WO2022110634A1

WO2022110634A1 - Silicon carbide single crystal wafer and ingot, and preparation method therefor

Info

Publication number: WO2022110634A1
Application number: PCT/CN2021/089587
Authority: WO
Inventors: 方帅; 高宇晗; 高超; 石志强; 杨世兴; 宗艳民
Original assignee: 山东天岳先进科技股份有限公司
Priority date: 2020-11-26
Filing date: 2021-04-25
Publication date: 2022-06-02

Abstract

The present application relates to a silicon carbide single crystal wafer and ingot, and a preparation method therefor, belonging to the field of semiconductor materials. The silicon carbide single crystal wafer comprises a nitrogen element. The silicon carbide single crystal wafer has hexagonal color spots of no greater than 50 in number, and edge parts forming the hexagonal color spots are perpendicular to a <10−10> direction. In the present application, a novel defect existing in a nitrogen-containing silicon carbide single crystal wafer is discovered, that is, hexagonal color spots. The color of the hexagonal color spots is different from the color of the silicon carbide body region. However, the novel defect is different from the planar hexagonal void defect and is not a hexagonal cavity, the hexagonal color spots may cause non-uniform resistivity in the silicon carbide single crystal wafer, which may severely affect electrical properties of a semiconductor device made from the silicon carbide single crystal wafer, for example causing a failure in a device made on the silicon carbide single crystal wafer. Thus, in the present application, a silicon carbide single crystal wafer and silicon carbide crystal ingot containing a small number of hexagonal color spots are provided.

Description

Silicon carbide single crystal wafer, crystal ingot and preparation method thereof

technical field

The application relates to a silicon carbide single crystal wafer, a crystal ingot and a preparation method thereof, belonging to the field of semiconductor materials.

Background technique

Silicon carbide single crystal is one of the most important third-generation semiconductor materials. It is widely used in power electronics, power electronics, and power electronics due to its large band gap, high saturation electron mobility, strong breakdown field, and high thermal conductivity. RF devices, optoelectronic devices and other fields. At present, the main preparation method of silicon carbide single crystal is physical vapor transport (PVT) method, which is also the most successful method for growing large-diameter SiC crystals so far. It is mainly to recrystallize and grow SiC crystals by transporting the gas phase source generated by the sublimation of silicon carbide raw materials at high temperature to the seed crystal.

Currently mature SiC devices include: silicon carbide Schottky diodes, which mainly use junction barrier Schottky diodes or hybrid p-n Schottky diode structures; silicon carbide metal-oxide-semiconductor field effect transistors, SiC power modules It has developed rapidly in the fields of photovoltaic power generation, wind power, electric vehicles, locomotive traction, ships, etc. Silicon carbide optoelectronic devices, SiC applications in optoelectronic devices mainly include green light emitting diodes, blue light emitting diodes and ultraviolet photodiodes.

Some companies have been able to provide Φ1-inch, 2-inch, 3-inch and 4-inch wafers, although large-sized single wafers are currently available. The current SiC wafer still has many structural defects, such as micropipes, dislocations, inclusions and damascene structures, etc., but there is still a certain gap in the large-scale use of devices, because the performance of the device depends on the quality of the SiC wafer. In particular, defects in SiC wafers can affect the quality of the fabricated devices. The micropipes, dislocations, inclusions and damascene structures existing in silicon carbide single crystal wafers have been well known and there are many research solutions. However, the quality requirements for SiC single crystal growth are high, the influencing factors are complex, and the understanding of the defects of SiC single crystal is still in the incomplete stage, and the quality of SiC single crystal is important to the prepared device, and needs to continue to improve. The quality of silicon carbide single crystal wafers is to ensure the quality of the fabricated devices.

SUMMARY OF THE INVENTION

In order to solve the above-mentioned problems, a silicon carbide single crystal wafer, an ingot and a preparation method thereof are provided. The present application finds a new type of defect existing in a nitrogen-containing silicon carbide single crystal wafer, that is, a hexagonal color spot. The color of the color spot is different from the color of the main area of silicon carbide, but it is not a hexagonal void unlike the plane hexagonal void defect. The hexagonal color spot will make the resistivity of the silicon carbide single crystal wafer uneven, which will Seriously affect the electrical properties of semiconductor devices made from silicon carbide single crystal wafers, such as making devices made on silicon carbide single crystal wafers fail, so the present application provides a silicon carbide single crystal containing a small number of hexagonal color spots Wafers and Silicon Carbide Ingots.

According to an aspect of the present application, a silicon carbide single crystal wafer is provided, the silicon carbide single crystal wafer contains nitrogen, and the silicon carbide single crystal wafer has no more than 50 hexagonal color spots, forming the The edges of the hexagonal colored spots are perpendicular to the <10-10> direction.

Optionally, the silicon carbide single crystal wafer has no more than 30 hexagonal color spots. Optionally, the upper limit of the number of hexagonal colored spots on the silicon carbide single crystal wafer is selected from 25, 20, 15, 10, 5 and 3, and the lower limit is selected from 25, 20, 15, 10, 5, 3 and 0. Preferably, the silicon carbide single crystal wafer has no more than 10 hexagonal color spots. More preferably, the silicon carbide single crystal wafer has no more than three hexagonal color spots. More preferably, the silicon carbide single crystal wafer has zero hexagonal color spots.

Optionally, the density of the number of hexagonal colored spots is less than 0.3/cm2. For example, the number of silicon carbide crystal planes of 4 inches and 100 mm is not more than 25. Further, the density of the number of hexagonal colored spots is less than 0.05/square centimeter. For example, the number of silicon carbide crystal planes of 4 inches and 100 mm is not more than four.

Optionally, the upper limit of the density of the hexagonal color spots is selected from 0.2\cm2, 0.1\cm2, 0.05\cm2, 0.04\cm2, and 0.03\cm2. Optionally, the density of the hexagonal colored spots is less than 0.05/cm2. For example, the number of silicon carbide crystal planes of a 4-inch 100 mm silicon carbide crystal plane is not more than four.

Optionally, the density change rate of the hexagonal color spots from the center to the edge on the surface of the silicon carbide single crystal wafer perpendicular to the growth direction is lower than 20%. Further, the density change rate of the hexagonal color spots from the center to the edge on the surface of the silicon carbide single crystal wafer perpendicular to the growth direction is lower than 10%.

Optionally, the diameter of the silicon carbide single crystal wafer is not less than 75mm. Preferably, the diameter of the silicon carbide single crystal wafer is not less than 100 mm. More preferably, the diameter of the silicon carbide single crystal wafer is not less than 150 mm.

Optionally, the nitrogen content in the silicon carbide single crystal wafer is 5×10 ¹⁷ to 5×10 ¹⁹ cm ⁻³ . Preferably, the nitrogen content in the silicon carbide single crystal wafer is 5×10 ¹⁸ to 1×10 ¹⁹ cm ⁻³ . More preferably, the silicon carbide single crystal wafer is N-type silicon carbide, and the nitrogen content in the silicon carbide single crystal wafer is 6×10 ¹⁸ to 9×10 ¹⁸ cm ⁻³ .

