Method for preparing zinc oxide doped target material, target material, thin film preparation method and thin film

Abstract

The present invention relates to the technical field of ceramic materials, and in particular to a method for preparing a zinc oxide-doped target material, a target material, a thin film preparation method, and a thin film. The method comprises the following steps: sand grinding raw material powder to obtain refined powder, preparing the refined powder into a slurry, and then spray granulating the slurry to obtain spray powder, cold isostatically pressing the spray powder to obtain a green blank, heating the green blank for degumming, and then high-temperature sintering to obtain a target material; the D50 particle size of the refined powder in the spray granulation process is 0.5 μm-0.65 μm, the particle size distribution range is 1.37-1.41, and the viscosity of the slurry is 500 cp-650 cp; a process optimization scheme adopted in the target material process of the present invention realizes an optimization method from empirical trial and error to model characterization and multivariable control, realizes controllability of powder particle size and distribution, improves the rationality of subsequent processes, and the prepared target material has high density, hardness and low resistivity, and the prepared thin film has good performance and a high piezoelectric coefficient.

Description

Technical Field

[0001] The present invention relates to the technical field of ceramic materials, and in particular to a method for preparing a zinc oxide-doped target material, a target material, a method for preparing a thin film, and a thin film. Background Art

[0002] Thin-film acoustic resonators operate based on the piezoelectric effect. When an alternating electric field is applied to a piezoelectric material, mechanical vibrations are generated. Conversely, mechanical vibrations also generate an alternating electric field. By exciting these vibrations at specific frequencies, signals of specific frequencies can be selected and processed. They are currently widely used in communications devices such as RF front-end modules in mobile phones and base stations, implementing functions such as filtering and frequency selection to improve signal transmission quality and spectrum utilization. They are also used in pressure sensors and gas sensors to sense changes in physical or chemical quantities by detecting changes in the frequency or amplitude of sound waves.

[0003] ZnO has good piezoelectric properties and a moderate piezoelectric coefficient. It can effectively convert electrical energy and mechanical energy into each other. It has a high sound velocity and can support the propagation of higher-frequency sound waves, which is conducive to the realization of high-frequency, high-performance thin-film acoustic resonators. It has high transparency in the visible light range and has great potential in the field of thin-film acoustic resonator preparation.

[0004] The preparation of ZnO thin film acoustic resonators usually adopts the magnetron sputtering process, and the ZnO material needs to be prepared into a target material first. CN110436915B discloses a zinc oxide doped target material for the piezoelectric layer of FBAR and its preparation method. The target material is doped with a total mass fraction of less than 50% of a dopant, and the dopant is selected from one or more doping particles containing Al, In, Ga, Mg, Ti, Zr, and Co elements. The average grain size of the target material is less than 5μm, the dopant phase size is less than 500nm, and the relative density of the target material is not less than 99%. CN114057481A discloses a zinc oxide target material preparation method and zinc oxide target material, which includes ball milling a zinc oxide substrate and a doping material to obtain a first-stage grinding slurry; sand milling the first-stage grinding slurry to obtain a second-stage grinding slurry; granulating the second-stage grinding slurry to obtain granules; cold isostatic pressing the granules to obtain a blank; sintering the blank, and cooling to obtain a zinc oxide target material. However, current methods for optimizing parameters in the target preparation process still primarily rely on experience, trial and error, and experimental verification. This cumbersome preparation process requires extensive experimental support, lacking systematic research on the impact of various preparation parameters on ceramic and even thin film properties. Furthermore, the lack of a rational and mature target preparation process results in unstable target performance, insufficient density, excessively high resistivity, and poor conductivity. This often makes RF magnetron sputtering suitable only for experimental applications and difficult to adapt to the needs of large-scale production. Summary of the Invention

[0005] In order to solve the deficiencies of the above-mentioned prior art, the object of the present invention is to provide a method for preparing a zinc oxide-doped target material, a target material, a method for preparing a thin film, and a thin film.

