A silicon carbide epitaxial gallium oxide film and its preparation method

Abstract

The present invention relates to the field of semiconductor material technology, and more specifically to a silicon carbide epitaxial gallium oxide thin film and a preparation method thereof. The present invention utilizes metal organic chemical vapor deposition to sequentially grow a silicon dioxide mask layer, an aluminum nitride low-temperature buffer layer, an aluminum nitride high-temperature buffer layer, and a gallium oxide thin film layer on a silicon carbide substrate. The silicon dioxide mask layer contains a small amount of aluminum nitride, which can rapidly transfer heat and thereby effectively improve the thermal conductivity of the gallium oxide thin film. The silicon dioxide mask layer, which is based on silicon carbide, is subjected to two plasma etching steps to increase the flatness of the aluminum nitride buffer layer, thereby effectively suppressing dislocations and step defects during the gallium oxide growth process and improving the growth quality of the gallium oxide thin film. This application utilizes heteroepitaxial technology to not only reduce the production cost of the gallium oxide thin film but also provide it with higher thermal conductivity. Compared with existing technologies, this invention has broad application prospects.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor materials, and in particular to a silicon carbide epitaxial gallium oxide film and a preparation method thereof. Background Art

[0002] With the increasing demand for low-loss, high-power, and high-performance power electronic devices in modern society's energy, information, and military sectors, wide-bandgap semiconductors have become a research hotspot due to their excellent material properties. Wide-bandgap semiconductor materials have received widespread attention and research in academia due to their large bandgap, excellent chemical stability, and high-temperature resistance. Among them, gallium oxide, an emerging semiconductor material, has a large bandgap, resulting in ultrahigh breakdown field strength, a large Baliga figure of merit, and a short UV cutoff edge, making it well-suited for use in high-voltage, high-power, low-loss power devices and deep-ultraviolet optoelectronic devices. However, the low electron mobility and poor thermal conductivity of gallium oxide films, as well as the challenges of growing large-scale, high-quality gallium oxide substrates, limit their application in high-frequency and high-efficiency electronic devices at high temperatures.

[0003] As a highly promising third-generation wide-bandgap semiconductor material, silicon carbide (SiC) holds promising market prospects in high-power and high-frequency power electronics. Its high thermal conductivity, excellent breakdown electric field strength, high electron saturation mobility, and outstanding high-temperature resistance make it an ideal substrate for manufacturing electronic devices requiring high frequency, high power density, and high-temperature stability. This makes it suitable for modern industrial sectors such as new energy vehicles, renewable energy, smart grids, and rail transit.

[0004] To address the low thermal conductivity of gallium oxide, existing technologies combine silicon carbide and gallium oxide, leveraging the advantages of both materials. For example, patent document CN110993504A discloses a method for preparing a Ga2O3 thin film based on a SiC substrate and a Ga2O3 thin film based on a SiC substrate. This invention comprises a SiC substrate layer, a Ga2O3 buffer layer, and a Ga2O3 thin film layer, with the Ga2O3 buffer layer being formed by annealing the Ga2O3 material layer. This invention combines two excellent semiconductor materials, silicon carbide and gallium oxide, but there is a significant lattice mismatch between the two, and the Ga2O3 buffer layer's ability to address this lattice mismatch needs to be improved.

[0005] Therefore, according to the above-mentioned related technologies, there is an urgent need to develop a silicon carbide epitaxial gallium oxide film and a preparation method thereof. Summary of the Invention

[0006] In view of this, the object of the present invention is to provide a silicon carbide epitaxial gallium oxide thin film and a preparation method thereof, so as to solve the problem of lattice mismatch between silicon carbide and gallium oxide in the prior art.

[0007] Based on the above objectives, the present invention provides a silicon carbide epitaxial gallium oxide film and a preparation method thereof.

[0008] A silicon carbide epitaxial gallium oxide film, comprising a silicon carbide substrate layer and a silicon dioxide mask layer, an aluminum nitride buffer layer, and a gallium oxide film layer sequentially formed on the surface of the silicon carbide substrate layer;

[0009] The thickness of the silicon carbide substrate layer is 450-550 μm, the thickness of the silicon dioxide mask layer is 90-110 nm, the aluminum nitride buffer layer consists of a low-temperature aluminum nitride buffer layer with a thickness of 30-45 nm and a high-temperature aluminum nitride buffer layer with a thickness of 210-250 nm, and the thickness of the gallium oxide thin film layer is 4-5 μm.

[0010] A method for preparing a silicon carbide epitaxial gallium oxide thin film comprises the following steps:

[0011] Step S1. Take a semi-insulating silicon carbide and ultrasonically clean it in deionized water for 10-15 minutes, then clean it with SPM solution for 10-15 minutes, and finally clean it with ultrapure water for 5-7 minutes. Dry it at 75-80°C for 3-5 minutes to obtain a silicon carbide substrate layer;

[0012] Step S2. Silane is supplied to a reaction chamber containing a silicon carbide substrate, and a silicon dioxide film is deposited on the silicon carbide using plasma-enhanced chemical vapor deposition. The deposition temperature is set to 340-360°C, the RF power for generating the plasma is set to 330-350W, and nitrogen is used as a carrier gas. The carrier gas flow rates of trimethylaluminum and NH3 are set to A1 and B1, respectively, and are continuously passed for 10-15 seconds. The silane gas flow rate is then set to 60-70 sccm. The resulting silicon dioxide film is annealed to obtain a silicon dioxide mask layer with the silicon carbide substrate.

