CN116716660A - Crystal growth method and crystal growth device - Google Patents

Abstract

The invention relates to a crystal growth method and a crystal growth device. The crystal growth method includes sequentially performing processes such as charging, ignition, melt pool expansion, crystal growth and cooling to obtain crystals; wherein, during the ignition process, the light source is The focus moves on the surface of the crystal raw material so that its surface melts to form a molten pool until the surface area of the molten pool expands to the target size. During the process of expanding the molten pool, the induction coil set on the outside of the crucible is activated, and the crystal raw material is simultaneously added into the crucible. The molten pool continues to expand downward until it contacts the seed crystal at the bottom of the crucible. During the growth of the crystal, the power of the induction coil is reduced, causing crystallization from the top of the seed crystal to continue from bottom to top until the crystal reaches the top of the molten pool. The crystal growth method and crystal growth device provided by the present invention can obtain an effective molten pool, form a radial temperature gradient, and improve the degree of crystal cleavage.

Description

A crystal growth method and crystal growth device

Technical field

The present invention relates to the technical field of crystal growth, and in particular to a crystal growth method and a crystal growth device.

Background technique

Crystal material is an extremely important functional material with various types and rich properties. It is widely used in precision devices such as mechanics, electricity, optics or thermal. Among them, semiconductor crystals are the basis for supporting communications, computers, automobiles and electronic information industries. Electronic devices, semiconductor devices, solid laser devices and optical devices prepared using semiconductor crystals have broad application prospects.

At present, gallium oxide crystal is the third generation semiconductor material developed after silicon carbide and gallium arsenide. It has a wider bandgap, higher breakdown electric field, higher thermal conductivity, and greater electron saturation. Speed, shorter UV cut-off absorption edge and higher radiation resistance, especially β-crystalline gallium oxide crystal, are expected to become the core material in the field of wide-bandgap semiconductors. However, there are still many challenges in the preparation method of gallium oxide crystals, such as volatilization and decomposition of raw materials, corrosion of iridium precious metal crucibles, thin crystal thickness, crystal spiral growth, and coloring problems.

Published on November 1, 2022, the Chinese patent with publication number CN115261973A discloses a method for growing large-sized gallium oxide crystals. This method uses a cold crucible or an alloy crucible to fill the gallium oxide raw material, and the pressure range is 0.1<p Gallium oxide crystal growth is performed in a pure oxygen atmosphere of <0.7MPa. In this method, if a cold crucible is used, metal Ga or graphite sheets need to be placed in the middle area of the gallium oxide raw material as an igniter, and the cold crucible is composed of a water-cooling flap and a water-cooling stage. During the growth process, the external powder Due to the water cooling effect, the material will not be heated and melted, thus forming a layer of unmelted shell, and the melt will grow crystals in the unmelted shell. This method has the following defects: (1) Metal Ga or graphite sheets are used as igniters. Metal Ga is liquid at room temperature and is expensive and not suitable for use as consumables. The electric spark formed by the graphite sheets fails to ignite the gallium oxide raw material. balls, but under the same process, alumina particles with higher melting points can ignite balls, and graphite flakes are reducing impurities. If they enter the melt, they will easily decompose the raw materials at high temperatures; (2) Add a water-cooled flap to the side wall of the crucible , although it can prevent the external powder from being melted, it takes away a lot of heat and forms a huge temperature difference in the radial direction. It is suitable for rapid growth methods such as the Czochralski method. The crystal is easy to crack and it is difficult to shape large-sized, High-quality gallium oxide crystal; (3) It is necessary to fill the furnace with high-purity oxygen, increasing the equipment structure and process steps.

Therefore, it is of great significance to provide a crystal growth method and a growth device that are beneficial to the growth of gallium oxide crystal and reduce the growth cost.

Contents of the invention

In view of the above problems, the purpose of the present invention is to provide a crystal growth method and a crystal growth device. Compared with the existing technology, the crystal growth method provided by the present invention has a simple process, can effectively reduce the radial temperature gradient of the molten pool, and suppress Gallium oxide decomposes to achieve the growth of large-sized and high-quality gallium oxide crystals; the crystal growth device provided by the invention can form a stable axial temperature gradient field, thereby promoting crystal growth.

In order to achieve the purpose of this invention, the present invention adopts the following technical solutions:

In a first aspect, the present invention provides a crystal growth method, which includes the following steps:

Loading: Fix the seed crystal at the bottom of the crucible and fill the crucible with crystal raw materials;

Ignition: Start the light source emitter located above the crucible, so that the focus of the light source moves on the surface of the crystal raw material to melt the surface to form a molten pool until the surface area of the molten pool expands to the target size;

Expanding the molten pool: Start the induction coil set outside the crucible, and simultaneously add crystal raw materials into the crucible. The molten pool continues to expand downward until it contacts the seed crystal at the bottom of the crucible;

Crystal growth: Gradually reduce the power of the induction coil to continuously crystallize from the top of the seed crystal from bottom to top until the crystal reaches the top of the molten pool;

Cooling: Gradually reduce the power of the induction coil until the power of the induction coil is turned off. After cooling, take out the crystal;

in,

In the crystal growth method, a thermal insulation layer is provided between the induction coil and the crucible;

During the growth process of the crystal, the cooling system located at the bottom of the seed crystal performs cooling simultaneously. The insulation layer can avoid heat loss and keep the temperature of the outer wall of the crucible at no less than 1400°C;

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.

The crystal growth method provided by the invention is sequentially provided with steps such as charging, ignition, melt pool expansion, crystal growth and cooling.

In the ignition process, by controlling the movement trajectory of the light source focus, the surface area of the molten pool is expanded to the target size to form an effective molten pool.

