Silicon carbide single crystal growth method, silicon carbide single crystal, crucible and growth system

Abstract

The present invention provides a method for growing a silicon carbide single crystal, a silicon carbide single crystal, a crucible, and a growth system. The growth method comprises: placing a silicon carbide seed crystal at the bottom of a crucible; covering the carbide seed crystal with a raw material block; wherein the raw material block comprises silicon and carbon elements; loading a flux into the area between the raw material block and the inner wall of the crucible; heating the crucible to melt the flux; pulling the raw material block upward so that the melted flux flows between the silicon carbide seed crystal and the raw material block, and the bottom surface of the raw material block contacts the flux; after a first preset time, pulling the raw material block upward so that it is separated from the melted flux; lowering the temperature of the crucible to a specified temperature to obtain a silicon carbide single crystal grown based on the silicon carbide seed crystal. The present invention eliminates or greatly reduces the possibility of the seed crystal falling. Before growth, the SiC seed crystal is covered by the raw material block above, which hinders the deposition of volatiles from the flux melt on the surface of the seed crystal and prevents a large number of defects generated in the early stages of growth.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor material manufacturing, in particular to a growth method of a silicon carbide single crystal, a silicon carbide single crystal, a crucible and a growth system. Background Art

[0002] Silicon carbide (SiC) is a third-generation semiconductor material with advantages such as a large bandgap, high breakdown field strength, high saturated electron mobility, high thermal conductivity, and good thermal and chemical stability. It is an ideal material for making high-frequency, high-voltage, radiation-resistant, and high-temperature resistant high-power devices. It has important application prospects in new energy vehicles, high-speed rail transit, aerospace, high-voltage smart grids, and clean energy, and has received widespread attention.

[0003] The crystallization quality and manufacturing cost of SiC single crystal substrates are the main factors restricting their large-scale application. Exploring and researching high-quality, large-size and low-cost SiC single crystal substrates is of great significance to fully realizing the application potential of SiC.

[0004] Compared to the established physical vapor transport (PVT) method, the high-temperature solution method offers advantages such as lower growth temperature (generally below 2000°C), a growth state closer to thermodynamic equilibrium, a more stable growth environment, and easier p-type doping. It is expected to develop into a more efficient method for large-scale growth of SiC single crystals. Therefore, the high-temperature solution method for growing SiC single crystals has received increasing attention in recent years.

[0005] Currently, the primary technique for growing SiC single crystals using high-temperature solutions is the top-seeded solution growth (TSSG) method. While this technique has made significant progress, it still faces several major challenges: First, the graphite crucible, as the sole carbon source, is constantly corroded and consumed during crystal growth. The Si content in the high-temperature solution also decreases as the crystal grows, causing the liquid level and Si / C ratio to fluctuate continuously, hindering long-term, stable crystal growth. Second, before crystal growth begins, volatiles from the flux melt adhere to the seed crystal surface, severely impacting the early crystallization quality. Third, during crystal growth, small SiC grains spontaneously nucleate in the high-temperature solution and float at the liquid surface, affecting the growth interface at the liquid surface. Fourth, the crystals lack physical constraints laterally, tending to grow into hexagonal crystals, increasing the difficulty of subsequent wafer processing. Therefore, developing new technologies to address the challenges facing the TSSG method is crucial for realizing the potential of the high-temperature solution method. Summary of the Invention

[0006] In view of the above problems, the present invention is proposed to provide a method for growing a silicon carbide single crystal, a silicon carbide single crystal, a crucible, and a growth system that overcome the above problems or at least partially solve the above problems.

[0007] An object of the present invention is to enable stable growth of silicon carbide single crystals and to obtain high-quality silicon carbide single crystals.

[0008] A further object of the present invention is to reduce energy consumption during the growth of silicon carbide single crystals.

[0009] According to one aspect of an embodiment of the present invention, a method for growing a silicon carbide single crystal is provided, comprising:

[0010] Placing a silicon carbide seed crystal at the bottom of the crucible;

[0011] Covering the carbonized seed crystal with a raw material block, wherein the raw material block includes silicon and carbon;

[0012] Filling the area between the raw material block and the inner wall of the crucible with flux;

[0013] heating the crucible to melt the flux;

[0014] Pulling the raw material block upwards so that the melted flux flows between the silicon carbide seed crystal and the raw material block, and the bottom surface of the raw material block contacts the flux;

[0015] After a first preset time period, the raw material block is pulled upward to separate it from the melted flux;

[0016] The temperature of the crucible is lowered to a specified temperature to obtain a silicon carbide single crystal grown based on the silicon carbide seed crystal.

[0017] Optionally, after the melted flux is flowed between the silicon carbide seed crystal and the raw material block, the method further comprises:

[0018] The temperature of the flux between the silicon carbide seed crystal and the raw material block is gradually reduced from top to bottom according to a preset gradient.

[0019] Optionally, the preset gradient is 2-30°C / cm; and / or

[0020] The temperature of the flux at the silicon carbide seed crystal is 1500-2000° C.; and / or

[0021] The thickness of the flux between the silicon carbide seed crystal and the raw material block is 5 to 30 mm.

