Method for growing large-size gallium oxide crystal by edge-defined film-fed growth method

Abstract

The invention relates to a method for growing a large-size gallium oxide crystal by an edge-defined film-fed growth method, and relates to the technical field of semiconductor materials, the growth method comprises the following steps: (1) filling high-purity beta-Ga2O3 powder into a mold, installing a seed crystal, sealing a growth furnace, pumping high vacuum, filling high-purity argon to positive pressure, and heating; (2) carrying out multi-stage variable-speed shouldering until the equal-diameter size is completely achieved; (3) rotating the crystal at a constant rotating speed of N1, increasing the rotating speed to N2 at 90-180 degrees of the fastest heat dissipation corner angle of the mold every 1-3 turns, keeping the rotating speed for 20-40s, and then returning to the original rotating speed, and circulating in a reciprocating manner; (4) switching atmosphere and multi-stage annealing, turning off a heating power supply, and cooling the crystal to room temperature along with the furnace; and (5) after the furnace temperature is completely reduced to room temperature, filling air into the furnace to atmospheric pressure, opening the hearth, and taking out the gallium oxide crystal. The crystal grown by adopting the growth method disclosed by the invention is relatively high in quality, relatively large in size and relatively low in defect.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of semiconductor materials, and particularly to a method for growing large-size gallium oxide crystals by a guiding mode method. BACKGROUND

[0002] Gallium oxide single crystal is an important semiconductor material, which has excellent properties such as high voltage resistance, high temperature resistance, high power, and radiation resistance. Gallium oxide single crystal is a wide band gap semiconductor with a band gap of 4.9 eV, which is higher than 3.2 eV of silicon carbide and 3.39 eV of gallium nitride, and can realize high temperature operation, so that the gallium oxide single crystal shows good stability in high temperature environment. Gallium oxide single crystal has a low carrier concentration and a high breakdown field strength, and is suitable for the preparation of high power devices. Gallium oxide single crystal also has excellent optical performance, which has good transmittance in the ultraviolet to infrared waveband, and has a high refractive index and a small free carrier absorption coefficient, so that gallium oxide single crystal has a wide application prospect in the fields of optoelectronic devices and optical sensors.

[0003] Among the methods for growing gallium oxide crystals, the dominant methods are guiding mode method, Czochralski method and casting method. However, these methods have certain limitations. In the growth of large-size crystals by the Czochralski method, (100) crystal plane is prone to produce twinning, resulting in small product specifications, and the control during the growth process is difficult. Although the casting method is grown in a crucible, it is limited by the specification of the crucible. On the one hand, it is difficult to take out the crystal from the crucible, and on the other hand, if the yield is to be improved, a larger and deeper crucible is needed, and too much iridium raw material is used to prepare the crucible. Although the guiding mode method is an important method for preparing large-size and high-quality crystals at present, there are still some technical problems: (1) the heating and heat preservation structure is circumferentially symmetrical, but the mold and the crystal are circumferentially asymmetrical, the gas vortex in the heat preservation cavity interferes, the heat transfer in the width and thickness directions of the crystal is uneven, which destroys the symmetry of the temperature field distribution, affects the stability of the shoulder process; (2) the temperature gradient near the solid-liquid interface is not suitable or asymmetrical, the heat transfer in the width and thickness directions of the large-size crystal is more uneven, which causes serious deformation of the crystallization interface (i.e. large interface deformation degree), affects the stable growth of the crystal, and causes defects to be generated; (3) there is a lack of real-time feedback of the solid-liquid interface morphology, the growth process is unstable, and the yield is strongly dependent on human experience; (4) the existence of defects such as twinning, dislocation and color center makes the electrical properties of the crystal uneven, and the carrier mobility and lifetime decrease.

[0004] In summary, the existing methods for growing gallium oxide crystals have many problems, and a new technical solution is needed to overcome these defects to meet the growing market demand for gallium oxide crystals. SUMMARY

[0005] In order to solve the above technical problems, the application provides a method for growing large-size gallium oxide crystals by a mode guiding method.

