Silicon carbide epitaxial gallium oxide film and preparation method thereof

Abstract

The invention relates to the technical field of semiconductor materials, in particular to a silicon carbide epitaxial gallium oxide thin film and a preparation method thereof.The preparation method includes the steps that 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 are sequentially grown on a silicon carbide substrate slice through a metal organic chemical vapor deposition method; wherein the silicon dioxide mask layer contains a small amount of aluminum nitride, so that a heat source can be quickly transferred, and the heat conductivity of the gallium oxide thin film can be effectively improved; according to the method, plasma etching is carried out on the silicon dioxide mask layer with silicon carbide as the substrate twice, the flatness of the aluminum nitride buffer layer surface is improved, dislocation and step type defects in the gallium oxide growth process are further effectively inhibited, and the growth quality of the gallium oxide film is improved. Through the heteroepitaxy technology, the production cost of the gallium oxide thin film can be reduced, meanwhile, the gallium oxide thin film has high heat conductivity, and compared with the prior art, the gallium oxide thin film has wide application prospects.

Description

Technical Field

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

[0002] With the continuous increase in the demand for low-loss, high-power, and high-performance power electronic devices in the fields of energy, information, and military in modern society, wide-bandgap semiconductors have become a current research hotspot due to their excellent material properties. Wide-bandgap semiconductor materials have received widespread attention and extensive research in the academic community due to their large bandgap, good chemical stability, and high temperature resistance. Among them, gallium oxide, as a new type of semiconductor material, has a large bandgap, making it have an ultra-high breakdown field strength, an ultra-large Baliga figure of merit, and a short ultraviolet cut-off edge, and can be well applied in high-voltage, high-power, low-loss power devices and deep ultraviolet optoelectronic devices. However, the low electron mobility, poor thermal conductivity of gallium oxide thin films, and the challenges of large-size and high-quality gallium oxide substrate growth technology limit its application in high-frequency and high-efficiency electronic devices at high temperatures.

[0003] Silicon carbide, as a promising third-generation wide-bandgap semiconductor material, has good market prospects in the fields of high-power and high-frequency power electronic devices. Its high thermal conductivity, excellent breakdown electric field strength, high electron saturation drift velocity, and excellent high-temperature resistance make silicon carbide very suitable as a substrate for manufacturing high-frequency, high-power density, and high-temperature stability electronic devices, and are applicable to modern industrial fields such as new energy vehicles, renewable energy, smart grids, and rail transit.

[0004] In order to solve the problem of low thermal conductivity of gallium oxide, existing technologies have combined silicon carbide and gallium oxide to make full use of the advantages of the two materials. For example, the patent technical literature CN110993504A discloses a preparation method of a Ga2O3 thin film based on a SiC substrate and a Ga2O3 thin film based on a SiC substrate. The invention consists of a SiC substrate layer, a Ga2O3 buffer layer, and a Ga2O3 thin film layer, and the Ga2O3 buffer layer is obtained by annealing a Ga2O3 material layer. This invention combines two excellent semiconductor materials, silicon carbide and gallium oxide, but there is a large lattice mismatch between them, and the ability of the Ga2O3 buffer layer to solve the lattice mismatch problem remains to be improved.

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

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

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

[0008] A silicon carbide epitaxial gallium oxide film, the 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 provided on its surface; 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 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 film layer is 4 - 5 μm.

[0009] A preparation method of a silicon carbide epitaxial gallium oxide film, comprising the following steps: Step S1. Take semi-insulating silicon carbide and place it in deionized water for ultrasonic cleaning for 10 - 15 min, then clean it with SPM solution for 10 - 15 min, and finally clean it with ultrapure water for 5 - 7 min, and dry it at 75 - 80 °C for 3 - 5 min to obtain a silicon carbide substrate layer; Step S2. Supply silane into the reaction chamber where the silicon carbide substrate is placed, and deposit a silicon dioxide film on the silicon carbide by plasma-enhanced chemical vapor deposition. Set the deposition temperature to 340 - 360 °C, the radio frequency power for generating plasma to 330 - 350 W, use nitrogen as the carrier gas, set the carrier gas flow rates of trimethylaluminum and NH3 to A1 and B1 respectively, and continuously introduce them for 10 - 15 s, then set the gas flow rate of silane to 60 - 70 sccm, and anneal the obtained silicon dioxide film to obtain a silicon dioxide mask layer with silicon carbide as the substrate; Step S3. Use nitrogen as the carrier gas and CHF3 as the etching gas to perform the first plasma etching on the silicon dioxide mask layer with silicon carbide as the substrate, then clean it with SPM solution for 12 - 15 min, then clean it with ultrapure water for 7 - 12 min, and dry it at 75 - 80 °C for 3 - 5 min to remove residual impurity particles and dirt on the surface, and obtain a silicon carbide substrate after the first plasma etching; Step S4. Use nitrogen as the carrier gas and CHF3 as the etching gas to perform the second plasma etching on the silicon dioxide mask layer with silicon carbide as the substrate, then clean it with SPM solution for 12 - 15 min, then clean it with ultrapure water for 7 - 12 min, and dry it at 75 - 80 °C for 3 - 5 min to obtain a silicon carbide substrate after the second plasma etching; Step S5. Load the silicon carbide substrate after secondary plasma etching into a metalorganic chemical vapor deposition chamber for epitaxial process. Set the reaction chamber pressure to 40 Torr. Use trimethylaluminum and NH3 as the Al source and N source, and N2 as the carrier gas. Set the carrier gas flow rate of trimethylaluminum to A2 by controlling the flowmeter. After pre-laying Al for 5 - 6 s, set the carrier gas flow rate of NH3 to B2 by controlling the flowmeter. Set the growth temperature to C1 to form a low-temperature aluminum nitride buffer layer, and then set the growth temperature to C2 to form a high-temperature aluminum nitride buffer layer; Step S6. Regulate the reaction chamber pressure to 35 - 40 mTorr, set the reaction chamber temperature to C3. Use triethylgallium and oxygen as the Ga source and O source, and N2 as the carrier gas. Control the carrier gas flow rates of triethylgallium and oxygen by controlling the flowmeter to obtain a gallium oxide epitaxial film on silicon carbide.

