Apparatus for manufacturing oxide single crystals, method for producing gallium oxide single crystals using the apparatus and gallium oxide single crystals thereby

Abstract

The present invention relates to an oxide single crystal manufacturing apparatus, a method for manufacturing a gallium oxide single crystal using the same, and a gallium oxide single crystal manufactured according to the same. More specifically, the invention relates to a single crystal manufacturing apparatus and a method for manufacturing a gallium oxide single crystal using the same, which can produce high-quality oxide crystals by applying a method of using the oxide pellet itself to be made into a single crystal as a crucible without using a separate crucible, thereby minimizing the problem of impurities being introduced by the crucible, and by applying a method of generating heat using a flame mixed with a hydrocarbon fuel gas and oxygen gas, thereby maintaining a high-oxygen atmosphere for the growth of the oxide single crystal.

Description

Technology Field

[0001] The present invention relates to an apparatus for manufacturing an oxide single crystal, a method for manufacturing a gallium oxide single crystal, and a gallium oxide single crystal. Background Technology

[0003] Since the single crystal of gallium oxide (specifically the β-Ga2O3 single crystal; hereinafter referred to as the β-Ga2O3 single crystal) was reported by Y. Tomm et al. in 2000 for single crystal growth by the FZ method and CZ method, research and development of crystal growth has initially been conducted as a substrate for fabricating GaN thin films for LEDs.

[0004] Recently, following the report by M. Higashiwaki et al. on the realization of a FET for a power device using a β-Ga2O3 single crystal, there is strong interest in manufacturing high-quality, large, and low-cost β-Ga2O3 single crystals for realizing wide-gap semiconductor substrates for power devices.

[0005] β-Ga2O3 single crystals for device applications can be grown using methods such as the Floating Zone (FZ) method, Czochralski (CZ) method, edge-defined film-fed growth (EFG) method, vertical Bridgman (VB) method, and HB method. Among these crystal growth methods, the FZ method does not require a container to hold the molten raw material due to its crystal growth principle, so the means to heat the raw material to the high temperature (melting point) can be realized relatively easily, and much research has been conducted on it to date. However, even considering the growth principle and temperature environment of the FZ method, there are technical limitations to scaling up high-quality crystals with suppressed structural defects such as dislocations. Although it has been extensively studied over the past decade, it can be said that it is not yet in a state where it can fully meet the demands of device applications.

[0006] Meanwhile, the CZ method and the EFG method have been used for growing many single crystals as methods for manufacturing large, high-quality single crystals suitable for industrial applications. Regarding the growth of β-Ga2O3 single crystals, it is estimated that research and development of the CZ method and the EFG method has been actively carried out since 2000. However, it has not yet been possible to provide large, high-quality, low-cost β-Ga2O3 single crystals capable of meeting future power device applications.

[0007] Currently, in order to solve the above problem, the VB method is receiving attention, and methods to manufacture large, high-quality, low-cost β-Ga2O3 single crystals using this method are being actively researched.

[0008] When crystal growth is performed using the CZ method and the EFG method, a crucible is required to maintain the molten raw material. Since the melting point of β-Ga2O3 is about 1800°C, which is a high temperature, high-melting-point metals such as Ir, Mo, and W can be considered as crucible materials for application based on the melting point.

[0009] However, it is known that when β-Ga2O3 is melted in a crucible at high temperatures exceeding 1800°C, Mo and W cannot be used as crucibles at all because the reducing power of the crucible material Mo or W is high, and they decompose by taking oxygen from β-Ga2O3 and oxidize themselves. As a result, it is recognized that Ir is the only high melting point metal that can be applied to CZ crucibles, EFG crucibles, and die materials.

[0010] However, through various experiments and theoretical considerations, it has become clear that there are actually major problems with Ir, which is currently used as CZ method crucible material and EFG method crucible material (including die material).

[0011] In other words, it was found that when Ir undergoes an oxidation reaction under an oxygen partial pressure exceeding several percent in a high-temperature furnace exceeding 1800°C, it becomes difficult to apply it as a stable crucible material. Meanwhile, it was also found that when β-Ga2O3 undergoes a decomposition reaction in which it loses oxygen under an oxygen partial pressure of 10% or less in high temperatures exceeding 1800°C, it becomes difficult to exist as a stable β-Ga2O3 molten solution.

[0012] As described above, it is clear that the oxygen partial pressure conditions required in the high-temperature furnace for the β-Ga2O3 raw material molten liquid and the oxygen partial pressure conditions required for the Ir crucible maintaining it are contradictory. In other words, it is recognized that Ir cannot be a suitable crucible material for containing the β-Ga2O3 raw material molten liquid.

[0013] To elaborate further, although the growth of β-Ga2O3 crystals using the conventional CZ and EFG methods with an Ir crucible is possible under a narrow range of oxygen partial pressures within the furnace, it has been experimentally revealed that the grown β-Ga2O3 crystals exhibit problems such as the occurrence of high-density oxygen defects, which are common in oxide crystals grown under oxygen deficiency, as well as issues of evaporation, weight loss, and degradation due to the oxidation of Ir. Furthermore, oxygen defects act as n-type impurities and generate high concentrations of donors, which makes the realization of p-type β-Ga2O3 extremely difficult, and thus poses many challenges in the realization of semiconductor devices.

