Silicon carbide single crystal growth method and silicon carbide single crystal

Abstract

The present invention belongs to the technical field of crystal growth, and provides a method for growing a silicon carbide single crystal and a silicon carbide single crystal. The method includes selecting silicon carbide powder with a set particle size as a raw material for growing a silicon carbide single crystal, evenly spreading it on the bottom of a heating container, and bonding a silicon carbide seed crystal to the top of the heating container; after placing the heating container into a single crystal growth device, sealing the single crystal growth device, and performing a vacuum treatment on the inside of the single crystal growth device; heating the inside of the single crystal growth device after the vacuum treatment, filling the single crystal growth device with a carrier gas to a preset growth pressure, and when heated to a set growth temperature, keeping the temperature for a preset time to grow the crystal; wherein the growth pressure is related to the particle size of the silicon carbide powder, and the larger the particle size of the powder, the smaller the growth pressure; after the crystal growth is completed, cooling the inside of the single crystal growth device, filling the single crystal growth device with a carrier gas to a preset cooling pressure, and naturally cooling the crystal to obtain a silicon carbide single crystal.

Description

Technical Field

[0001] The invention belongs to the technical field of crystal growth, and in particular relates to a silicon carbide single crystal growth method and a silicon carbide single crystal. Background Art

[0002] The statements in this section merely provide background information related to the present invention and do not necessarily constitute prior art.

[0003] As an important third-generation semiconductor material, silicon carbide has excellent properties that traditional semiconductor materials such as Si and GaAs do not have, such as high thermal conductivity, large bandgap, high breakdown field strength, high electron saturation rate, high temperature resistance, radiation resistance, and corrosion resistance. Therefore, it can enable devices to operate normally in harsh environments. It has important applications in modern power electronics, microwave radio frequency, optoelectronics and other fields.

[0004] The main methods for preparing silicon carbide single crystals include physical vapor transport (PVT), chemical vapor deposition (CVD), and flux (LPE). The most widely used and mature method is the physical vapor transport method. The crystal growth using this method mainly includes four stages: vacuuming the chamber, preheating stage, high temperature growth stage, cooling stage, etc. When using this method to grow silicon carbide crystals, it is necessary to place the silicon carbide powder as the raw material at the bottom of the graphite crucible, and place the silicon carbide seed crystal as the seed crystal at the top of the graphite crucible. By heating the graphite crucible and constructing a suitable temperature field in the crucible, the silicon carbide powder at the bottom of the crucible is sublimated and decomposed into chemical components such as Si, Si2C, and SiC2, and is transported from the bottom of the crucible to the seed crystal at the top of the crucible under the action of the temperature gradient to form a silicon carbide single crystal. The temperature field distribution in the crucible has an important influence on the sublimation, transmission, and recrystallization of silicon carbide powder, and is the core factor affecting the growth of silicon carbide single crystals.

[0005] The most commonly used heating method for physical vapor transport is induction heating. Induction heating is to generate a constantly changing magnetic field through a high-frequency current with a constantly changing direction in the coil, thereby inducing current in the graphite crucible to generate heat. However, due to the skin effect of the current, the heating position of the graphite crucible is distributed on the side wall of the crucible. When growing large-diameter silicon carbide single crystals, as the diameter of the graphite crucible increases, the radial temperature difference between the crucible wall and the center of the crucible will increase, and a large radial temperature gradient will be generated inside the silicon carbide powder. As a result, after the powder on both sides of the crucible sublimates and decomposes, in addition to a part of it being transported into the growth chamber, a considerable part of it is transported to the center of the material with a lower temperature and crystallizes, affecting the utilization efficiency of the powder and causing a decrease in the crystal growth rate. Although the radial and axial temperature gradients in the material can be reduced by changing the relative position between the crucible and the induction coil, at the same time, the axial temperature gradient in the growth chamber will increase and the radial temperature gradient at the growth front will decrease, which is not conducive to the growth of single crystals. Therefore, there is an urgent need for a method to improve the uniformity of temperature distribution inside the powder without reducing the axial temperature gradient in the growth chamber and increasing the radial temperature gradient at the growth front.

[0006] Chinese patent document CN 115044969 A discloses a growth device for improving the raw material transmission efficiency during the growth of silicon carbide crystals. In the invention, a graphite tube is placed along the axis of the crucible in the crystal growth crucible, and a graphite plate is placed inside the graphite tube to divide the loading area in the crucible into three parts. The advantage of the high thermal conductivity of the graphite tube and the graphite plate is used to achieve the purpose of reducing the radial temperature gradient inside the raw material. At the same time, the graphite tube and the graphite plate can block the outer raw material from being transmitted to the center, thereby forcing the powder to be transported to the seed crystal located at the top of the crucible and inhibiting the horizontal transportation of silicon carbide powder, thereby improving the powder transmission efficiency and increasing the growth rate of silicon carbide crystals. Although this method can reduce the radial temperature gradient inside the powder, it requires changing the crucible assembly and the process is complicated. Moreover, when using this method to increase the crystal growth rate, there are strict restrictions on the loading height. If the loading height is too high, if the high temperature zone is located at the top, it is not conducive to the transportation of the lower raw material; if the high temperature zone is located at the bottom, it will cause the upper part of the powder to crystallize and block the transportation of the raw material. Therefore, the loading amount in this method cannot be too high, that is, without changing the crucible loading height, it is impossible to provide sufficient silicon carbide source material, resulting in limited thickness of the grown crystal, and it cannot be used to grow large-sized, thick crystals.