Optionally, the silicon carbide single crystal wafer is a hexagonal single crystal. Preferably, the crystal form of the silicon carbide single crystal wafer is 4H-SiC or 6H-SiC.

Optionally, a large number of hexagonal color spots will be generated in the nitrogen-doped N-type silicon carbide single crystal, and the resistivity of the silicon carbide single crystal wafer when it is an N-type silicon carbide single crystal is 0.002Ω·cm～0.06Ω ·cm. Preferably, the resistivity of the silicon carbide single crystal wafer is 0.015Ω·cm to 0.028Ω·cm. More preferably, the resistivity of the silicon carbide single crystal wafer is 0.018Ω·cm˜0.022Ω·cm.

Optionally, the edges of the hexagonal colored spots further include voids.

Optionally, the outer area of the edge of the hexagonal color spot of the silicon carbide single crystal wafer is a silicon carbide main area, and the edge of the hexagonal color spot is surrounded by a hexagonal area, and the hexagonal area is The colors of the edges and voids of the colored spots are respectively different from the colors of the silicon carbide main region and the hexagonal region observed under an optical microscope; and/or

The sides of the hexagonal colored spots are respectively different in nitrogen content from the silicon carbide main region and the hexagonal region. The formation of hexagonal stains may be related to whether the distribution of nitrogen content is uniform, and the color of the edges of hexagonal stains shows different colors under different light intensities and aperture modes of an optical microscope, such as in polarized light mode. A light intensity and aperture mode under one of the following modes observes that the color of the sides of the hexagonal patch is whitish, while the silicon carbide bulk areas are yellow and the voids are black. For example, under another light intensity and aperture, the color of the edge of the hexagonal color spot is yellowish, while the main area of the silicon carbide is dark green, and the cavity is black.

Further, the color of the edge of the hexagonal color spot includes uniform and non-uniform colors; the border includes clear and unclear conditions. The shape of the hexagonal patch may appear blurred as a pentagon, quadrilateral, triangle, or a circle-like shape because one or more of the sides are short. When the area of the hexagonal patch is larger, the difference between the edge of the hexagonal patch and the hexagonal area will be more obvious; however, when the area of the hexagonal patch is smaller, the edge and The borders of the hexagonal area are blurred and may merge into one.

Preferably, the nitrogen content of the hexagonal region is not less than the nitrogen content of the silicon carbide main body region is greater than the nitrogen content of the edge of the hexagonal color spot. More preferably, the difference between the nitrogen content of the hexagonal region and the silicon carbide main region is A, and the difference between the nitrogen content of the silicon carbide main region and the edge of the hexagonal color spot is B. , the difference A is not less than B.

Optionally, the difference A is greater than B, and in N-type silicon carbide with a nitrogen content of 4×10 ¹⁸ to 1×10 ¹⁹ , the range of the difference A is 1.5×10 ¹⁸ -4.5×10 ¹⁸ cm ^-3 , preferably 2.5×10 ¹⁸ -4.5×10 ¹⁸ cm ^-3 , and the range of the difference B is 0.1×10 ¹⁸ -2.5×10 ¹⁸ cm ^-3 , preferably 0.4×10 ¹⁸ -1×10 ¹⁸ cm ^-3 .

According to an embodiment, the nitrogen contents of the hexagonal region, the silicon carbide main region, and the edge of the hexagonal color spot are 4.7×10 ¹⁸ cm ^-3 , 4×10 ¹⁸ cm -3 , 4.7×10 18 cm ^-3 , 7.7×10 ¹⁸ cm ^-3 .

Optionally, the hexagonal color spot forms a hexagon on the long crystal plane of the silicon carbide single crystal wafer; the edge of the hexagonal color spot is along the C-axis inside the silicon carbide single crystal wafer extend. The crystal form of the silicon carbide single crystal wafer is 4H-SiC or 6H-SiC.

Optionally, the hexagonal color spots are unequal hexagons. The width of the side portion of the hexagonal color spot is not greater than 1 mm; and/or the distance between the farthest two side portions among the six side portions of the hexagonal color spot is not greater than 5 mm. Preferably, the upper limit of the edge width range of the hexagonal color spot is selected from 70 μm, 60 μm, 50 μm, 40 μm, 30 μm, 20 μm or 10 μm. The upper limit of the distance range between the two farthest sides of the six sides of the hexagonal color spot is selected from 4mm, 3mm, 2mm, 1mm, 800μm, 500μm, 400μm, 300μm, 200μm, 100μm, 50μm or 10μm.

Preferably, the ratio of the sides of the hexagonal colored spots and the hexagonal regions to the area of the silicon carbide single crystal wafer is 0˜2 mm ² /6 inches.

Optionally, the sides of the hexagonal colored spots further include voids, and the number of voids contained in the sides of the hexagonal colored spots is not more than 10. Preferably, the number of cavities contained in the sides of the hexagonal colored spots is not more than 8. Preferably, the number of voids contained in the edge of the hexagonal color spot is not more than 5. More preferably, the number of voids contained in the edge of the hexagonal color spot is not more than three.

Optionally, the size of the cavity is not greater than 100 μm. Preferably, the size of the cavity is 10-100 μm. Further, the size of the cavity is 10-50 μm.

Alternatively, the void may be in the form of a hollow hexagonal defect.

Optionally, the side of the hexagonal color spot includes an inner side and an outer side, the inner side encloses a hexagonal area, and a cavity is included between the inner side and the outer side, No less than 80% of the voids are centered on one side of the central axis between the inner side and the outer side. The new type of defects is a nitrogen-containing silicon carbide single crystal wafer with a small number of hexagonal color spots and void defects. The silicon carbide single crystal wafer of the present application has uniform resistivity, and the semiconductor device prepared therefrom has excellent electrical properties; silicon carbide The performance of the single crystal wafer is excellent, such as the breakdown field strength, and the number of voids generated by the device extension is extremely low.

Optionally, not less than 90% of the voids are centered on one side of the central axis between the inner side and the outer side. Preferably, not less than 80% of the voids are centered in the connecting area of each side of the hexagonal color spot. The silicon carbide single crystal wafer has a small number of hexagonal color spots and voids, and the quality of the single wafer is high. The voids are more concentrated in the areas on the sides of the hexagonal stain and are easier to repair. Since the number of holes is a whole number, 80% of the number of holes will be rounded to the nearest whole number if the result contains a decimal point.

Optionally, the short sides of the sides of the hexagonal colored spots have more cavities than the sides.

