×10 -6 K -1 The larger temperature of the gallium nitride (GaN) single-crystal thin film or thick GaN single-crystal epitaxial layer facilitates the significant cooling process during fabrication. This allows the high thermal stress generated by the bottom silicon carbide (SiC) single-crystal substrate and the upper GaN epitaxial layer to be transferred first to the ultrathin porous amorphous magnesium-zinc oxide (MgZO) film layer with a gradually varying magnesium composition. Finally, the stress is concentrated in the central region with the highest magnesium concentration and the largest coefficient of thermal expansion, where it is partially or completely released. If the thickness of the subsequently fabricated thick GaN single-crystal epitaxial layer is not less than that of the SiC single-crystal substrate, the accumulated even greater thermal mismatch stress will be released in the ultrathin porous amorphous MgZO weakly bonded decoupling layer in the region with the highest magnesium composition. This will exacerbate the fragmentation of the ultrathin porous amorphous MgZO film layer at that location, leading to complete decoupling and self-peeling of the upper and lower layers.

[0025] This invention employs a reactive pulsed DC magnetron sputtering process, which is more conducive to the high-temperature single-crystal preparation and growth of aluminum nitride thin film materials, to first prepare a high-crystal-quality aluminum nitride single-crystal thin film template layer. Then, using the high-crystal-quality aluminum nitride single-crystal thin film as the template layer, a medium-low temperature pulsed DC magnetron sputtering process can be used to sequentially prepare and grow high-crystal-quality single crystals of ultrathin zinc oxide single-crystal thin film layers (first ultrathin zinc oxide single-crystal thin film layer and second ultrathin zinc oxide single-crystal thin film layer), ultrathin magnesium single-crystal thin film layer, and aluminum nitride single-crystal thin film nucleation layer. Subsequent heating and high-temperature high-vacuum annealing in a hydrogen atmosphere can further reduce limitations... The thermal decomposition of the ultrathin zinc oxide single crystal film between the upper and lower aluminum nitride single crystal film layers produces zinc and oxygen atoms, while the ultrathin metallic magnesium single crystal film (metallic magnesium melting point 648.8℃) melts and transforms into a liquid state. The zinc and oxygen components produced by thermal decomposition diffuse into the middle liquid ultrathin metallic magnesium film layer and undergo an alloying reaction, thus forming an upper and lower ultrathin porous zinc oxide film layer structure containing nanopores. The magnesium component in the liquid ultrathin metallic magnesium film layer also diffuses into the nanopores in the upper and lower ultrathin porous zinc oxide film layers and undergoes an alloying reaction, thus forming an ultrathin porous amorphous magnesium-zinc-oxygen weak bond decoupling layer in the middle. Using this ultrathin porous amorphous magnesium zinc oxide film as a weak bonding decoupling layer not only further improves the crystal quality of the aluminum nitride single crystal film nucleation layer in the weak bonding decoupling process during subsequent high-temperature and high-vacuum annealing in an ammonia atmosphere, but also more effectively coordinates and transfers the large thermal mismatch stress generated during the significant cooling process of gallium nitride single crystal films or gallium nitride single crystal thick epitaxial layers after material preparation. This large mismatch thermal stress is concentrated in the ultrathin porous amorphous magnesium zinc oxide film layer in the region where the magnesium composition gradually changes and the magnesium composition concentration is the highest, which is more conducive to promoting decoupling and reducing large mismatch stress. This enables the preparation of gallium nitride single crystal films and gallium nitride single crystal thick films with low stress, free from cracks and warping. By controlling the cooling rate, it is also beneficial to achieve complete self-peeling of gallium nitride single crystal thick film materials from silicon carbide single crystal substrates, thereby enabling the reuse of silicon carbide single crystal substrates.

[0026] Preferably, the thickness of the silicon carbide single crystal substrate in step S1 is 300-1000 μm.

[0027] Preferably, in step S1, the crystal structure of the silicon carbide single crystal substrate is one of 3C-SiC, 4H-SiC, and 6H-SiC, and the diameter of the silicon carbide single crystal substrate is one of 2 inches, 4 inches, 6 inches, and 8 inches.

[0028] The crystal structure and size of the silicon carbide single crystal substrate in this invention are not limited to the above-mentioned types.

[0029] Preferably, the thickness of the ultrathin magnesium single crystal film layer in step S5 is no greater than the sum of the thickness of the first ultrathin zinc oxide single crystal film layer in step S4 and the thickness of the second ultrathin zinc oxide single crystal film layer in step S6.

