Thermal field structure, device and method for growing gallium oxide crystals by the edge-defined film-fed growth method

Abstract

The present invention relates to the technical field of integrated circuit semiconductor manufacturing, and specifically relates to a thermal field structure, device and method for growing gallium oxide crystals by the edge-defined film-fed growth (EFG) method. It includes a first heat preservation barrel, and a crystal growth channel with a rectangular cross-section is arranged at the central axis of the first heat preservation barrel. The side wall of the first heat preservation barrel is provided with a first gas flow channel, a second gas flow channel and a third gas flow channel that respectively penetrate the side wall and communicate with the crystal growth channel. The inner diameters of the first gas flow channel, the second gas flow channel and the third gas flow channel increase in sequence. The second gas flow channel and the third gas flow channel are evenly distributed along the outer diameter of the first heat preservation barrel, and the first gas flow channel is located below the second gas flow channel and the third gas flow channel. The upper thermal field structure of the present invention is more flexible in improving the thermal field by opening gas flow channels with different inner diameters, and can effectively adjust the temperature field distribution in the furnace by controlling the opening and closing of the gas flow channels.

Description

Technical Field

[0001] The present invention relates to the technical field of integrated circuit semiconductor manufacturing, and particularly relates to a thermal field structure, device and method for growing gallium oxide crystals by the edge-defined film-fed growth (EFG) method. Background Art

[0002] As a kind of ultra-wide bandgap semiconductor material, single crystal gallium oxide (β-Ga2O3) has unique advantages. Its bandgap width is as high as 4.9 eV, and the breakdown field strength can reach about 8 MV / cm. It is suitable for the preparation of high-voltage and high-power devices and ultraviolet detectors, and is one of the most promising fourth-generation semiconductor materials for engineering applications. Due to the easy volatility of gallium oxide raw materials and the poor thermal conductivity of the crystal, the edge-defined film-fed growth (EFG) method is usually used for the preparation of large-size gallium oxide single crystals.

[0003] Although the edge-defined film-fed growth (EFG) method has successfully achieved the growth of large-size gallium oxide crystals, it has also brought some new challenges. The existing gallium oxide crystal growth process and its thermal field design still face many problems: 1. Improper control of temperature gradient: In single crystal growth, the uniformity of the temperature gradient is crucial. If the temperature gradient is too large or unevenly distributed, it will lead to stress concentration during crystal growth, which will in turn cause crystal cracking or melting problems. This may also result in defects in the crystal, such as twins or dislocations; 2. Insufficient thermal field stability: During the growth process, the fluctuations of the thermal field will affect the growth quality and consistency of the crystal. If the thermal field is unstable, it is easy to cause thermal stress inside the crystal, affect the quality of the crystal and lead to fluctuations in the growth rate, thereby reducing production efficiency and crystal consistency; 3. The contradiction between thermal field design and crystal size expansion: As the size of the gallium oxide single crystal increases, the thermal field design becomes more complex. Large-size crystals require a larger uniform heating area, but this will increase the difficulty of temperature control, and at the same time requires more precise thermal field adjustment to avoid uneven cooling or overheating areas in large-size crystals.

[0004] Regarding the thermal field problems during the shoulder-forming process, the patent "CN115874267 A" improves the flow field form of the insulation cavity by introducing air flow holes, but only considers the temperature field control during the shoulder-forming growth process, and does not consider the necking process in the early stage, the subsequent constant-diameter growth, tailing and cooling processes. This does not comprehensively consider the whole process of gallium oxide growth, and the equipment of this patent is complex and the transformation cost is large. It is not suitable for mass production and manufacturing, and is only limited to single-piece or customized equipment.

[0005] In view of the above problems, the present invention provides a method for improving the thermal field in the growth of gallium oxide crystals by the edge-defined film-fed growth (EFG) method. The structure form of the thermal insulation layer is redesigned, and air flow holes are introduced to more flexibly and stably improve the thermal field distribution during the whole growth process. On the one hand, the heat loss during crystal growth is improved by adjusting the opening and closing of the air flow holes in the thermal insulation layer; on the other hand, the introduction of air flow holes can ensure that the crystal grows in an oxidizing atmosphere. This technical solution can effectively improve the quality of the growth of gallium oxide single crystals. Summary of the Invention

[0006] One of the objectives of the present invention is to provide a thermal field structure for growing gallium oxide crystals by the EFG method. By opening air flow channels with different inner diameters, the way of improving the thermal field is more flexible.

