Charging device for growing silicon carbide single crystals by PVT method and application of charging device

Abstract

The invention discloses a charging device for growing silicon carbide single crystals through a PVT method and application of the charging device, and belongs to the technical field of silicon carbide single crystal growth equipment. The invention provides a charging device placed in a crucible body during growth of silicon carbide single crystals by a PVT method, the charging device is used for containing silicon carbide powder, the charging device comprises a barrel and a top cover detachably arranged on the barrel, the barrel comprises a side wall and a barrel bottom, and the top cover is detachably arranged on the barrel. The side wall of the cylinder body is made of a porous material which can allow gas-phase components decomposed by the silicon carbide powder to pass through but block carbon particles, and the top cover is made of a compact material which blocks the gas-phase components decomposed by the silicon carbide powder to pass through. The invention also provides a method for growing the single crystal by using the device, the loading device is used for growing the silicon carbide single crystal, the transmission path of the material atmosphere can be changed, a recrystallization area is prevented from blocking atmosphere transmission, the problem of mutation of the crystal growth rate is solved, the generation of a carbon inclusion is reduced, and the production efficiency is improved. And the quality of the prepared silicon carbide crystal is effectively improved.

Description

Technical Field

[0001] The invention belongs to the technical field of silicon carbide single crystal growth equipment, and in particular relates to a charging device for growing silicon carbide single crystals using a PVT method and an application thereof. Background Art

[0002] Silicon carbide (SiC), as a typical representative of the third-generation wide bandgap semiconductor materials, has excellent physical and chemical properties such as large bandgap width, high critical breakdown field strength, high carrier saturation mobility rate, high thermal conductivity, and good chemical stability. It is one of the ideal materials for preparing high-temperature, high-frequency, high-power, and high-voltage devices, and is widely used in new energy vehicles, photovoltaic power generation, rail transit, smart grid, 5G communications, aerospace, and other fields.

[0003] At present, the growth of silicon carbide single crystals mainly adopts physical vapor transport (PVT). The graphite crucible is heated to a high temperature of more than 2000°C by induction coil or resistance heating, and the pressure in the growth furnace is reduced to less than 10mbar by a mechanical pump. In this high temperature and low pressure environment, the silicon carbide powder loaded at the bottom of the crucible in the growth furnace sublimates into gas and is transferred from the high temperature silicon carbide powder area to the seed crystal area at the top of the crucible at a lower temperature along the concentration gradient to form crystals. Among them, the products of SiC powder sublimation and decomposition mainly include gas phase Si, Si2C, SiC2 and solid C. The specific reactions include:

[0004] 2SiC(s)=Si2C(g)+C(s)

[0005] 2SiC(s)=SiC2(g)+Si(g)

[0006] SiC(s)=Si(g)+C(s)

[0007] However, the existing PVT method for preparing silicon carbide single crystals still has some problems that need to be overcome, such as unstable crystal growth rate and easy formation of carbon inclusions. Summary of the invention

[0008] In view of the shortcomings of the prior art, the present invention provides a charging device for stabilizing the crystal growth rate and reducing inclusions in silicon carbide single crystals. The present application also provides a method for growing silicon carbide single crystals using the aforementioned charging device.

[0009] The technical solution of this application is:

[0010] A charging device for growing silicon carbide single crystals by a PVT method. When growing silicon carbide single crystals by a PVT method, the charging device is placed in a crucible body to hold silicon carbide powder; a silicon carbide seed crystal is fixed on the top of the crucible body;

[0011] The charging device includes a cylinder and a top cover detachably arranged on the cylinder, wherein the cylinder includes a side wall and a cylinder bottom; the side wall of the cylinder is made of a porous material that allows the gas phase components of the decomposed silicon carbide powder to pass through but blocks carbon particles; the top cover is composed of a dense material that blocks the gas phase components of the decomposed silicon carbide powder from passing through.

[0012] In some embodiments, in the crucible, the area between the side wall of the cylinder and the side wall of the crucible is not filled with silicon carbide powder or is filled with a small amount of silicon carbide powder.

[0013] In some embodiments, the charging device is placed in the central area of ​​the crucible body and is arranged coaxially or approximately coaxially with the silicon carbide seed crystal.

