Thermal field structure for adjusting thermal convection of aluminum nitride crystal growth furnace body

Abstract

The invention relates to the technical field of aluminum nitride crystal growth equipment, in particular to a thermal field structure for adjusting thermal convection of an aluminum nitride crystal growth furnace body. The heat preservation device comprises an upper heat preservation screen, an upper side heat preservation screen, a convection blocking screen, a lower side heat preservation screen and a lower heat preservation screen, the upper heat preservation screen is assembled in the upper side heat preservation screen, the upper side heat preservation screen is assembled above the convection blocking screen, the convection blocking screen is assembled above the lower side heat preservation screen, and the lower heat preservation screen is assembled in the lower side heat preservation screen. And all the heat preservation screens are circumferentially and symmetrically distributed. When the crucible is used as a thermal field structure of the aluminum nitride crystal growing furnace, a thermal convection area in the aluminum nitride crystal growing furnace can be divided into an upper part and a lower part, and the longitudinal temperature gradient of the crucible for growing the aluminum nitride crystal is increased, so that the growth rate of the aluminum nitride crystal is increased, and the yield of the aluminum nitride crystal is improved.

Description

Technical Field

[0001] The invention relates to the technical field of aluminum nitride crystal growth equipment, in particular to a thermal field structure for regulating thermal convection of an aluminum nitride crystal growth furnace. Background Art

[0002] Aluminum nitride (AlN) is one of the representatives of ultra-wide bandgap semiconductor materials. Its theoretical bandgap width reaches 6.2eV. AlN also has extremely high breakdown field strength and thermal conductivity, reaching 11.7×10 6 V•cm -1 and 3.4 W•cm -1 •K -1 In addition, the lattice mismatch and thermal mismatch between AlN single crystal and high Al content AlGaN material are close to zero, making it the most excellent substrate material for optoelectronic devices and power electronic devices. High Al content AlGaN epitaxy on AlN single crystal substrate is homogeneous epitaxy. Compared with heterogeneous (Si, sapphire, SiC substrate) epitaxy, the dislocation density of AlGaN epitaxial layer can be reduced by 10 3 ~10 4 times, which can achieve high breakdown voltage and high operating current of electronic devices, and provide better thermal conductivity, greatly improving device performance and reliability.

[0003] For example, CN107916454A involves a thermal field for an aluminum nitride crystal growth furnace, the growth furnace includes a furnace body, a support rod passing through the lower part of the furnace body, the thermal field includes a crucible arranged above the support rod, a heat insulation mechanism, and a multi-stage heating mechanism for heating the crucible arranged in the furnace body and distributed in sequence along the vertical direction, the heat insulation mechanism includes a first heat insulation screen arranged above the crucible, a second heat insulation screen arranged between the crucible and the support rod, a third heat insulation screen arranged around the outside of the crucible, and a fourth heat insulation screen arranged between the third heat insulation screen and the inner wall of the furnace body.

[0004] The above-mentioned thermal field for an aluminum nitride crystal growth furnace uses tungsten and boron nitride materials to effectively avoid the influence of oxygen impurities and carbon impurities in the graphite thermal field on the impurities of crystal growth; by setting a multi-stage heating mechanism, the temperature of the top and bottom of the crucible can be flexibly adjusted; by setting a movable support rod, it is not only convenient to adjust the temperature gradient of crystal growth, but also convenient to take out the crucible and then clean the furnace chamber. However, due to the upward transmission of hot gas, the temperature difference in the raw material area is too large, so that the volatilization rate of the bottom of the AlN raw material in the early stage of crystal growth is much greater than that of the top of the raw material, and the volatilization rate of the bottom of the raw material in the later stage of crystal growth is close to that of the top of the raw material. The change in the volatilization rate of the raw material in the early and late stages of crystal growth makes the crystal unable to grow stably, greatly affecting the crystallization quality of the crystal, and cannot meet the requirements of AlN crystal substrate productization.

[0005] In order to meet the requirements of AlN crystal substrate productization, a thermal field structure for regulating thermal convection in an aluminum nitride crystal growth furnace is proposed. Summary of the invention

[0006] The object of the present invention is to provide a thermal field structure for regulating thermal convection of an aluminum nitride crystal growth furnace to solve the problems raised in the above-mentioned background technology.