[0007] Another objective of the present invention is to provide a device for the thermal field structure of growing gallium oxide crystals by the EFG method. By opening air flow channels with different inner diameters around the thermal insulation layer of the upper thermal field structure, during the growth process, by adjusting the opening and closing of the air flow channels in the thermal insulation layer, the heat loss during crystal growth can be improved, the quality of the crystal during the growth process can be effectively controlled, and at the same time, it can ensure that the crystal grows in an oxidizing atmosphere, and the crystal defects caused by oxygen deficiency in gallium oxide crystals can be effectively reduced.

[0008] The third objective of the present invention is to provide a thermal field method for growing gallium oxide crystals by the EFG method. The way of improving the thermal field is more flexible, and rapid control can be achieved in multiple processes such as seeding - necking - shoulder broadening - isodiametric growth - pulling and finishing - cooling.

[0009] The solution adopted by the present invention to achieve the first objective is: a thermal field structure for growing gallium oxide crystals by the EFG method, including a first thermal insulation barrel. A crystal growth channel with a rectangular cross-section is provided at the central axis of the first thermal insulation barrel. The side wall of the first thermal insulation barrel is provided with a first air flow channel, a second air flow channel, and a third air flow channel that respectively penetrate the side wall and communicate with the crystal growth channel. The inner diameter of the first air flow channel, the inner diameter of the second air flow channel, and the inner diameter of the third air flow channel increase in sequence. The second air flow channel and the third air flow channel are evenly distributed along the outer diameter of the first thermal insulation barrel, and the first air flow channel is located below the second air flow channel and the third air flow channel.

[0010] Preferably, the first air flow channel, the second air flow channel, and the third air flow channel are respectively arranged on the side wall of the first thermal insulation barrel and horizontally penetrate the crystal growth channel and the side wall.

[0011] Preferably, there are multiple second gas flow channels, which are uniformly arranged in at least one row and horizontally penetrate the narrow side wall of the crystal growth channel. There are multiple third gas flow channels, which are uniformly arranged in at least one row and horizontally penetrate the wide side wall of the crystal growth channel. There are multiple first gas holes, which are uniformly distributed below the second gas flow channels and the third gas flow channels.

[0012] Preferably, the second gas flow channels are arranged in a single row, and the number of the second gas flow channels in each row is 4 - 6, with an inner diameter of 14 - 16 mm. The third gas flow channels are arranged in a single row, and the number of the third gas flow channels in each row is 3 - 5, with an inner diameter of 28 - 32 mm. The first gas flow channels are arranged in two rows, respectively located below the second gas flow channels and the third gas flow channels. The number of the first gas flow channels in each row is 1 - 2, with an inner diameter of 3 - 5 mm.

[0013] Preferably, the material of the first heat preservation barrel is zirconia.

[0014] The solution adopted to achieve the second object of the present invention is: an apparatus for growing gallium oxide crystals by the edge-defined film-fed growth (EFG) method, including an upper thermal field structure, a lower thermal field structure arranged under the upper thermal field structure, a crucible arranged in the lower thermal field structure, a mold arranged at the central position of the crucible, and a lifting mechanism arranged in the crystal growth channel. The upper thermal field structure, the crucible, the lower thermal field structure, the mold and the lifting mechanism are all coaxially arranged. A capillary slit is arranged at the central position of the mold, and the capillary slit communicates with the crystal growth channel. The upper thermal field structure is the thermal field structure for growing gallium oxide crystals by the EFG method according to any one of claims 1 - 5. During the growth process of gallium oxide crystals, the thermal field can be adjusted by opening and closing the first gas flow channel, the second gas flow channel and the third gas flow channel, so as to control the crystal growth quality.

[0015] Preferably, the lower thermal field structure includes a second heat preservation barrel and a heating coil arranged outside the second heat preservation barrel. The second heat preservation barrel includes a quartz tube, sand filled in the quartz tube, and a zirconium ring placed on the sand. The filling height of the sand is lower than the height of the quartz tube. The crucible is arranged at the central position of the zirconium ring. The heating coil, the quartz tube, the zirconium ring and the crucible are coaxially arranged.

[0016] As the hub connecting the upper thermal field structure and the lower thermal field structure, the zirconium ring not only plays a role in thermal field regulation, but also plays a positioning role for the placement of the crucible, ensuring that the crucible is at the central position of induction heating. The lower part of the zirconium ring is horizontally placed on the sand, with a good fine gap in cooperation with the quartz tube on the outside and a good fit with the iridium crucible lid on the inside. The height of the zirconium ring is slightly higher than that of the crucible for easy removal. The upper part of the zirconium ring is flush with the quartz tube to ensure the sealing of the furnace.

[0017] Preferably, the materials of both the crucible and the mold are iridium.

