A rare earth doped indium gallium zinc oxide target, a method of making the same, and a display device

Abstract

This invention discloses a rare-earth-doped indium gallium zinc oxide (IGaZ) target, its preparation method, and a display device thereof. The preparation method includes: dissolving indium, gallium, zinc, and rare-earth metals in an acidic solution at a specific molar ratio; converting them into acetate after co-precipitation and washing purification; mixing them with an organic solvent containing a stabilizer under ultrasonication and adjusting the pH to form a homogeneous sol; aging and filtering the sol; and forming a thin film with a thickness of 40-200 nm on a substrate through multilayer spin coating combined with intermediate heat treatment; finally, performing microwave segmented annealing on the thin film, sequentially performing low-temperature pre-annealing in air, medium-temperature pyrolysis annealing in nitrogen, and high-temperature densification annealing. This method achieves atomic-level uniform dispersion and deep purification of the components. The prepared target film has high density (≥99%) and low surface roughness (≤0.3 nm). Furthermore, the nanoscale second phase formed by rare-earth doping can effectively pin grain boundaries and reduce defect density, significantly improving the mobility and stability of thin-film transistors.

Description

Technical Field

[0001] This invention relates to the field of semiconductor materials and display device manufacturing, specifically to a rare-earth-doped indium gallium zinc oxide (IGZO) target for display devices such as thin-film transistors (TFTs), its high uniformity and high density preparation method, and its application in display devices. Background Technology

[0002] Indium gallium zinc oxide (IGZO), as a high-performance oxide semiconductor material, has become a core material for the channel layer of thin-film transistors (TFTs) in next-generation high-definition and flexible display devices due to its high mobility, high transparency, and good uniformity. Its performance directly depends on the quality of the IGZO target used for sputtering.

[0003] Currently, the mainstream high-end IGZO target preparation methods mostly adopt powder metallurgy or co-precipitation methods. However, these traditional methods have the following inherent defects, which limit the further improvement of IGZO film performance: (1) If the purity of the raw materials is insufficient, the alkali metal, heavy metal and other impurity ions contained therein are very likely to introduce lattice defects or segregate at the grain boundaries during subsequent high-temperature processing, forming leakage channels and damaging the electrical stability and reliability of the film. (2) In the traditional powder mixing process, it is difficult to achieve uniform mixing of metal oxide powders such as indium (In), gallium (Ga), and zinc (Zn) at the molecular level. This macroscopic or microscopic segregation of the components will lead to uneven composition of the sputtered film, resulting in fluctuations in electrical performance and affecting the uniformity of large-area display panels. (3) In the preparation route with metal chlorides as precursors, chloride ions (Cl) - Anions such as ) are difficult to completely remove. These residual anions may not only corrode equipment in subsequent processes, but also form impurities or induce abnormal oxygen vacancies during film annealing, becoming unstable factors in electrical performance. (4) To obtain functional films of sufficient thickness, single-layer thick film coating or deposition is often required. However, the huge internal stress generated by the rapid evaporation of solvents can easily lead to film cracking, warping or pinholes, seriously reducing the density and structural integrity of the film. (5) Traditional muffle furnace annealing is time-consuming and energy-intensive, and long-term high-temperature treatment may exacerbate the diffusion and segregation of rare earth dopants, which is not conducive to maintaining the uniform distribution of the nanoscale second phase and weakening its pinning effect on grain boundaries.

[0004] Therefore, developing an IGZO target preparation method that can control purity from the source, achieve atomic-level uniform distribution of components, avoid harmful impurities, and efficiently prepare high-quality thick films has become an urgent need to promote the development of display technology. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a rare-earth-doped indium gallium zinc oxide (IGZO) target and its preparation method. This method aims to obtain an IGZO target with highly uniform composition, no harmful anion residues, high film density, and excellent and stable electrical properties through precise control of the entire process, ultimately improving the performance and reliability of display devices using this target.