In the process of expanding the molten pool, crystal raw materials are continuously replenished into the crucible during the heating process of the induction coil, so that the expansion speed of the molten pool in the axial direction is much greater than the expansion speed in the radial direction, and the molten pool expands downward to contact faster. When reaching the seed crystal at the bottom, the molten pool absorbs electromagnetic induction energy in the radial direction and expands until it forms a thermal equilibrium with the radial heat dissipation, and forms a polycrystalline shell at the solid-liquid interface, which can protect the crucible from corrosion. The polycrystalline shell can also be recycled, significantly reducing production costs;

During the entire growth process, the outside of the crucible is insulated with an insulation layer to maintain the radial thermal balance effect and reduce the radial temperature gradient difference;

In the crystal growth process, the cooling rate during the crystal growth stage is controlled by adjusting the output power of the induction coil. The control is simple and reliable.

Using this temperature gradient method, the crystal growth rate is 0.5-2mm/h, and the cooling process has an in-situ annealing effect. Compared with the pull-up method, the internal stress of the crystal obtained by the present invention is smaller, which alleviates the cleavage caused by crystal plane slip. . In addition, the existing Czochralski method, film conduction method and traditional cold crucible method can only grow (010) crystals. The process provided by the present invention can regulate crystal growth and alleviate crystal growth by designing a stable axial temperature gradient temperature field. The stress between the planes allows the crystal to grow along the (010), (001) and (100) planes.

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 can perform cooling during the process of expanding the molten pool and/or ignition.

Preferably, the crystal is a gallium oxide crystal.

In the present invention, the crystal raw material is a solid, for example, it can be a raw material ingot, a raw material pellet or a raw material powder.

Preferably, the particle size of the crystal raw material is 3-10 mm, for example, it can be 3 mm, 4 mm, 5 mm or 10 mm, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable. The crystal raw materials in the crucible are placed loosely and cannot be compacted.

Preferably, a thermal insulation cover is provided on the top of the crucible, and at least one light-transmitting port is provided on the thermal insulation cover.

Preferably, the light-transmitting port is sealed with sapphire. The entire crucible cavity is relatively closed. During the crystal growth process, a nearly saturated gallium oxide vapor pressure is formed in the crucible, which inhibits the decomposition of gallium oxide.

Preferably, during the ignition process, the focus of the light source moves periodically in an elliptical trajectory on the surface of the crystal raw material. The invention promotes the crystal raw material to absorb energy by performing periodic motion of the elliptical trajectory through design, and melts the crystal raw material more effectively to form an effective molten pool.

Preferably, the long axis of the elliptical trajectory is ≥2cm, for example, it can be 2cm, 2.2cm, 2.4cm, 2.6cm, 2.8cm or 3cm, but is not limited to the listed values. Other unlisted values within the numerical range are also applicable. .

Preferably, the diameter of the molten pool of the target size is ≥5cm, for example, it can be 5cm, 5.5cm, 6cm, 6.5cm, 7cm, 7.5cm or 8cm, but is not limited to the listed values, and other values within the range are not listed. The same applies to numerical values. Generally speaking, the diameter of the molten pool in the ignition stage does not exceed the radius of the crucible, otherwise it will not be conducive to the formation of a polycrystalline shell.

Preferably, during the ignition process, the light source emitter used includes a laser emitter.

Preferably, the emission band of the laser transmitter can be 532nm, 808nm, 980nm, 1064nm, etc. The present invention does not exclude the possibility of using lasers in other wavelength bands. The present invention takes a 915nm laser as an example.

Preferably, the emission power of the laser transmitter is 100-300W, for example, it can be 100W, 120W, 150W, 180W, 200W, 220W, 250W, 280W or 300W, but is not limited to the listed values, and other values are not within the range of the values. The same applies to the listed values. The present invention does not rule out the possibility of using a high-power (for example, more than 300W) laser transmitter, but generally a laser with a smaller power (for example, 100-300W) has a tunable function and has a good energy-saving effect, so a low-power laser transmitter is preferred.

It should be noted that when the crystal raw material is in granular form, the reflectivity is high and the energy absorption rate is poor, so the laser power needs to be increased. When the crystal raw material is melted, a fluid melt is produced. The melt is easily absorbed by the surrounding crystal raw material. The surface of the crystal raw material that has absorbed the surrounding melt is in a "wet" state with low reflectivity and is easier to absorb energy, which can reduce the laser energy. power and reduce energy consumption. During the entire ignition process, the emission power of the laser transmitter does not need to be adjusted.

Preferably, the number of laser emitters is 4-8, for example, it can be 4, 5, 6, 7 or 8, but is not limited to the listed values, other unlisted values within the range of the values The same applies.

Preferably, during the process of expanding the molten pool and growing the crystal, the working frequency of the induction coil is 30-100kHz, for example, it can be 30kHz, 40kHz, 50kHz, 60kHz, 70kHz, 80kHz, 90kHz or 100kHz, but is not limited to the above. For listed values, other non-listed values within the value range are also applicable.

Preferably, during the process of expanding the molten pool and crystal growth, the working power of the induction coil is 40-100kW, for example, it can be 40kW, 45kW, 50kW, 55kW, 60kW, 65kW, 70kW, 75kW, 80kW, 85kW, 90kW, 95kW or 100kW, but not limited to the listed values, other unlisted values within the value range are also applicable.

Preferably, during the crystal growth process, the working power of the induction coil decreases at a rate of 0.05-0.2kW/h, for example, it can be 0.05kW/h, 0.06kW/h, 0.08kW/h, 0.1kW/h. h, 0.12kW/h, 0.14kW/h, 0.16kW/h, 0.18kW/h or 0.2kW/h, but are not limited to the listed values, and other unlisted values within the value range are also applicable; the crucible The temperature of the outer side wall decreases at a rate of 0.4-1°C/h, for example, it can be 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. , other unlisted values within the value range are also applicable.