[0006] The purpose of the present invention is achieved through the following technical means:

[0007] A method for preparing a zinc oxide-doped target material comprises sand grinding a raw material powder to obtain a refined powder, making the refined powder into a slurry, and then spray granulating the slurry to obtain a spray powder, cold isostatically pressing the spray powder to obtain a green blank, heating and degumming the green blank, and then sintering the green blank at a high temperature to obtain a target material;

[0008] In the spray granulation process, the D50 particle size of the refined powder is 0.5 μm to 0.65 μm, the particle size distribution range is 1.37 to 1.41, and the viscosity of the slurry is 500 cp to 650 cp.

[0009] Furthermore, in the spray granulation process, the atomizer frequency is greater than 320 Hz; the D50 particle size of the spray powder is 18-24 μm, the spray powder morphology is solid powder, and the particle size distribution range is 0.98-1.1, preferably 1.05.

[0010] Furthermore, the particle size distribution range = .

[0011] Furthermore, the sand grinding process controls the particle size of the refined powder by adjusting the sand grinding time and the mass ratio of sand to raw material powder.

[0012] Furthermore, the process parameters in the target material preparation process are obtained by determining variables, obtaining data through experimental design, and establishing a regression model and then solving it through a multi-objective optimization method.

[0013] Furthermore, the variables include input variables and output variables. The input variables include: spray powder morphology, D50 particle size of spray powder, particle size distribution range of spray powder, cold isostatic pressing pressure, degumming temperature platform interval value, holding time of each degumming temperature platform, degumming heating rate, degumming maximum temperature, and sintering temperature; the output variables include: target material density, target material resistivity, and target material hardness.

[0014] Furthermore, the zinc oxide doped target is an aluminum doped zinc oxide target or a magnesium doped zinc oxide target, the dopant used in the aluminum doped zinc oxide target is Al2O3, and the dopant used in the magnesium doped zinc oxide target is MgO or MgCO3; the doping concentration of aluminum in the aluminum doped zinc oxide target is 1~5 wt.%; the doping concentration of magnesium in the magnesium doped zinc oxide target is 10~40at.%.

[0015] Furthermore, the heating degumming is vacuum degumming. After the temperature is raised to 220°C, the heating rate is 0.1°C / min, and the temperature is kept warm for 120 minutes after each 30°C increase. When Al2O3 powder and MgO powder are used as dopants, the maximum degumming temperature is set to 460°C; when MgCO3 is used as a dopant, the maximum degumming temperature is set to 550°C.

[0016] Furthermore, a target material is prepared using the method.

[0017] Furthermore, a method for preparing a zinc oxide-doped thin film using the target material comprises using the target material to obtain a zinc oxide-doped thin film on a substrate by a pulsed DC magnetron sputtering method.

[0018] Furthermore, a zinc oxide doped thin film is prepared using the method.

[0019] Furthermore, the piezoelectric coefficient of the zinc oxide doped film is ≥20 pm / V.

[0020] The beneficial effects of the present invention are:

[0021] 1. During the preparation of refined powder, experiments and modeling are used to clarify the relationship between the mass ratio of sanding to raw powder, the sanding time, and the D50 particle size of the refined powder. This avoids ineffective processing, shortens sanding time, reduces sanding waste, avoids ineffective processing or the introduction of impurities, achieves controllability of powder particle size and distribution, and improves the stability of subsequent processes (cold isostatic pressing).

[0022] 2. The relationship between the particle size and morphology of the spray powder and the atomization frequency and viscosity of the slurry was discovered. By controlling the particle size and distribution of the refined powder, the slurry viscosity suitable for spray powdering and the atomizer frequency were obtained, and a solid spray powder with high roundness was obtained, which is suitable for target material preparation and avoids the decline in production efficiency and stability caused by excessively high viscosity.

[0023] 3. A target preparation process optimization scheme was proposed. Through a system of multi-scale process modeling, data-driven optimization, and multivariable control, the performance indicators were improved and comprehensively optimized, avoiding problems such as over-burning / under-burning in traditional empirical methods. The formation of defects in the sintering process was effectively controlled, and the transition from "trial and error" to "model-driven" was achieved. The controllable and predictable performance was achieved, and the research and development of new material systems was accelerated.

