Crucible and method for growing p-type SiC single crystal

Abstract

The present invention belongs to the field of semiconductor technology, and relates to a crucible and method for growing a p-type SiC single crystal. The crucible comprises an upper crucible, a lower crucible and a connecting rod, wherein the connecting rod is a hollow structure, one end of the connecting rod is connected to the lower end opening of the upper crucible, and the other end of the connecting rod is connected to the upper end opening of the lower crucible. An inner crucible is arranged in the lower part of the upper crucible, the inner crucible opening is upward, the side wall height of the inner crucible is less than the side wall height of the upper crucible, the space in the inner crucible is a SiC powder placement area, the space in the upper crucible above the inner crucible is a SiC single crystal growth area, a gap is formed between the inner crucible and the upper crucible, the lower end opening of the upper crucible is connected to the SiC single crystal growth area through the gap, and the upper cover of the upper crucible is arranged to allow the protective gas to enter the upper crucible from the upper cover of the upper crucible. The present invention can effectively reduce the temperature of the doping source, slowly release the doping source, improve the uniformity of the doping source release, and effectively solve the problem of unstable crystal form and quality degradation caused by the concentrated release of the doping source.

Description

Technical Field

[0001] The invention belongs to the technical field of semiconductors and relates to a crucible and a method for growing a p-type SiC single crystal. Background Art

[0002] The information disclosed in this background technology section is only intended to enhance the understanding of the overall background of the invention, and should not necessarily be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art.

[0003] The p-type SiC substrate is the basic material for preparing n-channel IGBTs. However, the p-type dopants in the common SiC have the characteristics of high vapor pressure and large ionization energy, which makes the preparation of p-type SiC substrates still have problems such as uneven doping, poor crystal stability, and high resistivity.

[0004] According to the inventor's research, from the perspective of the main doping technical means, the commonly used doping methods for growing p-type SiC using a PVT growth device include a dual induction heating zone doping method and a small crucible sealed slow release method. The main p-type doping elements are Al, B, etc. Since Al has the lowest ionization energy, Al has become the preferred doping element for preparing p-type SiC. The melting and boiling points of Al-containing compounds (Al4C3, Al2O3, etc.) are much lower than the temperature of the powder zone where the crystal grows, and it is difficult for traditional doping processes to achieve the purpose of uniformly releasing the Al source. The concentrated release of the Al source will lead to problems such as defect proliferation in the crystal, poor crystal stability, and uneven doping. The dual induction heating zone doping method is to place Al compounds with lower melting and boiling points in a heating zone with a lower temperature for high-temperature gasification, and place SiC powder that requires higher temperature sublimation in a high-temperature heating zone to achieve the purpose of uniform Al doping during the growth process. This method requires the equipment to be equipped with two independent heating systems to heat the SiC raw material sublimation zone and the doping source zone separately to achieve different temperatures between the two. This method requires a high configuration of the heating system, and there are problems such as mutual interference between the dual induction coils; at the same time, the "growth component backflow" phenomenon caused by the temperature gradient drive is very likely to occur during the single crystal growth process, which is not conducive to the growth of p-type SiC single crystals. The small crucible sealing rule physically seals the Al source at high temperature and releases it outward through the large vapor pressure of the Al compound. However, since the vapor pressure of the Al source is too large at high temperature, it is difficult to effectively control the release rate of Al only by relying on graphite material and thickness. Therefore, during the growth process, the Al source will still have the problem of premature release, resulting in extremely uneven Al doping concentration in the axial direction of the crystal. At the same time, the premature and concentrated release of the Al source will also cause large lattice distortion in the early stage, which will have an adverse effect on the crystal stability and crystal quality of the subsequently grown crystal.

[0005] Chinese patent CN113862789A discloses a crucible structure, device and method for preparing p-type 4H-SiC single crystal. According to the inventor's research, the invention adopts a dual induction coil heating method, and in the actual crystal growth process, the material components in the first crucible and the second crucible are in the same closed space, and the dopant distribution space in the second crucible is wider, and the edge area will be preferentially decomposed and released. Due to the consumption of the growth process, the vapor pressure generated by each component is in a dynamic state, and it cannot completely and effectively prevent the components used to grow SiC from being decomposed from SiC powder from flowing to the second crucible area. In addition, in the actual crystal growth process, the temperature of the central area of ​​the surface of the SiC powder in the first crucible is relatively low compared to the edge, and it is inevitable that the SiC powder will recrystallize at the position of the connecting channel mouth, affecting the transportation of the doping material components in the second crucible into the growth chamber, which is very likely to cause doping failure. In addition, the invention must use a dual induction coil as the heating system for single crystal growth, which has high requirements for the heating system, and it is easy to have problems such as the magnetic field interfering with each other during the operation of the dual induction coils, affecting the stability of the heating system.

