Beta-gallium-oxide casting method single crystal growth apparatus and method

Abstract

The application discloses a kind of beta-gallium oxide casting method single crystal growth device and method, device, the upper end opening outer periphery of blanking cylinder is equipped with card station, and the outer periphery surface of the opening of furnace body upper portion is clamped with card station.Blanking pipe is threaded through the upper portion of heat preservation structure and is equipped with mouth, and the upper end of blanking pipe is communicated with the lower end opening of blanking cylinder, and the lower end of blanking pipe is communicated with the feed inlet on crucible cover.Cargo bin cylinder is located in blanking cylinder.Cover plate cover is equipped in the upper end opening of cargo bin cylinder, and the upper end opening outer periphery surface of blanking cylinder is clamped with cover plate.Screen is equipped in cargo bin cylinder, and screen can reciprocate along the center line direction of cargo bin cylinder, and screen and the inner periphery wall of cargo bin cylinder are slidably sealed arrangement.Vibration structure is used to make screen reciprocate along the center line direction of cargo bin cylinder.Weighing sensor is equipped between cover plate and the upper end opening outer periphery surface of blanking cylinder.Cargo bin cover is equipped on the upper side of furnace body, and cargo bin cover cover is equipped in opening outer.This application device can realize large size low defect beta-gallium oxide single crystal growth.

Description

Technical Field

[0001] This invention relates to the field of wide bandgap semiconductor single crystal material preparation technology and supporting equipment, and particularly to a β-gallium oxide casting method for single crystal growth apparatus and method. Background Technology

[0002] β-gallium oxide (β-Ga2O3) is an ultrawide bandgap semiconductor material with a bandgap of approximately 4.8 eV. It possesses excellent properties such as high breakdown field strength, low on-resistance, good thermal stability, and high ultraviolet transmittance. It is a core material for the fabrication of high-voltage power devices, deep ultraviolet detectors, and high-frequency electronic devices, and has irreplaceable application value in fields such as new energy, rail transportation, aerospace, and optoelectronic communication.

[0003] Currently, the mainstream methods for preparing gallium oxide single crystals include the mold-guided method, the Czochralski method, the crucible lowering method, and the casting method. Among them, the casting method has become the preferred process for mass production of large-size gallium oxide single crystals due to its advantages of simple process, low equipment cost, and strong single crystal size scalability. However, the existing traditional casting method has significant technical defects: First, it generally adopts a one-time feeding mode. During the crystal growth process, the gallium oxide melt continuously evaporates and is consumed, and it is impossible to replenish the material in real time. This leads to a drop in the melt level, uneven composition, and deterioration of crystal quality in the later stage of crystal growth. The single crystal size is limited, making it difficult to stably prepare large-size single crystals of 6 inches and above. Second, there is no precise continuous feeding structure. Manual intermittent feeding can easily cause fluctuations in the furnace atmosphere and sudden temperature changes, which can cause defects such as dislocations, voids, cracks, and compositional segregation inside the single crystal, reducing the yield of single crystals. Third, the traditional control process is simple and lacks a precise gradient cooling and slow cooling mechanism. The thermal stress is concentrated during the single crystal growth process, which further affects the integrity of the single crystal and the consistency of electrical performance.

[0004] In existing technologies, most casting-based gallium oxide growth processes are only optimized for single-stage crystal growth, failing to address the core challenges of continuous production, stable melt composition, and large-size, low-defect growth. These processes suffer from weak mass production capabilities, unstable single-crystal quality, and size limitations, thus failing to meet the industrialization demands of high-end semiconductor devices for large-size, highly uniform, and low-defect gallium oxide single crystals. Therefore, there is an urgent need to develop a casting-based fabrication technology suitable for the growth of large-size, high-quality β-gallium oxide single crystals. Summary of the Invention

[0005] This invention provides a single crystal growth apparatus and method for β-gallium oxide casting, which can realize the growth of large-size, low-defect β-gallium oxide single crystals.

[0006] This invention provides a β-gallium oxide casting method single crystal growth apparatus, including a furnace body, a heat insulation structure, a crucible, and a crucible cover. The heat insulation structure is located inside the furnace body and includes a heat insulation space. A temperature control structure is used to control the temperature within the heat insulation space. The crucible is located within the heat insulation space. The crucible cover is located at the open end of the crucible. The crucible cover has a feed inlet. The upper part of the heat insulation structure has a through-hole. The upper part of the furnace body has an opening. The β-gallium oxide casting method single crystal growth apparatus also includes a feeding cylinder, a feeding tube, a hopper, a cover plate, a screen, a vibration structure, a weighing sensor, and a hopper cover. A retaining plate is located on the outer periphery of the upper opening of the feeding cylinder, engaging with the outer periphery of the opening. The feeding tube passes through the through-hole, with its upper end communicating with the lower opening of the feeding cylinder and its lower end communicating with the feed inlet. The hopper is located inside the feeding cylinder. A cover plate is installed at the upper opening of the hopper cylinder, and the cover plate is engaged with the outer circumference of the upper opening of the discharge cylinder. A screen is installed inside the hopper cylinder, and the screen can reciprocate along the centerline of the hopper cylinder. The screen is slidably sealed to the inner circumference of the hopper cylinder. A vibration structure is used to make the screen reciprocate along the centerline of the hopper cylinder. A load cell is located between the cover plate and the outer circumference of the upper opening of the discharge cylinder. The hopper cover is located on the upper side of the furnace body, covering the opening.

