A method for growing a thick film of GaN on a metal substrate

Abstract

The application relates to a method for growing a GaN thick film on a metal substrate. The method comprises the following steps: (1) preparing an etching stripping layer on a metal substrate, and then preparing a transition interface layer on the etching stripping layer; (2) introducing ammonia, growing a GaN thick film on the transition interface layer under the protection of ammonia and at a GaN thick film growth temperature; and (3) placing the GaN thick film into hydrofluoric acid for etching for 10-30 minutes, and then stripping to obtain the GaN thick film. The method for growing a GaN thick film on a metal substrate provided by the application grows the GaN thick film on a metal substrate with the same or similar thermal expansion coefficient as that of GaN, the grown GaN thick film is free of cracks, the qualified rate of the GaN thick film is improved, the production cost is reduced, the etching stripping layer is easy to be etched by hydrofluoric acid, the process of stripping the GaN thick film is simple and fast, and the GaN thick film is not damaged.

Description

Technical Field

[0001] This invention relates to a method for growing GaN thick films on a metal substrate, belonging to the field of optoelectronic power devices. Background Technology

[0002] GaN material is ideal for fabricating optoelectronic devices, especially blue-green LEDs and LDs. These light sources have broad application prospects and huge market potential in high-density optical information storage, high-speed laser printing, full-color dynamic high-brightness light displays, solid-state lighting sources, high-brightness signal detection, and communications. Furthermore, GaN semiconductor materials are also ideal for fabricating high-temperature, high-frequency, and high-power devices. GaN is a representative of nitride materials and one of the best wide-bandgap III-V compound semiconductor materials, making it one of the most advanced semiconductor materials in the world today.

[0003] Magnetron sputtering is a physical vapor deposition technique used to fabricate various special-function thin films, such as superconducting thin films, magnetic thin films, and superhard films. Sputtering involves bombarding the surface of a solid with particles of a certain energy. Molecules or atoms on the solid surface are ejected after being bombarded. Magnetron sputtering, on the other hand, introduces a magnetic field between two electrodes. Electrons are simultaneously subjected to different electric and magnetic fields, causing their trajectories to follow a cycloidal pattern. This results in uniform sputtering onto the desired substrate surface, leading to good film consistency and a fast deposition rate.

[0004] Due to the significant difference in thermal expansion coefficients and lattice matching between nitride materials and sapphire substrates, the stress in epitaxially grown nitrides is substantial, leading to cracks at the interface during growth. These cracks propagate to the surface with increasing thickness, making it difficult to grow GaN films thicker than 500 μm in heteroepitaxial growth due to large thermal mismatch. When GaN films exceed 500 μm, through-cracks are highly likely to occur, affecting the quality and performance of the GaN film. To reduce stress in grown nitride films, researchers have employed methods such as creating void structures on heterogeneously grown GaN before growing nitride films to release stress. Other studies have explored electrochemical etching to create nanoscale micro-defect pits on GaN, followed by metal-organic chemical vapor deposition (MOCVD) to grow GaN films and release heterojunction stress. However, these methods have not yielded significant results and have failed to produce thick GaN epitaxial layers, necessitating the search for new substrate materials.

[0005] Metals are diverse, and different metal materials have different coefficients of thermal expansion, making them suitable as substrates for GaN thick films. However, existing technologies face challenges such as the inability to directly grow GaN thick films on metal substrates, or the complex stripping methods after GaN thick film growth, which can easily damage the GaN thick film. In view of this, the present invention provides a method for growing GaN thick films on metal substrates. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a method for growing GaN thick films on metal substrates. The invention involves sputtering a SiO2 or SiN etching and release layer onto a metal substrate with a thermal expansion coefficient similar to or the same as that of GaN, followed by sputtering an Al2O3 transition interface layer, sequentially growing a GaN thick film. This method overcomes the limitation of heteroepitaxial growth of GaN thick films due to large thermal mismatch, providing a thick film for the fabrication of GaN self-supporting substrates. The grown epitaxial wafer is then immersed in hydrofluoric acid to achieve GaN thick-film separation. The separated GaN thick film can be applied to power devices and blue lasers based on homoepitaxial growth, meeting the application needs of high-efficiency, novel high-power power electronics, optoelectronics, and other fields.