[0006] Chinese patent CN108026663A discloses a method for preparing p-type 4H-SiC by double coil heating, using the second coil to achieve a lower temperature of the doping source, and realizing the slow and uniform release of the Al source (Al4C3). According to the inventor's research, its structural design is still to make the doping source and SiC powder in the same closed space. Since the pressure in each region is difficult to maintain balance, it is impossible to avoid the gas phase components such as Si2C, SiC2, and Si from the SiC powder area with a higher temperature to the Al source area with a lower temperature. The amount of transmission, resulting in SiC crystallization in the Al source area. And the distribution space of its doping source is wider, and the dopant at the edge of the crucible will preferentially decompose and release, which is not conducive to the uniform doping of the Al component. In addition, it is necessary to pass N2 into the method to maintain the stability of the p-type SiC crystal form, and N will introduce additional electron compensation holes in SiC. Since the energy level of the N element in SiC is shallow, a trace amount of N doping will appear with a high concentration of electrons, compensating holes, and therefore is not conducive to reducing the resistivity of the p-type SiC single crystal. The dual induction coil system used in this invention will cause the magnetic fields to interfere with each other during operation, affecting the stability of the heating system and the quality of the grown single crystal.

[0007] Chinese patent CN106894090B discloses a method for preparing high-quality, low-resistivity p-type SiC single crystals, which uses a small crucible to hold a doping source and place it in a powder area to grow a p-type SiC single crystal. However, the inventors found that the temperature of the powder area where the small crucible is placed is higher than the temperature at which the Al source is stably released, and the dopant and the crucible-grown SiC cannot be controlled separately. The small crucible alone cannot achieve the purpose of stable release, which is not conducive to the growth of p-type SiC with high doping uniformity. Summary of the invention

[0008] In order to address the deficiencies in the prior art, the purpose of the present invention is to provide a crucible and method for growing p-type SiC single crystals. The present invention can effectively reduce the temperature of the doping source, slowly release the doping source, improve the uniformity of the doping source release, and effectively solve the problem of unstable crystal form and quality degradation caused by concentrated release of the doping source.

[0009] In order to achieve the above object, the technical solution of the present invention is:

[0010] On the one hand, a crucible for growing a p-type SiC single crystal comprises an upper crucible, a lower crucible and a connecting rod, wherein the connecting rod is a hollow structure, one end of the connecting rod is connected to the lower end opening of the upper crucible, and the other end of the connecting rod is connected to the upper end opening of the lower crucible, an inner crucible is arranged in the lower part of the upper crucible, the inner crucible opening is upward, the height of the side wall of the inner crucible is less than the height of the side wall of the upper crucible, the space in the inner crucible is a SiC powder placement area, the space in the upper crucible above the inner crucible is a SiC single crystal growth area, a gap is formed between the inner crucible and the upper crucible, the lower end opening of the upper crucible is connected to the SiC single crystal growth area through the gap, and the upper cover of the upper crucible is arranged to allow protective gas to enter the upper crucible from the upper cover of the upper crucible.

[0011] In the present invention, by adjusting the length, diameter, material, etc. of the connecting rod, the temperature of the doping source can be effectively reduced, the doping source is released slowly, the uniformity of the doping source release is improved, and the problem of unstable crystal form and quality degradation caused by concentrated release of the doping source is effectively solved.

[0012] The crucible structure of the present invention allows the SiC powder placement area and the dopant placement area to be in an isolated state. By adjusting the length, diameter, material, wall thickness, etc. of the connecting rod between the upper crucible and the lower crucible, the purpose of separately adjusting the temperature of the SiC powder and the dopant can be achieved, effectively avoiding the problem of concentrated release of the dopant at an excessively high temperature. At the same time, by adjusting the channel width between the inner crucible and the inner wall of the upper crucible, the transport speed of the dopant gas phase component into the growth chamber can be effectively controlled to achieve controllable doping. By making the air inlet of the protective gas directly above the upper crucible, the characteristic that the protective gas partial pressure is higher than the partial pressure of the doping gas phase component is fully utilized to further suppress the concentrated release of the doping component.