[0007] Chinese patent document CN113026095A discloses a growth method for improving the growth rate of silicon carbide crystals prepared by the PVT method. The invention uses powders of different particle sizes to grow silicon carbide single crystals. Large-sized powders can provide sufficient particle gaps to promote the transport of gas phase components, and small-sized powders have sufficient powder activity to produce sufficient reaction gas phases, both of which simultaneously improve the growth rate of crystals (~105μm / h). However, since the particle size of the silicon carbide powder used in this method is generally small (10~500μm), the powder decomposition will be accelerated, the silicon component in the growth system will increase, and the inner wall of the graphite crucible will be easily corroded. The corroded graphite crucible will provide a large amount of carbon particles in the growth chamber, resulting in a large amount of carbon inclusions in the crystal, affecting the quality of the grown crystal. In addition, the invention requires mixing powders of different particle sizes in different mass ratios, and the process is relatively complicated and not suitable for industrial promotion.

[0008] In summary, the inventors have found that the current method for growing silicon carbide crystals requires changing the crucible structure, the process is relatively complex, and is not suitable for industrial promotion, and is not suitable for the growth of large diameter (eg, 6 inches and above) silicon carbide single crystals. Summary of the invention

[0009] In order to solve the technical problems existing in the above-mentioned background technology, the present invention provides a silicon carbide single crystal growth method and a silicon carbide single crystal, wherein the method does not need to change the heating container structure, is compatible with the current single crystal growth device, is simple and practical, and is conducive to promotion.

[0010] In order to achieve the above object, the present invention adopts the following technical solution:

[0011] A first aspect of the present invention provides a method for growing a silicon carbide single crystal.

[0012] In one or more embodiments, a method for growing a silicon carbide single crystal includes:

[0013] Select silicon carbide powder with a set particle size as the raw material for growing silicon carbide single crystals, spread it evenly on the bottom of the heating container, and bond the silicon carbide seed crystal to the top of the heating container;

[0014] After placing the heating container into the single crystal growth device, the single crystal growth device is sealed, and the interior of the single crystal growth device is vacuumed;

[0015] The inside of the single crystal growth device after vacuum treatment is heated, and a carrier gas is filled into the single crystal growth device to a preset growth pressure. After heating to a set growth temperature, the temperature is kept for a preset time to perform crystal growth; wherein the growth pressure is related to the particle size of the silicon carbide powder, and the larger the particle size of the powder, the smaller the growth pressure;

[0016] When the crystal growth is completed, the interior of the single crystal growth equipment is cooled down, a carrier gas is filled into the single crystal growth equipment to a preset cooling pressure, and the crystal is naturally cooled to obtain a silicon carbide single crystal.

[0017] As an embodiment, the silicon carbide single crystal growth method further includes:

[0018] The thickness of the prepared silicon carbide single crystal was measured to evaluate the growth height rate of the crystal.

[0019] The thickness of the silicon carbide single crystal refers to the thickness of the thinnest part of the crystal. The crystal thickness can be measured by a vernier caliper, a micrometer screw or a height gauge.

[0020] As an embodiment, the silicon carbide single crystal growth method further includes:

[0021] Observe the internal defects of the crystal and make a preliminary judgment on the crystal quality;

[0022] The grown crystals are cut, ground and polished to obtain silicon carbide wafers, and the quality of the wafers is characterized.

[0023] Among them, the internal defects of the crystal refer to whether there are inclusions, polymorphs, microtubes and other defects inside the crystal. These can be observed by irradiating the crystal with a strong light source, a halogen lamp or the like.

[0024] As an implementation mode, the quality characterization of the wafer includes: using an X-ray diffractometer to characterize the crystal quality of the crystal, and using a surface defect detector to study defects in the crystal (such as micropipes, inclusions, dislocations, etc. in the crystal).

[0025] As an embodiment, the silicon carbide powder is silicon carbide particles with a diameter of 1 to 20 mm.

[0026] As an embodiment, the silicon carbide powder is spread to a thickness of 50 to 100 mm at the bottom of the heating container.

[0027] As an embodiment, the silicon carbide seed crystal has a diameter of at least 2 inches.

[0028] As an embodiment, the diameter of the silicon carbide seed crystal is 6 inches or 8 inches.

[0029] As an implementation mode, after the interior of the single crystal growth device is evacuated, the pressure inside the single crystal growth device is no greater than 0.01 Pa.

[0030] As an implementation manner, the carrier gas is argon, hydrogen, nitrogen, helium or a mixture thereof.

[0031] As an implementation mode, the growth pressure of the silicon carbide single crystal is 1-50 mbar.

