Crystal growth method and crystal growth apparatus

Abstract

To provide a crystal growth method and a crystal growth apparatus.MEANS: A crystal growth method includes performing processes such as filling, ignition, molten pool expansion, crystal growth, cooling sequentially to obtain a crystal. In the process of the ignition, a focus of a light source is enabled to move on a surface of a crystal raw material such that the surface of the crystal raw material is molten to form a molten pool until the surface area of the molten pool is expanded to a target size; during the process of molten pool expansion, an induction coil disposed on the outer side of the crucible is activated, the crystal raw material is added to the crucible synchronously, the molten pool continuously expands downward until it comes into contact with the seed crystal at the bottom of the crucible; in the process of the crystal growth, power of the induction coil is reduced to achieve continuous crystallization from below to above the top of the seed crystal until it reaches the top of the molten pool. The inventive crystal growth method and crystal growth apparatus make it possible to acquire an effective molten pool, form a radial temperature gradient, and improve crystal cleavage levels.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to the technical field of crystal growth, and in particular to a crystal growth method and apparatus. [Background technology]

[0002] Crystalline materials are very important functional materials, not only are they diverse in type but also have rich performance, and are widely used in precision devices in mechanics, electricity, optics, thermology, etc. Among them, semiconductor crystals are the foundation supporting the communications, computer, automobile, and electronic information industries, and electronic devices, semiconductor devices, solid-state laser devices, and optical devices manufactured using semiconductor crystals have broad application prospects.

[0003] Gallium oxide crystals are currently the third generation semiconductor materials developed after silicon carbide and gallium arsenide, and have a wider band gap, higher breakdown field, higher thermal conductivity, higher electron saturation velocity, shorter UV-cut absorption edge, and higher radiation protection capability, and β-crystalline gallium oxide crystals in particular are expected to become an important material in the field of wide band gap semiconductors. However, the manufacturing method of gallium oxide crystals still faces many challenges, such as volatilization and decomposition of raw materials, corrosion of iridium precious metal crucibles, thin crystal thickness, spiral crystal growth, and coloration problems.

[0004] In the Chinese patent with the publication date of November 1, 2022 and the publication number CN115261973A, a method for growing large-sized gallium oxide crystals is disclosed. In this method, a gallium oxide raw material is loaded into a cold crucible or an alloy crucible, and gallium oxide crystal growth is carried out in an atmosphere of pure oxygen gas with a pressure range of 0.1 < p < 0.7 MPa. If a cold crucible is adopted in this method, it is necessary to put metal Ga or a graphite sheet into the middle region of the gallium oxide raw material as an igniter. Moreover, the cold crucible is composed of a water-cooled segment and a water-cooled table. During the growth process, external powder is not heated and melted by the action of water cooling, so a layer of unmelted shell is formed, and the melt grows crystals inside the unmelted shell. There are the following defects in this method. (1) Metal Ga or a graphite sheet is adopted as the igniter. Metal Ga is in a liquid state at room temperature and is expensive, not suitable for use as a consumable. Although the electric spark generated by the graphite sheet cannot ignite the gallium oxide raw material spheres, it can ignite aluminum oxide particle spheres with a higher melting point in the same process. Furthermore, the graphite sheet belongs to reducing impurities and is likely to decompose the raw material at high temperatures when entering the melt. (2) Since a water-cooled segment is added to the side wall of the crucible, external powder can be prevented from melting, but the amount of heat it takes away is extremely large, and a very large temperature difference is formed in the radial direction, which is suitable for rapid growth methods such as the pulling method. The crystals are prone to cracking, and it is difficult to form large-sized and high-quality gallium oxide crystals. (3) It is necessary to introduce high-purity oxygen gas into the furnace, increasing the device structure and process steps.

[0005] Therefore, it is of great significance to provide a crystal growth method and a growth device that are advantageous for gallium oxide crystal growth and reduce the growth cost.

Summary of the Invention

Problems to be Solved by the Invention

[0006] In response to the above-mentioned problems, the present invention aims to provide a crystal growth method and a crystal growth apparatus. Compared with the prior art, the crystal growth method of the present invention is simpler, effectively reduces the radial temperature gradient in the molten pool, suppresses the decomposition of gallium oxide, and enables the growth of large-sized, high-quality gallium oxide crystals. The crystal growth apparatus of the present invention can form a stable axial temperature gradient field to promote crystal growth. [Means for solving the problem]

[0007] In order to achieve the object of the present invention, the present invention provides the following technical solutions.

[0008] In a first aspect, the present invention provides a method for producing a medicament for the treatment of a pulmonary arthritis, comprising: a charging step of fixing a seed crystal to the bottom of a crucible and filling the crucible with a crystal raw material; an ignition step of activating a light source emitter located above the crucible and moving the focus of the light source on the surface of the raw crystal material to melt the surface and form a molten pool until the surface area of ​​the molten pool expands to a target size; a molten pool expansion step in which an induction coil provided outside the crucible is activated, crystal raw material is synchronously added into the crucible, and the molten pool continues to expand downward until it contacts the seed crystal at the bottom of the crucible; a crystal growing step in which the power of the induction coil is gradually reduced to continuously crystallize from below the top of the seed crystal to above it until the crystal reaches the top of the molten pool; a cooling step of gradually reducing the power of the induction coil until the induction coil is turned off, cooling the crystal, and then removing the crystal, In the crystal growth method, a heat insulating layer is provided between the induction coil and the crucible, During the crystal growth process, the cooling system located at the bottom of the seed crystal performs synchronous cooling, and the heat-insulating layer can avoid heat loss, and the temperature of the outer wall of the crucible is maintained at 1400°C or higher; In the process of expanding the molten pool, a polycrystalline shell layer is formed between the molten pool and the inner wall of the crucible.

[0009] The crystal growth method according to the present invention includes the steps of feeding, ignition, molten pool expansion, crystal growth, and temperature reduction in sequence.

[0010] In the ignition step, the movement trajectory of the light source focus is controlled to expand the surface area of ​​the molten pool until it forms a target size, thereby forming an effective molten pool.

