High temperature and high pressure ingot casting furnace for crystal materials and ingot casting method thereof

Abstract

The present invention discloses a high-temperature and high-pressure ingot casting furnace for crystal materials, comprising a furnace frame, a furnace body arranged on the furnace frame, a heat preservation device, a crucible assembly and a heater, wherein the heat preservation device comprises a heat preservation cover and a bottom heat preservation plate, and the heater comprises a top heating body and a power supply support foot, wherein the power supply support foot extends from the bottom of the heat preservation cover to the side wall of the furnace body through the gap between the outside of the crucible assembly and the heat preservation cover, and then is electrically connected to a heating power supply arranged outside the furnace body. By arranging the heat preservation cover to extend downward to the outside of the bottom heat preservation plate on all sides, the high-temperature and high-pressure gas inside the heat preservation device and the low-temperature gas outside the heat preservation device are effectively prevented from generating high-speed cold and heat convection, and the high-temperature gas is prevented from escaping, thereby ensuring the stability of the high-temperature and high-pressure thermal forming and reducing energy consumption; at the same time, the service life of the equipment is extended. The present invention also discloses an ingot casting method for a high-temperature and high-pressure ingot casting furnace for crystal materials.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and in particular to a high-temperature and high-pressure ingot casting furnace for crystal materials and an ingot casting method thereof. Background Art

[0002] The ingot casting technology of quartz and other crystalline materials is a key technology in semiconductor technology, especially in the preparation of silicon crystalline materials. Silicon is one of the most important raw materials in the semiconductor industry, and ingot casting technology is one of the key steps in converting silicon ore materials into a form that can be used to manufacture semiconductor devices and optical devices. Ingot casting technology is mainly used to produce polycrystalline silicon blocks and silicon dioxide crystal blocks, which are then further processed into various component parts. The ingot casting process can remove bubbles and impurities in the crystal material to form a polycrystalline silicon ingot with a certain geometric shape.

[0003] In the prior art, Chinese patent CN115072974A (September 20, 2022) "A casting furnace and casting method for producing quartz ingots by electric melting" discloses an ingot casting furnace for producing quartz ingots by electric melting, including a furnace body, a material frame, an insulation layer, a crucible assembly and a vacuum system. The material frame is arranged in the furnace body, the insulation layer is arranged inside the material frame to maintain the temperature, and the crucible is arranged inside the insulation layer to carry the quartz material. Among them, the side of the crucible assembly is composed of insulation bricks, insulation sand and a metal cylinder from the inside to the outside, and the bottom of the crucible assembly is composed of insulation bricks and a metal bottom plate from top to bottom; the metal cylinder and the metal bottom plate are split structures, and there is a gap between the two; the metal cylinder and the metal bottom plate are provided with a certain number of openings to speed up the vacuuming speed, improve production efficiency, and reduce bubbles and gas line residues in the quartz ingot. Under high temperature and high pressure process environment, gas will penetrate into the insulation bricks and insulation sand through the openings on the metal cylinder and the metal bottom plate. When the gas pressure in the furnace exceeds a certain pressure value, the heat convection becomes more intense, and the heat inside the crucible is quickly taken away by the high-pressure cold gas, causing the internal temperature to drop significantly, which cannot meet the process temperature requirements.

[0004] In addition, in traditional ingot casting equipment, the insulation device usually includes a split structure of an insulation tube and an insulation cover, the heating element and the crucible assembly are arranged in the insulation tube, and the insulation sealing surface between the insulation cover and the insulation tube is usually arranged on the upper part of the crucible assembly. In a high-temperature and high-pressure process environment, since the high-temperature gas floats to the insulation cover, the high-temperature gas can easily seep out of the insulation device from the insulation sealing surface, and generate strong heat convection with the low-temperature gas outside the insulation device, causing the high-temperature gas inside the insulation device to leak quickly to the outside, resulting in the failure of the insulation seal. More energy is required to make the temperature inside the insulation device reach the high temperature required by the process, resulting in a large amount of energy waste; at the same time, the leaked high-temperature gas can easily damage the components between the furnace body and the insulation device, such as the cooling system, vacuum system, etc. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a high-temperature and high-pressure ingot casting furnace for crystal materials with reliable insulation and sealing, aiming at the problem that the ingot casting furnace for crystal materials in the prior art is prone to failure of insulation sealing due to strong heat convection between the high-temperature gas in the insulation device and the external low-temperature gas under high-temperature process environment.

