Single crystal growth furnace and single crystal preparation method

Abstract

The invention provides a single crystal growth furnace and a single crystal preparation method, and belongs to the technical field of aluminum nitride single crystal preparation, the single crystal growth furnace comprises a furnace body, a tungsten-molybdenum thermal insulation body, a crucible hoisting cylinder and a tungsten crucible; the tungsten-molybdenum heat preservation body is arranged in the furnace body, an annular first containing cavity is formed between the tungsten-molybdenum heat preservation body and the inner circumferential wall of the furnace body, and a heater is arranged in the tungsten-molybdenum heat preservation body. The crucible hoisting cylinder is arranged in the second accommodating cavity, and the upper end of the crucible hoisting cylinder upwards extends out of the second accommodating cavity and is limited on the tungsten-molybdenum heat preservation body; a heat insulation assembly is arranged in the crucible hoisting barrel; the tungsten crucible is arranged in the second accommodating cavity and is arranged below the crucible hoisting barrel; the upper end of the tungsten crucible upwards extends into the crucible hoisting barrel and is connected with the heat insulation assembly; aluminum nitride seed crystals and aluminum nitride powder are arranged in the tungsten crucible, and the aluminum nitride powder is arranged below the crucible hoisting barrel; the single crystal preparation method adopts the single crystal growth furnace. The single crystal growth furnace and the single crystal preparation method provided by the invention are good in thermal insulation effect, simple to operate, long in service life and low in cost.

Description

Technical Field

[0001] The present invention belongs to the technical field of aluminum nitride single crystal preparation, and more specifically, relates to a single crystal growth furnace and a single crystal preparation method. Background Art

[0002] The physical vapor transport method uses high temperature to sublime solid raw materials into gas phase, and under the driving force of temperature difference, the gas phase components are transported to the position of the seed crystal at a lower temperature, where the gas phase components re-condense at the low temperature; in the process of preparing single crystal aluminum nitride through a crucible and a growth furnace, aluminum nitride powder is placed in the high temperature zone, and high-quality aluminum nitride seeds are placed in the relatively low temperature zone, and the temperature difference and concentration difference in the physical vapor transport method are used as the driving force to grow single crystal aluminum nitride.

[0003] To promote the growth of single crystal aluminum nitride, a large temperature difference needs to be maintained between the aluminum nitride powder and the aluminum nitride seed crystal, so this temperature difference is often achieved through the design of the heat preservation structure; in the prior art, high-purity tungsten is used for heat preservation, and combined with the structure of the lower flange lifting, the repeated disassembly and assembly of the tungsten heat preservation structure above the high-temperature furnace can be avoided. However, this heat preservation structure is complex, difficult to manufacture, has a short service life, and is difficult to maintain, so the cost of the equipment is relatively high. Summary of the Invention

[0004] The purpose of the present invention is to provide a single crystal growth furnace and a single crystal preparation method, aiming to solve the technical problems of the existing single crystal growth furnace with complex heat preservation structure, difficult manufacturing, short service life, difficult maintenance, and high cost.

[0005] To achieve the above purpose, the technical solution adopted by the present invention is:

[0006] In the first aspect, a single crystal growth furnace is provided, including:

[0007] A furnace body with an accommodation space inside;

[0008] A tungsten-molybdenum heat preservation body placed in the accommodation space, and a circular first accommodation cavity is formed between the tungsten-molybdenum heat preservation body and the inner peripheral wall of the furnace body, and a cooling medium is used to be introduced into the first accommodation cavity; a second accommodation cavity is provided in the tungsten-molybdenum heat preservation body, and a heater is provided in the second accommodation cavity;

[0009] A crucible hoisting cylinder is arranged in the second accommodation cavity, and the upper end of the crucible hoisting cylinder extends upward out of the second accommodation cavity and is limited on the tungsten-molybdenum heat preservation body; a heat insulation assembly is arranged in the crucible hoisting cylinder in a circular shape along its inner peripheral wall; and

[0010] A tungsten crucible is disposed in the second accommodating cavity and is placed below the crucible hoisting cylinder; the upper end of the tungsten crucible extends upward into the crucible hoisting cylinder and is connected to the heat insulation component; an aluminum nitride seed crystal and aluminum nitride powder are arranged in the tungsten crucible at intervals in the vertical direction, and the aluminum nitride powder is placed below the crucible hoisting cylinder.

