Method and apparatus for growing silicon carbide single crystal by liquid phase method

Abstract

The present application relates to the technical field of silicon carbide preparation, and particularly relates to a method for growing silicon carbide single crystal by liquid phase method. The present application provides a method for growing silicon carbide single crystal by liquid phase method, which comprises the following steps: arranging a bevel seed crystal holder in a position close to the inner wall of a crucible by a support frame connected with a seed crystal rotating lifting shaft; wherein the crucible is filled with high-temperature melt; installing a bias angle seed crystal on the bevel seed crystal holder according to a specific orientation relationship, and making the direction of a step flow structure on the bottom surface of the bias angle seed crystal parallel to the tangent of the inner wall of the crucible; immersing the bottom surface of the bias angle seed crystal into the high-temperature melt below the liquid level by the seed crystal rotating lifting shaft; rotating the bevel seed crystal holder to make the bias angle seed crystal move along the downstream direction of the step flow structure and do circular motion around the crucible axis in the crucible. The present application provides a method and device for growing silicon carbide single crystal by liquid phase method, and can grow high-quality large-size silicon carbide single crystal.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of silicon carbide preparation, in particular to a method and device for growing silicon carbide single crystal by liquid phase method. BACKGROUND

[0002] As one of the typical representatives of wide band gap semiconductors, silicon carbide has excellent characteristics such as large band gap, high breakdown field strength, high saturated electron mobility, high thermal conductivity, good thermal stability and chemical stability, and is an ideal substrate material for making high-frequency, high-voltage, high-efficiency and radiation-resistant, high-temperature-resistant power devices and blue light emitting diodes, which has a huge application prospect in new energy vehicles, high-speed rail transportation, aerospace, high-voltage smart grid and clean energy, and therefore has been widely concerned by the academic circles and governments of various countries.

[0003] At present, the crystalline quality and manufacturing cost of silicon carbide single crystal substrate are still one of the main factors restricting the further expansion of its application. Exploring and researching the method of obtaining high-quality, large-size and low-cost silicon carbide single crystal substrate plays a very important role in fully exerting the great application potential of silicon carbide.

[0004] At present, the mainstream method for growing silicon carbide single crystal substrate is physical vapor transport method (PVT), although this method has been relatively mature after decades of continuous research and improvement, and can currently supply a large amount of silicon carbide single crystal substrate to the market, but it still has some unavoidable limitations, mainly in the aspects of unstable growth environment, difficult to eliminate defects, low yield, high cost, difficult to expand the diameter, and difficult to realize continuous and effective P-type doping.

[0005] Compared with the gas phase method, the liquid phase method has low growth temperature, relatively stable growth environment, can realize the growth of crystal in the near equilibrium state, not only has relatively low growth cost, but also can realize higher crystal quality in theory. In addition, the liquid phase method also has good application prospect in the aspects of obtaining P-type substrate and expanding the diameter of crystal. However, the growth speed and quality of the silicon carbide single crystal by the current liquid phase method are difficult to meet the demand. SUMMARY

[0006] The embodiments of the present application provide a method and device for growing silicon carbide single crystal by liquid phase method, which can quickly grow high-quality and large-size silicon carbide single crystal.

[0007] In a first aspect, the embodiments of the present application provide a method for growing silicon carbide single crystal by liquid phase method, comprising:

[0008] The off-angle seed crystal is fixed on the bevel seed crystal holder according to a specific crystallographic orientation relationship; wherein the specific crystallographic orientation relationship is that the thickest side of the bevel seed crystal holder is aligned with the lowermost side of the off-angle seed crystal growth surface step flow, and the thinnest side of the bevel seed crystal holder is aligned with the uppermost side of the off-angle seed crystal growth surface step flow;

[0009] The seed crystal holder with the fixed off-angle seed crystal is installed on the support frame connected with the seed crystal rotating lifting shaft, and the step flow direction of the off-angle seed crystal is ensured to be parallel to the rotating tangential direction of the seed crystal rotating shaft;

[0010] The seed crystal assembly assembled according to the specific orientation requirement is arranged at a position close to the inner wall of the crucible; wherein the crucible is filled with high-temperature melt, and the crucible is coaxial with the seed crystal rotating lifting shaft;

[0011] The bottom surface of the off-angle seed crystal is immersed below the liquid surface of the high-temperature melt by using the seed crystal rotating lifting shaft;

[0012] The seed crystal holder is rotated to make the off-angle seed crystal move along the downstream direction of the step flow structure and perform circular motion in the crucible with the crucible axis as the rotation axis.

[0013] In a possible design, while the seed crystal holder is rotated to make the off-angle seed crystal move along the downstream direction of the step flow structure and perform circular motion in the crucible with the crucible axis as the rotation axis, the method further includes:

[0014] The crucible is rotated; wherein the rotating direction of the crucible is opposite to the rotating direction of the off-angle seed crystal.

[0015] In a possible design, the off-angle seed crystal is immersed below the liquid surface of the high-temperature melt by 2-8 mm.