[0013] Step S3. Using nitrogen as a carrier and CHF3 as an etching gas, the silicon dioxide mask layer on the silicon carbide substrate is subjected to a first plasma etching. The silicon carbide substrate is then cleaned with an SPM solution for 12-15 minutes, then rinsed with ultrapure water for 7-12 minutes, and dried at 75-80°C for 3-5 minutes to remove residual impurities and dirt on the surface, thereby obtaining a single plasma-etched silicon carbide substrate.

[0014] Step S4. Using nitrogen as a carrier and CHF3 as an etching gas, the silicon dioxide mask layer on the silicon carbide substrate is subjected to a second plasma etching, followed by cleaning with SPM solution for 12-15 minutes, then with ultrapure water for 7-12 minutes, and drying at 75-80°C for 3-5 minutes to obtain a second plasma-etched silicon carbide substrate;

[0015] Step S5. The silicon carbide substrate after secondary plasma etching is placed in a metal organic chemical vapor deposition chamber for epitaxial growth. The reaction chamber pressure is set to 40 Torr. Trimethylaluminum and NH3 are used as the Al and N sources, and N2 is used as the carrier gas. The trimethylaluminum carrier gas flow rate is set to A2 via a flow meter. After pre-laying Al for 5-6 seconds, the NH3 carrier gas flow rate is set to B2 via a flow meter. The growth temperature is set to C1 to form a low-temperature aluminum nitride buffer layer, and then the growth temperature is set to C2 to form a high-temperature aluminum nitride buffer layer.

[0016] Step S6. Regulate the reaction chamber pressure to 35-40 mTorr, set the reaction chamber temperature to C3, use triethylgallium and oxygen as Ga source and O source, N2 as carrier gas, and control the flowmeter to set the carrier gas flow of triethylgallium and oxygen to obtain a silicon carbide epitaxial gallium oxide film.

[0017] Preferably, the SPM solution in step S1 is obtained by mixing 98% by mass concentrated sulfuric acid and 30% by mass hydrogen peroxide in a volume ratio of 3.5-4.5:1, and the cleaning temperature is 135-145°C.

[0018] Preferably, in step S2, A1 is 10-12 sccm, and B1 is 30-35 sccm.

[0019] Preferably, the annealing temperature in step S2 is 1100-1200° C., and the annealing time is 50-60 min.

[0020] Preferably, in step S3, the plasma etching power is set to 45-60 W, the chamber pressure is 2.5-3 mTorr, the He gas pressure is 3-4 Torr, the N2 gas flow rate is 15-25 sccm, the CHF3 gas flow rate is 40-60 sccm, and the etching time is 50-70 s;

[0021] The SPM solution is obtained by mixing 98% concentrated sulfuric acid and 30% hydrogen peroxide in a volume ratio of 3.5-4.5:1, and the cleaning temperature is 135-145°C.

[0022] Preferably, in step S4, the plasma etching power is set to 25-32 W, the chamber pressure is 3-4 mTorr, the He gas pressure is 3-4 Torr, the N2 gas flow rate is 10-25 sccm, the CHF3 gas flow rate is 30-40 sccm, and the etching time is 30-45 s;

[0023] The SPM solution is obtained by mixing 98% concentrated sulfuric acid and 30% hydrogen peroxide in a volume ratio of 3.5-4.5:1, and the cleaning temperature is 135-145°C.

[0024] Preferably, in step S5, A2 is 180-200 sccm, and B2 is 2.5-3 slm.

[0025] Preferably, the growth temperature C1 in step S5 is 880-920°C;

[0026] The growth temperature C2 is 1150-1230°C.

[0027] Preferably, in step S6, the triethylgallium carrier gas flow rate is 35-45 sccm, and the oxygen flow rate is 1800-1950 sccm;

[0028] The growth temperature C3 of the silicon carbide epitaxial gallium oxide film is 750-850° C., and the growth time is 200-240 minutes.

[0029] Beneficial effects of the present invention:

[0030] The present invention provides a silicon carbide epitaxial gallium oxide thin film and a preparation method thereof. The present invention adopts metal organic chemical vapor deposition to sequentially grow a silicon dioxide mask layer, an aluminum nitride low-temperature buffer layer, an aluminum nitride high-temperature buffer layer, and a gallium oxide thin film layer on a silicon carbide substrate. Through heteroepitaxial growth, silicon carbide and gallium oxide are successfully combined, while effectively solving the problem of lattice mismatch between the two. As a result, the prepared gallium oxide thin film not only reduces production costs but also has higher thermal conductivity.

[0031] During the preparation of the silicon dioxide mask layer, a small amount of trimethylaluminum and ammonia are added. The aluminum nitride formed by the two has high thermal conductivity and is an excellent heat dissipation material. It can quickly transfer heat sources, thereby effectively improving the thermal conductivity of the gallium oxide film.

[0032] Subsequently, the silicon dioxide mask layer with silicon carbide as the substrate was plasma etched twice. Among them, the second plasma etching performed low-power fine-control etching based on the first rough etching, forming a large number of tiny and uneven aluminum nitride-doped silicon oxide points on the etched surface to form a crystal plane pinning effect, which provided a stable nucleation site for the subsequent suppression of defects such as crystal plane rotation, slip, and table formation during aluminum nitride growth, further inducing the nucleation of high-quality and regularly arranged aluminum nitride buffer layer, effectively suppressing dislocations and step-type defects in the gallium oxide growth process, and improving the growth quality of gallium oxide film. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only for the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0034] Figure 1 This is a flow chart for preparing a silicon carbide epitaxial gallium oxide thin film in the present invention;

[0035] Figure 2 This is a graph showing the thickness uniformity test results of the silicon carbide epitaxial gallium oxide film prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0036] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to specific embodiments.

