Silicon carbide epitaxial wafer, method of manufacturing the same, and use thereof

Abstract

The present application relates to the field of semiconductor materials, and discloses a silicon carbide epitaxial wafer, a preparation method and application thereof. The silicon carbide epitaxial wafer has a structure of two layers of doped silicon carbide epitaxial layers, and at least part of the surface defects of the lower doped silicon carbide epitaxial layer are filled by intrinsic silicon carbide. The device using the silicon carbide epitaxial wafer has small leakage current, low turn-on voltage and is not easy to be broken down.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of semiconductor materials, in particular to a silicon carbide epitaxial wafer and a preparation method and application thereof. BACKGROUND

[0002] Silicon carbide, as the third generation of semiconductor materials, has the advantages of wide band gap, high thermal conductivity, high critical breakdown field strength and high carrier saturation velocity, and can be widely used for making high-temperature, high-frequency, high-voltage and high-power devices, and has incomparable advantages over traditional silicon materials in new energy vehicles and military industries, and is the core of new energy vehicles, new generation of radars and satellite communication, and has important application value and broad development prospect, and has become the focus of the development of the current semiconductor industry. Especially in the case that the development of silicon electronic components has reached the limit, it is more important and urgent to study the third generation of wide band gap semiconductor materials, which will lead the third semiconductor industry revolution.

[0003] The thermal performance of silicon carbide is very stable, and the decomposition temperature is very high. The silicon carbide ingot is obtained by slowly depositing on a silicon carbide seed wafer by a physical vapor transport (PVT) method, and then the crystal is oriented, rolled, cut, ground and polished to form a substrate. Then, n-type or p-type silicon carbide is grown on the substrate by a high-temperature chemical vapor deposition (CVD) method to prepare an epitaxial wafer, and finally a silicon carbide device is prepared by processes such as photolithography, development, activation and electrode deposition.

[0004] The silicon carbide device has very high requirements for the surface morphology and defect density of the epitaxial layer, and the crystal quality of the silicon carbide epitaxial layer is largely dependent on the substrate. The defects of the substrate will continue to extend upward during the epitaxial process. Therefore, the epitaxial process has high requirements for the defect density of the substrate, and some defects will also be generated during the growth process of the epitaxial layer due to the influence of parameters such as temperature, pressure, gas flow and interface effect. Defects often become electron trapping centers or produce leakage current under the condition of device power-on, which greatly affects the performance of the device. In the existing silicon carbide epitaxial structure and its manufacturing process, a silicon carbide buffer layer is first grown on the substrate, and then a silicon carbide epitaxial layer is grown. Although the buffer layer has a certain inhibitory effect on defects, it is limited to the conversion of BPD defects, and a large number of defects such as carrot defects, triangular defects and TSD still exist in the epitaxial layer, resulting in large leakage current, high turn-on voltage and easy breakdown of the device. SUMMARY

[0005] The purpose of the present application is to overcome the problems of large leakage current, high turn-on voltage and easy breakdown of the device using the existing silicon carbide epitaxial wafer. The present application provides a new silicon carbide epitaxial wafer and a preparation method and application thereof. The device using the silicon carbide epitaxial wafer of the present application has small leakage current, low turn-on voltage and is not easy to be broken down.

[0006] To achieve the above object, the present application provides a silicon carbide epitaxial wafer, wherein the epitaxial wafer has a structure of two layers of doped silicon carbide epitaxial layers, and at least part of surface defects of the lower layer of doped silicon carbide epitaxial layer are filled by intrinsic silicon carbide.

[0007] In the second aspect of the present application, a silicon carbide epitaxial wafer is provided, wherein the epitaxial wafer comprises a silicon carbide substrate, a first doped silicon carbide epitaxial layer formed on the silicon carbide substrate, and a second doped silicon carbide epitaxial layer formed on the first doped silicon carbide epitaxial layer, wherein at least part of surface defects of the first doped silicon carbide epitaxial layer are filled by intrinsic silicon carbide.

[0008] Preferably, the silicon carbide epitaxial wafer further comprises a doped silicon carbide buffer layer formed between the silicon carbide substrate and the first doped silicon carbide epitaxial layer.

[0009] Preferably, the thickness of the silicon carbide substrate is 300-1000 μm.

[0010] Preferably, the thickness of the doped silicon carbide buffer layer is 0.5-3.0 μm, the doping concentration is 5E17-5E18 / cm 3 , and the doping element is nitrogen; more preferably, the thickness of the doped silicon carbide buffer layer 2 is 1.0-2.0 μm, the doping concentration is 1E18-3E18 / cm 3 , and the doping element is nitrogen.

[0011] Preferably, the silicon carbide epitaxial wafer further comprises a third doped silicon carbide epitaxial layer formed between the doped silicon carbide buffer layer and the first doped silicon carbide epitaxial layer, and a graphene layer formed on the third doped silicon carbide epitaxial layer.

[0012] Preferably, the thickness of the third doped silicon carbide epitaxial layer is 1.0-20.0 μm, the doping concentration is 1E15-1E17 / cm 3 , and the doping element is nitrogen; more preferably, the thickness of the third doped silicon carbide epitaxial layer is 2.0-10.0 μm, the doping concentration is 2E15-1E16 / cm 3 , and the doping element is nitrogen; further preferably, the thickness of the third doped silicon carbide epitaxial layer is 5.0-10.0 μm, the doping concentration is 2E15-6E15 / cm 3 , and the doping element is nitrogen.

[0013] Preferably, the graphene layer is a graphene layer of 2-10 atomic layers.

[0014] Preferably, the thickness of the first doped silicon carbide epitaxial layer is 3.0-30.0 μm, the doping concentration is 1E15-1E17 / cm 3, the doping element is nitrogen; more preferably, the first doped silicon carbide epitaxial layer has a thickness of 3-25.0 μm and a doping concentration of 2E15-2E16 / cm 3 , the doping element is nitrogen; more preferably, the first doped silicon carbide epitaxial layer has a thickness of 3-25.0 μm and a doping concentration of 2E15-2E16 / cm 3 , the doping element is nitrogen; more preferably, the first doped silicon carbide epitaxial layer has a thickness of 3-25.0 μm and a doping concentration of 2E15-2E16 / cm 3 , the doping element is nitrogen.

[0015] Preferably, the second doped silicon carbide epitaxial layer has a thickness of 2.0-25.0 μm and a doping concentration of 1E15-1E17 / cm 3 , the doping element is nitrogen; more preferably, the second doped silicon carbide epitaxial layer has a thickness of 2.0-15.0 μm and a doping concentration of 4E15-1E16 / cm 3 , the doping element is nitrogen; more preferably, the second doped silicon carbide epitaxial layer has a thickness of 2.0-15.0 μm and a doping concentration of 4E15-1E16 / cm 3 , the doping element is nitrogen.