[0007] In some embodiments, the cover plate has a through hole. The hopper cover has a rod shaft sealing hole. The vibration structure includes an elastic ring, a connector, a connecting rod, a motor bracket, a vibration motor, and a vibration rod. The elastic ring is located on the side of the cover plate away from the hopper cylinder and on the outer periphery of the through hole. The connector is located at the end of the elastic ring away from the cover plate. The connecting rod passes through the through hole and is connected to the screen and the connector. The motor bracket is located outside the furnace body. The vibration motor is mounted on the motor bracket. The upper end of the vibration rod is connected to the output end of the vibration motor, the vibration rod passes through the rod shaft sealing hole, and the vibration rod is slidably sealed to the inner peripheral wall of the rod shaft sealing hole. The lower end of the vibration rod faces the connector on the side away from the elastic ring.

[0008] In some embodiments, the upper part of the furnace body has an opening. The vibration structure also includes a rubber pad. The rubber pad is located on the side of the connector opposite to the elastic ring.

[0009] In some embodiments, the screens include multiple screens arranged along the centerline of the hopper cylinder, and the aperture of the lower screen in a pair of adjacent screens is smaller than that of the upper screen.

[0010] This invention provides a method for growing a single crystal using the aforementioned β-gallium oxide casting method with the above-described β-gallium oxide casting apparatus. The method includes the following steps: placing a gallium oxide seed crystal into a crucible and filling it with a first predetermined amount of gallium oxide material. Filling a hopper with a second predetermined amount of gallium oxide powder. Then, evacuating the furnace and replacing the air inside the furnace with argon gas to completely melt the gallium oxide material. Next, allowing a third predetermined amount of gallium oxide powder, less than the second predetermined amount, to fall into the crucible and melt. Subsequently, continuously replenishing the gallium oxide powder while maintaining a constant molten surface level in the crucible until all the gallium oxide powder is used up. Then, directionally solidifying and growing a β-gallium oxide single crystal.

[0011] In some embodiments, the pressure inside the furnace is maintained at 0.105 MPa after the air inside the furnace is replaced with argon.

[0012] In some embodiments, the gallium oxide material is completely melted by: controlling the temperature inside the insulation cavity to rise to 1820°C at a rate of 8-12°C / min, then rising to 1865°C at a rate of 5°C / min, and holding the temperature for 60 min.

[0013] In some embodiments, gallium oxide powder is continuously replenished and the molten liquid level in the crucible is kept constant in real time, including controlling the feeding rate of gallium oxide powder to be 0.5±0.05 g / min.

[0014] In some embodiments, the directional solidification growth of β-gallium oxide single crystals includes: controlling the temperature inside the insulation cavity to decrease at a rate of 0.5°C / h for 8 hours, then at a rate of 0.8°C / h for 5 hours, and then at a rate of 1°C / h for 50 hours, until the temperature is reduced to 1807°C.

[0015] In some embodiments, after directional solidification growth of β-gallium oxide single crystal, the temperature inside the insulation cavity is controlled to decrease to 1600°C at a rate of 5°C / h, held for 30 min, then decreased to 1400°C at a rate of 15°C / h, held for 30 min, and then decreased to room temperature at a rate of 25°C / h.

[0016] Compared with the prior art, the present invention has the following beneficial effects: In the device of this invention, the feeding cylinder, feeding pipe, hopper cylinder, cover plate, screen, vibration structure, weighing sensor, and hopper cover work together to achieve high-precision continuous feeding under fully enclosed conditions. This breaks through the technical bottleneck of single feeding in traditional casting methods, timely replenishes the raw material in the upper volume cavity of the crucible caused by the drop in liquid level after melting, and compensates for melt volatilization and loss in real time. It maintains uniform and stable melt liquid level, temperature, and composition throughout the process, completely solving the problem of crystal quality deterioration in the later stage of crystal growth, significantly improving the upper limit of single crystal size and crystal quality, and realizing the growth of large-size, low-defect β-gallium oxide single crystals. At the same time, it overcomes the shortcomings of manual intermittent feeding, which reduces the yield of single crystals, and eliminates the long waiting process for temperature field and atmosphere stabilization after furnace opening that exists in manual intermittent feeding, improving production efficiency by more than 30%. Moreover, the crystal growth process isolates the high-temperature gallium oxide melt from air, water vapor, and carbon impurities, improving the purity of single crystals.