[0037] The sources and properties of some of the raw materials used in the present invention are as follows:

[0038] Silicon carbide was purchased from Beijing Tianke Heda Semiconductor Co., Ltd.; concentrated sulfuric acid with a mass fraction of 98% was purchased from Henan Dongke Chemical Products Sales Co., Ltd.; hydrogen peroxide with a mass fraction of 30% was purchased from Sinopharm Chemical Reagent Co., Ltd.; CHF3 was purchased from Merck Group, Germany; trimethylaluminum was purchased from Wuhan Xinzhongke Chemical Co., Ltd.; NH3 was purchased from Anhui Wangshan Wangshui Special Gas Co., Ltd.

[0039] Example 1: A method for preparing a silicon carbide epitaxial gallium oxide thin film, comprising the following steps:

[0040] S1. A 450μm-thick silicon carbide substrate was ultrasonically cleaned in deionized water for 10 minutes, then rinsed with an SPM solution (98% concentrated sulfuric acid and 30% hydrogen peroxide in a volume ratio of 3.5:1) for 10 minutes at 135°C. Finally, the substrate was rinsed with ultrapure water for 5 minutes and dried at 75°C for 3 minutes to obtain a silicon carbide substrate.

[0041] S2. Silane was supplied to a reaction chamber containing a silicon carbide substrate, and a silicon dioxide film was deposited on the silicon carbide using plasma-enhanced chemical vapor deposition. The deposition temperature was set to 340°C, the RF power for generating the plasma was 330 W, and nitrogen was used as a carrier gas. The carrier gas flow rates of trimethylaluminum and NH3 were set to 10 sccm and 30 sccm, respectively, and the flow was continued for 15 seconds. The silane gas flow rate was then set to 60 sccm. The resulting silicon dioxide film was annealed at 1100°C for 60 minutes to obtain a silicon dioxide mask layer with the silicon carbide substrate.

[0042] S3. Using nitrogen as the carrier and CHF3 as the etching gas, the silicon dioxide mask layer on the silicon carbide substrate was subjected to a first plasma etching. The etching power was set to 45W, the chamber pressure was 2.5mTorr, the He gas pressure was 3Torr, the N2 gas flow rate was 15sccm, the CHF3 gas flow rate was 40sccm, and the etching time was 70s. The substrate was then rinsed with SPM solution for 12 minutes. The SPM solution was a mixture of 98% concentrated sulfuric acid and 30% hydrogen peroxide in a volume ratio of 3.5:1. The cleaning temperature was 135°C, and the substrate was then rinsed with ultrapure water for 7 minutes. The substrate was then dried at 75°C for 3 minutes to obtain a single plasma-etched silicon carbide substrate.

[0043] S4. Using nitrogen as the carrier and CHF3 as the etching gas, a second plasma etching was performed on the silicon dioxide mask layer with the silicon carbide substrate. The etching power was set to 25W, the chamber pressure was 3mTorr, the He gas pressure was 3Torr, the N2 gas flow rate was 10sccm, the CHF3 gas flow rate was 30sccm, and the etching time was 30s. The substrate was then rinsed with SPM solution for 12 minutes. The SPM solution was a mixture of 98% concentrated sulfuric acid and 30% hydrogen peroxide in a volume ratio of 3.5:1. The cleaning temperature was 135°C. The substrate was then rinsed with ultrapure water for 7 minutes and dried at 75°C for 3 minutes to obtain a silicon carbide substrate with secondary plasma etching.

[0044] S5. The silicon carbide substrate etched by the secondary plasma is placed in a metal organic chemical vapor deposition chamber for epitaxial growth. The reaction chamber pressure is set to 40 Torr. Trimethylaluminum and NH3 are used as the Al source and N source, and N2 is used as the carrier gas. The trimethylaluminum carrier gas flow rate is set to 180 sccm by controlling the flow meter. After pre-laying Al6s, the NH3 carrier gas flow rate is set to 2.5 slm by controlling the flow meter. The growth temperature is set to 880°C to form a low-temperature aluminum nitride buffer layer, and then the growth temperature is set to 1150°C to form a high-temperature aluminum nitride buffer layer.

[0045] S6. Regulate the reaction chamber pressure to 35 mTorr, use triethylgallium and oxygen as Ga and O sources, and use N2 as the carrier gas. Control the flowmeter to set the triethylgallium carrier gas flow rate to 35 sccm and the oxygen flow rate to 1800 sccm. Set the reaction chamber temperature to 750°C and grow for 240 minutes to obtain a silicon carbide epitaxial gallium oxide film.

[0046] Example 2: A method for preparing a silicon carbide epitaxial gallium oxide thin film, comprising the following steps:

[0047] S1. A 480 μm thick silicon carbide substrate was ultrasonically cleaned in deionized water for 12 minutes, followed by a 12-minute clean with an SPM solution (98% concentrated sulfuric acid and 30% hydrogen peroxide in a 4:1 volume ratio) at 140°C. Finally, the substrate was rinsed with ultrapure water for 6 minutes and dried at 78°C for 4 minutes to obtain a silicon carbide substrate.

[0048] S2. Silane was supplied to a reaction chamber containing a silicon carbide substrate, and a silicon dioxide film was deposited on the silicon carbide using plasma-enhanced chemical vapor deposition. The deposition temperature was set to 350°C, the RF power for generating the plasma was 340W, and nitrogen was used as a carrier gas. The carrier gas flow rates of trimethylaluminum and NH3 were set to 11sccm and 33sccm, respectively, and the flow was continued for 13 seconds. The silane gas flow rate was then set to 65sccm. The resulting silicon dioxide film was annealed at 1140°C for 55 minutes to obtain a silicon dioxide mask layer with the silicon carbide substrate.

