High-quality silicon carbide seed crystals, silicon carbide crystals, silicon carbide substrates, and methods for producing them

Abstract

The present invention provides high-quality silicon carbide seed crystals, silicon carbide crystals, and silicon carbide substrates, as well as methods for their manufacture. The present invention produces high-quality silicon carbide seed crystals, controls the impurity concentrations of silicon carbide powder, graphite crucibles, and thermal insulators, and combines specific crystal growth and wafer processing methods to produce high-quality silicon carbide substrates. The resulting silicon carbide substrates have high crystal quality, extremely low micropipe counts, extremely low screw dislocation and complex dislocation densities, and extremely low p-type impurity concentrations. They also exhibit excellent electrical properties and high surface quality.

Description

[Technical Field]

[0001] The present invention relates to the field of semiconductor materials, and more particularly to high quality silicon carbide seeds, silicon carbide crystals, silicon carbide substrates and methods for their manufacture. [Background technology]

[0002] Silicon carbide substrates, also known as silicon carbide wafers, are generally circular slices with diameters of 2, 3, 4, 6, or 8 inches, and thicknesses generally between 80 and 800 microns. Due to their excellent properties, including a wide bandgap, high thermal conductivity, high breakdown field strength, and high saturated electron drift rate, silicon carbide substrates are highly suitable for the manufacture of high-power, high-temperature, and high-frequency power electronics devices, and are expected to be widely used in fields such as new energy vehicles, rail transportation, aerospace, and smart grids.

[0003] However, to realize the large-scale practical application of silicon carbide substrates in fields such as new energy vehicles, rail transport, aerospace, and smart grids, the quality of the substrate must be sufficiently excellent. Substrate quality here refers to three aspects: the crystal quality of the substrate, the electrical properties of the substrate, and the surface quality of the substrate. The details are as follows:

[0004] First, regarding the crystalline quality of the substrate, crystalline defects in current silicon carbide substrates include micropipes, screw dislocations, and compound dislocation defects (i.e., compound dislocations consisting of screw dislocations and basal plane dislocations, compound dislocations consisting of screw dislocations and edge dislocations, and compound dislocations consisting of basal plane dislocations and edge dislocations). The presence of crystalline defects in the substrate can lead to failure or degradation of the performance of devices manufactured using the substrate.

[0005] Second, regarding the electrical properties of the substrate, the resistivity of conductive silicon carbide substrates is currently tuned mainly by controlling the amount of nitrogen doping. The nitrogen concentration in silicon carbide substrates is 5×10 20 / cm 3Because the p-type impurity concentration in the silicon carbide substrate can be increased to a high level, and it is extremely easy to compensate for the p-type impurity in the silicon carbide substrate, in the process of fabricating a conductive silicon carbide substrate, control of the p-type background impurity concentration in the silicon carbide substrate is ignored, resulting in a high p-type impurity concentration in the silicon carbide substrate. To control the resistivity in the silicon carbide substrate, the nitrogen doping amount is increased to compensate for the excessively high p-type impurity concentration in the substrate, resulting in high p-type impurity and nitrogen concentrations in the silicon carbide substrate. High p-type impurity and nitrogen concentrations lead to variations in device performance due to substrate fabrication and, in severe cases, can even affect the stability of device performance.

[0006] Third, regarding the surface quality of the substrate, insufficient processing of silicon carbide substrates can leave some scratches on the surface of the substrate. Before fabricating silicon carbide devices, an epitaxial layer must be grown on the surface of the silicon carbide substrate. This epitaxial layer is also composed of silicon carbide, has the same crystalline structure as the substrate, and is typically several microns to several tens of microns thick. The quality of this epitaxial layer is crucial to the performance and reliability of the subsequently fabricated devices. However, the quality of this epitaxial layer is highly dependent on the quality of the substrate, particularly the quality of the substrate surface. If scratches of a certain depth remain on the surface of the substrate, they will remain even after subsequent epitaxy. Scratches in the epitaxial layer can lead to problems such as leakage, destruction, or reduced reliability in the final fabricated device.

[0007] Currently, the primary method for growing silicon carbide crystals is the physical vapor transport method, the growth chamber of which is shown in Figure 6. Silicon carbide powder is placed in a graphite crucible. A SiC seed crystal, slightly cooler than the SiC powder, is placed on top of the crucible. The temperature inside the crucible is then raised to 2100-2400°C, causing the SiC powder to sublimate, producing the vapors SiC, SiC, and Si. The vapors produced by sublimation are transported from the surface of the SiC powder to the relatively cool SiC seed crystal due to the temperature gradient, where they crystallize to form bulk SiC crystals. However, the quality of silicon carbide substrates produced using this current manufacturing method is poor, which impacts their practical application. Summary of the Invention

[0008] In view of the above circumstances, an object of the present invention is to provide a high-quality silicon carbide seed crystal, silicon carbide crystal, silicon carbide substrate, and a method for manufacturing the same. The high-quality silicon carbide seed crystal and the silicon carbide substrate provided by the present invention can effectively reduce crystal defects and impurity concentrations and improve surface quality.

[0009] The present invention provides a high quality silicon carbide seed crystal, the silicon carbide seed crystal having at least one high quality region, The specifications for the high-quality region are: 0 micropipes, screw dislocation density <300 / cm 2 , complex dislocation density <20 / cm 2 , the difference between two points of the half-width of the X-ray rocking curve at any 1 cm interval is < 40 arc seconds, The area of ​​the high-quality area is >0.25 cm 2 is.

[0010] Preferably, the specifications for the high quality region are: 0 micropipes, screw dislocation density <100 / cm 2 , complex dislocation density <20 / cm 2 , the difference between two points of the half-width of the X-ray rocking curve at any 1 cm interval is < 40 arc seconds, The area of ​​the high-quality area is >1cm2 is.

[0011] Preferably, the specifications for the high quality region are: 0 micropipes, screw dislocation density <50 / cm 2 , complex dislocation density <20 / cm 2 , the difference between two points of the half-width of the X-ray rocking curve at any 1 cm interval is < 40 arc seconds, The area of ​​the high-quality area is >10cm 2 is.

[0012] Preferably, the specifications for the high quality region are: 0 micropipes, screw dislocation density <30 / cm 2 , complex dislocation density <5 / cm 2 , the difference between two points of the half-width of the X-ray rocking curve at any 1 cm interval is < 20 arc seconds, The area of ​​the high-quality area is >50cm 2 is.

[0013] The present invention further provides a method for producing high-quality silicon carbide seed crystals according to the above technical solution, comprising: a) performing a first diameter expansion growth on the initial seed crystal to obtain an initial grown crystal; b) processing the initial grown crystal to obtain an intermediate seed crystal including only an expansion region; c) performing a second diameter expansion growth on the intermediate seed crystal to obtain a high-grade seed crystal.

[0014] Preferably, in the first diameter expansion growth, The expansion angle of the seed crystal in the crucible is controlled to 5° to 50°. The temperature field distribution in the growth chamber is controlled as follows: Axial temperature gradient: The temperature gradually increases along the crystal growth direction from the surface of the seed crystal to the surface of the silicon carbide raw material, with a temperature gradient of 1 to 10°C / cm; Lateral temperature gradient: The temperature gradually increases from the center of the seed crystal to the edge of the seed crystal along the radial direction, with a temperature gradient of 0.5-5°C / cm; In the second diameter expansion growth, The expansion angle of the intermediate seed crystal in the crucible is controlled to 5° to 50°. The temperature field distribution in the growth chamber is controlled as follows: Axial temperature gradient: The temperature gradually increases along the crystal growth direction from the surface of the seed crystal to the surface of the silicon carbide raw material, with a temperature gradient of 1 to 10°C / cm; Lateral temperature gradient: The temperature gradually increases from the center of the seed crystal to the edge of the seed crystal along the radial direction, with a temperature gradient of 0.5 to 5°C / cm.

[0015] Preferably, after step c), further d) comparing the diameter of the high-grade seed crystal with the diameter required to produce a silicon carbide substrate; If the diameter of the high-quality seed crystal is greater than or equal to the diameter required for manufacturing a silicon carbide substrate, the seed crystal preparation process is terminated; When the diameter of the high-quality seed crystal is smaller than the diameter required for producing a silicon carbide substrate, the second diameter expansion growth step is repeated for the obtained high-quality seed crystal until the diameter of the obtained seed crystal becomes equal to or larger than the diameter required for producing a silicon carbide substrate.

[0016] The present invention further provides a high-quality silicon carbide crystal, wherein the seed crystal used to form the silicon carbide crystal is the high-quality silicon carbide seed crystal described in the above technical solution or the high-quality silicon carbide seed crystal produced by the production method described in the above technical solution; the silicon carbide crystal has at least one high quality region; The specifications for the high-quality region are: 0 micropipes, screw dislocation density <300 / cm 2 , complex dislocation density <20 / cm 2 , the difference between two points of the half-width of the X-ray rocking curve at any 1 cm interval is < 40 arc seconds, The area of ​​the high-quality area is >0.25 cm 2 is.

[0017] Preferably, the specifications for the high quality region are: 0 micropipes, screw dislocation density <100 / cm 2 , complex dislocation density <20 / cm2 , the difference between two points of the half-width of the X-ray rocking curve at any 1 cm interval is < 40 arc seconds, The area of ​​the high-quality area is >1cm 2 is.

[0018] Preferably, the specifications for the high quality region are: 0 micropipes, screw dislocation density <50 / cm 2 , complex dislocation density <20 / cm 2 , the difference between two points of the half-width of the X-ray rocking curve at any 1 cm interval is < 40 arc seconds, The area of ​​the high-quality area is >10cm 2 is.

[0019] Preferably, the specifications for the high quality region are: 0 micropipes, screw dislocation density <30 / cm 2 , complex dislocation density <5 / cm 2 , the difference between two points of the half-width of the X-ray rocking curve at any 1 cm interval is < 20 arc seconds, The area of ​​the high-quality area is >50cm 2 is.

[0020] The present invention further provides a method for producing silicon carbide crystals according to the above technical solution, including the following steps: A graphite crucible filled with silicon carbide powder and equipped with a SiC seed crystal is placed in a high-temperature furnace, and the furnace is first evacuated to reduce pressure. Then, a protective gas is filled to adjust the pressure, and the temperature is raised to the target pressure and target temperature. Crystal growth is carried out under the pressure and temperature conditions to obtain silicon carbide crystals.