[0018] The iridium crucible further includes a crucible lid. The radius of the crucible lid is slightly larger than that of the crucible. A through-hole equivalent to the size of the mold is provided on the crucible lid for the mold to pass through, so as to ensure good sealing. The iridium mold is placed at the central position of the crucible, and a slit with a certain width is opened in the center of the iridium mold to facilitate the transport of the melt in the crucible.

[0019] The solution adopted to achieve the third object of the present invention is: a method for improving the thermal field in the growth of gallium oxide crystals by the guide-mold method, which is realized by using the described device and includes the following steps:

[0020] Place gallium oxide in the crucible, install the mold, install the gallium oxide seed crystal at the end of the lifting mechanism, heat the crucible through the lower thermal field structure. After the melt in the crucible is transported to the top of the mold through the capillary slit of the mold, lower the lifting mechanism with the seed crystal to the top of the mold so that the seed crystal contacts the melt, and complete the processes of necking - shoulder broadening - equal-diameter growth - tailing - cooling, and finally grow gallium oxide single crystals. During the processes of necking - shoulder broadening - equal-diameter growth - tailing, keep the heating power unchanged, and only control the opening and closing of the first gas flow channel, the second gas flow channel, and the third gas flow channel to adjust the thermal field, which helps the high-quality growth of the crystal. The gases in the first gas flow channel, the second gas flow channel, and the third gas flow channel are kept consistent with the gas components in the device.

[0021] Preferably, during the processes of necking - shoulder broadening - equal-diameter growth - tailing, keep the heating power unchanged, and the specific operations for controlling the opening and closing of the first gas flow channel, the second gas flow channel, and the third gas flow channel are as follows:

[0022] (1) During the necking stage, open all the first gas flow channels, close all the second gas flow channels and the third gas flow channels, and the gas flow rate is between 1 - 5 m / s;

[0023] (2) During the shoulder broadening stage, open all the first gas flow channels, the second gas flow channels, and the third gas flow channels, and the gas flow rate is between 5 - 15 m / s;

[0024] (3) During the equal-diameter growth stage, close all the first gas flow channels, the second gas flow channels, and the third gas flow channels, keep the heating power unchanged, and the lifting speed also remains unchanged;

[0025] (4) During the lifting and tailing stage, open all the first gas flow channels, close all the second gas flow channels and the third gas flow channels, and the gas flow rate is between 1 - 5 m / s;

[0026] (5) During the cooling stage, heating is stopped, and all the first air flow channels, second air flow channels, and third air flow channels are opened. The air flow speed increases from small to large. Within the first 1 hour, the air flow rate is maintained at 1 - 5 m / s. After 1 hour, the air flow rate is increased to 10 - 20 m / s, and the holding time is 2 - 4 hours. Then, the crystal is taken out from all the air flow channels and allowed to cool naturally.

[0027] The present invention has the following advantages and beneficial effects:

[0028] For the upper thermal field structure of the present invention, by opening air flow channels with different inner diameters, the way to improve the thermal field is more flexible. By controlling the opening and closing of the air flow channels, the temperature field distribution in the furnace can be effectively adjusted.

[0029] The device of the present invention opens air flow channels with different inner diameters on the side wall of the upper thermal field structure. During the growth process, by adjusting the opening and closing of the air flow holes in the thermal insulation layer, the heat loss during crystal growth can be improved, and the crystal quality during crystal growth can be effectively controlled. The device of the present invention can ensure the growth of crystals in an oxidizing atmosphere, effectively reduce the crystal defects generated by gallium oxide crystals due to lack of oxygen, and the present invention provides a feasible technical solution for growing high-quality gallium oxide single crystals.

[0030] The method of the present invention can effectively regulate the temperature field distribution during the growth process by controlling the opening and closing of air flow channels with different inner diameters. Compared with the previous method of adjusting the heating power to improve the thermal field conditions in the furnace, the way to improve the thermal field of the invention is more flexible, and rapid control in multiple processes such as seeding - necking - shoulder - equal diameter growth - pulling tail - cooling can be realized. Brief Description of the Drawings

[0031] Figure 1 It is a schematic diagram of the thermal field structure for growing gallium oxide crystals by the guided mode method according to an embodiment of the present invention;

[0032] Figure 2 It is a schematic diagram of the device structure for growing gallium oxide crystals by the guided mode method according to Embodiment 2 of the present invention;

[0033] Figure 3 It is a gallium oxide single crystal substrate diagram prepared according to Embodiment 3 of the present invention;

[0034] Figure 4 It is an XRD diagram of the single crystal substrate prepared according to Embodiment 3 of the present invention;