[0024] 4. During the degumming process, a multi-level temperature platform is established and kept warm. A segmented slow heating + multi-level insulation strategy is adopted. The target material quality can be significantly improved by precisely controlling the decomposition and volatilization process of organic matter. Under the designed degumming process, organic matter such as binders (such as paraffin wax, PVA) and dispersants are decomposed step by step. Multiple platforms correspond to the pyrolysis range of organic matter with a specific molecular weight. During the insulation stage, the decomposition gas diffuses slowly to avoid instantaneous gas production that causes cracking of the green billet, ensuring that high-molecular organic matter is fully cracked and the residual amount is low. It is also synergistically optimized with the vacuum environment to keep the temperature difference inside the green billet low and avoid microcracks.

[0025] 5. An optimized and reasonable zinc oxide doped target preparation process was obtained. Through reasonable doping components, content, dopant selection, sanding process, spraying process, spray powder parameters, blank making, degumming and sintering process coordination, a good ceramic target with high density and hardness and low resistivity was obtained, which is suitable for large-scale production of medium-frequency and pulsed DC sputtering methods, and a thin film with excellent performance was obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. By referring to the drawings, the features and advantages of the present invention will be more clearly understood. The drawings are schematic and should not be understood as limiting the present invention in any way. Those skilled in the art can derive other drawings based on these drawings without inventive effort. Among them:

[0027] Figure 1 This is a graph showing the relationship between the spray granulation frequency and the spray powder morphology and particle size of the present invention.

[0028] Figure 2 This is a graph showing the mass ratio of abrasive to material and the particle size of the refined powder of the present invention.

[0029] Figure 3 This is a diagram of the distribution range of fine powder particle size under different sand grinding times.

[0030] Figure 4 Schematic diagram of the degumming process curve.

[0031] Figure 5 This is a graph showing the relationship between spray powder morphology and particle size and ceramic density.

[0032] Figure 6 This is a graph showing the relationship between spray powder morphology and particle size and ceramic hardness.

[0033] Figure 7 Diagram showing the relationship between cold isostatic pressing pressure and ceramic properties.

[0034] Figure 8 The microstructure of the prepared doped zinc oxide film.

[0035] Figure 9 This is the piezoelectric performance diagram of the thin film. DETAILED DESCRIPTION

[0036] In order to more clearly understand the above-mentioned objects, features and advantages of the present invention, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that the embodiments of the present invention and the features therein can be combined with each other without conflict.

[0037] The current target manufacturing process for magnetron sputtering usually involves component selection, powder refinement, slurry preparation, spray granulation after drying, and then isostatic pressing to prepare a blank, heating degumming, and high-temperature sintering to obtain the final target material.

[0038] The above process involves numerous parameters, including sanding parameters, powder particle size, slurry parameters, atomization parameters and granulation particle size, pressing pressure, sintering temperature, etc. Furthermore, the various parameters may influence and interact with each other, making it a complex multi-stage, multi-variable process. Currently, process parameter optimization relies mainly on empirical determination and experimental verification, lacking theoretical support. The workload required is enormous, and it is difficult to grasp the interactions between the various parameters and their synergistic effects on the final target material performance. There is a lack of a universal target material preparation parameter design method that can selectively select optimized parameter combinations based on the different performance requirements of the film, resulting in instability in the performance of the prepared film.

[0039] Based on the above problems, the present invention is based on accumulated experimental data and combined with the design of experimental verification methods. It comprehensively considers the parameters and interactions between each process in the target material manufacturing process, and their impact on the later target material performance, and proposes a target material preparation method that can perform targeted parameter design according to performance requirements.

[0040] The basic process of the target material preparation method of the present invention is: first, according to the specific components, commercially available raw material powders (ZnO powder, Al2O3 powder, MgO powder, MgCO3 powder) are sand-milled to obtain refined powder, and a solvent and a dispersant are added to obtain a slurry, the slurry is spray-granulated to obtain spray powder, and the spray powder is cold-isostatically pressed to obtain a blank, the obtained blank is heated and debonded, and then sintered at high temperature to obtain the target material.

[0041] In this process, the parameters in the target preparation process are first analyzed and classified, including:

[0042] (1) Initial parameters: raw material powder particle size, sanding time, sanding to material mass ratio, cold isostatic pressing pressure, degumming process (heating rate, holding platform range, holding time, maximum degumming temperature, degumming system (vacuum degumming or positive pressure degumming)), sintering temperature. The above refers to the raw materials used in the preparation process or the parameter values ​​initially adopted for the process parameters.