[0006] The technical solution adopted by the present invention to solve the above-mentioned technical problems is as follows: In a first aspect, the present invention provides a method for preparing a rare-earth-doped indium gallium zinc oxide target, comprising the following steps: (1) High-purity metallic indium, gallium, zinc and rare earth elements are dissolved in an acidic solution at a predetermined molar ratio, and a metal salt solution is obtained after complete dissolution; (2) Add ammonia to the metal salt solution obtained in step (1) to adjust the pH value to 6-8, and carry out a neutralization reaction at 40-60℃ to generate hydroxide precipitate; (3) The hydroxide precipitate is aged, filtered, and washed with pure water until the conductivity is below 300 μS•cm; (4) Add excess acetic acid to the washed hydroxide to convert it into acetate; (5) The obtained acetate solution was slowly added to an organic solvent containing a stabilizer under ultrasonic treatment, and the pH of the system was adjusted to 1-3 using glycerol to form a homogeneous sol; (6) After aging the sol for 12-24 hours, perform gradient filtration; (7) The filtered sol was coated onto the substrate by spin coating. After each layer was spin coated, heat treatment was performed. This process was repeated multiple times until the predetermined film thickness was achieved. (8) Perform microwave segmented annealing on the spin-coated film, including three stages: low-temperature pre-annealing, medium-temperature pyrolysis annealing and high-temperature densification annealing, to obtain the final target material.

[0007] Further, in step (1), the molar ratio of the metals indium, gallium, and zinc to the rare earth elements is (3~4):(1~2):(3~4):(1~2); The rare earth element is selected from at least one of praseodymium, neodymium, and samarium.

[0008] Further, in step (1), the acidic solution is nitric acid, and its amount is 1.8-3 times the total mass of the metal; the dissolution is carried out by heating treatment at a temperature of 60-110℃.

[0009] Furthermore, in step (5), the ultrasonic frequency is 20-40Hz, the power is 5kW, and the temperature is 40-60℃; The stabilizer is ethanolamine at a concentration of 0.5-2 mol / L; The organic solvent is N,N-dimethylformamide.

[0010] Further, in step (6), the gradient filtration is carried out using filter membranes or filter cloths of 10-50μm, 100-700nm and 20-70nm in sequence.

[0011] Further, in step (7), the spin coating speed is 2000-6000 rpm, the thickness of each spin coating layer is 10-20 nm, and each spin coating layer is placed in a microwave oven for heat treatment at 80-150℃ for 1-10 min after spin coating, with a total film thickness of 40-200 nm.

[0012] Further, in step (8), the low-temperature pre-annealing is carried out at 60-150℃ for 10-30 minutes in an air atmosphere; the medium-temperature pyrolysis annealing is carried out at 150-300℃ for 5-20 minutes in a nitrogen atmosphere; and the high-temperature densification annealing is carried out at 300-500℃ for 1-10 minutes in a nitrogen atmosphere.

[0013] In a second aspect, the present invention provides a rare earth-doped indium gallium zinc oxide target, characterized in that it is prepared by the preparation method described in any one of claims 1-7.

[0014] Furthermore, the target material is in the form of a thin film with a density of not less than 99% and a surface roughness of ≤0.3nm.

[0015] Thirdly, the present invention provides a display device comprising the above-mentioned rare-earth-doped indium gallium zinc oxide target.

[0016] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: (1) This invention uses high-purity (4N grade) metal raw materials and a full solution process to eliminate the introduction of impurities from the source. Through molecular-level mixing and co-precipitation, it achieves atomic-level uniform distribution of rare earth ions and matrix metal ions, overcoming the component segregation problem of traditional powder method. The component control deviation is ≤0.5% (better than the common 3% deviation of sputtering target materials).

[0017] (2) The entire process uses a nitrate-acetate precursor system, completely eliminating Cl. - The risk of residual corrosive anions is mitigated. By using a cleaning standard with fixed conductivity and controlling hydrolysis through acetic acid complexation, the generation of impurity phases and abnormal oxygen vacancies is effectively suppressed, thus improving the intrinsic stability of the material.

[0018] (3) During the annealing process, the doped rare earth elements such as Pr and Nd form nanoscale RInO3 (such as PrInO3) second phase with indium. These second phase particles can effectively pin the grain boundaries of IGZO, inhibit abnormal grain growth, and at the same time reduce the oxygen vacancy concentration in the film (which can be reduced to below 22%), significantly improving the bias stability and reliability of TFT devices.

