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] Crystal materials are very important functional materials, which are not only diverse in type but also rich in performance, and are widely used in precision devices in mechanics, electricity, optics, thermology, etc. Among them, semiconductor crystals are the foundation supporting the communication, 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] At present, gallium oxide crystal is the third generation semiconductor material developed after silicon carbide and gallium arsenide, and has a wider band gap, higher breakdown electric field, higher thermal conductivity, higher electron saturation velocity, shorter ultraviolet cut absorption edge and higher radiation protection ability, and β-crystal gallium oxide crystal is expected to become an important material in the field of wide band gap semiconductors. However, the manufacturing method of gallium oxide crystal still faces many challenges such as volatilization decomposition of raw materials, corrosion of iridium precious metal crucible, thin crystal thickness, spiral growth of crystal and coloring problems.

[0004] In the Chinese patent with a publication date of November 1, 2022 and a publication number of 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 in 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. This method has the following defects. (1) Metal Ga or a graphite sheet is adopted as an 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 from 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 it enters 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, forming a very large temperature difference in the radial direction, which is suitable for rapid growth methods such as the pulling method. 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 order to solve the above 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 has a simple process, effectively reduces the radial temperature gradient of the molten pool, inhibits the decomposition of gallium oxide, and realizes 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 composition comprising: A 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 until the surface area of ​​the molten pool expands to a target size, thereby melting the surface to form a molten pool; a molten pool expansion step in which an induction coil provided outside the crucible is started, and crystal raw material is added synchronously into the crucible, so that 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 the top of the molten pool until the crystal reaches the top of the molten pool; A temperature-reducing step of gradually reducing the power of the induction coil until the induction coil is turned off, and then cooling and 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, the cooling system located at the bottom of the seed crystal performs cooling synchronously, and the heat preservation layer can avoid heat loss, and the temperature of the outer wall of the crucible is maintained at not lower than 1400°C; 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 cooling, 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] In the molten pool expansion step, the crystal raw material is continuously added to the crucible synchronously during the heating process of the induction coil, so that the axial expansion speed of the molten pool is much faster than the radial expansion speed, and the molten pool expands downward faster until it contacts the seed crystal at the bottom, and the molten pool absorbs the electromagnetic induction energy and expands in the radial direction until it reaches thermal equilibrium with the radial heat dissipation, and 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, which significantly reduces the production cost.

[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 speed is 0.5-2mm / h, and the cooling process has the effect of in-situ annealing, so that the internal stress of the crystal according to the present invention is small compared to the pulling method process, and cleavage caused by sliding of the crystal planes is alleviated. In addition, the conventional pulling method, EDG (Edge-defined Film-fed Growth) method and traditional cold crucible method can only grow (010) crystals, but the process according to the present invention can adjust and control the crystal growth by designing a stable axial temperature gradient field, alleviate the stress between the crystal planes, and allow the crystal 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, raw balls, or raw powder.

[0018] Preferably, the grain size of the crystal raw material is 3-10 mm, and may be, 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 apply as well. The crystal raw material in the crucible is loose and not pressable.

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

[0020] Preferably, the permeable opening 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 formed in 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, so as to more effectively melt the raw material crystal and form an effective molten pool.

[0022] Preferably, the major axis of the elliptical path 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 recited values, and other unrecited values ​​within this range apply as well.

[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 apply as well. Generally, the diameter of the molten pool at the ignition stage should not exceed the radius of the crucible, otherwise it is detrimental 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 the 915 nm laser as an example.

[0026] Preferably, the radiation power of the laser emitter is 100-300W, and may be, for example, 100W, 120W, 150W, 180W, 200W, 220W, 250W, 280W or 300W, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable. The present invention does not exclude the possibility of using a high-power (e.g., 300W or more) laser emitter, and a low-power laser emitter is preferred because a typical low-power (e.g., 100-300W) laser has a modulation function and has a good energy-saving effect.

