Oxide sintered body

Abstract

This sintered oxide contains an In element, a Ga element, and a Zn element, contains an In2Ga2ZnO7 crystal phase and a Ga2ZnO4 crystal phase, has a relative density of more than 100.0%, and has a Zr content of 100 ppm by mass or less.

Description

Technical Field

[0001] This invention relates to an oxide sintered body containing an In-Ga-Zn composite oxide. Background Technology

[0002] In the field of thin film transistors (TFTs) used in display devices such as flat panel displays (FPDs), with the increasing functionality of FPDs, oxide semiconductors, represented by In-Ga-Zn composite oxides (IGZO) as shown in Patent Documents 1 and 2, have been pushed toward practical application, replacing the previous amorphous silicon.

[0003] In addition, in recent years, oxide semiconductors have shown the ability to achieve both high mobility (>10 cm⁻¹) and low mobility. 2 With its excellent characteristics of low voltage per volt (Vs) and extremely low off-leak current (<10-22 A / μm), it is expected to be a channel material for highly integrated vertical FETs in BEOL-compatible processes, where it can be hybridized with Si-CMOS LSI. Along with these expectations, the requirements for sputtering targets used to deposit oxide semiconductor films are also increasing.

[0004] Existing technical documents Patent documents Patent Document 1: Japanese Patent Application Publication No. 2014-105124 Patent Document 2: Japanese Patent Application Publication No. 2011-195406 Summary of the Invention

[0005] The problem that the invention aims to solve However, if the oxide sintered body disclosed in Patent Documents 1 and 2 is manufactured by mixing Ga2O3 powder and ZnO powder, pre-firing to produce Ga2ZnO4 powder, then pulverizing the Ga2ZnO4 powder and mixing it with In2O3 powder, the sintering of the oxide sintered body is not fully completed, resulting in a lack of density increase. Furthermore, Ga2ZnO4 powder is very hard, leading to the following problem: when mixed with In2O3 powder, ZrO2, used as the pulverizing medium for Ga2ZnO4 powder, is ground, resulting in a large amount of Zr-containing impurities.

[0006] In view of the above-mentioned problems, the present invention provides an oxide sintered body with high relative density and significantly reduced content of impurities including Zr.

[0007] Methods for solving problems The oxide sintered body of the present invention, which was completed to solve the above-mentioned problems, is an oxide sintered body containing In, Ga and Zn elements, characterized in that it contains In2Ga2ZnO7 crystalline phase and Ga2ZnO4 crystalline phase, has a relative density greater than 100.0%, and has a Zr content of less than 100 ppm by mass.

[0008] The oxide sintered body of the present invention is an oxide sintered body containing In, Ga and Zn elements, which contains In2Ga2ZnO7 crystalline phase and Ga2ZnO4 crystalline phase, has a relative density greater than 100.0%, and a Zr content of less than 100 ppm by mass, thereby achieving a high relative density and significantly reducing the content of impurities containing Zr.

[0009] The oxide sintered body of the present invention is an oxide sintered body containing In, Ga and Zn elements.

[0010] Furthermore, the oxide sintered body of the present invention and the sputtering target made therefrom have In2Ga2ZnO7 crystalline phase and Ga2ZnO4 crystalline phase. The oxide sintered body of the present invention is formed by mixing the In2Ga2ZnO7 crystalline phase and the Ga2ZnO4 crystalline phase to form a mottled pattern. Figure 2 This is a SEM image of the surface of the oxide sintered body of the present invention observed using a scanning electron microscope, showing areas that appear as black areas ( Figure 2 In the diagram, A represents the Ga2ZnO4 crystalline phase, specifically the whitish region ( Figure 2 B) in the figure represents the In2Ga2ZnO7 crystalline phase.

[0011] Figure 2 The SEM images shown can be taken as follows: Using diamond sandpaper of grit #180, #400, #800, #1000, and #2000, the cut surfaces formed by cutting the oxide sintered body of the present invention are ground in stages, and finally polished to achieve a mirror finish. Then, the mirror-finished cut surfaces are subjected to thermal etching at 1100°C for 1 hour, observed using a scanning electron microscope (SU3500, manufactured by Hitachi High-Tech Corporation), and SEM images of the grain boundaries appearing in the cut surfaces are taken.

