Zinc oxide-based sputtering target material as well as preparation method and application thereof

Abstract

The invention discloses a zinc oxide-based sputtering target material as well as a preparation method and application thereof, and belongs to the technical field of zinc oxide-based sputtering target materials. The preparation method comprises the following steps: smelting a magnesium ingot and a zinc ingot to obtain an alloy ingot; preparing the alloy ingot into magnesium oxide-doped zinc oxide powder by adopting a plasma gasification oxidation mode, and then preparing slurry from the zinc oxide powder, gallium oxide and rare earth oxide; and carrying out drying, compression molding, cold isostatic pressing and sintering on the slurry. Through smelting, sufficient solid solution of magnesium in zinc can be promoted, and the magnesium oxide doped zinc oxide powder with high solid solubility can be obtained. The doped magnesium oxide can regulate and control the forbidden bandwidth of zinc oxide, and better photoelectric properties of the film are obtained. By doping gallium oxide and rare earth oxide, n-type doping can be realized, weakly bound free electrons are introduced, the carrier mobility of zinc oxide is improved, and the resistivity of the material is reduced. The prepared zinc oxide-based target material is high in density, fine in crystal grain and uniform in organization structure, and the TCO thin film with excellent performance can be prepared easily.

Description

Technical Field

[0001] The invention relates to the technical field of zinc oxide-based sputtering target materials, and in particular to a zinc oxide-based sputtering target material and a preparation method and application thereof. Background Art

[0002] Solar energy is an important renewable energy source, and the development of solar cells is an important way to solve energy problems. The production of solar cells is mainly based on semiconductor materials. Its working principle is to use the photoelectric reaction of photoelectric materials after being irradiated by light energy to achieve energy conversion. Currently, more than 90% of solar cells on the market are single-crystal silicon cells, and the mainstream single-crystal silicon cell technologies include Perc, Topcon and HJT.

[0003] HJT (Heterojunction Technology) solar cells are a hybrid solar cell made of crystalline silicon substrate and amorphous silicon thin film, commonly known as heterojunction solar cells. In terms of cell structure, HJT cells use N-type crystalline silicon as the substrate. After cleaning and texturing, the deposition of intrinsic amorphous silicon thin film and P-type amorphous silicon thin film is completed on the front side in sequence to form a heterogeneous PN junction. Then, thinner intrinsic amorphous silicon thin film and N-type amorphous silicon thin film are deposited on the back of the silicon wafer in sequence to form a back surface field. In order to solve the problem of poor conductivity of amorphous silicon, a transparent conductive oxide (TCO) film needs to be deposited on both sides of the cell, and then the metal electrode polarization is completed using screen printing and other technologies. HJT cell technology has the advantages of high theoretical conversion efficiency, low temperature coefficient, and low attenuation coefficient, but the preparation cost of HTJ cells is relatively high.

[0004] In order to reduce the preparation cost of HJT batteries, the cost of TCO targets can be reduced. At present, the commonly used TCO films are mainly indium oxide system materials (the mass content of indium oxide is 98% or more) to obtain TCO films with high mobility, low resistivity and high transmittance, but indium is expensive and its reserves are scarce. The band gap width of zinc oxide is about 3.3eV, with good optical transmittance and low theoretical resistivity, but its band gap is lower than that of indium oxide (about 3.7eV), which will affect the performance of HJT battery devices. Therefore, finding a sputtering target that can be lower in cost than indium oxide-based targets and can also obtain TCO films with high mobility, low resistivity and high transmittance has become a current research difficulty.

[0005] In view of this, the present invention is proposed. Summary of the invention

[0006] The object of the present invention is to provide a zinc oxide-based sputtering target material and a preparation method and application thereof, so as to solve or improve the above-mentioned technical problems.

[0007] The present invention can be implemented like this:

[0008] In a first aspect, the present invention provides a method for preparing a zinc oxide-based sputtering target, comprising the following steps:

[0009] Smelting magnesium ingots and zinc ingots to obtain alloy ingots;

[0010] preparing the alloy ingot into zinc oxide powder doped with magnesium oxide;

[0011] The zinc oxide powder doped with magnesium oxide, gallium oxide and rare earth oxide are prepared into a slurry;

[0012] The slurry is dried, molded, cold isostatically pressed and sintered to obtain a zinc oxide-based sputtering target.

[0013] In an optional embodiment, the mass ratio of the zinc ingot to the magnesium ingot is 90:10 to 99:1.