[0032] As an implementation mode, when the powder particle size is 10-20 mm, the growth pressure is 1-30 mbar; when the powder particle size is 1-10 mm, the growth pressure is 5-50 mbar.

[0033] As an implementation mode, heating is performed at a preset heating rate to a set growth temperature.

[0034] As an implementation mode, the heating rate is 300-700°C / h.

[0035] As an embodiment, the growth temperature of the silicon carbide single crystal is 2100~2500℃.

[0036] As an implementation mode, the growth time of the silicon carbide single crystal is 30h~100h.

[0037] As an implementation mode, the cooling pressure is 300~1000 mbar.

[0038] A second aspect of the present invention provides a silicon carbide single crystal.

[0039] In one or more embodiments, a silicon carbide single crystal is obtained by the silicon carbide single crystal growth method as described above.

[0040] Compared with the prior art, the present invention has the following beneficial effects:

[0041] (1) The silicon carbide single crystal growth method of the present invention effectively improves the growth temperature field of large-diameter silicon carbide single crystals by using silicon carbide powder of a set particle size to grow large-diameter silicon carbide single crystals: to a certain extent, it solves the problem of inconsistency between the edge temperature inside the powder and the center temperature inside the powder due to the skin effect of the current in induction heating, reduces the radial temperature gradient inside the powder and the axial temperature gradient inside the powder, increases the axial temperature gradient in the growth chamber, inhibits the recrystallization of the powder in the crucible near the center of the powder and on the surface of the powder, improves the utilization rate of the silicon carbide powder, increases the transport speed of the gas phase components in the growth chamber, increases the thickness of the silicon carbide single crystal in the same time, and improves the production capacity of the silicon carbide single crystal.

[0042] (2) The silicon carbide single crystal growth method of the present invention effectively transfers the heat from the crucible wall to the center of the powder, improves the temperature uniformity in the large-diameter silicon carbide single crystal growth powder, improves the heating efficiency of the heating system, effectively reduces the energy consumption of silicon carbide single crystal growth, and reduces the single crystal growth cost.

[0043] (3) The silicon carbide single crystal growth method of the present invention makes full use of the corresponding relationship between the powder particle size and the growth pressure, and can reduce the axial ladder of the insulation assembly as much as possible while ensuring the single crystal growth rate. Therefore, the crystal can grow closer to the equilibrium state, and the quality of the grown crystal is better. In particular, it can significantly reduce secondary phase inclusions such as silicon droplets and carbon inclusions in the crystal.

[0044] (4) The method of the present invention effectively improves the uniformity of the temperature field inside the material by limiting the crucible loading height while ensuring the thickness of the single crystal growth. The axial temperature gradient inside the powder and the radial temperature gradient on the powder surface are both reduced to less than 0.5°C / cm.

[0045] (5) The method for growing silicon carbide single crystals in the present invention does not require changing the structure of the heating container (such as a crucible), is compatible with the current single crystal growth device, is simple and practical, and is easy to promote. The method in the present invention is suitable for the growth of large-diameter (over 6 inches) silicon carbide single crystals, and is also suitable for the growth of single crystals below 6 inches.

[0046] Advantages of additional aspects of the present invention will be given in part in the following description, and in part will become obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] 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.

[0048] Figure 1 It is a schematic diagram of the silicon carbide single crystal growth device in the present invention.

[0049] Figure 2 This is a temperature field diagram in a graphite crucible for growing a silicon carbide single crystal obtained in Example 1 of the present invention.

[0050] Figure 3 This is a photo of a silicon carbide crystal with a thickness of 37 mm and a diameter of 150 mm grown in Example 1 of the present invention.

[0051] Figure 4 It is a temperature field diagram in the graphite crucible for growing the silicon carbide single crystal obtained in Comparative Example 1 of the present invention.

[0052] Among them, 1 is the induction heating coil, 2 is the graphite crucible, 3 is the insulation material, 4 is the silicon carbide seed crystal, 5 is the grown silicon carbide single crystal, and 6 is the silicon carbide powder. T1 is the center temperature of the silicon carbide seed crystal, T2 is the edge temperature of the silicon carbide seed crystal, T3 is the center temperature of the surface of the silicon carbide powder, T4 is the edge temperature of the surface of the silicon carbide powder, T5 is the center temperature of the bottom of the silicon carbide powder, and T6 is the edge temperature of the bottom of the silicon carbide powder. The radial temperature gradient of the seed crystal surface is (T2-T1) / r, the axial temperature gradient in the growth chamber is (T3-T1) / L, the axial temperature gradient inside the powder is (T5-T3) / H, and the radial temperature gradient of the powder surface is (T4-T3) / R. Wherein, r is the radius of the silicon carbide seed crystal used, L is the length of the growth chamber of the crucible used, H is the spreading thickness of the silicon carbide powder used on the bottom of the graphite crucible, and R is the radius of the surface of the silicon carbide powder used after spreading. DETAILED DESCRIPTION

[0053] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0054] It should be noted that the following detailed descriptions are all illustrative and 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.

[0055] 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.