[0010] Preferably, the SPM solution in step S1 is obtained by mixing concentrated sulfuric acid with a mass fraction of 98% and hydrogen peroxide with a mass fraction of 30% at a volume ratio of 3.5 - 4.5:1, and the cleaning temperature is 135 - 145 °C.

[0011] Preferably, A1 in step S2 is 10 - 12 sccm and B1 is 30 - 35 sccm.

[0012] Preferably, the annealing temperature in step S2 is 1100 - 1200 °C and the annealing time is 50 - 60 min.

[0013] Preferably, the plasma etching power in step S3 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 concentrated sulfuric acid with a mass fraction of 98% and hydrogen peroxide with a mass fraction of 30% at a volume ratio of 3.5 - 4.5:1, and the cleaning temperature is 135 - 145 °C.

[0014] Preferably, the plasma etching power in step S4 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; The SPM solution is obtained by mixing concentrated sulfuric acid with a mass fraction of 98% and hydrogen peroxide with a mass fraction of 30% at a volume ratio of 3.5 - 4.5:1, and the cleaning temperature is 135 - 145 °C.

[0015] Preferably, A2 in step S5 is 180 - 200 sccm and B2 is 2.5 - 3 slm.

[0016] Preferably, the growth temperature C1 in step S5 is 880 - 920 °C; The growth temperature C2 is 1150 - 1230 °C.

[0017] Preferably, the flow rate of trimethylgallium carrier gas in step S6 is 35 - 45 sccm, and the flow rate of oxygen is 1800 - 1950 sccm; The growth temperature C3 of the gallium oxide thin film epitaxially grown on silicon carbide is 750 - 850 °C, and the growth time is 200 - 240 min.

[0018] Advantages of the present invention: The present invention provides a silicon carbide epitaxial gallium oxide thin film and a preparation method thereof. The present invention uses metalorganic 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 wafer. Through heteroepitaxy, silicon carbide and gallium oxide are successfully combined, and at the same time, the problem of lattice mismatch between the two is effectively solved, so that the prepared gallium oxide thin film can not only reduce production costs, but also has a high thermal conductivity; Among them, a small amount of trimethylaluminum and ammonia are added during the preparation process of the silicon dioxide mask layer. The aluminum nitride formed by the two has a high thermal conductivity and is a good heat dissipation material, which can quickly transfer heat sources, and thus can effectively improve the thermal conductivity of the gallium oxide thin film; Subsequently, the silicon dioxide mask layer with silicon carbide as the substrate is subjected to two plasma etching processes. Among them, the second plasma etching is a low-power micro-adjustment etching based on the first rough etching, and a large number of tiny and uneven aluminum nitride-doped silicon dioxide dots are formed on the etched surface to form a crystal plane pinning effect, providing a stable nucleation site for suppressing defects such as crystal plane rotation, slip, and mesa formation during the growth of aluminum nitride, further inducing the nucleation of high-quality regular arrangement of the aluminum nitride buffer layer, effectively suppressing dislocations and step-type defects during the growth of gallium oxide, and improving the growth quality of the gallium oxide thin film. Description of the drawings

[0019] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only those of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0020] Figure 1 is the preparation flow chart of the silicon carbide epitaxial gallium oxide thin film in the present invention; Figure 2It is a test result diagram of the thickness uniformity of the silicon carbide epitaxial gallium oxide film prepared in Example 1 of the present invention. Detailed implementation manners

[0021] To make the objectives, technical solutions and advantages of the present invention more clear and understandable, the present invention will be further described in detail below in conjunction with specific embodiments.