[0014] In an optional embodiment, the smelting is performed under vacuum or argon atmosphere conditions.

[0015] In an optional embodiment, the alloy ingot is prepared into zinc oxide powder doped with magnesium oxide by plasma gasification oxidation.

[0016] In an optional embodiment, the mass of gallium oxide is 0.5% to 2% of the mass of the zinc oxide powder doped with magnesium oxide;

[0017] and / or, the rare earth oxide comprises at least one of yttrium oxide, scandium oxide, cerium oxide, samarium oxide and lanthanum oxide;

[0018] And / or, the mass of the rare earth oxide is 0.3% to 1% of the mass of the zinc oxide powder doped with magnesium oxide.

[0019] In an optional embodiment, a dispersant and a binder are also added during the preparation of the slurry.

[0020] In an alternative embodiment, the dispersant includes at least one of polyvinyl pyrrolidone, dodecylbenzene sulfonate, and polycarboxylate.

[0021] In an alternative embodiment, the binder comprises polyvinyl alcohol.

[0022] In an optional embodiment, the mass of the dispersant is 0.5% to 1% of the mass of the zinc oxide powder doped with magnesium oxide.

[0023] In an optional embodiment, the mass of the binder is 0.5% to 2% of the mass of the zinc oxide powder doped with magnesium oxide.

[0024] In an alternative embodiment, drying is performed by spray drying.

[0025] In an optional embodiment, the inlet air temperature of the spray drying is 180°C to 230°C, the outlet air temperature is 90°C to 120°C, and the atomizer frequency is 100Hz to 130Hz.

[0026] In an optional embodiment, the pressure of the compression molding is 30MPa to 50MPa;

[0027] And / or, the pressure of cold isostatic pressing is 200 MPa to 280 MPa, and the holding time is 8 min to 15 min.

[0028] In an optional embodiment, sintering includes at least one of the following features:

[0029] Feature 1: The atmosphere during the sintering process is an oxygen-containing atmosphere, and the oxygen flow rate is 40L / min to 100L / min;

[0030] Feature 2: Sintering is carried out under normal pressure;

[0031] Feature 3: The heating rate of the sintering process is 1℃ / min~2℃ / min;

[0032] Feature 4: The maximum sintering temperature of the sintering process is 1450℃~1550℃, and the holding time is 10h~30h;

[0033] Feature 5: After the insulation is completed, the oxygen-containing atmosphere is replaced with an inert gas atmosphere and the temperature is naturally lowered. The flow rate of the inert gas is 10L / min to 40L / min.

[0034] In a second aspect, the present invention provides a zinc oxide-based sputtering target, which is prepared by the preparation method of any one of the aforementioned embodiments.

[0035] In an optional embodiment, the zinc oxide-based sputtering target has at least one of the following characteristics:

[0036] Feature 6: The density of zinc oxide-based sputtering target is not less than 99.5%;

[0037] Feature 7: The average grain size of the zinc oxide-based sputtering target does not exceed 12μm;

[0038] Feature 8: The bandgap width of zinc oxide-based sputtering targets is 3.5eV to 4.0eV;

[0039] Feature 9: The resistivity of zinc oxide-based sputtering targets does not exceed 2.0×10 -3 Ω·cm;

[0040] Feature 10: The electron mobility of zinc oxide-based sputtering targets is not less than 18 cm 2 / Vs.

[0041] In a third aspect, the present invention provides a TCO thin film, wherein the target material used for the TCO thin film is the zinc oxide-based sputtering target material of the aforementioned embodiment.

[0042] In a fourth aspect, the present invention provides a solar cell comprising the TCO film of the aforementioned embodiment.

[0043] In an alternative embodiment, the solar cell is a HJT cell.

[0044] The beneficial effects of the present invention include:

[0045] The preparation method of the zinc oxide-based sputtering target provided by the present invention has a simple process, high efficiency, and is suitable for batch production. By smelting zinc ingots and magnesium ingots to obtain alloy ingots, the full solid solution of magnesium in zinc can be promoted, and then when preparing doped zinc oxide powder, magnesium oxide-doped zinc oxide powder with high solid solubility can be obtained. Among them, doping with magnesium oxide can regulate the band gap width of zinc oxide and widen the band gap to obtain better thin film photoelectric properties. Furthermore, by doping with gallium oxide and rare earth oxides, n-type doping can be achieved, weakly bound free electrons are introduced, the carrier mobility of zinc oxide is significantly improved, and the resistivity of the material is reduced. The prepared zinc oxide-based target has high density, fine grains and uniform organizational structure, which is conducive to the preparation of a TCO film with a moderate band gap width and excellent electrical conductivity and visible light transmittance. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0047] Figure 1 The SEM image of the zinc oxide-based sputtering target is provided for Example 1. DETAILED DESCRIPTION

[0048] In order to make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the technical scheme in the embodiments of the present invention will be described clearly and completely below. If the specific conditions are not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be purchased commercially.

