Preparation method of alpha-phase gallium oxide film

Abstract

The invention discloses a preparation method of an alpha-phase gallium oxide thin film, which comprises the following steps of: preparing a precursor solution according to an influence rule of fogdrop characteristics on the quality of the alpha-phase gallium oxide thin film; cleaning the substrate slice; placing a substrate slice and cleaning gas in a reaction cavity; heating and controlling the temperature of the reaction cavity; atomizing, conveying and depositing the precursor solution; cooling the reaction cavity and taking out the gallium oxide thin film, and controlling the height of the horizontal channel reaction cavity, the atomization power and the atomization frequency to realize accurate regulation and control on fogdrop characteristics, so as to prepare the high-quality alpha-phase gallium oxide thin film. Compared with other film preparation modes, the method does not need a vacuum environment, is simple in process and environment-friendly, and has a commercialized prospect of realizing large-area alpha-phase gallium oxide film preparation with low cost and high quality.

Description

Technical Field

[0001] The invention relates to the technical field of semiconductor film preparation, and in particular to a method for preparing an alpha-phase gallium oxide film. Background Art

[0002] Driven by the global energy transformation and the "dual carbon" strategy, my country's demand for high-performance electronic devices in the fields of new energy vehicles, ultra-high voltage transmission, and national defense equipment is becoming increasingly urgent. Gallium oxide (Ga2O3), as the fourth-generation ultra-wide bandgap semiconductor material, has a wider bandgap width, higher critical breakdown field strength, and better Baliga figure of merit compared to silicon (Si), silicon carbide (SiC), and gallium nitride (GaN). It is an ideal material to meet the high power, low loss, and high performance requirements of future electronic devices.

[0003] α-Ga2O3, as a crystalline phase of gallium oxide, has a wider bandgap (5.3 eV) than Si (1.1 eV), SiC (3.3 eV), GaN (3.3 eV) and β-Ga2O3 (4.8 eV), and a breakdown field strength of up to 10 MV / cm, which is 4 times that of SiC (2.5 MV / cm) and 3 times that of GaN (3.3 MV / cm). As a key parameter for measuring the efficiency of semiconductor devices, α-Ga2O3 has a more excellent Baliga figure of merit (6726), which is 2 times that of β-Ga2O3, 20 times that of SiC and 8 times that of GaN, and has great application potential in the field of high-performance, low-power, high-power devices.

[0004] At the same time, since α-Ga2O3 is a corundum structural material, it has a low lattice mismatch with the same corundum-type oxide M2O3 (M = Al, In, Fe, Cr, V, Ti, Rh, Ir, etc.), and is not prone to phase separation problems during the alloying process. It has significant alloying advantages and can achieve extremely wide band gap regulation of 2.8-9 eV. Elemental oxides such as Rh, Ir and Cr are expected to achieve high-quality p-type doping and can be used with α-Ga2O3 to construct pn junction devices, effectively making up for the difficulty of p-type doping of gallium oxide materials and providing more possibilities for the development of new oxide semiconductor devices.

[0005] However, as a thermodynamically metastable phase, α-Ga2O3 can only be prepared by epitaxy. Compared with other thin film epitaxy methods, Mist Chemical Vapor Deposition (Mist-CVD) is one of the most commercially promising technologies for achieving low-cost, high-quality, large-area thin film epitaxy, due to its advantages such as no need for a vacuum environment, simple process and environmental friendliness.