[0022] The sources and properties of some raw materials used in the present invention are as follows: Silicon carbide was purchased from Beijing Tiankeheda 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 of Germany; trimethylaluminum was purchased from Wuhan Xinzhongke Chemical Co., Ltd.; NH3 was purchased from Anhui Wangshan Wangshui Special Gas Co., Ltd.

[0023] Example 1: A method for preparing a silicon carbide epitaxial gallium oxide film, comprising the following steps: S1. Take silicon carbide with a thickness of 450 μm, place it in deionized water and ultrasonically clean it for 10 min, then clean it with SPM solution for 10 min. The SPM solution is obtained by mixing concentrated sulfuric acid with a mass fraction of 98% and hydrogen peroxide with a mass fraction of 30% at a volume ratio of 3.5:1. The cleaning temperature is 135°C. Finally, clean it with ultrapure water for 5 min and dry it at 75°C for 3 min to obtain a silicon carbide substrate layer. S2. Supply silane into the reaction chamber where the silicon carbide substrate is placed, and deposit a silicon dioxide film on the silicon carbide by plasma-enhanced chemical vapor deposition. Set the deposition temperature to 340°C, the radio frequency power for generating plasma to 330 W, use nitrogen as the carrier gas, set the carrier gas flow rates of trimethylaluminum and NH3 to 10 sccm and 30 sccm respectively, and continuously introduce them for 15 s. Then set the gas flow rate of silane to 60 sccm, and anneal the obtained silicon dioxide film at 1100°C for 60 min to obtain a silicon dioxide mask layer with silicon carbide as the substrate. S3. Using nitrogen as the carrier gas and CHF3 as the etching gas, perform the first plasma etching on the silicon dioxide mask layer with silicon carbide as the substrate. Set the etching power to 45 W, the chamber pressure to 2.5 mTorr, the He gas pressure to 3 Torr, the N2 gas flow rate to 15 sccm, the CHF3 gas flow rate to 40 sccm, and the etching time to 70 s. Then clean it with SPM solution for 12 min. The SPM solution is obtained by mixing concentrated sulfuric acid with a mass fraction of 98% and hydrogen peroxide with a mass fraction of 30% at a volume ratio of 3.5:1. The cleaning temperature is 135°C. Then clean it with ultrapure water for 7 min and dry it at 75°C for 3 min to obtain a silicon carbide substrate after the first plasma etching. S4. Using nitrogen as the carrier gas and CHF3 as the etching gas, perform the second plasma etching on the silicon dioxide mask layer with silicon carbide as the substrate. Set the etching power to 25 W, the chamber pressure to 3 mTorr, the He gas pressure to 3 Torr, the N2 gas flow rate to 10 sccm, the CHF3 gas flow rate to 30 sccm, and the etching time to 30 s. Then, clean it with SPM solution for 12 min. The SPM solution is obtained by mixing concentrated sulfuric acid with a mass fraction of 98% and hydrogen peroxide with a mass fraction of 30% at a volume ratio of 3.5:1. The cleaning temperature is 135 °C. Then, clean it with ultrapure water for 7 min and dry it at 75 °C for 3 min to obtain the silicon carbide substrate after the second plasma etching; S5. Load the silicon carbide substrate after the second plasma etching into the metalorganic chemical vapor deposition chamber for the epitaxial process. Set the reaction chamber pressure to 40 Torr. Use trimethylaluminum and NH3 as the Al source and N source, and N2 as the carrier gas. By controlling the flowmeter, set the carrier gas flow rate of trimethylaluminum to 180 sccm. After pre-laying Al for 6 s, by controlling the flowmeter, set the carrier gas flow rate of NH3 to 2.5 slm. Set the growth temperature to 880 °C to form a low-temperature aluminum nitride buffer layer, and then set the growth temperature to 1150 °C to form a high-temperature aluminum nitride buffer layer; S6. Regulate the reaction chamber pressure to 35 mTorr. Use triethylgallium and oxygen as the Ga source and O source, and N2 as the carrier gas. Control the flowmeter to set the carrier gas flow rate of triethylgallium to 35 sccm and the oxygen flow rate to 1800 sccm. Grow at a reaction chamber temperature of 750 °C for 240 min to obtain the silicon carbide epitaxial gallium oxide thin film.