[0007] The technical solution of the present invention is as follows:

[0008] A method for growing a GaN thick film on a metal substrate includes the following steps:

[0009] (1) An etching release layer is prepared on a metal substrate, and then a transition interface layer is prepared on the etching release layer;

[0010] The coefficient of thermal expansion of the metal substrate is 0.9 to 1.1 times that of GaN;

[0011] (2) Introduce ammonia gas and heat it to the GaN thick film growth temperature under the protection of ammonia gas. Then, grow a GaN thick film on the transition interface layer by metal-organic chemical vapor deposition or hydride vapor phase epitaxy to obtain an epitaxial wafer with a GaN thick film.

[0012] (3) Place the epitaxial wafer in hydrofluoric acid and etch for 10-30 minutes. After peeling, a GaN thick film is obtained.

[0013] According to a preferred embodiment of the present invention, in step (1), the metal substrate is a molybdenum substrate or a hard alloy substrate, and the surface is mirror polished.

[0014] According to a preferred embodiment of the present invention, in step (1), the thickness of the metal substrate is 100~1000μm. If the metal substrate is too thin, it will not provide support; if it is too thick, it will cause the heating to be too slow, increasing the growth time. Furthermore, an excessively thick metal substrate will also increase the cost of the substrate.

[0015] According to a preferred embodiment of the present invention, in step (1), the corrosion stripping layer is SiO2 or SiN, and the thickness is 10~500nm.

[0016] According to a preferred embodiment of the present invention, in step (1), the transition interface layer is Al2O3 with a thickness of 10~500nm.

[0017] According to a preferred embodiment of the present invention, in step (1), the corrosion stripping layer and the transition interface layer are prepared by vapor phase epitaxy, pulsed laser deposition or magnetron sputtering; more preferably, magnetron sputtering is used.

[0018] According to a preferred embodiment of the present invention, in step (2), the ammonia flow rate is 0.2-500L and the growth temperature is 800-1300℃.

[0019] According to a preferred embodiment of the present invention, in step (2), when an organic chemical vapor deposition method is used, the growth pressure is 50-1000 mbar and the V / III ratio is 50-20000.

[0020] According to a preferred embodiment of the present invention, in step (2), when using the hydride vapor phase epitaxy method, the growth pressure is 50-1000 mbar and the V / III ratio is 10-2000.

[0021] According to a preferred embodiment of the present invention, in step (3), the concentration of hydrofluoric acid is 10-30%. Hydrofluoric acid reacts with SiO2 or SiN, allowing for complete peeling of the GaN thick film.

[0022] According to a preferred embodiment of the present invention, in step (3), the thickness of the GaN thick film obtained by stripping is 50~5000μm.

[0023] Any aspects not detailed in this invention are conventional prior art.

[0024] Beneficial effects:

[0025] 1. The method for growing GaN thick films on metal substrates provided by the present invention first prepares a SiO2 or SiN etching and release layer on the metal substrate, then prepares a transition interface layer on the etching and release layer, and then prepares a GaN thick film on the transition interface layer. This realizes the preparation of GaN thick films using metal materials as substrates. Furthermore, SiO2 or SiN is easily etched by hydrofluoric acid, and the process of peeling off the GaN thick film is simple and fast, without causing damage to the GaN thick film.

[0026] 2. The method for growing GaN thick films on metal substrates provided by the present invention grows GaN thick films on metal substrates with the same or similar coefficient of thermal expansion as GaN. Since there is no thermal mismatch problem between GaN and metal substrates, the thermal mismatch caused by high-temperature growth between substrate and GaN is completely eliminated. The grown GaN thick films are free of cracks, which improves the yield of GaN thick films and reduces production costs.

