Semi-insulating silicon carbide crystal and growth method and application thereof

Abstract

The invention relates to a semi-insulating silicon carbide crystal and a growth method and application thereof. The growth method sequentially comprises a charging step and a crystal growth step, the specific process of the charging step comprises the steps that crystal growth raw materials are assembled at the bottom of a charging device, the crystal growth raw materials comprise silicon carbide powder and doping agents, and a crystal growth raw material area is obtained; the dopant comprises a compound containing a deep energy level element; a first raw material layer, a second raw material layer and a third raw material layer are sequentially arranged in the crystal growth raw material area from top to bottom in the vertical direction by taking the direction vertical to the bottom surface of the charging device as the vertical direction; the doping concentrations of the dopants in the first raw material layer, the second raw material layer and the third raw material layer are increased in sequence. According to the growth method provided by the invention, the crystal growth raw material region is divided and the doping concentration of the crystal growth raw material region is designed, so that uniform distribution of deep-energy-level elements in the silicon carbide crystal is realized, and the semi-insulating silicon carbide crystal with uniformly distributed doping elements is obtained.

Description

Technical Field

[0001] The present invention relates to the technical field of silicon carbide crystal growth, and in particular to a semi-insulating silicon carbide crystal, a growth method thereof, and an application thereof. Background Art

[0002] Semi-insulating silicon carbide (SiC) substrates have higher bandgap energy, breakdown strength, and thermal conductivity compared to traditional silicon-based substrates, and are ideal materials for substrates used in gallium nitride-based devices. Currently, there is a wide demand in fields such as radar, high-voltage power stations, intelligent vehicles, and millimeter-wave communication.

[0003] Silicon carbide (SiC) single crystals are currently mainly grown and prepared by physical vapor transport (PVT). In order to obtain semi-insulating SiC single crystals, there are currently two methods based on the PVT method: The first method is to control the concentration of shallow-level impurity elements such as nitrogen and boron in the growth system within 1E15 cm -3 to obtain high-purity semi-insulating (HPSI) SiC crystals. However, due to the inability to completely and continuously isolate nitrogen in the growth working environment, and boron being a co-existing impurity of the graphite component, it is extremely difficult to reduce the concentration of shallow-level elements in the system at the technical level. And when the concentration of intrinsic point defects is too low, it cannot meet the compensation for a higher concentration of shallow-level impurity elements; The second method is to dope deep-level elements into silicon carbide. Deep-level elements such as V, as amphoteric elements, can both act as deep-level donors to compensate for shallow-level impurity element acceptors and as deep-level acceptors to compensate for shallow-level impurity element donors. The second doping method is simpler than the first method for preparing semi-insulating materials, with lower requirements for equipment modification, technical difficulty, and material purity, and is suitable for commercial production.

[0004] However, the uniform distribution of deep-level elements in SiC single crystals is a challenging problem. For example, the sublimation rate of vanadium (V) is faster than that of SiC powder during the high-temperature growth of SiC, and the maximum solubility of V in SiC single crystals is (3-5)E17 cm -3 , and the doping of V is likely to cause the precipitation of solid V in SiC single crystals, resulting in non-uniform distribution of V elements, and thus the electrical properties of the prepared SiC semi-insulating substrate wafers are inconsistent.

[0005] At present, the existing technology mainly uses micro-crucibles to fill dopants or mix dopants with SiC powder. Dong-Hun Lee et al. (Vanadium-doped semi-insulating SiC single crystal growth by usingporous graphite) use porous graphite to dope vanadium elements to grow and prepare semi-insulating silicon carbide crystals, fill vanadium carbide powder into the porous graphite and place it at the bottom of the crucible, and achieve vanadium doping through high-temperature sublimation transmission, or mix silicon carbide powder and vanadium carbide powder, cover the mixed powder with a porous graphite plate, and grow crystals; this prior art uses porous graphite to adjust the temperature field in the growth environment, so that the temperature distribution in the raw material area is more uniform, and at the same time, the temperature inside the growth chamber is reduced, which is conducive to maintaining the convex interface growth of the seed crystal, and the porous graphite stabilizes the gas flow rate and inhibits the excessive transmission of crystal edge materials. M.Bickermann et al. (On the preparation of semi-insulating SiC bulkcrystals by the PVT technique) add solid compounds to undoped silicon carbide raw materials to achieve boron or vanadium doping of crystals. However, the method disclosed in the above prior art still cannot well control the uniform doping in the SiC single crystal due to the corrosion of graphite in the late growth stage and the nonlinear characteristics of the doping element released by the doping in the powder.

[0006] Therefore, how to provide a growth method that can improve the uneven distribution of deep energy level elements in semi-insulating silicon carbide crystals has become a problem that needs to be solved urgently. Summary of the invention

[0007] In order to solve the above technical problems, the purpose of the present invention is to provide a semi-insulating silicon carbide crystal and its growth method and application. The growth method provided by the present invention achieves uniform distribution of deep energy level elements in the dopant in the silicon carbide crystal by dividing the crystal growth raw material area and designing the doping concentration of the dopant in the crystal growth raw material area, thereby obtaining a semi-insulating silicon carbide crystal with uniform distribution of doping elements.

[0008] To achieve this object, the present invention adopts the following technical solutions:

[0009] In a first aspect, the present invention provides a method for growing a semi-insulating silicon carbide crystal, the growth method sequentially comprising a charging step and a crystal growing step;

[0010] The specific process of the charging step includes: assembling crystal growth raw materials at the bottom of the charging device, the crystal growth raw materials including silicon carbide powder and dopants to obtain a crystal growth raw material area; the dopants include compounds containing deep energy level elements;

[0011] Taking the direction perpendicular to the bottom surface of the charging device as the vertical direction, a first raw material layer, a second raw material layer, and a third raw material layer are sequentially arranged in the vertical direction in the crystal growth raw material area; the doping concentrations of the dopants in the first raw material layer, the second raw material layer, and the third raw material layer increase sequentially in order.

[0012] In the growth method provided by the present invention, a dopant containing deep-level elements is introduced into the silicon carbide powder, and in the vertical direction of the charging device, the crystal growth raw material area assembled at the bottom of the charging device is divided into three raw material layers, and the doping concentrations of the dopants in each raw material layer are designed. Since the crystal growth step of the silicon carbide crystal is realized by heating the crystal growth raw material at the bottom for vapor sublimation, and the formed gas transfers from bottom to top to the surface of the raw material area and reaches the top of the device, and the deep-level elements have a faster sublimation rate than the silicon carbide powder during the high-temperature growth process, the sublimation rate of the powder in the upper raw material layer to the top of the device is faster. Therefore, the present invention designs that the doping concentrations of the dopants in the three raw material layers from top to bottom increase sequentially. On the one hand, it can delay the rapid sublimation of the high-concentration doping elements in the lower layer. On the other hand, it can enable the doping elements in the lower layer to carry out the powder in the upper layer when sublimating from the bottom of the crucible, so that the dopants in the crystal growth raw material area can sublimate to the top of the device with a uniform doping concentration, stabilizing the doping concentration of the dopant in the device cavity, thereby making the distribution of the deep-level elements doped inside the silicon carbide crystal more uniform during the crystal growth process, and further obtaining a semi-insulating silicon carbide crystal with a uniform doping structure. In addition, the deep-level elements introduced by the present invention dope the silicon carbide crystal, and can cooperate with the intrinsic point defects formed during the crystal growth process to compensate for shallow energy impurities, so as to prepare a semi-insulating silicon carbide crystal with excellent performance.