[0024] Example 2: A method for preparing a silicon carbide epitaxial gallium oxide thin film, comprising the following steps: S1. Take silicon carbide with a thickness of 480 μm and ultrasonically clean it in deionized water for 12 min, then clean it with SPM solution for 12 min. The SPM solution is obtained by mixing concentrated sulfuric acid with a mass fraction of 98% and hydrogen peroxide with a mass fraction of 30% at a volume ratio of 4:1. The cleaning temperature is 140 °C. Finally, clean it with ultrapure water for 6 min and dry it at 78 °C for 4 min to obtain the silicon carbide substrate layer; S2. Supply silane to the reaction chamber where the silicon carbide substrate is placed, and deposit a silicon dioxide thin film on the silicon carbide by plasma-enhanced chemical vapor deposition. Set the deposition temperature to 350 °C, the radio frequency power for generating plasma to 34 W. Using nitrogen as the carrier gas, set the carrier gas flow rates of trimethylaluminum and NH3 to 11 sccm and 33 sccm respectively, and continuously introduce them for 13 s. Then, set the gas flow rate of silane to 65 sccm. Anneal the obtained silicon dioxide thin film at 1140 °C for 55 min to obtain the silicon dioxide mask layer with silicon carbide as the substrate; S3. Using nitrogen as the carrier and CHF3 as the etching gas, perform the first plasma etching on the silicon dioxide mask layer with silicon carbide as the substrate. Set the etching power to 50 W, the chamber pressure to 2.8 mTorr, the He gas pressure to 3.5 Torr, the N2 gas flow rate to 20 sccm, the CHF3 gas flow rate to 45 sccm, and the etching time to 60 s. Then clean it with SPM solution for 14 min. The SPM solution is obtained by mixing concentrated sulfuric acid with a mass fraction of 98% and hydrogen peroxide with a mass fraction of 30% at a volume ratio of 4:1. The cleaning temperature is 140 °C. Then clean it with ultrapure water for 10 min and dry it at 78 °C for 4 min to obtain the silicon carbide substrate after the first plasma etching; S4. Using nitrogen as the carrier and CHF3 as the etching gas, perform the second plasma etching on the silicon dioxide mask layer with silicon carbide as the substrate. Set the etching power to 28 W, the chamber pressure to 3.5 mTorr, the He gas pressure to 3.5 Torr, the N2 gas flow rate to 13 sccm, the CHF3 gas flow rate to 35 sccm, and the etching time to 35 s. Then clean it with SPM solution for 14 min. The SPM solution is obtained by mixing concentrated sulfuric acid with a mass fraction of 98% and hydrogen peroxide with a mass fraction of 30% at a volume ratio of 4:1. The cleaning temperature is 140 °C. Then clean it with ultrapure water for 10 min and dry it at 78 °C for 4 min to obtain the silicon carbide substrate after the second plasma etching; S5. Load the silicon carbide substrate after the second plasma etching into the metalorganic chemical vapor deposition chamber for the epitaxial process. Set the reaction chamber pressure to 40 Torr. Use trimethylaluminum and NH3 as the Al source and N source, and N2 as the carrier gas. By controlling the flowmeter, set the carrier gas flow rate of trimethylaluminum to 190 sccm. After pre-laying Al for 5.5 s, by controlling the flowmeter, set the carrier gas flow rate of NH3 to 2.8 slm. Set the growth temperature to 900 °C to form a low-temperature aluminum nitride buffer layer, and then set the growth temperature to 1180 °C to form a high-temperature aluminum nitride buffer layer; S6. Regulate the reaction chamber pressure to 38 mTorr. Use triethylgallium and oxygen as the Ga source and O source, and N2 as the carrier gas. Control the flowmeter to set the carrier gas flow rate of triethylgallium to 40 sccm and the oxygen flow rate to 1850 sccm. Grow at 800 °C in the reaction chamber for 220 min to obtain the silicon carbide epitaxial gallium oxide thin film.