[0006] During the process of epitaxial growth of thin films by Mist-CVD, the core of this technology lies in delivering the gallium source to the surface of the high-temperature substrate through atomized droplets. Subsequently, a series of reactions occur on the substrate surface for the epitaxial growth of the thin film. During this process, the characteristics of the droplets (flow rate, quantity, size) are the key factors affecting the quality of the gallium oxide thin film grown by the Mist-CVD method. However, there is currently a gap in the mechanism of the effect of droplet characteristics on the epitaxial growth of α-phase gallium oxide thin films by the Mist-CVD method, and the comprehensive quality of α-phase gallium oxide thin films prepared by the Mist-CVD method still needs to be further improved. Summary of the Invention

[0007] The present invention aims at the deficiencies of the existing technology and provides a method for preparing α-phase gallium oxide thin films. According to the influence law of droplet characteristics on the quality of α-phase gallium oxide thin films, the precise control of droplet characteristics is achieved by controlling the height of the horizontal channel reaction chamber, the atomization power, and the atomization frequency, thereby preparing high-quality α-phase gallium oxide thin films. Compared with other preparation methods, it does not require a vacuum environment, has a simple process and is environmentally friendly, and has the commercial prospect of realizing the preparation of large-area α-phase gallium oxide thin films at low cost and high quality.

[0008] To achieve the above object, the present invention provides a method for preparing α-phase gallium oxide thin films, including the following steps: Step 1: Select a gallium compound to prepare a precursor solution; Step 2: Clean the substrate wafer to remove organic dirt and chemical substance residues on the surface of the substrate wafer; Step 3: Place the substrate wafer at a set position in the reaction chamber, and use a dilution gas to clean the reaction chamber to remove natural air; Step 4: Heat the reaction chamber to raise its temperature. Wait until the temperature reaches the target temperature and maintain it to make the temperature in the reaction chamber uniform and stable; Step 5: Atomize the precursor solution and transport the droplets to the reaction chamber for deposition reaction on the substrate wafer; Step 6: Stop atomization, stop heating the reaction chamber, and stop transporting the dilution gas at intervals in sequence until the reaction chamber reaches the cooling temperature and stop transporting the carrier gas, and then take out the gallium oxide thin film wafer.

[0009] Further, the specific content of Step 1 is as follows: Step 1.1: Select high-purity gallium acetylacetonate as the gallium source precursor substance for growing gallium oxide thin films; Step 1.2: Add gallium acetylacetonate to deionized water and drop hydrochloric acid with a concentration of 0.5 - 3% to prepare a 0.02 - 0.08 mol / L gallium acetylacetonate solution; Step 1.3: Put the prepared gallium acetylacetonate solution into the atomization chamber for standby.

[0010] Preferably, step 1 is specifically as follows: Step 1.1: Select high-purity gallium chloride as the gallium source precursor material for growing gallium oxide thin film; Step 1.2: Dissolve gallium chloride in deionized water to prepare a 0.1–0.5 mol / L gallium chloride solution; Step 1.3: Place the prepared gallium chloride solution in the atomization chamber for standby.

[0011] Furthermore, step 2 is specifically as follows: Step 2.1: Select the substrate wafer required for growing α-phase gallium oxide thin film; The substrate wafer is made of corundum-type oxide formed by any one of the elements Al, In, Fe, Cr, V, Ti, Rh, or Ir, or SiC or diamond; Step 2.2: Ultrasonically clean the substrate wafer with acetone, ethanol, and deionized water respectively to remove the organic dirt and chemical residue on the surface of the substrate wafer.

[0012] Furthermore, step 3 is specifically as follows: Step 3.1: A reaction chamber is arranged inside the quartz tube, a tube furnace is arranged outside the quartz tube, and a groove for accommodating the substrate wafer is arranged in the reaction chamber; Step 3.2: Place the substrate wafer in the groove; Step 3.3: Pass a dilution gas into the quartz tube to remove the residual air, and the dilution gas is any one of oxygen, nitrogen, air, argon, or helium.

[0013] Furthermore, in step 3.1, a horizontal microchannel is arranged inside the quartz tube as the reaction chamber, and the height of the horizontal microchannel is controlled to be 1–10 mm.

[0014] Furthermore, step 4 is specifically as follows: Step 4.1: Control the reaction chamber to rise to the target temperature in the range of 420–480 °C at a rate of 10 °C / min; Step 4.2: Maintain the target temperature for 10 min to make the temperature in the reaction chamber uniform and stable.