[0022] Optionally, after heating the crucible to melt the flux, the method further comprises:

[0023] Calculating the holding time after the flux is melted;

[0024] When the heat preservation time reaches a second preset time, the step of pulling the raw material block upward is performed.

[0025] Optionally, after the bottom surface of the raw material block is brought into contact with the flux, the method further comprises:

[0026] rotating the crucible and / or the raw material block; and / or

[0027] The crucible and / or the raw material block are moved up and down, and the bottom surface of the raw material block is kept in contact with the flux.

[0028] Optionally, when the crucible and the raw material block are rotated simultaneously, the crucible and the raw material block are rotated in opposite directions.

[0029] Optionally, before heating the crucible to melt the flux, the method further comprises:

[0030] placing the crucible into a single crystal growth furnace;

[0031] A protective gas is charged into the single crystal growth furnace, and the pressure in the single crystal growth furnace is adjusted to 0.1-2 atm.

[0032] Optionally, the protective gas includes nitrogen and / or argon.

[0033] Optionally, the molar ratio of silicon to carbon in the raw material block is 1:1, and

[0034] The silicon element and the carbon element of the raw material block are evenly distributed.

[0035] Optionally, the flux includes silicon and at least one of the following:

[0036] Transition metals, rare earth metals, Group IIIA metals and Group IVA metals.

[0037] According to another aspect of an embodiment of the present invention, there is provided a silicon carbide single crystal prepared by the silicon carbide single crystal growth method described in any one of the above.

[0038] According to another aspect of the embodiments of the present invention, there is further provided a crucible, comprising:

[0039] A crucible shell for growing the silicon carbide single crystal described above; and

[0040] The crucible shell is divided into a first section and a second section from top to bottom;

[0041] The second section tapers from top to bottom.

[0042] According to another aspect of the embodiment of the present invention, a raw material block is provided.

[0043] The raw material block is divided into a third section and a fourth section from top to bottom, and the fourth section is adapted to the second section of the crucible described above and is used in any one of the above-described methods for growing silicon carbide single crystals.

[0044] Optionally, the third section tapers from bottom to top.

[0045] Optionally, the raw material block further includes a fifth section, which is located between the third section and the fourth section, is perpendicular to the bottom of the raw material block, and is connected to the third section and the fourth section respectively.

[0046] According to another aspect of an embodiment of the present invention, a system for growing a silicon carbide single crystal is provided, comprising:

[0047] A single crystal growth furnace having a first opening and a second opening at the top and bottom, respectively;

[0048] The crucible mentioned above is located in the single crystal growth furnace;

[0049] a graphite shaft, inserted into the first opening, for connecting the raw material block;

[0050] a supporting shaft, inserted into the second opening and connected to the bottom of the crucible;

[0051] a heat-insulating layer, disposed around the outer surface of the crucible; and

[0052] A heating component is located between the inner wall of the single crystal growth furnace and the outer wall of the insulation layer, and is used for heating the crucible.

[0053] In the growth method of a silicon carbide single crystal of the present invention, a silicon carbide seed crystal is placed at the bottom of a crucible, and a raw material block is covered on the carbide seed crystal, wherein the raw material block includes silicon and carbon elements, and a flux is added to the area between the raw material block and the inner wall of the crucible. The crucible is heated to melt the flux, and the raw material block is pulled upward so that the melted flux flows between the silicon carbide seed crystal and the raw material block, and the bottom surface of the raw material block is in contact with the flux. After a first preset period of time, the raw material block is pulled upward to separate it from the molten flux, and the temperature of the crucible is lowered to a specified temperature to obtain a silicon carbide single crystal grown based on the silicon carbide seed crystal. During the growth of the silicon carbide single crystal in this embodiment, the melt and raw materials are located above the seed crystal. The crystal is firmly pressed to the bottom of the crucible under the action of the melt and its own gravity, and the possibility of the seed crystal falling is eliminated or greatly reduced. Before growth, the SiC seed crystal is covered by the raw material block above, which hinders the deposition of volatiles from the flux melt on the surface of the seed crystal, prevents a large number of defects generated in the early stage of growth, and is beneficial to improving the crystallization quality of the crystal. Since the crystal growth interface is located at the bottom of the flux melt, even if spontaneous SiC nuclei are generated in the melt, it will not affect the crystal growth interface. The crystal growth interface is more stable, which can improve the crystallization quality of the crystal. The Si and C required for crystal growth are all directly provided by the raw material block, and the Si content in the flux melt will not change. The growth system is more stable and durable, which is beneficial to the long-term stable growth of high-quality SiC crystals.

[0054] Furthermore, by gradually decreasing the temperature of the flux between the silicon carbide seed crystal and the raw material block from top to bottom according to a preset gradient, the high-temperature zone can be narrower, thereby reducing the required heat supply and greatly reducing energy consumption.

[0055] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are specifically listed below.

