Wafer-level high dielectric constant gallium oxide film and preparation method thereof

Abstract

The application discloses a wafer-level high-dielectric-constant gallium oxide film and a preparation method thereof. The preparation method comprises the following steps: dissolving gallium salt, ethylenediaminetetraacetic acid and polyethyleneimine in water, performing complexation reaction, and obtaining a gallium-based precursor solution through ultrafiltration; and spin-coating the gallium-based precursor solution on a substrate to form a preformed film, heating to 600-1000 DEG C in air to perform annealing treatment, and obtaining the wafer-level high-dielectric-constant gallium oxide film. The wafer-level high-dielectric-constant gallium oxide film prepared by the application has high dielectric constant and breakdown field strength at normal temperature, is dense, has uniform element distribution, has no defects such as pinholes and cracks, can realize precise regulation of the film thickness from sub-nanometer to nanometer, meets the differentiated demand of different semiconductor devices on the thickness of the gallium oxide film, and can be applied to the fields of ultraviolet photoelectric detection, field effect tubes and power electronic devices.

Description

Technical Field

[0001] This invention relates to the field of semiconductor materials technology, specifically to a wafer-level high dielectric constant gallium oxide thin film and its preparation method. Background Technology

[0002] Gallium oxide (Ga2O3), as a typical representative of the new generation of ultra-wide bandgap semiconductors, possesses advantages such as ultra-wide bandgap, ultra-high breakdown field strength, good dielectric properties, high carrier mobility, and high transmittance of visible light. These excellent properties make Ga2O3 a promising candidate for applications in ultraviolet photodetectors, field-effect transistors, and power electronic devices. Furthermore, gallium oxide optoelectronic devices, due to their short response wavelength and fast response speed, play a crucial role in applications such as radar, jamming, countermeasures, missile detection, and wireless communication.

[0003] Currently, existing technologies typically employ chemical vapor deposition (CVD), atomic layer deposition (ALD), and sputtering to prepare gallium oxide dielectric thin films. Furthermore, Yi et al. reported the preparation of ultrathin and uniform Ga2O3 thin films via extrusion printing and surface tension driven methods. Unlike traditional deposition methods that require nucleation on the channel material surface, this Ga2O3 integration technology is compatible with the dangling bond-free surface of two-dimensional semiconductors, enabling the formation of near-ideal van der Waals interfaces. The resulting film exhibits a high dielectric constant of approximately 30 and a breakdown field strength of 11 MV / cm (Nat. Electron. 2024, 7, 1126). Lee et al., through thickness optimization, heat treatment, and a unique nozzle tilting technique, successfully prepared aerosol-deposited Ga2O3 thin films with high breakdown field strength. These films exhibit a dielectric constant of 9.3 at 10 kHz and low leakage current characteristics, with a leakage current of 5.8 × 10⁻⁶ at 20 kV / cm. -11 A·cm -2 The breakdown field strength is as high as 5.5 MV / cm (SMALL STRUCT. 2024, 5, 2400321).

[0004] Existing methods for preparing gallium oxide thin films all suffer from significant technical limitations. Traditional methods such as CVD, ALD, and sputtering cannot create uniform nucleation sites on high-quality, dangling-bond-free two-dimensional semiconductor surfaces with a thickness of only a few nanometers. This results in poor interface quality of the prepared dielectric films, ultimately leading to a significant deterioration in the performance of related semiconductor devices. While extrusion printing and surface tension-driven methods can produce ultra-thin and uniform films, they suffer from a self-limiting problem in film thickness, with gallium oxide films produced at a thickness of approximately 3 nm. This makes it impossible to flexibly control the film thickness according to actual production needs. At present, achieving the industrial production of large-area, high-quality gallium oxide thin films remains a significant challenge. Summary of the Invention

[0005] The purpose of this invention is to solve the technical problems of existing technologies, such as difficulty in achieving large-area high-quality film formation, inability to control film thickness, complex preparation equipment, and poor process repeatability. This invention provides a wafer-level high-dielectric-constant gallium oxide thin film and its preparation method. The gallium oxide thin film obtained is of high quality, can achieve large-area film formation, and has a simple preparation process with good repeatability and controllable film thickness.

[0006] The above-mentioned objective of the present invention is achieved through the following technical solution:

[0007] The first aspect of this invention provides a method for preparing a wafer-level high-dielectric-constant gallium oxide thin film, comprising the following steps:

[0008] (1) Gallium salt, ethylenediaminetetraacetic acid and polyethyleneimine are dissolved in water and subjected to a complexation reaction. The gallium-based precursor solution is obtained by ultrafiltration. The mass ratio of gallium salt, ethylenediaminetetraacetic acid and polyethyleneimine is 1:(0.8-1.2):(1.5-2).

[0009] (2) Spin-coating the gallium-based precursor solution obtained in step (1) onto the substrate to form a preform film, and annealing the preform film in air to 600-1000 °C to obtain the wafer-level high dielectric constant gallium oxide thin film.

[0010] This invention solves the film quality problems caused by traditional gallium salt precursors, such as easy hydrolysis, poor dispersibility, uncontrollable nucleation, and severe particle agglomeration, through a dual-ligand synergistic complexation system of ethylenediaminetetraacetic acid (EDTA) and polyethyleneimine (PEI), combined with ultrafiltration purification technology. Simultaneously, it utilizes dual methods—controlling the concentration of the gallium-based precursor solution and controlling the spin-coating rate—to achieve control over the thickness of the gallium oxide film. This invention abandons expensive vapor deposition equipment and complex micro / nano fabrication processes, achieving wafer-level large-area film deposition based on an aqueous solution system. It combines the advantages of being environmentally friendly and suitable for industrial mass production, and efficient crystallization of the gallium oxide film can be achieved through an air-based annealing process.