[0043] (2) Intermediate parameters: D50 particle size of refined powder, particle size distribution range of refined powder, viscosity of refined powder slurry, pH value of slurry, atomization frequency of spray granulation, morphology of spray powder, D50 particle size of spray powder, particle size distribution range of spray powder. The above are parameter values ​​caused by the intermediate processing steps in the target preparation process.

[0044] (3) Performance parameters: density, resistivity, and hardness of the target material. The above are the parameters that characterize the target material performance after preparation.

[0045] The relationships among the above parameters are analyzed, and the relationships among the parameters are divided into explicit relationships and implicit relationships.

[0046] The explicit relationship is a relationship whose correlation can be obtained through an actual physical model, that is, a white box model. For example, the D50 particle size of the refined powder and the distribution range of the refined powder particle size can be obtained by controlling the sanding time and the sanding to material mass ratio.

[0047] Implicit relationships are relationships whose relevance cannot be captured through actual physical models, i.e., black-box models. For example, the D50 particle size and particle size distribution range of the refined powder, slurry viscosity, slurry pH, and atomization frequency of the spray granulation process can be used to determine the morphology, D50 particle size, and particle size distribution range of the spray powder. However, the degree of influence of each parameter cannot be determined through a specific physical model. For another example, the morphology, D50 particle size, and particle size distribution range of the spray powder, cold isostatic pressing pressure, debonding process, and sintering process determine the final performance of the target material, but the degree of influence of each parameter cannot be determined through a specific physical model.

[0048] Based on the above analysis, we first obtain various process parameters (including initial parameters and intermediate parameters) related to the target material performance parameters through preliminary experiments, and then analyze the relationship type between the parameters, and obtain their specific relationships based on various methods.

[0049] Focusing on parameters such as spray powder particle size, particle size distribution range, morphology, and various parameters of isostatic pressing, debonding, sintering, etc., the relationship between parameter design and target material performance is studied to perform parameter optimization design, specifically including:

[0050] First, set the input variables of the target preparation process, including:

[0051] : Spray powder morphology, where 1 represents solid and 0 represents hollow; : D50 particle size of spray powder ranges from 10 to 30 μm; : The particle size distribution range of the spray powder is calculated as follows: , ranging from 0.9 to 1.2; where D90, D10, and D50 are particle size D90, particle size D10, and particle size D50, respectively; : Cold isostatic pressing pressure ranges from 200 to 280 MPa; : Degumming temperature platform interval value (that is, after reaching a certain temperature, each time the temperature rises by the interval value, it is kept warm for a period of time, and the temperature during the warming period is the temperature platform), ranging from 20 to 50 ° C; : The holding time of each degumming temperature platform ranges from 90 to 150 minutes; : Degumming heating rate, that is, the heating rate between adjacent degumming temperature platforms, ranging from 0.05 to 0.2 °C / min; : The maximum degumming temperature ranges from 400 to 620°C; : Sintering temperature ranges from 1400 to 1600°C.

[0052] Output variables of the target preparation process include: : Target density; : target resistivity; : Target hardness.

[0053] According to the above variables, the experimental design is carried out. Latin hypercube sampling is used in this invention. , randomly select 0 or 1, except The range of each input variable (except for ) is divided into n equally probable intervals. A sample point is randomly selected from each interval. These sample points are combined to form n sample combinations, which are then fine-tuned as appropriate during the experiment to ensure maximum coverage of the parameter space. Experiments are conducted using the parameter values ​​of these sample combinations, and performance data (density, resistivity, and hardness) are measured to form a complete dataset. Each data entry in the dataset includes both the input and output variables. Table 1 shows some examples of the dataset.

[0054] Table 1 Dataset example

[0055]

[0056] After preprocessing the acquired dataset, a Gaussian process regression (GPR) model was established using a radial basis kernel (RBF). GPR is a statistical model based on data-driven learning (statistical learning), suitable for processing experimental data, with fast training speed and the ability to quickly establish input-output mapping relationships, which meets the requirements of the present invention. A white noise kernel was used to avoid overfitting, and maximum likelihood estimation was used for hyperparameter optimization. Alternatively, random forest (RF) and support vector regression (SVR) methods can be used for modeling.