In the process of crystal growth, the present invention regulates the cooling rate in the crystal growth stage by reducing the power of the induction coil, and controls the power reduction rate and the cooling rate within a specific range, which can provide a suitable temperature field and time for crystal growth and promote crystal growth. .

Preferably, during the process of expanding the melt pool, the adding rate of crystal raw materials is 300-500g/min, for example, it can be 300g/min, 320g/min, 350g/min, 380g/min, 400g/min, 420g/min , 450g/min, 480g/min or 500g/min, but not limited to the listed values, other unlisted values within the value range are also applicable.

Preferably, crystal raw materials are also added to the crucible during the ignition process.

Preferably, during the ignition process, the addition rate of the crystal raw material is 10-200g/min, for example, it can be 10g/min, 15g/min, 20g/min, 25g/min, 30g/min, 35g/min, 40g/min, 45g/min, 50g/min, 100g/min or 200g/min, but not limited to the listed values, other unlisted values within the value range are also applicable. During this process, the adding rate of the crystal raw material can be gradually increased from small to large, or the rate can be kept constant.

Preferably, the power reduction speed during the cooling process is 1-3kW/h, for example, it can be 1kW/h, 1.2kW/h, 1.5kW/h, 1.8kW/h, 2kW/h, 2.2kW/h, 2.5kW/h, 2.8kW/h or 3kW/h, but not limited to the listed values, other unlisted values within the value range are also applicable.

As a preferred technical solution of the present invention, the crystal growth method includes the following steps:

Loading: Fix the seed crystal at the bottom of the crucible, and fill the crucible with crystal raw materials. The crystals are gallium oxide crystals. The particle size of the crystal raw materials is 3-5 mm. The top of the crucible is provided with an insulation cover. The insulation cover The cover is provided with at least one light-transmitting port, and the light-transmitting port is sealed with sapphire;

Ignition: Start the laser emitter located above the crucible. The emission power of the laser emitter is 100-300W and the number is 4-8 units. Make the focus of the light source cycle on the surface of the crystal raw material in an elliptical trajectory with a long axis ≥ 2cm. Movement to melt the surface to form a molten pool, and at the same time, add crystal raw materials into the crucible at a rate of 10-200g/min until the surface area of the molten pool expands to a target size, and the diameter of the molten pool of the target size is ≥ 5cm;

Expanding the molten pool: Start the induction coil installed outside the crucible. There is an insulation layer between the induction coil and the crucible, and simultaneously add crystal raw materials into the crucible at a rate of 300-500g/min. The molten pool continues to expand downward until The seed crystal is in contact with the bottom of the crucible;

Crystal growth: Gradually reduce the power of the induction coil at a rate of 0.05-0.2kW/h, and the temperature of the outer wall of the crucible decreases at a rate of 0.4-1℃/h, so that the top of the seed crystal will continue to crystallize from bottom to top until the crystal Reach the top of the molten pool;

Cooling: Gradually reduce the power of the induction coil until the power of the induction coil is turned off. After cooling, take out the crystal;

Wherein, during the process of expanding the molten pool and growing the crystal, the working frequency of the induction coil is 30-100kHz, the working power of the induction coil is 40-100kW, and at the same time, the cooling system located at the bottom of the seed crystal operates synchronously to implement cooling. , and a polycrystalline shell is formed between the molten pool and the inner wall of the crucible.

In a second aspect, the present invention provides a crystal growth device, which is used in the crystal growth method described in the first aspect of the present invention; the crystal growth device includes: a crucible; and a Insulation layer; an induction coil arranged in the outer circumferential direction of the insulation layer; a crystal holder located below the crucible and used to fix the seed crystal, the seed crystal is deep into the crucible, and a crystal holder is provided in the crystal holder A cooling system; a light source emitter arranged above the crucible; and a feeding port arranged on the top of the crucible.

The crystal growth device provided by the present invention can focus the emitted light into the crucible by arranging a light source emitter above the crucible, melting the crystal raw material to form a molten pool, and can avoid the insufficient initial melting area in the ignition link of the existing crystal growth device. problem; through the insulation layer on the outer circumference of the crucible, the induction coil on the outside of the insulation layer, and the cooling system set up in the crystal seat, the radial temperature gradient can be reduced and an axial temperature gradient field can be formed to promote The crystal releases stress during the growth process and alleviates the dissociation problem caused by crystal plane slip, allowing gallium oxide crystals to grow along the (010), (001) and (100) planes.

Taking the preparation of gallium oxide crystal as an example, taking the axis of the crucible as the center line, the material distribution from the inside to the outside is the molten pool, gallium oxide polycrystalline shell, gallium oxide raw material, crucible, insulation layer and induction coil, while the molten pool is in the gravity It expands downward under the action of heat and heat until it contacts the seed crystal. Therefore, the present invention forms a stable axial temperature gradient field while ensuring that the radial temperature gradient is small.

Compared with the existing technology, the present invention has the following beneficial effects:

(1) The crystal growth method provided by the present invention controls the focus trajectory of the light source to form an effective molten pool that can carry a magnetic field, and the molten pool expands downward under the action of gravity and heat to contact the seed crystal at the bottom, forming a stable temperature gradient. temperature field, thereby promoting crystal growth.

(2) The crystal growth method provided by the present invention avoids the corrosion problem of the crucible by forming a polycrystalline shell layer, and the polycrystalline shell layer can be recycled, which can significantly reduce production costs.

(3) The crystal growth device provided by the present invention can reduce the radial temperature gradient, promote the radial hot and cold balance, improve the degree of crystal cleavage, and enable the gallium oxide crystal to grow along the ( 010), (001) and (100) plane growth.

Description of the drawings

Figure 1 is a schematic structural diagram of a crystal growth device according to Embodiment 1 of the present invention;

Among them, 1-camera; 2-feeding port; 3-light source emitter; 4-sapphire light transmission port; 5-insulation layer; 6-quartz glass tube; 7-crucible; 8-seed crystal; 9-upper thermocouple; 10-lower thermocouple; 11-crystal base; 12-induction coil; 13-substrate.

