Preparation method of oxide single crystal thick film

Abstract

The invention provides a preparation method of an oxide single crystal thick film, which comprises the following steps of: transferring a metal source precursor into a crucible of a metal source area of vacuum growth equipment, and simultaneously placing a substrate on a substrate support of a growth area of the vacuum growth equipment; vacuumizing the vacuum growth equipment, and heating the metal source region and the growth region from room temperature; filling inert gas into the vacuum growth equipment, continuously heating the growth area to 900 DEG C to 1400 DEG C, and simultaneously continuously heating the metal source area to 1100 DEG C to 1500 DEG C; the temperatures of the metal source region and the growth region are kept unchanged, carrier gas and reaction gas are introduced into the vacuum growth equipment, the carrier gas directionally conveys metal sub-oxide formed by reaction after the metal source precursor is heated to the surface of the substrate, and the reaction gas and the metal sub-oxide are fully mixed and react on the surface of the substrate to grow the oxide single crystal thick film. The preparation method is simple, low in cost and suitable for large-scale batch production.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor materials, and in particular to a method for preparing an oxide single crystal thick film. Background Art

[0002] With the rapid development of new energy, rail transit, and smart grids, the demand for high-voltage, high-power semiconductor power devices is growing increasingly urgent. Semiconductor oxide single crystals, as a new type of ultra-wide bandgap semiconductor material, are highly suitable for applications in solar-blind ultraviolet detection and high-power electronic devices due to their large band gap (3.6eV to 4.9eV), high breakdown field strength, and excellent thermal stability. As a result, they have become a hot topic for research and development.

[0003] The growth of large-scale wafers of oxide single crystals is fundamental to the development of semiconductor power devices and integrated circuits. Due to the high melting point of gallium oxide (Gal) at 1740°C and the unique properties of oxide single crystals, they easily decompose to form oxygen, sub-oxides, and even metal elements under high-temperature, oxygen-deficient conditions. The growth of stable oxide single crystals using melt methods (CZ, EFG, and VB) requires a high-temperature, oxygen-rich environment. This limits the crucible selection, as only precious metals such as iridium and platinum-rhodium alloys can withstand corrosion in such high-temperature, oxygen-rich environments. This significantly increases the manufacturing cost of semiconductor power devices.

[0004] Among vapor phase epitaxy methods, processes like molecular beam epitaxy (MBE) and metal-organic chemical vapor deposition (MOCVD) require equipment that can cost tens of millions of yuan, impose stringent operating conditions, and require complex equipment structures and gas paths. Furthermore, processes like pulsed laser deposition (PLD), low-pressure chemical vapor deposition (LPCVD), and ultrasonic atomization chemical vapor deposition (Mist-CVD) have limited operating conditions, resulting in low oxide single crystal growth rates that are disproportionate to energy consumption, making them unsuitable for large-scale industrial production. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for preparing oxide single crystal thick films, which is used to improve the technical problem that the existing method for preparing oxide single crystal thick films is difficult to adapt to industrial production due to high production cost and low thick film growth rate.

[0006] To solve the above technical problems, the present invention provides a method for preparing an oxide single crystal thick film, the method comprising:

[0007] S10, transferring the metal source precursor into a crucible in a metal source area of ​​a vacuum growth device, and placing the substrate on a substrate holder in a growth area of ​​the vacuum growth device;

[0008] S20, evacuating the vacuum growth equipment and heating the metal source region and the growth region from room temperature;

[0009] S30, filling the vacuum growth equipment with an inert gas, and continuing to heat the growth area to 900° C. to 1400° C., while continuing to heat the metal source area to 1100° C. to 1500° C.;

[0010] S40, maintaining the temperature of the metal source region and the growth region unchanged, introducing a carrier gas and a reaction gas into the vacuum growth apparatus, wherein the carrier gas directionally transports the metal suboxide formed by the reaction of the metal source precursor after being heated to the substrate surface, fully mixes with the reaction gas, and reacts to grow a thick oxide single crystal film on the substrate surface.

[0011] Preferably, the metal source precursor is a uniform mixture of metal oxide powder having the same properties as the oxide single crystal thick film to be grown and its corresponding metal element particles.

[0012] Preferably, the material of the metal element particles is any one of Ga, Sn or In, and the material of the metal oxide powder is any one of Ga2O3, SnO2 or In2O3.

[0013] Preferably, the molar ratio of metal oxide powder to metal element particles in the metal source precursor is 1:(1-6).

[0014] Preferably, in step S10, the vacuum growth equipment includes an outer tube for constructing a chamber required for crystal growth and an inner tube for protecting the metal source precursor from oxidation, and the outer wall of the inner tube and the inner wall of the outer tube form a sandwich;

[0015] The inner tube includes a crucible for carrying a metal source precursor and a guide tube connected to the crucible. An output port is provided on the side of the guide tube close to the substrate holder. The output port is located in the growth zone and is coaxially opposite to the substrate holder.

[0016] Preferably, in step S10, the substrate includes any one of a single crystal substrate with any crystal plane orientation and homogeneous with the oxide single crystal thick film to be grown, a heterogeneous substrate, and a heterogeneous substrate on which a buffer layer material homogeneous with the oxide single crystal thick film to be grown is grown;

[0017] The heterogeneous substrate is any one of a c-plane sapphire single crystal substrate, a (100)-plane MgO single crystal substrate, an r-plane sapphire single crystal substrate, an m-plane sapphire single crystal substrate and a (001)-plane yttrium-stabilized zirconia single crystal substrate with an angle of 0 to 6 degrees along the a-axis.

[0018] Preferably, in steps S30 and S40, the carrier gas and the inert gas are at least one of Ar and N2, and the reaction gas is at least one of CO2 and O2.

[0019] Preferably, in step S40, the flow ratio of the carrier gas to the reaction gas introduced into the vacuum growth equipment is 4:(1-5).

[0020] Preferably, in step S40: the carrier gas directionally transports the metal suboxide to the substrate in the growth zone via the inner tube, and the reaction gas or mixed gas is transported to the substrate in the growth zone via the interlayer; the mixed gas includes reaction gas and inert gas.