[0011] Compared with the prior art, the solution shown in the embodiment of the present application can hoist the tungsten crucible in the tungsten-molybdenum heat insulation body through the crucible hoisting cylinder, and form a heating space for heating the aluminum nitride powder outside the heater through the tungsten-molybdenum heat insulation body. Then, through the heat insulation component placed in the crucible hoisting cylinder, a heat insulation space is formed at the upper end of the tungsten crucible to form a relatively low-temperature area at the aluminum nitride seed crystal; in the present application, the above heat insulation component is used to increase the temperature difference in the vertical direction of the tungsten crucible, so that a temperature difference is formed between the aluminum nitride seed crystal and the aluminum nitride powder, and the sublimation and condensation processes of the aluminum nitride raw material occur in a space independent of the heating area, which can effectively avoid the adhesion of the tungsten-molybdenum heat insulation body caused by the deposition of the aluminum nitride raw material and the difficulty in the disassembly process, and can effectively extend the service life of the single crystal growth furnace; the single crystal growth furnace provided in the present application has good heat insulation effect, simple structure, low disassembly and installation operation difficulty, long service life, and low processing and use costs.

[0012] In combination with the first aspect, in a possible implementation manner, a first hoisting plate arranged in a ring shape is provided at the top of the tungsten crucible, and the first hoisting plate extends along the radial direction of the crucible hoisting cylinder and penetrates into the heat insulation component.

[0013] In some embodiments, the heat insulation component includes:

[0014] An upper heat insulation ring is placed above the first hoisting plate and is arranged around the axis of the crucible hoisting cylinder;

[0015] A lower heat insulation ring is placed between the first hoisting plate and the bottom wall of the crucible hoisting cylinder and is arranged around the outer peripheral wall of the tungsten crucible;

[0016] Wherein, both the lower heat insulation ring and the upper heat insulation ring are in the shape of a ring plate extending along the axial direction of the tungsten crucible; and the lower heat insulation ring and the upper heat insulation ring enclose a first heat insulation gap.

[0017] Exemplarily, the heat insulation component further includes a heat insulation ring piece arranged above the upper heat insulation ring. The heat insulation ring piece extends horizontally along the radial direction of the tungsten crucible and is fixed to the inner peripheral wall of the crucible hoisting cylinder; wherein, a second heat insulation gap is provided at the center of the heat insulation ring piece.

[0018] Exemplarily, the radial dimension of the second heat insulation gap is smaller than the radial dimension of the first heat insulation gap, and the radial dimension of the second heat insulation gap is smaller than the radial dimension of the tungsten crucible.

[0019] In some embodiments, multiple layers of the upper heat insulation ring are provided, and the multiple layers of the upper heat insulation ring are arranged at intervals inside and outside in the radial direction of the tungsten crucible; multiple layers of the lower heat insulation ring are provided, and the multiple layers of the lower heat insulation ring are arranged at intervals inside and outside in the radial direction of the tungsten crucible; multiple layers of the heat insulation ring plates are provided, and the multiple layers of the heat insulation ring plates are arranged at intervals above and below in the axial direction of the tungsten crucible.

[0020] In combination with the first aspect, in a possible implementation manner, a second lifting plate arranged in a ring shape is provided at the top of the crucible lifting cylinder, the second lifting plate extends horizontally in the radial direction of the crucible lifting cylinder, and is limited at the top of the tungsten-molybdenum heat insulation body.

[0021] In some embodiments, a support ring is provided between the bottom of the second lifting plate and the top of the tungsten-molybdenum heat insulation body, and the support ring is arranged around the outer peripheral wall of the crucible lifting cylinder.

[0022] In combination with the first aspect, in a possible implementation manner, the tungsten-molybdenum heat insulation body includes a heat insulation layer surrounding the second accommodation cavity, and a molybdenum tray placed on the top of the heat insulation layer; the upper end of the crucible lifting cylinder is limited on the molybdenum tray.

