Preparation method of gate oxide layer of switching device based on SiC substrate and switching device

Abstract

The invention provides a method for preparing a gate oxide layer of a switching device based on a SiC substrate and a switching device, and relates to the technical field of semiconductors. The invention uses an atomic layer deposition method to sequentially form an aluminum oxide film and a hafnium oxide film on the surface of a SiC substrate to form a gate oxide layer of a laminated structure. The thickness of the formed aluminum oxide film and the hafnium oxide film are uniform and the thickness can be precisely controlled, so as to ensure that the thickness and thickness of the entire gate oxide layer can accurately meet the requirements. Since aluminum oxide and hafnium oxide have higher dielectric constants, the laminated structure formed by the two can improve the overall dielectric constant of the gate oxide layer, increase the capacitance effect of the gate dielectric, and suppress tunneling leakage current. Annealing the aluminum oxide film and the hafnium oxide film can improve the crystallinity and interface quality of the film. Rapid thermal annealing is performed on the prepared switching device sample to further optimize the performance of the gate oxide layer and reduce defects and interface charges.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and in particular to a method for preparing a gate oxide layer of a switching device based on a SiC substrate and a switching device. Background Art

[0002] Silicon carbide material is a wide bandgap semiconductor material. It has many advantages such as large bandgap width, high breakdown field strength, radiation resistance, and the ability to work normally under high temperature conditions of several hundred degrees Celsius. In addition, the epitaxial growth technology of silicon carbide material is more mature than other common wide bandgap semiconductors. These factors jointly determine that SiC material is the preferred material for the preparation of various advanced power devices. The performance of traditional silicon-based devices is getting closer and closer to its material limit and it is difficult to meet application requirements. However, in recent years, with the vigorous development of new energy vehicles, smart grids, rail transit and other fields, which has brought huge demand, research on various power devices based on SiC materials has developed rapidly.

[0003] The quality of the gate dielectric layer of traditional switching devices based on SiC materials decreases as the size of the device decreases. The material mainly uses thermally oxidized SiO2. The traditional SiO2 gate dielectric layer has many physical limit problems caused by the reduction of film thickness. The dielectric constant of the thermally oxidized SiO2 gate oxide layer is relatively low, which limits the capacitance effect and electrical insulation performance of the device. In addition, the thermally oxidized SiO2 gate oxide layer is prone to pinholes caused by uneven oxidation, resulting in a short circuit between the gate and the substrate. The electric field strength is likely to exceed the breakdown field strength, causing the SiO2 gate dielectric layer to lose its original insulation effect, forming a quantum tunneling effect, causing tunneling current, and increasing the gate leakage current, resulting in increased power consumption and performance degradation of the device. In addition, the thickness of the thermally oxidized SiO2 gate oxide layer is easily limited, and it is difficult to achieve a larger gate oxide layer thickness. During the thermal oxidation process of SiC, due to the presence of C, the chemical reaction process of the thermal oxidation process is complex, and byproducts such as C, CO, and SiO will be produced, which is difficult to meet the application requirements of high dielectric constant, gate oxide thickness, and small leakage current. Summary of the invention

[0004] The object of the present invention is to provide a method for preparing a gate oxide layer of a switching device based on a SiC substrate and a switching device, so as to solve the problems raised in the above background technology.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] A method for preparing a gate oxide layer of a switching device based on a SiC substrate, the preparation method comprising:

[0007] Providing a SiC substrate, and forming an aluminum oxide film on the surface of the SiC substrate by using an atomic layer deposition method;

[0008] Using an atomic layer deposition method, a hafnium oxide film is formed on a surface of the aluminum oxide film away from the SiC substrate;

[0009] Annealing the aluminum oxide film and the hafnium oxide film, wherein the aluminum oxide film and the hafnium oxide film after annealing form a gate oxide layer of a stacked structure;

[0010] Vapor-depositing metal electrodes on the surface of the hafnium oxide film away from the SiC substrate and on the surface of the SiC substrate away from the aluminum oxide film to produce a switching device sample;

[0011] The switching device sample is subjected to a rapid thermal annealing process.