[0014] In some embodiments, the bottom of the cylinder is detachably connected to the side wall.

[0015] In some embodiments, a column is provided between the bottom of the cylinder and the top cover for supporting the top cover and transferring heat.

[0016] In some embodiments, the materials of the top cover, the bottom of the cylinder and the column are respectively one or more of graphite, tantalum carbide or tantalum, but are not limited to this material range. Optionally, the graphite is specifically isostatic graphite.

[0017] In some embodiments, the porous material is one or more of porous graphite, porous tantalum carbide or porous tantalum, with a pore size range of 0.1-50 μm, which can effectively penetrate the atmosphere of silicon carbide decomposition but can better block the transportation of carbon particles into the growth chamber.

[0018] In some embodiments, the cross-section of the charging device is the same as the cross-section of the crucible.

[0019] The cross section of the charging device is circular, the diameters of the top cover and the bottom of the cylinder are not greater than 80% of the cross section diameter of the crucible and not less than 20% of the cross section diameter of the crucible, and the height of the charging device is not greater than 80% of the height of the crucible.

[0020] A method for preparing a silicon carbide single crystal using the charging device comprises the following steps:

[0021] S1: Fix the silicon carbide seed crystal on the top of the crucible;

[0022] S2: Filling silicon carbide powder into a charging device;

[0023] S3: placing the charging device in the crucible so that the top cover is coaxial with the silicon carbide seed crystal, and placing the crucible in the growth furnace;

[0024] S4: According to the conditions required for the growth of silicon carbide single crystal, vacuum is evacuated, the crucible is heated, and an inert gas is introduced to make the crystal grow until the crystal growth is completed.

[0025] In some embodiments, the specific method of evacuating the growth furnace, heating the crucible and introducing the inert gas is: evacuating the furnace to a vacuum degree of 10 -5 Pa-10 2 Pa; heating the crucible to a temperature of 2000°C-2400°C; introducing an inert gas at the same time, adjusting the pressure in the furnace to 1-10mbar, and performing crystal growth; after the crystal growth is completed, adjusting the pressure in the growth chamber to 1000mbar, cooling to room temperature, and obtaining a SiC single crystal.

[0026] In some embodiments, the cap is parallel to a surface of the silicon carbide seed crystal.

[0027] Compared with the prior art, the beneficial effects of this application are:

[0028] (1) The charging device designed in the present invention can adjust the transmission path of the silicon carbide atmosphere, avoiding the recrystallization area blocking the transmission of the atmosphere for decomposing silicon carbide, thereby stabilizing the growth rate of silicon carbide;

[0029] (2) The charging device of the present invention has a carbon powder area in the middle and late stages of growth, which can well absorb the silicon atmosphere, reduce the silicon atmosphere from entering the growth chamber, reduce the corrosion of the crucible and graphite parts, and reduce the generation of carbon inclusions in the crystal, thereby growing a silicon carbide single crystal with almost no carbon inclusions and a thickness of 20 mm;

[0030] (3) The charging device of the present invention has a simple structure and design, low cost, and is easy to load and unload. There is no need to wait for the furnace to be loaded, and the furnace can be loaded in batches, thereby improving efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1A A cross-sectional view of the structure of a charging device designed for this application;

[0032] Figure 1B A cross-sectional view of the charging device designed for this application placed in the crucible;

[0033] Figure 2 A cross-sectional view of another charging device structure designed for this application;

[0034] Figure 3A Schematic diagram of the evolution and transmission path of silicon powder in the crucible during the growth of SiC single crystal in the comparative example (0-40h);

[0035] Figure 3BSchematic diagram of the evolution and transmission path of silicon powder in the crucible during the growth of SiC single crystal in the comparative example (50-80h);

[0036] Figure 4A Schematic diagram of carbon-silicon ratio distribution in the crucible during the growth of SiC single crystal in comparative example (0-40h);

[0037] Figure 4B Schematic diagram of carbon-silicon ratio distribution in the crucible during the growth of SiC single crystal in comparative example (50-80h);

[0038] Figure 5A Schematic diagram of the evolution and transmission path of silicon carbide powder during the growth of SiC single crystal in Example 1 (0-40h);