[0007] To achieve the above object, the present invention aims to provide a thermal field structure for regulating the thermal convection of an aluminum nitride crystal growth furnace, comprising an upper heat preservation screen, an upper side heat preservation screen, a convection barrier screen, a lower side heat preservation screen and a lower heat preservation screen; The upper insulation screen is installed in the upper insulation screen, the upper insulation screen is installed above the convection barrier screen, the convection barrier screen is installed above the lower insulation screen, and the lower insulation screen is installed in the lower insulation screen. The convection barrier screen is composed of 2-5 layers of tungsten film, and its inner diameter is 3-8mm larger than the outer diameter of the crucible.

[0008] As a further improvement of the technical solution, all the heat-insulating screens are symmetrically distributed around the circumference.

[0009] As a further improvement of the technical solution, the upper thermal insulation screen, the upper side thermal insulation screen, the lower side thermal insulation screen and the lower thermal insulation screen are all composed of 10-21 layers of tungsten / molybdenum thin films.

[0010] As a further improvement of the technical solution, the thickness of each tungsten / molybdenum thin layer is 0.3-1.0 mm, and the interval between each tungsten / molybdenum thin layer is 2-5 mm.

[0011] Compared with the prior art, the present invention has the following beneficial effects: In the thermal field structure for regulating the thermal convection of the aluminum nitride crystal growth furnace, a convection barrier screen is configured to divide the traditional single thermal convection area into two thermal convection areas. Through the separate control of the top heater and the main heater, independent control of each thermal convection area is achieved, thereby achieving a relatively small temperature gradient in the AlN raw material area and a large temperature gradient in the vapor transport area. This not only allows the raw material to sublime stably, but also increases the growth rate of the AlN crystal. The thermal field structure is simple and easy to manufacture and use. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 It is a schematic diagram of the thermal field structure in the conventional growth furnace of AlN crystal using the existing physical vapor transport method; Figure 2 This is the temperature distribution diagram of the crucible side wall during AlN crystal growth corresponding to the traditional thermal field structure; Figure 3 It is a schematic diagram of the thermal field structure in the physical vapor transport method AlN crystal growth furnace of the present invention; Figure 4 The temperature distribution diagram of the crucible side wall during AlN crystal growth corresponding to the thermal field structure of the present invention; Figure 5 This is a comparison diagram of thermal convection between the thermal field structure of the present invention and the traditional thermal field structure during AlN crystal growth; Figure 6 This is a comparison diagram of crucible wall temperature distribution between the thermal field structure of the present invention and the traditional thermal field structure.

[0013] The meaning of each number in the figure is: 1. Upper insulation screen; 2. Upper side insulation screen; 3. Convection barrier screen; 4. Lower side insulation screen; 5. Lower insulation screen; 6. Top heater; 7. Main heater; 8. Crucible; 9. AlN raw material area; 10. Vapor transport area. DETAILED DESCRIPTION

[0014] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0015] Physical vapor transport (PVT) is the most effective method for growing thick AlN single crystal ingots. High-quality AlN single crystals must be grown in a growth furnace with a tungsten / molybdenum thermal field structure. This is because the AlN crystal growth temperature is about 2300°C, and the growth furnace produces almost no impurity elements at such a high temperature. The PVT method AlN crystal growth atmosphere is nitrogen, and its growth pressure is generally 600-900mbar.

[0016] At present, in the thermal field structure of the traditional AlN growth furnace, the above growth temperature and growth pressure will cause strong thermal convection inside the thermal field. The thermal field structure and thermal convection diagram of the traditional crystal growth furnace are shown in the figure. Figure 1 As shown, in the thermal field structure, 1 is an upper thermal insulation screen, 2 is a side thermal insulation screen, 5 is a lower thermal insulation screen, 6 is a top heater, and 7 is a main heater.

[0017] The heat in the crystal growth furnace is provided by the heater. At high temperatures, under the action of the temperature gradient, a strong thermal convection effect is generated. The thermal convection path of nitrogen as a carrier gas is as follows: (1) The nitrogen in the furnace moves upward inside the heater and transfers heat to the upper end of the crucible; (2) Nitrogen moves from the top of the heater to the outside of the heater and reduces the temperature; (3) Nitrogen moves downward outside the heater and further reduces the temperature; (4) The nitrogen gas at the bottom of the heater moves toward the inside of the heater and gradually heats up, eventually forming a closed loop.