[0006] The technical solution to the technical problem of the present invention is: construct a high-temperature and high-pressure ingot casting furnace for crystal materials, comprising a furnace frame, a furnace body arranged on the furnace frame, a heat preservation device, a crucible assembly and a heater, the heat preservation device comprising a heat preservation cover arranged above the crucible assembly, a bottom heat preservation plate arranged at the bottom of the crucible assembly, the heat preservation cover extending downward to the outside of the bottom heat preservation plate around; the heater comprises a top heating body arranged between the top of the crucible assembly and the heat preservation cover, at least two power support feet are evenly distributed around the top heating body, one end of the power support foot is electrically connected to the top heating body, and the other end extends from the bottom of the heat preservation cover to the side wall of the furnace body through the gap between the outside of the crucible assembly and the heat preservation cover, and then is electrically connected to the heating power supply arranged outside the furnace body.

[0007] Furthermore, the thermal insulation cover includes a thermal insulation tube, a thermal insulation layer of the thermal insulation cover arranged on the entire inner surface of the thermal insulation tube, and a thermal insulation cover protective layer coated on the inner surface of the thermal insulation layer of the thermal insulation tube; it can prevent high-temperature and high-pressure gas from penetrating into the thermal insulation layer, prevent vaporized crystalline material from penetrating into the thermal insulation layer or reacting with the thermal insulation layer, and further extend the service life of the thermal insulation layer.

[0008] Furthermore, the top of the furnace body is also provided with a top temperature measuring device for detecting the top temperature of the inner side of the heat preservation cover, and the top of the heat preservation cover is provided with a first temperature measuring through hole, and the top temperature measuring device includes a first concentric cylinder embedded in the first temperature measuring through hole, a first temperature measuring tube inserted into the first concentric cylinder and extending through the top heating body to the top of the crucible assembly, and a first thermometer inserted into the first temperature measuring tube from the outside of the furnace body, and the bottom end of the first temperature measuring tube is closed and the top end is open; the top temperature measuring device can not only accurately detect the top temperature of the inner side of the heat preservation cover, but also prevent the low-temperature gas at the top of the heat preservation cover from passing through the first temperature measuring through hole and undergoing heat convection with the high-temperature gas at the bottom of the heat preservation cover under high pressure.

[0009] Furthermore, a sealing step matching the top surface of the heat preservation cover is provided at the top of the first temperature measuring tube, and an airtight seal is provided between the sealing step and the top surface of the heat preservation cover; a locking nut is provided on the first temperature measuring tube at the bottom surface of the heat preservation cover, further ensuring that the airtight seal at the first temperature measuring hole is reliable.

[0010] Furthermore, the crucible assembly includes an integrally formed crucible, a crucible isolation layer arranged on the inner side of the crucible, a crucible protective layer coated on the inner and outer surfaces of the crucible, and an isolation protective layer coated on the surface of the crucible isolation layer; the crucible protection layer can effectively prevent vaporized crystal material from penetrating into the crucible or reacting corrosively with the crucible, the isolation protective layer can prevent crystal material from penetrating into the crucible isolation layer, and the crucible isolation layer can prevent crystal material from directly separating from the crucible, making it convenient for the crystal material to separate from the crucible after forming an ingot.

[0011] Furthermore, the bottom insulation plate includes an insulation pallet, a pallet insulation layer fixed on the insulation pallet, and a bottom insulation protective layer coated on the inner and outer surfaces of the pallet insulation layer; the bottom insulation plate blocks the high-pressure and low-temperature gas at the bottom of the crucible assembly from directly exchanging heat with the crucible assembly, ensuring that the entire equipment can achieve high-temperature and high-pressure process conditions.

[0012] Furthermore, a accommodating groove is provided on the top of the support plate insulation layer, and the heater also includes a bottom heater arranged at the bottom of the crucible assembly, and the bottom heater includes a bottom heating body arranged in the accommodating groove, an electrode insulation tube embedded in the support plate insulation layer and the insulation support plate, and an induction electrode passing through the electrode insulation tube, and the top end of the induction electrode is electrically connected to the bottom heating body and the bottom end is electrically connected to the heating power supply outside the furnace body; the bottom heater can dissipate the waste heat at the bottom of the crucible assembly and improve the melting efficiency of the crystal material; at the same time, it can maintain the temperature of the bottom area of ​​the crucible assembly consistent with the temperature of other areas during the ingot casting stage, and will not affect the ingot quality due to temperature difference.

[0013] Furthermore, it also includes a first crucible support column that passes through the support plate insulation layer and the bottom heating body and is located between the top surface of the support plate insulation layer and the insulation support plate; so as to support the crucible assembly located on the top surface of the support plate insulation layer on the insulation support plate to ensure that the crucible assembly is effectively supported.