[0021] Preferably, in step S20: the vacuum growth device is evacuated to make the air pressure in the vacuum growth device reach the ultimate pressure of the vacuum growth device, and the metal source region and the growth region are heated from room temperature to a temperature not higher than the temperature at which the metal source precursor reacts; in step S30: the air pressure in the vacuum growth device after being filled with inert gas is near atmospheric pressure; in step S40: the air pressure in the vacuum growth device is (0.8-1.2)×10 5 Pa; The oxide single crystal thick film is a stable phase oxide formed by complete oxidation of metal suboxides.

[0022] The beneficial effects of the present invention are as follows: Different from the prior art, the present invention adopts the suboxide chemical vapor transport (SOCVT) method, taking advantage of the fact that metal suboxides are gaseous or have a higher saturated vapor pressure than complete metal oxides or their metal elements, and through the vapor phase epitaxial growth method, reduces the growth temperature of metal oxide single crystals, so that high-valent stable phase metal oxide single crystals can be efficiently grown without reaching the melting point. The raw materials only need to be carried in an ordinary corundum crucible, which greatly reduces the cost of growing metal oxide single crystals. In addition, the present invention uses internal and external double tubes to protect the metal source precursor from oxidation while ensuring that the reaction gas and the metal source are evenly mixed only on the surface of the substrate, and the reaction grows a thick film of high-valent stable phase metal oxide single crystals, thereby improving the raw material evaporation efficiency and raw material utilization. The above-mentioned preparation method is simple and inexpensive, and can be built on the basis of an ordinary growth furnace through simple modification. All gas paths can be composed of ordinary corundum standard parts through simple processing. The operation steps are simple and do not involve complicated operation processes. In addition, the crystallization quality of the oxide single crystal thick film obtained is good, the growth rate of the single crystal thick film is high, and it can adapt to large-scale batch production, thereby reducing the production cost of the oxide single crystal thick film, and promoting the application of the oxide single crystal thick film in the field of wide bandgap semiconductor materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a flow chart of a method for preparing an oxide single crystal thick film provided by an embodiment of the present invention;

[0024] Figure 2This is a simplified structural diagram of a vacuum growth device in a method for preparing an oxide single crystal thick film provided by an embodiment of the present invention;

[0025] Figure 3 This is a process principle diagram of the method for preparing an oxide single crystal thick film provided in Example 1 of the present invention;

[0026] Figure 4a to Figure 4e is the XRD pattern of the β-Ga2O3 single crystal thick film obtained by the preparation method of the oxide single crystal thick film provided in Examples 1 to 5 of the present invention;

[0027] Figure 5a to Figure 5e The XRD rocking curve spectrum of the (-310) or (-620) crystal plane of the β-Ga2O3 single crystal thick film obtained by the preparation method of the oxide single crystal thick film provided in Examples 1 to 5 of the present invention;

[0028] Figure 6a to Figure 6g is a cross-sectional SEM image of an oxide single crystal thick film obtained by the method for preparing an oxide single crystal thick film provided in Examples 1 to 7 of the present invention;

[0029] Figure 7a to Figure 7g These are surface SEM images of the oxide single crystal thick films obtained by the methods for preparing oxide single crystal thick films provided in Examples 1 to 7 of the present invention.

[0030] Description of reference numerals:

[0031] 101 - Metal source precursor 102 - Substrate 200 - Vacuum growth equipment

[0032] 201-Crucible 202-Inner tube 203-Substrate holder

[0033] 204 - interlayer 205 - outer tube 210 - metal source area

[0034] 211 - First air inlet 212 - Second air inlet 220 - Growth area DETAILED DESCRIPTION

[0035] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0036] In order to solve the technical problem that the preparation method of oxide single crystals in the prior art is difficult to adapt to industrial production due to high production cost and low growth rate, the present invention adopts the SOCVT method to grow oxide single crystal thick films, with good crystallization quality and high single crystal thick film growth rate. The maximum growth rate can reach 251.4μm / h, which can be adapted to large-scale batch production, thereby reducing the production cost of oxide single crystal thick films and promoting the application of oxide single crystal thick films in the field of wide bandgap semiconductor materials.

[0037] See also Figures 1 to 2 , Figure 1 This is a flow chart of a method for preparing an oxide single crystal thick film provided by an embodiment of the present invention; Figure 2 : is a simplified structural diagram of a vacuum growth device 200 in a method for preparing an oxide single crystal thick film provided by an embodiment of the present invention; wherein the above-mentioned preparation method includes:

[0038] S10 , transferring the metal source precursor 101 into the crucible 201 of the metal source area 210 in the vacuum growth device 200 , and placing the substrate 102 on the substrate holder 203 of the growth area 220 in the vacuum growth device 200 .

[0039] Specifically, step S10 also includes: first, providing a metal source precursor 101. The metal source precursor 101 can be simply metal, but this will result in a low oxide film growth rate. For example, when the metal source precursor 101 is Ga, Ga is in liquid form at 1100°C to 1500°C. At this temperature, its saturated vapor pressure is low, making it difficult for the carrier gas to transport Ga from the crucible 201 in the metal source region 210 to the surface of the substrate 102, resulting in a low growth rate of the β-Ga2O3 film.

[0040] Preferably, the metal source precursor 101 is a uniform mixture of high-purity metal oxide powder and its corresponding high-purity metal element small particles of the same nature as the oxide single crystal thick film to be grown; the above-mentioned high-purity metal small particles and high-purity metal oxide powder are all purchased from the market or made through simple processing, and their prices are much lower than high-valent stable phase oxide single crystal thick films. Since the high-purity metal oxide powder purchased on the market does not have the characteristics of single crystal thick films, it cannot be directly used as large-size wide bandgap semiconductor material single crystal thick films.

[0041] Specifically, when the small particles of high-purity metal element are Ga, the corresponding high-purity metal oxide powder is Ga2O3 powder; when the small particles of high-purity metal element are Sn, the corresponding high-purity metal oxide powder is SnO2 powder; when the small particles of high-purity metal element are In, the corresponding high-purity metal oxide powder is In2O3 powder.

[0042] Preferably, the molar ratio of the metal oxide powder to its corresponding metal element particles in the metal source precursor 101 is 1:(1 to 6); at this time, an appropriate amount of metal oxide powder can react with the metal element particles at high temperature to generate gaseous metal suboxides or vapor of solid or liquid metal suboxides with high saturated vapor pressure, which is then transported to the surface of the substrate 102 by the carrier gas.