[0056] Terminology explanation:

[0057] Radial temperature gradient at the growth front: in the present invention, it refers to the temperature difference between the edge of the silicon carbide seed crystal and the center of the silicon carbide seed crystal per unit length. Generally, if the radial temperature gradient at the growth front is too large, the more convex the shape of the grown crystal is, the greater the stress in the crystal is.

[0058] Axial temperature gradient in the growth chamber: In the present invention, it refers to the temperature difference between the center of the silicon carbide powder surface and the center of the silicon carbide seed crystal per unit length, which represents the driving force for the growth of the single crystal. The larger the axial temperature gradient in the growth chamber, the faster the single crystal growth rate.

[0059] Radial temperature gradient in the material: In the present invention, it refers to the temperature difference between the center of the silicon carbide powder surface and the edge of the silicon carbide powder surface per unit length. The larger the radial temperature gradient in the material, the easier it is for the edge powder to agglomerate toward the center, which is less conducive to the transmission of the growth component into the growth chamber. From the perspective of growing crystals, the smaller the radial temperature gradient in the material, the better.

[0060] Axial temperature gradient in the material: In the present invention, it refers to the temperature difference between the center of the surface of the silicon carbide powder and the center of the bottom of the silicon carbide powder per unit length. The larger the axial temperature gradient in the material, the easier it is for the components in the material released by sublimation to crystallize on the surface of the material, and the less conducive it is for the growth components to be transmitted into the growth chamber. From the perspective of growing crystals, the smaller the axial temperature gradient in the material, the better.

[0061] Large diameter silicon carbide single crystal: refers to a diameter of 6 inches and above.

[0062] <Silicon Carbide Single Crystal Growth Method>

[0063] In one or more embodiments, a method for growing a silicon carbide single crystal is provided, comprising:

[0064] Step 1: Select silicon carbide powder with a set particle size as the raw material for growing silicon carbide single crystals, spread it evenly on the bottom of the heating container, and bond the silicon carbide seed crystal to the top of the heating container.

[0065] Wherein, the silicon carbide powder is silicon carbide particles with a diameter of 1 to 20 mm.

[0066] The silicon carbide powder is spread at a thickness of 50 to 100 mm at the bottom of the heating container.

[0067] The silicon carbide seed crystal has a diameter of at least 2 inches.

[0068] Preferably, the diameter of the silicon carbide seed crystal is 6 inches or 8 inches.

[0069] Step 2: After placing the heating container into the single crystal growth device, the single crystal growth device is sealed and the interior of the single crystal growth device is vacuumed.

[0070] Wherein, after the interior of the single crystal growth equipment is vacuumed, the interior of the single crystal growth equipment is no greater than 0.01Pa.

[0071] In this step, the carrier gas is argon, hydrogen, nitrogen, helium or a mixture thereof.

[0072] Step 3: Heat the interior of the single crystal growth equipment after vacuum treatment, fill the single crystal growth equipment with carrier gas to a preset growth pressure, and when heated to the set growth temperature, keep warm for a preset time to grow the crystal; wherein, the growth pressure is related to the particle size of the silicon carbide powder, and the larger the powder particle size, the smaller the growth pressure.

[0073] Specifically, the growth pressure of the silicon carbide single crystal is 1-50 mbar.

[0074] When the powder particle size is 10~20 mm, the growth pressure is 1~30 mbar; when the powder particle size is 1~10 mm, the growth pressure is 5~50 mbar.

[0075] Specifically, the temperature is heated to a set growth temperature at a preset heating rate, for example, the heating rate is 300-700° C. / h.

[0076] Wherein, the growth temperature of the silicon carbide single crystal is 2100-2500° C. The growth time of the silicon carbide single crystal is 30 h-100 h.

[0077] Step 4: After the crystal growth is completed, the interior of the single crystal growth equipment is cooled down, a carrier gas is filled into the single crystal growth equipment to a preset cooling pressure, and the crystal is naturally cooled to obtain a silicon carbide single crystal.

[0078] Wherein, the cooling pressure is 300~1000 mbar.

[0079] In some other embodiments, the silicon carbide single crystal growth method further includes:

[0080] The thickness of the prepared silicon carbide single crystal was measured to evaluate the growth height rate of the crystal.

[0081] The thickness of the silicon carbide single crystal refers to the thickness of the thinnest part of the crystal. The crystal thickness can be measured by a vernier caliper, a micrometer screw or a height gauge.

[0082] In some other embodiments, the silicon carbide single crystal growth method further includes:

[0083] Observe the internal defects of the crystal and make a preliminary judgment on the crystal quality;

[0084] The grown crystals are cut, ground and polished to obtain silicon carbide wafers, and the quality of the wafers is characterized.

[0085] Among them, the internal defects of the crystal refer to whether there are inclusions, polymorphs, microtubes and other defects inside the crystal. These can be observed by irradiating the crystal with a strong light source, a halogen lamp or the like.

[0086] As an implementation mode, the quality characterization of the wafer includes: using an X-ray diffractometer to characterize the crystal quality of the crystal, and using a surface defect detector to study defects in the crystal (such as micropipes, inclusions, dislocations, etc. in the crystal).