[0023] In a second aspect, the present invention further provides a single crystal preparation method, which is prepared by using the single crystal growth furnace, and the single crystal preparation method includes the following steps:

[0024] S1. Place the aluminum nitride seed crystal and the aluminum nitride powder corresponding to each other up and down in the tungsten crucible, determine the specifications of the heat insulation assembly according to the size of the aluminum nitride seed crystal, and assemble the heat insulation assembly and the tungsten crucible into the crucible lifting cylinder to form an aluminum nitride growth structure;

[0025] S2. Place the aluminum nitride growth structure in the second accommodation cavity, and use nitrogen to displace the air in the single crystal growth furnace;

[0026] S3. Keep the pressure in the single crystal growth furnace at 500 - 800 mbar, and gradually raise the temperature in the single crystal growth furnace from room temperature to 2200 - 2300 °C within a preset time period, and then keep the temperature and pressure unchanged and continue for 120 h to grow aluminum nitride single crystals.

[0027] Since the single crystal preparation method provided in this application is prepared by using the above single crystal growth furnace, it has all the beneficial effects of the above single crystal growth furnace, has good heat insulation effect, high quality of the prepared single crystal product, low difficulty in the operation process, and low processing and use costs. Description of the Drawings

[0028] To more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the accompanying drawings required for use in the embodiments or the description of the prior art. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other accompanying drawings can be obtained based on these drawings.

[0029] Figure 1 Schematic structural diagram of a single crystal growth furnace provided by an embodiment of the present invention;

[0030] Figure 2 Schematic diagram of an aluminum nitride growth structure provided by an embodiment of the present invention Figure 1 ;

[0031] Figure 3 Schematic diagram of an aluminum nitride growth structure provided by an embodiment of the present invention Figure 2 ;

[0032] Figure 4 Schematic diagram of the temperature distribution of a partition structure provided by an embodiment of the present invention;

[0033] Figure 5 Schematic diagram of the temperature distribution without a partition structure provided by an embodiment of the present invention.

[0034] In the figure: 1. Furnace body; 11. First accommodation cavity; 2. Tungsten-molybdenum heat preservation body; 21. Second accommodation cavity; 22. Molybdenum tray; 23. Heat preservation layer; 3. Crucible hoisting cylinder; 31. Second hoisting plate; 32. Support ring; 4. Heat insulation component; 41. Upper heat insulation ring; 42. Lower heat insulation ring; 43. Heat insulation ring piece; 44. First heat insulation gap; 45. Second heat insulation gap; 5. Tungsten crucible; 51. First hoisting plate; 52. Tungsten substrate; 53. Aluminum nitride seed crystal; 54. Aluminum nitride powder; 6. Heater. Detailed implementation manners

[0035] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention clearer and more understandable, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0036] It should be noted that when an element is referred to as being "disposed on" another element, it can be directly on the other element or indirectly on the other element. It should be understood that the orientation or positional relationship indicated by terms such as "length", "width", "upper", "lower", "front", "rear", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings. These terms are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation to the present invention.

[0037] The terms "first" and "second" are used only for descriptive purposes and should not be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present invention, the meaning of "a plurality of" is two or more unless otherwise specifically defined.

[0038] Please refer to Figures 1 to 5 simultaneously. Now, the single crystal growth furnace and the single crystal preparation method provided by the present invention will be described. The single crystal growth furnace includes a furnace body 1, a tungsten-molybdenum heat-insulating body 2, a crucible hoisting cylinder 3, and a tungsten crucible 5. The furnace body 1 has an accommodation space inside. The tungsten-molybdenum heat-insulating body 2 is placed in the accommodation space, and a circular first accommodation cavity 11 is formed between the tungsten-molybdenum heat-insulating body 2 and the inner peripheral wall of the furnace body 1. A cooling medium is introduced into the first accommodation cavity 11. A second accommodation cavity 21 is provided inside the tungsten-molybdenum heat-insulating body 2, and a heater 6 is provided in the second accommodation cavity 21. The crucible hoisting cylinder 3 is disposed in the second accommodation cavity 21, and the upper end of the crucible hoisting cylinder 3 extends upward out of the second accommodation cavity 21 and is limited on the tungsten-molybdenum heat-insulating body 2. An insulating component 4 is provided in the crucible hoisting cylinder 3 in a circular shape along its inner peripheral wall. The tungsten crucible 5 is disposed in the second accommodation cavity 21 and is placed below the crucible hoisting cylinder 3. The upper end of the tungsten crucible 5 extends upward into the crucible hoisting cylinder 3 and is connected to the insulating component 4. Aluminum nitride seed crystals 53 and aluminum nitride powder 54 are provided in the tungsten crucible 5 at intervals in the vertical direction, and the aluminum nitride powder 54 is placed below the crucible hoisting cylinder 3.