[0021] Preferably, the target pressure is 100 to 5000 Pa, and the target temperature is 2050 to 2250°C.

[0022] Preferably, the silicon carbide powder has a boron elemental impurity concentration of <5×10 16 / cm 3 , aluminum element impurity concentration <5×10 15 / cm 3 and The specification of the graphite crucible is boron element impurity concentration <5×10 16 / cm 3 , aluminum element impurity concentration <5×10 15 / cm 3 and The specification for the insulation around the graphite crucible is that the boron element impurity concentration is <5 x 10 16 / cm 3 , aluminum element impurity concentration <5×10 15 / cm 3 is.

[0023] Preferably, the silicon carbide powder is produced by the following production method. S1: Mix silicon powder and graphite powder to obtain a mixed powder. S2: Synthesize the mixed powder under protective gas conditions to obtain silicon carbide powder.

[0024] Preferably, the graphite powder is a pretreated graphite powder; The method for obtaining the pretreated graphite powder includes calcining the original graphite powder under vacuum conditions, The temperature of the firing treatment is 2200 to 2400°C, and the time is 5 to 100 hours. The total impurity content of the original graphite powder is less than 10 ppm; the graphite crucible is a pretreated graphite crucible; The method for obtaining the pretreated graphite crucible includes baking the original crucible under vacuum conditions; The temperature of the firing treatment is 2200 to 2400°C, and the time is 5 to 100 hours. the insulation material is a pretreated insulation material; The method for obtaining the pretreated insulating material includes baking the original insulating material under vacuum conditions, The temperature of the firing treatment is 2200 to 2400° C., and the time is 5 to 100 hours.

[0025] The present invention further provides a high quality silicon carbide substrate, the silicon carbide substrate having at least one high quality region; The specifications for the high-quality region are: 0 micropipes, screw dislocation density <300 / cm2 , complex dislocation density <20 / cm 2 , the difference between two points of the half-width of the X-ray rocking curve at any 1 cm interval is < 40 arc seconds, The area of ​​the high-quality area is >0.25 cm 2 is.

[0026] Preferably, the specifications for the high quality region are: 0 micropipes, screw dislocation density <100 / cm 2 , complex dislocation density <20 / cm 2 , the difference between two points of the half-width of the X-ray rocking curve at any 1 cm interval is < 40 arc seconds, The area of ​​the high-quality area is >1cm 2 is.

[0027] Preferably, the specifications for the high quality region are: 0 micropipes, screw dislocation density <30 / cm 2 , complex dislocation density <5 / cm 2 , the difference between two points of the half-width of the X-ray rocking curve at any 1 cm interval is < 20 arc seconds, The area of ​​the high-quality area is >50cm 2 and In the silicon carbide substrate, the boron element impurity concentration is less than 5×10 15 / cm 3 , aluminum element impurity concentration <5×10 14 / cm 3 and The normal direction of the surface of the silicon carbide substrate is deviated from the c-axis crystal direction by an angle of 1 to 5 degrees.

[0028] The present invention further provides a method for manufacturing a high-quality silicon carbide substrate according to the above technical solution, comprising: K1: crystal processing a silicon carbide crystal to obtain a silicon carbide wafer; K2, wafer processing the silicon carbide wafer to obtain a silicon carbide substrate; wherein the silicon carbide crystal is the silicon carbide crystal described in the above technical solution or a silicon carbide crystal produced by the production method described in the above technical solution.

[0029] Preferably, the wafer processing comprises chemical mechanical polishing; The chemical mechanical polishing includes a first step chemical mechanical polishing and a second step chemical mechanical polishing, In the chemical mechanical polishing of the first step, the polishing liquid used is an alumina polishing liquid, the polishing pad used is a polyurethane polishing pad, and the Shore hardness of the polishing pad is 75 to 85; In the chemical mechanical polishing of the second step, the polishing liquid used is a silica polishing liquid, the polishing pad used is a nylon cloth, and the Shore hardness of the polishing pad is 60 to 75; The polishing rate of the chemical mechanical polishing in the first step is 10 to 30 times the polishing rate of the chemical mechanical polishing in the second step.

[0030] The present invention produces high-quality silicon carbide seed crystals, controls the impurity concentrations of silicon carbide powder, graphite crucibles, and thermal insulators, and combines specific crystal growth and wafer processing methods to obtain high-quality silicon carbide substrates with high crystal quality, extremely low micropipe counts, extremely low screw dislocation and complex dislocation densities, and extremely low p-type impurity concentrations, and exhibits excellent electrical properties and high surface quality.

[0031] As can be seen from the experimental results, the silicon carbide substrate provided by the present invention has at least one high-quality region, and in the high-quality region: the number of micropipes is 0, and the screw dislocation density is <30 / cm 2 , complex dislocation density <5 / cm 2 , the difference between two points of the half-width of the X-ray rocking curve at any 1 cm interval is less than 20 arc seconds, and the high-quality region is greater than 50 cm 2 The boron element impurity concentration of the obtained silicon carbide substrate is <5×10 15 / cm 3 , aluminum element impurity concentration <5×10 14 / cm 3 The resistivity of the substrate is <0.03 Ω·cm. The length of the scratch on the substrate surface is smaller than the radius of the substrate. [Brief explanation of the drawings]

[0032] [Figure 1] Topography of screw dislocations (TSDs), edge dislocations (TEDs), and basal plane dislocations (BPDs) in the substrate after etching with molten KOH. [Figure 2] FIG. 2 is a cross-sectional schematic view of an initial seed crystal and a grown crystal in the first diameter expansion growth of the present invention. [Figure 3] FIG. 1 is a plan view of an intermediate seed crystal including an isodiameter region and an diverging region. [Figure 4] FIG. 2 is a cross-sectional schematic view of an intermediate seed crystal and a grown crystal in the second diameter expansion growth of the present invention. [Figure 5] 1 is a schematic diagram of the misalignment angle between the normal to the silicon carbide substrate surface and the c-axis crystallographic direction of the substrate. [Figure 6] FIG. 1 is a schematic diagram of the structure of a growth chamber for growing silicon carbide crystals by physical vapor transport. [Figure 7] 1 is a schematic diagram of a silicon carbide substrate manufactured according to the present invention. [Figure 8] FIG. 1 is a schematic diagram of the micropipe distribution in the silicon carbide substrate obtained in Example 3. [Figure 9] 1 is a topography of micropipes of a silicon carbide substrate obtained in Example 3, taken by a transmission polarizing microscope. [Figure 10] FIG. 10 is a distribution diagram of screw dislocation density on the silicon carbide substrate obtained in Example 3. [Figure 11] 10 is a test chart of electrical characteristics of the silicon carbide substrate obtained in Example 3. [Figure 12] FIG. 1 is a schematic diagram of surface scratches on the silicon carbide substrate obtained in Example 3. [Figure 13] FIG. 10 is a distribution diagram of screw dislocation density in the silicon carbide substrate obtained in Example 6. [Figure 14] FIG. 10 is a graph showing the electrical characteristics of the silicon carbide substrate obtained in Example 6. [Figure 15] FIG. 1 is a schematic diagram of surface scratches on the silicon carbide substrate obtained in Example 6. DETAILED DESCRIPTION OF THE INVENTION

[0033] <About silicon carbide seed crystals:>

[0034] The present invention provides a high quality silicon carbide seed crystal, the silicon carbide seed crystal having at least one high quality region, The specifications for the high-quality region are: 0 micropipes, screw dislocation density <300 / cm 2 , complex dislocation density <20 / cm 2 The difference between two points of the half-width of the X-ray rocking curve at any 1 cm interval is less than 40 arc seconds, and the area of ​​the high-quality region is greater than 0.25 cm. 2 is.

[0035] In the present invention, the specifications of the high quality area are as follows: The screw dislocation density is preferably 200 / cm 2 less than 100 / cm 2 less than 50 particles / cm 2 Less than 30 cells / cm 2 is less than. The complex dislocation density is preferably 5 / cm 2 is less than. The difference between two points of the half-width of the X-ray rocking curve at any 1 cm interval is preferably less than 20 arc seconds. The area of ​​the high quality region is preferably 1 cm 2 More than 5cm, preferably 2 More than 10cm, preferably 2 More than 50cm, most preferably 2 It exceeds that. The shape of the high quality region includes a triangle, a square, a circle, or a polygon.

[0036] Silicon carbide substrates have many types of crystal defects, the most common of which are micropipes, screw dislocations, and compound dislocations consisting of any two of these types: screw dislocations, basal plane dislocations, and edge dislocations. Micropipes are a crystal defect unique to silicon carbide substrates. Micropipe defects are characterized by hollow tubes with diameters ranging from several microns to tens of microns along the c-axis of the crystal. Screw dislocations and edge dislocations are threading dislocations along the c-axis of the substrate. Basal plane dislocations are dislocations located in the c-plane of the substrate. After etching a substrate with molten KOH, different corrosion pit morphologies corresponding to different dislocation defects appear on the surface. A typical substrate with a surface normal misaligned by 4 degrees from the c-axis crystallographic direction appears on the surface with large hexagons, medium hexagons, small hexagons, and ellipses after etching with molten KOH. These correspond to micropipes, screw dislocations, edge dislocations, and basal plane dislocations, respectively. These two different types of dislocations together are called compound dislocations. Referring to Figure 1, Figure 1 shows the topography of screw dislocations (TSDs), edge dislocations (TEDs), and basal plane dislocations (BPDs) in a substrate after molten KOH etching. In the present invention, the distance between the geometric centers of a composite dislocation corrosion pit consisting of any two different types of dislocations is less than 30 microns, preferably less than 10 microns.

[0037] The full width at half maximum (FWHM) of an X-ray rocking curve is used to characterize the divergence of a diffracted beam of a parallel X-ray incident beam after reflection from the (0004) specific crystal plane in a silicon carbide substrate. The divergence of the diffracted beam is related to the density of crystal defects, such as micropipes, screw dislocations, and complex dislocations, in the silicon carbide substrate. The greater the defect density, the more divergent the diffracted beam and the larger the FWHM of the X-ray rocking curve. Conversely, the more convergent the diffracted beam, the smaller the FWHM of the X-ray rocking curve. In the present invention, the difference between two FWHMs of the X-ray rocking curves measured at any one-centimeter interval on the substrate surface is less than 40 arc seconds, preferably less than 20 arc seconds, indicating the overall quality of the substrate.

