A method for growing a silicon carbide single crystal with a misorientation angle by a liquid phase method

Abstract

The present application relates to a method for growing a misoriented silicon carbide single crystal by a liquid phase method, and belongs to the technical field of silicon carbide single crystal production. The method is performed by using a device for growing a silicon carbide single crystal by a liquid phase method, the device comprising a wedge-shaped seed crystal holder and a wedge-shaped seed crystal. The method comprises: arranging the wedge-shaped seed crystal on the wedge-shaped seed crystal holder to form a normal-oriented seed crystal surface, and then growing silicon carbide on the normal-oriented seed crystal surface by a liquid phase method to obtain a crystal ingot comprising the wedge-shaped seed crystal and a grown silicon carbide crystal; and taking the crystal ingot off the wedge-shaped seed crystal holder, and performing multi-wire slicing based on the inclined surface of the wedge-shaped seed crystal to obtain a misoriented silicon carbide single crystal. The method of the present application forms a normal-oriented seed crystal surface by using the wedge-shaped seed crystal and the wedge-shaped seed crystal holder for liquid phase growth, and then obtains a misoriented silicon carbide single crystal by multi-wire slicing. The method of the present application does not require a crystal orientation step, can reduce the process of misoriented single-wire slicing or flat grinding, saves processing time, and can recycle the new wedge-shaped seed crystal.

Description

Technical Field

[0001] This invention belongs to the field of silicon carbide single crystal production technology, and particularly relates to a method for growing off-angle silicon carbide single crystals by liquid phase method. Background Technology

[0002] Silicon carbide (SiC) is one of the most important third-generation semiconductor materials. Its unique characteristics, such as large bandgap and high critical breakdown field strength, make it an ideal material for manufacturing high-frequency, high-power, radiation-resistant and light-resistant integrated devices. It is currently widely used in many fields such as new energy vehicles, 5G communications, and aerospace.

[0003] For silicon carbide materials, to meet the needs of downstream device fabrication, the quality of midstream epitaxy is often required to meet certain standards. In addition to quality requirements, the epitaxial end also imposes angle restrictions on the substrate end. In silicon carbide single crystal growth technology, the physical vapor transport method (PVT) can directly employ off-angle growth due to its vapor-phase growth characteristics. Because it does not require liquid phase participation, there is no issue with meniscus control, and stable off-axis crystal growth can be achieved by controlling the thermal field gradient, thus obtaining substrates for off-angle epitaxy. However, the liquid phase method has irreplaceable advantages in the preparation of silicon carbide single crystals, such as lower dislocation density, higher crystal purity, and better doping uniformity. However, in liquid-phase silicon carbide growth, only by maintaining the correct crystal orientation can the consistency of crystal quality be guaranteed. Since high-quality crystal growth depends on the stability of the melt-solid interface, using an off-angle crystal orientation for off-angle growth will lead to severely uneven mass transfer and thermal field distribution on both sides of the solid-liquid interface, resulting in distortion of the meniscus morphology. This can lead to a phenomenon where one side grows faster than the other, or even some crystals detach from the melt, severely disrupting growth continuity. After crystal growth, one end may be thinner than the other, making it impossible to maintain a consistent meniscus and resulting in poor growth quality. Currently, there is no effective method in existing technology that can simultaneously achieve the growth stability of the liquid-phase method and meet the requirements for preparing off-angle single crystals.

[0004] Furthermore, although it is possible to obtain off-angle silicon carbide single crystals by growing positive-oriented silicon carbide single crystals through liquid phase method and then cutting them, when cutting positive-oriented ingots at off-angle, a large amount of waste material that cannot be used for substrate processing will be generated at the top and bottom ends of the ingot due to insufficient geometric dimensions. That is, the parts at the top and bottom ends that do not meet the size requirements cannot be effectively utilized, resulting in resource waste. Moreover, the typical off-angle cutting process of silicon carbide single crystals by liquid phase method is as follows: ingot → rounding → crystal orientation → double-sided off-angle single-line cutting or flat grinding → positive-oriented multi-line cutting. Among them, there are generally two methods for the off-angle single-line cutting step: (a) making a special off-angle mold for fixing, and then using a single line to cut at the positive angle. Although this method can achieve cutting, it requires increased costs. Off-angle molds are mostly disposable consumables, and the customization and consumption of molds continuously drive up production costs; (b) bonding the ingot at the positive angle and relying on high-end single-line cutting equipment with complex spatial posture adjustment capabilities to cut at the off-angle. Although this method avoids mold wear, it has stringent requirements on the precision and functionality of the cutting equipment, increasing equipment costs. Therefore, the existing method of "growing in the positive crystal orientation first and then cutting at a different angle" is not only cumbersome in the cutting process, but also has problems such as low material utilization and high cost.