[0012] Furthermore, the In2Ga2ZnO7 and Ga2ZnO4 phases contained in the oxide sintered body of the present invention and the sputtering target made therefrom can be identified by analyzing the peaks obtained using powder X-ray diffraction. Specifically, X-ray diffraction measurements are performed according to the following powder X-ray diffraction measurement conditions.

[0013] =Powder X-ray Diffraction Measurement Conditions= • Radiation source: CuKα rays • Tube voltage: 40kV Tube current: 30mA • Scanning speed: 5deg / min • Step size: 0.02 deg • Scanning range: 2θ = 20 degrees to 80 degrees X-ray analysis software: PDXL2 Version 2.1.3.6 The X-ray diffraction measurements were compared with the X-ray diffraction pattern of ICDD (International Centre for Diffraction Data) card No. 38-1097 corresponding to the crystal structure of the In2Ga2ZnO7 phase. If the X-ray diffraction patterns are consistent, it can be confirmed that the oxide sintered body of the present invention contains the In2Ga2ZnO7 phase. Furthermore, the X-ray diffraction patterns were compared with the X-ray diffraction pattern of ICDD card No. 38-1240 corresponding to the crystal structure of the Ga2ZnO4 phase. If the X-ray diffraction patterns are consistent, it can be confirmed that the oxide sintered body of the present invention contains the Ga2ZnO4 phase.

[0014] Furthermore, from the viewpoint of suppressing the number of arc occurrences during sputtering, the relative density of the oxide sintered body of the present invention and the sputtering target made therefrom is preferably greater than 100.0%. This is because by increasing the relative density, the volume resistivity of the oxide sintered body and the sputtering target made therefrom decreases, thereby suppressing charge concentration during sputtering. Moreover, the formation of high-potential regions caused by charge concentration and low-potential regions caused by charge deconcentration during sputtering can be suppressed, making it less likely for discharge to occur from high-potential regions to low-potential regions, thereby reducing the number of arc occurrences. The relative density of the oxide sintered body of the present invention is more preferably 100.5% or more, further preferably 101.0% or more, particularly preferably 101.5% or more, even more preferably 102.0% or more, even more preferably 102.5% or more, and even more preferably 103.0% or more. Furthermore, the upper limit of this relative density is not particularly limited, for example, it is 105.0% or less.

[0015] Here, the relative density of the oxide sintered body of the present invention and the sputtering target made therefrom is measured according to Archimedes' method. Specifically, the relative density is calculated by dividing the air mass of the target by its volume (mass of the target in water / specific gravity of water at the measurement temperature), relative to the theoretical density ρ (g / cm³) based on the following formula (X). 3 The percentage value of ) is used as the relative density (unit: %).

[0016]

Mathematical Formula 1

[0017] C1: Mass% of In2O3 in oxide sintered bodies or targets ρ1: Density of In2O3 (7.18 g / cm³) 3 ) C2: Mass% of Ga2O3 in oxide sintered bodies or targets ρ2: Density of Ga2O3 (5.95 g / cm³) 3 ) C3: Mass % of ZnO in oxide sintered bodies or targets ρ3: Density of ZnO (5.60 g / cm³) 3 ) Furthermore, the aforementioned mass percentages of In2O3, Ga2O3, and ZnO can be determined from the elemental analysis results of oxide sintered bodies or sputtering targets obtained using ICP-OES (inductively coupled plasma-optical emission spectrometer).

[0018] Furthermore, if the Zr content in the oxide sintered body of the present invention is 100 ppm by mass or less, the Zr-containing impurities contained in the oxide sintered body of the present invention are significantly reduced, which is preferable. More preferably, the Zr content in the oxide sintered body of the present invention is 50 ppm by mass or less, further preferably 30 ppm by mass or less, particularly preferably 20 ppm by mass or less, even more preferably 10 ppm by mass or less, even more preferably 5 ppm by mass or less, even more preferably 2 ppm by mass or less, even more preferably 1 ppm by mass or less, and even more preferably less than 1 ppm by mass.

