Heating device and heating method for silicon carbide single crystal growth

Abstract

The invention discloses a silicon carbide single crystal growth heating device which comprises a graphite crucible and a graphite sleeve arranged outside the graphite crucible in a sleeving mode, the graphite sleeve comprises a plurality of branch sleeves, the branch sleeves are stacked in the axial direction of the graphite crucible, and the branch sleeves are arranged according to the sequence that the electrical resistivity is sequentially increased from top to bottom. According to the silicon carbide single crystal growth heating device, the axial heating temperature of the graphite crucible is adjustable, the axial temperature gradient of the graphite crucible is increased, sublimated silicon carbide raw materials are more easily condensed at the top, and the production efficiency of silicon carbide crystallization is improved. The invention also provides a silicon carbide single crystal growth heating method.

Description

Technical Field

[0001] The present invention relates to the technical field of silicon carbide single crystal growth, and particularly relates to a heating device and a heating method for silicon carbide single crystal growth. Background Art

[0002] Silicon carbide is one of the relatively mature wide-bandgap semiconductor materials at present. Silicon carbide has excellent properties such as a wide bandgap, a fast carrier migration rate, high thermal conductivity and stability, and has great application potential in the production of high-temperature, high-frequency, and high-power electronic devices.

[0003] At present, the method for growing large-size silicon carbide single crystals is the PVT method. By heating silicon carbide powder to 2100 - 2450 °C, the silicon carbide powder decomposes and sublimes. A seed crystal is placed in the low-temperature area at the top, and the sublimated silicon carbide powder crystallizes at the top to form a silicon carbide single crystal. During the growth process of silicon carbide single crystals by the PVT method, a relatively high temperature is required for heating. Currently, an electromagnetic induction furnace controlled by power is commonly used, and the physical principle utilized is electromagnetic induction heating. When an alternating magnetic field is applied axially to the graphite crucible, an induced current is generated on the cross-section of the graphite crucible. Since the graphite crucible has resistance, Joule heat is generated, which is then used to heat the silicon carbide growth chamber. In the existing silicon carbide single crystal growth process, the above-mentioned method of directly heating the graphite crucible is generally used to control the axial temperature gradient of the graphite crucible temperature field by adjusting the thermal insulation structure outside the graphite crucible. This temperature control method results in a relatively small axial temperature gradient of the graphite crucible, making it inconvenient to adjust the temperature gradient, the grown silicon carbide crystal column is relatively thin, and the production efficiency of silicon carbide single crystals is low, which is not conducive to large-scale production. Summary of the Invention

[0004] In view of this, the present invention provides a heating device for silicon carbide single crystal growth, which enables the heating temperature along the axis of the graphite crucible to be adjustable, increases the axial temperature gradient of the graphite crucible, makes it easier for the sublimated silicon carbide raw material to condense at the top, and improves the production efficiency of silicon carbide crystallization.

[0005] The present invention also provides a heating method for silicon carbide single crystal growth.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] A heating device for silicon carbide single crystal growth, comprising a graphite crucible and a graphite sleeve sleeved outside the graphite crucible. The graphite sleeve includes a plurality of sub-sleeves, and the plurality of sub-sleeves are stacked axially along the graphite crucible. The sub-sleeves are arranged in the order of increasing resistivity from top to bottom.

[0008] Optionally, the inner diameters and outer diameters of the plurality of sub-sleeves are the same, and the plurality of sub-sleeves are coaxially arranged.

[0009] Optionally, the graphite sleeve includes a first sub-sleeve, a second sub-sleeve, and a third sub-sleeve. The first sub-sleeve, the second sub-sleeve, and the third sub-sleeve are stacked axially from top to bottom in sequence. The resistivity of the first sub-sleeve is less than that of the second sub-sleeve, and the resistivity of the second sub-sleeve is less than that of the third sub-sleeve.

[0010] Optionally, the resistivity of the first sub-sleeve is 2.0 - 9.5×10 -6 Ω / m, the resistivity of the second sub-sleeve is 9.6 - 12.0×10 -6 Ω / m, and the resistivity of the third sub-sleeve is 12.5 - 20.0×10 -6 Ω / m.

[0011] Optionally, the inner diameters and the wall thicknesses of the first sub-sleeve, the second sub-sleeve, and the third sub-sleeve are the same.

