Device and method for rapid growth of large-size high-quality silicon carbide single crystals

Abstract

The present invention relates to the technical field of crystal growth. Provided are a device and method for rapid growth of large-size high-quality silicon carbide single crystals. The device comprises a crucible assembly, a seed crystal assembly, a heating assembly disposed outside of the crucible assembly, and a thermal insulation assembly between the heating assembly and the crucible assembly. The crucible assembly comprises a crucible and a driving and rotating component disposed below the crucible for pushing and rotating the crucible. The seed crystal assembly comprises a seed crystal rod, a seed crystal holder, and a turbine heat dissipator. The seed crystal holder comprises a seed crystal holder base plate and a connecting rod fixedly connected to the seed crystal holder base plate. The connecting rod is connected to the seed crystal rod by a mortise-and-tenon joint structure, and the mortise-and-tenon joint structure is locked by a locking member. The turbine heat dissipator comprises a turbine shaft sleeve and turbine blades distributed on the turbine shaft sleeve. The turbine shaft sleeve is sleeved on the connecting rod. The turbine heat dissipator accelerates heat dissipation when rotating in a first direction, and suppresses heat dissipation when rotating in a second direction. The device provided by the present invention achieves rapid growth of large-size and high-quality silicon carbide single crystals.

Description

An apparatus and method for rapidly growing large-size, high-quality silicon carbide single crystals. Technical Field

[0001] This invention relates to the field of crystal growth technology, and in particular to an apparatus and method for rapidly growing large-size, high-quality silicon carbide single crystals. Background Technology

[0002] Silicon carbide, as a typical representative of wide bandgap semiconductors, has excellent properties such as large bandgap, high breakdown field strength, high saturated electron mobility, high thermal conductivity, and good thermal and chemical stability. It is an ideal substrate material for fabricating high-frequency, high-voltage, high-efficiency, radiation-resistant, and high-temperature-resistant high-power devices and blue light-emitting diodes. This makes it a promising material for applications in new energy vehicles, high-speed rail, aerospace, high-voltage smart grids, and clean energy, and has therefore attracted widespread attention from the academic community and governments around the world.

[0003] The mainstream method for growing silicon carbide single crystal substrates is physical vapor transport (PVT). Although this method has become relatively mature after decades of continuous research and improvement and can supply a large number of silicon carbide single crystal substrates to the market, it still has some unavoidable limitations. These limitations are mainly reflected in its unstable growth environment, difficulty in eliminating defects, low yield, high cost, difficulty in diameter expansion, and difficulty in achieving continuous and effective P-type doping.

[0004] Compared to the vapor-phase method, the liquid-phase growth method requires lower growth temperatures and offers a more stable growth environment, enabling near-equilibrium crystal growth. This not only results in lower growth costs but also theoretically allows for higher crystal quality. In liquid-phase silicon carbide single crystal growth, the uniformity of the radial temperature field of the crystal and the uniformity of heat dissipation from the seed crystal have a significant impact on the growth quality and rate of silicon carbide crystals, especially large-sized (4-8 inch) silicon carbide crystals. Currently, adjusting the size of the opening in the insulation felt above the crystal is generally used to change the heat dissipation rate and radial temperature gradient during crystal growth. However, this method struggles to simultaneously balance the heat dissipation rate and radial temperature gradient, and it cannot achieve in-situ real-time control of crystal heat dissipation during growth. Consequently, it fails to adequately balance crystal growth quality and rate, and it is also difficult to achieve stable growth over long periods. Summary of the Invention

[0005] To address one or more technical problems existing in the prior art, the present invention provides an apparatus and method for rapidly growing large-size, high-quality silicon carbide single crystals. The apparatus provided by the present invention can effectively improve the heat dissipation rate and heat dissipation uniformity of the crystal, and can control the radial temperature gradient and axial heat dissipation rate at the crystal growth interface in real time, so as to meet the heat dissipation requirements at each stage of crystal growth and realize the rapid growth of large-size, high-quality silicon carbide single crystals.

[0006] This invention provides an apparatus for rapidly growing large-size, high-quality silicon carbide single crystals. The apparatus includes a crucible assembly, a seed crystal assembly, a heating assembly disposed outside the crucible assembly, and a heat-insulating assembly located between the heating assembly and the crucible assembly. The crucible assembly includes a crucible and a pushing and rotating component disposed below the crucible for pushing and rotating the crucible. The seed crystal assembly includes a seed crystal rod, a seed crystal holder, and a turbine heat sink. The seed crystal holder includes a seed crystal holder substrate and a connecting rod fixedly connected to the seed crystal holder substrate. The connecting rod is connected to the seed crystal rod by a tenon and mortise structure. The tenon and mortise structure is locked by a locking component. The turbine heat sink includes a turbine shaft and turbine blades distributed on the turbine shaft. The turbine shaft is fitted onto the connecting rod. The turbine heat sink accelerates heat dissipation when rotating in a first direction and inhibits heat dissipation when rotating in a second direction.