Detailed ways

The technical solution of the present invention will be further described below through specific implementations. Those skilled in the art should understand that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

In a specific embodiment, the crystal growth method provided by the present invention is carried out in a crystal growth device. The crystal growth device is shown in Figure 1 and includes: a crucible 7 and an insulation layer 5 wrapped around the outer peripheral surface of the crucible 7 , the induction coil 12 arranged on the outer peripheral surface of the insulation layer 5 is located below the crucible 7 and is used to fix the crystal seat 11 of the seed crystal 8. The seed crystal 8 is deep into the crucible 7, and the crystal seat 11 is provided with a cooling system, a light source emitter 3 provided above the crucible 7, and a charging port 2 provided on the top of the crucible 7;

The top of the crucible 7 is provided with a thermal insulation cover, and two sapphire light-transmitting ports 4 are provided in the thermal insulation cover, and four light source emitters 3 are provided above each of the sapphire light-transmitting ports 4;

The insulation cover is provided with a feeding port 2, and a feeding pipe is provided in the feeding port 2. The feeding pipe is a quartz glass tube 6, the cooling system is a water cooling system, and the crucible 7 is a zirconia ceramic crucible. , the insulation layer 5 is a zirconia insulation layer, and the insulation cover is a zirconia insulation cover;

Two thermocouples are arranged between the outer wall of the crucible 7 and the insulation layer 5. The thermocouples include an upper thermocouple 9 and a lower thermocouple 10. The top of the upper thermocouple 9 is located on the top side of the crucible 7. , the top of the lower thermocouple 10 is located on the bottom side of the crucible 7 , a camera 1 is provided above the feeding port 2 , and a substrate 13 is provided at the bottom of the crucible 7 .

Example 1

This embodiment provides a crystal growth method. The crystal growth device used in the crystal growth method is shown in Figure 1 and includes a camera 1, a feeding port 2, a light source emitter 3, a sapphire light transmission port 4, an insulation layer 5, and quartz. Glass tube 6, crucible 7, insulation cover, seed crystal 8, upper thermocouple 9, lower thermocouple 10, crystal base 11, induction coil 12 and substrate 13. The diameter of the induction coil 12 is 800mm, and the insulation layer 5 The outer diameter is 700mm, and the inner diameter of the insulation layer 5 is 300mm.

The crystal growth method includes the following steps:

Loading: Use a granulator to granulate gallium oxide powder with a purity of 4N into particle balls with a diameter of 3mm; fix the seed crystal 8 at the bottom of the crucible 7, and move it toward the crucible with a thickness of 5mm, an outer diameter of 260mm, and a depth of 280mm. 7. Fill the medium with gallium oxide particles and put them in. Do not compact the gallium oxide particles and cover them with an insulation cover.

Ignition: Start the light source emitter 3 located above the crucible 7, that is, the laser emitter. The wavelength of the laser emitter is 915nm, and the power of a single unit is 200W, a total of 4 units; first adjust its output power to 120W to focus the laser on the particle ball. The surface melts the particle ball; when you see a dazzling light spot from the observation window, indicating that the surface particle ball is melted, reduce the power to 100W, and focus the laser on the surface of the particle ball in an elliptical trajectory with a long axis of 2cm. Movement to form a molten pool. During this period, particle balls were also added to the crucible 7 at a rate of 200 g/min until the surface area of the molten pool expanded to the target size, that is, the diameter of the molten pool was 5 cm.

Expanding the molten pool: Start the induction coil 12 set outside the crucible 7 and adjust the frequency to 30kHz. Gradually increase the power of the induction coil 12 to 45kW. As the power increases, it can be observed that the brightness of the molten pool increases and the area of the molten pool increases. Simultaneously add pellets into the crucible 7 at a rate of 300g/min until the total number of pellets reaches 3kg. Take out the feeding tube, that is, the quartz glass tube 6, and seal the feeding port 2 with sapphire;

After the melt in the molten pool has stabilized for 30 minutes, the temperature detected by the upper thermocouple 9 reaches 1630°C, and the temperature detected by the lower thermocouple 10 reaches 1580°C. At this time, the molten pool contacts the seed crystal 8 at the bottom of the crucible 7; the radial temperature of the crucible 7 When equilibrium is reached, a polycrystalline shell is formed between the molten pool and the inner wall of the crucible 7, and the diameter of the molten pool is maintained at 10 cm.

During this period, the cooling system located at the bottom of the seed crystal 8 operates synchronously to implement cooling.

Crystal growth: Gradually reduce the power of the induction coil 12 to 37kW at a rate of 0.05kW/h, and the cooling system located at the bottom of the seed crystal 8 continues to operate for cooling; during this process, the upper thermocouple 9 detects the cooling rate of the outer wall of the crucible 7 The lower thermocouple 10 detects that the cooling rate of the outer wall of the crucible 7 is about 0.8°C/h. The crystal grows upward from the seed crystal 8 below until it reaches the top of the molten pool; at the end of this stage, the upper The detection temperature of thermocouple 9 reaches 1530°C, and the detection temperature of lower thermocouple 10 reaches 1450°C.

Cooling: Gradually reduce the power of the induction coil 12 to 2kW at a rate of 2kW/h, then turn off the power of the induction coil 12, continue to cool, and then take out the crystal.

Using the crystal growth method provided in this embodiment, a 3.5-inch-level gallium oxide crystal with an outer size of φ90mm×200mm and a crystal mass of 1.9kg can be obtained. A 50×180mm×2mm sample can be obtained by processing. The X-ray diffraction test shows that the FWHM=108arcsec .

