Method for growing gallium oxide film by using fog chemical vapor deposition

Abstract

The invention discloses a method for growing a gallium oxide film by utilizing Mist-CVD (Chemical Vapor Deposition), which obviously improves the deposition rate (2.7-3.1 mu m / h) through pulse atomization (with the frequency of 1.5-2.5 MHz and the particle size of 1-5 mu m), a low-power plasma module (10-50 W, 400-600 DEG C), a microfluidic nozzle (10-50 mu m) and a multi-path precursor system, and improves the deposition rate (2.7-3.1 mu m / h) by 2-3 times compared with the deposition rate (0.5-1 mu m / h) in the prior art. And meanwhile, the crystal quality (FWHM reduction) and the uniformity (the standard deviation is 4.8-5.5 nm) of the thin film are optimized. A double-precursor system (gallium chloride, gallium acetylacetonate or gallium citrate) and an atomic layer deposition transition layer (5-10 nm) are adopted, online spectrum feedback control is combined, the defect density and energy consumption are reduced, and the method is suitable for large-scale production. The method provides a high-quality gallium oxide thin film for a power device and an ultraviolet detector, and has high-efficiency and low-cost industrial application potential.

Description

Technical Field

[0001] This invention relates to the technical field of gallium oxide thin films, and in particular to a method for growing gallium oxide thin films using fog chemical vapor deposition. Background Technology

[0002] Mist-CVD, as an emerging thin film preparation technology, has received widespread attention and rapid development in the field of oxide semiconductor materials in recent years. This technology transforms liquid precursors into aerosols through ultrasonic atomization, which are then transported via gas flow to a high-temperature reaction chamber to deposit high-quality thin films on a substrate. Gallium oxide (Ga2O3) is an ideal material for power devices, ultraviolet detectors, and transparent conductive films due to its wide bandgap (approximately 4.8-5.3 eV), high breakdown field strength (approximately 8 MV / cm), and excellent chemical and thermal stability. The Mist-CVD process for growing gallium oxide thin films is favored for its simple equipment, low cost, and adaptability to complex substrates. In existing technologies, gallium chloride or gallium nitrate are commonly used as precursors, combined with sapphire, silicon, or gallium oxide single-crystal substrates, and deposition is performed at high temperatures of 600-900℃. In recent years, research has further focused on improving film quality by optimizing atomization parameters, reaction chamber design, and precursor formulations; some processes have achieved crystal defect densities as low as 10-1. 16 cm -3 The presence of gallium oxide thin films with optical transmittance exceeding 85% lays the foundation for high-performance device applications. Furthermore, Mist-CVD exhibits lower energy consumption compared to other CVD technologies, driving its potential applications in the semiconductor industry.

[0003] However, existing Mist-CVD technology still has significant shortcomings in gallium oxide thin film preparation, particularly in deposition rate, which limits its application in large-scale production. Current deposition rates are typically in the range of 0.5-1 μm / h, far lower than the 5-10 μm / h of technologies such as metal-organic chemical vapor deposition (MOCVD), resulting in low production efficiency and difficulty in meeting the demands of industrial mass production. The main reasons for the low deposition rate are limited aerosol transport efficiency, slow precursor decomposition kinetics, and uneven gas flow distribution within the reaction chamber. Furthermore, increasing the deposition rate in existing technologies often results in a decrease in film quality, such as increased crystal defect density or worsened surface roughness, which further restricts the optimization of device performance. For large-scale production, existing technologies lack effective means to increase the deposition rate, and it is difficult to achieve an efficient and uniform deposition process while maintaining high film quality. Other shortcomings include insufficient precision in doping control, numerous defects at heterogeneous substrate interfaces, and energy consumption issues arising from high-temperature processes, all of which pose challenges to the industrial application of gallium oxide thin films. Compared to existing technologies, our invention aims to significantly improve the deposition rate while maintaining or improving the crystal quality and uniformity of the film, providing a new technical path for achieving efficient and low-cost gallium oxide film preparation. Summary of the Invention

[0004] This application provides a method for growing gallium oxide thin films using fog chemical vapor deposition, comprising the following steps: Step S1. Provide a liquid gallium precursor and generate an aerosol using a pulse atomization device. The pulse atomization device uses an ultrasonic generator with a frequency range of 1.5-2.5 MHz, a pulse interval of 0.1-1 seconds, and controls the aerosol particle size to be 1-5 μm. Step S2. The aerosol is transferred to the reaction chamber via an inert carrier gas. The reaction chamber is equipped with a low-power plasma module. The plasma module uses a radio frequency power supply with a power range of 10-50 W and a frequency of 13.56 MHz. The deposition temperature is controlled at 500-600℃. Step S3. Deposit a gallium oxide thin film on a substrate, the substrate being placed on a rotating base at a rotation speed of 10-50 rpm and a reaction chamber pressure of 0.1-10 Torr.