[0038] During growth of silicon carbide crystals by physical vapor transport, the majority of micropipes, screw dislocations, and compound dislocation defects in the silicon carbide seed crystal propagate along the crystal's c-axis direction to the newly grown crystal. To obtain high-quality silicon carbide substrates and reduce the density of micropipes, screw dislocations, and compound dislocations in the substrate, the present invention strictly controls the quality of the seed crystal used in the crystal growth process.

[0039] <About the manufacturing method of silicon carbide seed crystals:>

[0040] The present invention provides a method for producing high-quality silicon carbide seed crystals according to the above technical solution, which comprises: a) performing a first diameter expansion growth on the initial seed crystal to obtain an initial grown crystal; b) processing the initial grown crystal to obtain an intermediate seed crystal including only an expansion region; c) performing a second diameter expansion growth on the intermediate seed crystal to obtain a high-grade seed crystal.

[0041] Regarding step a): A first diameter expansion growth is performed on the primary seed crystal to obtain a primary grown crystal.

[0042] In the present invention, the type and source of the primary seed crystals are not particularly limited, and any commercially available SiC seed crystals may be used. Commercially available seed crystals usually have a certain number of micropipes, screw dislocations, and complex dislocation defects. The general specification is a micropipe density of 0.5 to 5 pieces / cm. 2 , screw dislocation density 500 to 1500 / cm 2 , complex dislocation density 30-60 / cm 2 In the present invention, by subjecting this initial seed crystal to diameter expansion growth treatment two or more times, it is possible to reduce seed crystal defects, improve the quality of the seed crystal, and obtain a high-quality seed crystal.

[0043] In the present invention, the seed crystal growth is controlled and the quality of the seed crystal is improved by selecting an appropriate expansion angle and controlling the temperature field distribution in the growth chamber. Here, the expansion angle refers to the angle between the seed crystal and the side wall of the crucible along the crystal growth direction. Referring to Figure 2, Figure 2 is a cross-sectional schematic diagram of the initial seed crystal and the grown crystal in the first expansion growth of the present invention.

[0044] In the present invention, in the first expansion growth, the expansion angle of the initial seed crystal in the crucible is selected to be 5° to 50°, preferably 15° to 35°, and more preferably 20° to 30°, and in some embodiments of the present invention, the expansion angle is 30° or 45°.

[0045] In the present invention, in the first diameter expansion growth, the temperature field distribution in the growth chamber, including the axial temperature gradient (i.e., along the crystal growth direction) and lateral temperature gradient (i.e., perpendicular to the crystal growth direction) in the growth chamber, is also controlled.

[0046] in particular, The temperature gradient in the axial direction: the temperature gradually increases along the crystal growth direction from the surface of the seed crystal to the surface of the silicon carbide raw material, and the temperature gradient is 1 to 10°C / cm. In some embodiments of the present invention, the temperature gradient is 2°C / cm or 3°C / cm. The lateral temperature gradient: the temperature gradually increases from the center of the seed crystal along the radial direction to the edge of the seed crystal, and the temperature gradient is 0.5 to 5°C / cm. In some embodiments of the present invention, the temperature gradient is 2°C / cm.

[0047] In the present invention, by controlling the expansion angle and temperature gradient as described above, silicon carbide crystals grow not only isodiametrically along the surface of the seed crystal, but also laterally along the crucible wall at an expansion angle Φ. Referring to FIG. 2, the grown crystal is divided into a central isodiametric region and expansion regions on both sides. Because most of the micropipes, screw dislocations, and complex dislocation defects in the initial seed crystal continue along the c-axis direction of the crystal into the newly grown crystal, the defect density of micropipes, screw dislocations, and complex dislocations in the isodiametric region crystals in the newly grown crystal remains relatively high. However, because the expansion region crystals in the newly grown crystal grow vertically outward from the sides of the isodiametric region crystals, the micropipes, screw dislocations, and complex dislocation defects in the initial seed crystal do not continue into the expansion region crystals. As a result, the crystals in the expansion region have significantly higher crystal quality than the crystals in the isodiametric region crystals.

[0048] Regarding step b): The primary grown crystal is processed to obtain an intermediate seed crystal containing only the expansion region.

[0049] In the present invention, it is preferable to first cut the initial-grown crystal obtained in step a), with the cutting direction parallel to the surface direction of the initial seed crystal (i.e., perpendicular to the crystal growth direction). For example, the lower part of the obtained initial-grown crystal is cut to obtain an intermediate seed crystal having an isodiameter region and an expanding diameter region. Referring to Figure 2, the lowest part of the obtained crystal is cut to obtain an intermediate seed crystal having an isodiameter region and an expanding diameter region. Referring to Figure 3, Figure 3 is a plan view of an intermediate seed crystal having an isodiameter region and an expanding diameter region.

[0050] In the present invention, after the cutting treatment, the intermediate seed crystal including the constant diameter region and the expanding diameter region is processed to obtain a high-quality intermediate seed crystal including only the expanding diameter region. In the present invention, the processing method is not particularly limited, and it is sufficient to obtain a seed crystal of the expanding diameter region by dividing the constant diameter region and the expanding diameter region. For example, the seed crystal of the expanding diameter region can be cut out by cutting.

[0051] Regarding step c): The intermediate seed crystal is subjected to a second diameter expansion growth to obtain a high-grade seed crystal.

[0052] In the present invention, in the second expansion growth, an appropriate expansion angle is similarly selected and the temperature field distribution in the growth chamber is controlled to control the growth of the seed crystal and improve the quality of the seed crystal. Referring to Figure 4, Figure 4 is a cross-sectional schematic diagram of the intermediate seed crystal and the grown crystal in the second expansion growth of the present invention.

[0053] In the present invention, in the second expansion growth, the expansion angle of the initial seed crystal in the crucible is selected to be 5° to 50°, preferably 15° to 35°, and in some embodiments of the present invention, the expansion angle is 30° or 45°.

[0054] In the present invention, in the second diameter expansion growth, the temperature field distribution in the growth chamber, including the axial temperature gradient and the lateral temperature gradient in the growth chamber, is also controlled.

[0055] in particular, The temperature gradient in the axial direction is a gradual increase in temperature from the surface of the seed crystal to the surface of the silicon carbide feedstock along the crystal growth direction, and the temperature gradient is 1 to 10°C / cm. In some embodiments of the present invention, the temperature gradient is 2°C / cm or 3°C / cm. The temperature gradient in the lateral direction gradually increases from the center of the seed crystal to the edge of the seed crystal along the radial direction, and the temperature gradient is 0.5 to 5°C / cm. In some embodiments of the present invention, the temperature gradient is 2°C / cm.

[0056] In the present invention, by controlling the expansion angle and temperature gradient, silicon carbide crystals are grown not only along the surface of the seed crystal but also laterally along the crucible wall at an expansion angle Φ. Because the defect density of micropipes, screw dislocations, and complex dislocations in the intermediate seed crystal itself is very low, these crystal defects rarely continue to the crystals in the isodiameter region of the newly grown crystal. Furthermore, the crystals in the expansion region of the newly grown crystal grow vertically outward from the side of the isodiameter region, so the above-mentioned crystal defects do not continue to the crystals in the expansion region. Therefore, high-quality crystals can be obtained by the above expansion growth.

[0057] In the present invention, after a high-quality crystal is obtained by the second diameter expansion growth, the high-quality crystal is cut in a cutting direction parallel to the surface direction of the intermediate seed crystal (i.e., perpendicular to the crystal growth direction), for example, by cutting out the lower part of the obtained intermediate growth crystal to obtain a high-quality seed crystal. Referring to Figure 4, the lowermost part of the obtained crystal is the high-quality seed crystal.

[0058] According to the present invention, after the above steps a) to c), preferably, step d) is further carried out: comparing the diameter of the high-quality seed crystal with the diameter required for producing a silicon carbide substrate to determine whether or not to repeat diameter expansion growth.

[0059] The high-quality seed crystals obtained in step c) are used to produce high-quality silicon carbide substrates. To ensure efficient production of silicon carbide substrates, the diameter of the seed crystals used to grow silicon carbide crystals is usually slightly larger than or equal to the diameter of the substrates to be produced.

[0060] If the diameter of the high-quality seed crystal is greater than or equal to the diameter required for manufacturing a silicon carbide substrate, the seed crystal preparation process is terminated; If the diameter of the high-quality seed crystal is smaller than the diameter required for producing a silicon carbide substrate, the second diameter expansion growth step is repeated for the obtained high-quality seed crystal until the diameter of the obtained seed crystal becomes equal to or larger than the diameter required for producing a silicon carbide substrate.

[0061] In some embodiments of the present invention, the diameter expansion growth is performed three times in total. The conditions for the first two diameter expansion growth steps are as described above, and the process system for the third diameter expansion growth step is as follows: The divergence angle is between 5° and 50°, preferably between 15° and 35°, and in some embodiments of the invention, the divergence angle is 30° or 45°.

[0062] The temperature gradient in the axial direction is a gradual increase in temperature from the surface of the seed crystal to the surface of the silicon carbide feedstock along the crystal growth direction, and the temperature gradient is 1 to 10°C / cm. In some embodiments of the present invention, the temperature gradient is 2°C / cm or 3°C / cm. The temperature gradient in the lateral direction is 0.5 to 5°C / cm, and the temperature gradually increases from the center of the seed crystal to the edge of the seed crystal along the radial direction. In some embodiments of the present invention, the temperature gradient is 2°C / cm.

[0063] In another embodiment of the present invention, the diameter expansion growth is performed four times in total. The conditions for the first three diameter expansion growth steps are as described above, and the process system for the fourth diameter expansion growth step is as follows: The expansion angle is between 5° and 50°, preferably between 15° and 35°, and in some embodiments of the present invention, the expansion angle is 30°.

[0064] The temperature gradient in the axial direction is 1 to 10°C / cm, and the temperature gradually increases from the surface of the seed crystal to the surface of the silicon carbide raw material along the crystal growth direction. In some embodiments of the present invention, the temperature gradient is 3°C / cm. The temperature gradient in the lateral direction is 0.5 to 5°C / cm, and the temperature gradually increases from the center of the seed crystal to the edge of the seed crystal along the radial direction. In some embodiments of the present invention, the temperature gradient is 2°C / cm.