[0012] Further, the step of providing the SiC substrate comprises:

[0013] Providing a prepared SiC substrate;

[0014] The prepared SiC substrate is ultrasonically cleaned in anhydrous ethanol for 10 minutes, and then heated to 75° C. and ultrasonically cleaned for 10 minutes in a mixed solution, wherein the mixed solution is composed of ammonia water, hydrogen peroxide and deionized water in a volume ratio of 2:1:7;

[0015] The SiC substrate was prepared by immersing the heated SiC substrate in a BOE solution for 1 minute to obtain a SiC substrate. The BOE solution was a mixture of hydrofluoric acid and ammonia water in a volume ratio of 1:6.

[0016] Furthermore, the specific steps of forming an aluminum oxide film on the surface of a SiC substrate using an atomic layer deposition method include:

[0017] The temperature of the first container containing the SiC substrate is controlled to be 100-300° C. and the pressure is 1 Torr-10 Torr. Trimethylaluminum is used as an aluminum precursor. The trimethylaluminum is introduced into the first container by carrying the trimethylaluminum with an inert gas, and the trimethylaluminum is adsorbed on the surface of the SiC substrate. The flow rate of the inert gas carrying the trimethylaluminum is 50 sccm-200 sccm.

[0018] Introducing an inert purge gas into the interior of the first container to purge the first container to remove unreacted trimethylaluminum and generated methane;

[0019] Introducing water vapor as an oxidant into the first container to react with trimethylaluminum adsorbed on the substrate to generate aluminum oxide, wherein the flow rate of the water vapor is 10 sccm-200 sccm;

[0020] Passing the inert gas for purging into the first container again to remove the remaining water vapor and methane produced by oxidation;

[0021] Repeat the above steps until an aluminum oxide film of required thickness is grown;

[0022] The inert gas is nitrogen or argon, and the flow rate of the inert gas for purging is 100 sccm-500 sccm.

[0023] Furthermore, the specific steps of using the atomic layer deposition method to form a hafnium oxide film on the surface of the aluminum oxide film include:

[0024] The temperature of the second container containing the SiC substrate with the aluminum oxide film is controlled to be 150-300° C. and the pressure is 1 Torr-10 Torr. Hafnium tetrachloride is used as a precursor of hafnium. The hafnium tetrachloride is introduced into the second container by carrying the hafnium tetrachloride through an inert gas, and the hafnium tetrachloride is adsorbed on the surface of the aluminum oxide film. The flow rate of the inert gas carrying the hafnium tetrachloride is 10 sccm-100 sccm.

[0025] Introducing an inert gas for purging into the interior of the second container to purge the second container to remove unreacted hafnium tetrachloride and generated chlorine gas;

[0026] Introducing water vapor as an oxidant into the second container to react with hafnium tetrachloride adsorbed on the substrate to generate hafnium oxide, wherein the flow rate of the water vapor is 10 sccm-200 sccm;

[0027] Passing the inert gas for purging into the interior of the second container again to remove the remaining water vapor and hydrogen chloride produced by oxidation;

[0028] Repeat the above steps until a hafnium oxide film of a required thickness is grown;

[0029] The inert gas is nitrogen or argon, and the flow rate of the inert gas for purging is 100 sccm-500 sccm.

[0030] Furthermore, the thickness of the aluminum oxide film is 7 nm, and the thickness of the hafnium oxide film is 3 nm.

[0031] Further, the steps of annealing the aluminum oxide film and the hafnium oxide film are as follows:

[0032] The aluminum oxide film and the hafnium oxide film are annealed in a space with a predetermined gas, wherein the predetermined gas includes at least one of argon, nitrogen, nitric oxide and nitrous oxide, the annealing temperature is 200° C., and the annealing time is 2 hours.

[0033] Furthermore, the step of performing rapid thermal annealing treatment on the switching device sample is:

[0034] The switching device sample is subjected to annealing treatment in a space with a predetermined gas, wherein the predetermined gas includes at least one of argon, nitrogen, nitric oxide and nitrous oxide, the annealing treatment is performed at a treatment temperature of 400° C., and the annealing treatment is performed for 5 minutes.

[0035] Furthermore, the metal electrode includes a 5 nm thick chromium layer and a 50 nm thick gold layer covering the surface of the chromium layer, and the chromium layer is attached to the surface of the hafnium oxide film away from the SiC substrate and the surface of the SiC substrate away from the aluminum oxide film.