[0019] Here, the Zr content in the oxide sintered body of the present invention can be determined by adding nitric acid, perchloric acid, or hydrogen peroxide to the sintered body as needed, heating and decomposing it to make it soluble, and then using an ICP (Inductively Coupled Plasma) emission spectrometer (Agilent Technologies: 720 ICP-OES) to measure the Zr concentration.

[0020] Furthermore, the oxide sintered body of the present invention is characterized in that the pinhole area ratio is less than 0.7%.

[0021] From the viewpoint of forming high-quality thin films, the pinhole area ratio of the oxide sintered body of the present invention, as a sputtering target, is preferably 0.7% or less. Furthermore, the pinhole area ratio of the oxide sintered body of the present invention is more preferably 0.6% or less, even more preferably 0.5% or less, particularly preferably 0.4% or less, and even more preferably 0.3% or less. Moreover, the lower limit of this pinhole area ratio is not particularly limited, for example, it is 0.01% or more.

[0022] Here, the pinhole area ratio can be measured as follows: It is measured by evaluating the crystalline phase on the surface of the oxide sintered body of the present invention using a scanning electron microscope (SEM).

[0023] Specifically, using diamond sandpaper of grit #180, #400, #800, #1000, and #2000, the cut surfaces formed by cutting the oxide sintered body of the present invention are ground in stages, and finally polished to achieve a mirror finish. Then, for the mirror-finished cut surfaces, a scanning electron microscope (SU3500, manufactured by Hitachi High-Tech Corporation) is used to randomly capture 10 fields of view with a magnification of 1000x and a range of 87.5μm × 125μm, obtaining 10 fields of view SEM images.

[0024] Next, using Pictbear (manufactured by Fenrir), the area occupied by pinholes with an equivalent circle diameter of 0.1 μm or larger in each SEM image was depicted and filled with color. Then, particle analysis software (manufactured by Sumitomo Metal Technology Co., Ltd.: Particle Analysis Version 3.0) was used to identify the SEM image after the pinhole filling and binarize it. At this point, the conversion value was set using μm units to represent 1 pixel.

[0025] Subsequently, the area of ​​the pinholes and the whole body were calculated separately using particle analysis software, and the percentage of pinholes relative to the whole body was obtained as the area ratio. Then, the average of the area ratios obtained from SEM images of every 10 fields of view was taken as the pinhole area ratio in the oxide sintered body of the present invention.

[0026] Furthermore, from the viewpoint of increased flexural strength, the average particle size of the In2Ga2ZnO7 phase contained in the oxide sintered body of the present invention is preferably 6.0 μm or less. More preferably, the average particle size of this In2Ga2ZnO7 phase is 5.5 μm or less, even more preferably 5.0 μm or less, particularly preferably 4.5 μm or less, even more preferably 4.0 μm or less, and still particularly preferably 3.5 μm or less. On the other hand, the average particle size of this In2Ga2ZnO7 phase is preferably 1.0 μm or more, more preferably 2.0 μm or more, and particularly preferably 3.0 μm or more.

[0027] The average particle size, i.e. the area equivalent circle diameter, of the In2Ga2ZnO7 phase contained in the oxide sintered body of the present invention can be calculated by image processing of SEM images taken using a scanning electron microscope.

[0028] Specifically, using diamond sandpaper of grit #180, #400, #800, #1000, and #2000, the cut surfaces formed by cutting the oxide sintered body of the present invention are ground in stages, and finally polished to achieve a mirror finish. Next, the mirror-finished cut surfaces are subjected to thermal etching at 1100°C for 1 hour, and observed using a scanning electron microscope (SU3500, manufactured by Hitachi High-Tech Corporation). Ten randomly selected fields of view are captured as BSE-COMP images at 1000x magnification, covering an area of ​​87.5μm × 125μm, thus obtaining ten fields of view SEM images.

[0029] Using the image processing software ImageJ, the obtained SEM images were plotted along the grain boundaries of the In2Ga2ZnO7 phase. After all plotting was completed, particle analysis was performed to obtain the area of ​​each particle. Then, the area equivalent circle diameter was calculated from the obtained area of ​​each particle. This operation was then performed on SEM images of 10 fields of view, and the average of the calculated area equivalent circle diameters of all particles was taken as the area equivalent circle diameter of the In2Ga2ZnO7 phase.