[0019] (4) By layering multiple thin coatings and supplementing with intermediate heat treatment, the problems of easy cracking and numerous pinholes in single-layer thick film spin coating are perfectly solved. The resulting film has a density of over 99.2% and an extremely low surface roughness (≤0.3 nm), providing an ideal film morphology for the fabrication of high-performance devices. At the same time, compared with traditional muffle furnace annealing, microwave annealing reduces the processing time by 90% and energy consumption by 70%. Its fast and efficient characteristics are particularly suitable for substrates with poor heat resistance, such as flexible polyimide (PI), and can effectively reduce rare earth ion diffusion caused by long-term high-temperature processing, ensuring doping uniformity and second-phase nanoscale.

[0020] (5) This invention employs a three-stage microwave annealing process: "low-temperature pre-annealing (60-150℃, air) - medium-temperature pyrolysis annealing (150-300℃, nitrogen) - high-temperature densification annealing (300-500℃, nitrogen)". This process thoroughly removes residual organic matter in the low-temperature stage, completes precursor pyrolysis and preliminary network formation in an inert atmosphere in the medium-temperature stage, and finally achieves film densification, crystallization optimization, and the formation of rare-earth nano-second phases through a short-time high-temperature stage. This segmented strategy precisely controls the phase transformation process. In particular, the short-time high-temperature treatment greatly suppresses the diffusion and segregation of rare-earth ions while ensuring high film quality, thus guaranteeing doping uniformity. Compared to the traditional long-duration one-stage annealing in a muffle furnace, this process reduces processing time by more than 90% and energy consumption by more than 70%, and is especially suitable for flexible substrates with poor heat resistance.

[0021] (6) From solution preparation and gradient filtration to multilayer spin coating and microwave annealing, the parameters of each step are quantitatively controlled (such as pH, conductivity, rotation speed, temperature and time window), the process has good repeatability, small batch difference, high yield, and strong industrialization potential. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the process flow of the thin film preparation method described in this invention.

[0023] Figure 2 The diagram shows a uniform thin film prepared by spin coating according to the method of the present invention. (a) is the target material prepared in Example 1, (b) is the target material prepared in Example 1, and (c) is the target material prepared in Example 1. Detailed Implementation