[0013] On the other hand, a method for growing a p-type SiC single crystal provides the above-mentioned crucible for growing the p-type SiC single crystal, comprising the following steps:

[0014] Pressing the dopant into a block to obtain a dopant block, and fixing the dopant block in the lower crucible;

[0015] Placing SiC powder in the SiC powder placement area;

[0016] Placing a SiC seed crystal on top of the upper crucible;

[0017] The crucible for growing the p-type SiC single crystal after adding the materials is placed in a single crystal growth furnace for single crystal growth;

[0018] During the single crystal growth process, protective gas is introduced with a pressure of 1 to 50 mbar, the temperature of the upper crucible cover is 2100 to 2500°C, the temperature in the lower crucible is 1000 to 2300°C, the temperature of the upper crucible cover is higher than the temperature in the lower crucible, and the single crystal growth time is 30 to 200 hours.

[0019] The method of the present invention can prepare a single crystal p-type SiC substrate with a resistivity not exceeding 0.2Ω·cm, an intra-chip resistivity non-uniformity not exceeding 10%, and an inter-chip resistivity non-uniformity not exceeding 5%.

[0020] In a third aspect, a p-type SiC single crystal is obtained by the above-mentioned p-type SiC single crystal growth method.

[0021] The crucible in the present invention is not only suitable for p-type SiC single crystals, but also for doping with other impurities. Therefore, in the fourth aspect, a crucible for growing p-type SiC single crystals is used in preparing other doped SiC single crystals, and the other doped SiC single crystals are other doped SiC single crystals except p-type SiC single crystals.

[0022] The beneficial effects of the present invention are:

[0023] (1) The crucible of the present invention is divided into two independent parts, and a connecting rod design is introduced. By limiting the size and material of the connecting rod, two independent temperature fields of SiC powder and doping source are realized, and the coupling degree of the temperature fields of the two is reduced. While ensuring the normal sublimation and decomposition of SiC powder, the doping source can still be kept at a low temperature, thus avoiding the problem of concentrated high-temperature release of the doping source at the source, and facilitating the acquisition of uniformly doped crystals.

[0024] (2) The crucible in the present invention makes full use of the "skin effect" of medium frequency induction heating. The temperature of the channel between the inner crucible where the SiC powder is placed and the upper crucible wall is close to the temperature of the upper crucible wall. Therefore, the doping gas will not crystallize when it is transported into the growth chamber through this channel; it also ensures that the SiC growth component will not flow back and block the doping gas. Therefore, the crucible design in the present invention solves the problem of crystallization of the doping component transport channel in principle, which is conducive to the continuous release of dopants and obtains crystals with high doping uniformity.

[0025] (3) The crucible of the present invention is cleverly designed to allow the carrier gas to be introduced directly above the upper crucible, which can fully utilize the characteristic that the partial pressure of the carrier gas is higher than the partial pressure of the dopant, and can further suppress the concentrated release of the dopant, which is beneficial to eliminating defects such as polymorphic inclusions in the crystal caused by the concentrated release of the dopant.

[0026] (4) The crucible of the present invention can use a single-coil heating system, which can avoid the problems of unstable equipment operation and high equipment cost caused by double-coil heating.

[0027] (5) The crucible of the present invention has a simple structure and is also applicable to other dopants, especially to impurities with high vapor pressure, and is easy to promote and use. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0029] Figure 1 Schematic diagram of the structure of the crucible used in the embodiment of the present invention, wherein A, upper crucible, B, connecting rod, C, lower crucible, 1, seed crystal, 2, SiC single crystal growth area, 3, SiC powder placement area, 4, inner crucible, 5, gap, 6, support ring;

[0030] Figure 2 is a temperature field simulation diagram of a crucible used in an embodiment of the present invention;

[0031] Figure 3 The resistivity mapping result diagram of the wafer processed in Example 1 of the present invention represents the resistivity variation within the same substrate;

[0032] Figure 4 The graph of the crystal resistivity of the wafer processed according to Example 1 of the present invention as a function of the distance from the seed crystal represents the resistivity variation between wafers of the substrate processed from the same crystal. DETAILED DESCRIPTION

[0033] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0034] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0035] In order to solve the problem that the concentrated release of doping sources during the growth of p-type SiC single crystals leads to unstable crystal form and deteriorated quality, the present invention provides a crucible and a method for growing p-type SiC single crystals.

[0036] A typical embodiment of the present invention provides a crucible for growing p-type SiC single crystals, comprising an upper crucible, a lower crucible and a connecting rod, wherein the connecting rod is a hollow structure, one end of the connecting rod is connected to the lower end opening of the upper crucible, and the other end of the connecting rod is connected to the upper end opening of the lower crucible, an inner crucible is arranged in the lower part of the upper crucible, the inner crucible opening is upward, the height of the side wall of the inner crucible is less than the height of the side wall of the upper crucible, the space in the inner crucible is a SiC powder placement area, the space in the upper crucible above the inner crucible is a SiC single crystal growth area, a gap is formed between the inner crucible and the upper crucible, the lower end opening of the upper crucible is connected to the SiC single crystal growth area through the gap, and the upper cover of the upper crucible is arranged to allow protective gas to enter the upper crucible from the upper cover of the upper crucible.