[0007] Preferably, the crucible is a graphite crucible.

[0008] Preferably, the mortise and tenon structure includes a tenon groove structure disposed at the lower end of the seed crystal rod and a tenon structure disposed at the upper end of the connecting rod; the locking component is fixed to the tenon groove structure by threads.

[0009] The present invention also provides a method for rapidly growing large-size, high-quality silicon carbide single crystals, implemented using the apparatus described in the first aspect, the method comprising the following steps:

[0010] S1. Place the flux and silicon in a crucible and heat until the mixture is completely liquefied to obtain a melt;

[0011] S2. After rotating the seed crystal rod along the second direction at a first preset speed for a first preset time, the seed crystal comes into contact with the melt to grow a silicon carbide single crystal. During the crystal growth process, the rotation direction and speed of the seed crystal rod are adjusted according to the heat dissipation requirements at different stages. The rotation direction of the crucible is always opposite to the rotation direction of the seed crystal.

[0012] Preferably, during crystal growth, after the seed crystal comes into contact with the melt, the seed crystal rod rotates along the second direction at a second preset speed for a second preset time. Then, at a third preset time, the speed is reduced to 0 and accelerated along the first direction to a third preset speed. Then, it rotates at the third preset speed for a fourth preset time. Finally, according to the thermal insulation performance decay curve of the thermal insulation material used in the thermal insulation component, the speed is reduced to the fourth preset speed at a fifth preset time to ensure that the heat dissipation rate remains stable.

[0013] Preferably, the second preset rotational speed is greater than the first preset rotational speed;

[0014] The third preset speed is greater than the second preset speed.

[0015] Preferably, the first preset rotational speed is 5 to 30 rpm;

[0016] The second preset speed is 10-60 rpm; and / or

[0017] The third preset speed is 60 to 240 rpm.

[0018] Preferably, during crystal growth, the crucible rotates at a speed of 2 to 10 rpm;

[0019] The crucible moves upward at a speed of 0–1000 μm / h; and / or

[0020] The pulling speed of the seed crystal rod is 0 to 1500 μm / h.

[0021] Preferably, the second preset time is 0.5 to 2 hours;

[0022] The third preset time is 0.5 to 2 hours;

[0023] The fourth preset time is 10-20 hours; and / or

[0024] The fifth preset time is 20 to 60 hours.

[0025] Preferably, after crystal growth is completed, at a sixth preset time, the rotation speed is reduced to 0 and accelerated to a fifth preset rotation speed in the second direction, and then maintained for a seventh preset time.

[0026] Compared with the prior art, the present invention has at least the following beneficial effects:

[0027] A turbine heat sink is installed above the seed crystal support substrate. The rotation of the seed crystal rod drives the turbine heat sink to rotate synchronously with the seed crystal support. This ensures that the airflow in the crucible during crystal growth is directed and directional under the drive of the turbine heat sink. This not only limits gas turbulence in the crucible but also rapidly transfers heat from the crucible walls to the center region, effectively improving the temperature uniformity at the crystal growth interface. This is beneficial for improving crystal growth quality and provides a foundation for the growth of large-size crystals. During crystal growth, the rotation of the turbine heat sink accelerates the directional heat flow rate, effectively improving the heat dissipation rate and uniformity. This allows the latent heat of crystallization to be promptly and uniformly dissipated from the growth interface, thus increasing the crystal growth rate. Furthermore, by controlling the rotation speed and direction of the turbine heat sink in real time through the seed crystal rod, the radial temperature gradient and axial heat dissipation rate at the crystal growth interface can be controlled, facilitating stable long-term crystal growth.

[0028] In this invention, the seed crystal holder and seed crystal rod are connected by a mortise and tenon structure and then locked by a locking component cylinder. This achieves a firm connection between the seed crystal rod and the seed crystal holder, and also limits the turbine radiator to prevent it from sliding during the rotation of the seed crystal holder. This structure has high reliability, can withstand greater rotational torque, and can meet greater torque transmission requirements. It better enables high-speed rotation of large-size crystals in a viscous melt during crystal growth, and can meet the process requirements of long-term high-speed rotation and pulling growth of large-size silicon carbide crystals. It overcomes the limitations of existing seed crystal rods and seed crystal holders, such as the inability to achieve higher crystal rotation requirements, difficulty in supporting high-speed rotation of larger-size crystals, easy wear or damage of connecting threads, and poor reusability, due to the weak connection between the seed crystal rod and the seed crystal holder.

[0029] The device provided by this invention can effectively improve the heat dissipation rate and heat dissipation uniformity of the crystal, and control the radial temperature gradient and axial heat dissipation rate at the crystal growth interface in real time, so as to meet the heat dissipation requirements of each stage of crystal growth and realize the long-term rapid and stable growth of large-size, high-quality silicon carbide single crystals.