Example 2

This embodiment provides a crystal growth method. The crystal growth device used in the crystal growth method is the same as that in Embodiment 1.

The crystal growth method includes the following steps:

Loading: Use a granulator to granulate gallium oxide powder with a purity of 4N into particle balls with a diameter of 10mm, fix the seed crystal at the bottom of the crucible, and move it into the crucible 7 with a thickness of 5mm, an outer diameter of 260mm, and a depth of 280mm. Fill the ball with gallium oxide particles.

Ignition: Start the laser emitter located above the crucible. The wavelength of the laser emitter is 915nm, and the power of a single unit is 200W. There are 4 units in total. Adjust the laser output power to 120W, let the laser focus on the surface of the particle ball to melt the particle ball; when you see a dazzling light spot from the observation window, reduce the power to 100W, and focus the laser on the surface of the particle ball with the long axis of 2cm. The elliptical trajectory performs periodic motion while adding particle balls into the crucible at a rate of 50 g/min until the surface area of the molten pool expands to a diameter of 5 cm.

Expanding the melt pool: Start the induction coil set outside the crucible and adjust the frequency to 30kHz. Gradually increase the power of the induction coil to 45kW. Synchronously add pellets into the crucible at a rate of 100g/min. Stop adding pellets until the total number of pellets is 3kg. , take out the quartz glass tube and seal the feeding port with sapphire;

After the melt in the molten pool is stable for 30 minutes, the temperature detected by the upper thermocouple reaches 1630°C, and the temperature detected by the lower thermocouple reaches 1580°C. The molten pool contacts the seed crystal at the bottom of the crucible; the radial temperature of the crucible reaches equilibrium, and the molten pool and crucible A polycrystalline shell is formed between the inner walls, and the diameter of the molten pool is maintained at 10cm.

During this period, the cooling system located at the bottom of the seed crystal operates simultaneously to implement cooling.

Crystal growth: Gradually reduce the power of the induction coil to 37kW at a rate of 0.05kW/h, and the cooling system located at the bottom of the seed crystal continues to operate for cooling; during this process, the upper thermocouple detects that the cooling rate of the outer wall of the crucible is approximately 0.6℃ /h, the lower thermocouple detects that the cooling rate of the outer wall of the crucible is about 0.8°C/h, and the crystal grows upward from the seed crystal below until it reaches the top of the molten pool; at the end of this stage, the temperature detected by the upper thermocouple reaches 1530°C , the temperature detected by the lower thermocouple reaches 1450℃.

Cooling: Gradually reduce the power of the induction coil to 2kW at a rate of 2kW/h, then turn off the power of the induction coil, continue to cool, and then take out the crystal.

In this embodiment, a 3.5-inch class gallium oxide crystal with an outer size of φ90mm×200mm and a crystal mass of 1.9kg can be obtained. A sample of 50×180mm×2mm can be obtained through processing. The X-ray diffraction test shows that the FWHM=110arcsec.

Example 3

This embodiment provides a crystal growth method. The only difference between the crystal growth device used in the crystal growth method and Embodiment 1 is that both the upper thermocouple and the lower thermocouple are arranged inside the crucible, and the upper thermocouple is arranged close to the crucible. On one side of the top of the inner wall of the crucible, the lower thermocouple is placed on the side close to the bottom of the inner wall of the crucible. After the thermocouple is inserted into the crucible, the inserted pore is sealed with alumina glue. The outer diameter of the insulation layer is 700mm. The inner diameter of the insulation layer is 280mm.

The crystal growth method includes the following steps:

Loading: Use a granulator to granulate gallium oxide powder with a purity of 4N into particle balls with a diameter of 3mm, fix the seed crystal at the bottom of the crucible, and fill it into a crucible with a thickness of 5mm, an outer diameter of 260mm, and a depth of 280mm. Balls filled with gallium oxide particles;

Ignition: Start the laser emitter located above the crucible. The wavelength of the laser emitter is 915nm, and the power of a single unit is 200W. There are 4 units in total. Adjust the laser output power to 120W, let the laser focus on the surface of the particle ball to melt the particle ball; when you see a dazzling light spot from the observation window, reduce the power to 100W, and focus the laser on the surface of the particle ball with the long axis 2cm The elliptical trajectory performs periodic motion while adding particle balls into the crucible at a rate of 200g/min until the surface area of the molten pool expands to a diameter of 5cm.

Expanding the melt pool: Start the induction coil set outside the crucible and adjust the frequency to 30kHz. Gradually increase the power of the induction coil to 42kW. Synchronously add pellets into the crucible at a rate of 300g/min. Stop adding pellets until the total number of pellets is 3kg. , take out the feeding tube, which is the quartz glass tube, and seal the feeding port with sapphire;

After the melt in the molten pool is stable for 30 minutes, the temperature detected by the upper thermocouple reaches 1680°C, and the temperature detected by the lower thermocouple reaches 1630°C. At this time, the molten pool contacts the seed crystal at the bottom of the crucible; the radial temperature of the crucible reaches equilibrium, and the molten pool A polycrystalline shell is formed between it and the inner wall of the crucible, and the diameter of the molten pool is maintained at 10cm.

During this period, the cooling system located at the bottom of the seed crystal operates simultaneously to implement cooling.

Crystal growth: Gradually reduce the power of the induction coil to 32kW at a rate of 0.05kW/h, and the cooling system located at the bottom of the seed crystal continues to operate synchronously for cooling; during this process, the upper thermocouple detects that the cooling rate of the outer wall of the crucible is approximately 0.4℃ /h, the lower thermocouple detects that the cooling rate of the outer wall of the crucible is about 0.6°C/h, and the crystal grows upward from the seed crystal part below until it reaches the top of the molten pool. At the end of this stage, the temperature detected by the upper thermocouple reaches 1600 ℃, the temperature detected by the lower thermocouple reaches 1510℃.