[0017] The screen in the device of this invention can simultaneously disperse powder, break up agglomerates, and filter impurities, thus solving the problems of poor flowability and bridging blockage of gallium oxide powder from the root. Only powders of qualified particle size enter the crucible, preventing large particles from agglomerating and causing localized rapid cooling of the melt, and significantly reducing single crystal cracking, dislocations, and inclusion defects.

[0018] In the method of this invention, each step works synergistically to achieve a stable melt state and crystal growth environment, precisely match the phase transformation growth characteristics of β-gallium oxide single crystals, ensure that the single crystal grows in a single crystal direction, effectively suppress the generation of impurities, twins and lattice defects, realize the growth of large-size, low-defect β-gallium oxide single crystals, and effectively release the internal thermal stress of the single crystal, suppress defects such as cracks, dislocations and component segregation, and prepare large-size single crystals with good integrity and high uniformity. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a cross-sectional view of the growth device in an embodiment of the present invention; Figure 2 This is a schematic diagram of a β-gallium oxide single crystal in Embodiment 1 of the present invention; Figure 3 This is a high-resolution XRD rocking curve of the β-gallium oxide single crystal in Example 1 of the present invention; Figure 4 This is an AFM image of the surface morphology of the β-gallium oxide single crystal in Example 1 of the present invention. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this invention clearer, the 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 merely illustrative and not intended to limit the invention.

[0022] To address the technical challenges of traditional casting methods, such as single-feeding, unstable melts, numerous defects, size limitations, and inability to achieve continuous mass production, this study aims to realize the stable, continuous, and large-scale preparation of large-size, low-defect, and highly uniform β-Ga2O3 single crystals. (See also...) Figure 1 The present invention provides a single crystal growth apparatus for β-gallium oxide casting, comprising a furnace body 1, a heat preservation structure 2, a temperature control structure, a crucible 5, a crucible cover 7, a feeding cylinder 8, a feeding pipe 9, a hopper cylinder 10, a cover plate 11, a screen 12, a vibration structure, a weighing sensor 13, and a hopper cover 14.

[0023] An opening is provided at the top of the furnace body 1.

[0024] The insulation structure 2 is located inside the furnace body 1 and has an insulation space. The upper part of the insulation structure 2 has a through-hole. The through-hole and the opening are vertically aligned. The upper part of the insulation structure 2 also has a through-hole.

[0025] The temperature control structure is used to control the temperature inside the insulated cavity. The temperature control structure includes an induction coil 4, a heating element 6, and a heating element 6. The induction coil 4 is located on the outer peripheral wall of the insulation material. The heating element 6 is located on the inner peripheral wall of the insulated space. The heating element 6 is made of iridium. A thermocouple 3 is located inside the through-hole, and the thermocouple 3 is sealed to the inner peripheral wall of the through-hole.

[0026] Crucible 5 is located within the insulated space and is used to contain gallium oxide seed crystal 22 and the cake material. Crucible 5 is made of iridium.

[0027] The crucible lid 7 is located at the open end of the crucible 5. The crucible lid 7 has a feed inlet. The feed inlet and the through-hole are vertically aligned. The feed inlet is located at the center of the crucible lid 7. The crucible lid 7 is made of iridium.

[0028] The centerline of the feed cylinder 8 extends vertically. A retaining platform is provided on the outer periphery of the upper opening of the feed cylinder 8, engaging with the outer periphery of the opening. The lower part of the feed cylinder 8 has a tapered structure that gradually tapers from top to bottom. A first connecting boss is provided on the outer periphery of the lower opening of the feed cylinder 8. The feed cylinder 8 is made of metal, such as stainless steel.

[0029] The centerline of the feed pipe 9 extends vertically. The feed pipe 9 has a through-hole, with its upper end connected to the lower opening of the feed cylinder 8, and its lower end connected to the feed inlet. A second connecting boss is provided on the outer periphery of the upper opening of the feed pipe 9, and the second connecting boss is fitted and connected to the first connecting boss. The outer periphery of the lower opening of the feed pipe 9 is fitted and connected to the outer periphery of the feed inlet. The feed pipe 9 is made of high-temperature resistant material.

[0030] The centerline of the hopper cylinder 10 extends vertically. The hopper cylinder 10 is located inside the feed cylinder 8. The hopper cylinder 10 is made of metal, such as stainless steel.

[0031] The cover plate 11 is horizontally positioned. It covers the upper opening of the hopper cylinder 10 and engages with the outer circumferential surface of the upper opening of the discharge cylinder 8. The cover plate 11 has a through hole, which coincides with the center line of the hopper cylinder 10. The cover plate 11 is made of metal, such as stainless steel.