[0011] During the molten pool expansion step, the crystal raw material is continuously replenished into the crucible synchronously with the induction coil heating process, so that the axial expansion rate of the molten pool is much faster than the radial expansion rate, causing the molten pool to expand downward faster until it contacts the seed crystal at the bottom. The molten pool absorbs electromagnetic induction energy and expands radially until it reaches thermal equilibrium with the heat dissipation in the radial direction. At the same time, a polycrystalline shell layer is formed at the solid-liquid interface to protect the crucible from corrosion. The polycrystalline shell layer can be recycled and reused, significantly reducing production costs.

[0012] During the entire growth process, the outside of the crucible is kept warm by a heat-insulating layer to maintain the thermal equilibrium effect in the radial direction and reduce the temperature gradient difference in the radial direction.

[0013] In the crystal growth step, the temperature drop rate in the crystal growth stage is controlled by adjusting the output power from the induction coil, which is simple and reliable to control.

[0014] By using this temperature gradient method, the crystal growth rate is 0.5-2 mm / h, and the temperature drop process has an in-situ annealing effect, which reduces the internal stress of the crystal in accordance with the present invention compared to the pulling method, and alleviates cleavage due to sliding of the crystal planes. Furthermore, while conventional pulling methods, EDG (Edge-defined Film-fed Growth) methods, and traditional cold crucible methods can only grow crystals with the (010) plane, the process of the present invention regulates and controls crystal growth by designing a stable axial temperature gradient field, alleviating stress between the crystal planes and allowing crystals to grow along the (010), (001), and (100) planes.

[0015] In the present invention, the cooling system at the bottom of the seed crystal can not only perform cooling during the crystal growth process, but also perform cooling during the expansion and / or ignition of the molten pool.

[0016] Preferably, the crystal is a gallium oxide crystal.

[0017] In the present invention, the crystal raw material is a solid, and may be, for example, a raw ingot, a raw sphere, or a raw powder.

[0018] Preferably, the grain size of the crystal raw material is 3 to 10 mm, for example, 3 mm, 4 mm, 5 mm, or 10 mm, but is not limited to the listed values, and other unlisted values ​​within this range also apply. The crystal raw material in the crucible is loose and cannot be pressed.

[0019] Preferably, the crucible is provided at its top with a heat insulating cover having at least one transmission port.

[0020] Preferably, the permeation port is sealed with sapphire, so that the entire cavity of the crucible is relatively sealed, and during the crystal growth process, a vapor pressure of gallium oxide close to saturation is generated within the crucible, suppressing decomposition of gallium oxide.

[0021] Preferably, during the ignition process, the focal point of the light source moves periodically along an elliptical trajectory on the surface of the raw material crystal, and the present invention designs and performs the periodic movement along an elliptical trajectory to promote the raw material crystal to absorb energy, thereby more effectively melting the raw material crystal and forming an effective molten pool.

[0022] Preferably, the major axis of the elliptical locus is 2 cm or more, and may be, for example, 2 cm, 2.2 cm, 2.4 cm, 2.6 cm, 2.8 cm, or 3 cm, but is not limited to the listed values, and other unlisted values ​​within this range also apply.

[0023] Preferably, the diameter of the molten pool of the target size is 5 cm or more, for example, 5 cm, 5.5 cm, 6 cm, 6.5 cm, 7 cm, 7.5 cm, or 8 cm, but is not limited to the recited values, and other unrecited values ​​within this range also apply. Generally, the diameter of the molten pool at the ignition stage should not exceed the radius of the crucible, otherwise it is disadvantageous to the formation of a polycrystalline shell layer.

[0024] Preferably, in the ignition process, the light source emitter used comprises a laser emitter.

[0025] Preferably, the emission wavelength band of the laser emitter may be 532 nm, 808 nm, 980 nm, 1064 nm, etc. The present invention does not exclude the possibility of using lasers of other wavelength bands, and the present invention takes a 915 nm laser as an example.

[0026] Preferably, the radiation power of the laser emitter is 100 to 300 W, and may be, for example, 100 W, 120 W, 150 W, 180 W, 200 W, 220 W, 250 W, 280 W, or 300 W, but is not limited to these numerical values, and other unrecited numerical values ​​within this numerical range also apply. The present invention does not exclude the possibility of using a high-power laser emitter (e.g., 300 W or more). However, low-power laser emitters (e.g., 100 to 300 W) are generally preferred because they have modulation capabilities and are energy-saving.

[0027] Furthermore, when the crystal raw material is in a granular state, it has high reflectivity and poor energy absorption, making it necessary to increase the laser power. After the crystal raw material melts, it produces a fluid melt that is easily absorbed by the surrounding crystal raw material. The surface of the crystal raw material that has absorbed the surrounding melt becomes "wet," has low reflectivity, and absorbs energy more easily, reducing the laser power and energy consumption. During the entire ignition process, the radiation power of the laser emitter does not need to be adjusted.

[0028] Preferably, the number of laser emitters is 4 to 8, for example, 4, 5, 6, 7, or 8, but is not limited to the listed numbers, and other unlisted numbers within this range also apply.

[0029] Preferably, during the molten pool expansion process and the crystal growth process, the operating frequency of the induction coil is 30 to 100 kHz, for example, 30 kHz, 40 kHz, 50 kHz, 60 kHz, 70 kHz, 80 kHz, 90 kHz, or 100 kHz, but is not limited to the listed values, and other unlisted values ​​within this range also apply.

[0030] Preferably, during the molten pool expansion process and the crystal growth process, the operating power of the induction coil is 40 to 100 kW, for example, 40 kW, 45 kW, 50 kW, 55 kW, 60 kW, 65 kW, 70 kW, 75 kW, 80 kW, 85 kW, 90 kW, 95 kW, or 100 kW, but is not limited to the listed values, and other unlisted values ​​within this range also apply.

[0031] Preferably, during the crystal growth, the operating power of the induction coil is decreased at a rate of 0.05 to 0.2 kW / h, e.g., 0.05 kW / h, 0.06 kW / h, 0.08 kW / h, 0.1 kW / h, 0.12 kW / h, 0.14 kW / h, 0.16 kW / h, 0.18 kW / h, or 0.2 kW / h, but is not limited to these values ​​and any other values ​​not listed within this range also apply. The temperature of the outer wall of the crucible is decreased at a rate of 0.4 to 1°C / h, e.g., 0.4°C / h, 0.5°C / h, 0.6°C / h, 0.8°C / h, or 1°C / h, but is not limited to these values ​​and any other values ​​not listed within this range also apply.

