Apparatus and method for producing polycrystalline silicon carbide, polycrystalline silicon carbide and applications thereof

Abstract

The present application relates to an apparatus and a method for preparing polycrystalline silicon carbide, polycrystalline silicon carbide and its applications. The apparatus comprises: a crucible; a graphite substrate disposed in the crucible and located at the upper portion of the crucible; an air passage structure disposed in the crucible for air passage into the crucible; a baffle disposed in the crucible, having a spacing with the graphite substrate and projecting to cover the graphite substrate, the baffle having a spacing with the bottom wall of the crucible; and a heater disposed in the crucible and located below the baffle. The apparatus can be used to manufacture polycrystalline silicon carbide with low resistivity.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of semiconductor manufacturing, in particular to an apparatus and a method for preparing polycrystalline silicon carbide, polycrystalline silicon carbide and application thereof. BACKGROUND

[0002] Silicon carbide wafers can be used as precursors to manufacture silicon carbide devices. At present, more researches are focused on silicon carbide single crystal substrates, but the high difficulty and high cost of the preparation process restrict the process of breaking through the large size of silicon carbide single crystal substrates.

[0003] Researches on polycrystalline silicon carbide show that polycrystalline silicon carbide can replace single crystal silicon carbide to some extent in the field of power devices and new energy.

[0004] When preparing polycrystalline silicon carbide by heavy nitrogen-doped physical vapor transport method, the resistivity of polycrystalline silicon carbide is high. SUMMARY

[0005] Therefore, it is necessary to provide an apparatus and a method for preparing polycrystalline silicon carbide, polycrystalline silicon carbide and application thereof aiming at at least one of the above problems.

[0006] In a first aspect, the present application provides an apparatus for preparing polycrystalline silicon carbide, which comprises: a crucible; a graphite substrate arranged in the crucible and located at the upper part of the crucible; a gas passage structure arranged in the crucible for passing gas into the crucible; a baffle arranged in the crucible, which has a spacing with the graphite substrate and projects to cover the graphite substrate, and the baffle has a spacing with the bottom wall of the crucible; and a heater arranged in the crucible and located below the baffle.

[0007] The graphite substrate can be used to generate polycrystalline silicon carbide; the baffle can block part of the heat radiation of the bottom powder, avoid the direct radiation of the heat radiation in the central region to the silicon carbide grown below the graphite substrate, and further weaken the convection of the bottom gas flow and the upper gas flow and improve the gas flow state; the heater only directly heats the part of the crucible below the baffle, which can avoid the temperature of the upper part of the crucible and the graphite substrate being too high.

[0008] The apparatus for preparing polycrystalline silicon carbide of the present application can provide low-temperature growth conditions and can be used to manufacture polycrystalline silicon carbide with low resistivity.

[0009] In some embodiments, the apparatus for preparing polycrystalline silicon carbide is configured to have a temperature of the graphite substrate lower than 1900℃ when working. For example, the apparatus is configured to have a temperature of the graphite substrate 360-380℃ lower than the temperature of the part of the crucible being heated when working.

[0010] In this way, the graphite substrate has a lower temperature; the gas experiences a larger temperature difference, which is conducive to forming polycrystalline silicon carbide with lower resistivity.

[0011] In some embodiments, the distance between the graphite substrate and the baffle plate ranges from 70mm to 90mm. Exemplarily, the distance between the baffle plate and the heater along the height direction ranges from 0mm to 20mm.

[0012] In this way, the temperature of the graphite substrate is reduced, and the heater focuses on heating the powder.

[0013] In some embodiments, the ratio of the outer diameter of the baffle plate to the inner diameter of the crucible ranges from 60% to 80%.

[0014] In this way, the gas flow and the cooling effect are balanced, and the growth state is controlled.

[0015] In some embodiments, the device for preparing polycrystalline silicon carbide further comprises a heat preservation structure, which is arranged outside the crucible and above the baffle plate. Exemplarily, the gas passage structure is arranged at the position of the graphite substrate on the side wall of the crucible.

[0016] In this way, the gas can be introduced as needed, the basic temperature of the crucible can be maintained, the energy consumption of the heater is not too large, and in addition, the temperature difference of the crucible is not too large to affect the structural reliability.