[0030] Preferably, the first cooling rate in step S11 is not less than 10°C / min.

[0031] Preferably, the second cooling rate in step S13 is not less than 15°C / min.

[0032] Preferably, the baking parameters for the silicon carbide single crystal substrate in step S15 are: temperature 1100-1200℃, vacuum degree 5-50Pa.

[0033] A second aspect of the present invention provides a gallium nitride single-crystal material, which is prepared by the above-described preparation method.

[0034] The third aspect of the present invention provides an application of gallium nitride single-crystal material, which is used as a homogeneous substrate in the development and production of gallium nitride-based power electronic devices, gallium nitride-based microwave radio frequency devices, gallium nitride-based light-emitting diode devices, gallium nitride-based laser diode devices, and gallium nitride-based ultraviolet detectors.

[0035] Therefore, the present invention employs the above-described method for preparing gallium nitride single-crystal wafers using a silicon carbide single-crystal substrate, which has the following beneficial effects:

[0036] 1. This invention utilizes a first ultrathin zinc oxide single crystal thin film layer, an ultrathin magnesium single crystal thin film layer, and a second ultrathin zinc oxide single crystal thin film layer to form a gradually decreasing magnesium composition ultrathin porous amorphous magnesium-zinc-oxygen weak bonding decoupling layer during the heating process. Using this ultrathin porous amorphous magnesium-zinc-oxygen film layer as a weak bonding decoupling layer not only helps to further improve the crystallization quality of the aluminum nitride single crystal thin film nucleation layer, but also can more effectively coordinate the transfer of large thermal mismatch tensile stress generated by the significant cooling during the material preparation process of gallium nitride single crystal thin film or gallium nitride single crystal thick film epitaxial layer, thus realizing the preparation of gallium nitride single crystal thin film and gallium nitride single crystal thick film without cracks, warping, and low stress.

[0037] 2. This invention achieves complete self-peeling of gallium nitride single-crystal thick film material from silicon carbide single-crystal substrate by controlling the cooling rate. The silicon carbide single-crystal substrate can be reused, which not only reduces production costs but also eliminates the need for laser peeling to remove the silicon carbide single-crystal substrate, thereby improving the efficiency and yield of the entire material preparation process.

[0038] 3. The gallium nitride single-crystal material prepared by this invention is suitable for various gallium nitride-based device applications. For example, it can be used as a homogeneous substrate to develop and produce power electronic devices, microwave radio frequency devices, light-emitting diode (LED) devices, laser diode (LD) devices, and ultraviolet detectors. This versatility provides a solid foundation for the future development of gallium nitride-based electronic and optoelectronic devices, promoting the development of numerous new technologies.

[0039] The technical solution of the present invention will be further described in detail below through embodiments. Attached Figure Description

[0040] Figure 1 This is a diagram of the material structure prepared in steps S1-S11 of the present invention;

[0041] Figure 2 This is a diagram of the material structure prepared in steps S1-S7 of the present invention;

[0042] Figure 3 This is a diagram of the material structure prepared in steps S1-S9 of the present invention;

[0043] Figure 4 This is a structural diagram of the material prepared before cooling in steps S1-S13 of the present invention;

[0044] Figure 5 This is a structural diagram of the material prepared after cooling in steps S1-S13 of the present invention.

[0045] Figure 6 The self-supporting gallium nitride single-crystal material prepared in step S14 of this invention;

[0046] In the figure: 101, silicon carbide single crystal substrate; 2011, aluminum nitride single crystal thin film template layer; 2021, first ultrathin zinc oxide single crystal thin film layer; 2022, ultrathin magnesium single crystal thin film layer; 2023, second ultrathin zinc oxide single crystal thin film layer; 2031, aluminum nitride single crystal thin film nucleation layer; 201, high-quality aluminum nitride single crystal thin film template layer; 202, magnesium composition graded ultrathin porous amorphous magnesium-zinc-oxygen weak bonding decoupling layer; 203, high-quality aluminum nitride single crystal thin film nucleation layer; 301, crack-free, low-stress gallium nitride single crystal thin film template layer; 4011, gallium nitride single crystal thick film epitaxial layer; 401, crack-free, warp-free, low-stress self-supporting gallium nitride single crystal thick film material; 402 is crack-free, warp-free, low-stress self-supporting gallium nitride single crystal wafer material. Detailed Implementation

[0047] The present invention will be further described below. It should be noted that this embodiment is based on the present technical solution and provides detailed implementation methods and specific operation processes, but the present invention is not limited to this embodiment.