[0030] Furthermore, from the viewpoint of reducing abnormal discharge, the average particle size of the Ga2ZnO4 phase contained in the oxide sintered body of the present invention is preferably 1.0 μm or more and 4.5 μm or less. More preferably, the average particle size of the Ga2ZnO4 is 1.5 μm or more and 4.0 μm or less, and even more preferably 2.0 μm or more and 3.5 μm or less.

[0031] The average particle size, i.e., the area equivalent circle diameter, of the Ga2ZnO4 phase contained in the oxide sintered body of the present invention can be calculated by image processing of SEM images taken using a scanning electron microscope, just like the average particle size of the In2Ga2ZnO7 phase.

[0032] Specifically, using the image processing software ImageJ, the obtained SEM images were depicted along the grain boundaries of the Ga2ZnO4 phase. After all depictions were completed, particle analysis was performed to obtain the area of ​​each particle. Then, the area equivalent circle diameter was calculated from the obtained area of ​​each particle. This operation was then performed on SEM images of 10 fields of view, and the average of the calculated area equivalent circle diameters of all particles was taken as the area equivalent circle diameter of the Ga2ZnO4 phase.

[0033] Furthermore, the oxide sintered body of the present invention is characterized in that the atomic ratio of the above-mentioned In, Ga and Zn elements satisfies the following formula.

[0034] 0.15<In / (In+Ga+Zn)<0.35 0.4 < Ga / (In + Ga + Zn) < 0.6 0.15<Zn / (In+Ga+Zn)<0.35 The oxide sintered body of the present invention satisfies all three formulas above in terms of the atomic ratios of In, Ga and Zn elements, and contains In2Ga2ZnO7 phase and Ga2ZnO4 phase in the best proportion in the oxide sintered body of the present invention, which is therefore preferred.

[0035] The ratio of In / (In+Ga+Zn) is more preferably 0.17 < In / (In+Ga+Zn) < 0.33, and even more preferably 0.2 < In / (In+Ga+Zn) < 0.3.

[0036] Furthermore, Ga / (In+Ga+Zn) is more preferably 0.42 < Ga / (In+Ga+Zn) < 0.58, and even more preferably 0.45 < Ga / (In+Ga+Zn) < 0.55.

[0037] Furthermore, Zn / (In+Ga+Zn) is more preferably 0.17 < Zn / (In+Ga+Zn) < 0.33, and even more preferably 0.2 < Zn / (In+Ga+Zn) < 0.3.

[0038] Here, the atomic ratio of In, Ga and Zn elements in the oxide sintered body of the present invention can be calculated from the measured concentrations of In, Ga and Zn elements by measuring each concentration using an ICP emission spectrometer (Agilent Technologies: 720 ICP-OES).

[0039] In addition, the oxide sintered body of the present invention is characterized in that its flexural strength is 150 MPa or more.

[0040] If the oxide sintered body of the present invention exhibits such high flexural strength, it is preferable that, when used as a sputtering target, even if an unintentional abnormal discharge occurs during sputtering, the target is less likely to crack or break. The flexural strength of the oxide sintered body of the present invention is preferably 160 MPa or more, more preferably 165 MPa or more, and particularly preferably 170 MPa or more. There is no particular limitation on the upper limit of this flexural strength; for example, it is 250 MPa or less. Furthermore, the specific method for measuring the flexural strength is described below.

[0041] Furthermore, the sputtering target of the present invention is characterized in that it comprises the oxide sintered body of the present invention described above.

[0042] The sputtering target of the present invention, by incorporating the oxide sintered body described above, can significantly suppress the number of arc occurrences, thereby further suppressing particle generation and enabling the high-yield formation of high-quality oxide semiconductor films. Furthermore, it can significantly reduce the incorporation of Zr-containing impurities into the oxide semiconductor film.

[0043] In addition, as an example of the method for manufacturing oxide sintered bodies of the present invention, the filter forming method will be described below.

[0044] First, weigh out In₂O₃ powder, Ga₂O₃ powder, and ZnO powder as raw materials, place them in a pot, and pulverize and mix these materials. Then, add an organic additive and a dispersion medium to obtain a slurry. Examples of organic additives include known binders and dispersants. Furthermore, there are no particular limitations on the dispersion medium; water, alcohol, etc., can be appropriately selected depending on the application.