[0018] Under such heat convection, the temperature of the top of the crucible is higher than the temperature of the bottom of the crucible (here Figure 5-6 As shown, the bottom of the crucible is located at the lower end d0 of the heater, the top of the crucible is located at the upper end d3 of the heater, the bottom of the raw material is located at the highest crucible temperature d1, and the top of the raw material is located at the crucible d2), and the temperature distribution from the bottom of the AlN raw material to the top of the crucible tends to decrease linearly, as shown in Figure 2 However, the commercialization of AlN single crystal substrates has put forward higher requirements on the thermal field structure of the AlN growth furnace. In terms of the growth of high-quality AlN single crystals, the AlN raw material must be able to achieve stable sublimation, that is, the AlN raw material area has a small temperature gradient; in terms of the rapid growth of AlN thick crystals, the AlN vapor must be able to achieve rapid transportation, that is, the vapor transportation area has a large temperature gradient.

[0019] However, the temperature distribution from the bottom of the AlN raw material to the top of the crucible, which tends to decrease linearly under the traditional thermal field structure, can no longer meet the requirements of AlN single crystal substrate commercialization, mainly manifested in the following aspects: (1) AlN raw materials cannot sublime stably: When growing AlN crystals under the traditional thermal field structure, the upward transmission of hot gas leads to a large temperature difference in the raw material area, which makes the volatilization rate of the bottom of the AlN raw material in the early stage of crystal growth much greater than that of the top of the raw material, while in the later stage of crystal growth, the volatilization rate of the bottom of the raw material approaches that of the top of the raw material. The change in the volatilization rate of the raw material in the early and late stages of crystal growth makes the crystal unable to grow stably, which greatly affects the crystallization quality of the crystal.

[0020] (2) Slow growth rate of AlN crystals: Due to the upward transmission of hot gas, the temperature difference in the vapor transport area is insufficient, the driving force for AlN vapor transport is small, and the transport rate is slow, resulting in slow crystal growth.

[0021] Although the new generation of AlN crystal growth furnaces currently use a heating method that uses a top heater and a main heater to coordinate the temperature distribution of the crucible, it still cannot effectively solve the above two problems under the strong thermal convection.

[0022] In view of the above two problems, the thermal field structure of the commercialized AlN crystal growth furnace requires that, on the one hand, the AlN raw material area has a relatively small temperature gradient, and on the other hand, the vapor transport area has a large temperature gradient, thereby meeting the requirements for the commercialization of AlN crystal substrates.

[0023] In order to obtain the temperature gradient requirements for AlN crystal substrate commercialization, please refer to Figure 1-6As shown, the present invention proposes a thermal field structure for regulating thermal convection of an aluminum nitride crystal growth furnace. According to the differences in thermal field structures and materials, the thermal field structure for regulating thermal convection of an aluminum nitride crystal growth furnace provided by the present invention is further described through the following specific embodiments. Example

[0024] This embodiment is a traditional thermal field structure, such as Figure 1 The specific configuration is as follows: The upper heat-insulating screen 1 is assembled in the side heat-insulating screen 2, the lower heat-insulating screen 5 is assembled in the side heat-insulating screen 2, and all the heat-insulating screens are symmetrical in their circumferences.

[0025] Among them, the upper insulation screen 1, the side insulation screen 2, and the lower insulation screen 5 are composed of 8 layers of tungsten thin films and 5 layers of molybdenum thin films. The thickness of each tungsten / molybdenum thin film is 0.5 mm, and the interval between each tungsten / molybdenum thin film is 5 mm. The bottom temperature of the crystal growth raw material is 2300°C, the growth atmosphere is nitrogen, the growth pressure is 800 mBar, and the growth time is 80 hours.

[0026] When the conventional thermal field structure in the above embodiment is used for AlN crystal growth, the average sublimation rate of the AlN raw material is 0.95 g / h, and the crystal growth rate is 150 um / h. Example

[0027] like Figure 3 As shown, the difference between this embodiment and embodiment 1 is that the thermal field structure is configured as follows: The upper insulation screen 1 is installed in the upper insulation screen 2, the upper insulation screen 2 is installed above the convection barrier screen 3, the convection barrier screen 3 is installed above the lower insulation screen 4, the lower insulation screen 5 is installed in the lower insulation screen 4, and all the insulation screens are symmetrical in shape.

[0028] Among them, the upper insulation screen 1, the upper side insulation screen 2, the lower side insulation screen 4 and the lower insulation screen 5 are composed of 8 layers of tungsten film and 5 layers of molybdenum film, the thickness of each layer of tungsten / molybdenum film is 0.5mm, and the interval between each layer of tungsten / molybdenum film is 5mm. The convection barrier screen 3 is composed of 3 layers of tungsten film, and its inner diameter is 8mm larger than the outer diameter of the crucible.