[0065] In the present invention, the diameter of the high-quality seed crystal is preferably 0.5 to 10 mm larger, more preferably 1 to 5 mm larger, than the diameter of the substrate to be produced.

[0066] The present invention provides a method for producing a high-quality SiC seed crystal by the above-described production method, and using the SiC seed crystal as a seed crystal for producing a silicon carbide substrate, thereby effectively reducing crystal defects in the silicon carbide substrate and obtaining a high-quality silicon carbide substrate.

[0067] <About silicon carbide crystals:>

[0068] The present invention provides a high-quality silicon carbide crystal, wherein a seed crystal used to form the silicon carbide crystal is a high-quality SiC seed crystal described in the above technical solution or a high-quality SiC seed crystal manufactured by the manufacturing method described in the above technical solution; the silicon carbide crystal has at least one high quality region; The specifications for the high-quality region are: 0 micropipes, screw dislocation density <300 / cm 2 , complex dislocation density <20 / cm 2 , the difference between two points of the half-width of the X-ray rocking curve at any 1 cm interval is < 40 arc seconds, The area of ​​the high-quality area is >0.25 cm 2 is.

[0069] In the present invention, the specifications of the high quality area are as follows: The screw dislocation density is preferably 200 / cm 2 less than 100 / cm 2 less than 50 particles / cm 2 Less than 30 cells / cm 2 is less than. The complex dislocation density is preferably 5 / cm 2 is less than. The difference between two points of the half-width of the X-ray rocking curve at any 1 cm interval is preferably less than 20 arc seconds. The area of ​​the high quality region is preferably 1 cm 2 More than 5cm, preferably 2 More than 10cm, preferably 2 More than 50cm, most preferably 2 It exceeds that. The shape of the high quality region includes a triangle, a square, a circle, or a polygon.

[0070] In the present invention, the boron element impurity concentration of the silicon carbide crystal is preferably 5×10 16 / cm 3 less than 1×10 16 / cm 3 less than 5 × 10 15 / cm 3 is less than.

[0071] In the present invention, the aluminum element impurity concentration of the silicon carbide crystal is preferably 5×10 15 / cm3 less than 1×10 15 / cm 3 less than 5 × 10 14 / cm 3 .

[0072] In the present invention, the normal direction of the silicon carbide crystal surface is deviated from the c-axis crystal direction by an angle of 0 to 8 degrees, preferably 1 to 5 degrees.

[0073] Silicon carbide substrates have many different crystal structures, with 4H and 6H being the most common. These two structures are identical in the c-plane, but differ along the c-axis direction. The 4H crystal structure forms a period of four silicon-carbon double atomic layers along the c-axis direction in an ABCB stacking sequence, followed by repeated stacking. On the other hand, the 6H crystal structure forms a period of six silicon-carbon double atomic layers along the c-axis direction in an ABCACB stacking sequence, followed by repeated stacking. The crystal structure of silicon carbide substrates currently used in large-scale commercial applications is 4H, in order to maintain the 4H crystal structure of the epitaxial layer during the subsequent epitaxy process. The normal direction of the silicon carbide substrate surface is often offset by a certain angle from the c-axis crystal direction of the substrate. In the present invention, the offset angle is 0 to 8 degrees, preferably 1 to 5 degrees, and more preferably 4 degrees. Referring to Figure 5, Figure 5 is a schematic diagram of the offset angle between the normal direction of the silicon carbide substrate surface and the c-axis crystal direction of the substrate.

[0074] <About the manufacturing method of silicon carbide crystals:>

[0075] The present invention provides a method for producing a silicon carbide crystal according to the above technical solution, comprising: The present invention provides a manufacturing method including the steps of placing a graphite crucible filled with silicon carbide powder and equipped with a SiC seed crystal into a high-temperature furnace, first evacuating the furnace to reduce pressure, then filling it with a protective gas to adjust the pressure, and simultaneously raising the temperature to a target pressure and target temperature, and performing crystal growth under the pressure and temperature conditions to obtain silicon carbide crystals.

[0076] FIG. 6 is a schematic diagram of the structure of a growth chamber for growing silicon carbide crystals by physical vapor transport, showing a graphite lid (1), a graphite crucible (2), a silicon carbide powder (3), a binder (4), a SiC seed crystal (5), a grown crystal (6), a heat insulating material (7), an inner surface of the heat insulating material (8), and an outer surface of the heat insulating material (9). Specifically, the SiC seed crystal is fixed to the top of the graphite lid by bonding or mechanical fixation, silicon carbide powder is placed in the graphite crucible, and the graphite lid with the SiC seed crystal fixed thereto is assembled to the graphite crucible. The assembled graphite crucible is then placed in a high-temperature furnace for the crystal growth process. The distance between the surface of the silicon carbide powder and the SiC seed crystal is preferably 20 to 60 mm. In some embodiments of the present invention, the distance is 30 mm or 40 mm.

[0077] The band gap of silicon carbide substrates is 3.2 eV, and intrinsic silicon carbide substrates are non-conductive. Because silicon and carbon in silicon carbide substrates are both tetravalent elements, nitrogen doping is often used to adjust the resistivity of silicon carbide substrates and obtain conductive silicon carbide substrates. Because nitrogen is a pentavalent element, it can provide excess electrons to contribute to conductivity, resulting in conductive silicon carbide substrates. When the concentration of p-type impurities such as boron or aluminum in a silicon carbide substrate is high, one electron is captured, reducing the number of electrons involved in conductivity in the silicon carbide substrate and increasing the resistivity of the silicon carbide substrate, since both boron and aluminum are trivalent elements. To control the resistivity of conductive silicon carbide substrates, the amount of nitrogen doping is often increased to compensate for the p-type impurities in the silicon carbide substrate and maintain a constant resistivity. This ultimately results in high concentrations of both p-type impurities and nitrogen in the conductive silicon carbide substrate. High p-type impurity and nitrogen concentrations lead to variations in device performance during substrate manufacturing, and in serious cases, can even affect the stability of device performance. In the present invention, to obtain high-quality conductive silicon carbide substrates, the p-type impurity concentrations, mainly boron and aluminum element impurity concentrations, in the conductive silicon carbide substrate are strictly controlled.

[0078] The raw materials and consumables used in growing silicon carbide crystals using the physical vapor transport method mainly include silicon carbide raw materials, graphite crucibles, and insulation wrapped around the graphite crucibles. Because the temperature during crystal growth can reach as high as 2100°C, boron and aluminum impurities in the silicon carbide raw materials, graphite crucibles, and insulation sublimate into gases during crystal growth, which then infiltrate the newly grown crystals and affect the electrical properties of the product. In this invention, the boron and aluminum impurity concentrations in the silicon carbide raw materials, graphite crucibles, and insulation are strictly controlled to control the boron and aluminum impurities in the newly grown crystals.

[0079] <1. Silicon carbide powder:>

[0080] In the present invention, the control target of the silicon carbide powder is to have a boron element impurity concentration of preferably 5×10 16 / cm 3 less than 1×10 16 / cm 3 less than 5 × 10 15 / cm 3 The aluminum element impurity concentration is preferably less than 5×10 15 / cm 3 less than 1×10 15 / cm 3 less than 5 × 10 14 / cm 3 is less than.

[0081] In the present invention, the particle size of the silicon carbide powder is preferably 200 to 5000 μm.

[0082] In the present invention, the silicon carbide powder is preferably produced by the following production method. S1: Mix silicon powder and graphite powder to obtain mixed powder. S2: Sintering the mixed powder under protective gas conditions to obtain silicon carbide powder.

[0083] Regarding step S1: In the present invention, the silicon powder is preferably a high-purity silicon powder, and the purity is preferably 99.99999% or more. In the present invention, the particle size of the silicon powder is preferably 10 to 500 μm. In the present invention, there are no particular limitations on the source of the silicon powder, and it may be a general commercially available product.

[0084] In the present invention, the graphite powder is preferably pretreated graphite powder. The pretreatment method preferably involves calcining the original graphite powder under vacuum conditions. Here, the original graphite powder is preferably high-purity graphite powder with a total impurity content of <10 ppm. In the present invention, there is no particular limitation on the source of the original graphite powder, and it may be a common commercially available product. The calcination temperature is preferably 2200 to 2400°C. In some embodiments of the present invention, the calcination temperature is 2200°C or 2250°C. The calcination time is preferably 5 to 100 hours. In some embodiments of the present invention, the calcination time is 10 hours or 30 hours. Specifically, after placing the graphite powder in a high-temperature furnace, the furnace is evacuated and the vacuum pump unit is constantly operating to maintain the vacuum condition. The temperature in the furnace is then increased to the target temperature, and calcination is continued.

[0085] To further improve the removal of boron and aluminum impurities, during the 5-100 hour sintering process, the present invention preferably first turns off the vacuum pump unit to stop evacuation, then fills with inert gas until the pressure reaches 1,000-70,000 Pa, and holds for 1-60 minutes. Then, the vacuum pump unit is turned back on to evacuate again, maintaining a vacuum condition while the vacuum pump unit is constantly operating to continue sintering. Here, the inert gas is preferably argon gas. In some embodiments of the present invention, the pressure is 50,000 Pa. In some embodiments of the present invention, the holding time is 10 minutes.

[0086] In the present invention, the boron impurity content in the graphite powder is reduced to <5 × 10 by the above pretreatment method. 16 / cm 3 , more preferably 5 × 10 15 / cm3 Aluminum impurity content <5×10 15 / cm 3 , more preferably 5 × 10 14 / cm 3 It can be less than.

[0087] In the present invention, the mass ratio of the silicon powder to the graphite powder is preferably (1.00-1.05): 1. In some embodiments of the present invention, the mass ratio is 1.00:1 or 1.05:1.

[0088] In the present invention, silicon powder and graphite powder are mixed uniformly and then placed in a graphite crucible in a high-temperature furnace. Preferably, the furnace is first evacuated and then filled with a protective gas until the pressure reaches 100 to 50,000 Pa, and then the temperature is raised to the target temperature for synthesis. In some embodiments of the present invention, the pressure is 1,000 Pa or 5,000 Pa.

[0089] In the present invention, the temperature of the synthesis treatment is preferably 1800 to 2200°C, and in some embodiments of the present invention, the temperature is 1850°C or 1900°C. The time period of the synthesis treatment is preferably 5 to 20 hours, and in some embodiments of the present invention, the time period is 8 hours or 12 hours. The protective gas is preferably argon gas. The synthesis treatment above causes a high-temperature solid-state reaction between silicon powder and graphite powder, resulting in silicon carbide powder.