[0039] It should be understood that the crucible hoisting cylinder 3 provided in the present application can not only realize the hoisting of the tungsten crucible 5, but also sink the tungsten crucible 5 by means of the length of the crucible hoisting cylinder 3 itself, so as to place the bottom of the tungsten crucible 5 at the central heating part of the heater 6, thereby realizing the heating of the aluminum nitride powder 54 at the bottom of the tungsten crucible 5. Further, the crucible hoisting cylinder 3 also provides convenience for the installation of the internal insulating component 4 and can facilitate the setting of a multi-layer insulating structure.

[0040] Specifically, the tungsten crucible 5 is filled with aluminum nitride powder 54 inside, a tungsten substrate 52 is arranged above the aluminum nitride powder 54, an aluminum nitride seed crystal 53 formed by sintering aluminum nitride wafers is arranged at the bottom of the tungsten substrate 52, and the aluminum nitride seed crystal 53 faces the aluminum nitride powder 54.

[0041] Optionally, the heater 6 is in an annular structure and surrounds the second accommodation cavity 21, and is arranged around the crucible lifting cylinder 3; the heater 6 extends in the vertical direction, and both the crucible lifting cylinder 3 and the tungsten crucible 5 are placed in the heating area surrounded by the heater 6, wherein the tungsten crucible 5 is located at the middle position of the heater 6 to heat the aluminum nitride powder 54.

[0042] It should be understood that when the heater 6 is heating, the aluminum nitride powder 54 sublimes and turns into a gas phase. Driven by the temperature difference, the gas-phase components are transmitted upward to the aluminum nitride seed crystal 53 with a lower temperature, and the gas-phase components re-condense at the low-temperature aluminum nitride seed crystal 53.

[0043] Exemplarily, to heat the aluminum nitride powder 54, the aluminum nitride powder 54 is placed below the crucible lifting cylinder 3. To achieve the temperature difference between the aluminum nitride seed crystal 53 and the aluminum nitride powder 54, optionally, the aluminum nitride seed crystal 53 is placed below the crucible lifting cylinder 3 and close to the bottom of the crucible lifting cylinder 3; or, the aluminum nitride seed crystal 53 is placed inside the crucible lifting cylinder 3 and close to the bottom of the crucible lifting cylinder 3. Specifically, the specific position of the aluminum nitride seed crystal 53 can be set according to actual needs.

[0044] Optionally, the furnace body 1 is made of stainless steel material, and a lifting flange is arranged at the top of the furnace body 1 for easy opening; further, the cooling medium introduced into the first accommodation cavity 11 between the top lifting flange and the furnace body 1 and the tungsten-molybdenum heat-insulating body 2 can be selected as cooling water.