[0032] The present invention adjusts and controls the temperature drop rate during the crystal growth stage by reducing the power of the induction coil during the crystal growth process, and controls the power drop rate and temperature drop rate within a specific range, providing an appropriate temperature field and time for crystal growth and promoting crystal growth.

[0033] Preferably, during the molten pool expansion process, the crystal raw material addition rate is 300 to 500 g / min, for example, 300 g / min, 320 g / min, 350 g / min, 380 g / min, 400 g / min, 420 g / min, 450 g / min, 480 g / min, or 500 g / min, but is not limited to the listed values, and other unlisted values ​​within this range also apply.

[0034] Preferably, during the ignition process, a crystal raw material is further added to the crucible.

[0035] Preferably, during the ignition process, the addition rate of the crystal raw material is 10 to 200 g / min, for example, 10 g / min, 15 g / min, 20 g / min, 25 g / min, 30 g / min, 35 g / min, 40 g / min, 45 g / min, 50 g / min, 100 g / min, or 200 g / min, but is not limited to the listed values, and other unlisted values ​​within this range also apply. During this process, the addition rate of the crystal raw material may gradually increase from low to high, or may remain constant.

[0036] Preferably, during the temperature drop process, the power drop rate is 1 to 3 kW / h, and may be, for example, 1 kW / h, 1.2 kW / h, 1.5 kW / h, 1.8 kW / h, 2 kW / h, 2.2 kW / h, 2.5 kW / h, 2.8 kW / h, or 3 kW / h, but is not limited to the listed values, and other unlisted values ​​within this range also apply.

[0037] As a preferred technical solution of the present invention, the crystal growth method includes: a charging step in which a seed crystal is fixed to the bottom of a crucible, a crystal raw material is filled into the crucible, the crystal is a gallium oxide crystal, the particle size of the crystal raw material is 3 to 5 mm, a heat-insulating cover having at least one permeation port is provided on the top of the crucible, and the permeation port is sealed with sapphire; an ignition step of starting a laser emitter located above the crucible, the laser emitter having a radiation power of 100-300W and a number of 4-8, periodically moving the focus of the light source on the surface of the crystal raw material in an elliptical locus with a major axis of 2cm or more until the surface area of ​​the molten pool expands to a target size, thereby melting the surface to form a molten pool, and adding the crystal raw material to the crucible at a rate of 10-200g / min, so that the diameter of the molten pool of the target size is 5cm or more; a molten pool expansion step in which an induction coil installed outside the crucible is activated, a heat insulating layer is installed between the induction coil and the crucible, and crystal raw materials are synchronously added into the crucible at a rate of 300 to 500 g / min, so that the molten pool continues to expand downward until it contacts the seed crystal at the bottom of the crucible; a crystal growth step in which the power of the induction coil is gradually reduced at a rate of 0.05 to 0.2 kW / h, and the temperature of the outer wall of the crucible is decreased at a rate of 0.4 to 1°C / h, so that the crystal is continuously crystallized from below the top of the seed crystal to above it until it reaches the top of the molten pool; a cooling step in which the power of the induction coil is gradually reduced until the induction coil is turned off, and the crystal is cooled and then removed; However, during the molten pool expansion process and the crystal growth process, the operating frequency of the induction coil is 30 to 100 kHz, and the operating power of the induction coil is 40 to 100 kW. At the same time, the cooling system located at the bottom of the seed crystal operates synchronously to perform cooling, and a polycrystalline shell layer is formed between the molten pool and the inner wall of the crucible.

[0038] In a second aspect, the present invention provides a crystal growth apparatus for use in the crystal growth method according to the first aspect of the present invention, the crystal growth apparatus comprising: a crucible; a heat-insulating layer wrapped around the outer periphery of the crucible; an induction coil arranged in the outer circumferential direction of the heat-insulating layer; a susceptor located below the crucible for fixing a seed crystal, the seed crystal being inserted deep within the crucible and having a cooling system provided within the susceptor; a light source emitter provided above the crucible; and a raw material addition port provided at the top of the crucible.

[0039] The crystal growth apparatus of the present invention has a light source emitter installed above the crucible, which can concentrate the emitted light within the crucible and melt the crystal raw material to form a molten pool, thereby avoiding the problem of insufficient initial melting area during the ignition step that occurs in conventional crystal growth apparatuses.The heat-insulating layer installed on the outer surface of the crucible, the induction coil around the outer periphery of the heat-insulating layer, and the cooling system installed on the susceptor reduce the radial temperature gradient and form an axial temperature gradient field, which promotes stress release in the crystal during growth and alleviates the problem of cleavage caused by sliding of the crystal planes, allowing gallium oxide crystals to grow along the (010), (001), and (100) planes.

[0040] Taking the preparation of gallium oxide crystals as an example, the arrangement of materials from the inside to the outside, with the axis of the crucible as the midline, is sequentially: molten pool, gallium oxide polycrystalline shell layer, gallium oxide raw material, crucible, heat retention layer, and induction coil. The molten pool will expand downward under the influence of gravity and heat until it contacts the seed crystal, so the present invention can form a stable axial temperature gradient field while ensuring a small radial temperature gradient. [Effects of the Invention]

[0041] Compared with the prior art, the present invention has the following beneficial effects:

[0042] (1) The crystal growth method of the present invention can promote crystal growth by controlling the trajectory of the light source focus to form an effective molten pool that can be loaded with a magnetic field, and by expanding the molten pool downward under the influence of gravity and heat until it contacts the seed crystal at the bottom, thereby forming a stable temperature gradient field.

[0043] (2) The crystal growth method according to the present invention can avoid the problem of crucible corrosion by forming a polycrystalline shell layer, and the polycrystalline shell layer can be recovered, thereby significantly reducing production costs.