[0024] This invention provides a rare-earth-doped indium gallium zinc oxide (IGZO) target (thin film morphology) and its preparation method. The core process flow of the preparation method includes the following steps (S1-S8), please refer to [link / reference]. Figure 1 The specific plan for each step is as follows: (1) Raw material dissolution: Metals indium (In), gallium (Ga), zinc (Zn), and at least one rare earth element (RE) with a purity of 4N (99.99%) or higher are weighed according to the molar ratio of In:Ga:Zn:RE = (3~4):(1~2):(3~4):(1~2). The metal mixture is added to an acidic solution (nitric acid), with the amount of acidic solution being 1.8~3 times the total mass of the metals. The mixture is heated and stirred at 60~110℃ until the metals are completely dissolved, forming a clear metal salt solution. This step uses high-purity metal raw materials, avoiding the introduction of impurities such as alkali metals and heavy metals from the source. Complete dissolution in the acidic solution ensures that the metal ions are uniformly dispersed at the molecular level, laying the foundation for subsequent uniform doping and reaction, and solving the problem of component segregation in traditional powder mixing methods. (2) Coprecipitation: Concentrated ammonia is added dropwise to the above solution to adjust the pH to 6-8. A neutralization reaction is then carried out at 40-60℃ to coprecipitate all metal ions as hydroxides. This step, under mild and controllable conditions, forms a uniform hydroxide coprecipitate, ensuring that the elements initially achieve uniform recombination in the solid phase. (3) Precipitation and Purification: The hydroxide precipitate is aged for 4-8 hours, followed by filtration. The precipitate is repeatedly washed with pure water until the conductivity of the washing solution is below 300 μS·cm. In this step, aging makes the precipitate structure more stable. Washing to a fixed low conductivity effectively removes excess ammonium ions and acid anion impurities introduced in the previous step, preventing these impurities from forming impurities or inducing abnormal oxygen vacancies during subsequent high-temperature treatment. This standardized cleaning procedure is key to achieving high process repeatability; (4) Complexation Conversion: Add excess acetic acid to the purified hydroxide and stir until the precipitate is completely converted, forming an acetate complex solution or a homogeneous suspension. In this step, acetate ions act as a mild complexing agent, replacing the traditional easily hydrolyzed inorganic salt system. They can form stable complexes with metal ions, thereby effectively controlling the hydrolysis rate of metal ions during the subsequent sol formation process and avoiding problems such as local precipitation or uneven particle size. (5) Sol preparation: The above acetate solution was slowly added dropwise to an organic solvent (N,N-dimethylformamide) containing the stabilizer ethanolamine (concentration 0.5~2mol / L) at 40~60℃ under ultrasonic waves (frequency 20~40Hz, power 5kW). Simultaneously, glycerol was used to adjust the pH of the system to 1~3. This step utilizes the cavitation effect of ultrasound to break up micro-agglomerates, combined with the dispersing effect of the stabilizer ethanolamine, to achieve nanoscale dispersion of the sol particles. Glycerol is used to precisely control the reaction environment, together obtaining a highly uniform sol with good storage stability. (6) Sol aging and gradient filtration: The obtained sol was aged at room temperature for 12-24 hours, followed by three-stage gradient filtration: sequentially passing it through filter membranes or filter cloths with a diameter of 10-50 μm (preliminary), 100-700 nm (intermediate), and 20-70 nm (final). In this step, aging matures the sol system. Gradient filtration removes larger particles and residual agglomerates of different sizes step by step, ensuring that the sol used for spin coating has extremely high purity and uniformity, which is an important prerequisite for obtaining defect-free, smooth films. (7) Multilayer spin coating and intermediate heat treatment: The filtered sol is spin-coated onto the substrate at a speed of 2000~6000 rpm, with the thickness of each wet film controlled at 10~20 nm. After each spin coating, the substrate is immediately placed in a microwave oven and heat-treated at 80~150℃ for 1~10 minutes. This "spin coating-heat treatment" step is repeated multiple times until the total film thickness reaches 40~200 nm. This step uses multilayer thin-layer spin coating instead of single thick film coating, which can significantly reduce the internal stress caused by the rapid evaporation of solvent during the drying of each film layer, thereby effectively avoiding film cracking, warping and pinhole formation. Intermediate heat treatment can solidify each film layer in time, enhance the interlayer bonding and overall density, and realize the preparation of high-quality micron-level thick films; (8) Microwave segmented annealing: The spin-coated multilayer film is placed in a microwave oven for programmed segmented annealing. This process is divided into three stages based on temperature and reaction objectives. By precisely controlling the atmosphere and parameters, the film structure is optimized and its performance is improved. Low-temperature pre-annealing (air atmosphere, 60~150℃, 10~30 minutes): The main purpose of this stage is to thoroughly remove residual organic solvents, complexing agents, and physically adsorbed water from the film. An air atmosphere is chosen because the oxygen in it promotes the low-temperature oxidative decomposition of residual organic matter, causing it to escape in gaseous form. At this lower temperature, the main components of the film are stable and will not undergo adverse oxidation. Intermediate-temperature pyrolysis annealing (nitrogen atmosphere, 150~300℃, 5~20 minutes): The core of this stage is to complete the thermal decomposition of the metal-organic precursor and the initial network formation. An inert nitrogen atmosphere is used to provide a low oxygen partial pressure environment, preventing excessive oxidation of the film within the sensitive pyrolysis temperature range. This suppresses the formation of defects such as excess oxygen vacancies, and promotes the formation of a less defective, more uniform amorphous or microcrystalline oxide network. High-temperature densification annealing (nitrogen atmosphere, 300~500℃, 1~10 minutes): The goal of this stage is to achieve film densification, crystallinity control, and the formation of a specific second phase. Continuous nitrogen protection prevents excessive oxidation of rare earth ions and provides suitable thermodynamic conditions for the reaction of rare earth elements (such as Pr, Nd) with indium (In) to generate the target nanoscale second phase (such as PrInO3). A short holding time is crucial; it effectively inhibits the diffusion and segregation of rare earth ions at high temperatures, ensuring their uniform distribution and the nanoscale structure of the second phase. This microwave-assisted segmented annealing process, through precise matching of the timing and atmosphere of "low-temperature air impurity removal and medium-to-high-temperature nitrogen-protected reaction," synergistically achieves the complete removal of organic impurities, effective suppression of defects, and the construction of an ideal microstructure. Microwave heating itself offers advantages such as speed, bulk heating, and high energy efficiency. Combined with the aforementioned segmented strategy, the entire heat treatment process is significantly shortened (more than 90% shorter than the traditional muffle furnace method) and energy consumption is drastically reduced (more than 70% lower). Ultimately, this process promotes high densification of the film (density ≥99%) in a very short time and ensures the uniformity of rare-earth doping and the effective formation of the nano-second phase, enabling it to continuously pin grain boundaries and reduce oxygen vacancy concentration, ultimately endowing the IGZO film with excellent and uniform electrical properties and stability. This process is particularly suitable for flexible substrates, demonstrating strong technological advancement and application potential.