[0005] As a preferred embodiment of a method for growing gallium oxide thin films using fog chemical vapor deposition, the liquid gallium precursor includes one or a combination of gallium chloride, gallium nitrate, or gallium acetylacetonate. The precursor is dissolved in deionized water or ethanol solvent at a concentration of 0.01-0.5 mol / L, and 0.05-0.2 wt% of a stabilizer, namely polyethylene glycol or polyvinylpyrrolidone, is added to the solvent.

[0006] As a preferred embodiment of a method for growing gallium oxide thin films using fog chemical vapor deposition, the method further includes a multi-path precursor atomization system in the reaction chamber. The multi-path precursor atomization system includes at least two independent nozzles, one for atomizing the gallium precursor and the other for atomizing the dopant precursor. The dopant precursor is tin chloride, silane, magnesium nitrate, or zinc chloride. The dopant concentration is adjusted by an independent flow controller within a range of 10. 16 -10 20 cm -3 The accuracy of the flow controller is 0.1 sccm.

[0007] As a preferred technical solution for growing gallium oxide thin films using fog chemical vapor deposition, the multi-path precursor fogging system is equipped with an online spectrometer and a feedback control unit. The spectrometer uses ultraviolet-visible spectroscopy technology and monitors wavelengths in the range of 200-800 nm. The feedback control unit adjusts the nozzle flow rate via a servo motor, with a response time of less than 0.5 seconds.

[0008] As a preferred technical solution for growing gallium oxide thin films using fog chemical vapor deposition, the substrate is a silicon, sapphire, or gallium oxide single crystal substrate. Before depositing the gallium oxide thin film, a transition layer with a thickness of 5-10 nm is pre-deposited on the substrate by atomic layer deposition. The transition layer is aluminum oxide, zinc oxide, or aluminum nitride. The deposition temperature is 200-300℃, and the number of cycles is 50-100. The surface of the transition layer is treated with oxygen plasma with a treatment power of 50-100 W for 30-60 s.

[0009] As a preferred technical solution for growing gallium oxide thin films using fog chemical vapor deposition, the substrate is pretreated before deposition. The pretreatment includes the following steps: ultrasonic cleaning with acetone and isopropanol for 5-10 minutes in sequence, drying with nitrogen, and annealing in a vacuum environment at 300-400°C for 30 minutes. After the transition layer is deposited, it is subjected to rapid heat treatment in an argon atmosphere at a temperature of 400-500°C for 1-3 minutes.

[0010] As a preferred technical solution for a method of growing gallium oxide thin films using fog chemical vapor deposition, the liquid gallium precursor includes a first precursor and a second precursor. The first precursor is gallium chloride, dissolved in deionized water, with a concentration of 0.1-0.3 mol / L. The second precursor is gallium acetylacetonate, dissolved in ethanol, with a concentration of 0.05-0.2 mol / L. The two precursors are atomized separately by a dual-nozzle atomizing device. The dual-nozzle device adopts a coaxial structure, and the nozzle outlet spacing is 2-5 mm. The two aerosols are mixed at the inlet of the reaction chamber by a vortex mixer with a mixer rotation speed of 100-500 rpm.

[0011] 8. The method according to claim 1, characterized in that a low-temperature microwave plasma module is introduced into the atomization chamber, the module adopts a microwave power supply with a power of 50-100 W and a frequency of 2.45 GHz, the aerosol residence time in the plasma environment is 0.1-0.5 seconds, generating an intermediate containing gallium-oxygen free radicals, the deposition temperature of the reaction chamber is 400-500℃, the carrier gas is nitrogen or argon, and the flow rate is 1-5 L / min.

[0012] As a preferred technical solution for a method of growing gallium oxide thin films using fog chemical vapor deposition, the pulsed atomizing device employs a microfluidic nozzle, which includes multiple parallel channels with a channel size of 10-50 μm. The channel walls are coated with a hydrophobic coating made of polytetrafluoroethylene. The nozzle is driven by a 1-5 kV electrostatic field, the electrode spacing is 1-3 mm, and the atomization frequency is synchronized with pulsed ultrasound with a frequency range of 1.5-2.5 MHz.