[0005] In summary, it is essential to provide a method for growing off-angle silicon carbide single crystals using a liquid phase method. Summary of the Invention

[0006] To address one or more technical problems existing in the prior art, the present invention provides a method for growing off-angle silicon carbide single crystals using a liquid phase method.

[0007] This invention provides a method for growing off-angle silicon carbide single crystals using a liquid-phase method. The method employs an apparatus for growing silicon carbide single crystals using a liquid-phase method, the apparatus comprising a wedge-shaped seed holder and a wedge-shaped seed. The method includes the following steps:

[0008] (1) The wedge-shaped seed crystal is placed on the wedge-shaped seed crystal holder to form a positive crystal seed crystal surface, and then silicon carbide is grown by liquid phase method on the positive crystal seed crystal surface to obtain a crystal ingot including the wedge-shaped seed crystal and the silicon carbide grown crystal.

[0009] (2) Remove the ingot from the wedge-shaped seed crystal holder, and then perform multi-line cutting based on the inclined surface of the wedge-shaped seed crystal included in the ingot to obtain a silicon carbide single crystal with an off-angle.

[0010] Preferably, in step (2), after multi-line cutting based on the inclined surface of the wedge-shaped seed crystal included in the ingot, a new wedge-shaped seed crystal can be obtained, and the new wedge-shaped seed crystal is recycled in step (1).

[0011] Preferably, the method further includes a step of rounding the silicon carbide grown crystals included in the ingot obtained in step (1) before removing the ingot from the wedge-shaped seed crystal holder.

[0012] Preferably, the tilt angle of the wedge-shaped seed crystal holder and the tilt angle of the wedge-shaped seed crystal are both no greater than 4°.

[0013] Preferably, the inclined surface of the wedge-shaped seed crystal holder is bonded to the inclined surface of the wedge-shaped seed crystal by an adhesive.

[0014] Preferably, the wedge-shaped seed crystal holder is connected to the seed crystal rod; the length of the seed crystal rod is 400~500mm.

[0015] Preferably, the seed crystal rod is connected to the seed crystal rod rotation and lifting device.

[0016] Preferably, the wedge-shaped seed crystal holder includes a positive angle portion and an off-angle portion, the positive angle portion is vertically connected to a seed crystal rod, and the inclined surface of the off-angle portion is bonded to the inclined surface of the wedge-shaped seed crystal by an adhesive.

[0017] Preferably, the thickness of the positive angle portion is 5~25mm.

[0018] Preferably, in step (2), when performing multi-line cutting, the cutting angle error is no greater than 0.2°.

[0019] Compared with the prior art, the present invention has at least the following beneficial effects:

[0020] (1) The method of the present invention forms a positive crystal seed surface by using a wedge seed crystal and a wedge seed crystal holder with the same tilt angle. The positive crystal seed surface can be used as the liquid phase growth surface to obtain a crystal ingot including a wedge seed crystal and a silicon carbide grown crystal. The silicon carbide grown crystal part is still positive crystal, and there is no problem of the off-angle growth affecting the crystal growth quality. That is, the present invention obtains off-angle silicon carbide single crystal by using the positive crystal seed surface as the liquid phase growth surface.

