Method for growing off-angle silicon carbide single crystal by liquid phase method

Abstract

The invention relates to a method for growing an inclined-angle silicon carbide single crystal by a liquid phase method, and belongs to the technical field of silicon carbide single crystal production. The method is carried out by adopting a device for growing silicon carbide single crystals by a liquid phase method, the device comprises a wedge-shaped seed crystal support and wedge-shaped seed crystals, and the method comprises the following steps: arranging the wedge-shaped seed crystals on the wedge-shaped seed crystal support to form a normal crystal orientation seed crystal face, and then growing silicon carbide on the normal crystal orientation seed crystal face by the liquid phase method, obtaining a crystal ingot comprising wedge-shaped seed crystals and silicon carbide growth crystals; and taking down the crystal ingot from the wedge-shaped seed crystal support, and carrying out multi-line cutting by taking the inclined surface of the wedge-shaped seed crystal as a reference to obtain the inclined-angle silicon carbide single crystal. According to the method disclosed by the invention, the wedge-shaped seed crystal and the wedge-shaped seed crystal support form a positive crystal orientation seed crystal face for liquid phase growth, and then multi-line cutting is carried out to obtain the inclined-angle silicon carbide single crystal, the multi-line cutting does not need a crystal orientation step, an inclined-angle single-line cutting or flat grinding process can be reduced, the processing time is saved, and a new wedge-shaped seed crystal can be obtained for cyclic utilization.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of silicon carbide single crystal production, and particularly relates to a method for growing a silicon carbide single crystal with a deviation angle by a liquid phase method. BACKGROUND

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

[0003] For silicon carbide materials, in order to meet the downstream device preparation requirements, the middle-stream epitaxial quality is required to reach a certain standard, and in addition to the quality requirement, the angle is also limited for the substrate end. In the silicon carbide single crystal growth technology, the physical vapor transport method (PVT method) can directly adopt a deviation angle growth method due to its gas phase growth characteristics. Since it does not need to participate in the liquid phase, there is no problem of meniscus control, and stable off-axis crystal growth can be achieved by adjusting the thermal field gradient, and a deviation angle epitaxial substrate can be obtained. However, the liquid phase method has irreplaceable advantages in preparing silicon carbide single crystals, such as lower dislocation density, higher crystal purity, and better doping uniformity. However, when growing silicon carbide by the liquid phase method, only the growth in the positive crystal direction can ensure the consistency of the growth crystal quality. Since the high-quality growth of the crystal depends on the stability of the melt and solid phase interface, if a deviation angle crystal direction is used for deviation angle growth, the mass transfer and thermal field distribution on both sides of the solid-liquid interface will be seriously uneven, the meniscus shape will be distorted, and then the growth rate on one side will be fast, the growth on the other side will be slow, and even part of the crystal will be separated from the melt. Phenomenon, which seriously destroys the growth continuity, after crystal growth, it will appear thin at one end and thick at the other end, cannot maintain the same meniscus, and the growth quality is poor. At present, there is no effective means in the prior art that can balance the growth stability of the liquid phase method and the preparation requirements of the deviation angle single crystal.

[0004] In addition, although a positive crystal direction silicon carbide single crystal can be obtained by growing a positive crystal direction silicon carbide single crystal through a liquid phase method and then performing subsequent cutting processing, when the positive crystal direction crystal ingot is cut at an off-angle, a large amount of waste material that cannot be used for substrate processing will be generated at the upper and lower ends of the crystal ingot due to insufficient geometric size, that is, the upper and lower ends do not meet the size requirements and cannot be effectively utilized, resulting in resource waste. Moreover, the typical off-angle cutting process of the liquid phase method silicon carbide single crystal is as follows: crystal ingot → rounding → crystal orientation → double-sided off-angle single-line cutting or flat grinding → positive crystal direction multi-line cutting. In the off-angle single-line cutting link, there are generally two methods: (a) a special off-angle mold is made for fixation, and then single-line cutting at a positive angle is performed. This method can achieve cutting, but requires additional costs. The off-angle mold is mostly a consumable product, and the customization and consumption of the mold continuously increase the production cost; (b) the crystal ingot is bonded in a positive angle manner, and off-angle cutting is performed by relying on high-end single-line cutting equipment with complex spatial posture adjustment capability. This method avoids mold loss, but requires high precision and function of the cutting equipment, which increases the equipment cost. Therefore, the existing method of "first growing a positive crystal direction, and then cutting at an off-angle" has problems of complicated cutting process, low material utilization rate and high cost.