[0049] The zinc oxide-based sputtering target material provided by the present invention and its preparation method and application are described in detail below.

[0050] The present invention provides a method for preparing a zinc oxide-based sputtering target, comprising the following steps:

[0051] Smelting magnesium ingots and zinc ingots to obtain alloy ingots;

[0052] preparing the alloy ingot into zinc oxide powder doped with magnesium oxide;

[0053] The zinc oxide powder doped with magnesium oxide, gallium oxide and rare earth oxide are prepared into a slurry;

[0054] The slurry is dried, molded, cold isostatically pressed and sintered to obtain a zinc oxide-based sputtering target.

[0055] In some optional embodiments, the mass ratio of the zinc ingot to the magnesium ingot can be 90:10 to 99:1, such as 90:10, 91:9, 92:8, 93:7, 94:6, 95:5, 96:4, 97:3, 98:2 or 99:1, or other values ​​within the range of 90:10 to 99:1.

[0056] Illustratively, the purity of the zinc ingot may be ≥99.99%, and the purity of the magnesium ingot may also be ≥99.99%.

[0057] The above-mentioned magnesium ingot is mainly used to provide a magnesium source to dope magnesium oxide in zinc oxide. The band gap width of zinc oxide can be adjusted by doping with magnesium oxide to widen its band gap and obtain better thin film photoelectric performance. If the amount of magnesium ingot used is too small, it cannot effectively play the role of regulating the band gap width of zinc oxide; if the amount of magnesium ingot used is too large, although the band gap width of zinc oxide can be adjusted, it will also cause the conductivity of the material to decrease.

[0058] In some optional embodiments, the smelting of the magnesium ingots and zinc ingots is carried out under vacuum or argon atmosphere conditions to avoid direct oxidation of magnesium and zinc during the smelting process, and also to avoid the problem of reaction between magnesium and nitrogen that may occur when using a nitrogen atmosphere.

[0059] In some optional embodiments, the alloy ingot can be prepared into zinc oxide powder doped with magnesium oxide by plasma gasification oxidation, and the process is carried out under pure oxygen conditions. Specifically, the alloy ingot can be first heated to 500°C to 620°C in a graphite crucible to melt it, and then introduced into a reaction chamber through a liquid guide tube, and high-purity oxygen is introduced into the reaction chamber. The plasma generated by the high-frequency power supply gasifies the metal liquid. In this process, the gasified metal alloy can fully react with oxygen, and after cooling, zinc oxide powder with high solid solubility and uniformly doped with magnesium oxide can be obtained.

[0060] It should be noted that conventional zinc oxide-based targets containing magnesium oxide are directly mixed with zinc oxide and magnesium oxide. In the magnesium-doped zinc-based targets obtained in this way, zinc and magnesium are difficult to be evenly dispersed, thereby reducing the performance of the targets. The present invention first smelts magnesium ingots and zinc ingots, and during the smelting process, magnesium can be fully dissolved and evenly doped in zinc; further, the evenly doped alloy ingot is oxidized, so that magnesium in the alloy ingot forms magnesium oxide and zinc forms zinc oxide, thereby obtaining zinc oxide powder with high solid solubility and evenly doped with magnesium oxide, which is beneficial to improving the light transmittance and conductivity of the film prepared thereby.

[0061] In some optional embodiments, the mass of gallium oxide is 0.5% to 2% of the mass of the zinc oxide powder doped with magnesium oxide, such as 0.5%, 1%, 1.5% or 2%, etc., and may also be other values ​​within the range of 0.5% to 2%.

[0062] If the mass of gallium oxide is lower than 0.5%, it is not conducive to improving the carrier mobility of zinc oxide; if the mass of gallium oxide is higher than 2%, the light transmittance of the film will be reduced.

[0063] The rare earth oxide may illustratively but not limitatively include at least one of yttrium oxide, scandium oxide, cerium oxide, samarium oxide, and lanthanum oxide.

[0064] In some optional embodiments, the mass of the rare earth oxide can be 0.3% to 1% of the mass of the zinc oxide powder doped with magnesium oxide, such as 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9% or 1%, etc., or it can be other values ​​within the range of 0.3% to 1%.

