Apparatus for growing silicon carbide single crystals by the solution method

Abstract

The present invention relates to an apparatus for growing silicon carbide single crystals by a solution process, including a growth crucible, a seed crystal rod, an induction heating device, and a source block to which a growth source material can be supplied. The growth crucible includes a crucible body for containing the growth source material and a crucible lid with an opening. One end of the seed crystal rod, to which the seed crystal is fixed, enters the crucible body through the opening. The density of the source block is lower than that of the liquid growth source material, and the source block floats on the surface of the liquid growth source material. The apparatus of the present invention shortens the carbon supply distance and provides a sufficient and stable carbon source over a long period of time during the silicon carbide single crystal growth process, significantly reducing the occurrence of encrustations and effectively improving the growth quality of the single crystal. It also effectively suppresses burn-through on the crucible wall and prevents solution leakage from affecting the temperature field and ultimately damaging the single crystal furnace.

Description

[Technical Field]

[0001] The present invention relates to the field of silicon carbide single crystal manufacturing technology, and in particular to an apparatus for growing silicon carbide single crystals by a solution method. [Background technology]

[0002] Silicon carbide (SiC) is a third-generation semiconductor material with advantages such as a wide band gap, high critical breakdown field strength, and high saturated drift velocity, making it an ideal material for manufacturing high-temperature, high-frequency, high-voltage, and high-power devices. It is currently widely used in many fields, including rail transit, new energy vehicles, 5G communications, and aerospace.

[0003] In silicon carbide single crystal growth technology, a stable supply of carbon is a centrally important factor for single crystal growth. In particular, in the growth of silicon carbide single crystals by the solution method, an insufficient carbon supply can lead to problems such as encapsulation of the solution during crystal growth and cracking of the crystal.

[0004] The solution growth technique for silicon carbide single crystals involves the transport and supply of carbon elements through the interaction of convective mass transfer, which involves the interaction of forced convection due to seed crystal rotation and natural convection due to concentration differences within the growth system, and diffusive mass transfer, which is the diffusion of the carbon source at the solid-liquid interface during crystal growth. However, in solution growth of silicon carbide single crystals, carbon on the surface of the growth crucible is consumed as the crystal grows, moving the carbon supply location away from the growth site. This weakens the diffusive mass transfer effect, making it difficult to ensure a sufficient supply of carbon necessary for crystal growth. This leads to defects such as solution encapsulation and crystal cracking, which affect crystal quality and degrade the crystal growth quality. Furthermore, during long-term growth, the growth crucible (graphite crucible), which serves as the carbon source, is gradually consumed as the crystal growth progresses, or the growth crucible melts down, causing the solution to flow into the furnace and damage the single crystal furnace, which disrupts the progress of the experiment and results in significant economic losses.

[0005] Therefore, it is highly desirable to provide a new solution method for growing silicon carbide single crystals. Summary of the Invention

[0006] The present invention has been made to solve the problems of the prior art, and aims to provide an apparatus for growing silicon carbide single crystals by the solution method. The apparatus of the present invention can firstly shorten and maintain a constant carbon supply distance during the solution method growth of silicon carbide single crystals, and secondly provide a sufficient and stable carbon source over a long period of time during the growth of silicon carbide single crystals, thereby significantly reducing the occurrence of encrustations and effectively improving the quality of single crystal growth. It also effectively prevents melt-through of the crucible wall, preventing solution leakage from affecting the temperature field and damaging the single crystal furnace. It also improves the reproducibility and stability of single crystal growth experiments, enables long-term growth, reduces the crucible wall thickness, and reduces costs.

[0007] The present invention provides an apparatus for growing silicon carbide single crystals by a solution method, comprising a growth crucible, a seed crystal rod having a seed crystal fixed thereto, an induction heating device for heating, and a raw material block capable of supplying a growth raw material, wherein the growth crucible comprises a crucible body for accommodating the growth raw material and a crucible lid having an opening, one end of the seed crystal rod to which the seed crystal is fixed enters the inside of the crucible body through the opening, the density of the raw material block capable of supplying the growth raw material is lower than the density of the liquid growth raw material, and the raw material block capable of supplying the growth raw material floats on the surface of the liquid growth raw material.

[0008] Preferably, the source block from which the growth source material can be supplied is a silicon carbide block.

[0009] Preferably, the raw material block capable of supplying the growth raw material is a graphite block for supplying carbon.

[0010] Preferably, the carbon supply graphite block is a ring-shaped carbon supply graphite block, and the ring-shaped carbon supply graphite block is arranged in close contact with the inner wall of the crucible body, or the ring-shaped carbon supply graphite block has an outer diameter slightly smaller than the inner diameter of the crucible body.

[0011] Preferably, the apparatus further includes a graphite block connecting member, the crucible wall of the crucible body being provided with a slot extending downward from the top, one end of the graphite block connecting member being provided with a ring engaged with the slot, and the other end of the graphite block connecting member being connected to a carbon supply graphite block having a density lower than that of the liquid growth raw material, the carbon supply graphite block floating on the surface of the liquid growth raw material.

[0012] Preferably, the graphite block connecting member is disposed in contact with the crucible wall of the crucible body, and / or the ring is movable up and down within the slot.

[0013] Preferably, the graphite block connecting member and the ring are both made of graphite.

[0014] Preferably, the end of the seed crystal rod to which the seed crystal is not fixed is connected to an actuator for controlling the elevation and rotation of the seed crystal rod.

[0015] Preferably, the growth source material contains silicon and one or more metal sources selected from Al, Ti, Cr, Fe, Y, Yb, Pr, La, Cu, Ce, Sn, Ge, and Co.

[0016] Preferably, the crucible body has a crucible wall thickness of 10 to 30 mm, a bottom thickness of 15 to 40 mm, the starting position of the slot at the top of the crucible wall of the crucible body is 2 to 5 mm from the inside of the crucible wall, and the depth of the slot is 10 to 50 mm.

[0017] Preferably, the slot is arranged in a ring shape within the crucible wall of the crucible body, the slot is a ring-shaped slot, the graphite block connecting member is a ring-shaped graphite block connecting member, and the carbon supply graphite block is a ring-shaped carbon supply graphite block.

[0018] Preferably, the thickness of the carbon supply graphite block is 10 to 30 mm, and the width of the carbon supply graphite block is 10 to 30 mm.

[0019] Preferably, two symmetrical slots are provided in the radial direction of the crucible wall of the crucible body, the number of the carbon supplying graphite blocks is two, and the number of the graphite block connecting members is two.

[0020] Preferably, the thickness of the carbon supply graphite block is 10 to 30 mm, the width of the carbon supply graphite block is 10 to 30 mm, and the sum of the lengths of the two carbon supply graphite blocks is smaller than the difference between the inner diameter of the crucible body and the diameter of the seed crystal.

[0021] Preferably, a heat insulating layer is provided between the growth crucible and the induction heating device.

[0022] Preferably, the heat-insulating layer includes an upper heat-insulating region located above the growth crucible, a peripheral heat-insulating region located around the growth crucible, and a lower heat-insulating region located below the growth crucible, and the upper heat-insulating region is provided with a through hole for passing a seed crystal rod corresponding to the opening of the crucible lid.

[0023] Preferably, the temperature field during growth of silicon carbide single crystals by the solution method is controlled by changing the shape of the peripheral heat-retaining region.

[0024] Preferably, the outer shape of the peripheral heat-retaining region is cylindrical, regular truncated cone, or inverted truncated cone.

[0025] Preferably, when the outer shape of the peripheral heat-retaining region is a regular truncated cone, the temperature gradient between the seed crystal and the liquid surface of the growth raw material is increased, and the growth rate of the silicon carbide single crystal is further increased, thereby improving crystal productivity.

[0026] Preferably, when the outer shape of the peripheral heat-retaining region is an inverted truncated cone shape, the temperature gradient between the seed crystal and the liquid surface of the growth raw material is reduced, and the growth rate of the silicon carbide single crystal is further reduced, thereby improving the crystal quality.

