Graphite heater

Abstract

The invention discloses a graphite heater, and belongs to the field of silicon carbide production equipment. Comprising a furnace body, a crucible arranged in the furnace body and a heating structure for heating the crucible, the heating structure is composed of a side face heating assembly and a top heating assembly. The top heating assembly comprises a guide cylinder, and a cylinder body of the guide cylinder extends into the furnace body. The crucible has the beneficial effects that in the crystal growing and pulling process, the axial temperature gradient and the radial temperature uniformity in the crucible are poor, so that the impurity distribution uniformity of a long crystal is poor, and the quality of the long crystal is influenced; the device is additionally provided with the guide cylinder, the guide cylinder can guide the heat emitted by the heating assembly on the side surface to descend, and the heat is concentrated at the bottom of the guide cylinder, so that the temperature gradient change is very small, and the crystal growth is facilitated.

Description

Technical Field

[0001] The invention relates to a graphite heater and belongs to the field of silicon carbide production equipment. Background Art

[0002] Silicon carbide is a high-quality wide-bandgap semiconductor material. Currently, silicon carbide single crystals cannot be formed by melting, and the sublimation growth technology based on the improved Lely method - physical vapor transport is a common method for obtaining silicon carbide single crystals. The growth principle of silicon carbide single crystals prepared by the PVT method is: high-purity silicon carbide powder source decomposes at high temperature to form gaseous substances, which are driven by supersaturation and sublimate to the seed crystal at the cold end for growth. Among them, the supersaturation is caused by the temperature gradient between the seed crystal and the powder source.

[0003] In order to generate a temperature gradient between the hot end raw material and the cold end seed crystal, the existing technology is that the heating resistor (graphite heater) is generally located at the bottom and around the crucible, so that the crucible has a relatively good temperature gradient in the axial direction. The existing crucible generally adopts an external heating form, and the heater adopts a cylindrical birdcage-shaped graphite heater, and the bottom is generally connected to an electrode. The crucible is placed inside the heater to achieve the heating requirements of the crucible.

[0004] However, as people's demand for single crystal raw materials has greatly increased, the diameter of the crucible has become larger and larger. The heating efficiency of the existing heater has been difficult to meet the heating needs of the crucible. The axial temperature gradient and radial temperature uniformity in the crucible are poor, which in turn makes the impurity distribution uniformity of the grown crystals poor, affecting the quality of the grown crystals. Summary of the invention

[0005] The object of the present invention is to provide a graphite heater which can effectively solve the above-mentioned problems.

[0006] In order to solve the above technical problems, the present invention is achieved through the following technical solutions: It comprises a furnace body, a crucible arranged in the furnace body, and a heating structure for heating the crucible; Wherein, the heating structure is composed of a side heating component and a top heating component; the top heating component includes a guide tube, and the tube body of the guide tube extends into the furnace body.

[0007] Furthermore: a first graphite tube is arranged on the side wall of the guide tube, and a plurality of first expansion gaps are arranged on the first graphite tube; a heat collecting ring groove is arranged on the bottom of the guide tube, and the groove wall of the heat collecting ring groove is arranged inclined.

[0008] Furthermore: a first graphite ring is arranged at the bottom of the heat collecting ring groove, and a second graphite ring is arranged at the groove wall of the heat collecting ring groove, and the first graphite ring and the second graphite ring are integrally formed.

[0009] Furthermore: there are three heat collecting ring grooves, the groove width of which gradually decreases from the inside to the outside, and a circular groove is arranged in the middle position of the bottom of the guide tube, the groove wall of the circular groove is arranged inclined, a graphite disk is arranged at the bottom of the circular groove, and the groove wall of the circular groove is also arranged with the second graphite ring.

[0010] Furthermore: two adjacent second graphite rings are connected via a graphite plate.