[0043] Then, a substrate 102 is provided. The substrate 102 is any one of: a single crystal substrate with any crystal plane orientation and homogeneous with the oxide single crystal thick film to be grown, a foreign substrate on which a buffer layer material homogeneous with the oxide single crystal thick film to be grown is grown, or a foreign substrate. The foreign substrate is any one of a c-plane sapphire single crystal substrate with an a-axis bevel angle of 0-6°, a (100)-plane MgO single crystal substrate, an r-plane sapphire single crystal substrate, an m-plane sapphire single crystal substrate, and a (001)-plane yttrium-stabilized zirconia single crystal substrate.

[0044] In this embodiment, a c-plane sapphire single crystal substrate with a 6° bevel along the a-axis can grow a better quality oxide single crystal thick film than an ordinary c-plane sapphire single crystal substrate, which can greatly improve the orientation and crystallinity of the oxide single crystal thick film. This is mainly due to the following reasons: First, the bevel changes the atomic arrangement and step structure on the surface of the substrate 102. This change provides a more favorable nucleation site and growth mode for the initial growth of the thick film, allowing the thick film to grow more uniformly and orderly, reducing the formation of defects. Second, the bevel can change the stress distribution on the surface, which helps to alleviate the stress generated by lattice mismatch and other reasons during the growth of the thick film, thereby reducing the dislocation density in the thick film and improving the crystallization quality of the thick film. Third, the special bevel angle can affect the diffusion and adsorption process of the deposited atoms, making it easier for the atoms in the thick film to find a suitable position for arrangement, thereby forming a more complete and higher-quality crystal structure.

[0045] Finally, a vacuum growth apparatus 200 is provided, and the metal source precursor 101 is transferred into the crucible 201 of the metal source region 210 of the vacuum growth apparatus 200. Simultaneously, the substrate 102 is placed on the substrate holder 203 of the growth region 220 of the vacuum growth apparatus 200. Specifically, before placing the substrate 102 on the substrate holder 203 of the growth region 220 of the vacuum growth apparatus 200, the substrate 102 is sequentially cleaned using acetone, anhydrous ethanol, and deionized water, and then blown dry using high-purity N2 gas to ensure the cleanliness of the substrate 102.

[0046] In an embodiment of the present invention, vacuum growth apparatus 200 includes a metal source region 210 and a growth region 220. An inner tube 202 is disposed in the center of metal source region 210. One end of inner tube 202 is connected to a first gas inlet 211, and the other end of inner tube 202 has an outlet located in growth region 220.

[0047] Specifically, the vacuum growth equipment 200 also includes: a substrate holder 203 for placing the substrate 102, an outer tube 205 for constructing the chamber required for crystal growth, the inner wall of the outer tube 205 and the outer wall of the inner tube 202 forming an interlayer 204 in the vacuum growth equipment 200, and one end of the interlayer 204 is connected to the second air inlet 212.

[0048] Specifically, the inner tube 202 includes the crucible 201 , which is fixedly connected to the flow guide tube. The inner tube 202 is coaxial with the substrate holder 203 , and the output port of the inner tube 202 is located 5 to 7 cm away from the substrate holder 203 in the growth zone 220 .

[0049] In the embodiment of the present invention, the vacuum growth equipment 200 is preferably a vertical growth furnace.

[0050] S20 , vacuuming the vacuum growth device 200 , and heating the metal source region 210 and the growth region 220 from room temperature.

[0051] Specifically, step S20 further includes:

[0052] First, the vacuum growth device 200 is evacuated so that the air pressure in the vacuum growth device 200 reaches the ultimate pressure of the vacuum growth device (0.01 to 5 Pa). Then, the temperature of the vacuum growth device 200 is heated from room temperature to a first preset temperature at a heating rate of 2 to 5°C / min through the heating program of the vacuum growth device 200. The first preset temperature is not higher than the temperature at which the metal source precursor reacts. Preferably, the first preset temperature is 150°C to 200°C. During the above heating process, continuous exhaust is performed to maintain the air pressure in the vacuum growth device 200 at 0.01 to 5 Pa, which helps to expel air and other impurity gases in the vacuum growth device 200 and create a clean environment.

[0053] S30 , inert gas is filled into the vacuum growth equipment 200 , and the growth area 220 is further heated to 900° C. to 1400° C., while the metal source area 210 is further heated to 1100° C. to 1500° C.

[0054] Specifically, when the temperature of the vacuum growth equipment 200 reaches the first preset temperature, 1 atm of inert gas is filled into the vacuum growth equipment 200 through the first air inlet 211 and all air valves are closed so that the air pressure in the vacuum growth equipment 200 is close to normal pressure. At this time, the inert gas can play a role in protecting and stabilizing the reaction environment, avoiding the metal source precursor 101 from evaporating in large quantities in advance during the heating process and causing waste of raw materials, thereby ensuring the utilization rate of raw materials for subsequent single crystal growth and reducing production costs.

[0055] Then, the temperature of the metal source area 210 is heated from the first preset temperature to 1100°C~1500°C at a heating rate of 5~10°C / min through the heating program of the vacuum growth equipment 200. At the same time, the temperature of the growth area 220 is heated from the first preset temperature to 900°C~1400°C at a heating rate of 5~10°C / min through the heating program of the vacuum growth equipment 200 to ensure that the temperature of the metal source area 210 is greater than the temperature of the growth area 220.

[0056] In this step, by setting the temperature of the metal source region 210 to be higher than the temperature of the growth region 220, the temperature distribution required for step S30 is provided. On the one hand, the higher temperature can accelerate the evaporation rate of the metal suboxide, so that the metal suboxide is transferred to the surface of the substrate 102 more quickly. On the other hand, when the reaction gas is CO2, it is ensured that CO2 exhibits reducing properties in the metal source region 210 and oxidizing properties in the growth region 220, so that the metal suboxide hardly reacts with CO2 in the metal source region 210, but reacts with CO2 on the surface of the substrate 102.

[0057] S40, keeping the temperatures of the metal source region 210 and the growth region 220 unchanged, introducing a carrier gas and a reaction gas into the vacuum growth equipment 200, the carrier gas directionally transports the metal suboxide formed by the reaction of the metal source precursor 101 after being heated to the surface of the substrate 102, fully mixes with the reaction gas, and reacts to grow a thick oxide single crystal film on the surface of the substrate 102.