[0013] As a preferred technical solution for a method of growing gallium oxide thin films using fog chemical vapor deposition, the liquid gallium precursor is gallium citrate dissolved in deionized water at a concentration of 0.05-0.2 mol / L. 0.1-0.5 wt% of a surfactant, such as sodium dodecyl sulfate or Tween 80, is added to the solvent. The method further includes sequentially depositing a gallium oxide layer and a zinc oxide layer by switching precursor nozzles during the deposition process. The zinc oxide layer uses a zinc nitrate precursor at a concentration of 0.1-0.3 mol / L, and the deposition time is 1-5 minutes, forming a gallium oxide / zinc oxide heterojunction structure with a heterojunction thickness ratio of 1:1 to 3:1.

[0014] The beneficial effects of this application are as follows: By introducing pulsed atomization (frequency 1.5-2.5 MHz, pulse interval 0.1-1 second, aerosol particle size 1-5 μm), low-power plasma module (power 10-50 W, deposition temperature 400-600°C), microfluidic nozzle (channel size 10-50 μm, electrostatic field drive 1-5 kV), and multi-path precursor atomization system, the deposition rate of gallium oxide thin films is significantly improved (experimental data reaches 2.7-3.1 μm / h, which is 2-3 times higher than the prior art of 0.5-1 μm / h), while maintaining excellent film crystal quality (FWHM lower than the control example) and thickness uniformity (standard deviation 4.8-5.5 nm, better than the control example of 10.8-12.3 nm). The dual precursor system (gallium chloride, gallium acetylacetonate, or gallium citrate) and atomic layer deposition transition layer (5-10 nm) optimize the interface quality and reduce the crystal defect density. Low-temperature microwave plasma (50-100 W) and online spectral feedback control (response time <0.5 seconds) further improve doping accuracy and process stability, solving the problems of low deposition rate, poor uniformity and high energy consumption at high temperatures in the existing Mist-CVD technology. This provides a reliable technical path for the efficient and low-cost large-scale production of gallium oxide thin films, and is suitable for industrial applications in fields such as power devices and ultraviolet detectors. Detailed Implementation

[0015] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the examples in the specification.

[0016] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0017] Secondly, the term "an embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places throughout this specification does not necessarily refer to the same embodiment, nor is it a single embodiment or an embodiment selectively excluded from other embodiments.

[0018] Example 1 A method for growing gallium oxide thin films using fog chemical vapor deposition, employing a custom Mist-CVD system (model: MistTech-1000, reaction chamber volume 5 L), includes the following steps: Precursor preparation: A dual precursor system was prepared. The first precursor was gallium chloride (99.99% purity, Sigma-Aldrich), dissolved in deionized water (resistivity 18.2 MΩ·cm) at a concentration of 0.1 mol / L. The second precursor was gallium acetylacetonate (99.9% purity, Alfa Aesar), dissolved in ethanol (analytical grade, 99.8%) at a concentration of 0.05 mol / L. 0.05 wt% polyethylene glycol (molecular weight 4000, Merck) was added to both as a stabilizer. The mixture was magnetically stirred (StirPro-500, 500 rpm) at 25°C for 30 minutes until completely dissolved.

[0019] Atomization: Two precursors are atomized separately using a dual-nozzle atomizing device (coaxial structure, nozzle outlet spacing 2 mm, quartz material, model: DualNozzle-200). The aerosols are then mixed at the inlet of the reaction chamber by a vortex mixer (model: VortexMix-100, speed 100 rpm). A pulsed atomizing device is equipped with a microfluidic nozzle (channel size 10 μm, silicon-based material, channel wall coated with 0.1 μm thick PTFE, model: MicroFlow-50), driven by a 1 kV electrostatic field (electro-Mist-500, electrode spacing 1 mm), and an ultrasonic generator (model: SonoTek-200, frequency 1.5 MHz, power 20 W) with a pulse interval of 0.1 seconds, generating aerosol particles with a size of 1-3 μm. The atomization chamber temperature is 30℃.

[0020] Doping control: The reaction chamber is equipped with a multi-path precursor atomization system, including three independent nozzles (made of 316L stainless steel, model: MultiNozzle-300), which atomize gallium chloride, gallium acetylacetonate, and tin chloride (purity 99.9%, concentration 0.01mol / L, doping concentration 10). 16 cm -3 The dopant flow rate is regulated by a high-precision flow controller (model: MFC-Alicat, accuracy 0.1 sccm), and it is equipped with an online spectrometer (model: UVSpec-2000, wavelength range 200-800 nm, resolution 1 nm) and a feedback control unit (servo motor model: ServoTech-300, response time 0.3 seconds).