[0011] Further: the crucible includes a graphite pot body and a quartz pot body arranged in the graphite pot body, a tray is arranged at the lower end of the graphite pot body, and a lifting device is arranged at the lower end of the tray; the lifting device includes a lifting rod and a driving device for driving the lifting rod to move, and the driving device includes mounting plates arranged on both sides of the end of the lifting rod, one of the mounting plates is provided with a limit rod, and the other mounting plate is threadedly connected with a screw, and a motor is arranged at the end of the screw.

[0012] Furthermore: a mounting ring is arranged on the outer periphery of the guide tube, a sealing ring is arranged on the end of the mounting ring, and a sealing groove matching the sealing ring is arranged on the graphite pot body.

[0013] Furthermore: a rotating assembly is also provided at the lower end of the crucible, and the rotating assembly includes a mounting path arranged in the lifting rod, a rotating rod is arranged in the mounting path, and a rotating disk is fixed to the upper end of the rotating rod; a mounting groove is provided on the upper end surface of the tray, and the rotating disk is arranged in the mounting groove through a bearing; a driven ring is fixed to the outer periphery of the rotating rod, and a plurality of limit strips are evenly distributed on the circumference of the driven ring, and limit slots are provided between the limit strips; the rotating assembly also includes a driving motor, and a reducer is provided at the output end of the driving motor, and a gear is provided at the output end of the reducer, and the teeth of the gear are meshed with the limit slots.

[0014] Further: the side heating assembly includes a second graphite cylinder, a plurality of second expansion gaps are arranged on the cylinder wall of the second graphite cylinder, and the second graphite cylinder is fixed to the furnace body by bolts.

[0015] Furthermore: the inner wall of the furnace body is provided with an upper insulation ring, a middle insulation ring and a lower insulation ring; the middle insulation ring is arranged between the upper insulation ring and the lower insulation ring, and the materials of the upper insulation ring, the middle insulation ring and the lower insulation ring are graphite felt.

[0016] The beneficial effects are: 1. During the process of crystal growth and crystal pulling, the axial temperature gradient and radial temperature uniformity in the crucible are poor, which leads to poor uniformity of impurity distribution in the grown crystals, affecting the quality of the grown crystals. Therefore, a guide tube is added to the device, which can guide the heat emitted by the heating component on the side downward and concentrate the heat at the bottom of the guide tube, so that the temperature gradient change can be very small, which is conducive to crystal growth.

[0017] 2. A heat collecting ring groove is provided at the bottom of the guide tube. When the hot air flows through the bottom of the guide tube, the hot air will move upward into the heat collecting ring groove, which can keep the heat at the bottom of the guide tube. The bottom of the guide tube is closer to silicon carbide, so this setting can increase the crystal growth rate of silicon carbide.

[0018] 3. The lifting device can adjust the height of the crucible, so that the distance between the silicon material in the crucible and the bottom of the guide tube above can be adjusted, thereby achieving the purpose of controlling the temperature of the silicon material; the temperature gradient can be better controlled.

[0019] 4. The rotating component can control the rotation of the entire crucible, and at the same time drive the silicon material to rotate, so that the crystal can be subjected to a more balanced temperature. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] For ease of explanation, the present invention is described in detail with reference to the following specific implementations and the accompanying drawings.

[0021] Figure 1 It is a structural schematic diagram of the present invention; Figure 2 It is the parts diagram of the guide tube of the present invention; Figure 3 This is a structural diagram of the bottom surface of the guide tube of the present invention; Figure 4 is a cross-sectional view of the guide tube of the present invention; Figure 5 This is a schematic diagram of the first graphite ring structure of the present invention; Figure 6 is a cross-sectional view of a first graphite ring of the present invention; Figure 7 It is a parts diagram of the rotating assembly of the present invention.