[0058] Specifically, step S40 also includes: first, keeping the temperature of each temperature zone of the vacuum growth equipment 200 unchanged, continuously introducing a carrier gas into the growth equipment through the first air inlet 211, and continuously introducing a reaction gas or a gas mixed with a reaction gas and an inert gas in any proportion into the growth equipment through the gas valve of the second air inlet 212, and continuously discharging the reacted gas through the exhaust port below the growth zone 220; wherein the carrier gas and the inert gas are both at least one of Ar and N2, and the reaction gas is at least one of CO2 and O2.

[0059] Specifically, the carrier gas transports the gaseous metal suboxide or the vapor of the solid or liquid metal suboxide with high saturated vapor pressure formed by the reaction of the metal source precursor 101 after heating to the substrate 102 in the growth area 220. The reaction gas enters the substrate 102 in the growth area 220 from the interlayer 204, and the two are evenly mixed. At this time, the gas pressure in the vacuum growth equipment 200 is at or near atmospheric pressure, specifically 0.8×10 5 Pa~1.2×10 5 Pa.

[0060] In the first embodiment, the metal source precursor 101 is a mixture of Ga and Ga2O3, the carrier gas is Ar, and the reaction gas is CO2.

[0061] At this time, the main chemical reaction formula occurring in the metal source region 210 is as follows:

[0062] 4Ga(l)+Ga2O3(s)→3Ga2O(g)(1);

[0063] Since the Gibbs free energy of the following reaction (2) increases positively with increasing temperature until it is greater than 0, CO2 hardly oxidizes Ga2O in the metal source region 210. At this time, CO2 exhibits reducing properties, thereby ensuring the gas phase transport of Ga2O.

[0064] When the gaseous metal suboxide Ga2O is transported by the carrier gas to the surface of the substrate 102 in the growth zone 220, since the temperature of the substrate 102 is lower than that of the metal source region 210, the CO2 exhibits oxidizing properties and oxidizes the Ga2O to Ga2O3, thereby growing a β-Ga2O3 single crystal thick film. The main chemical reactions occurring in the growth zone 220 at this time are as follows:

[0065] 2Ga2O(g)+CO2(g)→2Ga2O3(s)+3CO(g)(2).

[0066] In the second embodiment, the metal source precursor 101 is a mixture of Ga and Ga2O3, the carrier gas is Ar, and the reaction gas is O2; wherein, since the vacuum growth equipment 200 is a "dual-pipeline design" (including the inner tube 202 channel and the interlayer 204 channel), O2 enters the growth zone 220 through the interlayer 204. This design can prevent O2 from oxidizing the metal Ga in the crucible 201 in the metal source region 210 to become Ga2O3 which is difficult to evaporate, thereby preventing reaction (1) from being carried out. It can also reduce the oxidation of Ga2O into Ga2O3 during transportation, and prevent it from reaching the surface of the substrate 102 to grow a Ga2O3 single crystal thick film, resulting in waste of metal source materials.

[0067] At this time, the main chemical reaction formula occurring in the metal source region 210 is as follows:

[0068] 4Ga(l)+Ga2O3(s)→3Ga2O(g)(1);

[0069] When the gaseous metal suboxide Ga2O is transported by Ar to the surface of the substrate 102 in the growth region 220, O2 can oxidize Ga2O to Ga2O3 to grow a β-Ga2O3 single crystal thick film. At this time, the main chemical reactions occurring in the growth region 220 are as follows:

[0070] Ga2O(g)+O2(g)→Ga2O3(s)(3);

[0071] In the third embodiment, the metal source precursor 101 is a mixture of Sn and SnO2, the carrier gas is Ar, and the reaction gas is CO2; at this time, the main chemical reaction formula occurring in the vacuum growth apparatus 200 is as follows:

[0072] In the metal source region 210: Sn(s)+SnO2(s)→2SnO(s)(4);

[0073] SnO(s)→SnO(g)(5);

[0074] In the growth zone 220: SnO(g) + CO2(g) → SnO2(s) + CO(g) (6);

[0075] SnO has a high saturated vapor pressure at 1100° C. to 1500° C., and is thus efficiently transported to the growth region 220 by Ar, and is fully mixed and reacted with CO 2 on the surface of the substrate 102 to grow a SnO 2 single crystal thick film.

[0076] In the fourth embodiment, the metal source precursor 101 is a mixture of In and In2O3, the carrier gas is Ar, and the reaction gas is CO2; at this time, the main chemical reaction formula occurring in the vacuum growth apparatus 200 is as follows:

[0077] In the metal source region 210: 4In(l)+In2O3(s)→3In2O(g)(7);

[0078] In the growth region 220: In2O(g)+2CO2(g)→In2O3(s)+2CO(g)(8);

[0079] In2O is in a gaseous state and is thus efficiently transported to the growth region 220 by Ar, where it is fully mixed and reacted with CO2 on the surface of the substrate 102 to grow an In2O3 single crystal thick film.

[0080] In step S40, the ratio of the carrier gas to the reactant gas flow rate introduced into the growth apparatus is 4:(1-5). If the reactant gas flow rate is too low, insufficient reactants may be provided, resulting in an incomplete reaction or poor product crystallization quality. Excessive reactant gas flow rate may waste resources, cause a runaway reaction, or generate unnecessary byproducts. This step, by precisely controlling the flow rates of the various gases, ensures uniform thickness, accurate composition, and high crystallization quality of the deposited oxide single crystal thick film.

[0081] In a specific embodiment, the flow rate of the carrier gas introduced into the growth device 200 is 50-300 sccm, and the flow rate of the reaction gas introduced into the growth device 200 is 50-200 sccm.

[0082] In this step, the maximum growth rate of the oxide single crystal thick film obtained using this preparation method can reach 251.4 μm / h (relative to the β-Ga2O3 single crystal thick film). The time for the carrier gas and reaction gas to be introduced is determined by the required thickness of the oxide single crystal film. The thicker the desired oxide single crystal film, the longer the carrier gas and reaction gas introduction time.

[0083] Afterwards, when the thickness of the oxide single crystal thick film reaches the preset target, the gas valves of the first gas inlet 211 and the second gas inlet 212 as well as the gas outlet valve are closed at the same time, and the cooling program is controlled to uniformly reduce the temperature of the vacuum growth equipment 200 from the second preset temperature to room temperature, and finally a high-valence stable phase metal oxide single crystal thick film is obtained.