[0014] To solve this problem, a method for growing β-Ga2O3 crystals in an atmospheric atmosphere using the VB method with a Pt-Rh alloy crucible has been proposed. It has been found that growing β-Ga2O3 crystals in the atmosphere suppresses the decomposition of β-Ga2O3 and that using a Pt-Rh crucible solves the problem of crucible oxidation at high temperatures. However, it has been experimentally revealed that when β-Ga2O3 is exposed to molten liquid at high temperatures while immersed in a Pt-Rh crucible for a long time, a large amount of Rh is detected as an impurity in the grown β-Ga2O3 crystals.

[0015] Although the CZ, EFG, and VB methods are all advantageous for scaling up, large amounts of unintended Si impurities are still being detected. It has been revealed that when devices are fabricated using β-Ga2O3 crystals containing large amounts of Si impurities, insufficient insulation is achieved, posing a problem for their use as substrates for device fabrication. Furthermore, it has been found that in β-Ga2O3 crystals grown by the CZ and EFG methods, large amounts of Ga impurities generated by the decomposition of β-Ga2O3 in a low-oxygen atmosphere are detected within the grown crystals. Prior art literature

[0017] Japanese Publication No. 2013-237591

[0018] N. Ueda, H. Hosono, R. Waseda, H. Kawazoe, Appl. Phys. Lett. 70(1997) 3561. The problem to be solved

[0019] The present invention was devised to solve the above problems, and the objective of the present invention is to provide a single crystal manufacturing apparatus and a method for manufacturing a gallium oxide single crystal using the same, which prevents the intervention of unintended impurities and produces high-quality oxide crystals of ultra-wide bandgap semiconductor gallium oxide, which is essential for manufacturing extreme environment materials and devices, without a crucible containing molten gallium oxide, by using flame fusion.

[0020] The technical problems that the present invention aims to solve are not limited to those mentioned above, and other unmentioned technical problems will be clearly understood by those skilled in the art from the description below. means of solving the problem

[0022] To achieve the above objective, the present invention provides an oxide single crystal manufacturing apparatus characterized by comprising: a heat source unit (100) for melting oxide pellets; a growth unit (200) composed of refractory material that loads the oxide pellets and is a space for growing an oxide single crystal; a driving unit (300) for moving the entire growth unit to grow the oxide single crystal; and a measuring unit (400) for measuring the temperature of the growth unit throughout the entire oxide single crystal growth process.

[0023] The heat source unit (100) comprises: a fuel gas supply unit (101) made of hydrocarbon; an oxygen gas supply unit (102); a fuel pressure regulator (103) for regulating the pressure of fuel injected into the fuel pipe; an oxygen pressure regulator (104) for regulating the pressure of oxygen; a pre-mixing area unit (107) which is a space where the fuel gas and the oxygen gas are mixed; a fuel pipe (109) through which the fuel gas flows into the pre-mixing area unit (107); an oxygen pipe (110) through which the oxygen gas flows; a fuel flow rate regulator (105) for regulating the amount of fuel gas flowing into the pre-mixing area unit (107); an oxygen flow rate regulator (106) for regulating the amount of oxygen gas; and a nozzle (108) through which the mixed gas of fuel gas and oxygen gas mixed in the pre-mixing area unit (107) is discharged to the outside. It is characterized by including a height adjuster (111) that adjusts the distance between the growth section (200) and the nozzle (108).

[0024] The growth unit (200) is characterized by including a refractory and insulating material (201) for creating an independent oxygen atmosphere with heat resistance from the heat generated from the heat source unit (100) and the surrounding air.

[0025] The above driving unit (300) is characterized by comprising: a support (304) that supports the growth unit (200); a conveyor belt (301) that moves the entire support (304) linearly; a motor (302) for driving the conveyor belt (301); a microcontroller (303) for controlling the driving of the motor (302); and a computer (C) for controlling the microcontroller (303).

[0026] The above measuring unit (400) is characterized by including an infrared camera (401) that measures the temperature of the growth unit (200); and a computer (C) that receives temperature data measured from the infrared camera.

[0027] In addition, the present invention provides a method for manufacturing a gallium oxide single crystal, characterized by comprising: a sample preparation step (S1) of processing gallium oxide powder to produce gallium oxide pellets; a growth preparation step (S2) of loading the gallium oxide powder pellets into an oxide single crystal manufacturing apparatus to create a growth atmosphere and preheating; and a single crystal growth step (S3) of driving a motor to grow a single crystal and produce a gallium oxide single crystal.

[0028] The sample preparation step (S1) is characterized by comprising: a calcination step (S110) for removing organic impurities and moisture from the oxide powder and converting the oxide powder into a beta-phase oxide powder; a mixing step (S120) for mixing the calcined oxide powder; a cold pressing step (S130) for making the mixed oxide powder into a compressed powder; and a sintering step (S140) for heat treating the cold-pressed oxide powder to produce pellets.

[0029] The growth preparation step (S2) comprises: a step (S210) of loading the oxide pellet prepared in the sample preparation step (S1) into an oxide single crystal manufacturing apparatus; a step (S220) of adjusting the pressure of the fuel gas and oxygen gas for initial flame ignition; a step (S230) of adjusting the flow rate of the fuel gas and oxygen gas; an ignition step (S240) for generating a flame; a step (S250) of preheating the growth section and the oxide pellet after raising the temperature to just before the melting point of the oxide pellet; a step (S260) of adjusting the ratio of the fuel gas and oxygen gas so that the melting region of the oxide pellet is formed into an oxygen atmosphere; and a melting step (S270) of heating the sample by raising the temperature above the melting point of the oxide pellet.