[0065] If the mass of the rare earth oxide is lower than 0.3% or higher than 1%, it is not conducive to improving the carrier mobility of zinc oxide.

[0066] By simultaneously doping a small amount of gallium oxide and rare earth oxides, the metal ion valence of these oxides is +3 or +4, n-type doping can be achieved, introducing weakly bound free electrons, which can significantly improve the carrier mobility of zinc oxide and reduce the resistivity of the material; in addition, it can also ensure that the film has good light transmittance.

[0067] In some optional embodiments, a dispersant and a binder are added during the preparation of the slurry. The dispersant may exemplarily but not limitatively include at least one of polyvinyl pyrrolidone, dodecylbenzene sulfonate and polycarboxylate. The binder may exemplarily but not limitatively include polyvinyl alcohol and the like.

[0068] The mass of the dispersant may be 0.5% to 1% of the mass of the zinc oxide powder doped with magnesium oxide, such as 0.5%, 0.6%, 0.7%, 0.8%, 0.9% or 1%, etc., or other values ​​within the range of 0.5% to 1%.

[0069] The mass of the binder can be 0.5% to 2% of the mass of the zinc oxide powder doped with magnesium oxide, such as 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.2%, 1.5%, 1.8% or 2%, etc., or other values ​​within the range of 0.5% to 2%.

[0070] In some optional embodiments, drying is performed by spray drying.

[0071] Illustratively, the inlet air temperature for spray drying can be 180°C to 230°C, such as 180°C, 185°C, 190°C, 195°C, 200°C, 205°C, 210°C, 215°C, 220°C, 225°C or 230°C, or other values ​​within the range of 180°C to 230°C.

[0072] The outlet air temperature of the spray drying can be 90°C to 120°C, such as 90°C, 95°C, 100°C, 105°C, 110°C, 115°C or 120°C, etc., or other values ​​within the range of 90°C to 120°C.

[0073] The atomizer frequency of the spray drying can be 100 Hz to 130 Hz, such as 100 Hz, 105 Hz, 110 Hz, 115 Hz, 120 Hz, 125 Hz or 130 Hz, etc., or other values ​​within the range of 100 Hz to 130 Hz.

[0074] By spray drying under the above conditions, a dry powder having good flowability can be obtained.

[0075] In some optional embodiments, the compression molding pressure may be 30 MPa to 50 MPa, such as 30 MPa, 35 MPa, 40 MPa, 45 MPa or 50 MPa, or other values ​​within the range of 30 MPa to 50 MPa.

[0076] In some optional embodiments, the pressure of cold isostatic pressing can be 200 MPa to 280 MPa, such as 200 MPa, 210 MPa, 220 MPa, 230 MPa, 240 MPa, 250 MPa, 260 MPa, 270 MPa or 280 MPa, or other values ​​within the range of 200 MPa to 280 MPa.

[0077] The holding time of cold isostatic pressing can be 8 minutes to 15 minutes, such as 8 minutes, 9 minutes, 10 minutes, 11 minutes, 12 minutes, 13 minutes, 14 minutes or 15 minutes, or other values ​​within the range of 8 minutes to 15 minutes.

[0078] In some optional embodiments, the atmosphere of the sintering process is an oxygen-containing atmosphere, such as an air atmosphere or an oxygen atmosphere, etc. The oxygen flow rate can be 40 L / min to 100 L / min, such as 40 L / min, 50 L / min, 60 L / min, 70 L / min, 80 L / min, 90 L / min or 100 L / min, etc., and can also be other values ​​within the range of 40 L / min to 100 L / min.

[0079] The use of oxygen-containing atmosphere in the early stage of sintering can prevent zinc oxide from losing oxygen during the sintering process, which can cause the pores to be difficult to close and reduce the density. In addition, by controlling the oxygen flow rate at 40L / min to 100L / min, if the oxygen flow rate is too low, it cannot effectively balance the oxygen lost by zinc oxide during the sintering process. If the oxygen flow rate is too high, it will cause waste.

[0080] Sintering is carried out under normal pressure conditions, where "normal pressure" can be understood as 1 standard atmospheric pressure, which is approximately 0.1013 MPa.

[0081] The heating rate of the sintering process can be 1°C / min to 2°C / min, such as 1°C / min, 1.5°C / min or 2°C / min, or other values ​​within the range of 1°C / min to 2°C / min.