[0030] Based on the provided device and combined with the heat dissipation requirements at different stages of the silicon carbide crystal growth process, this invention regulates the heat dissipation rate on the back of the seed crystal by controlling the rotation direction and speed of the turbine heat sink through the seed crystal rod. This can effectively improve the heat dissipation rate and uniformity of the crystal, and control the radial temperature gradient and axial heat dissipation rate at the crystal growth interface in real time to meet the heat dissipation requirements at each stage of crystal growth, thereby achieving rapid growth of large-size, high-quality silicon carbide single crystals. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0032] Figure 1 is a schematic diagram of the structure of a device for rapidly growing large-size, high-quality silicon carbide single crystals provided by the present invention;

[0033] Figure 2 is a schematic diagram of the assembly process of the seed crystal component in the device for rapidly growing large-size, high-quality silicon carbide single crystals provided by the present invention.

[0034] Figure 3 is a graph showing the change of the seed crystal rod rotation direction and rotation speed over time during the growth of a large-size, high-quality silicon carbide single crystal provided by the present invention.

[0035] Figure 4 is an optical photograph of a 4-inch high-quality silicon carbide single crystal provided in Embodiment 2 of the present invention;

[0036] Figure 5 is an optical photograph of a 6-inch high-quality silicon carbide single crystal provided in Embodiment 3 of the present invention;

[0037] Figure 6 is a graph showing the rocking curve test results of the 6-inch high-quality silicon carbide single crystal provided in Embodiment 3 of the present invention;

[0038] Figure 7 is an optical photograph of a 4-inch silicon carbide single crystal provided in Comparative Example 1 of the present invention;

[0039] Figure 8 is an optical photograph of a 6-inch silicon carbide single crystal provided in Comparative Example 2 of this invention;

[0040] Figure 9 is an optical photograph of a 4-inch silicon carbide single crystal provided in Comparative Example 3 of this invention.

[0041] Reference numerals: 1-Crucible assembly; 11-Crucible; 12-Rotating component; 2-Seed crystal assembly; 21-Seed crystal rod; 211-Tongue and groove structure; 22-Seed crystal holder; 221-Seed crystal holder substrate; 222-Connecting rod; 223-Tongue structure; 23-Turbine radiator; 231-Turbine shaft; 232-Turbine blade; 24-Locking component; 3-Insulation assembly; 4-Heating assembly; 5-Furnace cavity. Detailed Implementation

[0042] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0043] In the description of the embodiments of the present invention, unless otherwise expressly specified and limited, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance; unless otherwise specified or stated, the term "multiple sets" refers to two or more sets; the terms "connection," "fixed," etc., should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, an integral connection, or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium. The terms "comprising," "including," or any other variations thereof are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes the element. Those skilled in the art can understand the specific meaning of the above terms in the present invention according to the specific circumstances.

[0044] In this specification, it should be understood that the directional terms such as "upper" and "lower" used in the description of the embodiments of the present invention are used to describe the angles shown in the accompanying drawings and should not be construed as limiting the embodiments of the present invention. Furthermore, in the context, it should also be understood that when it is mentioned that one element is connected "upper" or "lower" to another element, it can be directly connected to the other element "upper" or "lower," or indirectly connected to the other element "upper" or "lower" through an intermediate element.

[0045] As shown in Figures 1-2, this invention provides an apparatus for rapidly growing large-size, high-quality silicon carbide single crystals. The apparatus includes a crucible assembly 1, a seed crystal assembly 2, a heating assembly 4 disposed outside the crucible assembly 1, and a heat-insulating assembly 3 located between the heating assembly 4 and the crucible assembly 1. The crucible assembly 1 includes a crucible 11 and a pushing and rotating component 12 disposed below the crucible 11 for pushing and rotating the crucible 11. The seed crystal assembly 2 includes a seed crystal rod 21, a seed crystal holder 22, and a turbine heat sink 23. The crystal holder 22 includes a seed crystal holder substrate 221 and a connecting rod 222 fixedly connected to the seed crystal holder substrate 221; the connecting rod 222 is connected to the seed crystal rod 21 by a tenon and mortise structure; the tenon and mortise structure is locked by a locking component 24; the turbine radiator 23 includes a turbine shaft cylinder 231 and turbine blades 232 distributed on the turbine shaft cylinder 231; the turbine shaft cylinder 231 is fitted onto the connecting rod 222; the turbine radiator 23 accelerates heat dissipation when rotating in a first direction and suppresses heat dissipation when rotating in a second direction.