[0045] The single-crystal growth furnace and the single-crystal preparation method provided by the present invention, compared with the prior art, can lift the tungsten crucible 5 into the tungsten-molybdenum heat-insulating body 2 through the crucible lifting cylinder 3, and form a heating space for heating the aluminum nitride powder 54 outside the heater 6 through the tungsten-molybdenum heat-insulating body 2. Then, through the heat-insulating component 4 placed in the crucible lifting cylinder 3, a heat-insulating space is formed at the upper end of the tungsten crucible 5 to form a relatively low-temperature area at the aluminum nitride seed crystal 53; in this application, the above heat-insulating component 4 is used to increase the temperature difference of the tungsten crucible 5 in the vertical direction, form a temperature difference between the aluminum nitride seed crystal 53 and the aluminum nitride powder 54, and make the sublimation and condensation processes of the aluminum nitride raw material occur in a space independent of the heating area, which can effectively avoid the adhesion of the tungsten-molybdenum heat-insulating body 2 caused by the deposition of the aluminum nitride raw material and the difficulty in the disassembly process, and can effectively extend the service life of the single-crystal growth furnace; the single-crystal growth furnace provided in this application has good heat-insulating and heat-preserving effects, a simple structure, low disassembly and assembly operation difficulty, a long service life, and low processing and use costs.

[0046] Please refer to Figure 2 or Figure 3 , in some possible embodiments, a first lifting plate 51 is annularly arranged at the top of the tungsten crucible 5. The first lifting plate 51 extends radially along the crucible lifting cylinder 3 and penetrates into the heat insulation component 4.

[0047] By providing the first lifting plate 51, it is convenient to lift the tungsten crucible 5 into the crucible lifting cylinder 3.

[0048] Please refer to Figure 2 or Figure 3 , in some embodiments, the heat insulation component 4 includes an upper heat insulation ring 41 and a lower heat insulation ring 42; the upper heat insulation ring 41 is placed above the first lifting plate 51 and is arranged around the axis of the crucible lifting cylinder 3; the lower heat insulation ring 42 is placed between the first lifting plate 51 and the bottom wall of the crucible lifting cylinder 3 and is arranged around the outer peripheral wall of the tungsten crucible 5; wherein, both the lower heat insulation ring 42 and the upper heat insulation ring 41 are in the shape of an annular plate extending along the axial direction of the tungsten crucible 5; and the lower heat insulation ring 42 and the upper heat insulation ring 41 enclose a first heat insulation gap 44.

[0049] By providing the upper heat insulation ring 41 and the lower heat insulation ring 42, heat insulation and temperature reduction above the tungsten crucible 5 are achieved, so as to realize a low-temperature region at the aluminum nitride seed crystal 53, and further realize the temperature difference required for single crystal growth.

[0050] Furthermore, by separating the heat insulation component 4 into the upper heat insulation ring 41 and the lower heat insulation ring 42, the lower heat insulation ring 42 can be supported below the first lifting plate 51, thus facilitating the pulling out of the tungsten crucible 5 from the crucible lifting cylinder 3.

[0051] By making both the lower heat insulation ring 42 and the upper heat insulation ring 41 in the shape of an annular plate extending along the axial direction of the tungsten crucible 5, heat insulation in the vertical direction is realized.

[0052] Please refer to Figure 2 , exemplarily, the heat insulation component 4 further includes a heat insulation ring piece 43 arranged above the upper heat insulation ring 41. The heat insulation ring piece 43 extends horizontally along the radial direction of the tungsten crucible 5 and is fixed to the inner peripheral wall of the crucible lifting cylinder 3; wherein, the center of the heat insulation ring piece 43 has a second heat insulation gap 45.

[0053] By providing the heat insulation ring piece 43, heat insulation and temperature reduction above the tungsten crucible 5 are achieved to ensure a relatively low temperature of the aluminum nitride seed crystal 53 in the tungsten crucible 5; and since the heat insulation ring piece 43 extends horizontally along the radial direction of the tungsten crucible 5, heat insulation in the horizontal direction can be realized, which complements the lower heat insulation ring 42 and the upper heat insulation ring 41 to ensure the temperature difference required for the experiment.

[0054] Please refer to Figure 2, Exemplarily, the radial dimension of the second heat insulation gap 45 is smaller than that of the first heat insulation gap 44, and the radial dimension of the second heat insulation gap 45 is smaller than the radial dimension of the tungsten crucible 5.

[0055] By reasonably reducing the second heat insulation gap 45, a heat insulation structure is formed at the upper horizontal plane, and the reserved second heat insulation gap 45 can still ensure normal ventilation.