[0036] The present invention further provides a switch device based on a SiC substrate, comprising a gate oxide layer and a metal electrode, wherein the gate oxide layer and the metal electrode are manufactured by the above method.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] The present invention uses an atomic layer deposition method to sequentially form an aluminum oxide film and a hafnium oxide film on the surface of a SiC substrate to form a gate oxide layer of a stacked structure. The aluminum oxide film and the hafnium oxide film have uniform thickness and can be precisely controlled in thickness, thereby ensuring that the thickness and thickness of the entire gate oxide layer can accurately meet the requirements. Since aluminum oxide and hafnium oxide have relatively high dielectric constants, the stacked structure formed by the two can improve the overall dielectric constant of the gate oxide layer, increase the capacitance effect of the gate dielectric, and suppress tunneling leakage current. Annealing the aluminum oxide film and the hafnium oxide film can improve the crystallinity and interface quality of the film and improve the performance of the gate oxide layer. Rapid thermal annealing is performed on the prepared switching device sample to further optimize the performance of the gate oxide layer. Annealing can promote the rearrangement of the lattice inside the aluminum oxide film and the hafnium oxide film, improve crystallinity, reduce defects and interface charges, thereby improving the quality and performance of the gate oxide layer, improving the interface quality between the aluminum oxide film and the SiC substrate, reducing the charge shielding effect of the interface, and improving the electrical insulation of the gate dielectric. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 It is a schematic diagram of the process of the present invention;

[0040] Figure 2 It is a schematic diagram of the process flow of the processing technology of the present invention;

[0041] Figure 3 A topographical diagram of the surface of a SiC substrate in an atomic force microscope of the present invention;

[0042] Figure 4 The figure is a morphology image of the surface of the hafnium oxide film in the atomic force microscope of the present invention;

[0043] Figure 5This is a capacitance test diagram of the gate oxide layer of the stacked structure in the present invention. DETAILED DESCRIPTION

[0044] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific embodiments of the present invention are described in detail below in conjunction with the accompanying drawings. In the following description, many specific details are set forth to facilitate a full understanding of the present application. However, the present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present invention, so the present invention is not limited by the specific embodiments disclosed below.

[0045] It should be noted that, unless otherwise defined, the technical terms or scientific terms used in the present invention should be the common meanings understood by people with ordinary skills in the field to which the present invention belongs. The words "first", "second" and similar words used in the present invention do not indicate any order, quantity or importance, but are only used to distinguish different components. "Include" or "comprise" and similar words mean that the elements or objects appearing before the word include the elements or objects listed after the word and their equivalents, without excluding other elements or objects. "Connect" or "connected" and similar words are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect.

[0046] "Up", "down", "left", "right", etc. are only used to indicate relative position relationships. When the absolute position of the object being described changes, the relative position relationship may also change accordingly.

[0047] Example:

[0048] See also Figures 1 to 5 , the present invention provides a technical solution:

[0049] A method for preparing a gate oxide layer of a switching device based on a SiC substrate, comprising:

[0050] Step 1: Provide a SiC substrate, and form an aluminum oxide (Al2O3) thin film on the surface of the SiC substrate using an atomic layer deposition method.

[0051] In this embodiment, the step of providing the SiC substrate includes:

[0052] A prepared SiC substrate is provided. The prepared SiC substrate is a raw material for generating a SiC substrate. Since the surface of the prepared SiC substrate may have impurities and pollutants, etc., it needs to be cleaned, heated and soaked in a BOE solution to ensure that the obtained SiC substrate meets subsequent processing requirements.

[0053] The prepared SiC substrate is placed in anhydrous ethanol for ultrasonic cleaning for 10 minutes to remove impurities, pollutants, grease, etc. on the surface of the SiC substrate to ensure the cleanliness of the surface of the SiC substrate, and then heated to 75°C in a mixed solution for ultrasonic cleaning for 10 minutes to further clean and activate the surface of the SiC substrate and improve the surface activity and roughness to facilitate subsequent chemical reactions and material bonding. The mixed solution is composed of a mixture of ammonia water, hydrogen peroxide and deionized water in a volume ratio of 2:1:7.