[0046] A turbine heat sink is installed above the seed crystal support substrate. The rotation of the seed crystal rod drives the turbine heat sink to rotate synchronously with the seed crystal support. This ensures that the airflow in the crucible during crystal growth is directed and directional under the drive of the turbine heat sink. This not only limits gas turbulence in the crucible but also rapidly transfers heat from the crucible walls to the center region, effectively improving the temperature uniformity at the crystal growth interface. This is beneficial for improving crystal growth quality and provides a foundation for the growth of large-size, high-quality crystals. During crystal growth, the rotation of the turbine heat sink accelerates the directional heat flow rate, effectively improving the heat dissipation rate and uniformity. This allows the latent heat of crystallization to be promptly and uniformly dissipated from the growth interface, thus increasing the crystal growth rate. Furthermore, by controlling the rotation speed and direction of the turbine heat sink in real time via the seed crystal rod, the radial temperature gradient and axial heat dissipation rate at the crystal growth interface can be controlled, facilitating stable long-term crystal growth.

[0047] In this invention, the seed crystal holder and seed crystal rod are connected by a mortise and tenon structure and then locked by a locking component cylinder. This achieves a firm connection between the seed crystal rod and the seed crystal holder, and also limits the turbine radiator to prevent it from sliding during the rotation of the seed crystal holder. This structure has high reliability, can withstand greater rotational torque, and can meet greater torque transmission requirements. It better enables high-speed rotation of large-size crystals in a viscous melt during crystal growth, and can meet the process requirements of long-term high-speed rotation and pulling growth of large-size silicon carbide crystals. It overcomes the limitations of existing seed crystal rods and seed crystal holders, such as the inability to achieve higher crystal rotation requirements, difficulty in supporting high-speed rotation of larger-size crystals, easy wear or damage of connecting threads, and poor reusability, due to the weak connection between the seed crystal rod and the seed crystal holder.

[0048] As shown in Figure 2, the assembly process of the seed crystal assembly and turbine radiator in the device provided by the present invention includes: fitting the turbine radiator onto the connecting rod that is fixedly connected to the seed crystal support base plate; then connecting the connecting rod and the seed crystal rod through a tenon and mortise structure; and then locking the tenon and mortise structure through a locking component. At the same time, the turbine radiator can be limited, preventing the turbine radiator from moving axially during rotation.

[0049] According to some preferred embodiments, the crucible 11 is a graphite crucible.

[0050] According to some preferred embodiments, the mortise and tenon structure includes a tenon groove structure 211 disposed at the lower end of the seed crystal rod 21 and a tenon structure 223 disposed at the upper end of the connecting rod 222; the locking member 24 is fixed to the tenon groove structure by threads.

[0051] In some preferred embodiments of the present invention, the cross-section of the turbine shaft sleeve and the connecting rod is polygonal, preferably one of triangle, square, rectangle, trapezoid, pentagon, and hexagon; thus, a greater torque can be provided during rotation, while preventing the turbine radiator from sliding relative to the connecting rod.

[0052] According to some preferred embodiments, the device further includes a furnace cavity 5.

[0053] The present invention also provides a method for rapidly growing large-size, high-quality silicon carbide single crystals, implemented using the apparatus described in the first aspect, the method comprising the following steps:

[0054] S1. Place the flux and silicon in a crucible and heat until the mixture is completely liquefied to obtain a melt;

[0055] S2. After rotating the seed crystal rod along the second direction at a first preset speed for a first preset time, the seed crystal comes into contact with the melt to grow a silicon carbide single crystal. During the crystal growth process, the rotation direction and speed of the seed crystal rod are adjusted according to the heat dissipation requirements at different stages. The rotation direction of the crucible is always opposite to the rotation direction of the seed crystal.

[0056] Based on the provided device and combined with the heat dissipation requirements at different stages of the silicon carbide crystal growth process, this invention regulates the heat dissipation rate on the back of the seed crystal by controlling the rotation direction and speed of the turbine heat sink through the seed crystal rod. This can effectively improve the heat dissipation rate and uniformity of the crystal, and control the radial temperature gradient and axial heat dissipation rate at the crystal growth interface in real time to meet the heat dissipation requirements at each stage of crystal growth, thereby achieving long-term, rapid, and stable growth of large-size, high-quality silicon carbide single crystals.

[0057] According to some preferred embodiments, during crystal growth, after the seed crystal comes into contact with the melt, the seed crystal rod rotates along the second direction at a second preset speed for a second preset time. Then, at a third preset time, the speed is reduced to 0 and accelerated along the first direction to a third preset speed. Then, it rotates at the third preset speed for a fourth preset time. Finally, according to the thermal insulation performance decay curve of the thermal insulation material used in the thermal insulation component, the speed is reduced to the fourth preset speed at a fifth preset time to ensure that the heat dissipation rate remains stable.

[0058] According to some preferred embodiments, the second preset speed is greater than the first preset speed;

[0059] The third preset speed is greater than the second preset speed.