[0016] In a possible design, the linear rotating speed of the center of the off-angle seed crystal is 0.3-2 m / s, and the angular speed of the crucible is 5-30 rpm.

[0017] In a possible design, the method further includes:

[0018] The back side of the bevel seed crystal holder is thick on one side and thin on the other side, and when the off-angle seed crystal is assembled on the bevel seed crystal holder, the orientation correspondence relationship between the two is ensured: when the Si surface of the off-angle seed crystal is used as the growth surface, the secondary positioning edge of the seed crystal needs to be located on the side with smaller thickness of the bevel seed crystal holder, and when the C surface of the off-angle seed crystal is used as the growth surface, the secondary positioning edge of the seed crystal needs to be located on the side with larger thickness of the bevel seed crystal holder, so as to ensure the long-term stability of the solid / liquid interface during the growth of the off-angle seed crystal; wherein the inclination angle of the bevel of the bevel seed crystal holder is 5-30 degrees.

[0019] In a possible design, during growth of the silicon carbide single crystal, the method comprises the following steps:

[0020] The depth of the seed crystal rotating lifting shaft for immersing the off-angle seed crystal below the high-temperature melt surface is within a preset range.

[0021] In a second aspect, an embodiment of the present application provides a device for growing a silicon carbide single crystal by a liquid phase method, which is used to implement any of the above methods, and the device comprises the following:

[0022] A seed crystal rotating lifting shaft is connected to an external rotating mechanism at one end and connected to a support frame at the other end, and the off-angle seed crystal is fixed on the support frame by a seed crystal holder.

[0023] A furnace cavity shell has an induction coil inside for heating a crucible, and the crucible is wrapped with a heat preservation material outside.

[0024] A crucible support tray is used to place the crucible, and a crucible rotating lifting shaft is connected to the bottom.

[0025] In a possible design, the support frame comprises a planetary rotating support frame, and the planetary rotating support frame comprises a plurality of radial sub-supports, and each of the sub-supports is provided with a seed crystal holder.

[0026] In a possible design, the off-angle seed crystal is provided with a main positioning edge and a secondary positioning edge, the direction of the main positioning edge is the same as the extension direction of the step flow structure of the off-angle seed crystal, and the direction of the secondary positioning edge is perpendicular to the direction of the main positioning edge.

[0027] In a possible design, the crucible is a graphite crucible.

[0028] Compared with the prior art, the present application has at least the following beneficial effects:

[0029] The off-angle seed crystal can effectively solve the problem of growth interface tilting in the growth of the silicon carbide single crystal by the liquid phase method, thereby realizing long-term stable growth of the off-angle seed crystal in the growth of the silicon carbide single crystal by the liquid phase method, which is of great significance for further improving the crystal quality and growth rate.

[0030] Further, the growth device provided by the present application realizes the movement mode of the seed crystal rotating around the axis of the crucible in a planetary manner, and cooperates with the special limitation of the seed crystal orientation, and thus the movement state of the melt in the crucible relative to the step flow structure of the seed crystal surface is realized, that is, the downstream direction of the step flow structure of the seed crystal growth surface is opposite to the relative flow direction of the high-temperature melt at all times, so that the solute can migrate against the step flow in the growth interface, the average free migration distance of the solute in the growth interface can be effectively shortened, the solute deposition efficiency can be improved, and thus the crystal growth rate can be effectively improved, the crystal defect density can be reduced, and the crystal quality can be improved.

[0031] In addition, it is found by the present application that the stability of the crystal growth interface can be effectively improved by immersing the seed crystal below the liquid surface by a certain height, and a better reverse step flow working state is formed. Since the lower surface of the off-angle seed crystal is in a step shape, and the solid-liquid interface is also in a step shape, when the off-angle seed crystal moves below the liquid surface, the liquid has a tendency to flow along the solid-liquid interface, but the solid-liquid interface is irregularly stepped, and finally the liquid flow at the solid-liquid interface is in an irregular wave shape, the wave-shaped liquid flow continuously impacts different surfaces of the step flow structure, and promotes the growth of the crystal. In addition, the locally fluctuating interface can also form a small turbulent flow near the interface, which increases the diffusion of the solute without violently disturbing the liquid surface. BRIEF DESCRIPTION OF DRAWINGS

[0032] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description are some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without any creative labor.