[0037] In the present invention, by adjusting the length, diameter, material, etc. of the connecting rod, the temperature of the doping source can be effectively reduced, the doping source is released slowly, the uniformity of the doping source release is improved, and the problem of unstable crystal form and quality degradation caused by concentrated release of the doping source is effectively solved.

[0038] In some embodiments, a fixing pit is provided at the bottom of the lower crucible, and the fixing pit is used to fix and place the dopant block, so as to prevent the displacement of the dopant due to the shaking of the crucible during the assembly process before growth. Preferably, the fixing pit is located at the center of the bottom of the lower crucible.

[0039] The connecting rod is made of high temperature resistant, low thermal conductivity material, etc., in order to prevent the heat at the bottom of the upper crucible from being transferred to the lower crucible through the connecting rod; in some embodiments, the connecting rod is made of isostatic graphite, alumina ceramics, etc.

[0040] In some embodiments, the length of the connecting rod is 10-100 mm. The temperature inside the lower crucible can be adjusted by adjusting the length of the connecting rod, so that the temperature in the lower crucible can be adjusted between 1000-2300°C.

[0041] In some embodiments, the wall thickness of the connecting rod is 2-10 mm. If the wall thickness of the connecting rod is too thin, the strength of the connecting rod will be too low and it will be easy to be damaged; if the wall thickness of the connecting rod is too thick, it will be difficult to achieve the purpose of slowing down the heat transfer from the side wall of the crucible to the dopant placement area.

[0042] The height of the lower crucible of the present invention is 10-60 mm, and the diameter of the lower crucible is 50-100 mm.

[0043] In some embodiments, a support ring is disposed at the bottom of the upper crucible to support the inner crucible. The support ring may be in the shape of a Great Wall, a sawtooth shape, or a non-circumferential fulcrum.

[0044] In some embodiments, the connecting rod, the upper crucible, and the lower crucible are kept concentric.

[0045] In some embodiments, the inner crucible is concentric with the upper crucible. This structure can ensure the axial symmetry of the temperature field and prevent the temperature field from being biased.

[0046] In some embodiments, the width of the gap formed between the inner crucible and the inner wall of the upper crucible is 0.1 to 0.5 mm. The gap is used to transport doping components into the growth chamber. If the gap is too small, the resistance to transporting doping components into the growth chamber is too large, resulting in doping failure; if the gap is too large, the SiC growth gas phase components are easily transported to the lower crucible under the action of the temperature gradient, resulting in growth failure.

[0047] In some embodiments, the connection between the connecting rod and the upper crucible and the connection between the connecting rod and the lower crucible are both threaded connections, which are tightly connected to the bottom of the upper crucible and the top of the lower crucible through the threads to prevent the doping components from leaking out of the crucible.

[0048] The material of the upper crucible and its upper cover is generally isostatic graphite. Isostatic graphite can withstand high temperatures above 2500°C. At the same time, since isostatic graphite has a certain porosity, in order to ensure that the protective gas enters the upper crucible from the upper cover of the upper crucible, the protective gas is introduced from the reserved opening above the single crystal growth furnace and penetrates into the upper crucible through the upper cover. In order to further promote the carrier gas to enter the upper crucible through the upper cover of the upper crucible, air holes can be set on the upper cover of the upper crucible.

[0049] The materials of the connecting rod and the lower crucible are generally isostatically pressed graphite, alumina ceramics, etc.

[0050] Another embodiment of the present invention provides a method for growing a p-type SiC single crystal, providing a crucible for growing the p-type SiC single crystal, comprising the following steps:

[0051] Pressing the dopant into a block to obtain a dopant block, and fixing the dopant block in the lower crucible;

[0052] Placing SiC powder in the SiC powder placement area;

[0053] Placing a SiC seed crystal on top of the upper crucible;

[0054] The crucible for growing the p-type SiC single crystal after adding the materials is placed in a single crystal growth furnace for single crystal growth;

[0055] During the single crystal growth process, protective gas is introduced with a pressure of 1 to 50 mbar, the temperature of the upper crucible cover is 2100 to 2500°C, the temperature in the lower crucible is 1000 to 2300°C, the temperature of the upper crucible cover is higher than the temperature in the lower crucible, and the single crystal growth time is 30 to 200 hours.