[0011] Further, in step (1), the ratio of gallium salt to water is 1 g : 15-20 mL.

[0012] Further, in step (1), the gallium salt is Ga(NO3)3 (gallium nitrate).

[0013] Furthermore, in step (1), the complexation reaction takes 3-4 hours.

[0014] Further, in step (1), the specific operation of ultrafiltration is as follows: add water to dilute the solution after complexation reaction to complete one ultrafiltration operation, and repeat the above operation of adding water to dilute and ultrafiltration 2-4 times; based on the addition of 1 g gallium salt, the volume of water added at one time during ultrafiltration is 15-25 mL.

[0015] In a specific implementation, in step (1), the specific operation of ultrafiltration is as follows: pour the solution after complexation reaction into an ultrafiltration cup, add water to dilute it, place the ultrafiltration cup on a magnetic stirrer to stir, and at the same time, introduce nitrogen gas into the ultrafiltration cup to start ultrafiltration until the solution volume is reduced to the initial value, thus completing one ultrafiltration operation.

[0016] Furthermore, in step (1), the concentration of the gallium-based precursor solution can be measured using an inductively coupled plasma (ICP-PAP) analyzer. The ICP-PAP analyzer can accurately determine the gallium content in the solution, thereby determining the effective concentration of the gallium-based precursor solution. This provides a precise numerical basis for subsequent concentration-based thin film thickness control, ensuring the accuracy and repeatability of the thin film thickness control.

[0017] Further, in step (2), the substrate is a silicon substrate or an alumina substrate, and the silicon substrate is a polished silicon substrate, a silicon dioxide substrate or a quartz substrate.

[0018] Furthermore, in step (2), the substrate is prepared by a pretreatment process involving heating with a piranha solution, washing, drying, and hydrophilic treatment.

[0019] Furthermore, the piranha solution is prepared by mixing 30% hydrogen peroxide solution and 98% concentrated sulfuric acid solution in a volume ratio of 3:7.

[0020] Furthermore, the heating treatment is performed at a temperature of 140-160 °C for 20-40 min; the hydrophilic treatment is performed for 8-12 min.

[0021] In a specific embodiment, the substrate undergoes the following pretreatment: the substrate is placed in a piranha solution, heated at 140-160 °C for 20-40 min, then ultrasonically cleaned three times with ultrapure water, and finally dried with nitrogen.

[0022] Furthermore, in step (2), the annealing temperature is 600-800 ℃.

[0023] Furthermore, in step (2), the annealing process takes 3-4 hours.

[0024] Further, in step (2), a concentrated or diluted gallium-based precursor solution is spin-coated onto a substrate to form a preform; the concentration method is to heat the gallium-based precursor solution at 70-80°C in an air atmosphere; the dilution method is to mix the gallium-based precursor solution with water at a volume ratio of 1:(0.1-1).

[0025] Furthermore, in step (2), the spin coating speed is 3000-8000 rpm.

[0026] The present invention can control the thickness of gallium oxide thin films by controlling the concentration of the gallium-based precursor solution or by adjusting the spin coating rate.

[0027] The second aspect of the present invention provides a wafer-level high dielectric constant gallium oxide thin film prepared by the preparation method described in the first aspect.

[0028] The wafer-level high dielectric constant gallium oxide thin film provided by this invention has high crystallinity and high density, and the elements are evenly distributed with no impurity residue.

[0029] The above-described technical solution of the present invention has the following beneficial effects:

[0030] 1. The wafer-level high dielectric constant gallium oxide thin film prepared by this invention has a high dielectric constant and breakdown field strength at room temperature. At the same time, the film is dense, the element distribution is uniform, and there are no defects such as pinholes or cracks. By dual control of the concentration of gallium-based precursor solution and spin coating rate, the film thickness can be precisely controlled from sub-nanometer to nanometer level, which can meet the differentiated requirements of different semiconductor devices for gallium oxide film thickness. It can be applied to ultraviolet photodetectors, field-effect transistors and power electronic devices.

[0031] 2. The gallium-based precursor solution prepared by this invention forms a stable multi-component complex system through synergistic complexation of two ligands, which can be stably stored in air for more than six months, greatly improving the repeatability and stability of the process. The preparation method uses water as a solvent, eliminating toxic and harmful organic solvents, and does not require expensive vapor deposition, sputtering and other equipment. The process is simple, convenient to operate and has low preparation cost, and can realize wafer-level large-area film formation, meeting the needs of large-scale industrial production of semiconductor materials. Attached Figure Description

[0032] Figure 1 The image shows the X-ray diffraction (XRD) pattern of the wafer-level high dielectric constant gallium oxide thin film prepared in Example 1.

[0033] Figure 2 Thickness diagram of the wafer-level high dielectric constant gallium oxide thin film prepared in Example 1, as measured by atomic force microscopy (AFM).

[0034] Figure 3The images are scanning electron microscope (SEM) images (scale bar is 2 μm) of the wafer-level high dielectric constant gallium oxide thin films prepared in Examples 1-6; where (a) is Example 1, (b) is Example 2, (c) is Example 3, (d) is Example 4, (e) is Example 5, and (f) is Example 6.