[0022] Description of reference numerals: 1. furnace body; 2. crucible; 21. graphite pot body; 22. quartz pot body; 23. tray; 24. lifting device; 241. lifting rod; 242. driving device; 2421. mounting plate; 2422. limit rod; 2423. screw rod; 2424. motor; 3. side heating assembly; 4. top heating assembly; 5. guide tube; 6. first graphite tube; 7. heat collecting ring groove; 8. first graphite ring; 9. Two graphite rings; 10. circular groove; 11. graphite disk; 12. graphite plate; 13. mounting ring; 14. sealing ring; 15. sealing groove; 16. rotating assembly; 161. mounting channel; 162. rotating rod; 163. rotating disk; 164. driven ring; 165. limit strip; 166. driving motor; 167. reducer; 168. gear; 17. upper insulation ring; 18. middle insulation ring; 19. lower insulation ring. DETAILED DESCRIPTION

[0023] Embodiments of the present invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to be used to explain the present invention, but should not be understood as limiting the present invention.

[0024] See also Figure 1-7 This is an embodiment of a graphite heater of the present invention. See also Figure 1 : It includes a furnace body 1, a crucible 2 arranged in the furnace body 1, and a heating structure for heating the crucible 2; wherein the heating structure is composed of a side heating component 3 and a top heating component 4; the top heating component 4 includes a guide tube 5, and the barrel of the guide tube 5 extends into the furnace body 1.

[0025] When the device is in use, silicon carbide is placed in the crucible 2, and the heating structure emits heat to heat the silicon carbide in the crucible 2. As the temperature rises, the silicon carbide begins to grow and pull crystals. However, during the process of crystal growth and pulling, the axial temperature gradient and radial temperature uniformity in the crucible 2 are poor, which in turn makes the impurity distribution uniformity of the grown crystals poor, affecting the quality of the grown crystals. Therefore, a guide tube 5 is added to the device. The guide tube 5 can guide the heat emitted by the side heating component 3 to descend and concentrate the heat at the bottom of the guide tube 5. In this way, the temperature gradient change can be very small, which is conducive to crystal growth.

[0026] See also Figure 2 , Figure 3In order to increase the gathering of hot air, the device is provided with a first graphite tube 6 on the side wall of the guide tube 5, and a plurality of first expansion gaps are provided on the first graphite tube 6; the first graphite tube 6 can generate heat, and after the guide tube 5 is extended into the crucible 2, the heat transfer of the side heating component 3 needs to be transferred to the silicon carbide through the crucible 2, and the heat dissipated by the first graphite tube 6 can be directly dissipated inside the crucible 2, the heat transfer is faster, and the temperature gradient is maintained more stably; the first expansion gap on the first graphite tube 6 is to cope with the thermal expansion of graphite and prevent the graphite from deforming due to heating.

[0027] See also Figure 3 : A heat collecting annular groove 7 is arranged at the bottom of the guide tube 5 in the present device, and the groove wall of the heat collecting annular groove 7 is arranged inclined.

[0028] According to the principle of hot air rising, higher temperature heat will move upward, so the gas will directly flow through the bottom of the guide tube 5 and move upward along the side of the guide tube 5; in order to retain the high-temperature heat, a heat collecting ring groove 7 is provided at the bottom of the guide tube 5. When the hot gas flows through the bottom of the guide tube 5, the hot gas will move upward into the heat collecting ring groove 7, which can retain the heat at the bottom of the guide tube 5. The bottom of the guide tube 5 is closer to silicon carbide, so this arrangement can increase the crystal growth rate of silicon carbide.

[0029] The groove wall of the heat collecting annular groove 7 is inclined to facilitate the hot air flow to enter the heat collecting annular groove 7 .

[0030] See also Figure 4 , Figure 5 : A first graphite ring 8 is arranged at the bottom of the heat collecting ring groove 7 of the device, and a second graphite ring 9 is arranged at the groove wall of the heat collecting ring groove 7, and the first graphite ring 8 and the second graphite ring 9 are integrally formed.