[0027] The present invention has at least the following advantageous effects compared to the prior art: (1) The apparatus of the present invention includes a raw material block capable of supplying a growth raw material, preferably a carbon-supplying graphite block. The density of the carbon-supplying graphite block is smaller than the density of the liquid growth raw material, and the carbon-supplying graphite block can float on the surface of the liquid growth raw material and provide a carbon source in the growth process of silicon carbide single crystals. However, the positional stability of the carbon-supplying graphite block is relatively poor, resulting in relatively poor supply stability as a carbon source. In a preferred embodiment of the present invention, the apparatus includes a carbon supply graphite block and a graphite block connecting member. The carbon supply graphite block is movable up and down in contact with the crucible wall via the graphite block connecting member through a slot provided in the crucible wall, thereby providing high installation stability for the carbon supply graphite block. The carbon supply graphite block is made of graphite and has a low density characteristic that is lower than the density of the growth raw material. This allows it to float on the surface of the growth raw material solution for a long period of time during the growth process, thereby providing a sufficient and stable carbon source for growing silicon carbide single crystals on the surface, which is the growth interface. At the growth interface, as the growth process progresses, the carbon supply graphite block becomes thinner only at the position in contact with the liquid surface of the growth raw material solution, while other installations remain unchanged. This maintains a constant carbon supply distance during the silicon carbide single crystal growth process, thereby making the growth of the silicon carbide single crystal more stable, improving the growth quality of the silicon carbide single crystal, and suppressing the burn-through phenomenon of the crucible.

[0028] (2) In the apparatus of the present invention, preferably, the graphite block connecting members and slots allow the carbon supply graphite block to float stably on the surface of the growth raw material while following the crucible wall for a long period of time. Compared with carbon supply devices that increase the thickness of the graphite crucible wall, directly add carbon powder, or insert graphite material into the growth raw material solution, the carbon supply method of the apparatus of the present invention is stable and does not affect the convection in the growth system, which would affect the crystal quality due to the influence of convection, and does not increase costs due to increased wall thickness. The apparatus of the present invention not only fulfills the role of providing a sufficient carbon source, but also shortens the carbon supply distance and maintains it constant, ensuring the amount of carbon supplied by diffusive mass transfer, without affecting the convection in the growth system, and making crystal growth more stable, making it a very stable carbon supply device.

[0029] (3) In the device of the present invention, in the growth of silicon carbide single crystals by the solution method, firstly, the carbon supply distance can be shortened and maintained constant, and secondly, a sufficient and stable carbon source can be supplied for the growth of silicon carbide single crystals for a long time, which greatly reduces the occurrence of encrustations and effectively improves the quality of single crystal growth. It also effectively prevents the melting of the crucible wall, especially the melting of the crucible wall at the surface of the growth raw material solution, prevents the leakage of the growth-promoting solution (growth raw material) from affecting the temperature field, and ultimately prevents damage to the single crystal furnace, improving the reproducibility and stability of single crystal growth experiments. [Brief explanation of the drawings]

[0030] It should be noted that the drawings are merely for the purpose of explaining the present invention, and the size, dimensions, number, etc. of each part do not necessarily correspond to the actual ones. [Figure 1] FIG. 1 shows a schematic diagram of an apparatus for growing silicon carbide single crystals by a solution method in some embodiments of the present invention. [Figure 2] FIG. 2 shows a schematic diagram of an apparatus for growing silicon carbide single crystals by a solution method according to some other embodiments of the present invention. [Figure 3] FIG. 3 is a schematic diagram showing the configuration of an apparatus for growing silicon carbide single crystals by a solution method according to Example 1 of the present invention. [Figure 4] FIG. 4 is a schematic diagram showing the configuration of an apparatus for growing silicon carbide single crystals by a solution method according to a second embodiment of the present invention. [Figure 5] FIG. 5 is a schematic diagram showing the configuration of an apparatus for growing silicon carbide single crystals by a solution method according to a third embodiment of the present invention. [Figure 6] FIG. 6 shows an external view of the silicon carbide single crystal obtained in Example 1 of the present invention. [Figure 7] FIG. 7 shows an external view of the silicon carbide single crystal obtained in Example 2 of the present invention. [Figure 8] FIG. 8 shows an external view of the silicon carbide single crystal obtained in Example 3 of the present invention. [Figure 9] FIG. 9 shows temperature gradient curves of the apparatus for growing silicon carbide single crystals by the solution method provided in Examples 1 to 3 of the present invention. In FIG. 9, (a) shows the temperature gradient curve of the apparatus for growing silicon carbide single crystals by the solution method provided in Example 1, (b) shows the temperature gradient curve of the apparatus for growing silicon carbide single crystals by the solution method provided in Example 2, and (c) shows the temperature gradient curve of the apparatus for growing silicon carbide single crystals by the solution method provided in Example 3. [Figure 10] FIG. 10 is a schematic diagram showing the occurrence of burn-through of the graphite crucible in the growth interface region after growing a silicon carbide single crystal by a solution method using the apparatus according to Comparative Example 1 of the present invention. [Figure 11] FIG. 11 shows an external view of the silicon carbide single crystal obtained in Comparative Example 1 of the present invention.

[0031] In the figure, 1: growth crucible, 1-1: crucible body, 1-2: crucible lid, 2: seed crystal rod, 3: seed crystal, 4: induction coil, 5: slot, 6: graphite block for carbon supply, 7: graphite block connecting member, 8: ring, 9: growth raw material, 10: heat-insulating layer, 10-1: upper heat-insulating area, 10-2: peripheral heat-insulating area, 10-3: lower heat-insulating area. DETAILED DESCRIPTION OF THE INVENTION

[0032] In order to clarify the objectives, embodiments and advantages of the present invention, the following will clearly and completely describe the embodiments of the present invention with reference to the examples of the present invention, but it is clear that the described examples are only some examples of the present invention and do not represent all examples. All other examples obtained by those skilled in the art based on the embodiments of the present invention without creative ingenuity shall fall within the protection scope of the present invention.

[0033] The present invention provides an apparatus for growing silicon carbide single crystals by a solution process. For example, as shown in FIG. 1 , the apparatus includes a growth crucible 1, a seed crystal rod 2 to which a seed crystal 3 is fixed, an induction heater, and a source block to which a growth source material can be supplied. In the present invention, the source block to which the growth source material can be supplied is, for example, a silicon carbide block, a graphite block for supplying carbon, or another source block to which a growth source material can be supplied. The growth crucible 1 includes a crucible body 1-1 that contains the growth source material and a crucible lid 1-2 having an opening. One end of the seed crystal rod 2 to which the seed crystal 3 is fixed enters the inside of the crucible body 1-1 through the opening. The density of the source block to which the growth source material can be supplied is smaller than the density of the liquid growth source material, and the source block to which the growth source material can be supplied floats on the surface of the liquid growth source material.

[0034] In some preferred embodiments, the source block from which the growth feedstock can be provided is a silicon carbide block.

[0035] In some preferred embodiments, the source block capable of supplying the growth source material is a graphite block for supplying carbon, as shown in FIG.

[0036] In some preferred embodiments, the carbon supply graphite block 6 is a ring-shaped carbon supply graphite block, which is closely attached to the inner wall of the crucible body, or the outer diameter of the ring-shaped carbon supply graphite block is slightly smaller than the inner diameter of the crucible body.

[0037] In some preferred embodiments, the apparatus further includes a graphite block connecting member 7. A slot 5 is formed in the crucible wall of the crucible body 1-1 from the top downward, one end of the graphite block connecting member 7 is provided with a ring 8 that is engaged with the slot 5, and the other end of the graphite block connecting member 7 is connected to a carbon supply graphite block that has a density lower than that of the liquid growth raw material, and the carbon supply graphite block floats on the surface of the liquid growth raw material.