[0057] Based on the Gaussian process regression (GPR) model, multi-objective optimization is performed, and the objective function is:

[0058]

[0059]

[0060]

[0061] The objective function is to maximize density, minimize resistivity and maximize hardness.

[0062] The NSGA-II algorithm was used to find the Pareto optimal solution set with a population size of 100, an iteration number of 200, a crossover probability of 0.9, and a mutation probability of 0.1. The optimized parameter combination was obtained.

[0063] According to the morphology, D50 particle size and particle size distribution range of the spray powder required in the target material preparation process, the relationship between the various parameters of the spray granulation process and the above-mentioned spray powder parameters was studied. After research, it was found that the particle size, distribution range and morphology of the spray powder are related to the atomization frequency and the viscosity of the slurry, and the viscosity of the slurry is related to the particle size and particle size distribution range of the refined powder. The particle size of the spray powder after drying decreases with the increase of the atomizer frequency, while changing the atomizer frequency has no obvious effect on the morphology of the particles. Increasing the viscosity of the slurry helps to form a solid spray powder with high roundness, but too high a viscosity will also lead to a decrease in production efficiency and stability. In addition, too high a viscosity will cause the droplet size to increase during atomization, and the particle size of the spray powder formed after drying will also increase accordingly. Therefore, it is necessary to control it in combination with the frequency of the atomizer and increase the atomizer frequency.

[0064] At the same time, the viscosity of the slurry is closely related to the particle size and range of the refined powder. Sufficiently fine powder has a large specific surface area, and more solvent and dispersant molecules are adsorbed on the particle surface, which enhances the liquid bridge effect between particles and increases the slurry viscosity. However, a larger distribution range of refined powder particle size will lead to uneven distribution of powder in the slurry and large differences in shrinkage after drying, resulting in a wide distribution range of spray powder particle size. An appropriate increase in viscosity will also lead to a larger distribution range of spray powder particle size.

[0065] Therefore, based on the above analysis of the results, as well as the required spray powder morphology, D50 particle size, and particle size distribution range (obtained through parameter optimization design method), a fine powder with a suitable particle size (D50=0.5μm~0.65μm) and a particle size distribution range of 1.37~1.41 was selected according to the above relationship, and sodium polycarboxylate was used as a dispersant, the pH was controlled to 7.5 (experimental results show that the dispersion effect is best at pH 7.5), a suitable high viscosity slurry (500 cp~650cp) was prepared, and a suitable atomizer frequency (greater than 320Hz) was selected to obtain a spray powder suitable for target material preparation. Figure 1 As shown in the figure, the horizontal axis of the small box corresponds to the powder particle size (μm), the coordinate value is 0~50, and the vertical axis is the interval distribution (%), the coordinate value range is 0~14. It can be seen that by adopting an atomization frequency of 350Hz, a good spray powder with a reasonable particle size (D50=20μm), a reasonable particle size distribution range (1.05) and a solid powder morphology can be obtained.

[0066] Since the refined powder used in the present invention is obtained by sand-milling commercially available raw material powder using approximately 0.3 mm zirconium oxide sand as the medium, further research was conducted to investigate the relationship between the two. The research revealed that there is a nonlinear relationship between the sand-milling time, the sand-to-material mass ratio, and the D50 particle size and particle size range of the refined powder. In actual production, in order to achieve the desired D50 particle size and particle size range, the sand-milling time and sand-to-material mass ratio used can be determined experimentally. Based on analysis of the obtained experimental data, the D50 particle size of the refined powder can also be determined using the following relationship:

[0067] (1)

[0068] Where, is the D50 particle size of the refined powder, is the particle size of raw material powder D50, is the mass ratio coefficient, is the mass ratio of frosted sand to raw material powder, is the critical mass ratio of abrasive to raw powder, and its value can be determined through experiments. For example, for raw powder with D50=1μm, is 0.1, is the sanding time coefficient, is the sanding time in hours, is the critical sanding time, and its value can be determined through experiments. For example, for raw material powder with D50=1μm, is 4. and Obtained through nonlinear regression fitting.

[0069] The particle size distribution range of the refined powder decreases rapidly at first and then gradually stabilizes as the grinding time increases. This is also a nonlinear relationship. Therefore, the relationship between the particle size distribution range and the grinding time can be determined experimentally. The corresponding grinding time can be selected according to the required particle size distribution range, and then the corresponding grinding and raw material powder mass ratio can be selected according to the above formula (1). The D50 particle size of the refined powder obtained by sand grinding according to the above method is as follows: Figure 2 As shown, the particle size distribution range is as follows Figure 3 shown.