[0013] Preferably, the doping concentrations of the dopants in the first raw material layer, the second raw material layer, and the third raw material layer are respectively denoted as C T 、C M and C B , where C M satisfies 2C T -10C T , for example 2C T 、3C T 、4C T 、5C T 、6C T 、7C T 、8C T 、9C T or 10C T etc., C B satisfies 10C T -30C T , for example 10C T 、12C T 、14CT 、16C T 、18C T 、20C T 、22C T 、24C T 、26C T 、28C T or 30C T etc.

[0014] In the present invention, by regulating the relationship between the doping concentrations of the dopants in the first raw material layer, the second raw material layer, and the third raw material layer, it is possible to make the concentration of the doped elements released from the powder in the ingot raw material area linear during the crystal growth process, and the concentration of the deep-level elements sublimated into the cavity of the loading device more uniform, so that the distribution of the doped elements in the grown semi-insulating silicon carbide crystal is more uniform.

[0015] Preferably, in the vertical direction, the height ratio of the first raw material layer, the second raw material layer, and the third raw material layer is (0.5 - 1.5):(0.5 - 1.5):(0.5 - 1.5), where the selection range of the first raw material layer is 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, or 1.5, etc.; the selection range of the second raw material layer is 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, or 1.5, etc.; the selection range of the third raw material layer is 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, or 1.5, etc.

[0016] Preferably, with the direction parallel to the bottom surface of the loading device as the horizontal direction, each raw material layer includes an inner raw material area and an outer raw material area covering the side surface of the inner raw material area in the horizontal direction, and the doping concentration of the dopant in the outer raw material area is lower than the doping concentration of the dopant in the inner raw material area.

[0017] In the present invention, each raw material layer is further divided into an inner raw material area and an outer raw material area in the horizontal direction, and the doping concentration of the dopant in the outer raw material area of each raw material layer is further adjusted to be lower than that in the inner raw material area. This is because the outer raw material area is close to the side wall of the charging device, and the temperature in the area close to the side wall is higher, presenting a temperature gradient in the horizontal direction. As a result, the growth and sublimation rates of the powder in the outer raw material area in the same horizontal direction are faster. Moreover, the sublimation rate of deep-level elements during high-temperature growth is faster than that of silicon carbide powder. Therefore, further adjusting the doping concentration of the dopant in the outer raw material area to be lower than that in the inner raw material area can ensure that the doping concentrations of the deep-level elements sublimated to the top of the device cavity in the inner and outer sides of the same raw material layer are uniform, so that during the subsequent crystal growth process, the deep-level doping elements can be evenly distributed in the silicon carbide crystal.

[0018] Preferably, the ingot raw materials in the ingot raw material area are divided into six regions in total.

[0019] Preferably, in the charging step, the third raw material layer, the second raw material layer, and the first raw material layer are sequentially loaded from the bottom surface of the charging device.

[0020] Preferably, during the assembly process of each raw material layer, a graphite cylinder is placed at the center of the charging device to divide each raw material layer into an inner area and an outer area, and the ingot raw materials with corresponding doping concentrations are filled into the inner raw material area and the outer raw material area respectively.

[0021] Preferably, in each raw material layer, the doping concentration of the dopant in the outer raw material area is denoted as C O , and the doping concentration of the dopant in the inner raw material area is denoted as C I , where C I satisfies 5C O - 10C O , for example, 5C O , 6C O , 7C O , 8C O , 9C O or 10C O etc.

[0022] The present invention further adjusts the relationship between the doping concentrations of the dopants in the inner raw material area and the outer raw material area, so as to make the doping concentrations of the deep-level elements sublimated from the inner and outer sides of each raw material layer into the cavity more uniform, and further make the distribution of the deep-level doping elements in the obtained semi-insulating silicon carbide crystal more uniform.

[0023] Preferably, in each region of the crystal growth raw material region, based on the total mass of the crystal growth raw material being 100 wt%, the doping concentration of the dopant is 0.01 - 3 wt%, such as 0.01 wt%, 0.05 wt%, 0.1 wt%, 0.2 wt%, 0.4 wt%, 0.6 wt%, 0.8 wt%, 1.0 wt%, 1.2 wt%, 1.4 wt%, 1.6 wt%, 1.8 wt%, 2.0 wt%, 2.2 wt%, 2.4 wt%, 2.6 wt%, 2.8 wt% or 3 wt%, etc.

[0024] In the present invention, the statement "in each region of the crystal growth raw material region, based on the total mass of the crystal growth raw material being 100 wt%, the doping concentration of the dopant is 0.01 - 3 wt%" means that the doping concentration of the dopant in the crystal growth raw material region all meets the above range, that is, the doping concentration of the dopant in the region with the lowest doping concentration (i.e., the outer raw material region of the first raw material layer) is above 0.01 wt%, and the doping concentration of the dopant in the region with the highest doping concentration (i.e., the inner raw material region of the third raw material layer) is below 3 wt%.

[0025] The present invention regulates the doping concentration of the dopant in the crystal growth raw material region within a specific range, aiming to prevent the precipitation of deep-level doping elements in the form of solid particles in the silicon carbide crystal when the concentration is too high.

[0026] Preferably, in each raw material layer, the ratio of the diameter of the inner raw material region to the inner diameter of the side surface of the charging device is independently selected from 1:(1.5 - 2), such as 1:1.5, 1:1.6, 1:1.7, 1:1.8, 1:1.9 or 1:2, etc.

[0027] Preferably, the diameters of the inner raw material regions in the first raw material layer, the second raw material layer, and the third raw material layer are equal.

[0028] Preferably, in each raw material layer, the ratio of the diameter of the inner raw material region to the outer diameter of the outer raw material region is independently selected from 1:(1.5 - 2), such as 1:1.5, 1:1.6, 1:1.7, 1:1.8, 1:1.9 or 1:2, etc.

[0029] Preferably, the outer diameters of the outer raw material regions in the first raw material layer, the second raw material layer, and the third raw material layer are equal.

[0030] Preferably, the average particle size of the silicon carbide powder is 6 - 100 mesh, such as 6 mesh, 10 mesh, 20 mesh, 30 mesh, 40 mesh, 50 mesh, 60 mesh, 70 mesh, 80 mesh, 90 mesh or 100 mesh, etc.

[0031] Preferably, the purity of the silicon carbide powder is above 6N, such as 6N, 7N or 8N, etc.

[0032] Preferably, the deep-level element includes any one or a combination of at least two of vanadium, titanium, chromium, cobalt or nickel.

[0033] Preferably, the dopant includes any one or a combination of at least two of vanadium carbide, vanadium oxide, titanium oxide, chromium oxide, nickel carbide, cobalt carbide or cobalt oxide.