[0005] In summary, it is necessary to provide a method for growing an off-angle silicon carbide single crystal by a liquid phase method. SUMMARY

[0006] In order to solve one or more technical problems existing in the prior art, the present application provides a method for growing an off-angle silicon carbide single crystal by a liquid phase method.

[0007] The present application provides a method for growing an off-angle silicon carbide single crystal by a liquid phase method, which is performed by using a device for growing a silicon carbide single crystal by a liquid phase method. The device comprises a wedge-shaped seed crystal holder and a wedge-shaped seed crystal. The method comprises the following steps: (1) The wedge-shaped seed crystal is arranged on the wedge-shaped seed crystal holder to form a positive crystal direction seed crystal surface, and then a silicon carbide is grown on the positive crystal direction seed crystal surface by a liquid phase method to obtain a crystal ingot comprising a wedge-shaped seed crystal and a silicon carbide growth crystal; (2) The crystal ingot is taken off from the wedge-shaped seed crystal holder, and then multi-line cutting is performed with the inclined surface of the wedge-shaped seed crystal included in the crystal ingot as a reference to obtain an off-angle silicon carbide single crystal.

[0008] Preferably, in step (2), after the multi-line cutting with the inclined surface of the wedge-shaped seed crystal included in the crystal ingot as a reference, a new wedge-shaped seed crystal can also be obtained, which is recycled for use in step (1).

[0009] Preferably, the method further comprises a step of rounding the silicon carbide growth crystal included in the crystal ingot obtained in step (1) before the crystal ingot is taken off from the wedge-shaped seed crystal holder.

[0010] Preferably, the inclination angle of the wedge-shaped seed crystal holder and the inclination angle of the wedge-shaped seed crystal are both not more than 4°.

[0011] Preferably, 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.

[0012] Preferably, the wedge-shaped seed crystal holder is connected to a seed crystal rod; the length of the seed crystal rod is 400-500 mm.

[0013] Preferably, the seed crystal rod is connected to a seed crystal rod rotation and pulling device.

[0014] Preferably, the wedge-shaped seed crystal holder comprises a right-angle portion and an off-angle portion; the right-angle portion is connected perpendicularly to a seed crystal rod; the inclined surface of the off-angle portion is bonded together with the inclined surface of the wedge-shaped seed crystal by an adhesive.

[0015] Preferably, the thickness of the right-angle portion is 5-25 mm.

[0016] Preferably, in step (2), when multi-wire sawing is performed, the sawing angle error is not more than 0.2°.

[0017] Compared with the prior art, the present application has at least the following beneficial effects: (1) The present application forms a right-orientation seed crystal surface by using a wedge-shaped seed crystal and a wedge-shaped seed crystal holder with the same inclination angle, and obtains a crystal ingot comprising a wedge-shaped seed crystal and a silicon carbide growth crystal by using the right-orientation seed crystal surface as a liquid phase growth surface, wherein the silicon carbide growth crystal part is still right-orientation, and there is no problem of off-angle growth affecting the quality of the crystal ingot, that is, the present application obtains an off-angle silicon carbide single crystal by using a right-orientation seed crystal surface as a liquid phase growth surface.

[0018] (2) The present application can perform multi-wire sawing by using the inclined surface of the wedge-shaped seed crystal as a reference, and this kind of multi-wire sawing does not need a crystal orientation step, and can reduce the off-angle single-wire sawing or flat grinding process, save the processing time, and recycle the off-angle crystal ingot with an ineffective size after multi-wire sawing as a new wedge-shaped seed crystal, which effectively utilizes the crystal of the size insufficient part of the silicon carbide obtained by the liquid phase method due to multi-wire sawing, and improves the resource utilization rate. In the prior art, a right-orientation crystal ingot is first obtained by the liquid phase method, and then off-angle sawing is performed, and generally the sawing error is controlled within ±0.5°. The present application only needs to control the angle when the wedge-shaped seed crystal is initially prepared, and then the inclined surface of the wedge-shaped seed crystal can be used as a reference to perform multi-wire sawing, which is simple to operate, and the sawing angle error can be controlled within ±0.2°, which can greatly ensure the consistency of the batch. BRIEF DESCRIPTION OF DRAWINGS

[0019] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the embodiments will be briefly introduced as follows. Obviously, the drawings in the following description are some embodiments of the present application, and other drawings can be obtained by those skilled in the art without any creative effort on the basis of these drawings. The drawings of the present application are provided only for the purpose of illustration, and the proportions, sizes and quantities of the parts in the drawings are not necessarily consistent with those of the actual products.