[0048] Example 1

[0049] This embodiment provides a method for preparing gallium nitride single-crystal wafers using a 4-inch 3C-SiC single-crystal substrate, such as... Figure 1 , Figure 2 , Figure 3 and Figure 4 As shown, it includes the following steps:

[0050] S1. Place a 500µm thick 4-inch 3C-SiC single crystal substrate 101, high-purity aluminum metal target, high-purity zinc metal target, high-purity magnesium metal target, and high-purity liquid gallium metal target into the growth chamber of the pulsed DC magnetron sputtering equipment, and evacuate to a pressure of 1×10⁻⁶. -5 Ultra-high vacuum of Pa;

[0051] S2. The substrate temperature is raised to 1200℃, and the surface of the 4-inch 3C-SiC single crystal substrate is baked at high temperature and high vacuum under a 10Pa hydrogen atmosphere to completely remove the residual oxide layer and adsorbed impurities on the surface.

[0052] S3. Adjust the substrate heating temperature to 800℃, use a high-purity aluminum metal target as the target material, high-purity nitrogen as the reaction gas, and high-purity argon as the sputtering gas, and use reactive pulse DC magnetron sputtering single target sputtering to deposit a 200nm thick aluminum nitride single crystal thin film template layer on a 4-inch 3C-SiC single crystal substrate.

[0053] S4. Adjust the substrate heating temperature to 600℃, use high-purity zinc metal as the target material, high-purity oxygen as the reaction gas, and high-purity argon as the sputtering gas, and use reactive pulse DC magnetron sputtering single-target sputtering to deposit a 20nm thick first ultrathin zinc oxide single crystal thin film layer 2021 with a single C-axis preferred orientation on the aluminum nitride single crystal thin film template layer 2011.

[0054] S5. Adjust the substrate heating temperature to 550℃, use high-purity metallic magnesium as the target material and high-purity argon as the sputtering gas, and use pulsed DC magnetron sputtering single-target sputtering to deposit a 10nm thick ultrathin metallic magnesium single crystal thin film layer 2022 with a single C-axis preferred orientation on the first ultrathin zinc oxide single crystal thin film layer 2021.

[0055] S6. Adjust the substrate heating temperature to 600℃, use high-purity zinc metal as the target material, high-purity oxygen as the reaction gas, and high-purity argon as the sputtering gas, and use reactive pulse DC magnetron sputtering to deposit a second ultrathin zinc oxide single crystal thin film layer 2023 with a thickness of 20nm and a single C-axis preferred orientation on the ultrathin magnesium single crystal thin film layer 2022.

[0056] S7. Adjust the substrate heating temperature to 650℃, use a high-purity aluminum target as the target material, high-purity nitrogen as the reaction gas, and high-purity argon as the sputtering gas, and use reactive pulse DC magnetron sputtering to deposit a 200nm thick aluminum nitride single crystal thin film nucleation layer 2031 with a single C-axis preferred orientation on the second ultrathin zinc oxide single crystal thin film layer 2023.

[0057] S8. Heat the substrate to 900°C and perform high-temperature, high-vacuum annealing for 2 hours under a hydrogen atmosphere pressure of 50Pa.

[0058] During the initial heating process, when the heating temperature is higher than the melting point of metallic magnesium, the middle ultrathin metallic magnesium single crystal film layer first melts into a liquid state. As the temperature continues to rise, the upper and lower first ultrathin zinc oxide single crystal film layers and the second ultrathin zinc oxide single crystal film layer thermally decompose to form nanopores. The generated zinc atoms and oxygen atoms diffuse into the middle liquid ultrathin metallic magnesium film layer, while the liquid metallic magnesium diffuses into the nanopores formed in the upper and lower first ultrathin zinc oxide single crystal film layers and the second ultrathin zinc oxide single crystal film layer, resulting in an alloying reaction. In the middle, a 50nm thick ultrathin porous amorphous magnesium-zinc-oxygen weak bond decoupling layer 202 with a magnesium composition that first increases and then decreases is formed, and the weak bond decoupling between the bottom aluminum nitride single crystal film template layer 2011 and the top aluminum nitride single crystal film template layer 2031 is realized.