[0025] Example 3: A method for preparing a silicon carbide epitaxial gallium oxide thin film, comprising the following steps: S1. Take silicon carbide with a thickness of 520 μm, ultrasonically clean it in deionized water for 12 min, and then clean it with SPM solution for 12 min. The SPM solution is obtained by mixing concentrated sulfuric acid with a mass fraction of 98% and hydrogen peroxide with a mass fraction of 30% at a volume ratio of 4:1. The cleaning temperature is 140 °C. Finally, clean it with ultrapure water for 6 min and dry it at 78 °C for 4 min to obtain a silicon carbide substrate layer; S2. Supply silane into the reaction chamber where the silicon carbide substrate is placed, and deposit a silicon dioxide thin film on the silicon carbide by plasma-enhanced chemical vapor deposition. Set the deposition temperature at 350 °C, the radio frequency power for generating plasma at 340 W, use nitrogen as the carrier gas, set the carrier gas flow rates of trimethylaluminum and NH3 at 11 sccm and 33 sccm respectively, and continuously introduce them for 13 s. Then set the gas flow rate of silane at 65 sccm, and anneal the obtained silicon dioxide thin film at 1180 °C for 55 min to obtain a silicon dioxide mask layer with silicon carbide as the substrate; S3. Using nitrogen as the carrier gas and CHF3 as the etching gas, perform the first plasma etching on the silicon dioxide mask layer with silicon carbide as the substrate. Set the etching power at 55 W, the chamber pressure at 2.8 mTorr, the He gas pressure at 3.5 Torr, the N2 gas flow rate at 20 sccm, the CHF3 gas flow rate at 50 sccm, and the etching time at 60 s. Subsequently, clean it with SPM solution for 14 min. The SPM solution is obtained by mixing concentrated sulfuric acid with a mass fraction of 98% and hydrogen peroxide with a mass fraction of 30% at a volume ratio of 4:1. The cleaning temperature is 140 °C. Then clean it with ultrapure water for 10 min and dry it at 78 °C for 4 min to obtain a silicon carbide substrate after the first plasma etching; S4. Using nitrogen as the carrier gas and CHF3 as the etching gas, perform the second plasma etching on the silicon dioxide mask layer with silicon carbide as the substrate. Set the etching power at 28 W, the chamber pressure at 3.5 mTorr, the He gas pressure at 3.5 Torr, the N2 gas flow rate at 13 sccm, the CHF3 gas flow rate at 35 sccm, and the etching time at 40 s. Subsequently, clean it with SPM solution for 14 min. The SPM solution is obtained by mixing concentrated sulfuric acid with a mass fraction of 98% and hydrogen peroxide with a mass fraction of 30% at a volume ratio of 4:1. The cleaning temperature is 140 °C. Then clean it with ultrapure water for 10 min and dry it at 78 °C for 4 min to obtain a silicon carbide substrate after the second plasma etching; S5. Load the silicon carbide substrate etched by secondary plasma into the metal-organic chemical vapor deposition chamber for epitaxial process. Set the reaction chamber pressure to 40 Torr. Use trimethylaluminum and NH3 as the Al source and N source, and N2 as the carrier gas. Set the carrier gas flow rate of trimethylaluminum to 190 sccm through controlling the flowmeter. After pre-laying Al for 5.5 s, set the carrier gas flow rate of NH3 to 2.8 slm through controlling the flowmeter. Set the growth temperature to 900 °C to form a low-temperature aluminum nitride buffer layer, and then set the growth temperature to 1200 °C to form a high-temperature aluminum nitride buffer layer; S6. Regulate the reaction chamber pressure to 38 mTorr. Use triethylgallium and oxygen as the Ga source and O source, and N2 as the carrier gas. Control the flowmeter to set the carrier gas flow rate of triethylgallium to 40 sccm and the oxygen flow rate to 1900 sccm. Grow for 210 min under the condition that the reaction chamber temperature is set to 800 °C, and then the silicon carbide epitaxial gallium oxide thin film is obtained.

[0026] Example 4: A method for preparing a silicon carbide epitaxial gallium oxide thin film, comprising the following steps: S1. Take silicon carbide with a thickness of 550 μm and place it in deionized water for ultrasonic cleaning for 15 min, and then clean it with SPM solution for 15 min. The SPM solution is obtained by mixing concentrated sulfuric acid with a mass fraction of 98% and hydrogen peroxide with a mass fraction of 30% at a volume ratio of 4.5:1. The cleaning temperature is 145 °C. Finally, clean it with ultrapure water for 7 min and dry it at 80 °C for 5 min to obtain a silicon carbide substrate layer; S2. Supply silane into the reaction chamber where the silicon carbide substrate is placed, and deposit a silicon dioxide thin film on the silicon carbide by plasma-enhanced chemical vapor deposition. Set the deposition temperature to 360 °C, the radio frequency power for generating plasma to 350 W. Use nitrogen as the carrier, and set the carrier gas flow rates of trimethylaluminum and NH3 to 12 sccm and 35 sccm respectively, and continuously introduce them for 10 s. Then set the gas flow rate of silane to 70 sccm, and anneal the obtained silicon dioxide thin film at 1200 °C for 50 min to obtain a silicon dioxide mask layer with silicon carbide as the substrate; S3. Use nitrogen as the carrier and CHF3 as the etching gas to perform the first plasma etching on the silicon dioxide mask layer with silicon carbide as the substrate. Set the etching power to 60 W, the chamber pressure to 3 mTorr, the He gas pressure to 4 Torr, the N2 gas flow rate to 25 sccm, the CHF3 gas flow rate to 60 sccm, and the etching time to 70 s. Then clean it with SPM solution for 15 min. The SPM solution is obtained by mixing concentrated sulfuric acid with a mass fraction of 98% and hydrogen peroxide with a mass fraction of 30% at a volume ratio of 4.5:1. The cleaning temperature is 145 °C. Then clean it with ultrapure water for 12 min and dry it at 80 °C for 5 min to obtain the silicon carbide substrate etched by primary plasma; S4. Using nitrogen as the carrier gas and CHF3 as the etching gas, perform the second plasma etching on the silicon dioxide mask layer with silicon carbide as the substrate. Set the etching power to 32 W, the chamber pressure to 4 mTorr, the He gas pressure to 4 Torr, the N2 gas flow rate to 15 sccm, the CHF3 gas flow rate to 40 sccm, and the etching time to 45 s. Then, clean it with SPM solution for 15 min. The SPM solution is obtained by mixing concentrated sulfuric acid with a mass fraction of 98% and hydrogen peroxide with a mass fraction of 30% at a volume ratio of 4.5:1. The cleaning temperature is 145 °C. Then, clean it with ultrapure water for 12 min and dry it at 80 °C for 5 min to obtain the silicon carbide substrate after the second plasma etching; S5. Load the silicon carbide substrate after the second plasma etching into the metal organic chemical vapor deposition chamber for the epitaxial process. Set the reaction chamber pressure to 40 Torr. Using trimethylaluminum and NH3 as the Al source and N source respectively, and N2 as the carrier gas. By controlling the flowmeter, set the carrier gas flow rate of trimethylaluminum to 200 sccm. After pre-laying Al for 5 s, by controlling the flowmeter, set the carrier gas flow rate of NH3 to 3 slm. Set the growth temperature to 920 °C to form a low-temperature aluminum nitride buffer layer, and then set the growth temperature to 1230 °C to form a high-temperature aluminum nitride buffer layer; S6. Regulate the reaction chamber pressure to 40 mTorr. Using triethylgallium and oxygen as the Ga source and O source respectively, and N2 as the carrier gas. Control the flowmeter to set the carrier gas flow rate of triethylgallium to 45 sccm and the oxygen flow rate to 1950 sccm. Grow at 850 °C in the reaction chamber for 200 min to obtain the gallium oxide epitaxial film on silicon carbide.