[0027] In addition, when the crystal raw material is in a granular form, it has a high reflectivity and a poor energy absorption rate, so the laser power needs to be improved. After the crystal raw material melts, it produces a fluid melt, which is easily absorbed by the surrounding crystal raw material, and the surface of the crystal raw material that has absorbed the surrounding melt becomes "wet", has a low reflectivity, and absorbs energy more easily, which reduces the laser power and reduces 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 the 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 and crystal growth processes, the operating frequency of the induction coil is 30-100 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 recited values, and other unrecited 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 40-100 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 recited values, and other unrecited values ​​within this numerical 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, for example, 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 the listed values, and other unlisted values ​​within this range are also applicable. The temperature of the outer wall of the crucible is decreased at a rate of 0.4 to 1°C / h, for example, 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 the listed values, and other unlisted values ​​within this range are also applicable.

[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, controls the power drop rate and temperature drop rate within a specific range, and provides an appropriate temperature field and time for crystal growth, thereby accelerating crystal growth.

[0033] Preferably, during the molten pool expansion process, the crystal raw material addition rate is 300-500 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 numerical range also apply.

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

[0035] Preferably, in the ignition process, the crystal raw material addition rate may be 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 are also applicable. In this process, the crystal raw material addition rate may gradually increase from small to large, or may be 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 step of fixing a seed crystal to the bottom of a crucible, filling the crucible with a crystal raw material, the crystal being a gallium oxide crystal, the crystal raw material having a particle size of 3 to 5 mm, a heat-insulating cover having at least one transmission port provided on the top of the crucible, and sealing the transmission port with sapphire; A laser emitter located above the crucible is started, the radiation power of the laser emitter is 100-300W, the number of the laser emitters is 4-8, and the focus of the light source is periodically moved on the surface of the crystal raw material in an elliptical locus with a major axis of 2 cm 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 the crystal raw material is added to the crucible at a rate of 10-200 g / min, and the diameter of the molten pool of the target size is 5 cm or more; a molten pool expansion step in which an induction coil provided outside the crucible is started, a heat insulating layer is provided between the induction coil and the crucible, and crystal raw materials are added synchronously 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 growing step in which the power of the induction coil is gradually reduced at a rate of 0.05-0.2 kW / h, and the temperature of the outer wall of the crucible is decreased at a rate of 0.4-1°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 of gradually reducing the power of the induction coil 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 30-100 kHz, and the operating power of the induction coil is 40-100 kW. At the same time, a 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 inside 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 disposed above the crucible, which can concentrate the emitted light inside the crucible and melt the crystal raw material to form a molten pool, thereby avoiding the problem of insufficient initial melting area in the ignition step that occurs in conventional crystal growth apparatuses. The heat-insulating layer disposed on the outer surface of the crucible, the induction coil in the outer circumferential direction of the heat-insulating layer, and the cooling system disposed on the susceptor reduce the radial temperature gradient and form an axial temperature gradient field, which promotes the crystal to release stress during the growth process and alleviates the cleavage problem caused by the sliding of the crystal planes, allowing the gallium oxide crystal to grow along the (010), (001) and (100) planes.

[0040] Taking the preparation of gallium oxide crystals as an example, the axis of the crucible is the midline, and the arrangement of materials from inside to outside is, in order, a molten pool, a gallium oxide polycrystalline shell layer, a gallium oxide raw material, a crucible, a heat retention layer and an induction coil. Under the action of gravity and heat, the molten pool expands downward until it contacts the seed crystal, so that the present invention can form a stable axial temperature gradient field while ensuring that the radial temperature gradient is small. Effect 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 focal trajectory of the light source to form an effective molten pool to which a magnetic field can be applied, and by allowing the molten pool to expand downward under the action 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 of the present invention can avoid the problem of crucible corrosion by forming a polycrystalline shell layer, and the polycrystalline shell layer is recoverable, which significantly reduces production costs.