[0031] The first graphite ring 8 and the second graphite ring 9 are integrally formed. When temperature control is required, the first graphite ring 8 and the second graphite ring 9 can be allowed to generate heat, and the heat emitted will be closer to the silicon carbide in the crucible 2, which can further increase the control of the temperature gradient.

[0032] There are three heat collecting annular grooves 7 in the present device, and the groove width of the heat collecting annular grooves 7 gradually decreases from the inside to the outside; such an arrangement can gather the thermal airflow in all directions and at multiple levels.

[0033] See also Figure 6 , and a circular groove 10 is arranged in the middle of the bottom of the guide tube 5, and the circular groove 10 also has the function of gathering the hot air flow; the groove wall of the circular groove 10 is arranged inclined, so that the hot air can easily enter the circular groove 10; A graphite disk 11 is provided at the bottom of the circular groove 10, and a second graphite ring 9 is also provided at the wall of the circular groove 10; with this arrangement, when temperature control is required, the graphite disk 11 and the second graphite ring 9 can be allowed to generate heat, and the heat emitted is closest to the silicon carbide in the crucible 2, which can further increase the control of the temperature gradient.

[0034] Two adjacent second graphite rings 9 are connected via a graphite plate 12 .

[0035] Three first graphite rings 8 of different sizes are integrally formed with a plurality of second graphite rings 9 and a graphite disk 11, so as to be conveniently connected with a graphite electrode. When power is turned on, all the first graphite rings 8, the second graphite rings 9 and the graphite disk 11 can be heated.

[0036] See also Figure 1 The crucible 2 includes a graphite pot body 21 and a quartz pot body 22 arranged in the graphite pot body 21, a tray 23 is arranged at the lower end of the graphite pot body 21, and a lifting device 24 is arranged at the lower end of the tray 23; the lifting device 24 includes a lifting rod 241 and a driving device 242 for driving the lifting rod 241 to move, and the driving device 242 includes mounting plates 2421 arranged on both sides of the end of the lifting rod 241, a limiting rod 2422 is arranged in one of the mounting plates 2421, and a screw 2423 is threadedly connected in the other mounting plate 2421, and a motor 2424 is arranged at the end of the screw 2423.

[0037] The graphite pot body 21 used in this device is a three-flap pot, which is mainly used to hold the quartz pot body 22. The inner diameter of the graphite pot body 21 is processed to match the outer dimensions of the quartz pot body 22. At the same time, the graphite pot body 21 itself has a certain strength to bear the weight of the silicon material and the quartz pot body 22; See also Figure 1 The tray 23 is mainly used to hold up the entire crucible 2. At the same time, a lifting device 24 is provided at the lower end of the tray 23. The height of the crucible 2 can be adjusted by the lifting device 24, so that the distance between the silicon material in the crucible 2 and the bottom of the guide tube 5 above can be adjusted, thereby achieving the purpose of controlling the temperature of the silicon material; the temperature gradient can be better controlled.

[0038] When the lifting device 24 is in use, the motor 2424 in the driving device 242 works to drive the screw rod 2423 to rotate, thereby driving the entire lifting rod 241 to be lifted and lowered under the action of the limit rod 2422; automatic control can be achieved.

[0039] A mounting ring 13 is disposed on the outer periphery of the guide tube 5 , a sealing ring 14 is disposed at the end of the mounting ring 13 , and a sealing groove 15 matching the sealing ring 14 is disposed on the graphite pot body 21 .

[0040] In the present device, when the crucible 2 is rising, the upper pot edge of the crucible 2 will approach the lower end surface of the mounting ring 13 located on the outer periphery of the guide tube 5, until the upper pot edge of the crucible 2 contacts the lower end surface of the mounting ring 13 located on the outer periphery of the guide tube 5, and the sealing ring 14 will also be inserted into the sealing groove 15 located on the graphite pot body 21; thus, a closed space is formed, the size of the space is very small, the thermal disturbance is small, and the temperature is more uniform, which is conducive to the growth of silicon crystals; at the same time, when the closed space is formed, the top heating component 4 can be turned on, so that the temperature control will be more excellent, and the use effect will be better in the later stage of silicon material growth; at the same time, the side heating component 3 will also heat the entire crucible 2, and the stable control will be more excellent.