[0030] The oxide single crystal growth step (S3) is characterized by comprising: a step (S310) of starting oxide single crystal growth by driving a linear motor in a state where an oxide molten liquid (S203) is created above the melting point of the growth preparation step (S2); a temperature maintenance step (S320) of controlling the fuel and oxygen gas flow rates and pressures to maintain the temperature of the growth section; an oxygen atmosphere maintenance step (S330) of controlling the flow rates and pressures to maintain the oxygen atmosphere of the growth section; a growth step (S340) of growing the oxide single crystal; a cooling step (S350) of cooling the oxide single crystal that has been grown; and a single crystal extraction step (360) of extracting the oxide single crystal grown on the oxide pellet.

[0031] In addition, the present invention provides a gallium oxide single crystal characterized by being manufactured according to the above-described manufacturing method. Effects of the invention

[0033] By means of the above-mentioned solution to the problem, the present invention can minimize the problem of impurities being introduced by the crucible by applying a method of using the oxide pellet itself, which is intended to be made into a single crystal, as a crucible without using a separate crucible.

[0034] In addition, by applying a method of mixing hydrocarbon-based fuel gas and oxygen gas and generating heat using a flame, it is possible to maintain a high-oxygen atmosphere in the growth atmosphere of the oxide single crystal by controlling the partial pressure of the oxygen gas, thereby enabling the production of high-quality oxide single crystals with few defects.

[0035] In addition, the single crystal produced by the manufacturing apparatus of the present invention is expected to be used as an ultra-wide bandgap semiconductor material essential for manufacturing power devices and materials for extreme environments, as it obtains high-quality crystals by preventing the intervention of unintended impurities during growth.

[0037] The effects of the present invention are not limited to those mentioned above, and other unmentioned effects will be clearly understood by those skilled in the art from the description in the claims. Brief explanation of the drawing

[0039] FIG. 1 shows an oxide single crystal manufacturing apparatus according to one embodiment of the present invention. FIG. 2 shows a heat source part (100) of an oxide single crystal manufacturing apparatus according to one embodiment of the present invention. FIG. 3 shows a growth section (200) of an oxide single crystal manufacturing apparatus according to an embodiment of the present invention. FIG. 4 shows a driving unit (300) of an oxide single crystal manufacturing device according to an embodiment of the present invention. FIG. 5 shows a measuring unit (400) of an oxide single crystal manufacturing apparatus according to an embodiment of the present invention. FIG. 6 is a process block diagram for explaining a method for manufacturing a gallium oxide single crystal according to an embodiment of the present invention. FIG. 7 is a process block diagram for explaining steps S1 to S3 of a method for manufacturing a gallium oxide single crystal according to an embodiment of the present invention. FIG. 8 illustrates the detailed steps of step S1 of the method for manufacturing a gallium oxide single crystal according to an embodiment of the present invention. FIG. 9 shows a temperature graph of an electric furnace during the calcination step (S110) of a method for manufacturing a gallium oxide single crystal according to an embodiment of the present invention. FIG. 10 shows a photograph of an oxide pellet produced through the cold pressing step (S130) of a method for producing a gallium oxide single crystal according to an embodiment of the present invention. FIG. 11 shows a temperature graph of an electric furnace during the sintering step (S140) of a method for manufacturing a gallium oxide single crystal according to an embodiment of the present invention. FIG. 12 shows an algorithm for growing a single crystal in the oxide single crystal growth step (S3) of a gallium oxide single crystal manufacturing method according to an embodiment of the present invention. FIG. 13 shows a temperature graph in the oxide single crystal growth step (S3) of the gallium oxide single crystal manufacturing method according to one embodiment of the present invention. FIG. 14 shows a micrograph of a gallium oxide single crystal sample grown once by the gallium oxide single crystal manufacturing method according to one embodiment of the present invention. FIG. 15 shows the results measured using X-ray diffraction analysis and neutron diffraction analysis of a gallium oxide single crystal prepared according to an embodiment of the present invention. (a) is a peak of the rocking curve of X-ray diffraction in the (400) plane direction appearing around 17°, (b) is 2theta / theta scan data of X-ray diffraction measured from 10° to 80° along the (h00) direction, and (c) has a rocking curve peak of neutron diffraction in the (020) plane direction appearing around (020) 25°. FIG. 16 shows the measurement results of a gallium oxide single crystal prepared according to an embodiment of the present invention using ultraviolet-visible-near-infrared spectroscopy. FIG. 17 shows the measurement results using secondary ion mass spectrometry of a gallium oxide single crystal prepared according to an embodiment of the present invention. Specific details for implementing the invention

[0040] The terms used in this invention have been selected based on currently widely used general terms, taking into account their functions within the invention; however, these terms may vary depending on the intent of those skilled in the art, case law, the emergence of new technologies, etc. Additionally, in specific cases, terms have been arbitrarily selected by the applicant, and in such cases, their meanings will be described in detail in the relevant description of the invention. Therefore, the terms used in this invention should be defined not merely by their names, but based on their meanings and the overall content of the invention.

[0041] Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as generally understood by those skilled in the art to which the present invention pertains. Terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant technology, and should not be interpreted in an ideal or overly formal sense unless explicitly defined in this application.

[0042] When a part of a specification is described as “comprising” a certain component, this means that, unless specifically stated otherwise, it does not exclude other components but may include additional components.

[0043] Embodiments of the present invention are described below with reference to the attached drawings so that those skilled in the art can easily implement them. However, the present invention may be embodied in various different forms and is not limited to the embodiments described herein.