Cooling: Gradually reduce the power of the induction coil to 2kW at a rate of 2kW/h, then turn off the power of the induction coil, continue to cool, and then take out the crystal.

In the crystal growth method provided by this embodiment, since the thermocouple is inserted inside the crucible closer to the melt and the melt raw material spherical shell layer, the detection temperature is higher. Since the insulation layer is thicker, the insulation effect is better, and the radial temperature gradient is smaller. Small, the crystal growth time is extended, and the power of the induction coil is reduced. In this embodiment, a 3.5-inch gallium oxide crystal with an outer size of φ90mm×200mm and a crystal mass of 1.9kg can be processed to obtain a 60×180mm×2mm sample. X-ray Diffraction test results show FWHM=88arcsec.

Example 4

This embodiment provides a crystal growth method. The difference between the crystal growth device used in the crystal growth method and Embodiment 1 is only that eight light source emitters are provided.

The only difference between the crystal growth method and Embodiment 1 is that during the ignition process, the number of laser emitters used is 8, the wavelength is 915nm, and the power of a single unit is 200W.

Compared with the crystal growth method provided in this embodiment, the number of laser emitters is increased to 8, which makes the initial melting of the particle balls faster, so the feeding rate can be accelerated, but it does not affect the crystal growth results and is disadvantageous. The impact is the observation of a small amount of white volatiles, that is, volatilized gallium oxide vapor, which affects the observation of experimental phenomena.

Example 5

This embodiment provides a crystal growth method. The crystal growth device used in the crystal growth method is the same as that in Embodiment 1.

The crystal growth method includes the following steps:

Loading: Use a granulator to granulate gallium oxide powder with a purity of 4N into particle balls with a diameter of 3mm, fix the seed crystal at the bottom of the crucible, and fill it into a crucible with a thickness of 5mm, an outer diameter of 260mm, and a depth of 280mm. Balls filled with gallium oxide particles.

Ignition: Start the laser emitter located above the crucible. The wavelength of the laser emitter is 915nm, and the power of a single unit is 200W. There are 4 units in total. Adjust the laser output power to 120W, let the laser focus on the surface of the particle ball to melt the particle ball; when you see a dazzling light spot from the observation window, reduce the power to 100W, and focus the laser on the surface of the particle ball with the long axis as The 2cm elliptical trajectory performs periodic motion while adding particle balls into the crucible at a rate of 200g/min until the surface area of the molten pool expands to a diameter of 5cm;

Expanding the melt pool: Start the induction coil set outside the crucible and adjust the frequency to 30kHz. Gradually increase the power of the induction coil to 45kW. Synchronously add pellets into the crucible at a rate of 300g/min. Stop adding pellets until the total number of pellets is 3kg. , and take out the feeding tube, which is the quartz glass tube, and seal the feeding port with sapphire;

After the melt in the molten pool is stable for 30 minutes, the temperature detected by the upper thermocouple reaches 1630°C, and the temperature detected by the lower thermocouple reaches 1580°C. The molten pool contacts the seed crystal at the bottom of the crucible; the radial temperature of the crucible reaches equilibrium, and the molten pool and crucible A polycrystalline shell is formed between the inner walls, and the diameter of the molten pool is maintained at 10cm;

During this period, the cooling system located at the bottom of the seed crystal operates simultaneously to implement cooling.

Crystal growth: Gradually reduce the power of the induction coil to 37kW at a rate of 0.2kW/h, and the cooling system located at the bottom of the seed crystal continues to operate for cooling; during this process, the upper thermocouple detects that the cooling rate of the outer wall of the crucible is approximately 2.4°C /h, the lower thermocouple detects that the cooling rate of the outer wall of the crucible is about 3.2°C/h, and the crystal grows upward from the seed crystal below until it reaches the top of the molten pool; at the end of this stage, the temperature detected by the upper thermocouple reaches 1530°C , the temperature detected by the lower thermocouple reaches 1450℃.

Cooling: Gradually reduce the power of the induction coil to 2kW at a rate of 2kW/h, then turn off the power of the induction coil 12, continue to cool, and then take out the crystal.

Compared with the crystal growth method provided in this embodiment, the cooling rate is increased to 0.2kw/h, and the crystal growth time is shortened. This embodiment can obtain a 3.5-inch-level gallium oxide crystal with an outer size of φ90mm×200mm. The crystal The mass is 1.9kg, and the sample is processed to 60×180mm×2mm. The X-ray diffraction test shows that the FWHM=425arcsec.

Example 6

This embodiment provides a crystal growth method. The crystal growth device used in the crystal growth method is the same as that in Embodiment 1.

The crystal growth method includes the following steps:

Loading: Use a granulator to granulate gallium oxide powder with a purity of 4N into particle balls with a diameter of 3mm, fix the seed crystal at the bottom of the crucible, and fill it into a crucible with a thickness of 5mm, an outer diameter of 260mm, and a depth of 280mm. Balls filled with gallium oxide particles.

Ignition: Start the laser emitter located above the crucible. The wavelength of the laser emitter is 915nm, and the power of a single unit is 200W. There are 4 units in total. Adjust its output power to 120W, let the laser focus on the surface of the particle ball to melt the particle ball; when you see a dazzling light spot from the observation window, reduce the power to 100W, and focus the laser on the surface of the particle ball with the long axis as The 2cm elliptical trajectory performs periodic motion while adding particle balls into the crucible at a rate of 200g/min until the surface area of the molten pool expands to a diameter of 5cm;

Expanding the melt pool: Start the induction coil set outside the crucible and adjust the frequency to 30kHz. Gradually increase the power of the induction coil to 45kW. Synchronously add pellets into the crucible at a rate of 100g/min. Stop adding pellets until the total number of pellets is 3kg. , and take out the quartz glass tube and seal the feeding port with sapphire;

After the melt in the molten pool is stable for 30 minutes, the temperature detected by the upper thermocouple 9 reaches 1630°C, and the temperature detected by the lower thermocouple reaches 1580°C. The molten pool contacts the seed crystal at the bottom of the crucible; the radial temperature of the crucible reaches equilibrium, and the molten pool and A polycrystalline shell is formed between the inner walls of the crucible, and the diameter of the molten pool is maintained at 10cm.