[0059] S9. The substrate temperature is raised to 1100℃, and high-temperature high-vacuum annealing is performed for 2 hours under an ammonia atmosphere pressure of 50Pa. The crystal quality of the bottom aluminum nitride single crystal thin film template layer 2011 is improved, transforming it into a high-quality aluminum nitride single crystal thin film template layer 201. The grains in the top aluminum nitride single crystal thin film nucleation layer 2031 fuse, recrystallize, and form a dislocation density of 1×10⁻⁶. 8 cm -2 Furthermore, a high-quality aluminum nitride single-crystal thin film nucleation layer 203 with a surface flatness of no more than 1.0 nm and higher crystal quality;

[0060] S10. Adjust the substrate heating temperature to 800℃, using high-purity liquid gallium metal as the target, high-purity nitrogen as the reaction gas, and high-purity argon as the sputtering gas, and perform reactive pulsed DC magnetron sputtering to deposit a 3000nm thick layer with a dislocation density of 5×10⁻⁶ on the aluminum nitride single crystal thin film nucleation layer 203 with higher crystal quality. 8 cm -2 A gallium nitride single-crystal thin film template layer with a surface flatness of 1.0 nm;

[0061] S11. Adjust the first cooling rate to 10℃ / min to rapidly cool down to room temperature. The thermal mismatch stress generated during the cooling process of the 4-inch 3C-SiC single crystal substrate 101 and the gallium nitride single crystal thin film template layer is first transferred to the magnesium composition gradient ultrathin porous amorphous magnesium zinc oxygen weak bonding decoupling layer 202 containing nanopores in the middle and released in the magnesium zinc oxygen film layer with the highest magnesium composition concentration in the middle. After cooling down, the crack-free low-stress gallium nitride single crystal thin film template layer 301 that is weakly bonded and decoupled from the 4-inch 3C-SiC single crystal substrate is obtained.

[0062] S12. The crack-free, low-stress gallium nitride single crystal thin film template layer 301, which is weakly bonded and decoupled from the 4-inch 3C-SiC single crystal substrate, is placed in the reaction chamber of the hydride vapor phase epitaxy equipment as a homogeneous epitaxial substrate. A 2000µm thick gallium nitride single crystal thick film epitaxial layer 4011 is rapidly epitaxially grown at a growth temperature of 1050℃ using a near-atmospheric pressure hydride vapor phase epitaxy process.

[0063] S13. Adjust the second cooling rate to 15℃ / min to rapidly cool down to room temperature. The thermal mismatch tensile stress generated during the cooling process of the 4-inch 3C-SiC single crystal substrate 101 and the gallium nitride single crystal thick film epitaxial layer material 4011 is first transferred to the magnesium composition gradient ultrathin porous amorphous magnesium zinc oxygen weak bonding decoupling layer 202 containing nanopores in the middle, and is concentrated in the magnesium zinc oxygen film layer with the highest magnesium composition in the middle to release. After cooling, the material is taken out to obtain the crack-free, warp-free, low-stress self-supporting gallium nitride single crystal thick film material 401 that is completely decoupled and self-peeled from the 4-inch 3C-SiC single crystal substrate 101.

[0064] S14. The self-peeled, crack-free, warp-free, low-stress, self-supporting gallium nitride single-crystal thick film material 401 is cut, ground, and polished to remove the magnesium composition gradient ultrathin porous amorphous magnesium-zinc-oxygen weak bonding decoupling layer 202 containing nanopores on the back side, the aluminum nitride single-crystal thin film nucleation layer 203, the gallium nitride single-crystal thin film template layer 301 with high defect density, and part of the gallium nitride single-crystal thick film epitaxial layer 401, thus obtaining 3 pieces with a thickness of 500µm and a dislocation density of 1×10⁻⁶. 6 cm -2 A crack-free, warp-free, low-stress, self-supporting gallium nitride single crystal 402 with a surface roughness of 0.5nm;

[0065] S15. The self-peeled 4-inch 3C-SiC single crystal substrate is placed in a high-temperature, high-vacuum baking oven filled with hydrogen chloride gas and baked completely at 1100°C. After removing the residual ultrathin porous amorphous magnesium-zinc-oxygen weak bonding decoupling layer 202 on the surface, it is placed in the growth chamber of a pulsed DC magnetron sputtering device. Steps S4 to S14 are repeated to achieve the low-cost fabrication of a reusable 4-inch 3C-SiC single crystal substrate and a self-supporting gallium nitride single crystal wafer 402.