[0035] Figure 4 AFM morphology and surface roughness of the wafer-level high dielectric constant gallium oxide thin films prepared in Examples 1-6 are shown; where (a) is Example 1, (b) is Example 2, (c) is Example 3, (d) is Example 4, (e) is Example 5, and (f) is Example 6.

[0036] Figure 5 The images are transmission electron microscope (TEM) images of the wafer-level high dielectric constant gallium oxide thin films prepared in Examples 12 and 20; where (a) is Example 12 and (b) is Example 20.

[0037] Figure 6 The image shows the thickness data of the wafer-level high dielectric constant gallium oxide thin films prepared in Examples 1-42.

[0038] Figure 7 AFM morphology and surface roughness of the wafer-level high dielectric constant gallium oxide thin films prepared in Examples 43-48 are shown; wherein, (a) is Example 43, (b) is Example 44, (c) is Example 45, (d) is Example 46, (e) is Example 47, and (f) is Example 48.

[0039] Figure 8 AFM morphology and surface roughness of the wafer-level high dielectric constant gallium oxide thin films prepared in Examples 49-54 are shown; where (a) is Example 49, (b) is Example 50, (c) is Example 51, (d) is Example 52, (e) is Example 53, and (f) is Example 54.

[0040] Figure 9 The image shows the AFM morphology and surface roughness of the wafer-level high dielectric constant gallium oxide thin film prepared in Example 55.

[0041] Figure 10 The images show the physical image and thickness uniformity characterization diagram of the wafer-level high dielectric constant gallium oxide thin film prepared in Example 55; where (a) is the physical image and (b) is the thickness contour characterization diagram.

[0042] Figure 11 The images show the gallium-based precursor solutions prepared in Example 1 and Comparative Examples 3-6 before ultrafiltration.

[0043] Figure 12The images show the surface morphology of the wafer-level high dielectric constant gallium oxide thin films prepared in Examples 1, 63-65 and Comparative Examples 3-6 under an optical microscope.

[0044] Figure 13 The bandgap diagrams are for the wafer-level high dielectric constant gallium oxide thin films prepared in Examples 56-61.

[0045] Figure 14 The dielectric constant-voltage characteristic curves of the gallium oxide thin films prepared in Example 62 and Comparative Examples 1-2 are shown; where (a) is Example 62, (b) is Comparative Example 1, and (c) is Comparative Example 2.

[0046] Figure 15 The current density-voltage characteristic curves of the gallium oxide thin films prepared in Example 62 and Comparative Examples 1-2 are shown; where (a) is Example 62, (b) is Comparative Example 1, and (c) is Comparative Example 2. Detailed Implementation

[0047] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the specification of this invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0048] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments described are not intended to limit the present invention.

[0049] Unless otherwise specified, the experimental methods used in the following examples are conventional methods, and the materials and reagents used are commercially available.

[0050] Example 1

[0051] A method for preparing a wafer-level high-dielectric-constant gallium oxide thin film includes the following steps:

[0052] (1) Dissolve 10 g of polyethyleneimine and 5 g of ethylenediaminetetraacetic acid in 50 mL of water, add 5 g of Ga(NO3)3, stir thoroughly for 4 h to allow a complexation reaction to occur, forming a homogeneous and stable reaction solution. The mass ratio of Ga(NO3)3, ethylenediaminetetraacetic acid and polyethyleneimine is 1:1:2. Pour the above reaction solution into an Amicon 200 mL ultrafiltration cup, use an Ultracel ultrafiltration membrane (membrane diameter of 63.5 mm), dilute with water, place the ultrafiltration cup on a magnetic stirrer and stir, and simultaneously introduce nitrogen gas into the ultrafiltration cup to start ultrafiltration until the volume of the reaction solution is reduced to the initial value, completing one ultrafiltration operation. Repeat this dilution ultrafiltration operation 3 times, and finally adjust the solution to 50 mL to filter out uncomplexed anions and cations and molecules with a molecular weight of less than 10,000. A gallium-based precursor solution was prepared by using small molecule impurities at a concentration of g / mol. The concentration of the gallium-based precursor solution was detected by inductively coupled plasma atomic absorption spectrometry, and the gallium content concentration was found to be 51.34 mg / L.

[0053] (2) Select a 1 cm × 1 cm polished silicon substrate and place it in a piranha solution (prepared by mixing 30% hydrogen peroxide solution and 98% concentrated sulfuric acid solution in a volume ratio of 3:7) for surface pretreatment. After completion, it is ultrasonically cleaned three times with ultrapure water and then dried with a nitrogen gun. It is then hydrophilically treated for 10 min using a plasma cleaner (model PDC-002) to obtain a pretreated polished silicon substrate for later use. Place the dried polished silicon substrate on a spin coater and drop the above gallium-based precursor solution onto the substrate surface. Spin coat it at a speed of 3000 rpm to spread the gallium-based precursor solution evenly on the substrate surface to form a pre-film. Transfer the polished silicon substrate with the pre-film to a tube furnace and heat it to 600 ℃ in an air atmosphere. Hold it for annealing for 4 h. After annealing, cool it to room temperature with the furnace to obtain a wafer-level high dielectric constant gallium oxide thin film with a thickness of 8 nm.

[0054] The XRD pattern of the wafer-level high-dielectric-constant gallium oxide thin film prepared in Example 1 is shown below. Figure 1 As shown, this demonstrates the successful fabrication of a high-quality β-phase gallium oxide thin film; the thickness diagram obtained from AFM testing is shown below. Figure 2 As shown.