[0034] Preferably, a first wire mesh is provided on the surface of the first raw material layer on the side away from the second raw material layer.

[0035] Preferably, a second wire mesh is provided between the first raw material layer and the second raw material layer.

[0036] Preferably, a third wire mesh is provided between the second raw material layer and the third raw material layer.

[0037] In the present invention, wire meshes are provided above each raw material layer. On the one hand, the presence of the wire meshes can control the sublimation of the doped elements and the silicon carbide powder, making the distribution of the doped elements in the silicon carbide more uniform and reducing the number of carbon coatings in the silicon carbide crystal; on the other hand, the wire meshes provided above each layer can serve as a heat conduction heat source, which is beneficial to the gas-phase sublimation and transmission of the silicon carbide powder in each layer, thereby promoting the preparation of semi-insulating silicon carbide crystals.

[0038] Preferably, the first wire mesh, the second wire mesh and the third wire mesh are all circular sheets.

[0039] Preferably, in the vertical direction, the thicknesses of the first wire mesh, the second wire mesh and the third wire mesh are independently selected from 1-2 mm, such as 1 mm, 1.2 mm, 1.4 mm, 1.6 mm, 1.8 mm or 2 mm, etc.

[0040] Preferably, the mesh numbers of the first wire mesh, the second wire mesh and the third wire mesh are independently selected from 50-500 meshes, such as 50 meshes, 100 meshes, 150 meshes, 200 meshes, 250 meshes, 300 meshes, 350 meshes, 400 meshes, 450 meshes or 500 meshes, etc.

[0041] Preferably, the diameters of the first wire mesh, the second wire mesh and the third wire mesh are equal to the inner diameter of the side surface of the charging device.

[0042] Preferably, the materials of the first wire mesh, the second wire mesh and the third wire mesh are independently selected from any one of high-temperature resistant metals or high-temperature resistant metal carbides.

[0043] Preferably, the high-temperature resistant metal includes any one of tantalum metal, tungsten metal or niobium metal.

[0044] Preferably, the high-temperature resistant metal carbide includes any one of niobium carbide, tantalum carbide, titanium carbide, or tungsten carbide.

[0045] Preferably, a perforated plate is further disposed above the side of the first wire mesh away from the first raw material layer.

[0046] In the present invention, arranging the perforated plate above the first wire mesh can further improve the uniformity of the distribution of doped elements in the prepared silicon carbide crystal, and by cooperating the perforated plate with the wire mesh, it is beneficial to reduce the number of carbon inclusions in the prepared semi-insulating silicon carbide crystal.

[0047] Preferably, in the vertical direction, the thickness of the perforated plate is 1-5 mm, such as 1 mm, 1.5 mm, 2 mm, 2.5 mm, 3 mm, 3.5 mm, 4 mm, 4.5 mm, or 5 mm, etc.

[0048] Preferably, the diameter of the perforated plate is equal to the inner diameter of the side surface of the charging device.

[0049] Preferably, the porosity of the perforated plate is 30-70%, such as 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, or 70%, etc.

[0050] Preferably, the perforated plate and the first wire mesh are spaced apart in the vertical direction, and the distance between the perforated plate and the first wire mesh in the vertical direction is 2-5 mm, such as 2 mm, 2.5 mm, 3 mm, 3.5 mm, 4 mm, 4.5 mm, or 5 mm, etc.

[0051] In the present invention, controlling the spacing between the perforated plate and the first wire mesh can reduce the corrosion of the wire mesh on the perforated plate at high temperature, improve the service life of the perforated plate, and at the same time avoid the influence of the corrosion of the perforated plate on the growth quality and purity of the obtained semi-insulating silicon carbide crystal.

[0052] Preferably, the perforated plate includes a high-temperature resistant perforated plate.

[0053] Preferably, the material of the high-temperature resistant perforated plate is any one of a porous ceramic plate, a porous graphite plate, or a porous silicon carbide plate.

[0054] Preferably, the charging step further includes: placing a silicon carbide seed crystal on the top of the charging device.

[0055] Preferably, the crystal form of the silicon carbide seed crystal includes any one of the 4H silicon carbide crystal form or the 6H silicon carbide crystal form.

[0056] Preferably, the silicon carbide seed crystal includes a 0° orientation silicon carbide seed crystal.

[0057] Preferably, the specific process of the crystal growth step includes: placing the assembled loading device in a crystal growth device, evacuating the crystal growth device and then introducing an inert gas, and heating the loading device to grow a silicon carbide seed crystal.

[0058] Preferably, in the crystal growth step, the pressure of the crystal growth device after introducing the inert gas is 100 - 1000 Pa, such as 100 Pa, 200 Pa, 300 Pa, 400 Pa, 500 Pa, 600 Pa, 700 Pa, 800 Pa, 900 Pa or 1000 Pa, etc.

[0059] Preferably, the inert gas includes argon.

[0060] Preferably, in the crystal growth step, the loading device is heated to a temperature of 2100 - 2200 °C at the top of the loading device, such as 2100 °C, 2110 °C, 2120 °C, 2130 °C, 2140 °C, 2150 °C, 2160 °C, 2170 °C, 2180 °C, 2190 °C or 2200 °C, etc.

[0061] In the present invention, "heating the loading device to a temperature of 2100 - 2200 °C at the top of the loading device" means heating to a temperature of 2100 - 2200 °C at the center of the upper surface of the loading device.

[0062] Preferably, during the growth of the silicon carbide seed crystal, the pressure of the crystal growth device is maintained at 100 - 1000 Pa, such as 100 Pa, 200 Pa, 300 Pa, 400 Pa, 500 Pa, 600 Pa, 700 Pa, 800 Pa, 900 Pa or 1000 Pa, etc.

[0063] Preferably, during the growth of the silicon carbide seed crystal, the top temperature of the crystal growth device is maintained at 2100 - 2200 °C, such as 2100 °C, 2110 °C, 2120 °C, 2130 °C, 2140 °C, 2150 °C, 2160 °C, 2170 °C, 2180 °C, 2190 °C or 2200 °C, etc.

[0064] Preferably, the growth time of the silicon carbide seed crystal is 80 - 120 h, such as 80 h, 90 h, 100 h, 110 h or 120 h, etc.

[0065] Preferably, the loading device includes a graphite crucible.

[0066] Preferably, the crystal growth device includes a PVT induction coil growth furnace (physical vapor transport induction coil growth furnace).

[0067] Preferably, the crystal growth apparatus includes the furnace body, and the charging device and the induction coil disposed inside the furnace body, and the induction coil is disposed on the side of the charging device.

[0068] In the present invention, the height of the induction coil is not specifically limited. Only by adjusting the position of the induction coil, the overall high-temperature region of the graphite crucible can be located in the height region corresponding to the third raw material layer and the second raw material layer in the crystal growth raw material region.

[0069] Preferably, the growth method further includes annealing after the crystal growth step.

[0070] In the present invention, annealing the grown crystal after the crystal growth step is beneficial to promoting the increase of intrinsic point defects, so that the intrinsic point defects can cooperate with deep-level elements to compensate for shallow-level impurities, thereby promoting the preparation of semi-insulating silicon carbide crystals.