[0087] The following is a corresponding specific embodiment using an example in which a heating container is a graphite crucible and a single crystal growth furnace is used as the single crystal growth equipment.

[0088] It should be noted that the heating container and the single crystal growth furnace are both existing structures, and those skilled in the art can specifically select corresponding devices or equipment according to actual needs.

[0089] The silicon carbide single crystal growth device of this embodiment is as follows: Figure 1 shown.

[0090] The method of the present invention is applicable to the growth of large-diameter (6 inches or more) silicon carbide single crystals, and is also applicable to the growth of single crystals below 6 inches.

[0091] Example 1

[0092] This embodiment provides a method for growing a silicon carbide single crystal, which specifically includes the following steps:

[0093] (1) Charging the furnace: Select silicon carbide powder with a particle size of 1 mm as the raw material for growing silicon carbide single crystals, spread it evenly on the bottom of the graphite crucible with a spreading thickness of 100 mm, and place a 6-inch diameter 4H-SiC seed crystal on the top of the graphite crucible.

[0094] (2) Vacuuming: Place the graphite crucible in the single crystal growth furnace and use a mechanical pump to evacuate to 0.01 Pa.

[0095] (3) Heating growth: Fill the furnace with argon gas to a pressure of 50 mbar, heat the graphite crucible, and raise the temperature to 2100°C at a rate of 300°C / h, and keep it at this temperature for 100h. The temperature field in the graphite crucible for the growth of silicon carbide single crystals is as follows: Figure 2 shown.

[0096] (4) Cooling: Reduce the system heating power to cool down, fill with argon gas to a pressure of 1000 mbar and cool naturally to obtain a silicon carbide single crystal.

[0097] (5) Opening the furnace: Take out the graphite crucible from the growth furnace and obtain silicon carbide single crystals. It is found that the silicon carbide powder is all in a loose state, and there is no crystal inside or on the surface of the powder. This indicates that the temperature field in the material is evenly distributed. Figure 4 shown.

[0098] (6) Test characterization: such as Figure 3As shown in the figure, the thickness of the silicon carbide single crystal tested with a vernier caliper is 36.72 mm, the crystal growth height rate is about 367 μm / h, and no defects such as microtubes and inclusions in the crystal are observed using a halogen lamp. The crystal was cut, ground and polished, and the (004) surface rocking curve of the wafer was tested using an X-ray diffractometer. The half-peak width was only 20 arc seconds, indicating that the crystal quality was high. The surface defect detector was used to study the microtubes, inclusions, dislocations and other defects in the crystal. The results showed that the microtube density in the wafer was zero, there were no secondary phase defects such as silicon droplets and carbon inclusions, and the total dislocation density was 3200 cm -2 It is shown that the 6-inch silicon carbide single crystal prepared by this method has a fast growth rate, a thick crystal and high quality.

[0099] Example 2

[0100] The difference from Example 1 is:

[0101] This embodiment provides a method for growing a silicon carbide single crystal, which specifically includes the following steps:

[0102] (1) Charging the furnace: Select silicon carbide powder with a particle size of 10 mm as the raw material for growing silicon carbide single crystals, spread it evenly on the bottom of the graphite crucible with a spreading thickness of 80 mm, and place a 4H-SiC seed crystal with a diameter of 8 inches on the top of the graphite crucible.

[0103] (2) Vacuuming: Place the graphite crucible in the single crystal growth furnace and use a molecular pump to evacuate the pressure to 0.001 Pa.

[0104] (3) Heating growth: A mixed gas of Ar and N2 was filled into the furnace with a flow ratio of 20:1 until the pressure reached 5 mbar. The graphite crucible was heated at a rate of 700°C / h to 2500°C and kept at this temperature for 30 h.

[0105] (4) Cooling: Reduce the system heating power to cool down, fill with argon gas to a pressure of 300 mbar and cool naturally to obtain a silicon carbide single crystal.

[0106] (5) Opening the furnace: The graphite crucible in the growth furnace was taken out to obtain a silicon carbide single crystal. It was found that the silicon carbide powder was all in a loose state, and there was no crystal inside or on the surface of the powder. This shows that the temperature field in the material is evenly distributed.

[0107] (6) Test characterization: The thickness of the silicon carbide single crystal was 15.6 mm using a vernier caliper, and the crystal growth rate was about 520 μm / h. No defects such as microtubes and inclusions were observed in the crystal using a halogen lamp. The crystal was cut, ground and polished, and the (004) surface rocking curve of the wafer was tested using an X-ray diffractometer. The half-peak width was only 28 arc seconds, indicating that the crystal quality was high. The surface defect detector was used to study the microtubes, inclusions, dislocations and other defects in the crystal. The results showed that the microtube density in the wafer was zero, there were no secondary phase defects such as silicon droplets and carbon inclusions, and the total dislocation density was 4580 cm -2 This indicates that the 8-inch silicon carbide single crystal prepared by this method has a fast growth rate and high quality.