[0039] Figure 5B Schematic diagram of the evolution and transmission path of silicon carbide powder during the growth of SiC single crystal in Example 1 (50-80h);

[0040] Fig. 6A Schematic diagram of the carbon-silicon ratio distribution in the crucible during the growth of the SiC single crystal in Example 1 (0-40h);

[0041] Figure 6B Schematic diagram of the carbon-silicon ratio distribution in the crucible during the growth of the SiC single crystal in Example 1 (50-80h);

[0042] Figure 7 This is a graph showing the carbon inclusion detection results of a silicon carbide single crystal wafer prepared in a comparative example;

[0043] Figure 8 This is a graph showing the carbon inclusion detection results of a silicon carbide single crystal wafer produced after assembling the charging device;

[0044] Fig. 9 This is a comparison chart of the growth rates of the silicon carbide single crystals of Comparative Example 1 and Example 1.

[0045] Description of Reference Numerals

[0046] 1-top cover, 2-side wall, 3-bottom of cylinder, 4-column, 5-crucible body, 6-crucible cover, 7-silicon carbide seed crystal. DETAILED DESCRIPTION

[0047] In order to make the purpose, technical solutions and advantages of the present invention clearer and easier to understand, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0048] The applicant has found that due to the influence of the edge heating method, in the actual PVT process of growing silicon carbide crystals, the silicon carbide powder on the crucible wall and the bottom of the crucible will first undergo sublimation and decomposition reaction, and the powder at the upper position of the center of the powder will undergo recrystallization in most cases due to the relatively low temperature, forming a large-grained polycrystalline area. This area hinders the normal transmission of the atmosphere, so it can only be transmitted upward along the position close to the crucible, resulting in a sudden change in the growth rate. The sudden change in rate is often accompanied by the generation of polymorphism and the proliferation of dislocations. In addition, the excessive silicon atmosphere during the growth process will corrode the graphite crucible and graphite parts, and the corroded crucible and graphite parts will change their shape, thereby changing the temperature field, and the change in the temperature field will also affect the crystal growth, which is very likely to cause defects such as polymorphism and microtubes. Moreover, after the crucible and graphite parts are corroded, carbon particles will be generated, thereby generating inclusions in the crystal. Carbon inclusions are a structural defect that is difficult to eliminate. Once generated in a single crystal, they are often accompanied by the formation of microtube defects in the subsequent crystal growth process, affecting the crystal quality.

[0049] To solve the above problems, the applicant has designed a charging device for growing silicon carbide single crystals by PVT method, such as Figure 1A As shown, the charging device is used to hold silicon carbide powder in a crucible for preparing silicon carbide single crystals by PVT method. Its structure includes a cylinder and a top cover 1 detachably arranged on the cylinder, and the cylinder includes a side wall 2 and a cylinder bottom 3.

[0050] like Figure 1B As shown, when growing silicon carbide single crystals by the PVT method, the charging device is placed in the crucible body 5 to hold silicon carbide powder; the charging device is placed in the central area of ​​the crucible body 5, coaxially or approximately coaxially with the silicon carbide seed crystal 7 disposed above the crucible cover 6. The area between the side wall 2 of the cylinder and the side wall of the crucible body 5 does not hold silicon carbide powder.

[0051] In order to facilitate the containing of silicon carbide powder, the connection between the top cover 1 and the cylinder body can be configured as a detachable connection, such as a threaded connection or a snap connection.

[0052] To achieve the design purpose, the material of the side wall 2 is a porous material through which the atmosphere of silicon carbide decomposition can pass but carbon particles cannot pass. Optionally, the porous material can be one or more of porous graphite, porous tantalum carbide or porous tantalum, with a pore size of 0.1-50 μm. The top cover 1 is made of a relatively dense material through which the atmosphere of silicon carbide decomposition cannot pass.

[0053] The top cover 1 and the bottom 3 of the cylinder body can be made of materials with good thermal conductivity and corrosion resistance, such as isostatic graphite material, tantalum carbide material, and tantalum material, with a thermal conductivity of 1000-2000 W / (m·K).

[0054] Optionally, the cross section of the charging device is the same as the cross section of the inner cavity of the crucible.