[0056] In some embodiments, the compacting pressure of the dopant is not less than 10 MPa. The volume of the dopant block is 0.5 to 3.0 cm 3The reduction in the volume of the doping source keeps the temperature inside the entire dopant block as constant as possible, thereby promoting the stable release of dopants during the growth process.

[0057] In some embodiments, the dopant includes but is not limited to Al4C3, Al2O3, AlN or a combination thereof.

[0058] The seed crystal is placed on the seed crystal holder or the upper cover.

[0059] In some embodiments, the crucible is placed in a single crystal growth furnace, the growth chamber is evacuated to below 0.1 Pa, and then heated and a protective gas is introduced.

[0060] In some embodiments, the protective gas includes but is not limited to Ar, H2 or He, etc. The gas inlet of the protective gas is located just above the upper crucible, in order to further suppress the excessive upward transfer of the Al component gas.

[0061] In some embodiments, the heating system of the single crystal growth furnace is a single induction coil or multiple induction coils, preferably a single induction coil, in order to improve the equipment operation stability and reduce the equipment cost.

[0062] In some embodiments, the p-type SiC single crystal is subjected to cutting, grinding and polishing to obtain a p-type SiC single crystal substrate.

[0063] A third embodiment of the present invention provides a p-type SiC single crystal obtained by the above-mentioned method for growing a p-type SiC single crystal.

[0064] A fourth embodiment of the present invention provides an application of a crucible for growing a p-type SiC single crystal in preparing other doped SiC single crystals, wherein the other doped SiC single crystals are other doped SiC single crystals except the p-type SiC single crystals.

[0065] In order to enable those skilled in the art to more clearly understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below in combination with specific embodiments and comparative examples.

[0066] The crucible used in the following embodiments of the present invention for growing a p-type SiC single crystal is as follows: Figure 1As shown, it includes an upper crucible A, a lower crucible C and a connecting rod B. The connecting rod B is a hollow structure. One end of the connecting rod B is connected to the lower end opening of the upper crucible A, and the other end of the connecting rod B is connected to the upper end opening of the lower crucible C. The lower part of the upper crucible A is protected by a support ring 6, which supports an inner crucible 4. The inner crucible 4 opens upward, and the side wall height of the inner crucible 4 is less than the side wall height of the upper crucible A. The space in the inner crucible 4 is a SiC powder placement area 3, and the space in the upper crucible A above the inner crucible 4 is a SiC single crystal growth area 2. A gap 5 is formed between the inner crucible 4 and the upper crucible A, and the lower end opening of the upper crucible A is connected to the SiC single crystal growth area 2 through the gap 5. The upper crucible A and its upper cover are made of isostatic graphite. The isostatic graphite has porosity and can allow protective gas to pass through. The protective gas is introduced from the upper reserved opening of the single crystal growth furnace through the upper cover of the upper crucible A and penetrates into the growth crucible, and the seed crystal 1 is placed on the upper cover. The lower crucible C and the connecting rod B are made of isostatic graphite. A fixing pit is arranged at the bottom center of the lower crucible C, and the upper crucible A, the connecting rod B, the lower crucible C and the fixing pit are arranged concentrically.

[0067] The temperature field simulation diagram of the crucible is shown in Figure 2 As shown. When a single crystal grows, there are heating coils around both the upper and lower crucibles. However, 1) the length of the heating coils around the upper crucible is greater than that around the lower crucible; 2) the diameter, length, and material of the heating rod result in the lower crucible having a worse induction heating effect than the upper crucible. These two factors determine that the temperature of the lower crucible must be lower than that of the upper crucible.

[0068] Embodiment 1:

[0069] The method for growing a p-type SiC single crystal comprises the following steps:

[0070] 1) Weigh 10 g of Al4C3 powder using a high-precision balance, and use a press to apply a pressure of 10 MPa to compress the Al4C3 powder into a block.

[0071] 2) The compressed Al4C3 dopant is placed in the pit at the bottom of the lower crucible and fixed.

[0072] 3) The lower crucible and the upper crucible are tightly connected by an isostatic graphite connecting rod with a length of 100 mm and a wall thickness of 2 mm through a threaded structure.

[0073] 4) 3 kg of SiC powder was placed in the inner crucible and fixed with a Great Wall-shaped support ring structure. The gap between the inner crucible and the inner wall of the crucible was 0.1 mm.

[0074] 5) Place a 4-inch 4H-SiC seed crystal on the top of the upper crucible, with the carbon surface as the growth surface, and tighten the upper crucible cover.

[0075] 6) Place the crucible in a single crystal growth furnace and evacuate the growth chamber to below 0.1 Pa.