[0027] 3. The method for growing GaN thick films on metal substrates provided by the present invention uses metal substrates as substrates. Compared with other oxide substrates or composite oxide substrates, metal substrates have better thermal conductivity, fewer defects in the grown GaN thick films, and higher quality. The metal substrates can also be reused after being peeled off. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the structure of growing a GaN thick film on a metal substrate in Embodiment 1 of the present invention.

[0029] Figure 2 This is a schematic diagram of the structure of growing a GaN thick film on a metal substrate in Embodiment 2 of the present invention. Detailed Implementation

[0030] To make the technical problems, technical solutions and advantages of the present invention clearer, the present invention will be further described below through embodiments and in conjunction with the accompanying drawings. However, the present invention is not limited thereto. All matters not described in detail in the present invention are based on conventional techniques in the art.

[0031] Example 1

[0032] like Figure 1 As shown, a method for growing a GaN thick film on a metal substrate includes the following steps:

[0033] (1) A SiO2 etching and release layer with a thickness of 200 nm was prepared on a 200 μm metal substrate by magnetron sputtering, and then an Al2O3 transition interface layer with a thickness of 200 nm was prepared on the SiO2 etching and release layer.

[0034] The metal substrate is a molybdenum substrate, and its coefficient of thermal expansion is 0.95 times that of GaN.

[0035] (2) Introduce 50L of ammonia gas, and under the protection of ammonia gas, heat up to 1100℃. Then, grow a GaN thick film on the Al2O3 transition interface layer by metal-organic chemical vapor deposition to obtain an epitaxial wafer with a GaN thick film.

[0036] (3) The epitaxial wafer is placed in 10% hydrofluoric acid and etched for 30 minutes, and then peeled off to obtain a GaN thick film.

[0037] In step (2), the growth pressure of the metal-organic chemical vapor deposition method is 200 mbar and the V / III ratio is 800.

[0038] Example 2

[0039] like Figure 2 As shown, a method for growing a GaN thick film on a metal substrate includes the following steps:

[0040] (1) A SiN etching and release layer with a thickness of 300 nm was prepared on a metal substrate with a thickness of 300 μm by magnetron sputtering, and then an Al2O3 transition interface layer with a thickness of 300 nm was prepared on the SiN etching and release layer.

[0041] The metal substrate is a hard alloy substrate, and its coefficient of thermal expansion is 1.1 times that of GaN.

[0042] (2) 60L of ammonia gas is introduced, and the temperature is raised to 1100℃ under the protection of ammonia gas. Then, GaN thick film is grown on Al2O3 transition interface layer by hydride vapor phase epitaxy method to obtain epitaxial wafer with GaN thick film.

[0043] (3) The epitaxial wafer is placed in 20% hydrofluoric acid and etched for 15 minutes, and then peeled off to obtain a GaN thick film.

[0044] In step (2), the growth pressure of the hydride vapor phase epitaxy method is 300 mbar and the V / III ratio is 1000.

[0045] Example 3

[0046] A method for growing a GaN thick film on a metal substrate includes the following steps:

[0047] (1) A SiO2 etching and release layer with a thickness of 10 nm was prepared on a 100 μm metal substrate by magnetron sputtering, and then an Al2O3 transition interface layer with a thickness of 10 nm was prepared on the SiO2 etching and release layer.

[0048] The metal substrate is a molybdenum substrate, and its coefficient of thermal expansion is 0.95 times that of GaN.

[0049] (2) Introduce 50L of ammonia gas, and under the protection of ammonia gas, heat up to 1100℃. Then, grow a GaN thick film on the Al2O3 transition interface layer by metal-organic chemical vapor deposition to obtain an epitaxial wafer with a GaN thick film.