Optionally, the ratio of the sides of the hexagonal colored spots and the hexagonal regions to the area of the silicon carbide single crystal wafer is 0˜2 mm ² /6 inches. Preferably, the ratio of the sides of the hexagonal colored spots and the hexagonal regions to the area of the silicon carbide single crystal wafer is 0˜1.5 mm ² /6 inches. According to another aspect of the present application, a method for preparing the silicon carbide single crystal wafer is provided, the method comprising the following steps:

1) Preparation of silicon carbide single crystal ingot:

providing a crucible having a nitrogen channel, the nitrogen channel being disposed in the sidewall of the crucible and extending around the inner cavity of the crucible, the inner sidewall of the nitrogen channel being less dense than the outer sidewall of the nitrogen channel;

The silicon carbide seed crystal is placed on the top of the crucible and the silicon carbide raw material is placed on the bottom of the crucible, and the crucible is assembled with a thermal insulation structure and placed in a crystal growth furnace;

The silicon carbide single crystal ingot is grown by the physical vapor transport method. During the growth of the silicon carbide single crystal, nitrogen is infiltrated into the inner cavity of the crucible through the nitrogen gas channel to adjust the nitrogen content in the prepared silicon carbide single crystal ingot. distributed;

2) The prepared silicon carbide single crystal ingot is subjected to a step including cutting, that is, the silicon carbide single crystal wafer is prepared.

Optionally, the nitrogen channel is a spiral channel, the spiral channel extends spirally around the inner cavity of the crucible along the axial direction of the crucible, and is wound between the bottom and the top of the crucible at least once.

Preferably, the inner liner and the outer shell are respectively barrel-shaped, the inner liner sleeve is provided in the outer shell to be tightly and detachably connected, a spiral nitrogen channel is formed at the interface between the inner liner and the outer shell, and the air inlet and outlet of the nitrogen channel are both arranged in the crucible The bottom end of the crucible, that is, the spiral nitrogen channel is wound twice between the bottom and the top of the crucible, and the principle of nitrogen flow is similar to that of circulating water.

Optionally, the wall thickness C of the part of the lining forming the nitrogen channel is 3-5mm, the wall thickness C is too small and easy to be eroded, and the nitrogen directly passes into the inner cavity of the crucible to affect the stability of crystal growth, and the wall thickness C is too large. It is easy to hinder the diffusion of nitrogen into the crucible. This setting method increases the permeability of nitrogen without affecting the heat generation.

Optionally, the method for growing a silicon carbide single crystal ingot by a physical vapor transport method includes the following steps:

Control the temperature and pressure of the crystal growth furnace and the flow of inert gas into the crystal growth furnace to clean and remove impurities in the crystal growth furnace;

Heating stage: adjust the temperature of the crystal growth furnace to 1800～2400K, control the pressure in the crucible to be 0.6×10 ⁵ to 1.2×10 ⁵ Pa, and the flow rate of the inert gas into the crystal growth furnace is 50-500mL/min. The nitrogen flow V ₁ of the nitrogen channel is 20-200 mL/min;

Crystal growth stage: increase the nitrogen flow V ₂ into the nitrogen channel to 50-500mL/min, the V ₂ is greater than V ₁ , the crystal growth temperature is 2200K-2800K, the crystal growth pressure is 100-5000Pa, and the holding time is 80～ 120h, the silicon carbide single crystal ingot was prepared.

Optionally, the crystal growth stage includes a first crystal growth stage and a second crystal growth stage, the time ratio of the first crystal growth stage to the second crystal growth stage is 1:0.8-1.2, and the first crystal growth stage is 1:0.8-1.2. The nitrogen inlet and nitrogen outlet of the second crystal growth stage were exchanged.

Preferably, the flow rate of the inert gas is 300-400 mL/min. More preferably, the flow rate of the inert gas is 300 mL/min. Preferably, the inert gas is argon and/or helium.

Preferably, the nitrogen flow rate V ₁ in the heating stage is 40-100 mL/min. More preferably, the nitrogen flow rate V ₁ in the heating stage is 60 mL/min. Preferably, the nitrogen flow rate V ₂ in the crystal growth stage is 110˜400 mL/min. More preferably, the nitrogen flow rate V ₂ in the crystal growth stage is 300 mL/min. The control methods of nitrogen partial pressure and flow rate in different stages of the present application can reduce the number and density of hexagonal color spots. Preferably, the nitrogen is high-purity nitrogen with a purity of not less than 99.99%.

Optionally, the crucible includes an inner liner and an outer shell, the inner liner forms an inner side wall of the nitrogen gas channel, the outer shell forms an outer side wall of the nitrogen gas channel, and the density of the inner liner is lower than that of the outer shell . Preferably, the density of the inner liner is not greater than 1.75 g/cm ³ . Preferably, the density of the shell is not less than 1.85 g/cm ³ . More preferably, the density of the shell is not less than 1.90 g/cm ³ . Preferably, the crucible is made of graphite. The shell is made of denser graphite material, which reduces the loss of atmosphere at high temperature, especially the escape of evaporated silicon atmosphere, and reduces the carbon-rich atmosphere that may cause hexagonal stains. Nitrogen penetrates slowly into the lining and diffuses according to the concentration gradient. Since the densities of the lining and the outer shell are different, the resistance to diffusion is greater, so the nitrogen diffuses more into the interior, while inside the crucible, The nitrogen concentration at the edge of the seed face is greater than that at the center of the seed face, even though the PVT method would result in the presence of radial temperatures, this structure and ventilation will balance out the inhomogeneity brought about by the PVT method, resulting in a very, very high resistivity. Evenly and effectively reduce the number of hexagonal spots.

Optionally, the silicon carbide raw material is silicon carbide polycrystalline or silicon carbide powder. Further, the silicon carbide raw material is silicon carbide powder, the silicon carbide raw material filled in the crucible includes an upper layer raw material and a lower layer raw material, the upper layer raw material is smaller than the particle size of the lower layer raw material, and the proportion of the upper layer raw material in the silicon carbide raw material is ratio is 30-40V%. Preferably, the particle size of the upper layer raw material is 5-10 mm, and the particle size of the lower layer raw material is 20-30 mm. The larger gap between the raw materials with large particles in the bottom layer will increase the thermal radiation rate between the raw materials and increase the uniformity of temperature distribution in the raw materials in the bottom layer, so that the raw materials will evaporate faster at a suitable temperature, but the raw materials with large particles will evaporate faster. It will cause uneven transmission of the atmosphere into the growth chamber. Therefore, small particles of 5-10mm are placed on top of the raw materials to provide smaller atmosphere channels, so that the originally stronger atmosphere can flow through more and denser small channels evenly. open to make the atmosphere more uniform. After the atmosphere is uniform, the supersaturation of the crystal growth plane will become uniform, so that the crystal growth will be more stable, and the number and density of hexagonal color spots will be effectively reduced. On the other hand, using large-particle SIC powder as the raw material for the lower layer can slow down the time for the complete carbonization of the raw material particles, so as to reduce the carbon-rich atmosphere that may cause hexagonal color spots.