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

[0045] [Figure 1] FIG. 1 is a structural schematic diagram of a crystal growth apparatus in accordance with a first embodiment 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 retention 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 PREFERRED EMBODIMENTS

[0047] The technical solutions of the present invention will be described below by using more 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 according to the present invention is carried out in a crystal growth apparatus, which includes a crucible 7, a heat-insulating layer 5 wrapped around the outer periphery of the crucible 7, an induction coil 12 provided on the outer periphery 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 being provided within the susceptor 11, a light source emitter 3 provided above the crucible 7, and a raw material addition port 2 provided at the top of the crucible 7, as shown in FIG. A heat-insulating cover is provided on the top of the crucible 7, and two sapphire transmission holes 4 are provided in the heat-insulating cover. Four light source emitters 3 are provided above each of the sapphire transmission holes 4. A raw material addition port 2 is provided in the heat-insulating cover, 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, the thermocouples including an upper thermocouple 9 and a lower thermocouple 10, the top end of the upper thermocouple 9 being located on the top side of the crucible 7 and the top end of the lower thermocouple 10 being located on the bottom side of the crucible 7, a camera 1 being provided above the raw material addition port 2, and a substrate 13 being 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 includes a camera 1, a raw material addition port 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, as shown in Fig. 1. The diameter of the induction coil 12 is 800mm, the outer diameter of the heat-insulating layer 5 is 700mm, and the inner diameter of the heat-insulating layer 5 is 300mm.

[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 closed.

[0052] Ignition: The laser emitter, which is the light source emitter 3 located above the crucible 7, is started up, the wavelength of the laser emitter is 915 nm, the power of a single unit is 200 W, and there are four units in total. First, the output power is adjusted to 120 W, and the laser is focused on the surface of the particle ball to melt the particle ball. When a dazzling spot is seen from the observation window, it indicates that the particle ball on the surface is melted. At this time, the power is reduced to 100 W, and the focus of the laser is periodically moved on the surface of the particle ball in an elliptical trajectory with a major axis of 2 cm to form a molten pool. During this time, the particle balls are added to the crucible 7 at the same time at a rate of 200 g / min, and the surface area of ​​the molten pool is expanded until it reaches the target size, that is, the diameter of the molten pool is 5 cm.

[0053] Molten pool expansion: The induction coil 12 installed outside the crucible 7 was started and the frequency was adjusted to 30 kHz, and the power of the induction coil 12 was gradually increased to 45 kW. It can be observed that the brightness of the molten pool increases and the area of ​​the molten pool increases with the increase in power. Synchronously, the particle balls were added to the crucible 7 at a rate of 300 g / min up to a total of 3 kg of particle balls, and the addition was stopped, the quartz glass tube 6, which was the supply tube, was taken out, and the raw material addition port 2 was sealed with sapphire.

[0054] After the melt in the molten pool was stable for 30 min, 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 was formed between the molten pool and the inner wall of the crucible 7, and the diameter of the molten pool was maintained at 10 cm.

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

[0056] Crystal growth: The power of the induction coil 12 was reduced to 37 kW in stages 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 about 0.6°C / h at the outer wall of the crucible 7, and the lower thermocouple 10 detected a temperature drop rate of about 0.8°C / h at the outer wall of the crucible 7, and 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 temperature detected by the upper thermocouple 9 reached 1530°C, and the temperature detected by the lower thermocouple 10 reached 1450°C.

[0057] Temperature drop: The power of the induction coil 12 was gradually reduced to 2 kW 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 embodiment, 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. A sample of 50 × 180 mm × 2 mm was obtained by processing, and 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 granulated 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 emitter located above the crucible was started, the wavelength of the laser emitter was 915 nm, the power of a single unit was 200 W, and there were four in total. 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 the particle ball. When a bright spot was seen through the observation window, the power was reduced to 100 W, and the focus of the laser was periodically moved on the surface of the particle ball in an elliptical trajectory with a major axis of 2 cm. At the same time, the particle ball was added to the crucible at a rate of 50 g / min, and the surface area of ​​the molten pool was expanded to a diameter of 5 cm.