[0066] Gallium nitride-based power electronic devices were developed and manufactured using a 4-inch self-supporting gallium nitride single-crystal 402 as a homogeneous substrate.

[0067] Example 2

[0068] This embodiment provides a method for preparing gallium nitride single-crystal wafers using a 6-inch 4H-SiC single-crystal substrate, such as... Figure 1 , Figure 2 , Figure 3 and Figure 4 As shown, it includes the following steps:

[0069] S1. Place a 500µm thick 6-inch 4H-SiC single crystal substrate 101, high-purity aluminum metal target, high-purity zinc metal target, high-purity magnesium metal target, and high-purity liquid gallium metal target into the growth chamber of the pulsed DC magnetron sputtering equipment, and evacuate to a pressure of 1×10⁻⁶. -5 Ultra-high vacuum of Pa;

[0070] S2. The substrate temperature is raised to 1200℃, and the surface of the 6-inch 4H-SiC single crystal substrate is baked at high temperature and high vacuum under a 10Pa hydrogen atmosphere to completely remove the residual oxide layer and adsorbed impurities on the surface.

[0071] S3. Adjust the substrate heating temperature to 800℃, use a high-purity aluminum metal target as the target material, high-purity nitrogen as the reaction gas, and high-purity argon as the sputtering gas, and use reactive pulse DC magnetron sputtering single target sputtering to deposit a 300nm thick aluminum nitride single crystal thin film template layer on a 6-inch 4H-SiC single crystal substrate.

[0072] S4. Adjust the substrate heating temperature to 600℃, use high-purity zinc metal as the target material, high-purity oxygen as the reaction gas, and high-purity argon as the sputtering gas, and use reactive pulse DC magnetron sputtering single-target sputtering to deposit a 20nm thick first ultrathin zinc oxide single crystal thin film layer 2021 with a single C-axis preferred orientation on the aluminum nitride single crystal thin film template layer 2011.

[0073] S5. Adjust the substrate heating temperature to 550℃, use high-purity metallic magnesium as the target material and high-purity argon as the sputtering gas, and use pulsed DC magnetron sputtering single-target sputtering to deposit a 20nm thick ultrathin metallic magnesium single crystal thin film layer 2022 with a single C-axis preferred orientation on the first ultrathin zinc oxide single crystal thin film layer 2021.

[0074] S6. Adjust the substrate heating temperature to 600℃, use high-purity zinc metal as the target material, high-purity oxygen as the reaction gas, and high-purity argon as the sputtering gas, and use reactive pulse DC magnetron sputtering to deposit a second ultrathin zinc oxide single crystal thin film layer 2023 with a thickness of 20nm and a single C-axis preferred orientation on the ultrathin magnesium single crystal thin film layer 2022.

[0075] S7. Adjust the substrate heating temperature to 650℃, use a high-purity aluminum metal target as the target material, high-purity nitrogen as the reaction gas, and high-purity argon as the sputtering gas, and use reactive pulse DC magnetron sputtering to deposit a 300nm thick aluminum nitride single crystal thin film nucleation layer 2031 with a single C-axis preferred orientation on the second ultrathin zinc oxide single crystal thin film layer 2023.

[0076] S8. Heat the substrate to 900°C and perform high-temperature, high-vacuum annealing for 3 hours under a hydrogen atmosphere pressure of 50Pa.

[0077] During the initial heating process, when the heating temperature is higher than the melting point of metallic magnesium, the middle ultrathin metallic magnesium single crystal film layer first melts into a liquid state. As the temperature continues to rise, the upper and lower first ultrathin zinc oxide single crystal film layers and the second ultrathin zinc oxide single crystal film layer thermally decompose to form nanopores. The generated zinc atoms and oxygen atoms diffuse into the middle liquid ultrathin metallic magnesium film layer, while the liquid metallic magnesium diffuses into the nanopores formed in the upper and lower first ultrathin zinc oxide film layers and the second ultrathin zinc oxide film layer, resulting in an alloying reaction. A 60nm thick ultrathin porous amorphous magnesium-zinc-oxygen weak bond decoupling layer 202 with a magnesium composition that first increases and then decreases is formed in the middle, and the weak bond decoupling between the bottom aluminum nitride single crystal film template layer 2011 and the top aluminum nitride single crystal film template layer 2031 is realized.