[0044] (3) The crystal growth apparatus of the present invention reduces the radial temperature gradient, promotes radial thermal equilibrium, and improves the cleavage of the crystal by using an induction coil for heating and a heat-insulating layer for heat retention, enabling gallium oxide crystals to grow along the (010), (001), and (100) planes. [Brief explanation of the drawings]

[0045] [Figure 1] FIG. 1 is a structural schematic diagram of a crystal growth apparatus in Example 1 of the present invention. [Explanation of symbols]

[0046] 1: camera; 2: raw material addition port; 3: light source emitter; 4: sapphire transmission port; 5: heat insulation layer; 6: quartz glass tube; 7: crucible; 8: seed crystal; 9: upper thermocouple; 10: lower thermocouple; 11: susceptor; 12: induction coil; 13: substrate. DETAILED DESCRIPTION OF THE INVENTION

[0047] The technical solutions of the present invention will be further described below by way of specific embodiments. It should be clear to those skilled in the art that the above examples are merely for understanding the present invention and should not be considered as specifically limiting the present invention.

[0048] In one specific embodiment, the crystal growth method of the present invention is carried out in a crystal growth apparatus, which includes, as shown in Figure 1, a crucible 7, a heat-insulating layer 5 wrapped around the outer surface of the crucible 7, an induction coil 12 attached to the outer surface of the heat-insulating layer 5, a susceptor 11 located below the crucible 7 for fixing a seed crystal 8, the seed crystal 8 being inserted deep inside the crucible 7, and a cooling system installed within the susceptor 11, a light source emitter 3 installed above the crucible 7, and a raw material addition port 2 installed at the top of the crucible 7. A heat-insulating cover is provided on the top of the crucible 7, two sapphire transmission holes 4 are provided in the heat-insulating cover, and four light source emitters 3 are provided above each of the sapphire transmission holes 4; The heat-insulating cover is provided with a raw material addition port 2, a supply pipe is provided in the raw material addition port 2, the supply pipe is a quartz glass tube 6, the cooling system is a water-cooling system, the crucible 7 is a zirconia ceramic crucible, the heat-insulating layer 5 is a zirconia heat-insulating layer, and the heat-insulating cover is a zirconia heat-insulating cover, Two thermocouples are provided between the outer wall of the crucible 7 and the heat-insulating layer 5, and the thermocouples include an upper thermocouple 9 and a lower thermocouple 10, with the top end of the upper thermocouple 9 located on the top side of the crucible 7 and the top end of the lower thermocouple 10 located on the bottom side of the crucible 7, a camera 1 is provided above the raw material addition port 2, and a substrate 13 is provided at the bottom of the crucible 7.

[0049] Example 1 This embodiment provides a crystal growth method. The crystal growth apparatus used in the crystal growth method, as shown in Figure 1, includes a camera 1, a raw material inlet 2, a light source emitter 3, a sapphire transmission port 4, a heat-insulating layer 5, a quartz glass tube 6, a crucible 7, a heat-insulating cover, a seed crystal 8, an upper thermocouple 9, a lower thermocouple 10, a susceptor 11, an induction coil 12, and a substrate 13. The diameter of the induction coil 12 is 800 mm, the outer diameter of the heat-insulating layer 5 is 700 mm, and the inner diameter of the heat-insulating layer 5 is 300 mm.

[0050] The crystal growth method includes the following steps.

[0051] Preparation: Gallium oxide powder with a purity of 4N was pelletized into spheres with a diameter of 3 mm using a pelletizer. Seed crystals 8 were fixed to the bottom of crucible 7, and the crucible 7, which was 5 mm thick, 260 mm in outer diameter, and 280 mm deep, was filled with the gallium oxide spheres. The gallium oxide spheres were added without compaction, and the heat-retaining cover was then closed.

[0052] Ignition: The laser emitters (light source emitters 3) located above the crucible 7 were activated. Each laser emitter had a wavelength of 915 nm and a power of 200 W, for a total of four. First, the output power was adjusted to 120 W, and the laser was focused on the surface of the particle to melt it. A bright spot was visible through the observation window, indicating that the particle on the surface had melted. At this point, the power was reduced to 100 W, and the laser focus was periodically moved along an elliptical trajectory with a major axis of 2 cm on the surface of the particle to form a molten pool. Simultaneously, particle spheres were added to the crucible 7 at a rate of 200 g / min, and the molten pool expanded until its surface area reached the target size, i.e., a diameter of 5 cm.

[0053] Weld pool expansion: The induction coil 12 installed outside the crucible 7 was activated and adjusted to a frequency of 30 kHz. The power of the induction coil 12 was gradually increased to 45 kW. As the power increased, the brightness of the weld pool increased, and the area of ​​the weld pool also increased. Synchronously, particles were added to the crucible 7 at a rate of 300 g / min until a total of 3 kg of particles was reached. The addition was then stopped, the quartz glass tube 6, which served as the supply tube, was removed, and the raw material inlet 2 was sealed with a sapphire tube.

[0054] After the melt in the molten pool had stabilized for 30 minutes, the temperature detected by the upper thermocouple 9 reached 1630°C, and the temperature detected by the lower thermocouple 10 reached 1580°C. At this time, the molten pool contacted the seed crystal 8 at the bottom of the crucible 7. The radial temperature of the crucible 7 reached equilibrium, and a polycrystalline shell layer formed between the molten pool and the inner wall of the crucible 7, maintaining the diameter of the molten pool at 10 cm.

[0055] During this time, the cooling system located at the bottom of the seed crystal 8 was operated synchronously to perform cooling.

[0056] Crystal growth: The power of the induction coil 12 was gradually reduced to 37 kW at a rate of 0.05 kW / h, and the cooling system located at the bottom of the seed crystal 8 continued to operate to cool the crystal. During this process, the upper thermocouple 9 detected a temperature drop rate of approximately 0.6°C / h at the outer wall of the crucible 7, and the lower thermocouple 10 detected a temperature drop rate of approximately 0.8°C / h at the outer wall of the crucible 7. The crystal grew upward from the lower seed crystal 8 until it reached the top of the molten pool. At the end of this stage, the temperatures detected by the upper thermocouple 9 and the lower thermocouple 10 reached 1530°C and 1450°C, respectively.

[0057] Temperature reduction: The power of the induction coil 12 was reduced to 2 kW in stages at a rate of 2 kW / h, and then the power supply to the induction coil 12 was turned off to continue cooling, after which the crystal was taken out.