Optionally, the coating is a TaC coating. The provision of the coating prevents the backside evaporation of the seed crystals during the growth process, which causes void defects on the hexagonal color spots. Preferably, the coating is formed by a CVD method (chemical vapor deposition), a PVD method (physical vapor deposition) or an MBE method (molecular beam epitaxy).

Optionally, the roughness of the silicon surface of the silicon carbide seed crystal is Ra<0.5. In order to reduce the number of internal dislocations in the silicon carbide single crystal, in particular, TSD (screw dislocations). Before crystal growth, the carbon surface of the seed crystal is finely polished to make the surface sufficiently smooth, and the Si surface is also finely polished to make it scratch-free and as smooth as possible.

Optionally, the middle part of the silicon carbide raw material is filled with silicon powder. Preferably, the silicon powder is loaded in a loader provided with a through hole, and the loader is loaded in the middle part of the silicon carbide raw material. The silicon carbide raw material is filled with silicon powder to compensate for the silicon in the sublimation atmosphere during the growth of silicon carbide single crystal, and the silicon powder is further placed in the middle because the temperature in the heating coil heating crucible in the PVT growth method is the lowest, so that the silicon powder will not be in the sublimation atmosphere. Premature volatilization in the early stage of crystal growth to reduce the carbon-rich atmosphere that can cause hexagonal stains.

According to another aspect of the present application, a silicon carbide single crystal ingot is provided, and the silicon carbide single crystal ingot is processed by including a cutting step to form a silicon carbide single crystal wafer; the silicon carbide single crystal wafer is selected from any of the above The silicon carbide single crystal wafer or the silicon carbide single crystal wafer is selected from the silicon carbide single crystal wafer prepared by any of the above-mentioned methods.

Optionally, the silicon carbide single crystal ingot is processed to form a silicon carbide single crystal wafer through the steps of cutting and polishing. Further, the silicon carbide single crystal ingot is subjected to end face processing, multi-wire cutting, grinding, mechanical polishing, chemical mechanical polishing, cleaning and packaging to form a silicon carbide single crystal wafer that is ready to use out of the box.

Optionally, in the growth direction of the silicon carbide single crystal extending along the C-axis, the width of the edge of the hexagonal color spot increases, the width of the edge of the hexagonal color spot increases, and the hexagonal color spot increases. The distance between the two farthest edges among the six edges of the edge-shaped patch increases.

Optionally, the edge of the hexagonal color spot further includes a cavity, and the cavity extends along the growth direction of the silicon carbide single crystal along the C-axis.

Optionally, the hexagonal color spots will appear in a part of the growth direction of the silicon carbide single crystal extending along the C-axis of the silicon carbide single crystal ingot, that is, the silicon carbide single crystal obtained by cutting the same silicon carbide single crystal ingot. The number of hexagonal colored spots in the wafers varies.

Optionally, it includes the method for preparing a silicon carbide single crystal ingot in step 1) of the method for preparing a silicon carbide single crystal wafer described in any one of the above.

In this application, the hexagonal color spot is a new type of defect in the silicon carbide single crystal wafer, and each edge of the hexagonal color spot is flush with the surface of the silicon carbide main body area, not a hexagonal pit , but it exhibits a hexagonal or nearly hexagonal shape with a different color from the main area of the silicon carbide. This application defines the area formed by the edge of the hexagonal color spot as a hexagonal color spot. other parts of the application.

In the present application, the number of cavities included in the sides of the hexagonal colored spots refers to the number of cavities included in all the sides of each hexagonal colored spot unless otherwise specified.

The beneficial effects of this application include but are not limited to:

1. A silicon carbide single crystal wafer according to the present application, having a novel defect found in nitrogen-containing silicon carbide single crystal wafers, namely a hexagonal color spot, the color of the hexagonal color spot is different from the color of the silicon carbide main region However, unlike the plane hexagonal void defect, it is not a hexagonal void. The hexagonal color spot will make the resistivity of the silicon carbide single crystal wafer uneven, which will seriously affect the semiconductor device made from the silicon carbide single crystal wafer. Electrical properties, such as failure of devices fabricated on silicon carbide single crystal wafers, the silicon carbide single crystal wafers of the present application contain a small number of hexagonal color spots.

2. According to the silicon carbide single crystal wafer of the present application, it is found that the novel defect existing in the silicon carbide single crystal wafer containing nitrogen is hexagonal color spot, the void defect existing on the hexagonal color spot, the hexagonal color spot. The color of the spot is different from the color of the main area of silicon carbide, but it is not a hexagonal void unlike the plane hexagonal void defect. The hexagonal color spot will make the resistivity of the silicon carbide single crystal wafer uneven, which will seriously affect the The electrical properties of semiconductor devices made of silicon carbide single crystal wafers, such as making devices made on silicon carbide single crystal wafers fail; the presence of voids not only affects the performance of silicon carbide single crystal wafers such as breakdown field strength, but also voids may It extends to the device made by using the silicon carbide single crystal wafer as a single wafer; the silicon carbide single crystal wafer of the present application contains hexagonal color spots and a small number of voids.

3. The silicon carbide single crystal wafer according to the present application has low defect density of dislocations, carbon inclusions, stacking faults, etc., and uniform resistivity.

4. According to the preparation method of the silicon carbide single crystal wafer of the present application, the obtained silicon carbide single crystal wafer has few hexagonal color spots, few void defects, dislocations and carbon inclusions on the hexagonal color spots. , stacking fault and other defect density is low, the resistivity is uniform; the control method is simple, and the operation is convenient.

5. According to the silicon carbide single crystal ingot of the present application, the silicon carbide ingot of the present application contains hexagonal color spots and a small number of voids, and the present application has a new defect found in the nitrogen-containing silicon carbide ingot, namely hexagonal The color of the hexagonal color spot is different from the color of the main area of the silicon carbide, but it is not a hexagonal void unlike the plane hexagonal void defect. The hexagonal color spot will make the silicon carbide ingot. The non-uniform resistivity will seriously affect the silicon carbide single crystal wafer prepared from the silicon carbide ingot, and then affect the electrical properties of the prepared semiconductor device. For example, the device made on the silicon carbide single crystal wafer will fail. The silicon ingot contains a small number of hexagonal color spots.

6. According to the silicon carbide single crystal ingot of the present application, it is found that the existence of voids not only affects the properties of silicon carbide single crystal wafers such as breakdown field strength, but also voids may extend to silicon carbide single crystal wafers as single wafers. in the device.

Description of drawings

The drawings described herein are used to provide further understanding of the present application and constitute a part of the present application. The schematic embodiments and descriptions of the present application are used to explain the present application and do not constitute an improper limitation of the present application. In the attached image:

FIG. 1 is a schematic view of the assembled crucible inside the crystal growth furnace.

2a, 2b, and 2c are schematic diagrams of three hexagonal color spots existing in the silicon carbide single crystal wafer 2# in the early stage of crystal growth in the silicon carbide single crystal ingot according to Example 1 of the present application, respectively.