[0015] Furthermore, step 5 is specifically as follows: Step 5.1: Atomize the precursor solution; Step 5.2: Open the carrier gas and the dilution gas to transport the droplets to the reaction chamber, and the carrier gas is any one of oxygen, nitrogen, air, argon, or helium; Step 5.3: Control the deposition reaction time in the reaction chamber to obtain a gallium oxide thin film with the required thickness.

[0016] Further, in step 5.1, an ultrasonic atomizer is used to atomize the precursor solution, and the operating frequency of the ultrasonic atomization sheet is selected to be 1 - 5 MHz.

[0017] Further, step 6 is specifically as follows: Step 6.1: Stop atomizing the precursor solution and maintain the delivery of the carrier gas and the dilution gas. Step 6.2: Stop heating the reaction chamber, close the delivery of the dilution gas, and maintain the delivery of the carrier gas; control the temperature of the reaction chamber to decrease at a rate lower than 10 °C / min. Step 6.3: After the reaction chamber has cooled to room temperature, close the carrier gas and take out the gallium oxide thin film sheet.

[0018] The beneficial effects of this solution can be known from the description of the above solution. Compared with the prior art, it has the following beneficial effects: (1) This solution adopts a horizontal microchannel - type reaction chamber structure. Compared with the inclined - type and vertical - type reaction chambers, the horizontal microchannel - type reaction chamber can better control the temperature field and flow field distribution in the reaction chamber, making the temperature field and flow field distribution more uniform, and thus effectively improving the uniformity of the thin film. (2) The droplet characteristics (flow rate, size, and quantity) are the key factors in the process of growing α - phase gallium oxide thin films by the Mist - CVD method. Based on the influence law of droplet characteristics on the quality of α - phase gallium oxide thin films, this solution precisely controls the droplet characteristics by controlling the height of the horizontal - channel reaction chamber, the atomization power, and the atomization frequency, and then prepares high - quality α - phase gallium oxide thin films. (3) Compared with other thin - film preparation methods, this solution does not require a vacuum environment, has a simple process and is environmentally friendly, and has the commercial prospect of realizing the preparation of large - area α - phase gallium oxide thin films at low cost and high quality. Description of the Drawings

[0019] Figure 1 is the implementation flowchart of the present invention; Figure 2 is the physical diagram of the growth profile of the gallium oxide thin film of the present invention; Figure 3 is the surface topography diagram of the gallium oxide thin film of the present invention; Figure 4 is the transmittance characterization diagram of the gallium oxide thin film of the present invention; Figure 5 is the band - gap width characterization diagram of the gallium oxide thin film of the present invention; Figure 6 is the X - ray diffraction scanning diagram of the gallium oxide thin film of the present invention. Detailed Embodiments

[0020] To clearly illustrate the technical features of this solution, the following elaborates on this solution through specific embodiments.

[0021] Based on the research on growth temperature, reaction chamber structure, substrate position, horizontal channel reaction chamber height, atomization power, and atomization frequency respectively, the present invention proposes a method for preparing α-phase gallium oxide thin films. Example 1

[0022] As Figure 1 shown, it includes the following steps: Step 1: Preparation of precursor solution, specifically: Step 1.1: Select gallium acetylacetonate with a purity of 99.99% as the gallium source precursor material for growing gallium oxide thin films; Step 1.2: Add gallium acetylacetonate to deionized water and drop 0.5 - 3% hydrochloric acid to prepare a 0.02–0.08 mol / L gallium acetylacetonate solution; High-purity (99.99%) gallium acetylacetonate has stable properties but is not easily soluble in water, so hydrochloric acid is dropped into the solution to promote the dissolution of gallium acetylacetonate; The effect is the best when the concentration of the gallium acetylacetonate solution is 0.05 mol / L and the concentration of hydrochloric acid is 1%; Step 1.3: Put the prepared gallium acetylacetonate solution into the atomization chamber for standby.