[0050] (3) The epitaxial wafer is placed in 20% hydrofluoric acid and etched for 20 minutes to obtain a GaN thick film.

[0051] In step (2), the growth pressure of the metal-organic chemical vapor deposition method is 300 mbar and the V / III ratio is 1000.

[0052] Example 4

[0053] A method for growing a GaN thick film on a metal substrate includes the following steps:

[0054] (1) A SiN etching and release layer with a thickness of 500 nm was prepared on a metal substrate with a thickness of 1000 μm by magnetron sputtering, and then an Al2O3 transition interface layer with a thickness of 500 nm was prepared on the SiO2 etching and release layer.

[0055] The metal substrate is a hard alloy substrate, and its coefficient of thermal expansion is 1.1 times that of GaN.

[0056] (2) 60L of ammonia gas is introduced, and the temperature is raised to 1100℃ under the protection of ammonia gas. Then, GaN thick film is grown on Al2O3 transition interface layer by hydride vapor phase epitaxy method to obtain epitaxial wafer with GaN thick film.

[0057] (3) The epitaxial wafer is placed in 30% hydrofluoric acid and etched for 10 minutes to obtain a GaN thick film.

[0058] In step (2), the growth pressure of the hydride vapor phase epitaxy method is 200 mbar and the V / III ratio is 1200.

[0059] Comparative Example 1

[0060] The existing electrochemical etching method is used to grow GaN thick films, specifically as follows:

[0061] First, a 2μm GaN seed crystal is grown on a sapphire substrate. Then, the sapphire with the GaN seed crystal is placed in a KOH solution with a KOH to H2O ratio of 5:1. Nanoscale micro-defect pores are etched on the surface of the GaN seed crystal by conventional electrochemical etching method. The depth of the nanopores is less than 3nm and the diameter is less than 3nm. Then, a GaN thick film is grown by metal-organic chemical vapor deposition.

[0062] Among them, the growth pressure of the metal-organic chemical vapor deposition method is 200 mbar and the V / III ratio is 800.

[0063] Comparative Example 2

[0064] A method for growing a GaN thick film on a metal substrate includes the following steps:

[0065] (1) An Al2O3 transition interface layer with a thickness of 200 nm was prepared on a 200 μm metal substrate by magnetron sputtering;

[0066] The metal substrate is a molybdenum substrate, and its coefficient of thermal expansion is 0.95 times that of GaN.

[0067] (2) Introduce 50L of ammonia gas, and under the protection of ammonia gas, heat up to 1100℃. Then, grow a GaN thick film on the Al2O3 transition interface layer by metal-organic chemical vapor deposition to obtain an epitaxial wafer with a GaN thick film.

[0068] (3) The GaN thick film is stripped by laser stripping.

[0069] In step (2), the growth pressure of the metal-organic chemical vapor deposition method is 200 mbar and the V / III ratio is 800.

[0070] Test case

[0071] Using the methods of Example 1, Comparative Example 1, and Comparative Example 2 of the present invention, GaN thick films with thicknesses of 50 μm, 100 μm, 500 μm, 1000 μm, 3000 μm, and 5000 μm were grown, respectively. Ten growth samples were collected for each thickness, and the presence or absence of cracks on the surface of the GaN thick films was recorded in Tables 1 and 2.

[0072] Table 1: Statistics on GaN Thick Film Peeling

[0073]

[0074] As can be seen from Table 1, the present invention can grow and prepare GaN thick films with a thickness of 50-5000 μm, and the yield is very high. All 3000 μm GaN thick films are free of cracks, and among 10 samples of 5000 μm GaN thick films, only 1 showed cracking, that is, 90% are free of cracks.

[0075] Comparative Example 1, which uses existing technology, shows that cracking begins to appear in GaN films with a thickness of 100 μm, and all GaN films with a thickness of 3000-5000 μm crack.