[0056] Based on the following detailed description of specific embodiments of the present invention in conjunction with the accompanying drawings, those skilled in the art will become more aware of the above and other objects, advantages and features of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiment below. The accompanying drawings are for illustration purposes only and are not to be considered as limiting the present invention. The same reference symbols are used throughout the drawings to represent the same components. In the drawings:

[0058] Figure 1 A schematic flow chart of a method for growing a silicon carbide single crystal according to an embodiment of the present invention is shown;

[0059] Figure 2 The present invention shows a schematic structural diagram of a crucible according to an embodiment of the present invention;

[0060] Figure 3 It shows the structural schematic of the raw material block according to one embodiment of the present invention;

[0061] Figure 4 It shows the structural schematic of a raw material block according to another embodiment of the present invention;

[0062] Figure 5 It shows the structural schematic of a raw material block according to another embodiment of the present invention;

[0063] Figure 6 FIG2 shows a schematic structural diagram of a system for growing a silicon carbide single crystal according to an embodiment of the present invention;

[0064] Figure 7 A schematic structural diagram of a growth system for silicon carbide single crystal according to another embodiment of the present invention is shown. DETAILED DESCRIPTION

[0065] Exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although exemplary embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the present disclosure to those skilled in the art.

[0066] Figure 1 The figure shows a flow chart of a method for growing a silicon carbide single crystal according to an embodiment of the present invention. The silicon carbide single crystal of this embodiment can be referred to as SiC single crystal, and the silicon carbide seed crystal can be referred to as SiC seed crystal. Figure 1 As shown, the growth method may at least include the following steps S102 to S114.

[0067] Step S102: placing a silicon carbide seed crystal at the bottom of the crucible.

[0068] In the prior art TSSG method for growing SiC single crystals, in order to make the silicon carbide seed crystal firmly adhere to the seed crystal rod, a sufficiently large bonding strength is required to overcome the weight of the crystal and the axial force of the melt surface tension. Therefore, the requirements for bonding the seed crystal are very high, otherwise the crystal will easily fall during the growth process. In this step, the carbide seed crystal is at the bottom of the crucible. During the growth of the silicon carbide single crystal, the solvent melt (molten solvent) and the raw material block are located above the carbide seed crystal. The crystal is firmly pressed to the bottom of the crucible under the action of the solvent melt and its own gravity, and the possibility of the seed crystal falling does not exist or can be greatly reduced. In the prior art, the silicon carbide seed crystal is often set at the top. This step breaks through this ideological shackles and places the silicon carbide seed crystal at the bottom of the crucible, that is, in the opposite position, achieving very good results.

[0069] Step S104: Covering the carbonized seed crystal with a raw material block. The raw material block may include silicon and carbon. Of course, the raw material block may only consist of silicon and carbon.

[0070] In this step, the raw material block can be completely covered on the carbonized seed crystal, that is, it can cover the top and side of the carbonized seed crystal, so that the carbonized seed crystal can be in a completely separated state from the flux in step S106. The raw material block can be cylindrical, frustum or conical, and the height can be 20 to 200 mm, for example, 40 mm, 60 mm, 100 mm, 150 mm, etc., and its bottom diameter is larger than the diameter of the SiC seed crystal and smaller than the inner diameter of the crucible. In the top seeding method of growing SiC single crystals in the prior art, during the heating stage before the SiC seed crystal contacts the high-temperature melt liquid surface, the volatiles of the high-temperature melt will be deposited on the surface of the SiC seed crystal, seriously damaging the surface quality of the SiC seed crystal before growth, resulting in a large number of crystal defects in the early stage of crystal growth, affecting the crystallization quality of the crystal. In this step, the SiC seed crystal is covered by the raw material block above before growth, which hinders the deposition of volatiles of the flux melt on the surface of the seed crystal, prevents the generation of a large number of defects in the early stage of growth, and is conducive to improving the crystallization quality of the crystal. Furthermore, in the prior art TSSG method for growing SiC single crystals, since the crystal growth interface is located at the upper liquid surface of the flux melt, crystal growth is easily affected by spontaneous SiC nuclei floating at the liquid surface, resulting in instability of the crystal growth interface. In the present invention, since the crystal growth interface is located at the bottom of the flux melt, even if spontaneous SiC nuclei are generated in the flux melt, they will not affect the crystal growth interface. The crystal growth interface of the present invention is more stable, and the crystal quality of the crystal can be improved.

[0071] Step S106: adding flux to the area between the raw material block and the inner wall of the crucible.

[0072] In this step, the area between the raw material block and the inner wall of the crucible can also be understood as the side area of ​​the raw material block. Filling the area between the raw material block and the inner wall of the crucible allows the flux to flow more easily to the silicon carbide seed crystals at the bottom when the raw material block is pulled upward after the flux melts.

[0073] Step S108: heating the crucible to melt the flux.

[0074] Step S110 : pulling the raw material block upwards, so that the melted flux flows between the silicon carbide seed crystal and the raw material block, and the bottom surface of the raw material block contacts the flux.

[0075] In this step, the bottom surface of the raw material block is in full contact with the flux, that is, the entire bottom surface can be in contact with the flux. Of course, it can also be understood that the upper surface of the molten flux is in full contact with the bottom surface of the raw material block, and the growth of the silicon carbide single crystal begins after contact. In the prior art, in the TSSG method for growing SiC single crystals, a carbon (C) source is provided for crystal growth by corroding a graphite crucible, and a Si source is provided for crystal growth by using silicon (Si) in a flux melt. This will cause the crucible to be gradually corroded, the Si content in the flux melt to gradually decrease, and the height of the flux melt liquid level to be difficult to accurately calibrate, which is not conducive to the long-term stable growth of the crystal. In the present invention, the Si and C required for crystal growth are all directly provided by the raw material block, and the Si content in the flux melt will not change. The growth process is more stable and lasting, which is conducive to the long-term stable growth of high-quality SiC crystals.