[0012] Optionally, the inner diameters of the first sub-sleeve, the second sub-sleeve, and the third sub-sleeve are greater than the maximum diameter of the graphite crucible.

[0013] Optionally, the inner diameter of the sub-sleeve is 130 - 230 mm, the wall thickness of the sub-sleeve is 5 - 30 mm, and the height of the sub-sleeve is 1 - 1000 mm.

[0014] Optionally, a heat-insulating layer is provided outside the sub-sleeve;

[0015] An insertion limit structure is provided on the end faces of adjacent sub-sleeves that are close to each other.

[0016] As can be seen from the above technical solutions, the silicon carbide single crystal growth heating device provided by the present invention includes a plurality of sub-sleeves sleeved outside the graphite crucible. By changing the sub-sleeves with different resistivities placed at different positions, the magnitude of Joule heat generated at different parts of the heating device can be regulated, so as to achieve the purpose of regulating the temperature gradient. By stacking sub-sleeves with different resistivities and replacing sub-sleeves with different resistivities, the heating temperature of the graphite crucible along the axis can be controlled and adjusted, so that the temperature gradient can be adjusted according to needs, meeting the requirement of a large temperature gradient for silicon carbide single crystal growth and making the grown silicon carbide crystal column thicker. By arranging the sub-sleeves in the order of increasing resistivity from top to bottom, it is convenient to make the heat generation at different parts of the graphite sleeve different, increasing the axial temperature gradient of the graphite crucible, reducing the top temperature, making it easier for the sublimated silicon carbide raw material to condense at the top, improving the raw material utilization rate, and improving the production efficiency.

[0017] The present invention also provides a method for heating the growth of silicon carbide single crystals. The silicon carbide single crystals are crystallized by applying the above-mentioned heating device for the growth of silicon carbide single crystals. By axially sleeving split sleeves made of graphite with different resistivities on the outer edge of the graphite crucible, the heating temperature at different axial positions of the graphite crucible is different, and the heating temperature gradually increases from the top to the bottom of the graphite crucible.

[0018] The method for heating the growth of silicon carbide single crystals of the present invention crystallizes silicon carbide by applying the above-mentioned heating device for the growth of silicon carbide single crystals. Therefore, it has the advantages of the above-mentioned heating device for the growth of silicon carbide single crystals, which will not be elaborated here. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0020] Figure 1 It is a schematic cross-sectional structure diagram of the heating device for the growth of silicon carbide single crystals provided by the embodiment of the present invention;

[0021] Figure 2 It is a schematic structure diagram of the heating device for the growth of silicon carbide single crystals provided by the embodiment of the present invention;

[0022] Figure 3 It is a schematic connection structure diagram of the first split sleeve and the second split sleeve provided by an embodiment of the present invention;

[0023] Figure 4 For Figure 3 It is a schematic structure diagram of the first split sleeve at an angle provided by the embodiment;

[0024] Figure 5 For Figure 3 It is a schematic structure diagram of the first split sleeve at another angle provided by the embodiment;

[0025] Figure 6 For Figure 3 It is a schematic structure diagram of the second split sleeve at an angle provided by the embodiment;

[0026] Figure 7 For Figure 6 It is a schematic cross-sectional structure diagram at the A-A position of;

[0027] Figure 8 It is a schematic connection structure diagram of the first split sleeve and the second split sleeve provided by another embodiment of the present invention;

[0028] Figure 9 ForFigure 8 Schematic structural diagram of the first split sleeve provided by the embodiment at one angle;

[0029] Figure 10 For Figure 8 Schematic structural diagram of the first split sleeve provided by the embodiment at another angle;

[0030] Figure 11 For Figure 8 Schematic structural diagram of the second split sleeve provided by the embodiment at one angle;

[0031] Figure 12 For Figure 11 Schematic cross-sectional structure diagram at the B-B position of

[0032] Wherein:

[0033] 1. First split sleeve,

[0034] 101. Insertion column, 102. Insertion convex edge,

[0035] 2. Second split sleeve,

[0036] 201. Insertion slot, 202. Insertion ring groove,

[0037] 3. Third split sleeve,

[0038] 4. Graphite crucible,

[0039] 5. Thermal insulation layer. Detailed implementation manners

[0040] The present invention discloses a heating device for growing silicon carbide single crystals, which enables the heating temperature of the graphite crucible to be adjustable along the axial direction, enlarges the axial temperature gradient of the graphite crucible, makes the sublimated silicon carbide raw material easier to condense at the top, and improves the production efficiency of silicon carbide crystallization.