[0014] Furthermore, it also includes a second crucible support column arranged through the support plate insulation layer and the insulation support plate, the top end of the second crucible support column is flush with the top surface of the support plate insulation layer and the bottom end thereof extends to the inner wall of the furnace body; the entire crucible assembly is placed on the furnace body through the second crucible support column to further ensure that the crucible assembly is effectively supported.

[0015] Furthermore, it also includes a crucible lifting device arranged on the furnace frame, the furnace body includes a furnace shell and a lower furnace cover sealed at the lower end opening of the furnace shell by a locking device, the bottom insulation plate is positioned on the top surface of the lower furnace cover, the crucible lifting device includes a lifting slide plate arranged below the lower furnace cover, a connecting rod connected between the lifting slide plate and the lower furnace cover, a guide slide column vertically arranged on the furnace frame, a lifting screw rod vertically rotatably arranged on the furnace frame, and a driving motor driving the lifting screw rod to rotate forward and reversely, and a threaded hole matching the lifting screw rod thread is provided on the lifting slide plate; it is convenient to quickly adjust the position of the crucible assembly when loading or opening the furnace.

[0016] Another technical problem to be solved by the present invention is that the ingot casting method of the ingot casting furnace in the prior art is not suitable for the high temperature and high pressure ingot casting process, and provides an ingot casting method of a high temperature and high pressure ingot casting furnace for crystalline materials.

[0017] The technical solution of the technical problem of the present invention is: constructing a casting method of a high-temperature and high-pressure ingot casting furnace for a crystalline material, comprising the following steps:

[0018] S10. A high temperature and high pressure ingot furnace is provided for the crystalline material as described above;

[0019] S20. Furnace loading stage: placing the crystal raw material into the crucible assembly and closing the furnace body;

[0020] S30. Vacuuming stage: evacuating the furnace body so that the vacuum degree in the furnace body is less than a preset value and maintained;

[0021] S40. Preheating stage: Control the heater to heat the crucible assembly until the furnace temperature reaches 950-1000°C, and then fill the furnace with inert gas until the vacuum degree in the furnace reaches 25-30Pa;

[0022] S50. High temperature melting stage: the furnace temperature is raised to 1820-2000°C in stages, while the inert gas is continuously filled into the furnace body and the gas in the furnace body is discharged, and the vacuum degree in the furnace body is maintained at 25-30Pa;

[0023] S60. High-pressure shaping stage: Inert gas is charged into the furnace body to increase the pressure in the furnace body until the pressure in the furnace body reaches 1-2MPa, and the pressure is maintained for 2-3 hours; inert gas is continuously charged into the furnace body until the pressure in the furnace body reaches the preset process pressure value, and the pressure is maintained for 3-5 hours;

[0024] S70. Cooling annealing stage: cooling the furnace temperature to 1150-1250°C and maintaining the furnace temperature for 10-20 hours;

[0025] S80. Cool the furnace temperature to room temperature, open the furnace body, and take out the finished crystal ingot.

[0026] The high-temperature and high-pressure ingot casting furnace and the ingot casting method of the crystal material described in the present invention have the following beneficial effects: by arranging the four sides of the insulation cover to extend downward to the outside of the bottom insulation plate, the insulation cover can cover the entire crucible assembly inside the insulation cover, and the high-temperature gas generated by the crucible assembly can be controlled in the middle and upper area inside the insulation cover, effectively preventing the high-temperature and high-pressure gas inside the insulation device and the low-temperature gas outside the insulation device from generating cold and hot convection, effectively preventing the high-temperature gas from escaping, ensuring the stability of high-temperature and high-pressure thermal formation, and reducing energy consumption; at the same time, extending the service life of the equipment; by arranging a heater including a top heating body, and evenly arranging at least two power support feet around the top heating body, the power support feet pass through the gap between the outside of the crucible assembly and the insulation cover and extend from the bottom of the insulation cover to the side wall of the furnace body. Among them, the top heating body can realize the melting of the crystal material from top to bottom, which speeds up the melting speed; at the same time, the power-leading support feet are set to lead electricity from the bottom of the insulation cover to the top heating body, avoiding damage to the integrity of the insulation cover and preventing high-speed convection caused by opening holes required for the power-leading support feet on the insulation cover, further ensuring the stability of the high-temperature and high-pressure thermal field. At the same time, the power-leading support feet can support the top heating body, avoiding the need to set a positioning structure or positioning piece for the top heating body in the insulation cover, thus ensuring the integrity of the insulation cover. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a structural schematic diagram of a preferred embodiment of a high-temperature and high-pressure ingot casting furnace for crystal materials according to the present invention in a closed furnace state;