[0045] Here, the method for pulverizing and mixing can be either dry pulverization or wet pulverization.

[0046] Specifically, dry grinding involves adding In2O3 powder, Ga2O3 powder, and ZnO powder, along with Ga2ZnO4 balls (hereinafter referred to as GZO media) as grinding media, to a pot and mixing them by ball milling, thereby dry grinding the In2O3 powder, Ga2O3 powder, and ZnO powder.

[0047] Using a filter, the mixture containing dry-crushed In2O3 powder, Ga2O3 powder and ZnO powder in the pot is separated from the GZO medium to obtain a mixture containing the dry-crushed In2O3 powder, Ga2O3 powder and ZnO powder.

[0048] Subsequently, dry-milled In₂O₃ powder, Ga₂O₃ powder, and ZnO powder, an organic additive (e.g., a dispersant), and a dispersion medium (e.g., water) are placed in another pot, and GZO medium is added as the milling medium. The pot is then mixed to liquefy the mixture. Alternatively, the mixture containing the dry-milled In₂O₃ powder, Ga₂O₃ powder, and ZnO powder may not be removed from the pot. Instead, an organic additive (e.g., a dispersant) and a dispersion medium (e.g., water) are added to the pot containing the dry-milled mixture and mixed to liquefy the mixture.

[0049] On the other hand, wet grinding involves placing In2O3 powder, Ga2O3 powder, ZnO powder, organic additives (such as dispersants), and a dispersion medium (such as water) into a pot, then adding GZO medium as the grinding medium, and ball milling the pot to wet grind the In2O3 powder, Ga2O3 powder, and ZnO powder.

[0050] The mixture of In2O3 powder, Ga2O3 powder and ZnO powder contained in the pot is filtered using a filter to separate it from the GZO medium, thereby obtaining the mixture slurry.

[0051] The mixture slurry obtained in this way is flowed into a molding die, and the dispersion medium is removed, thereby obtaining a molded body. Examples of molding dies include metal molds, plaster molds, and resin molds.

[0052] A sintered body is obtained by firing the resulting molded body. During firing, the In2Ga2ZnO7 and Ga2ZnO4 phases are formed. If the firing temperature of the molded body is greater than 1400°C and less than 1530°C, a high-density and high-strength oxide sintered body can be obtained. Then, the obtained sintered body is machined into an arbitrary shape to obtain the oxide sintered body of the present invention.

[0053] In addition, as another example of the method for manufacturing oxide sintered bodies of the present invention, the CIP forming method will be described below.

[0054] First, the process before pulverizing and mixing the In2O3 powder, Ga2O3 powder and ZnO powder as raw materials to obtain a slurry is the same as the process described in the above-mentioned filter-type forming method, so the explanation is omitted.

[0055] A dried powder is obtained by spray drying the mixture slurry obtained in the above manner. A molded body is obtained by filling the obtained dried powder into a molding die and pressing it.

[0056] Next, the obtained shaped body is fired to obtain a sintered body. During firing, the In2Ga2ZnO7 and Ga2ZnO4 phases are formed. If the firing temperature of the shaped body is greater than 1400°C and less than 1530°C, a high-density and high-strength oxide sintered body can be obtained. Then, the obtained sintered body is machined into an arbitrary shape to obtain the oxide sintered body of the present invention.

[0057] The method for manufacturing the oxide sintered body of the present invention does not include the step of pulverizing and mixing Ga2O3 powder and ZnO powder and pre-firing to form a pre-fired powder composed of crystalline Ga2ZnO4. Therefore, the highly hard crystalline Ga2ZnO4 contained in the pre-fired powder is absent. Even when using a pulverizing medium composed of ZrO2, the content of Zr-containing impurities in the resulting oxide sintered body of the present invention can be significantly reduced. Furthermore, by using a pulverizing medium composed of Ga2ZnO4 instead of a pulverizing medium composed of ZrO2, the content of Zr-containing impurities in the resulting oxide sintered body of the present invention can be further reduced.