[0017] In a second aspect, the application provides a method for preparing polycrystalline silicon carbide, which utilizes the device for preparing polycrystalline silicon carbide described above to heat the powder in the crucible and form polycrystalline silicon carbide on the graphite substrate through physical vapor transport.

[0018] The method of the embodiments of the application can form low-resistivity polycrystalline silicon carbide based on a lower-temperature graphite substrate in the physical vapor transport method by utilizing the device. The method for preparing polycrystalline silicon carbide of the embodiments of the application is simple to perform, low in cost, and good in product quality; it can break through the resistivity limit of 30mΩ·cm and help to prepare polycrystalline silicon carbide with a resistivity of less than 20mΩ·cm.

[0019] In some embodiments, the gas pressure in the crucible ranges from 2mbar to 15mbar. Exemplarily, the gas introduced into the crucible comprises 0 VOL% to 30 VOL% of argon and 70 VOL% to 100 VOL% of nitrogen. Exemplarily, the temperature of the graphite substrate is 360℃ to 380℃ lower than the temperature of the heated powder.

[0020] In this way, the preparation of polycrystalline silicon carbide through the physical vapor transport method in a dinitrogen environment can be achieved.

[0021] In some embodiments, the powder is heated to 2220℃, the temperature of the graphite substrate is configured to be 1840℃, and the gas pressure in the crucible is 2mbar.

[0022] Thus, the polycrystalline silicon carbide with an average resistivity lower than 9 mΩ·cm can be prepared.

[0023] In a third aspect, the present application provides a polycrystalline silicon carbide prepared by the device for preparing polycrystalline silicon carbide or the method for preparing polycrystalline silicon carbide.

[0024] The polycrystalline silicon carbide of the embodiments of the present application has a low resistivity and good performance, and is helpful to replace monocrystalline silicon carbide in some fields.

[0025] In a fourth aspect, the present application provides an application of the polycrystalline silicon carbide in the preparation of semiconductor devices.

[0026] The embodiments of the present application apply the polycrystalline silicon carbide in the preparation of semiconductor devices, reduce the cost, and realize good performance of the semiconductor devices. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 FIG. 1 is a structural schematic diagram of a device for preparing polycrystalline silicon carbide according to one or more embodiments;

[0028] Figure 2 FIG. 1 is a structural schematic diagram of a device for preparing polycrystalline silicon carbide according to one or more embodiments;

[0029] Figure 3 FIG. 1 is a structural schematic diagram of a device for preparing polycrystalline silicon carbide according to one or more embodiments;

[0030] Figure 4 FIG. 1 is a structural schematic diagram of a device for preparing polycrystalline silicon carbide according to one or more embodiments;

[0031] FIG. 1 is a structural schematic diagram of a device for preparing polycrystalline silicon carbide according to one or more embodiments;

[0032] 1000, a device for preparing polycrystalline silicon carbide. DETAILED DESCRIPTION

[0033] In order to make the above objectives, features and advantages of the present application more obvious and easy to understand, the specific embodiments of the present application will be described in detail below with reference to the drawings. In the following description, a large number of specific details are set forth in order to facilitate a full understanding of the present application. However, the present application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without departing from the spirit of the present application, so the present application is not limited to the specific embodiments of the following disclosed embodiments.

[0034] In the description of the present application, it needs to be understood that the orientation or positional relationship indicated by the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "back", "left", "right", "vertical", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present application and simplifying the description, and does not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation of the present application.

[0035] In the present application, unless otherwise explicitly specified and limited, the first feature is "on" or "under" the second feature, which can be direct contact between the first and second features, or indirect contact through an intermediate medium. Moreover, the first feature "above", "above" and "above" the second feature can be directly above or obliquely above the first feature, or only indicate that the horizontal height of the first feature is higher than that of the second feature. The first feature "below", "below" and "below" the second feature can be directly below or obliquely below the first feature, or only indicate that the horizontal height of the first feature is less than that of the second feature.

[0036] In addition, the terms "first", "second", "third" and the like are only for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first", "second" can explicitly or implicitly include at least one of the features. For example, the first airway can also be referred to as the second airway, and the second airway can also be referred to as the first airway. In the description of the present application, the meaning of "multiple" is at least two, such as two, three, etc., unless otherwise explicitly specified and limited.