[0027] Comparative Example 1: In this comparative example, compared with Example 1, trimethylaluminum and ammonia were not added during the preparation process of the silicon dioxide mask layer, and the rest of the steps and parameters were the same. This comparative example will not be repeated here. Finally, the gallium oxide epitaxial film on silicon carbide was obtained.

[0028] Comparative Example 2: In this comparative example, compared with Example 1, only the thickness of the silicon dioxide mask layer was adjusted from "90 - 110 nm" to "230 - 370 nm", and the rest of the steps and parameters were the same. This comparative example will not be repeated here. Finally, the gallium oxide epitaxial film on silicon carbide was obtained.

[0029] Comparative Example 3: In this comparative example, compared with Example 1, only the thickness of the silicon dioxide mask layer was adjusted from "90 - 110 nm" to "20 - 30 nm", and the rest of the steps and parameters were the same. This comparative example will not be repeated here. Finally, the gallium oxide epitaxial film on silicon carbide was obtained.

[0030] Comparative Example 4: S1. Take silicon carbide with a thickness of 450 μm, ultrasonically clean it in deionized water for 10 min, and then clean it with SPM solution for 10 min. The SPM solution is obtained by mixing concentrated sulfuric acid with a mass fraction of 98% and hydrogen peroxide with a mass fraction of 30% at a volume ratio of 3.5:1. The cleaning temperature is 135 °C. Finally, clean it with ultrapure water for 5 min and dry it at 75 °C for 3 min to obtain a silicon carbide substrate layer; S2. Supply silane to the reaction chamber where the silicon carbide substrate is placed, and deposit a silicon dioxide thin film on the silicon carbide by plasma-enhanced chemical vapor deposition. Set the deposition temperature to 340 °C, the radio frequency power for generating plasma to 330 W, use nitrogen as the carrier gas, set the carrier gas flow rates of trimethylaluminum and NH3 to 10 sccm and 30 sccm respectively, and continuously introduce them for 15 s. Then set the gas flow rate of silane to 60 sccm, and anneal the obtained silicon dioxide thin film at 1100 °C for 60 min to obtain a silicon dioxide mask layer with silicon carbide as the substrate; S3. Using nitrogen as the carrier gas and CHF3 as the etching gas, perform plasma etching on the silicon dioxide mask layer with silicon carbide as the substrate. Set the etching power to 35 W, the chamber pressure to 3 mTorr, the He gas pressure to 3 Torr, the N2 gas flow rate to 15 sccm, the CHF3 gas flow rate to 40 sccm, and the etching time to 80 s. Subsequently, clean it with SPM solution for 12 min. The SPM solution is obtained by mixing concentrated sulfuric acid with a mass fraction of 98% and hydrogen peroxide with a mass fraction of 30% at a volume ratio of 3.5:1. The cleaning temperature is 135 °C. Then clean it with ultrapure water for 7 min and dry it at 75 °C for 3 min to obtain a plasma-etched silicon carbide substrate; S4. Load the plasma-etched silicon carbide substrate into the metalorganic chemical vapor deposition chamber for epitaxial growth. Set the reaction chamber pressure to 40 Torr, use trimethylaluminum and NH3 as the Al source and N source, and N2 as the carrier gas. By controlling the flow meter, set the carrier gas flow rate of trimethylaluminum to 180 sccm. After pre-laying Al for 6 s, by controlling the flow meter, set the carrier gas flow rate of NH3 to 2.5 slm, set the growth temperature to 880 °C to form a low-temperature aluminum nitride buffer layer, and then set the growth temperature to 1150 °C to form a high-temperature aluminum nitride buffer layer; S5. Regulate the reaction chamber pressure to 35 mTorr, use triethylgallium and oxygen as the Ga source and O source, and N2 as the carrier gas. Control the flow meter to set the carrier gas flow rate of triethylgallium to 35 sccm and the oxygen flow rate to 1800 sccm, and grow at a reaction chamber temperature of 750 °C for 240 min to obtain a silicon carbide epitaxial gallium oxide thin film.