[0021] Precursor activation: A low-temperature microwave plasma module (model: MicroWave-2450, power 50 W, frequency 2.45 GHz) is introduced into the atomization chamber. The aerosol stays in the plasma environment for 0.1 seconds to generate an intermediate containing gallium-oxygen free radicals.

[0022] Aerosol transport and deposition: Aerosols were transported to the reaction chamber using high-purity nitrogen (99.999% purity, 1 L / min flow rate). The reaction chamber was equipped with an RF plasma module (RFGenix-13, 10 W power, 13.56 MHz frequency), with a deposition temperature of 500℃ (PID temperature control, ±1℃ accuracy) and a reaction chamber pressure of 0.1 Torr (via a vacuum pump, VacPump-500). The substrate was c-plane sapphire (2 inches in diameter, 0.5 mm thick, EpiTech), placed on a rotating base (10 rpm rotation speed, StepMotor-50 motor).

[0023] Substrate treatment: The sapphire substrate was cleaned for 5 minutes each in an ultrasonic cleaner (CleanTech-300, 40 kHz) using acetone (analytical grade, 99.5%) and isopropanol (analytical grade, 99.7%), followed by nitrogen drying and placement in a vacuum annealing furnace (VacuAnneal-200, pressure 10). -5 Torr), annealed at 300°C for 30 minutes. A 5 nm thick alumina transition layer was pre-deposited using an atomic layer deposition apparatus (model: ALD-Picosun-R200) ​​with trimethylaluminum (TMA, 99.99%) and water at a deposition temperature of 200°C for 50 cycles. The surface of the transition layer was treated with oxygen plasma (power 50 W, gas flow rate 50 sccm, apparatus model: PlasmaPro-100) for 30 seconds, followed by rapid heat treatment at 400°C for 1 minute in an argon atmosphere (flow rate 100 sccm) (apparatus model: RTP-Anneal-600).

[0024] Thin film deposition: By switching the precursor nozzle, gallium oxide and zinc oxide layers are deposited sequentially. The zinc oxide layer uses zinc nitrate precursor (purity 99.9%, concentration 0.1 mol / L, dissolved in deionized water, with 0.1 wt% sodium dodecyl sulfate added) for 1 minute. The gallium oxide layer is deposited for 3 minutes, forming a gallium oxide / zinc oxide heterojunction structure with a thickness ratio of 3:1. The total deposition time is 60 minutes.

[0025] Example 2 A method for growing gallium oxide thin films using fog chemical vapor deposition, employing a Mist-CVD system (model: MistTech-1000), includes the following steps: Precursor preparation: The liquid gallium precursor was prepared by dissolving gallium nitrate (purity 99.9%, Alfa Aesar) in ethanol (analytical grade, 99.8%) at a concentration of 0.5 mol / L. 0.2 wt% polyvinylpyrrolidone (PVP, molecular weight 10000, Sigma-Aldrich) was added as a stabilizer and the mixture was magnetically stirred at 40°C (StirPro-500, 600 rpm) for 40 minutes.

[0026] Atomization: A pulse atomization device is used, equipped with a microfluidic nozzle (channel size 50 μm, silicon-based material, channel wall coated with 0.1 μm thick polytetrafluoroethylene, model: MicroFlow-50), driven by a 5 kV electrostatic field (electrode spacing 3 mm, device model: ElectroMist-500), and an ultrasonic generator (frequency 2.5 MHz, power 25 W). The pulse interval is set to 1 second, generating aerosol particles with a size of 3-5 μm. The atomization chamber temperature is 35℃.

[0027] Doping control: The reaction chamber is equipped with a multi-path precursor atomization system, including three independent nozzles, which atomize gallium nitrate and tin chloride (purity 99.9%, concentration 0.01 mol / L, doping concentration 10). 16 cm -3 ) and magnesium nitrate (purity 99.9%, concentration 0.01 mol / L, doping concentration 10) 18 cm -3 The dopant flow rate is adjusted by a flow controller (accuracy 0.1 sccm), and it is equipped with an online spectrometer (wavelength range 200-800 nm) and a feedback control unit (servo motor response time 0.4 seconds).

[0028] Precursor activation: A low-temperature microwave plasma module (power 100 W, frequency 2.45 GHz) is introduced into the atomization chamber, and the aerosol is held for 0.5 seconds to generate an intermediate containing gallium-oxygen free radicals.

[0029] Aerosol transport and deposition: Aerosols were transported to the reaction chamber using high-purity argon gas (5 L / min). The reaction chamber was equipped with an RF plasma module (50 W power, 13.56 MHz frequency). The deposition temperature was 600 °C, and the reaction chamber pressure was 10 Torr. The substrate was silicon (100 crystal orientation, 4 inches, 0.525 mm thickness, SiliconTech), placed on a rotating base (50 rpm rotation speed).