[0055] Example 2

[0056] A method for preparing a wafer-level high dielectric constant gallium oxide thin film is basically the same as that in Example 1, except that in step (2), spin coating is performed at a speed of 4000 rpm; the thickness of the final wafer-level high dielectric constant gallium oxide thin film is 7.7 nm.

[0057] Example 3

[0058] A method for preparing a wafer-level high dielectric constant gallium oxide thin film is basically the same as that in Example 1, except that in step (2), spin coating is performed at a speed of 5000 rpm; the thickness of the final wafer-level high dielectric constant gallium oxide thin film is 7.43 nm.

[0059] Example 4

[0060] A method for preparing a wafer-level high dielectric constant gallium oxide thin film is basically the same as that in Example 1, except that in step (2), spin coating is performed at a speed of 6000 rpm; the thickness of the final wafer-level high dielectric constant gallium oxide thin film is 7.19 nm.

[0061] Example 5

[0062] A method for preparing a wafer-level high dielectric constant gallium oxide thin film is basically the same as that in Example 1, except that in step (2), spin coating is performed at a speed of 7000 rpm; the thickness of the final wafer-level high dielectric constant gallium oxide thin film is 6.9 nm.

[0063] Example 6

[0064] A method for preparing a wafer-level high dielectric constant gallium oxide thin film is basically the same as that in Example 1, except that in step (2), spin coating is performed at a speed of 8000 rpm; the thickness of the final wafer-level high dielectric constant gallium oxide thin film is 6.76 nm.

[0065] SEM images of the wafer-level high-dielectric-constant gallium oxide thin films prepared in Examples 1-6 are shown below. Figure 3 As shown, the film surface is uniform, smooth, dense, and continuous.

[0066] The AFM morphology and surface roughness of the wafer-level high-dielectric-constant gallium oxide thin films prepared in Examples 1-6 are shown below. Figure 4 The thin film shown has low surface roughness and high interface quality.

[0067] Example 7

[0068] A method for preparing a wafer-level high dielectric constant gallium oxide thin film is basically the same as that in Example 1, except that: in step (1), the gallium-based precursor solution is placed in an oven and heated to 80 °C for concentration treatment, and the concentration of the gallium-based precursor solution is detected by an inductively coupled plasma analyzer, and the gallium content concentration is measured to be 76.9 mg / L; the thickness of the finally obtained wafer-level high dielectric constant gallium oxide thin film is 9.99 nm.

[0069] Example 8

[0070] A method for preparing a wafer-level high dielectric constant gallium oxide thin film is basically the same as that in Example 1, except that: in step (1), the gallium-based precursor solution is placed in an oven and heated to 80 °C for concentration treatment, and the concentration of the gallium-based precursor solution is detected by an inductively coupled plasma analyzer, and the gallium content concentration is measured to be 96.4 mg / L; the thickness of the finally obtained wafer-level high dielectric constant gallium oxide thin film is 13.6 nm.

[0071] Example 9

[0072] A method for preparing a wafer-level high dielectric constant gallium oxide thin film is basically the same as that in Example 1, except that: in step (1), the gallium-based precursor solution is placed in an oven and heated to 80 °C for concentration treatment, and the concentration of the gallium-based precursor solution is detected by an inductively coupled plasma analyzer, and the gallium content concentration is measured to be 112.2 mg / L; the thickness of the finally obtained wafer-level high dielectric constant gallium oxide thin film is 32.6 nm.

[0073] Example 10

[0074] A method for preparing a wafer-level high dielectric constant gallium oxide thin film is basically the same as that in Example 1, except that: in step (1), the gallium-based precursor solution is mixed with water for dilution treatment, and the concentration of the gallium-based precursor solution is detected by an inductively coupled plasma analyzer, and the gallium content concentration is measured to be 13.14 mg / L; the thickness of the finally obtained wafer-level high dielectric constant gallium oxide thin film is 4.37 nm.

[0075] Example 11

[0076] A method for preparing a wafer-level high dielectric constant gallium oxide thin film is basically the same as that in Example 1, except that: in step (1), the gallium-based precursor solution is mixed with water for dilution treatment, and the concentration of the gallium-based precursor solution is detected by an inductively coupled plasma analyzer, and the gallium content concentration is measured to be 8.27 mg / L; the thickness of the finally obtained wafer-level high dielectric constant gallium oxide thin film is 2.04 nm.

[0077] Example 12

[0078] A method for preparing a wafer-level high dielectric constant gallium oxide thin film is basically the same as that in Example 1, except that: in step (1), the gallium-based precursor solution is mixed with water for dilution treatment, and the concentration of the gallium-based precursor solution is detected by an inductively coupled plasma analyzer, and the gallium content concentration is measured to be 2.11 mg / L; the thickness of the finally obtained wafer-level high dielectric constant gallium oxide thin film is 0.77 nm.

[0079] Examples 13-17

[0080] A method for preparing a wafer-level high-dielectric-constant gallium oxide thin film is basically the same as that in Example 7, except that in step (2), spin coating is performed at rotation speeds of 4000 rpm, 5000 rpm, 6000 rpm, 7000 rpm, and 8000 rpm, respectively. The thicknesses of the wafer-level high-dielectric-constant gallium oxide thin films finally obtained in Examples 13-17 are 8.1 nm, 7.76 nm, 7.52 nm, 7.36 nm, and 7.21 nm, respectively.