[0090] In the present invention, the silicon carbide powder produced by the above-mentioned production method can effectively reduce the boron and aluminum impurity contents in the silicon carbide powder, thereby obtaining silicon carbide powder with the purity specifications described above. When this powder is used as a raw material for growing silicon carbide substrates, it can be advantageous in reducing the boron and aluminum impurity contents in the product and improving the electrical properties of the product.

[0091] <2.SiC seed crystal:>

[0092] In the present invention, the SiC seed crystal is a high-quality SiC seed crystal as described in the above technical solution, or a high-quality SiC seed crystal manufactured by the manufacturing method as described in the above technical solution.

[0093] 3. Graphite crucible:

[0094] In the present invention, the graphite crucible is preferably a pretreated graphite crucible. In the present invention, the method for pretreating the graphite crucible is the same as the method for treating the pretreated graphite powder described above, i.e., the original graphite crucible is sintered under vacuum conditions. The temperature for the sintering is preferably 2200 to 2400°C, and in some embodiments of the present invention, the temperature for the sintering is 2200°C or 2250°C. The duration of the sintering is preferably 5 to 100 hours, and in some embodiments of the present invention, the duration of the sintering is 10 hours or 30 hours. Specifically, after the graphite crucible is placed in a high-temperature furnace, the furnace is evacuated and the vacuum pump unit is constantly operating to maintain the vacuum conditions. Furthermore, the temperature in the furnace is raised to the target temperature, and sintering is maintained.

[0095] To further improve the removal of boron and aluminum impurities, during the 5-100 hour sintering process, the present invention preferably first turns off the vacuum pump unit to stop evacuation, then fills with inert gas until the pressure reaches 1,000-70,000 Pa, and holds for 1-60 minutes. Then, the vacuum pump unit is turned back on to evacuate again, maintaining the vacuum condition while the vacuum pump unit is constantly running to continue sintering. Here, the inert gas is preferably argon gas. This process effectively removes boron and aluminum impurities from the graphite crucible, resulting in a high-purity graphite crucible. In some embodiments of the present invention, the pressure is 50,000 Pa. In some embodiments of the present invention, the holding time is 10 minutes.

[0096] <4. Insulation:>

[0097] In the present invention, the insulating material is also primarily a carbon material, such as graphite soft felt or graphite hard felt. In the present invention, the insulating material is preferably a pretreated insulating material. In the present invention, the method for pretreating the insulating material is the same as the method for pretreating the pretreated graphite powder described above, i.e., the original insulating material is calcined under vacuum conditions. The calcination temperature is preferably 2200 to 2400°C, and in some embodiments of the present invention, the calcination temperature is 2200°C or 2250°C. The calcination time is preferably 5 to 100 hours, and in some embodiments of the present invention, the calcination time is 10 hours or 30 hours. Specifically, after placing the insulating material in a high-temperature furnace, the furnace is evacuated and the vacuum pump unit is constantly operating to maintain the vacuum condition. The temperature in the furnace is then raised to the target temperature, and calcination is continued.

[0098] To further improve the removal effect of boron and aluminum impurities, during the 5-100 hour sintering process, the present invention preferably first turns off the vacuum pump unit to stop evacuation, then fills with inert gas until the pressure reaches 1,000-70,000 Pa, and maintains this pressure for 1-60 min. Then, the vacuum pump unit is turned back on to evacuate again, maintaining vacuum conditions while the vacuum pump unit is constantly operating to continue sintering. Here, the inert gas is preferably argon gas. In some embodiments of the present invention, the pressure is 50,000 Pa. In some embodiments of the present invention, the maintenance time is 10 min. The above process effectively removes boron and aluminum impurities from the insulating material, resulting in a high-purity insulating material. To improve the purity of the insulating material, the inside of the insulating material (i.e., the surface in contact with the graphite crucible) and the outside of the insulating material must be sintered at high temperatures to improve the purity of the insulating material as a whole.

[0099] <5. Process:>

[0100] The assembled graphite crucible is placed in a high-temperature furnace, and then the furnace is first evacuated to reduce the pressure, and then a protective gas is filled to adjust the pressure, while the temperature is raised to the target pressure and target temperature, and crystal growth is carried out under the pressure and temperature conditions to obtain silicon carbide crystals.

[0101] In the present invention, the furnace is evacuated preferably to 10 Pa or less, and the vacuum state is maintained by constantly operating the vacuum pump unit. The temperature inside the furnace is then increased, preferably to 500 to 1000°C in the present invention, and in some embodiments of the present invention, to 800°C or 1000°C. After the temperature increase, the temperature is preferably maintained for 1 to 5 hours, and in some embodiments of the present invention, the temperature maintenance time is 1 hour or 3 hours.

[0102] In the present invention, to improve the removal of volatile components from the furnace insulation, graphite crucible, and silicon carbide powder, during the 1-5 hour heat-retention period, preferably, the vacuum pump unit is first turned off and the evacuation tube is stopped, and an inert gas is introduced until the pressure reaches 1,000-70,000 Pa. This is maintained for 1-60 minutes, and then the vacuum pump unit is turned back on and the evacuation is continued until the pressure reaches 1 Pa or less. The vacuum pump unit is constantly operating to maintain the vacuum state and continue the high-temperature treatment. In some embodiments of the present invention, the pressure is 50,000 Pa or 70,000 Pa. In some embodiments of the present invention, the retention time is 5 minutes or 10 minutes.

[0103] In the present invention, after removing the volatile components from the insulation, graphite crucible, and silicon carbide powder in the furnace, the vacuum pump unit is turned off and the vacuum line is stopped. An inert gas is introduced into the furnace until the pressure reaches 5,000 to 70,000 Pa (in some embodiments of the present invention, the pressure is 50,000 Pa or 70,000 Pa). The temperature in the furnace is increased to the crystal growth temperature and maintained for 1 to 10 hours (in some embodiments of the present invention, the maintenance time is 2 hours or 2.5 hours). The pressure in the furnace is then reduced to the pressure required for crystal growth, and full-scale crystal growth begins. The required pressure for crystal growth is 100 to 5,000 Pa, preferably 100 to 1,500 Pa. In some embodiments of the present invention, this pressure is 1,500 Pa or 2,000 Pa. The crystal growth temperature is 2,050 to 2,250°C, preferably 2,100 to 2,200°C. In some embodiments of the present invention, the temperature is 2,150°C or 2,220°C. After growth is complete, the crystal is annealed in situ. After the in situ annealing is complete, the temperature inside the furnace is lowered to room temperature, the high-temperature furnace is opened, and the silicon carbide crystal product is taken out.

[0104] The silicon carbide crystal produced by the above-described production method of the present invention can effectively reduce the defects and impurity content of the crystal, thereby improving the quality of the silicon carbide crystal.

[0105] <About silicon carbide substrates:>

[0106] Silicon carbide substrates, also known as silicon carbide wafers, are generally circular slices with diameters of 2, 3, 4, 6, and 8 inches, and thicknesses generally between 80 and 800 microns. Commercially available silicon carbide substrates typically contain a certain number of micropipes, screw dislocations, and complex dislocation defects, with typical specifications being a micropipe density of 0.5 to 5 per cm. 2 , screw dislocation density 500 to 1500 / cm 2 , complex dislocation density 30-60 / cm 2 The length of the scratch on the surface is 1R to 6R (where R represents the radius of the substrate).

[0107] The present invention provides a high quality silicon carbide substrate, the silicon carbide substrate having at least one high quality region; The specifications for the high-quality region are: 0 micropipes, screw dislocation density <300 / cm 2 , complex dislocation density <20 / cm 2 , the difference between two points of the half-width of the X-ray rocking curve at any 1 cm interval is < 40 arc seconds, The area of ​​the high-quality area is >0.25 cm 2 is.

[0108] In the present invention, the specifications of the high quality area are as follows: The screw dislocation density is preferably 200 / cm 2 less than 100 / cm 2 less than 50 particles / cm 2 Less than 30 cells / cm 2 is less than. The complex dislocation density is preferably 5 / cm 2 is less than. The difference between two points of the half-width of the X-ray rocking curve at any 1 cm interval is preferably less than 20 arc seconds. The area of ​​the high quality region is preferably 1 cm 2 More than 5cm, preferably 2 More than 10cm, preferably 2 More than 50cm, most preferably 2 It exceeds that. The shape of the high quality region includes a triangle, a square, a circle, or a polygon.

[0109] In the present invention, the boron element impurity concentration of the silicon carbide substrate is preferably 5×10 16 / cm 3 less than 1×10 16 / cm 3 less than 5 × 10 15 / cm 3 is less than.

[0110] In the present invention, the aluminum element impurity concentration of the silicon carbide substrate is preferably 5×1015 / cm 3 less than 1×10 15 / cm 3 less than 5 × 10 14 / cm 3 is less than.

[0111] In the present invention, the normal direction of the silicon carbide substrate surface is deviated from the c-axis crystal direction by an angle of 0 to 8 degrees, preferably 1 to 5 degrees.

[0112] In the present invention, the resistivity of the silicon carbide substrate is <0.03 Ω·cm, preferably less than 0.023 Ω·cm.

[0113] In the present invention, the length of the scratch on the surface of the silicon carbide substrate is smaller than the radius of the substrate.

[0114] <About the manufacturing method of silicon carbide substrates:>

[0115] The present invention provides K1: crystal processing a silicon carbide crystal to obtain a silicon carbide wafer; K2, wafer processing the silicon carbide wafer to obtain a silicon carbide substrate; wherein the silicon carbide crystal is the silicon carbide crystal described in the above technical solution or a silicon carbide crystal manufactured by the manufacturing method described in the above technical solution.

[0116] Regarding step K1, In the present invention, the crystal processing method is not particularly limited and may be any conventional process in the art, including outer cylindrical grinding, surface grinding, single crystal orientation, positioning edge processing, and multi-wire cutting, and cut sheets are obtained by the above processing steps.

[0117] Regarding step K2, In the present invention, the wafer processing includes chemical mechanical polishing. In the present invention, double-side grinding and mechanical polishing are preferably further performed before the chemical mechanical polishing. In the present invention, the double-side grinding and mechanical polishing methods are not particularly limited, and conventional operations known to those skilled in the art may be used.