[0025] To enable those skilled in the art to better understand the technical solution of the present invention, a detailed description is provided below in conjunction with specific embodiments and comparative examples. Process parameters not specifically specified in the following embodiments are generally performed under conventional conditions or conditions recommended by the manufacturer. Unless otherwise specified, all reagents and materials used are commercially available analytical grade or higher purity products.

[0026] Example 1 The method for preparing praseodymium (Pr)-doped IGZO thin films in this embodiment is as follows: (1) Raw material dissolution: Weigh 4N metal according to the In:Ga:Zn:Pr molar ratio of 3:2:3:2, add nitric acid of 1.8 times its total mass, and heat and stir in a water bath at 60°C until completely dissolved; (2) Coprecipitation: Add concentrated ammonia to adjust the pH to 6, and stir the reaction in a constant temperature water bath at 40℃ to generate hydroxide coprecipitate; (3) Purification: The precipitate was aged for 4 hours and then filtered under pressure. It was washed with pure water until the conductivity of the washing solution was 280 μS·cm. (4) Complexation transformation: Add excess acetic acid and stir until a clear solution is formed; (5) Sol preparation: Under the assistance of ultrasound (20Hz, 5kW, 40℃), the above solution was slowly added dropwise to N,N-dimethylformamide containing 0.1L of 1.25mol / L ethanolamine, and the pH of the system was adjusted to 1 with glycerol; (6) Aging and gradient filtration: The sol was aged at room temperature for 12 hours, and then subjected to three-stage gradient filtration using a 30μm filter cloth, a 500nm filter membrane, and a 50nm filter membrane in sequence; (7) Multilayer spin coating: The filtered sol was spin-coated onto the silicon wafer at 2000 rpm. After each layer was spin-coated, it was immediately heat-treated in a microwave oven at 80°C for 10 minutes. The spin coating was repeated 4 times, and the total film thickness was about 40 nm. (8) Microwave segmented annealing: Anneal in a microwave oven according to the following program: pre-annealing at 60°C for 30 minutes in air atmosphere; pyrolysis annealing at 150°C for 20 minutes in nitrogen atmosphere; densification annealing at 300°C for 10 minutes in nitrogen atmosphere.

[0027] Example 2 The method for preparing neodymium (Nd)-doped IGZO thin films in this embodiment is as follows: (1) Raw material dissolution: Weigh the metals according to the In:Ga:Zn:Nd molar ratio of 3.5:1.5:3.5:1.5, add nitric acid 2.4 times its total mass, and dissolve at 85℃. (2) Co-precipitation: Adjust the pH to 7 by adding ammonia dropwise, and co-precipitate at 50℃; (3) Purification: The hydroxide was aged for 6 hours and washed until the conductivity was 200 μS·cm; (4) Complexation transformation: Add excess acetic acid and stir until a clear solution is formed; (5) Sol preparation: Under ultrasonic conditions (30Hz, 5kW, 50℃), the solution was added dropwise to N,N-dimethylformamide containing 0.1L 0.5mol / L ethanolamine, and the pH was adjusted to 1.5 with glycerol; (6) Aging and gradient filtration: The sol was aged for 18 hours, and then three-stage gradient filtration was performed using a 20μm filter cloth, a 300nm filter membrane, and a 30nm filter membrane in sequence; (7) Multilayer spin coating: Spin coating was performed at 4000 rpm, and each layer was heat-treated in a microwave oven at 115°C for 5.5 minutes after spin coating. The spin coating was repeated 6 times, with a total film thickness of approximately 120 nm. (8) Microwave segmented annealing: pre-annealing at 105℃ in air atmosphere for 20 minutes; pyrolysis annealing at 225℃ in nitrogen atmosphere for 12.5 minutes; densification annealing at 400℃ in nitrogen atmosphere for 5.5 minutes.