[0020] Figure 1 is a structure diagram of a wedge-shaped seed crystal holder and a wedge-shaped seed crystal forming a positive crystal direction seed crystal surface included in the device for growing silicon carbide single crystal by liquid phase method adopted in some specific embodiments of the present application; Figure 2 is a structure diagram of a wedge-shaped seed crystal holder and a wedge-shaped seed crystal forming a positive crystal direction seed crystal surface included in the device for growing silicon carbide single crystal by liquid phase method adopted in some specific embodiments of the present application; Figure 3 is a diagram of multi-wire cutting based on the inclined surface of the wedge-shaped seed crystal included in the crystal ingot in some specific embodiments of the present application; Figure 4 is a physical diagram of the silicon carbide growth crystal obtained on the wedge-shaped seed crystal in Embodiment 1 of the present application; Figure 5 is a front view of the silicon carbide growth crystal obtained in Embodiment 1 of the present application; Figure 6 is a physical diagram of the positive crystal direction silicon carbide single crystal obtained on the positive crystal direction seed crystal in Comparative Example 1 of the present application; Figure 7 is a front view of the positive crystal direction silicon carbide single crystal obtained in Comparative Example 1 of the present application; Figure 8 is a physical diagram of the off-angle silicon carbide single crystal obtained on the 4° off seed crystal in Comparative Example 2 of the present application; Figure 9 is a front view of the off-angle silicon carbide single crystal obtained in Comparative Example 2 of the present application; Figures 1 to 3 In the figure: 1: wedge-shaped seed crystal holder; 11: positive angle part; 12: off-angle part; 2: wedge-shaped seed crystal; 21: positive crystal direction seed crystal surface; 3: seed crystal rod; 4: silicon carbide growth crystal; 5: inclined surface of the wedge-shaped seed crystal included in the crystal ingot; 6: off-angle crystal ingot. DETAILED DESCRIPTION

[0021] In order to make the objects, technical solutions and advantages of the present application clearer, the technical solutions will be described clearly and completely below in combination with the embodiments in the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all the other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the present application.

[0022] The present application provides a method for growing a misoriented silicon carbide single crystal by liquid phase method, which is carried out by using a device for growing a silicon carbide single crystal by liquid phase method, for example, as shown in Figure 1 The device comprises a wedge-shaped seed crystal holder 1 and a wedge-shaped seed crystal 2; the method comprises the following steps: (1) The wedge-shaped seed crystal 2 is arranged on the wedge-shaped seed crystal holder 1 to form a positive crystal orientation seed crystal surface 21, and then a silicon carbide is grown by liquid phase method on the positive crystal orientation seed crystal surface 21 to obtain a crystal ingot comprising the wedge-shaped seed crystal 2 and a silicon carbide growth crystal 4, for example, as shown in Figure 2 In the present application, the wedge-shaped seed crystal holder 1 and the wedge-shaped seed crystal 2 have the same inclination angle, and the positive crystal orientation seed crystal surface 21 is formed by the cooperation of the wedge-shaped seed crystal 2 and the inclined surface of the wedge-shaped seed crystal holder 1, for example, as shown in Figure 1 In the present application, the wedge-shaped seed crystal holder 1 is connected with a seed crystal rod 3, and the positive crystal orientation seed crystal surface 21 is perpendicular to the seed crystal rod 3 (crystal growth direction); the present application does not make specific limitation on the process conditions for growing a silicon carbide by liquid phase method, which can be selected conventionally by those skilled in the art; (2) The crystal ingot is taken off from the wedge-shaped seed crystal holder 1, and then a multi-wire sawing is carried out based on the inclined surface 5 of the wedge-shaped seed crystal included in the crystal ingot, that is, the multi-wire sawing is carried out along the upper surface (inclined surface) of the wedge-shaped seed crystal included in the crystal ingot to obtain a misoriented silicon carbide single crystal, for example, as shown in Figure 3 .