[0058] Using the crystal growth method of this example, a gallium oxide crystal with a 3.5-inch level and an outer size of φ90 mm × 200 mm was obtained. The crystal mass was 1.9 kg, and a sample of 50 × 180 mm × 2 mm was obtained by processing. An X-ray diffraction test showed a FWHM of 108 arcsec.

[0059] Example 2 This embodiment provides a crystal growth method, and the crystal growth apparatus used in the crystal growth method is the same as that in the first embodiment.

[0060] The crystal growth method includes the following steps.

[0061] Preparation: Gallium oxide powder with a purity of 4N was pelletized into spheres with a diameter of 10 mm using a pelletizer. A seed crystal was fixed to the bottom of the crucible, and the gallium oxide spheres were filled into a crucible 7 with a thickness of 5 mm, an outer diameter of 260 mm, and a depth of 280 mm.

[0062] Ignition: The laser emitters located above the crucible were activated. Each laser emitter had a wavelength of 915 nm and a power of 200 W, for a total of four. The laser output power was adjusted to 120 W, and the laser was focused on the surface of the particle to melt it. When a bright spot was visible through the observation window, the power was reduced to 100 W, and the laser focus was periodically moved on the surface of the particle in an elliptical trajectory with a major axis of 2 cm. At the same time, the particle was added to the crucible at a rate of 50 g / min, expanding the surface area of ​​the molten pool to a diameter of 5 cm.

[0063] Molten pool expansion: The induction coil installed outside the crucible was activated and the frequency was adjusted to 30 kHz. The power of the induction coil was gradually increased to 45 kW. Synchronously, particles were added to the crucible at a rate of 100 g / min until a total of 3 kg of particles was reached. The addition was then stopped, the quartz glass tube was removed, and the raw material addition port was sealed with sapphire.

[0064] After the melt in the molten pool had stabilized for 30 min, the temperature detected by the upper thermocouple reached 1630°C, and the temperature detected by the lower thermocouple reached 1580°C, and the molten pool contacted the seed crystal at the bottom of the crucible. The radial temperature of the crucible reached equilibrium, and a polycrystalline shell layer formed between the molten pool and the inner wall of the crucible, maintaining the diameter of the molten pool at 10 cm.

[0065] During this time, the cooling system located at the bottom of the seed crystal was operated synchronously to perform cooling.

[0066] Crystal growth: The induction coil power was gradually reduced to 37 kW at a rate of 0.05 kW / h, and the cooling system located at the bottom of the seed crystal continued to operate to cool the crystal. During this process, the upper thermocouple detected a temperature drop rate of approximately 0.6°C / h at the outer wall of the crucible, and the lower thermocouple detected a temperature drop rate of approximately 0.8°C / h at the outer wall of the crucible. The crystal grew upward from the lower seed crystal until it reached the top of the molten pool. At the end of this stage, the temperatures detected by the upper thermocouple reached 1530°C and the lower thermocouple reached 1450°C.

[0067] Temperature reduction: The power of the induction coil was reduced to 2 kW in stages at a rate of 2 kW / h, and then the power supply to the induction coil was turned off to continue cooling, after which the crystal was taken out.

[0068] According to this example, a gallium oxide crystal with a 3.5-inch level and an outer size of φ90 mm × 200 mm was obtained. The mass of the crystal was 1.9 kg, and a sample of 50 × 180 mm × 2 mm was obtained by processing. An X-ray diffraction test showed a FWHM of 110 arcsec.

[0069] Example 3 This example provides a crystal growth method. The crystal growth apparatus used in this crystal growth method differs from that in Example 1 in that the upper and lower thermocouples are both installed inside the crucible, the upper thermocouple is installed on the inner wall of the crucible closer to the top, and the lower thermocouple is installed on the inner wall of the crucible closer to the bottom. After the thermocouples are inserted into the crucible, the insertion gap is sealed with aluminum oxide adhesive. The outer diameter of the heat-insulating layer is 700 mm, and the inner diameter of the heat-insulating layer is 280 mm.

[0070] The crystal growth method includes the following steps.

[0071] Preparation: Gallium oxide powder with a purity of 4N was pelletized into spheres with a diameter of 3 mm using a pelletizer. A seed crystal was fixed to the bottom of the crucible, and the crucible, which was 5 mm thick, 260 mm in outer diameter, and 280 mm deep, was filled with the gallium oxide spheres.

[0072] Ignition: The laser emitters located above the crucible were activated. Each laser emitter had a wavelength of 915 nm and a power of 200 W, for a total of four. The laser output power was adjusted to 120 W, and the laser was focused on the surface of the particle to melt it. When a bright spot was visible through the observation window, the power was reduced to 100 W, and the laser focus was moved periodically on the surface of the particle in an elliptical trajectory with a major axis of 2 cm. At the same time, the particle was added to the crucible at a rate of 200 g / min, expanding the surface area of ​​the molten pool to a diameter of 5 cm.

[0073] Molten pool expansion: The induction coil installed outside the crucible was activated and the frequency was adjusted to 30 kHz. The power of the induction coil was gradually increased to 42 kW. Synchronously, particle balls were added to the crucible at a rate of 300 g / min until a total of 3 kg of particle balls was reached. The addition was then stopped, the quartz glass tube serving as the supply tube was removed, and the raw material addition port was sealed with sapphire.

[0074] After the melt in the molten pool had stabilized for 30 min, the temperature detected by the upper thermocouple reached 1680°C, and the temperature detected by the lower thermocouple reached 1630°C, at which point the molten pool contacted the seed crystal at the bottom of the crucible. The radial temperature of the crucible reached equilibrium, and a polycrystalline shell layer formed between the molten pool and the inner wall of the crucible, maintaining the diameter of the molten pool at 10 cm.

[0075] During this time, the cooling system located at the bottom of the seed crystal was operated synchronously to perform cooling.