[0035] Figure 5 It is an XRD diagram of another single crystal substrate of the single crystal substrate prepared according to Embodiment 3 of the present invention;

[0036] Figure 6 It is a gallium oxide single crystal substrate diagram prepared in Comparative Example 1;

[0037] In the figure: 1, base; 2, heating coil; 3, sand and gravel; 4, quartz tube; 5, zirconium ring; 6, crucible; 7, crucible cover; 8, mold; 81, capillary slit; 9, gallium oxide crystal; 10, first insulation barrel; 11, air flow channel; 12, seed crystal rod; 13, crystal growth channel; Z1 and K1, first air flow channels; Z2-Z5, second air flow channels; K2-K5, third air flow channels. Specific Embodiment

[0038] For a better understanding of the present invention, the following embodiments are further descriptions of the present invention, but the content of the present invention is not limited to the following embodiments only.

[0039] Embodiment 1

[0040] As Figure 1 shown, a thermal field structure for growing gallium oxide crystals by the edge-defined film-fed growth method includes a first insulation barrel 10. A crystal growth channel 13 with a rectangular cross-section is provided at the central axis of the first insulation barrel 10. First air flow channels Z1 and K1, second air flow channels Z2-Z5, and third air flow channels K2-K5 that penetrate the side wall and communicate with the crystal growth channel 13 are provided on the side wall of the first insulation barrel 10. The inner diameters of the first air flow channels Z1 and K1, the inner diameters of the second air flow channels Z2-Z5, and the inner diameters of the third air flow channels K2-K5 increase in sequence. The second air flow channels Z2-Z5 and the third air flow channels K2-K5 are evenly distributed along the outer diameter of the first insulation barrel 10. The first air flow channels Z1 and K1 are located below the second air flow channels Z2-Z5 and the third air flow channels K2-K5.

[0041] In this embodiment, the first air flow channels Z1 and K1, the second air flow channels Z2-Z5, and the third air flow channels K2-K5 are respectively provided on the side wall of the first insulation barrel 10 and horizontally penetrate the crystal growth channel 13 and the side wall.

[0042] In this embodiment, there are multiple second air flow channels Z2-Z5, which are evenly arranged in at least one column and horizontally penetrate the narrow side wall of the crystal growth channel 13. There are multiple third air flow channels K2-K5, which are evenly arranged in at least one column and horizontally penetrate the wide side wall of the crystal growth channel 13. There are multiple first air flow holes Z1 and K1, which are evenly distributed below the second air flow channels Z2-Z5 and the third air flow channels K2-K5.

[0043] In this embodiment, the second gas flow channels Z2-Z5 are arranged in a single row. The number of second gas flow channels Z2-Z5 in each row is 4-6, and the inner diameter is 14-16 mm. The third gas flow channels K2-K5 are arranged in a single row. The number of third gas flow channels K2-K5 in each row is 3-5, and the inner diameter is 28-32 mm. The first gas flow channels Z1 and K1 are arranged in two rows, located below the second gas flow channels Z2-Z5 and the third gas flow channels K2-K5 respectively. The number of first gas flow channels Z1 and K1 in each row is 1-2, and the inner diameter is 3-5 mm.

[0044] In this embodiment, the material of the first heat preservation barrel 10 is zirconia.

[0045] In this embodiment, during the growth process, in order to change the thermal field more conveniently and flexibly, gas flow channels 11 are opened around the first heat preservation barrel 10. During the crystal growth process, the gas flow channels 11 can be flexibly opened and closed to adjust the heat loss, helping the crystal to grow with high quality. The gas flow channels 11 in the embodiment penetrate through the four sides of the cuboid crystal growth channel 13. There are 4 third gas flow channels K2-K5 with a diameter of 30 mm and 1 first gas flow channel K1 with a diameter of 4 mm opened on the wide surface. There are 5 second gas flow channels Z2-Z5 with a diameter of 15 mm and 1 first gas flow channel Z1 with a diameter of 4 mm opened on the narrow surface. The number of opened and closed gas flow channels 11 in the area can be adjusted in real time to control the thermal field in the furnace, and further control the crystal growth quality.