[0006] In a first aspect, the application provides a method for growing large-size gallium oxide crystals by a mode guiding method, the growing method comprising the following steps: (1) high-purity β-Ga2O3 powder is loaded into a mold, a seed crystal is installed, the seed crystal is oriented to a (100) surface, a growing furnace is sealed, high vacuum is extracted to ≤1×10 -3 Pa, high-purity argon is filled to 1.01-1.02 atm, the temperature is raised to 1750-1800℃ at a rate of 100-150℃ / h, and the temperature is kept at 1750-1800℃ for 2-3 h; (2) the seed crystal is slowly contacted with the melt, the pulling speed starts at V1, the heating power is set to P1, when the shoulder is stable, the pulling speed is linearly increased to V2, and the heating power is simultaneously slowly increased to P2, when the shoulder size is close to 90%-95% of the target diameter, the pulling speed is reduced to V3, and the power P2 is kept stable for a period of time until the equal diameter size is completely reached; (3) the crystal is uniformly rotated at a speed of N1, every 1-3 turns in the 90-180° of the fastest cooling corner of the mold, the speed is accelerated to N2 and kept for 20-40 s and then returned to the original speed, and the reciprocating cycle is repeated; (4) after the crystal growth is completed and separated from the melt, the high-purity argon is immediately turned off, the mixed gas containing 3-5% oxygen in inert gas is introduced into the furnace, the flow rate is 2-3 L / min, the temperature is kept at 1250-1350℃ for 4-6 h, the temperature is slowly reduced to 800-900℃ at a rate of 30-50℃ / h, the temperature is kept constant for 2-3 h, the heating power is turned off, and the crystal is cooled to room temperature with the furnace; (5) when the furnace temperature is completely reduced to room temperature, air is filled into the furnace to atmospheric pressure, the furnace is opened, and the gallium oxide crystal is taken out.

[0007] In the above technical solution, in step (1), high-vacuum degassing utilizes the principle that the mean free path of gas molecules is long in a low-pressure environment, so that the gas molecules adsorbed in the raw materials and the furnace body can easily escape and be extracted. The melt is homogenized by keeping the temperature at 1750-1800℃ for a period of time, so that the melt composition and temperature tend to be consistent. A thermodynamically stable melt source is provided for crystal growth. Bubbles and impurities are avoided from being wrapped into the crystal in subsequent growth.

[0008] In step (2), during the seeding stage, the low growth rate and heat input make the crystal growth dominated by the lattice structure of the seed crystal, ensuring the perfect continuation of the lattice. In the shoulder expansion stage, as the crystal surface area increases, the radiation heat dissipation increases. The power is simultaneously increased to compensate for this heat loss, prevent the melt from supercooling, and maintain a stable solid-liquid interface. In the shoulder transition buffer stage, the short period of speed reduction before the constant diameter stage gives the crystal internal thermal stress a relaxation time. It can effectively reorganize and annihilate a large number of dislocations generated in the rapid shoulder expansion process, preventing them from extending into the constant diameter part. It can significantly reduce the probability of twinning, dislocation, etc. in the shoulder. It improves the transition success rate from the shoulder to the constant diameter and improves the yield. P1 and P2 are highly customized parameters that need to be determined by experiments for each device and each specific thermal field configuration.

[0009] In step (3), increasing the rotation speed in the area with fast heat dissipation is equivalent to increasing the effective heat dissipation time of that area, compensating for the additional heat loss caused by the geometry of that area, and achieving dynamic balance of the circumferential heat field. It can effectively inhibit the generation and extension of defects (small-angle grain boundaries, dislocation clusters).

[0010] In step (4), in a high-temperature and oxygen-rich environment, oxygen molecules have enough kinetic energy and chemical potential to diffuse into the crystal, filling the oxygen vacancies caused by the lack of oxygen in the growth environment, and eliminating oxygen vacancy-related color centers, making the crystal change from brown-yellow to colorless and transparent. Above 900°C, the crystal still has good plasticity, and slow cooling allows it to release thermal stress through slight dislocation slip and recombination, avoiding the generation of new dislocations or causing the crystal to crack. It can effectively eliminate color centers and optimize optical and electrical properties. It releases the thermal stress inside the crystal and reduces the dislocation density. Integrating annealing after growth eliminates the secondary annealing process, improving efficiency and avoiding surface contamination. The inert gas can be any one of argon, helium, neon, xenon, and the preferred is argon.