[0060] According to some preferred embodiments, the first preset speed is 5 to 30 rpm (for example, it can be 5 rpm, 10 rpm, 15 rpm, 20 rpm, 25 rpm or 30 rpm).

[0061] According to some preferred embodiments, the second preset speed is 10 to 60 rpm (for example, it can be 10 rpm, 20 rpm, 30 rpm, 40 rpm, 50 rpm or 60 rpm).

[0062] According to some preferred embodiments, the third preset speed is 60 to 240 rpm (for example, it can be 60 rpm, 80 rpm, 100 rpm, 120 rpm, 150 rpm, 180 rpm, 200 rpm, 220 rpm or 240 rpm).

[0063] According to some preferred embodiments, during crystal growth, the crucible rotates at a speed of 2 to 10 rpm (for example, 2 rpm, 3 rpm, 4 rpm, 5 rpm, 6 rpm, 7 rpm, 8 rpm, 9 rpm or 10 rpm).

[0064] According to some preferred embodiments, during crystal growth, the crucible moves upward at a speed of 0 to 1000 μm / h (for example, it can be 0 μm / h, 100 μm / h, 200 μm / h, 300 μm / h, 400 μm / h, 500 μm / h, 600 μm / h, 700 μm / h, 800 μm / h, 900 μm / h or 1000 μm / h).

[0065] According to some preferred embodiments, during crystal growth, the pulling speed of the seed crystal rod is 0 to 1500 μm / h (for example, it can be 0 μm / h, 100 μm / h, 200 μm / h, 300 μm / h, 400 μm / h, 500 μm / h, 600 μm / h, 700 μm / h, 800 μm / h, 900 μm / h, 1000 μm / h, 1100 μm / h, 1200 μm / h, 1300 μm / h, 1400 μm / h or 1500 μm / h).

[0066] According to some preferred embodiments, the second preset time is 0.5 to 2 hours (for example, it can be 0.5 hours, 0.6 hours, 0.8 hours, 1 hour, 1.2 hours, 1.4 hours, 1.6 hours, 1.8 hours or 2 hours).

[0067] According to some preferred embodiments, the third preset time is 0.5 to 2 hours (for example, it can be 0.5 hours, 0.6 hours, 0.8 hours, 1 hour, 1.2 hours, 1.4 hours, 1.6 hours, 1.8 hours or 2 hours).

[0068] According to some preferred embodiments, the fourth preset time is 10 to 20 hours (for example, it can be 10 hours, 11 hours, 12 hours, 13 hours, 14 hours, 15 hours, 16 hours, 17 hours, 18 hours, 19 hours or 20 hours).

[0069] According to some preferred embodiments, the fifth preset time is 20 to 60 hours (for example, it can be 20 hours, 24 hours, 30 hours, 36 hours, 40 hours, 48 ​​hours, 50 hours, 56 hours, 58 hours or 60 hours).

[0070] According to some preferred embodiments, after crystal growth is completed, at a sixth preset time, the rotation speed is reduced to 0 and accelerated to a fifth preset rotation speed in the second direction, and then maintained for a seventh preset time.

[0071] According to some preferred embodiments, the sixth preset time is 10 to 60 minutes (for example, it can be 10 minutes, 20 minutes, 30 minutes, 40 minutes, 50 minutes or 60 minutes).

[0072] According to some preferred embodiments, the seventh preset time is 10 to 30 hours (for example, it can be 10 hours, 12 hours, 14 hours, 15 hours, 16 hours, 18 hours, 20 hours, 22 hours, 24 hours, 26 hours, 28 hours or 30 hours).

[0073] In some specific embodiments of the present invention, the seed rod rotation process in the silicon carbide crystal growth process includes the following multiple stages, as shown in Figure 3.

[0074] First stage: t0-t1 (first preset time), at this time the seed crystal has not yet come into contact with the melt. The seed crystal rotates uniformly along the second direction at the first preset speed v1 to ensure that the seed crystal is heated evenly before growth.

[0075] The second stage: t1-t2 (second preset time). At time t1, the seed crystal comes into contact with the melt, and crystal growth begins. At this time, the seed crystal rotation speed becomes the second preset speed v2, and then rotates at a constant speed v2, where v2 > v1. At this time, the large second-direction rotation of the turbine radiator reduces the heat dissipation rate of the seed crystal in the back direction, inhibits crystal growth, and causes the seed crystal surface to undergo reverse dissolution to obtain an ideal initial growth surface, which is beneficial to improving the quality of crystal growth.

[0076] The third stage: t2-t3 (third preset time), first the seed crystal rod speed is uniformly reduced from v2 to 0, and then uniformly accelerated to the third preset speed v3 along the first direction (where v3>v2), thereby achieving a slow increase in the heat dissipation rate on the back of the seed crystal and gradually increasing the crystal growth rate.