[0016] According to a third aspect of the present application, there is provided a method for preparing a silicon carbide epitaxial wafer, wherein the method comprises the following steps,

[0017] 1) a step of depositing doped silicon carbide on a silicon carbide substrate by vapor deposition to form a first doped silicon carbide epitaxial layer;

[0018] 2) a step of in-situ etching the surface of the first doped silicon carbide epitaxial layer in a hydrogen atmosphere to form pits at surface defects;

[0019] 3) a step of depositing intrinsic silicon carbide on the surface of the etched first doped silicon carbide epitaxial layer by vapor deposition;

[0020] 4) a step of removing the intrinsic silicon carbide outside the pits;

[0021] 5) a step of depositing doped silicon carbide by vapor deposition to form a second doped silicon carbide epitaxial layer.

[0022] Preferably, the method further comprises a step of depositing a doped silicon carbide buffer layer on a silicon carbide substrate by vapor deposition before forming the first doped silicon carbide epitaxial layer.

[0023] Preferably, the method further comprises the step of: after forming the doped silicon carbide buffer layer, depositing doped silicon carbide on the silicon carbide substrate by vapor deposition to form a third doped silicon carbide epitaxial layer, and subjecting the surface of the third doped silicon carbide epitaxial layer to high-temperature decomposition at a temperature of 1400-1600°C to form a graphene layer.

[0024] Preferably, the thickness of the doped silicon carbide buffer layer is 0.5-3.0 μm, the doping concentration is 5E17-5E18 / cm 3 , and the doping element is nitrogen; more preferably, the thickness of the doped silicon carbide buffer layer 2 is 1.0-2.0 μm, the doping concentration is 1E18-3E18 / cm 3 , and the doping element is nitrogen.

[0025] Preferably, the thickness of the third doped silicon carbide epitaxial layer is 1.0-20.0 μm, the doping concentration is 1E15-1E17 / cm 3 , and the doping element is nitrogen; more preferably, the thickness of the third doped silicon carbide epitaxial layer is 2.0-10.0 μm, the doping concentration is 2E15-1E16 / cm 3 , and the doping element is nitrogen; further preferably, the thickness of the third doped silicon carbide epitaxial layer is 5.0-10.0 μm, the doping concentration is 2E15-6E15 / cm 3 , and the doping element is nitrogen.

[0026] Preferably, the graphene layer is a graphene layer of 2-10 atomic layers.

[0027] Preferably, the thickness of the first doped silicon carbide epitaxial layer is 3.0-30.0 μm, the doping concentration is 1E15-1E17 / cm 3 , and the doping element is nitrogen; more preferably, the thickness of the first doped silicon carbide epitaxial layer is 3-25.0 μm, the doping concentration is 2E15-2E16 / cm 3 , and the doping element is nitrogen; further preferably, the thickness of the first doped silicon carbide epitaxial layer is 3.0-15.0 μm, the doping concentration is 6E15-2E16 / cm 3 , and the doping element is nitrogen; still further preferably, the thickness of the first doped silicon carbide epitaxial layer is 3.0-8.0 μm, the doping concentration is 8E15-2E16 / cm 3 , and the doping element is nitrogen.

[0028] Preferably, the thickness of the second doped silicon carbide epitaxial layer is 2.0-25.0 μm, the doping concentration is 1E15-1E17 / cm 3, the doping element is nitrogen; more preferably, the thickness of the second doped silicon carbide epitaxial layer is 2.0-15.0 μm, and the doping concentration is 4E15-1E16 / cm 3 , the doping element is nitrogen; more preferably, the thickness of the second doped silicon carbide epitaxial layer is 2.0-10.0 μm, and the doping concentration is 8E15-1E16 / cm 3 , the doping element is nitrogen.

[0029] Preferably, in step 2), the etching time is 5-20 minutes.

[0030] Preferably, in step 4), the intrinsic silicon carbide outside the pits is removed by in-situ hydrogen etching or chemical polishing.

[0031] Preferably, the conditions of the vapor deposition include: temperature is 1500-1700 ℃, and pressure is 50-200 mbar.

[0032] According to a fourth aspect of the present application, there is provided a use of the silicon carbide epitaxial wafer according to the first aspect and the second aspect in the preparation of a silicon carbide power device.

[0033] By the above technical solution, the defect position in the epitaxial growth process of the silicon carbide epitaxial wafer is introduced with intrinsic silicon carbide, the conductive performance of the intrinsic silicon carbide is poor, the transmission of the carrier at the defect position is reduced, and thus the carrier is prevented from being captured by the defect, so that the device using the silicon carbide epitaxial wafer of the present application has small leakage current, low opening voltage and is not easy to be broken down. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 is a structural schematic diagram of a silicon carbide epitaxial wafer according to an embodiment of the present application.

[0035] Figure 2 is a structural schematic diagram of a silicon carbide epitaxial wafer according to another embodiment of the present application.

[0036] REFERENCE SIGNS

[0037] 1: silicon carbide substrate; 2: doped silicon carbide buffer layer; 3: first doped silicon carbide epitaxial layer; 4: second doped silicon carbide epitaxial layer; 5: intrinsic silicon carbide; 6: third doped silicon carbide epitaxial layer; 7: graphene layer. DETAILED DESCRIPTION

[0038] The endpoints of the ranges and any values disclosed herein are not limited to the precise values recited as the exact dimensions are not critical to the invention. Any numeric range recited is intended to include all values from the lower value to the upper value, inclusive of both values, and to sub-ranges falling within the specified range. In this disclosure and during the claiming of the invention, any Al and / or A2 are intended to mean one or more than one, one, two, three, four, five, six, seven, eight, nine, ten, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 or more than 20.

[0039] According to the first aspect of the present invention, there is provided a silicon carbide epitaxial wafer, wherein the epitaxial wafer has a structure of two layers of doped silicon carbide epitaxial layers, and at least part of surface defects of the lower layer of doped silicon carbide epitaxial layer are filled by intrinsic silicon carbide.

[0040] The silicon carbide epitaxial wafer of the present invention introduces intrinsic silicon carbide at the defect position during epitaxial growth, and uses the poor conductivity of intrinsic silicon carbide to reduce the transport of carriers at the defect position, thereby avoiding the capture of carriers by defects. Thus, the device using the silicon carbide epitaxial wafer of the present invention has small leakage current, low turn-on voltage and is not easy to be broken down.

[0041] Preferably, all surface defects of the lower layer of doped silicon carbide epitaxial layer are filled by intrinsic silicon carbide.

[0042] According to the second aspect of the present invention, there is provided a silicon carbide epitaxial wafer, as shown in Figure 1 The epitaxial wafer comprises a silicon carbide substrate 1, a first doped silicon carbide epitaxial layer 3 formed on the silicon carbide substrate 1, and a second doped silicon carbide epitaxial layer 4 formed on the first doped silicon carbide epitaxial layer 3, wherein at least part of surface defects of the first doped silicon carbide epitaxial layer 3 are filled by intrinsic silicon carbide 5.