[0033] Figure 1 is a device schematic diagram of a specific embodiment of the present application for growing high-quality silicon carbide single crystals;

[0034] Figure 2a is a schematic diagram of the position of the seed crystal holder when the Si surface is grown in the present application;

[0035] Figure 2b is a schematic diagram of the rotation direction of the seed crystal holder and the crucible when the Si surface is grown in the present application;

[0036] Figure 2c is a schematic diagram of the position of the seed crystal holder when the C surface is grown in the present application;

[0037] Figure 2d is a schematic diagram of the rotation direction of the seed crystal holder and the crucible when the C surface is grown in the present application;

[0038] Figure 3is a front optical photograph of a silicon carbide single crystal grown according to Example 1 of the present application;

[0039] Figure 4 is a side edge optical photograph of a silicon carbide single crystal grown according to Example 1 of the present application;

[0040] Figure 5 is a front optical photograph of a silicon carbide single crystal grown according to Comparative Example 1 of the present application;

[0041] Figure 6 is a side edge optical photograph of a silicon carbide single crystal grown according to Comparative Example 1 of the present application;

[0042] Figure 7 is a front optical photograph of a silicon carbide single crystal grown according to Comparative Example 2 of the present application;

[0043] Figure 8 is a side edge optical photograph of a silicon carbide single crystal grown according to Comparative Example 2 of the present application.

[0044] In the drawings:

[0045] 1 - seed crystal rotating lifting shaft; 2 - furnace cavity shell; 3 - heat insulating material; 4 - crucible; 5 - support frame; 6 - induction coil; 7 - seed crystal holder; 8 - off-angle seed crystal; 8-1 : step flow structure; 8-2: physical surface of off-angle seed crystal; 8-3: micro crystal face; 9 - high temperature melt; 10 - crucible support tray; 11 - crucible rotating lifting shaft. DETAILED DESCRIPTION

[0046] In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are some but not all of the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0047] In the description of the embodiments of the present application, unless otherwise explicitly specified and limited, the terms "first", "second" are only for the purpose of description and cannot be understood as indicating or implying relative importance; unless otherwise specified or stated, the term "multiple" means two or more; the terms "connection", "fixation" and the like should be understood in a broad sense, for example, "connection" can be fixed connection, can be detachable connection, or integrally connected, or electrically connected; can be directly connected, or indirectly connected through an intermediate medium. For a person of ordinary skill in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0048] In the description of the present specification, it needs to be understood that the "upper", "lower" and other orientation words described in the embodiments of the present application are described in the angle shown in the drawings, and should not be understood as the limitation of the embodiments of the present application. In addition, in the context, it also needs to be understood that when referring to one element connected to another element "on" or "under", it can not only be directly connected to another element "on" or "under", but also indirectly connected to another element "on" or "under" through an intermediate element.

[0049] As shown in Figure 1 , Figures 2a to 2d The present application provides a method for growing silicon carbide single crystal by liquid phase method, comprising:

[0050] The off-angle seed crystal is fixed on the bevel seed crystal holder according to a specific crystallographic orientation relationship; wherein the specific crystallographic orientation relationship is that the downstream side of the off-angle seed crystal growth surface step flow is aligned with the thickest side of the bevel seed crystal holder, and the upstream side of the off-angle seed crystal growth surface step flow is aligned with the thinnest side of the bevel seed crystal holder;

[0051] The seed crystal holder with the fixed off-angle seed crystal is installed on the support frame connected with the seed crystal rotating lifting shaft, and the step flow direction of the off-angle seed crystal is parallel to the rotational tangential direction of the seed crystal rotating shaft;

[0052] The seed crystal assembly assembled according to the specific orientation requirement is arranged at the position close to the inner wall in the crucible; wherein the crucible is filled with high-temperature melt, and the crucible is coaxial with the seed crystal rotating lifting shaft;

[0053] The bottom surface of the off-angle seed crystal is immersed below the liquid surface of the high-temperature melt by using the seed crystal rotating lifting shaft;

[0054] The seed crystal holder is rotated to make the off-angle seed crystal move along the downstream direction of the step flow structure and make circular motion around the crucible axis in the crucible.

[0055] In the crystal growth, the growth by using the off-angle seed crystal can greatly increase the density of the step flow at the seed crystal growth interface, and has a very important role in improving the crystal growth quality, improving the crystal growth rate, and inhibiting the phase transition of the crystal. Further, the reverse step flow migration of the solute in the growth interface can effectively shorten the average free migration distance of the solute in the growth interface, improve the solute deposition efficiency, and thus can effectively improve the crystal growth rate, reduce the crystal defect density, and improve the crystal quality. In order to realize the step flow structure reverse step flow growth at the growth interface, that is, the downstream direction of the step flow structure is opposite to the flow direction of the high-temperature melt, the off-angle seed crystal is arranged at a position close to the side wall in the crucible through a seed crystal holder, and the off-angle seed crystal makes a circular motion around the central axis of the crucible. During the circular motion, the downstream direction of the step flow structure is opposite to the relative flow direction of the high-temperature melt at all times, and finally the solute migrates in the growth interface in the reverse step flow.

[0056] It should be noted that the step flow structure is a plurality of continuous dihedral angle structures, that is, a plurality of angles formed by two mutually perpendicular planes are distributed in one direction, and the projection of the direction in which the plane intersecting the horizontal plane at a large angle is directed in the horizontal plane is the downstream direction of the step flow structure.

[0057] Please refer to Figure 1 The physical surface of the off-angle seed crystal has a step flow structure, the step flow structure is formed by the surface of the microscopically inclined crystal plane, and the step flow structure looks like a plane on the macroscopic view, but is a stepped structure after magnification.