[0063] Molten pool expansion: The induction coil installed outside the crucible was started and the frequency was adjusted to 30 kHz, and the power of the induction coil was gradually increased to 45 kW. Synchronously, the particle balls were added to the crucible at a rate of 100 g / min until the total amount of the particle balls reached 3 kg. The addition was 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 was stable for 30 min, the temperature detected by the upper thermocouple reached 1630°C, 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 was formed between the molten pool and the inner wall of the crucible, and the diameter of the molten pool was maintained 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 power of the induction coil 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 continued to operate to cool it down. During this process, the upper thermocouple detected a temperature drop rate of about 0.6°C / h at the outer wall of the crucible, and the lower thermocouple detected a temperature drop rate of about 0.8°C / h at the outer wall of the crucible, and the crystal grew upward from the lower seed until it reached the top of the molten pool. At the end of this stage, the temperature detected by the upper thermocouple reached 1530°C and the temperature detected by the lower thermocouple reached 1450°C.

[0067] Temperature drop: The power of the induction coil was gradually reduced to 2 kW 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 embodiment, a gallium oxide crystal having a 3.5-inch level and an outer size of φ90 mm × 200 mm can be obtained. The mass of the crystal is 1.9 kg. A sample of 50 × 180 mm × 2 mm can be obtained by processing, and an X-ray diffraction test can be performed to obtain a FWHM of 110 arcsec.

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

[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 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.

[0072] Ignition: The laser emitter located above the crucible was started, the wavelength of the laser emitter was 915 nm, the power of a single unit was 200 W, and there were four in total. 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 the particle ball. When a dazzling spot was seen through the observation window, the power was reduced to 100 W, and the focus of the laser was periodically moved on the surface of the particle ball in an elliptical trajectory with a major axis of 2 cm. At the same time, the particle ball was added to the crucible at a rate of 200 g / min, and the surface area of ​​the molten pool was expanded to a diameter of 5 cm.

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

[0074] After the melt in the molten pool was stable 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 time 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 was formed between the molten pool and the inner wall of the crucible, and the diameter of the molten pool was maintained 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 power of the induction coil 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 continued to operate to cool it down. During this process, the upper thermocouple detected a temperature drop rate of about 0.4°C / h at the outer wall of the crucible, and the lower thermocouple detected a temperature drop rate of about 0.6°C / h at the outer wall of the crucible, and the crystal grew upward from the lower seed until it reached the top of the molten pool. At the end of this stage, the temperature detected by the upper thermocouple reached 1600°C, and the temperature detected by the lower thermocouple reached 1510°C.

[0077] Temperature drop: The power of the induction coil was gradually reduced to 2 kW 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 according to this embodiment, the thermocouple is inserted inside the crucible and is closer to the melt and the shell layer of the melt raw material sphere, so the detection temperature is higher, the heat retention layer is thicker, so the heat retention effect is better, the radial temperature gradient is smaller, the crystal growth time is extended, and the power of the induction coil is reduced. According to this embodiment, a gallium oxide crystal with a 3.5-inch level and an outer size of φ90mm×200mm can be obtained, and the mass of the crystal is 1.9kg. A sample of 60×180mm×2mm is obtained by processing, and FWHM=88arcsec is obtained by X-ray diffraction testing.

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

[0080] The crystal growth method is different from Example 1 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, compared with Example 1, the number of laser emitters is increased to 8, which makes the initial melting of the particle spheres faster, thereby improving the material addition rate, but does not affect the crystal growth results. The unfavorable effect is that a small amount of white product, i.e., the generated gallium oxide vapor, is visible, 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 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.

[0085] Ignition: The laser emitter located above the crucible was started, the wavelength of the laser emitter was 915 nm, the power of a single unit was 200 W, and there were four in total. 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 the particle ball. When a dazzling spot was seen through the observation window, the power was reduced to 100 W, and the focus of the laser was periodically moved on the surface of the particle ball in an elliptical trajectory with a major axis of 2 cm. At the same time, the particle ball was added to the crucible at a rate of 200 g / min, and the surface area of ​​the molten pool was expanded to a diameter of 5 cm.