[0077] Fourth stage: t3-t4 (fourth preset time), the seed crystal rotates at a constant speed v3 to maintain a stable heat dissipation rate;

[0078] Fifth stage: t4-t5 (fifth preset time). Considering that the heat dissipation will be faster due to the continuous decline in the heat insulation performance of the insulation material during the long growth process, the rotation speed of the radiator is reduced from the third preset speed v3 to the fourth preset speed v4 according to the decay curve of the heat insulation performance of the insulation material. Dynamic compensation is made for the heat dissipation rate to maintain a stable heat dissipation rate.

[0079] Sixth stage: t5-t6 (sixth preset time). At time t5, the crystal is slowly pulled out of the melt. First, the rotation speed of the seed crystal rod is uniformly reduced from the fourth preset speed v4 to 0, and then uniformly accelerated to the first preset speed v1 along the first direction to reduce the heat dissipation rate of the seed crystal back and prevent the crystal from cooling too quickly, which would cause the crystal to crack due to thermal stress.

[0080] Stage 7: t6-t7 (seventh preset time), the seed crystal rotates at a constant speed v1 to ensure uniform radial temperature distribution while allowing the crystal to undergo in-situ annealing at a low heat dissipation rate after growth. It should be noted that the rotational speed of the seed crystal rod at time t6 in stages 6 and 7 is not necessarily v1; this is merely an example and not a limitation.

[0081] To more clearly illustrate the technical solution and advantages of the present invention, the present invention will be further described below with reference to embodiments. The present invention does not specifically limit the source of the reagents used in the embodiments and comparative examples; they can be directly purchased or synthesized in-house.

[0082] The testing methods for the performance data of silicon carbide crystals obtained by the embodiments and comparative examples of this invention are as follows:

[0083] Crystal size and quality determination: The processed crystal is placed on standard coordinate paper or standard calipers for size confirmation; the crystal form is determined using a laser confocal Raman scattering instrument; the rocking curve of the crystal is measured using an XRD diffractometer to determine its crystal quality.

[0084] Example 1

[0085] As shown in Figure 1-2, an apparatus for rapidly growing large-size, high-quality silicon carbide single crystals includes:

[0086] The crucible assembly 1, the seed crystal assembly 2, the heating assembly 4 disposed outside the crucible assembly 1, and the heat insulation assembly 3 located between the heating assembly 4 and the crucible assembly 1; wherein, the heat insulation assembly 3 is a heat insulation material, and the heating assembly 4 is an induction heating coil;

[0087] Crucible assembly 1 includes a crucible 11 and a driving rotating component 12 for driving the crucible 11 to rotate; the crucible 11 is a graphite crucible;

[0088] The seed crystal assembly includes a seed crystal rod 21, a seed crystal holder 22, and a turbine radiator 23. The seed crystal holder 22 includes a seed crystal holder substrate 221 and a connecting rod 222 fixedly connected to the seed crystal holder substrate 221. The connecting rod 222 is connected to the seed crystal rod 21 by a mortise and tenon structure. The mortise and tenon structure includes a tenon groove structure 211 at the lower end of the seed crystal rod 21 and a tenon structure 223 at the upper end of the connecting rod 222. The mortise and tenon structure is locked by a locking member 24. The locking member 24 is fixed to the tenon groove structure 211 by threads. The turbine radiator 23 includes a turbine shaft cylinder 231 and turbine blades 232 distributed on the turbine shaft cylinder 231. The turbine shaft cylinder 231 is fitted onto the connecting rod 222. The turbine radiator 23 accelerates heat dissipation when rotating in a first direction and suppresses heat dissipation when rotating in a second direction.

[0089] Example 2

[0090] A method for rapidly growing large-size, high-quality silicon carbide single crystals, implemented using the apparatus of Example 1, includes:

[0091] S1. After assembling the device, close the furnace chamber and perform a vacuum treatment on the furnace chamber. When the furnace chamber pressure is less than or equal to 1×10 -4 After Pa, high-purity argon gas is introduced into the furnace cavity as a protective gas. The flux and silicon are placed in a crucible and heated to 1800℃ to completely liquefy the raw materials in the crucible and obtain a melt. The flux is Cr; the mass ratio of Cr to Si is 40:60, and the total mass of Cr and Si is 12kg.