[0028] Example 3 The method for preparing samarium (Sm)-doped IGZO thin films in this embodiment is as follows: (1) Raw material dissolution: Weigh the metals according to the In:Ga:Zn:Sm molar ratio of 4:1:4:1, add nitric acid three times its total mass, and dissolve at 110℃; (2) Co-precipitation: Add ammonia dropwise to adjust the pH to 8, and co-precipitate at 60℃; (3) Purification: The hydroxide was aged for 8 hours and washed until the conductivity was 120 μS·cm; (4) Complexation transformation: Add excess acetic acid and stir until a clear solution is formed; (5) Sol preparation: Under ultrasonic conditions (40 Hz, 5 kW, 60℃), the solution was added dropwise to N,N-dimethylformamide containing 0.1 L 2 mol / L ethanolamine, and the pH was adjusted to 3 with glycerol; (6) Aging and gradient filtration: The sol was aged for 24 hours. Three-stage gradient filtration was then performed sequentially using a 40μm filter cloth, a 100nm filter membrane, and a 20nm filter membrane. (7) Multilayer spin coating: Spin coating was performed at 6000 rpm, and each layer was heat-treated in a microwave oven at 150°C for 1 minute after spin coating. The spin coating was repeated 10 times, with a total film thickness of approximately 200 nm. (8) Microwave segmented annealing: pre-annealing at 150℃ in air for 10 minutes; pyrolysis annealing at 300℃ in nitrogen for 5 minutes; densification annealing at 500℃ in nitrogen for 1 minute.

[0029] Comparative Example 1 (without rare earth doping) The preparation method is exactly the same as in Example 1, but the rare earth metal praseodymium (Pr) is not added in step 1. That is, only indium, gallium and zinc are used, and the molar ratio is adjusted to 3:2:3:0. Other steps and parameters remain unchanged.

[0030] Comparative Example 2 (without gradient filtering) The preparation method is basically the same as in Example 1, but in step 6, the three-stage gradient filtration is not performed. Instead, a simple filtration is performed using a 200-mesh sieve (about 75 μm). The other steps and parameters are the same as in Example 1.

[0031] Comparative Example 3 (Non-segmented annealing) The preparation method is basically the same as in Example 1, but in step 8, microwave segmented annealing is not used. The spin-coated film is placed in a conventional muffle furnace and annealed in one step by directly heating to 400°C at 10°C / min in an air atmosphere and holding for 30 minutes, and then cooled in the furnace.

[0032] Performance Testing and Results Analysis The IGZO thin films prepared in the above examples and comparative examples were used to fabricate TFT devices with a bottom-gate top-contact structure, and their performance was tested. The main tests and characterization included: thin film density (measured by X-ray reflectance method, XRR), surface roughness (AFM), thin film field-effect mobility, threshold voltage (Vth), subthreshold swing (SS), and on / off current ratio (Ion / Ioff). The test results are summarized in Table 1 below.

[0033] Table 1 Performance test results of the films obtained in Examples 1-3 and Comparative Examples 1-3 Table 1 shows that: (1) The rare earth-doped IGZO films prepared in Examples 1-3 all exhibited extremely high density (≥99%) and extremely low surface roughness (≤0.3nm), proving the decisive role of the "multilayer spin coating + gradient filtration + microwave segmented annealing" process in improving the morphology quality of the film. The corresponding TFT devices exhibited high mobility (>44cm). 2 (2) Comparative Example 1 was not doped with rare earth elements. Its film density was acceptable, but its electrical performance was comprehensively degraded, especially its mobility decreased significantly (only 10.2 cm⁻¹). 2 / Vs), threshold voltage drifted positively, and SS value deteriorated. This confirms the key role of rare earth doping in forming a second phase (such as PrInO3) in pinning grain boundaries, suppressing defects, and improving carrier transport capacity. (3) Comparative Example 2 did not undergo gradient filtration, and the film density dropped sharply to 89%, and the roughness increased sharply to 1.2 nm. Although the mobility was better than the undoped sample, the film quality was poor, resulting in weak uniformity and reliability of the device. This shows that gradient filtration is indispensable for removing large particles in the sol and obtaining a smooth and dense film. (4) Comparative Example 3 used conventional single annealing, and the film density (90%) and roughness (0.8 nm) were worse than those of the example, and the electrical performance also declined. This shows that the microwave segmented annealing process of the present invention achieves better film densification and structural optimization in a shorter time and better controls the doping uniformity.