[0023] Step 2: Cleaning of the substrate, specifically: Step 2.1: Select the substrate required for growing α-phase gallium oxide thin films. The substrate material can be any one of corundum-type oxides formed by elements such as Al, In, Fe, Cr, V, Ti, Rh, or Ir, or SiC or diamond; Since the lattice mismatch between sapphire and α-phase gallium oxide is only 4.8% and 3.5% in the a-axis and c-axis respectively, this means that high-quality α-phase gallium oxide thin films can be heteroepitaxially grown on sapphire substrates. At the same time, sapphire technology is mature and inexpensive, and large-area, high-quality, and low-cost sapphire wafers can be provided as the epitaxial substrates for α-phase gallium oxide, which will further reduce the epitaxial cost of the thin films. Therefore, sapphire Al2O 3. .

[0024] Step 2.2: Ultrasonically clean the substrate with acetone, ethanol, and deionized water respectively to remove organic dirt and chemical residues on the surface of the substrate; The ultrasonic cleaning time is set to 5 min respectively, and this time is sufficient to achieve efficient cleaning of the substrate surface.

[0025] Step 3: Placement of the substrate and cleaning of the reaction chamber gas, specifically: Step 3.1: There is a reaction chamber inside the quartz tube, a tube furnace is arranged outside the quartz tube, and a groove for accommodating the substrate is arranged in the reaction chamber; The reaction chamber structure can be selected as inclined, horizontal microchannel or vertical; since the horizontal microchannel reaction chamber structure can precisely control the temperature field and flow field in the reaction chamber, and uniform temperature field and flow field conditions are necessary conditions for realizing uniform film growth, the horizontal microchannel reaction chamber structure is selected. A horizontal microchannel is arranged inside the quartz tube as the reaction chamber, and the height of the horizontal microchannel is controlled to be 1-10 mm, and the corresponding droplet flow rate is 0.17–1.67 m / s. In this embodiment, the width of the horizontal microchannel is 3 cm, and the effect is the best when the height of the horizontal microchannel is 4 mm, and the corresponding droplet flow rate is 0.42m / s; Relationship between the change of microchannel height and the change of droplet flow rate: Among them, the influence of the microchannel width on the film quality can be ignored, and it mainly lies in the influence of the microchannel height. The change of the microchannel height will adjust the flow rate of the droplets in the reaction chamber, and then affect the replenishment and gasification rate of the droplets, and have an impact on the quality of the film. Experiments show that when the microchannel height is in the range of 4-10 mm, as the microchannel height decreases, the flow rate of the droplets gradually increases, so that more droplets are replenished to the substrate surface per unit time for reaction. At the same time, the convective heat transfer coefficient near the wall surface increases, which accelerates the evaporation rate of the droplets, resulting in smaller particle sizes. More abundant and fine droplets contribute to higher-quality films; when the microchannel height is in the range of 1-4 mm, as the microchannel height further decreases, the flow rate of the droplets further increases, which significantly increases the convective heat transfer coefficient near the wall surface, resulting in some droplets gasifying prematurely to form solid particles. The solid particles, as nucleation sites, will cause the film growth to be disordered, and thus lead to a decrease in quality. When the microchannel height is 4 mm, the film quality is the best, and the corresponding droplet flow rate is 0.42 m / s.

[0026] Groove structures can be engraved in the front, middle and rear sections of the horizontal microchannel reaction chamber for placing the substrate wafers.

[0027] Step 3.2: Place the substrate wafer in the groove; in actual operation, in the groove in the middle and rear of the reaction chamber, the growth of gallium oxide film on the substrate wafer is better. At a position 2 cm away from the heat generation position of the heating furnace in the reaction chamber, it is more suitable for the growth of the film.

[0028] Step 3.3: Introduce a dilution gas into the quartz tube to remove the residual air. The dilution gas is any one of oxygen, nitrogen, air, argon or helium. Among them, nitrogen, as a protective gas, can further reduce the surface roughness of the substrate wafer during the heating process of the reaction chamber, providing more favorable conditions for the growth of α-phase gallium oxide film.