[0038] In some preferred embodiments, the present invention provides an apparatus for growing silicon carbide single crystals by a solution method, as shown in FIG. 2 , which includes a growth crucible 1, a seed crystal rod 2 to which a seed crystal 3 is fixed, an induction heater (shown as an induction coil in the drawing), a graphite block 6 (made of graphite) for supplying carbon, and a graphite block connecting member 7. In the present invention, the growth crucible 1 is a graphite crucible, and the induction heater is used to heat the growth crucible, melt the growth source material 9 into a liquid, and maintain the growth temperature of the silicon carbide single crystal in the growth system. The present invention does not require any special requirements for the induction heater, and a conventional design in the art may be used. The induction heater includes an induction coil 4 (also referred to as a heating coil) installed coaxially with the seed crystal rod 2, and the induction heater heats the growth crucible by electromagnetic induction. The growth crucible comprises a crucible body 1-1 and a crucible lid 1-2, and in the present invention, the crucible body and the crucible lid are joined, for example, by a screw joint, the thickness of the wall of the crucible body is greater than the thickness of the wall of the crucible lid, the outer wall of the crucible body is on the same plane as the outer wall of the crucible lid, and the inner wall of the crucible body exceeds the inner wall of the crucible lid. The crucible body 1-1 contains the growth raw material 9 and is, for example, cylindrical. The crucible lid 1-2 has an opening. One end of the seed crystal rod 2 to which the seed crystal 3 is fixed enters the inside of the crucible body 1-1 through the opening. The crucible wall of the crucible body 1-1 has a slot 5 extending downward from the top. One end (upper end) of the graphite block connecting member 7 has a ring 8 engaged with the slot 5. The other end (lower end) of the graphite block connecting member 7 is connected to a carbon supply graphite block 6 having a density lower than that of the liquid growth raw material 9. The carbon supply graphite block 6 floats on the surface of the liquid growth raw material 9.That is, in the process of growing silicon carbide single crystals by the solution method using the above-mentioned apparatus, the carbon supply graphite block floats on the surface of the liquid growth raw material and is used to further replenish the carbon source necessary for growing the silicon carbide single crystal. In the process of growing silicon carbide single crystals by the solution method, the crucible body serves as the main carbon source, and the carbon supply graphite block floats on the surface of the liquid growth raw material, thereby supplying carbon to the growth of the silicon carbide single crystal and allowing the silicon carbide single crystal to grow. The carbon supply graphite block serves as a secondary carbon source as follows: the carbon supply graphite block floats on the surface of the liquid growth raw material, and the portion of the carbon supply graphite block that comes into contact with the liquid growth raw material dissolves to supply carbon, and the portion of the carbon supply graphite block that does not come into contact with the liquid growth raw material continues to float to the surface of the liquid growth raw material and dissolves to supply carbon. In the present invention, the density of the carbon supply graphite block is lower than the density of the liquid growth source material, and the arrangement of the graphite block connecting member, ring, and slot ensures that unmelted carbon supply graphite block floats on the surface of the liquid growth source material, thereby ensuring that the carbon supply graphite block continues to melt. In the present invention, the slot allows the graphite block connecting member to move up and down in contact with the inner surface of the crucible wall via the ring, so that the carbon supply graphite block moves up and down in contact with the inner surface of the crucible wall. In the present invention, the carbon supply graphite block, graphite block connecting member, and ring may be integrally connected, for example, by being integrally molded.

[0039] The silicon carbide single crystal growth apparatus according to the present invention comprises a carbon supply graphite block and a graphite block connecting member. The carbon supply graphite block is movable up and down in contact with the crucible wall via the graphite block connecting member by installing a slot in the crucible wall, providing excellent installation stability. In addition, the carbon supply graphite block is made of graphite, and therefore has a lower density than the growth raw material. During the growth process, the carbon supply graphite block always floats on the surface of the growth raw material solution, forming a growth interface, providing a sufficient and stable carbon source for the growth of the silicon carbide single crystal. At the growth interface, as the growth process progresses, the carbon supply graphite block becomes thinner only at the position in contact with the liquid surface of the growth raw material solution, with no changes in other installations. This maintains a constant carbon supply distance during the silicon carbide single crystal growth process, making the growth of the silicon carbide single crystal more stable, improving the growth quality of the silicon carbide single crystal, and suppressing the crucible burn-through phenomenon. In the present invention, the graphite block for supplying carbon can be stably floated on the surface of the liquid growth raw material on the inner wall of the crucible for a long period of time due to the graphite block connecting member and slot. Compared to carbon supply devices that increase the thickness of the graphite crucible wall, directly add carbon powder, or inject graphite material into the growth raw material solution, the carbon supply method of the device of the present invention is installed stably and does not affect the convection within the growth system, which in turn does not affect the crystal quality. The carbon supply device of the present invention not only serves to supply a sufficient carbon source, but also shortens and maintains the carbon supply distance constant, which does not affect the convection within the growth system, resulting in more stable crystal growth and a very stable carbon supply device. The device of the present invention, when used in the solution growth of silicon carbide single crystals, firstly shortens the carbon supply position and maintains a constant carbon supply distance; secondly, it supplies a sufficient and stable carbon source for the growth of silicon carbide single crystals over a long period of time, greatly reducing the occurrence of encrustations and effectively improving the quality of single crystal growth; and also effectively inhibiting crucible wall melt-through, particularly melt-through of the crucible wall at the surface of the growth raw material solution, preventing the leakage of growth solution from affecting the temperature field and ultimately damaging the single crystal furnace, thereby improving the reproducibility and stability of single crystal growth experiments.

[0040] In some preferred embodiments, the graphite block connecting member 7 is disposed in contact with the crucible wall of the crucible body 1-1, and / or the ring 8 is movable up and down within the slot 5.

[0041] In some preferred embodiments, the graphite block connecting member 7 and the ring 8 are both made of graphite material.

[0042] In some preferred embodiments, the end of the seed crystal rod 2 to which the seed crystal 3 is not attached is connected to an actuator, and the actuator controls the elevation and rotation of the seed crystal rod, i.e., controls the elevation and rotation of the seed crystal. In the present invention, the actuator controlling the elevation and rotation of the seed crystal rod is not particularly limited and may be of a design commonly used in the technical field. In the present invention, the apparatus for growing silicon carbide single crystals by the solution method may include, for example, a rotation device for rotating the growth crucible. In the present invention, the configuration of the rotation device is not particularly limited and may be a configuration commonly used in the technical field.

[0043] In some preferred embodiments, the growth source 9 includes silicon and one or more metal sources of Al, Ti, Cr, Fe, Y, Yb, Pr, La, Cu, Ce, Sn, Ge, and Co.

[0044] In the present invention, there is no need to specifically limit parameters such as the thickness of the crucible wall of the crucible body, the thickness of the bottom of the crucible body, the depth of the slot, the width of the slot, and the size of the graphite block for supplying carbon, and these may be designed by a person skilled in the art as needed. When designing an apparatus for growing silicon carbide single crystals using this solution method, first determine the size of the graphite crucible body to match the size of the silicon carbide single crystal to be grown, then determine the size of the crucible lid and the size of the intermediate opening from the size of the crucible body to ensure that the seed crystal can fit inside the crucible, both the crucible body and the crucible lid are made of graphite, a slot is provided in the crucible wall from the top of the crucible body downward, and the graphite block connecting member and ring are designed so that the carbon graphite block can move up and down in contact with the crucible wall of the crucible body, for example, the thickness of the crucible body can be 10 to 30 mm, the distance from the start position of the slot at the top of the crucible wall of the crucible body to the inside of the crucible wall can be, for example, 2 to 5 mm, the depth of the slot can be a groove of, for example, 10 to 50 mm, and the thickness of the bottom of the crucible body can be, for example, 15 to 40 mm.

[0045] In some preferred embodiments, the crucible body 1-1 has a crucible wall thickness of 10 to 30 mm (e.g., 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, or 30 mm), and the crucible body 1-1 has a bottom thickness of 15 to 40 mm (e.g., 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, or 40 mm). At the top of the crucible wall of the crucible body 1-1, the starting position for providing the slot 5 is 2 to 5 mm (e.g., 2, 2.5, 3, 3.5, 4, 4.5 or 5 mm) away from the inside of the crucible wall, and the depth of the slot 5 is 10 to 50 mm (e.g., 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49 or 50 mm). Preferably, in the height direction of the crucible body, the bottom of the slot is higher than the liquid level of the contained liquid growth raw material, and in the present invention, the width of the slot provided is not particularly limited, and may be, for example, a width such that the slot does not penetrate the thickness of the crucible wall in the thickness direction of the crucible wall, and the starting position of the slot is 2 to 5 mm from the inside of the crucible wall, and preferably, for example, 2 to 10 mm.

[0046] In some preferred embodiments, the slot 5 is provided in a ring shape on the inner side of the crucible wall of the crucible body 1-1, the slot 5 is a ring-shaped slot, the graphite block connecting member 7 is a ring-shaped graphite block connecting member, the carbon supply graphite block 6 is a ring-shaped carbon supply graphite block, the thickness of the carbon supply graphite block 6 is 10 to 30 mm (for example, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, or 30 mm), and the width of the carbon supply graphite block 6 is 10 to 30 mm. (e.g., 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29 or 30 mm).