[0030] Substrate preparation: The silicon substrate was ultrasonically cleaned with acetone and isopropanol for 10 minutes each, dried with nitrogen, and then annealed in a vacuum annealing furnace at 400°C for 30 minutes. A 10 nm thick zinc oxide transition layer was pre-deposited by atomic layer deposition (using diethylzinc and water, deposition temperature 300°C, 100 cycles). The surface of the transition layer was treated with 100 W oxygen plasma for 60 seconds, followed by rapid heat treatment at 500°C for 3 minutes in an argon atmosphere.

[0031] Thin film deposition: By switching the precursor nozzle, gallium oxide and zinc oxide layers are deposited sequentially. The zinc oxide layer uses zinc nitrate precursor (concentration 0.3 mol / L, with 0.5 wt% Tween 80 added) for 5 minutes. The gallium oxide layer is deposited for 5 minutes, forming a gallium oxide / zinc oxide heterojunction structure with a thickness ratio of 1:1. The total deposition time is 45 minutes.

[0032] Example 3 A method for growing gallium oxide thin films using fog chemical vapor deposition, employing a Mist-CVD system (model: MistTech-1000), includes the following steps: Precursor preparation: A dual precursor system was prepared. The first precursor was gallium chloride (0.3 mol / L, dissolved in deionized water), and the second precursor was gallium acetylacetonate (0.2 mol / L, dissolved in ethanol). 0.1 wt% polyethylene glycol (molecular weight 6000) was added to both as a stabilizer, and the mixture was stirred at 30°C for 35 minutes.

[0033] Atomization: Atomization is achieved using a dual-nozzle atomizing device (nozzle outlet spacing 5 mm, model: DualNozzle-200). The aerosols are then mixed by a vortex mixer (500 rpm). The pulse atomizing device is equipped with microfluidic nozzles (channel size 30 μm, PTFE coating), driven by a 3 kV electrostatic field (electrode spacing 2 mm), and an ultrasonic generator (frequency 2.0 MHz, power 22 W) with a pulse interval of 0.5 seconds. This generates aerosol particles with a size of 2-4 μm, and the atomization chamber temperature is 32℃.

[0034] Doping control: The reaction chamber is equipped with a multi-path precursor atomization system to atomize gallium chloride, gallium acetylacetonate, and silane (doping concentration 10). 17 cm -3 The dopant flow rate is regulated by a flow controller (accuracy 0.1 sccm), and it is equipped with an online spectrometer and a feedback control unit (response time 0.4 seconds).

[0035] Precursor activation: A low-temperature microwave plasma module (75 W power, 2.45 GHz frequency) is introduced into the atomization chamber, and the aerosol stays for 0.3 seconds.

[0036] Aerosol transport and deposition: Aerosols were transported using high-purity nitrogen (flow rate 3 L / min). The reaction chamber was equipped with an RF plasma module (power 30 W, frequency 13.56 MHz), the deposition temperature was 550℃, and the reaction chamber pressure was 5 Torr. The substrate was a gallium oxide single crystal (β-Ga2O3, 2 inches, thickness 0.6 mm), placed on a rotating base (rotation speed 30 rpm).

[0037] Substrate treatment: The gallium oxide single crystal substrate was ultrasonically cleaned with acetone and isopropanol for 8 minutes each, dried with nitrogen, and annealed at 350°C for 30 minutes. An 8 nm thick aluminum nitride transition layer was pre-deposited by atomic layer deposition (deposition temperature 250°C, 80 cycles). The surface of the transition layer was treated with 80 W oxygen plasma for 45 seconds, followed by rapid heat treatment at 450°C for 2 minutes.

[0038] Thin film deposition: Gallium oxide and zinc oxide layers (zinc nitrate precursor, concentration 0.2 mol / L, with 0.3 wt% Tween 80 added) were deposited sequentially by switching precursor nozzles, with a deposition time of 3 minutes for each layer, a thickness ratio of 2:1, and a total deposition time of 50 minutes.

[0039] Example 4 A method for growing gallium oxide thin films using fog chemical vapor deposition, employing a Mist-CVD system (model: MistTech-1000), includes the following steps: Precursor preparation: The liquid gallium precursor was prepared by dissolving gallium citrate (99.9% purity, self-made) in deionized water at a concentration of 0.05 mol / L, adding 0.1 wt% sodium dodecyl sulfate (99% purity) as a surfactant, and stirring at 35°C for 45 minutes.