[0021] (2) This invention enables multi-line cutting based on the inclined surface of the wedge-shaped seed crystal. This multi-line cutting eliminates the need for crystal orientation steps and reduces the need for single-line cutting or flat grinding at off-angle, saving processing time. Furthermore, off-angle ingots with substandard effective dimensions after multi-line cutting can be recycled as new wedge-shaped seed crystals. This effectively utilizes the crystals with insufficient dimensions caused by multi-line cutting in liquid-phase silicon carbide, improving resource utilization. In the prior art, positive-oriented ingots are first grown using the liquid-phase method, and then off-angle cutting is performed. Generally, the cutting error is controlled within ±0.5°. This invention only requires controlling the angle when initially producing the wedge-shaped seed crystal, and subsequent multi-line cutting can be performed based on the inclined surface of the wedge-shaped seed crystal. The operation is simple, and the cutting angle error can be controlled within ±0.2°, which can greatly ensure batch consistency. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly described 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. The drawings of the present invention are provided for illustrative purposes only, and the proportions, sizes, and quantities of the parts in the drawings may not be consistent with the actual product.

[0023] Figure 1 This is a schematic diagram of the structure of the apparatus for growing silicon carbide single crystals by liquid phase method in some specific embodiments of the present invention, including the wedge-shaped seed crystal holder and the wedge-shaped seed crystal forming the positive crystal orientation seed crystal surface.

[0024] Figure 2 This is a schematic diagram of the structure of the apparatus for growing silicon carbide single crystals by liquid phase method in some specific embodiments of the present invention, including a wedge-shaped seed crystal holder and a wedge-shaped seed crystal forming a positive crystal towards the seed crystal surface for liquid phase growth of silicon carbide.

[0025] Figure 3 This is a schematic diagram of multi-line cutting based on the inclined surface of the wedge-shaped seed crystal included in the ingot in some specific embodiments of the present invention;

[0026] Figure 4 This is a physical image of silicon carbide grown on a wedge-shaped seed crystal, as shown in Embodiment 1 of the present invention.

[0027] Figure 5 This is a front view of the silicon carbide grown crystal obtained in Example 1 of the present invention;

[0028] Figure 6 This is a physical image of a positive-oriented silicon carbide single crystal obtained on a positive-oriented seed crystal in Comparative Example 1 of the present invention;

[0029] Figure 7This is a front view of the positive-crystal silicon carbide single crystal obtained in Comparative Example 1 of the present invention;

[0030] Figure 8 This is a physical image of the silicon carbide single crystal with a deflection angle obtained on a seed crystal at 4°off in Comparative Example 2 of this invention.

[0031] Figure 9 This is a front view of the off-angle silicon carbide single crystal obtained in Comparative Example 2 of the present invention.

[0032] Figures 1 to 3 In the middle: 1: wedge-shaped seed crystal holder; 11: positive angle portion; 12: off-angle portion; 2: wedge-shaped seed crystal; 21: positive crystal orientation seed crystal surface; 3: seed crystal rod; 4: silicon carbide grown crystal; 5: tilted surface of the wedge-shaped seed crystal included in the crystal ingot; 6: off-angle crystal ingot. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with the embodiments thereof. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0034] This invention provides a method for growing off-angle silicon carbide single crystals using a liquid-phase method, employing an apparatus for growing silicon carbide single crystals using a liquid-phase method, such as... Figure 1 As shown, the device includes a wedge-shaped seed crystal holder 1 and a wedge-shaped seed crystal 2; the method includes the following steps:

[0035] (1) The wedge-shaped seed crystal 2 is placed on the wedge-shaped seed crystal holder 1 to form a positive crystal orientation seed crystal surface 21, and then silicon carbide is grown on the positive crystal orientation seed crystal surface 21 by liquid phase method to obtain a crystal ingot including the wedge-shaped seed crystal 2 and the silicon carbide grown crystal 4, for example, as Figure 2 As shown; in this invention, the wedge-shaped seed crystal holder 1 and the wedge-shaped seed crystal 2 have the same tilt angle, and the wedge-shaped seed crystal 2 and the wedge-shaped seed crystal holder 1 are matched to form a positive crystal orientation seed crystal surface 21, for example, as... Figure 1 As shown; in this invention, a seed crystal rod 3 is connected to the wedge-shaped seed crystal holder 1, and the positive crystal orientation seed crystal surface 21 formed therein is perpendicular to the seed crystal rod 3 (crystal growth direction); this invention does not impose specific limitations on the process conditions for liquid phase growth of silicon carbide, and those skilled in the art can choose conventionally;

[0036] (2) Remove the ingot from the wedge-shaped seed crystal holder 1, and then perform multi-line cutting with the inclined surface 5 of the wedge-shaped seed crystal included in the ingot as the reference, that is, perform multi-line cutting along the upper surface (inclined surface) parallel to the wedge-shaped seed crystal included in the ingot to obtain a silicon carbide single crystal with an off-angle, for example, as Figure 3 As shown.