[0028] Figure 2 It is a schematic structural diagram of a preferred embodiment of a high-temperature and high-pressure ingot casting furnace for crystal materials according to the present invention in an open furnace state;

[0029] Figure 3 The figure is a schematic structural diagram of a heat preservation cover in a preferred embodiment of a high-temperature and high-pressure ingot casting furnace for crystal materials according to the present invention;

[0030] Figure 4 It is a schematic structural diagram of a crucible assembly in a preferred embodiment of a high-temperature and high-pressure ingot casting furnace for crystal materials according to the present invention;

[0031] Figure 5 Shown is a schematic structural diagram of a bottom heater in a preferred embodiment of a high-temperature and high-pressure ingot casting furnace for crystalline materials according to the present invention. DETAILED DESCRIPTION

[0032] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0033] It should also be noted that the directions or positional relationships indicated by terms such as “upper”, “lower”, “front”, “back”, “left”, “right”, “vertical”, “horizontal”, “top”, “bottom”, “inside” and “outside” are based on the directions or positional relationships shown in the accompanying drawings and are only for the convenience of describing the present invention and simplifying the description. They do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction. Therefore, they should not be understood as limiting the present invention.

[0034] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0035] like Figure 1 , 2As shown in Figures 3, 4 and 5, in a preferred embodiment of the high-temperature and high-pressure ingot casting furnace of the crystal material of the present invention, it mainly includes a furnace frame 1, a furnace body 10 arranged on the furnace frame 1, a heat preservation device 20, a crucible assembly 30 and a heater. The heat preservation device 20 is arranged in the furnace body 10, and the crucible assembly 30 and the heater are arranged in the heat preservation device 20. It is preferred that the furnace body 10 includes a furnace shell 11, an upper furnace cover 12 and a lower furnace cover 13, and the upper and lower furnace covers 13 are respectively sealed at the upper and lower openings of the furnace shell 11 through a locking mechanism 14. The heat preservation device 20 includes a heat preservation cover 21 and a bottom heat preservation plate 22, wherein the heat preservation cover 21 is arranged above the crucible assembly 30, the bottom heat preservation plate 22 is arranged at the bottom of the crucible assembly 30, and the four sides of the heat preservation cover 21 extend downward to the outside of the bottom heat preservation plate 22, that is, the four sides of the heat preservation cover 21 contain the crucible assembly 30 and the bottom heat preservation plate 22 inside, so that the heat preservation cover 21 as a whole is in the shape of a tube that is inverted on the crucible assembly 30. Specifically, the heat preservation cover 21 may include a heat preservation tube 23, a heat preservation cover insulation layer 24 and a heat preservation cover protection layer 25. The heat preservation tube 23 is preferably made of a hard heat preservation material resistant to high temperature and high pressure, and an integrated molding process is adopted to ensure that the entire heat preservation tube 23 has no obvious convection pores or obvious seams, so as to prevent the vaporized crystal material 2 from penetrating into the heat preservation cover insulation layer 24 through the gaps or seams. The heat preservation cover insulation layer 24 is arranged on the outer surface of the heat preservation tube 23, and the heat preservation cover protection layer 25 is coated and arranged on the inner surface of the heat preservation cover insulation layer 24, which is used to prevent the high temperature and high pressure airflow from penetrating into the heat preservation cover insulation layer 24, and prevent the vaporized crystal material from penetrating into the heat preservation cover insulation layer 24 or reacting with the heat preservation cover insulation layer 24 (corroding the insulation layer), thereby greatly extending the service life of the heat preservation cover insulation layer 24. The heat preservation cover protection layer 25 may be a SiC coating, or a protective layer made of a high temperature tungsten alloy material.

[0036] When high-pressure gas is charged into the furnace body 10, as the internal gas pressure increases, the low-temperature gas sinks to the bottom of the crucible assembly 30, and the heat exchange rate between the high-pressure low-temperature gas at the bottom of the crucible assembly 30 and the crucible assembly 30 is accelerated, causing the temperature at the bottom of the crucible assembly 30 to drop rapidly, and the drop rate will become faster and faster, resulting in the ingot casting process temperature requirement being unable to be met. Figure 1 , 2 As shown in Figures 5 and 6, in this preferred embodiment, the bottom insulation plate 22 is preferably provided including an insulation support plate 26, a support plate insulation layer 27 and a bottom insulation protection layer 28. Among them, the support plate insulation layer 27 is fixedly arranged above the insulation support plate 26, and the bottom insulation protection layer 28 is coated on the outer surface of the support plate insulation layer 27. By arranging the bottom insulation plate 22 at the bottom of the crucible assembly 30, the high-pressure and low-temperature gas at the bottom of the crucible assembly 30 is blocked from directly exchanging heat with the crucible assembly 30, thereby overcoming the problem of the rapid drop in the temperature at the bottom of the crucible assembly 30 under high pressure conditions, and ensuring that the entire equipment can achieve high-temperature and high-pressure process conditions.