[0032] The screen 12 is horizontally positioned. Located inside the hopper 10, the screen 12 can reciprocate along the centerline of the hopper 10. The screen 12 is slidably sealed to the inner circumferential wall of the hopper 10. At this time, the hopper 10 above the screen 12 stores gallium oxide powder 24. When the screen 12 vibrates up and down at high frequency, it continuously impacts and breaks up the agglomerated gallium oxide powder 24 within the hopper 10. Large, clump-like gallium oxide powder 24 is trapped on the screen 12 and repeatedly vibrated and broken. Gallium oxide powder 24 of the correct particle size passes through the screen 12 and falls into the feed cylinder 8, completely solving the problem of bridging and clogging of the gallium oxide powder 24. The screens 12 include multiple screens, such as two, arranged along the centerline of the hopper cylinder 10. In any two adjacent screens 12, the aperture of the lower screen 12 is smaller than that of the upper screen 12. For example, the lower screen 12 has an aperture of 0.2 mm, while the upper screen 12 has an aperture of 1 mm. This allows the upper screen 12 to perform a large-aperture pre-screening, intercepting hard impurities and large agglomerates, while the lower screen 12 serves as a standard sieve layer matching the particle size of the gallium oxide crystal growth raw material. The screens 12 are metal woven grading screens and can be made of stainless steel.

[0033] The weighing sensor 13 is located between the cover plate 11 and the outer periphery of the upper opening of the feeding cylinder 8, and collects real-time data on the structure of the hopper cylinder 10 and the total weight of the gallium oxide powder 24 inside the hopper cylinder 10. The weighing sensor 13 is connected to the industrial control computer via a signal acquisition module. The industrial control computer calculates the real-time feeding rate of the gallium oxide powder 24 based on the weight difference per unit time. The industrial control computer presets a standard feeding flow rate matching the gallium oxide crystal growth rate and adjusts the vibration frequency and amplitude of the vibration structure in a closed loop according to the actual flow rate deviation. Alumina high-temperature resistant insulating pads are mounted on both the upper and lower end faces of the weighing sensor 13. The weighing sensor 13 includes multiple sets, such as two sets, with each set of weighing sensors 13 arranged around the upper opening of the feeding cylinder 8, or the two sets of weighing sensors 13 arranged symmetrically from left to right. The weighing sensor 13 is an S-type weighing sensor 13, and the weighing accuracy error of the S-type weighing sensor 13 is ≤0.05g.

[0034] The hopper cover 14 is horizontally positioned. Located on the upper side of the furnace body 1, the hopper cover 14 covers the opening, simultaneously covering the feed cylinder 8, cover plate 11, and weighing sensor 13, thus sealing the upper part of the furnace body 1. The hopper cover 14 has a rod shaft sealing hole, which corresponds vertically to the through hole. The hopper cover 14 also has a sensor wire sealing hole for the signal wire of the weighing sensor 13 to pass through. The inner circumferential wall of the sensor wire sealing hole is sealed to the signal wire. The sensor wire sealing hole is filled with high-temperature resistant epoxy sealant to achieve a static seal, preventing air leakage.

[0035] The vibration structure is used to make the screen 12 reciprocate along the center line of the hopper cylinder 10, such as performing high-frequency small-amplitude up-and-down reciprocating vibration. The vibration structure includes an elastic ring 15, a connector 16, a connecting rod 17, a motor bracket 18, a vibration motor 19, a vibration rod 20, and a rubber pad 21.

[0036] The centerline of the elastic ring 15 extends vertically. The elastic ring 15 is located on the side of the cover plate 11 away from the hopper cylinder 10, and is located on the outer periphery of the through hole. The elastic ring 15 can be a spring or a rubber ring.

[0037] The connector 16 is horizontally positioned. The connector 16 is located at the end of the elastic ring 15 opposite to the cover plate 11.

[0038] The connecting rod 17 is vertically arranged. The connecting rod 17 passes through the through hole and connects to the screen 12 and the connector 16. At this time, the connecting rod 17, the elastic ring 15, and the connector 16 are all covered within the hopper cover 14. The connecting rod 17 is a T-shaped metal connecting rod. A fixing nut is provided on the connecting rod 17, and the fixing nut is connected to the screen 12.

[0039] The motor bracket 18 is located outside the furnace body 1, that is, it is separated from the furnace body 1.

[0040] The centerline of the output end of the vibration motor 19 extends vertically. The vibration motor 19 is connected to an industrial control computer to achieve automation. The vibration motor 19 is mounted on the motor bracket 18, which separates the vibration motor 19 from the furnace body 1 and thus completely separates it from the crucible 5, so that the vibration will not disturb the surface of the molten liquid and generate turbulence.

[0041] The vibrating rod 20 is vertically positioned. The upper end of the vibrating rod 20 is connected to the output end of the vibrating motor 19. The vibrating rod 20 passes through the rod shaft sealing hole, and the vibrating rod 20 is slidably sealed to the inner circumferential wall of the rod shaft sealing hole. The lower end of the vibrating rod 20 faces the connector 16 on the side away from the elastic ring 15. At this time, the vibrating motor 19 is located outside the hopper cover 14. A high-temperature resistant flexible graphite dynamic sealing ring is installed between the vibrating rod 20 and the inner circumferential wall of the rod shaft sealing hole to achieve zero leakage during operation, preventing leakage of the protective atmosphere inside the furnace and infiltration of outside air. The vibration amplitude of the vibrating rod 20 is adjustable in the range of 0.5~3mm (e.g., 0.5mm, 1.5mm, 3mm), and the vibration frequency is adjustable in the range of 5~25Hz (e.g., 5Hz, 15Hz, 25Hz). The industrial control computer enables stepless continuous closed-loop adjustment of parameters to adapt to gallium oxide powder 24 with different bulk densities and particle sizes.