[0076] Crystal growth: The induction coil power was gradually reduced to 32 kW at a rate of 0.05 kW / h, and the cooling system located at the bottom of the seed crystal continued to operate to cool the crystal. During this process, the upper thermocouple detected a temperature drop rate of approximately 0.4°C / h at the outer wall of the crucible, and the lower thermocouple detected a temperature drop rate of approximately 0.6°C / h at the outer wall of the crucible. The crystal grew upward from the lower seed crystal until it reached the top of the molten pool. At the end of this stage, the temperatures detected by the upper thermocouple reached 1600°C and the lower thermocouple reached 1510°C.

[0077] Temperature reduction: The power of the induction coil was reduced to 2 kW in stages at a rate of 2 kW / h, and then the power supply to the induction coil was turned off to continue cooling, after which the crystal was taken out.

[0078] In the crystal growth method of this example, the thermocouple was inserted inside the crucible, closer to the melt and the melt raw material sphere shell layer, resulting in a higher detection temperature, a thicker heat-insulating layer for better heat retention, a smaller radial temperature gradient, a longer crystal growth time, and reduced induction coil power. According to this example, a 3.5-inch gallium oxide crystal with an outer size of φ90mm x 200mm was obtained, weighing 1.9kg. A 60 x 180mm x 2mm sample was processed, and an X-ray diffraction test showed a FWHM of 88 arcsec.

[0079] Example 4 This embodiment provides a crystal growth method, in which the crystal growth apparatus used in the crystal growth method is different from that in the first embodiment only in that it is provided with eight light source emitters.

[0080] The crystal growth method differs from Example 1 only in that the number of laser emitters used in the ignition process is 8, the wavelength is 915 nm, and the power of a single unit is 200 W.

[0081] In the crystal growth method of this embodiment, the number of laser emitters is increased to 8 compared to Example 1, which allows for faster initial melting of the particle spheres and therefore improves the material addition rate, but does not affect the crystal growth results. The only adverse effect is the appearance of a small amount of white product, i.e., the produced gallium oxide vapor, which affects the observation of the test phenomenon.

[0082] Example 5 This embodiment provides a crystal growth method, and the crystal growth apparatus used in the crystal growth method is the same as that in the first embodiment.

[0083] The crystal growth method includes the following steps.

[0084] Preparation: Gallium oxide powder with a purity of 4N was pelletized into spheres with a diameter of 3 mm using a pelletizer. A seed crystal was fixed to the bottom of the crucible, and the crucible, which was 5 mm thick, 260 mm in outer diameter, and 280 mm deep, was filled with the gallium oxide spheres.

[0085] Ignition: The laser emitters located above the crucible were activated. Each laser emitter had a wavelength of 915 nm and a power of 200 W, for a total of four. The laser output power was adjusted to 120 W, and the laser was focused on the surface of the particle to melt it. When a bright spot was visible through the observation window, the power was reduced to 100 W, and the laser focus was moved periodically on the surface of the particle in an elliptical trajectory with a major axis of 2 cm. At the same time, the particle was added to the crucible at a rate of 200 g / min, expanding the surface area of ​​the molten pool to a diameter of 5 cm.

[0086] Molten pool expansion: The induction coil installed outside the crucible was activated and the frequency was adjusted to 30 kHz. The power of the induction coil was gradually increased to 45 kW. Synchronously, particle balls were added to the crucible at a rate of 300 g / min until a total of 3 kg of particle balls was reached. The addition was then stopped, the quartz glass tube used as the supply tube was removed, and the raw material addition port was sealed with sapphire.

[0087] After the melt in the molten pool had stabilized for 30 min, the temperature detected by the upper thermocouple reached 1630°C, and the temperature detected by the lower thermocouple reached 1580°C, and the molten pool contacted the seed crystal at the bottom of the crucible. The radial temperature of the crucible reached equilibrium, and a polycrystalline shell layer formed between the molten pool and the inner wall of the crucible, maintaining the diameter of the molten pool at 10 cm.

[0088] During this time, the cooling system located at the bottom of the seed crystal was operated synchronously to perform cooling.

[0089] Crystal growth: The induction coil power was gradually reduced to 37 kW at a rate of 0.2 kW / h, and the cooling system located at the bottom of the seed crystal continued to operate to cool the crystal. During this process, the upper thermocouple detected a temperature drop rate of approximately 2.4°C / h at the outer wall of the crucible, and the lower thermocouple detected a temperature drop rate of approximately 3.2°C / h at the outer wall of the crucible. The crystal grew upward from the lower seed crystal until it reached the top of the molten pool. At the end of this stage, the temperatures detected by the upper thermocouple reached 1530°C and the lower thermocouple reached 1450°C.

[0090] Temperature reduction: The power of the induction coil was reduced to 2 kW in stages at a rate of 2 kW / h, and then the power supply to the induction coil 12 was turned off to continue cooling, after which the crystal was taken out.

[0091] In the crystal growth method according to this example, the temperature drop rate was increased to 0.2 kW / h and the crystal growth time was shortened compared to Example 1. According to this example, a gallium oxide crystal with a 3.5-inch level and an outer size of φ90 mm × 200 mm was obtained, and the mass of the crystal was 1.9 kg. After processing, a sample of 60 × 180 mm × 2 mm was obtained, and an X-ray diffraction test showed a FWHM of 425 arcsec.

[0092] Example 6 This embodiment provides a crystal growth method, and the crystal growth apparatus used in the crystal growth method is the same as that in the first embodiment.

[0093] The crystal growth method includes the following steps.

[0094] Preparation: Gallium oxide powder with a purity of 4N was pelletized into spheres with a diameter of 3 mm using a pelletizer. A seed crystal was fixed to the bottom of the crucible, and the crucible, which was 5 mm thick, 260 mm in outer diameter, and 280 mm deep, was filled with the gallium oxide spheres.

[0095] Ignition: The laser emitters located above the crucible were activated. Each had a wavelength of 915 nm and a power of 200 W, for a total of four. The output power was adjusted to 120 W, and the laser was focused on the surface of the particle to melt it. When a bright spot was visible through the observation window, the power was reduced to 100 W, and the laser focus was moved periodically on the surface of the particle in an elliptical trajectory with a major axis of 2 cm. At the same time, the particle was added to the crucible at a rate of 200 g / min, expanding the surface area of ​​the molten pool to a diameter of 5 cm.