[0047] In some preferred embodiments, two symmetrical slots 5 are provided in the radial direction of the crucible wall of the crucible body 1-1, the number of the carbon supply graphite blocks 6 is two, the number of the graphite block connecting members 7 is two, the thickness of the carbon supply graphite blocks 6 is 10 to 30 mm (e.g., 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, or 30 mm), and the width of the carbon supply graphite blocks 6 is 10 to 30 mm. (e.g., 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, or 30 mm), and the sum of the lengths L of the two carbon-supplying graphite blocks 6 is smaller than the difference between the inner diameter of the crucible body 1-1 and the diameter of the seed crystal 3.

[0048] In some specific embodiments, as shown in Figures 1 to 5, the induction heating device is disposed outside the growth crucible and includes an induction coil 4 arranged coaxially with the seed crystal rod 2, and the growth crucible is disposed at the center of the induction coil 4. In the present invention, when growing silicon carbide single crystals by the solution method using the above-mentioned device for growing silicon carbide single crystals by the solution method, the entire device is placed in a single crystal furnace.

[0049] In a more specific embodiment, as shown in FIG. 2 , the apparatus includes a growth crucible (graphite crucible) 1, a seed crystal rod 2, the induction heating device, a graphite block connecting member 7, and a carbon-supplying graphite block 6. The growth crucible (graphite crucible) 1 contains a growth raw material 9 for growing a silicon carbide single crystal by a solution method and provides the main carbon source for growth. The growth crucible includes a crucible body 1-1 and a crucible lid 1-2. The crucible body 1-1 and the crucible lid 1-2 are screw-connected. The crucible body 1-1 contains the growth raw material 9. A slot 5 is formed in the crucible wall of the crucible body 1-1 from the top downward. The crucible lid 1-2 has an opening in its center for inserting a seed crystal 3. The seed crystal 3 is fixed to one end of the seed crystal rod 2, and an actuator is connected to the other end to control the elevation and rotation of the seed crystal 3. One end of the seed crystal rod 2, to which the seed crystal 3 is fixed, enters the crucible body 1-1 through an opening in the crucible lid 1-2. The induction heating device heats the growth crucible and is disposed outside the growth crucible. The induction heating device includes an induction coil 4 disposed coaxially with the seed crystal rod 2, and the growth crucible is disposed at the center of the induction coil 4. The graphite block connecting member 7 (made of graphite) has a ring 8 (made of graphite) attached to a slot 5 at one end and a carbon supply graphite block 6 with a density lower than that of the liquid growth raw material 9 connected to the other end. The carbon supply graphite block 6 floats on the surface of the liquid growth raw material 9 and is used to further replenish the carbon source required for growing the silicon carbide single crystal. The graphite block connecting member 7 is disposed in contact with the crucible wall of the crucible body 1-1, and the ring 8 is movable up and down within the slot 5. In the present invention, the slot 5 allows the graphite block connecting member 7 to move up and down in contact with the inside of the crucible wall via the ring 8, thereby allowing the carbon supply graphite block 6 to move up and down in contact with the inside of the crucible wall.

[0050] In the present invention, the graphite crucible first contains raw materials for growing silicon carbide single crystals by a solution method, and then serves as the main carbon source for crystal growth. A slot is formed in the crucible wall from top to bottom, and a ring of a graphite block connecting member is fitted into the slot, allowing it to move up and down in contact with the crucible wall. The carbon-supply graphite block is connected to the ring and the slot of the graphite crucible by the graphite block connecting member and floats inside the crucible body. The slot allows the graphite block connecting member to move up and down in contact with the inner surface of the crucible wall via the ring, allowing the carbon-supply graphite block to move up and down in contact with the inner surface of the crucible wall. Because the density of the carbon-supply graphite block is lower than that of the liquid growth raw material, the carbon-supply graphite block can always float on the surface of the liquid growth raw material, providing a sufficient carbon source for the growth of silicon carbide single crystals at the growth interface. The seed crystal is attached to the lower part of the seed crystal rod, and the seed crystal and the seed crystal are bonded together with, for example, an epoxy resin or a phenolic resin. The seed crystal enters the crucible body through an opening in the crucible lid and comes into contact with the liquid growth raw material. The upper part of the seed crystal rod is connected to an actuator, and the upper end of the seed crystal rod is connected to the actuator by, for example, a screw joint, allowing the seed crystal to be moved up and down and rotated. The growth raw material is a mixture containing silicon and at least one metal raw material, and supplies the silicon element necessary for growing a silicon carbide single crystal by a solution method and dissolves the graphite crucible and the carbon supply graphite block to supply the carbon element for crystal growth.

[0051] In the present invention, the solution growth apparatus for silicon carbide single crystals is used to grow silicon carbide single crystals by the solution method, which firstly shortens the carbon supply distance during solution growth of silicon carbide single crystals, and secondly, provides a sufficient and stable carbon source, significantly reducing the occurrence of encrustations and improving the quality of single crystal growth. It also effectively prevents burn-through of the graphite crucible wall, preventing solution leakage from affecting the temperature field and ultimately preventing damage to the single crystal furnace, improving the reproducibility and stability of single crystal growth experiments. In the present invention, a solution growth method for silicon carbide single crystals using the apparatus includes, for example, the following steps: (1) Select a growth material for growing silicon carbide single crystals, and ensure that the density of the growth material after melting and becoming liquid is greater than the density of the graphite block for carbon; (2) The growth raw material is placed in a growth crucible body, which is heated by the induction heating device to melt the growth raw material into a liquid. Specifically, after the growth raw material is placed in the crucible body, an apparatus for growing silicon carbide single crystals by the solution method is assembled, and the growth crucible is heated by the induction heating device to melt the growth raw material into a liquid. For example, a crucible body containing the growth raw material, a seed crystal rod to which a seed crystal is fixed, an induction heating device, a graphite block for supplying carbon, a graphite block connecting member, etc. are assembled as an apparatus for growing silicon carbide single crystals by the solution method, and the growth crucible is heated by the induction heating device to melt the growth raw material into a liquid. In the present invention, the assembly process of the apparatus for growing silicon carbide single crystals by the solution method is not specifically disclosed, and those skilled in the art can make actual adjustments based on the configuration of the apparatus in the present invention. In the present invention, the growth raw material is melted into a liquid in, for example, a vacuum environment, (3) A silicon carbide single crystal is grown by lowering a seed crystal fixed to a seed crystal rod until it contacts the surface of the liquid growth raw material. Specifically, in the present invention, after the temperature reaches the process temperature, the seed crystal fixed to a seed crystal rod is lowered until it contacts the surface of the liquid growth raw material. Because the temperature at the seed crystal is low, the Si and C elements in the solution are crystallized at the seed crystal, thereby growing a silicon carbide single crystal and producing a silicon carbide single crystal. During the crystal growth process, the seed crystal is rotated while being pulled up. During the crystal growth stage, the seed crystal is started to be pulled up and rotated according to a program setting, and the movement is continued to grow the crystal. The pulling speed may be, for example, 10 to 1500 μm / h, and the rotation speed may be, for example, 5 to 300 rpm. During the crystal growth process, the carbon supply graphite block floats on the surface of the liquid growth source material, thereby continuously supplying carbon to the growth of the silicon carbide single crystal. Specifically, the carbon supply graphite block floats on the surface of the liquid growth source material, and the portion where the carbon supply graphite block and the liquid growth source material come into contact melts to continuously supply carbon. The portion where the carbon supply graphite block and the liquid growth source material do not come into contact continues to float on the surface of the liquid growth source material and melts to continuously supply carbon. In the present invention, after growth is completed, the process is cooled to room temperature to obtain a silicon carbide ingot (silicon carbide single crystal). The present invention does not particularly limit the parameters in the crystal growth process, and silicon carbide crystal growth parameters commonly used in the technical field may be used.

[0052] In the present invention, a more specific method includes the steps of: a. determining the single crystal growth size, and based on the size, determining the sizes of the crucible body, crucible lid, intermediate opening, and carbon supply graphite block of the graphite crucible; b. selecting the composition type of the growth raw material, calculating the density of the selected growth raw material, and ensuring that the density of the liquid growth raw material obtained after melting is greater than the density of the carbon supply graphite block; c. after the size is determined, preparing the growth raw material as required and charging it into the crucible body of the graphite crucible; and d. placing the graphite crucible in a single crystal furnace, fixing a seed crystal to one end of a seed crystal rod, and connecting an actuator to the other end. During the heating stage, the single crystal furnace is evacuated and then filled with a special gas such as helium, nitrogen, or argon. The temperature is then increased using electric power. The induction heater heats the graphite crucible, completely dissolving the growth material into a solution. The carbon supply graphite block, which has a density lower than that of the liquid growth material, floats on the surface of the liquid growth material and dissolves to provide carbon. Supporting elements such as graphite block connecting members, rings, and slots ensure that the undissolved carbon supply graphite block remains suspended on the surface of the liquid growth material and continues to dissolve and provide carbon. During the crystal growth stage, the seed crystal is pulled and rotated according to a program, and crystal growth continues. During the cooling stage, the power input is reduced to lower the temperature, and the crystal is withdrawn from the liquid growth material and the rotation is stopped. After the temperature is reduced, the single crystal furnace body is opened, the graphite crucible is removed, the crucible lid is opened, and the grown crystal is removed, yielding a silicon carbide single crystal.