[0118] In the present invention, the chemical mechanical polishing preferably includes a first step of chemical mechanical polishing and a second step of chemical mechanical polishing performed sequentially. Chemical mechanical polishing is a technique that combines chemical and mechanical actions: first, the surface material of the workpiece undergoes a chemical reaction with the components in the polishing solution to form a soft layer that is relatively easy to remove; then, under the mechanical action of the abrasive grains in the polishing solution and the polishing pad, the soft layer is removed, re-exposing the workpiece surface; thus, the workpiece surface is polished through a process in which both chemical and mechanical actions occur simultaneously.

[0119] In the first chemical mechanical polishing, the polishing liquid used is an alumina polishing liquid, and the alumina polishing liquid refers to a polishing liquid in which the abrasive grains are alumina. In the present invention, the source of the alumina polishing liquid is not particularly limited, and it may be a commonly available commercially available product.

[0120] In the first chemical mechanical polishing, the polishing pad used is a polyurethane polishing pad, and the Shore hardness of the polishing pad is preferably 75 to 85.

[0121] In the first chemical mechanical polishing, the pressure of the polishing head is preferably 100 to 450 g / cm 2 and in some embodiments of the invention, the pressure is 230 g / cm 2 or 400g / cm 2 The polishing rate is preferably 0.5 to 2 microns / hour, and in some embodiments of the present invention, the polishing rate is 1.1 microns / hour or 1.5 microns / hour.

[0122] In the second chemical mechanical polishing, the polishing liquid used is a silica polishing liquid, and the silica polishing liquid refers to a polishing liquid in which the abrasive grains are silica. In the present invention, the source of the silica polishing liquid is not particularly limited, and any commonly available commercially available product may be used.

[0123] In the second chemical mechanical polishing, the polishing pad used is a nylon cloth, and the Shore hardness of the polishing pad is preferably 60-75.

[0124] In the second chemical mechanical polishing, the pressure of the polishing head is preferably 150 to 400 g / cm 2 and in some embodiments of the invention, the pressure is 350 g / cm 2 or 400g / cm 2 The polishing rate is preferably 20 to 100 nanometers / hour, and in some embodiments of the present invention, the polishing rate is 25 nanometers / hour or 35 nanometers / hour.

[0125] In the present invention, the polishing rate of the first step chemical mechanical polishing is 10 to 30 times the polishing rate of the second step chemical mechanical polishing.

[0126] The present invention improves the surface quality of the substrate after the above processing, and can obtain a high-quality surface in which the scratch length is shorter than the radius of the substrate. According to the manufacturing method of the present invention, silicon carbide substrates of various sizes, specifically, diameters of 2 inches, 3 inches, 4 inches, and 6 inches and thicknesses between 80 and 800 microns, can be manufactured. Referring to Figure 7, Figure 7 is a schematic diagram of a silicon carbide substrate manufactured according to the present invention.

[0127] The silicon carbide substrate provided in the present invention has the following advantageous effects: 1. High crystal quality, extremely low number of micropipes, and extremely low screw dislocation density and complex dislocation density. 2. The p-type impurity concentration is extremely low, resulting in excellent electrical properties. 3. High surface quality.

[0128] The devices manufactured using the above-mentioned high-quality silicon carbide substrates have excellent performance, good consistency, and high reliability, meeting the demand for high-performance, high-reliability devices in fields such as new energy vehicles, rail transportation, aerospace, and smart grids.

[0129] In order to further understand the present invention, preferred embodiments of the present invention will now be described with reference to examples, but it should be understood that these descriptions are not intended to limit the scope of the invention as claimed, but are intended only to further illustrate the features and advantages of the present invention. <Example 1: Preparation of SiC seed crystal>

[0130] S1 provided the initial seed crystal: micropipe density 2 / cm 2 , screw dislocation density 1000 / cm 2 , complex dislocation density 50 / cm 2 .

[0131] S2, the first expansion growth was performed: the expansion angle was selected to be 45°, and the axial temperature gradient in the growth chamber was controlled so that the temperature gradually increased from the surface of the seed crystal to the surface of the silicon carbide raw material along the crystal growth direction, with a temperature increase gradient of 2°C / cm. The lateral temperature gradient was controlled so that the temperature gradually increased from the center of the seed crystal to the edge of the seed crystal along the radial direction, with a temperature increase gradient of 2°C / cm.

[0132] In step S3, the crystal grown in step S2 was cut to obtain an intermediate seed crystal containing both the constant diameter region and the expanding diameter region, which was then further processed to obtain a high-quality intermediate seed crystal containing only the expanding diameter region.

[0133] S4, the second expansion growth was performed: the expansion angle was selected to be 45°, and the axial temperature gradient in the growth chamber was controlled so that the temperature gradually increased from the surface of the seed crystal to the surface of the silicon carbide raw material along the crystal growth direction, with the temperature gradient being 2°C / cm. The lateral temperature gradient was controlled so that the temperature gradually increased from the center of the seed crystal to the edge of the seed crystal along the radial direction, with the temperature gradient being 2°C / cm.

[0134] The obtained crystal was cut in a direction parallel to the surface of the medium-grade seed crystal to obtain a high-grade seed crystal with a diameter of 53 mm and a thickness of 500 μm.

[0135] S5, the third expansion growth was performed: the expansion angle was selected to be 45°, and the axial temperature gradient in the growth chamber was controlled so that the temperature gradually increased from the surface of the seed crystal to the surface of the silicon carbide raw material along the crystal growth direction, with a temperature increase gradient of 2°C / cm. The lateral temperature gradient was controlled so that the temperature gradually increased from the center of the seed crystal to the edge of the seed crystal along the radial direction, with a temperature increase gradient of 2°C / cm.

[0136] The obtained crystal was cut in a direction parallel to the surface of the high-quality seed crystal to obtain a high-quality seed crystal having a diameter of 103 mm and a thickness of 500 μm. <Example 2: Preparation of silicon carbide powder>

[0137] S1. Graphite powder pretreatment: High-purity graphite powder (total impurity content <10 ppm) was placed in a high-temperature furnace. The furnace was evacuated and the vacuum pump unit was constantly running. The temperature inside the furnace was then raised to 2250°C and held for 10 hours. During this heating process, the vacuum pump unit was first turned off, and argon gas was introduced up to 50,000 Pa. This was held for 10 minutes. The vacuum pump was then turned back on, and the furnace was evacuated again with the vacuum pump unit constantly running. This resulted in pretreated graphite powder.

[0138] The boron impurity content of the obtained pretreated graphite powder was 5.5 × 10 15 / cm 3 , aluminum impurity content is 4×10 14 / cm 3 It was.

[0139] S2: Silicon powder and pretreated graphite powder were mixed in a mass ratio of 1.00:1 and placed in a graphite crucible in a high-temperature furnace. The furnace was then evacuated and filled with argon gas until the pressure reached 5000 Pa. The temperature in the furnace was then increased to 1900°C and maintained at that temperature for 8 hours to obtain silicon carbide powder. <Example 3: Preparation of silicon carbide substrate>

[0140] <1. Sample Preparation> S1, the graphite felt insulation material and the graphite crucible were pretreated, and the pretreatment operation and conditions were similar to those of the graphite powder pretreatment in step S1 of Example 2.

[0141] S2: The SiC seed crystal obtained in Example 1 was fixed to the upper part of the graphite lid by bonding, the silicon carbide powder obtained in Example 2 was placed in the graphite crucible, and the graphite lid with the SiC seed crystal fixed thereto was assembled to the graphite crucible. Here, the distance from the surface of the silicon carbide powder to the SiC seed crystal was 40 mm.

[0142] In step S3, the graphite crucible assembled in step S2 was placed in a high-temperature furnace, and the furnace was evacuated to 10 Pa or less with the vacuum pump unit constantly operating. The temperature inside the furnace was raised to 800°C and maintained at that temperature for 3 hours. During the heat retention process, the vacuum pump was first turned off, argon gas was filled up to a pressure of 50,000 Pa, and maintained at that temperature for 10 minutes. After that, the vacuum pump was turned on and the furnace was evacuated again with the vacuum pump unit constantly operating.

[0143] S4: After the above treatment, the vacuum pump was turned off, argon gas was filled up to 50,000 Pa, the temperature inside the furnace was raised to the crystal growth temperature of 2,150 °C, and held for 2 hours, after which the pressure inside the furnace was reduced to the pressure necessary for crystal growth of 1,500 Pa, and crystal growth was carried out. After growth was completed, in-situ annealing was performed, and the temperature was lowered to room temperature, and the crystal was removed.

[0144] S5: The crystal was subjected to cylindrical grinding, the flat surface was ground, the single crystal was oriented, the positioning edge was processed, and the multi-wire cutting was performed to obtain a cut sheet.

[0145] S6: The cut sheet was subjected to double-side grinding, mechanical polishing, and chemical mechanical polishing to obtain a high-quality silicon carbide substrate with a diameter of 100 mm and a thickness of 350 μm.

[0146] Here, the chemical mechanical polishing preferably included sequentially performing a first step of chemical mechanical polishing and a second step of chemical mechanical polishing.

[0147] First step: Chemical mechanical polishing: Alumina polishing solution (alumina D50 particle size: 200 nm) and polyurethane polishing pad (Shore hardness 78) were used, and the polishing head pressure was 400 g / cm. 2 The polishing rate was 1.5 microns / hour.

[0148] The second step, chemical mechanical polishing, was performed using a silica polishing solution (silica D50 particle size: 100 nm) and a nylon cloth polishing pad (Shore hardness: 65). The polishing head pressure was 400 g / cm. 2 The polishing rate was 35 nanometers / hour.

[0149] <2. Sample Test> The crystal defects, impurity concentration, surface quality and electrical characteristics of the obtained silicon carbide substrate were measured, and the following findings were obtained.

[0150] Continuous area is 30cm 2 The crystal defects in this region are 0 micropipes and a screw dislocation density of 206 / cm. 2 , complex dislocation density is 8 / cm 2 The difference between two points of the half-width of the X-ray rocking curve at any 1 cm interval was less than 20 arc seconds. The test results are shown in Figures 8 to 10. Figure 8 is a schematic diagram of the distribution of micropipes in the silicon carbide substrate obtained in Example 3. The micropipes are polygonal areas of zero area, and the area is 30 cm. 2 Fig. 9 is a topography of the micropipes of the silicon carbide substrate obtained in Example 3, taken by a transmission polarizing microscope. Fig. 10 is a distribution map of the screw dislocation density on the silicon carbide substrate obtained in Example 3.