[0042] The rubber pad 21 is horizontally positioned. The rubber pad 21 is located on the side of the connector 16 opposite to the elastic ring 15.

[0043] In summary, the device of this invention, with its feeding cylinder 8, feeding pipe 9, hopper cylinder 10, cover plate 11, screen 12, vibration structure, weighing sensor 13, and hopper cover 14 working together, achieves high-precision continuous feeding under fully enclosed conditions. This breaks through the technical bottleneck of single-feeding in traditional casting methods, promptly replenishes the raw material in the upper cavity of the crucible 5 due to the drop in liquid level after melting, and compensates for melt volatilization and loss in real time. It maintains uniform and stable melt liquid level, temperature, and composition throughout the process, completely solving the problem of crystal quality deterioration in the later stages of crystal growth, and significantly improving the upper limit of single crystal size and crystal quality. At the same time, it overcomes the shortcomings of manual intermittent feeding, which reduces the yield of single crystals, and eliminates the long waiting process for temperature field and atmosphere stabilization after furnace opening, which is present in manual intermittent feeding, thus increasing production efficiency by more than 30%. Moreover, it isolates the high-temperature gallium oxide melt from air, water vapor, and carbon impurities throughout the crystal growth process, improving the purity of single crystals.

[0044] The screen 12 in the device of the present invention can simultaneously disperse, break up agglomerates, and filter impurities, thus solving the problem of poor flowability and bridging of gallium oxide powder 24 from the root. Only qualified particle size powder 24 enters the crucible 5, preventing large particle agglomeration from causing local rapid cooling of the melt 23, and significantly reducing single crystal cracking, dislocation, and inclusion defects.

[0045] The weighing sensor 13 and drive motor in the device of this invention can achieve automated and precise control of the entire crystal growth process by connecting to an industrial control computer, eliminating the need for real-time manual monitoring, avoiding human operation errors, improving process stability and mass production consistency, reducing labor production costs, adapting to the industrial mass production needs of gallium oxide single crystals (such as mass production of β-phase gallium oxide substrates), and can be applied in fields such as high-voltage power devices, solar-blind ultraviolet detectors, and radio frequency devices.

[0046] Embodiments of the present invention provide a method for growing single crystals using the above-described β-gallium oxide casting method with β-gallium oxide, comprising the following steps: (1) Place gallium oxide single crystal seed 22 into crucible 5 and fill it with a first set amount of gallium oxide material. Fill gallium oxide powder 24 into hopper 10 with a second set amount. Then evacuate furnace body 1 and replace the air in furnace body 1 with argon gas.

[0047] In the above steps, a gallium oxide single crystal seed 22 is placed at the center of the crucible 5. The gallium oxide single crystal seed 22 is a gallium oxide single crystal seed with a (010) crystal orientation. The gallium oxide material can be gallium oxide cake, mainly because the cake has a high density (about 3 times that of the powder 24), allowing for a larger loading capacity in the crucible 5 (relative to the powder 24), and a smaller drop in the liquid level after melting (relative to the powder 24). The gallium oxide material can also be gallium oxide powder. Both gallium oxide cake and gallium oxide powder can be made from 5N-grade high-purity gallium oxide powder, or they can be made by mixing 5N-grade high-purity gallium oxide powder with a dopant. For this purpose, the dopant is uniformly premixed into the 5N-grade high-purity gallium oxide powder. The dopant can be a 5N-grade ferric oxide dopant or a 5N-grade tin oxide dopant. The amount of 5N-grade ferric oxide dopant can be 0.02%–0.08% of the gallium oxide material, such as 0.02%, 0.05%, or 0.08%. The amount of 5N-grade tin oxide dopant can be 0.03%–0.05% of the gallium oxide material, such as 0.03%, 0.04%, or 0.05%. The initial set amount can be 3000g. After filling the gallium oxide material, seal the furnace side door.

[0048] Gallium oxide powder 24 has a higher purity than cake material (which is prone to contamination by impurities during the pressing and sintering process). Powder 24 is easier to control in micro-feeding, resulting in more uniform falling and less disturbance to the melt surface, thus reducing thermal stress during single crystal growth. Gallium oxide powder 24 can be 5N-grade high-purity gallium oxide powder or a mixture of 5N-grade high-purity gallium oxide powder and dopant. Therefore, the dopant is uniformly premixed into the 5N-grade high-purity gallium oxide powder. The dopant can be 5N-grade ferric oxide dopant or 5N-grade tin oxide dopant. The amount of 5N-grade ferric oxide dopant can be 0.02%–0.08% of the gallium oxide material, such as 0.02%, 0.05%, or 0.08%. The amount of 5N-grade tin oxide dopant can be 0.03%–0.05% of the gallium oxide material, such as 0.03%, 0.04%, or 0.05%. When filling the hopper 10 with a second set amount of gallium oxide powder 24, the weight of the gallium oxide powder 24 is obtained by the weighing sensor 13. Before obtaining the weight of the gallium oxide powder 24 by the weighing sensor 13, the weighing sensor 13 is zero-point calibrated. The second set amount can be 3000g. After filling the gallium oxide powder 24, the hopper cover 14 is locked.