[0056] Please refer to Figure 2 , In some embodiments, multiple layers of upper heat insulation ring segments 41 are provided, and the multiple layers of upper heat insulation ring segments 41 are arranged at intervals inside and outside in the radial direction of the tungsten crucible 5; multiple layers of lower heat insulation ring segments 42 are provided, and the multiple layers of lower heat insulation ring segments 42 are arranged at intervals inside and outside in the radial direction of the tungsten crucible 5; multiple layers of heat insulation ring plates 43 are provided, and the multiple layers of heat insulation ring plates 43 are arranged at intervals above and below in the axial direction of the tungsten crucible 5.

[0057] By respectively arranging the lower heat insulation ring segment 42, the upper heat insulation ring segment 41, and the heat insulation ring plate 43 into multiple layers, the heat preservation and insulation effect is improved, and thus a large temperature difference required during single crystal growth is achieved.

[0058] Please refer to Figure 2 , In some possible embodiments, a second lifting plate 31 arranged in a ring shape is provided at the top of the crucible lifting cylinder 3. The second lifting plate 31 extends horizontally in the radial direction of the crucible lifting cylinder 3 and is limited at the top of the tungsten-molybdenum heat insulation body 2.

[0059] By providing the second lifting plate 31, it is convenient to lift the crucible lifting cylinder 3 into the tungsten-molybdenum heat insulation body 2.

[0060] Optionally, as another lifting example of the crucible lifting cylinder 3, a plurality of groups of connecting ear plates can also be arranged at intervals at the top of the crucible lifting cylinder 3, and the connecting ear plates are lifted and limited on the tungsten-molybdenum heat insulation body 2.

[0061] Please refer to Figure 2 , In some embodiments, a support ring 32 is provided between the bottom of the second lifting plate 31 and the top of the tungsten-molybdenum heat insulation body 2. The support ring 32 is arranged around the outer peripheral wall of the crucible lifting cylinder 3.

[0062] By providing the support ring 32, it is convenient to support the second lifting plate 31, and thus it is convenient to lift the crucible lifting cylinder 3 out of the second accommodating cavity 21.

[0063] Specifically, the number of support rings 32 can be set to multiple layers according to actual needs, and its height can be set according to actual needs.

[0064] Please refer to Figure 1, in some possible embodiments, the tungsten-molybdenum heat-insulating body 2 includes a heat-insulating layer 23 that encloses a second accommodation cavity 21, and a molybdenum tray 22 placed on top of the heat-insulating layer 23; the upper end of the crucible hoisting cylinder 3 is limited on the molybdenum tray 22.

[0065] Specifically, the heat-insulating layer 23 includes a side heat-insulating screen fixed to the bottom of the furnace body 1, and a bottom heat-insulating screen and a top heat-insulating screen connected to the side heat-insulating screen; wherein, the bottom heat-insulating screen is fixed to the bottom of the furnace body 1, and further, air-permeable holes are provided through the bottom heat-insulating screen and the bottom of the furnace body 1 up and down; an installation hole suitable for the crucible hoisting cylinder 3 to extend into is provided on the top heat-insulating screen.

[0066] By providing the molybdenum tray 22, it is convenient to set a support ring 32 on the top to support the crucible hoisting cylinder 3.

[0067] The present invention also provides a single crystal preparation method, which is prepared by using a single crystal growth furnace. The single crystal preparation method includes the following steps:

[0068] First. Place an aluminum nitride seed crystal 53 and aluminum nitride powder 54 corresponding up and down in the tungsten crucible 5, determine the specifications of the heat-insulating component 4 according to the size of the aluminum nitride seed crystal 53, and assemble the heat-insulating component 4 and the tungsten crucible 5 into the crucible hoisting cylinder 3 to form an aluminum nitride growth structure;

[0069] Second. Place the aluminum nitride growth structure in the second accommodation cavity 21, and use nitrogen to displace the air in the single crystal growth furnace;

[0070] Third. Keep the pressure in the single crystal growth furnace at 500 - 800 mbar, and gradually raise the temperature in the single crystal growth furnace from room temperature to 2200 - 2300 °C within a preset time period, and then keep the temperature and pressure unchanged and continue for 120 h to grow aluminum nitride single crystals.