[0092] S2. Once the temperature of the mixed melt stabilizes, the seed crystal rod is rotated along the second direction at a first preset speed (10 rpm) for a first preset time (30 min) to bring the seed crystal into contact with the melt, allowing crystal growth to occur and a silicon carbide single crystal to be obtained. During crystal growth, the seed crystal is a silicon carbide wafer with a diameter of 100 mm, the diameter of the seed crystal support substrate is 100 mm, and the maximum diameter of the bottom of the turbine heat sink is 120 mm. After the silicon carbide seed crystal comes into contact with the melt, the seed crystal rod is rotated along the second direction at a second preset speed (30 rpm) for a second preset time (1 h). At a third preset time (1.5 h), the speed is reduced to 0 and accelerated along the first direction to a third preset speed (200 rpm), and then rotated at the third preset speed (200 rpm) for a fourth preset time (15 h). Finally, based on the thermal insulation performance decay curve of the thermal insulation material used in the thermal insulation component, the speed is reduced to a fourth preset speed (150 rpm) at a fifth preset time (50 h) to ensure that the heat dissipation rate remains stable. During crystal growth, the upward pulling speed of the seed crystal rod is 560 μm / h, the upward moving speed of the crucible is 360 μm / h, the rotation direction of the crucible is always opposite to that of the seed crystal rod, and the rotation speed of the crucible is 5 rpm. After crystal growth is completed, at the sixth preset time (30 min), the speed is decelerated to 0 and accelerated along the second direction to the fifth preset speed (20 rpm), and maintained for the seventh preset time (24 h).

[0093] The optical photograph of the 4-inch silicon carbide single crystal grown in this embodiment is shown in Figure 4. The crystal surface is the original growth surface without processing. It can be seen that the crystal growth surface is very smooth, indicating that the crystal crystallization quality is excellent. The average growth rate of the crystal is 200 μm / h.

[0094] Example 3

[0095] A method for rapidly growing large-size, high-quality silicon carbide single crystals, implemented using the apparatus of Example 1, includes:

[0096] S1. After assembling the device, close the furnace chamber and perform a vacuum treatment on the furnace chamber. When the furnace chamber pressure is less than or equal to 1×10 -4 After Pa, high-purity argon gas is introduced into the furnace cavity as a protective gas. The flux and silicon are placed in a crucible and heated to 1800℃ to completely liquefy the raw materials in the crucible and obtain a melt. The flux is Cr; the mass ratio of Cr to Si is 40:60, and the total mass of Cr and Si is 12kg.

[0097] S2. Once the temperature of the mixed melt stabilizes, the seed crystal rod is rotated along the second direction at a first preset speed (20 rpm) for a first preset time (30 min) to bring the seed crystal into contact with the melt, allowing crystal growth to occur and a silicon carbide single crystal to be obtained. During crystal growth, the seed crystal is a silicon carbide wafer with a diameter of 150 mm, the diameter of the seed crystal support substrate is 150 mm, and the maximum diameter of the bottom of the turbine heat sink is 170 mm. After the silicon carbide seed crystal comes into contact with the melt, the seed crystal rod is rotated along the second direction at a second preset speed (50 rpm) for a second preset time (1 h), then at a third preset time (2 h), the speed is reduced to 0 and accelerated along the first direction to a third preset speed (200 rpm), and then rotated at the third preset speed (200 rpm) for a fourth preset time (510 h). Finally, based on the thermal insulation performance decay curve of the thermal insulation material used in the thermal insulation component, the speed is reduced to the fourth preset speed (120 rpm) at a fifth preset time (50 h) to ensure that the heat dissipation rate remains stable. During crystal growth, the upward pulling speed of the seed crystal rod is 500 μm / h, the upward moving speed of the crucible is 300 μm / h, the rotation direction of the crucible is always opposite to that of the seed crystal rod, and the rotation speed of the crucible is 5 rpm. After crystal growth is completed, at the sixth preset time (1h), the seed crystal rotation speed is reduced to 0 and accelerated along the second direction to the fifth preset rotation speed (40 rpm), and maintained for the seventh preset time (30h).

[0098] An optical photograph of the 6-inch silicon carbide single crystal grown in this embodiment is shown in Figure 5. The crystal surface is the original, unprocessed growth surface. It can be seen that the crystal growth surface is very smooth, indicating that the crystallization quality is excellent. The average growth rate of the crystal is 160 μm / h.

[0099] The X-ray rocking curve test results of the 6-inch silicon carbide single crystal grown in this embodiment are shown in Figure 6. The full width at half maximum (FWHM) of the X-ray rocking curves at five uniformly distributed points are 32.4, 32.4, 28.8, 32.4, and 28.8 arcsec, respectively, and the average FWHM is 30.96 arcsec. This proves that high-quality 6-inch silicon carbide crystals can be grown using the apparatus and method provided by this invention.

[0100] Comparative Example 1

[0101] It is basically the same as Example 2, except that the apparatus for growing silicon carbide single crystals does not have a turbine heat sink 23.

[0102] As shown in Figure 7, an optical photograph of a 4-inch silicon carbide single crystal grown using the apparatus and method of this comparative example clearly shows that although the central region of the crystal has high crystal quality and a smooth surface, the edge region has a large number of defects, and the average growth rate of the crystal is 60 μm / h. It is evident that without the apparatus provided by this invention, the radial temperature difference at the solid-liquid interface is large, and the heat dissipation efficiency is low, resulting in poor crystal quality in the edge region.