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

[0087] After the melt in the molten pool was stable for 30 min, the temperature detected by the upper thermocouple reached 1630°C, 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 was formed between the molten pool and the inner wall of the crucible, and the diameter of the molten pool was maintained 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 power of the induction coil 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 continued to operate to cool it down. During this process, the upper thermocouple detected a temperature drop rate of about 2.4°C / h at the outer wall of the crucible, and the lower thermocouple detected a temperature drop rate of about 3.2°C / h at the outer wall of the crucible, and the crystal grew upward from the lower seed until it reached the top of the molten pool. At the end of this stage, the temperature detected by the upper thermocouple reached 1530°C and the temperature detected by the lower thermocouple reached 1450°C.

[0090] Temperature drop: The power of the induction coil was reduced to 2 kW at a rate of 2 kW / h in a stepwise manner, 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 embodiment, 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 embodiment, 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 60×180 mm×2 mm was obtained by processing, and an X-ray diffraction test showed FWHM=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 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.

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

[0096] Molten pool expansion: The induction coil installed outside the crucible was started and the frequency was adjusted to 30 kHz, and the power of the induction coil was gradually increased to 45 kW. Synchronously, the particle balls were added to the crucible at a rate of 100 g / min until the total amount of the particle balls reached 3 kg. The addition was 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 was stable for 30 min, the temperature detected by the upper thermocouple 9 reached 1630°C, 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 was 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 power of the induction coil was gradually reduced to 37 kW at a rate of 0.5 kW / h, and the cooling system located at the bottom of the seed crystal 8 continued to operate to perform cooling. During this process, the upper thermocouple detected the temperature drop rate at the outer wall of the crucible varying between 3°C / h and 10°C / h, and the lower thermocouple detected the temperature drop rate at the outer wall of the crucible varying between 5°C / h and 16°C / h, and the crystal grew upward from the lower seed crystal until it reached the top of the molten pool. At the end, the temperature detected by the upper thermocouple reached 1530°C, and the temperature detected by the lower thermocouple reached 1450°C.

[0099] Temperature drop: The power of the induction coil was gradually reduced to 2 kW 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 according to this embodiment, the descending speed of the electromagnetic induction coil is increased to 0.5 kW / h compared to Example 1. According to this embodiment, gallium oxide crystals of 3.5 inch level and outer size of φ90 mm×200 mm can be obtained, but problems such as crystal cracking, color variation, bubbles, layered or striped polycrystalline defects, etc. are observed in the X-ray diffraction test, and it is presented as a non-single crystal.

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

[0102] The following steps were performed:

[0103] (1) 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 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 emitter located above the crucible was started, the wavelength of the laser emitter was 915 nm, and the power of each was 200 W, totaling four. The output power was adjusted to 120 W, and the laser was focused on the surface of the particle ball to melt the particle ball. When a bright spot was seen through the observation window, the power was reduced to 100 W, and at the same time, the particle ball was added to the crucible at a rate of 200 g / min, and the surface area of ​​the molten pool was expanded to a diameter of 3 cm.

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

[0106] Comparative Example 2 The apparatus used in this comparative example differs from that in Example 1 only in that no quartz glass tube is provided and the raw material addition port of the heat-insulating cover is sealed with sapphire. In the method of this comparative example, no material is 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 spheres with a diameter of 3 mm 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 emitter located above the crucible was started, the wavelength of the laser emitter 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 the particle ball. When a bright spot was seen through the observation window, the power was reduced to 100 W, and at the same time, the particle ball was added to the crucible at a rate of 200 g / min, and the surface area of ​​the molten pool was expanded to a diameter of 5 cm.