[0082] The highest sintering temperature of the sintering process may be 1450°C to 1550°C, such as 1450°C, 1480°C, 1500°C, 1520°C or 1550°C, or other values ​​within the range of 1450°C to 1550°C.

[0083] The holding time of the sintering process can be 10 h to 30 h, such as 10 h, 15 h, 20 h, 25 h or 30 h, or other values ​​within the range of 10 h to 30 h.

[0084] After the insulation is completed, the oxygen-containing atmosphere is replaced with an inert gas atmosphere and the temperature is naturally lowered. The flow rate of the inert gas can be 10L / min to 40L / min, such as 10L / min, 15L / min, 20L / min, 25L / min, 30L / min, 35L / min or 40L / min, etc., or other values ​​within the range of 10L / min to 40L / min.

[0085] By changing to an inert atmosphere (such as argon or nitrogen) during the cooling stage of sintering, the oxygen vacancy concentration of the target can be increased, thereby reducing the resistivity of the target. If the flow rate of the inert gas is too high, it will lead to excessive oxygen loss, the target will easily crack and cannot be used normally; if the flow rate of the inert gas is too low, oxygen vacancies cannot be formed, and the resistivity of the target is high.

[0086] Furthermore, the sintered target blank can be subjected to machining such as grinding and wire cutting as required.

[0087] Correspondingly, the present invention also provides a zinc oxide-based sputtering target, which is prepared by the above preparation method.

[0088] In some optional embodiments, the density of the zinc oxide-based sputtering target is not less than 99.5%, such as 99.6% to 99.8%.

[0089] In some optional embodiments, the average grain size of the zinc oxide-based sputtering target does not exceed 12 μm, such as 6.5 μm to 9 μm.

[0090] In some optional embodiments, the band gap width of the zinc oxide-based sputtering target is 3.5 eV to 4.0 eV, such as 3.5 eV to 3.9 eV.

[0091] In some optional embodiments, the resistivity of the zinc oxide-based sputtering target is no more than 2.0×10 -3 Ω·cm, for example, it can be 0.7×10 -3 Ω·cm~1.8×10 -3 Ω·cm.

[0092] In some optional embodiments, the electron mobility of the zinc oxide-based sputtering target is not less than 18 cm 2 / Vs, for example, it can be 19cm 2 / Vs~38cm 2 / Vs.

[0093] In addition, the present invention also provides a TCO film, and the target material used for the TCO film is the above-mentioned zinc oxide-based sputtering target material.

[0094] The TCO film has high mobility, low resistivity and high light transmittance.

[0095] In addition, the present invention also provides a solar cell, which contains the above TCO film and has good photoelectric performance.

[0096] In some exemplary embodiments, the solar cell may be a HJT cell.

[0097] The features and performance of the present invention are further described in detail below in conjunction with the embodiments.

[0098] Example 1

[0099] This embodiment provides a zinc oxide-based target material, and the preparation method thereof includes:

[0100] S1: Add zinc ingot and magnesium ingot into the crucible of a smelting furnace, and smelt them under vacuum to obtain alloy ingots.

[0101] Among them, the mass ratio of zinc ingots to magnesium ingots is 98:2, and the purity of zinc ingots and magnesium ingots is not less than 99.99%.

[0102] S2: preparing the alloy ingot into zinc oxide powder doped with magnesium oxide by plasma gasification oxidation.

[0103] Specifically, the alloy ingot is placed in a graphite crucible and heated to melt, and then introduced into a reaction chamber through a liquid guide tube, high-purity oxygen is introduced into the reaction chamber, and the plasma generated by a high-frequency power supply vaporizes the metal liquid, oxidizes during the vaporization process, and cools to obtain zinc oxide powder doped with magnesium oxide. The melting temperature is 550°C, and the plasma is provided by a high-frequency power supply with a frequency of 200KHz.

[0104] S3: The zinc oxide powder doped with magnesium oxide is mixed with gallium oxide and yttrium oxide powder, and then a dispersant polyvinyl pyrrolidone and a binder polyvinyl alcohol are added and ball-milled in a sand mill to prepare a slurry.

[0105] The mass of gallium oxide is 1.5% of the mass of zinc oxide powder doped with magnesium oxide, the mass of yttrium oxide is 0.5% of the mass of zinc oxide powder doped with magnesium oxide, and the mass of the dispersant and the binder are each independently 0.5% of the mass of zinc oxide powder doped with magnesium oxide.

[0106] S4: The slurry is passed into a flow spray drying tower for spray drying to obtain dry powder.