[0081] Examples 18-22

[0082] A method for preparing a wafer-level high-dielectric-constant gallium oxide thin film is basically the same as that in Example 8, except that in step (2), spin coating is performed at rotation speeds of 4000 rpm, 5000 rpm, 6000 rpm, 7000 rpm, and 8000 rpm, respectively. The thicknesses of the wafer-level high-dielectric-constant gallium oxide thin films finally obtained in Examples 18-22 are 12.4 nm, 11.5 nm, 10.7 nm, 9.8 nm, and 9 nm, respectively.

[0083] TEM images of the wafer-level high-dielectric-constant gallium oxide thin films prepared in Examples 12 and 20 are shown below. Figure 5 As shown, the wafer-level high dielectric constant gallium oxide thin film prepared by this invention possesses high-quality crystallization characteristics regardless of whether it is in the sub-nanometer or nanometer thickness range.

[0084] Examples 23-27

[0085] A method for preparing a wafer-level high-dielectric-constant gallium oxide thin film is basically the same as that in Example 9, except that in step (2), spin coating is performed at rotation speeds of 4000 rpm, 5000 rpm, 6000 rpm, 7000 rpm, and 8000 rpm, respectively. The thicknesses of the wafer-level high-dielectric-constant gallium oxide thin films finally obtained in Examples 23-27 are 28.49 nm, 26.42 nm, 24.66 nm, 22.04 nm, and 20.63 nm, respectively.

[0086] Examples 28-32

[0087] A method for preparing a wafer-level high-dielectric-constant gallium oxide thin film is basically the same as that in Example 10, except that in step (2), spin coating is performed at rotation speeds of 4000 rpm, 5000 rpm, 6000 rpm, 7000 rpm, and 8000 rpm, respectively. The thicknesses of the wafer-level high-dielectric-constant gallium oxide thin films finally obtained in Examples 28-32 are 4.18 nm, 4 nm, 3.78 nm, 3.66 nm, and 3.54 nm, respectively.

[0088] Examples 33-37

[0089] A method for preparing a wafer-level high-dielectric-constant gallium oxide thin film is basically the same as that in Example 11, except that in step (2), spin coating is performed at rotation speeds of 4000 rpm, 5000 rpm, 6000 rpm, 7000 rpm, and 8000 rpm, respectively. The thicknesses of the wafer-level high-dielectric-constant gallium oxide thin films finally obtained in Examples 33-37 are 2.01 nm, 1.98 nm, 1.95 nm, 1.93 nm, and 1.92 nm, respectively.

[0090] Examples 38-42

[0091] A method for preparing a wafer-level high-dielectric-constant gallium oxide thin film is basically the same as that in Example 12, except that in step (2), spin coating is performed at rotation speeds of 4000 rpm, 5000 rpm, 6000 rpm, 7000 rpm, and 8000 rpm, respectively. The thicknesses of the wafer-level high-dielectric-constant gallium oxide thin films finally obtained in Examples 38-42 are 0.74 nm, 0.7 nm, 0.685 nm, 0.66 nm, and 0.65 nm, respectively.

[0092] The thickness data of the wafer-level high dielectric constant gallium oxide thin films prepared in Examples 1-42 are shown in the figure below. Figure 6 As shown, the preparation method provided by the present invention can precisely control the thickness of the grown gallium oxide film.

[0093] Examples 43-48

[0094] A method for preparing a wafer-level high-dielectric-constant gallium oxide thin film is basically the same as that in Examples 7-12, except that in step (2), a 1 cm × 1 cm silicon dioxide substrate is selected and spin-coated at a speed of 6000 rpm. The thicknesses of the wafer-level high-dielectric-constant gallium oxide thin films finally obtained in Examples 43-48 are 7.52 nm, 10.7 nm, 24.66 nm, 3.78 nm, 1.97 nm, and 0.685 nm, respectively.

[0095] The AFM morphology and surface roughness of the wafer-level high-dielectric-constant gallium oxide thin films prepared in Examples 43-48 are shown below. Figure 7 As shown, the preparation method provided by the present invention can grow high-quality gallium oxide thin films on silicon dioxide substrates and has universality.

[0096] Examples 49-54

[0097] A method for preparing a wafer-level high-dielectric-constant gallium oxide thin film is basically the same as that in Examples 7-12, except that in step (2), a 1 cm × 1 cm alumina substrate is selected and spin-coated at a speed of 6000 rpm. The thicknesses of the wafer-level high-dielectric-constant gallium oxide thin films finally obtained in Examples 49-54 are 7.52 nm, 10.7 nm, 24.66 nm, 3.78 nm, 1.97 nm, and 0.685 nm, respectively.

[0098] The AFM morphology and surface roughness of the wafer-level high-dielectric-constant gallium oxide thin films prepared in Examples 49-54 are shown below. Figure 8 As shown, the preparation method provided by the present invention can grow high-quality gallium oxide thin films on alumina substrates and has universality.

[0099] Example 55

[0100] A method for preparing a wafer-level high dielectric constant gallium oxide thin film is basically the same as that in Example 12, except that in step (2), a three-inch polished silicon substrate is selected and spin-coated at a speed of 6000 rpm; the thickness of the final wafer-level high dielectric constant gallium oxide thin film is 0.685 nm.