[0054] The SiC substrate is prepared by immersing the SiC substrate in a BOE solution for 1 minute after heating to obtain a SiC substrate. The BOE solution is a mixture of hydrofluoric acid and ammonia water in a volume ratio of 1:6, which can etch and planarize the surface of the SiC substrate, remove oxides and tiny defects on the surface of the substrate, and improve the surface flatness.

[0055] This step can obtain a clean, flat, and chemically stable SiC substrate surface, thereby providing good basic conditions for making it suitable for subsequent process steps such as material deposition and device preparation.

[0056] In this embodiment, the specific steps of forming an aluminum oxide (Al2O3) film on the surface of a SiC substrate using an atomic layer deposition method include:

[0057] The temperature of the first container containing the SiC substrate is controlled to be 100-300° C. and the pressure is controlled to be 1 Torr-10 Torr to promote the reaction and control the reaction rate so that the SiC substrate reaches an ideal growth condition;

[0058] Trimethylaluminum is used as an aluminum precursor. The trimethylaluminum is introduced into the first container by carrying the trimethylaluminum with an inert gas, and the trimethylaluminum is adsorbed on the surface of the SiC substrate. The flow rate of the inert gas carrying the trimethylaluminum is 50 sccm.

[0059] -200sccm, trimethylaluminum as a precursor has good volatility and stability, and is easily converted into aluminum oxide (Al2O3) in the gas phase. By carrying trimethylaluminum with inert gas, its transportation and adsorption in the reaction chamber can be controlled to achieve uniform surface deposition;

[0060] Introducing an inert gas for purging into the interior of the first container to purge the first container, so as to remove unreacted trimethylaluminum and generated methane, which can effectively remove unreacted precursors and by-products and maintain the cleanliness of the reaction chamber. The generated methane is removed to avoid its influence on the reaction while maintaining the stability of the reaction environment;

[0061] Water vapor is introduced into the interior of the first container as an oxidant to react with trimethylaluminum adsorbed on the substrate to form aluminum oxide (Al2O3). The flow rate of the water vapor is 10sccm-200sccm. Water vapor is highly active as an oxidant and can react with trimethylaluminum to form aluminum oxide (Al2O3). By controlling the flow rate of the water vapor, the growth rate of aluminum oxide (Al2O3) and the film thickness can be adjusted.

[0062] The inert gas for purging is introduced into the first container again to remove the remaining water vapor and methane produced by oxidation, effectively removing the remaining water vapor and methane produced to ensure the purity and uniformity of the aluminum oxide (Al2O3) film.

[0063] Repeat the above steps until an aluminum oxide (Al2O3) film of the required thickness is grown. By repeating the above steps, atomic layer deposition can be achieved to obtain an aluminum oxide (Al2O3) film with good quality, uniformity and purity. In this embodiment, the thickness of the aluminum oxide (Al2O3) film is 7nm.

[0064] Furthermore, the inert gas is nitrogen or argon, and the flow rate of the inert gas for purging is 100 sccm

[0065] -500sccm.

[0066] Step 2: Using an atomic layer deposition method, a hafnium oxide (HfO 2 ) film is formed on the surface of the aluminum oxide (Al 2 O 3 ) film away from the SiC substrate.

[0067] In this embodiment, the specific steps of using the atomic layer deposition method to form a hafnium oxide (HfO2) film on the surface of an aluminum oxide (Al2O3) film include:

[0068] Controlling the temperature of the second container containing the SiC substrate with the aluminum oxide (Al2O3) film to 150-300°C and the pressure to 1 Torr-10 Torr helps promote the reaction and achieve optimized growth conditions;

[0069] Hafnium tetrachloride is used as a precursor of hafnium. The hafnium tetrachloride is carried by an inert gas and introduced into the interior of a second container. The hafnium tetrachloride is adsorbed on the surface of an aluminum oxide (Al2O3) film. The flow rate of the inert gas carrying the hafnium tetrachloride is 10sccm-100sccm. Hafnium tetrachloride as a precursor of hafnium has good volatility and stability and is easily converted into hafnium oxide (HfO2) in the gas phase. By carrying the hafnium tetrachloride by an inert gas, its transportation and adsorption in the reaction chamber can be controlled to achieve uniform surface deposition.