[0071] Exemplarily, when the size of the prepared aluminum nitride single crystal is 2 inches, a lower heat-insulating ring 42 with a height of 10 mm can be placed between the crucible hoisting cylinder 3 and the tungsten crucible 5, and the lower heat-insulating ring 42 has three layers with diameters of 120 mm, 100 mm, and 80 mm respectively; an upper heat-insulating ring 41 with a height of 40 mm is placed above the tungsten crucible 5, and the upper heat-insulating ring 41 has four layers with diameters of 120 mm, 100 mm, 80 mm, and 60 mm respectively; the heat-insulating ring pieces 43 are arranged in 5 layers and are evenly spaced. Preferably, the diameter of the outermost heat-insulating ring piece 43 is 130 mm, and the inner diameter of the innermost heat-insulating ring piece 43 is 25 mm.

[0072] Exemplarily, when the size of the prepared aluminum nitride single crystal is 4 inches, a lower heat insulation ring 42 with a height of 30 mm can be placed between the crucible lifting cylinder 3 and the tungsten crucible 5. The lower heat insulation ring 42 has three layers with diameters of 130 mm, 120 mm, and 110 mm respectively; an upper heat insulation ring 41 with a height of 20 mm is placed above the tungsten crucible 5. The upper heat insulation ring 41 has two layers with diameters of 130 mm and 120 mm respectively; the heat insulation ring pieces 43 are arranged in 3 layers and are evenly spaced. Preferably, the diameter of the outermost heat insulation ring piece 43 is 130 mm, and the inner diameter of the innermost heat insulation ring piece 43 is 110 mm.

[0073] Since the single crystal preparation method provided in this application is prepared using the above single crystal growth furnace, it has all the beneficial effects of the above single crystal growth furnace, with good heat preservation and insulation effects, high quality of the prepared single crystal products, low difficulty in the operation process, and low processing and use costs.

[0074] In addition, please refer to Figure 4 and Figure 5 , for the convenience of description, in this application, the crucible lifting cylinder 3 and the internal heat insulation component 4 are defined as a partition structure; to further determine the heat preservation and insulation effect of the single crystal growth furnace provided in this application, this application conducts a simulation comparison on the thermal fields with and without the partition structure in this device. Among them, the maximum temperature difference without using the partition structure is 120 °C, and the maximum temperature difference with the partition structure reaches 164 °C. It can be seen that the temperature difference has been significantly improved. Further, after using the partition structure, the energy consumption of the equipment can be reduced from 23.5 kW to 19.8 kW, with a reduction rate of 15.7%. It can be seen that setting this partition structure can significantly reduce the growth cost of aluminum nitride single crystals.

[0075] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A single crystal growth furnace, characterized in that: include: A furnace body (1) having a receiving space therein; The tungsten-molybdenum heat-insulating body (2) is placed in the accommodating space and forms an annular first accommodating cavity (11) with the inner peripheral wall of the furnace body (1), wherein the first accommodating cavity (11) is used to pass a cooling medium; a second accommodating cavity (21) is provided in the tungsten-molybdenum heat-insulating body (2), wherein a heater (6) is provided in the second accommodating cavity (21); A crucible hanging tube (3) is arranged in the second accommodating cavity (21), and the upper end of the crucible hanging tube (3) extends upward out of the second accommodating cavity (21) and is limited on the tungsten-molybdenum insulation body (2); a heat insulation component (4) is arranged in an annular shape along the inner peripheral wall of the crucible hanging tube (3); and A tungsten crucible (5) is arranged in the second accommodating chamber (21) and is placed below the crucible hanging tube (3); the upper end of the tungsten crucible (5) extends upward into the crucible hanging tube (3) and is connected to the heat insulation component (4); aluminum nitride seed crystals (53) and aluminum nitride powder (54) are arranged in an upper and lower interval in the tungsten crucible (5), and the aluminum nitride powder (54) is placed below the crucible hanging tube (3).

2. The single crystal growth furnace according to claim 1, characterized in that: A first hanging plate (51) arranged in an annular shape is provided on the top of the tungsten crucible (5); the first hanging plate (51) extends horizontally along the radial direction of the crucible hanging tube (3) and penetrates into the heat insulation component (4).