[0071] Preferably, the pressure of the annealing is 70000 - 90000 Pa, such as 70000 Pa, 75000 Pa, 80000 Pa, 85000 Pa or 90000 Pa, etc.

[0072] Preferably, the power of the annealing is 0.8 - 0.9 times the power of the crystal growth step, such as 0.8, 0.85 or 0.9, etc.

[0073] In the present invention, "the power of the annealing is 0.8 - 0.9 times the power of the crystal growth step" means that the power in the annealing stage is set to 0.8 - 0.9 times the power corresponding to maintaining the top temperature of the charging device at 2100 - 2200 °C in the crystal growth step.

[0074] Preferably, the time of the annealing is 15 - 25 h, such as 15 h, 16 h, 17 h, 18 h, 19 h, 20 h, 21 h, 22 h, 23 h, 24 h or 25 h, etc.

[0075] In a second aspect, the present invention provides a semi-insulating silicon carbide crystal, which is prepared by the growth method according to the first aspect.

[0076] The semi-insulating silicon carbide crystal provided by the present invention is prepared by a specific growth method, and has deep-level element doping therein. The deep-level elements are uniformly distributed in the semi-insulating silicon carbide crystal, and cooperate with the intrinsic point defects in the crystal to compensate for shallow-level impurities, so that the semi-insulating silicon carbide crystal has more excellent performance.

[0077] In a third aspect, the present invention provides an application of the semi-insulating silicon carbide crystal according to the second aspect, and the semi-insulating silicon carbide crystal is applied to radar, high-voltage power stations, intelligent vehicles or millimeter-wave communication.

[0078] The semi-insulating silicon carbide crystal provided by the present invention is applicable to any application field that can be conceived by those skilled in the art.

[0079] Compared with the prior art, the present invention has at least the following beneficial effects:

[0080] (1) In the growth method provided by the present invention, a dopant containing deep-level elements is introduced into the silicon carbide powder, and in the vertical direction of the charging device, the long crystal raw material area assembled at the bottom of the charging device is divided into three raw material layers, and the doping concentrations of the dopants in each raw material layer are designed. It is designed that the doping concentrations of the dopants in the three raw material layers from top to bottom increase in sequence, which can delay the rapid sublimation of the high-concentration doped elements in the lower layer, so that the dopants in the long crystal raw material area can sublime to the top of the device with a uniform doping concentration, and stabilize the doping concentration of the dopants in the device cavity, thereby making the distribution of the deep-level elements doped inside the silicon carbide crystal more uniform during the crystal growth process, and obtaining a semi-insulating silicon carbide crystal with a uniform doping structure. In addition, the deep-level elements introduced by the present invention dope the silicon carbide crystal, which can cooperate with the intrinsic point defects formed during the crystal growth process to compensate for shallow energy impurities, so as to prepare a semi-insulating silicon carbide crystal with excellent performance.

[0081] (2) The semi-insulating silicon carbide crystal provided by the present invention is prepared by a specific growth method, and has deep-level element doping inside. Among them, the deep-level elements are uniformly distributed in the semi-insulating silicon carbide crystal, and they cooperate with the intrinsic point defects in the crystal to compensate for shallow-level impurities, so that the semi-insulating silicon carbide crystal has more excellent performance. Description of the Drawings

[0082] Figure 1 is a schematic front sectional structure view of the charging device after the raw materials are assembled provided by the present invention.

[0083] Figure 2 is a schematic top view structure of the first raw material layer in the long crystal raw material area provided by the present invention.

[0084] Among them, 1, graphite tray; 2, first raw material layer; 2-1, first inner raw material area; 2-2, first outer raw material area; 3, second raw material layer; 3-1, second inner raw material area; 3-2, second outer raw material area; 4, third raw material layer; 4-1, third inner raw material area; 4-2, third outer raw material area; 5, first wire mesh; 6, second wire mesh; 7, third wire mesh; 8, perforated plate; X, horizontal direction; Y, vertical direction. Detailed Embodiments

[0085] The technical solution of the present invention will be further described below in conjunction with the accompanying drawings and through specific embodiments. However, the following examples are only simple examples of the present invention and do not represent or limit the scope of the protection of the present invention. The scope of protection of the present invention shall be subject to the claims.

[0086] In a specific embodiment, the method for growing a semi-insulating silicon carbide crystal provided by the present invention is prepared by using a charging device after assembling the raw materials as shown in Figure 1 As shown in Figure 1 As shown, a crystal growth raw material area is provided at the bottom of the charging device, and a graphite support 1 is provided at the top of the charging device. The silicon carbide seed crystal is fixedly placed on the graphite support 1.

[0087] Taking the direction perpendicular to the bottom surface of the charging device as the vertical direction Y, the crystal growth raw material area is sequentially provided with a first raw material layer 2, a second raw material layer 3, and a third raw material layer 4 from top to bottom in the vertical direction Y. Taking the direction parallel to the bottom surface of the charging device as the horizontal direction X, the first raw material layer 2 is divided into a first inner raw material area 2-1 and a first outer raw material area 2-2 in the horizontal direction X. Specifically, the top view structural schematic diagram is as shown in Figure 2 As shown, the second raw material layer 3 is divided into a second inner raw material area 3-1 and a second outer raw material area 3-2 in the horizontal direction X, and the third raw material layer 4 is divided into a third inner raw material area 4-1 and a third outer raw material area 4-2 in the horizontal direction X. The crystal growth raw materials in the crystal growth raw material area are divided into six regions in total. In each raw material layer, the outer raw material area is arranged to cover the side surface of the inner raw material area.

[0088] A first wire mesh 5 is further provided on the surface of the first raw material layer 2 on the side away from the second raw material layer 3. A second wire mesh 6 is further provided between the first raw material layer 2 and the second raw material layer 3. A third wire mesh 7 is further provided between the second raw material layer 3 and the third raw material layer 4. The first wire mesh 5, the second wire mesh 6, and the third wire mesh 7 are all circular sheets, and their diameters are all equal to the inner diameter of the side surface of the charging device. A perforated plate 8 is further provided above the side of the first wire mesh 5 away from the first raw material layer 2. The diameter of the perforated plate 8 is equal to the inner diameter of the side surface of the charging device. The perforated plate 8 and the first wire mesh 5 are arranged at intervals in the vertical direction Y.

[0089] In the vertical direction Y, the height ratio of the first raw material layer 2, the second raw material layer 3, and the third raw material layer 4 is (0.5 - 1.5):(0.5 - 1.5):(0.5 - 1.5); the ratio of the diameter of the first inner raw material area 2-1, the second inner raw material area 3-1, and the third inner raw material area 4-1 to the bottom diameter of the charging device is independently selected from 1:(1.5 - 2), and the ratio of the diameter of the first inner raw material area 2-1, the second inner raw material area 3-1, and the third inner raw material area 4-1 to the outer diameter of the first outer raw material area 2-2, the second outer raw material area 3-2, and the third outer raw material area 4-2 is independently selected from 1:(1.5 - 2). In the vertical direction Y, the thicknesses of the first wire mesh 5, the second wire mesh 6, and the third wire mesh 7 are independently selected from 1 - 2 mm, the thickness of the porous plate 8 is 1 - 5 mm, and the porous plate 8 and the first wire mesh 5 are spaced apart in the vertical direction Y, and the spacing in the vertical direction Y is 2 - 5 mm. The mesh numbers of the first wire mesh 5, the second wire mesh 6, and the third wire mesh 7 are independently selected from 50 - 500 meshes; the porosity of the porous plate 8 is 30 - 70%.