[0037] In the present application, unless otherwise explicitly specified and limited, the terms "connected", "connected" and the like should be broadly understood, for example, it can be fixedly connected, or it can be detachably connected, or it can be integrated; it can be flexible connection, or it can be rigid connection in at least one direction; it can be mechanical connection, or it can be electrical connection; it can be directly connected, or it can be indirectly connected through an intermediate medium, or it can be directly connected while there is an intermediate medium, or it can be the internal communication of two elements or the interaction relationship between two elements, unless otherwise explicitly limited. The terms "installation", "setting", "fixing" and the like can be broadly understood as connection. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0038] The term "layer" or "region" as used herein refers to a portion of material that includes a certain area and has a certain thickness. The layer can extend horizontally, vertically, and / or along a tapered surface. The layer can be a region of a uniform or non-uniform continuous structure, which has a thickness perpendicular to the direction of extension that can be no greater than the thickness of the continuous structure. The layer can include multiple layers, which can be stacked or can extend discretely. The shapes of various regions, layers, and their relative sizes and positions in the drawings are merely exemplary and can deviate in practice due to manufacturing tolerances or technical limitations, and can be adjusted according to actual needs.

[0039] Reference Figure 1 , Figure 1 An apparatus for preparing polycrystalline silicon carbide in an embodiment of the present application is shown. For the convenience of description, a spatial rectangular coordinate system XYZ is established, Figure 1 The cross section shown can be parallel to the XZ plane, and the Z-axis direction can be parallel to the height direction. In an exemplary embodiment, the apparatus 1000 for preparing polycrystalline silicon carbide includes a crucible 1, a graphite substrate 2, a baffle 3, and a heater 4.

[0040] The crucible 1 is used to hold the powder. In the height direction, the crucible 1 includes oppositely arranged top and bottom walls 11 and 12, and further includes a side wall 13. The crucible 1 can be generally cylindrical. Exemplarily, the height of the crucible 1 is 310-330 mm, for example 330 mm. The inner diameter of the crucible 1 can be 177 mm. Exemplarily, the top wall 11 can be detachable and can be sealingly fitted with the side wall 13.

[0041] The graphite substrate 2 is arranged in the crucible 1 and can be located in the upper part of the crucible 1. Specifically, the graphite substrate 2 can be located in the crucible 1 and can be arranged inside the top wall 11 and can be embedded in the top wall 11. The farther the distance between the graphite substrate 2 and the bottom wall 12, the more conducive to maintaining a low temperature during operation. The graphite substrate 2 can be removed from the crucible 1 or detached with the top wall 11.

[0042] The apparatus 1000 for preparing polycrystalline silicon carbide further includes a gas passage structure 6. The gas passage structure 6 is arranged in the crucible 1 to communicate the inside and outside of the crucible 1, for example, can be configured with a first gas passage and a second gas passage to respectively introduce and exhaust gas, and can introduce gas as needed. For example, it can be used to introduce nitrogen. The gas passage structure 6 can be located in the upper part of the crucible 1.

[0043] The baffle 3 is arranged in the crucible 1 and can be located approximately in the middle or above the middle in the height direction. The baffle 3 is spaced apart from the bottom wall 12 of the crucible 1, and the powder in the crucible 1 can be below the baffle 3. The top surface of the powder pile can be spaced apart from the baffle 3. The baffle 3 is spaced apart from the graphite substrate 2, so that there is enough space for the growth of silicon carbide below the graphite substrate 2. The projection of the baffle 3 in the height direction covers the graphite substrate 2, which helps to avoid the graphite substrate 2 directly facing the powder. There is space between the baffle 3 and the side wall 13 of the crucible 1, which allows the gas to flow from the lower part to the upper part.

[0044] The device 1000 for preparing polycrystalline silicon carbide can further include a support rod 7. The support rod 7 is thinner than the baffle 3, and the support rod 7 can be connected to the bottom wall 12 to support the baffle 3. In other embodiments, the support rod 7 can also be connected to the side wall 13.

[0045] The heater 4 is arranged in the crucible 1, and specifically, can surround the outer periphery of the side wall 13. In the height direction, the position of the heater 4 is lower than that of the baffle 3. The heater 4 directly heats only the part of the crucible 1 below the baffle 3, which can avoid the temperature of the upper part of the crucible 1 and the graphite substrate 2 being too high. Exemplarily, no heating device is arranged above the baffle 3.