[0096] Molten pool expansion: The induction coil installed outside the crucible was activated and the frequency was adjusted to 30 kHz. The power of the induction coil was gradually increased to 45 kW. Synchronously, particles were added to the crucible at a rate of 100 g / min until a total of 3 kg of particles was reached. The addition was then stopped, the quartz glass tube was removed, and the raw material addition port was sealed with sapphire.

[0097] After the melt in the molten pool had stabilized for 30 min, the temperature detected by the upper thermocouple 9 reached 1630°C, and the temperature detected by the lower thermocouple reached 1580°C, and the molten pool contacted the seed crystal at the bottom of the crucible. The radial temperature of the crucible reached equilibrium, and a polycrystalline shell layer formed between the molten pool and the inner wall of the crucible, maintaining the diameter of the molten pool at 10 cm.

[0098] Crystal growth: The induction coil power was gradually reduced to 37 kW at a rate of 0.5 kW / h, and the cooling system located at the bottom of seed crystal 8 continued to operate to cool the crystal. During this process, the upper thermocouple detected a temperature drop rate on the outer wall of the crucible varying between 3°C / h and 10°C / h, and the lower thermocouple detected a temperature drop rate on the outer wall of the crucible varying between 5°C / h and 16°C / h. The crystal grew upward from the lower seed crystal until it reached the top of the molten pool. At the end of the process, the temperatures detected by the upper thermocouple reached 1530°C and the lower thermocouple reached 1450°C.

[0099] Temperature reduction: The power of the induction coil was reduced to 2 kW in stages at a rate of 2 kW / h, and then the power supply to the induction coil was turned off to continue cooling, after which the crystal was taken out.

[0100] In the crystal growth method of this example, the electromagnetic induction coil lowering speed was increased to 0.5 kW / h compared to Example 1. Gallium oxide crystals with a 3.5-inch level and an outer size of φ90 mm × 200 mm were obtained according to this example, but problems such as crystal cracking, color variation, bubbles, and layered or striped polycrystalline defects appeared. X-ray diffraction analysis revealed multiple miscellaneous peaks, indicating that the crystals were not single crystals.

[0101] Comparative Example 1 The apparatus used in this comparative example is the same as that used in Example 1.

[0102] The following steps were performed:

[0103] (1) Gallium oxide powder with a purity of 4N was pelletized into 3 mm diameter spheres using a pelletizer. A seed crystal was fixed to the bottom of a crucible, and the gallium oxide spheres were filled into a crucible with a thickness of 5 mm, an outer diameter of 260 mm, and a depth of 280 mm.

[0104] (2) The laser emitters located above the crucible were activated. Each had a wavelength of 915 nm and a power of 200 W, for a total of four. The output power was adjusted to 120 W, and the laser was focused on the surface of the particle to melt it. When a bright spot was visible through the observation window, the power was reduced to 100 W. At the same time, the particle was added to the crucible at a rate of 200 g / min, expanding the surface area of ​​the molten pool to a diameter of 3 cm.

[0105] (3) The induction coil installed outside the crucible was activated and the frequency was adjusted to 30 kHz. The power of the induction coil was gradually increased to 45 kW, and it was observed that no change occurred in the molten pool with the increase in power.

[0106] Comparative Example 2 The equipment used in this comparative example differs from that in Example 1 only in that it does not have a quartz glass tube and the raw material addition port of the heat insulating cover is sealed with sapphire. In the method of this comparative example, material is not added continuously during the molten pool expansion stage.

[0107] The following steps were performed:

[0108] (1) Gallium oxide powder with a purity of 4N was pelletized into 3 mm diameter spheres using a pelletizer. A seed crystal was fixed to the bottom of a crucible, and the gallium oxide spheres were filled into a crucible with a thickness of 5 mm, an outer diameter of 260 mm, and a depth of 280 mm.

[0109] (2) The laser emitters located above the crucible were activated. The wavelength of the laser emitters was 915 nm, and the power of each was 200 W, for a total of four. The output power of the laser was adjusted to 120 W, and the laser was focused on the surface of the particle ball to melt it. When a bright spot was seen through the observation window, the power was reduced to 100 W. The laser focus was periodically moved along an elliptical trajectory with a major axis of 2 cm on the surface of the particle sphere. At the same time, particle balls were added to the crucible at a rate of 200 g / min, and the surface area of ​​the molten pool was expanded until it reached a diameter of 5 cm.

[0110] (3) The induction coil outside the crucible was turned on and its frequency adjusted to 30 kHz. The power of the induction coil was gradually increased to 45 kW and continued for 30 min. During this time, no crystal raw material was added, but the cooling system located at the bottom of the seed crystal operated synchronously to perform cooling. It was observed that the radial expansion rate of the molten pool was significantly faster than that in Example 1, no polycrystalline shell layer was formed between the molten pool and the crucible, and the molten pool could not expand downward to contact the seed crystal at the bottom of the crucible. Therefore, the next stage of testing was not performed.

[0111] Comparative Example 3 The apparatus used in this comparative example differs from that in Example 1 only in that a water-cooled segment is used instead of a crucible and a heat-insulating layer, the induction coil is provided on the outer surface of the water-cooled segment, and one thermocouple is provided within the water-cooled segment and attached to the inner wall of the water-cooled segment.

[0112] The following steps were performed:

[0113] (1) Gallium oxide powder with a purity of 4N was pelletized into 3 mm diameter spheres using a pelletizer. A seed crystal was fixed to the bottom of a crucible, and the gallium oxide spheres were filled into a crucible with a thickness of 5 mm, an outer diameter of 260 mm, and a depth of 280 mm.

[0114] (2) The laser emitters located above the crucible were activated. The wavelength of each laser emitter was 915 nm, and the power of each was 200 W, for a total of four. The output power was adjusted to 120 W, and the laser was focused on the surface of the particle ball to melt it. When a bright spot was visible through the observation window, the power was reduced to 100 W. The laser focus was periodically moved along an elliptical trajectory with a major axis of 2 cm on the surface of the particle sphere. At the same time, particle spheres were added to the crucible at a rate of 200 g / min to expand the surface area of ​​the molten pool until the diameter of the molten pool was 5 cm.