[0053] In some preferred embodiments, the solution growth apparatus for silicon carbide single crystals further includes a heat-insulating layer disposed between the growth crucible and the induction heating device, as shown in FIGS. 3 to 5 . That is, a heat-insulating layer 10 is disposed between the growth crucible and the induction heating device. Specifically, the heat-insulating layer 10 is disposed between the growth crucible 1 and the induction coil 4 of the induction heating device. The induction coil of the induction heating device is disposed outside the growth crucible and coaxial with the seed crystal rod. The heat-insulating layer is, for example, a layer of carbon felt, and is disposed outside the growth crucible and between the growth crucible and the heating coil. The growth crucible is disposed at the center of the induction coil of the induction heating device. In the present invention, the heat-insulating carbon felt may be either a hard carbon felt or a soft carbon felt. When the soft carbon felt is used, its thickness may be, for example, an integer value between 2 and 15 mm. In the present invention, the heat-insulating layer is formed by laying a layer of carbon hard felt or carbon soft felt, preferably carbon soft felt. The carbon soft felt is not particularly limited and may be a commercially available product. The present invention does not particularly limit the size of the central region of the induction coil, and those skilled in the art may design it as needed. For example, the diameter of the central region of the induction coil may be 350 to 500 mm.

[0054] In the present invention, the entire apparatus is placed in a single crystal furnace, and the heat-retaining layer is provided to stabilize the temperature field and improve the quality of the crystal.

[0055] In some preferred embodiments, the growth crucible 1 is made of graphite made of high-purity graphite with a purity of 99.95% or more. In the present invention, the graphite material refers to graphite with a purity of 99.95% or more unless otherwise specified, and has a density of 1.70 to 2.00 g / cm. 3 It is graphite.

[0056] In some preferred embodiments, the heat-insulating layer 10 includes an upper heat-insulating region 10-1 located above the growth crucible 1, a peripheral heat-insulating region 10-2 located around the growth crucible 1, and a lower heat-insulating region 10-3 located below the growth crucible 1, and the upper heat-insulating region has a through hole corresponding to the opening of the crucible lid, allowing a seed crystal rod to pass through the through hole. Specifically, the temperature holding layer 10 includes an upper heat-holding region 10-1 located above the growth crucible 1 and between it and the induction coil 4, a peripheral heat-holding region 10-2 located around the growth crucible 1 and between it and the induction coil 4, and a lower heat-holding region 10-3 located below the growth crucible 1 and between it and the induction coil 4. The outer diameter of the peripheral heat-holding region 10-2 can be, for example, an integer value of 130 to 480 mm depending on the temperature field requirements. The upper heat-holding region 10-1 has a through hole for passing the seed crystal rod 2 corresponding to the opening of the crucible lid 1-2. For example, a through hole for passing the end of the seed crystal rod 2 to which the seed crystal 3 is not fixed is provided. The diameter of the through hole can be, for example, an integer value of 20 to 150 mm.

[0057] Control of the temperature field is important in growing silicon carbide single crystals by the solution method. A stable temperature field is effective in stabilizing the environment during crystal growth and can improve experimental reproducibility. Furthermore, changing the temperature field can further enhance selectivity in silicon carbide single crystal growth and ensure growth quality and growth rate. Therefore, the silicon carbide single crystal growth apparatus of the present invention can maintain a short and constant carbon supply distance, supplying a sufficient and stable carbon source over a long period of time during the silicon carbide single crystal growth process and ensuring versatility of the apparatus. Having a variable and adjustable stable temperature field is extremely important, as it allows the growth rate of silicon carbide single crystals to be changed as needed to ensure the growth quality of silicon carbide single crystals. However, it has been difficult to achieve a stable temperature field with conventional silicon carbide single crystal growth apparatuses by the solution method.

[0058] In some preferred embodiments, the temperature field for growing silicon carbide single crystals by the solution method is controlled by changing the outer shape of the peripheral heat-retaining region 10-2. In the present invention, by changing the outer shape of the peripheral heat-retaining region in this way, it is possible to easily manufacture the device, ensure high production reproducibility, improve the yield of silicon carbide single crystals, and increase the variability of the device. It has been discovered that by changing the outer shape of the heat-retaining layer, it is possible to stably control changes in the temperature field, and by changing the outer shape of the peripheral heat-retaining region, it is possible to control the temperature field for growing silicon carbide single crystals by the solution method. It has been found that this is an entirely new control method that allows for diversified adjustment of the temperature field for growing silicon carbide single crystals and increases the possibility of growing silicon carbide single crystals.

[0059] In some preferred embodiments, the outer shape of the peripheral thermal region 10-2 is cylindrical, a regular truncated cone, or an inverted truncated cone. In some embodiments, the outer shape of the peripheral thermal region 10-2 is cylindrical, as shown in Figure 3, in some embodiments, the outer shape of the peripheral thermal region 10-2 is a regular truncated cone, as shown in Figure 4, and in some embodiments, the outer shape of the peripheral thermal region 10-2 is an inverted truncated cone, as shown in Figure 5.

[0060] In some preferred embodiments, when the peripheral heat-retaining region 10-2 has a regular truncated cone shape, the temperature gradient between the seed crystal and the liquid surface of the growth source material is increased, thereby increasing the growth rate of the silicon carbide single crystal and improving crystal productivity, as shown in FIG. 4. For example, when the device is not used, the range of crystal growth rates is small when the temperature is constant. However, when the device is used, the growth rate range can be expanded to 15 to 280 μm / h, further increasing the possibility of crystal growth. When the peripheral heat-retaining region 10-2 has an inverted truncated cone shape, the temperature gradient between the seed crystal and the liquid surface of the growth source material is reduced, as shown in FIG. 5. This reduces the growth rate of the silicon carbide single crystal, thereby increasing the amount of carbon source supplied and improving crystal quality.

[0061] In particular, the temperature field includes a temperature gradient, a temperature, a specific temperature distribution, etc., and the stabilization of the temperature field may be the stabilization of a large temperature gradient, and stabilization mainly refers to maintaining the state, and whether a large or small temperature gradient is maintained from start to finish is said to be a stable temperature field. In the present invention, the temperature gradient change is controllable and does not change during growth. In the present invention, after the outer shape of the peripheral heat-retaining region is determined, the temperature gradient change is determined before the growth of the silicon carbide single crystal, and then the entire growth process is kept in a balanced state.