[0045] The present invention will be described in detail below.

[0047] The present invention provides an oxide single crystal manufacturing apparatus (T) characterized by comprising a heat source unit (100) for melting oxide pellets, a growth unit (200) composed of refractory material that loads the oxide pellets and is a space for growing an oxide single crystal, a driving unit (300) for moving the entire growth unit to grow the oxide single crystal, and a measuring unit (400) for measuring the temperature of the growth unit throughout the growth process.

[0048] As shown in FIG. 2, the heat source unit (100) is characterized by including a fuel gas supply unit (101) and an oxygen gas supply unit (102), a pressure regulator (103) for controlling the pressure of fuel injected into the fuel pipe, a pressure regulator (104) for controlling the pressure of oxygen, a pre-mixing area unit (107) which is a space where the fuel gas and oxygen gas are mixed, a fuel pipe (109) into which the fuel gas flows into the pre-mixing area unit (107), an oxygen pipe (110) into which the oxygen gas flows, a fuel flow rate regulator (105) for controlling the amount of fuel gas flowing into the pre-mixing area unit (107), an oxygen flow rate regulator (106) for controlling the amount of oxygen gas, a nozzle (108) through which the mixed gas of fuel gas and oxygen gas mixed in the pre-mixing area unit (107) is discharged to the outside, and a height regulator (111) for controlling the distance between the growth unit (200) and the nozzle (108).

[0049] The above fuel gas uses a gas composed mainly of hydrocarbons and may include gases such as hydrogen, propane, butane, and acetylene.

[0050] The fuel pressure regulator (103), oxygen pressure regulator (104), fuel flow regulator (105), and oxygen flow regulator (106) may be analog or digital devices, and more preferably, may be digital devices capable of communication functions, but are not limited thereto.

[0051] As shown in FIG. 3, the growth unit (200) is characterized by comprising a refractory and insulating material (201) for creating an independent oxygen atmosphere with heat resistance from the heat generated from the heat source unit (100) and surrounding air, an oxide pellet (202), a flame (204) that forms the oxygen atmosphere with the heat generated from the heat source unit (100), an oxide molten liquid (203) in which the oxide pellet (202) heated by the flame is melted, and an oxide single crystal (205) in which the oxide molten liquid (203) is slowly cooled and crystallized.

[0052] According to one embodiment of the present invention, since the oxide sample is subjected to strong gas pressure by a flame, the sample is not prepared in powder form, but is prepared in the form of pellets through cold pressing and sintering processes, thereby preventing loss of raw materials and allowing the molten liquid to be contained without a crucible.

[0053] The above refractory and insulating material (201) may be selected from materials suitable for refractory and insulating materials depending on the melting point of the oxide to be melted, and preferably may be made of zirconia, but is not limited thereto.

[0054] As shown in FIG. 4, the above driving unit (300) is characterized by including a support (304) that supports the growth unit (200), a conveyor belt (301) that moves the entire support (304) linearly, a motor (302) for driving the conveyor belt (301), a microcontroller (303) for controlling the driving of the motor (302), and a computer (C) for controlling the microcontroller.

[0055] The above refractory and insulating material (201) and the oxide pellet are both placed on a conveyor belt, and the oxide pellet is heated by a flame, and after the internal temperature of the refractory and insulating material (201) reaches an equilibrium state, when a molten liquid is formed in the oxide pellet, the entire refractory and insulating material (201) is installed to move horizontally by the conveyor belt.

[0056] The above support (304) is a part exposed to high temperature during the oxide single crystal growth process, and can be selected from a suitable metal-based material with a sufficiently high melting point so that the support (304) is not damaged, and preferably can be one or more selected from the group consisting of aluminum and stainless steel, but is not limited thereto.

[0057] The above conveyor belt (301) is connected to a motor (302), and the motor (302) is connected to a microcontroller (303). The movement of the conveyor belt (301) is controlled by the microcontroller (303) and driven by the motor (302).

[0058] The microcontroller (303) is connected to the computer (C) and is characterized by receiving command signals through a program installed on the computer (C).

[0059] As shown in FIG. 5, the above measuring unit (400) is characterized by including an infrared camera (401) that measures the temperature of the growth unit (200) and a computer (C) that receives temperature data measured from the infrared camera.

[0060] The infrared camera (401) measures the temperature of the growth unit (200) and is characterized by transmitting the temperature data of the growth unit (200) to a computer in real time and outputting it as an image by a program that can view it as a real-time image.

[0061] In addition, the system is characterized by controlling the system through an algorithm that measures the temperature of the infrared camera (401) and, if the temperature falls below the temperature set in the program, adjusts the fuel flow regulator (105) to raise the temperature, and if the temperature rises above the temperature set in the program, adjusts the fuel flow regulator (105) to lower the temperature so that the set temperature is maintained.

[0063] In addition, the present invention provides a method for manufacturing a gallium oxide single crystal, characterized by comprising: a sample preparation step (S1) of processing gallium oxide powder to produce gallium oxide pellets; a growth preparation step (S2) of loading the gallium oxide powder pellets into an oxide single crystal manufacturing apparatus to create a growth atmosphere and preheating; and a single crystal growth step (S3) of driving a motor to grow a single crystal and produce a gallium oxide single crystal.

[0064] As illustrated in FIG. 7 (a) and FIG. 8, the sample preparation step (S1) is characterized by comprising: a calcination step (S110) for removing organic impurities and moisture from the gallium oxide powder and converting the gallium oxide powder into beta-phase gallium oxide powder; a mixing step (S120) for mixing the calcined powder; a cold pressing step (S130) for making the mixed powder into a compressed powder; and a sintering step (S140) for heat treating the cold-pressed gallium oxide powder to produce pellets.