[0049] S3. Using nitrogen as the carrier and CHF3 as the etching gas, the silicon dioxide mask layer on the silicon carbide substrate was subjected to a first plasma etching. The etching power was set to 50W, the chamber pressure was 2.8mTorr, the He gas pressure was 3.5Torr, the N2 gas flow rate was 20sccm, the CHF3 gas flow rate was 45sccm, and the etching time was 60s. The substrate was then cleaned with SPM solution for 14 minutes. The SPM solution was a mixture of 98% concentrated sulfuric acid and 30% hydrogen peroxide in a volume ratio of 4:1. The cleaning temperature was 140°C, and the substrate was then rinsed with ultrapure water for 10 minutes and dried at 78°C for 4 minutes to obtain a single plasma-etched silicon carbide substrate.

[0050] S4. Using nitrogen as the carrier and CHF3 as the etching gas, a second plasma etching was performed on the silicon dioxide mask layer with the silicon carbide substrate. The etching power was set to 28W, the chamber pressure was 3.5mTorr, the He gas pressure was 3.5Torr, the N2 gas flow rate was 13sccm, the CHF3 gas flow rate was 35sccm, and the etching time was 35s. The substrate was then cleaned with SPM solution for 14 minutes. The SPM solution was prepared by mixing 98% concentrated sulfuric acid and 30% hydrogen peroxide in a volume ratio of 4:1 at a cleaning temperature of 140°C. The substrate was then rinsed with ultrapure water for 10 minutes and dried at 78°C for 4 minutes to obtain a silicon carbide substrate with secondary plasma etching.

[0051] S5. The silicon carbide substrate after secondary plasma etching was placed in a metal organic chemical vapor deposition chamber for epitaxial growth. The reaction chamber pressure was set to 40 Torr. Trimethylaluminum and NH3 were used as Al and N sources, and N2 was used as the carrier gas. The trimethylaluminum carrier gas flow rate was set to 190 sccm by controlling the flow meter. After pre-laying Al for 5.5 seconds, the NH3 carrier gas flow rate was set to 2.8 slm by controlling the flow meter. The growth temperature was set to 900°C to form a low-temperature aluminum nitride buffer layer, and then the growth temperature was set to 1180°C to form a high-temperature aluminum nitride buffer layer.

[0052] S6. Regulate the reaction chamber pressure to 38 mTorr, use triethylgallium and oxygen as Ga and O sources, and use N2 as the carrier gas. Control the flowmeter to set the triethylgallium carrier gas flow rate to 40 sccm and the oxygen flow rate to 1850 sccm. Set the reaction chamber temperature to 800°C and grow for 220 minutes to obtain a silicon carbide epitaxial gallium oxide film.

[0053] Example 3: A method for preparing a silicon carbide epitaxial gallium oxide thin film, comprising the following steps:

[0054] S1. A 520 μm thick silicon carbide substrate was ultrasonically cleaned in deionized water for 12 minutes, then rinsed with an SPM solution (98% concentrated sulfuric acid and 30% hydrogen peroxide in a 4:1 volume ratio) for 12 minutes at 140°C. Finally, the substrate was rinsed with ultrapure water for 6 minutes and dried at 78°C for 4 minutes to obtain a silicon carbide substrate.

[0055] S2. Silane was supplied to a reaction chamber containing a silicon carbide substrate, and a silicon dioxide film was deposited on the silicon carbide using plasma-enhanced chemical vapor deposition. The deposition temperature was set to 350°C, the RF power for generating the plasma was 340W, and nitrogen was used as a carrier gas. The carrier gas flow rates of trimethylaluminum and NH3 were set to 11sccm and 33sccm, respectively, and the flow was continued for 13 seconds. The silane gas flow rate was then set to 65sccm. The resulting silicon dioxide film was annealed at 1180°C for 55 minutes to obtain a silicon dioxide mask layer with the silicon carbide substrate.

[0056] S3. Using nitrogen as the carrier and CHF3 as the etching gas, the silicon dioxide mask layer on the silicon carbide substrate was subjected to a first plasma etching. The etching power was set to 55W, the chamber pressure was 2.8mTorr, the He gas pressure was 3.5Torr, the N2 gas flow rate was 20sccm, the CHF3 gas flow rate was 50sccm, and the etching time was 60s. The substrate was then cleaned with SPM solution for 14 minutes. The SPM solution was a mixture of 98% concentrated sulfuric acid and 30% hydrogen peroxide in a volume ratio of 4:1. The cleaning temperature was 140°C, and the substrate was then rinsed with ultrapure water for 10 minutes and dried at 78°C for 4 minutes to obtain a single plasma-etched silicon carbide substrate.

[0057] S4. Using nitrogen as the carrier and CHF3 as the etching gas, a second plasma etching was performed on the silicon dioxide mask layer with the silicon carbide substrate. The etching power was set to 28W, the chamber pressure was 3.5mTorr, the He gas pressure was 3.5Torr, the N2 gas flow rate was 13sccm, the CHF3 gas flow rate was 35sccm, and the etching time was 40s. The substrate was then cleaned with SPM solution for 14 minutes. The SPM solution was a mixture of 98% concentrated sulfuric acid and 30% hydrogen peroxide in a volume ratio of 4:1. The cleaning temperature was 140°C, and the substrate was then rinsed with ultrapure water for 10 minutes and dried at 78°C for 4 minutes to obtain a silicon carbide substrate with secondary plasma etching.