[0029] Step 4: Heat up and control the temperature of the reaction chamber, specifically: Step 4.1: Control the reaction chamber to increase the temperature to the target temperature of 420 - 480 °C at a rate of 10 °C / min; it has been experimentally proven that the growth temperature range of the α-phase gallium oxide thin film is 420 - 480 °C. When the temperature is below this range, the thin film will be in an amorphous state, and when it is above this range, part of the α-phase gallium oxide thin film will transform into the ε-phase state. Further experiments have shown that when the growth temperature is 480 °C, the critical temperature for the phase transformation of the α-phase gallium oxide, the quality of the thin film is the best.

[0030] Step 4.2: Maintain the target temperature for 10 min to make the temperature in the reaction chamber uniform and stable.

[0031] Step 5: Atomization, transportation, and deposition of the precursor solution, specifically: Step 5.1: Atomize the precursor solution. The atomization methods that can be adopted include ultrasonic, pressure, rotary, and electrostatic. Since the droplets are finer and more uniform during ultrasonic atomization, and it is small in size and convenient to operate, using an ultrasonic atomizer to atomize the precursor solution has a better effect; Turn on the DC power supply to ultrasonically atomize the precursor solution. Control the size of the droplets by adjusting the frequency of the ultrasonic atomization sheet, and control the number of droplets by controlling the current of the DC power supply. After precise atomization, turn on the carrier gas and dilution gas, and control the gas flow by adjusting the carrier gas flowmeter and dilution gas flowmeter, and then blow the droplet group into the reaction chamber to achieve thin film growth.

[0032] In this embodiment, the working voltage of the ultrasonic atomization sheet is 24 V, and the current adjustment range is 0 - 1 A. The atomization quantity is sufficient to meet the growth of the α-phase gallium oxide thin film. When the working current changes between 0.4 - 0.8 A, the corresponding atomized precursor solution amounts are 10 - 30 ml. Experiments have shown that in the research, it is found that as the working current increases, the comprehensive quality of the thin film shows a trend of first increasing and then decreasing. When the working current is 0.6 A and the corresponding reaction solution amount is 20 ml, the quality of the thin film is the best.

[0033] The change in atomization frequency will affect the size of the droplet diameter. As the atomization frequency increases, the droplet group will become finer. Experiments show that as the fineness of the droplet group increases, on the one hand, it effectively increases the contact area between the droplet group and the substrate surface, making the precursor utilization more sufficient; on the other hand, due to the decrease in the droplet diameter, the precursor material provided by a single droplet decreases, which can effectively inhibit the longitudinal growth of the island-like structure on the film surface; at the same time, the fine droplets make the distribution of nucleation sites more uniform, prompting the atomic arrangement to be more regular, and thus gradually increasing the film quality. Through experimental verification, when the working frequency of the ultrasonic atomization sheet is selected from 1 - 5 MHz, it is suitable for the growth of α-phase gallium oxide thin films. However, there is a lower limit threshold for the droplet diameter. When the atomization frequency exceeds 3 MHz, the too-small droplets will gasify in advance to generate solid particles, resulting in a decrease in film quality. When the atomization frequency is 3.0 MHz, the film quality is the best.

[0034] Step 5.2: Turn on the carrier gas and dilution gas to transport the droplets to the reaction chamber. The carrier gas can be any one of oxygen, nitrogen, air, argon, or other inert gases. Among them, using oxygen as the carrier gas can further improve the crystallization quality of the film, and using nitrogen as the dilution gas can promote the smoothness of the film surface;

[0035] In this embodiment, when the carrier gas flow rate is controlled at 1 - 5 L / min and the dilution gas flow rate is controlled at 1 - 5 L / min, both are suitable for the growth of gallium oxide thin films. Among them, when the carrier gas flow rate is 1 L / min and the dilution gas flow rate is 2 L / min, the effect is the best.

[0036] Step 5.3: Control the deposition reaction time in the reaction chamber to obtain a gallium oxide thin film with the required thickness;

[0037] In this embodiment, when the reaction time is controlled at 1 h, the film thickness already meets the material requirements of the horizontal power device. If a thicker film needs to be grown, the reaction time can be appropriately increased.