[0041] See also Figure 7 A rotating assembly 16 is also provided at the lower end of the crucible 2, and the rotating assembly 16 includes a mounting channel 161 arranged in the lifting rod 241, a rotating rod 162 is provided in the mounting channel 161, and a rotating disk 163 is fixed to the upper end of the rotating rod 162; a mounting groove is provided on the upper end surface of the tray 23, and the rotating disk 163 is arranged in the mounting groove through a bearing; a driven ring 164 is fixed to the outer periphery of the rotating rod 162, and a plurality of limit bars 165 are evenly distributed on the circumference of the driven ring 164, and limit grooves are provided between the limit bars 165; the rotating assembly 16 also includes a driving motor 166, and a reducer 167 is provided at the output end of the driving motor 166, and a gear 168 is provided at the output end of the reducer 167, and the teeth of the gear 168 are meshed with the limit grooves.

[0042] When silicon material grows, irregular crystals will be formed, so the temperature of the entire crystal cannot be completely uniform during heating. In order to address this problem, the device is provided with a rotating component 16; the rotating component 16 can control the entire crucible 2 to rotate, and at the same time drive the silicon material to rotate, so that the crystal can be subjected to a more balanced temperature.

[0043] The specific working principle of the rotating assembly 16 is as follows: the driving motor 166 drives the reducer 167, the reducer 167 drives the gear 168, and then the gear 168 applies a force to the limit bar 165, so that the driven ring 164 drives the entire rotating rod 162 to rotate, and the purpose of driving the crucible 2 to rotate is achieved through the rotating disk 163; Since heat dissipation needs to be prevented in this device, the internal volume of the entire device should not be too large. At the same time, the setting of the lifting device 24 occupies part of the space, so the rotating rod 162 is set in the installation path 161 inside the lifting rod 241. When the lifting rod 241 is raised or lowered, the entire rotating rod 162 will also be raised or lowered accordingly; in order not to affect the normal use of the rotating component 16, the present device is provided with a limit bar 165, which is equivalent to thickening the thickness of the gear.

[0044] The side heating assembly 3 in the device includes a second graphite cylinder, a plurality of second expansion gaps are arranged on the cylinder wall of the second graphite cylinder, and the second graphite cylinder is fixed to the furnace body 1 by bolts.

[0045] The side heating assembly 3 is a heating structure commonly used in graphite heaters. The second graphite tube is connected to an electrode. When powered on, the second graphite tube emits heat. The second expansion gap is to prevent the second graphite tube from expanding and deforming due to heat.

[0046] The inner wall of the furnace body 1 is provided with an upper insulation ring 17, a middle insulation ring 18, and a lower insulation ring 19; the middle insulation ring 18 is arranged between the upper insulation ring 17 and the lower insulation ring 19, and the upper insulation ring 17, the middle insulation ring 18, and the lower insulation ring 19 are made of graphite felt.

[0047] The insulation ring in the device is divided into three sections, namely, an upper insulation ring 17, a middle insulation ring 18, and a lower insulation ring 19; the upper insulation ring 17 and the lower insulation ring 19 have the same thickness and are larger than the middle insulation ring 18. This arrangement is mainly to take into account the problem of hot air accumulation.

[0048] The above description is only a specific embodiment of the present invention, but the technical features of the present invention are not limited thereto. Any changes or modifications made by any technician in the field of the present invention are included in the patent scope of the present invention.

Claims

1. A graphite heater, characterized in that: The invention comprises a furnace body (1), a crucible (2) arranged in the furnace body (1), and a heating structure for heating the crucible (2); wherein the heating structure is composed of a side heating component (3) and a top heating component (4); the top heating component (4) comprises a guide tube (5), and the tube body of the guide tube (5) extends into the furnace body (1).