[0043] According to the present invention, the silicon carbide substrate is not particularly limited and can be prepared by a method commonly used in the art, for example, a silicon carbide ingot can be obtained by slow deposition on a silicon carbide seed wafer using a physical vapor transport (PVT) method, and then the substrate can be prepared by processes such as crystal orientation, rounding, cutting, grinding and polishing.

[0044] The thickness of the silicon carbide substrate is 300-1000 μm, preferably 400-500 μm.

[0045] In the present invention, as shown in Figure 1 In order to reduce the surface defects of the doped silicon carbide epitaxial layer, preferably, a doped silicon carbide buffer layer 2 is formed on the silicon carbide substrate, and the thickness of the doped silicon carbide buffer layer 2 is 0.5-3.0 μm, and the doping concentration is 5E17-5E18 / cm 3, the doping element being nitrogen; more preferably, the doped silicon carbide buffer layer 2 has a thickness of 1.0 to 2.0 μm and a doping concentration of 1E18 to 3E18 / cm 3 , the doping element being nitrogen.

[0046] In another preferred embodiment of the present application, as shown in Figure 2 , preferably, the silicon carbide epitaxial wafer further comprises a third doped silicon carbide epitaxial layer 6 formed between the doped silicon carbide buffer layer 2 and the first doped silicon carbide epitaxial layer 3 and a graphene layer 7 formed on the third doped silicon carbide epitaxial layer 6.

[0047] Preferably, the third doped silicon carbide epitaxial layer has a thickness of 1.0 to 20.0 μm and a doping concentration of 1E15 to 1E17 / cm 3 , the doping element being nitrogen; more preferably, the third doped silicon carbide epitaxial layer has a thickness of 2.0 to 10.0 μm and a doping concentration of 2E15 to 1E16 / cm 3 , the doping element being nitrogen; further preferably, the third doped silicon carbide epitaxial layer has a thickness of 5.0 to 10.0 μm and a doping concentration of 2E15 to 6E15 / cm 3 , the doping element being nitrogen.

[0048] As specific examples of the thickness of the third doped silicon carbide epitaxial layer, there can be mentioned, for example, 1.0 μm, 2.0 μm, 3.0 μm, 4.0 μm, 5.0 μm, 6.0 μm, 7.0 μm, 8.0 μm, 9.0 μm, 10.0 μm, 11.0 μm, 12.0 μm, 13.0 μm, 14.0 μm, 15.0 μm, 16.0 μm, 17.0 μm, 18.0 μm, 19.0 μm, 20.0 μm, and the like, and a range defined by any two of these values.

[0049] As specific examples of the doping concentration of the third doped silicon carbide epitaxial layer, there can be mentioned, for example, 1E15 / cm 3 , 2E15 / cm 3 , 3E15 / cm 3 , 4E15 / cm 3 , 5E15 / cm 3 , 6E15 / cm 3 , 7E15 / cm 3 , 8E15 / cm 3 , 9E15 / cm 3 , 1E16 / cm 3 , 2E16 / cm 3 , 3E16 / cm 3 , 4E16 / cm 3 , 5E16 / cm3 , 6E16 / cm 3 , 7E16 / cm 3 , 8E16 / cm 3 , 9E16 / cm 3 , 1E17 / cm 3 and a range constituted by any two values among them.

[0050] In the present application, a graphene layer is formed on the third doped silicon carbide epitaxial layer. Preferably, the graphene layer is a graphene layer of 2-10 atomic layers.

[0051] According to the present application, by forming a graphene layer, the uniformity of the current can be improved by using the characteristic that the graphene electron has high lateral mobility.

[0052] Those skilled in the art should understand that, when the doped silicon carbide buffer layer, the third doped silicon carbide epitaxial layer and the graphene layer are not formed, the first doped silicon carbide epitaxial layer is formed on the silicon carbide substrate; when the doped silicon carbide buffer layer is formed, the third doped silicon carbide epitaxial layer and the graphene layer are not formed, the first doped silicon carbide epitaxial layer is formed on the doped silicon carbide buffer layer; when the doped silicon carbide buffer layer, the third doped silicon carbide epitaxial layer and the graphene layer are formed, the first doped silicon carbide epitaxial layer is formed on the graphene layer.

[0053] In the present application, preferably, the thickness of the first doped silicon carbide epitaxial layer is 3.0-30.0 μm, the doping concentration is 1E15-1E17 / cm 3 , the doping element is nitrogen; more preferably, the thickness of the first doped silicon carbide epitaxial layer is 3-25.0 μm, the doping concentration is 2E15-2E16 / cm 3 , the doping element is nitrogen; further preferably, the thickness of the first doped silicon carbide epitaxial layer is 3.0-15.0 μm, the doping concentration is 6E15-2E16 / cm 3 , the doping element is nitrogen; more further preferably, the thickness of the first doped silicon carbide epitaxial layer is 3.0-8.0 μm, the doping concentration is 8E15-2E16 / cm 3 , the doping element is nitrogen.

[0054] As specific examples of the thickness of the first doped silicon carbide epitaxial layer, for example, 3.0 μm, 4.0 μm, 5.0 μm, 6.0 μm, 7.0 μm, 8.0 μm, 9.0 μm, 10.0 μm, 11.0 μm, 12.0 μm, 13.0 μm, 14.0 μm, 15.0 μm, 16.0 μm, 17.0 μm, 18.0 μm, 19.0 μm, 20.0 μm, 21.0 μm, 22.0 μm, 23.0 μm, 24.0 μm, 25.0 μm, 26.0 μm, 27.0 μm, 28.0 μm, 29.0 μm, 30.0 μm, and the like, and a range defined by any two of these values can be given.

[0055] As specific examples of the doping concentration of the first doped silicon carbide epitaxial layer, for example, 1E15 / cm 3 , 2E15 / cm 3 , 3E15 / cm 3 , 4E15 / cm 3 , 5E15 / cm 3 , 6E15 / cm 3 , 7E15 / cm 3 , 8E15 / cm 3 , 9E15 / cm 3 , 1E16 / cm 3 , 2E16 / cm 3 , 3E16 / cm 3 , 4E16 / cm 3 , 5E16 / cm 3 , 6E16 / cm 3 , 7E16 / cm 3 , 8E16 / cm 3 , 9E16 / cm 3 , 1E17 / cm 3 , and the like, and a range defined by any two of these values can be given.

[0056] In the present application, a second doped silicon carbide epitaxial layer is formed on the first doped silicon carbide epitaxial layer. Preferably, the thickness of the second doped silicon carbide epitaxial layer is 2.0-25.0 μm, the doping concentration is 1E15-1E17 / cm 3 , and the doping element is nitrogen; more preferably, the thickness of the second doped silicon carbide epitaxial layer is 2.0-15.0 μm, the doping concentration is 4E15-1E16 / cm 3 , and the doping element is nitrogen; further preferably, the thickness of the second doped silicon carbide epitaxial layer is 2.0-10.0 μm, the doping concentration is 8E15-1E16 / cm 3 , and the doping element is nitrogen.