[0084] In the vacuum growth device 200 of the method for preparing an oxide single crystal thick film provided in an embodiment of the present invention, the substrate 102 is placed on the substrate holder 203 located at the bottom of the vacuum growth device 200, and there is no need to fix the substrate 102 additionally. Compared with the method of fixing the substrate 102 on the top, it will not cause uneven force on the substrate 102 and will not introduce problems of doping impurities.

[0085] The effects of the above-mentioned method for preparing the oxide single crystal thick film are described below through specific examples.

[0086] Example 1:

[0087] See also Figure 3 , Figure 3 is a process principle diagram of the method for preparing an oxide single crystal thick film provided in Example 1 of the present invention; Figure 3 It can be seen that the specific preparation process of the method for preparing the oxide single crystal thick film provided in Example 1 of the present invention is as follows:

[0088] (1) A mixed raw material of 99.99% pure Ga and 99.99% pure Ga2O3 is provided. The above raw materials are obtained from the market, wherein the raw material Ga2O3 is a metal oxide powder of the same nature as the oxide single crystal thick film to be grown, and the molar ratio of Ga to Ga2O3 is 4:1 (Ga is 5.98g, Ga2O3 is 4.02g); the preparation method of the above mixed raw materials is as follows: a certain mass of Ga2O3 powder is weighed using weighing paper and an electronic balance; a reagent bottle containing Ga is slightly heated (the melting point of metallic Ga is 29.76°C) to slightly melt the solid Ga, and liquid Ga is sucked and transferred using a pipette; a mixture of Ga droplets and Ga2O3 powder is stirred using a ceramic rod until the Ga is dispersed from large droplets into small droplets covered by Ga2O3 powder, ensuring sufficient contact between Ga and Ga2O3.

[0089] (2) A substrate 102 is provided. The substrate 102 is a c-plane sapphire single crystal substrate that is beveled at 6° along the a-axis.

[0090] (3) The mixed raw material of Ga and Ga2O3 is loaded into the crucible 201; the substrate 102 is attached to the substrate holder 203 and then placed in the growth area 220 of the vacuum growth equipment 200;

[0091] (4) The temperature of the vacuum growth device 200 was heated from room temperature to 150° C. at a heating rate of 5° C. / min. During the heating process, a mechanical pump was turned on to continuously pump air before the temperature reached 150° C., maintaining the pressure in the chamber of the vacuum growth device 200 at 5 Pa. At 150° C., 1 atm of Ar was filled into the vacuum growth device 200 and all gas valves were closed.

[0092] (5) The temperature of the metal source region 210 is heated from 150°C to 1400°C at a heating rate of 10°C / min through the heating program of the vacuum growth device 200. At the same time, the temperature of the growth region 220 is heated from 150°C to 1300°C at a heating rate of 10°C / min through the heating program of the vacuum growth device 200. Then, the above temperature is kept unchanged, all the gas valves are opened, and Ar gas is introduced into the inner tube 202 of the vacuum growth device 200 and its flow rate is maintained at 200 sccm. The Ar gas introduction time is 30 minutes. At the same time, the reaction gas CO2 is introduced into the interlayer 204 of the vacuum growth device 200 and its flow rate is maintained at 150 sccm. The CO2 introduction time is 30 minutes, ensuring that the Ar:CO2 flow ratio is 4:3. At the same time, the rotation speed of the substrate holder 203 is maintained at 10 rpm, and a β-Ga2O3 single crystal thick film is deposited and grown on the surface of the substrate 102. At this time, the gas pressure in the vacuum growth device 200 is 8×10 4 Pa (i.e., using a mechanical pump of the vacuum growth apparatus 200 to extract air, and using a throttle valve at the outlet to control the air pressure in the growth apparatus);

[0093] (6) After the growth is completed, all air valves are closed and each temperature zone is cooled at a cooling rate of 5°C / min.

[0094] Example 2:

[0095] The method for preparing the oxide single crystal thick film provided in Example 2 of the present invention is substantially the same as the method for preparing the oxide single crystal thick film provided in Example 1 of the present invention, except that: in step (5), the gas pressure in the vacuum growth apparatus 200 is adjusted to 1.0×10 5 Pa.

[0096] Example 3:

[0097] The method for preparing the oxide single crystal thick film provided in Example 3 of the present invention is substantially the same as the method for preparing the oxide single crystal thick film provided in Example 1 of the present invention, except that: in step (5), the gas pressure in the vacuum growth apparatus 200 is adjusted to 1.2×105 Pa (i.e., reducing the flow rate of the throttle valve at the gas outlet of the vacuum growth apparatus 200 so that there is enough CO2 to fully react with Ga2O at the substrate 102).

[0098] Example 4:

[0099] The method for preparing the oxide single crystal thick film provided in Example 4 of the present invention is substantially the same as the method for preparing the oxide single crystal thick film provided in Example 1 of the present invention, except that: in step (5), the gas pressure in the vacuum growth apparatus 200 is adjusted to 1.0×10 5 Pa; in step (5), the flow rate of the reaction gas CO2 into the interlayer 204 of the vacuum growth device 200 is 100 sccm, and the introduction time of CO2 is 30 min to ensure that the Ar: CO2 flow ratio is 2:1.

[0100] Example 5:

[0101] The method for preparing the oxide single crystal thick film provided in Example 5 of the present invention is substantially the same as the method for preparing the oxide single crystal thick film provided in Example 1 of the present invention, except that: in step (5), the gas pressure in the vacuum growth apparatus 200 is adjusted to 1.0×10 5 Pa; in step (5), the flow rate of the reaction gas CO2 introduced into the interlayer 204 of the vacuum growth apparatus 200 is 250 sccm, and the introduction time of CO2 is 30 min, ensuring that the Ar: CO2 flow ratio is 4:5.

[0102] Example 6:

[0103] The method for preparing the oxide single crystal thick film provided in Example 6 of the present invention is substantially the same as the method for preparing the oxide single crystal thick film provided in Example 1 of the present invention, except that:

[0104] In step (1), a mixed raw material of 99.99% pure Sn and 99.99% pure SnO2 is provided, and the molar ratio of Sn to SnO2 is 1:1 (Sn is 4.41g, SnO2 is 5.59g); the above mixed raw material is prepared as follows: a certain mass of Sn powder with a particle size less than 30μm and SnO2 powder with a particle size less than 70nm are weighed using weighing paper and an electronic balance; and the Sn powder and SnO2 powder are ground using a mortar until they are uniformly mixed.