[0151] Impurity concentration: Boron element impurity concentration is 4.5 x 10 15 / cm 3 , aluminum element impurity concentration is 3.5 × 10 14 / cm 3 It was.

[0152] Electrical properties: resistivity was 0.022 Ω cm, and resistivity variation was 1.77%. The test results are shown in Figure 11, which is a diagram of the electrical properties of the silicon carbide substrate obtained in Example 3, with the distribution of test data on the left and the data generation results on the right.

[0153] Surface quality: The length of the scratches accumulated on the surface was only 0.6R (where R represents the radius of the substrate, and the test equipment is Candela CS920). The test results are shown in Figure 12, which is a schematic diagram of the surface scratches on the silicon carbide substrate obtained in Example 3. Example 4: Preparation of SiC seed crystals

[0154] S1, provided the initial seed crystal: micropipe density 1 / cm 2 , screw dislocation density 600 / cm 2 , complex dislocation density 30 / cm 2 .

[0155] S2, the first expansion growth was performed: the expansion angle was selected to be 30°, and the axial temperature gradient in the growth chamber was controlled so that the temperature gradually increased from the surface of the seed crystal to the surface of the silicon carbide raw material along the crystal growth direction, with a temperature increase gradient of 3°C / cm. The lateral temperature gradient was controlled so that the temperature gradually increased from the center of the seed crystal to the edge of the seed crystal along the radial direction, with a temperature increase gradient of 2°C / cm.

[0156] In step S3, the crystal grown in step S2 was cut to obtain an intermediate seed crystal containing both the constant diameter region and the expanding diameter region, which was then further processed to obtain a high-quality intermediate seed crystal containing only the expanding diameter region.

[0157] S4, the second expansion growth was performed: the expansion angle was selected to be 30°, and the axial temperature gradient in the growth chamber was controlled so that the temperature gradually increased from the surface of the seed crystal to the surface of the silicon carbide raw material along the crystal growth direction, with a temperature increase gradient of 3°C / cm. The lateral temperature gradient was controlled so that the temperature gradually increased from the center of the seed crystal to the edge of the seed crystal along the radial direction, with a temperature increase gradient of 2°C / cm.

[0158] The resulting crystal was cut parallel to the surface of the intermediate seed crystal to obtain a high-grade seed crystal with a diameter of 53 mm and a thickness of 500 μm.

[0159] S5, the third expansion growth was performed: the expansion angle was selected to be 30°, and the axial temperature gradient in the growth chamber was controlled so that the temperature gradually increased from the surface of the seed crystal to the surface of the silicon carbide raw material along the crystal growth direction, with a temperature increase gradient of 3°C / cm. The lateral temperature gradient was controlled so that the temperature gradually increased from the center of the seed crystal to the edge of the seed crystal along the radial direction, with a temperature increase gradient of 2°C / cm.

[0160] The obtained crystal was cut in a direction parallel to the surface of the high-quality seed crystal to obtain a high-quality seed crystal with a diameter of 103 mm and a thickness of 500 μm.

[0161] S5, the fourth expansion growth was performed: the expansion angle was selected to be 30°, and the axial temperature gradient in the growth chamber was controlled so that the temperature gradually increased from the surface of the seed crystal to the surface of the silicon carbide raw material along the crystal growth direction, with a temperature increase gradient of 3°C / cm. The lateral temperature gradient was controlled so that the temperature gradually increased from the center of the seed crystal to the edge of the seed crystal along the radial direction, with a temperature increase gradient of 2°C / cm.

[0162] The obtained crystal was cut in a direction parallel to the surface of the high-quality seed crystal to obtain a high-quality seed crystal having a diameter of 153 mm and a thickness of 500 μm. <Example 5: Preparation of silicon carbide powder>

[0163] S1. Graphite powder pretreatment: High-purity graphite powder (total impurity content <10 ppm) was placed in a high-temperature furnace. The furnace was evacuated and the vacuum pump unit was constantly running. The temperature inside the furnace was then raised to 2200°C and held for 30 hours. During this heating process, the vacuum pump unit was first turned off, and argon gas was introduced up to 50,000 Pa. This was held for 10 minutes. The vacuum pump was then turned back on, and the furnace was evacuated again with the vacuum pump unit constantly running. This resulted in pretreated graphite powder.

[0164] The boron impurity content of the obtained pretreated graphite powder was 4.5 × 10 15 / cm 3 , aluminum impurity content is 4.5 × 10 14 / cm 3 It was.

[0165] S2: Silicon powder and pretreated graphite powder were mixed in a mass ratio of 1.05:1 and placed in a graphite crucible in a high-temperature furnace. The furnace was then evacuated and filled with argon gas until the pressure reached 1000 Pa. The temperature in the furnace was then increased to 1850°C and maintained at that temperature for 12 hours to obtain silicon carbide powder. Example 6: Preparation of silicon carbide substrate

[0166] <1. Sample Preparation> S1, the graphite felt insulation material and the graphite crucible were pretreated, and the pretreatment operation and conditions were similar to those of the graphite powder pretreatment in step S1 of Example 2.

[0167] The SiC seed crystal obtained in Example 4 was fixed to the upper part of the graphite lid by bonding, the silicon carbide powder obtained in Example 5 was placed in the graphite crucible, and the graphite lid with the SiC seed crystal fixed thereto was assembled to the graphite crucible. Here, the distance from the surface of the silicon carbide powder to the SiC seed crystal was 30 mm.

[0168] In step S3, the graphite crucible assembled in step S2 was placed in a high-temperature furnace, and the furnace was evacuated to 10 Pa or less with the vacuum pump unit constantly operating. The temperature inside the furnace was raised to 1000°C and maintained at that temperature for 1 hour. During the heat retention process, the vacuum pump was first turned off, argon gas was filled up to a pressure of 70,000 Pa, and maintained at that temperature for 5 minutes. Then, the vacuum pump was turned on and the furnace was evacuated again with the vacuum pump unit constantly operating.

[0169] S4: After the above treatment, the vacuum pump was turned off, argon gas was charged up to 70,000 Pa, the temperature inside the furnace was raised to the crystal growth temperature of 2,220°C, and held for 2.5 hours, after which the pressure inside the furnace was reduced to the pressure required for crystal growth of 2,000 Pa, and crystal growth was carried out. After growth was completed, in-situ annealing was performed, and the temperature was lowered to room temperature, after which the crystal was removed.

[0170] S5: The crystal was subjected to cylindrical grinding, the flat surface was ground, the single crystal was oriented, the positioning edge was processed, and the multi-wire cutting was performed to obtain a cut sheet.

[0171] S6: The cut sheet was subjected to double-side grinding, mechanical polishing, and chemical mechanical polishing to obtain a high-quality silicon carbide substrate with a diameter of 150 mm and a thickness of 350 μm.

[0172] Here, the chemical mechanical polishing preferably included sequentially performing a first step of chemical mechanical polishing and a second step of chemical mechanical polishing.

[0173] First step: Chemical mechanical polishing: Alumina polishing solution (alumina D50 particle size: 200 nanometers) and polyurethane polishing pad (Shore hardness 75) were used, and the polishing head pressure was 230 g / cm. 2 The polishing rate was 1.1 microns / hour.

[0174] Second step: Chemical mechanical polishing: Use silica polishing solution (silica D50 particle size: 100 nanometers) and nylon cloth polishing pad (Shore hardness 60), and polishing head pressure is 350 g / cm 2 The polishing rate was 25 nanometers / hour.

[0175] <2. Sample Test> The crystal defects, impurity concentration, surface quality and electrical characteristics of the obtained silicon carbide substrate were measured, and the following findings were obtained.

[0176] Continuous area is 65cm 2 There is a high-quality region with 0 micropipes and a screw dislocation density of 75 / cm. 2 , complex dislocation density is 6 / cm 2 The difference between any two points of the half-width of the X-ray rocking curve at 1 cm intervals was less than 20 arc seconds. The test results are shown in FIG. 13, which is a distribution diagram of the screw dislocation density of the silicon carbide substrate obtained in Example 6.

[0177] Impurity concentration: The boron element impurity concentration is preferably 3.5×10 15 / cm 3 , aluminum element impurity concentration is 3.1 × 10 14 / cm 3 It was.

[0178] Electrical properties: resistivity was 0.02 Ω·cm, and resistivity variation was 0.82%. The test results are shown in Figure 14, which is a diagram of the electrical properties of the silicon carbide substrate obtained in Example 6, with the distribution of test data on the left and the data generation results on the right.

[0179] Surface quality: The length of the scratches accumulated on the surface was only 0.3R (where R represents the radius of the substrate, and the test equipment is Candela CS920). The test results are shown in Figure 15, which is a schematic diagram of the surface scratches on the silicon carbide substrate obtained in Example 6.

[0180] From the above examples, it can be seen that the silicon carbide substrate provided by the present invention has high crystal quality, an extremely small number of micropipes, an extremely low density of screw dislocations and complex dislocations, and at the same time, an extremely low concentration of p-type impurities, exhibits excellent resistivity, and also has high surface quality.

[0181] Although the principles and embodiments of the present invention have been described herein using specific examples, the above description of the embodiments is only used to help understand the method and gist of the present invention, including the optimal method, and enables any person skilled in the art to practice the present invention, including manufacturing and using any device or system, and implementing any combined method. It should be noted that those skilled in the art may make some improvements and modifications to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the scope of protection of the claims. The scope of patent protection for the present invention is defined by the claims and may include other embodiments that may be conceived by a person skilled in the art. If these other embodiments have structural elements close to the literal language of the claims, or if they contain equivalent structural elements that are not substantially different from the literal language of the claims, these other embodiments should also be included within the scope of the claims.

Claims

1. 1. A method for producing high quality silicon carbide seeds, comprising: the high quality silicon carbide seed crystal has at least one high quality region; the high quality region is a triangular region, a square region, a circular region, or a polygonal region; After the high-quality silicon carbide seed crystal is etched by molten KOH, corrosion pits corresponding to dislocation defects appear on the surface of the high-quality silicon carbide seed crystal, and the high-quality region is determined by measuring the X-ray rocking curve of the high-quality silicon carbide seed crystal; The specifications for the high quality region are: 0 micropipes, screw dislocation density <300 / cm ２ , complex dislocation density <20 / cm ２ , the difference between two points of the half-width of the X-ray rocking curve at any 1 cm interval is less than 40 arc seconds; 65 cm 2 ≧ area of ​​the high quality region > 0.25 cm ２ and The manufacturing method includes: a) performing a first diameter expansion growth on the initial seed crystal to obtain an initial grown crystal; b) processing the initial grown crystal to obtain an intermediate seed crystal including only an expansion region; and c) performing a second diameter expansion growth on the intermediate seed crystal to obtain a high-grade seed crystal.