[0076] Step S112: After a first preset time period, the raw material block is pulled upward to separate it from the melted flux.

[0077] In this step, the bottom surface of the raw material block separates from the molten flux, halting the growth of the silicon carbide single crystal. It will be appreciated that the growth process of the silicon carbide single crystal begins with the bottom surface of the raw material block contacting the flux in step S110 and ends with the bottom surface of the raw material block separating from the molten flux in step S112. The first preset duration can be any value between 20 and 100 hours, for example, 30 hours, 40 hours, 50 hours, 60 hours, or 80 hours.

[0078] Step S114: Lowering the crucible temperature to a specified temperature to obtain a silicon carbide single crystal grown from the silicon carbide seed crystal. Generally, the specified temperature can be room temperature, such as any value between 0-40°C, for example, 10°C, 15°C, 20°C, 25°C, 30°C, etc. This step can also involve slowly cooling the crucible to the specified temperature. The slow cooling rate can generally be selected to be 5-20°C / h, for example, 16°C / h or 18°C / h, which can protect the crucible.

[0079] In this embodiment, a silicon carbide seed crystal is placed at the bottom of a crucible, and a raw material block is covered on the carbide seed crystal, wherein the raw material block includes silicon and carbon elements. A flux is added to the area between the raw material block and the inner wall of the crucible, and the crucible is heated to melt the flux. The raw material block is pulled upward so that the melted flux flows between the silicon carbide seed crystal and the raw material block, and the bottom surface of the raw material block is in contact with the flux. After a first preset period of time, the raw material block is pulled upward to separate it from the molten flux, and the temperature of the crucible is lowered to a specified temperature to obtain a silicon carbide single crystal grown based on the silicon carbide seed crystal. During the growth of the silicon carbide single crystal in this embodiment, the melt and raw materials are located above the seed crystal. The crystal is firmly pressed to the bottom of the crucible under the action of the melt and its own gravity, and the possibility of the seed crystal falling is eliminated or greatly reduced. Before growth, the SiC seed crystal is covered by the raw material block above, which hinders the deposition of volatiles from the flux melt on the surface of the seed crystal, prevents a large number of defects generated in the early stage of growth, and is beneficial to improving the crystallization quality of the crystal. Since the crystal growth interface is located at the bottom of the flux melt, even if spontaneous SiC nuclei are generated in the melt, it will not affect the crystal growth interface. The crystal growth interface is more stable, which can improve the crystallization quality of the crystal. The Si and C required for crystal growth are all directly provided by the raw material block, and the Si content in the flux melt will not change. The growth system is more stable and durable, which is beneficial to the long-term stable growth of high-quality SiC crystals.

[0080] In one embodiment of the present invention, after allowing the melted flux to flow between the silicon carbide seed crystal and the raw material block, the method may further include:

[0081] The temperature of the flux between the silicon carbide seed crystal and the raw material block is gradually reduced from top to bottom according to a preset gradient.

[0082] In this embodiment, the temperature of the flux between the silicon carbide seed crystal and the raw material block is gradually reduced from top to bottom according to a preset gradient, which can make the high-temperature zone narrower, thereby reducing the required heat supply and greatly reducing energy consumption. Generally, during the growth of the silicon carbide single crystal, the temperature of the flux between the silicon carbide seed crystal and the raw material block can be kept in a state of gradually decreasing from top to bottom. Heating can be performed by using heating methods such as induction heating or resistance heating. In the present invention, the temperature of the flux is gradually reduced from top to bottom according to a preset gradient by providing an insulation layer on the outer surface of the crucible. Specifically, an insulation layer is provided on the outer surface of the crucible, and the insulation performance of the top of the insulation layer is weak (the insulation performance of the insulation layer gradually decreases and increases from top to bottom), so that the temperature of the flux between the silicon carbide seed crystal and the raw material block is reduced from top to bottom according to a preset gradient.

[0083] In one embodiment of the present invention, the preset gradient may be 2-30°C / cm; and / or

[0084] The temperature of the flux at the silicon carbide seed crystal may be 1500-2000° C.; and / or

[0085] The thickness of the flux between the silicon carbide seed crystal and the raw material block may be 5 to 30 mm.

[0086] In this embodiment, for example, the preset gradient may be 4°C / cm, 7°C / cm, 11°C / cm, 18°C / cm or 25°C / cm. The temperature of the flux between the silicon carbide seed crystal and the raw material block is adjusted from top to bottom (e.g., Figure 7 h is a straight line, which gradually decreases from top to bottom along the straight line. While reducing energy consumption, it can also avoid excessive gradients, avoid affecting the speed of Si and C transmission in the flux, and is also beneficial to the control of the flux temperature. In general, the temperature of the flux at the silicon carbide seed crystal (such as Figure 7 The temperature T) of the flux at h0 is 1500-2000℃, which is conducive to the rapid growth of silicon carbide single crystals. For example, the temperature of the flux at the silicon carbide seed crystal can be 1550℃, 1600℃, 1650℃, 1750℃ or 1800℃. The flux melted can be called flux melt. The thickness of the flux melt between the silicon carbide seed crystal and the raw material block (such as Figure 7 The thickness between h1 and h0 can be controlled to be 5 to 30 mm, such as 10 mm, 15 mm, 20 mm, or 25 mm. Controlling the thickness of the flux melt to 5 to 30 mm can ensure that it can fully exert its effect while avoiding excessive heat consumption, thereby reducing energy consumption.