[0049] When evacuating furnace body 1, evacuate furnace body 1 to a vacuum level of 1×10. -4 Pa. The air inside furnace 1 was replaced four times with argon gas. The argon gas was 5N high-purity argon gas.

[0050] After replacing the air inside furnace 1 with argon, the pressure inside furnace 1 is maintained at 0.105 MPa (slight positive pressure). This slight positive pressure high-purity argon protection effectively suppresses the thermal decomposition and volatilization of gallium oxide at high temperatures, reduces the introduction of impurities, lowers the single crystal defect density, and improves the purity and performance stability of the single crystal.

[0051] (2) Completely melt the gallium oxide material. Then, a third set amount of gallium oxide powder 24 is dropped into the crucible 5 and melted. The third set amount is less than the second set amount. Subsequently, gallium oxide powder 24 is continuously replenished, and the melt level in the crucible 5 is kept constant in real time until the gallium oxide powder 24 is used up. Then, β-gallium oxide single crystal is directionally solidified and grown.

[0052] In the above steps, to completely melt the gallium oxide material, the following steps are taken: controlling the temperature inside the insulation cavity to rise to 1820°C at a rate of 8-12°C / min, causing the gallium oxide to slightly melt; then raising the temperature to 1865°C at a rate of 5°C / min and holding it at that temperature for 60 minutes, allowing the gallium oxide to completely melt and form a homogeneous and stable melt, at which point the liquid level drops. After the gallium oxide material has completely melted, the device's control system automatically switches to a rapid replenishment mode. When controlling the temperature inside the insulation cavity to rise to 1820°C at a rate of 8-12°C / min, the heating rate can be 8°C / min, 10°C / min, 12°C / min, etc.

[0053] Under constant temperature conditions of 1865℃, a third set amount of gallium oxide powder 24 is dropped into crucible 5 and melted. The third set amount is less than the second set amount to quickly replenish the material and promptly fill the material in the upper volume cavity of crucible 5 after the liquid level drops. The third set amount can be 1800g.

[0054] The process of allowing the third set amount of gallium oxide powder 24 to fall into the crucible 5 and melt includes: starting the vibration motor 19, causing the vibration rod 20 to drive the screen 12 to vibrate at a maximum frequency of 25Hz, continuously loosening and sieving the gallium oxide powder 24, and allowing gallium oxide powder 24 of qualified particle size to fall into the crucible 5. After the third set amount of material is fed, the temperature is kept constant for 30 minutes to allow the newly added raw material to fully melt. After the third set amount of gallium oxide powder 24 has fallen into the crucible 5 and melted, the control system of the device automatically switches to micro-feeding mode.

[0055] Under constant temperature conditions of 1865℃, gallium oxide powder 24 was continuously replenished, and the molten liquid level in crucible 5 was maintained constant in real time until the gallium oxide powder 24 was used up. Micro-replenishment was then carried out to compensate for melt evaporation and loss in real time. The weight of gallium oxide powder 24 continuously replenished was 1200g, and the duration was 40 hours.

[0056] Continuously replenish gallium oxide powder 24 and maintain a constant melt level in crucible 5 in real time, including controlling the feeding rate of gallium oxide powder 24 to 0.5±0.05 g / min. The feeding rate is adjusted based on empirical values ​​of melt loss rate. When the feeding rate of gallium oxide powder 24 is controlled at 0.5±0.05 g / min, the weighing sensor 13 uploads weight data every 100 ms, and the industrial control computer calculates the instantaneous feeding rate in real time; if the rate is lower than 0.45 g / min, the vibration frequency is automatically increased to 25 Hz, and if the rate is higher than 5.05 g / min, the vibration frequency is automatically decreased to 10 Hz to stabilize the feeding flow rate.

[0057] Directional solidification growth of β-gallium oxide single crystals includes: controlling the temperature inside the insulation cavity to decrease at a rate of 0.5℃ / h for 8 hours, then at a rate of 0.8℃ / h for 5 hours, and then at a rate of 1℃ / h for 50 hours, until the temperature is reduced to 1807℃.

[0058] After directionally solidifying and growing β-gallium oxide single crystals, the temperature inside the insulation cavity is controlled to decrease to 1600℃ at a rate of 5℃ / h and held for 30 min. Then, it is decreased to 1400℃ at a rate of 15℃ / h and held for 30 min. Subsequently, it is decreased to room temperature (25℃) at a rate of 25℃ / h, and the β-gallium oxide single crystals are removed.