[0107] Among them, the inlet air temperature of the spray drying is 200°C, the outlet air temperature is 110°C, and the atomizer frequency is 120Hz.

[0108] S5: The dried powder is molded, encapsulated, and then cold isostatically pressed to obtain a green body.

[0109] Among them, the compression molding pressure is 40MPa; the cold isostatic pressing pressure is 260MPa, and the holding time is 10min.

[0110] S6: The above green blank is sintered at normal pressure in an oxygen atmosphere in a sintering furnace. The oxygen flow rate is 60L / min, the heating rate is 1℃ / min, the maximum sintering temperature is 1550℃, and the insulation time is 20h. After the insulation is completed, the oxygen atmosphere is replaced with an argon atmosphere with an argon flow rate of 20L / min until it is naturally cooled to room temperature to obtain a target blank.

[0111] S7: The cooled target blank is subjected to wire cutting, grinding and other machining processes according to the specified size to obtain the final zinc oxide-based sputtering target.

[0112] The SEM image of the zinc oxide-based sputtering target is as follows: Figure 1 As shown by Figure 1 It can be seen that the zinc oxide-based target has a small average grain size and a uniform organizational structure.

[0113] Example 2

[0114] This embodiment provides a zinc oxide-based target material, and the preparation method thereof includes:

[0115] S1: Add zinc ingot and magnesium ingot into the crucible of a smelting furnace, and smelt them under vacuum to obtain alloy ingots.

[0116] Among them, the mass ratio of zinc ingots to magnesium ingots is 95:5, and the purity of zinc ingots and magnesium ingots is not less than 99.99%.

[0117] S2: preparing the alloy ingot into zinc oxide powder doped with magnesium oxide by plasma gasification oxidation.

[0118] Specifically, the alloy ingot is placed in a graphite crucible and heated to melt, and then introduced into a reaction chamber through a liquid guide tube, high-purity oxygen is introduced into the reaction chamber, and the plasma generated by a high-frequency power supply vaporizes the metal liquid, oxidizes during the vaporization process, and cools to obtain zinc oxide powder doped with magnesium oxide. The melting temperature is 580°C, and the plasma is provided by a high-frequency power supply with a frequency of 220KHz.

[0119] S3: The zinc oxide powder doped with magnesium oxide is mixed with gallium oxide and cerium oxide powder, and then a dispersant ammonium polycarboxylate and a binder polyvinyl alcohol are added and ball-milled in a sand mill to prepare a slurry.

[0120] The mass of gallium oxide is 1% of the mass of zinc oxide powder doped with magnesium oxide, the mass of yttrium oxide is 0.6% of the mass of zinc oxide powder doped with magnesium oxide, and the mass of the dispersant and the binder are each independently 0.5% of the mass of zinc oxide powder doped with magnesium oxide.

[0121] S4: The slurry is passed into a flow spray drying tower for spray drying to obtain dry powder.

[0122] Among them, the inlet air temperature of the spray drying is 210°C, the outlet air temperature is 100°C, and the atomizer frequency is 120Hz.

[0123] S5: The dried powder is molded, encapsulated, and then cold isostatically pressed to obtain a green body.

[0124] Among them, the compression molding pressure is 40MPa; the cold isostatic pressing pressure is 240MPa, and the holding time is 9min.

[0125] S6: The above green blank is sintered at normal pressure in an oxygen atmosphere in a sintering furnace. The oxygen flow rate is 50L / min, the heating rate is 1℃ / min, the maximum sintering temperature is 1530℃, and the insulation time is 15h. After the insulation is completed, the oxygen atmosphere is replaced with an argon atmosphere with an argon flow rate of 15L / min until it is naturally cooled to room temperature to obtain a target blank.

[0126] S7: The cooled target blank is subjected to wire cutting, grinding and other machining processes according to the specified size to obtain the final zinc oxide-based sputtering target.

[0127] Example 3

[0128] This embodiment provides a zinc oxide-based target material, and the preparation method thereof includes:

[0129] S1: Add zinc ingot and magnesium ingot into the crucible of a smelting furnace, and smelt them under vacuum to obtain alloy ingots.

[0130] Among them, the mass ratio of zinc ingots to magnesium ingots is 92:8, and the purity of zinc ingots and magnesium ingots is not less than 99.99%.

[0131] S2: preparing the alloy ingot into zinc oxide powder doped with magnesium oxide by plasma gasification oxidation.