[0058] In some embodiments of the present application, while the seed crystal holder is rotated to make the off-angle seed crystal make a circular motion around the crucible axis as the rotation axis in the downstream direction of the step flow structure in the crucible, the method further comprises:

[0059] Rotating the crucible; wherein the rotation direction of the crucible is opposite to the rotation direction of the off-angle seed crystal.

[0060] In this embodiment, the off-angle seed crystal is rotated in the opposite direction of the crucible, which can increase the convection of the solution and accelerate the diffusion of the solute.

[0061] In some embodiments of the present application, the off-angle seed crystal is immersed below the liquid surface of the high-temperature melt by 2-8 mm.

[0062] In the embodiment, the off-angle seed crystal is immersed in the high-temperature solution below the liquid surface by 2-8 mm, and a better reverse step flow can be formed. Since the lower surface of the off-angle seed crystal is in a step shape, and the solid-liquid interface is also in a step shape, when the off-angle seed crystal moves below the liquid surface, the liquid has a tendency to flow along the solid-liquid interface. However, the solid-liquid interface is in an irregular step shape, and finally the liquid flow at the solid-liquid interface is in an irregular wave shape. The wave-shaped liquid flow continuously impacts different surfaces of the step flow structure, promoting the growth of the crystal. In addition, the locally fluctuating interface can also form a small amount of turbulence near the interface, which increases the diffusion of the solute without severely disturbing the liquid surface.

[0063] In some embodiments of the present application, when the off-angle seed crystal rotates around the crucible axis in a planetary manner, the linear velocity of the seed crystal center region is 0.3-2 m / s, the angular velocity of the crucible is 5-30 rpm, and the rotation direction of the crucible is opposite to the rotation direction of the seed crystal.

[0064] In the embodiments of the present application, by making the off-angle seed crystal rotate around the crucible axis in a planetary manner and making the crucible rotate in the opposite direction, the melt in the crucible can move in a reverse step flow relative to the step flow structure of the surface of the off-angle seed crystal. Thus, the Si and C solutes in the melt have an inertia of reverse step flow migration at the seed crystal growth interface. The size of the solute migration inertia is positively correlated with the linear velocity of the planetary rotation of the off-angle seed crystal and the rotation speed of the crucible. A solute migration inertia of a suitable size can effectively increase the rate at which the Si and C solutes migrate to the root of the step and deposit and grow at the growth interface. This not only greatly increases the crystal growth rate, but also effectively avoids crystal defects caused by insufficient solute supply at the root of the step flow, thereby greatly improving the crystal quality. However, once the rotation speed exceeds the reasonable range, the beneficial effects cannot be achieved. When the rotation speed is too low, the solute has a very small migration inertia, and the effect of improving the crystal growth rate and quality is minimal. When the rotation speed is too large, the melt in the crucible is subjected to too much mechanical disturbance, which is not conducive to the stable growth of the growth interface, and can cause very serious crystal defects.

[0065] In some embodiments of the present application, further comprising:

[0066] The inclined seed crystal holder has a large thickness on one side and a small thickness on the other side. When the off-angle seed crystal is assembled on the inclined seed crystal holder, the orientation correspondence between the two is ensured: when the Si surface of the off-angle seed crystal is used as the growth surface, the secondary positioning edge of the seed crystal needs to be located on the side with the small thickness of the inclined seed crystal holder; when the C surface of the off-angle seed crystal is used as the growth surface, the secondary positioning edge of the seed crystal needs to be located on the side with the large thickness of the inclined seed crystal holder, so as to ensure the long-term stability of the solid / liquid interface during the growth of the off-angle seed crystal. The inclination angle of the inclined surface of the inclined seed crystal holder is 5-30 degrees.

[0067] In the liquid-phase growth of silicon carbide single crystals, the solid-liquid interface energy between the silicon carbide crystal and the high-temperature solution exhibits strong anisotropy, particularly in the (0001) plane and (000) plane of the silicon carbide crystal. The solid-liquid interfacial energy between the crystal surface and the high-temperature melt is much lower than that between the crystal side surfaces. Crystal family and Solid-liquid interface energy between crystal facets and high-temperature solutions. In the liquid-phase growth of SiC single crystals, without artificial intervention, crystal facets with larger solid-liquid interface energy with the high-temperature solution are thermodynamically unstable, with a larger growth rate in the normal direction, and these facets easily disappear as the crystal grows. Conversely, crystal facets with smaller solid-liquid interface energy with the high-temperature solution are thermodynamically more stable, with a smaller growth rate in the normal direction, and these facets tend to eventually remain as stable solid-liquid interfaces as the crystal grows. The microscopic crystal facets exposed on the surface of unbiased silicon carbide seed crystals are basically (0001) or (000) planes. Low interface energy crystal planes, such as the (0001) plane, and silicon carbide seed crystal surfaces with deflection angles, except for the (0001) plane or (000) plane. In addition to such low interface energy crystal planes, a large amount of [unclear text] will also be exposed. and Crystal planes with high interfacial energy, such as those with a family of crystal planes. Therefore, during liquid-phase growth using off-angle seed crystals, and High interface energy crystal planes like those in a family of crystal planes will gradually disappear, eventually leaving only the (0001) plane or (000) plane. With a low interfacial energy crystal plane like the α-plane, the solid-liquid interface will become tilted, which will seriously affect the stability of the solid-liquid interface during crystal growth and severely affect the crystal quality.