[0062] In some preferred embodiments of the present invention, the size of the heat-insulating carbon felt is determined based on the sizes of the growth crucible and induction coil, with the outer diameter of the heat-insulating layer being slightly smaller than the size of the central region of the induction coil, for example, 20 to 60 mm smaller than the diameter of the central region of the induction coil. Furthermore, the number of layers of carbon felt is determined based on the height of the induction coil and the position of the growth crucible (when the growth crucible is located at the middle position in the height direction of the induction coil, the overall degree of induction heating is higher; when the growth crucible is located in the lower region of the induction coil, the high temperature line of the growth environment is moved up, resulting in a slower crystal growth rate; when the growth crucible is located in the upper region of the induction coil, the high temperature line of the growth environment is moved down, resulting in a faster crystal growth rate). After determining the relative positions of the growth crucible and the induction coil, for example, after determining that the growth crucible is located at the middle position of the induction coil, specifically, for example, determining that the growth crucible is located at the middle position in the radial and vertical directions of the induction coil, the number of layers of carbon felt laid in the lower heat-insulating area is determined, and the arrangement of the carbon felt in the peripheral part of the growth crucible is further adjusted according to the experimental needs. In the present invention, the carbon felt is laid in layers, and the peripheral heat-insulating area of ​​the growth crucible has a different outer shape, and the outer diameter of the carbon felt in the peripheral heat-insulating area is 20 to 60 mm smaller than the diameter of the central area of ​​the induction coil and the inner diameter is the same as the outer diameter of the growth crucible, and the outer diameters of the carbon felt in the peripheral heat-insulating area may be the same or different.Regions with larger outer diameters have better temperature retention capabilities, while regions with smaller outer diameters have better heat dissipation capabilities. The outer diameter of the carbon felt is determined according to experimental needs. When the outer diameters of the carbon felt portions are all the same on the top and bottom, i.e., the outer diameters of the peripheral heat-retaining regions are all the same on the top and bottom, the outer shape of the peripheral heat-retaining region is cylindrical. When the outer diameters of the carbon felt portions increase sequentially from top to bottom, i.e., the outer diameter of the peripheral heat-retaining region increases sequentially from top to bottom, and the outer shape of the peripheral heat-retaining region is a regular truncated cone. In this case, since the outer diameter of the peripheral heat-retaining region increases sequentially from top to bottom, the heat-retaining capability of the peripheral heat-retaining region increases sequentially from top to bottom, which increases the temperature gradient between the seed crystal and the liquid surface of the growth raw material, increases the growth rate of the silicon carbide single crystal, and improves the productivity of the single crystal. On the other hand, if the outer diameter of the carbon felt portion gradually decreases from top to bottom, i.e., the outer diameter of the peripheral heat-retaining region gradually decreases from top to bottom, i.e., the outer shape of the peripheral heat-retaining region is an inverted truncated cone. In this case, since the outer diameter of the peripheral heat-retaining region gradually decreases from top to bottom, the heat-retaining capacity of the peripheral heat-retaining region gradually decreases from top to bottom, reducing the temperature gradient between the seed crystal and the liquid surface of the growth material, thereby reducing the growth rate of the silicon carbide single crystal, resulting in a more sufficient supply of carbon source and improved crystal quality. The growth material is charged into the growth crucible, and a seed crystal rod with a fixed seed crystal is placed into the crucible body. An upper carbon felt (upper heat-retaining region) with an outer diameter 20 to 60 mm smaller than the center diameter of the induction coil and a through-hole in the center larger than the outer diameter of the seed crystal rod is placed in accordance with the predetermined temperature field. The seed crystal rod is connected to an actuator that moves the seed crystal up and down (raise and lower) and rotates it. When growing silicon carbide single crystals by the solution method using this preferred apparatus, after pretreatment such as vacuum, the induction coil power is switched on to begin heating. After a predetermined time, the growth material melts, and the seed crystal is lowered by an actuator connected to the seed crystal rod until it contacts the liquid surface of the growth material, initiating single crystal growth. After growth is complete, the temperature is lowered to room temperature, and the resulting grown single crystal, i.e., silicon carbide single crystal, is removed.By growing a single crystal using the solution method silicon carbide single crystal growth apparatus of the present invention shown in Figures 4 and 5, the temperature field change can be increased, and as shown in Figure 4, the temperature gradient can be increased to improve the crystal growth rate and productivity, or as shown in Figure 5, the temperature gradient can be decreased to slow the crystal growth rate, resulting in a more sufficient supply of carbon source and improving crystal quality.

[0063] The present invention will be further explained below with reference to examples, but the scope of the present invention is not limited to these examples.

[0064] Example 1 This embodiment provides an apparatus for growing silicon carbide single crystals by a solution method, the schematic diagram of which is shown in FIG. 3, in which: A growth crucible (graphite crucible) for containing raw materials for growing silicon carbide single crystals by a solution method and for supplying a main carbon source (principal carbon source) for growth, the growth crucible being cylindrical and comprising a crucible body and a crucible lid, the crucible body and the crucible lid being screw-joined, the crucible body containing the growth raw materials, the crucible wall of the crucible body having a slot extending downward from the top, in particular, two symmetrical slots in the radial direction of the crucible wall of the crucible body, and the crucible lid having an opening in a central position for the entry of a seed crystal.

[0065] A seed crystal rod has a seed crystal fixed to one end and an actuator connected to the other end to control the elevation and rotation of the seed crystal, and the end for fixing the seed crystal (silicon carbide seed crystal) enters the inside of the crucible body through the opening in the crucible lid.

[0066] an induction heating apparatus for heating a growth crucible, the induction heating apparatus being positioned coaxially with the seed rod and having an induction coil;

[0067] The graphite block connecting member and the carbon supply graphite block were provided with two carbon supply graphite blocks (made of graphite) and two graphite block connecting members. One end of the graphite block connecting member (made of graphite) was provided with a ring (made of graphite) engaged with the slot, and the other end of the graphite block connecting member was connected with a carbon supply graphite block having a density lower than that of the liquid growth raw material and floating on the surface of the liquid growth raw material to further increase the carbon source necessary for growing the silicon carbide single crystal. The graphite block connecting member was provided in contact with the crucible wall of the crucible body, and the ring was movable up and down in the slot. The slot allowed the graphite block connecting member to move up and down in contact with the inner surface of the crucible wall via the ring, thereby allowing the carbon supply graphite block to move up and down in contact with the inner surface of the crucible wall.

[0068] In this example, the graphite crucible had an inner diameter of 150 mm, an outer diameter of 185 mm, and a height of 100 mm, the silicon carbide seed crystal was 4H-SiC grown by the PVT method and had a diameter of 100 mm and a thickness of 0.5 mm, the starting position for providing the slot at the top of the crucible wall of the crucible body was 4 mm from the inside of the crucible wall, the depth of the slot was 35 mm, the thickness of the carbon supply graphite block was 20 mm, the width of the carbon supply graphite block was 20 mm, the length of the carbon supply graphite block was 15 mm, and the sum of the lengths of the two carbon supply graphite blocks was 30 mm.

[0069] The solution growth apparatus for silicon carbide single crystals in this example included a heat-insulating layer between the growth crucible and the induction coil. The heat-insulating layer was made of carbon felt and laid in a layer on the outside of the growth crucible. It was located between the growth crucible and the induction coil. The growth crucible was installed at a central position inside the induction coil of the induction heating device, and the induction coil was installed coaxially with the seed crystal rod. The heat-insulating layer included an upper heat-insulating region located above the growth crucible and between the induction coil, a peripheral heat-insulating region located between the periphery of the growth crucible and the induction coil, and a lower heat-insulating region located below the growth crucible and between the induction coil. The upper heat-insulating region corresponded to the opening of the crucible lid and had a through-hole for passing the seed crystal rod through. The outer diameter of the upper heat-insulating region was 40 mm smaller than the diameter of the central region of the induction coil, and the outer diameter of the lower temperature region was 40 mm smaller than the diameter of the central region of the induction coil. The growth crucible was located at the midpoint of the induction coil in the radial and vertical directions, the peripheral heat-retaining region was cylindrical, the outer diameter of the peripheral heat-retaining region was the same at the top and bottom, the outer diameter of the peripheral heat-retaining region was 40 mm smaller than the diameter of the central region of the induction coil, the inner diameter was the same as the outer diameter of the growth crucible, and the diameter of the central region of the induction coil was 420 mm.

[0070] The growth of silicon carbide single crystals by the solution method using the apparatus for growing silicon carbide single crystals by the solution method in this example included the following steps: (1) A growth raw material for growing silicon carbide single crystals was selected, and the density of the growth raw material after melting into a liquid was ensured to be greater than the density of the graphite block for carbon. The growth raw material used in this example was a mixture of Si, Cr, and Al, and the contents of these three components in the growth raw material were, by mass%, Si: 50%, Cr: 40%, and Al: 10%.

[0071] (2) The graphite crucible contains the uniformly mixed growth materials, and the mixture is pumped to a temperature of 2 × 10 -4After evacuating the chamber to below 1 Pa, Ar gas at 0.8 atm was introduced as the atmospheric gas, and the graphite crucible was heated with an induction heater to completely dissolve the growth raw material into a liquid state.

[0072] (3) After the temperature reaches the process temperature of 1800°C, the seed crystal fixed to the seed crystal rod is lowered until it contacts the liquid surface of the liquid growth material. Because the temperature at the position of the seed crystal is low, the Si and C elements in the solution are crystallized at the position of the seed crystal to grow the silicon carbide single crystal. During the crystal growth process, the seed crystal is rotated while being pulled up. The silicon carbide seed crystal is slowly pulled up at a speed of 0.02 mm / h. While rotating the silicon carbide seed crystal at a speed of 40 rpm, the graphite crucible is rotated at 20 The crucible was rotated in the opposite direction at a speed of 1000 rpm, and during the crystal growth process, the graphite crucible served as the main carbon source for growing the silicon carbide single crystal, and the carbon supply graphite block was floated on the surface of the liquid growth raw material and continuously provided as a secondary carbon source for growing the silicon carbide single crystal. After the crystal growth process was continued for 60 hours, the silicon carbide seed crystal was pulled up at a speed of 3 mm / h, the grown silicon carbide single crystal was separated from the surface of the liquid growth raw material, the rotation was stopped, and the temperature was gradually lowered to room temperature, completing the entire silicon carbide crystal growth process by the solution method and obtaining a silicon carbide single crystal.