[0132] Specifically, the alloy ingot is placed in a graphite crucible and heated to melt, and then introduced into a reaction chamber through a liquid guide tube, high-purity oxygen is introduced into the reaction chamber, and the plasma generated by a high-frequency power supply vaporizes the metal liquid, oxidizes during the vaporization process, and cools to obtain zinc oxide powder doped with magnesium oxide. The melting temperature is 620°C, and the plasma is provided by a high-frequency power supply with a frequency of 230KHz.

[0133] S3: The zinc oxide powder doped with magnesium oxide is mixed with gallium oxide and yttrium oxide powder, and then dodecylbenzene sulfonate as a dispersant and polyvinyl alcohol as a binder are added and ball-milled in a sand mill to prepare a slurry.

[0134] The mass of gallium oxide is 0.5% of the mass of zinc oxide powder doped with magnesium oxide, the mass of scandium oxide is 0.3% of the mass of zinc oxide powder doped with magnesium oxide, and the mass of the dispersant and the binder are each independently 0.8% of the mass of zinc oxide powder doped with magnesium oxide.

[0135] S4: The slurry is passed into a flow spray drying tower for spray drying to obtain dry powder.

[0136] Among them, the inlet air temperature of the spray drying is 180°C, the outlet air temperature is 90°C, and the atomizer frequency is 100Hz.

[0137] S5: The dried powder is molded, encapsulated, and then cold isostatically pressed to obtain a green body.

[0138] Among them, the compression molding pressure is 30MPa; the cold isostatic pressing pressure is 200MPa, and the holding time is 15min.

[0139] S6: The above green blank is sintered at normal pressure in an oxygen atmosphere in a sintering furnace. The oxygen flow rate is 40L / min, the heating rate is 1.5℃ / min, the maximum sintering temperature is 1520℃, and the insulation time is 30h. After the insulation is completed, the oxygen atmosphere is replaced with an argon atmosphere with an argon flow rate of 10L / min until it is naturally cooled to room temperature to obtain a target blank.

[0140] S7: The cooled target blank is subjected to wire cutting, grinding and other machining processes according to the specified size to obtain the final zinc oxide-based sputtering target.

[0141] Comparative Example 1

[0142] The difference between this comparative example and Example 1 is that magnesium oxide and zinc oxide are directly mixed in a mass ratio of 98:2 to obtain a mixed oxide; and the mixed oxide is prepared according to S3 to S7.

[0143] Comparative Example 2

[0144] The difference between this comparative example and Example 1 is that in S1, the mass ratio of the zinc ingot to the magnesium ingot is 85:15.

[0145] Comparative Example 3

[0146] The difference between this comparative example and Example 1 is that in S3, an equal amount of gallium oxide is replaced by aluminum oxide.

[0147] Comparative Example 4

[0148] The difference between this comparative example and Example 1 is that in S3, no yttrium oxide powder is used, and the mass of gallium oxide is 2% of the mass of zinc oxide powder doped with magnesium oxide.

[0149] Comparative Example 5

[0150] The difference between this comparative example and Example 1 is that in S3, gallium oxide is not used, and the mass of yttrium oxide powder is 2% of the mass of zinc oxide powder doped with magnesium oxide.

[0151] Comparative Example 6

[0152] The difference between this comparative example and Example 1 is that in S3, the mass of gallium oxide is 2.5% of the mass of zinc oxide powder doped with magnesium oxide.

[0153] Comparative Example 7

[0154] The difference between this comparative example and Example 1 is that in S3, the mass of yttrium oxide is 1.5% of the mass of zinc oxide powder doped with magnesium oxide.

[0155] Comparative Example 8

[0156] The difference between this comparative example and Example 1 is that in S6, the entire sintering process is always carried out under an argon atmosphere.

[0157] Comparative Example 9

[0158] The difference between this comparative example and Example 1 is that in S6, the entire sintering process is always carried out under an oxygen atmosphere.

[0159] Test example

[0160] The zinc oxide-based sputtering targets prepared in the above Examples 1 to 3 and Comparative Examples 1 to 9 were subjected to performance tests, and the results are shown in Table 1.

[0161] Among them, the density is obtained by testing the relative density using the water displacement method;

[0162] The average grain size was measured by scanning electron microscopy;

[0163] The bandgap width was measured by optical absorption spectroscopy;

[0164] The resistivity was measured by the four-probe method;

[0165] The mobility was measured by the Hall test method.