[0011] Optionally, in step (2), V1 is 0.5-0.8 mm / h, V2 is 1.5-2.0 mm / h, and V3 is 1.0-1.5 mm / h.

[0012] In the above technical solution, the initial pulling speed V1 is 0.5-0.8 mm / h, which indicates that the latent heat released per unit time is less, and the temperature field at the solid-liquid interface is more easily maintained stable, which is conducive to the formation of a flat and stable initial growth interface. It gives atoms enough time to arrange in order along the lattice structure of the seed crystal, ensuring that the newly grown crystal can perfectly inherit the crystal orientation of the seed crystal, and avoiding the generation of polycrystals, twinning and other defects from the source.

[0013] The intermediate pulling speed V2 is 1.5-2.0 mm / h. Once the stable crystal nucleus is formed, the speed can be appropriately increased to rapidly expand the crystal shoulder to the target size. At a lower speed, specific crystal faces, such as the (100) face, can excessively develop, leading to irregular crystal shape or facet effect, which is prone to introduce inclusions and dislocations. A moderate speed increase can inhibit the dominant growth of these harmful crystal faces and promote the crystal to expand in a more uniform radial manner. Under the premise of ensuring crystal quality, the shoulder shaping is completed quickly and symmetrically, and the facet defects are inhibited.

[0014] The late-stage pulling speed V3 is 1.0-1.5 mm / h. During the rapid shoulder expansion stage, a large amount of thermal stress is accumulated in the crystal due to the dramatic change in shape. Before entering the diameter-constant growth stage which is extremely sensitive to defects, the speed is appropriately reduced to allow the internal stress to relax through slight sliding and recombination of dislocations. The heat dissipation conditions of the crystal change abruptly from the shoulder shaping to the diameter-constant growth. Reducing the speed in advance and stabilizing for a period of time can allow the solid-liquid interface and the thermal field to smoothly transition to the stable state required for diameter-constant growth, avoiding the proliferation of dislocations or even cracks at the shoulder joint due to abrupt changes. The quality and yield of the diameter-constant part are improved.

[0015] Optionally, in the step (3), N1 is 3-7 rpm and N2 is 12-18 rpm.

[0016] In the above technical solution, uniform rotation at N1 speed can drive the melt at the solid-liquid interface to produce a gentle convection, which helps to reduce temperature fluctuations and impurity enrichment near the interface, making the growth interface more stable. When the crystal rotates to the fastest heat dissipation corner region 90-180°, the speed is suddenly increased to N2. The high-speed rotation can destroy the stagnant boundary layer of the melt at the interface, greatly enhancing the heat transfer efficiency from the melt inside to the crystal surface in this region. At the same time, the heat dissipation of the crystal in this region to the environment is also enhanced. The uniformization of the circumferential thermal field is an important condition for obtaining a symmetric and flat solid-liquid interface, thereby effectively preventing defects such as twinning and cracking caused by interface distortion. Actively and periodically supplying heat to the fastest heat dissipation region compensates for the additional heat loss in this region due to the geometric shape. After such periodic and local heat strengthening, the effective heat dissipation of each point on the crystal tends to be consistent.

[0017] Optionally, the growth furnace comprises an induction coil, an insulation layer, a crucible, a mold, a heat shield, a seed crystal lifting and rotating mechanism, a thermoelectric corner, a control mechanism.

[0018] In the above technical solution, when high frequency or medium frequency alternating current passes through the coil, a rapidly changing magnetic field is generated. This alternating magnetic field penetrates the heat preservation layer and induces a strong eddy current in the electrically conductive iridium crucible and mold. The eddy current generates a large amount of heat due to the resistance effect when flowing in the iridium body, thereby heating itself and ultimately melting the raw material. By controlling the input power of the coil, the temperature of the mechanism can be accurately controlled.