[0057] As specific examples of the thickness of the second doped silicon carbide epitaxial layer, for example, 2.0 μm, 3.0 μm, 4.0 μm, 5.0 μm, 6.0 μm, 7.0 μm, 8.0 μm, 9.0 μm, 10.0 μm, 11.0 μm, 12.0 μm, 13.0 μm, 14.0 μm, 15.0 μm, 16.0 μm, 17.0 μm, 18.0 μm, 19.0 μm, 20.0 μm, 21.0 μm, 22.0 μm, 23.0 μm, 24.0 μm, 25.0 μm, and the like, and a range defined by any two of these values can be given.

[0058] As specific examples of the doping concentration of the second doped silicon carbide epitaxial layer, for example, 1E15 / cm2, 2E15 / cm2, 3E15 / cm2, 4E15 / cm2, 5E15 / cm2, 6E15 / cm2, 7E15 / cm2, 8E15 / cm2, 9E15 / cm2, 1E16 / cm2, 2E16 / cm2, 3E16 / cm2, 4E16 / cm2, 5E16 / cm2, 6E16 / cm2, 7E16 / cm2, 8E16 / cm2, 9E16 / cm2, 1E17 / cm2, and the like, and a range defined by any two of these values can be given. 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 and the like, and a range defined by any two of these values can be given.

[0059] In the present application, preferably, all surface defects of the first doped silicon carbide epitaxial layer are filled by intrinsic silicon carbide.

[0060] According to a third aspect of the present application, there is provided a method for producing a silicon carbide epitaxial wafer, wherein the method comprises the steps of,

[0061] 1) a step of depositing doped silicon carbide on a silicon carbide substrate by vapor deposition to form a first doped silicon carbide epitaxial layer;

[0062] 2) a step of in-situ etching the surface of the first doped silicon carbide epitaxial layer in a hydrogen atmosphere to form pits at surface defects;

[0063] ​​​​​​​​​​​​​​​​​​3) a step of depositing intrinsic silicon carbide on the surface of the first doped silicon carbide epitaxial layer after etching by vapor deposition;

[0064] 4) a step of removing the intrinsic silicon carbide outside the pits;

[0065] 5) a step of depositing doped silicon carbide by vapor deposition to form a second doped silicon carbide epitaxial layer.

[0066] According to the present application, the silicon carbide substrate is as described above, and in the present application, in order to reduce defects on the surface of the doped silicon carbide epitaxial layer, preferably, the method of the present application further comprises: a step of depositing doped silicon carbide on the silicon carbide substrate by vapor deposition to form a doped silicon carbide buffer layer before forming the first doped silicon carbide epitaxial layer.

[0067] Preferably, the thickness of the doped silicon carbide buffer layer is 0.5-3 μm, the doping concentration is 5E17-5E18 / cm 3 , and the doping element is nitrogen; more preferably, the thickness of the doped silicon carbide buffer layer is 1.0-2.0 μm, the doping concentration is 1E18-3E18 / cm 3 , and the doping element is nitrogen.

[0068] According to the present application, preferably, the method of the present application further comprises: a step of depositing doped silicon carbide on the silicon carbide substrate by vapor deposition to form a third doped silicon carbide epitaxial layer after forming the doped silicon carbide buffer layer, and a step of forming a graphene layer by high-temperature decomposition of the surface of the third doped silicon carbide epitaxial layer at a temperature of 1400-1600°C. Specific temperatures can be mentioned, for example: 1400°C, 1450°C, 1500°C, 1550°C, 1600°C, etc., as well as ranges formed by any two of the above values.

[0069] Preferably, the thickness of the third doped silicon carbide epitaxial layer is 1.0-20.0 μm, the doping concentration is 1E15-1E17 / cm 3 , and the doping element is nitrogen; more preferably, the thickness of the third doped silicon carbide epitaxial layer is 2.0-10.0 μm, the doping concentration is 2E15-1E16 / cm 3 , and the doping element is nitrogen; further preferably, the thickness of the third doped silicon carbide epitaxial layer is 5.0-10.0 μm, the doping concentration is 2E15-6E15 / cm 3 , and the doping element is nitrogen.

[0070] Specific examples of the thickness of the third doped silicon carbide epitaxial layer include: 1.0 μm, 2.0 μm, 3.0 μm, 4.0 μm, 5.0 μm, 6.0 μm, 7.0 μm, 8.0 μm, 9.0 μm, 10.0 μm, 11.0 μm, 12.0 μm, 13.0 μm, 14.0 μm, 15.0 μm, 16.0 μm, 17.0 μm, 18.0 μm, 19.0 μm, 20.0 μm, etc., and any range of any two of these values.

[0071] Specific examples of the doping concentration of the third doped silicon carbide epitaxial layer include, for example, 1E15 / cm. 3 2E15 / cm 3 3E15 / cm 3 4E15 / cm 3 5E15 / cm 3 6E15 / cm 3 7E15 / cm 3 8E15 / cm 3 9E15 / cm 3 1E16 / cm 3 2E16 / cm 3 3E16 / cm 3 4E16 / cm 3 5E16 / cm 3 6E16 / cm 3 7E16 / cm 3 8E16 / cm 3 9E16 / cm 3 1E17 / cm 3 And so on, as well as the range formed by any two of them.

[0072] In this invention, a graphene layer is formed by high-temperature decomposition of the surface of the third doped silicon carbide epitaxial layer at a temperature of 1400-1600°C.

[0073] The time for the aforementioned high-temperature decomposition can be, for example, 2-10 minutes, preferably 3-5 minutes. Specific times can be, for example, 2 minutes, 3 minutes, 4 minutes, 5 minutes, 6 minutes, 7 minutes, 8 minutes, 9 minutes, 10 minutes, etc., as well as any range formed by any two of the above values.

[0074] According to the present invention, by subjecting the surface of the third doped silicon carbide epitaxial layer to high-temperature decomposition at a temperature of 1400-1600°C, the Si element is separated while the C element remains in situ, thereby forming a graphene layer. Preferably, the graphene layer is a graphene layer of 2-10 atomic layers.

[0075] Those skilled in the art should understand that, when the doped silicon carbide buffer layer, the third doped silicon carbide epitaxial layer and the graphene layer are not formed, the first doped silicon carbide epitaxial layer is formed on the silicon carbide substrate by vapor deposition; when the doped silicon carbide buffer layer is formed, the third doped silicon carbide epitaxial layer and the graphene layer are not formed, the first doped silicon carbide epitaxial layer is formed on the doped silicon carbide buffer layer by vapor deposition; when the doped silicon carbide buffer layer, the third doped silicon carbide epitaxial layer and the graphene layer are formed, the first doped silicon carbide epitaxial layer is formed on the graphene layer by vapor deposition.