[0166] Table 1 Test results

[0167] It can be seen from Table 1 that the zinc oxide-based sputtering target provided in the embodiment of the present invention has a high density and small grains, a moderate band gap, a low resistivity, and a high electron mobility. The zinc oxide-based sputtering target provided in the embodiment is overall superior to the zinc oxide-based sputtering target provided in the comparative example.

[0168] In summary, the preparation method of the zinc oxide-based sputtering target provided by the present invention is simple, easy to operate, and can realize industrial production. The zinc oxide-based sputtering target prepared by the method has high density, fine grains, uniform structure, moderate bandgap width, and low resistivity, which is conducive to the preparation of TCO thin films with excellent performance.

[0169] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a zinc oxide-based sputtering target, characterized in that: The following steps are involved: Smelting magnesium ingots and zinc ingots to obtain alloy ingots; preparing the alloy ingot into zinc oxide powder doped with magnesium oxide; The magnesium oxide-doped zinc oxide powder, gallium oxide and rare earth oxide are prepared into a slurry; The slurry is dried, molded, cold isostatically pressed and sintered to obtain a zinc oxide-based sputtering target.

2. The preparation method according to claim 1, characterized in that: The mass ratio of the zinc ingot to the magnesium ingot is 90:10 to 99:1; and / or, the smelting is carried out under vacuum or argon atmosphere conditions; And / or, the alloy ingot is prepared into zinc oxide powder doped with magnesium oxide by plasma gasification oxidation.

3. The preparation method according to claim 1, characterized in that: The mass of the gallium oxide is 0.5% to 2% of the mass of the zinc oxide powder doped with magnesium oxide; and / or, the rare earth oxide comprises at least one of yttrium oxide, scandium oxide, cerium oxide, samarium oxide and lanthanum oxide; And / or, the mass of the rare earth oxide is 0.3% to 1% of the mass of the magnesium oxide-doped zinc oxide powder.

4. The preparation method according to claim 1, characterized in that: A dispersant and a binder are also added during the preparation of the slurry; Preferably, the dispersant comprises at least one of polyvinyl pyrrolidone, dodecylbenzene sulfonate and polycarboxylate; Preferably, the binder comprises polyvinyl alcohol; Preferably, the mass of the dispersant is 0.5% to 1% of the mass of the magnesium oxide-doped zinc oxide powder; Preferably, the mass of the binder is 0.5% to 2% of the mass of the magnesium oxide-doped zinc oxide powder.

5. The preparation method according to any one of claims 1 to 4, characterized in that: Drying is carried out by spray drying; Preferably, the inlet air temperature of the spray drying is 180°C to 230°C, the outlet air temperature is 90°C to 120°C, and the atomizer frequency is 100Hz to 130Hz.

6. The preparation method according to any one of claims 1 to 4, characterized in that: The pressure of compression molding is 30MPa~50MPa; And / or, the pressure of cold isostatic pressing is 200 MPa to 280 MPa, and the holding time is 8 min to 15 min.

7. The preparation method according to any one of claims 1 to 4, characterized in that: Sintering includes at least one of the following features: Feature 1: The atmosphere during the sintering process is an oxygen-containing atmosphere, and the oxygen flow rate is 40L / min to 100L / min; Feature 2: Sintering is carried out under normal pressure; Feature 3: The heating rate of the sintering process is 1℃ / min~2℃ / min; Feature 4: The maximum sintering temperature of the sintering process is 1450℃~1550℃, and the holding time is 10h~30h; Feature 5: After the insulation is completed, the oxygen-containing atmosphere is replaced with an inert gas atmosphere and the temperature is naturally lowered. The flow rate of the inert gas is 10L / min to 40L / min.

8. A zinc oxide-based sputtering target, characterized in that: Prepared by the preparation method according to any one of claims 1 to 7; Preferably, the zinc oxide-based sputtering target has at least one of the following characteristics: Feature 6: The density of the zinc oxide-based sputtering target is not less than 99.5%; Feature 7: The average grain size of the zinc oxide-based sputtering target does not exceed 12 μm; Feature 8: The bandgap width of the zinc oxide-based sputtering target is 3.5 eV to 4.0 eV; Feature 9: The resistivity of the zinc oxide-based sputtering target is no more than 2.0×10 -3 Ω·cm; Feature 10: The electron mobility of the zinc oxide-based sputtering target is not less than 18 cm 2 / Vs.

9. A TCO film, characterized in that: The target material used for the TCO film is the zinc oxide-based sputtering target material as described in claim 8.

10. A solar cell, characterized in that: The solar cell comprises the TCO film according to claim 9; Preferably, the solar cell is a HJT cell.

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