[0046] The baffle 3 can block part of the thermal radiation of the bottom powder, avoid the central area thermal radiation directly irradiating the silicon carbide grown below the graphite substrate 2, and further weaken the convection of the bottom gas flow and the upper gas flow and improve the gas flow state. Figure 1 The arrows shown in the middle crucible 1 represent the direction of thermal radiation. Most of the thermal radiation of the powder is blocked by the baffle 3, and the thermal radiation of the edge area can be upward. The baffle 3 also has a certain temperature, which further radiates upward.

[0047] The graphite substrate 2 can achieve a lower temperature, and the gas crystallizes at the graphite substrate 2. Unlike the single crystal growth method which limits the crystal direction by means of a seed crystal, polycrystalline silicon carbide can be generated at the graphite substrate 2. The device 1000 for preparing polycrystalline silicon carbide can provide low-temperature growth conditions and can be used to manufacture polycrystalline silicon carbide with low resistivity.

[0048] Exemplarily, the gas channel structure 6 is arranged at the position of the side wall 13 of the crucible 1 corresponding to the graphite substrate 2. The gas channel structure 6 can be porous graphite. The gas channel structure 6 can be stacked on the side wall 13, and the top wall 11 is stacked on the gas channel structure 6. The gas channel structure 6 can withstand high temperature and ensure the sealing effect.

[0049] The graphite substrate 2 can have a circular truncated cone structure with a wide top and a narrow bottom, and the gas channel structure 6 can correspond to the side wall of the graphite substrate 2.

[0050] The device 1000 for preparing polycrystalline silicon carbide can further comprise a heat preservation structure 5 arranged outside the crucible 1 and above the baffle 3, and a lower edge of the heat preservation structure 5 can be flush with an upper edge of the baffle 3. The heat preservation structure 5 can also wrap a part of the top wall 11, for example, flush with an outer periphery of the graphite substrate 2. The heat preservation structure 5 helps maintain the basic temperature of the crucible 1, avoids excessive energy consumption of the heater 4, and further helps avoid excessive temperature difference of the crucible 1 affecting the structural reliability. The heat preservation structure 5 avoids the position of the baffle 3 and the graphite substrate 2, and helps achieve a large temperature difference between the graphite substrate 2 and the bottom of the crucible 1.

[0051] The device 1000 for preparing polycrystalline silicon carbide can further comprise a temperature sensor 8 arranged on the graphite substrate 2, which can monitor the temperature of the graphite substrate 2, and help better confirm, control and adjust the working state of the device 1000 for preparing polycrystalline silicon carbide.

[0052] For example, the distance between the graphite substrate 2 and the baffle 3 can be 70mm to 90mm, for example, 90mm, which helps reduce the temperature of the graphite substrate 2. The distance between the baffle 3 and the heater 4 in the height direction can be 0mm to 20mm, for example, 20mm, which helps the heater 4 focus more on heating the powder and avoid the temperature of the baffle 3 being too high.

[0053] The ratio of the outer diameter of the baffle 3 to the inner diameter of the crucible 1 can be 60% to 80%. The baffle 3 can be substantially a circular plate and can be coaxially arranged with the cylindrical inner hole of the crucible 1. For example, the outer diameter of the baffle 3 is 140mm, and a larger baffle 3 can reduce the temperature of the graphite substrate 2. For example, the baffle 3 can be arranged in other shapes, and based on the normal plane of the Z-axis direction, the area of the baffle 3 can be 36% to 64% of the area of the inner hole of the crucible 1. The baffle 3 can balance the gas flow and the cooling effect and control the growth state of silicon carbide.

[0054] The materials of the baffle 3 and the support rod 7 can include graphite. The surface of the baffle 3 and the support rod 7 can be a tantalum carbide plating layer, which helps reduce the waste of raw materials during the growth process and reduce the loss caused by error crystallization during the gas transmission process. For example, the material of the crucible 1 can be purified graphite.

[0055] The device 1000 for preparing polycrystalline silicon carbide can be configured to have a temperature of the graphite substrate 2 lower than 1900℃ during operation. The graphite substrate 2 has a lower temperature, which helps the prepared polycrystalline silicon carbide have a lower resistivity. For example, the device 1000 for preparing polycrystalline silicon carbide is configured to have a temperature of the graphite substrate 2 lower than the temperature of the part heated in the crucible 1 by 360℃ to 380℃ during operation. The device 1000 for preparing polycrystalline silicon carbide of the embodiments of the present application can achieve a larger temperature difference, and the gas experiences a larger temperature difference, which is conducive to forming polycrystalline silicon carbide with a lower resistivity.