[0040] Atomization: A pulse atomization device is used, equipped with a microfluidic nozzle (channel size 20 μm, polytetrafluoroethylene coating), driven by a 2 kV electrostatic field (electrode spacing 1.5 mm), and an ultrasonic generator (frequency 1.8 MHz, power 21 W) with a pulse interval of 0.3 seconds to generate aerosol particles with a size of 1-4 μm. The atomization chamber temperature is 30℃.

[0041] Doping control: The reaction chamber is equipped with a multi-path precursor atomization system to atomize gallium citrate and zinc chloride (doping concentration 10). 19 cm -3 The dopant flow rate is regulated by a flow controller (accuracy 0.1 sccm), and it is equipped with an online spectrometer and a feedback control unit (response time 0.5 seconds).

[0042] Precursor activation: A low-temperature microwave plasma module (50 W power, 2.45 GHz frequency) is introduced into the atomization chamber, and the aerosol stays for 0.2 seconds.

[0043] Aerosol transport and deposition: Aerosols were transported using high-purity argon gas (flow rate 2 L / min). The reaction chamber was equipped with an RF plasma module (power 20 W, frequency 13.56 MHz), the deposition temperature was 400℃, and the reaction chamber pressure was 1 Torr. The substrate was sapphire (2 inches, thickness 0.5 mm) placed on a rotating base (rotation speed 20 rpm).

[0044] Substrate treatment: The sapphire substrate was ultrasonically cleaned with acetone and isopropanol for 7 minutes each, dried with nitrogen, and annealed at 350°C for 30 minutes. A 6 nm thick alumina transition layer was pre-deposited by atomic layer deposition (deposition temperature 250°C, 60 cycles). The surface of the transition layer was treated with 60 W oxygen plasma for 40 seconds, followed by rapid heat treatment at 400°C for 1 minute.

[0045] Thin film deposition: Gallium oxide and zinc oxide layers (zinc nitrate precursor, concentration 0.1 mol / L, with 0.1 wt% sodium dodecyl sulfate added) were deposited sequentially by switching precursor nozzles, with a deposition time of 2 minutes for each layer, a thickness ratio of 3:1, and a total deposition time of 40 minutes.

[0046] Example 5 A method for growing gallium oxide thin films using fog chemical vapor deposition, employing a Mist-CVD system (model: MistTech-1000), includes the following steps: Precursor preparation: A liquid gallium precursor was prepared as gallium citrate (0.2 mol / L, dissolved in deionized water), with 0.5 wt% Tween 80 (98% purity, Sigma-Aldrich) added as a surfactant. The mixture was stirred at 40°C for 50 minutes. A dual-precursor system was prepared, with the second precursor being gallium acetylacetonate (0.1 mol / L, dissolved in ethanol, with 0.1 wt% polyvinylpyrrolidone added).

[0047] Atomization: Atomization is achieved through a dual-nozzle atomizing device (nozzle outlet spacing 3 mm), with the aerosols mixed by a vortex mixer (300 rpm). The pulse atomizing device is equipped with microfluidic nozzles (channel size 40 μm, PTFE coating), driven by a 4 kV electrostatic field (electrode spacing 2.5 mm), and an ultrasonic generator (frequency 2.2 MHz, power 23 W) with a pulse interval of 0.8 seconds, generating aerosol particles of 2-5 μm in size. The atomization chamber temperature is 33℃.

[0048] Doping control: The reaction chamber is equipped with a multi-path precursor atomization system to atomize gallium citrate, gallium acetylacetonate, and magnesium nitrate (doping concentration 10). 20 cm -3The dopant flow rate is regulated by a flow controller (accuracy 0.1 sccm), and it is equipped with an online spectrometer and a feedback control unit (response time 0.3 seconds).

[0049] Precursor activation: A low-temperature microwave plasma module (100 W power, 2.45 GHz frequency) is introduced into the atomization chamber, and the aerosol stays for 0.5 seconds.

[0050] Aerosol transport and deposition: Aerosols were transported using high-purity nitrogen (flow rate 4 L / min). The reaction chamber was equipped with an RF plasma module (power 40 W, frequency 13.56 MHz), the deposition temperature was 500 °C, and the reaction chamber pressure was 8 Torr. The substrate was silicon (4 inches, thickness 0.525 mm), placed on a rotating base (rotation speed 40 rpm).

[0051] Substrate treatment: The silicon substrate was ultrasonically cleaned with acetone and isopropanol for 9 minutes each, dried with nitrogen, and annealed at 400°C for 30 minutes. A 10 nm thick zinc oxide transition layer was pre-deposited by atomic layer deposition (deposition temperature 300°C, 100 cycles). The surface of the transition layer was treated with 100 W oxygen plasma for 60 seconds, followed by rapid heat treatment at 500°C for 3 minutes.