[0059] The processes described above work together to stabilize the melt state and crystal growth environment, precisely match the phase transformation growth characteristics of β-gallium oxide single crystals, ensure that the single crystal grows in a single crystal direction, effectively suppress the generation of impurities, twins and lattice defects, realize the growth of large-size, low-defect β-gallium oxide single crystals, and effectively release the internal thermal stress of the single crystal, suppress defects such as cracks, dislocations and compositional segregation. The prepared large-size single crystals have good integrity and high uniformity.

[0060] The method of this invention can stably prepare 8-inch large-size β-gallium oxide single crystals with a smooth, crack-free surface and an internal dislocation density ≤5×10⁻⁶. 3 cm -2 The composition uniformity error is ≤0.5%, there are no impurities or voids, and the electrical properties are highly uniform.

[0061] The following detailed description is provided with reference to specific embodiments: Example 1 (1) Place a (010) oriented gallium oxide single crystal seed crystal 22 in the center of the crucible 5 and fill it with gallium oxide cake material, wherein the gallium oxide cake material is made by mixing 3000g of 5N grade high-purity gallium oxide powder and 0.02% of 5N grade iron oxide dopant in the amount of 5N grade high-purity gallium oxide powder.

[0062] (2) Gallium oxide powder 24 is filled into the hopper cylinder 10, wherein the gallium oxide powder 24 is a mixture of 3000g of 5N grade high-purity gallium oxide powder and 0.02% of 5N grade ferric oxide dopant.

[0063] (3) Evacuate furnace body 1 to a vacuum level of 1×10 -4 The pressure inside the furnace body 1 was maintained at 0.105 MPa by replacing the air in the furnace body 1 with 5N high-purity argon gas 4 times.

[0064] (4) Control the temperature inside the insulation cavity to rise to 1820°C at a rate of 12°C / min to make the gallium oxide cake slightly melt, and then raise the temperature to 1865°C at a rate of 5°C / min and hold the temperature for 60 min to make the gallium oxide cake completely melt.

[0065] (5) Under constant temperature of 1865℃, start the vibration motor 19, so that the vibration rod 20 drives the screen 12 to vibrate at the maximum frequency of 25Hz. The gallium oxide powder 24 is continuously loosely screened. The gallium oxide powder 24 with qualified particle size falls into the crucible 5. After the feed reaches 1800g, keep the temperature constant for 30min to fully melt the new raw material.

[0066] (6) Under constant temperature of 1865℃, the feeding rate of gallium oxide powder 24 is controlled at 0.5±0.05g / min and maintained for 40 hours until the remaining 1200g of gallium oxide powder 24 is used up.

[0067] (7) Control the temperature inside the insulation cavity to decrease at a rate of 0.5℃ / h for 8 hours, then at a rate of 0.8℃ / h for 5 hours, and then at a rate of 1℃ / h for 50 hours until the temperature drops to 1807℃, thereby achieving directional solidification growth of β-gallium oxide single crystal.

[0068] (8) The temperature inside the insulation cavity is controlled to decrease to 1600℃ at a rate of 5℃ / h, and held for 30 min. Then, it is decreased to 1400℃ at a rate of 15℃ / h, and held for 30 min. Subsequently, it is decreased to room temperature at a rate of 25℃ / h. The β-gallium oxide single crystal is taken out, which is 200 mm (8 inches) in diameter and (010) crystal orientation β-phase gallium oxide. Then, it is oriented, sliced, ground and polished to obtain the epitaxial substrate of gallium oxide power device.

[0069] Experimental Example 1 The performance of the β-gallium oxide single crystal in Example 1 of this invention was tested, and the results are as follows: Figure 2 This is a schematic diagram of a β-gallium oxide single crystal in Embodiment 1 of the present invention. As can be seen, the crystals grown in this invention are free of impurities and voids, and there are no through cracks. The ingots are thick, which makes the number of substrates that can be cut from a single ingot 3 to 4 times that of the traditional VB method, and reduces the amount of iridium crucible consumables by at least 80%.

[0070] Figure 3 The image shows a high-resolution XRD rocking curve of a β-gallium oxide single crystal in Example 1 of this invention. The full width at half maximum (FWHM) of the XRD (010) plane rocking curve is 71.64 arcsec; the global average is approximately 75.13 arcsec. This indicates that the present invention has a small FWHM value, low lattice distortion, and high single-crystal integrity, which meets the requirements for epitaxial growth of high-voltage power devices.

[0071] Figure 4 The image shows the surface morphology of the β-gallium oxide single crystal in Example 1 of this invention (AFM image). (010) Gallium oxide morphology observation: surface roughness RQ / RMS = 0.132 nm. It can be seen that the single crystal surface of this invention is flat.