Figures 3a, 3b, and 3c are schematic diagrams of three hexagonal color spots existing in the silicon carbide single crystal wafer 8# in the middle stage of crystal growth obtained from the silicon carbide single crystal ingot involved in Example 1 of the present application, respectively.

4a, 4b, and 4c are respectively hexagonal color spots at the same C-axis position in three continuous silicon carbide single crystal wafers extending along the growth direction in the silicon carbide single crystal ingot according to Example 1 of the application.

FIG. 5 is a hexagonal color spot of the silicon carbide single crystal wafer 8# involved in Example 1 of the application.

FIG. 6 is the hexagonal color spot in FIG. 5 after etching.

Nitrogen content associated with a hexagonal color spot in the silicon carbide single crystal wafer in FIG. 4c in FIG. 7 in silicon carbide single crystal wafer 8#.

8 is a schematic structural diagram of a silicon carbide single crystal wafer according to an embodiment;

FIG. 9 is a schematic structural diagram of several consecutive silicon carbide single crystal wafers cut from a silicon carbide ingot according to an embodiment.

Detailed ways

The present application will be described in detail below with reference to the examples, but the present application is not limited to these examples.

Unless otherwise specified, the raw materials and catalysts in the examples of the present application are purchased through commercial channels.

The analytical method in the embodiment of the application is as follows:

The morphology of hexagonal stains was observed by Olympus multifunctional optical microscope;

Using secondary ion mass spectrometry, SIMS is Secondary Ion Mass Spectroscopy to detect the nitrogen content of silicon carbide single crystal;

Use Raman spectrometer to test the elemental composition of silicon carbide single crystal wafer;

Using high-resolution XRD, the half-width of the wafer is measured to detect the crystal quality and crystal structure such as crystal orientation.

Example 1

Referring to FIG. 1 , the sidewall of the crucible is provided with a nitrogen gas channel 6 . The nitrogen gas channel 6 is arranged in the sidewall of the crucible and extends around the inner cavity of the crucible. The inner sidewall of the nitrogen gas channel is less dense than the outer sidewall of the nitrogen gas channel.

As an embodiment, the crucible 2 includes a lining 21 and an outer shell 22, the sidewall of the crucible forms a nitrogen gas channel 6, the nitrogen gas channel 6 is a spiral channel, the spiral channel extends spirally around the inner cavity of the crucible along the axial direction of the crucible, and the nitrogen gas channel is at the bottom of the crucible. and the top at least once. For example, the nitrogen gas channel extends from the gas inlet 71 at the bottom of the crucible to the top of the crucible and then extends to the bottom of the crucible to form the gas outlet 72 .

Specifically, the inner liner 21 and the outer shell 22 are respectively barrel-shaped, the inner liner 21 is sleeved in the outer shell 22, the inner liner 21 and the outer shell 22 are sealed and spliced together, and a spiral nitrogen gas channel is formed at the interface between the inner liner 21 and the outer shell 22 , that is, the inner wall of the lining 21 and the inner wall of the outer shell 22 are each made in half, and the two are spliced together to form a spiral channel. The air inlet 71 and the air outlet 72 of the nitrogen channel are both arranged at the bottom end of the crucible, that is, the spiral nitrogen channel is at the bottom of the crucible and the gas outlet 72. Wrap twice between the tops.

As an embodiment, the wall thickness C of the lining forming the nitrogen channel 6 is 3-5mm, and the wall thickness C is too small to be easily eroded. It is easy to hinder the diffusion of nitrogen into the crucible. This setting method increases the permeability of nitrogen without affecting the heat generation.

Example 2

Referring to FIG. 1 , according to an embodiment of the present application, a method for preparing a silicon carbide single crystal ingot using the crucible of Example 1 includes the following steps:

1) Preparation of silicon carbide single crystal ingot:

The crucible with the nitrogen gas channel of Example 1 is provided, the nitrogen gas channel is arranged in the sidewall of the crucible and extends around the inner cavity of the crucible, and the inner sidewall of the nitrogen gas channel is less dense than the outer sidewall of the nitrogen gas channel;

The silicon carbide seed crystal 1 is placed on the top of the crucible 2 and the silicon carbide raw material 3 is placed on the bottom of the crucible 2, the crucible 2 is assembled with the heat preservation structure 3 and placed in the crystal growth furnace 4, and the induction coil 5 is used for heating;

The temperature controller 12 controls the temperature of the crystal growth furnace, controls the pressure through the vacuum system 8, and passes the inert gas flow into the crystal growth furnace 10 through the inert gas system 9 to clean and remove impurities in the crystal growth furnace 10;

Heating stage: adjust the temperature of the crystal growth furnace to 1800-2400K, control the pressure in the crucible 2 to be 0.6×10 ⁵ to 1.2×10 ⁵ Pa, and the flow rate of the inert gas into the crystal growth furnace 10 to be 50-500mL/min, The nitrogen flow V ₁ passing into the nitrogen channel is 20-200 mL/min;

Crystal growth stage: increase the nitrogen flow V ₂ into the nitrogen channel to 50-500mL/min, V ₂ is greater than V ₁ , the crystal growth temperature is 2200K-2800K, the crystal growth pressure is 100-5000Pa, and the holding time is 80-120h;

Stop feeding nitrogen, and continue feeding inert gas, and the flow rate of feeding inert gas remains unchanged;

Cooling stage: turn off the intermediate frequency heating power supply, increase the circulating water flow in the quartz tube of the crystal growth furnace, and quickly cool the crystal growth furnace chamber.

After the cooling is completed, the furnace is opened to obtain a 4-inch, 6-inch or 8-inch N-type silicon carbide single crystal ingot with uniform resistivity;

2) The prepared silicon carbide single crystal ingot is subjected to a step including cutting, that is, a silicon carbide single crystal wafer is prepared.

The direction of the edge of the hexagonal color spot detected by X-ray diffraction on the prepared silicon carbide single crystal wafer is perpendicular to the <10-10> direction. A schematic structural diagram of a prepared silicon carbide single crystal wafer is shown in FIG. 8 , and a schematic structural diagram of a prepared silicon carbide ingot cut into a silicon carbide single crystal wafer is shown in FIG. 9 .