Crystal growth: Gradually reduce the power of the induction coil to 37kW at a rate of 0.5kW/h, and the cooling system located at the bottom of the seed crystal 8 continues to operate for cooling; during this process, the upper thermocouple detects that the cooling rate of the outer wall of the crucible is 3°C /h-10℃/h. The lower thermocouple detects that the cooling rate of the outer wall of the crucible changes between 5℃/h-16℃/h. The crystal can also grow upward from the seed crystal below until it reaches the melting point. The top of the pool; at the end, the upper thermocouple detection temperature reaches 1530°C, and the lower thermocouple detection temperature reaches 1450°C.

Cooling: Gradually reduce the power of the induction coil to 2kW at a rate of 2kW/h, then turn off the power of the induction coil, continue to cool, and then take out the crystal.

Compared with the crystal growth method provided in this embodiment, the decreasing rate of the electromagnetic induction coil is increased to 0.5kw/h. This embodiment can also obtain a 3.5-inch gallium oxide crystal with an overall size of φ90mm×200mm. However, The crystal has problems such as cracking, uneven color, bubbles, layered or striped polycrystalline defects, etc.; X-ray diffraction test shows many impurity peaks, indicating that it is not single crystal.

Comparative example 1

The device used in this comparative example is the same as that of Example 1.

Follow these steps:

(1) Use a granulator to granulate gallium oxide powder with a purity of 4N into particle balls with a diameter of 3mm, fix the seed crystal at the bottom of the crucible, and fill the crucible with a thickness of 5mm, an outer diameter of 260mm, and a depth of 280mm. Gallium oxide particles.

(2) Start the laser emitter located above the crucible. The wavelength of the laser emitter is 915nm, and the power of a single laser emitter is 200W. There are 4 laser emitters in total. Adjust its output power to 120W, let the laser focus on the surface of the particle ball to melt the particle ball; when you see a dazzling light spot from the observation window, reduce the power to 100W, and add the particle ball into the crucible at a rate of 200g/min. Until the surface area of the molten pool expands to a diameter of 3cm.

(3) Start the induction coil set outside the crucible and adjust the frequency to 30kHz. Gradually increase the power of the induction coil to 45kW. As the power increases, no changes in the molten pool are observed.

Comparative example 2

The difference between the device used in this comparative example and that of Example 1 is that there is no quartz glass tube and the feeding port of the thermal insulation cover is sealed with sapphire; the method of this comparative example does not continuously feed materials during the molten pool expansion stage.

Follow these steps:

(1) Use a granulator to granulate gallium oxide powder with a purity of 4N into particle balls with a diameter of 3mm, fix the seed crystal at the bottom of the crucible, and fill it into a crucible with a thickness of 5mm, an outer diameter of 260mm, and a depth of 280mm. Balls filled with gallium oxide particles.

(2) Start the laser emitter located above the crucible. The wavelength of the laser emitter is 915nm, and the power of a single laser emitter is 200W. There are 4 laser emitters in total. Adjust the laser output power to 120W, let the laser focus on the surface of the particle balls to melt the particles; when you see a dazzling light spot from the observation window, reduce the power to 100W, and at the same time add the particles into the crucible at a rate of 200g/min. Until the surface area of the molten pool expands to a diameter of 5cm.

(3) Start the induction coil set outside the crucible and adjust the frequency to 30kHz. Gradually increase the power of the induction coil to 45kW and continue for 30 minutes. During this period, no crystal raw materials are added, but the cooling system located at the bottom of the seed crystal operates synchronously. Cooling; it can be observed that the expansion speed of the molten pool in the radial direction is significantly faster than that of Example 1, no polycrystalline shell is formed between the molten pool and the crucible, and the molten pool cannot expand downward to contact Seed crystals at the bottom of the crucible, so the next step of the experiment was not carried out.

Comparative example 3

The only difference between the device used in this comparative example and the device in Example 1 is that the crucible and insulation layer are replaced with water-cooled flaps, the induction coil is arranged on the outer peripheral surface of the water-cooled flap, and a thermocouple is arranged inside the water-cooled flap and connected with the water-cooled flap. The inner wall of the water-cooling flap fits snugly.

Follow these steps:

(1) Use a granulator to granulate gallium oxide powder with a purity of 4N into particle balls with a diameter of 3mm, fix the seed crystal at the bottom of the crucible, and fill it into a crucible with a thickness of 5mm, an outer diameter of 260mm, and a depth of 280mm. Balls filled with gallium oxide particles;

(2) Start the laser emitter located above the crucible. The wavelength of the laser emitter is 915nm, and the power of a single laser emitter is 200W. There are 4 laser emitters in total. Adjust its output power to 120W, let the laser focus on the surface of the particle ball to melt the particle ball; when you see a dazzling light spot from the observation window, reduce the power to 100W, and add the particle ball into the crucible at a rate of 200g/min. Until the surface area of the molten pool expands to a molten pool diameter of 5 cm.

(3) Start the induction coil set on the outside of the crucible and adjust the frequency to 30kHz, gradually increase the power of the induction coil to 45kW, and simultaneously add pellets into the crucible at a rate of 300g/min. Stop adding pellets until the total number of pellets is 3kg. Take out the quartz glass tube and seal the feeding port with sapphire; during this period, the water-cooling flap has been cooling;

After the melt in the molten pool stabilized for 30 minutes, the thermocouple detected the temperature of 50°C. A polycrystalline shell 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.