[0019] The heat preservation layer is made of porous ceramic fiber materials such as zirconia and alumina, and is wrapped around the outer periphery of the hot zone. It greatly reduces the radiation and convection loss of heat to the furnace wall, improves the thermal efficiency, and protects the furnace body.

[0020] The crucible is made of high-purity iridium metal, which mainly functions to hold a large amount of gallium oxide polycrystalline raw material and withstand extremely high melting temperatures.

[0021] The mold is rectangular, which uses the capillary phenomenon to draw the molten gallium oxide from the crucible body to the top of the mold. It provides a local and stable growth interface, and the seed crystal contacts the melt here and starts to grow.

[0022] The heat shield is made of high-temperature resistant metal plates such as molybdenum and tungsten, which is arranged at the lower part of the crucible in this application, can change the heat dissipation conditions of the local area, and the heat shield is arranged on the crystal pulling path, which can control the axial temperature gradient, which is crucial for preventing the crystal from cracking. At the same time, it can also prevent high-temperature heat radiation from directly irradiating on the coil, causing the coil to overheat or insulation failure.

[0023] The seed crystal lifting and rotating mechanism plays the role of crystal seeding, pulling and rotating. During the crystal growth process, the seed crystal is slowly lowered to contact the melt at the top of the mold. It is pulled upwards at a set speed, guiding the continuous growth of the crystal from the solid-liquid interface. After the growth is completed, the crystal is quickly lifted away from the high-temperature zone. Rotation can drive the melt at the solid-liquid interface to flow, which helps to reduce the composition undercooling, making the temperature and solute distribution at the interface more uniform. For a rectangular mold, rotation helps to compensate for the circumferential thermal asymmetry, obtaining a more uniform crystal quality.

[0024] The thermocouple is a tungsten-rhenium thermocouple arranged near the mold for measuring and controlling the growth temperature. It is used to monitor the axial temperature gradient on the crystal pulling path. The temperature signal measured by the thermocouple is transmitted to the temperature controller, which compares it with the set value and automatically adjusts the input power of the coil to achieve accurate temperature control.

[0025] The control mechanism receives temperature data from the thermocouple and accurately controls the power of the coil, the moving speed of the pulling mechanism and the rotating speed of the rotating mechanism according to the required temperature during the growth process, ensuring that the entire growth process is automatically and stably carried out.

[0026] Optionally, the growth furnace further comprises a high-precision balance, a plurality of infrared thermometers and an encoder; the high-precision balance is arranged at the upper part of the seed lifting and rotating mechanism, the infrared thermometers are aimed at different positions of the top edge of the mold and the surface of the crystal respectively, and the encoder is arranged in the seed lifting and rotating mechanism.

[0027] In the technical solution, the high-precision balance continuously outputs the weight data of the crystal. The control mechanism calculates the change rate of the weight with respect to time in real time, and converts the change rate into a linear growth rate in real time in combination with the density and cross-sectional area of the crystal. The growth rate directly reflects the mass transport condition at the solid-liquid interface. Maintaining the constant growth rate makes the growth interface at a stable solid-liquid interface, ensures the stability of the crystal diameter, and realizes the diameter control.

[0028] The plurality of infrared thermometers are aimed at different positions of the top edge of the mold. For example, one aiming point is arranged at the center of the long side, the center of the short side and the corner of the rectangular mold respectively. One or more aiming points are arranged on the crystal pulling path for aiming at the surface of the crystal and monitoring the temperature gradient of the crystal itself.

[0029] The encoder can accurately feed back the real-time rotating speed and rotating angle position of the seed and the crystal. The real-time position and pulling speed of the pulling rod can also be accurately fed back.

[0030] In a second aspect, the application provides a large-size gallium oxide crystal grown by the mode guiding method, which is prepared by the method for growing a large-size gallium oxide crystal by the mode guiding method.

[0031] Optionally, the size of the gallium oxide crystal is 4 inches.

[0032] In a third aspect, the application provides an application of a gallium oxide substrate obtained by cutting, grinding, polishing and cleaning the large-size gallium oxide crystal grown by the mode guiding method in a semiconductor device.