[0055] Optional, such as Figure 2 As shown, the charging device may also be provided with a column 4, which may be connected to the bottom 3 of the cylinder at one end and to the top cover 1 at the other end, or may have a certain gap with the top cover 1. The column 4 may be made of a material with good thermal conductivity and corrosion resistance, such as isostatic graphite, tantalum carbide, and tantalum. The column 4 is provided to utilize its heat conduction effect to reduce the temperature difference between the upper and lower parts of the charging device and reduce the formation of crystals of silicon carbide powder near the top cover 1.

[0056] In the embodiment of the present application, the cross-section of the inner cavity of the crucible is circular. According to experiments, the top cover 1 and the lower wall 3 are circular in shape, and the diameters of the top cover 1 and the bottom 3 of the cylinder are not more than 80% of the diameter of the crucible, and not less than 20% of the diameter of the crucible, respectively. The diameters of the top cover 1 and the bottom 3 of the cylinder can be equal or unequal; the height of the charging device is not higher than 80% of the height of the crucible, and not less than 20% of the height of the crucible. Within this range, a better technical effect can be achieved. The present application can regulate the transmission of the gas phase components of the decomposed SiC powder by adjusting the size of the charging device.

[0057] The method for growing a silicon carbide single crystal using the above-mentioned charging device can be carried out by the following steps:

[0058] S1: Fixing the silicon carbide seed crystal at the upper part of the crucible;

[0059] S2: Filling silicon carbide powder into a charging device;

[0060] S3: Place the charging device at the center bottom of the crucible, concentric with the seed crystal, and place the crucible in the growth furnace.

[0061] S4: Evacuate the furnace to a vacuum degree of 10 -5 Pa-10 2 Pa, check whether the furnace is sealed; heat the single crystal growth furnace to make the temperature in the crucible reach 2000℃-2400℃, introduce inert gas to adjust the growth, the pressure is 1-10mbar, and crystal growth is carried out; after the crystal growth is completed, adjust the pressure in the growth chamber to 1000mbar, cool it to room temperature, and obtain SiC single crystals with uniform growth rate and less carbon inclusions.

[0062] The silicon carbide seed crystal may be 6H-SiC or 4H-SiC.

[0063] When the silicon carbide seed crystal is 6H-SiC, the silicon surface is the growth surface, and when the silicon carbide seed crystal is 4H-SiC, the carbon surface is the growth surface.

[0064] In the embodiment of the present application, the particle size of the silicon carbide powder used to grow the silicon carbide single crystal is 0.5-1 mm.

[0065] The present application has found through specific experiments that when the above-mentioned charging device is set in the crucible, in the early stage of silicon carbide single crystal growth, the gas phase components of the decomposed silicon carbide powder are uniformly transmitted from the side wall to the growth chamber for single crystal growth; as the growth proceeds, the side wall 2 does not have a large particle size area, and thus does not hinder the transmission of the powder decomposition atmosphere. In the early stage of growth, the growth rate is basically constant. In the late stage of growth, the powder near the top cover 1 and the bottom 3 of the cylinder has a large particle size area, but since it does not hinder the atmosphere transmission at the side wall 2, it does not affect the growth rate, and the recrystallization area is small, which improves the utilization rate of the powder. In the late stage of growth, a graphitized area appears near the side wall, and the graphite absorbs the silicon atmosphere of the decomposed powder, and the silicon atmosphere entering the growth chamber is correspondingly reduced. The silicon atmosphere in the growth chamber is reduced, the degree of corrosion of the crucible body and the guide is reduced, the carbon particles produced are reduced, and the carbon inclusions of the grown crystals are less.

[0066] The embodiment of the present application takes the example that the area inside the crucible, that is, between the side wall of the cylinder and the side wall of the crucible body, is not filled with silicon carbide powder. Of course, in other embodiments, a small amount of silicon carbide powder can also be contained.

[0067] The following further illustrates the technical solution of the present application and demonstrates its superiority through comparative examples and examples 1 to 5. The comparative examples and examples 1 to 5 use the same growth furnace and crucible.