[0108] Example 3

[0109] The difference from Example 1 is:

[0110] This embodiment provides a method for growing a silicon carbide single crystal, which specifically includes the following steps:

[0111] (1) Charging the furnace: Select silicon carbide powder with a particle size of 20 mm as the raw material for growing silicon carbide single crystals, spread it evenly on the bottom of the graphite crucible with a thickness of 50 mm, and place a 4H-SiC seed crystal with a diameter of 8 inches on the top of the graphite crucible.

[0112] (2) Vacuuming: Place the graphite crucible in the single crystal growth furnace and use a molecular pump to evacuate the pressure to 0.001 Pa.

[0113] (3) Heating growth: A mixed gas of Ar and H2 was filled into the furnace with a flow ratio of 20:1 until the pressure reached 1 mbar. The graphite crucible was heated at a rate of 500°C / h to 2500°C and kept at this temperature for 50 h.

[0114] (4) Cooling: Reduce the system heating power to cool down, fill with argon gas to a pressure of 800 mbar and cool naturally to obtain a silicon carbide single crystal.

[0115] (5) Opening the furnace: The graphite crucible in the growth furnace was taken out to obtain a silicon carbide single crystal. It was found that the silicon carbide powder was all in a loose state, and there was no crystal inside or on the surface of the powder. This shows that the temperature field in the material is evenly distributed.

[0116] (6) Test characterization: The thickness of the silicon carbide single crystal was tested with a vernier caliper and was found to be 25.0 mm. The crystal growth rate was about 500 μm / h. No defects such as microtubes and inclusions were observed in the crystal using a halogen lamp. The crystal was cut, ground and polished, and the (004) surface rocking curve of the wafer was tested using an X-ray diffractometer. The half-peak width was only 26 arc seconds, indicating that the crystal quality was high. The surface defect detector was used to study the microtubes, inclusions, dislocations and other defects in the crystal. The results showed that the microtube density in the wafer was zero, there were no secondary phase defects such as silicon droplets and carbon inclusions, and the total dislocation density was 3860 cm -2 This indicates that the 8-inch silicon carbide single crystal prepared by this method has a fast growth rate and high quality.

[0117] Comparative Example 1

[0118] In this embodiment, silicon carbide powder with a particle size of 0.3 mm is used to grow large-diameter silicon carbide single crystals, and the other growth conditions are exactly the same as in Example 1. After the growth is completed, the graphite crucible is taken out of the growth furnace to obtain a silicon carbide single crystal, and it is found that crystallization occurs inside the silicon carbide powder and in the middle of the surface of the material. This shows that the axial temperature gradient and the radial temperature gradient in the material are large. In addition, it is found that the graphite crucible is severely corroded. The thickness of the silicon carbide single crystal tested with a vernier caliper is 10.2 mm, and the crystal growth height rate is about 102 μm / h. A halogen lamp is used to observe the presence of microtubes, inclusions and other defects in the crystal. The crystal was cut, ground and polished, and the rocking curve of the chip (004) surface was tested with an X-ray diffractometer. The half-peak width was 82 arc seconds, indicating that the crystallization quality of the crystal was poor; a surface defect detector was used to study the microtubes, inclusions, dislocations and other defects in the crystal. The results showed that the density of microtubes in the chip was 0.33 cm -2 There are many carbon inclusion defects, and the carbon inclusions induce a large number of microtubes and dislocation defects in the crystal. The microtube density in the wafer is 12.5 cm -2 , the total dislocation density exceeds 10000cm -2 , and cannot be used for the preparation of related devices. This shows that the 6-inch silicon carbide single crystal prepared in this embodiment has a slow growth rate and poor quality.

[0119] Comparative Example 2

[0120] In this embodiment, silicon carbide powder with a particle size of 30 mm is selected to grow a large-diameter silicon carbide single crystal, and the other growth conditions are exactly the same as those in Example 2. Open the furnace: Take out the graphite crucible in the growth furnace to obtain a silicon carbide single crystal. It is found that the silicon carbide powder is all in a loose state, and there is no crystallization inside or on the surface of the powder. It shows that the temperature field distribution in the material is uniform. It was found that the crystal diameter was only 160 mm, and the 20 mm edge of the seed crystal was severely decomposed; the thickness of the silicon carbide single crystal was tested with a vernier caliper to be 3.3 mm, and the crystal growth height rate was about 110 μm / h. A halogen lamp was used to observe defects such as microtubes and inclusions in the crystal. The crystal was cut, ground and polished, and the chip (004) surface rocking curve was tested with an X-ray diffractometer. The half-peak width was 62 arc seconds, indicating that the crystal quality was poor; a surface defect detector was used to study defects such as microtubes, inclusions, and dislocations in the crystal. The results showed that the microtube density in the chip was zero, and there were no secondary phase defects such as silicon droplets and carbon inclusions, but due to the total dislocation density of 8580 cm in the crystal -2 It is explained that the silicon carbide crystal prepared in this method has an unqualified diameter due to severe decomposition of the seed crystal edge, and there are also problems such as slow crystal growth rate and high dislocation density.