[0076] 7) Introduce protective gas Ar directly above the crucible, turn on the heating power supply, set the temperature of the upper crucible cover to 2100°C, the temperature inside the lower crucible to 1600°C, the pressure to 1 mbar, and keep warm for 300 hours to grow single crystals.

[0077] After the growth is completed, the protective gas is introduced to atmospheric pressure and the temperature is lowered to room temperature to obtain a 4-inch p-type 4H-SiC single crystal. The single crystal is cut, ground and polished to obtain a 4-inch p-type 4H-SiC substrate. The half-peak width of the diffraction peak of the p-type substrate tested by HRXRD is 20 arcsec, indicating that the crystal quality is good. The Raman mapping test shows that the 4H-SiC ratio of the p-type SiC substrate is 100%, and the resistivity tester shows that the resistivity of the substrate is 0.18Ω·cm, the resistivity inhomogeneity within the sheet is less than 5%, and the resistivity uniformity between sheets is not less than 3%. Figure 3 As shown. This shows that the prepared p-type SiC substrate has high quality and high electrical uniformity, and the substrate can be used to prepare high-power power electronic devices. The relationship between resistivity and the distance from the seed crystal (the distance from the seed crystal to the growing crystal as it grows thicker) is shown as Figure 4 As shown, it indicates that the inter-sheet resistivity of the substrate processed from the same crystal remains basically unchanged.

[0078] Embodiment 2:

[0079] The method for growing a p-type SiC single crystal comprises the following steps:

[0080] 1) Weigh 30 g of Al2O3 powder using a high-precision balance, and use a press to apply a pressure of 20 MPa to compress the Al4C3 powder into a block.

[0081] 2) The compressed Al4C3 dopant is placed in the pit at the bottom of the lower crucible and fixed.

[0082] 3) The lower crucible and the upper crucible are tightly connected by a 50 mm long, 4 mm thick alumina ceramic connecting rod through a threaded structure.

[0083] 4) 5 kg of SiC powder was placed in the inner crucible and fixed with a Great Wall-shaped support ring structure. The gap between the inner crucible and the inner wall of the crucible was 0.2 mm.

[0084] 5) Place an 8-inch 6H-SiC seed crystal on the top of the upper crucible, with the silicon surface as the growth surface, and tighten the upper crucible cover.

[0085] 6) Place the crucible in a single crystal growth furnace and evacuate the growth chamber to below 0.1 Pa.

[0086] 7) Introduce protective gas Ar directly above the crucible, turn on the heating power supply, set the temperature of the upper crucible cover to 2200°C, the temperature inside the lower crucible to 1500°C, the pressure to 50 mbar, and keep warm for 100 hours to grow single crystals.

[0087] After the growth is completed, the protective gas is introduced to atmospheric pressure and the temperature is lowered to room temperature to obtain an 8-inch p-type 6H-SiC single crystal. The single crystal is cut, ground and polished to obtain an 8-inch p-type 6H-SiC substrate. The half-peak width of the diffraction peak of the p-type substrate tested by HRXRD is 26 arcsec, indicating that the crystal quality is good. The Raman mapping test shows that the 6H-SiC ratio of the p-type SiC substrate is 100%, and the resistivity tester shows that the resistivity of the substrate is 0.082Ω·cm, the resistivity inhomogeneity within the sheet is less than 3%, and the resistivity inhomogeneity between sheets is less than 2%. It shows that the prepared p-type SiC substrate has high quality and high electrical uniformity. The substrate can be used to prepare high-power power electronic devices.

[0088] Embodiment 3:

[0089] The method for growing a p-type SiC single crystal comprises the following steps:

[0090] 1) Weigh 5 g of Al4C3 powder using a high-precision balance, and use a press to apply a pressure of 40 MPa to compress the Al4C3 powder into a block.

[0091] 2) The compressed Al4C3 dopant is placed in the pit at the bottom of the lower crucible and fixed.

[0092] 3) The lower crucible and the upper crucible are tightly connected by an isostatic graphite connecting rod with a length of 10 mm and a wall thickness of 10 mm through a threaded structure.

[0093] 4) Place 1 kg of SiC powder in the inner crucible and fix it with a Great Wall-shaped support ring structure. The gap between the inner crucible and the inner wall of the crucible is 0.5 mm.

[0094] 5) Place a 2-inch 15R-SiC seed crystal on the top of the upper crucible, with the silicon surface as the growth surface, and tighten the upper crucible cover.

[0095] 6) Place the crucible in a single crystal growth furnace and evacuate the growth chamber to 0.01 Pa.

[0096] 7) Introduce protective gas Ar directly above the crucible, turn on the heating power supply, set the temperature of the upper crucible cover to 2500°C, the temperature inside the lower crucible to 2300°C, the pressure to 5 mbar, and keep warm for 50 hours to grow single crystals.