[0068] In the liquid-phase growth of silicon carbide single crystals, the solid-liquid interface between the silicon carbide crystal and the high-temperature solution exhibits strong anisotropy. During the growth of the seed crystal with an off-angle, the crystal growth rate is lower on the upstream side of the step flow and higher on the downstream side. Therefore, the solid-liquid interface tilts due to the inconsistent growth rates on both sides during crystal growth, disrupting the stable growth state of the solid-liquid interface and leading to a deterioration in crystal growth quality. To address this problem, this invention, based on the fundamental principles of crystal growth, addresses the anisotropy in growth rate caused by the off-angle of the seed crystal by developing a slanted seed crystal holder. By reducing the axial heat dissipation rate on the side with a faster growth rate and increasing the axial heat dissipation rate on the side with a slower growth rate, the axial growth rates in the upstream and downstream regions of the step flow are kept consistent during the growth of the seed crystal, thereby stabilizing the crystal growth interface and improving crystal growth quality.

[0069] In some embodiments of the present invention, the growth process of silicon carbide single crystal includes:

[0070] The depth of the off-angle seed crystal immersed below the surface of the high-temperature melt is within a preset range when the seed crystal rotating lifting shaft is lifted.

[0071] As the silicon carbide single crystal is continuously generated on the seed crystal, the depth of the crystal immersed in the liquid surface will increase, and if the immersion depth exceeds the preset range, such as 5mm, the growth of the subsequent silicon carbide single crystal will be affected, therefore, the off-angle seed crystal needs to be gradually lifted to keep the immersion depth within the preset range.

[0072] The embodiment of the present application also provides a specific preparation method.

[0073] The technical scheme provided by the present application mainly includes the following steps:

[0074] The solubility aid raw material is loaded into the graphite crucible according to the proportion;

[0075] The silicon carbide seed crystal is bonded on the heat-dissipating anisotropic seed crystal holder according to the specific orientation requirement, the side with small thickness of the seed crystal holder is aligned with the upstream side of the seed crystal growth surface step flow, and the side with large thickness of the seed crystal holder is aligned with the downstream side of the seed crystal growth surface step flow; for the standard off-angle silicon carbide seed crystal: when the C-polar surface grows, the side with large thickness of the graphite holder is aligned with the secondary positioning edge of the seed crystal; when the Si-polar surface grows, the side with small thickness of the graphite holder is aligned with the secondary positioning edge of the seed crystal.

[0076] The seed crystal holder with the assembled seed crystal is installed on the planetary rotating support frame, and the tangent direction of the seed crystal rotation is perpendicular to the secondary positioning edge of the seed crystal.

[0077] The above-mentioned crucible and seed crystal related components are placed into the single crystal growth furnace, and the heat preservation material is placed around the crucible;

[0078] The planetary rotating support frame with the installed seed crystal holder is connected with the seed crystal rotating lifting shaft of the equipment, and the position of the seed crystal is higher than the raw material surface;

[0079] The furnace chamber is closed, vacuum treatment is performed on the furnace chamber, and after the air pressure in the furnace chamber is less than or equal to 1E-4 Pa, protective gas is filled into the furnace chamber;

[0080] The crucible is heated to completely liquefy the solubility aid raw material in the crucible, and the crucible is left for a period of time;

[0081] The seed crystal is slowly pushed down so that the seed crystal is just in complete contact with the liquid surface, and the crystal growth starts;

[0082] After the crystal growth starts, the seed crystal rotating lifting shaft is rotated clockwise to make the seed crystal rotate around the edge of the inner wall of the crucible in a planetary manner; at the same time, the crucible is rotated counterclockwise;

[0083] The seed crystal is slowly lifted upwards during the crystal growth process.

[0084] After the growth is finished, the crystal is slowly pulled away from the liquid surface, and then slowly cooled down;

[0085] After the crystal is cooled to room temperature, the furnace chamber is opened, and the crystal is taken off from the seed crystal holder.

[0086] The embodiment of the present application provides a device for growing silicon carbide single crystal by liquid phase method, which is used to realize any of the above methods, and the device comprises:

[0087] The seed crystal rotating lifting shaft is connected with the external rotating mechanism at one end and connected with the support frame at the other end, and the off-angle seed crystal is fixed on the support frame through the seed crystal holder;

[0088] The furnace chamber shell is internally provided with an induction coil for heating the crucible, and the crucible is wrapped with heat preservation material outside;

[0089] The crucible support tray is used for placing the crucible, and the bottom is connected with the crucible rotating lifting shaft.