[0090] The PVT induction coil growth furnace used in the following examples includes a furnace body, and an assembled graphite crucible and induction coil located inside the furnace body. The induction coil is arranged on the side of the graphite crucible, and the position of the induction coil is adjusted so that the overall high-temperature zone position of the graphite crucible is in the height regions corresponding to the third raw material layer and the second raw material layer in the crystal growth raw material area.

[0091] For the mixture composed of the dopant and silicon carbide powder involved in the following examples, the silicon carbide powder and the dopant with different doping concentrations are mixed evenly by a ball mill. The mixing speed is 200 rpm, and the mixing time is 5 h.

[0092] Example 1

[0093] This example provides a method for growing semi-insulating silicon carbide crystals, including the following steps:

[0094] (1) Loading: Assemble the crystal growth raw materials at the bottom of the graphite crucible. The crystal growth raw materials include silicon carbide powder and vanadium carbide dopant to obtain a crystal growth raw material area. Among them, the average particle size of the silicon carbide powder is 50 meshes, and the purity is 6N; place a 4H silicon carbide crystal form on the graphite support at the top of the graphite crucible, and the silicon carbide seed crystal is a 0° oriented silicon carbide seed crystal.

[0095] Wherein, taking the bottom surface perpendicular to the graphite crucible as the vertical direction, in the crystal growth raw material area, a first raw material layer, a second raw material layer, and a third raw material layer with a height ratio of 1:1:1 are sequentially arranged from top to bottom in the vertical direction. Taking the direction parallel to the bottom surface of the graphite crucible as the horizontal direction, the first raw material layer, the second raw material layer, and the third raw material layer are each provided with an inner raw material area and an outer raw material area covering the side surface of the inner raw material area in the horizontal direction. The crystal growth raw materials in the crystal growth raw material area are divided into six regions in total. In each raw material layer, the ratio of the diameter of the inner raw material area to the inner diameter of the side surface of the graphite crucible is 1:2, and the ratio of the diameter of the inner raw material area to the outer diameter of the outer raw material area is also 1:2.

[0096] The doping concentrations of vanadium carbide dopants in the first raw material layer, the second raw material layer, and the third raw material layer are respectively denoted as C T , C M and C B , where C M satisfies 5C T , C B satisfies 15C T ; in each raw material layer, the doping concentration of vanadium carbide dopant in the outer raw material area is denoted as C O , and the doping concentration of vanadium carbide dopant in the inner raw material area is denoted as C I , where C I all satisfy 8C O ; taking the total mass of the crystal growth raw materials in the outer raw material area of the first raw material layer as 100 wt%, the doping concentration of vanadium carbide dopant in the outer raw material area of the first raw material layer is 0.02 wt%.

[0097] A first wire mesh is further provided on the surface of the first raw material layer on the side away from the second raw material layer. A second wire mesh is provided between the first raw material layer and the second raw material layer, and a third wire mesh is provided between the second raw material layer and the third raw material layer. The diameters of the first wire mesh, the second wire mesh, and the third wire mesh are equal to the inner diameter of the side surface of the graphite crucible. The thicknesses of the first wire mesh, the second wire mesh, and the third wire mesh in the vertical direction are all 1.5 mm, their materials are all tantalum metal, and their mesh numbers are all 200 meshes; a porous ceramic plate with a porosity of 30% is further provided above the side away from the first raw material layer of the first wire mesh, its thickness in the vertical direction is 3 mm, the diameter of the porous ceramic plate is equal to the inner diameter of the side surface of the graphite crucible, and the porous ceramic plate and the first wire mesh are spaced apart in the vertical direction, and the distance between them in the vertical direction is 3 mm.

[0098] Specifically, the charging process is as follows: First, place a graphite cylinder in the central area of the bottom surface of the graphite crucible. Divide the bottom of the graphite crucible into an inner raw material area and an outer raw material area. Lay a mixture composed of vanadium carbide dopant and silicon carbide powder corresponding to the doping concentration of the third raw material layer on the inner and outer raw material areas on the bottom surface of the graphite crucible to obtain the third raw material layer. Then, take out the graphite cylinder and place a third wire mesh on the third raw material layer. Secondly, place the graphite cylinder again in the central area on the surface of the third wire mesh away from the third raw material layer. Divide the inner and outer raw material areas above the surface of the third wire mesh. Lay a mixture composed of vanadium carbide dopant and silicon carbide powder corresponding to the doping concentration of the second raw material layer on the inner and outer raw material areas on the surface of the third wire mesh to obtain the second raw material layer. Then, take out the graphite cylinder and place a second wire mesh on the second raw material layer. Then, place the graphite cylinder in the central area on the surface of the second wire mesh away from the second raw material layer. Divide the inner and outer raw material areas above the surface of the second wire mesh. Lay a mixture composed of vanadium carbide dopant and silicon carbide powder corresponding to the doping concentration of the first raw material layer on the inner and outer raw material areas on the surface of the second wire mesh to obtain the first raw material layer. Then, take out the graphite cylinder, place a first wire mesh on the first raw material layer, and set a perforated plate at an interval above the surface on the side of the first wire mesh away from the first raw material layer. Finally, place a silicon carbide seed crystal on the graphite support at the top of the graphite crucible to obtain the assembled graphite crucible.

[0099] (2) Crystal growth: Place the assembled graphite crucible in a PVT induction coil growth furnace. After evacuating the PVT induction coil growth furnace, introduce argon gas until the pressure in the PVT induction coil growth furnace is 500 Pa, and heat the graphite crucible until the temperature in the central area at the top of the graphite crucible is 2100 °C. Maintain the pressure in the furnace at 500 Pa and maintain the temperature in the central area at the top of the graphite crucible at 2100 °C to carry out the silicon carbide seed crystal growth process. The growth time of the silicon carbide seed crystal is 100 h.

[0100] (3) Annealing: After crystal growth, increase the pressure of the PVT induction coil growth furnace to 80000 Pa, adjust the annealing power of the PVT induction coil growth furnace to 0.8 times the power corresponding to the crystal growth step, and maintain this power and pressure for 20 h of annealing.

[0101] (4) Take out the crystal obtained at the top of the graphite crucible, complete the furnace opening, and obtain a vanadium element-doped semi-insulating silicon carbide crystal.

[0102] Example 2

[0103] This example provides a method for growing a semi-insulating silicon carbide crystal, including the following steps:

[0104] (1) Loading: The crystal growth raw materials are assembled at the bottom of the graphite crucible. The crystal growth raw materials include silicon carbide powder and vanadium oxide dopant, obtaining a crystal growth raw material area. Among them, the average particle size of the silicon carbide powder is 50 mesh and the purity is 7N; a 6H silicon carbide crystal form is placed on the graphite support at the top of the graphite crucible, and the silicon carbide seed crystal is a 0° oriented silicon carbide seed crystal.