[0041] The present invention also provides a method for growing silicon carbide single crystals.

[0042] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0043] Please refer to Figure 1 And Figure 2, The silicon carbide single crystal growth heating device of the present invention includes a graphite crucible 4 and a graphite sleeve sleeved outside the graphite crucible 4. The graphite sleeve includes a plurality of sub-sleeves, and the plurality of sub-sleeves are stacked along the axial direction of the graphite crucible 4. The sub-sleeves are arranged in the order of increasing resistivity from top to bottom.

[0044] Among them, the outer diameter of the graphite crucible 4 is smaller than the inner diameter of the graphite sleeve, so that the graphite sleeve can be placed inside the graphite sleeve. Different sub-sleeves are made of high-purity graphite materials with different resistance values.

[0045] The silicon carbide single crystal growth heating device of the present invention includes a graphite crucible 4 and a graphite sleeve. After the two are assembled, they are placed in a single crystal furnace. After an alternating current is applied to the induction heating coil, the graphite sleeve in the single crystal furnace is in the time-harmonic electromagnetic field generated by the induction coil. Under the action of the time-harmonic electromagnetic field, the graphite sleeve generates eddy currents and generates resistive heat to increase the temperature of the graphite sleeve, thereby heating the graphite crucible 4. Since a plurality of sub-sleeves of the present invention are sleeved outside the graphite crucible 4, by changing the sub-sleeves with different resistivities placed at different positions, the magnitude of the Joule heat generated at different parts of the heating device is regulated, so as to achieve the purpose of regulating the temperature gradient. By stacking sub-sleeves with different resistivities and replacing sub-sleeves with different resistivities, the heating temperature of the graphite crucible 4 along the axial direction is controllable and adjustable, so that the temperature gradient can be adjusted according to needs, meeting the requirements of the large temperature gradient for the growth of silicon carbide single crystals, and making the grown silicon carbide crystal column thicker. By using sub-sleeves arranged in the order of increasing resistivity from top to bottom, it is convenient to make different parts of the graphite sleeve generate different amounts of heat, increasing the axial temperature gradient, reducing the temperature at the top, making it easier for the sublimated silicon carbide raw material to condense at the top, improving the raw material utilization rate, and improving production efficiency.

[0046] To improve the stability of the chamber formed after the sub-sleeves are stacked, the inner diameters and outer diameters of the plurality of sub-sleeves are the same, and the plurality of sub-sleeves are coaxially arranged.

[0047] Specifically, referring to Figure 1 and Figure 2 , the graphite sleeve includes a first sub-sleeve 1, a second sub-sleeve 2 and a third sub-sleeve 3. The first sub-sleeve 1, the second sub-sleeve 2 and the third sub-sleeve 3 are stacked axially from top to bottom in sequence. The resistivity of the first sub-sleeve 1 is less than that of the second sub-sleeve 2, and the resistivity of the second sub-sleeve 2 is less than that of the third sub-sleeve 3, so that the temperature at the bottom of the graphite crucible 4 is higher and the temperature at the top is lower, meeting the crystallization requirements.

[0048] Among them, the resistivity of the first sub-sleeve 1 is 2.0 - 9.5×10 -6 Ω / m, and the resistivity of the second sub-sleeve 2 is 9.6 - 12.0×10-6 Ω / m, the resistivity of the third sub-sleeve 3 is 12.5 - 20.0×10 -6 Ω / m. In one embodiment, the resistivity of the first sub-sleeve 1 is 8×10 -6 Ω / m, the resistivity of the second sub-sleeve 2 is 10×10 -6 Ω / m, and the resistivity of the third sub-sleeve 3 is 13×10 -6 Ω / m. In other embodiments, the specific resistivity of the first sub-sleeve 1, the second sub-sleeve 2, and the third sub-sleeve 3 can also be set according to specific needs, which will not be elaborated here.