[0076] In the present application, preferably, the thickness of the first doped silicon carbide epitaxial layer is 3.0-30.0 μm, the doping concentration is 1E15-1E17 / cm 3 , and the doping element is nitrogen; more preferably, the thickness of the first doped silicon carbide epitaxial layer is 3-25.0 μm, the doping concentration is 2E15-2E16 / cm 3 , and the doping element is nitrogen; further preferably, the thickness of the first doped silicon carbide epitaxial layer is 3.0-15.0 μm, the doping concentration is 6E15-2E16 / cm 3 , and the doping element is nitrogen; still further preferably, the thickness of the first doped silicon carbide epitaxial layer is 3.0-8.0 μm, the doping concentration is 8E15-2E16 / cm 3 , and the doping element is nitrogen.

[0077] As specific examples of the thickness of the first doped silicon carbide epitaxial layer, for example, 3.0 μm, 4.0 μm, 5.0 μm, 6.0 μm, 7.0 μm, 8.0 μm, 9.0 μm, 10.0 μm, 11.0 μm, 12.0 μm, 13.0 μm, 14.0 μm, 15.0 μm, 16.0 μm, 17.0 μm, 18.0 μm, 19.0 μm, 20.0 μm, 21.0 μm, 22.0 μm, 23.0 μm, 24.0 μm, 25.0 μm, 26.0 μm, 27.0 μm, 28.0 μm, 29.0 μm, 30.0 μm, etc., and a range formed by any two values among them can be mentioned.

[0078] As specific examples of the doping concentration of the first doped silicon carbide epitaxial layer, for example, 1E15 / cm 3 , 2E15 / cm 3 , 3E15 / cm 3 , 4E15 / cm 3 , 5E15 / cm 3 , 6E15 / cm 3 , 7E15 / cm 3, 8E15 / cm 3 , 9E15 / cm 3 , 1E16 / cm 3 , 2E16 / cm 3 , 3E16 / cm 3 , 4E16 / cm 3 , 5E16 / cm 3 , 6E16 / cm 3 , 7E16 / cm 3 , 8E16 / cm 3 , 9E16 / cm 3 , 1E17 / cm 3 and ranges defined by any two of them.

[0079] In the present application, pits are formed at the surface defects by in-situ etching of the surface of the first doped silicon carbide epitaxial layer in a hydrogen atmosphere. Specifically, pits are easily formed at the defect locations because the etching rate is faster at the defect locations.

[0080] Preferably, the etching is adjusted to a temperature of 1500-1700°C and a time of 5-20 minutes; more preferably, the etching is adjusted to a temperature of 1550-1650°C and a time of 10-15 minutes.

[0081] The shape of the pits can be one or more of, for example, a V-shaped pit, a cylindrical shape, and a strip shape.

[0082] In the present application, the first doped silicon carbide epitaxial layer is deposited with intrinsic silicon carbide by vapor deposition after etching the surface of the first doped silicon carbide epitaxial layer. The pits are filled by depositing the intrinsic silicon carbide, and a flat silicon carbide surface is obtained.

[0083] The thickness of the deposited intrinsic silicon carbide is not particularly limited, as long as the pits are filled. For ease of operation, the intrinsic silicon carbide is preferably also deposited on portions other than the pits. In this case, the first doped silicon carbide epitaxial layer can be obtained by removing the intrinsic silicon carbide from the portions other than the pits, and the surface of the first doped silicon carbide epitaxial layer is flat and the pits are filled with intrinsic silicon carbide.

[0084] The thickness of the deposited intrinsic silicon carbide is not particularly limited, as long as the pits are filled. For ease of operation, the intrinsic silicon carbide is preferably also deposited on portions other than the pits. In this case, the first doped silicon carbide epitaxial layer can be obtained by removing the intrinsic silicon carbide from the portions other than the pits, and the surface of the first doped silicon carbide epitaxial layer is flat and the pits are filled with intrinsic silicon carbide.

[0085] The method for removing the intrinsic silicon carbide from the portions other than the pits is not particularly limited, and can be performed by a method commonly used in the art, such as in-situ hydrogen etching or chemical polishing.

[0086] In the present application, doped silicon carbide is further deposited by vapor deposition to form a second doped silicon carbide epitaxial layer. Preferably, the second doped silicon carbide epitaxial layer has a thickness of 2.0 to 25.0 μm and a doping concentration of 1E15 to 1E17 / cm 3 , the doping element being nitrogen; more preferably, the second doped silicon carbide epitaxial layer has a thickness of 2.0 to 15.0 μm and a doping concentration of 4E15 to 1E16 / cm 3 , the doping element being nitrogen; further preferably, the second doped silicon carbide epitaxial layer has a thickness of 2.0 to 10.0 μm and a doping concentration of 8E15 to 1E16 / cm 3 , the doping element being nitrogen.

[0087] As specific examples of the thickness of the second doped silicon carbide epitaxial layer, for example, there can be mentioned 2.0 μm, 3.0 μm, 4.0 μm, 5.0 μm, 6.0 μm, 7.0 μm, 8.0 μm, 9.0 μm, 10.0 μm, 11.0 μm, 12.0 μm, 13.0 μm, 14.0 μm, 15.0 μm, 16.0 μm, 17.0 μm, 18.0 μm, 19.0 μm, 20.0 μm, 21.0 μm, 22.0 μm, 23.0 μm, 24.0 μm, 25.0 μm, and the like, and a range defined by any two of these values.

[0088] As specific examples of the doping concentration of the second doped silicon carbide epitaxial layer, for example, there can be mentioned 1E15 / cm 3 , 2E15 / cm 3 , 3E15 / cm 3 , 4E15 / cm 3 , 5E15 / cm 3 , 6E15 / cm 3 , 7E15 / cm 3 , 8E15 / cm 3 , 9E15 / cm 3 , 1E16 / cm 3 , 2E16 / cm 3 , 3E16 / cm 3 , 4E16 / cm 3 , 5E16 / cm 3 , 6E16 / cm 3 , 7E16 / cm 3 , 8E16 / cm 3 , 9E16 / cm 3 , 1E17 / cm 3 , and the like, and a range defined by any two of these values.

[0089] In addition, the conditions of the vapor deposition in each of the steps can include a temperature of 1500-1700 °C and a pressure of 50-200 mbar. The time of the deposition is determined according to the target thickness.

[0090] According to a third aspect of the present application, the application provides a use of the silicon carbide epitaxial wafer according to the first aspect of the present application in the preparation of a silicon carbide power device.

[0091] The present application will be described in detail below by way of examples, but the present application is not limited to the following examples.

[0092] In the following examples, the silicon carbide substrate was purchased from CREE, USA, and the thickness was 430 μm.