(4) Gradually reduce the power of the induction coil to 37kW at a rate of 0.05kW/h, and the water-cooled flap is constantly cooling.

(5) Gradually reduce the power of the induction coil to 2kW at a rate of 2kW/h, then turn off the power of the induction coil, continue to cool, and then take out the crystal.

In the method provided in this comparative example, the water-cooled flap causes extremely serious heat dissipation, the radial temperature gradient is large, and the heat is absorbed by the shell layer at an accelerated rate. It is difficult for the melt to achieve downward breakdown, cannot contact the bottom seed crystal, and spontaneously nucleates during the cooling stage. shape.

Comparative example 4

The device used in this comparative example is the same as that in comparative example 3.

The only difference between the crystal growth method and Comparative Example 3 is that in the process of expanding the molten pool, the induction coil arranged outside the water-cooling flap is started and its power is increased to 80kW; in the process of crystal growth, , gradually reducing the power of the induction coil to 72kW at a rate of 0.05kW/h.

Compared with the crystal growth method provided in Example 1, the crystal growth method provided in this comparative example adopts a water-cooled valve and increases the power of the induction coil, resulting in extremely serious heat dissipation and a large radial temperature gradient. The obtained crystal is a polycrystalline with a glassy luster on the surface, and Exterior cracks present.

Comparative example 5

The device used in this comparative example is the same as that of Example 1.

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 less than 3 mm.

Follow these steps:

(1) Fix the seed crystal at the bottom of the crucible, and fill the crucible with a thickness of 5mm, an outer diameter of 260mm, and a depth of 280mm with gallium oxide powder;

(2) Start the laser emitter located above the crucible. The wavelength of the laser emitter is 915nm, and the power of a single unit is 200W. There are 4 units in total. Adjust its output power to 120W, let the laser focus on the surface of the particle ball to melt the powder; when you see a dazzling light spot from the observation window, reduce the power to 100W, and focus the laser on the surface of the powder with a long axis of 2cm. The elliptical trajectory performed periodic motion while powder was added into the crucible at a rate of 200 g/min. The duration of this stage was consistent with the ignition stage in Example 1, but no obvious signs of expansion of the molten pool were observed.

The applicant declares that the above are only specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the technical field should understand that any person skilled in the technical field will not use the invention disclosed in the present invention. Within the technical scope, changes or substitutions that can be easily imagined fall within the protection scope and disclosure scope of the present invention.

Claims (10)

1. A crystal growth method, characterized in that the crystal growth method comprises the steps of:

and (2) charging: fixing seed crystal at the bottom of the crucible, and filling crystal raw material into the crucible;

igniting: starting a light source emitter above the crucible, and enabling a focus of the light source to move on the surface of the crystal raw material so as to enable the surface of the crystal raw material to be melted to form a molten pool until the surface area of the molten pool is enlarged to a target size;

expanding a molten pool: starting an induction coil arranged on the outer side of the crucible, synchronously adding crystal raw materials into the crucible, and continuously expanding a molten pool downwards until the molten pool contacts with seed crystals at the bottom of the crucible;

crystal growth: gradually reducing the power of the induction coil to enable the crystal to be continuously crystallized from the top of the seed crystal from bottom to top until the crystal reaches the top of the molten pool;

and (3) cooling: gradually reducing the power of the induction coil until the power supply of the induction coil is turned off, and taking out the crystal after cooling;

wherein,,

an insulating layer is arranged between the induction coil and the crucible;

in the process of crystal growth, a cooling system positioned at the bottom of the seed crystal synchronously carries out cooling;

in the process of expanding the molten pool, a polycrystalline shell layer is formed between the molten pool and the inner side wall of the crucible.

2. The crystal growth method according to claim 1, wherein the crystal is a gallium oxide crystal;

preferably, the particle size of the crystal raw material is 3-10mm.

3. The crystal growth method according to claim 1 or 2, wherein a heat-retaining cover is provided on the top of the crucible, and at least one light-transmitting opening is provided on the heat-retaining cover;

preferably, the light transmission opening is sealed by sapphire.

4. A crystal growth method according to any one of claims 1 to 3, wherein during the ignition, the focal point of the light source is periodically moved in an elliptical trajectory on the surface of the crystal raw material;

preferably, the long axis of the elliptical track is more than or equal to 2cm;

preferably, the diameter of the melt pool of the target size is not less than 5cm, preferably 5-8cm.

5. A crystal growth method according to any one of claims 1 to 4, wherein the light source emitter used during the ignition comprises a laser emitter;

the emission power of the laser emitter is 100-300W;

the number of the laser transmitters is 4-8.

6. The crystal growth method according to any one of claims 1 to 5, wherein the operating frequency of the induction coil during the melt expansion bath and crystal growth is 30 to 100kHz;

preferably, the working power of the induction coil is 40-100kW in the process of the molten expanding pool and crystal growth.

7. The crystal growth method according to any one of claims 1 to 6, wherein the operating power of the induction coil decreases at a rate of 0.05 to 0.2kW/h during the crystal growth.

8. The crystal growth method according to any one of claims 1 to 7, wherein the rate of addition of the crystal raw material during the melt expansion bath is 300 to 500g/min.

9. A crystal growth method according to any one of claims 1 to 8, wherein crystal feedstock is also added to the crucible during the firing.

10. A crystal growth apparatus for use in the crystal growth method according to any one of claims 1 to 9, characterized in that the crystal growth apparatus comprises:

a crucible;

an insulating layer wrapped on the outer peripheral surface of the crucible;

the induction coil is arranged on the outer circumference of the heat preservation layer;

the crystal seat is positioned below the crucible and used for fixing seed crystals, the seed crystals penetrate into the crucible, and a cooling system is arranged in the crystal seat;

a light source emitter disposed above the crucible;

and a feed inlet arranged at the top of the crucible.