[0037] This invention utilizes a wedge-shaped seed crystal paired with a wedge-shaped seed crystal holder at the same tilt angle to form a positive-oriented seed crystal surface. This allows for the production of an ingot comprising a wedge-shaped seed crystal and a silicon carbide grown crystal, using the positive-oriented seed crystal surface as the liquid-phase growth surface. The silicon carbide grown crystal portion remains positive-oriented, eliminating the problem of off-angle growth affecting crystal growth quality. In other words, this invention obtains off-angle silicon carbide single crystals by using the positive-oriented seed crystal surface as the liquid-phase growth surface. Furthermore, this invention enables multi-wire cutting based on the tilted surface of the wedge-shaped seed crystal. This multi-wire cutting eliminates the need for crystal orientation steps and reduces the need for single-wire cutting or flat grinding at off-angle, saving processing time. Additionally, off-angle ingots 6 with substandard effective dimensions after multi-wire cutting can be recycled as new wedge-shaped seed crystals. This effectively utilizes the dimensionally deficient portion of liquid-phase silicon carbide crystals caused by multi-wire cutting, improving resource utilization. In existing technologies, a positive crystal ingot is first grown using a liquid phase method, and then a skew angle is cut. Generally, the cutting error is controlled within ±0.5°. In this invention, the angle only needs to be controlled when the wedge seed crystal is made for the first time. Subsequently, multi-line cutting can be performed based on the inclined surface of the wedge seed crystal. The operation is simple, and the angle error can be controlled within ±0.2°, which can greatly ensure the consistency of batches.

[0038] According to some preferred embodiments, in step (2), after multi-line cutting based on the inclined surface 5 of the wedge-shaped seed crystal included in the ingot, a new wedge-shaped seed crystal can be obtained, for example, such as... Figure 3 As shown, the new wedge seed crystal is recycled in step (1); in this invention, after multi-line cutting based on the inclined surface of the wedge seed crystal included in the crystal ingot, the last part of the off-angle crystal ingot 6 that does not meet the size still retains the morphological characteristics of the wedge seed crystal, that is, it has the same inclined angle and shape structure as the original wedge seed crystal. This part of the off-angle crystal ingot can be used as a new wedge seed crystal to achieve recycling.

[0039] This invention reduces the need for prefabrication of wedge seed crystals by recycling the off-angle crystal ingots after multi-wire cutting. The residue after multi-wire cutting can be used directly as new wedge seed crystals without additional processing, thus improving material utilization and saving material costs. Furthermore, the off-angle crystal ingots after multi-wire cutting have the same tilt angle and structure as the original wedge seed crystals, ensuring the stability of the off-angle of the subsequently grown crystals and avoiding the introduction of parameter deviations.

[0040] According to some preferred embodiments, the method further includes a step of rounding the silicon carbide growth crystal 4 included in the ingot obtained in step (1) before removing the ingot from the wedge-shaped seed crystal holder 1; the silicon carbide single crystal grown by liquid phase method usually presents a hexagonal shape, and the present invention preferably rounds the hexagonal silicon carbide growth crystal; in the present invention, the multi-wire cutting is performed by a multi-wire cutting machine, and the present invention does not specifically limit the process conditions of the multi-wire cutting and the rounding, which can be conventionally selected by those skilled in the art.

[0041] According to some preferred embodiments, in step (1), before growing silicon carbide by liquid phase method, the surface of the wedge seed crystal can be remelted (i.e., reverse dissolution treatment), which is beneficial to the in-situ flattening of the wedge seed crystal surface and also beneficial to improving the crystal quality of the initial growth layer; the present invention does not make specific limitations on the remelting treatment, and those skilled in the art can make conventional choices.

[0042] According to some preferred embodiments, the tilt angle θ of the wedge-shaped seed crystal holder 1 and the tilt angle θ of the wedge-shaped seed crystal 2 are both no greater than 4°, for example, 0.5°~4°, corresponding to the commonly used silicon carbide wafer tilt angle range; in this invention, the tilt angle of the wedge-shaped seed crystal holder 1 and the tilt angle of the wedge-shaped seed crystal 2 are the same.