[0105] Among them, taking the direction perpendicular to the bottom surface of the graphite crucible as the vertical direction, the crystal growth raw material area is sequentially provided with a first raw material layer, a second raw material layer, and a third raw material layer with a height ratio of 1:0.9:0.8 from top to bottom in the vertical direction. Taking the direction parallel to the bottom surface of the graphite crucible as the horizontal direction, the first raw material layer, the second raw material layer, and the third raw material layer are each provided with an inner raw material area and an outer raw material area covering the side surface of the inner raw material area in the horizontal direction. The crystal growth raw materials in the crystal growth raw material area are divided into six regions in total. In each raw material layer, the ratio of the diameter of the inner raw material area to the inner diameter of the side surface of the graphite crucible is 1:1.8, and the ratio of the diameter of the inner raw material area to the outer diameter of the outer raw material area is also 1:1.8.

[0106] The doping concentrations of the vanadium oxide dopant in the first raw material layer, the second raw material layer, and the third raw material layer are respectively denoted as C T , C M and C B , where C M satisfies 2C T , C B satisfies 10C T ; in each raw material layer, the doping concentration of the vanadium oxide dopant in the outer raw material area is denoted as C O , and the doping concentration of the vanadium oxide dopant in the inner raw material area is denoted as C I , where C I all satisfy 5C O ; taking the total mass of the crystal growth raw materials in the outer raw material area of the first raw material layer as 100 wt%, the doping concentration of the vanadium oxide dopant in the outer raw material area of the first raw material layer is 0.05 wt%.

[0107] On the surface of the first raw material layer on the side away from the second raw material layer, a first wire mesh is further provided. A second wire mesh is also provided between the first raw material layer and the second raw material layer, and a third wire mesh is further provided between the second raw material layer and the third raw material layer. The diameters of the first wire mesh, the second wire mesh, and the third wire mesh are equal to the inner diameter of the side surface of the graphite crucible. The thicknesses of the first wire mesh, the second wire mesh, and the third wire mesh in the vertical direction are all 1 mm, their materials are all tantalum metal, and their mesh numbers are all 100 meshes. Above the side of the first wire mesh away from the first raw material layer, a porous ceramic plate with a porosity of 30% is further provided. Its thickness in the vertical direction is 1 mm, the diameter of the porous ceramic plate is equal to the inner diameter of the side surface of the graphite crucible, and the porous ceramic plate and the first wire mesh are spaced apart in the vertical direction, and the distance between the two in the vertical direction is 2 mm.

[0108] Except for adopting the above structure and materials in this embodiment, specifically, the loading process is the same as that in Embodiment 1.

[0109] (2) Crystal growth: Place the assembled graphite crucible in a PVT induction coil growth furnace. After evacuating the PVT induction coil growth furnace, then introduce argon until the pressure in the PVT induction coil growth furnace is 1000 Pa, and heat the graphite crucible until the temperature in the central area at the top of the graphite crucible is 2100 °C. Maintain the pressure in the furnace at 1000 Pa, and maintain the temperature in the central area at the top of the graphite crucible at 2100 °C to carry out the silicon carbide seed crystal growth process. The growth time of the silicon carbide seed crystal is 80 h.

[0110] (3) Annealing: After the crystal growth is completed, increase the pressure of the PVT induction coil growth furnace to 70000 Pa, adjust the annealing power of the PVT induction coil growth furnace to 0.8 times the corresponding power in the crystal growth step, and maintain this power and pressure for 25 h of annealing.

[0111] (4) Take out the crystal obtained at the top of the graphite crucible, complete the furnace opening, and obtain a vanadium element-doped semi-insulating silicon carbide crystal.

[0112] Embodiment 3

[0113] This embodiment provides a method for growing a semi-insulating silicon carbide crystal, including the following steps:

[0114] (1) Loading: Assemble the crystal growth raw materials at the bottom of the graphite crucible. The crystal growth raw materials include silicon carbide powder and titanium oxide dopant to obtain a crystal growth raw material area. Among them, the average particle size of the silicon carbide powder is 100 meshes, and the purity is 6N; place a 6H silicon carbide crystal form on the graphite support at the top of the graphite crucible, and the silicon carbide seed crystal is a 0° orientation silicon carbide seed crystal.

[0115] Among them, taking the bottom surface of the graphite crucible as the vertical direction, in the crystal growth raw material area, a first raw material layer, a second raw material layer, and a third raw material layer with a height ratio of 0.8:1:1.2 are sequentially arranged from top to bottom in the vertical direction. Taking the direction parallel to the bottom surface of the graphite crucible as the horizontal direction, in the first raw material layer, the second raw material layer, and the third raw material layer, an inner raw material area and an outer raw material area covering the side surface of the inner raw material area are respectively arranged in the horizontal direction. The crystal growth raw materials in the crystal growth raw material area are divided into six regions in total. In each raw material layer, the ratio of the diameter of the inner raw material area to the inner diameter of the side surface of the graphite crucible is 1:1.9, and the ratio of the diameter of the inner raw material area to the outer diameter of the outer raw material area is also 1:1.9.

[0116] The doping concentrations of the titanium oxide dopant in the first raw material layer, the second raw material layer, and the third raw material layer are respectively denoted as C T , C M and C B , where C M satisfies 10C T , C B satisfies 30C T ; in each raw material layer, the doping concentration of the titanium oxide dopant in the outer raw material area is denoted as C O , and the doping concentration of the titanium oxide dopant in the inner raw material area is denoted as C I , where C I all satisfy 10C O ; taking the total mass of the crystal growth raw materials in the outer raw material area of the first raw material layer as 100wt%, the doping concentration of the titanium oxide dopant in the outer raw material area of the first raw material layer is 0.01wt%.

[0117] A first wire mesh is also arranged on the surface of the first raw material layer on the side far from the second raw material layer. A second wire mesh is also arranged between the first raw material layer and the second raw material layer. A third wire mesh is also arranged between the second raw material layer and the third raw material layer. The diameters of the first wire mesh, the second wire mesh, and the third wire mesh are equal to the inner diameter of the side surface of the graphite crucible. The thicknesses of the first wire mesh, the second wire mesh, and the third wire mesh in the vertical direction are all 2mm. Their materials are all titanium carbide, and their mesh numbers are all 500 meshes; a porous graphite plate with a porosity of 70% is also arranged above the side of the first wire mesh far from the first raw material layer. Its thickness in the vertical direction is 5mm. The diameter of the porous graphite plate is equal to the inner diameter of the side surface of the graphite crucible. The porous graphite plate and the first wire mesh are arranged at intervals in the vertical direction, and the distance between them in the vertical direction is 5mm.

[0118] Except for adopting the above-mentioned structure and materials in this embodiment, specifically, the loading process is the same as that in Embodiment 1.