[0072] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A single crystal growth apparatus for β-gallium oxide casting, characterized in that, The apparatus includes a furnace body, a heat insulation structure, a temperature control structure, a crucible, and a crucible lid. The heat insulation structure is located inside the furnace body and has a heat insulation space. The temperature control structure controls the temperature within the heat insulation cavity. The crucible is located within the heat insulation space, and the crucible lid is located at the open end of the crucible. The crucible lid has a feed inlet. The upper part of the heat insulation structure has a through-hole. The upper part of the furnace body has an opening. The β-gallium oxide casting single crystal growth apparatus further includes: The feeding cylinder has a clamping platform on the outer periphery of its upper opening, and the clamping platform engages with the outer periphery of the opening. A feeding pipe extends through the through-hole, with its upper end connected to the lower opening of the feeding cylinder and its lower end connected to the feeding port. A hopper is located inside the feed hopper; A cover plate is placed over the upper opening of the hopper cylinder, and the cover plate is engaged with the outer circumferential surface of the upper opening of the discharge cylinder. A screen is disposed inside the silo cylinder, and the screen can reciprocate along the center line of the silo cylinder. The screen is slidably sealed to the inner peripheral wall of the silo cylinder. A vibration structure is used to make the screen reciprocate along the centerline of the hopper cylinder; A weighing sensor is located between the cover plate and the outer peripheral surface of the upper opening of the feed cylinder; A hopper cover is located on the upper side of the furnace body, and the hopper cover covers the opening.

2. The β-gallium oxide casting single crystal growth apparatus as described in claim 1, characterized in that, The cover plate is provided with a through hole; the hopper cover is provided with a rod shaft sealing hole; the vibration structure includes: An elastic ring is provided on the side of the cover plate away from the hopper cylinder, and the elastic ring is provided on the outer periphery of the through hole; A connector is located at the end of the elastic ring opposite to the cover plate; A connecting rod passes through the through hole and is connected to the screen and the connector. The motor support is located outside the furnace body; Vibration motor, mounted on a motor bracket; A vibrating rod is connected to the output end of a vibrating motor. The vibrating rod passes through the rod shaft sealing hole and is slidably sealed to the inner circumferential wall of the rod shaft sealing hole. The lower end of the vibrating rod faces the side of the connector that is away from the elastic ring.

3. The β-gallium oxide casting single crystal growth apparatus as described in claim 1, characterized in that, The vibration structure also includes: A rubber pad is provided on the side of the connector opposite to the elastic ring.

4. The β-gallium oxide casting single crystal growth apparatus as described in claim 1, characterized in that, The screens include multiple screens, each of which is arranged along the center line of the hopper cylinder. The aperture of the lower screen in a pair of adjacent screens is smaller than that of the upper screen.

5. A method for growing a single crystal using the β-gallium oxide casting method employing the β-gallium oxide casting method single crystal growth apparatus according to any one of claims 1-4, characterized in that, Includes the following steps: A gallium oxide single crystal seed is placed in the crucible, and a first predetermined amount of gallium oxide material is filled in; a second predetermined amount of gallium oxide powder is filled into the hopper; then the furnace body is evacuated, and the air inside the furnace body is replaced with argon gas; The gallium oxide material is completely melted; then a third set amount of gallium oxide powder is dropped into the crucible and melted, the third set amount being less than the second set amount; then the gallium oxide powder is continuously replenished, and the melt level in the crucible is kept constant in real time until the gallium oxide powder is used up; then β-gallium oxide single crystal is directionally solidified and grown.

6. The method for single crystal growth of β-gallium oxide by casting as described in claim 5, characterized in that, After replacing the air inside the furnace with argon, the pressure inside the furnace is maintained at 0.105 MPa.

7. The method for single crystal growth of β-gallium oxide by casting as described in claim 5, characterized in that, To completely melt the gallium oxide material, the process includes: controlling the temperature inside the insulation cavity to rise to 1820°C at a rate of 8-12°C / min, then rising to 1865°C at a rate of 5°C / min, and holding the temperature for 60 minutes.

8. The method for single crystal growth of β-gallium oxide by casting as described in claim 5, characterized in that, Continuously replenishing the gallium oxide powder and maintaining a constant melt level in the crucible in real time includes controlling the feeding rate of the gallium oxide powder to be 0.5 ± 0.05 g / min.

9. The method for single crystal growth of β-gallium oxide by casting as described in claim 5, characterized in that, Directional solidification growth of β-gallium oxide single crystals includes: controlling the temperature inside the insulation cavity to decrease at a rate of 0.5℃ / h for 8 hours, then at a rate of 0.8℃ / h for 5 hours, and then at a rate of 1℃ / h for 50 hours, until the temperature is reduced to 1807℃.

10. The method for single crystal growth of β-gallium oxide by casting as described in claim 5, characterized in that, After directional solidification growth of β-gallium oxide single crystal, the temperature inside the insulation cavity is controlled to decrease to 1600℃ at a rate of 5℃ / h and held for 30 min, then decreased to 1400℃ at a rate of 15℃ / h and held for 30 min, and then decreased to room temperature at a rate of 25℃ / h.

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