[0023] The method of the present application forms a positive crystal direction seed crystal surface by a wedge-shaped seed crystal and a wedge-shaped seed crystal holder with the same inclination angle, and obtains a crystal ingot including the wedge-shaped seed crystal and a silicon carbide growth crystal by taking the positive crystal direction seed crystal surface as a liquid phase growth surface, wherein the silicon carbide growth crystal part is still positive crystal direction, and there is no problem of growth quality affected by an off-angle, that is, the present application obtains an off-angle silicon carbide single crystal by taking the positive crystal direction seed crystal surface as the liquid phase growth surface. The present application can perform multi-wire slicing based on the inclined surface of the wedge-shaped seed crystal. This multi-wire slicing does not need a crystal orientation step, and can reduce the off-angle single-wire slicing or flat grinding process, save the processing time, and recycle the off-angle crystal ingot 6 with an ineffective size after multi-wire slicing as a new wedge-shaped seed crystal, which effectively utilizes the crystal of the insufficient size part of the silicon carbide caused by multi-wire slicing in the liquid phase method, and improves the resource utilization rate. In the prior art, the positive crystal direction crystal ingot is first obtained by the liquid phase method, and then the off-angle slicing is performed, and the slicing error is generally controlled within ±0.5°. The present application only needs to control the angle during the initial preparation of the wedge-shaped seed crystal, and then the multi-wire slicing can be performed based on the inclined surface of the wedge-shaped seed crystal. The operation is simple, the angle error can be controlled within ±0.2°, and the consistency of the batch can be greatly guaranteed.

[0024] According to some preferred embodiments, in step (2), after multi-wire slicing based on the inclined surface 5 of the wedge-shaped seed crystal included in the crystal ingot, a new wedge-shaped seed crystal can also be obtained, for example, as shown in FIG. Figure 3 In the present application, after multi-wire slicing based on the inclined surface of the wedge-shaped 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-shaped seed crystal, that is, has the same inclination angle and shape structure as the original wedge-shaped seed crystal. This part of the off-angle crystal ingot can be used as a new wedge-shaped seed crystal, realizing recycling.

[0025] The present application recycles the off-angle crystal ingot after multi-wire slicing as a wedge-shaped seed crystal, reduces the pre-preparation demand of the wedge-shaped seed crystal, directly uses the residual material after multi-wire slicing as a new wedge-shaped seed crystal without additional processing, improves the material utilization rate, and saves the material cost. Moreover, the off-angle crystal ingot after multi-wire slicing has the same inclination angle and structure as the original wedge-shaped seed crystal, ensures the stability of the crystal off-angle in subsequent growth, and avoids introducing parameter deviation.

[0026] According to some preferred embodiments, the method further comprises a step of performing a rounding treatment on the silicon carbide growth crystal 4 included in the crystal ingot obtained in step (1) before the crystal ingot is removed from the wedge-shaped seed crystal holder 1; a silicon carbide single crystal grown by a liquid phase method usually presents a hexagonal shape, and the present application preferably performs a rounding treatment on the hexagonal silicon carbide growth crystal; in the present application, the multi-wire sawing is performed by a multi-wire sawing machine, and the process conditions of the multi-wire sawing and the rounding are not specifically limited in the present application, and can be routinely selected by those skilled in the art.

[0027] According to some preferred embodiments, in step (1), a surface remelting treatment (i.e. inverse dissolution treatment) can be performed on the wedge-shaped seed crystal before the silicon carbide is grown by a liquid phase method, which is beneficial to in-situ flattening of the surface of the wedge-shaped seed crystal and also beneficial to improving the crystal quality of the initial growth layer; the inverse dissolution treatment is not specifically limited in the present application, and can be routinely selected by those skilled in the art.

[0028] According to some preferred embodiments, the inclination angle θ of the wedge-shaped seed crystal holder 1 and the inclination angle θ of the wedge-shaped seed crystal 2 are both not greater than 4°, for example, 0.5°-4°, which corresponds to the commonly used silicon carbide wafer inclination angle range; in the present application, the inclination angle of the wedge-shaped seed crystal holder 1 and the inclination angle of the wedge-shaped seed crystal 2 are the same.