[0121] Comparative Example 3

[0122] In this embodiment, the pressure of argon gas filled in the furnace during heating growth is 1 mbar, and the other growth conditions are exactly the same as in Example 1. Open the furnace: Take out the graphite crucible from the growth furnace to obtain a silicon carbide single crystal. It is found that the silicon carbide powder is all in bulk, and there is no crystallization inside or on the surface of the powder. It shows that the temperature field distribution in the material is uniform. The thickness of the silicon carbide single crystal tested with a vernier caliper is 48.57 mm, and the crystal growth height rate is about 486 μm / h. A halogen lamp is used to observe the presence of microtubes, inclusions and other defects in the crystal. The crystal was cut, ground and polished, and the rocking curve of the chip (004) surface was tested with an X-ray diffractometer. The half-peak width was 85 arc seconds, indicating that the crystal quality was poor; a surface defect detector was used to study the microtubes, inclusions, dislocations and other defects in the crystal. The results showed that the density of microtubes in the chip was 0.41 cm -2 There are many carbon inclusion defects, and the carbon inclusions induce a large number of microtubes and dislocation defects in the crystal. There are large areas of fog inclusions in the wafer, and the total dislocation density exceeds 10000cm -2 .It shows that the 6-inch silicon carbide single crystal prepared in this embodiment has a fast growth rate but poor quality.

[0123] Comparative Example 4

[0124] In this embodiment, the spreading thickness of the silicon carbide powder at the bottom of the graphite crucible is 150mm, and the other growth conditions are exactly the same as in Example 1. Open the furnace: Take out the graphite crucible from the growth furnace to obtain a silicon carbide single crystal. It is found that the silicon carbide powder is in block form, and crystals appear inside and on the surface of the powder. This shows that the temperature field distribution in the material is uneven. It was found that the crystal diameter was only 140mm, and the 5mm edge of the seed crystal was severely decomposed. This was due to the uneven temperature field in the material, which resulted in the inability to effectively transport the growth components into the growth chamber; the thickness of the silicon carbide single crystal tested with a vernier caliper was 15.2mm, and the crystal growth height rate was about 152 μm / h. A halogen lamp was used to observe defects such as microtubes and inclusions in the crystal. The crystal was cut, ground and polished, and the rocking curve of the wafer (004) surface was tested by an X-ray diffractometer. The half-peak width was 82 arc seconds, indicating that the crystal quality was poor. The surface defect detector was used to study the microtubes, inclusions, dislocations and other defects in the crystal. The results showed that the microtube density in the wafer was zero, and there were no secondary phase defects such as silicon droplets and carbon inclusions. However, the crystal did not meet the standards due to the decomposition of the seed crystal edge. This shows that the silicon carbide crystal prepared in this method has problems such as unqualified diameter and slow crystal growth rate due to the severe decomposition of the seed crystal edge.

[0125] Comparative Example 5

[0126] In this embodiment, the paving thickness of silicon carbide powder at the bottom of the graphite crucible is 30 mm, and the other growth conditions are exactly the same as those in Example 1. Open the furnace: Take out the graphite crucible from the growth furnace to obtain a silicon carbide single crystal. It is found that although the silicon carbide powder is all in bulk, there is no crystallization inside or on the surface of the powder, but the powder residue is small, and the surface of the crystal is decomposed and carbonized. It shows that although the temperature field distribution in the material is uniform, the loading amount is insufficient. The thickness of the silicon carbide single crystal tested by a vernier caliper is 12.36 mm, the crystal growth height rate is about 124 μm / h, and a halogen lamp is used to observe defects such as microtubes and inclusions in the crystal. The crystal is cut, ground and polished, and the chip (004) surface rocking curve is tested by an X-ray diffractometer, and the half-peak width is 29 arc seconds; the surface defect detector is used to study the defects such as microtubes, inclusions, and dislocations in the crystal. The results show that the microtube density in the chip is zero, and there are no secondary phase defects such as silicon droplets and carbon inclusions. It shows that there is a problem in this method that a thicker crystal cannot be grown due to a small loading amount.

[0127] Comparative Example 6

[0128] In this embodiment, the pressure of argon gas filled in the furnace during heating growth is 100mbar, and the other growth conditions are exactly the same as those in Example 1. Open the furnace: Take out the graphite crucible in the growth furnace to obtain a silicon carbide single crystal. It is found that the silicon carbide powder is all in a loose state, and there is no crystallization inside or on the surface of the powder. It shows that the temperature field distribution in the material is uniform. It was found that the crystal diameter is only 130mm, and the 10mm edge of the seed crystal is severely decomposed; the thickness of the silicon carbide single crystal tested with a vernier caliper is 1.34mm, and the crystal growth height rate is about 134μm / h. A halogen lamp is used to observe defects such as microtubes and inclusions in the crystal. The crystal is cut, ground and polished, and the chip (004) surface rocking curve is tested by an X-ray diffractometer. The half-peak width is 69 arc seconds, indicating that the crystal quality is poor; a surface defect detector is used to study defects such as microtubes, inclusions, and dislocations in the crystal. The results show that the microtube density in the chip is zero, and there are no secondary phase defects such as silicon droplets and carbon inclusions, but due to the total dislocation density of 9160cm in the crystal -2 It is explained that the silicon carbide crystal prepared in this method has an unqualified diameter due to severe decomposition of the seed crystal edge, and there are also problems such as slow crystal growth rate and high dislocation density. Table 1 shows the temperature gradient and growth power results between different embodiments and comparative examples calculated using numerical simulation software.