[0119] (2) Crystal growth: Place the assembled graphite crucible in a PVT induction coil growth furnace. After evacuating the PVT induction coil growth furnace, introduce argon gas until the pressure in the PVT induction coil growth furnace reaches 500 Pa, and heat the graphite crucible until the temperature in the central region at the top of the graphite crucible is 2200 °C. Maintain the pressure in the furnace at 500 Pa and maintain the temperature in the central region at the top of the graphite crucible at 2200 °C to carry out the silicon carbide seed crystal growth process. The growth time of the silicon carbide seed crystal is 120 h.

[0120] (3) Annealing: After crystal growth is completed, increase the pressure of the PVT induction coil growth furnace to 90000 Pa, adjust the annealing power of the PVT induction coil growth furnace to 0.9 times the corresponding power in the crystal growth step, and maintain this power and pressure for 15 h of annealing.

[0121] (4) Take out the crystal obtained at the top of the graphite crucible, complete the furnace opening, and obtain a semi-insulating silicon carbide crystal doped with titanium element.

[0122] Example 4

[0123] The difference between this example and Example 1 is only that: in the growth method of the semi-insulating silicon carbide crystal provided in this example, in each raw material layer, the doping concentrations of the vanadium carbide dopant in the outer raw material area and the inner raw material area are equal, that is, C I = C O . The rest of the content is the same as that in Example 1.

[0124] Example 5

[0125] The difference between this example and Example 1 is only that: in the growth method of the semi-insulating silicon carbide crystal provided in this example, in each raw material layer, the doping concentrations of the vanadium carbide dopant in the inner raw material area and the outer raw material area are swapped, that is, the doping concentration of the vanadium carbide dopant in the inner raw material area is lower than that in the outer raw material area. The rest of the content is the same as that in Example 1.

[0126] Example 6

[0127] The difference between this example and Example 1 is only that: in the growth method of the semi-insulating silicon carbide crystal provided in this example, the porous ceramic plate is omitted. The rest of the content is the same as that in Example 1.

[0128] Example 7

[0129] The difference between this example and Example 1 is only that: in the growth method of the semi-insulating silicon carbide crystal provided in this example, the first wire mesh, the second wire mesh, and the third wire mesh are omitted. The rest of the content is the same as that in Example 1.

[0130] Example 8

[0131] The difference between this embodiment and Embodiment 1 is only that: in the growth method of the semi-insulating silicon carbide crystal provided in this embodiment, the annealing process in step (3) is omitted. The rest of the content is the same as that in Embodiment 1.

[0132] Comparative Example 1

[0133] The difference between this comparative example and Embodiment 1 is only that: no dopant is added in the growth method provided in this comparative example. The rest of the content is the same as that in Embodiment 1.

[0134] Comparative Example 2

[0135] The difference between this comparative example and Embodiment 1 is only that: in the growth method provided in this comparative example, the doping concentrations of the vanadium carbide dopants in the first raw material layer, the second raw material layer, and the third raw material layer are all equal, and the doping concentration of the vanadium carbide dopant in the outer raw material region of each raw material layer is 0.02 wt%. The rest of the content is the same as that in Embodiment 1.

[0136] Comparative Example 3

[0137] The difference between this comparative example and Embodiment 1 is only that: in the growth method provided in this comparative example, the doping concentrations of the vanadium carbide dopants in the first raw material layer and the third raw material layer are replaced, that is, the doping concentrations of the vanadium carbide dopants in the first raw material layer, the second raw material layer, and the third raw material layer decrease in sequence. The rest of the content is the same as that in Embodiment 1.

[0138] The silicon carbide crystals obtained in the above Embodiments 1-8 and Comparative Examples 1-3 are processed through processes such as surface grinding, rounding, cutting, and polishing to obtain silicon carbide wafers, and resistivity testing and optical uniformity testing are performed on them. The test results are shown in Table 1.

[0139] Table 1

[0140]

[0141]

[0142] It can be seen from the test results that:

[0143] (1) It can be seen from Embodiments 1 to 3 that the growth method provided by the present invention realizes the uniform distribution of deep-level elements in the dopant in the silicon carbide crystal by dividing the crystal growth raw material region and designing the doping concentration of the dopant in the crystal growth raw material region. The average resistivity is greater than 1E5 Ω·cm, and a semi-insulating silicon carbide crystal with a uniform doping structure is obtained.

[0144] (2) It can be seen from the comparison between Example 1 and Examples 4-5 that if the doping concentration of the dopant in the outer raw material area of each raw material layer in the crystal growth raw material area of the present invention is equal to or higher than that in the inner raw material area, it will lead to uneven doping concentration of deep-level elements sublimated into the cavity, resulting in uneven distribution of doped elements in the silicon carbide crystal, further increasing the structural defects in the obtained silicon carbide crystal, and then causing an increase in resistivity.

[0145] (3) It can be seen from the comparison between Example 1 and Example 6 that if the porous ceramic plate is omitted in the present invention, flocculent and banded inclusions will aggregate in the silicon carbide single crystal, and the precipitated particles will form leakage current under high-frequency and high-voltage conditions, reducing the reliability of the silicon carbide crystal in subsequent applications.

[0146] (4) It can be seen from the comparison between Example 1 and Example 7 that if the first wire mesh, the second wire mesh and the third wire mesh are omitted in the present invention, the temperature gradient between the powder materials will become larger, and the single crystal growth rate of sublimation in the seed crystal area will become slower, and even the silicon carbide seed crystal cannot grow effectively.

[0147] (5) It can be seen from the comparison between Example 1 and Example 8 that if the annealing process is omitted in the present invention, the intrinsic point defects of the crystal will decrease, the resistivity of the silicon carbide crystal will decrease, and the electrical properties will decrease.

[0148] (6) It can be seen from the comparison between Example 1 and Comparative Example 1 that the doping of deep-level elements in the present invention can increase the resistivity of the silicon carbide crystal, thus realizing the preparation of semi-insulating silicon carbide crystals; if the doping of deep-level elements is omitted, the resistivity of the obtained silicon carbide crystal is less than 1E5 Ω·cm, which indicates that semi-insulating silicon carbide crystals have not been prepared.

[0149] (7) It can be seen from the comparison between Example 1 and Comparative Examples 2-3 that the volatilization rate of the deep-level elements in the present invention is faster than the sublimation rate of the silicon carbide powder and the solubility in the silicon carbide single crystal is low. Unreasonable doping design makes the doped elements precipitate as solid particles in the silicon carbide single crystal. Although the resistivity exceeds the measurement range, it will still cause structural defects in the verification of the silicon carbide crystal, and the structural defects will cause leakage current phenomenon when the silicon carbide crystal is applied to a high-frequency and high-voltage environment, affecting the subsequent application reliability of the silicon carbide crystal.