[0046] Embodiment 2

[0047] As Figure 2 shown, a device for growing gallium oxide crystals by the edge-defined film-fed growth (EFG) method includes an upper thermal field structure, a lower thermal field structure arranged under the upper thermal field structure, a crucible 6 arranged in the lower thermal field structure, a mold 8 arranged at the central position of the crucible, and a lifting mechanism arranged in the crystal growth channel 13. The upper thermal field structure, the crucible, the lower thermal field structure, the mold and the lifting mechanism are all coaxially arranged. A capillary slit 81 is arranged at the central position of the mold. The capillary slit communicates with the crystal growth channel 13. The upper thermal field structure is the thermal field structure of the device for growing gallium oxide crystals by the EFG method disclosed in Embodiment 1. During the growth process of gallium oxide crystals, the thermal field can be adjusted by opening and closing the first gas flow channels Z1 and K1, the second gas flow channels Z2-Z5 and the third gas flow channels K2-K5, and further control the crystal growth quality.

[0048] In this embodiment, the lower thermal field structure includes a second heat preservation barrel and a heating coil 2 disposed outside the second heat preservation barrel. The second heat preservation barrel includes a quartz tube 4, sand 3 filled in the quartz tube 4, and a zirconium ring 5 placed on the sand 3. The filling height of the sand 3 is lower than the height of the quartz tube 4. The crucible 6 is disposed at the central position of the zirconium ring 5. The heating coil 2, the quartz tube 4, the zirconium ring 5, and the crucible 6 are coaxially arranged.

[0049] As the hub connecting the upper thermal field structure and the lower thermal field structure, the zirconium ring 5 not only plays a role in thermal field regulation, but also plays a positioning role for the placement of the crucible 6, ensuring that the crucible 6 is at the central position of induction heating. The lower part of the zirconium ring 5 is horizontally placed on the sand 3, with a fine gap in good fit with the outer side of the quartz tube 4 and a good fit with the crucible lid 7 on the inner side. The height of the zirconium ring 5 is slightly higher than that of the crucible 6 for easy removal. The upper part of the zirconium ring 5 is flush with the quartz tube 4 to ensure the sealing of the furnace.

[0050] In this embodiment, the materials of the crucible 6 and the mold 8 are both iridium.

[0051] The crucible 6 further includes a crucible lid 7. The radius of the crucible lid 7 is slightly larger than the radius of the crucible 6. The crucible lid 7 is provided with a through hole corresponding to the size of the mold 8 for the mold to pass through, ensuring good sealing. The mold 8 is placed at the central position of the crucible 6.

[0052] Specifically, for the assembly method of a device for growing gallium oxide crystals by the guiding mold method, first fix the position of the base 1 to ensure that it does not slip. The base 1 is in the shape of a solid cylinder. Then fix the quartz tube 4 on the base 1. The quartz tube 4 is in the shape of a hollow cylinder, ensuring that the quartz tube 4 is concentric with the base 1. Then fill the sand 3 into the quartz tube 4. The sand 3 has relatively fine particles. Then perform a leveling treatment on the sand 3 to make the surface of the sand 3 flat without concavities and convexities. The filling height of the sand 3 needs to be lower than the height of the quartz tube 4.

[0053] The heating coil 2 is a device that provides heat source for the furnace, playing a role in heating the iridium crucible 6. It is located outside the quartz tube 4, ensuring that the quartz tube 4 is concentric with the heating coil 2. The material of the heating coil 2 is copper.

[0054] Place the zirconium ring 5 on the leveled sand 3, ensuring that the zirconium ring 5 is in concentric fit with the quartz tube 4. The upper part of the zirconium ring 5 is flush with the quartz tube 4. The material of the zirconium ring 5 is zirconia, and the shape of the zirconium ring 5 is a hollow cylinder. The zirconium ring 5, the quartz tube 4, and the sand 3 form the second heat preservation barrel.

[0055] Place the crucible 6 at the central position inside the zirconium ring 5. A mold 8 is embedded at the central position inside the crucible 6. The shape of the mold 8 is a cuboid. There is a capillary slit 81 at the central position of the mold 8 to facilitate the transport of the gallium oxide melt. Then, cover the crucible lid 7 onto the crucible 6 to ensure concentric fit between the crucible lid 7 and the zirconium ring 5. The materials of the crucible 6, the mold 8, and the crucible lid 7 in the equipment are all made of iridium.

[0056] Place the first insulation barrel 10 on top of the zirconium ring 5 and the quartz tube 4 to ensure concentricity between the first insulation barrel 10 and the quartz tube 4. There are air flow channels opened around the first insulation barrel 10, and a cuboid crystal growth channel 13 is opened at the central position. The dimensions of the cuboid should be larger than the dimensions of crystal growth. The material of the first insulation barrel 10 is zirconia.