[0043] According to some preferred embodiments, the inclined surface of the wedge-shaped seed crystal holder 1 and the inclined surface of the wedge-shaped seed crystal 2 are bonded together by an adhesive, so that the lower surface of the wedge-shaped seed crystal 2 forms a positive crystal orientation seed crystal surface 21. The present invention does not specifically limit the adhesive, and those skilled in the art can choose conventionally. In the present invention, the inclined surface of the wedge-shaped seed crystal holder and the inclined surface of the wedge-shaped seed crystal are bonded together by an adhesive (i.e., glue bonding), which can ensure that the wedge-shaped seed crystal will not fall off during crystal growth.

[0044] According to some preferred embodiments, the wedge-shaped seed crystal holder 1 is connected to the seed crystal rod 3; the length of the seed crystal rod 3 is 400~500mm (e.g. 400, 450 or 500mm), which helps to ensure that the wedge-shaped seed crystal can enter the growth crucible, and has a margin to ensure that the positive crystal orientation of the wedge-shaped seed crystal is liquid-contacted and pulled out.

[0045] According to some preferred embodiments, the seed crystal rod 3 is connected to a seed crystal rod rotation and lifting device, which is used to control the seed crystal rod 3 to lift and rotate.

[0046] According to some preferred embodiments, for example, Figure 1 and Figure 2As shown, the wedge-shaped seed crystal holder 1 includes a positive angle portion 11 and an off-angle portion 12. The positive angle portion 11 is vertically connected to the seed crystal rod 3. The inclined surface of the off-angle portion 12 is bonded to the inclined surface of the wedge-shaped seed crystal 2 by an adhesive, so that the lower surface of the wedge-shaped seed crystal 2 forms a positive crystal orientation seed crystal surface 21.

[0047] According to some preferred embodiments, the thickness of the positive angle portion 11 is 5~25mm (e.g., 5, 10, 15, 20 or 25mm); in this invention, the selection of the thickness of the positive angle portion is mainly based on heat dissipation considerations, and different heat dissipation requirements can be formulated according to different processes. Preferably, the thickness of the positive angle portion is 5~25mm; this invention does not specifically limit the thickness of the deflection angle portion 12, and the thickness of the deflection angle portion can be determined according to the diameter and deflection angle of the wedge-shaped seed crystal holder.

[0048] According to some preferred embodiments, in step (2), when performing multi-line cutting, the cutting angle error is no greater than 0.2°.

[0049] According to some specific embodiments, the method for growing off-angle silicon carbide single crystals by liquid phase includes the following steps:

[0050] (1) The wedge-shaped seed crystal 2 is placed on the wedge-shaped seed crystal holder 1 to form a positive crystal orientation seed crystal surface 21, and the apparatus for liquid-phase growth of silicon carbide single crystals is assembled. Then, silicon carbide is grown in the positive crystal orientation on the positive crystal orientation seed crystal surface 21 using the apparatus, and the growth surface is positive crystal orientation, to obtain an ingot including the wedge-shaped seed crystal 2 and the silicon carbide grown crystal 4, such as Figure 2 As shown.

[0051] (2) First, the silicon carbide growth crystal 4 included in the crystal ingot obtained in step (1) is rounded. Then, the crystal ingot is removed from the wedge seed crystal holder 1. Then, multi-line cutting is performed with the inclined surface 5 of the wedge seed crystal included in the crystal ingot as the reference (i.e., along the upper surface parallel to the wedge seed crystal) to obtain the off-angle silicon carbide single crystal. After multi-line cutting with the inclined surface of the wedge seed crystal included in the crystal ingot as the reference, the last part of the off-angle crystal ingot 6 that does not meet the size can be recycled as a new wedge seed crystal and continue to grow off-angle silicon carbide single crystal as a wedge seed crystal.