[0049] Among them, the inner diameters and the wall thicknesses of the first sub-sleeve 1, the second sub-sleeve 2, and the third sub-sleeve 3 are the same, so that the graphite sleeve formed by splicing the first sub-sleeve 1, the second sub-sleeve 2, and the third sub-sleeve 3 is a regular cylindrical toroidal surface. It can be understood that the inner diameters of the first sub-sleeve 1, the second sub-sleeve 2, and the third sub-sleeve 3 are greater than the maximum diameter of the graphite crucible 4, so that the first sub-sleeve 1, the second sub-sleeve 2, and the third sub-sleeve 3 can be smoothly sleeved outside the graphite crucible 4.

[0050] Specifically, the inner diameter of the sub-sleeve is 130 - 230 mm, the wall thickness of the sub-sleeve is 5 - 30 mm, and the height of the sub-sleeve is 1 - 1000 mm. During actual production, the specific parameters of the sub-sleeve are selected by those skilled in the art within the numerical range according to actual needs. In one embodiment, the inner diameters of the three sub-sleeves are 180 mm, the wall thickness is 10 mm, and the height is 300 mm. Among them, a heat-insulating layer 5 is provided outside the sub-sleeve.

[0051] In order to ensure the structural stability of the graphite sleeve formed by stacking multiple sub-sleeves, a plug-in limiting structure is provided on the end faces of adjacent sub-sleeves that are close to each other. In one embodiment, the plug-in limiting structure includes a plug-in post 101 and a plug-in groove 201 respectively arranged on adjacent sub-sleeves, and the plug-in post 101 is inserted into the plug-in groove 201. As Figures 3 to 7 shown, a plug-in post 101 is provided on the end face of the first sub-sleeve 1 close to the second sub-sleeve 2, and a plug-in groove 201 is provided on the end face of the second sub-sleeve 2 close to the first sub-sleeve 1, and the plug-in groove 201 and the plug-in post 101 are arranged in cooperation. The number of the plug-in grooves 201 and the plug-in posts 101 is the same, and at least two plug-in posts 101 are provided. As Figure 4 shown, four plug-in posts 101 are provided.

[0052] In another embodiment, the plug-in limiting structure includes a plug-in convex edge 102 and a plug-in ring groove 202 respectively arranged on adjacent sub-sleeves, and the plug-in convex edge 102 and the plug-in ring groove 202 are arranged in corresponding cooperation, and the plug-in convex edge 102 is inserted into the plug-in ring groove 202. As Figures 8 to 12As shown in the figure, on the end face of the first split sleeve 1 close to the second split sleeve 2, there is a plugging convex edge 102, and on the end face of the second split sleeve 2 close to the first split sleeve 1, there is a plugging annular groove 202.

[0053] Three kinds of graphite with resistivity of 8×10 -6 Ω / m, 10×10 -6 Ω / m, and 13×10 -6 Ω / m are respectively made into the first split sleeve 1, the second split sleeve 2, and the third split sleeve 3. The three graphite sleeves are spliced together in the order that the resistivity decreases from top to bottom, and then a heat insulation layer 5 is equipped outside the sleeves. The above structure is placed in the center of the coil in an electromagnetic single crystal furnace, and a silicon carbide growth device capable of regulating the temperature gradient can be obtained.

[0054] The silicon carbide single crystal growth heating device of the present invention uses high-purity graphite materials with different resistances to make split sleeves, so that different parts of the graphite sleeves generate different amounts of heat, increasing the axial temperature gradient, reducing the temperature at the top, making it easier for the sublimated silicon carbide raw materials to crystallize at the top, improving the utilization rate of raw materials, and improving production efficiency.

[0055] Example 1

[0056] The graphite crucible 4 and the graphite sleeve are assembled together according to Figure 1 and placed in a single crystal furnace. Silicon carbide single crystals are grown by the traditional PVT method. The pressure of the crystal growth furnace is controlled at 5 - 10 mbar, the temperature is 2000 - 2300 °C, the total growth time is 100 h, and after growth, it is cooled to room temperature.

[0057] Comparative Example 1

[0058] The same heat insulation structure as in Example 1 is installed on the same graphite crucible 4 as in Example 1. The assembled device is placed in the center of the coil, and the comparative experiment device is assembled. After assembly, it is placed in a single crystal furnace, and the long crystal raw materials are heated by the conventional PVT method. The pressure of the crystal growth furnace is controlled at 5 - 10 mbar, the temperature is 2000 - 2300 °C, the total growth time is 100 h, and after growth, it is cooled to room temperature. After growth, it is cooled to room temperature. The experimental results are compared in Table 1.