[0087] In one embodiment of the present invention, after heating the crucible to melt the flux, the method may include:

[0088] Calculate the holding time after the flux melts;

[0089] When the heat preservation time reaches the second preset time, the step of pulling the raw material block upward is performed.

[0090] In this embodiment, the holding time after the flux is melted is calculated. When the holding time reaches a second preset time, the temperature of each portion of the melted flux can be made more uniform. Then, the step of pulling the raw material block upward is performed to facilitate smoother growth of the silicon carbide single crystal. The second preset time can be any value between 0.5 and 2 hours, for example, 0.8 hours, 1.0 hours, or 1.5 hours.

[0091] In one embodiment of the present invention, after contacting the bottom surface of the raw material block with the flux, the method may include:

[0092] Rotating the crucible and / or the raw material block; and / or

[0093] The crucible and / or raw material block is moved up and down, and the bottom surface of the raw material block is kept in contact with the flux.

[0094] In this embodiment, rotating the crucible and / or the raw material block can increase the dissolution rate of the raw material block and increase the flow rate of the flux after melting, thereby increasing the transmission rate of Si and C in the flux melt, making the solute (Si and C) supply more sufficient, and thus significantly increasing the growth rate of the silicon carbide single crystal. Similarly, moving the crucible and / or the raw material block up and down can also increase the flow rate of the flux after melting, increase the transmission rate of Si and C in the melt, make the solute supply more sufficient, and thus significantly increase the growth rate of the silicon carbide single crystal. It can be understood that the crucible and / or the raw material block can be rotated and / or moved up and down during the process from the beginning to the end of the growth of the silicon carbide single crystal.

[0095] In one embodiment of the present invention, when the crucible and the raw material block are rotated simultaneously, the crucible and the raw material block are rotated in opposite directions.

[0096] In this embodiment, when the crucible and the raw material block rotate simultaneously, the crucible and the raw material block are rotated in opposite directions. For example, when the crucible rotates clockwise, the raw material block rotates counterclockwise. This can make the relative rotation speed of the crucible and the raw material block faster, further increase the flow rate of the flux after melting, and increase the transmission speed of Si and C in the melt, thereby significantly increasing the growth rate of silicon carbide single crystals. In addition, the crucible and the raw material block can be rotated at a uniform speed or at a variable speed, such as accelerated rotation or decelerated motion. Specifically, for example, the rotation speed can be ±0 to 200 r / min, and the rotation acceleration can be ±0 to 30 r / min. 2 The up and down movement rate can be 0-3000 μm / h; preferably, the rotation speed can be ±20-180 r / min, and the rotation acceleration can be ±5-25 r / min 2 , the up and down movement rate can be 50 ~ 2000μm / h.

[0097] In one embodiment of the present invention, before heating the crucible to melt the flux, the method may further include:

[0098] The crucible is placed in a single crystal growth furnace;

[0099] A protective gas is filled into the single crystal growth furnace, and the pressure in the single crystal growth furnace can be adjusted to 0.1 to 2 atm.

[0100] In this embodiment, the crucible is placed in a single crystal growth furnace, a protective gas is introduced into the single crystal growth furnace, and the pressure in the single crystal growth furnace is adjusted to 0.1 to 2 atm. This can make the entire silicon carbide single crystal growth process safer and reduce the interference of substances such as oxygen on the growth of the silicon carbide single crystal. The pressure can be adjusted to 0.1 to 2 atm, specifically, for example, 0.2, 0.5, 0.9, 1.2, or 1.5 atm.

[0101] In one embodiment of the present invention, the shielding gas may include nitrogen and / or argon.

[0102] In this embodiment, nitrogen and / or argon are both inert gases that can play a relatively good protective role. Of course, this embodiment can also use other inert gases that can play a protective role.

[0103] In one embodiment of the present invention, the molar ratio of silicon to carbon in the raw material block is 1:1, and the silicon and carbon elements in the raw material block are evenly distributed.

[0104] In this embodiment, the molar ratio of silicon to carbon in the raw material block is 1:1, and the silicon and carbon elements in the raw material block are evenly distributed, which helps the silicon carbide single crystal grow faster and improves the quality of the silicon carbide single crystal.

[0105] In one embodiment of the present invention, the flux may include silicon and at least one of the following:

[0106] Transition metals, rare earth metals, Group IIIA metals and Group IVA metals.