[0065] According to one embodiment of the present invention, the gallium oxide sample is not prepared in powder form because it is subjected to strong gas pressure by a flame, but is prepared in the form of pellets through cold pressing and sintering processes, thereby preventing loss of raw materials and allowing the molten liquid to be contained without a crucible.

[0066] And as illustrated in FIG. 7 (b), the growth atmosphere formation and preheating step (S2) comprises: a step (S210) of loading the sintered gallium oxide pellets produced in the sample preparation step (S1) into an oxide single crystal manufacturing apparatus (T); a step (S220) of adjusting the pressure of the fuel gas and oxygen gas for initial flame ignition; a step (S230) of adjusting the flow rate of the fuel gas and oxygen gas; an ignition step (S240) for generating a flame; a step (S250) of preheating the growth section and the gallium oxide pellets after raising the temperature to just before the melting point of the gallium oxide pellets; a step (S260) of adjusting the ratio of the fuel gas and oxygen gas so that the melting region of the gallium oxide pellets is formed into an oxygen atmosphere; and a melting step (S270) of heating the sample by raising the temperature above the melting point of the gallium oxide pellets.

[0067] As illustrated in FIG. 7(c), the single crystal growth step (S3) is characterized by including: a step (S310) of starting the growth of a gallium oxide single crystal by driving a linear motor in a state where a molten gallium oxide (S203) is created above the melting point of the growth atmosphere composition and preheating step (S2); a temperature maintenance step (S320) of controlling the fuel and oxygen gas flow rate and pressure to maintain the temperature of the growth unit (200); an oxygen atmosphere maintenance step (S330) of controlling the flow rate and pressure to maintain the oxygen atmosphere of the growth unit (200); a growth step (S340) of growing a gallium oxide single crystal (205); a cooling step (S350) of cooling the grown gallium oxide single crystal; and a single crystal extraction step (360) of extracting the gallium oxide single crystal grown on the upper part of the gallium oxide pellet.

[0068] Hereinafter, gallium oxide according to one embodiment of the present invention The single crystal manufacturing method is explained in detail for each process as follows.

[0069] The above gallium oxide powder calcination step (S110) is gallium oxide It is characterized by selecting a crucible material that does not react with the powder to form a new compound, loading gallium oxide powder into the crucible, heating it to an appropriate temperature in an electric furnace, maintaining it for an appropriate time, and naturally cooling it to ambient temperature without a cooling device.

[0070] Platinum or a platinum-based alloy that is not chemically reactive with gallium oxide powder is most suitable as the material for the crucible to hold the gallium oxide powder.

[0071] As shown in FIG. 9, 100g of gallium oxide in the gallium oxide powder calcination step (S110) It is characterized by loading a platinum crucible containing powder into an electric furnace, heating it to 1,000 ℃ for 6 hours and maintaining it at 1,000 ℃ for 20 hours, and then turning off the power to the electric furnace and allowing it to cool naturally to ambient temperature.

[0072] As shown in FIG. 8, the above raw material powder mixing step (S120) is characterized by performing a milling process to finely reduce the particle size of the gallium oxide powder that has undergone the gallium oxide powder calcination step (S110), make the particle size distribution uniform, and ensure that the gallium oxide powder is well mixed.

[0073] The above milling process may use a mortar and pestle, a ball mill, or a high-energy ball mill device. In the present invention, the gallium oxide powder of about 90 to 100 g, which has undergone the calcination step (S110), can be milled for 30 minutes using a mortar and pestle.

[0074] The above gallium oxide powder cold pressing step (S130) is characterized by placing the powder obtained from the above gallium oxide powder mixing step (S120) into a die made of an alloy metal capable of receiving the powder and pressing it without applying heat to form it into a pellet shape.

[0075] In the cold pressing step (S130) for making the mixed powder into compressed powder, 40g of gallium oxide powder obtained from the gallium oxide powder mixing step (S120) is loaded into a cylindrical die made of stainless steel with a diameter of 1.5 inches, and after maintaining it at a pressure of 70 MPa for 5 minutes using a hydraulic press device, the cold-pressed gallium oxide powder can be separated. The cold pressing step process can be performed twice in the same way.

[0076] The above sintering step (S140) is characterized by loading the pellets, made through the gallium oxide powder cold pressing step (S130) as shown in FIG. 10, into an alumina crucible using a non-chemically reactive platinum crucible lid as a support, and then, as shown in FIG. 11, heating the pellets in an electric furnace to 1,450°C for 8 hours and maintaining the temperature at 1,450°C for 20 hours, after which the power to the electric furnace is turned off and the pellets are naturally cooled to ambient temperature.

[0077] As illustrated in FIG. 3, the gallium oxide pellet loading step (S210) is characterized by preparing two gallium oxide pellets (202) manufactured through the gallium oxide powder sintering step (S140) and stacking the gallium oxide pellets (202) on the bottom of the growth section (200) of the single crystal manufacturing device (T) so that the molten liquid does not overflow to the bottom of the growth section (200) during the melting process.

[0078] The above fuel gas and oxygen gas pressure control step (S220) and the above fuel gas and oxygen gas flow rate control step (S230) are characterized by controlling to have appropriate pressure and flow rate for igniting an initial flame.