2. The specifications for the high quality region are: 0 micropipes, screw dislocation density <100 / cm ２ , complex dislocation density <20 / cm ２ , the difference between two points of the half-width of the X-ray rocking curve at any 1 cm interval is less than 40 arc seconds; The area of ​​the high quality region > 1 cm ２ The method according to claim 1, wherein

3. The specifications of the high quality region are: 0 micropipes, complex dislocation density <20 / cm ２ , the difference between two points of the half-width of the X-ray rocking curve at any 1 cm interval is less than 40 arc seconds; The area of ​​the high quality area > 10 cm ２ The method according to claim 1, wherein

4. The specifications of the high-quality region are that the number of micropipes is 0, and the difference between two points of the half-width of the X-ray rocking curve at any 1 cm interval is less than 20 arc seconds; The area of ​​the high quality area > 50 cm ２ The method according to claim 1, wherein

5. In the first diameter expansion growth, The expansion angle of the initial seed crystal in the crucible is controlled to 5° to 50°. The temperature field distribution in the growth chamber is Axial temperature gradient: the temperature gradually increases along the crystal growth direction from the surface of the seed crystal to the surface of the silicon carbide raw material, with a temperature increase gradient of 1 to 10°C / cm; Lateral temperature gradient: the temperature gradually increases from the center of the seed crystal to the edge of the seed crystal along the radial direction, and the temperature gradient is controlled to be 0.5 to 5°C / cm; In the second diameter expansion growth, The expansion angle of the intermediate seed crystal in the crucible is controlled to 5° to 50°. The temperature field distribution in the growth chamber is Axial temperature gradient: the temperature gradually increases along the crystal growth direction from the surface of the seed crystal to the surface of the silicon carbide raw material, with a temperature increase gradient of 1 to 10°C / cm; The method of claim 1, wherein the temperature gradient in the lateral direction is gradually increased from the center of the seed crystal to the edge of the seed crystal along the radial direction, and the temperature gradient is controlled to be 0.5 to 5°C / cm.

6. After step c), further d) comparing the diameter of the high-grade seed crystal with the diameter required to produce a silicon carbide substrate; If the diameter of the high-quality seed crystal is greater than or equal to the diameter required for manufacturing a silicon carbide substrate, the seed crystal preparation process is terminated; 6. The manufacturing method according to claim 1, further comprising a step of repeating the second diameter expansion growth step for the obtained high-quality seed crystal when the diameter of the high-quality seed crystal is smaller than the diameter required for manufacturing the silicon carbide substrate, until the diameter of the obtained seed crystal becomes equal to or larger than the diameter required for manufacturing the silicon carbide substrate.

7. A method for producing silicon carbide crystals, comprising: the silicon carbide crystal has at least one high quality region; the high quality region is a triangular region, a square region, a circular region, or a polygonal region; After the silicon carbide crystal is etched with molten KOH, etching pits corresponding to dislocation defects appear on the surface of the silicon carbide crystal, and the high-quality region is determined by measuring the X-ray rocking curve of the silicon carbide crystal; The specifications for the high quality region are: 0 micropipes, screw dislocation density <300 / cm ２ , complex dislocation density <20 / cm ２ , the difference between two points of the half-width of the X-ray rocking curve at any 1 cm interval is less than 40 arc seconds; 65 cm 2 ≧ area of ​​the high quality region > 0.25 cm ２ and The manufacturing method includes: a step of performing a first diameter expansion growth on the initial seed crystal to obtain an initial grown crystal; processing the initial grown crystal to obtain an intermediate seed crystal including only an expansion region; a step of performing a second diameter expansion growth on the intermediate seed crystal to obtain a high-grade seed crystal; a graphite crucible filled with silicon carbide powder and containing a high-grade SiC seed crystal is placed in a high-temperature furnace, the furnace is first evacuated to reduce pressure, a protective gas is then filled to adjust the pressure, and the temperature is raised to a target pressure and a target temperature, and crystal growth is carried out under the pressure and temperature conditions to obtain silicon carbide crystals.

8. The specifications for the high quality region are: 0 micropipes, screw dislocation density <100 / cm ２ , complex dislocation density <20 / cm ２ , the difference between two points of the half-width of the X-ray rocking curve at any 1 cm interval is less than 40 arc seconds; The area of ​​the high quality region > 1 cm ２ The method according to claim 7, wherein

9. The specifications of the high-quality region are that the number of micropipes is 0, and the difference between two points of the half-width of the X-ray rocking curve at any 1 cm interval is less than 40 arc seconds; The area of ​​the high quality area > 10 cm ２ The method according to claim 7, wherein

10. The specifications of the high-quality region are that the number of micropipes is 0, and the difference between two points of the half-width of the X-ray rocking curve at any 1 cm interval is less than 20 arc seconds; The area of ​​the high quality area > 50 cm ２ The method according to claim 7, wherein

11. The manufacturing method according to claim 7, wherein the target pressure is 100 to 5000 Pa and the target temperature is 2050 to 2250°C.

12. The silicon carbide powder has a boron element impurity concentration of <5×10 １６ / cm ３ , aluminum element impurity concentration <5×10 １５ / cm ３ and The specifications of the graphite crucible are: boron element impurity concentration <5 × 10 １６ / cm ３ , aluminum element impurity concentration <5×10 １５ / cm ３ and The specifications for the heat insulating material around the graphite crucible are: boron element impurity concentration <5 × 10 １６ / cm ３ , aluminum element impurity concentration <5×10 １５ / cm ３ The method according to claim 7, wherein

13. The method according to claim 7 or 12, wherein the silicon carbide powder is produced by the following method. S1: Mix silicon powder and graphite powder to obtain a mixed powder. S2: Synthesize the mixed powder under protective gas conditions to obtain silicon carbide powder.

14. The silicon carbide powder is S1: Mixing silicon powder and graphite powder to obtain a mixed powder; S2: synthesizing the mixed powder under protective gas conditions to obtain silicon carbide powder; the graphite powder is a pretreated graphite powder; The method for obtaining the pretreated graphite powder includes calcining the original graphite powder under vacuum conditions, The temperature of the firing treatment is 2200 to 2400°C, and the time is 5 to 100 hours. The total impurity content of the original graphite powder is <10 ppm; the graphite crucible is a pretreated graphite crucible; The method for obtaining the pretreated graphite crucible includes baking the original crucible under vacuum conditions; The temperature of the firing treatment is 2200 to 2400°C, and the time is 5 to 100 hours. the insulation material is a pretreated insulation material; The method for obtaining the pretreated insulating material includes baking the original insulating material under vacuum conditions, The method according to claim 12, wherein the firing temperature is 2200 to 2400°C and the firing time is 5 to 100 hours.

15. 1. A method for manufacturing a high quality silicon carbide substrate, comprising: the high quality silicon carbide substrate has at least one high quality region; the high quality region is a triangular region, a square region, a circular region, or a polygonal region; After the high-quality silicon carbide substrate is etched by molten KOH, corrosion pits corresponding to dislocation defects appear on the surface of the high-quality silicon carbide substrate, and the high-quality region is determined by measuring an X-ray rocking curve of the high-quality silicon carbide substrate; The specifications for the high quality region are: 0 micropipes, screw dislocation density <300 / cm ２ , complex dislocation density <20 / cm ２ , the difference between two points of the half-width of the X-ray rocking curve at any 1 cm interval is less than 40 arc seconds; 65 cm 2 ≧ area of ​​the high quality region > 0.25 cm ２ and The manufacturing method includes: a step of performing a first diameter expansion growth on the initial seed crystal to obtain an initial grown crystal; processing the initial grown crystal to obtain an intermediate seed crystal including only an expansion region; a step of performing a second diameter expansion growth on the intermediate seed crystal to obtain a high-grade seed crystal; a graphite crucible filled with silicon carbide powder and containing a high-grade SiC seed crystal is placed in a high-temperature furnace, the furnace is first evacuated to reduce pressure, and then a protective gas is filled to adjust the pressure, while the temperature is raised to a target pressure and a target temperature, and crystal growth is carried out under the pressure and temperature conditions to obtain a silicon carbide crystal; K2. The method of manufacturing a silicon carbide substrate, comprising the steps of: (a) wafer-processing the silicon carbide crystal; and (b) obtaining a silicon carbide substrate.

16. The specifications for the high quality region are: 0 micropipes, screw dislocation density <100 / cm ２ , complex dislocation density <20 / cm ２ , the difference between two points of the half-width of the X-ray rocking curve at any 1 cm interval is less than 40 arc seconds; The area of ​​the high quality region > 1 cm ２ The method according to claim 15, wherein

17. The specifications of the high-quality region are that the number of micropipes is 0, and the difference between two points of the half-width of the X-ray rocking curve at any 1 cm interval is less than 20 arc seconds; The area of ​​the high quality area > 50 cm ２ and In the silicon carbide substrate, the boron element impurity concentration is less than 5×10 １５ / cm ３ , aluminum element impurity concentration <5×10 １４ / cm ３ and 16. The method according to claim 15, wherein the normal direction of the silicon carbide substrate surface is deviated from the c-axis crystal direction by an angle of 1 to 5 degrees.

18. the wafer processing includes chemical mechanical polishing; The chemical mechanical polishing includes a first step chemical mechanical polishing and a second step chemical mechanical polishing, In the chemical mechanical polishing of the first step, the polishing liquid used is an alumina polishing liquid, the polishing pad used is a polyurethane polishing pad, and the Shore hardness of the polishing pad is 75 to 85; In the chemical mechanical polishing of the second step, the polishing liquid used is a silica polishing liquid, the polishing pad used is a nylon cloth, and the Shore hardness of the polishing pad is 60 to 75; 16. The manufacturing method according to claim 15, wherein the polishing rate of the first step of chemical mechanical polishing is 10 to 30 times that of the second step of chemical mechanical polishing.

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