[0107] In this embodiment, the flux may include at least one of transition metals, rare earth metals, group IIIA metals and group IVA metals and silicon, which is beneficial to the transport of Si and C in the flux melt. 0.7 Cr 0.25 Al 0.02 La 0.03 The composition and ratio of the co-solvent of the present invention significantly influence the carbon solubility, viscosity, and solid-liquid interfacial energy of the co-solvent melt, thereby directly impacting crystal growth. Specifically, carbon solubility and viscosity increase the dissolution and transport of solute C, improving the crystal growth rate and quality. Furthermore, solid-liquid interfacial energy enhances the stability of the crystal growth interface, thereby improving the crystal quality.

[0108] Based on the same technical concept, an embodiment of the present invention further provides a silicon carbide single crystal prepared by the silicon carbide single crystal growth method according to any one of the above embodiments.

[0109] In this embodiment, the silicon carbide single crystal can be a p-type, n-type or semi-insulating SiC single crystal. The subsequent wafer processing of the silicon carbide single crystal in this embodiment is very simple.

[0110] Figure 2 FIG. 1 shows a schematic structural diagram of a crucible according to an embodiment of the present invention. Figure 2 Based on the same technical concept, an embodiment of the present invention further provides a crucible 200. Crucible 200 may include a crucible shell 201. Crucible shell 201 is used to grow the silicon carbide single crystal of the above embodiment; crucible shell 201 is divided from top to bottom into a first section 203 and a second section 204; second section 204 tapers from top to bottom.

[0111] In this embodiment, the crucible shell 201 has a notch 202 at the top, which can be used to take and place silicon carbide seed crystals, raw material blocks, flux, etc. The second section 204 tapers from top to bottom to form a structure similar to an inverted cone, so that the crystal diameter expansion and shape can be controlled through the bottom structure of the crucible 200 (the second section 204), thereby avoiding or greatly reducing the probability of growing hexagonal crystals. The cross-section of the crucible shell 201 can be circular. The diameter of the bottom of the crucible shell 201 can be 2-8 inches, for example, 3 or 5 inches. The size of the SiC single crystal grown at the bottom of the crucible shell 201 is the same as the size of the bottom of the crucible shell 201, and its diameter can also be 2-8 inches. The shape of the SiC single crystal is also circular, that is, the surface of the SiC single crystal can be circular, making the subsequent wafer processing of the silicon carbide single crystal very simple. Crucible 200 also features high-temperature resistance and flux corrosion resistance. Specifically, crucible shell 201 can be made of tungsten carbide or tantalum carbide, or a tungsten or tantalum crucible with its inner wall subjected to high-temperature carbonization, or a graphite crucible with an inner wall coated with a high-temperature, flux-resistant, and corrosion-resistant coating. The first section 203 can be perpendicular to the bottom of crucible shell 201. Crucible 200 is protected from corrosion during silicon carbide single crystal growth.

[0112] Figure 3 FIG1 shows the structural schematic of a raw material block according to an embodiment of the present invention. Figure 3 Based on the same concept, the present invention further provides a raw material block 300. The raw material block 300 can be divided from top to bottom into a third section 301 and a fourth section 302. The fourth section 302 is compatible with the second section 204 of the crucible 200 of the above embodiment and is used in the silicon carbide single crystal growth method of any of the above embodiments.

[0113] In this embodiment, the fourth section 302 is adapted to fit within the second section 204 of the crucible 200 of the aforementioned embodiment. Specifically, the fourth section 302 tapers from top to bottom, and the outer surface of the fourth section 302 is completely aligned with the inner surface of the second section 204. When the raw material block 300 is placed within the crucible 200, it can easily and completely cover the silicon carbide seed crystal.

[0114] In one embodiment of the present invention, the third section 301 tapers from bottom to top.

[0115] In this embodiment, the third section 301 of the raw material block 300 is gradually reduced from bottom to top, which can leave a larger space for the flux 403 and is also conducive to observing the state of the flux 403. Specifically, the shape of the third section 301 can be as follows: Figure 4 shown.

[0116] In one embodiment of the present invention, the raw material block 300 may further include a fifth section 303. The fifth section 303 is located between the third section 301 and the fourth section 302, is perpendicular to the bottom of the raw material block 300, and is connected to the third section 301 and the fourth section 302 respectively.

[0117] In this embodiment, the fifth section 303 is located between the third section 301 and the fourth section 302, and is perpendicular to the bottom of the raw material block 300. It is connected to the third section 301 and the fourth section 302 respectively. Before the raw material block 300 is pulled upward, the molten flux 403 can be effectively prevented from flowing onto the silicon carbide seed crystal 405. Specifically, the fifth section 303 can be as follows Figure 5 shown.

[0118] See also Figure 6 and Figure 7 Based on the same technical concept, an embodiment of the present invention also provides a growth system for silicon carbide single crystals. Figure 6 The silicon carbide single crystal of the growth system shown is in the state before growth. Figure 7The silicon carbide single crystal in the growth system shown is in a growing state. The growth system may include a single crystal growth furnace 400, a graphite shaft 401, a support shaft 406, an insulation layer 402, a heating element 404, and a crucible 200 according to any of the above-described embodiments. The single crystal growth furnace 400 has a first opening 407 and a second opening 408 at the top and bottom, respectively. The crucible 200 is located in the single crystal growth furnace 400. The graphite shaft 401 is inserted into the first opening 407 for connecting to the raw material block 300. The support shaft 406 is inserted into the second opening 408 and connected to the bottom of the crucible 200. The insulation layer 402 is disposed around the outer surface of the crucible 200. The flux 403 is located between the raw material block 300 and the inner surface of the crucible 200. The heating element 404 is located between the inner wall of the single crystal growth furnace 400 and the outer wall of the insulation layer 402 for heating the crucible 200. There may be multiple heating elements 404 distributed between the inner wall of the single crystal growth furnace 400 and the outer wall of the insulation layer 402, in the area opposite the flux 403, to heat the entire flux 403. The insulation performance of the insulation layer 402 gradually increases from top to bottom, thereby causing the temperature of the flux 103 between the silicon carbide seed crystal 405 and the raw material block 300 to decrease from top to bottom according to a preset gradient.