[0068] Comparative Example

[0069] A method for preparing a SiC single crystal comprises the following steps:

[0070] S1: Fixing the silicon carbide seed crystal at the upper part of the crucible;

[0071] S2: Filling SiC powder at the bottom of the crucible;

[0072] S3: placing the crucible in a growth furnace;

[0073] S4: Evacuate the furnace to a vacuum degree of 10 -5 Pa-10 2 Pa; heat the single crystal growth furnace to make the temperature in the crucible reach 2000℃-2400℃, and at the same time introduce inert gas to adjust the growth, the pressure is 1-10mbar, and crystal growth is carried out; after the crystal growth is completed, adjust the pressure in the growth chamber to 1000mbar, cool it to room temperature, and obtain a SiC single crystal.

[0074] At different stages of preparing SiC single crystals, after stopping the furnace and stopping the growth, the particle size of silicon carbide powder at different positions in the crucible was sampled and tested. It was found that the powder near the edge of the crucible was completely carbonized into graphite powder, and the powder near the upper center area of ​​the powder was crystallized into large particles. The powder transformation process was simulated as follows Figure 3A and Figure 3B The schematic diagram of the evolution and transmission path of silicon carbide powder in the crucible is shown in the figure. The arrows in the figure indicate the atmosphere transmission path of silicon carbide decomposition. The powder is transmitted upward into the growth chamber. In the early stage of growth, the powder has a uniform diameter. As the growth progresses, the powder near the crucible area gradually carbonizes into graphite, and the powder particle size decreases; in addition, silicon carbide crystals are generated on the upper wall of the powder, and the powder particle size increases, blocking the atmosphere transmission and causing rate fluctuations.

[0075] At the same time, at different stages of preparing SiC single crystals, the carbon-silicon ratio distribution at different positions in the growth chamber was simulated, and the following results were obtained: Figure 4A and Figure 4B The carbon-silicon ratio distribution diagram in the crucible during the growth of SiC single crystals is shown in the figure. The carbon-silicon ratio in the growth chamber is about 0.28-0.62. Since the powder is carbonized into graphite near the crucible, but the silicon atmosphere is transmitted upward, the graphite cannot absorb the excess silicon atmosphere. The silicon atmosphere in the growth chamber increases, and the excess silicon atmosphere corrodes the graphite parts and crucible in the growth chamber.

[0076] Example 1

[0077] This embodiment uses a charging device to grow high-quality SiC single crystals. The charging device is shown in Figure 1, including a cylinder and a top cover 1 that is detachably arranged on the cylinder. The cylinder includes a side wall 2 and a cylinder bottom 3. The side wall 2 and the cylinder bottom 3 are spirally connected. The top cover 1 and the cylinder bottom 3 have a diameter of 150 mm and a thickness of 5 mm, and are made of isostatic graphite. The side wall 2 is made of porous tantalum, with a thickness of 7 mm and a height of 140 mm.

[0078] The method for growing high-quality SiC single crystal using the charging device comprises the following steps:

[0079] S1: Fixing the silicon carbide seed crystal at the upper part of the crucible;

[0080] S2: Filling SiC powder into a charging device;

[0081] S3: Place the charging device at the center bottom of the crucible, concentric with the seed crystal. Place the crucible in the growth furnace;

[0082] S4: Evacuate the furnace to a vacuum degree of 10 -5 Pa-10 2Pa; heat the single crystal growth furnace to make the temperature in the crucible reach 2000℃-2400℃, and at the same time introduce inert gas to adjust the growth, the pressure is 1-10mbar, and crystal growth is carried out; after the crystal growth is completed, adjust the pressure in the growth chamber to 1000mbar, cool it to room temperature, and obtain a SiC single crystal.

[0083] At different stages of preparing SiC single crystals, after stopping the furnace and stopping the growth, the particle size of silicon carbide powder at different positions in the crucible was sampled and tested. It was found that the powder near the side wall was completely carbonized into graphite powder, and the powder at the center of the crucible position on the upper part of the powder was recrystallized into large particles. The powder transformation process was simulated and the following results were obtained: Figure 5A and Figure 5B The schematic diagram of the evolution and transmission path of silicon carbide powder in the crucible is shown. The powder in the charging device is transmitted from the side wall 2 to the growth chamber. In the early stage of growth, the particle size of the powder is uniform. As the growth progresses, the powder near the side wall 2 is gradually carbonized into graphite, and the particle size of the powder decreases. In addition, in the upper part of the powder, silicon carbide crystals are recrystallized on the upper wall, and the particle size increases, but it does not block the transmission of the atmosphere from the side wall. In addition, the graphite near the side wall absorbs excess silicon atmosphere, reducing the corrosion of the silicon atmosphere on the graphite parts and crucible in the growth chamber.