[0037] like Figure 1 , 2 As shown in Figures 3 and 4, in this preferred embodiment, the heater is preferably provided including a top heater 41 and a bottom heater 50 to achieve heating of the crucible from top to bottom. Different from the conventional furnace body 10 in which the heater is arranged around the crucible, the upper and lower heating can heat the crystal raw material in the crucible from the upper and lower directions, thereby increasing the melting speed of the crystal material; at the same time, the space on the sides of the crucible is vacated for the heat preservation cover 21. Among them, the top heater 41 is arranged between the top of the crucible assembly 30 and the heat preservation cover 21, and at least two power-leading support legs 42 are evenly arranged around the top heater 41. One end of the power-leading support leg 42 is electrically connected to the top heater 41, and the other end passes through the gap between the outside of the crucible assembly 30 and the heat preservation cover 21 and extends from the bottom of the heat preservation cover 21 to the side wall of the furnace body 10, and is electrically connected to the heating power supply (not shown in the figure) arranged outside the furnace body 10. In this way, the power-leading support leg 42 can both energize the top heater 41 and support the top heater 41 between the top of the crucible assembly 30 and the heat preservation cover 21. It is best to coat the surface of the top heating body 41 and the power support pin 42 with a silicon carbide protective layer to prevent the vaporized crystal material from reacting and corroding them.

[0038] In order to monitor the temperature in the heat preservation device in real time, in the preferred embodiment, a top temperature measuring device 60 for detecting the top temperature of the inner side of the heat preservation cover 21 is preferably provided on the top of the furnace body 10 so as to adjust the operation of the top heating body 41. It is preferred to open a first temperature measuring through hole 20a on the top of the heat preservation cover 21, and set the top temperature measuring device 60 to include a first concentric cylinder 61, a first temperature measuring tube 62 and a first thermometer 63. Among them, the first concentric cylinder 61 is embedded in the first temperature measuring through hole 20a to prevent the crystal material from penetrating into the heat preservation cover insulation layer 24. The first temperature measuring tube 62 is inserted into the first concentric cylinder 61 and extends through the top heating body 41 to the top of the crucible assembly 30, and the first thermometer 63 is inserted into the first temperature measuring tube 62 from the outside of the furnace body. The bottom end of the first temperature measuring tube 62 is set to be closed and the top end is set to be open. In order to ensure that the gas in the furnace body 10 will not leak from the first temperature measuring through hole to the outside of the furnace body 10 in a high-pressure environment, a sealing step 62a is preferably provided at the top of the temperature measuring tube, the bottom surface of the sealing step 62a matches the top surface of the heat preservation cover 21, an air seal 64 is provided between the sealing step 62a and the top surface of the heat preservation cover 21, and a locking nut 65 is provided at the bottom surface of the first temperature measuring tube 62 located at the heat preservation cover 21. When the locking nut 65 is locked on the temperature measuring tube, the sealing step 62a presses the air seal 64 against the top surface of the heat preservation cover 21, thereby ensuring that the high-pressure gas cannot leak.

[0039] like Figure 1 , 2As shown in Figures 5 and 6, in this preferred embodiment, the heater further includes a bottom heater 50, and a receiving groove 22a is preferably provided on the bottom insulation plate 22 to accommodate the bottom heater 50. Specifically, the receiving groove 22a can be provided on the top of the support plate insulation layer 27, and the bottom heater 50 includes a bottom heating body 51, an electrode insulation tube 52, and an electric lead electrode 53. Among them, the bottom heating body 51 is provided in the receiving groove 22a, and the electrode insulation tube 52 is embedded on the insulation support plate 26 and the support plate insulation layer 27, and the electric lead electrode 53 is passed through the electrode insulation tube 52, so that the top end of the electric lead electrode 53 is electrically connected to the bottom heating body 51 and the bottom end is electrically connected to the external heating power supply (not shown in the figure) of the furnace body 10. Specifically, an insulating cylinder can be embedded in the lower furnace cover 13, and the electric lead electrode 53 is passed through the insulating cylinder to be electrically connected to the external heating power supply.