Example 3 Preparation of Silicon Carbide Single Crystal Ingot 1#

The preparation method of silicon carbide single crystal ingot 1# comprises the following steps:

The crucible with the nitrogen gas channel of Example 1 is provided, the nitrogen gas channel is arranged in the side wall of the crucible and extends around the inner cavity of the crucible, the inner wall density of the nitrogen gas channel is 1.70g/cm ³ , and the density of the outer shell is 1.90g/cm ³ ;

The silicon carbide seed crystal is placed on the top of the crucible and the silicon carbide powder is placed on the bottom of the crucible, and the heat preservation structure is assembled outside the crucible and sealed in the crystal growth furnace;

Control the temperature and pressure of the crystal growth furnace and the flow of argon gas into the crystal growth furnace to clean and remove impurities in the crystal growth furnace;

Heating stage: adjust the temperature of the crystal growth furnace to 2200K, control the pressure in the crucible to be 0.9×10 ⁵ Pa, the flow rate of argon gas into the crystal growth furnace is 300mL/min, and the flow rate V ₁ of nitrogen gas into the nitrogen channel is 40mL /min;

Crystal growth stage: increase the nitrogen flow V ₂ into the nitrogen channel to 200 mL/min, the growth temperature to 2400 K, the growth pressure to 1000 Pa, and the holding time to 100 h;

Stop feeding nitrogen, and continue feeding inert gas, and the flow rate of argon is unchanged;

Cooling stage: turn off the intermediate frequency heating power supply, increase the circulating water flow in the quartz tube of the crystal growth furnace, and quickly cool the crystal growth furnace cavity.

After the cooling is completed, the furnace is opened to obtain an N-type silicon carbide single crystal ingot 1# with uniform resistivity.

For the preparation of silicon carbide single crystal wafers, the silicon carbide single crystal ingot 1# is processed by end face processing, multi-wire cutting, grinding, mechanical polishing, chemical mechanical polishing, cleaning and packaging to form a 6-inch silicon carbide single crystal that is ready to use out of the box. For wafers, the preparation method is not limited to a 6-inch silicon carbide single crystal, but can also be 4 inches, 8 inches, and 12 inches. Taking the silicon carbide single crystal wafers of the following dimensions as an example, the silicon carbide single crystal ingot 1# has produced multiple silicon carbide single crystal wafers with a thickness of 350±25 μm and a size of 6 inches, from the seed crystal along the crystal growth direction They are silicon carbide single crystal wafer 1#, silicon carbide single crystal wafer 2#, silicon carbide single crystal wafer 3#, silicon carbide single crystal wafer 4#, etc., and so on. Among them, silicon carbide single crystal wafer 2# belongs to the initial stage of crystal growth, silicon carbide single crystal wafer 8# belongs to the middle stage of crystal growth, and the number of hexagonal color spots in the silicon carbide single crystal wafer is the same.

Figures 2a, 2b, and 2c respectively show three different hexagonal color spots in the silicon carbide single crystal wafer 1#. Figures 3a, 3b, and 3c respectively show three different hexagonal color spots existing in the silicon carbide single crystal wafer 4#. Figures 4a, 4b, and 4c are extensions of the same hexagonal color spot existing in silicon carbide single crystal wafers 6#, 7#, and 8#, respectively.

The number of hexagonal colored spots in the silicon carbide single crystal wafer is 10, the content of voids on all hexagonal colored spots is 25 in total, the nitrogen content is 6-8×10 ¹⁸ cm ^-3 , and the resistivity is 0.020-0.024Ω·cm, and the total area of the edge and cubic area of the hexagonal stain is 2 square millimeters.

Example 4 Preparation of Silicon Carbide Single Crystal Ingot 2#

The difference between the preparation method of the silicon carbide single crystal ingot 2# of the present embodiment and the silicon carbide single crystal ingot 1# of the embodiment 3 is that the crystal growth stage includes a first crystal growth stage and a second crystal growth stage. The time ratio between the crystallization stage and the second crystallization stage is 1:1, the nitrogen inlet and nitrogen outlet of the first crystallization stage and the second crystallization stage are exchanged, and the specific steps of crystallization include:

The first crystal growth stage: first increase the nitrogen flow rate to 200ml/min, control the temperature of the infrared thermometer to 2200K, control the absolute pressure in the growth chamber to 1000Pa, and grow for 50h;

The second crystal growth stage: Swap the nitrogen gas inlet and outlet, the gas inlet in stage one becomes the gas outlet, and the gas outlet becomes the gas inlet, control the temperature of the infrared thermometer to 2400K, and control the absolute temperature in the growth chamber. The pressure is 1000Pa, and the growth is 50h.

The number of hexagonal colored spots in the silicon carbide single crystal wafer is 5, the content of cavities existing on all hexagonal colored spots is 5 in total, and the 5 cavities are located near the outer edge, and the nitrogen content is 8- 9×10 ¹⁸ cm ^-3 , the resistivity is 0.018-0.021Ω·cm, and the total area of the edge and cubic area of the hexagonal color spot is less than 0.8 square millimeter.

The number of hexagonal colored spots in the silicon carbide single crystal wafer was 0.027/cm 2 , and the density change rate was 4%.

Example 5 Preparation of Silicon Carbide Single Crystal Ingot 3#

The difference between the preparation method of the silicon carbide single crystal ingot 3# of the present embodiment and the silicon carbide single crystal ingot 2# of the embodiment 4 is that:

Heating stage: adjust the temperature of the crystal growth furnace to 1800K, control the pressure in the crucible to be 0.6×10 ⁵ Pa, the flow rate of argon gas into the crystal growth furnace is 50mL/min, and the flow rate V ₁ of nitrogen gas into the nitrogen channel is 20mL /min;

The specific steps of crystal growth include:

The first crystal growth stage: first increase the nitrogen flow rate to 150ml/min, control the temperature of the infrared thermometer to 2200K, control the absolute pressure in the growth chamber to 200Pa, and grow for 50h;

The second crystal growth stage: Swap the nitrogen gas inlet and outlet, the gas inlet in stage 1 becomes the gas outlet, and the gas outlet becomes the gas inlet, control the temperature of the infrared thermometer to 2200K, and control the absolute temperature in the growth chamber. The pressure is 200Pa, and the growth is 50h.

The number of hexagonal colored spots in the silicon carbide single crystal wafer is 8, the content of voids on all hexagonal colored spots is 15 in total, the nitrogen content is 7-8×10 ¹⁸ cm ^-3 , the resistivity It is 0.019-0.022Ω·cm, and the total area of the edge and cubic area of the hexagonal stain is 1.2 square millimeters.

The number of hexagonal colored spots in the silicon carbide single crystal wafer was 0.044 pieces/cm 2 , and the density change rate was 14%.

Example 6 Preparation of Silicon Carbide Single Crystal Ingot 4#

The difference between the preparation method of the silicon carbide single crystal ingot 4# of the present embodiment and the silicon carbide single crystal ingot 1# of the embodiment 3 is that the silicon carbide raw material filled in the crucible includes an upper layer raw material and a lower layer raw material, and the particle size of the upper layer raw material is It is 8mm, the particle size of the lower layer raw material is 25mm, and the proportion of the upper layer raw material in the silicon carbide raw material is 75V%.

The number of hexagonal colored spots in the silicon carbide single crystal wafer is 7, and the content of voids on all hexagonal colored spots is a total of 14, of which 8 are located near the inner edge, and 4 are At the position near the outer edge of the cavity, the nitrogen content is 7-8×10 ¹⁸ cm ^-3 , the resistivity is 0.019-0.022Ω·cm, and the total area of the edge and cubic area of the hexagonal stain is 1.7 mm2.