[0119] The following describes in detail the method for growing a silicon carbide single crystal according to the present invention through some specific examples.

[0120] Example 1

[0121] The crucible 200 used in this embodiment is a tungsten carbide crucible with an inner diameter of 130 mm and a height of 200 mm. The bottom diameter of the crucible 200 is 100 mm, and the inclination angle a of the bottom cone is 30°. The silicon carbide seed crystal 405 used is a 4-inch semi-insulating SiC single crystal crystal. The raw material block 300 used is a SiC polycrystalline block with a diameter of 110 mm and a height of 150 mm. The flux 403 used is Si 0.65 Cr 0.3 Co 0.05 , control the total amount of flux 403 so that the thickness of flux 403 melt (the thickness between h1 and h0) is 20mm. According to the above steps, put the crucible 200 into the single crystal growth furnace 400, and then use the mechanical pump and molecular pump to evacuate the furnace chamber of the single crystal growth furnace 400 to 10 -4Pa, and then 0.1atm of Ar gas is filled into the furnace chamber as a protective gas. The crucible 200 is heated by the heating component 404, so that the temperature of the flux 403 melt at the liquid surface is 1850°C, and the temperature field is controlled so that the temperature of the flux 403 melt at the liquid surface is higher than its temperature at the silicon carbide seed crystal 405, and the temperature of the flux 403 melt is gradually reduced from top to bottom in the axial direction of the crucible 200 (vertical line h) according to a preset gradient of 5°C / cm. During the growth process, the raw material block 300 rotates counterclockwise at a speed of 30r / min, and the crucible 200 rotates clockwise at a speed of 5r / min; at the same time, the raw material block 300 slowly moves downward at a speed of 120μm / h, and the crucible 200 slowly moves downward at a speed of 150μm / h. After 60 hours of crystal growth, the raw material block 300 is pulled upward at a speed of 3 mm / h to separate it from the liquid surface of the flux 403. After in-situ annealing, the temperature is slowly lowered to room temperature, and the crystal is finally removed. The downward movement speed of the raw material block 300 can generally be slower than the downward movement speed of the crucible 200.

[0122] The SiC crystals grown in this embodiment are round in shape rather than hexagonal. This is due to the physical constraints imposed by the bottom of the crucible 200 on the lateral space for crystal growth, effectively limiting the SiC crystals from developing into a hexagonal shape, which is beneficial for subsequent wafer processing.

[0123] Example 2

[0124] During the crystal growth process, the downward moving speeds of the raw material block 300 and the crucible 200 were increased to 240 μm / h and 300 μm / h, respectively. Other conditions were the same as those in Example 1.

[0125] In this embodiment, the growth rate of the crystal is significantly improved. This is because the speed of movement of the raw material block 300 and the crucible 200 is increased, thereby increasing the dissolution rate of the raw material block 300 and improving the growth rate of the crystal.

[0126] Example 3

[0127] The shape of the raw material block 300 used for crystal growth is changed to Figure 4 The shape shown in FIG. 1 is shown, wherein the chamfered bottom surface of the raw material block 300 (fourth section 302) and the inverted conical bottom surface of the crucible 200 (second section 204) are completely aligned. Simultaneously, the downward movement speeds of the raw material block 300 and crucible 200 during crystal growth were increased to 200 μm / h and 300 μm / h, respectively, with all other conditions remaining the same as in Example 1.

[0128] By improving the shape of raw material block 300, more space is left for flux 403, making it easier to observe the state of flux 403 melt before growth. At the same time, the chamfered structure at the bottom of raw material block 300 can separate flux 403 melt from the SiC seed crystal at the bottom, effectively preventing flux 403 melt from prematurely flowing down onto the SiC seed crystal.

[0129] Example 4

[0130] During the crystal growth process, the rotation speeds of the raw material block 300 and the crucible 200 were increased to 120 r / min and 10 r / min, respectively. Other growth conditions remained the same as those in Example 1, and crystal growth was continued.

[0131] After increasing the rotation speed of the crucible 200 and the raw material block 300, the growth rate and quality of the crystal are improved. This is because the flow rate of the flux 403 melt is accelerated after increasing the rotation speed, which increases the transmission speed of Si and C in the flux 403 melt and makes the solute supply more sufficient.

[0132] The above describes the technical solution of the present invention in detail through several specific embodiments. The parameters given in the above embodiments are only exemplary and not restrictive. When the technology provided by the present invention is actually implemented, it is necessary to perform corresponding optimization according to the actual situation.