[0052] Thin film deposition: Gallium oxide and zinc oxide layers (zinc nitrate precursor, concentration 0.3 mol / L, with 0.5 wt% Tween 80 added) were deposited sequentially by switching precursor nozzles, with a deposition time of 5 minutes for each layer, a thickness ratio of 1:1, and a total deposition time of 55 minutes.

[0053] Comparison Example Compare with Example 1 The difference between this comparative example and Example 1 is that the dopant precursor (tin chloride) and gallium chloride are premixed and atomized through a single nozzle, without a multi-path precursor atomization system, independent flow controller, and online spectral feedback control unit. The remaining features (such as pulsed atomization, plasma module, microfluidic nozzle, substrate treatment, and heterojunction deposition) are consistent with Example 1.

[0054] Compare with Example 2 The difference between this comparative example and Example 1 is that the dopant precursor (tin chloride) and gallium chloride are premixed and atomized through a single nozzle, without a multi-path precursor atomization system, independent flow controller, and online spectral feedback control unit. The remaining features (such as pulsed atomization, plasma module, microfluidic nozzle, substrate treatment, and heterojunction deposition) are consistent with Example 1.

[0055] Compare with Example 3 The difference between this comparative example and Example 1 is that a conventional ultrasonic atomization device (frequency 1.5 MHz, continuous atomization) is used, without microfluidic nozzles and electrostatic field drive, and the aerosol particle size is 2-10 μm. The remaining features (such as pulsed atomization, plasma module, multi-path precursor system, substrate treatment, heterojunction deposition) are the same as in Example 1.

[0056] Performance testing methods Deposition rate: After deposition, the sample was cooled to room temperature (25℃), and the precise deposition time was recorded (accurate to 1 second, using a digital timer). The film thickness was measured using an ellipsometry, selecting 5 points each at the center and edge of the substrate (2 cm from the center) (9 points in total). Each point was measured 3 times, and the Cauchy model was fitted (error <1%) to obtain the thickness value. Deposition rate was calculated as: Deposition rate = Average thickness / Deposition time (μm / h). Thickness uniformity was calculated as: Standard deviation of thickness (σ) / Average thickness (%).

[0057] Table 1

[0058] Examples 1 to 5 (2.7-3.1 μm / h) significantly improved deposition efficiency compared to Control Examples 1 to 3 (0.9-1.2 μm / h), reaching more than 50% of the MOCVD level (5-10 μm / h) in the background art, thus solving the problem of "low deposition rate". The superior performance of the examples is attributed to the pulsed atomization (1.5-2.5 MHz, particle size 1-5 μm) optimizing aerosol transport efficiency, the low-power plasma module (10-50 W, 400-600°C) promoting precursor decomposition kinetics, and the microfluidic nozzle (10-50 μm, 1-5 kV electrostatic field driven) improving atomization accuracy and uniformity. Example 2 (3.1 μm / h) exhibited the highest deposition rate due to high-frequency atomization (2.5 MHz) and high-power plasma (50 W). Comparative Example 1, lacking pulsed atomization and a plasma module, had the lowest deposition rate (0.9 μm / h), and the high temperature (800°C) resulted in poor thickness uniformity (standard deviation 12.3 nm). Comparative Examples 2 and 3, with their single nozzle and lack of microfluidic nozzles respectively, limited aerosol distribution and deposition efficiency. The low standard deviation (4.8–5.5 nm) of the examples indicates superior thickness uniformity compared to the comparative examples (10.8–12.3 nm), thanks to the rotating base (10–50 rpm) and vortex mixer (100–500 rpm). These results validate the significant advantages of the technical features of this invention in improving deposition rate and uniformity, making it suitable for large-scale production needs.

[0059] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for growing gallium oxide thin films using fog chemical vapor deposition, characterized in that, Includes the following steps: Step S1. Provide a liquid gallium precursor and generate an aerosol using a pulse atomization device. The pulse atomization device uses an ultrasonic generator with a frequency range of 1.5-2.5 MHz, a pulse interval of 0.1-1 seconds, and controls the aerosol particle size to be 1-5 μm. Step S2. The aerosol is transferred to the reaction chamber via an inert carrier gas. The reaction chamber is equipped with a low-power plasma module. The plasma module uses a radio frequency power supply with a power range of 10-50 W and a frequency of 13.56 MHz. The deposition temperature is controlled at 500-600℃. Step S3. Deposit a gallium oxide thin film on a substrate, the substrate being placed on a rotating base at a rotation speed of 10-50 rpm and a reaction chamber pressure of 0.1-10 Torr.