[0029] 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 adhesive is not specifically limited in the present application, and can be routinely selected by those skilled in the art; in the present application, the inclined surface of the wedge-shaped seed crystal holder and the inclined surface of the wedge-shaped seed crystal are bonded (i.e. glued) together by an adhesive, which can ensure that the wedge-shaped seed crystal does not fall off during crystal growth.

[0030] According to some preferred embodiments, the wedge-shaped seed crystal holder 1 is connected to a seed crystal rod 3; the length of the seed crystal rod 3 is 400-500 mm (for example, 400, 450 or 500 mm), which is beneficial to ensuring that the wedge-shaped seed crystal can enter the growth crucible and also has a surplus amount to ensure that the wedge-shaped seed crystal can be connected to the liquid and pulled off in the positive crystal orientation seed crystal surface.

[0031] According to some preferred embodiments, the seed crystal rod 3 is connected to a seed crystal rod rotating and pulling device, and the seed crystal rod rotating and pulling device is used to control the seed crystal rod 3 to perform lifting and rotating.

[0032] According to some preferred embodiments, for example, as shown in Figure 1 and Figure 2As shown, the wedge-shaped seed holder 1 includes a normal angle part 11 and an inclined angle part 12, the normal angle part 11 is vertically connected with a seed rod 3, and the inclined surface of the inclined angle part 12 is bonded together with 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 normal crystal direction seed crystal surface 21.

[0033] According to some preferred embodiments, the thickness of the normal angle part 11 is 5-25 mm (for example, 5, 10, 15, 20, or 25 mm); in the present application, the selection of the thickness of the normal angle part is mainly based on the consideration of heat dissipation, and different heat dissipation requirements can be formulated according to different processes, and preferably, the thickness of the normal angle part is 5-25 mm; the present application does not specifically limit the thickness of the inclined angle part 12, and the thickness of the inclined angle part can be determined according to the diameter and the inclined angle of the wedge-shaped seed holder.

[0034] According to some preferred embodiments, in step (2), when multi-wire cutting is performed, the cutting angle error is not greater than 0.2°.

[0035] According to some specific embodiments, the method for growing an inclined angle silicon carbide single crystal by a liquid phase method includes the following steps: (1) The wedge-shaped seed crystal 2 is arranged on the wedge-shaped seed holder 1 to form a normal crystal direction seed crystal surface 21 and the device for growing a silicon carbide single crystal by a liquid phase method is assembled, and then the device is used to grow a silicon carbide on the normal crystal direction seed crystal surface 21, the growth surface is a normal crystal direction, and a crystal ingot including a wedge-shaped seed crystal 2 and a silicon carbide growth crystal 4 is obtained, as shown in Figure 2 .

[0036] (2) The silicon carbide growth crystal 4 included in the crystal ingot obtained in step (1) is first subjected to a rounding treatment, then the crystal ingot is taken off from the wedge-shaped seed holder 1, and then multi-wire cutting is performed with the inclined surface 5 of the wedge-shaped seed crystal included in the crystal ingot as a reference (i.e., along the upper surface parallel to the wedge-shaped seed crystal), to obtain an inclined angle silicon carbide single crystal; after the multi-wire cutting is performed with the inclined surface of the wedge-shaped seed crystal included in the crystal ingot as a reference, the last part of the inclined angle crystal ingot 6 that does not meet the size can still be recycled as a new wedge-shaped seed crystal, and the inclined angle silicon carbide single crystal growth is continued as a wedge-shaped seed crystal.

[0037] According to some preferred embodiments, the device for growing silicon carbide single crystal by liquid phase method comprises a crucible body, a crucible cover with an opening, and a seed rod 3; one end of the seed rod 3 is connected with a wedge-shaped seed holder 1, the wedge-shaped seed holder 1 is connected with a wedge-shaped seed crystal 2, the wedge-shaped seed holder 1 and the wedge-shaped seed crystal 2 have the same inclination angle, the inclined surface of the wedge-shaped seed 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 forms a positive crystal orientation seed surface 21; the end of the seed rod 3 connected with the wedge-shaped seed holder 1 extends into the interior of the crucible body through the opening of the crucible cover; the crucible body and the crucible cover constitute a growth crucible, the device further comprises a heat preservation layer arranged outside the growth crucible, the outside of the heat preservation layer is provided with an induction heating device for heating, the induction heating device comprises an induction coil, the induction coil is coaxially arranged with the seed rod 3, and the induction heating device heats the growth crucible through electromagnetic induction; the device further comprises a seed rod rotation lifting device for controlling the lifting and rotation of the seed rod 3 and a crucible rotation lifting device for controlling the lifting and rotation of the crucible body.