[0133] It should be noted that the above embodiments are intended only to illustrate the technical solutions of the present invention and are not intended to limit them. While specific process parameters can be optimized and adjusted, the two core concepts of the present invention and the basic structure of the growth apparatus are clear. Those skilled in the relevant art should understand that modifications or equivalent substitutions to the technical solutions of the present invention do not depart from the spirit and scope of the technical solutions of the present invention and are intended to be encompassed by the claims of the present invention.

[0134] According to any one of the above optional embodiments or a combination of multiple optional embodiments, the embodiments of the present invention can achieve the following beneficial effects:

[0135] In the growth method of a silicon carbide single crystal of the present invention, a silicon carbide seed crystal is placed at the bottom of a crucible, and a raw material block is covered on the carbide seed crystal, wherein the raw material block includes silicon and carbon elements, and a flux is added to the area between the raw material block and the inner wall of the crucible. The crucible is heated to melt the flux, and the raw material block is pulled upward so that the melted flux flows between the silicon carbide seed crystal and the raw material block, and the bottom surface of the raw material block is in contact with the flux. After a first preset period of time, the raw material block is pulled upward to separate it from the molten flux, and the temperature of the crucible is lowered to a specified temperature to obtain a silicon carbide single crystal grown based on the silicon carbide seed crystal. During the growth of the silicon carbide single crystal in this embodiment, the melt and raw materials are located above the seed crystal. The crystal is firmly pressed to the bottom of the crucible under the action of the melt and its own gravity, and the possibility of the seed crystal falling is eliminated or greatly reduced. Before growth, the SiC seed crystal is covered by the raw material block above, which hinders the deposition of volatiles from the flux melt on the surface of the seed crystal, prevents a large number of defects generated in the early stage of growth, and is beneficial to improving the crystallization quality of the crystal. Since the crystal growth interface is located at the bottom of the flux melt, even if spontaneous SiC nuclei are generated in the melt, it will not affect the crystal growth interface. The crystal growth interface is more stable, which can improve the crystallization quality of the crystal. The Si and C required for crystal growth are all directly provided by the raw material block, and the Si content in the flux melt will not change. The growth system is more stable and durable, which is beneficial to the long-term stable growth of high-quality SiC crystals.

[0136] In the description provided herein, numerous specific details are described. However, it is understood that embodiments of the present invention may be practiced without these specific details. In some instances, well-known methods, structures, and techniques are not shown in detail so as not to obscure the understanding of this description.

[0137] At this point, those skilled in the art will recognize that, although a number of exemplary embodiments of the present invention have been shown and described in detail herein, many other variations or modifications consistent with the principles of the present invention may be directly determined or derived from the disclosure of the present invention without departing from the spirit and scope of the present invention. Therefore, the scope of the present invention should be understood and deemed to cover all such other variations or modifications.

Claims

1. A method for growing a silicon carbide single crystal, characterized in that: include: Placing a silicon carbide seed crystal at the bottom of the crucible; Covering the silicon carbide seed crystal with a raw material block; wherein the raw material block includes silicon and carbon elements; Filling the area between the raw material block and the inner wall of the crucible with flux; heating the crucible to melt the flux; calculating a holding time after the flux is melted, and when the holding time reaches a second preset time, pulling the raw material block upward so that the melted flux flows between the silicon carbide seed crystal and the raw material block, and the bottom surface of the raw material block contacts the flux; After a first preset time period, the raw material block is pulled upward to separate it from the melted flux; Lowering the temperature of the crucible to a specified temperature to obtain a silicon carbide single crystal grown based on the silicon carbide seed crystal; After the bottom surface of the raw material block is brought into contact with the flux, the method further comprises: rotating the crucible and / or the raw material block; and / or Moving the crucible and / or the raw material block up and down, and keeping the bottom surface of the raw material block in contact with the flux; The crucible is a crucible resistant to corrosion by flux; The molar ratio of silicon to carbon in the raw material block is 1:

1.

2. The growth method according to claim 1, characterized in that After the melted flux is flowed between the silicon carbide seed crystal and the raw material block, the method further includes: The temperature of the flux between the silicon carbide seed crystal and the raw material block is gradually reduced from top to bottom according to a preset gradient.

3. The growth method according to claim 2, wherein: The preset gradient is 2-30°C / cm; and / or The temperature of the flux at the silicon carbide seed crystal is 1500-2000° C.; and / or The thickness of the flux between the silicon carbide seed crystal and the raw material block is 5-30 mm.

4. The growth method according to claim 1, wherein When the crucible and the raw material block are rotated simultaneously, the crucible and the raw material block are rotated in opposite directions.

5. The growth method according to claim 1, characterized in that Before heating the crucible to melt the flux, the method further comprises: placing the crucible into a single crystal growth furnace; A protective gas is charged into the single crystal growth furnace, and the pressure in the single crystal growth furnace is adjusted to 0.1-2 atm.

6. The growth method according to claim 5, characterized in that The protective gas includes nitrogen and / or argon.

7. The growth method according to claim 1, characterized in that The silicon element and the carbon element of the raw material block are evenly distributed.

8. The growth method according to claim 1, wherein: The flux comprises silicon and at least one of the following: Transition metals, rare earth metals, Group IIIA metals and Group IVA metals.

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