[0040] In order to detect the temperature of the bottom of the crucible, a bottom temperature measuring device 80 can also be set on the bottom insulation plate 22. Referring to the setting of the top temperature measuring device 60 mentioned above, the bottom temperature measuring device 80 can be set to also include a second concentric cylinder embedded in the bottom insulation plate 22, and a second temperature measuring tube inserted into the second concentric cylinder and extending through the bottom heating body 51 to the bottom of the crucible assembly 30. The second thermometer is inserted into the second temperature measuring tube to detect the temperature of the bottom of the crucible assembly 30 so as to adjust the operation of the bottom heating body 51.

[0041] like Figure 1 , 2 As shown in Figures 4 and 5, in this preferred embodiment, the crucible assembly 30 is preferably provided to include a crucible 31, a crucible isolation layer 32, a crucible protection layer 33 and an isolation protection layer 34. The crucible 31 can be provided in a cylindrical shape, and the crucible 31 is provided to be integrally formed, that is, the bottom and the circumferential side of the cylindrical crucible 31 are seamlessly connected to prevent the high-temperature and high-pressure crystal material from penetrating from the crucible isolation layer 32 to the crucible surface. The crucible isolation layer 32 is provided on the inner side of the crucible, and the crucible isolation layer 32 is preferably made of zirconium oxide material, which can not only isolate the crucible 31 from the crystal material 2, and prevent the crystal material 2 from directly contacting the crucible 31, but also can achieve heat preservation for the internal crystal material 2, and prevent the molten crystal material 2 from directly conducting heat to the crucible 31. The crucible protection layer 33 is coated on the inner and outer surfaces of the crucible to prevent vaporized crystal materials from penetrating into the crucible; the isolation protection layer 34 is coated on the surface of the crucible isolation layer 32 to prevent the crystal materials from directly contacting the crucible isolation layer 32, to prevent the inner crucible isolation layer 32 from being damaged by the crystal materials, and to avoid material waste. The crucible protection layer 33 can be made of silicon carbide coating, and the isolation protection layer 34 can be made of high-temperature tungsten alloy material.

[0042] In the above embodiment, the first crucible support column 35 is preferably provided between the top surface of the support plate insulation layer 27 and the insulation support plate 26, and the first crucible support column 35 passes through the support plate insulation layer 27 and the bottom heating body 51. Since the bottom of the crucible assembly 30 is in direct contact with the support plate insulation layer 27, the relative position between the insulation support plate 26 and the bottom of the crucible is positioned.

[0043] In the above embodiment, it is preferred that a second crucible support column 36 is disposed between the top surface of the support plate insulation layer 27 and the bottom of the inner wall of the furnace body 10, the top end of which directly contacts the bottom of the crucible assembly 30, and the bottom end of which extends through the support plate insulation layer 27 and the insulation support plate 26 to the inner bottom of the furnace body 10. Specifically, the bottom end of the second crucible support column 36 directly extends to the lower furnace cover 13.

[0044] In the above embodiment, a crucible lifting device for controlling the crucible assembly 30 to float up and down may also be provided. The crucible lifting device includes a lifting slide 71 provided below the lower furnace cover 13, a connecting rod 72 connected between the lifting slide 71 and the lower furnace cover 13, a guide slide 73 vertically provided on the furnace frame 1, a lifting screw 74 vertically rotating on the furnace frame 1, and a driving motor (not shown in the figure) for driving the lifting screw 74 to rotate forward or reversely. The driving motor drives the lifting screw 74 to rotate forward or reversely, driving the lifting slide 71 to rise or fall along the guide slide 73, and driving the lower furnace cover 13 to rise and fall through the connecting rod 72, so that the crucible assembly 30 and the bottom insulation board 22 connected to the upper furnace cover 12 through the first crucible support column 35 and / or the second crucible support column 36 are lifted and lowered, so as to load or remove the ingot.

[0045] In this preferred embodiment, a process gas path system (not shown in the figure) may also be included to control the vacuum degree in the furnace body 10 and to fill the furnace body 10 with inert gas; a water cooling system (not shown in the figure) may also be provided as needed to accelerate the cooling speed of the furnace body 10 after the preparation of the silicon carbide single crystal is completed.