[0093] Example 1

[0094] 1) Depositing doped silicon carbide (thickness: 1.0 μm, doping concentration: 1E18 / cm 3 , doping element: nitrogen) on the silicon carbide substrate by vapor deposition to form a doped silicon carbide buffer layer;

[0095] 2) Depositing doped silicon carbide (thickness: 6.0 μm, doping concentration: 1E16 / cm 3 , doping element: nitrogen) on the doped silicon carbide buffer layer by vapor deposition to form a first doped silicon carbide epitaxial layer;

[0096] 3) In-situ etching the surface of the first doped silicon carbide epitaxial layer in a hydrogen atmosphere, etching temperature: 1600 °C, etching time: 15 minutes, forming pits at the surface defects;

[0097] 4) Depositing intrinsic silicon carbide (thickness: 0.5 μm) on the surface of the etched first doped silicon carbide epitaxial layer by vapor deposition to obtain a flat silicon carbide surface;

[0098] 5) Removing the intrinsic silicon carbide outside the pits by in-situ hydrogen etching, etching temperature: 1600 °C, etching time: 10 minutes;

[0099] 6) Depositing doped silicon carbide (thickness: 5.0 μm, doping concentration: 1E16 / cm 3 , doping element: nitrogen) by vapor deposition to form a second doped silicon carbide epitaxial layer, thereby obtaining a silicon carbide epitaxial wafer A1.

[0100] Example 2

[0101] 1) Depositing doped silicon carbide (thickness: 1.0 μm, doping concentration: 2E18 / cm 3 , doping element: nitrogen) on the silicon carbide substrate by vapor deposition to form a doped silicon carbide buffer layer;

[0102] 2) Deposit doped silicon carbide (thickness 3.0 μm, doping concentration 2E16 / cm²) onto the doped silicon carbide buffer layer by vapor deposition. 3 (with nitrogen as the doping element), forming the first doped silicon carbide epitaxial layer;

[0103] 3) In-situ etching of the surface of the first doped silicon carbide epitaxial layer was performed in a hydrogen atmosphere at a temperature of 1600°C for 15 minutes to form pits at surface defects.

[0104] 4) An intrinsic silicon carbide (0.5 μm thick) is deposited on the surface of the first doped silicon carbide epitaxial layer after etching by vapor deposition to obtain a smooth silicon carbide surface;

[0105] 5) The intrinsic silicon carbide outside the pits is removed by in-situ hydrogen etching at a temperature of 1600°C for 10 minutes.

[0106] 6) Deposit doped silicon carbide (2.0 μm thickness, doping concentration 5E15 / cm³) via vapor deposition. 3 (The doping element is nitrogen) to form a second doped silicon carbide epitaxial layer, thereby obtaining silicon carbide epitaxial wafer A2.

[0107] Example 3

[0108] 1) Deposit doped silicon carbide (1.0 μm thickness, 3E18 / cm² doping concentration) on a silicon carbide substrate by vapor deposition. 3 (with nitrogen as the doping element), forming a doped silicon carbide buffer layer;

[0109] 2) Deposit doped silicon carbide (8 μm thick, doping concentration 8E15 / cm²) onto the doped silicon carbide buffer layer by vapor deposition. 3 (with nitrogen as the doping element), forming the first doped silicon carbide epitaxial layer;

[0110] 3) In-situ etching of the surface of the first doped silicon carbide epitaxial layer was performed in a hydrogen atmosphere at a temperature of 1600°C for 15 minutes to form pits at surface defects.

[0111] 4) An intrinsic silicon carbide (0.5 μm thick) is deposited on the surface of the first doped silicon carbide epitaxial layer after etching by vapor deposition to obtain a smooth silicon carbide surface;

[0112] 5) The intrinsic silicon carbide outside the pits is removed by in-situ hydrogen etching at a temperature of 1600°C for 10 minutes.

[0113] 6) Deposit doped silicon carbide (10 μm thickness, doping concentration 8E15 / cm³) via vapor deposition. 3, the doping element being nitrogen), to form a third doped silicon carbide epitaxial layer.

[0114] Example 4

[0115] 1) Depositing doped silicon carbide (thickness of 1.0 μm, doping concentration of 1E18 / cm 3 , the doping element being nitrogen) on a silicon carbide substrate by vapor deposition to form a doped silicon carbide buffer layer;

[0116] 2) Depositing doped silicon carbide (thickness of 3.0 μm, doping concentration of 1E16 / cm 3 , the doping element being nitrogen) on the doped silicon carbide buffer layer by vapor deposition to form a third doped silicon carbide epitaxial layer;

[0117] 3) High-temperature decomposition (decomposition time of 6 minutes) of the surface of the third doped silicon carbide epitaxial layer at a temperature of 1400°C, and a graphene layer of 4-6 atomic layers is formed as observed by transmission electron microscopy;

[0118] 4) Depositing doped silicon carbide (thickness of 5.0 μm, doping concentration of 1E16 / cm 3 , the doping element being nitrogen) on the graphene layer by vapor deposition to form a first doped silicon carbide epitaxial layer;

[0119] 5) In-situ etching of the surface of the first doped silicon carbide epitaxial layer in a hydrogen atmosphere, etching temperature of 1600°C, etching time of 15 minutes, and pits are formed at surface defects;

[0120] 6) Depositing intrinsic silicon carbide (thickness of 0.5 μm) on the surface of the etched first doped silicon carbide epitaxial layer by vapor deposition to obtain a flat silicon carbide surface;

[0121] 7) Removing the intrinsic silicon carbide outside the pits by in-situ hydrogen etching, etching temperature of 1600°C, etching time of 10 minutes;

[0122] 8) Depositing doped silicon carbide (thickness of 3.0 μm, doping concentration of 1E16 / cm 3 , the doping element being nitrogen) by vapor deposition to form a second doped silicon carbide epitaxial layer, thereby obtaining a silicon carbide epitaxial wafer A4.

[0123] Example 5

[0124] 1) Depositing doped silicon carbide (thickness of 2.0 μm, doping concentration of 1E18 / cm 3 , the doping element being nitrogen) on a silicon carbide substrate by vapor deposition to form a doped silicon carbide buffer layer;

[0125] 2) depositing doped silicon carbide (thickness of 5.0 μm, doping concentration of 4E15 / cm 3 , doping element of nitrogen) on the doped silicon carbide buffer layer by vapor deposition to form a third doped silicon carbide epitaxial layer;

[0126] 3) performing high-temperature decomposition on the surface of the third doped silicon carbide epitaxial layer at a temperature of 1400°C (decomposition time of 5 minutes) to form a graphene layer of 4-10 atomic layers;

[0127] 4) depositing doped silicon carbide (thickness of 18 μm, doping concentration of 4E15 / cm 3 , doping element of nitrogen) on the graphene layer by vapor deposition to form a first doped silicon carbide epitaxial layer;

[0128] 5) performing in-situ etching on the surface of the fourth doped silicon carbide epitaxial layer in a hydrogen atmosphere, etching temperature of 1600°C, etching time of 15 minutes, to form pits at surface defects;

[0129] 6) depositing intrinsic silicon carbide (thickness of 0.5 μm) on the etched surface of the fourth doped silicon carbide epitaxial layer by vapor deposition to obtain a flat silicon carbide surface;

[0130] 7) removing the intrinsic silicon carbide outside the pits by in-situ hydrogen etching, etching temperature of 1600°C, etching time of 10 minutes;

[0131] 8) depositing doped silicon carbide (thickness of 12.0 μm, doping concentration of 4E15 / cm 3 , doping element of nitrogen) by vapor deposition to form a second doped silicon carbide epitaxial layer, thereby obtaining a silicon carbide epitaxial wafer A5.