[0058] S5. The silicon carbide substrate after secondary plasma etching was placed in a metal organic chemical vapor deposition chamber for epitaxial growth. The reaction chamber pressure was set to 40 Torr. Trimethylaluminum and NH3 were used as Al and N sources, and N2 was used as the carrier gas. The trimethylaluminum carrier gas flow rate was set to 190 sccm by controlling the flow meter. After pre-laying Al for 5.5 seconds, the NH3 carrier gas flow rate was set to 2.8 slm by controlling the flow meter. The growth temperature was set to 900°C to form a low-temperature aluminum nitride buffer layer, and then the growth temperature was set to 1200°C to form a high-temperature aluminum nitride buffer layer.

[0059] S6. Regulate the reaction chamber pressure to 38 mTorr, use triethylgallium and oxygen as Ga and O sources, and use N2 as the carrier gas. Control the flowmeter to set the triethylgallium carrier gas flow rate to 40 sccm and the oxygen flow rate to 1900 sccm. Set the reaction chamber temperature to 800°C and grow for 210 minutes to obtain a silicon carbide epitaxial gallium oxide film.

[0060] Example 4: A method for preparing a silicon carbide epitaxial gallium oxide thin film, comprising the following steps:

[0061] S1. A 550μm-thick silicon carbide substrate was ultrasonically cleaned in deionized water for 15 minutes, followed by a 15-minute clean with an SPM solution (98% concentrated sulfuric acid and 30% hydrogen peroxide in a volume ratio of 4.5:1) at 145°C. Finally, the substrate was rinsed with ultrapure water for 7 minutes and dried at 80°C for 5 minutes to obtain a silicon carbide substrate.

[0062] S2. Silane was supplied to a reaction chamber containing a silicon carbide substrate, and a silicon dioxide film was deposited on the silicon carbide using plasma-enhanced chemical vapor deposition. The deposition temperature was set to 360°C, the RF power for generating the plasma was 350W, and nitrogen was used as a carrier gas. The carrier gas flow rates of trimethylaluminum and NH3 were set to 12 sccm and 35 sccm, respectively, and the flow was continued for 10 seconds. The silane gas flow rate was then set to 70 sccm. The resulting silicon dioxide film was annealed at 1200°C for 50 minutes to obtain a silicon dioxide mask layer with the silicon carbide substrate.

[0063] S3. Using nitrogen as the carrier and CHF3 as the etching gas, the silicon dioxide mask layer on the silicon carbide substrate was subjected to a first plasma etching. The etching power was set to 60W, the chamber pressure was 3mTorr, the He gas pressure was 4Torr, the N2 gas flow rate was 25sccm, the CHF3 gas flow rate was 60sccm, and the etching time was 70s. The substrate was then rinsed with SPM solution for 15 minutes. The SPM solution was a mixture of 98% concentrated sulfuric acid and 30% hydrogen peroxide in a volume ratio of 4.5:1. The cleaning temperature was 145°C, and the substrate was then rinsed with ultrapure water for 12 minutes and dried at 80°C for 5 minutes to obtain a single plasma-etched silicon carbide substrate.

[0064] S4. Using nitrogen as the carrier and CHF3 as the etching gas, a second plasma etching was performed on the silicon dioxide mask layer with the silicon carbide substrate. The etching power was set to 32W, the chamber pressure was 4mTorr, the He gas pressure was 4Torr, the N2 gas flow rate was 15sccm, the CHF3 gas flow rate was 40sccm, and the etching time was 45s. The substrate was then rinsed with SPM solution for 15min. The SPM solution was a mixture of 98% concentrated sulfuric acid and 30% hydrogen peroxide in a volume ratio of 4.5:1. The cleaning temperature was 145°C. The substrate was then rinsed with ultrapure water for 12min and dried at 80°C for 5min to obtain a silicon carbide substrate with secondary plasma etching.

[0065] S5. The silicon carbide substrate after secondary plasma etching was placed in a metal organic chemical vapor deposition chamber for epitaxial growth. The reaction chamber pressure was set to 40 Torr. Trimethylaluminum and NH3 were used as Al and N sources, and N2 was used as the carrier gas. The trimethylaluminum carrier gas flow rate was set to 200 sccm by controlling the flow meter. After pre-laying Al5s, the NH3 carrier gas flow rate was set to 3 slm by controlling the flow meter. The growth temperature was set to 920°C to form a low-temperature aluminum nitride buffer layer, and then the growth temperature was set to 1230°C to form a high-temperature aluminum nitride buffer layer.

[0066] S6. Regulate the reaction chamber pressure to 40 mTorr, use triethylgallium and oxygen as Ga and O sources, and use N2 as the carrier gas. Control the flowmeter to set the triethylgallium carrier gas flow rate to 45 sccm and the oxygen flow rate to 1950 sccm. Set the reaction chamber temperature to 850°C and grow for 200 minutes to obtain a silicon carbide epitaxial gallium oxide film.

[0067] Comparative Example 1:

[0068] Compared with Example 1, in this comparative example, trimethylaluminum and ammonia were not added during the preparation of the silicon dioxide mask layer. The remaining steps and parameters were the same and will not be repeated in this comparative example. Finally, a silicon carbide epitaxial gallium oxide thin film was obtained.

[0069] Comparative Example 2:

[0070] Compared with Example 1, this comparative example only adjusts "the thickness of the silicon dioxide mask layer is 90-110nm" to "the thickness of the silicon dioxide mask layer is 230-370nm", and the remaining steps and parameters are the same, which will not be repeated in this comparative example. Finally, a silicon carbide epitaxial gallium oxide thin film is obtained.