[0150] In summary, in the growth method provided by the present invention, a dopant containing deep-level elements is introduced into the silicon carbide powder. In the vertical direction of the charging device, the crystal growth raw material area assembled at the bottom of the charging device is divided into three raw material layers, and the doping concentrations of the dopants in each raw material layer are designed. The doping concentrations of the dopants in the three raw material layers from top to bottom are designed to increase in sequence. On the one hand, it can delay the rapid sublimation of the high-concentration doped elements in the lower layer. On the other hand, it can enable the doped elements in the lower layer to carry out the powder in the upper layer when sublimating upward from the bottom of the crucible, so that the dopants in the crystal growth raw material area can sublimate to the top of the device with a uniform doping concentration, stabilizing the doping concentration of the dopants in the device cavity, thereby making the distribution of the deep-level elements doped inside the silicon carbide crystal more uniform during the crystal growth process, and obtaining a semi-insulating silicon carbide crystal with a uniform doping structure. In addition, the deep-level elements introduced in the present invention dope the silicon carbide crystal, and can cooperate with the intrinsic point defects formed during the crystal growth process to compensate for shallow energy impurities, so as to prepare a semi-insulating silicon carbide crystal with excellent performance.

[0151] The applicant declares that the above description is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by any person skilled in the art within the technical scope disclosed by the present invention fall within the protection scope and the disclosure scope of the present invention.

Claims

1. A method for growing a semi-insulating silicon carbide crystal, characterized in that: The growth method comprises a charging step and a crystal growing step in sequence; The specific process of the charging step includes: assembling crystal growth raw materials at the bottom of the charging device, the crystal growth raw materials including silicon carbide powder and dopants to obtain a crystal growth raw material area; the dopants include compounds containing deep energy level elements; Taking the direction perpendicular to the bottom surface of the charging device as the vertical direction, the crystal growth material area is sequentially arranged with a first material layer, a second material layer and a third material layer from top to bottom in the vertical direction; the doping concentration of the dopant in the first material layer, the second material layer and the third material layer increases in sequence.

2. The growth method according to claim 1, characterized in that The doping concentrations of the dopant in the first material layer, the second material layer and the third material layer are respectively denoted as C T , C M and C B , where C M Meeting 2C T -10C T , C B Meeting 10C T -30C T ; Preferably, in the vertical direction, the height ratio of the first raw material layer, the second raw material layer and the third raw material layer is (0.5-1.5):(0.5-1.5):(0.5-1.5); Preferably, with the direction parallel to the bottom surface of the charging device as the horizontal direction, each raw material layer includes an inner raw material area and an outer raw material area covering the side of the inner raw material area in the horizontal direction, and the doping concentration of the dopant in the outer raw material area is lower than the doping concentration of the dopant in the inner raw material area; Preferably, the crystal growth raw material in the crystal growth raw material area is divided into six areas; Preferably, in the loading step, the third raw material layer, the second raw material layer and the first raw material layer are loaded in order from the bottom surface of the loading device; Preferably, in each of the raw material layers, the doping concentration of the dopant in the outer raw material region is denoted by C O The doping concentration of the dopant in the inner raw material region is denoted as C I , where C I Meeting the 5Cs O -10C O ; Preferably, in each area of ​​the crystal growth material area, the doping concentration of the dopant is 0.01-3wt% based on the total mass of the crystal growth material being 100wt%; Preferably, in each of the raw material layers, the ratio of the diameter of the inner raw material zone to the inner diameter of the side of the charging device is independently selected from 1:(1.5-2); Preferably, in each of the raw material layers, the ratio of the diameter of the inner raw material zone to the outer diameter of the outer raw material zone is independently selected from 1:(1.5-2).

3. The growth method according to claim 1 or 2, characterized in that: The average particle size of the silicon carbide powder is 6-100 mesh; Preferably, the purity of the silicon carbide powder is above 6N; Preferably, the deep level element includes any one or a combination of at least two of vanadium, titanium, chromium, cobalt or nickel; Preferably, the dopant includes any one of vanadium carbide, vanadium oxide, titanium oxide, chromium oxide, cobalt carbide, cobalt oxide or nickel carbide, or a combination of at least two thereof.

4. The growth method according to any one of claims 1 to 3, characterized in that: A first wire mesh is provided on a surface of the first raw material layer on a side away from the second raw material layer; Preferably, a second wire mesh is provided between the first raw material layer and the second raw material layer; Preferably, a third wire mesh is provided between the second raw material layer and the third raw material layer; Preferably, in the vertical direction, the thicknesses of the first screen, the second screen and the third screen are independently selected from 1-2 mm; Preferably, the mesh sizes of the first screen, the second screen and the third screen are independently selected from 50-500 meshes; Preferably, the diameters of the first screen, the second screen and the third screen are equal to the inner diameter of the side of the charging device; Preferably, the materials of the first wire mesh, the second wire mesh and the third wire mesh are independently selected from any one of high temperature resistant metals or high temperature resistant metal carbides; Preferably, the high temperature resistant metal includes any one of metal tantalum, metal tungsten or metal niobium; Preferably, the high temperature resistant metal carbide includes any one of niobium carbide, tantalum carbide, titanium carbide or tungsten carbide.

5. The growth method according to claim 4, characterized in that: A porous plate is also arranged above the first screen on a side away from the first raw material layer; Preferably, in the vertical direction, the thickness of the porous plate is 1-5 mm; Preferably, the diameter of the porous plate is equal to the inner diameter of the side of the charging device; Preferably, the porosity of the porous plate is 30-70%; Preferably, the porous plate and the first wire mesh are spaced apart in the vertical direction, and the distance between the porous plate and the first wire mesh in the vertical direction is 2-5 mm; Preferably, the porous plate comprises a high temperature resistant porous plate; Preferably, the material of the high temperature resistant porous plate is any one of a porous ceramic plate, a porous graphite plate or a porous silicon carbide plate.

6. The growth method according to any one of claims 1 to 5, characterized in that: The charging step further includes: placing a silicon carbide seed crystal on top of the charging device; Preferably, the crystal form of the silicon carbide seed crystal includes any one of a 4H silicon carbide crystal form or a 6H silicon carbide crystal form; Preferably, the silicon carbide seed crystal comprises a 0° oriented silicon carbide seed crystal.

7. The growth method according to any one of claims 1 to 6, characterized in that: The specific process of the crystal growth step includes: placing the assembled charging device in a crystal growth device, evacuating the crystal growth device and introducing an inert gas, and heating the charging device to grow silicon carbide seed crystals; Preferably, in the crystal growth step, the pressure of the crystal growth device after the inert gas is introduced is 100-1000 Pa; Preferably, in the crystal growth step, the charging device is heated to a temperature of 2100-2200° C. at the top of the charging device; Preferably, during the growth of the silicon carbide seed crystal, the pressure of the crystal growth device is maintained at 100-1000 Pa; Preferably, during the growth of the silicon carbide seed crystal, the top temperature of the charging device is maintained at 2100-2200° C.; Preferably, the growth time of the silicon carbide seed crystal is 80-120 hours.

8. The growth method according to any one of claims 1 to 7, characterized in that: The growth method further comprises annealing after the crystal growth step; Preferably, the annealing pressure is 70000-90000Pa; Preferably, the power of the annealing step is 0.8-0.9 times the power of the crystal growth step; Preferably, the annealing time is 15-25 hours.

9. A semi-insulating silicon carbide crystal, characterized in that: The semi-insulating silicon carbide crystal is prepared by the growth method according to any one of claims 1-8.

10. A use of the semi-insulating silicon carbide crystal according to claim 9, characterized in that: The semi-insulating silicon carbide crystal is used in radar, high-voltage power station, smart car or millimeter wave communication.

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