[0078] S9. The substrate temperature is raised to 1100℃, and high-temperature high-vacuum annealing is performed for 3 hours under an ammonia atmosphere pressure of 50Pa. The crystal quality of the bottom aluminum nitride single crystal thin film template layer 2011 is improved, transforming it into a high-quality aluminum nitride single crystal thin film template layer 201. The grains in the top aluminum nitride single crystal thin film nucleation layer 2031 fuse, recrystallize, and form a dislocation density of 5×10⁻⁶. 7 cm -2 A higher crystal quality aluminum nitride single crystal thin film nucleation layer 203 with a surface flatness of no more than 1.0 nm;

[0079] S10. Adjust the substrate heating temperature to 800℃, and use high-purity liquid gallium metal as the target, high-purity nitrogen as the reaction gas, and high-purity argon as the sputtering gas to deposit a 5000nm thick layer with a dislocation density of 1×10⁻⁶ on the aluminum nitride single crystal thin film nucleation layer 203 with higher crystal quality by reactive pulsed DC magnetron sputtering. 8 cm -2 A gallium nitride single-crystal thin film template layer with a surface flatness of 1.0 nm;

[0080] S11. Adjust the first cooling rate to 10℃ / min to rapidly cool down to room temperature. The thermal mismatch stress generated during the cooling process of the 6-inch 4H-SiC single crystal substrate 101 and the gallium nitride single crystal thin film template layer is first transferred to the magnesium composition gradient ultrathin porous amorphous magnesium zinc oxygen weak bonding decoupling layer 202 containing nanopores in the middle, and is released in the magnesium zinc oxygen film layer with the highest magnesium composition concentration in the middle. After cooling down, the crack-free low-stress gallium nitride single crystal thin film template layer 301 that is weakly bonded and decoupled from the 6-inch 4H-SiC single crystal substrate 101 is obtained.

[0081] S12. The crack-free, low-stress gallium nitride single crystal thin film template layer 301, which is weakly bonded and decoupled from the 6-inch 4H-SiC single crystal substrate, is placed in the reaction chamber of the hydride vapor phase epitaxy equipment as a homogeneous epitaxial substrate. A 3000µm thick gallium nitride single crystal thick film epitaxial layer 4011 is rapidly epitaxially grown at a growth temperature of 1050℃ using a near-atmospheric pressure hydride vapor phase epitaxy process.

[0082] S13. Adjust the second cooling rate to 15℃ / minute to rapidly cool down to room temperature. The thermal mismatch stress generated during the cooling process of the 6-inch 4H-SiC single crystal substrate 101 and the gallium nitride single crystal thick film epitaxial layer material 4011 is first transferred to the magnesium composition gradient ultrathin porous amorphous magnesium zinc oxygen weak bonding decoupling layer 202 containing nanopores in the middle and concentrated in the magnesium zinc oxygen film layer with the highest magnesium composition in the middle. After cooling, the material is taken out to obtain the crack-free, warp-free, low-stress self-supporting gallium nitride single crystal thick film material 401 that is completely decoupled and self-peeled from the 6-inch 4H-SiC single crystal substrate.

[0083] S14. The self-peeled, crack-free, warp-free, low-stress, self-supporting gallium nitride single-crystal thick film material 401 is cut, ground, and polished to remove the back side containing nanopores, the magnesium composition gradient ultrathin porous amorphous magnesium-zinc-oxygen weak bonding decoupling layer 202, the aluminum nitride single-crystal thin film nucleation layer 203, the gallium nitride single-crystal thin film template layer 301 with high defect density, and part of the gallium nitride single-crystal thick film epitaxial layer 401, resulting in 5 wafers with a thickness of 500µm and a dislocation density of 5×10⁻⁶. 5 cm -2 A crack-free, warp-free, low-stress, self-supporting gallium nitride single crystal 402 with a surface roughness of 0.5nm;

[0084] S15. After rinsing the self-peeled 6-inch 4H-SiC single crystal substrate in a dilute hydrofluoric acid solution to completely remove the residual ultrathin porous amorphous magnesium zinc oxygen weak bond decoupling layer 202 on the surface, dry it, and then place it in the growth chamber of a pulsed DC magnetron sputtering equipment. Repeat steps S4 to S14 to achieve the low-cost fabrication of 6-inch 4H-SiC single crystal substrates that can be reused and self-supporting gallium nitride single wafers 402.

[0085] Gallium nitride-based laser diode devices were fabricated using the aforementioned 6-inch self-supporting gallium nitride single wafer as a homogeneous substrate.