[0033] In summary, the application has at least one of the following beneficial technical effects: 1. By the multi-stage variable-speed shoulder forming in step (2), a large number of dislocations generated in the rapid shoulder-expanding process can be effectively recombined and annihilated, so that the dislocations are prevented from extending into the diameter-keeping part, and the probability of generating twins and dislocations in the shoulder part can be significantly reduced. The transition success rate from the shoulder forming to the diameter-keeping part is improved, and the yield is improved.

[0034] 2. In step (3), the rotating speed is increased in the region with fast heat dissipation, which is equivalent to increasing the effective heat dissipation time of the region, compensating for the additional heat loss of the region caused by the geometric shape, achieving dynamic balance of the circumferential heat field, and effectively inhibiting the generation and extension of defects (small-angle grain boundaries and dislocation clusters).

[0035] 3. By switching atmosphere and multi-stage annealing treatment through step (4), color centers can be effectively eliminated, optical and electrical properties can be optimized, thermal stress in the crystal can be released, dislocation density can be reduced, annealing is integrated after growth, the process of secondary furnace annealing is saved, efficiency is improved and surface contamination is avoided. BRIEF DESCRIPTION OF DRAWINGS

[0036] Figure 1 is a schematic diagram of the overall structure of the growth furnace of embodiment 1 of the present application; Figure 2 is a rocking curve half peak width graph of a gallium oxide crystal in embodiment 5 of the present application; Figure 3 is an XRD graph of a gallium oxide substrate in embodiment 5 of the present application; Figure 4 is an AFM graph of a gallium oxide substrate in application example 1 of the present application.

[0037] Reference signs: 1 - induction coil, 2 - heat insulation layer, 3 - crucible, 4 - mold, 5 - heat shield, 6 - seed crystal lifting and rotating mechanism, 7 - melt, 8 - seed crystal, 9 - gallium oxide crystal. DETAILED DESCRIPTION

[0038] The present application will be further described in detail below in conjunction with embodiments.

[0039] The materials used in the following embodiments can be obtained by market purchase.

[0040] Embodiment 1: The present embodiment provides a method for growing a large-size gallium oxide crystal by a mode guiding method.

[0041] As shown in Figure 1 , the growth furnace includes an induction coil 1, a heat insulation layer 2, an iridium crucible 3, a mold 4, a heat shield 5, a seed crystal lifting and rotating mechanism 6, and a control mechanism (not shown).

[0042] The growth method includes the following steps: S1, high-purity β-Ga2O3 powder is loaded into the mold 4, the seed crystal 8 is installed, the seed crystal 8 is oriented to the (100) surface, the growth furnace is sealed, high vacuum ≤1×10 -3 Pa is filled with high-purity argon to 1.01 atm, the temperature is raised to 1750℃ at 100℃ / h, and the temperature is kept at 1750℃ for 3h.

[0043] S2, the seed crystal 8 is slowly contacted with the melt 7, the pulling speed is started at 0.5 mm / h, the heating power is set to 80.5 kW, when the shoulder is formed stably, the pulling speed is linearly increased to 1.5 mm / h, and the heating power is slowly increased to 82.5 kW at the same time, when the shoulder size is close to 90% of the target diameter, the pulling speed is reduced to 1.0 mm / h, and the power is kept at 82.5 kW for a period of time until the full diameter size is reached.

[0044] S3, the crystal is rotated at a uniform speed of 3 rpm, every 1 circle, 90° of the fastest heat dissipation corner of the mold 4, the speed is accelerated to 12 rpm and kept for 40 s and then returned to the original speed, and the reciprocating cycle is repeated.

[0045] S4, after the crystal growth is completed and separated from the melt, the high-purity argon gas is immediately turned off, the inert gas mixed gas containing 3% oxygen is introduced into the furnace, the flow rate is 2 L / min, the temperature is kept at 1250℃ for 6 h, the temperature is slowly reduced to 800℃ at a rate of 30℃ / h, the temperature is kept constant for 3 h, the heating power is turned off, and the crystal is cooled to room temperature with the furnace.