[0110] (3) The induction coil installed outside the crucible was started and the frequency was adjusted to 30 kHz, and 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 was operated synchronously to perform cooling. It can be observed that the radial expansion speed of the molten pool is obviously faster than that of Example 1, no polycrystalline shell layer is formed between the molten pool and the crucible, and the molten pool cannot expand downward to contact the seed crystal at the bottom of the crucible, so 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 peripheral 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 spheres with a diameter of 3 mm 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 emitter located above the crucible was started, the wavelength of the laser emitter was 915 nm, the power of each was 200 W, and there were four in total. The output power was adjusted to 120 W, and the laser was focused on the surface of the particle ball to melt the particle ball. When a bright spot was seen through the observation window, the power was reduced to 100 W, and at the same time, the particle ball was added to the crucible at a rate of 200 g / min, and the surface area of ​​the molten pool was expanded to a diameter of 5 cm.

[0115] (3) The induction coil installed outside the crucible was started and the frequency was adjusted to 30 kHz, and the power of the induction coil was gradually increased to 45 kW, and in sync, the particle balls were added to the crucible at a rate of 300 g / min until the total amount of the particle balls reached 3 kg, and then 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-cooling segment performed cooling throughout.

[0116] After the melt in the molten pool was stable 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, with the water-cooled segment providing 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 causes a very serious heat dissipation, a large radial temperature gradient, and the heat is absorbed by the shell layer more quickly, 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 that in the third comparative example.

[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 with Example 1, the crystal growth method of this comparative example used water-cooled segments and increased the power of the induction coil, which resulted in extremely severe heat dissipation and a large radial temperature gradient. The crystals obtained 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 in the first embodiment.

[0124] The crystal raw material used in this comparative example is gallium oxide powder with a purity of 4N. The gallium oxide powder is not granulated, and 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 a crucible having 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 emitter located above the crucible was started, the wavelength of the laser emitter was 915 nm, the power of a single unit was 200 W, and there were four in total. The output power was adjusted to 120 W, and the laser was focused on the surface of the particle ball to melt the powder. When a bright spot was seen through the observation window, the power was reduced to 100 W, and the focus of the laser was periodically moved on the surface of the powder in an elliptical trajectory with a major axis of 2 cm, and at the same time, the powder was added to the crucible at a rate of 200 g / min. It was observed that the duration of this stage was consistent with the time used for the ignition stage in Example 1, but there was no obvious sign of the molten pool expanding.

[0128] The applicant declares that the above 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 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 until the surface area of ​​the molten pool expands to a target size, thereby melting the surface to form a molten pool; a molten pool expansion step in which an induction coil provided outside the crucible is started, and crystal raw material is added synchronously into the crucible, so that 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 the top of the molten pool until the crystal reaches the top of the molten pool; A temperature-reducing step of gradually reducing the power of the induction coil until the induction coil is turned off, and then cooling and removing the crystal, A heat insulating layer is provided between the induction coil and the crucible, During the crystal growth, a cooling system located at the bottom of the seed crystal performs cooling synchronously; During the process of expanding the molten pool, a polycrystalline shell layer is formed between the molten pool and the inner wall of the crucible. A crystal growth method comprising:

2. the crystal is a gallium oxide crystal, The grain 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. During the ignition process, the focus of the light source moves periodically along an elliptical trajectory on the surface of the raw crystal 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 process, the light source emitter used includes a laser emitter; The radiation power of the laser emitter is between 100 and 300 W; The number of the laser emitters is 4 to 8; 2. The crystal growth method according to claim 1 .

6. During the molten pool expansion and crystal growth, the operating frequency of the induction coil is 30-100 kHz; During the molten pool expansion and crystal growth steps, the operating power of the induction coil is 40-100 kW.

2. The crystal growth method according to claim 1 .

7. During the crystal growth, 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. During the molten pool expansion process, the crystal raw material is added at a rate of 300-500 g / min; 2. The crystal growth method according to claim 1 .

9. During the ignition process, a crystal raw material is further added to the crucible.

2. The crystal growth method according to claim 1 .

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

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