[0029] When the thermal field structure obtained in the above embodiment is used for AlN crystal growth, the average sublimation rate of the AlN raw material is 1.00 g / h, and the crystal growth rate is 180 um / h. Example

[0030] The difference between this embodiment and embodiment 2 is that the convection barrier screen 3 is composed of two layers of tungsten film.

[0031] Compared with Example 2, the average sublimation rate of the AlN raw material in this example is 0.99 g / h, and the crystal growth rate is 165 um / h.

[0032] Compared with Example 2, in this embodiment, due to the reduction in the number of convection barrier screens 3, the temperature gradient in the vapor transport zone is smaller than that in Example 2, and the average sublimation rate and crystal growth rate of the AlN raw material decrease. Example

[0033] The difference between this embodiment and embodiment 2 is that the inner diameter of the convection barrier 3 is 3 mm larger than the outer diameter of the crucible.

[0034] Compared with Example 2, the average sublimation rate of the AlN raw material in this example is 1.05 g / h, and the crystal growth rate is 190 um / h.

[0035] Compared with Example 2, in this embodiment, since the distance between the convection barrier screen 3 and the crucible is reduced, the temperature gradient in the vapor transport zone is greater than that in Example 2, and the average sublimation rate and crystal growth rate of the AlN raw material are improved. Example

[0036] The difference between this embodiment and embodiment 4 is that the convection barrier screen 3 is composed of 5 layers of tungsten film.

[0037] Compared with Example 4, the average sublimation rate of the AlN raw material in this example is 1.10 g / h, and the crystal growth rate is 200 um / h.

[0038] Compared with Example 4, in this embodiment, due to the increase in the number of convection barrier screens 3, the temperature gradient in the vapor transport zone is greater than that in Example 4, and the average sublimation rate and crystal growth rate of the AlN raw material are improved.

[0039] Table 1: Comparison of average sublimation rate and crystal growth rate of AlN raw materials in Examples 1-5 Average sublimation rate of AlN raw material / (g / h) Crystal growth rate / (um / h) Example 1 0.95 150 Example 2 1.00 180 Example 3 0.99 165 Example 4 1.05 190 Example 5 1.10 200 It can be seen from Table 1 that, compared with Example 1, the average sublimation rate and crystal growth rate of the AlN raw material of the thermal field structure for regulating thermal convection of the aluminum nitride crystal growth furnace provided in Examples 2-5 are improved. Therefore, it can be explained that the thermal field structure for regulating thermal convection of the aluminum nitride crystal growth furnace provided by the present invention has a higher average sublimation rate and crystal growth rate of the AlN raw material, and can meet the requirements of AlN crystal substrate productization.

[0040] In summary, in the process of AlN single crystal product growth, the AlN raw material must be able to sublime stably and the AlN crystal must be able to grow rapidly. The thermal field structure of the AlN crystal growth furnace determines the internal heat convection mode. The traditional thermal field structure can only form a single heat convection area. The heat generated by the heater is transferred from the high temperature zone to the low temperature zone through nitrogen, causing the temperature from the bottom of the raw material in the crucible to the top of the crucible to decrease linearly, and effective regulation cannot be achieved.

[0041] like Figure 3The heat field structure of the present invention is provided with a convection barrier screen 3, which divides the traditional single heat convection area into two heat convection areas. Through the separate control of the top heater and the main heater, each heat convection area is independently controlled, thereby achieving a relatively small temperature gradient in the AlN raw material area and a large temperature gradient in the vapor transport area, such as Figure 4 As shown. Through process optimization, compared with the traditional thermal field structure, while ensuring that the temperature at the crucible d1 and the crucible top d3 remains unchanged, the temperature difference in the AlN raw material area is significantly reduced, that is, T4 < T2, and the temperature difference in the vapor transport area is significantly increased, that is, T3 > T1, where d2 is the turning point of the temperature reduction slope, as shown in Figure 5-6 shown.

[0042] The advantage of the device of the present invention is that through the design of the thermal field structure of the AlN crystal growth furnace, a small temperature gradient is formed in the AlN raw material area and a large temperature gradient is formed in the vapor transport area, which can not only make the raw material sublime stably, but also improve the growth rate of the AlN crystal. The thermal field structure is easy to manufacture and use.