[0115] (3) The induction coil installed outside the crucible was started and the frequency was adjusted to 30 kHz. The power of the induction coil was gradually increased to 45 kW. Synchronously, the particles were added to the crucible at a rate of 300 g / min until a total of 3 kg of particles was added. The addition was stopped, the quartz glass tube was removed, and the raw material addition port was sealed with sapphire. During this time, the water-cooled segment performed cooling throughout.

[0116] After the melt in the molten pool had stabilized for 30 min, the temperature detected by the thermocouple was 50°C, and a polycrystalline shell layer was formed between the molten pool and the inner wall of the crucible, but the molten pool did not contact the seed crystal at the bottom of the crucible.

[0117] (4) The induction coil power was gradually reduced to 37 kW at a rate of 0.05 kW / h, and the water-cooled segments performed the cooling throughout.

[0118] (5) The power of the induction coil was reduced to 2 kW stepwise at a rate of 2 kW / h, and then the power of the induction coil was turned off and the crystal was taken out after continued cooling.

[0119] In the method according to this comparative example, the water-cooling segment caused a very serious heat dissipation, a large radial temperature gradient, and the heat was absorbed more quickly by the shell layer, making it difficult for the melt to break downward and unable to contact the seed crystal at the bottom, resulting in spontaneous nucleation during the cooling stage.

[0120] Comparative Example 4 The apparatus used in this comparative example is the same as the apparatus used in comparative example 3.

[0121] The crystal growth method differs from Comparative Example 3 only in that during the molten pool expansion process, the induction coil installed outside the water-cooled segment is activated and its power is increased to 80 kW, and during the crystal growth process, the power of the induction coil is gradually reduced to 72 kW at a rate of 0.05 kW / h.

[0122] Compared to Example 1, the crystal growth method of this comparative example used water-cooled segments and increased the power of the induction coil, resulting in extremely severe heat dissipation and a large radial temperature gradient. The resulting crystals were polycrystalline with a glass-like gloss on the surface and had external cracks.

[0123] Comparative Example 5 The apparatus used in this comparative example is the same as that used in Example 1.

[0124] The crystal raw material used in this comparative example is gallium oxide powder with a purity of 4N, and the gallium oxide powder is not granulated, so that the particle size of the powder is smaller than 3 mm.

[0125] The following steps were performed:

[0126] (1) A seed crystal was fixed to the bottom of a crucible, and the crucible, which had a thickness of 5 mm, an outer diameter of 260 mm, and a depth of 280 mm, was filled with gallium oxide powder.

[0127] (2) The laser emitters located above the crucible were activated. The wavelength of each laser emitter was 915 nm, and the power of each was 200 W, for a total of four. The output power was adjusted to 120 W, and the laser was focused on the surface of the particle sphere to melt the powder. When a bright spot was visible through the observation window, the power was reduced to 100 W, and the laser focus was periodically moved on the surface of the powder in an elliptical trajectory with a major axis of 2 cm. At the same time, the powder was added to the crucible at a rate of 200 g / min. At this stage, Although the duration of the ignition step coincided with that used in Example 1, no obvious signs of expansion of the molten pool were observed.

[0128] The applicant declares that the above content is only a specific embodiment of the present invention, and the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any modifications or replacements that can be easily conceived within the technical scope disclosed in the present invention are all included in the protection scope and disclosure scope of the present invention.

Claims

1. a charging step of fixing a seed crystal to the bottom of a crucible and filling the crucible with a crystal raw material; an ignition step of activating a light source emitter located above the crucible and moving the focus of the light source on the surface of the raw crystal material to melt the surface and form a molten pool until the surface area of ​​the molten pool expands to a target size; a molten pool expansion step in which an induction coil provided outside the crucible is activated, crystal raw material is synchronously added into the crucible, and the molten pool continues to expand downward until it contacts the seed crystal at the bottom of the crucible; a crystal growing step in which the power of the induction coil is gradually reduced to continuously crystallize from below the top of the seed crystal to above it until the crystal reaches the top of the molten pool; a cooling step of gradually reducing the power of the induction coil until the induction coil is turned off, cooling the crystal, and then removing the crystal, a heat insulating layer is provided between the induction coil and the crucible; In the crystal growing step, a cooling system located at the bottom of the seed crystal performs cooling synchronously; In the molten pool expanding step, a polycrystalline shell layer is formed between the molten pool and the inner wall of the crucible. A crystal growth method characterized by:

2. the crystal is a gallium oxide crystal, The particle size of the crystal raw material is 3 to 10 mm.

2. The crystal growth method according to claim 1.

3. A heat-insulating cover having at least one transmission port is provided on the top of the crucible, The transmission port is sealed with sapphire.

2. The crystal growth method according to claim 1.

4. In the ignition step, the focus of the light source is periodically moved along an elliptical locus on the surface of the crystal raw material; The major axis of the elliptical locus is 2 cm or more; The diameter of the molten pool of the target size is 5 cm or more, and preferably 5 to 8 cm.

2. The crystal growth method according to claim 1.

5. In the ignition step, the light source emitter used includes a laser emitter; The radiation power of the laser emitter is 100-300 W; The number of the laser emitters is 4 to 8.

2. The crystal growth method according to claim 1.

6. In the molten pool expansion step and the crystal growth step, the operating frequency of the induction coil is 30 to 100 kHz; In the molten pool expansion step and the crystal growth step, the operating power of the induction coil is 40 to 100 kW.

2. The crystal growth method according to claim 1.

7. During the crystal growth step, the operating power of the induction coil is decreased at a rate of 0.05 to 0.2 kW / h.

2. The crystal growth method according to claim 1.

8. In the molten pool expansion step, the crystal raw material is added at a rate of 300 to 500 g / min.

2. The crystal growth method according to claim 1.

9. In the ignition step, a crystal raw material is further added to the crucible.

2. The crystal growth method according to claim 1.

10. A crystal growth apparatus used in the crystal growth method according to any one of claims 1 to 9, A crucible and a heat-insulating layer that wraps around the outer circumferential surface of the crucible; an induction coil provided in the outer circumferential direction of the heat-retaining layer; a susceptor located below the crucible for fixing a seed crystal, the seed crystal being deep inside the crucible, and the susceptor having a cooling system; a light source emitter disposed above the crucible; a raw material addition port provided at the top of the crucible.

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