[0090] In some embodiments of the present application, the support frame comprises a planetary rotating support frame, and the planetary rotating support frame comprises a plurality of radial sub-supports, and each of the sub-supports is installed with a seed crystal holder.

[0091] In some embodiments of the present application, the off-angle seed crystal is processed with a main positioning edge and a secondary positioning edge, the direction of the main positioning edge is the same as the extension direction of the step flow structure of the off-angle seed crystal, and the direction of the secondary positioning edge is perpendicular to the direction of the main positioning edge.

[0092] In some embodiments of the present application, the crucible is a graphite crucible.

[0093] The present application will be further described in detail through specific embodiments and in combination with the drawings. It should be pointed out that the given embodiments are only for illustrating the implementation process of the present application and the beneficial effects brought by the present application, and are not for limiting the scope of the present application.

[0094] In a specific embodiment of the present application, the back surface of the in-situ variable temperature seed crystal holder is provided with 6 groups of annular heating wires distributed radially along the seed crystal holder and independently adjustable in heating power and 6 groups of high-temperature resistant thermocouple temperature measuring instruments distributed radially along the seed crystal holder.

[0095] Embodiment 1

[0096] This embodiment adopts the device and method for rapidly growing high-quality large-size cubic silicon carbide single crystal provided by the present application to grow 4-inch cubic silicon carbide single crystal, mainly including the following steps:

[0097] The fluxing agent raw materials were loaded into a graphite crucible according to the following ratio: Cr:Si:Co:Al = 20:50:20:10, and the total mass of the raw materials was 8 kg.

[0098] A silicon carbide seed crystal with a 4-degree offset is bonded to a heat-dissipating anisotropic seed crystal holder in a specific direction. The Si polar surface is selected as the growth surface, and the side of the graphite holder with the smaller thickness is aligned with the secondary positioning edge of the seed crystal.

[0099] Install the assembled seed crystal holder on the planetary rotating support frame, ensuring that the tangential direction of the seed crystal rotation is perpendicular to the secondary positioning edge of the seed crystal.

[0100] Place the crucible and seed crystal-related components into the single crystal growth furnace, and place insulation material around the crucible.

[0101] Connect the planetary rotating support frame with the seed crystal holder installed to the seed crystal rotating lifting shaft of the equipment, while ensuring that the seed crystal position is higher than the raw material surface;

[0102] The furnace chamber was closed and evacuated. When the furnace chamber pressure was less than or equal to 1E-4 Pa, protective gas was introduced into the furnace chamber.

[0103] The crucible is heated to 1800℃ to completely liquefy the co-solvent material in the crucible, and then left to stand for a period of time.

[0104] Slowly push the seed crystal down until it is 5mm below the liquid surface, and crystal growth begins.

[0105] After crystal growth begins, the seed crystal rotation and pulling shaft is rotated clockwise, causing the seed crystal to rotate planetarily around the inner edge of the crucible, resulting in a linear velocity of 0.8 m / s in the central region of the seed crystal; at the same time, the crucible is rotated counterclockwise at a speed of 10 rpm.

[0106] During crystal growth, the seed crystal is slowly pulled upwards at a pulling speed of 0.3 mm / h;

[0107] After growth is complete, the crystals are slowly pulled off the liquid surface and then slowly cooled.

[0108] After the crystal has cooled to room temperature, open the furnace chamber and remove the crystal from the seed crystal holder.

[0109] Appendix Figure 3 This is a front optical photograph of the silicon carbide single crystal grown in Example 1. It can be seen that the crystal surface is very smooth and bright, indicating excellent crystal growth quality. (Attached) Figure 4This is a side optical photograph of the crystal grown in Example 1. The crystal's side edges are also smooth and flat, indicating excellent crystal growth stability. The crystal thickness can reach 10 mm, the growth rate is approximately 300 μm / h, the groove-like defect density on the crystal surface is zero, and the average half-width at half-maximum (FWHM) of the crystal rocking curve is only 18 arcseconds. The experimental results of Example 1 effectively demonstrate that the growth apparatus and method provided by this invention can achieve rapid growth of high-quality silicon carbide single crystals.

[0110] Comparative Example 1:

[0111] In this comparative example, a silicon carbide seed crystal with a 4-degree offset is also used for liquid-phase growth of silicon carbide crystals. The difference from Example 1 is that the apparatus and process provided by this invention are not used; instead, the 4-degree offset silicon carbide seed crystal is bonded to a heat-dissipating isotropic cylindrical seed crystal holder. All other growth processes remain consistent with Example 1.