[0070] A method for preparing a zinc oxide-doped target material obtained according to the above method specifically comprises the following steps:

[0071] (1) First, according to the specific components, commercially available raw material powders (ZnO powder, Al2O3 powder, MgO powder, MgCO3 powder) were used to dope ZnO powder, respectively, using Al2O3 powder, MgO powder, and MgCO3 powder as dopants to prepare aluminum-doped zinc oxide ceramic targets, first magnesium-doped zinc oxide ceramic targets, and second magnesium-doped zinc oxide ceramic targets. The particle size of the raw material powder was 1 micron, and zirconia sand of about 0.3 mm was used as the grinding medium. The fine powder was obtained by sand milling, with a sand milling to raw material powder mass ratio of 1:10, and the sand milling time was 4 hours.

[0072] (2) Using refined powder, adding solvent, and using anionic dispersant sodium polycarboxylate as dispersant, a slurry is prepared, and spray powder is produced. The viscosity of the slurry is 500~650cp (preferably 528cp), and the atomizer frequency is not less than 320Hz (preferably 350Hz). A solid spray powder with a D50 particle size of 20μm and a distribution range of 1.05 is obtained.

[0073] (3) Use spray powder and add binder to perform cold isostatic pressing of the blank at a cold isostatic pressing pressure of 250 MPa.

[0074] (4) Heating degumming. The degumming method is vacuum degumming. The degumming process is as follows: after rapidly heating (0.44℃ / min) to 220℃, the heating rate is controlled at 0.1℃ / min, and the temperature is kept for 120 minutes after each 30℃ heating, that is, the temperatures are kept at 220℃, 250℃, 280℃, 310℃, 340℃, 370℃, 400℃, 430℃, and 460℃ for 120 minutes each. When Al2O3 powder and MgO powder are used as dopants, the maximum degumming temperature is set to 460℃. When MgCO3 is used as a dopant, the maximum degumming temperature is set to 550℃. An example of the degumming heating process curve is shown below. Figure 4 shown.

[0075] (5) Sintering: the sintering temperature of the Al-doped ZnO ceramic target is 1550°C, the ceramic density is 95.68%, and the resistivity is 1.105×10-3 Ω•cm, hardness 277.7HV1.

[0076] The sintering temperature of Mg-doped ZnO ceramic target with MgO as dopant is 1400℃, the ceramic density is 95.96%, and the resistivity is 1.196×10 -3 Ω•cm, hardness 277.16HV1.

[0077] The sintering temperature of Mg-doped ZnO ceramic target with MgCO3 as dopant is 1400℃, the ceramic density is 87.59%, and the resistivity is 1.384×10 -3 Ω•cm, hardness 261.42HV1.

[0078] The above-mentioned parameter optimization design method of the present invention, by selecting reasonable input parameter combination and output parameter combination, solves the problem that key process parameters and their interaction research in the prior art are not comprehensive, is difficult to quantify the problem of parameter influence on performance from the system, and is usually optimized based on a single performance, cannot carry out multi-index balance, causes the problem of performance imbalance in the magnetron sputtering process. In specific parameter type selection, parameters such as spray powder morphology, D50 particle size and particle size distribution range are used as input parameters, and the key influencing factors affecting its bulk density and sintering densification process when the blank is pressed are obtained. And the parameters such as temperature platform interval, holding time, heating rate and maximum temperature of the degumming process are used for optimization design, can realize accurate control of organic matter decomposition speed, avoid the problems such as cracking or residue of the blank easily caused by relying on empirical method in traditional degumming.

[0079] Figure 5 and Figure 6 The results show the effects of different particle sizes and morphologies of spray powder on target performance. In the figure, the spray powder used in No. 1 has a D50 of 10 μm and a hollow powder morphology. The spray powder used in No. 2 has a D50 of 20 μm and a hollow powder morphology. The spray powder used in No. 3 has a D50 of 30 μm and a hollow powder morphology. The spray powder used in No. 4 has a D50 of 20 μm and a solid powder morphology. As can be seen from the figure, the density of the spray powder obtained by the optimized process parameters is ( Figure 6 ) and hardness ( Figure 6 ) have been optimized.