[0046] S5, when the furnace temperature is completely reduced to room temperature, air is filled into the furnace to atmospheric pressure, the furnace is opened, and the gallium oxide crystal 9 is taken out.

[0047] Embodiment 2: The embodiment provides a method for growing a large-size gallium oxide crystal by a mode method.

[0048] The crystal growth furnace used is the same as that in embodiment 1.

[0049] The growth method comprises the following steps: S1, high-purity β-Ga2O3 powder is loaded into the mold, a seed crystal is installed, the seed crystal is oriented to the (100) surface, the growth furnace is sealed, high vacuum ≤1×10 -3 Pa, high-purity argon gas is filled to 1.02 atm, the temperature is increased to 1800℃ at a rate of 150℃ / h, and the temperature is kept constant at 1800℃ for 2 h.

[0050] S2, the seed crystal is slowly contacted with the melt, the pulling speed is started at 0.8 mm / h, the heating power is set to 81.5 kW, when the shoulder is formed stably, the pulling speed is linearly increased to 2.0 mm / h, and the heating power is slowly increased to 85 kW at the same time, when the shoulder size is close to 95% of the target diameter, the pulling speed is reduced to 1.5 mm / h, and the power is kept at 85 kW for a period of time until the full diameter size is reached.

[0051] S3, the crystal is rotated at a uniform speed of 7 rpm, every 3 circles, 180° of the fastest heat dissipation corner of the mold, the speed is accelerated to 18 rpm and kept for 20 s and then returned to the original speed, and the reciprocating cycle is repeated.

[0052] S4, immediately after the crystal growth is completed and separated from the melt, the high-purity argon is turned off, and a mixed gas of inert gas containing 5% oxygen is introduced into the furnace at a flow rate of 3 L / min, and the temperature is kept constant at 1350°C for 4 h, the temperature is decreased to 900°C at a slow rate of 50°C / h, and the temperature is kept constant for 2 h, the heating power is turned off, and the crystal is allowed to cool to room temperature along with the furnace.

[0053] S5, when the temperature of the furnace is completely decreased to room temperature, air is filled into the furnace to atmospheric pressure, the furnace is opened, and the gallium oxide crystal is taken out.

[0054] Example 3: The present example provides a method for growing a large-size gallium oxide crystal by a die method.

[0055] The growth furnace used for the crystal is the same as that in Example 1.

[0056] The growth method comprises the following steps: S1, high-purity β-Ga2O3 powder is loaded into a mold, a seed crystal is installed, the seed crystal is oriented to a (100) surface, a growth furnace is sealed, high vacuum is extracted to ≤1×10 -3 Pa, high-purity argon is filled to 1.01 atm, the temperature is increased to 1800°C at a rate of 130°C / h, and the temperature is kept constant at 1800°C for 2.5 h.

[0057] S2, the seed crystal is slowly contacted with the melt, the pulling starts at a rate of 0.7 mm / h, the heating power is set to 81 kW, when the shoulder is stable, the pulling rate is linearly increased to 1.8 mm / h, and the heating power is simultaneously slowly increased to 83.5 kW, when the shoulder size is close to 92% of the target diameter, the pulling rate is decreased to 1.2 mm / h, and the power is kept at 83.5 kW for a period of time until the constant diameter size is completely reached.

[0058] S3, the crystal is uniformly rotated at a speed of 5 rpm, every 2 turns, the 135° of the fastest heat dissipation corner of the mold is accelerated to 15 rpm and kept for 30 s, and then returned to the original speed, and the reciprocating cycle is repeated.

[0059] S4, immediately after the crystal growth is completed and separated from the melt, the high-purity argon is turned off, and a mixed gas of inert gas containing 3% oxygen is introduced into the furnace at a flow rate of 3 L / min, and the temperature is kept constant at 1300°C for 5 h, the temperature is decreased to 850°C at a slow rate of 40°C / h, and the temperature is kept constant for 2.5 h, the heating power is turned off, and the crystal is allowed to cool to room temperature along with the furnace.

[0060] S5, when the temperature of the furnace is completely decreased to room temperature, air is filled into the furnace to atmospheric pressure, the furnace is opened, and the gallium oxide crystal is taken out.