[0038] Step 6: Cooling the reaction chamber and taking out the gallium oxide thin film sheet, specifically: Step 6.1: Stop atomizing the precursor solution and maintain the transportation of the carrier gas and dilution gas for 10 min to make the film reaction more complete; Step 6.2: Stop heating the reaction chamber, close the transportation of the dilution gas, and maintain the transportation of the carrier gas. The oxygen environment during the cooling process can further promote the growth of the α-phase gallium oxide thin film and reduce the internal defects of the film; control the reaction chamber to cool at a rate lower than 10 °C / min. Due to the difference in the thermal expansion coefficients of the sapphire substrate and α-phase gallium oxide, too fast a cooling rate will cause cracks in the film. When the film cooling rate is lower than 10 °C / min, the film cracks can be effectively avoided; Step 6.3: After the reaction chamber has cooled down to room temperature, turn off the carrier gas and take out the gallium oxide thin film sheet.

[0039] During the operation of this embodiment, a 0.05 mol / L gallium acetylacetonate solution was used, and 1% hydrochloric acid was added dropwise to the solution; a 4 mm high horizontal channel was used as the reaction chamber, with a corresponding droplet flow rate of 0.42 m / s and a reaction chamber temperature of 480 °C; an ultrasonic atomization sheet with a frequency of 3 MHz was used; the atomization working voltage was 24 V, the working current was 0.6 A, and the corresponding reaction solution volume was 20 ml; oxygen was used as the carrier gas with a flow rate of 1 L / min; nitrogen was used as the dilution gas with a flow rate of 2 L / min, and the obtained gallium oxide thin film had excellent quality.

[0040] Currently, the key parameters of α-Ga2O3 thin films are the full width at half maximum (FWHM), surface roughness expressed as root mean square (RMS), the bandgap width (E g ), the thin film thickness, and the thin film growth rate. To achieve higher-quality ultra-high voltage power electronic devices and high-performance solar-blind ultraviolet detectors, the thin film is required to have higher crystallization quality, lower surface roughness, a more obvious ultraviolet cut-off edge, a wider bandgap width, and an appropriate thickness.

[0041] Figure 2 This is the physical diagram of the growth profile of the gallium oxide thin film in this embodiment. The thickness of the thin film was measured by scanning electron microscopy (SEM) to be 433 nm. Generally, the requirements for the thin film thickness of gallium oxide horizontal power devices and solar-blind ultraviolet detectors are in the nanometer level, and a thin film thickness of 433 nm is sufficient to meet the manufacturing of gallium oxide horizontal power devices and solar-blind ultraviolet detectors.

[0042] Figure 3 This is the surface morphology diagram of the gallium oxide thin film in this embodiment. The surface roughness of the thin film was measured by atomic force microscopy (AFM), and its root mean square (RMS) was as low as 1.66 nm, indicating that the thin film has an extremely smooth surface.

[0043] Figure 4 This is the transmittance characterization diagram of the gallium oxide thin film in this embodiment measured by ultraviolet-visible spectrophotometer (UV-Vis). The thin film has good transmittance > 80% in the visible light band and has an obvious ultraviolet cut-off edge at 232 nm in the ultraviolet band.

[0044] Such as Figure 5As shown, the bandgap width of the gallium oxide thin film calculated from the transmittance of the thin film is as high as 5.32 eV, which can achieve a higher breakdown voltage compared to silicon carbide (3.3 eV) and gallium nitride (3.4 eV), and is more suitable for the manufacture of high-performance and low-loss high-power devices. After measuring the transmittance of the thin film with a UV-visible spectrophotometer, the bandgap width of the thin film can be calculated according to the Tauc formula. For gallium oxide materials, the formula is as follows: (αhv) 2 =B(hv-E g )

[0045] In the formula, α is the absorption coefficient (unit: %), hv is the photon energy (unit: electron volt eV), B is the proportionality constant, and E g is the bandgap width (unit: electron volt eV). Therefore, the bandgap width of the thin film can be determined by plotting the relationship between (αhv) 2 (unit: relative value a.u.) and hv, and extrapolating the linear part to the x-axis intercept.