[0070] Introducing an inert gas for purging into the interior of the second container to purge the second container is used to remove unreacted hafnium tetrachloride and generated chlorine gas, which can effectively remove unreacted precursors and by-products and maintain the cleanliness of the reaction chamber. The generated chlorine gas is removed to avoid its influence on the reaction while maintaining the stability of the reaction environment.

[0071] Introducing water vapor as an oxidant into the interior of the second container to react with hafnium tetrachloride adsorbed on the substrate to generate hafnium oxide (HfO2), wherein the flow rate of the water vapor is 10sccm-200sccm. The water vapor as an oxidant can react with hafnium tetrachloride to generate a hafnium oxide (HfO2) film. By controlling the flow rate of the water vapor, the growth rate and film thickness of the hafnium oxide (HfO2) can be adjusted;

[0072] The inert gas for purging is introduced into the second container again to remove the remaining water vapor and hydrogen chloride generated by oxidation, which can effectively remove the remaining water vapor and hydrogen chloride generated, thereby ensuring the purity and uniformity of the hafnium oxide (HfO2) film;

[0073] Repeat the above steps until a hafnium oxide (HfO2) film of the required thickness is grown, and atomic layer deposition can be achieved to obtain a hafnium oxide (HfO2) film with good quality, uniformity and purity. In this embodiment, the target thickness of the hafnium oxide (HfO2) film is 3nm.

[0074] Furthermore, the inert gas is nitrogen or argon, and the flow rate of the inert gas for purging is 100 sccm

[0075] -500sccm.

[0076] The deposition of aluminum oxide (Al2O3) thin films is usually carried out at relatively low temperatures and pressures, generally controlled within the range of 100-300°C and 1Torr-10 Torr, because the deposition reaction of aluminum oxide (Al2O3) is relatively easy to proceed, and the temperature and pressure can ensure the reaction while avoiding the influence of film thermal decomposition or impurities.

[0077] The deposition of hafnium oxide (HfO2) thin films requires higher temperatures and pressures, generally controlled within the range of 150-300°C and 1-10 Torr. This is because the thermal decomposition temperature of hafnium tetrachloride is relatively high, and high temperature conditions are required to promote the reaction. In addition, higher pressure helps to increase the reaction rate and improve the uniformity of the film.

[0078] Trimethylaluminum is an organic aluminum compound with high volatility and low pyrolysis temperature. This allows it to undergo deposition reactions at relatively low temperatures and pressures. Hafnium tetrachloride is an inorganic gas with a high pyrolysis temperature, which requires increasing the deposition temperature and pressure to promote the pyrolysis and reaction of hafnium tetrachloride.

[0079] An aluminum oxide (Al2O3) film and a hafnium oxide (HfO2) film are sequentially formed on the surface of a SiC substrate using an atomic layer deposition method to form a gate oxide layer of a stacked structure. The thickness of the aluminum oxide (Al2O3) film and the hafnium oxide (HfO2) film formed are uniform and the thinness can be precisely controlled to ensure that the thickness and thinness of the entire gate oxide layer can accurately meet the requirements. Since aluminum oxide (Al2O3) and hafnium oxide (HfO2) have high dielectric constants, the stacked structure formed by the two can improve the overall dielectric constant of the gate oxide layer, increase the capacitance effect of the gate dielectric, and suppress tunneling leakage current.

[0080] Step 3: Annealing the aluminum oxide (Al2O3) film and the hafnium oxide (HfO2) film, wherein the annealed aluminum oxide (Al2O3) film and the hafnium oxide (HfO2) film form a gate oxide layer of a stacked structure.

[0081] In this embodiment, the steps of annealing the aluminum oxide (Al2O3) film and the hafnium oxide (HfO2) film are as follows:

[0082] The aluminum oxide (Al2O3) film and the hafnium oxide (HfO2) film are annealed in a space with a predetermined gas, wherein the predetermined gas includes at least one of argon, nitrogen, nitric oxide and nitrous oxide, the annealing temperature is 200°C, and the annealing time is 2 hours.