[0046] In a preferred embodiment of the process for preparing a silicon carbide single crystal according to the present invention, the following steps are included:

[0047] S10. A high temperature and high pressure ingot furnace is provided for the crystalline material as described above;

[0048] S20. Furnace loading stage: placing the crystal raw material into the crucible assembly and closing the furnace body;

[0049] S30. Vacuuming stage: evacuating the furnace body so that the vacuum degree in the furnace body is less than a preset value and maintained;

[0050] S40. Preheating stage: Control the heater to heat the crucible assembly until the furnace temperature reaches 950-1000°C, and then fill the furnace with inert gas until the vacuum degree in the furnace reaches 25-30Pa;

[0051] S50. High temperature melting stage: the furnace temperature is raised to 1820-2000°C in stages, while the inert gas is continuously filled into the furnace body and the gas in the furnace body is discharged, and the vacuum degree in the furnace body is maintained at 25-30Pa;

[0052] S60. High-pressure shaping stage: Inert gas is charged into the furnace body to increase the pressure in the furnace body until the pressure in the furnace body reaches 1-2MPa, and the pressure is maintained for 2-3 hours; inert gas is continuously charged into the furnace body until the pressure in the furnace body reaches the preset process pressure value, and the pressure is maintained for 3-5 hours;

[0053] S70. Cooling annealing stage: cooling the furnace temperature to 1150-1250°C and maintaining the furnace temperature for 10-20 hours;

[0054] The furnace temperature was cooled to room temperature, the furnace body was opened, and the finished crystal ingot was taken out.

[0055] In the furnace loading stage of step S20, the driving motor can be used to control the crucible lifting device to lower the crucible assembly to the outside of the furnace body, and then add an appropriate amount of crystal raw material into the crucible assembly; then the crucible lifting device is controlled to raise the crucible assembly into the furnace body, and then the lower furnace cover and the upper furnace cover are locked at the upper and lower ends of the furnace shell by the locking mechanism, thereby closing the furnace body.

[0056] During the vacuuming stage of step S30, the preset value of the vacuum degree in the furnace body may be 8-12Pa.

[0057] In the high temperature melting stage of step S50, the temperature rising stage can be divided into the following stages:

[0058] S51. Control the resistance heater to raise the chamber temperature in the furnace to 1750-1780°C; continuously fill the furnace with inert gas and exhaust the gas in the furnace to maintain the vacuum degree in the furnace at 25-30Pa; maintain the constant temperature for 1-2 hours.

[0059] S52. Control the resistance heater to raise the temperature of the chamber inside the furnace to 1800-1810°C; continuously fill the furnace with inert gas and exhaust the gas inside the furnace to maintain the vacuum degree inside the furnace at 25-30Pa; maintain the constant temperature for 20-30 hours.

[0060] S53. Control the resistance heater to raise the temperature of the chamber inside the furnace to 1820-2000°C; continuously fill the furnace with inert gas and exhaust the gas inside the furnace to maintain the vacuum degree inside the furnace at 25-30Pa; maintain the constant temperature for 10-20 hours.

[0061] Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in the field without making any creative work, any modifications, equivalent substitutions, improvements, etc. made should be included in the protection scope of the present invention.

Claims

1. A high-temperature and high-pressure ingot casting furnace for crystalline materials, comprising a furnace frame, a furnace body arranged on the furnace frame, a heat preservation device, a crucible assembly and a heater, characterized in that: The heat preservation device comprises a heat preservation cover arranged above the crucible assembly and a bottom heat preservation plate arranged at the bottom of the crucible assembly, and the four sides of the heat preservation cover extend downward to the outside of the bottom heat preservation plate; The heater includes a top heating body arranged between the top of the crucible assembly and the heat-insulating cover, at least two power-leading support pins are evenly distributed around the top heating body, one end of the power-leading support pin is electrically connected to the top heating body, and the other end passes through the gap between the outside of the crucible assembly and the heat-insulating cover and extends from the bottom of the heat-insulating cover to the side wall of the furnace body, and then is electrically connected to a heating power supply arranged outside the furnace body.

2. The high temperature and high pressure ingot casting furnace for crystal materials according to claim 1, characterized in that: The heat-insulating cover comprises a heat-insulating cylinder, a heat-insulating layer of the heat-insulating cover arranged on the entire inner surface of the heat-insulating cylinder, and a heat-insulating cover protective layer coated on the inner surface of the heat-insulating layer of the heat-insulating cylinder.

3. The high temperature and high pressure ingot casting furnace for crystal materials according to claim 1, characterized in that: The top of the furnace body is also provided with a top temperature measuring device for detecting the top temperature inside the heat preservation cover. The top of the heat preservation cover is provided with a first temperature measuring through hole. The top temperature measuring device includes a first concentric cylinder embedded in the first temperature measuring through hole, a first temperature measuring tube inserted into the first concentric cylinder and extending through the top heating body to above the crucible assembly, and a first thermometer inserted into the first temperature measuring tube from the outside of the furnace body. The bottom end of the first temperature measuring tube is closed and the top end is open.