[0105] In step (2), a substrate 102 is provided. The substrate 102 is a c-plane sapphire single crystal substrate with a 6° bevel along the a-axis and including a SnO2 buffer layer prepared by magnetron sputtering.

[0106] In step (3), a mixture of Sn and SnO2 is loaded into the crucible 201; the substrate 102 is attached to the substrate holder 203 and then placed in the growth zone 220 of the vacuum growth device 200;

[0107] In step (5), the temperature of the metal source region 210 is heated from 150°C to 1400°C at a heating rate of 10°C / min by the heating program of the vacuum growth device 200, and the temperature of the growth region 220 is heated from 150°C to 1200°C at a heating rate of 10°C / min by the heating program of the vacuum growth device 200; then, the above-mentioned temperatures are kept unchanged, all the gas valves are opened, and the flow rate of Ar gas is 200 sccm into the inner tube 202 of the vacuum growth device 200, and the Ar gas is introduced for 360 min; at the same time, the flow rate of the reaction gas CO2 is 200 sccm into the interlayer 204 of the vacuum growth device 200, and the CO2 is introduced for 360 min, ensuring that the Ar:CO2 flow ratio is 1:1, and the rotation speed of the substrate holder 203 is kept at 10 rpm, and a SnO2 single crystal thick film is deposited and grown on the surface of the substrate 102; at this time, the gas pressure in the vacuum growth device 200 is 1.0×10 5 Pa.

[0108] Example 7:

[0109] The method for preparing the oxide single crystal thick film provided in Example 7 of the present invention is substantially the same as the method for preparing the oxide single crystal thick film provided in Example 6 of the present invention, except that:

[0110] In step (2), a substrate 102 is provided. The substrate 102 is an r-plane sapphire single crystal substrate including a SnO2 buffer layer prepared by magnetron sputtering.

[0111] In step (5), the temperature of the metal source region 210 is heated from 150°C to 1400°C at a heating rate of 10°C / min by the heating program of the vacuum growth device 200, and the temperature of the growth region 220 is heated from 150°C to 1100°C at a heating rate of 10°C / min by the heating program of the vacuum growth device 200; then, the above-mentioned temperatures are kept unchanged, all the gas valves are opened, and the flow rate of Ar gas is 200 sccm into the inner tube 202 of the vacuum growth device 200, and the Ar gas is introduced for 180 minutes; at the same time, the flow rate of the reaction gas CO2 is 200 sccm into the interlayer 204 of the vacuum growth device 200, and the CO2 is introduced for 180 minutes, ensuring that the Ar:CO2 flow ratio is 1:1, and the rotation speed of the substrate holder 203 is kept at 10 rpm, and a SnO2 single crystal thick film is deposited and grown on the surface of the substrate 102; at this time, the gas pressure in the vacuum growth device 200 is 1.0×10 5 Pa.

[0112] See also Figures 4a to 4e , Figures 4a to 4e is the HR-XRD (high resolution X-ray diffraction) spectrum of the oxide single crystal thick film obtained by the preparation method of the oxide single crystal thick film provided in Examples 1 to 5 of the present invention; Figures 4a to 4e It can be seen that in the oxide single crystal thick films prepared in Examples 1 to 5 of the present invention: the diffraction peak corresponding to the (-310) crystal plane (β-Ga2O3) appears at 37.25°, and the diffraction peak corresponding to the (-620) crystal plane (β-Ga2O3) appears at 79.47°. The above crystal phase structure characterization proves that the β-Ga2O3 single crystal thick film grown by the preparation method of the oxide single crystal thick film provided in Examples 1 to 5 of the present invention is (-310) oriented.

[0113] See also Figures 5a to 5e , Figure 5a to Figure 5e The XRD rocking curve of the (-310) or (-620) crystal plane of the β-Ga2O3 single crystal thick film obtained by the preparation method of the oxide single crystal thick film provided in Examples 1 to 5 of the present invention is shown; Figure 5a to Figure 5e It can be seen that the full width at half maximum (FWHM) of the XRD rocking curve corresponding to the (-620) crystal plane in the oxide single crystal thick film (β-Ga2O3) prepared in Example 1 of the present invention is 0.177°; the full width at half maximum of the XRD rocking curve corresponding to the (-620) crystal plane in the oxide single crystal thick film (β-Ga2O3) prepared in Example 2 of the present invention is 0.116°; the full width at half maximum of the XRD rocking curve corresponding to the (-620) crystal plane in the oxide single crystal thick film prepared in Example 3 of the present invention is 0.170°; the full width at half maximum of the XRD rocking curve corresponding to the (-310) crystal plane in the oxide single crystal thick film prepared in Example 4 of the present invention is 0.182°; the full width at half maximum of the XRD rocking curve corresponding to the (-310) crystal plane in the oxide single crystal thick film prepared in Example 5 of the present invention is 0.245°.

[0114] Specifically, the results of the half-width at half maximum of the XRD rocking curve corresponding to the (-310) or (-620) crystal plane in the oxide single crystal thick film (β-Ga2O3) prepared in Examples 1 to 5 of the present invention show that the (-310) oriented β-Ga2O3 single crystal thick film prepared in Examples 1 to 5 of the present invention has high crystallization quality and fewer defects.

[0115] See also Figure 6a to Figure 6e , Figure 6a to Figure 6e is a cross-sectional SEM (scanning electron microscope) image of an oxide single crystal thick film obtained by the method for preparing an oxide single crystal thick film provided in Examples 1 to 5 of the present invention; wherein Figure 6aIt can be seen that the β-Ga2O3 single crystal thick film prepared in Example 1 of the present invention is uniform and dense, and its thickness can reach 35.1 μm; Figure 6b It can be seen that the β-Ga2O3 single crystal thick film prepared in Example 2 of the present invention is uniform and dense, and its thickness can reach 56.7μm; Figure 6c It can be seen that the β-Ga2O3 single crystal thick film prepared in Example 3 of the present invention is uniform and dense, and its thickness can reach 117.4 μm; Figure 6d It can be seen that the β-Ga2O3 single crystal thick film prepared in Example 4 of the present invention is uniform and dense, and its thickness can reach 55.4μm; Figure 6e It can be seen that the β-Ga2O3 single crystal thick film prepared in Example 5 of the present invention is uniform and dense, and its thickness can reach 80.1

[0116] μm.