[0052] According to some preferred embodiments, the apparatus for growing silicon carbide single crystals by liquid phase method includes a crucible body, a crucible lid with an opening, and a seed crystal rod 3; one end of the seed crystal rod 3 is connected to a wedge-shaped seed crystal holder 1, and a wedge-shaped seed crystal 2 is connected to the wedge-shaped seed crystal holder 1. The wedge-shaped seed crystal holder 1 and the wedge-shaped seed crystal 2 have the same tilt angle, and the tilted surfaces of the wedge-shaped seed crystal holder 1 and the wedge-shaped seed crystal 2 are bonded together by an adhesive, so that the lower surface of the wedge-shaped seed crystal forms a positive crystal orientation seed crystal surface 21; one end of the seed crystal rod 3 connected to the wedge-shaped seed crystal holder 1 passes through the crucible lid. The opening extends into the interior of the crucible body; the crucible body and the crucible cover constitute a growth crucible. The device also includes a heat insulation layer disposed on the outside of the growth crucible, and an induction heating device for heating is disposed on the outside of the heat insulation layer. The induction heating device includes an induction coil, which is coaxially disposed with the seed crystal rod 3. The induction heating device heats the growth crucible through electromagnetic induction. The device also includes a seed crystal rod rotation and lifting device for controlling the lifting and rotation of the seed crystal rod 3 and a crucible rotation and lifting device for controlling the lifting and rotation of the crucible body.

[0053] In the liquid-phase growth of silicon carbide according to the present invention, there are no particularly limited process parameters for the rotation speed of the seed crystal rod, the pulling speed of the seed crystal rod, and the rotation speed of the crucible body. Those skilled in the art can conventionally select these parameters. For example, the seed crystal rod can rotate clockwise at a speed of 40 to 100 rpm, while the crucible body can rotate counterclockwise at a speed of 20 to 50 rpm. The pulling speed of the seed crystal rod can be controlled, for example, at 80 to 300 µm / h, to ensure that the actual growth rate of the silicon carbide single crystal is basically consistent with the pulling speed, thereby achieving a stable interface morphology.

[0054] The present invention will be further described below by way of examples, but the scope of protection of the present invention is not limited to these embodiments.

[0055] Example 1

[0056] This embodiment provides a method for growing off-angle silicon carbide single crystals using a liquid-phase method. The method employs a liquid-phase silicon carbide single crystal growth apparatus, which includes a crucible body, a crucible lid with an opening, and a seed crystal rod. One end of the seed crystal rod is connected to a wedge-shaped seed crystal holder, and a wedge-shaped seed crystal is connected to the wedge-shaped seed crystal holder. The wedge-shaped seed crystal holder and the wedge-shaped seed crystal have the same tilt angle, both being 4°. The wedge-shaped seed crystal holder includes a positive angle portion and an off-angle portion. The positive angle portion is vertically connected to the seed crystal rod, and the tilted surface of the off-angle portion is bonded to the tilted surface of the wedge-shaped seed crystal with an adhesive, so that the lower surface of the wedge-shaped seed crystal forms a positive angle. The seed crystal is oriented towards the seed crystal face; one end of the seed crystal rod connected to the wedge-shaped seed crystal holder extends through the opening of the crucible cover into the interior of the crucible body; the crucible body and the crucible cover constitute a growth crucible; the device also includes a heat insulation layer disposed on the outside of the growth crucible, and an induction heating device for heating is disposed on the outside of the heat insulation layer; the induction heating device includes an induction coil, the induction coil being coaxially disposed with the seed crystal rod, and the induction heating device heating the growth crucible through electromagnetic induction; the device also includes a seed crystal rod rotation and lifting device for controlling the lifting and rotation of the seed crystal rod and a crucible rotation and lifting device for controlling the lifting and rotation of the crucible body.

[0057] The method includes the following steps:

[0058] ① The wedge-shaped seed crystal is placed on the wedge-shaped seed crystal holder to form a positive crystal seed crystal surface, and the apparatus for liquid-phase growth of silicon carbide single crystal is assembled. The growth material is placed in the crucible body and heated to obtain a high-temperature melt. Then, the positive crystal seed crystal surface formed on the lower surface of the wedge-shaped seed crystal is brought into contact with the high-temperature melt, and silicon carbide is grown in the liquid phase on the positive crystal seed crystal surface to obtain a crystal ingot including the wedge-shaped seed crystal and the silicon carbide grown crystal. In the heating stage, the furnace is evacuated, then filled with the protective gas argon, and then the power is turned on to heat up, so that the growth material in the growth crucible melts to obtain a high-temperature melt. The growth material used in this embodiment is a mixture of Si, Cr and Al. In the growth material, the mass percentage of these three components is Si: 50%, Cr: 48%, and Al: 2%.