[0101] AFM morphology and surface roughness at different locations of the wafer-level high-dielectric-constant gallium oxide thin film prepared in Example 55 are shown below. Figure 9 As shown, the three-inch gallium oxide film prepared in Example 55 has extremely low surface roughness and the overall roughness is basically consistent.

[0102] The physical image and thickness uniformity characterization diagram of the wafer-level high dielectric constant gallium oxide thin film prepared in Example 55 are shown below. Figure 10 As shown, the film has a uniform overall thickness and excellent surface flatness.

[0103] Examples 56-61

[0104] A method for preparing a wafer-level high-dielectric-constant gallium oxide thin film is basically the same as that in Examples 7-12, except that in step (2), a 1 cm × 1 cm quartz substrate is selected and spin-coated at a speed of 3000 rpm. The thicknesses of the wafer-level high-dielectric-constant gallium oxide thin films finally obtained in Examples 56-61 are 9.99 nm, 13.6 nm, 32.6 nm, 4.37 nm, 2.04 nm, and 0.77 nm, respectively.

[0105] Example 62

[0106] A method for preparing a wafer-level high dielectric constant gallium oxide thin film is basically the same as that in Example 4, except that: in step (2), a 13 mm × 15 mm FTO substrate is selected and spin-coated at a speed of 6000 rpm; the thickness of the final wafer-level high dielectric constant gallium oxide thin film is 7.19 nm.

[0107] Example 63

[0108] A method for preparing a wafer-level high dielectric constant gallium oxide thin film is basically the same as that in Example 1, except that in step (1), the mass ratio of Ga(NO3)3, ethylenediaminetetraacetic acid and polyethyleneimine is 1:1.2:2.

[0109] Example 64

[0110] A method for preparing a wafer-level high dielectric constant gallium oxide thin film is basically the same as that in Example 1, except that in step (1), the mass ratio of Ga(NO3)3, ethylenediaminetetraacetic acid and polyethyleneimine is 1:0.8:2.

[0111] Example 65

[0112] A method for preparing a wafer-level high dielectric constant gallium oxide thin film is basically the same as that in Example 1, except that in step (1), the mass ratio of Ga(NO3)3, ethylenediaminetetraacetic acid and polyethyleneimine is 1:0.8:1.8.

[0113] Comparative Example 1

[0114] A method for preparing a gallium oxide thin film includes the following steps:

[0115] (1) Dissolve 10 g of polyethyleneimine in 50 mL of water, add 5 g of Ga(NO3)3, stir thoroughly for 4 h and a complexation reaction occurs to form a homogeneous and stable reaction solution; place the above reaction solution in an ultrafiltration system, dilute with water and then perform ultrafiltration treatment. This dilution and ultrafiltration operation is repeated 3 times. Finally, the solution is brought to a final volume of 50 mL to filter out uncomplexed anions and cations and small molecule impurities with a molecular weight of less than 10000 g / mol, and a gallium-based precursor solution is obtained; the concentration of the gallium-based precursor solution is detected by inductively coupled plasma analyzer, and its gallium content concentration is measured to be 41.43 mg / L.

[0116] (2) Select a 13 mm × 15 mm FTO substrate and place it in a piranha solution (prepared by mixing 30% hydrogen peroxide solution and 98% concentrated sulfuric acid solution in a volume ratio of 3:7) for surface pretreatment. After completion, it is ultrasonically cleaned three times with ultrapure water and then dried with a nitrogen gun to obtain a pretreated FTO substrate for use. Place the dried FTO substrate on a spin coater and drop the above gallium-based precursor solution onto the substrate surface. Spin coat at a speed of 6000 rpm to make the gallium-based precursor solution spread evenly on the substrate surface to form a pre-film. Transfer the FTO substrate with the pre-film to a tube furnace and heat it to 600 ℃ in an air atmosphere. Hold it for annealing for 4 h. After annealing, cool it to room temperature with the furnace to obtain a gallium oxide thin film.

[0117] Comparative Example 2

[0118] A method for preparing a gallium oxide thin film includes the following steps:

[0119] (1) Dissolve 10 g of polyethyleneimine in 50 mL of water, add 10 g of Ga(NO3)3, stir thoroughly for 4 h and a complexation reaction occurs to form a homogeneous and stable reaction solution; place the above reaction solution in an ultrafiltration system, dilute with water and then perform ultrafiltration treatment. This dilution and ultrafiltration operation is repeated 3 times. Finally, the solution is brought to a final volume of 50 mL to filter out uncomplexed anions and cations and small molecule impurities with a molecular weight of less than 10000 g / mol, and a gallium-based precursor solution is obtained; the concentration of the gallium-based precursor solution is detected by inductively coupled plasma analyzer, and its gallium content concentration is measured to be 96.43 mg / L.

[0120] (2) Select a 13 mm × 15 mm FTO substrate and place it in a piranha solution (prepared by mixing 30% hydrogen peroxide solution and 98% concentrated sulfuric acid solution in a volume ratio of 3:7) for surface pretreatment. After completion, it is ultrasonically cleaned three times with ultrapure water and then dried with a nitrogen gun to obtain a pretreated FTO substrate for use. Place the dried FTO substrate on a spin coater and drop the above gallium-based precursor solution onto the substrate surface. Spin coat at a speed of 6000 rpm to make the gallium-based precursor solution spread evenly on the substrate surface to form a pre-film. Transfer the FTO substrate with the pre-film to a tube furnace and heat it to 600 ℃ in an air atmosphere. Hold it for annealing for 4 h. After annealing, cool it to room temperature with the furnace to obtain a gallium oxide thin film.