[0057] After the melt in the crucible 6 is transported to the top of the mold 8 through the slit of the iridium mold 8, lower the seed crystal rod 12 with the seed crystal to the top of the mold 8 so that the seed crystal contacts the melt to complete the seeding operation. Then, lift the melt upward and complete processes such as necking - shoulder broadening - equal diameter growth - ending - cooling through the thermal field control described in Content Five, and finally grow the gallium oxide single crystal 9.

[0058] Example 3

[0059] A method for improving the thermal field in growing gallium oxide crystals by the edge-defined film-fed growth (EFG) method, implemented using the described device, includes the following steps:

[0060] Place gallium oxide in the crucible 6, install the mold 8, install the gallium oxide seed crystal at the end of the seed crystal rod 12, heat the crucible 6 through the lower thermal field structure. After the melt in the crucible 6 is transported to the top of the mold 8 through the capillary slit 81 of the mold 8, lower the seed crystal rod 12 with the seed crystal to the top of the mold 8 so that the seed crystal contacts the melt, and complete the processes of necking - shoulder broadening - equal diameter growth - ending - cooling. Finally, grow the gallium oxide single crystal. During the processes of necking - shoulder broadening - equal diameter growth - ending, keep the heating power unchanged, control the opening and closing of the air flow channel 11 to adjust the thermal field to assist in the high-quality growth of the crystal, and the gas in the air flow channel 11 is kept consistent with the gas composition inside the device.

[0061] In this example, during the processes of necking - shoulder broadening - equal diameter growth - ending, keep the heating power unchanged. The specific operations for controlling the opening and closing of the first air flow channel, the second air flow channel, and the third air flow channel are as follows:

[0062] (1) During the necking stage, open all the first air flow channels, close all the second air flow channels and the third air flow channels, and the gas flow rate is between 1 - 5 m / s;

[0063] (2) During the shoulder broadening stage, open all the first air flow channels, the second air flow channels, and the third air flow channels, and the gas flow rate is between 5 - 15 m / s;

[0064] (3) During the equal-diameter growth stage, close all the first gas flow channels, the second gas flow channels, and the third gas flow channels, keep the heating power unchanged, and also keep the pulling speed unchanged;

[0065] (4) During the pulling tailing stage, open all the first gas flow channels, close all the second gas flow channels and the third gas flow channels, and the gas flow rate is between 1 - 5 m / s;

[0066] (5) During the cooling stage, stop heating, open all the first gas flow channels, the second gas flow channels, and the third gas flow channels, the air flow speed increases from small to large. Within the first 1 h, the air flow rate remains at 1 - 5 m / s. After 1 h, the air flow rate increases to 10 - 20 m / s, and the holding time is 2 h. Then take out the crystal from all the gas flow channels to let it cool naturally.

[0067] Specifically, during the necking stage, it is required that the cross-sectional area of the crystal is as small as possible, and the heat loss on the crystal surface needs to be reduced. Open the gas flow channels Z1 and K1 on both sides of the first heat preservation barrel 10, and the gas flow rate is as small as possible, with the flow rate between 1 - 5 m / s. Close the gas flow channels K2 - K5 and Z2 - Z5 on both sides.

[0068] During the shoulder broadening stage, the cross-sectional area of the crystal needs to become larger. At this time, it is necessary to increase the heat loss on the crystal surface. Open the gas flow channels K1 - K5 and Z1 - Z5, and at the same time increase the gas flow rate. In order to avoid the crystal shifting due to excessive air flow, the gas flow rate is between 5 - 15 m / s.

[0069] During the equal-diameter growth stage, in order to keep the cross-section of the crystal stable, close all the gas flow channels, keep the heating power unchanged, and also keep the pulling speed unchanged.

[0070] During the pulling tailing stage, the cross-section of the crystal needs to be continuously reduced. Open the gas flow channels Z1 and K1 on both sides of the first heat preservation barrel 10, close the other gas flow channels, and the gas flow speed is 1 - 5 m / s.

[0071] During the cooling stage, open all the gas flow channels 11, the air flow speed increases from small to large. Within the first 1 h, the air flow rate remains at 1 - 5 m / s. After 1 h, the air flow rate increases to 10 - 20 m / s, and the holding time is 2 h. Then close the gas flow channels 11 and take out the crystal to let it cool naturally.

[0072] During the necking - shoulder broadening - equal-diameter growth stage, change the opening and closing of the gas flow channels 11 according to actual needs. The gas in the gas flow channels 11 is consistent with the gas components in the furnace cavity, and can be gas components such as carbon dioxide (CO2), argon (Ar), or a mixed gas of CO2 / O2, etc.