[0031] Performance Test: RBS Roughness Test: The silicon carbide epitaxial gallium oxide thin films prepared in Examples 1-4 and Comparative Examples 1-4 were respectively placed in a constant temperature oven at 23-27 °C, and then placed in an AFM scanning stage for atomic force microscope microscopy testing. After the scanning was completed, the RBS roughness of the silicon carbide epitaxial gallium oxide was obtained according to the AFM image; Thermal conductivity test: The silicon carbide epitaxial gallium oxide thin films prepared in Examples 1-4 and Comparative Examples 1-4 were respectively placed on the stage. In a cycle of 0-2000 ns, at a pulse width of 10 ns, a UV pulsed laser with a wavelength of 355 nm was used to rapidly heat, and at the same time, a continuous laser with a wavelength of 532 nm was used to continuously detect the change in the surface reflection of the gallium oxide thin film. After the two lasers were focused vertically on the sample surface through a microscope and reflected, the reflected light passed through a filter with a wavelength of 355 nm to filter out the heating laser, and only the measuring laser entered the photodetector. The experimental data of the thermal conductivity of the gallium oxide thin film were displayed and exported by an oscilloscope connected to the photodetector. The reflectivity ∆R / R of the gallium oxide thin film at 50 ns, 100 ns, 200 ns, 300 ns, and 500 ns was respectively recorded.

[0032] Table 1 Item RBS Roughness / nm ∆R / R at 50 ns ∆R / R at 100 ns ∆R / R at 200 ns ∆R / R at 300 ns ∆R / R at 500 ns 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 Data analysis: As can be seen from Table 1, the silicon carbide epitaxial gallium oxide prepared by the present invention has a smaller RBS roughness and a higher thermal conductivity. Among them, the faster the decrease rate of the reflectivity ∆R / R of the gallium oxide thin film, the higher the thermal conductivity, that is, the better the growth quality of the gallium oxide thin film. This may be because in the present invention, 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 are sequentially grown on the silicon carbide substrate wafer. First, a small amount of aluminum nitride is contained in the silicon dioxide mask layer, which has a high thermal conductivity and can rapidly transfer heat sources, thereby effectively improving the thermal conductivity of the gallium oxide thin film; secondly, the silicon dioxide mask layer is subjected to two plasma etching processes, which can reduce the surface roughness of the gallium oxide thin film. Moreover, the second plasma etching is a low-power micro-control etching based on the first rough etching, and a large number of tiny and uneven aluminum nitride-doped silicon dioxide dots are formed on the etched surface to form a pinning effect, providing a stable nucleation site for suppressing defects such as crystal plane rotation, slip, and mesa formation during the growth of aluminum nitride, and further inducing the high-quality regular arrangement of the aluminum nitride buffer layer; 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, which can form a relatively smooth surface at low temperature, reduce the lattice mismatch between silicon carbide and gallium oxide, and avoid a large number of dislocations and cracks in the gallium oxide thin film. And the aluminum nitride high-temperature layer has good chemical stability, which can effectively improve the growth quality of the gallium oxide thin film; In Comparative Example 1, since trimethylaluminum and ammonia were not added during the preparation of the silicon dioxide mask layer, that is, a small amount of aluminum nitride was not contained in the silicon dioxide mask layer. As can be seen from Table 1, its RBS roughness is larger and its thermal conductivity is lower. This may be because aluminum nitride has a 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 of Comparative Example 1 is worse than that of Example 1; in Comparative Example 2, since the thickness of the silicon dioxide mask layer was adjusted from "90 - 110 nm" to "230 - 370 nm", as can be seen from Table 1, its RBS roughness is larger and its thermal conductivity is lower. This may be because the mask layer is too thick, and a large amount of heat and mechanical stress will be generated during the etching process, which will cause certain damage to the silicon carbide substrate, thereby affecting the growth of the subsequent aluminum nitride and gallium oxide layers. Therefore, the thermal conductivity of Comparative Example 2 is worse than that of Example 1; in Comparative Example 3, since the thickness of the silicon dioxide mask layer was adjusted from "90 - 110 nm" to "20 - 30 nm", as can be seen from Table 1, its RBS roughness is larger and its thermal conductivity is lower. This may be because plasma etching has directionality and will preferentially react at the thinner part, resulting in uneven etching. Moreover, high-energy ions will penetrate the mask layer during the etching process and directly act on the substrate to cause damage. Therefore, the thermal conductivity of Comparative Example 3 is worse than that of Example 1; in Comparative Example 4, since the silicon dioxide mask layer was only subjected to plasma etching once during the preparation of the silicon carbide epitaxial gallium oxide thin film, as can be seen from Table 1, its RBS roughness is larger and its thermal conductivity is lower. This may be because the second plasma etching with a lower power 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 from appearing in the buffer layer, further induce the nucleation of high-quality regular arrangement of the aluminum nitride buffer layer, effectively inhibit the dislocations during the growth of the gallium oxide, and improve the growth quality of the gallium oxide thin film. Therefore, the thermal conductivity of Comparative Example 4 is worse than that of Example 1.