4. The high temperature and high pressure ingot casting furnace for crystal materials according to claim 3, characterized in that: A sealing step matching the top surface of the heat preservation cover is provided at the top of the first temperature measuring tube, and an airtight seal is provided between the sealing step and the top surface of the heat preservation cover; a locking nut is provided on the bottom surface of the heat preservation cover on the first temperature measuring tube.

5. The high temperature and high pressure ingot casting furnace for crystal materials according to claim 1, characterized in that: The crucible assembly comprises an integrally formed crucible, a crucible isolation layer arranged inside the crucible, a crucible protection layer coated on the inner and outer surfaces of the crucible, and an isolation protection layer coated on the surface of the crucible isolation layer.

6. The high temperature and high pressure ingot casting furnace for crystal materials according to claim 1, characterized in that: The bottom insulation board comprises an insulation support board, a support board insulation layer fixed on the insulation support board, and a bottom insulation protective layer coated on the outer surface of the support board insulation layer.

7. The high temperature and high pressure ingot casting furnace for crystal materials according to claim 6, characterized in that: A accommodating groove is provided on the top of the support plate insulation layer, and the heater also includes a bottom heater arranged at the bottom of the crucible assembly, and the bottom heater includes a bottom heating body arranged in the accommodating groove, an electrode insulation tube embedded in the support plate insulation layer and the insulation support plate, and an electric lead electrode passing through the electrode insulation tube, wherein the top end of the electric lead electrode is electrically connected to the bottom heating body and the bottom end thereof is electrically connected to the heating power supply outside the furnace body.

8. The high temperature and high pressure ingot casting furnace for crystal materials according to claim 7, characterized in that: It also includes a first crucible support column that passes through the support plate insulation layer and the bottom heating body and is located between the top surface of the support plate insulation layer and the insulation support plate.

9. The high temperature and high pressure ingot casting furnace for crystal materials according to claim 6, characterized in that: It also includes a second crucible support column that passes through the support plate insulation layer and the insulation support plate, wherein the top end of the second crucible support column is flush with the top surface of the support plate insulation layer and the bottom end thereof extends to the inner side wall of the furnace body.

10. The high temperature and high pressure ingot casting furnace for crystal materials according to claim 1, characterized in that: The crucible lifting device also includes a crucible lifting device arranged on the furnace frame, the furnace body includes a furnace shell and a lower furnace cover sealed at the lower end opening of the furnace shell by a locking device, the bottom insulation plate is positioned on the top surface of the lower furnace cover, the crucible lifting device includes a lifting slide plate arranged below the lower furnace cover, a connecting rod connected between the lifting slide plate and the lower furnace cover, a guide slide column vertically arranged on the furnace frame, a lifting screw rod vertically rotatably arranged on the furnace frame, and a driving motor driving the lifting screw rod to rotate forward and reversely, and a threaded hole matching the thread of the lifting screw rod is opened on the lifting slide plate.

11. A method for casting an ingot of a crystalline material using a high temperature and high pressure ingot casting furnace, characterized in that: The following steps are involved: S10. A high temperature and high pressure ingot casting furnace is provided for the crystalline material as claimed in any one of claims 1 to 10; S20. Furnace loading stage: placing the crystal raw material into the crucible assembly and closing the furnace body; S30. Vacuuming stage: evacuating the furnace body so that the vacuum degree in the furnace body is less than a preset value and maintained; S40. Preheating stage: Control the heater to heat the crucible assembly until the furnace temperature reaches 950-1000°C, and then fill the furnace with inert gas until the vacuum degree in the furnace reaches 25-30Pa; S50. High temperature melting stage: the furnace temperature is raised to 1820-2000°C in stages, while the inert gas is continuously filled into the furnace body and the gas in the furnace body is discharged, and the vacuum degree in the furnace body is maintained at 25-30Pa; S60. High-pressure ingot casting stage: Inert gas is charged into the furnace body to increase the pressure in the furnace body until the pressure in the furnace body reaches 1-2MPa, and the pressure is maintained for 2-3 hours; inert gas is further charged into the furnace body until the pressure in the furnace body reaches the preset process pressure value, and the pressure is maintained for 3-5 hours; S70. Cooling annealing stage: cooling the furnace temperature to 1150-1250°C and maintaining the furnace temperature for 10-20 hours; S80. Cool the furnace temperature to room temperature, open the furnace body, and take out the finished crystal ingot.

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