[0073] When silicon carbide single crystals were grown for 60 hours by the solution method using the apparatus of this example, there was no melting down into the graphite crucible, and there was also no melting down of the liquid surface of the growth raw material onto the crucible wall.

[0074] Silicon carbide single crystals were grown by the solution method using the apparatus of this example, and the silicon carbide single crystals were grown at a single crystal growth rate of 100 μm / h. The growth rate was moderate, and the silicon carbide single crystals had smooth, flat surfaces and were of good quality. The appearance of the silicon carbide single crystals obtained in this example is shown in FIG. 6.

[0075] Example 2 Example 2 was substantially the same as Example 1, with the following differences: The solution growth apparatus for silicon carbide single crystals used in this example differs from the solution growth apparatus for silicon carbide single crystals used in Example 1 in the outer shape of the heat-retaining layer, and a schematic diagram of the solution growth apparatus for silicon carbide single crystals in this example is shown in Figure 4. Specifically, the outer shape of the peripheral heat-retaining zone is different. In this example, the peripheral heat-retaining zone is a regular truncated cone, and the inner diameter of the peripheral heat-retaining zone is the same as the outer diameter of the growth crucible. The outer diameter of the peripheral heat-retaining zone increases from top to bottom, allowing the heat-retaining capacity of the peripheral heat-retaining zone to increase from top to bottom, thereby increasing the temperature gradient between the seed crystal and the liquid surface of the growth source material, increasing the growth rate of the silicon carbide single crystal, and thereby improving crystal productivity. In this example, the upper outer diameter of the peripheral heat-retaining zone was 40 mm larger than the outer diameter of the growth crucible, and the lower outer diameter of the peripheral heat-retaining zone was 40 mm smaller than the diameter of the central region of the induction coil, which was 420 mm.

[0076] When silicon carbide single crystals were grown for 60 hours by the solution method using the apparatus of this example, there was no melting down into the graphite crucible, and there was also no melting down of the liquid surface of the growth raw material onto the crucible wall.

[0077] Silicon carbide single crystals were grown by the solution method using the apparatus of this example, growing them at a single crystal growth rate of 140 μm / h. The silicon carbide single crystal growth rate was fast, improving crystal productivity, and the overall crystal quality was adequate. However, compared to when the apparatus of Example 1 was used, the crystal surface was less smooth, and relatively more trenches and step bunching occurred, which affected the crystal quality to a certain extent. An external view of the silicon carbide single crystals obtained in this example is shown in FIG. 7.

[0078] Example 3 Example 3 was substantially the same as Example 1, with the following differences: The apparatus for growing silicon carbide single crystals by the solution method used in this example differs from the apparatus for growing silicon carbide single crystals by the solution method in Example 1 in the shape of the heat-retaining layer, and a schematic diagram of the apparatus for growing silicon carbide single crystals by the solution method in this example is shown in Figure 5. Specifically, the outer shape of the peripheral heat-insulating zone is different. In this embodiment, the peripheral heat-insulating zone is in the shape of an inverted truncated cone. The inner diameter of the peripheral heat-insulating zone is the same as the outer diameter of the growth crucible, but the outer diameter of the peripheral heat-insulating zone gradually decreases from top to bottom, allowing the heat-insulating capacity of the peripheral heat-insulating zone to gradually decrease from top to bottom. This reduces the temperature gradient between the seed crystal and the liquid surface of the growth raw material and reduces the growth rate of the silicon carbide single crystal, thereby ensuring a more sufficient supply of carbon source and improving crystal quality. In this embodiment, the upper outer diameter of the peripheral heat-insulating zone is 40 mm smaller than the diameter of the central region of the induction coil, and the lower outer diameter of the peripheral heat-insulating zone is 40 mm larger than the outer diameter of the growth crucible, and the diameter of the central region of the induction coil is 420 mm.

[0079] When silicon carbide single crystals were grown for 60 hours by the solution method using the apparatus of this example, there was no melting down into the graphite crucible, and there was also no melting down of the liquid surface of the growth raw material onto the crucible wall.

[0080] Silicon carbide single crystals were grown by the solution method using the apparatus of this example, and the silicon carbide single crystals were grown at a single crystal growth rate of 60 μm / h. Although the growth rate was slow, the surface of the resulting silicon carbide single crystals was very smooth and even, of very good quality, and no macroscopic defects were observed. However, the quality of the silicon carbide single crystals obtained in this example was improved compared to when the apparatus of Example 1 was used, and an external view of the silicon carbide single crystals obtained in this example is shown in FIG. 8.

[0081] In the present invention, the apparatus of Examples 1 to 3 was assembled without charging any growth material, heated, and the temperature gradient was measured. In the measurement method, the temperature measurement point was located on the backside of the seed crystal. The seed crystal was moved to a position 1 cm from the bottom of the crucible body by an actuator. The stable temperature at this position was measured using a temperature measuring device. The temperature at this position was controlled to 1800°C. The seed crystal was then moved to measure temperatures at distances of 2 cm, 3 cm, 4 cm, 5 cm, and 6 cm, respectively. A temperature gradient curve for each example was obtained by graphical calculation, and the results are shown in Figure 9. As shown in Figure 9, the temperature gradient in the temperature field of Example 1 was approximately 20°C / cm, the temperature gradient in the temperature field of Example 2 was approximately 28°C / cm, and the temperature gradient in the temperature field of Example 3 was approximately 14°C / cm. Increasing the temperature gradient increased the crystal growth rate and relatively deteriorated the crystal quality. Decreasing the temperature gradient slowed the crystal growth rate but significantly improved the crystal quality.

[0082] Comparative Example 1 The apparatus for growing silicon carbide single crystals by the solution method used in this comparative example did not include a graphite block for carbon, a graphite block connecting member, or a ring, and the crucible wall of the growth crucible was not provided with a slot. That is, the apparatus in this comparative example was equipped with the following parts: A growth crucible (graphite crucible) for containing growth raw materials used in growing silicon carbide single crystals by the solution method and for supplying a carbon source for growth, the growth crucible comprising a crucible body for containing the growth raw materials and a crucible lid having an opening in the center for receiving a seed crystal, the crucible body and the crucible lid being screw-connected.

[0083] A seed crystal rod has a seed crystal fixed to one end and an actuator connected to the other end to control the elevation and rotation of the seed crystal, and the end to which the seed crystal (silicon carbide seed crystal) is fixed enters the inside of the crucible body through the opening in the crucible lid.

[0084] an induction heating apparatus for heating a growth crucible, the induction heating apparatus being positioned coaxially with the seed rod and having an induction coil;

[0085] A heat-insulating layer was installed between the growth crucible and the induction coil. The heat-insulating layer was a carbon hard felt whose size was determined according to the growth crucible. The carbon hard felt was processed to fit the size so that it was wrapped around the outside of the growth crucible to form a heat-insulating layer. In this comparative example, the heat-insulating layer was integrally formed from carbon hard felt. The growth crucible and the heat-insulating layer were both placed in a furnace, the growth crucible was located at the center of the induction coil (the center position in both the radial and vertical directions of the induction coil), and the outer diameter of the heat-insulating layer was slightly smaller than the size of the central region of the induction coil, and the outer diameter of the heat-insulating layer was 40 mm smaller than the diameter of the central region of the induction coil. The graphite crucible used in this comparative example had an inner diameter of 150 mm, an outer diameter of 185 mm, and a height of 100 mm. The silicon carbide seed crystal was 4H—SiC grown by the PVT method, and had a diameter of 100 mm and a thickness of 0.5 mm.

[0086] To grow silicon carbide single crystals by solution growth using the apparatus for growing silicon carbide single crystals by solution growth of this comparative example, the following steps were carried out: (1) A growth raw material for growing silicon carbide single crystals was selected. The growth raw material used in this comparative example was a mixture of Si, Cr, and Al. The contents of these three components in the growth raw material were, by mass%, Si: 50%, Cr: 40%, and Al: 10%.