[0086] Therefore, the present invention employs the above-mentioned method for preparing gallium nitride single crystal wafers using silicon carbide single crystal substrates. The resulting gallium nitride single crystal wafers have advantages such as no cracks, no warping, low stress, and low dislocation density, and can be applied to the research and development and production of gallium nitride-based electronic and optoelectronic devices.

[0087] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for preparing gallium nitride single-crystal wafers using a silicon carbide single-crystal substrate, characterized in that, Includes the following steps: S1. Place the silicon carbide single crystal substrate, high-purity aluminum metal target, high-purity zinc metal target, high-purity magnesium metal target, and high-purity liquid gallium metal target into the growth chamber of the magnetron sputtering equipment, and evacuate to a pressure not exceeding 5 × 10⁻⁶. -5 Pa; S2. Heat the substrate to 1100-1200℃ and bake the surface of the silicon carbide single crystal substrate in a hydrogen atmosphere of 5-50Pa to completely remove the residual oxide layer and adsorbed impurities on the surface. S3. Adjust the substrate heating temperature to 750-850℃, use a high-purity aluminum metal target as the target material, high-purity nitrogen as the reaction gas, and high-purity argon as the sputtering gas to sputter and deposit a 100-300nm thick aluminum nitride single crystal thin film template layer on a silicon carbide single crystal substrate. S4. Adjust the substrate heating temperature to 500-600℃, use high-purity zinc metal as the target material, high-purity oxygen as the reaction gas, and high-purity argon as the sputtering gas, and sputter deposit a first ultrathin zinc oxide single crystal thin film layer with a thickness of 10-20nm and a single C-axis preferred orientation on the aluminum nitride single crystal thin film template layer. S5. Adjust the substrate heating temperature to 500-600℃, use high-purity magnesium metal as the target material and high-purity argon gas as the sputtering gas, and sputter to deposit an ultra-thin magnesium metal single crystal thin film layer with a thickness of 10-40nm and a single C-axis preferred orientation on the first ultra-thin zinc oxide single crystal thin film layer. S6. Adjust the substrate heating temperature to 500-600℃, use high-purity zinc metal as the target material, high-purity oxygen as the reaction gas, and high-purity argon as the sputtering gas, and sputter deposit a second ultrathin zinc oxide single crystal thin film layer with a thickness of 10-20nm and a single C-axis preferred orientation on the ultrathin magnesium single crystal thin film layer. S7. Adjust the substrate heating temperature to 500-600℃, use a high-purity aluminum target as the target material, high-purity nitrogen as the reaction gas, and high-purity argon as the sputtering gas, and sputter deposit a 100-300nm thick aluminum nitride single crystal thin film nucleation layer with a single C-axis preferred orientation on the second ultrathin zinc oxide single crystal thin film layer. S8. Heat the substrate to 700-900℃ and anneal it in a hydrogen atmosphere of 10-100Pa for 0.5-5 hours. During the initial heating process, when the heating temperature exceeds the melting point of metallic magnesium, the ultrathin metallic magnesium single crystal film layer melts, and the first and second ultrathin zinc oxide single crystal film layers undergo thermal decomposition. The generated zinc and oxygen atoms diffuse into the middle ultrathin metallic magnesium single crystal film layer. The molten metallic magnesium decomposes into the upper and lower first and second ultrathin zinc oxide single crystal film layers to form nanopores for diffusion. Finally, an ultrathin porous amorphous magnesium-zinc-oxygen weak bond decoupling layer with a magnesium composition that first increases and then decreases is formed, thereby achieving partial weak bond decoupling between the bottom aluminum nitride single crystal film template layer and the top aluminum nitride single crystal film nucleation layer. S9. Heat the substrate to 1100-1200℃ and anneal it for 1-10 hours in an ammonia atmosphere at 10-100Pa to fuse and recrystallize the grains in the nucleation layer of the aluminum nitride single crystal film to form a dislocation density not exceeding 1×10⁻⁶. 8 cm -2 Furthermore, a high-quality aluminum nitride single-crystal thin film nucleation layer with a surface flatness of no more than 1.0 nm; S10. Adjust the substrate heating temperature to 700-900℃, using high-purity liquid gallium metal as the target, high-purity nitrogen as the reaction gas, and high-purity argon as the sputtering gas, to sputter and deposit a 1000-5000 nm thick layer with a dislocation density not exceeding 5×10⁻⁶ on a high-quality aluminum nitride single-crystal thin film nucleation layer. 