[0056] The application provides a method 2000 for preparing polycrystalline silicon carbide, which can use the aforementioned device 1000 for preparing polycrystalline silicon carbide. In an exemplary embodiment, the method 2000 for preparing polycrystalline silicon carbide can include heating the powder in the crucible 1 to form polycrystalline silicon carbide on the graphite substrate 2 by physical vapor transport.

[0057] The method 2000 for preparing polycrystalline silicon carbide can form low-resistivity polycrystalline silicon carbide based on a lower-temperature graphite substrate 2 in the physical vapor transport method; can achieve an internal temperature gradient and a top temperature based on the structural characteristics of the device 1000 for preparing polycrystalline silicon carbide; can be independent of precise temperature control, the method is simple to perform, low in cost, low in production equipment and process requirements, and good in product quality.

[0058] The gas pressure in the crucible 1 can range from 2 mbar to 15 mbar, for example, 4 mbar, 8 mbar, or 13 mbar. The gas input into the crucible 1 includes 0 VOL% to 30 VOL% of argon and 70 VOL% to 100 VOL% of nitrogen. A fixed gas composition and flow rate can be used to make the gas input more simple, and the preparation of polycrystalline silicon carbide by the physical vapor transport method in a diazotization environment can be achieved. Exemplarily, the proportion of nitrogen can be 80 VOL% or 90 VOL%. Exemplarily, the polycrystalline silicon carbide manufactured in the embodiments of the application is nitrogen-doped polycrystalline silicon carbide.

[0059] In combination with Table 1, in Comparative Example One, nitrogen-doped polycrystalline silicon carbide is prepared by using a conventional method for preparing single-crystal silicon carbide, the heating temperature is 2220℃, the temperature gradient is 3.3℃ / cm, the axial temperature difference of the upper and lower hot zones is 100℃, the crystal growth temperature is 2120℃, the gas composition is 100 VOL% of nitrogen, and the flow rate is 10 ml / min. The average resistivity of the wafer after wire cutting is 1723 mΩ·cm.

[0060] In Comparative Example Two, the device 1000 for preparing polycrystalline silicon carbide of the embodiments of the application is used, but the baffle 3 is not arranged, the heating temperature is 2280℃, the axial temperature difference of the hot zones is 260℃, the crystal growth temperature is 2020℃, and the average resistivity of the polycrystalline silicon carbide wafer obtained is 214 mΩ·cm.

[0061] In the embodiments of the application, the temperature of the graphite substrate 2 during work can be lower than 1900℃. Exemplarily, the temperature of the graphite substrate 2 is 360℃ to 380℃ lower than the temperature of the powder being heated.

[0062] In the first embodiment, the inner diameter of the crucible 1 is 177 mm; the baffle 3 has an outer diameter of 140 mm, a thickness of 20 mm, and a distance of 90 mm from the graphite substrate 2; the heater 4 is 20 mm lower than the baffle 3; the support rod 7 has a diameter of 40 mm and a height of about 200 mm. The heating temperature is 2260℃, the axial temperature difference of the hot zone is 360℃, the crystal growth temperature is 1900℃, and the average resistivity of the obtained polycrystalline silicon carbide wafer is 58.7 mΩ·cm. The resistivity distribution of the wafer is shown in FIG. 1. Figure 2

[0063] In the second embodiment, the heating temperature is 2250℃, the axial temperature difference of the hot zone is 375℃, the crystal growth temperature is 1875℃, and the average resistivity of the obtained polycrystalline silicon carbide wafer is 11.9 mΩ·cm. The resistivity distribution of the wafer is shown in FIG. 2. Figure 3

[0064] In the third embodiment, the heating temperature is 2220℃, the axial temperature difference of the hot zone is 380℃, the crystal growth temperature is 1840℃, and the average resistivity of the obtained polycrystalline silicon carbide wafer is 8.8 mΩ·cm, which is lower than 9 mΩ·cm. The resistivity distribution of the wafer is shown in FIG. 3. Figure 4

[0065] In each of the comparative examples and the embodiments, the same gas can be used, and the power of the heater 4 can be controlled to some extent based on the target temperature of the graphite substrate 2.