3. The single crystal growth furnace according to claim 2, characterized in that: The thermal insulation component (4) comprises: An upper heat-insulating ring (41) is placed above the first hanging plate (51) and is arranged around the axis of the crucible hanging tube (3); A lower heat-insulating ring (42) is placed between the first hanging plate (51) and the bottom wall of the crucible hanging tube (3), and is arranged around the outer peripheral wall of the tungsten crucible (5); The lower heat-insulating ring (42) and the upper heat-insulating ring (41) are both in the shape of ring plates extending along the axial direction of the tungsten crucible (5); and the lower heat-insulating ring (42) and the upper heat-insulating ring (41) enclose a first heat-insulating gap (44).

4. The single crystal growth furnace according to claim 3, characterized in that: The thermal insulation assembly (4) further comprises a thermal insulation ring sheet (43) arranged above the upper thermal insulation ring ring (41), wherein the thermal insulation ring sheet (43) extends horizontally along the radial direction of the tungsten crucible (5) and is fixed to the inner circumferential wall of the crucible hanging tube (3); wherein a second thermal insulation gap (45) is provided at the center of the thermal insulation ring sheet (43).

5. The single crystal growth furnace according to claim 4, characterized in that: The radial dimension of the second thermal insulation gap (45) is smaller than the radial dimension of the first thermal insulation gap (44), and the radial dimension of the second thermal insulation gap (45) is smaller than the radial dimension of the tungsten crucible (5).

6. The single crystal growth furnace according to claim 5, characterized in that: The upper heat-insulating ring (41) is provided with multiple layers, and the multiple layers of the upper heat-insulating ring (41) are arranged at intervals in the radial direction of the tungsten crucible (5); the lower heat-insulating ring (42) is provided with multiple layers, and the multiple layers of the lower heat-insulating ring (42) are arranged at intervals in the radial direction of the tungsten crucible (5); the heat-insulating ring sheet (43) is provided with multiple layers, and the multiple layers of the heat-insulating ring sheet (43) are arranged at intervals in the upper and lower directions along the axial direction of the tungsten crucible (5).

7. The single crystal growth furnace according to claim 1, characterized in that: A second hanging plate (31) arranged in an annular shape is provided on the top of the crucible hanging tube (3); the second hanging plate (31) extends horizontally along the radial direction of the crucible hanging tube (3) and is limited at the top of the tungsten-molybdenum insulation body (2).

8. The single crystal growth furnace according to claim 7, characterized in that: A support ring (32) is provided between the bottom of the second hanging plate (31) and the top of the tungsten-molybdenum insulation body (2), and the support ring (32) is arranged around the outer peripheral wall of the crucible hanging tube (3).

9. The single crystal growth furnace according to claim 1, characterized in that: The tungsten-molybdenum insulation body (2) comprises an insulation layer (23) surrounding the second accommodating cavity (21), and a molybdenum tray (22) placed on top of the insulation layer (23); the upper end of the crucible hanging tube (3) is limited on the molybdenum tray (22).

10. A method for preparing a single crystal, characterized in that: The single crystal is prepared by using the single crystal growth furnace according to any one of claims 1 to 9, and the single crystal preparation method comprises the following steps: S1. The aluminum nitride seed crystal (53) and the aluminum nitride powder (54) are placed in the upper and lower parts of the tungsten crucible (5) correspondingly, and the specifications of the thermal insulation component (4) are determined according to the size of the aluminum nitride seed crystal (53), and the thermal insulation component (4) and the tungsten crucible (5) are assembled into the crucible hanging tube (3) to form an aluminum nitride growth structure; S2. placing the aluminum nitride growth structure in the second accommodating chamber (21), and replacing the air in the single crystal growth furnace with nitrogen; S3. Maintain the pressure in the single crystal growth furnace at 500-800 mbar, and gradually increase the temperature in the single crystal growth furnace from room temperature to 2200-2300°C within a preset time period, and then maintain the temperature and pressure unchanged for 120 hours to grow aluminum nitride single crystals.

Images