[0112] Appendix Figure 5 This is a front optical photograph of the silicon carbide crystal grown in Comparative Example 1. Numerous groove-like defects can be seen on the crystal surface, especially on the sub-positioning edge (i.e., the downstream side of the step flow), while fewer groove-like defects are found on the upstream side of the step flow. The overall crystal growth quality is very poor. (Attached) Figure 6 The optical photograph of the side edge of the silicon carbide crystal grown in Comparative Example 1 clearly shows that the growth surface of the crystal is tilted, with the tilt angle exactly equal to the seed crystal's angle of 4 degrees. It can be seen that without heat dissipation intervention on the back side of the seed crystal, the growth rate on the downstream side of the step flow is significantly higher than that on the upstream side, causing the equilibrium state of the growth interface to be disrupted and severely damaging the crystal quality.

[0113] The growth results of Example 1 and Comparative Example 1 demonstrate that the device provided by the present invention can effectively solve the problems faced by the growth of off-angle seed crystals in liquid phase method, avoid the growth interface from tilting and becoming unstable, and significantly improve the crystal growth quality and growth rate.

[0114] Comparative Example 2:

[0115] In this comparative example, silicon carbide seed crystals with a 4-degree offset are also used for liquid phase growth of silicon carbide crystals. The only difference from Example 1 is that the seed crystal planetary rotation process provided by this invention is not used.

[0116] Figure 7 The image shows a front-facing optical photograph of the silicon carbide crystal grown in Comparative Example 2. The crystal surface is very smooth and bright, indicating high crystal quality. Figure 8 The image shows an optical photograph of the side edge of the silicon carbide crystal grown in Comparative Example 2. It can be seen that the crystal thickness is very small, only 1.5 mm, and the crystal growth rate is only 45 μm / h.

[0117] The crystal growth results of the comparative example 2 fully prove that the seed crystal planetary rotation method provided by the present application can realize the reverse step flow migration of solute in the crystal growth interface, and can effectively improve the crystal growth rate.

[0118] Comparative example 3

[0119] The present comparative example and the example 1 are basically the same, except that the Si face growth seed crystal is aligned in the opposite way when assembled on the graphite holder, that is, the side with the larger thickness of the graphite holder is aligned with the auxiliary positioning edge of the seed crystal.

[0120] The growth interface of the silicon carbide crystal grown in the present comparative example is very seriously inclined, and the inclination angle can reach 10 degrees, which is obviously larger than the inclination angle of the crystal grown in the example 1. At the same time, due to the serious inclination of the crystal growth interface, the stability of the crystal growth interface is seriously destroyed, and the crystal growth quality is very poor.

[0121] The results of the comparative example 3 fully prove the importance and necessity of the strict orientation correspondence between the inclined angle seed crystal and the inclined surface seed crystal holder proposed in the present application. Assembling the seed crystal according to the orientation correspondence provided by the present application can effectively suppress the instability of the crystal growth interface due to the inclination, and if assembled in the opposite way, it not only cannot suppress the interface inclination, but also can exacerbate the interface inclination, resulting in a poorer crystal quality.

[0122] Comparative example 4

[0123] The present comparative example and the example 1 are basically the same, except that the seed crystal is not immersed below the liquid surface during the growth process, and the lower surface of the seed crystal just contacts and is flush with the liquid surface.

[0124] Although the growth interface of the silicon carbide crystal grown in the present comparative example does not incline, the thickness of the crystal is only 5 mm, the growth rate is reduced to about 150 μm / h, and there are a small amount of channel-shaped defects on the surface of the crystal, which is caused by insufficient diffusion of the growth interface.

[0125] The growth results of the comparative example 4 prove that the immersion of the seed crystal below the liquid surface by a certain distance proposed in the present application can further effectively improve the rate and efficiency of the reverse step flow migration of solute, which is beneficial to improve the crystal growth rate and quality.

[0126] Comparative example 5

[0127] The present comparative example and the example 1 are basically the same, except that the depth of the seed crystal immersed in the melt during the crystal growth process exceeds the depth range defined in the present application, and the lower surface of the seed crystal is immersed in the liquid surface by 10 mm.

[0128] The growth interface of the silicon carbide crystal grown in the present comparative example does not tilt, the thickness of the crystal can reach 15 mm, and the growth rate is increased to about 450 μm / h, but there are a large number of trench-like defects and polycrystalline nucleation islands on the surface of the crystal, and the quality of the crystal is very poor, because the solute inverse step flow diffusion effect at the growth interface is too strong, which leads to the deposition of solute at the growth interface tending to be disordered, and then seriously affecting the quality of the crystal growth.

[0129] The growth results of Comparative Example 5 prove that the present application can further effectively improve the rate and efficiency of solute inverse step flow migration by immersing the seed crystal below the liquid surface by a certain distance, which is beneficial to improving the growth rate and quality of the crystal, but too large immersion depth will also cause adverse effects.

[0130] Comparative Example 6

[0131] The present comparative example is basically the same as Example 1, except that the linear speed of the seed crystal rotation exceeds the range of the linear speed of the seed crystal rotation defined in the present application, and the linear speed of the seed crystal is 3 m / s.