[0080] Figure 7 The results show the comparison of the effects of different cold isostatic pressing pressures on target performance. It can be seen from the figure that with the optimized process parameters (250MPa), the density and hardness reach the highest, and the resistivity is reduced.

[0081] The method for preparing a doped ZnO thin film using the prepared doped ZnO ceramic comprises the following steps:

[0082] (1) The obtained doped ZnO ceramic target is subjected to homogenization heat treatment, followed by cutting, surface treatment and cleaning to prepare for magnetron sputtering doped ZnO thin film preparation;

[0083] (2) Substrate preparation: Select a non-magnetic material with high resistivity as the substrate material; the preferred substrate material is a high resistivity silicon wafer (resistivity > 1000Ω.cm).

[0084] (3) Target and substrate cleaning: The substrate is ultrasonically cleaned, and the target is cleaned with deionized water and anhydrous ethanol, and then blown dry under N2 flow.

[0085] (4) Thin film sputtering: The sputtering temperature is room temperature and the vacuum degree is 3.0~4.0×10 -4 Pa, doped ZnO thin films were obtained by pulsed DC magnetron sputtering.

[0086] Doped ZnO thin films include Al-doped ZnO thin films and Mg-doped ZnO thin films. Figure 8 As shown in the figure, (a) is the surface organization diagram, and (b) is the cross-sectional organization diagram. Figure 9 shown.

[0087] The doping concentration of the Al-doped ZnO film is 1-5 wt.%, the grain size is 80-100 nm, the surface roughness Ra is not higher than 6.5 nm, and the maximum height difference is not higher than 60 nm; preferably 2 wt.%, in which case the surface roughness Ra is 6.41 nm, the maximum height difference is 57.7 nm, and the piezoelectric coefficient d is 33 is 4.6 pm / V.

[0088] The Mg-doped ZnO film has a doping concentration of 10 to 40 at.%, preferably 30 at.%. The resulting film exhibits a columnar crystal structure and a surface roughness Ra of 0.746 nm. The piezoelectric coefficient increases and then decreases with Mg doping, reaching a maximum of 46.6 pm / V at a doping concentration of 30 at.%, exceeding that of AlScN films used in conventional FBAR devices.

[0089] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A method for preparing a zinc oxide-doped target material, wherein the zinc oxide-doped target material is a magnesium-doped zinc oxide target material, wherein the dopant is MgO. The method comprises sand grinding a raw material powder to obtain a refined powder, forming the refined powder into a slurry, and then spray granulating the slurry to obtain a spray powder, cold isostatically pressing the spray powder to obtain a green blank, heating the green blank to degumming, and then high-temperature sintering to obtain the target material, wherein: In the process of spray granulation, the D50 particle size of the refined powder is 0.5μm~0.65μm, the particle size distribution range is 1.37~1.41, the viscosity of the slurry is 500cp~650cp, the atomizer frequency is greater than 320Hz, the D50 particle size of the spray powder is 18~24μm, the spray powder morphology is solid powder, the particle size distribution range is 0.98~1.1, and the particle size distribution range is = ; The cold isostatic pressing pressure is 250 MPa; The heating degumming is vacuum degumming. After the temperature is raised to 220°C, the heating rate is 0.1°C / min, and the temperature is kept for 120 minutes after each 30°C increase. The maximum degumming temperature is set to 460°C. The high temperature sintering temperature is 1400℃.

2. The method for preparing a zinc oxide-doped target according to claim 1, wherein: The doping concentration of magnesium in the target material is 10~40at.%.

3. A zinc oxide-doped target prepared by the method for preparing a zinc oxide-doped target according to any one of claims 1 to 2.

4. A method for preparing a zinc oxide-doped thin film using the zinc oxide-doped target according to claim 3, characterized in that: The zinc oxide doped target material is used to obtain a zinc oxide doped thin film on a substrate by adopting a pulsed DC magnetron sputtering method.

5. The zinc oxide-doped thin film prepared by the method for preparing a zinc oxide-doped thin film according to claim 4, characterized in that: The piezoelectric coefficient of the film is not less than 20pm / V.

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