[0084] At the same time, at different stages of preparing SiC single crystals, the carbon-silicon ratio distribution at different positions in the growth chamber was simulated, and the following results were obtained: Fig. 6A and Figure 6B The carbon-silicon ratio distribution diagram in the crucible shown in the figure shows that the closer to the seed crystal, the lower the temperature and the lower the carbon-silicon ratio. As the growth proceeds, the carbon-silicon ratio in the seed crystal area increases. The carbon-silicon ratio in the growth chamber of Example 1 is about 0.51-0.67. The silicon atmosphere ratio is reduced, which reduces the possibility of silicon atmosphere corroding the graphite parts and crucible in the growth chamber.

[0085] Example 2

[0086] A charging device, the main structure and material are the same as those in Example 1, except that the diameter of the top cover 1 is 170 mm, the diameter of the bottom 3 of the cylinder is 130 mm, and the overall shape of the charging device is a truncated cone. A method for growing high-quality SiC single crystals using the charging device, the steps and conditions are the same as those in Example 1.

[0087] Example 3

[0088] A charging device, the main structure and material are the same as those in Example 1, except that the diameter of the top cover 1 is 130 mm, the diameter of the bottom 3 of the cylinder is 170 mm, and the overall shape of the charging device is an inverted truncated cone. A method for growing high-quality SiC single crystals using the charging device, the steps and conditions are the same as those in Example 1.

[0089] Example 4

[0090] A charging device, the main structure and material are the same as those in Example 1, except that the top cover 1 and the bottom 3 of the cylinder have a diameter of 130 mm, and the overall shape of the charging device is cylindrical. A method for growing high-quality SiC single crystals using the charging device, the steps and conditions are the same as those in Example 1.

[0091] Example 5

[0092] A charging device, the main structure and material are the same as those of embodiment 1, except that a column 4 is added, the diameter of the column 4 is 15 mm, and the column material is isostatic graphite material, such as Figure 2 The method for growing high-quality SiC single crystal using the charging device has the same steps and conditions as those in Example 1.

[0093] The silicon carbide single crystals obtained in the comparative example and Example 1 were respectively prepared into wafers, and then the carbon inclusions inside the wafers were detected using instruments. The results are as follows: Figure 7 and Figure 8 As shown, the SiC single crystal grown by the charging device of the present invention has almost no carbon-free inclusions, while the wafer prepared by the single crystal grown in the ordinary crucible in the control example has more carbon inclusions detected.

[0094] The growth rate (g / h) of the silicon carbide single crystal preparation process of the comparative example and Example 1 was tested. At different growth stages of the preparation of SiC single crystal, the crystal was weighed after stopping the furnace. The crystal weight is shown in Table 1, and the crystal growth rate is shown in Table 2. A graph is drawn for comparison, as shown in Table 2. Fig. 9 As shown in Table 1, Table 2 and Fig. 9 It can be seen that the growth rate in Example 1 is significantly more stable than that in the comparative example. The growth rate of the silicon carbide single crystal in Example 1 is more uniform and grows linearly. However, the growth rate in the comparative example is faster at the beginning and the end, but significantly decreases in the middle stage, and the growth rate is obviously not uniform enough.