[0046] Figure 6 This is the high-resolution X-ray diffraction (HR-XRD) scan pattern of the gallium oxide thin film in this embodiment. The full width at half maximum of the thin film is as low as 37 arcsec (the smaller the full width at half maximum, the higher the crystallization quality of the thin film), highlighting that the thin film has excellent crystallization quality.

[0047] The comparison with other current work is shown in the following table Research team Method Full width at half maximum (arcsec) Root mean square (nm) Band gap width (eV) Thickness (nm) Growth rate (nm / min) [Park] Mist-CVD 92 1.12 (1×1 μm) - 224 4 [Cheng] Mist-CVD 90 1.64 (5×5 μm) 5.29 686 11 [Ma] Mist-CVD 86 2.90 (2×2 μm) 5.03 8000 17 [Wang] Mist-CVD 83 - 5.36 2900 24 [Xu] Mist-CVD 72 2.18 (5×5 μm) 5.31 619 10 [Shinohara] Mist-CVD 60 1.00 (1×1 μm) 5.3 240 5 [Nakabayashi] Mist-CVD 55 3.25 (5×5 μm) - 430 22 [Kim] Mist-CVD 42 2.91 (1×1 μm) - 440 4 This scheme Mist-CVD 37 1.66 (5×5 μm) 5.32 433 7 In current works, the root mean square (RMS) of the thin films prepared by Cheng and Park et al. is relatively low (RMS ≈ 1.5 nm), but the crystallinity is poor (FWHM > 90 arcsec); Kim and Nakabayashi et al. achieved better crystallization quality (FWHM < 50 arcsec), but the surface is relatively rough (RMS ≈ 3 nm). In contrast, in this scheme, by exploring the mechanism of the effect of droplet characteristics on thin film growth, while improving the crystallization quality of the thin film (FWHM = 37 arcsec), the surface roughness is reduced (RMS = 1.66 nm), and the bandgap width of the thin film reaches 5.32 eV, having excellent comprehensive performance. Example 2

[0048] This embodiment is different from Embodiment 1 in that since gallium acetylacetonate is an organic substance and is likely to introduce carbon impurities during the reaction process, in order to further avoid the influence of carbon impurities on the film quality, gallium chloride with a purity of 99.99% is selected as the precursor substance to replace gallium acetylacetonate. And in Step 1, there is no need to drop hydrochloric acid. Dissolve gallium chloride in deionized water to prepare a 0.1–0.5 mol / L gallium chloride solution for standby. Preparing a 0.2 mol / L gallium oxide solution has the best effect.

[0049] The technical features not described in the present invention can be achieved by or adopted the prior art, and will not be elaborated here. Of course, the above description is not a limitation of the present invention, and the present invention is not limited to the above examples. Changes, modifications, additions or substitutions made by those of ordinary skill in the art within the scope of the essence of the present invention should also fall within the protection scope of the present invention.

Claims

1. A method for preparing an α-phase gallium oxide thin film, characterized in that, It includes the following steps: Step 1: Select a gallium compound to prepare a precursor solution; Step 2: Clean the substrate wafer to remove organic dirt and chemical residues on the surface of the substrate wafer; Step 3: Place the substrate wafer at the set position in the reaction chamber, and use a dilution gas to clean the reaction chamber to remove natural air; Step 4: Heat the reaction chamber to raise its temperature. When the temperature reaches the target temperature and is maintained, the temperature in the reaction chamber is made uniform and stable; Step 5: Atomize the precursor solution and transport the droplets to the reaction chamber for deposition reaction on the substrate wafer; Step 6: Stop atomization, stop heating the reaction chamber, and stop transporting the dilution gas at intervals in sequence until the reaction chamber reaches the cooling temperature and stop transporting the carrier gas, and then take out the gallium oxide thin film wafer.