[0117] Specifically, by comparing Examples 1 to 3, it can be seen that when the pressure in the vacuum growth device 200 in step (5) is 1.2×10 5 Pa, the prepared β-Ga2O3 single crystal thick film is thicker.

[0118] Specifically, by comparing Example 2, Example 4 and Example 5, it can be seen that when the flow rate of the reaction gas CO2 introduced into the interlayer 204 of the vacuum growth equipment 200 in step (5) is 250 sccm and the CO2 introduction time is 30 minutes, that is, the Ar:CO2 flow ratio is 4:5, the prepared β-Ga2O3 single crystal thick film is thicker.

[0119] See also Figure 6f to Figure 6g , Figure 6f to Figure 6g is a cross-sectional SEM image of an oxide single crystal thick film obtained by the method for preparing an oxide single crystal thick film provided in Examples 6 to 7 of the present invention; wherein Figure 6f It can be seen that the SnO2 thick film prepared in Example 6 of the present invention is relatively uniform and dense, and its thickness can reach 18.2 μm; Figure 6g It can be seen that the SnO2 thick film prepared in Example 7 of the present invention is relatively uniform and dense, and its thickness can reach 25.6 μm.

[0120] See also Figure 7a to Figure 7e , Figure 7a to Figure 7e is a surface SEM image of the oxide single crystal thick film obtained by the method for preparing the oxide single crystal thick film provided in Examples 1 to 5 of the present invention; wherein Figure 7a As shown in Figure 7e, the surface morphology of the β-Ga2O3 single crystal thick film prepared in Examples 1 to 5 of the present invention is smooth and has fewer surface defects.

[0121] See also Figure 7f to Figure 7g , Figure 7f to Figure 7gis a surface SEM image of the oxide single crystal thick film obtained by the preparation method of the oxide single crystal thick film provided in Examples 6 to 7 of the present invention; Figure 7f It can be seen that the SnO2 thick film prepared in Example 6 of the present invention is relatively smooth and has its characteristic surface texture; Figure 7g It can be seen that the SnO2 thick film prepared in Example 7 of the present invention is relatively smooth and has its characteristic surface texture.

[0122] Compared with the prior art, the advantages of the method for preparing the oxide single crystal thick film provided by the present invention are as follows:

[0123] (1) The preparation method provided by the present invention uses a uniform mixture of metal elemental particles with a purity of 99.99% or more and metal oxide powder with a purity of 99.99% or more (the same as the oxide single crystal thick film to be grown), which can fully react at high temperature to generate metal suboxides as the metal source for growing the oxide single crystal thick film, which can effectively improve the raw material utilization rate of the metal source; at the same time, the metal suboxide is in a gaseous state or has a higher saturated vapor pressure than the metal oxide in the stable phase of complete metal oxidation, thereby accelerating the evaporation of the metal source, thereby effectively improving the growth rate of the oxide single crystal thick film;

[0124] (2) The preparation method provided by the present invention selects a c-plane sapphire single crystal substrate with a 0-6° bevel along the a-axis or a c-plane sapphire single crystal substrate with a buffer layer grown thereon, which can significantly improve the orientation and crystallinity of the oxide single crystal thick film, wherein the material of the buffer layer is the same as that of the oxide single crystal thick film;

[0125] (3) The preparation method provided by the present invention mainly uses CO2 as the reaction gas. Compared with O2, which has strong oxidizing properties, CO2 can show both oxidizing and reducing properties in different temperature ranges. In the growth zone 220 with a lower temperature, CO2 can oxidize the gaseous metal suboxide or the vapor of solid or liquid metal suboxide with high saturated vapor pressure into a high-valent stable phase metal oxide. At this time, CO2 shows oxidizing properties; in the high-temperature zone, since the Gibbs free energy of CO2 and metal suboxide to form a complete oxide increases positively with temperature until it is greater than 0, CO2 does not tend to oxidize the metal suboxide. At this time, CO2 shows reducing properties, thereby ensuring the gas phase transport of the metal suboxide.

[0126] (4) In the preparation method provided by the present invention, the vacuum growth device 200 has the following advantages by providing an inner tube 202 in the metal source region 210 and an outer tube 205 of the vacuum growth device 200 to form a double-pipe design: on the one hand, it prevents the metal or metal suboxide from being oxidized by the reaction gas to form a stable phase metal oxide that is not easily evaporated; on the other hand, it utilizes the carrier gas to effectively and directionally transport the metal suboxide, so that the metal suboxide and the oxygen source gas (i.e., the reaction gas) meet only in the region where the substrate 102 is located (i.e., the growth region 220) and an effective oxidation reaction occurs, thereby growing a high-valence stable phase metal oxide single crystal thick film;

[0127] (5) The outer tube 205 of the vacuum growth device 200 of the preparation method provided by the present invention, the crucible 201 for holding the metal source precursor 101, and the inner tube 202 consisting of the guide tube fixedly connected thereto are all standard parts of ordinary corundum, which are easy to process and low in cost; the vacuum growth device 200 has multiple independently controlled temperature ranges, the metal source zone 210 is set at a temperature of 1100°C to 1500°C, and the growth zone 220 is set at a temperature of 900°C to 1400°C, and a high-valence stable phase metal oxide single crystal thick film can be grown in a temperature range far below the melting point of the oxide;

[0128] (6) In the preparation method provided by the present invention, the growth gas pressure in the vacuum growth device 200 is atmospheric pressure or near atmospheric pressure; the flow ratio of the carrier gas to the reaction gas introduced into the growth device is 4:(1-5), which ensures the crystallization quality of the high-valent stable phase metal oxide single crystal thick film while ensuring the thick film growth rate, and the maximum growth rate can reach 251.4μm / h.