[0073] Such as Figure 3The gallium oxide single crystal substrate of a thermal field improvement method for growing gallium oxide crystals by the edge-defined film-fed growth (EFG) method provided in this embodiment is shown as follows. Figure 3 Through reasonable control of the gas flow holes, the thermal field is further controlled. By the gas flow hole regulation scheme introduced in the present invention, the process thermal field of the entire process of gallium oxide crystal growth is optimized. The smoothness of the surface morphology of the grown gallium oxide crystal is greatly improved. The optimized surface looks more uniform and has fewer particles.

[0074] As Figure 4 The XRD pattern of the single crystal substrate of a thermal field improvement method for growing gallium oxide crystals by the EFG method provided in this embodiment is shown as follows. Figure 4 In the XRD scanning in it, the angle ranges from 15° to 16.2°, the vertical axis is the intensity, and there is a single sharp peak, and the peak appears at about ω = 15.6°. The calculated FWHM of this peak is 115.2 arcsec, indicating that the angular difference at half of the intensity of the peak width is 115.2 arcseconds.

[0075] As Figure 5 The XRD pattern of the single crystal substrate of a thermal field improvement method for growing gallium oxide crystals by the EFG method provided in this embodiment is shown as follows. Figure 5 The XRD scanning results in it show that the FWHM of the crystal is 72 arcsec. The FWHM after thermal field optimization is 43.2 arcsec smaller than that before optimization. This indicates that the peak width in the left figure is relatively narrow, indicating that the measured signal has a higher resolution. A narrower peak width means higher precision of the system, and the signal is concentrated in a smaller angular range, indicating that higher-quality crystals can be obtained through thermal field optimization.

[0076] Comparative Example 1

[0077] The existing method for growing gallium oxide single crystals is generally as follows: The temperature is raised to slightly higher than the melting point of gallium oxide by an iridium heating element to completely melt the gallium oxide raw material, and the molten gallium oxide is transported to the top of the iridium mold through capillary siphon effect and evenly spreads on the top until the entire mold surface is covered. Subsequently, the seed crystal rod equipped with the seed crystal is slowly lowered, and the end of the seed crystal is kept at a height of 3 - 5 millimeters from the top of the iridium mold for seed crystal preheating. After 5 to 10 minutes of preheating, seed crystal inoculation is started. When the seed crystal is fully combined with the melt at the top of the mold, it enters the crystal pulling stage. In order to prevent defects in the seed crystal from being transmitted to the crystal interior, necking treatment is required by increasing the heating power of the iridium heating element to ensure the high quality of the crystal. Then, shoulder broadening growth is carried out by reducing the heating power of the heating element, so that the crystal gradually expands laterally until it covers the entire mold. After that, the equal-diameter growth process is carried out. After the crystal growth is completed, the temperature is gradually lowered to room temperature, and the crystal is taken out, and finally a gallium oxide single crystal is obtained.

[0078] As Figure 6As shown: The gallium oxide single crystal substrate prepared in this comparative example Figure 6 The gallium oxide single crystal in it is obtained only by controlling the whole process growth process through the change of heating power. The surface twins and polycrystalline morphologies of the gallium oxide single crystal are obvious, the surface is rough, obvious cracks and peeling phenomena appear in the edge part of the material, and obvious longitudinal stripes exist on the material surface, which is significantly related to the inappropriate thermal field distribution.

[0079] The above is the preferred implementation manner of the present invention. Of course, the scope of the rights of the present invention cannot be limited thereby. It should be pointed out that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and changes can still be made, and these improvements and changes are also regarded as the protection scope of the present invention.

Claims

1. A thermal field structure for growing gallium oxide crystals by the edge-defined film-fed growth method, characterized in that: It includes a first heat preservation barrel, where a crystal growth channel with a rectangular cross-section is arranged at the central axis of the first heat preservation barrel. The side wall of the first heat preservation barrel is provided with a first air flow channel, a second air flow channel, and a third air flow channel that respectively penetrate the side wall and communicate with the crystal growth channel. The inner diameters of the first air flow channel, the second air flow channel, and the third air flow channel increase in sequence. The second air flow channel and the third air flow channel are evenly distributed along the outer diameter of the first heat preservation barrel, and the first air flow channel is located below the second air flow channel and the third air flow channel. The first air flow channel, the second air flow channel, and the third air flow channel are respectively arranged on the side wall of the first heat preservation barrel and horizontally penetrate the crystal growth channel and the side wall. There are multiple second air flow channels, which are evenly arranged in at least one row and horizontally penetrate the narrow side wall of the crystal growth channel. There are multiple third air flow channels, which are evenly arranged in at least one row and horizontally penetrate the wide side wall of the crystal growth channel. There are multiple first air flow channels, which are evenly distributed below the second air flow channel and the third air flow channel.