[0043] Comparative Example 1 The difference between this comparative example and Example 5 is that the number of tungsten / molybdenum thin layers of the upper insulation screen 1, the upper side insulation screen 2, the lower side insulation screen 4, and the lower insulation screen 5 are different, and there are two examples as follows: When the upper insulation screen 1, the upper side insulation screen 2, the lower side insulation screen 4, and the lower insulation screen 5 are composed of 5 layers of tungsten thin films and 3 layers of molybdenum thin films, the insulation effect of the insulation screen decreases. Under the same energy consumption, the temperature of the AlN raw material zone between d1 and d2 can only reach 1700°C, which cannot meet the process requirements of crystal growth. At this time, the average sublimation rate and crystal growth rate of the AlN raw material are both zero; in this comparative example, in order to make the temperature of the AlN raw material zone between d1 and d2 reach 2300°C, the energy consumption will increase by more than 2 times, which does not meet the cost control requirements of AlN crystal substrate productization.

[0044] When the upper insulation screen 1, the upper side insulation screen 2, the lower side insulation screen 4, and the lower insulation screen 5 are composed of 12 layers of tungsten thin films and 11 layers of molybdenum thin films, the insulation effect of the insulation screen is increased, and the ability to increase the temperature difference in the vapor transport zone through the convection barrier screen 3 is reduced. When the temperature of the AlN raw material zone between d1 and d2 reaches 2300°C, the average sublimation rate and crystal growth rate of the AlN raw material are 1.10g / h and 60um / h, respectively.

[0045] This comparative example shows that when the tungsten / molybdenum thin film composition of the upper insulation screen 1, the upper side insulation screen 2, the lower side insulation screen 4 and the lower insulation screen 5 is 10-21 layers, better raw material sublimation and growth effects are achieved.

[0046] Comparative Example 2 The difference between this comparative example and Example 5 is that the thickness of the tungsten / molybdenum film of the upper insulation screen 1, the upper side insulation screen 2, the lower side insulation screen 4, and the lower insulation screen 5 are different, and there are the following two examples: When the thickness of the tungsten / molybdenum film of the upper insulation screen 1, the upper side insulation screen 2, the lower side insulation screen 4, and the lower insulation screen 5 is 0.2 mm, since the tungsten / molybdenum film is a brittle material, the above insulation screens will be broken under the action of thermal stress during the heating and cooling process, and cannot be used as insulation materials for AlN crystal growth.

[0047] When the thickness of the tungsten / molybdenum film of the upper insulation screen 1, the upper insulation screen 2, the lower insulation screen 4, and the lower insulation screen 5 is 1.1 mm, the heat conduction cross-sectional area of ​​the insulation screen increases by 2.2 times compared with Example 5, and the ability to increase the temperature difference in the vapor transport zone through the convection barrier screen 3 decreases. When the temperature of the AlN raw material zone between d1 and d2 reaches 2300°C, the average sublimation rate and crystal growth rate of the AlN raw material are 1.10 g / h and 80 um / h, respectively. In addition, since the thickness of the tungsten / molybdenum film increases by 2.2 times compared with Example 5, the thermal field cost will increase by 2.2 times, which does not meet the cost control requirements of the AlN crystal substrate productization.

[0048] This comparative example shows that when the thickness of the tungsten / molybdenum film is 0.3-1.0 mm, the normal operation of the thermal insulation screen can be ensured, which can not only have better raw material sublimation and growth effects, but also meet the cost control requirements of AlN crystal substrate productization.

[0049] Comparative Example 3 The difference between this comparative example and Example 5 is that the spacing distance between each layer of tungsten / molybdenum thin film is different among the upper insulation screen 1, the upper side insulation screen 2, the lower side insulation screen 4 and the lower insulation screen 5. There are two examples as follows: When the tungsten / molybdenum thin film intervals of the upper insulation screen 1, the upper side insulation screen 2, the lower side insulation screen 4, and the lower insulation screen 5 are 1 mm, the insulation layers will contact each other due to thermal stress during the heating and cooling process, and a stable temperature distribution cannot be achieved, which does not meet the process stability requirements for the commercialization of AlN crystal substrates.