[0121] Comparative Example 3

[0122] A method for preparing a wafer-level high dielectric constant gallium oxide thin film is basically the same as that in Example 1, except that in step (1), the mass ratio of Ga(NO3)3, ethylenediaminetetraacetic acid and polyethyleneimine is 1:0.5:1.

[0123] Comparative Example 4

[0124] A method for preparing a wafer-level high dielectric constant gallium oxide thin film is basically the same as that in Example 1, except that in step (1), the mass ratio of Ga(NO3)3, ethylenediaminetetraacetic acid and polyethyleneimine is 1:2:3.

[0125] Comparative Example 5

[0126] A method for preparing a wafer-level high dielectric constant gallium oxide thin film is basically the same as that in Example 1, except that in step (1), the mass ratio of Ga(NO3)3, ethylenediaminetetraacetic acid and polyethyleneimine is 1:1.5:1.

[0127] Comparative Example 6

[0128] A method for preparing a wafer-level high dielectric constant gallium oxide thin film is basically the same as that in Example 1, except that in step (1), the mass ratio of Ga(NO3)3, ethylenediaminetetraacetic acid and polyethyleneimine is 1:2:2.

[0129] Figure 11 These are photographs of the gallium-based precursor solutions prepared in Example 1 and Comparative Examples 3-6 before ultrafiltration. Figure 12 These are surface morphology images of wafer-level high-dielectric-constant gallium oxide thin films prepared in Examples 1, 63-65, and Comparative Examples 3-6, under an optical microscope. Figure 11 and Figure 12 It can be seen that the ratio of Ga(NO3)3, ethylenediaminetetraacetic acid (EDTA), and polyethyleneimine has a significant impact on the degree of crosslinking and the properties of the prepared film: excessive polyethyleneimine leads to an increase in uncomplexed free segments, reducing the film's density; excessive Ga(NO3)3 enhances the coordination with the functional groups of polyethyleneimine, potentially increasing the film's brittleness. Gallium-based precursor solutions prepared with Ga(NO3)3, EDTA, and polyethyleneimine within a suitable ratio range are clear and transparent (before ultrafiltration). Insufficient or excessive polyethyleneimine will cause turbidity or precipitation in the solution.

[0130] Compare with Example 1

[0131] A method for preparing a gallium oxide thin film, referring to the literature (Int. J. Energy Res. 2025, 2025, 19), includes the following steps:

[0132] 0.319 g of gallium nitrate was dissolved in 5 mL of methanol, and then stirred thoroughly at a constant temperature of 30 °C for 15 min to ensure complete dissolution and obtain a gallium nitrate solution. Similarly, 1.0936 g of cerium acetylacetone hydrate was dissolved in a prepared mixture of 3 mL of methanol and 6 mL of acetic acid, and then stirred at 60 °C for 15 min to form a homogeneous solution, which was then mixed with the gallium nitrate solution. This process was carried out at 60 °C with vigorous stirring for 30 min to ensure thorough mixing and reaction of the components. The resulting mixture was then spin-coated onto a 4H-SiC substrate at a spin speed of 3000 rpm for 30 s to obtain a uniform coating required for subsequent experiments. Subsequently, the coating was annealed at 900 °C in a horizontal tube furnace under a N2-O2-N2 atmosphere with a gas flow rate of 100 mL / min and a heating rate of 10 °C / min to obtain a gallium oxide thin film.

[0133] Compare with Example 2

[0134] A method for preparing a gallium oxide thin film, referring to the literature (Small. 2025, 21, 37), includes the following steps:

[0135] First, a solution was prepared by mixing 1.5 g of polypropylene carbonate (PPC) with 10 g of anisole and stirring at 60 °C for 12 h. A transparent polydimethylsiloxane (PDMS) film was placed on a glass slide and coated with the PPC solution at 5000 rpm for 60 s; subsequently, the coated film was baked at 100 °C for 10 min. Liquid gallium was then dropped onto the PDMS / PPC film heated to 40 °C. The droplet was then strongly compacted using another PDMS film placed on a glass slide, forming an ultrathin GaO layer on the PDMS / PPC film. X A monolayer, namely a gallium oxide thin film. The prepared gallium oxide thin film uses a PPC film as a sacrificial layer and is transferred to a silicon dioxide substrate using a dry transfer technique.

[0136] Compare with Example 3

[0137] A method for preparing a gallium oxide thin film, referring to the literature (Small Struct. 2024, 5, 2400321), includes the following steps:

[0138] Ga2O3 powder with an average particle size of approximately 3 μm and a particle size distribution coefficient of 5.7 was deposited on a Pt / Ti / Si substrate using atomic deposition. During atomic deposition, the powder particles solidified and deposited by impacting the substrate under the acceleration of the carrier gas. Nitrogen gas was used as the carrier gas to accelerate the deposition of Ga2O3 aerosol to form a Ga2O3 film. The gas flow rate was maintained at 5 L / min using a mass flow controller. When using the nozzle tilting method, the nozzle was tilted at a 45° angle to spray the aerosol onto the substrate, and a 3 μm thick Ga2O3 film was formed after 10 scans. The Ga2O3 film was then subjected to air heat treatment in a box furnace, held at 800 °C for 2 h, with a heating / cooling rate of 1 °C / min.