[0079] The flame ignition step (S240) is characterized by applying heat above the ignition point to the tip of the nozzle (108) to generate a flame in the gas coming out of the nozzle (108). The fuel gas used in the flame ignition step (S240) is portable LPG gas mixed with butane and propane gas in a 9:1 ratio.

[0080] The above preheating step (S250) is characterized by controlling the pressure and flow rate of fuel and oxygen gas to prevent the gallium oxide pellet (202) from cracking due to thermal shock, and slowly heating it to just before the melting temperature of the gallium oxide pellet (202), which is about 1,850°C, and maintaining the temperature of the growth part (200) until it reaches a thermal equilibrium state.

[0081] The oxygen atmosphere creation step (S260) is characterized by controlling the oxygen pressure and flow rate to maintain an appropriate oxygen partial pressure for the gallium oxide pellet (202) to melt and to maintain the temperature in the preheating step (S250).

[0082] The melting step (S270), which heats the sample by raising the temperature above the melting point of the gallium oxide pellet, is characterized by controlling the flow rate and pressure of fuel and oxygen gas to heat above the melting point while maintaining the oxygen atmosphere formed in the oxygen atmosphere formation step (S260), thereby melting the gallium oxide pellet (202) to produce a molten gallium oxide liquid (203).

[0083] In the melting step (S270), since the molten gallium oxide must be sufficient to form a crystal size on the upper part of the gallium oxide pellet (202), the area of ​​the flame (205) which is higher than the melting point must be sufficiently large.

[0084] In addition, if the area of ​​the flame (205) which is higher than the melting point becomes larger than the diameter of the pellet (202), the molten gallium oxide (203) may overflow to the bottom of the growth section (200), so the pressure and flow rate of the fuel gas and oxygen gas must be appropriately controlled to maintain the area of ​​the flame (205).

[0085] The above linear motor driving step (S310) and single crystal growth step (S320) are characterized by driving a linear motor to grow a gallium oxide single crystal when the molten gallium oxide (203), which has been melted above the melting point in the melting step (S270), reaches a thermal equilibrium state inside the growth section (200), and continuously adjusting the pressure and flow rate of fuel and oxygen gas to maintain the temperature and oxygen atmosphere at the time when melting begins.

[0086] In the above linear motor driving step (S310), the movement speed of the motor can be performed at 0.3 to 0.7 mm / min, and preferably at 0.5 mm / min. The slower the movement speed of the motor, the larger the size of the crystal and the better the quality of the crystal can be.

[0087] According to one embodiment of the present invention, when a thermal equilibrium state is reached in the linear motor driving step (S310), the temperature is about 1,950°C, the pressure of the fuel gas is about 0.05 MPa, and the pressure of the oxygen gas is about 0.02 MPa.

[0088] The above single crystal growth step (S320) is characterized by being controlled by an algorithm as shown in FIG. 12 to continuously maintain the temperature and oxygen atmosphere while the entire growth unit (200) is placed on the support (304) of the driving unit (300) and moves at a constant speed in a straight line.

[0089] Additionally, the cooling step (S330) is characterized by rapidly reducing the flow rate and pressure of fuel and oxygen gas to reduce the temperature of the flame (204) when the gallium oxide single crystal growth is completed, and covering the upper part of the growth section (200) with a refractory and insulating material (201) to slowly cool the temperature of the growth section (200) to ambient temperature.

[0090] In addition, the single crystal extraction step (S340) is characterized by appropriately processing the gallium oxide single crystal (205) formed on the upper part of the gallium oxide pellet (202) cooled to ambient temperature to select the single crystal.

[0091] In addition, the present invention provides a gallium oxide single crystal characterized by being manufactured according to the above-described manufacturing method.

[0093] Hereinafter, the present invention will be described in detail with reference to examples to specifically explain the invention. However, the embodiments according to the present invention may be modified in various different forms, and the scope of the present invention is not to be interpreted as being limited to the embodiments described below. The embodiments of this specification are provided to more completely explain the present invention to those with average knowledge in the art.

[0095] <Example> β-Ga 2 O 3 manufacturing of crystals

[0096] 1. β-Ga 2 O 3 Manufacture of pellets

[0097] (a) 100g of β-Ga2O3 powder was placed in a platinum crucible and positioned in the center of an electric furnace.

[0098] (b) The temperature was raised to 1,000°C in an electric furnace for 6 hours, maintained at 1,000°C for 20 hours, and then cooled to ambient temperature with the electric furnace power turned off.

[0099] (c) The β-Ga2O3 powder calcined in (b) was placed in a mortar and pestle and ground for 30 minutes.

[0100] (d) 40 g of the β-Ga2O3 powder ground in (c) was placed into a circular alloy metal die with a diameter of 1.5 inches and held at a pressure of 70 MPa for 5 minutes using a hydraulic press. This was repeated twice.

[0101] (e) Two lumps of cold-pressed β-Ga2O3 powder removed from the die were placed on a platinum crucible lid support, placed in an alumina crucible, and positioned in the center of the electric furnace.

[0102] (f) The temperature was raised to 1,450°C in an electric furnace for 8 hours, maintained at 1,450°C for 20 hours, and then cooled to ambient temperature with the electric furnace power turned off.

[0103] 2. β-Ga 2 O 3 Manufacturing of single crystals

[0104] (g) The β-Ga2O3 pellets sintered in (f) were loaded into the lower central part of the growth section.