[0132] Example 6

[0133] 1) depositing doped silicon carbide (thickness of 2.0 μm, doping concentration of 1E18 / cm 3 , doping element of nitrogen) on a silicon carbide substrate by vapor deposition to form a doped silicon carbide buffer layer;

[0134] 2) depositing doped silicon carbide (thickness of 10.0 μm, doping concentration of 2E15 / cm 3 , doping element of nitrogen) on the doped silicon carbide buffer layer by vapor deposition to form a third doped silicon carbide epitaxial layer;

[0135] 3) performing high-temperature decomposition on the surface of the third doped silicon carbide epitaxial layer at a temperature of 1600°C (decomposition time of 15 minutes) to form a graphene layer of 4-10 atomic layers;

[0136] 4) Depositing doped silicon carbide (thickness 25.0 μm, doping concentration 2E15 / cm 3 , doping element nitrogen) on the graphene layer by vapor deposition to form a first doped silicon carbide epitaxial layer;

[0137] 5) In-situ etching the surface of the first doped silicon carbide epitaxial layer under hydrogen atmosphere, etching temperature 1600°C, etching time 15 minutes, forming pits at surface defects;

[0138] 6) Depositing intrinsic silicon carbide (thickness 0.5 μm) on the surface of the etched first doped silicon carbide epitaxial layer by vapor deposition to obtain a flat silicon carbide surface;

[0139] 7) Removing the intrinsic silicon carbide outside the pits by in-situ hydrogen etching, etching temperature 1600°C, etching time 10 minutes;

[0140] 8) Depositing doped silicon carbide (thickness 25.0 μm, doping concentration 2E15 / cm 3 , doping element nitrogen) by vapor deposition to form a second doped silicon carbide epitaxial layer, thereby obtaining a silicon carbide epitaxial wafer A6.

[0141] Comparative Example 1

[0142] The method of Example 1 was followed, except that steps 3) to 5) were not performed, and a second doped silicon carbide epitaxial layer was formed directly on the first doped silicon carbide epitaxial layer, with a thickness of 10 μm and a doping concentration of 1E16; thereby obtaining a silicon carbide epitaxial wafer D1.

[0143] Test Example 1

[0144] The silicon carbide epitaxial wafers A1 to A6 and D1 obtained in Examples 1 to 6 and Comparative Example 1 were used respectively, and a gate electrode, a source electrode and a drain electrode were prepared on the epitaxial wafer by photolithography, film plating and other processes, to prepare a silicon carbide MOS tube. A semiconductor discrete device static tester was used to test the leakage current between the gate electrode and the source electrode with a fixed voltage between the gate electrode and the source electrode, to test the on voltage between the gate electrode and the source electrode with a fixed voltage between the drain electrode and the source electrode, and to test the breakdown voltage between the drain electrode and the source electrode with a fixed voltage of 0 between the gate electrode and the source electrode. The results are shown in Table 1.

[0145] Table 1

[0146] Leakage current (in μA) Turn-on voltage (V) Breakdown voltage (V) A1 0.5 2.8 1500 A2 0.3 2.6 650 A3 0.8 3.2 1800 A4 0.4 2.75 1600 A5 2.0 3.9 3000 A6 3.0 4.5 3500 D1 5.0 5.0 1200

[0147] Embodiments A1, A4 and D1 have the same thickness and carrier concentration of the epitaxial layer, wherein the comparative example D1 is a common epitaxial layer structure, A1 comprises a structure of a first epitaxial layer and a second epitaxial layer, and A4 comprises a structure of a first epitaxial layer, a second epitaxial layer and a third epitaxial layer. As shown by the test data in Table 1, compared with D1, A1 and A4 have smaller leakage current, smaller on voltage and larger breakdown voltage, which indicates that compared with the existing common epitaxial layer structure, the structure of the present application can significantly reduce the leakage current and on voltage, and significantly improve the breakdown voltage.

[0148] In addition, by comparing A1 and A4, it can be seen that A4 comprising a structure of a first epitaxial layer, a second epitaxial layer and a third epitaxial layer can further reduce the leakage current and on voltage, and improve the breakdown voltage.

[0149] The above describes the preferred embodiments of the present application, but the present application is not limited thereto. Within the technical concept of the present application, various simple modifications can be made to the technical solutions of the present application, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be considered as disclosed by the present application, and all fall within the protection scope of the present application.

Claims

1. A silicon carbide epitaxial wafer, characterized in that, The epitaxial wafer includes a silicon carbide substrate, a first doped silicon carbide epitaxial layer formed on the silicon carbide substrate, and a second doped silicon carbide epitaxial layer formed on the first doped silicon carbide epitaxial layer. At least a portion of the surface pits in the first doped silicon carbide epitaxial layer are filled with intrinsic silicon carbide. These pits are formed at surface defects by in-situ etching of the surface of the first doped silicon carbide epitaxial layer under a hydrogen atmosphere. The silicon carbide epitaxial wafer further includes a doped silicon carbide buffer layer formed between the silicon carbide substrate and the first doped silicon carbide epitaxial layer. The silicon carbide epitaxial wafer further includes a third doped silicon carbide epitaxial layer formed between the doped silicon carbide buffer layer and the first doped silicon carbide epitaxial layer, and a graphene layer formed on the third doped silicon carbide epitaxial layer.

2. The silicon carbide epitaxial wafer according to claim 1, wherein, The thickness of the silicon carbide substrate is 300-1000 μm.

3. The silicon carbide epitaxial wafer according to claim 1, wherein, The thickness of the doped silicon carbide buffer layer is 0.5-3.0 μm, and the doping concentration is 5E17-5E18 / cm. 3 The doping element is nitrogen.

4. The silicon carbide epitaxial wafer according to claim 3, wherein, The thickness of the doped silicon carbide buffer layer is 1.0-2.0 μm, and the doping concentration is 1E18-3E18 / cm. 3 The doping element is nitrogen.