[0059] ② After silicon carbide growth is completed, the silicon carbide grown crystals included in the ingot obtained in step ① are rounded, and then the ingot is removed from the wedge-shaped seed crystal holder. Then, multi-line cutting is performed with the inclined surface of the wedge-shaped seed crystal included in the ingot as the reference to obtain off-angle silicon carbide single crystals. In this step ②, after multi-line cutting with the inclined surface of the wedge-shaped seed crystal included in the ingot as the reference, the last part of the off-angle ingot with the substandard effective size is used as a new wedge-shaped seed crystal and recycled in step ① to continue off-angle silicon carbide single crystal growth.

[0060] This embodiment shows a physical image of silicon carbide grown on a wedge-shaped seed crystal, as shown below. Figure 4 As shown, this embodiment yields a front view of the silicon carbide grown crystal. Figure 5 As shown; from Figure 4 and Figure 5 The results show that the silicon carbide crystals grown using this embodiment have good quality because they are grown in the positive crystal direction, which can stably control the meniscus of the solid-liquid interface. The crystal surface is flat, without grooves. After multi-wire cutting, the silicon carbide single crystals obtained by the orientation instrument have an offset angle of 4.1°, with a deviation of less than 0.2°.

[0061] Comparative Example 1

[0062] This comparative example provides a method for growing silicon carbide single crystals using a liquid phase method. The method employs an apparatus for growing silicon carbide single crystals using a liquid phase method, which is essentially the same as the apparatus for growing silicon carbide single crystals using a liquid phase method in Example 1. The difference lies in that: neither the seed crystal holder nor the seed crystal in the apparatus of this comparative example has an inclined angle; both the seed crystal holder and the seed crystal are perpendicular to the seed crystal rod and are respectively a positive crystal orientation seed crystal holder and a positive crystal orientation seed crystal; the seed crystal holder and the seed crystal are bonded together by an adhesive.

[0063] The method includes: assembling the apparatus for liquid-phase growth of silicon carbide single crystals; placing growth raw materials in the crucible body and heating the growth raw materials to obtain a high-temperature melt; then contacting the lower surface of the positive-oriented seed crystal with the high-temperature melt and performing liquid-phase growth of silicon carbide to obtain a positive-oriented silicon carbide single crystal; wherein, during the heating stage, the furnace is evacuated, then filled with the protective gas argon, and then the power is turned on to heat up, so that the growth raw materials in the growth crucible melt to obtain a high-temperature melt; the growth raw materials used in this comparative example are composed of a mixture of Si, Cr and Al, and the mass percentage of these three components in the growth raw materials is Si: 50%, Cr: 48%, and Al: 2%.

[0064] This comparative example shows a physical image of a positive-oriented silicon carbide single crystal obtained on a positive-oriented seed crystal, as shown below. Figure 6 As shown, the front view of the positive-oriented silicon carbide single crystal obtained in this comparative example is as follows. Figure 7 As shown; from Figure 6 and Figure 7The results show that the positive-oriented silicon carbide single crystals obtained by this comparative growth method have good quality due to the stable control of the meniscus at the solid-liquid interface caused by positive-oriented growth, resulting in a smooth crystal surface without grooves. However, when cutting at a 4° angle, taking a 4-inch (100mm diameter) crystal as an example, trigonometric calculations show that the remaining ingot thickness that does not meet the effective size standard reaches 7mm, which is wasted. Furthermore, this method of obtaining 4°-angled silicon carbide single crystals by "first positive-oriented growth and then cutting at a 4° angle" also has problems such as a complicated cutting process and high cost.

[0065] from Figure 5 and Figure 7 The results show that, although the silicon carbide grown crystal obtained in Example 1 of the present invention and the positive-oriented silicon carbide single crystal obtained in Comparative Example 1 have the common phenomenon of residual droplets during the liquid phase growth process, the surfaces of both are generally smooth, the quality is comparable, and both perform well.