[0050] When the tungsten / molybdenum thin intervals of the upper insulation screen 1, the upper side insulation screen 2, the lower side insulation screen 4, and the lower insulation screen 5 are 6 mm, the interlayer heat convection increases, which reduces the ability of the convection barrier screen 3 to increase the temperature difference in the vapor transport zone. The average sublimation rate and crystal growth rate of the AlN raw material are 1.10 g / h and 100 um / h, respectively.

[0051] This comparative example shows that when the interval between each tungsten / molybdenum thin layer is 2-5mm, the mutual contact between the insulation layers can be avoided, a stable temperature distribution can be achieved, the requirements for process stability in the commercialization of AlN crystal substrates can be met, and better raw material sublimation and growth effects can be ensured.

[0052] Comparative Example 4 The difference between this comparative example and Example 5 is that the number of layers of the convection barrier screen 3 is different, and there are two examples as follows: When the number of convection barrier screens 3 is 1, the ability of the convection barrier screens 3 to increase the temperature difference in the vapor transport zone is reduced, and the average sublimation rate and crystal growth rate of the AlN raw material are 1.10 g / h and 155 um / h, respectively.

[0053] When the number of convection barrier screens 3 is 6, the ability of the convection barrier screens 3 to increase the temperature difference in the vapor transport zone is too strong. Although the average sublimation rate and crystal growth rate of the AlN raw material are 1.10 g / h and 230 um / h, respectively, the crystal growth quality of the crystal in the crystal growth zone deteriorates due to the excessively fast crystal growth rate.

[0054] This comparative example can illustrate that when the tungsten film composition of the convection barrier screen 3 is 2-5 layers, it is possible to achieve better raw material sublimation and growth effects while ensuring the quality of crystallization.

[0055] Comparative Example 5 The difference between this comparative example and Example 5 is that the inner diameter of the convection barrier 3 is larger than the outer diameter of the crucible. There are two examples as follows: When the inner diameter of the convection barrier 3 is 2 mm larger than the outer diameter of the crucible, the average sublimation rate and crystal growth rate of the AlN raw material are 1.10 g / h and 220 um / h respectively. The crystal growth rate in the crystal growth area is too fast, resulting in poor crystal quality. In addition, since the distance between the convection barrier 3 and the outer diameter of the crucible is only 1 mm, it is very easy to collide and break during the crucible assembly process.

[0056] When the inner diameter of the convection barrier screen 3 is larger than the outer diameter of the crucible by 9 mm, the ability of the convection barrier screen to increase the temperature difference in the vapor transport zone decreases, and the average sublimation rate and crystal growth rate of the AlN raw material are 1.10 g / h and 130 um / h, respectively.

[0057] This comparative example shows that when the inner diameter of the convection barrier 3 is 3-8 mm larger than the outer diameter of the crucible, the crystal quality can be ensured and better raw material sublimation and growth effects can be achieved, thereby meeting the requirements for AlN crystal substrate productization.

[0058] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. The above embodiments and descriptions are only preferred examples of the present invention and are not intended to limit the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A thermal field structure for regulating thermal convection in an aluminum nitride crystal growth furnace, characterized in that: It comprises an upper heat-insulating screen (1), an upper side heat-insulating screen (2), a convection barrier screen (3), a lower side heat-insulating screen (4) and a lower heat-insulating screen (5); The upper heat-insulating screen (1) is mounted inside the upper heat-insulating screen (2), the upper heat-insulating screen (2) is mounted above the convection barrier screen (3), the convection barrier screen (3) is mounted above the lower heat-insulating screen (4), the lower heat-insulating screen (5) is mounted inside the lower heat-insulating screen (4), the convection barrier screen (3) is composed of 2 to 5 layers of tungsten film, and its inner diameter is 3 to 8 mm larger than the outer diameter of the crucible.

2. The thermal field structure for regulating thermal convection of an aluminum nitride crystal growth furnace according to claim 1, characterized in that: All thermal insulation screens are distributed symmetrically around the circumference.

3. The thermal field structure for regulating thermal convection of an aluminum nitride crystal growth furnace according to claim 1, characterized in that: The upper heat-insulating screen (1), the upper heat-insulating screen (2), the lower heat-insulating screen (4) and the lower heat-insulating screen (5) are all composed of 10 to 21 layers of tungsten / molybdenum thin films.

4. The thermal field structure for regulating thermal convection of an aluminum nitride crystal growth furnace according to claim 3, characterized in that: The thickness of each tungsten / molybdenum thin layer is 0.3-1.0mm, and the interval between each tungsten / molybdenum thin layer is 2-5mm.

Images