[0066] Table 1: Parameters and effects of the comparative examples and the embodiments

[0067]

[0068] The present application provides polycrystalline silicon carbide prepared by the aforementioned device 1000 for preparing polycrystalline silicon carbide or by the aforementioned method 2000 for preparing polycrystalline silicon carbide, which can break through the resistivity limit of 30 mΩ·cm and help to prepare polycrystalline silicon carbide with a resistivity of less than 20 mΩ·cm. The polycrystalline silicon carbide of the present application has a low resistivity and good performance; it can help to replace single-crystal silicon carbide in some fields.

[0069] The present application provides the use of the aforementioned polycrystalline silicon carbide in the preparation of semiconductor devices. The use of the aforementioned polycrystalline silicon carbide in the preparation of semiconductor devices reduces costs and achieves better performance of semiconductor devices.

[0070] The present application provides polycrystalline silicon carbide wafers or cut wafers. The polycrystalline silicon carbide can be etched, doped, deposited, and bonded. Semiconductor devices include but are not limited to diodes, field effect transistors, insulated gate bipolar transistors, light emitting diodes, and high electron mobility transistors.

[0071] ​​​The technical features of each of the above disclosed embodiments can be combined in any manner. For the sake of brevity, not all possible combinations of the technical features of the above described embodiments are described, however, it is to be understood that the scope of the present specification includes all possible combinations of the technical features.

[0072] In the above disclosed embodiments, unless otherwise explicitly specified and limited, the execution order of each step is not limited, for example, the steps can be executed in parallel, or executed in different order. The sub-steps of each step can also be executed in an interleaved manner. The above described various forms of flow can be used, and the steps can also be reordered, added or deleted, as long as the desired results of the technical solutions provided in the present application can be achieved, and the present application is not limited in this regard.

[0073] The above disclosed embodiments only express several implementation manners of the present application, and the description is relatively specific and detailed, but it should not be understood as a limitation on the patent protection scope of the present application. It should be noted that, for those skilled in the art, without departing from the concept of the present application, several modifications and improvements can be made, which all belong to the patent protection scope required by the present application. Therefore, the patent protection scope of the present application should be subject to the appended claims.

Claims

1. Apparatus for preparing polycrystalline silicon carbide, characterized in that, The device comprises: a crucible; a graphite substrate arranged in the crucible and located at the upper part of the crucible; an air passage structure arranged in the crucible for air passage into the crucible; a baffle arranged in the crucible, spaced from the graphite substrate and projected to cover the graphite substrate, the baffle being spaced from the bottom wall of the crucible; and a heater arranged in the crucible and located below the baffle.

2. The apparatus for producing polycrystalline silicon carbide according to claim 1, characterized by, The device is configured to have the temperature of the graphite substrate lower than 1900℃ during operation, and the temperature of the graphite substrate is 360-380℃ lower than the temperature of the heated part in the crucible.

3. The apparatus for producing polycrystalline silicon carbide according to claim 1, wherein The distance between the graphite substrate and the baffle ranges from 70mm to 90mm. The distance between the baffle and the heater in the height direction ranges from 0mm to 20mm.

4. The apparatus for producing polycrystalline silicon carbide according to claim 1, wherein The ratio of the outer diameter of the baffle to the inner diameter of the crucible ranges from 60% to 80%.

5. The apparatus for producing polycrystalline silicon carbide according to any one of claims 1 to 4, characterized by, Further comprising a heat preservation structure arranged outside the crucible and above the baffle. The air passage structure is arranged at the position of the side wall of the crucible corresponding to the graphite substrate.

6. A method for producing polycrystalline silicon carbide, characterized by, The device for preparing polycrystalline silicon carbide according to any one of claims 1-5 is used to heat the powder in the crucible, and polycrystalline silicon carbide is formed on the graphite substrate through physical vapor transport.

7. The method for producing polycrystalline silicon carbide according to claim 6, characterized by, The air pressure in the crucible ranges from 2mbar to 15mbar. The gas introduced into the crucible comprises 0 VOL% to 30 VOL% of argon and 70 VOL% to 100 VOL% of nitrogen. The temperature of the graphite substrate is 360-380℃ lower than that of the heated powder.

8. The method for producing polycrystalline silicon carbide according to claim 6, characterized by, The powder is heated to 2220℃, and the temperature of the graphite substrate is configured to be 1840℃. The air pressure in the crucible is 2mbar.

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