[0097] After the growth is completed, the protective gas is introduced to atmospheric pressure and the temperature is lowered to room temperature to obtain a 2-inch p-type 15R-SiC single crystal. The single crystal is cut, ground and polished to obtain a 2-inch p-type 15R-SiC substrate. The half-peak width of the diffraction peak of the p-type substrate tested by HRXRD is 51arcsec, indicating that the crystal quality is good. The Raman mapping test shows that the 15R-SiC ratio of the p-type SiC substrate is 100%, and the resistivity tester shows that the resistivity of the substrate is 0.062Ω·cm, the resistivity inhomogeneity within the sheet is less than 8%, and the resistivity inhomogeneity between sheets is less than 5%. It shows that the prepared p-type SiC substrate has high quality and high electrical uniformity. The substrate can be used to prepare high-power power electronic devices.

[0098] Comparative Example 1:

[0099] The conditions are the same as those in Example 1, except that the gap between the inner crucible and the inner wall of the crucible is 10 mm; because the gap between the inner crucible and the upper crucible wall is too large, it cannot prevent the SiC powder from decomposing into Si2C, SiC2 and other components to transfer to the dopant placement area with lower temperature, resulting in the formation of a large amount of SiC crystals at the bottom of the lower crucible, affecting the stability of the growing components; at the same time, the gap between the inner crucible and the upper crucible wall is too large, causing the dopant components in the lower crucible to quickly reach the growth front, resulting in concentrated doping in the early stage of growth, leading to deterioration of crystal quality. After HRXRD test characterization, the half-peak width of the diffraction peak is 90 arcsec, and the crystal quality is poor. After Raman testing, the processed substrate has two crystal forms, 4H and 6H. The resistivity tester shows that the resistivity non-uniformity within the substrate sheet exceeds 20%, and the resistivity non-uniformity between sheets exceeds 50%. The poor quality of the substrate cannot be used for the preparation of related devices.

[0100] Comparative Example 2:

[0101] The conditions are the same as those in Example 1, except that the gap between the inner crucible and the inner wall of the crucible is 0.05 mm; since the gap between the inner crucible and the upper crucible wall is too small, the dopant in the lower crucible cannot be effectively transmitted to the growth chamber through the channel, resulting in too low a doping component in the growth chamber, causing doping failure. The resistivity of the grown crystal was tested, and the resistivity in the substrate was 10 5 Ω·cm, the substrate exhibits semi-insulating properties and cannot be used for the preparation of related high-power power electronic devices.

[0102] Comparative Example 3

[0103] The conditions are the same as those in Example 1, except that the length of the connecting rod is 5 mm, which cannot effectively reduce the temperature of the doping source area. The Al compound decomposes and releases prematurely, resulting in uneven Al doping. The initial release of Al affects the nucleation of a single crystal. After HRXRD test characterization, the half-peak width of the diffraction peak of the p-type SiC substrate is 122 arcsec, and the crystal quality is poor. After Raman testing, the processed SiC substrate has three crystal forms: 4H, 6H, and 15R. The resistivity tester shows that the resistivity non-uniformity within the substrate sheet exceeds 20%, and the resistivity non-uniformity between sheets exceeds 80%. The poor quality of the substrate cannot be used for the preparation of related high-power power electronic devices.

[0104] Comparative Example 4

[0105] The conditions are the same as those in Example 1, except that the length of the connecting rod is 150 mm, which results in a large temperature difference between the doping source in the lower crucible and the SiC powder in the upper crucible. The doping source temperature is too low to sublimate and decompose, resulting in doping failure. After HRXRD test characterization, the half-peak width of the diffraction peak of the p-type SiC substrate is 25 arcsec. After Raman test, the processed SiC substrate is 4H-SiC. The resistivity tester shows that the resistivity of the substrate is 10 6 Ω·cm, the substrate resistivity is relatively high and cannot be used for the preparation of related high-power power electronic devices.

[0106] Comparative Example 5

[0107] The conditions are the same as those in Example 1, except that the carrier gas is introduced into the chamber from the bottom of the crucible, causing the doping source at the bottom of the lower crucible to be carried into the growth chamber by the carrier gas, so that the concentration of the doping component is different before, during and after the growth. The half-peak width of the diffraction peak of the p-type substrate tested by HRXRD is 42 arcsec, indicating that the crystal quality is good. The Raman mapping test shows that the 4H-SiC ratio of the p-type SiC substrate is 100%, and the resistivity tester shows that the resistivity non-uniformity within the substrate sheet exceeds 20%, and the resistivity non-uniformity between sheets exceeds 40%. The substrate resistivity distribution is uneven and cannot be used for the preparation of related high-power power electronic devices.