2. The method according to claim 1, characterized in that, The liquid gallium precursor includes one or a combination of gallium chloride, gallium nitrate, or gallium acetylacetonate. The precursor is dissolved in deionized water or ethanol solvent at a concentration of 0.01-0.5 mol / L, and 0.05-0.2 wt% of a stabilizer, namely polyethylene glycol or polyvinylpyrrolidone, is added to the solvent.

3. The method according to claim 1, characterized in that, The method further includes setting up a multi-path precursor atomization system in the reaction chamber. The multi-path precursor atomization system includes at least two independent nozzles, one for atomizing the gallium precursor and the other for atomizing the dopant precursor. The dopant precursor is tin chloride, silane, magnesium nitrate, or zinc chloride. The dopant concentration is adjusted by an independent flow controller within a range of 10. 16 -10 20 cm -3 The accuracy of the flow controller is 0.1 sccm.

4. The method according to claim 3, characterized in that, The multi-path precursor atomization system is equipped with an online spectrometer and a feedback control unit. The spectrometer uses ultraviolet-visible spectroscopy technology and monitors wavelengths in the range of 200-800nm. The feedback control unit adjusts the nozzle flow rate via a servo motor, with a response time of less than 0.5 seconds.

5. The method according to claim 1, characterized in that, The substrate is a silicon, sapphire, or gallium oxide single crystal substrate. Before depositing the gallium oxide thin film, a transition layer with a thickness of 5-10 nm is pre-deposited on the substrate by atomic layer deposition. The transition layer is aluminum oxide, zinc oxide, or aluminum nitride. The deposition temperature is 200-300℃, and the number of cycles is 50-100. The surface of the transition layer is treated with oxygen plasma with a treatment power of 50-100 W and a time of 30-60 s.

6. The method according to claim 5, characterized in that, The substrate is pretreated before deposition, and the pretreatment includes the following steps: ultrasonic cleaning with acetone and isopropanol for 5-10 minutes in sequence, drying with nitrogen, and annealing in a vacuum environment at 300-400°C for 30 minutes. After the transition layer is deposited, it is subjected to rapid heat treatment in an argon atmosphere at a temperature of 400-500°C for 1-3 minutes.

7. The method according to claim 1, characterized in that, The liquid gallium precursor includes a first precursor and a second precursor. The first precursor is gallium chloride, dissolved in deionized water at a concentration of 0.1-0.3 mol / L. The second precursor is gallium acetylacetonate, dissolved in ethanol at a concentration of 0.05-0.2 mol / L. The two precursors are atomized separately by a dual-nozzle atomizing device. The dual-nozzle device adopts a coaxial structure with a nozzle outlet spacing of 2-5 mm. The two aerosols are mixed at the inlet of the reaction chamber by a vortex mixer at a speed of 100-500 rpm.

8. The method according to claim 1, characterized in that, A low-temperature microwave plasma module is introduced into the atomization chamber. The module uses a microwave power supply with a power of 50-100 W and a frequency of 2.45 GHz. The aerosol residence time in the plasma environment is 0.1-0.5 seconds, generating an intermediate containing gallium-oxygen free radicals. The deposition temperature in the reaction chamber is 400-500℃, and the carrier gas is nitrogen or argon with a flow rate of 1-5 L / min.

9. The method according to claim 1, characterized in that, The pulsed atomizing device employs a microfluidic nozzle, which includes multiple parallel channels with a channel size of 10-50 μm. The channel walls are coated with a hydrophobic coating made of polytetrafluoroethylene. The nozzle is driven by a 1-5 kV electrostatic field, with an electrode spacing of 1-3 mm. The atomization frequency is synchronized with the pulsed ultrasonic wave, with a frequency range of 1.5-2.5 MHz.

10. The method according to claim 1, characterized in that, The liquid gallium precursor is gallium citrate, dissolved in deionized water at a concentration of 0.05-0.2 mol / L. 0.1-0.5 wt% of a surfactant, such as sodium dodecyl sulfate or Tween 80, is added to the solvent. The method further includes sequentially depositing a gallium oxide layer and a zinc oxide layer by switching precursor nozzles during the deposition process. The zinc oxide layer uses a zinc nitrate precursor at a concentration of 0.1-0.3 mol / L, and the deposition time is 1-5 minutes, forming a gallium oxide / zinc oxide heterojunction structure with a heterojunction thickness ratio of 1:1 to 3:1.

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