[0103] Comparative Example 2

[0104] It is basically the same as Example 3, except that the apparatus for growing silicon carbide crystals does not have a turbine heat sink 23.

[0105] After the silicon carbide seed crystal comes into contact with the melt, the seed crystal rod rotates in a single phase at a speed of 200 rpm until the growth is complete.

[0106] As shown in Figure 8, an optical photograph of a 6-inch silicon carbide single crystal grown using the apparatus and method described in this comparative example clearly shows numerous defects on the crystal surface, indicating very poor crystal quality. Furthermore, the average crystal growth rate is only 50 μm / h. This demonstrates that without the apparatus and method provided by this invention, the problems of slow and uneven heat dissipation are even more pronounced when growing large-sized silicon carbide crystals.

[0107] Comparative Example 3

[0108] The process is basically the same as in Example 2, except that after the silicon carbide seed crystal comes into contact with the melt, the seed crystal rod rotates unidirectionally at a speed of 200 rpm until the crystal growth is completed.

[0109] An optical photograph of a 4-inch silicon carbide single crystal grown using the apparatus and method described in this comparative example is shown in Figure 9. During crystal growth, there was no dynamic control process for the heat dissipation rate. In the later stages of crystal growth, due to the gradual degradation of the insulation performance of the insulation material, the heat dissipation rate of the crystal gradually increased, resulting in an excessively fast growth rate in the later stages and the generation of numerous crystal defects. The average growth rate of this crystal was 230 μm / h.

[0110] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for rapidly growing large-size, high-quality silicon carbide single crystals, characterized in that, The method includes the following steps: S1. Place the flux and silicon in a crucible and heat until the mixture is completely liquefied to obtain a melt; S2. After rotating the seed crystal rod along the second direction at a first preset speed for a first preset time, the seed crystal comes into contact with the melt to grow a silicon carbide single crystal. During the crystal growth process, the rotation direction and speed of the seed crystal rod are adjusted according to the heat dissipation requirements at different stages. The rotation direction of the crucible is always opposite to the rotation direction of the seed crystal. During the crystal growth process, after the seed crystal comes into contact with the melt, the seed crystal rod rotates along the second direction at a second preset speed for a second preset time. Then, at a third preset time, the speed is reduced to 0 and accelerated along the first direction to a third preset speed. Then, it rotates at the third preset speed for a fourth preset time. Finally, according to the heat insulation performance decay curve of the heat insulation material used in the heat insulation component, the speed is reduced to the fourth preset speed at a fifth preset time to ensure that the heat dissipation rate remains stable. The second preset speed is greater than the first preset speed. The third preset speed is greater than the second preset speed. The first preset speed is 5-30 rpm. The second preset speed is 10-60 rpm. The third preset speed is 60-240 rpm. The method is achieved by an apparatus for rapidly growing large-size, high-quality silicon carbide single crystals. The apparatus includes a crucible assembly, a seed crystal assembly, a heating assembly disposed outside the crucible assembly, and a heat-insulating assembly located between the heating assembly and the crucible assembly. The crucible assembly includes a crucible and a pushing and rotating component disposed below the crucible for pushing and rotating the crucible; The seed crystal assembly includes a seed crystal rod, a seed crystal holder, and a turbine heat sink; the seed crystal holder includes a seed crystal holder substrate and a connecting rod fixedly connected to the seed crystal holder substrate; the connecting rod and the seed crystal rod are connected by a tenon and mortise structure; the tenon and mortise structure is locked by a locking component. The turbine radiator includes a turbine shaft and turbine blades distributed on the turbine shaft; the turbine shaft is fitted onto the connecting rod; the turbine radiator accelerates heat dissipation when rotating in a first direction and inhibits heat dissipation when rotating in a second direction.

2. The method according to claim 1, characterized in that, The crucible is a graphite crucible.

3. The method according to claim 1, characterized in that, The mortise and tenon structure includes a tenon groove structure at the lower end of the seed crystal rod and a tenon structure at the upper end of the connecting rod; the locking component is fixed to the tenon groove structure by threads.

4. The method according to claim 1, characterized in that, During crystal growth, the crucible rotates at a speed of 2 to 10 rpm; The crucible moves upward at a speed of 0–1000 μm / h; and / or The pulling speed of the seed crystal rod is 0 to 1500 μm / h.

5. The method according to claim 1, characterized in that, The second preset time is 0.5 to 2 hours; The third preset time is 0.5 to 2 hours; The fourth preset time is 10-20 hours; and / or The fifth preset time is 20 to 60 hours.

6. The method according to claim 1, characterized in that, After crystal growth is completed, at the sixth preset time, the rotation speed is reduced to 0 and accelerated to the fifth preset speed in the second direction, and then maintained for the seventh preset time.

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