[0087] (2) The graphite crucible contains the uniformly mixed growth materials, and the mixture is pumped to a temperature of 2 × 10 -4 After evacuating the chamber to below 1 Pa, Ar gas at 0.8 atm was introduced as the atmospheric gas, and the graphite crucible was heated with an induction heater to completely dissolve the growth raw material into a liquid state.

[0088] (3) After the temperature reached the process temperature of 1800°C, the seed crystal attached to the seed crystal rod was lowered until it contacted the surface of the liquid growth material. Because the temperature at the seed crystal was low, the Si and C elements in the solution were crystallized at the seed crystal position, causing the growth of a silicon carbide single crystal. This produced a silicon carbide single crystal. During the crystal growth process, the seed crystal was rotated while being pulled up. The silicon carbide seed crystal was slowly pulled up at a speed of 0.02 mm / h. While rotating the silicon carbide seed crystal at a speed of 40 rpm, the graphite crucible was rotated in the opposite direction at a speed of 20 rpm. The crystal growth process continued for 60 hours, after which the silicon carbide seed crystal was pulled up at a speed of 3 mm / h. The grown silicon carbide single crystal was separated from the surface of the liquid growth material and the rotation was stopped. The temperature was gradually lowered to room temperature, completing the silicon carbide crystal growth process by the solution method and obtaining a silicon carbide single crystal.

[0089] In Comparative Example 1, a conventional solution growth system for silicon carbide single crystals was selected. The size of the growth crucible was determined, and the insulation and temperature fields were set based on this. Adjustments were not possible after the size was determined; instead, the temperature field was determined based on the position of the heated object within the induction coil. This limited flexibility and limited the development capabilities of solution growth. Furthermore, because this system used a standard graphite crucible to grow silicon carbide single crystals, the combined effects of convection and diffusion facilitated the dissolution and transport of carbon in the carbon dissolution region of the crucible as growth progressed, leading to continued crystal growth. The carbon dissolution region includes a high-temperature region and a growth interface region favorable for diffusion. In the growth interface region, the single crystal growth surface was far from the carbon source after melting in the crucible, resulting in insufficient carbon supply and defects such as solution encapsulation. Furthermore, the crucible melted near the growth liquid surface, causing the liquid to leak, affecting the temperature field and potentially flowing into the single crystal furnace, potentially damaging the system.

[0090] When silicon carbide single crystal was grown for 60 hours using the apparatus of this comparative example, a significant burn-through phenomenon was observed in the growth interface region of the growth crucible (graphite crucible), as shown in FIG.

[0091] Using the apparatus of this comparative example, silicon carbide single crystals were grown by the solution method at a single crystal growth rate of 92 μm / h. Although the growth rate was moderate, diffusive mass transfer was insufficient, and many large grooves were observed on the surface due to carbon deficiency, resulting in poor quality. An external view of the silicon carbide single crystal obtained in this comparative example is shown in Figure 11.

[0092] In the description of the present invention, the positions or positional relationships indicated by terms such as "upper," "lower," "upper," "lower," "top," "bottom," and "inside" are based on the positions or positional relationships shown in FIGS. 1 to 5. However, this is for the purpose of facilitating and simplifying the description of the present invention, and does not disclose or suggest that the referred-to devices or elements necessarily have a specific position, a specific positional configuration, or an operation, and therefore should not be understood as limiting the present invention.

[0093] In the description of the present invention, unless otherwise clearly specified and defined, the term "connection" may refer to, for example, a fixed connection, a detachable connection, or an integral connection, or may be directly connected or indirectly connected via an intermediate medium. The specific meaning of the terms in the present invention may be obvious to those skilled in the art. Parts of the present invention not described in detail are techniques known to those skilled in the art.

[0094] Finally, the above-described embodiments are only intended to illustrate the technical solutions of the present invention, and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the above-described embodiments, those skilled in the art should understand that they may still make modifications to the technical solutions described in the above-described embodiments without departing from the spirit and scope of the technical solutions of the embodiments of the present invention, or make equivalent substitutions for some technical features thereof.

Claims

1. An apparatus for growing silicon carbide single crystals by a solution method, comprising a growth crucible, a seed crystal rod to which a seed crystal is fixed, an induction heater for heating, and a raw material block to which a growth raw material can be supplied, the growth crucible includes a crucible body that accommodates a growth raw material and a crucible lid having an opening, and one end of the seed crystal rod to which the seed crystal is fixed enters the inside of the crucible body through the opening; the density of the raw material block to which the growth raw material can be supplied is lower than the density of the liquid growth raw material, and the raw material block to which the growth raw material can be supplied floats on the surface of the liquid growth raw material; the raw material block capable of supplying the growth raw material is a graphite block for carbon supply, the apparatus further comprising a graphite block connecting member; an apparatus for growing silicon carbide single crystals by a solution method, characterized in that a slot is formed in the crucible wall of the crucible body from the top downward, one end of the graphite block connecting member is provided with a ring that is engaged with the slot, and the other end of the graphite block connecting member is connected to a carbon supply graphite block having a density lower than that of the liquid growth raw material, and the carbon supply graphite block floats on the surface of the liquid growth raw material.

2. The graphite block connecting member is disposed in contact with the crucible wall of the crucible body, and / or 2. The device of claim 1, wherein said ring is movable up and down within said slot.

3. 2. The device according to claim 1, wherein the graphite block connecting member and the ring are both made of graphite material.

4. 2. The apparatus according to claim 1, wherein the end of the seed crystal rod to which the seed crystal is not fixed is connected to an actuator for controlling the elevation and rotation of the seed crystal rod.

5. 2. The apparatus of claim 1, wherein the growth source material comprises silicon and one or more metal sources selected from the group consisting of Al, Ti, Cr, Fe, Y, Yb, Pr, La, Cu, Ce, Sn, Ge, and Co.

6. The crucible body has a crucible wall thickness of 10 to 30 mm and a bottom thickness of 15 to 40 mm, At the top of the crucible wall of the crucible body, the start position of providing the slot is 2 to 5 mm from the inner side of the crucible wall; 2. The device of claim 1, wherein the depth of the slot is between 10 and 50 mm.

7. the slots are arranged in a ring shape within the crucible wall of the crucible body; 2. The apparatus of claim 1, wherein the slot is a ring-shaped slot, the graphite block connecting member is a ring-shaped graphite block connecting member, and the carbon feeder graphite block is a ring-shaped carbon feeder graphite block.

8. 8. The apparatus according to claim 7, wherein the thickness of the carbon supply graphite block is 10 to 30 mm, and the width of the carbon supply graphite block is 10 to 30 mm.

9. two symmetrical slots are provided in the radial direction of the crucible wall of the crucible body; The number of the carbon supplying graphite blocks is two, 2. The apparatus according to claim 1, wherein the number of said graphite block connecting members is two.

10. 10. The apparatus of claim 9, wherein the thickness of the carbon supply graphite block is 10 to 30 mm, the width of the carbon supply graphite block is 10 to 30 mm, and the sum of the lengths of the two carbon supply graphite blocks is smaller than the difference between the inner diameter of the crucible body and the diameter of the seed crystal.

11. 2. The apparatus of claim 1, wherein a heat insulating layer is provided between the growth crucible and the induction heating device.

12. the heat-retaining layer includes an upper heat-retaining region located above the growth crucible, a peripheral heat-retaining region located around the growth crucible, and a lower heat-retaining region located below the growth crucible; The apparatus according to claim 11, wherein the upper heat-retaining region is provided with a through-hole corresponding to the opening of the crucible lid for passing a seed crystal rod therethrough.

13. 13. The apparatus according to claim 12, wherein the temperature field during the growth of silicon carbide single crystals by the solution method is controlled by changing the shape of the peripheral heat-retaining region.

14. The device according to claim 12, wherein the outer shape of the peripheral heat-retaining region is a cylinder, a regular truncated cone, or an inverted truncated cone.

15. 15. The apparatus according to claim 14, wherein when the outer shape of the peripheral heat-retaining region is a regular truncated cone, the temperature gradient between the seed crystal and the liquid surface of the growth raw material is increased, and the growth rate of the silicon carbide single crystal is further increased, thereby improving crystal productivity.

16. 15. The apparatus according to claim 14, wherein when the outer shape of the peripheral heat-retaining area is an inverted truncated cone shape, the temperature gradient between the seed crystal and the liquid surface of the growth raw material is reduced, and the growth rate of the silicon carbide single crystal is further reduced, thereby improving the crystal quality.

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