[0105] (h) LPG fuel gas mixed with propane and butane in a 9:1 ratio and oxygen gas were used, and the valve of the gas cylinder was opened to ignite the flame, and the fuel gas pressure regulator and the oxygen gas pressure regulator were adjusted appropriately to ignite the flame.

[0106] (i) After igniting the flame, the fuel gas flow meter and oxygen gas flow meter were slowly opened, and the fuel gas pressure regulator and oxygen gas pressure regulator were adjusted to raise the temperature of the flame.

[0107] (j) Once the flame temperature rose to about 1,450℃, the pressure gauge and flow meter were controlled by applying the algorithm shown in Fig. 12 to create a high-oxygen atmosphere so that the β-Ga2O3 pellets would not vaporize and fly away. When the β-Ga2O3 pellets are exposed to a high-oxygen atmosphere, the powder does not vaporize and fly away.

[0108] (k) When a high oxygen atmosphere is formed at 1,450°C or higher, the algorithm shown in Fig. 12 is applied as in (j) to slowly increase the flow rate and pressure of the fuel gas and oxygen gas to melt the pellets of β-Ga2O3 to create a molten liquid, and the temperature is raised to 1,950°C and maintained for about 10 minutes until the entire system reaches a state of thermal equilibrium.

[0109] (l) When the β-Ga2O3 molten solution was generated and reached thermal equilibrium, and the area of ​​the molten solution was maintained at a constant level, the motor was driven to start single crystal growth. The motor speed was set so that the entire growth section moved at 0.5 mm / min.

[0110] (m) The algorithm shown in Fig. 12 was applied to maintain the growth temperature and oxygen atmosphere stably until the single crystal growth was finished.

[0111] (n) When single crystal growth was complete, the temperature of the flame was turned off and the crystal was slowly cooled.

[0112] (o) A single crystal was extracted from the top of a cooled β-Ga2O3 pellet.

[0114] <Experimental Example> β-Ga 2 O 3 Evaluation of the decision

[0115] As a β-Ga2O3 single crystal sample prepared according to one embodiment of the present invention, the β-Ga2O3 single crystal sample shown in FIG. 14 is a microscope image of a β-Ga2O3 single crystal sample grown once by the process of the above example (preparation of β-Ga2O3 crystal).

[0116] The structure of a β-Ga2O3 single crystal sample prepared according to one embodiment of the present invention is shown in (a), (b), and (c) respectively, when measured using single crystal X-ray diffraction analysis and neutron diffraction analysis shown in FIG. 15. (a) is the peak of the Rocking curve of X-ray diffraction in the (400) plane direction appearing around 17°, (b) is the 2theta / theta scan data of X-ray diffraction measured from 10° to 80° according to the (h00) direction, and (c) is the Rocking curve peak of neutron diffraction in the (020) plane direction appearing around (020) 25°.

[0117] In addition, the crystal structure and lattice constants of a β-Ga2O3 single crystal sample prepared according to an embodiment of the present invention were confirmed through single crystal X-ray diffraction analysis and are shown in Table 1. Referring to Table 1, the crystal structure is monoclinic, and the lattice constant values ​​are a = 12.231 Å, b = 3.0329 Å, c = 5.8077 Å, α = 90°, β = 103.784°, γ = 90°, and the unit cell volume is 209.44 Å. 3 It was possible to confirm that it was.

[0118]

[0119] In addition, by measuring the β-Ga2O3 single crystal sample prepared according to one embodiment of the present invention using ultraviolet-visible-near-infrared spectroscopy, it was confirmed that the indirect bandgap value was 4.21 eV, as shown in FIG. 16.

[0120] In addition, through measurement using secondary ion mass spectrometry of a β-Ga2O3 single crystal sample prepared according to one embodiment of the present invention, as shown in FIG. 17, the Si impurity was 2.28 x 10⁻⁶ 16 and Fe impurities are 2.85 x 10 16 , N impurities are 3.53 x 10 15 , Sn impurities are 2.38 x 10 16 It was possible to confirm that it was.

[0122] Specific embodiments of the present invention have been examined so far. Those skilled in the art will understand that the present invention may be embodied in modified forms without departing from the essential characteristics of the invention. Therefore, the disclosed embodiments should be considered in an illustrative rather than a restrictive sense. The scope of the present invention is defined by the claims, not by the foregoing description, and all variations within the scope of equivalents should be interpreted as being included in the present invention. Explanation of the symbols

[0124] 100 : Heat source section 200 : Growth section 300 : Driving unit 400 : Measuring unit 101: Fuel gas supply unit 102: Oxygen gas supply unit 103: Fuel pressure regulator 104: Oxygen pressure regulator 105: Fuel flow regulator 106: Oxygen flow regulator 107: Pre-mixing area 108: Nozzle 109 : Fuel line 110 : Oxygen line 111: Height adjuster 201: Fireproof and thermal insulation 202: Raw material powder pellets 203: Molten gallium oxide 204: Flame 205: Gallium Oxide Single Crystal 301: Conveyor belt 302: Motor 303: Microcontroller 304: Support 401: Infrared camera C: Computer S1: Sample preparation step S2: Gallium oxide single crystal growth preparation step S3: Single crystal growth step S110: Gallium oxide powder calcination step S120: Gallium oxide powder mixing step S130: Gallium oxide powder cold pressing step S140: Gallium oxide powder sintering step S210: Gallium oxide pellet loading step S220: Fuel gas and oxygen gas pressure control step S230: Fuel gas and oxygen gas flow control step S240: Flame ignition stage S250: Preheating stage S260: Oxygen atmosphere formation step S270: Melting step S310: Motor driving step S320: Single crystal growth step S330: Cooling step S340: Single crystal extraction step