[0095] Table 1

[0096] Long time (h) Comparative Example Crystal Weight (g) Example 1 Crystal weight (g) 0 56.902 56.902 10 115.6 117.23 20 165.21 177.07 30 202.54 236.63 40 257.02 295.29 50 324.35 358.11 60 390.75 421.07 70 460.5 484.73 80 533.69 549.78

[0097] Table 2

[0098]

[0099] The velocity non-uniformity is defined as the standard deviation (stdev) of the velocity / the average velocity. The growth velocity non-uniformity and the number of carbon inclusions in the silicon carbide single crystals prepared in Examples 1-5 and the comparative example were tested and the results were tabulated and compared. The results are shown in Table 3:

[0100] Table 3

[0101] Example Speed ​​non-uniformity Number of carbon inclusions Comparative Example 1 20.22％ 318 Example 1 3.73％ 0 Example 2 3.72％ 2 Example 3 3.71％ 1 Example 4 3.74％ 2 Example 5 3.75％ 0

[0102] It can be seen from the data in Table 3 that, compared with the comparative example close to the existing PVT method, the method for preparing silicon carbide single crystal using the charging device provided in Examples 1-5 of the present application can significantly reduce or even eliminate carbon inclusions in the single crystal; at the same time, the growth rate in the examples is more uniform. Therefore, the charging device and preparation method provided in the present application can prepare silicon carbide single crystals with more uniform growth rate and fewer inclusions.

[0103] The above is only an embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various changes and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the scope of the claims of the present application.

Claims

1. A charging device for growing silicon carbide single crystals by PVT method, characterized in that: When growing silicon carbide single crystals by the PVT method, the charging device is placed in the crucible body and is used to hold silicon carbide powder; The charging device comprises a cylinder and a top cover detachably arranged on the cylinder, wherein the cylinder comprises a side wall and a cylinder bottom; The side wall of the cylinder is made of a porous material that allows the gas phase components of the decomposed silicon carbide powder to pass through but blocks carbon particles; The top cover is composed of a dense material that blocks the gas phase components decomposed from the silicon carbide powder from passing through.

2. The charging device for growing silicon carbide single crystal by PVT method according to claim 1, characterized in that: In the crucible body, the area between the side wall of the cylinder and the side wall of the crucible body does not contain silicon carbide powder or contains a small amount of silicon carbide powder.

3. The charging device for growing silicon carbide single crystal by PVT method according to claim 1, characterized in that: The charging device is placed in the crucible body and is arranged coaxially or approximately coaxially with the silicon carbide seed crystal.

4. The charging device for growing silicon carbide single crystal by PVT method according to claim 1, characterized in that: A column is arranged between the bottom of the cylinder and the top cover, one end of the column is connected to the top cover, and the other end is connected to the bottom of the cylinder.

5. The charging device for growing silicon carbide single crystal by PVT method according to claim 4, characterized in that: The materials of the top cover, the bottom of the cylinder and the pillars are one or more of graphite, tantalum carbide or tantalum.

6. The charging device for growing silicon carbide single crystal by PVT method according to claim 1, characterized in that: The porous material is one or more of porous graphite, porous tantalum carbide or porous tantalum.

7. The charging device for growing silicon carbide single crystal by PVT method according to claim 6, characterized in that: The porous graphite, porous tantalum carbide or porous tantalum has a pore size of 0.1-50 μm.

8. The charging device for growing silicon carbide single crystal by PVT method according to claim 1, characterized in that: The cross section of the charging device is circular, the diameters of the top cover and the bottom of the cylinder are not greater than 80% of the cross section diameter of the crucible and not less than 20% of the cross section diameter of the crucible, and the height of the charging device is not greater than 80% of the height of the crucible.

9. Use of the charging device according to any one of claims 1 to 8 in preparing silicon carbide single crystals, characterized in that: The steps include: S1: Fix the silicon carbide seed crystal on the top of the crucible; S2: Filling silicon carbide powder into a charging device; S3: placing the charging device in the crucible so that the top cover is coaxial or approximately coaxial with the silicon carbide seed crystal, and placing the crucible in the growth furnace; S4: According to the conditions required for the growth of silicon carbide single crystal, the growth furnace is evacuated, the crucible is heated, and an inert gas is introduced to allow the crystal to grow until the crystal growth is completed.

10. The use according to claim 9, characterized in that: The specific method of evacuating the growth furnace, heating the crucible and introducing the inert gas is as follows: evacuating the furnace to a vacuum degree of 10 -5 Pa-10 2 Pa; heat the crucible to make the temperature inside the crucible reach 2000℃-2400℃; at the same time, introduce inert gas and adjust the pressure in the furnace to 1-10mbar.

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