[0061] Example 4: This example provides a method for growing a large size gallium oxide crystal by a die method.

[0062] The growth furnace used for the crystal is the same as that of Example 1, except that the growth furnace further comprises a high-precision balance (not shown), four infrared thermometers (not shown), and an encoder (not shown). The infrared thermometers are aimed at the center of one long side, the center of one short side, and two corners of the rectangular mold, respectively.

[0063] The steps of the growth method are the same as those of Example 3.

[0064] Example 5: This example provides a method for growing a large size gallium oxide crystal by a die method.

[0065] The growth furnace used for the crystal is the same as that of Example 4, except that the growth furnace comprises six infrared thermometers. The infrared thermometers are aimed at the center of two long sides, the center of one short side, two corners, and one crystal surface of the rectangular mold, respectively.

[0066] The steps of the growth method are the same as those of Example 3.

[0067] Comparative Example 1: This comparative example provides a comparative gallium oxide crystal, which uses the same growth furnace as that of Example 5. The difference is that in step S2, only the seed crystal is slowly contacted with the melt, and the pulling starts at a speed of 2 mm / h, the heating power is set to 81 kW, and there is no multi-stage variable speed shoulder process.

[0068] Comparative Example 2: This comparative example provides a comparative gallium oxide crystal, which uses the same growth furnace as that of Example 5. The difference is that in step S3, only the crystal is uniformly rotated at a speed of 5 rpm, and there is no process of increasing the rotation speed.

[0069] Comparative Example 3: This comparative example provides a comparative gallium oxide crystal, which uses the same growth furnace as that of Example 5. The difference is that in step S4, only the cooling is performed at a rate of 40°C / h until room temperature, and there is no process of switching the atmosphere and multi-stage annealing.

[0070] Test sample processing: The gallium oxide crystals of Examples 1-5 and the comparative gallium oxide crystals of Comparative Examples 1-3 are processed into single crystal wafers with a size of 10 mm x 10 mm x 1 mm, and the following detection methods are used: 1. Lattice constant: The lattice constant of different single crystal wafers is detected by X-ray diffraction method.

[0071] 2. Rocking curve full width at half maximum: The rocking curve full width at half maximum of different single crystal wafers is detected by X-ray diffractometer.

[0072] 3. The screw dislocation density (TSD) and edge dislocation density (TED) of different single crystal wafers were tested, and the test results are shown in Table 1.

[0073] Table 1 The data from Examples 1-3, especially Example 3, show that by properly proportioning the growth process, the gallium oxide crystal of this application can reach 4 inches, with low dislocation density, a rocking curve half-width of 59.6 arcseconds, and high crystal quality.

[0074] Compared to Example 3, Example 4 used a growth furnace with the addition of a high-precision balance, four infrared thermometers, and an encoder. The resulting gallium oxide crystal was of superior quality to that obtained in Example 3. This is because the high-precision balance can continuously output crystal weight data. The control mechanism calculates the rate of change of weight over time in real time and, combined with crystal density and cross-sectional area, converts it into a linear growth rate. The growth rate directly reflects the mass transport at the solid-liquid interface. Maintaining a constant growth rate ensures a stable solid-liquid interface, guaranteeing a stable crystal diameter and achieving constant diameter control. Infrared thermometers are aimed at different positions on the top edge of the mold. Non-contact measurement of the mold temperature assesses the circumferential uniformity of the thermal field. The encoder accurately feeds back the real-time rotational speed and rotational angle of the seed crystal and the crystal. It also accurately feeds back the real-time position and lifting speed of the lifting rod.

[0075] Compared to Example 4, Example 5 involved adjusting the number and aiming position of the infrared thermometers in the crystal growth furnace, resulting in a gallium oxide crystal of superior quality compared to that obtained in Example 4. Figure 2 As shown, the (100) oriented β-Ga2O3 diffraction peaks obtained in Example 5 (i.e., (200), (400), (600), and (800)) show no other oriented peaks. Figure 3 The FWHM curve shown is 51.7 arcsec, indicating that the quality of the product is good.