[0033] Those of ordinary skill in the art should understand that the discussion of any of the above embodiments is only exemplary and is not intended to imply that the scope of the present invention is limited to these examples; under the concept of the present invention, the technical features in the above embodiments or different embodiments can also be combined, and the steps can be implemented in any order, and there are many other variations in different aspects of the present invention as described above. For the sake of brevity, they are not provided in detail.

[0034] The present invention aims 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 principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A silicon carbide epitaxial gallium oxide thin film, characterized in that, 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 that are sequentially disposed on its surface; 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 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 film layer is 4 - 5 μm.

2. The preparation method of the silicon carbide epitaxial gallium oxide thin film according to claim 1, characterized in that, It includes the following steps: Step S1. Take semi-insulating silicon carbide and place it in deionized water for ultrasonic cleaning for 10 - 15 min, then clean it with SPM solution for 10 - 15 min, and finally clean it with ultrapure water for 5 - 7 min, and dry it at 75 - 80 °C for 3 - 5 min to obtain the silicon carbide substrate layer; Step S2. Supply silane into the reaction chamber where the silicon carbide substrate is placed, and deposit a silicon dioxide film on the silicon carbide by plasma-enhanced chemical vapor deposition. Set the deposition temperature to 340 - 360 °C, the radio frequency power for generating plasma to 330 - 350 W, use nitrogen as the carrier gas, set the carrier gas flow rates of trimethylaluminum and NH3 to A1 and B1 respectively, and continuously introduce them for 10 - 15 s. Then set the gas flow rate of silane to 60 - 70 sccm, and anneal the obtained silicon dioxide film to obtain the silicon dioxide mask layer with silicon carbide as the substrate; ​ ​ ​ ​ 3. The preparation method of the silicon carbide epitaxial gallium oxide thin film according to claim 2, wherein, In step S1, the SPM solution is obtained by mixing concentrated sulfuric acid with a mass fraction of 98% and hydrogen peroxide with a mass fraction of 30% at a volume ratio of 3.5 - 4.5:1, and the cleaning temperature is 135 - 145°C.

4. The method for preparing a silicon carbide epitaxial gallium oxide thin film according to claim 2, wherein, In step S2, A1 is 10 - 12 sccm and B1 is 30 - 35 sccm.

5. The method for preparing a silicon carbide epitaxial gallium oxide thin film according to claim 2, wherein In step S2, the annealing temperature is 1100 - 1200°C and the annealing time is 50 - 60 min.

6. The method for preparing a silicon carbide epitaxial gallium oxide thin film according to claim 2, 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 concentrated sulfuric acid with a mass fraction of 98% and hydrogen peroxide with a mass fraction of 30% at 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 2, 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 concentrated sulfuric acid with a mass fraction of 98% and hydrogen peroxide with a mass fraction of 30% at a volume ratio of 3.5 - 4.5:1, and the cleaning temperature is 135 - 145°C.

8. The method for preparing a silicon carbide epitaxial gallium oxide thin film according to claim 2, wherein, In step S5, A2 is 180 - 200 sccm and B2 is 2.5 - 3 slm.

9. The method for preparing a gallium oxide thin film by epitaxial oxidation of silicon carbide according to claim 2, characterized in that, In step S5, the growth temperature C1 is 880 - 920°C; The growth temperature C2 is 1150 - 1230°C.

10. The method for preparing a silicon carbide epitaxial gallium oxide thin film according to claim 2, wherein In step S6, the trimethylgallium carrier gas flow rate is 35 - 45 sccm and the oxygen flow rate is 1800 - 1950 sccm; The growth temperature C3 of the gallium oxide thin film epitaxially grown on silicon carbide is 750 - 850°C and the growth time is 200 - 240 min.

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