[0071] Comparative Example 3:

[0072] Compared with Example 1, this comparative example only adjusts "the thickness of the silicon dioxide mask layer is 90-110nm" to "the thickness of the silicon dioxide mask layer is 20-30nm", and the remaining steps and parameters are the same, which will not be repeated in this comparative example. Finally, a silicon carbide epitaxial gallium oxide film is obtained.

[0073] Comparative Example 4:

[0074] S1. A 450μm-thick silicon carbide substrate was ultrasonically cleaned in deionized water for 10 minutes, then rinsed with an SPM solution (98% concentrated sulfuric acid and 30% hydrogen peroxide in a volume ratio of 3.5:1) for 10 minutes at 135°C. Finally, the substrate was rinsed with ultrapure water for 5 minutes and dried at 75°C for 3 minutes to obtain a silicon carbide substrate.

[0075] S2. Silane was supplied to a reaction chamber containing a silicon carbide substrate, and a silicon dioxide film was deposited on the silicon carbide using plasma-enhanced chemical vapor deposition. The deposition temperature was set to 340°C, the RF power for generating the plasma was 330 W, and nitrogen was used as a carrier gas. The carrier gas flow rates of trimethylaluminum and NH3 were set to 10 sccm and 30 sccm, respectively, and the flow was continued for 15 seconds. The silane gas flow rate was then set to 60 sccm. The resulting silicon dioxide film was annealed at 1100°C for 60 minutes to obtain a silicon dioxide mask layer with the silicon carbide substrate.

[0076] S3. Using nitrogen as the carrier and CHF3 as the etching gas, the silicon dioxide mask layer on the silicon carbide substrate was plasma etched. The etching power was set to 35W, the chamber pressure was 3mTorr, the He gas pressure was 3Torr, the N2 gas flow rate was 15sccm, the CHF3 gas flow rate was 40sccm, and the etching time was 80s. The substrate was then rinsed with SPM solution for 12 minutes. The SPM solution was a mixture of 98% concentrated sulfuric acid and 30% hydrogen peroxide in a volume ratio of 3.5:1. The cleaning temperature was 135°C, and the substrate was rinsed with ultrapure water for 7 minutes. The substrate was then dried at 75°C for 3 minutes to obtain the plasma-etched silicon carbide substrate.

[0077] S4. The silicon carbide substrate after secondary plasma etching was placed in a metal organic chemical vapor deposition chamber for epitaxial growth. The reaction chamber pressure was set to 40 Torr. Trimethylaluminum and NH3 were used as Al and N sources, and N2 was used as the carrier gas. The trimethylaluminum carrier gas flow rate was set to 180 sccm by controlling the flow meter. After pre-laying Al6s, the NH3 carrier gas flow rate was set to 2.5 slm by controlling the flow meter. The growth temperature was set to 880°C to form a low-temperature aluminum nitride buffer layer, and then the growth temperature was set to 1150°C to form a high-temperature aluminum nitride buffer layer.

[0078] S5. Regulate the reaction chamber pressure to 35 mTorr, use triethylgallium and oxygen as Ga and O sources, and use N2 as the carrier gas. Control the flowmeter to set the triethylgallium carrier gas flow rate to 35 sccm and the oxygen flow rate to 1800 sccm. Set the reaction chamber temperature to 750°C and grow for 240 minutes to obtain a silicon carbide epitaxial gallium oxide film.

[0079] Performance testing:

[0080] RBS roughness test:

[0081] The silicon carbide epitaxial gallium oxide films prepared in Examples 1-4 and Comparative Examples 1-4 were respectively placed in a constant temperature box at 23-27°C, and then placed on an AFM scanning station for atomic force microscopy testing. After the scanning was completed, the RBS roughness of the silicon carbide epitaxial gallium oxide was obtained based on the AFM image.

[0082] Thermal conductivity test:

[0083] The silicon carbide epitaxial gallium oxide films prepared in Examples 1-4 and Comparative Examples 1-4 were respectively placed on a stage. Rapid heating was performed using a 355nm ultraviolet pulsed laser with a pulse width of 10ns over a period of 0-2000ns. Simultaneously, changes in surface reflectance of the gallium oxide film were continuously monitored using a 532nm continuous laser. The two laser beams were focused vertically through a microscope and irradiated the sample surface before being reflected. The reflected light passed through a 355nm wavelength filter to filter out the heating laser, leaving only the measurement laser light entering the photodetector. Experimental thermal conductivity data of the gallium oxide film was displayed and derived using an oscilloscope connected to the photodetector. The reflectivity ∆R / R of the gallium oxide film was recorded at 50ns, 100ns, 200ns, 300ns, and 500ns, respectively.

[0084] Table 1

[0085] project RBS roughness / nm ∆R / R at 50ns ∆R / R at 100ns ∆R / R at 200ns ∆R / R at 300ns ∆R / R at 500ns Example 1 1.335 0.92 0.79 0.23 0.12 0.06 Example 2 1.289 0.93 0.81 0.24 0.15 0.06 Example 3 1.537 0.92 0.80 0.23 0.11 0.08 Example 4 1.365 0.93 0.79 0.20 0.14 0.09 Comparative Example 1 3.167 0.95 0.86 0.33 0.25 0.14 Comparative Example 2 4.326 0.97 0.89 0.36 0.28 0.17 Comparative Example 3 4.785 0.98 0.90 0.38 0.30 0.20 Comparative Example 4 3.685 0.96 0.87 0.35 0.27 0.15

[0086] Data Analysis:

[0087] As can be seen from Table 1, the silicon carbide epitaxial gallium oxide prepared by the present invention has a smaller RBS roughness and higher thermal conductivity. Specifically, the faster the reflectivity ∆R / R decrease rate of the gallium oxide film, the higher the thermal conductivity, that is, the better the growth quality of the gallium oxide film. This may be because the present invention sequentially grows a silicon dioxide mask layer, an aluminum nitride low-temperature buffer layer, an aluminum nitride high-temperature buffer layer, and a gallium oxide film layer on the silicon carbide substrate. First, the silicon dioxide mask layer contains a small amount of aluminum nitride, which has high thermal conductivity and can quickly transfer heat sources, thereby effectively improving the thermal conductivity of the gallium oxide film. Second, the silicon dioxide mask layer is plasma etched twice, which can reduce the surface roughness of the gallium oxide film. The second plasma etching performs low-power fine-tuning etching on the basis of the first rough etching, forming a large number of tiny and uneven aluminum nitride-doped silicon oxide points on the etched surface to form a pinning effect, providing stable nucleation sites for the subsequent inhibition of defects such as crystal plane rotation, slip, and mesa formation during aluminum nitride growth, further inducing the nucleation of high-quality and regularly arranged aluminum nitride buffer layers. Furthermore, the aluminum nitride buffer layer includes an aluminum nitride low-temperature buffer layer and an aluminum nitride high-temperature buffer layer. The lattice constant difference between aluminum nitride and gallium oxide is small, and aluminum nitride can be grown at low temperature to form a relatively smooth surface, reducing the lattice mismatch between silicon carbide and gallium oxide, and avoiding a large number of dislocations and cracks in the gallium oxide film. The aluminum nitride high-temperature layer has good chemical stability and can effectively improve the growth quality of the gallium oxide film.

[0088] In Comparative Example 1, since trimethylaluminum and ammonia were not added during the preparation of the silicon dioxide mask layer, that is, the silicon dioxide mask layer did not contain a small amount of aluminum nitride, it can be seen from Table 1 that its RBS roughness is large and its thermal conductivity is low. This may be because aluminum nitride has high thermal conductivity and is a good heat dissipation material. Adding a small amount of aluminum nitride to silicon dioxide can further improve the thermal conductivity of the mask layer and better transfer the heat source. Therefore, the thermal conductivity exhibited by Comparative Example 1 is worse than that of Example 1; in Comparative Example 2, since "the thickness of the silicon dioxide mask layer is 90-110nm" is adjusted to "the thickness of the silicon dioxide mask layer is 230-370nm", it can be seen from Table 1 that its RBS roughness is large and its thermal conductivity is low. This may be because the mask layer is too thick, which will generate large heat and mechanical stress during the etching process, causing certain damage to the silicon carbide substrate, thereby affecting the subsequent growth of aluminum nitride and gallium oxide layers. Therefore, the thermal conductivity exhibited by Comparative Example 2 is worse than that of Example 1; in Comparative Example 3, since "the thickness of the silicon dioxide mask layer is 90-110nm" is adjusted to "the thickness of the silicon dioxide mask layer is 230-370nm", it can be seen from Table 1 that its RBS roughness is large and its thermal conductivity is low. This may be because the mask layer is too thick, which will generate large heat and mechanical stress during the etching process, causing certain damage to the silicon carbide substrate, thereby affecting the subsequent growth of aluminum nitride and gallium oxide layers. Therefore, the thermal conductivity exhibited by Comparative Example 2 is worse than that of Example 1; ” is adjusted to “the thickness of the silicon dioxide mask layer is 20-30nm”. It can be seen from Table 1 that its RBS roughness is large and its thermal conductivity is low. This may be because plasma etching is directional and will react preferentially in thinner areas, resulting in uneven etching. In addition, high-energy ions will penetrate the mask layer and directly act on the substrate during the etching process, causing damage. Therefore, the thermal conductivity exhibited by Comparative Example 3 is worse than that of Example 1. In Comparative Example 4, since the silicon dioxide mask layer is only plasma etched once during the preparation of the silicon carbide epitaxial gallium oxide film, it can be seen from Table 1 that its RBS roughness is large and its thermal conductivity is low. This may be because the second lower-power plasma etching can correct the large protrusions and depressions that appear in the first etching, improve the flatness of the etched surface, prevent a large number of cracks in the buffer layer, further induce the nucleation of high-quality and regularly arranged aluminum nitride buffer layer, effectively suppress dislocations in the gallium oxide growth process, and improve the growth quality of the gallium oxide film. Therefore, the thermal conductivity exhibited by Comparative Example 4 is worse than that of Example 1.

[0089] Those skilled in the art should understand that the discussion of any of the above embodiments is merely illustrative and is not intended to imply that the scope of the present invention is limited to these examples. Within the scope of the present invention, the technical features in the above embodiments or different embodiments may be combined, the steps may be implemented in any order, and there are many other variations of the different aspects of the present invention as described above, which are not provided in detail for the sake of simplicity.