[0038] In the process of growing silicon carbide by liquid phase method in the present application, the process parameters such as the rotation speed of the seed rod, the lifting speed of the seed rod, and the rotation speed of the crucible body are not particularly limited, and can be routinely selected by those skilled in the art, for example, the seed rod can rotate clockwise at a speed of 40-100 rpm, and the crucible body can rotate counterclockwise at a speed of 20-50 rpm; the lifting speed of the seed rod can be controlled at 80-300 µm / h, for example, to ensure that the actual growth rate of the silicon carbide single crystal is basically consistent with the lifting speed, so as to realize stable interface morphology.

[0039] The present application will be further described below by way of examples, but the scope of protection of the present application is not limited to these examples.

[0040] Example 1 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.

[0041] The method includes the following steps: 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%.

[0042] 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.

[0043] The embodiment obtains a real picture of the silicon carbide growth crystal on the wedge seed crystal, as shown in Figure 4 The embodiment obtains a front view of the silicon carbide growth crystal, as shown in Figure 5 From the results of Figure 4 and Figure 5 , it can be known that the silicon carbide growth crystal obtained by the embodiment can stably control the meniscus of the solid-liquid interface due to the normal crystal growth, the crystal surface is flat, no groove, and the quality is good; after the multi-wire sawing, the off-angle of the silicon carbide single crystal obtained by the embodiment is 4.1°, and the deviation is less than 0.2°.

[0044] Comparative Example 1 The comparative example provides a method for growing a silicon carbide single crystal by a liquid phase method, which is carried out by using a device for growing a silicon carbide single crystal by a liquid phase method, the device is basically the same as the device for growing a silicon carbide single crystal by a liquid phase method in the embodiment 1, the difference is that the device in the comparative example does not include the seed crystal holder and the seed crystal with an inclination angle, the seed crystal holder and the seed crystal are both arranged perpendicularly to the seed crystal rod, which are normal crystal growth seed crystal holder and normal crystal growth seed crystal; the seed crystal holder and the seed crystal are bonded together by an adhesive.

[0045] The method comprises: assembling the device for growing a silicon carbide single crystal by a liquid phase method, filling the growth raw material in the crucible body and heating the growth raw material to obtain a high-temperature melt, and then contacting the lower surface of the normal crystal growth seed crystal with the high-temperature melt and growing a silicon carbide by a liquid phase method to obtain a normal crystal growth silicon carbide single crystal; wherein, in the heating stage, the furnace is vacuumized, then argon gas is filled, and then the power is turned on to heat, so that the growth crucible is melted to obtain a high-temperature melt; the growth raw material used in the comparative example is mixed by Si, Cr and Al, and the mass percentage of the three components in the growth raw material is Si: 50%, Cr: 48%, and Al: 2%.

[0046] The comparative example obtains a real picture of the normal crystal growth silicon carbide single crystal on the normal crystal growth seed crystal, as shown in Figure 6 The comparative example obtains a front view of the normal crystal growth silicon carbide single crystal, as shown in Figure 7 From the results of Figure 6 and Figure 7 , it can be known that the normal crystal growth silicon carbide single crystal obtained by the comparative example can stably control the meniscus of the solid-liquid interface due to the normal crystal growth, the crystal surface is flat, no groove, and the quality is good. However, when the subsequent 4° off-angle cutting is carried out, taking a 4-inch (diameter 100 mm) crystal as an example, according to the calculation of the trigonometric function, the thickness of the crystal ingot with the remaining effective size not meeting the standard reaches 7 mm, which is wasted, and the method of "first normal crystal growth and then off-angle cutting" to obtain a 4° off-angle silicon carbide single crystal also has problems of complicated cutting process and high cost.

[0047] From Figure 5 and Figure 7 As can be seen from the results, the silicon carbide growth crystal obtained by the embodiment 1 and the normal crystal direction silicon carbide single crystal obtained by the comparative example 1, although there is a common phenomenon of residual droplets in the liquid phase method growth process, the overall surface of both is flat, the quality is equivalent and both show excellent performance.