2. The preparation method of the α-phase gallium oxide thin film according to claim 1, characterized in that, The specific content of Step 1 is as follows: Step 1.1: Select high-purity gallium acetylacetonate as the gallium source precursor material for growing the gallium oxide thin film; Step 1.2: Add gallium acetylacetonate to deionized water, and drop hydrochloric acid with a concentration of 0.5 - 3% to prepare a 0.02–0.08 mol / L gallium acetylacetonate solution; Step 1.3: Put the prepared gallium acetylacetonate solution into the atomization chamber for standby.

3. The preparation method of the α-phase gallium oxide thin film according to claim 1, characterized in that, The specific content of Step 1 is as follows: Step 1.1: Select high-purity gallium chloride as the gallium source precursor material for growing the gallium oxide thin film; Step 1.2: Dissolve gallium chloride in deionized water to prepare a 0.1–0.5 mol / L gallium chloride solution; Step 1.3: Put the prepared gallium chloride solution into the atomization chamber for standby.

4. The preparation method of the α-phase gallium oxide thin film according to claim 1, characterized in that, The specific content of Step 2 is as follows: Step 2.1: Select a substrate wafer required for growing the α-phase gallium oxide thin film; The material of the substrate wafer is corundum-type oxide formed by any one of the elements Al, In, Fe, Cr, V, Ti, Rh, or Ir, or SiC or diamond; Step 2.2: Ultrasonically clean the substrate wafer with acetone, ethanol, and deionized water in sequence to remove organic dirt and chemical residues on the surface of the substrate wafer.

5. The preparation method of the α-phase gallium oxide thin film according to claim 1, characterized in that, The specific content of Step 3 is as follows: Step 3.1: A reaction chamber is arranged inside a quartz tube, a tube furnace is arranged outside the quartz tube, and a groove for accommodating the substrate wafer is arranged in the reaction chamber; Step 3.2: Place the substrate wafer in the groove; Step 3.3: Pass a dilution gas into the quartz tube to remove the residual air. The dilution gas is any one of oxygen, nitrogen, air, argon, or helium.

6. The preparation method of the α-phase gallium oxide thin film according to claim 5, characterized in that, In Step 3.1, a horizontal microchannel is arranged inside the quartz tube as the reaction chamber, and the height of the horizontal microchannel is controlled to be 1 - 10 mm.

7. The method for preparing the α-phase gallium oxide thin film according to claim 1, characterized in that, The specific content of Step 4 is as follows: Step 4.1: Control the reaction chamber to rise to the target temperature in the range of 420 - 480 °C at a rate of 10 °C / min; Step 4.2: Maintain the target temperature for 10 min to make the temperature in the reaction chamber uniform and stable.

8. The method for preparing the α-phase gallium oxide thin film according to claim 1, wherein The specific content of Step 5 is as follows: Step 5.1: Atomize the precursor solution; Step 5.2: Start transporting the carrier gas and the dilution gas to transport the droplets to the reaction chamber. The carrier gas is any one of oxygen, nitrogen, air, argon, or helium; Step 5.3: Control the deposition reaction time in the reaction chamber to obtain a gallium oxide thin film with the required thickness.

9. The preparation method of the α-phase gallium oxide thin film according to claim 8, wherein In the said step 5.1, an ultrasonic atomizer is used to atomize the precursor solution, and the operating frequency of the ultrasonic atomization sheet is selected to be 1 - 5 MHz.

10. The preparation method of the α-phase gallium oxide thin film according to claim 1, wherein, The said step 6 is specifically as follows: Step 6.1: Stop atomizing the precursor solution and maintain the delivery of the carrier gas and the dilution gas. Step 6.2: Stop heating the reaction chamber, close the delivery of the dilution gas, and maintain the delivery of the carrier gas; control the temperature of the reaction chamber to decrease at a rate lower than 10 °C / min. Step 6.3: After the reaction chamber has cooled to room temperature, close the carrier gas and take out the gallium oxide thin film sheet.

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