The number of hexagonal colored spots in the silicon carbide single crystal wafer was 0.038/cm 2 , and the density change rate was 11%.

Example 7 Preparation of silicon carbide single crystal ingot 5#

The difference between the preparation method of the silicon carbide single crystal ingot 4# of the present embodiment and the silicon carbide single crystal ingot 1# of the embodiment 3 is that the backside of the silicon carbide seed crystal is epitaxially coated with TaC, and the silicon surface of the silicon carbide seed crystal is The roughness Ra<0.5, the middle part of the silicon carbide raw material is filled with silicon powder.

The number of hexagonal colored spots in the silicon carbide single crystal wafer is 6, and the content of cavities on all hexagonal colored spots is 13 in total, of which 3 cavities are close to the inner side, and 9 cavities Near the outer edge, the nitrogen content is 7-8×10 ¹⁸ cm ^-3 , the resistivity is 0.019-0.022 Ω·cm, and the total area of the edge and cubic area of the hexagonal stain is 1.5 mm2.

The number of hexagonal colored spots in the silicon carbide single crystal wafer was 0.033/cm 2 , and the density change rate was 7%.

Example 8 Detection of Hexagonal Color Spot Defects in Silicon Carbide Single Crystal Ingots 1#-5#

The hexagonal color spots existing in the silicon carbide single crystal ingots 1#-5# were detected respectively, and the sides of the hexagonal color spots were measured by the X-ray orientation instrument to be perpendicular to the <10-10>direction; Raman detection was carried out. It is found that the hexagonal stain is not polytype; the corrosion test of the hexagonal stain shows that it is not a dislocation, especially not a screw dislocation (TSD dislocation for short). A picture of a hexagonal stain before corrosion (Fig. 5) and after corrosion (Fig. 6). The hexagonal stain, edge dislocation and screw dislocation are all hexagonal corrosion pits after corrosion. It can be seen that the size of the corrosion pits of the etched edge dislocations and screw dislocations is smaller than that of the hexagonal stains, and the size of the corrosion pits of the screw dislocations is about tens of microns higher than that of the edge dislocations. The size of the corrosion pit of edge dislocation is several to ten microns. The size of the corrosion pit is related to the corrosion process, but in general, the size of the edge dislocation and screw dislocation after etching is smaller than that of the hexagonal color spot. The size of the corrosion pits is small, and the distribution of edge dislocations and screw dislocations has no obvious relationship with the hexagonal stains. The detection structure of nitrogen element shows that the difference value of nitrogen content in the hexagonal area is greater than that of the main area of silicon carbide, and the difference value of nitrogen content in the main area of silicon carbide is B, and the difference value of A is greater than difference B. Referring to FIG. 7 , the nitrogen content of the relevant hexagonal area, the silicon carbide main area, and the edge of the hexagonal color spot in a hexagonal color spot in FIG. 4 c in the silicon carbide single crystal wafer 8# is 7.7× 10 ¹⁸ cm ^-3 , 4.7×10 ¹⁸ cm ^-3 , 4×10 ¹⁸ cm ^-3 .

Comparative Example 1 Preparation of Silicon Carbide Single Crystal Ingot D1#

The difference between the preparation method of the silicon carbide single crystal ingot D1# of the present embodiment and the silicon carbide single crystal ingot 1# of the embodiment 3 is that the nitrogen gas channel does not exist on the side wall of the crucible, but nitrogen and argon gas are directly passed into Inside the crystal growth furnace.

The number of hexagonal colored spots in the silicon carbide single crystal wafer is 55, and the content of voids on all hexagonal colored spots is 90 in total, of which at least one of the hexagonal colored spots has voids. The number is 12; among them, 26 cavities are located near the inner edge, 28 cavities are located near the outer edge, and 36 cavities are located in the middle; the nitrogen content is 3×10 ¹⁸ to 5×10 ¹⁸ cm ^-3 , The resistivity was 0.023-0.030 Ω·cm, and the total area of the sides and cubic areas of the hexagonal colored spots was 3.9 square millimeters.

The number of hexagonal colored spots in the silicon carbide single crystal wafer was 0.301/cm 2 , and the density change rate was 35%.

Comparative Example 2 Preparation of Silicon Carbide Single Crystal Ingot D2#

The difference between the preparation method of the silicon carbide single crystal ingot D2# of this embodiment and the silicon carbide single crystal ingot 1# of Example 3 is that the nitrogen flow rate in the heating stage is 100mL/min, and the nitrogen flow rate in the crystal growth stage is 50mL/min. min.

The number of hexagonal colored spots in the silicon carbide single crystal wafer is 60, and the content of voids on the hexagonal colored spots is 102. Among them, the number of voids on at least one hexagonal colored spot is 15; among them, 42 holes are near the inner side, 42 holes are near the outer side, and 18 holes are in the middle; the nitrogen content is 1×10 ¹⁸ ～ 2×10 ¹⁸ cm ^-3 , the resistivity It is 0.035-0.045Ω·cm, and the total area of the edge and cubic area of the hexagonal stain is 4.0 square millimeters.

The number of hexagonal colored spots in the silicon carbide single crystal wafer was 0.33 pieces/square centimeter, and the density change rate was 37%.

The above are only the embodiments of the present application, and the protection scope of the present application is not limited by these specific embodiments, but is determined by the claims of the present application. Various modifications and variations of this application are possible for those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the technical ideas and principles of the present application shall be included within the protection scope of the present application.

Claims

A silicon carbide single crystal wafer, characterized in that the silicon carbide single crystal wafer contains nitrogen, and the silicon carbide single crystal wafer has no more than 50 hexagonal color spots, forming the hexagonal color spots. The edge of the spot is perpendicular to the <10-10> direction.
The silicon carbide single crystal wafer according to claim 1, wherein the silicon carbide single crystal wafer has no more than 30 hexagonal color spots;

Preferably, the silicon carbide single crystal wafer has no more than 5 hexagonal color spots;

More preferably, the silicon carbide single crystal wafer has no more than three hexagonal color spots.
The silicon carbide single crystal wafer according to claim 1, wherein the diameter of the silicon carbide single crystal wafer is not less than 75 mm;

Preferably, the diameter of the silicon carbide single crystal wafer is not less than 100mm;

More preferably, the diameter of the silicon carbide single crystal wafer is not less than 150 mm.
The silicon carbide single crystal wafer according to claim 1, wherein the nitrogen content in the silicon carbide single crystal wafer is 5×10 17 to 5×10 19 cm −3 ;

Preferably, the nitrogen content in the silicon carbide single crystal wafer is 5×10 18 to 1×10 19 cm −3 ;