[0048] Comparative example 2 The present comparative example provides a method for growing a silicon carbide single crystal with an off-angle, which is carried out by using a device for growing a silicon carbide single crystal by a liquid phase method, which is basically the same as the device for growing a silicon carbide single crystal by a liquid phase method in the embodiment 1, except that the device in the present comparative example includes a seed crystal holder without an inclination angle, which is arranged perpendicularly to the seed crystal rod, being a normal crystal direction seed crystal holder, and the seed crystal is a 4° off seed crystal (4° off-angle seed crystal).

[0049] The method comprises: assembling the device for growing a silicon carbide single crystal by a liquid phase method, charging and heating the growth raw material in the main body of the crucible to obtain a high-temperature melt, then contacting the lower surface of the 4° off seed crystal with the high-temperature melt and growing a silicon carbide by a liquid phase method to obtain a silicon carbide single crystal with an off-angle; wherein, during the heating stage, the furnace is vacuumized, then argon gas is filled, then the power is turned on to heat, and the growth crucible is melted to obtain a high-temperature melt; the growth raw material used in the present comparative example is mixed by Si, Cr and Al, and the mass percentage of the three components in the growth raw material is Si: 50%, Cr: 48%, and Al: 2%.

[0050] The actual figure of the silicon carbide single crystal with an off-angle obtained by the present comparative example on the 4° off seed crystal is shown in FIG. 2, the front view of the silicon carbide single crystal with an off-angle obtained by the present comparative example is shown in FIG. 3, and the side view of the silicon carbide single crystal with an off-angle obtained by the present comparative example is shown in FIG. 4. Figure 8 Figure 9 As can be seen from FIG. 2, the silicon carbide single crystal with an off-angle obtained by the present comparative example shows a phenomenon of thin at one end and thick at the other end, and as can be seen from FIG. 4, the surface of the crystal has many grooves and the quality of the crystal is poor. Figure 8 Figure 9

[0051] The part of the present application not described in detail is the technology known to those skilled in the art.

[0052] Finally, it should be pointed out that: the above embodiments 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 embodiments, those skilled in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, 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 a off-angle silicon carbide single crystal by a liquid phase method, characterized by, The method is performed by using a device for growing silicon carbide single crystal, the device comprising a wedge-shaped seed crystal holder and a wedge-shaped seed crystal, the method comprising the following steps: (1) setting the wedge-shaped seed crystal on the wedge-shaped seed crystal holder to form a normal seed crystal surface, and then growing silicon carbide on the normal seed crystal surface by a liquid phase method to obtain a crystal ingot comprising the wedge-shaped seed crystal and a silicon carbide growth crystal; (2) taking the crystal ingot off the wedge-shaped seed crystal holder, and then performing multi-wire sawing with the inclined surface of the wedge-shaped seed crystal included in the crystal ingot as a reference to obtain a silicon carbide single crystal with an off-angle.

2. The method according to claim 1, wherein: in step (2), after the multi-wire sawing with the inclined surface of the wedge-shaped seed crystal included in the crystal ingot as a reference, a new wedge-shaped seed crystal is obtained, and the new wedge-shaped seed crystal is recycled for use in step (1).

3. The method of claim 1, wherein, The method further comprises a step of performing rounding treatment on the silicon carbide growth crystal included in the crystal ingot obtained in step (1) before the crystal ingot is taken off the wedge-shaped seed crystal holder.

4. The method according to claim 1, wherein: the inclination angle of the wedge-shaped seed crystal holder and the inclination angle of the wedge-shaped seed crystal are both not greater than 4°.

5. The method according to claim 4, wherein: 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.

6. The method according to claim 1, wherein: the wedge-shaped seed crystal holder is connected to a seed crystal rod; the length of the seed crystal rod is 400-500 mm.

7. The method according to claim 6, wherein: the seed crystal rod is connected to a seed crystal rod rotating pulling device.

8. The method according to claim 1, wherein: the wedge-shaped seed crystal holder comprises a normal-angle portion and an off-angle portion, the normal-angle portion is perpendicularly connected to a seed crystal rod, and the inclined surface of the off-angle portion is bonded together with the inclined surface of the wedge-shaped seed crystal by an adhesive.

9. The method according to claim 8, wherein: the thickness of the normal-angle portion is 5-25 mm.

10. The method according to any one of claims 1-9, wherein: in step (2), when performing the multi-wire sawing, the cutting angle error is not greater than 0.2°.

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