2. The graphite heater according to claim 1, characterized in that: The side wall of the guide tube (5) is provided with a first graphite tube (6), and the first graphite tube (6) is provided with a plurality of first expansion gaps; the bottom of the guide tube (5) is provided with a heat collecting annular groove (7), and the groove wall of the heat collecting annular groove (7) is arranged inclined.

3. The graphite heater according to claim 2, characterized in that: A first graphite ring (8) is arranged at the bottom of the heat collecting ring groove (7), and a second graphite ring (9) is arranged at the wall of the heat collecting ring groove (7); the first graphite ring (8) and the second graphite ring (9) are integrally formed.

4. The graphite heater according to claim 3, characterized in that: There are three heat collecting annular grooves (7), the groove width of which gradually decreases from the inside to the outside, and a circular groove (10) is arranged in the middle of the bottom of the guide tube (5), the groove wall of the circular groove (10) is arranged obliquely, a graphite disk (11) is arranged at the groove bottom of the circular groove (10), and the groove wall of the circular groove (10) is also arranged with the second graphite ring (9).

5. The graphite heater according to claim 4, characterized in that: Two adjacent second graphite rings (9) are connected via a graphite plate (12).

6. The graphite heater according to claim 5, characterized in that: The crucible (2) comprises a graphite pot body (21) and a quartz pot body (22) arranged in the graphite pot body (21); a tray (23) is arranged at the lower end of the graphite pot body (21); a lifting device (24) is arranged at the lower end of the tray (23); the lifting device (24) comprises a lifting rod (241) and a driving device (242) for driving the lifting rod (241) to move; the driving device (242) comprises mounting plates (2421) arranged at both sides of the end of the lifting rod (241); a limit rod (2422) is arranged in one of the mounting plates (2421); a screw rod (2423) is threadedly connected in the other mounting plate (2421); a motor (2424) is arranged at the end of the screw rod (2423).

7. The graphite heater according to claim 6, characterized in that: A mounting ring (13) is provided on the outer periphery of the guide tube (5), a sealing ring (14) is provided at the end of the mounting ring (13), and a sealing groove (15) matching the sealing ring (14) is provided on the graphite pot body (21).

8. The graphite heater according to claim 7, characterized in that: A rotating assembly (16) is also provided at the lower end of the crucible (2), the rotating assembly (16) comprising a mounting path (161) arranged in the lifting rod (241), a rotating rod (162) being provided in the mounting path (161), and a rotating disk (163) being fixed to the upper end of the rotating rod (162); a mounting groove is provided on the upper end surface of the tray (23), and the rotating disk (163) is arranged in the mounting groove via a bearing; a driven ring (164) is fixed to the outer circumference of the rotating rod (162), a plurality of limit bars (165) are evenly distributed on the circumference of the driven ring (164), and limit grooves are provided between the limit bars (165); the rotating assembly (16) further comprises a driving motor (166), a reducer (167) is provided at the output end of the driving motor (166), a gear (168) is provided at the output end of the reducer (167), and the teeth of the gear (168) are meshed with the limit grooves.

9. The graphite heater according to claim 1, characterized in that: The side heating assembly (3) comprises a second graphite cylinder, a plurality of second expansion gaps are arranged on the cylinder wall of the second graphite cylinder, and the second graphite cylinder is fixed to the furnace body (1) by means of bolts.

10. The graphite heater according to claim 1, characterized in that: An upper thermal insulation ring (17), a middle thermal insulation ring (18), and a lower thermal insulation ring (19) are arranged on the inner wall of the furnace body (1); the middle thermal insulation ring (18) is arranged between the upper thermal insulation ring (17) and the lower thermal insulation ring (19); and the upper thermal insulation ring (17), the middle thermal insulation ring (18), and the lower thermal insulation ring (19) are made of graphite felt.

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