2. The thermal field structure for growing gallium oxide crystals by the guiding mode method according to claim 1, characterized in that: The second air flow channel is arranged in a single row, and the number of second air flow channels in each row is 4 - 6, with an inner diameter of 14 - 16 mm. The third air flow channel is arranged in a single row, and the number of third air flow channels in each row is 3 - 5, with an inner diameter of 28 - 32 mm. The first air flow channel is arranged in two rows, respectively located below the second air flow channel and the third air flow channel. The number of first air flow channels in each row is 1 - 2, with an inner diameter of 3 - 5 mm.

3. The thermal field structure for growing gallium oxide crystals by the guiding mode method according to claim 1, wherein: The material of the first heat preservation barrel is zirconia.

4. An apparatus for growing gallium oxide crystals by the edge-defined film-fed growth method, characterized in that: It includes an upper thermal field structure, a lower thermal field structure arranged under the upper thermal field structure, a crucible arranged in the lower thermal field structure, a mold arranged at the central position of the crucible, and a lifting mechanism arranged in the crystal growth channel. The upper thermal field structure, the crucible, the lower thermal field structure, the mold, and the lifting mechanism are all coaxially arranged. A capillary slit is arranged at the central position of the mold, and the capillary slit communicates with the crystal growth channel. The upper thermal field structure is the thermal field structure for growing gallium oxide crystals by the edge-defined film-fed growth method as described in any one of claims 1 - 3. During the growth process of gallium oxide crystals, the thermal field can be adjusted by opening and closing the first air flow channel, the second air flow channel, and the third air flow channel, thereby regulating the crystal growth quality.

5. The device for growing gallium oxide crystals by the edge-defined film-fed growth method according to claim 4, wherein: The lower thermal field structure includes a second heat preservation barrel and a heating coil surrounding the second heat preservation barrel. The second heat preservation barrel includes a quartz tube, sand filled in the quartz tube, and a zirconium ring placed on the sand. The filling height of the sand is lower than the height of the quartz tube. The crucible is arranged at the central position of the zirconium ring. The heating coil, the quartz tube, the zirconium ring, and the crucible are coaxially arranged.

6. The device for growing gallium oxide crystals by the guiding mode method according to claim 4, characterized in that: The materials of the crucible and the mold are both iridium.

7. A method for improving the thermal field in the growth of gallium oxide crystals by the edge-defined film-fed growth (EFG) method, characterized in that: It is realized by using the device as described in any one of claims 4 - 6, and includes the following steps: Place gallium oxide in a crucible, install the mold, install the gallium oxide seed crystal at the end of the lifting mechanism, heat the crucible through the lower thermal field structure. After the melt in the crucible is transported to the top of the mold through the capillary slit of the mold, lower the lifting mechanism with the seed crystal to the top of the mold so that the seed crystal contacts the melt, and complete the processes of necking - shoulder broadening - isodiametric growth - tailing - cooling. Finally, grow a gallium oxide single crystal. During the processes of necking - shoulder broadening - isodiametric growth - tailing, keep the heating power unchanged, and control the opening and closing of the first gas flow channel, the second gas flow channel and the third gas flow channel to adjust the thermal field to assist the high-quality growth of the crystal. The gases in the first gas flow channel, the second gas flow channel and the third gas flow channel are consistent with the gas components in the device; The specific operations of controlling the opening and closing of the first gas flow channel, the second gas flow channel and the third gas flow channel while keeping the heating power unchanged during the processes of necking - shoulder broadening - isodiametric growth - tailing are as follows: (1) In the necking stage, open all the first gas flow channels, close all the second gas flow channels and the third gas flow channels, and the gas flow rate is between 1 - 5 m / s; (2) In the shoulder broadening stage, open all the first gas flow channels, the second gas flow channels and the third gas flow channels, and the gas flow rate is between 5 - 15 m / s; (3) In the isodiametric growth stage, close all the first gas flow channels, the second gas flow channels and the third gas flow channels, keep the heating power unchanged, and the lifting speed also remains unchanged; (4) In the tailing stage of lifting, open all the first gas flow channels, close all the second gas flow channels and the third gas flow channels, and the gas flow rate is between 1 - 5 m / s; (5) In the cooling stage, stop heating, open all the first gas flow channels, the second gas flow channels and the third gas flow channels, the air flow speed increases from small to large. In the first 1 h, the air flow rate remains at 1 - 5 m / s. After 1 h, the air flow rate is increased to 10 - 20 m / s and kept for 2 - 4 h, and then take out the crystal from all the gas flow channels to make it cool naturally.

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