[0059] Table 1: Comparison of experimental results

[0060]

[0061] Through the result analysis of Example 1 and Comparative Example 1, it can be seen that the silicon carbide single crystal growth heating device of the present invention can effectively improve the utilization rate of sublimated silicon carbide, enable more gaseous silicon carbide molecules to be used for crystallization, and significantly increase the crystal weight and greatly improve the production efficiency under the condition of equivalent evaporation.

[0062] The present invention also provides a heating method for growing silicon carbide single crystals. The above-mentioned heating device for growing silicon carbide single crystals is used for silicon carbide crystallization. By axially sleeving split sleeves made of graphite with different resistivity values along the outer edge of the graphite crucible 4, the heating temperatures at different axial positions of the graphite crucible 4 are different, and the heating temperature gradually increases from the top to the bottom of the graphite crucible 4.

[0063] In the description of this solution, it should be understood that the orientation or positional relationship indicated by terms such as "upper", "lower", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it cannot be understood as a limitation to this solution.

[0064] In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features.

[0065] In this specification, the various embodiments are described in a progressive manner. Each embodiment focuses on the differences from other embodiments. The same or similar parts among the various embodiments can be referred to each other.

[0066] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be obvious to those skilled in the art. The general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to these embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A heating device for growing silicon carbide single crystals, characterized in that, It includes a graphite crucible and a graphite sleeve sleeved outside the graphite crucible. The graphite sleeve includes a plurality of sub-sleeves, and the plurality of sub-sleeves are stacked along the axial direction of the graphite crucible. The sub-sleeves are arranged in the order that the resistivity increases successively from top to bottom.

2. The silicon carbide single crystal growth heating device according to claim 1, wherein, The inner diameters and outer diameters of the plurality of sub-sleeves are the same, and the plurality of sub-sleeves are coaxially arranged.

3. The silicon carbide single crystal growth heating device according to claim 1, characterized in that, The graphite sleeve includes a first sub-sleeve, a second sub-sleeve and a third sub-sleeve. The first sub-sleeve, the second sub-sleeve and the third sub-sleeve are stacked successively from top to bottom along the axial direction. The resistivity of the first sub-sleeve is less than that of the second sub-sleeve, and the resistivity of the second sub-sleeve is less than that of the third sub-sleeve.

4. The silicon carbide single crystal growth heating device according to claim 3, wherein The resistivity of the first sub-sleeve is 2.0 to 9.5×10 -6 Ω / m, the resistivity of the second sub-sleeve is 9.6 to 12.0×10 -6 Ω / m, and the resistivity of the third sub-sleeve is 12.5 to 20.0×10 -6 Ω / m.

5. The silicon carbide single crystal growth heating device according to claim 3, characterized in that, The inner diameters and the wall thicknesses of the first sub-sleeve, the second sub-sleeve and the third sub-sleeve are the same.

6. The silicon carbide single crystal growth heating device according to claim 3, characterized in that, The inner diameters of the first sub-sleeve, the second sub-sleeve and the third sub-sleeve are larger than the maximum diameter of the graphite crucible.

7. The silicon carbide single crystal growth heating device according to claim 1, wherein The inner diameter of the sub-sleeve is 130 - 230 mm, the wall thickness of the sub-sleeve is 5 - 30 mm, and the height of the sub-sleeve is 1 - 1000 mm.

8. The silicon carbide single crystal growth heating device according to claim 1, wherein A heat insulation layer is provided outside the sub-sleeve; An insertion limit structure is provided on the end faces of adjacent sub-sleeves that are close to each other.

9. A method for heating the growth of a single crystal of silicon carbide, characterized in that, When using the silicon carbide single crystal growth heating device according to any one of claims 1 - 8 for silicon carbide crystallization, by sleeving sub-sleeves made of graphite with different resistivities along the axial direction outside the graphite crucible, the heating temperatures at different positions along the axial direction of the graphite crucible are different, and the heating temperature gradually increases from the top to the bottom of the graphite crucible.

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