[0076] Therefore, compared with the prior art, the method of the present invention for growing GaN thick films with reduced stress can produce GaN thick films with a thickness of 50-5000 μm. There are no cracks or very few cracks at 500-3000 μm, and only a small number of cracks (10%) at 5000 μm. This is because the present invention grows GaN on a metal substrate with the same or similar coefficient of thermal expansion as GaN. Since there is no thermal mismatch between GaN and the metal substrate, the thermal mismatch caused by high-temperature growth between the substrate and GaN is completely eliminated, resulting in 90% crack-free production and extremely high yield.

[0077] Table 2: Statistics on GaN Thick Film Peeling

[0078]

[0079] As can be seen from Table 1, the present invention can grow and prepare GaN thick films with a thickness of 50-5000 μm, and the yield is very high. All 3000 μm GaN thick films are free of cracks or fragments. Among 10 samples of 5000 μm GaN thick films, only 1 showed cracking, that is, 90% are free of cracks.

[0080] Comparative Example 2, which uses existing technology, shows that cracks begin to appear when a 100 μm GaN thick film is grown, and the 1000-5000 μm GaN thick film is completely shattered after laser ablation.

[0081] Therefore, it can be seen that the laser lift-off method in Comparative Document 2 utilizes ultraviolet pulsed laser irradiation at the interface between the epitaxial layer and the substrate. The high-energy laser causes GaN to rapidly thermally decompose into nitrogen gas and gallium droplets, thus instantly decomposing the first layer of GaN on the substrate, thereby obtaining the lift-off film peeled off from the original substrate. However, in application, the high-energy laser irradiation on the sapphire substrate with poor thermal conductivity will instantly generate thermal shock, producing Ga and N2 gas. Since the N2 cannot be discharged from the sample in time, it will cause cracks or even fragmentation of the epitaxial GaN thick film, resulting in a relatively low yield of laser lift-off, leading to a decrease in both yield and pass rate.

[0082] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for growing a GaN thick film on a metal substrate, characterized in that, The steps include the following: (1) An etching release layer is prepared on a metal substrate, and then a transition interface layer is prepared on the etching release layer; The metal substrate is a molybdenum substrate or a cemented carbide substrate with a thickness of 100~1000μm and a mirror-polished surface; the thermal expansion coefficient of the metal substrate is 0.9~1.1 times that of GaN; the etching and stripping layer is SiO2 or SiN with a thickness of 10~500nm; and the transition interface layer is Al2O3 with a thickness of 10~500nm. (2) Introduce ammonia gas and heat it to the GaN thick film growth temperature under the protection of ammonia gas. Then, grow a GaN thick film on the transition interface layer by metal-organic chemical vapor deposition or hydride vapor phase epitaxy to obtain an epitaxial wafer with a GaN thick film. (3) Place the epitaxial wafer in hydrofluoric acid and etch for 10-30 minutes. After peeling, a GaN thick film is obtained.

2. The method for growing GaN thick films as described in claim 1, characterized in that, In step (1), the corrosion stripping layer and the transition interface layer are prepared by vapor phase epitaxy, pulsed laser deposition or magnetron sputtering.

3. The method for growing GaN thick films as described in claim 1, characterized in that, In step (2), the ammonia flow rate is 0.2-500L and the growth temperature is 800-1300℃.

4. The method for growing GaN thick films as described in claim 1, characterized in that, In step (2), when using organic chemical vapor deposition, the growth pressure is 50-1000 mbar and the V / III ratio is 50-20000; when using hydride vapor phase epitaxy, the growth pressure is 50-1000 mbar and the V / III ratio is 10-2000.

5. The method for growing GaN thick films as described in claim 1, characterized in that, In step (3), the concentration of hydrofluoric acid is 10-30%. Hydrofluoric acid reacts with SiO2 or SiN, and the GaN thick film can be completely peeled off.

6. The method for growing GaN thick films as described in claim 1, characterized in that, In step (3), the thickness of the GaN thick film obtained by stripping is 50~5000μm.

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