[0076] This is because placing one or more infrared thermometers along the crystal pulling path allows for targeting the crystal surface and monitoring the temperature gradient within the crystal itself. This non-contact measurement of the crystal surface temperature enables the assessment of the circumferential uniformity of the thermal field.

[0077] Application Example 1: The large-size gallium oxide crystal of Embodiment 5 of this application is cut, ground, polished, and cleaned to obtain a gallium oxide substrate, such as... Figure 4As shown, the roughness of the substrate surface is less than 0.107 nm, which indicates that the processing process is low in damage to the gallium oxide substrate surface obtained by the application, and further indicates that the gallium oxide crystal obtained by the application is low in defects, high in growth quality, and high in yield.

[0078] The above are preferred embodiments of the application, and do not limit the protection scope of the application, so: any equivalent changes made in the structure, shape, principle of the application should be covered within the protection scope of the application.

Claims

1. A method of growing a large size gallium oxide crystal by a mode method, characterized by, The growth method comprises the following steps: (1) high purity β-Ga2O3 powder is loaded into a mold, a seed crystal is installed, the seed crystal is oriented to a (100) surface, a growth furnace is sealed, high vacuum ≤1×10 -3 Pa is extracted, high purity argon is filled to 1.01-1.02 atm, temperature is raised to 1750-1800℃ at 100-150℃ / h, and the temperature is kept at 1750-1800℃ for 2-3h; (2) Slowly contact the seed crystal with the melt, start pulling at a speed of V1, set the heating power to P1, when the shoulder forms a stable shape, linearly increase the pulling speed to V2, while synchronously slowly increase the heating power to P2, when the shoulder size is close to 90%-95% of the target diameter, reduce the pulling speed to V3, and keep the power P2 stable for a period of time until the full diameter is reached; (3) The crystal rotates at a uniform speed of N1, and every 1-3 turns, the speed is accelerated to N2 at the 90-180° of the fastest heat dissipation corner of the mold for 20-40s and then returns to the original speed, and the reciprocating cycle is repeated; (4) After the crystal growth is completed and separated from the melt, immediately close the high-purity argon, introduce a mixed gas containing 3-5% oxygen into the furnace, the flow rate is 2-3 L / min, keep the temperature at 1250-1350℃ for 4-6h, slowly reduce the temperature to 800-900℃ at a rate of 30-50℃ / h, keep the temperature stable for 2-3h, turn off the heating power, and let the crystal cool to room temperature with the furnace; (5) When the furnace temperature is completely reduced to room temperature, fill the furnace with air to atmospheric pressure, open the furnace, and take out the gallium oxide crystal.

2. The method of claim 1, wherein the method is characterized by: In the step (2), V1 is 0.5-0.8 mm / h, V2 is 1.5-2.0 mm / h, and V3 is 1.0-1.5 mm / h.

3. The method of claim 1, wherein the method further comprises: In the step (3), N1 is 3-7 rpm, and N2 is 12-18 rpm.

4. The method of claim 1, wherein the method further comprises, The growth furnace comprises an induction coil, an insulation layer, a crucible, a mold, a heat shield, a seed crystal lifting and rotating mechanism, a thermoelectric corner, and a control mechanism.

5. The method of claim 4, wherein the method further comprises the step of: The growth furnace further comprises a high-precision balance, a plurality of infrared thermometers, and an encoder; the high-precision balance is arranged on the upper part of the seed crystal lifting and rotating mechanism, the infrared thermometers are aimed at different positions on the top edge of the mold and the surface of the crystal respectively, and the encoder is arranged in the seed crystal lifting and rotating mechanism.

6. A bulk gallium oxide crystal, characterized by, The large-size gallium oxide crystal is prepared by the method for growing a large-size gallium oxide crystal by the mode method according to any one of claims 1-5.

7. The bulk gallium oxide crystal of claim 6, wherein The size of the gallium oxide crystal is 4 inches.

8. Use of a gallium oxide substrate in a semiconductor device, characterized in that The gallium oxide substrate is obtained by cutting, grinding, polishing, and cleaning the large-size gallium oxide crystal according to any one of claims 6-7.

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