5. The silicon carbide epitaxial wafer according to claim 1, wherein, The thickness of the third doped silicon carbide epitaxial layer is 1.0-20.0 μm, and the doping concentration is 1E15-1E17 / cm. 3 The doping element is nitrogen.

6. The silicon carbide epitaxial wafer according to claim 5, wherein, The thickness of the third doped silicon carbide epitaxial layer is 2.0-10.0 μm, and the doping concentration is 2E15-1E16 / cm². 3 The doping element is nitrogen.

7. The silicon carbide epitaxial wafer according to claim 6, wherein, The thickness of the third doped silicon carbide epitaxial layer is 5.0-10.0 μm, and the doping concentration is 2E15-6E15 / cm. 3 The doping element is nitrogen.

8. The silicon carbide epitaxial wafer according to claim 1, wherein, The graphene layer is a graphene layer with 2-10 atomic layers.

9. The silicon carbide epitaxial wafer according to claim 1, wherein, The thickness of the first doped silicon carbide epitaxial layer is 3.0-30.0 μm, and the doping concentration is 1E15-1E17 / cm. 3 The doping element is nitrogen.

10. The silicon carbide epitaxial wafer according to claim 9, wherein, The thickness of the first doped silicon carbide epitaxial layer is 3-25.0 μm, and the doping concentration is 2E15-2E16 / cm². 3 The doping element is nitrogen.

11. The silicon carbide epitaxial wafer according to claim 10, wherein, The thickness of the first doped silicon carbide epitaxial layer is 3.0-15.0 μm, and the doping concentration is 6E15-2E16 / cm². 3 The doping element is nitrogen.

12. The silicon carbide epitaxial wafer according to claim 11, wherein, The thickness of the first doped silicon carbide epitaxial layer is 3.0-8.0 μm, and the doping concentration is 8E15-2E16 / cm². 3 The doping element is nitrogen.

13. The silicon carbide epitaxial wafer according to any one of claims 1-11, wherein, The thickness of the second doped silicon carbide epitaxial layer is 2.0-25.0 μm, and the doping concentration is 1E15-1E17 / cm. 3 The doping element is nitrogen.

14. The silicon carbide epitaxial wafer according to claim 13, wherein, The thickness of the second doped silicon carbide epitaxial layer is 2.0-15.0 μm, and the doping concentration is 4E15-1E16 / cm. 3 The doping element is nitrogen.

15. The silicon carbide epitaxial wafer according to claim 14, wherein, The thickness of the second doped silicon carbide epitaxial layer is 2.0-10.0 μm, and the doping concentration is 8E15-1E16 / cm. 3 The doping element is nitrogen.

16. A method for preparing a silicon carbide epitaxial wafer, characterized in that, This method Includes the following steps, 1) The step of depositing doped silicon carbide on a silicon carbide substrate by vapor deposition to form a first doped silicon carbide epitaxial layer; 2) The step of in-situ etching the surface of the first doped silicon carbide epitaxial layer in a hydrogen atmosphere to form pits at surface defects; 3) The step of depositing intrinsic silicon carbide on the surface of the etched first doped silicon carbide epitaxial layer by vapor deposition; 4) The step of removing intrinsic silicon carbide other than the pits; 5) The step of depositing doped silicon carbide by vapor deposition to form a second doped silicon carbide epitaxial layer. The method further includes the step of depositing doped silicon carbide on a silicon carbide substrate by vapor deposition before forming the first doped silicon carbide epitaxial layer; After forming the doped silicon carbide buffer layer, a third doped silicon carbide epitaxial layer is formed by depositing doped silicon carbide on the silicon carbide substrate by vapor deposition, and the surface of the third doped silicon carbide epitaxial layer is decomposed at a temperature of 1400-1600°C to form a graphene layer.

17. The method according to claim 16, wherein, The thickness of the doped silicon carbide buffer layer is 0.5-3.0 μm, and the doping concentration is 5E17-5E18 / cm. 3 The doping element is nitrogen.

18. The method according to claim 17, wherein, The thickness of the doped silicon carbide buffer layer is 1.0-2.0 μm, and the doping concentration is 1E18-3E18 / cm. 3 The doping element is nitrogen.

19. The method of claim 16, wherein, The thickness of the third doped silicon carbide epitaxial layer is 1.0-20.0 μm, and the doping concentration is 1E15-1E17 / cm. 3 The doping element is nitrogen.

20. The method according to claim 19, wherein, The thickness of the third doped silicon carbide epitaxial layer is 2.0-10.0 μm, and the doping concentration is 2E15-1E16 / cm². 3 The doping element is nitrogen.

21. The method according to claim 20, wherein, The thickness of the third doped silicon carbide epitaxial layer is 5.0-10.0 μm, and the doping concentration is 2E15-6E15 / cm. 3 The doping element is nitrogen.

22. The method according to claim 16, wherein, The graphene layer is a graphene layer with 2-10 atomic layers.

23. The method according to any one of claims 16-22, wherein, The thickness of the first doped silicon carbide epitaxial layer is 3.0-30.0 μm, and the doping concentration is 1E15-1E17 / cm. 3 The doping element is nitrogen.

24. The method according to claim 23, wherein, The thickness of the first doped silicon carbide epitaxial layer is 3-25.0 μm, and the doping concentration is 2E15-2E16 / cm². 3 The doping element is nitrogen.

25. The method according to claim 24, wherein, The thickness of the first doped silicon carbide epitaxial layer is 3.0-15.0 μm, and the doping concentration is 6E15-2E16 / cm². 3 The doping element is nitrogen.

26. The method of claim 25, wherein, The thickness of the first doped silicon carbide epitaxial layer is 3.0-8.0 μm, and the doping concentration is 8E15-2E16 / cm². 3 The doping element is nitrogen.

27. The method according to any one of claims 16-22, wherein, The thickness of the second doped silicon carbide epitaxial layer is 2.0-25.0 μm, and the doping concentration is 1E15-1E17 / cm. 3 The doping element is nitrogen.

28. The method according to claim 27, wherein, The thickness of the second doped silicon carbide epitaxial layer is 2.0-15.0 μm, and the doping concentration is 4E15-1E16 / cm. 3 The doping element is nitrogen.

29. The method according to claim 28, wherein, The thickness of the second doped silicon carbide epitaxial layer is 2.0-10.0 μm, and the doping concentration is 8E15-1E16 / cm. 3 The doping element is nitrogen.

30. The method according to any one of claims 16-22, wherein, In step 2), the etching time is 5-20 minutes.

31. The method according to any one of claims 16-22, wherein, In step 4), the intrinsic silicon carbide outside the pits is removed by in-situ hydrogen etching or chemical polishing.

32. The method according to any one of claims 16-22, wherein, The conditions for vapor deposition in each step include: a temperature of 1500-1700℃ and a pressure of 50-200mbar.

33. The use of the silicon carbide epitaxial wafer according to any one of claims 1-15 in the fabrication of silicon carbide power devices.

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