[0090] The present invention is intended to cover all such substitutions, modifications and variations that fall within the broad scope of the appended claims. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a silicon carbide epitaxial gallium oxide thin film, characterized in that: The following steps are involved: Step S1. Take a semi-insulating silicon carbide and ultrasonically clean it in deionized water for 10-15 minutes, then clean it with SPM solution for 10-15 minutes, and finally clean it with ultrapure water for 5-7 minutes. Dry it at 75-80°C for 3-5 minutes to obtain a silicon carbide substrate layer; Step S2. Silane is supplied to a reaction chamber containing a silicon carbide substrate, and a silicon dioxide film is deposited on the silicon carbide using plasma-enhanced chemical vapor deposition. The deposition temperature is set to 340-360°C, the RF power for generating the plasma is set to 330-350W, and nitrogen is used as a carrier gas. The carrier gas flow rates of trimethylaluminum and NH3 are set to A1 and B1, respectively, and are continuously passed for 10-15 seconds. The silane gas flow rate is then set to 60-70 sccm. The resulting silicon dioxide film is annealed to obtain a silicon dioxide mask layer with the silicon carbide substrate. Step S3. Using nitrogen as a carrier and CHF3 as an etching gas, the silicon dioxide mask layer on the silicon carbide substrate is subjected to a first plasma etching, followed by cleaning with an SPM solution for 12-15 minutes, then with ultrapure water for 7-12 minutes, and drying at 75-80°C for 3-5 minutes to obtain a single plasma-etched silicon carbide substrate; Step S4. Using nitrogen as a carrier and CHF3 as an etching gas, the silicon dioxide mask layer on the silicon carbide substrate is subjected to a second plasma etching, followed by cleaning with SPM solution for 12-15 minutes, then with ultrapure water for 7-12 minutes, and drying at 75-80°C for 3-5 minutes to obtain a second plasma-etched silicon carbide substrate; Step S5. The silicon carbide substrate after secondary plasma etching is placed in a metal organic chemical vapor deposition chamber for epitaxial growth. The reaction chamber pressure is set to 40 Torr. Trimethylaluminum and NH3 are used as the Al and N sources, and N2 is used as the carrier gas. The trimethylaluminum carrier gas flow rate is set to A2 by controlling the flow meter. After pre-laying Al for 5-6 seconds, the NH3 carrier gas flow rate is then controlled to B2 by controlling the flow meter. The growth temperature is set to C1 to form a low-temperature aluminum nitride buffer layer, and then the growth temperature is set to C2 to form a high-temperature aluminum nitride buffer layer. Step S6. The reaction chamber pressure is adjusted to 35-40 mTorr, the reaction chamber temperature is set to C3, triethylgallium and oxygen are used as Ga and O sources, and N2 is used as a carrier gas. The flow rate of triethylgallium and oxygen carrier gas is set by a flow meter to obtain a silicon carbide epitaxial gallium oxide film. The thickness of the silicon dioxide mask layer is 90-110 nm.

2. The method for preparing a silicon carbide epitaxial gallium oxide thin film according to claim 1, wherein: The SPM solution in step S1 is obtained by mixing 98% concentrated sulfuric acid and 30% hydrogen peroxide in a volume ratio of 3.5-4.5:1, and the cleaning temperature is 135-145°C.

3. The method for preparing a silicon carbide epitaxial gallium oxide thin film according to claim 1, wherein: In step S2, A1 is 10-12 sccm, and B1 is 30-35 sccm.

4. The method for preparing a silicon carbide epitaxial gallium oxide thin film according to claim 1, wherein: The annealing temperature in step S2 is 1100-1200° C., and the annealing time is 50-60 min.

5. The method for preparing a silicon carbide epitaxial gallium oxide thin film according to claim 1, wherein: In step S3, the plasma etching power is set to 45-60 W, the chamber pressure is 2.5-3 mTorr, the He gas pressure is 3-4 Torr, the N2 gas flow rate is 15-25 sccm, the CHF3 gas flow rate is 40-60 sccm, and the etching time is 50-70 s; The SPM solution is obtained by mixing 98% concentrated sulfuric acid and 30% hydrogen peroxide in a volume ratio of 3.5-4.5:1, and the cleaning temperature is 135-145°C.

6. The method for preparing a silicon carbide epitaxial gallium oxide thin film according to claim 1, wherein: In step S4, the plasma etching power is set to 25-32 W, the chamber pressure is 3-4 mTorr, the He gas pressure is 3-4 Torr, the N2 gas flow rate is 10-15 sccm, the CHF3 gas flow rate is 30-40 sccm, and the etching time is 30-45 s; The SPM solution is obtained by mixing 98% concentrated sulfuric acid and 30% hydrogen peroxide in a volume ratio of 3.5-4.5:1, and the cleaning temperature is 135-145°C.

7. The method for preparing a silicon carbide epitaxial gallium oxide thin film according to claim 1, wherein: In step S5, A2 is 180-200 sccm, and B2 is 2.5-3 slm.

8. The method for preparing a silicon carbide epitaxial gallium oxide thin film according to claim 1, characterized in that: The growth temperature C1 in step S5 is 880-920° C. The growth temperature C2 is 1150-1230°C.

9. The method for preparing a silicon carbide epitaxial gallium oxide thin film according to claim 1, wherein: In step S6, the triethylgallium carrier gas flow rate is 35-45 sccm, and the oxygen flow rate is 1800-1950 sccm; The growth temperature C3 of the silicon carbide epitaxial gallium oxide film is 750-850° C., and the growth time is 200-240 minutes.

10. A silicon carbide epitaxial gallium oxide thin film, characterized in that: The silicon carbide epitaxial gallium oxide thin film is prepared by the method for preparing a silicon carbide epitaxial gallium oxide thin film according to any one of claims 1 to 9; The silicon carbide epitaxial gallium oxide film includes a silicon carbide substrate layer and a silicon dioxide mask layer, an aluminum nitride buffer layer, and a gallium oxide film layer sequentially formed on the surface thereof; The thickness of the silicon carbide substrate layer is 450-550 μm, the aluminum nitride buffer layer is composed of a low-temperature aluminum nitride buffer layer with a thickness of 30-45 nm and a high-temperature aluminum nitride buffer layer with a thickness of 210-250 nm, and the thickness of the gallium oxide thin film layer is 4-5 μm.

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