[0139] Compare with Example 4

[0140] A method for preparing a gallium oxide thin film, referring to the literature (J. Mater. Sci.: Mater. Electron. 2021, 32, 8347), includes the following steps:

[0141] A 0.2 M Ga₂O₃ precursor solution was prepared by dissolving Ga(NO₃)₃·xH₂O in 2-methoxyethanol and stirring the solution overnight at room temperature. The silicon substrate was ultrasonically cleaned and treated with oxygen plasma. The Ga₂O₃ precursor solution was then spin-coated onto the substrate at 3000 rpm for 30 s, followed by annealing at 150 °C for 20 min. Subsequently, the film was post-annealed at 550 °C for 1 h.

[0142] Test Example 1

[0143] The electrical properties of the gallium oxide thin films prepared in the examples, comparative examples, and control examples were tested. The test methods were as follows: the gallium oxide thin films grown on the quartz substrate were tested using an ultraviolet spectrophotometer to measure the absorption spectrum in the wavelength range of 190-400 nm, and then the band gap was calculated using the Tauc formula; a silver electrode was deposited on the surface of the gallium oxide thin film grown on the FTO substrate to construct a vertical structure device, the capacitance-voltage curve of the gallium oxide thin film was measured by LCR, the dielectric constant of the film was calculated, and the breakdown field strength characteristics of the film were characterized by DC breakdown test.

[0144] The bandgap diagrams of the wafer-level high-dielectric-constant gallium oxide thin films prepared in Examples 56-61 are shown below. Figure 13 As shown, the band gap increases with decreasing thickness, reaching a maximum of 6.05 eV.

[0145] The electrical properties of the gallium oxide thin films prepared in Examples 1, 62, Comparative Examples 1-2, and Control Examples 1-4 were tested as follows: Figure 14-15 As shown in Table 1:

[0146] Table 1. Dielectric constant and breakdown field strength data of gallium oxide thin films.

[0147]

[0148] Figure 14 The dielectric constant-voltage characteristic curves of the gallium oxide thin films prepared in Example 62 and Comparative Examples 1-2 are shown. Figure 15 The current density-voltage characteristic curves of the gallium oxide thin films prepared in Example 62 and Comparative Examples 1-2 are shown.

[0149] from Figure 14-15 As shown in Table 1, ethylenediaminetetraacetic acid (EDTA) effectively enhances the coordination complexation between polyethyleneimine and gallium ions, significantly inhibiting the hydrolysis and aggregation of gallium ions in aqueous solution. This results in highly uniform dispersion of gallium ions in the solution, providing favorable conditions for the subsequent preparation of large-area, defect-free uniform thin films. Compared with Comparative Examples 1-4, the gallium oxide thin films prepared by the polymer-assisted deposition method of this invention exhibit superior overall performance, demonstrating significant advantages in both film quality and dielectric properties.

[0150] In summary, this invention utilizes a dual-ligand synergistic complexation system formed by polyethyleneimine and ethylenediaminetetraacetic acid, combined with ultrafiltration purification technology, to prepare a gallium-based precursor solution with uniform dispersion and controllable viscosity. By controlling the concentration of the precursor solution and the spin-coating rate, the thickness of the gallium oxide film can be precisely controlled from sub-nanometer to nanometer scale. Furthermore, the vertically grown gallium oxide film can achieve an atomically smooth, defect-free surface, thereby effectively maintaining the high dielectric properties of the material. Subsequent annealing in an air atmosphere further promotes the complete pyrolysis of the complex and the efficient crystallization of gallium oxide, ultimately yielding a high-quality gallium oxide film with high crystallinity, good density, and excellent electrical properties, with a maximum band gap of 6.05 eV, a dielectric constant of 41.5, and a breakdown field strength of 8.913 MV / cm.

[0151] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art should understand that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing a wafer-level high-dielectric-constant gallium oxide thin film, characterized in that, Includes the following steps: (1) Gallium salt, ethylenediaminetetraacetic acid and polyethyleneimine are dissolved in water and subjected to a complexation reaction. The gallium-based precursor solution is obtained by ultrafiltration. The mass ratio of gallium salt, ethylenediaminetetraacetic acid and polyethyleneimine is 1:(0.8-1.2):(1.5-2). (2) Spin-coating the gallium-based precursor solution obtained in step (1) onto the substrate to form a preform film, and annealing the preform film in air to 600-1000 °C to obtain the wafer-level high dielectric constant gallium oxide thin film; the substrate is prepared by pretreatment steps of heating with piranha solution, cleaning, drying and hydrophilic treatment.

2. The preparation method according to claim 1, characterized in that, In step (1), the ratio of gallium salt to water is 1 g : 15-20 mL.

3. The preparation method according to claim 1, characterized in that, In step (1), the complexation reaction takes 3-4 hours.

4. The preparation method according to claim 1, characterized in that, In step (2), the substrate is a silicon substrate or an aluminum oxide substrate.

5. The preparation method according to claim 1, characterized in that, The piranha solution is prepared by mixing 30% hydrogen peroxide solution and 98% concentrated sulfuric acid solution in a volume ratio of 3:7; the heat treatment temperature is 140-160 ℃ and the time is 20-40 min.

6. The preparation method according to claim 1, characterized in that, In step (2), the annealing process takes 3-4 hours.

7. The preparation method according to claim 1, characterized in that, In step (2), the spin coating speed is 3000-8000 rpm.

8. A wafer-level high dielectric constant gallium oxide thin film prepared by the preparation method according to any one of claims 1-7.

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