[0034] Figure 2 The images show actual photos of the targets prepared in Examples 1-3. As can be seen, the surface of the film is uniform and flat, without any obvious protrusions, depressions or cracks.

[0035] In summary, this invention, through a unique raw material system, process steps, and parameter control, has achieved synergistic effects and successfully prepared a high-performance rare-earth-doped IGZO target (thin film), which has broad application prospects in the field of display devices.

[0036] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing a rare-earth-doped indium gallium zinc oxide target, characterized in that... This includes the following steps: (1) High-purity metallic indium, gallium, zinc and rare earth elements are dissolved in an acidic solution at a predetermined molar ratio, and a metal salt solution is obtained after complete dissolution; (2) Add ammonia to the metal salt solution obtained in step (1) to adjust the pH value to 6-8, and carry out a neutralization reaction at 40-60℃ to generate hydroxide precipitate; (3) The hydroxide precipitate is aged, filtered, and washed with pure water until the conductivity is below 300 μS·cm; (4) Add excess acetic acid to the washed hydroxide to convert it into acetate; (5) The obtained acetate solution was slowly added to an organic solvent containing a stabilizer under ultrasonic treatment, and the pH of the system was adjusted to 1-3 using glycerol to form a homogeneous sol; (6) After aging the sol for 12-24 hours, perform gradient filtration; (7) The filtered sol was coated onto the substrate by spin coating. After each layer was spin coated, heat treatment was performed. This process was repeated multiple times until the predetermined film thickness was achieved. (8) Perform microwave segmented annealing on the spin-coated film, including three stages: low-temperature pre-annealing, medium-temperature pyrolysis annealing and high-temperature densification annealing, to obtain the final target material.

2. The preparation method according to claim 1, characterized in that... In step (1), the molar ratio of the metals indium, gallium, and zinc to the rare earth elements is (3~4):(1~2):(3~4):(1~2); The rare earth element is selected from at least one of praseodymium, neodymium, and samarium.

3. The preparation method according to claim 1, characterized in that... In step (1), the acidic solution is nitric acid, and its amount is 1.8-3 times the total mass of the metal; during dissolution, a heating treatment is performed at a temperature of 60-110℃.

4. The preparation method according to claim 1, characterized in that... In step (5), the ultrasonic frequency is 20-40Hz, the power is 5kW, and the temperature is 40-60℃; The stabilizer is ethanolamine at a concentration of 0.5-2 mol / L; The organic solvent is N,N-dimethylformamide.

5. The preparation method according to claim 1, characterized in that... In step (6), the gradient filtration is carried out using filter membranes or filter cloths of 10-50μm, 100-700nm and 20-70nm in sequence.

6. The preparation method according to claim 1, characterized in that... In step (7), the spin coating speed is 2000-6000 rpm, the thickness of each spin coating layer is 10-20 nm, and each spin coating layer is placed in a microwave oven at 80-150℃ for 1-10 min after spin coating, with a total film thickness of 40-200 nm.

7. The preparation method according to claim 1, characterized in that... In step (8), the low-temperature pre-annealing is carried out at 60-150℃ for 10-30 minutes in an air atmosphere; the medium-temperature pyrolysis annealing is carried out at 150-300℃ for 5-20 minutes in a nitrogen atmosphere; and the high-temperature densification annealing is carried out at 300-500℃ for 1-10 minutes in a nitrogen atmosphere.

8. A rare-earth-doped indium gallium zinc oxide target, characterized in that... It is prepared by the preparation method described in any one of claims 1-7.

9. The target material according to claim 8, characterized in that... The target material is in the form of a thin film with a density of not less than 99% and a surface roughness of ≤0.3nm.

10. A display device, characterized in that... It comprises the rare earth-doped indium gallium zinc oxide target as described in any one of claims 8-9.

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