[0066] Comparative Example 2

[0067] This comparative example provides a method for growing off-angle silicon carbide single crystals using a liquid phase method. The method is carried out using an apparatus for growing silicon carbide single crystals using a liquid phase method. The apparatus is basically the same as the apparatus for growing silicon carbide single crystals using a liquid phase method in Example 1. The difference is that the seed crystal holder included in the apparatus of this comparative example does not have an inclination angle. The seed crystal holder is set perpendicular to the seed crystal rod and is a positive crystal orientation seed crystal holder. The seed crystal is a 4°off seed crystal (off-angle 4° seed crystal).

[0068] The method includes: assembling the apparatus for liquid-phase growth of silicon carbide single crystals; placing growth raw materials in the crucible body and heating the growth raw materials to obtain a high-temperature melt; then contacting the lower surface of the 4°off seed crystal with the high-temperature melt and performing liquid-phase growth of silicon carbide to obtain a deflected-angle silicon carbide single crystal; wherein, during the heating stage, the furnace is evacuated, then filled with the protective gas argon, and then the power is turned on to heat up, so that the growth raw materials in the growth crucible melt to obtain a high-temperature melt; the growth raw materials used in this comparative example are composed of a mixture of Si, Cr and Al, and the mass percentage of these three components in the growth raw materials is Si: 50%, Cr: 48%, and Al: 2%.

[0069] This comparative example shows a physical image of a silicon carbide single crystal with an off-angle obtained on a 4° off seed crystal, as shown below. Figure 8 As shown, this comparative example shows a front view of a silicon carbide single crystal with an off-angle. Figure 9 As shown; from Figure 8 It can be seen that the silicon carbide single crystals grown at the offset angle in this comparative example exhibit a phenomenon of being thinner at one end and thicker at the other, and from... Figure 9 It can be seen that the crystal surface has many grooves, indicating poor crystal quality.

[0070] The parts of this invention not described in detail are techniques known to those skilled in the art.

[0071] 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 growing off-angle silicon carbide single crystals using a liquid-phase method, characterized in that, The method involves growing silicon carbide single crystals using a liquid-phase method, the apparatus comprising a wedge-shaped seed holder and a wedge-shaped seed crystal, and the method comprising the following steps: (1) The wedge-shaped seed crystal is placed on the wedge-shaped seed crystal holder to form a positive crystal orientation seed crystal surface, and then silicon carbide is grown on the positive crystal orientation seed crystal surface by liquid phase method to obtain a crystal ingot including the wedge-shaped seed crystal and the silicon carbide grown crystal, wherein the silicon carbide grown crystal is positive crystal orientation; the wedge-shaped seed crystal holder includes a positive angle portion and an off-angle portion, the positive angle portion is vertically connected to a seed crystal rod, and the inclined surface of the off-angle portion is bonded to the inclined surface of the wedge-shaped seed crystal by an adhesive so that the lower surface of the wedge-shaped seed crystal forms the positive crystal orientation seed crystal surface, and the positive crystal orientation seed crystal surface is perpendicular to the seed crystal rod; the wedge-shaped seed crystal holder and the wedge-shaped seed crystal have the same inclination angle; (2) Remove the crystal ingot from the wedge-shaped seed crystal holder, and then perform multi-line cutting based on the inclined surface of the wedge-shaped seed crystal included in the crystal ingot to obtain a silicon carbide single crystal with an off-angle. In step (2), after multi-line cutting based on the inclined surface of the wedge-shaped seed crystal included in the ingot, a new wedge-shaped seed crystal can be obtained, and the new wedge-shaped seed crystal is recycled in step (1).

2. The method according to claim 1, characterized in that, The method further includes a step of rounding the silicon carbide growth crystals included in the ingot obtained in step (1) before removing the ingot from the wedge-shaped seed crystal holder.

3. The method according to claim 1, characterized in that: The tilt angle of the wedge-shaped seed crystal holder and the tilt angle of the wedge-shaped seed crystal are both no greater than 4°.

4. The method according to claim 1, characterized in that: The length of the seed crystal rod is 400~500mm.

5. The method according to claim 4, characterized in that: The seed crystal rod is connected to the seed crystal rod rotation and lifting device.

6. The method according to claim 1, characterized in that: The thickness of the positive angle portion is 5~25mm.

7. The method according to any one of claims 1 to 6, characterized in that: In step (2), when performing multi-line cutting, the cutting angle error is no greater than 0.2°.

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