[0129] Table 1 Temperature gradient and growth power results between different examples and comparative examples

[0130]

[0131] With the help of numerical simulation software, the present invention finds that when a silicon carbide single crystal is grown by a physical vapor transport method, the temperature field distribution in the crucible can be significantly changed by only changing the particle size of the silicon carbide powder without changing the crucible structure. A preferred scheme that can effectively improve the temperature field of the crucible for growing large-diameter silicon carbide single crystals has been determined through a large number of experimental verifications and simulations. The present invention uses silicon carbide powder of a suitable particle size as a source material, which can effectively adjust the temperature field in the growth chamber and the temperature field in the material of a large-diameter silicon carbide single crystal, thereby improving the quality of the silicon carbide single crystal and growing large-diameter silicon carbide single crystals. The method of the present invention effectively overcomes the problem of the same-direction coupling between the axial temperature gradient of the growth chamber and the axial temperature gradient inside the powder faced by the induction heating method for growing silicon carbide crystals, and achieves the increase of the axial temperature gradient of the growth chamber under the premise of reducing the axial temperature gradient inside the powder. In the present invention, on the one hand, by selecting a suitable powder particle size, the temperature uniformity inside the powder is improved, the crystallization phenomenon on the surface of the powder is reduced, and the crystallization in the center of the powder is weakened, the transmission and utilization efficiency of the powder is improved, and the growth rate of the crystal is increased, so that thick crystals can be grown in a short time. On the other hand, since the heat of the side wall of the crucible is fully utilized, the method of the present invention has low energy consumption for single crystal growth and can effectively reduce the cost of single crystal growth. The grown silicon carbide crystals are observed and analyzed, and the method does not introduce obvious defects such as inclusions, polymorphs, and microtubes.

[0132] <Large diameter silicon carbide single crystal>

[0133] In one or more embodiments, a large-diameter silicon carbide single crystal is obtained by the silicon carbide single crystal growth method as described above.

[0134] 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 method for growing a silicon carbide single crystal, characterized in that: include: Select silicon carbide powder with a set particle size as the raw material for growing silicon carbide single crystals, spread it evenly on the bottom of the heating container, and bond the silicon carbide seed crystal to the top of the heating container; After placing the heating container into the single crystal growth device, the single crystal growth device is sealed, and the inside of the single crystal growth device is vacuumed; The inside of the single crystal growth device after vacuum treatment is heated, and a carrier gas is filled into the single crystal growth device to a preset growth pressure. After heating to a set growth temperature, the temperature is kept for a preset time to perform crystal growth; wherein the growth pressure is related to the particle size of the silicon carbide powder, and the larger the particle size of the powder, the smaller the growth pressure; When the crystal growth is completed, the temperature inside the single crystal growth equipment is lowered, a carrier gas is filled into the single crystal growth equipment to a preset cooling pressure, and the crystal is naturally cooled to obtain a silicon carbide single crystal; The diameter of the silicon carbide seed crystal is 6 inches or 8 inches; The silicon carbide powder is silicon carbide particles with a diameter of 1-20 mm; the growth pressure of the silicon carbide single crystal is 1-50 mbar; when the powder particle size is 10-20 mm, the growth pressure is 1-30 mbar; when the powder particle size is 1-10 mm, the growth pressure is 5-50 mbar.

2. The method for growing a silicon carbide single crystal according to claim 1, wherein: The silicon carbide single crystal growth method further comprises: The thickness of the prepared silicon carbide single crystal was measured to evaluate the growth height rate of the crystal.

3. The method for growing a silicon carbide single crystal according to claim 1 or 2, characterized in that: The silicon carbide single crystal growth method further comprises: Observe the internal defects of the crystal and make a preliminary judgment on the crystal quality; The grown crystals are cut, ground and polished to obtain silicon carbide wafers, and the quality of the wafers is characterized.

4. The method for growing a silicon carbide single crystal according to claim 1, wherein: The silicon carbide powder is spread at a thickness of 50 to 100 mm at the bottom of the heating container.

5. The method for growing a silicon carbide single crystal according to claim 1, wherein: The silicon carbide seed crystal has a diameter of at least 2 inches.

6. The method for growing a silicon carbide single crystal according to claim 1, wherein: After the single crystal growth equipment is vacuumed, the temperature inside the single crystal growth equipment is no greater than 0.01 Pa; or The carrier gas is argon, hydrogen, nitrogen, helium or a mixture thereof.

7. The method for growing a silicon carbide single crystal according to claim 1, wherein: Heating to a set growth temperature at a preset heating rate; or Heating to a set growth temperature at a preset heating rate, wherein the heating rate is 300-700°C / h; or The growth temperature of the silicon carbide single crystal is 2100-2500° C. or The growth time of the silicon carbide single crystal is 30h~100h; or The cooling pressure is 300-1000 mbar.

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