[0083] By annealing the aluminum oxide (Al2O3) film and the hafnium oxide (HfO2) film, the crystallization and grain growth of the aluminum oxide (Al2O3) film and the hafnium oxide (HfO2) film can be promoted, thereby improving the structure of the film. During the annealing process, crystal defects and stress will be released and reduced, making the film smoother and more stable. In addition, defects and impurities in the film can be eliminated, thereby improving the purity of the film. A pure film can allow the gate oxide layer to provide better electrical properties and interface characteristics.

[0084] And through annealing treatment, the interface between the aluminum oxide (Al2O3) film and the hafnium oxide (HfO2) film can be optimized. During the annealing process, the bonding and interaction of the interface will be improved, thereby improving the stability of the interface and the ability to regulate the interface energy level.

[0085] Step 4: Metal electrodes are evaporated on the surface of the hafnium oxide (HfO2) film away from the SiC substrate and on the surface of the SiC substrate away from the aluminum oxide (Al2O3) film to make a switching device sample.

[0086] In this embodiment, the metal electrode includes a 5nm thick chromium layer and a 50nm thick gold layer covering the surface of the chromium layer. The chromium layer is attached to the surface of the hafnium oxide (HfO2) film away from the SiC substrate, and the surface of the SiC substrate away from the aluminum oxide (Al2O3) film. The metal electrode is evaporated on the surface of the hafnium oxide (HfO2) film away from the SiC substrate and the surface of the SiC substrate away from the aluminum oxide (Al2O3) film using physical vapor deposition or chemical vapor deposition.

[0087] The chromium layer is usually used as an adhesion layer to provide better metal adhesion and adhesion, while the gold layer has good electrical conductivity and chemical stability, allowing the metal electrode to provide better electrical performance and durability while meeting specific application requirements.

[0088] Step 5: subjecting the switching device sample to rapid thermal annealing treatment.

[0089] The steps of performing rapid thermal annealing treatment on the switching device sample are as follows:

[0090] In this embodiment, the switching device sample is annealed in a space with a predetermined gas, wherein the predetermined gas includes at least one of argon, nitrogen, nitric oxide and nitrous oxide, the annealing temperature is 400° C., and the annealing time is 5 minutes.

[0091] In this embodiment, the crystal structure of the switching device sample is improved by rapid thermal annealing, the grains are rearranged and grown, the interface between the material and the metal electrode is optimized, the stability and electrical properties of the interface are improved, and the performance and stability of the switching device are improved.

[0092] This embodiment uses a stacked gate oxide layer composed of aluminum oxide (Al2O3) film and hafnium oxide (HfO2) film to effectively improve the dielectric constant and thickness of the gate oxide layer, effectively suppress tunneling leakage current, and simplify the gate dielectric structure.

[0093] The present invention further provides a switch device based on a SiC substrate, wherein the switch device comprises a gate oxide layer and a metal electrode, and the gate oxide layer and the metal electrode are manufactured by the above method.