8 cm -2 A gallium nitride single-crystal thin film template layer with a surface flatness of no more than 1.0 nm; S11. Rapidly cool to room temperature according to the preset first cooling rate. The thermal mismatch tensile stress generated during the cooling process of the silicon carbide single crystal substrate and gallium nitride single crystal thin film template layer is first transferred to the magnesium composition-gradient ultrathin porous amorphous magnesium-zinc-oxygen weak bond decoupling layer containing nanopores in the middle, and partially released in the high magnesium composition region in the middle. Cool down and remove to obtain a crack-free, low-stress gallium nitride single crystal thin film template layer that is partially weakly decoupled from the silicon carbide single crystal substrate; the first cooling rate is not less than 10℃ / min. S12. A crack-free, low-stress gallium nitride single crystal thin film template layer, which is weakly bonded and decoupled from the silicon carbide single crystal substrate, is placed in the reaction chamber of a hydride vapor phase epitaxy equipment as a gallium nitride homogeneous epitaxial substrate. A gallium nitride single crystal thick film epitaxial layer material with a thickness of 300-3000µm is rapidly epitaxially grown at a growth temperature of 1000-1100℃ using a near-atmospheric pressure hydride vapor phase epitaxy process. S13. Rapidly cool to room temperature according to the preset second cooling rate. The thermal mismatch tensile stress generated during the cooling process of the silicon carbide single crystal substrate and the gallium nitride single crystal thick film epitaxial layer material is first transferred to the magnesium composition gradient ultrathin porous amorphous magnesium zinc oxygen weak bonding decoupling layer containing nanopores in the middle, and completely released in the middle high magnesium composition region. After cooling, the material is removed to obtain a crack-free, warp-free, low-stress self-supporting gallium nitride single crystal thick film material that is completely decoupled and self-peeled from the silicon carbide single crystal substrate; the second cooling rate is not less than 15℃ / min. S14. Crack-free, warp-free, low-stress, self-supporting gallium nitride single-crystal thick film material is cut, ground, and polished to remove the magnesium composition-gradient ultrathin porous amorphous magnesium-zinc-oxygen weak bonding decoupling layer containing nanopores on the back side, the aluminum nitride single-crystal thin film nucleation layer, and the gallium nitride single-crystal thin film epitaxial layer with high defect density, as well as part of the gallium nitride single-crystal thick film epitaxial layer material, to obtain multiple wafers with a thickness of not less than 200µm and a dislocation density of not more than 1×10⁻⁶. 6 cm -2 A crack-free, warp-free, low-stress, self-supporting gallium nitride single-crystal material with a surface roughness of no more than 0.5 nm; S15. After rinsing the self-peeled silicon carbide single crystal substrate in a dilute hydrofluoric acid solution or baking it in a high-temperature, high-vacuum baking furnace with hydrogen chloride or chlorine gas to completely remove the residual magnesium component on the surface, the gradient ultrathin porous amorphous magnesium zinc oxygen weak bond decoupling layer is placed in the growth chamber of the magnetron sputtering equipment, and steps S3 to S14 are repeated to realize the reuse of silicon carbide single crystal substrate and the preparation of self-supporting gallium nitride single crystal wafer material.

2. The method for preparing gallium nitride single-crystal wafers using a silicon carbide single-crystal substrate according to claim 1, characterized in that, In step S1, the thickness of the silicon carbide single crystal substrate is 300-1000 μm.

3. The method for preparing gallium nitride single-crystal wafers using a silicon carbide single-crystal substrate according to claim 1, characterized in that, In step S1, the crystal structure of the silicon carbide single crystal substrate is one of 3C-SiC, 4H-SiC, and 6H-SiC, and the diameter of the silicon carbide single crystal substrate is one of 2 inches, 4 inches, 6 inches, and 8 inches.

4. The method for preparing gallium nitride single-crystal wafers using a silicon carbide single-crystal substrate according to claim 1, characterized in that, The thickness of the ultrathin magnesium single crystal film layer in step S5 is no greater than the sum of the thickness of the first ultrathin zinc oxide single crystal film layer in step S4 and the thickness of the second ultrathin zinc oxide single crystal film layer in step S6.

5. The method for preparing gallium nitride single-crystal wafers using a silicon carbide single-crystal substrate according to claim 1, characterized in that, The baking parameters for the silicon carbide single crystal substrate in step S15 are: temperature 1100-1200℃, vacuum degree 5-50Pa.

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