[0108] Comparative Example 6

[0109] The conditions are the same as those in Example 1, except that the dopant has not been pressed by a press, resulting in a high chemical activity of the dopant and a fast decomposition rate, resulting in different concentrations of the doping components before, during and after growth. The HRXRD test shows that the half-peak width of the p-type substrate diffraction peak is 42 arcsec, indicating that the crystal quality is good. The Raman mapping test shows that the 4H-SiC ratio of the p-type SiC substrate is 100%, and the resistivity tester shows that the resistivity non-uniformity of the substrate sheet exceeds 15%, and the resistivity non-uniformity between sheets exceeds 30%. The substrate resistivity distribution is uneven and cannot be used for the preparation of related high-power power electronic devices.

[0110] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A crucible for growing a p-type SiC single crystal, characterized in that: The utility model comprises an upper crucible, a lower crucible and a connecting rod, wherein the connecting rod is a hollow structure, one end of the connecting rod is connected to the lower end opening of the upper crucible, and the other end of the connecting rod is connected to the upper end opening of the lower crucible. An inner crucible is arranged in the lower part of the upper crucible, the inner crucible opens upward, the side wall height of the inner crucible is less than the side wall height of the upper crucible, the space in the inner crucible is a SiC powder placement area, the space in the upper crucible above the inner crucible is a SiC single crystal growth area, a gap is formed between the inner crucible and the upper crucible, the lower end opening of the upper crucible is connected to the SiC single crystal growth area through the gap, and the upper cover of the upper crucible is arranged to enable protective gas to enter the upper crucible from the upper cover of the upper crucible.

2. The crucible for growing a p-type SiC single crystal according to claim 1, wherein: A fixing pit is provided at the bottom of the lower crucible, and the fixing pit is used to fix and place the dopant block; Alternatively, the connecting rod is made of isostatic graphite or alumina ceramic.

3. The crucible for growing a p-type SiC single crystal according to claim 1, wherein: The length of the connecting rod is 10 to 100 mm; Alternatively, the wall thickness of the connecting rod is 2 to 10 mm.

4. The crucible for growing a p-type SiC single crystal according to claim 1, wherein: A support ring is arranged at the bottom of the upper crucible, and the support ring supports the inner crucible; Or, the connecting rod, the upper crucible and the lower crucible are kept concentric; Or, the inner crucible is concentric with the upper crucible; Alternatively, the connection mode between the connecting rod and the upper crucible, and the connection mode between the connecting rod and the lower crucible are both threaded connections.

5. The crucible for growing a p-type SiC single crystal according to claim 1, wherein: The width of the gap formed between the inner crucible and the inner wall of the upper crucible is 0.1 to 0.5 mm.

6. A method for growing a p-type SiC single crystal, characterized in that: A crucible for growing a p-type SiC single crystal according to any one of claims 1 to 5 is provided, comprising the following steps: Pressing the dopant into a block to obtain a dopant block, and fixing the dopant block in the lower crucible; Placing SiC powder in the SiC powder placement area; Placing a SiC seed crystal on top of the upper crucible; The crucible for growing the p-type SiC single crystal after adding the materials is placed in a single crystal growth furnace for single crystal growth; During the single crystal growth process, protective gas is introduced with a pressure of 1 to 50 mbar, the temperature of the upper crucible cover is 2100 to 2500°C, the temperature in the lower crucible is 1000 to 2300°C, the temperature of the upper crucible cover is higher than the temperature in the lower crucible, and the single crystal growth time is 30 to 200 hours.

7. The method for growing a p-type SiC single crystal according to claim 6, wherein: The compacting pressure of the dopant is not less than 10MPa; Or, the dopant is Al4C3, Al2O3, AlN or a combination thereof; Alternatively, the crucible is placed in a single crystal growth furnace, the growth chamber is evacuated to below 0.1 Pa, and then heated and a protective gas is introduced.

8. The method for growing a p-type SiC single crystal according to claim 6, wherein: The protective gas is Ar, H2, He or any combination thereof; Or, the heating system of the single crystal growth furnace is a single induction coil or a plurality of induction coils; Alternatively, the p-type SiC single crystal is cut, ground and polished to obtain a p-type SiC single crystal substrate.

9. The method for growing a p-type SiC single crystal according to claim 6, wherein: The heating system of the single crystal growth furnace is a single induction coil.

10. Use of a crucible for growing a p-type SiC single crystal in preparing a doped SiC single crystal, wherein the doped SiC single crystal is an Al-doped p-type SiC single crystal.

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