[0094] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0095] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A method for preparing a gate oxide layer of a switching device based on a SiC substrate, characterized in that: The preparation method comprises: Providing a SiC substrate, and forming an aluminum oxide film on the surface of the SiC substrate by using an atomic layer deposition method; Using an atomic layer deposition method, a hafnium oxide film is formed on a surface of the aluminum oxide film away from the SiC substrate; Annealing the aluminum oxide film and the hafnium oxide film, wherein the aluminum oxide film and the hafnium oxide film after annealing form a gate oxide layer of a stacked structure; Vapor-depositing metal electrodes on the surface of the hafnium oxide film away from the SiC substrate and on the surface of the SiC substrate away from the aluminum oxide film to produce a switching device sample; Performing a rapid thermal annealing treatment on the switching device sample; The specific steps of forming an aluminum oxide film on the surface of a SiC substrate using an atomic layer deposition method include: The temperature of the first container containing the SiC substrate is controlled to be 100-300° C. and the pressure is 1 Torr-10 Torr. Trimethylaluminum is used as an aluminum precursor. The trimethylaluminum is introduced into the first container by carrying the trimethylaluminum with an inert gas, and the trimethylaluminum is adsorbed on the surface of the SiC substrate. The flow rate of the inert gas carrying the trimethylaluminum is 50 sccm-200 sccm. Introducing an inert purge gas into the interior of the first container to purge the first container to remove unreacted trimethylaluminum and generated methane; Introducing water vapor as an oxidant into the first container to react with trimethylaluminum adsorbed on the substrate to generate aluminum oxide, wherein the flow rate of the water vapor is 10 sccm-200 sccm; Passing the inert gas for purging into the first container again to remove the remaining water vapor and methane produced by oxidation; Repeat the above steps until an aluminum oxide film of required thickness is grown; The inert gas is nitrogen or argon, and the flow rate of the inert gas for purging is 100 sccm-500 sccm; The specific steps of using atomic layer deposition to form a hafnium oxide film on the surface of an aluminum oxide film include: The temperature of the second container containing the SiC substrate with the aluminum oxide film is controlled to be 150-300° C. and the pressure is 1 Torr-10 Torr. Hafnium tetrachloride is used as a precursor of hafnium. The hafnium tetrachloride is introduced into the second container by carrying the hafnium tetrachloride through an inert gas, and the hafnium tetrachloride is adsorbed on the surface of the aluminum oxide film. The flow rate of the inert gas carrying the hafnium tetrachloride is 10 sccm-100 sccm. Introducing an inert gas for purging into the interior of the second container to purge the second container to remove unreacted hafnium tetrachloride and generated chlorine gas; Introducing water vapor as an oxidant into the second container to react with hafnium tetrachloride adsorbed on the substrate to generate hafnium oxide, wherein the flow rate of the water vapor is 10 sccm-200 sccm; Passing the inert gas for purging into the interior of the second container again to remove the remaining water vapor and hydrogen chloride produced by oxidation; Repeat the above steps until a hafnium oxide film of a required thickness is grown; The inert gas is nitrogen or argon, and the flow rate of the inert gas for purging is 100 sccm-500 sccm.

2. The method for preparing a gate oxide layer of a switching device based on a SiC substrate according to claim 1, characterized in that: The step of providing the SiC substrate comprises: Providing a prepared SiC substrate; The prepared SiC substrate is ultrasonically cleaned in anhydrous ethanol for 10 minutes, and then heated to 75° C. and ultrasonically cleaned for 10 minutes in a mixed solution, wherein the mixed solution is composed of ammonia water, hydrogen peroxide and deionized water in a volume ratio of 2:1:7; The SiC substrate was prepared by immersing the heated SiC substrate in a BOE solution for 1 minute to obtain a SiC substrate. The BOE solution was a mixture of hydrofluoric acid and ammonia water in a volume ratio of 1:

6.

3. The method for preparing a gate oxide layer of a switching device based on a SiC substrate according to claim 1, characterized in that: The thickness of the aluminum oxide film is 7 nm, and the thickness of the hafnium oxide film is 3 nm.

4. The method for preparing a gate oxide layer of a switching device based on a SiC substrate according to claim 1, characterized in that: The steps of annealing the aluminum oxide film and the hafnium oxide film are as follows: The aluminum oxide film and the hafnium oxide film are annealed in a space with a predetermined gas, wherein the predetermined gas includes at least one of argon, nitrogen, nitric oxide and nitrous oxide, the annealing temperature is 200° C., and the annealing time is 2 hours.

5. The method for preparing a gate oxide layer of a switching device based on a SiC substrate according to claim 1, characterized in that: The steps of performing rapid thermal annealing treatment on the switching device sample are as follows: The switching device sample is subjected to annealing treatment in a space with a predetermined gas, wherein the predetermined gas includes at least one of argon, nitrogen, nitric oxide and nitrous oxide, the annealing treatment is performed at a treatment temperature of 400° C., and the annealing treatment is performed for 5 minutes.

6. The method for preparing a gate oxide layer of a switching device based on a SiC substrate according to claim 1, characterized in that: The metal electrode includes a 5 nm thick chromium layer and a 50 nm thick gold layer covering the surface of the chromium layer. The chromium layer is attached to the surface of the hafnium oxide film away from the SiC substrate and the surface of the SiC substrate away from the aluminum oxide film.

7. A switching device based on a SiC substrate, characterized in that: It comprises a gate oxide layer and a metal electrode, and the gate oxide layer and the metal electrode are manufactured by the method according to any one of claims 1 to 6.

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