More preferably, the silicon carbide single crystal wafer is N-type silicon carbide, and the nitrogen content in the silicon carbide single crystal wafer is 6×10 18 to 9×10 18 cm −3 .
The silicon carbide single crystal wafer according to claim 1, wherein the silicon carbide single crystal wafer is a hexagonal single crystal; preferably, the crystal type of the silicon carbide single crystal wafer is 4H-SiC or 6H -SiC; and/or

The resistivity of the silicon carbide single crystal wafer is 0.002Ω·cm˜0.06Ω·cm; preferably, the resistivity of the silicon carbide single crystal wafer is 0.015Ω·cm˜0.028Ω·cm.
The silicon carbide single crystal wafer according to any one of claims 1 to 5, wherein the outer region of the edge of the hexagonal color spot of the silicon carbide single crystal wafer is a silicon carbide main region, and the The sides of the hexagonal colored spots are surrounded by a hexagonal area, and the sides of the hexagonal colored spots are respectively different from the color of the silicon carbide main area and the hexagonal area observed under an optical microscope; and/or

The sides of the hexagonal colored spots are respectively different in nitrogen content from the silicon carbide main region and the hexagonal region;

Preferably, the nitrogen content of the hexagonal area is not less than the nitrogen content of the silicon carbide main area and is greater than the nitrogen content of the edge of the hexagonal color spot;

More preferably, the difference between the nitrogen content of the hexagonal region and the silicon carbide main region is A, and the difference between the nitrogen content of the silicon carbide main region and the edge of the hexagonal color spot is B. , the difference A is not less than the difference B.
The silicon carbide single crystal wafer according to claim 6, wherein the hexagonal color spot forms a hexagon on the long crystal plane of the silicon carbide single crystal wafer;

The edge of the hexagonal color spot extends along the C-axis inside the silicon carbide single crystal wafer.
The silicon carbide single crystal wafer according to claim 6, wherein the hexagonal color spots are unequal hexagons;

The width of the side of the hexagonal color spot is not more than 1mm; and/or

The distance between the two farthest sides among the six sides of the hexagonal color spot is not more than 5 mm.
The silicon carbide single crystal wafer according to any one of claims 1 to 8, wherein the side of the hexagonal color spot further comprises a cavity, and the side of the hexagonal color spot includes a cavity. The number is not more than 10;

Preferably, the number of cavities contained in the edge of the hexagonal color spot is no more than 8;

Preferably, the number of voids contained in the edge of the hexagonal color spot is not more than 5;

More preferably, the number of voids contained in the edge of the hexagonal color spot is not more than three.
The silicon carbide single crystal wafer according to claim 9, wherein the size of the cavity is not greater than 100 μm;

Preferably, the size of the cavity is 10-100 μm.
The silicon carbide single crystal wafer according to claim 9, wherein the cavity extends along the C-axis inside the silicon carbide single crystal wafer.
The silicon carbide single crystal wafer according to any one of claims 1 to 8, wherein the edge of the hexagonal color spot includes an inner side and an outer side, and the inner side is surrounded by six In the square area, voids are included between the inner side and the outer side, and no less than 80% of the centers of the voids are located on one side of the central axis between the inner side and the outer side.
The silicon carbide single crystal wafer according to claim 12, wherein a center of the voids in an amount not less than 90% is on one side of a central axis between the inner side and the outer side;

Preferably, not less than 80% of the voids are centered in the connecting area of each side of the hexagonal color spot.
The silicon carbide single crystal wafer according to claim 12, wherein the side portion of the hexagonal color spot and the hexagonal region occupy a ratio of 0 to 2 mm 2 /6 of the area of the silicon carbide single crystal wafer inch;

Preferably, the ratio of the sides of the hexagonal colored spots and the hexagonal regions to the area of the silicon carbide single crystal wafer is 0˜1.5 mm 2 /6 inches.
The method for preparing a silicon carbide single crystal wafer according to any one of claims 1-14, the method comprising the steps of:

1) Preparation of silicon carbide single crystal ingot:

providing a crucible having a nitrogen channel, the nitrogen channel being disposed in the sidewall of the crucible and extending around the inner cavity of the crucible, the inner sidewall of the nitrogen channel being less dense than the outer sidewall of the nitrogen channel;

The silicon carbide seed crystal is placed on the top of the crucible and the silicon carbide raw material is placed on the bottom of the crucible, and the crucible is assembled with a thermal insulation structure and placed in a crystal growth furnace;

The silicon carbide single crystal ingot is grown by the physical vapor transport method. During the growth of the silicon carbide single crystal, nitrogen is infiltrated into the inner cavity of the crucible through the nitrogen gas channel to adjust the nitrogen content in the prepared silicon carbide single crystal ingot. distributed;

2) The prepared silicon carbide single crystal ingot is subjected to a step including cutting, namely, a wafer containing the silicon carbide single crystal is prepared.
The method for preparing a silicon carbide single crystal wafer according to claim 15, wherein the method for growing a silicon carbide single crystal ingot by a physical vapor transport method comprises the following steps:

Control the temperature and pressure of the crystal growth furnace and the flow of inert gas into the crystal growth furnace to clean and remove impurities in the crystal growth furnace;

Heating stage: adjust the temperature of the crystal growth furnace to 1800～2400K, control the pressure in the crucible to be 0.6×10 5 to 1.2×10 5 Pa, and the flow rate of the inert gas into the crystal growth furnace is 50-500mL/min. The nitrogen flow V 1 of the nitrogen channel is 20-200 mL/min;

Crystal growth stage: increase the nitrogen flow V 2 into the nitrogen channel to 50-500mL/min, the V 2 is greater than V 1 , the crystal growth temperature is 2200K-2800K, the crystal growth pressure is 100-5000Pa, and the holding time is 80～ 120h, the silicon carbide single crystal ingot was prepared.
The method for preparing a silicon carbide single crystal wafer according to claim 16, wherein the crystal growth stage comprises a first crystal growth stage and a second crystal growth stage, the first crystal growth stage and the second crystal growth stage The time ratio of the stages is 1:0.8-1.2, and the nitrogen inlet and outlet of the first crystal growth stage and the second crystal growth stage are exchanged.
A silicon carbide single crystal ingot, characterized in that the silicon carbide single crystal ingot is processed to form a silicon carbide single crystal wafer by including a cutting step;

The silicon carbide single crystal wafer is selected from the silicon carbide single crystal wafer described in any one of claims 1-14 or the silicon carbide single crystal wafer is prepared from the method described in any one of claims 15-17 of silicon carbide single crystal wafers.
The silicon carbide single crystal ingot according to claim 18, wherein the width of the side portion of the hexagonal color spot increases along the growth direction of the silicon carbide single crystal extending along the C axis, and the hexagonal The width of the side portions of the color spot increases, and the distance between the two farthest side portions among the six side portions of the hexagonal color spot increases.
The silicon carbide single crystal ingot according to claim 19, wherein the cavity extends along a growth direction of the silicon carbide single crystal extending along the C-axis.