[0129] In summary, different from the prior art, the present invention provides a method for preparing an oxide single crystal thick film, the method comprising: first, transferring a metal source precursor 101 into a crucible 201 of a metal source region 210 in a vacuum growth device 200, and placing a substrate 102 on a substrate holder 203 of a growth region 220 in the vacuum growth device 200; second, evacuating the vacuum growth device 200 to maintain the gas pressure at the ultimate pressure of the vacuum device (0.01-5 Pa), and heating the growth region 220 and the metal source region 210 from room temperature to 150°C-200°C. ℃; again, the growth device 200 is filled with inert gas to make its gas pressure close to normal pressure, the temperature of the growth zone 220 is heated to 900℃~1400℃, and the temperature of the metal source zone 210 is heated to 1100℃~1500℃; finally, the temperatures of the growth zone 220 and the metal source zone 210 are kept unchanged, and the carrier gas and the reaction gas are introduced into the vacuum growth device 200. The carrier gas directionally transports the metal suboxide formed by the reaction of the metal source precursor 101 after being heated to the surface of the substrate 102, fully mixes with the reaction gas, and reacts on the surface of the substrate 102 to grow a thick oxide single crystal film. The present invention utilizes the suboxide chemical vapor transport (SOCVT) method, taking advantage of the fact that metal suboxides are gaseous or have a higher saturated vapor pressure than complete metal oxides or their metal elements. Through vapor phase epitaxy, the growth temperature of metal oxide single crystals is lowered, allowing efficient growth of high-valent, stable-phase metal oxide single crystals without reaching the melting point. The raw materials only need to be carried in an ordinary corundum crucible, significantly reducing the cost of growing metal oxide single crystals. Furthermore, the present invention utilizes internal and external dual tubes to protect the metal source precursor from oxidation while ensuring that the reaction gas and metal source are uniformly mixed only on the substrate surface. This allows for the reaction to grow a thick film of high-valent, stable-phase metal oxide single crystals, improving both raw material evaporation efficiency and raw material utilization. The oxide single crystal thick film preparation method of the present invention is simple and inexpensive, and can be constructed by simply modifying an ordinary growth furnace. All gas paths can be constructed by simply processing ordinary corundum standard parts; the operation steps are simple and do not involve complicated operation processes; the prepared oxide single crystal thick film has good crystallization quality and a high growth rate of the single crystal thick film, and can be adapted to large-scale batch production, thereby reducing the production cost of the oxide single crystal thick film and promoting the application of the oxide single crystal thick film in the field of wide bandgap semiconductor materials.

[0130] It should be noted that the above embodiments all belong to the same inventive concept, and the description of each embodiment has its own focus. For any details not described in individual embodiments, reference may be made to the description in other embodiments.

[0131] The above embodiments merely illustrate the implementation methods of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the patent. It should be noted that a person skilled in the art may make a number of modifications and improvements without departing from the concept of the present invention, and these modifications and improvements fall within the scope of protection of the present invention. Therefore, the scope of protection of the patent for this invention shall be based on the appended claims.

Claims

1. A method for preparing an oxide single crystal thick film, characterized in that: The method comprises: S10, transferring the metal source precursor into a crucible in a metal source region of a vacuum growth device, and placing a substrate on a substrate holder in a growth region of the vacuum growth device; S20, evacuating the vacuum growth device, and heating the metal source region and the growth region from room temperature; S30, filling the vacuum growth device with an inert gas, and continuing to heat the growth zone to 900° C. to 1400° C., and simultaneously continuing to heat the metal source zone to 1100° C. to 1500° C.; S40, keeping the temperatures of the metal source area and the growth area unchanged, introducing a carrier gas and a reaction gas into the vacuum growth equipment, wherein the carrier gas directionally transports the metal suboxide formed by the reaction of the metal source precursor after being heated to the surface of the substrate, is fully mixed with the reaction gas, and reacts to grow a single crystal thick oxide film on the surface of the substrate.

2. The method for preparing an oxide single crystal thick film according to claim 1, characterized in that: In the step S10, the metal source precursor is a uniform mixture of metal oxide powder having the same properties as the oxide single crystal thick film to be grown and its corresponding metal element particles.

3. The method for preparing an oxide single crystal thick film according to claim 2, characterized in that: The material of the metal element particles is any one of Ga, Sn or In, and the material of the metal oxide powder is any one of Ga2O3, SnO2 or In2O3.

4. The method for preparing an oxide single crystal thick film according to claim 2, characterized in that: The molar ratio of the metal oxide powder to the metal element particles in the metal source precursor is 1:(1-6).

5. The method for preparing an oxide single crystal thick film according to claim 1, characterized in that: In the step S10, the vacuum growth equipment includes an outer tube for constructing a chamber required for crystal growth and an inner tube for protecting the metal source precursor from oxidation, and the outer wall of the inner tube and the inner wall of the outer tube form a sandwich; The inner tube comprises a crucible for carrying the metal source precursor and a guide tube connected to the crucible, and an output port is arranged on a side of the guide tube close to the substrate holder, and the output port is located in the growth zone and coaxially opposite to the substrate holder.

6. The method for preparing an oxide single crystal thick film according to claim 1, characterized in that: In the step S10, the substrate includes any one of a single crystal substrate with any crystal plane orientation and homogeneous with the oxide single crystal thick film to be grown, a heterogeneous substrate, and a heterogeneous substrate on which a buffer layer material homogeneous with the oxide single crystal thick film to be grown is grown; The heterogeneous substrate is any one of a c-plane sapphire single crystal substrate beveled 0 to 6 degrees along the a-axis, a (100)-plane MgO single crystal substrate, an r-plane sapphire single crystal substrate, an m-plane sapphire single crystal substrate and a (001)-plane yttrium-stabilized zirconia single crystal substrate.

7. The method for preparing an oxide single crystal thick film according to claim 1, characterized in that: In the steps S30 and S40, the carrier gas and the inert gas are at least one of Ar and N2, and the reaction gas is at least one of CO2 and O2.

8. The method for preparing an oxide single crystal thick film according to claim 7, characterized in that: In the step S40, the flow ratio of the carrier gas to the reaction gas introduced into the vacuum growth device is 4:(1-5).

9. The method for preparing an oxide single crystal thick film according to claim 5, characterized in that: In the step S40: the carrier gas transports the metal suboxide to the substrate in the growth zone via the inner tube, and the reaction gas or mixed gas is transported to the substrate in the growth zone via the interlayer; the mixed gas includes the reaction gas and an inert gas.

10. The method for preparing an oxide single crystal thick film according to claim 1, characterized in that: In the step S20, the vacuum growth device is evacuated to make the air pressure in the vacuum growth device reach the limit pressure of the vacuum growth device, and the metal source region and the growth region are heated from room temperature to a temperature not higher than the temperature at which the metal source precursor reacts; in the step S30, the air pressure in the vacuum growth device after being filled with inert gas is near normal pressure; in the step S40, the air pressure in the vacuum growth device is (0.8-1.2)×10 5 Pa; the oxide single crystal thick film is a stable phase oxide formed by complete oxidation of the metal suboxide.

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