[0132] The growth interface of the silicon carbide crystal grown in the present comparative example does not tilt, the thickness of the crystal can reach 20 mm, and the growth rate is increased to about 600 μm / h, but there are a large number of serious trench-like defects and polycrystalline nucleation islands on the surface of the crystal, and the quality of the crystal is very poor, because the linear speed of the seed crystal rotation is too large, which leads to the deposition of solute at the growth interface tending to be disordered, and then seriously affecting the quality of the crystal growth.

[0133] Comparative Example 7

[0134] The present comparative example is basically the same as Example 1, except that the linear speed of the seed crystal rotation is lower than the range of the linear speed of the seed crystal rotation defined in the present application, and the linear speed of the seed crystal is 0.1 m / s.

[0135] The growth interface of the silicon carbide crystal grown in the present comparative example does not tilt, and the growth surface of the crystal is also very bright, and the quality of the crystal is very high, but the thickness of the crystal is only 3 mm, and the growth rate is increased to about 90 μm / h, because the linear speed of the seed crystal rotation is too small, and the intensity of the solute convection is too weak, which leads to low solute transport efficiency, and then seriously limits the crystal growth rate.

[0136] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the present application, but not to limit them; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing examples, or make equivalent replacement for part of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for growing silicon carbide single crystals using a liquid-phase method, characterized in that, include: An off-angle seed crystal is fixed onto a slanted seed crystal holder according to a specific crystallographic orientation relationship. This specific crystallographic orientation relationship is as follows: the downstream side of the step flow on the growth surface of the off-angle seed crystal is aligned with the side of the slanted seed crystal holder with the greatest thickness, and the upstream side of the step flow on the growth surface of the off-angle seed crystal is aligned with the side of the slanted seed crystal holder with the least thickness. The back side of the slanted seed crystal holder has a greater thickness on one side and a smaller thickness on the other. When assembling the off-angle seed crystal onto the slanted seed crystal holder, the orientation correspondence between the two is ensured: when the Si face of the off-angle seed crystal is used as the growth surface, the secondary positioning edge of the seed crystal must be located on the side of the slanted seed crystal holder with less thickness; when the C face of the off-angle seed crystal is used as the growth surface, the secondary positioning edge of the seed crystal must be located on the side of the slanted seed crystal holder with greater thickness, to ensure long-term stability of the solid / liquid interface during the growth of the off-angle seed crystal. The slant angle of the slanted seed crystal holder is 5~30 degrees. The seed crystal holder with the fixed angled seed crystal is installed on the support frame connected to the seed crystal rotation lifting shaft, and the step flow direction of the angled seed crystal is parallel to the rotation tangential direction of the seed crystal rotation shaft; the support frame includes a planetary rotation support frame, which includes multiple radial sub-supports, and each sub-support is equipped with a seed crystal holder. The seed crystal assembly, pre-assembled according to specific orientation requirements, is placed inside the crucible near the inner wall; wherein, the crucible contains high-temperature melt, and the crucible is coaxial with the seed crystal rotation and lifting axis; The bottom surface of the off-angle seed crystal is immersed below the surface of the high-temperature melt using the seed crystal rotation and lifting shaft. Rotate the seed crystal holder so that the off-angle seed crystal moves in a circular motion within the crucible along the downstream direction of the stepped flow structure, with the crucible axis as the axis of rotation. The off-angle seed crystal is immersed 2-8 mm below the surface of the high-temperature melt; The linear velocity of the rotation of the seed crystal center at the deflection angle is 0.3~2m / s, and the angular velocity of the crucible is 5~30rpm.

2. The method according to claim 1, characterized in that, While rotating the seed crystal holder to make the off-angle seed crystal move in a circular motion within the crucible about the crucible axis along the downstream direction of the stepped flow structure, the process also includes: The crucible is rotated; wherein the direction of rotation of the crucible is opposite to the direction of rotation of the angled seed crystal.

3. The method according to claim 1, characterized in that, The growth process of silicon carbide single crystals includes: The lifting and rotating shaft of the seed crystal is used to immerse the angled seed crystal below the surface of the high-temperature melt to a depth within a preset range.

4. An apparatus for growing silicon carbide single crystals using a liquid-phase method, characterized in that, The apparatus for implementing the method as described in any one of claims 1-3 includes: The seed crystal rotating lifting shaft is connected to an external rotating mechanism at one end and to a support frame at the other end. The angled seed crystal is fixed on the support frame by a seed crystal holder. The furnace cavity shell contains an induction coil for heating the crucible, and the crucible is wrapped with heat-insulating material. The crucible support tray is used to place the crucible, and the bottom is connected to the crucible rotation and lifting shaft.

5. The apparatus according to claim 4, characterized in that, The off-angle seed crystal is processed with a main positioning edge and a secondary positioning edge. The direction of the main positioning edge is the same as the extension direction of the step flow structure of the off-angle seed crystal, and the direction of the secondary positioning edge is perpendicular to the direction of the main positioning edge.

6. The apparatus according to claim 4, characterized in that, The crucible is a graphite crucible.

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