Claims

Claim 1 An oxide single crystal manufacturing apparatus comprising: a heat source unit (100) for melting oxide pellets; a growth unit (200) composed of refractory material that is a space for loading oxide pellets and growing oxide single crystals; a driving unit (300) for moving the entire growth unit to grow oxide single crystals; and a measuring unit (400) for measuring the temperature of the growth unit throughout the entire oxide single crystal growth process, wherein the oxide single crystal manufacturing apparatus is characterized by using the oxide pellets themselves as a crucible without using a separate crucible, and wherein the growth unit (200) is characterized by raising the temperature to just before the melting point of the oxide pellets, forming an oxygen atmosphere, raising the temperature above the melting point of the oxide pellets to heat the oxide pellets to create a molten liquid, and continuously maintaining the oxygen atmosphere to cause the molten liquid to crystallize. Claim 2 In claim 1, the heat source unit (100) comprises: a fuel gas supply unit (101) made of hydrocarbon; an oxygen gas supply unit (102); a fuel pressure regulator (103) for regulating the pressure of fuel injected into the fuel pipe; an oxygen pressure regulator (104) for regulating the pressure of oxygen; a pre-mixing area unit (107) which is a space where the fuel gas and the oxygen gas are mixed; a fuel pipe (109) into which the fuel gas flows into the pre-mixing area unit (107); an oxygen pipe (110) into which the oxygen gas flows; a fuel flow rate regulator (105) for regulating the amount of fuel gas flowing into the pre-mixing area unit (107); an oxygen flow rate regulator (106) for regulating the amount of oxygen gas; and a nozzle (108) through which the mixed gas of fuel gas and oxygen gas mixed in the pre-mixing area unit (107) is discharged to the outside. An oxide single crystal manufacturing apparatus characterized by including a height adjuster (111) for adjusting the distance between the growth unit (200) and the nozzle (108). Claim 3 An oxide single crystal manufacturing apparatus according to claim 1, wherein the growth unit (200) comprises a refractory and insulating material (201) for creating an independent oxygen atmosphere with heat resistance from the heat generated from the heat source unit (100) and the surrounding air. Claim 4 An oxide single crystal manufacturing apparatus according to claim 1, wherein the driving unit (300) comprises: a support (304) that supports the growth unit (200); a conveyor belt (301) that moves the entire support (304) linearly; a motor (302) for driving the conveyor belt (301); a microcontroller (303) for controlling the driving of the motor (302); and a computer (C) for controlling the microcontroller (303). Claim 5 An oxide single crystal manufacturing apparatus according to claim 1, wherein the measuring unit (400) comprises: an infrared camera (401) for measuring the temperature of the growth unit (200); and a computer (C) for receiving temperature data measured from the infrared camera. Claim 6 The method comprises: a sample preparation step (S1) for manufacturing gallium oxide pellets by processing gallium oxide powder; a growth preparation step (S2) for loading the gallium oxide powder pellets into an oxide single crystal manufacturing device to create a growth atmosphere and preheat; and a single crystal growth step (S3) for manufacturing a gallium oxide single crystal by driving a motor to grow a single crystal. The growth preparation step (S2) includes: a step (S210) of loading the gallium oxide pellets manufactured in the sample preparation step (S1) into the growth section of the oxide single crystal manufacturing device; a step (S220) of adjusting the pressure of fuel gas and oxygen gas for initial flame ignition; a step (S230) of adjusting the flow rate of the fuel gas and oxygen gas; an ignition step (S240) for generating a flame; a step (S250) of preheating the growth section and the gallium oxide pellets after raising the temperature to just before the melting point of the gallium oxide pellets; and a step (S260) of adjusting the ratio of the fuel gas and oxygen gas so that the melting region of the gallium oxide pellets is formed into an oxygen atmosphere. A method for manufacturing a gallium oxide single crystal, characterized by including the step (S270) of heating a sample by raising the temperature above the melting point of the gallium oxide pellet to create a molten liquid and crystallizing the molten liquid by maintaining an oxygen atmosphere. Claim 7 A method for manufacturing a gallium oxide single crystal according to claim 6, wherein the sample preparation step (S1) comprises: a calcination step (S110) for removing organic impurities and moisture from the gallium oxide powder and converting the gallium oxide powder into a beta-phase gallium oxide powder; a mixing step (S120) for mixing the calcined gallium oxide powder; a cold pressing step (S130) for making the mixed gallium oxide powder into a compressed powder; and a sintering step (S140) for heat treating the cold-pressed gallium oxide powder to produce pellets. Claim 8 delete Claim 9 In claim 6, the single crystal growth step (S3) comprises: a step (S310) of starting the growth of a gallium oxide single crystal by driving a linear motor in a state where a molten gallium oxide is created at a temperature above the melting point of the growth preparation step (S2); a temperature maintenance step (S320) of controlling the flow rate and pressure of fuel gas and oxygen gas to maintain the temperature of the growth section; an oxygen atmosphere maintenance step (S330) of controlling the flow rate and pressure to maintain the oxygen atmosphere of the growth section; a growth step (S340) of growing the gallium oxide single crystal; a cooling step (S350) of cooling the gallium oxide single crystal that has been grown; and a single crystal extraction step (360) of extracting the gallium oxide single crystal grown on the upper part of the gallium oxide pellet. Claim 10 Gallium oxide single crystal characterized by being manufactured according to the manufacturing method of claim 6.

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