[0058] The oxide sintered body of the present invention, obtained by the above-described method for manufacturing the oxide sintered body of the present invention, and a substrate are bonded together to obtain the sputtering target of the present invention. Examples of substrates include Cu, Al, Ti, or stainless steel. As the bonding material, conventional bonding materials used for bonding ITO targets, such as In metal, can be used. The bonding method is also the same as that used for conventional ITO target bonding.

[0059] The method for manufacturing the film of the present invention is characterized in that a thin film is formed on a substrate by sputtering using the sputtering target of the present invention.

[0060] Using the sputtering target of the present invention, a thin film is formed on a substrate by sputtering, thereby enabling the high-quality thin film to be formed with high yield.

[0061] Specifically, by using the sputtering target of the present invention, high-quality thin films, such as oxide semiconductor films, can be formed on a substrate through sputtering. Examples of substrates include glass substrates, resin substrates, and silicon substrates.

[0062] Furthermore, in this specification, when expressed as "X~Y" (where X and Y are arbitrary numbers), unless otherwise specified, it includes the meaning of "X or more and Y or less," and also includes the meaning of "preferably greater than X" or "preferably less than Y." Additionally, when expressed as "X or more" (where X is any number) or "Y or less" (where Y is any number), it also includes the meaning of "preferably greater than X" or "preferably less than Y."

[0063] The effects of the invention The oxide sintered body of the present invention has a high relative density and significantly reduces the content of impurities containing Zr. Attached Figure Description

[0064] Figure 1 This is a summary table of the physical properties and measurement results of the oxide sintered bodies of Examples 1-4 and Comparative Examples 1-5 of the present invention.

[0065] Figure 2 The image shows a SEM image of the surface of the oxide sintered body of the present invention observed using a scanning electron microscope. Detailed Implementation

[0066] The following examples further illustrate the oxide sintered body according to embodiments of the present invention. However, these examples do not limit the scope of the present invention.

[0067] (Example 1) In₂O₃ powder (median diameter D₅₀ = 0.6 μm), Ga₂O₃ powder (median diameter D₅₀ = 1.5 μm), and ZnO powder (median diameter D₅₀ = 0.8 μm) were weighed according to the mixing ratio of In, Ga, and Zn with an atomic ratio of In:Ga:Zn = 1:2:1. The powders were placed in a pot and dry-mixed for 24 hours using a ball mill with a grinding medium (GZO medium) to obtain a mixed raw material powder. Furthermore, the mixed raw material powder was not pre-calcined after grinding and mixing.

[0068] Here, the median diameter D50 of each powder was measured using a Microtrac BEL Corp. MT3300EXII particle size distribution measuring device. Water was used as the solvent for the measurement sample. Furthermore, the refractive index of the measured material was set to 2.20.

[0069] Next, add 0.2% by mass of acrylic emulsion binder relative to the mixed raw material powder as a binder, 0.6% by mass of ammonium polycarboxylate relative to the mixed raw material powder as a dispersant, and 20% by mass of water relative to the mixed raw material powder as a dispersion medium to the pot. Then, use a grinding medium (GZO medium) to ball mill and mix for 24 hours to obtain a slurry mixture.

[0070] The mixture slurry obtained in this way is flowed into an aluminum mold, and the dispersion medium is drained to obtain a shaped body.

[0071] Next, the resulting molded body was fired in an atmospheric environment at a firing temperature of 1410°C, a firing time of 10 hours, a heating rate of 300°C / h, and a cooling rate of 50°C / h to obtain a fired body. Then, the fired body was machined to a width of 210 mm × a length of 710 mm × a thickness of 6 mm to obtain the oxide sintered body of Example 1. Furthermore, the machining was performed using a #170 grinding stone.

[0072] (Example 2) In Example 2, the firing temperature was changed to 1450°C, but otherwise the same manufacturing method as in Example 1 was performed to obtain the oxide sintered body of Example 2.

[0073] (Example 3) In Example 3, the firing temperature was changed to 1500°C, but otherwise the same manufacturing method as in Example 1 was performed to obtain the oxide sintered body of Example 3.

[0074] (Example 4) In Example 4, the pulverizing medium was changed to ZrO2, and the firing temperature was changed to 1450°C. Otherwise, the same manufacturing method as in Example 1 was implemented to obtain the oxide sintered body of Example 4.

[0075] (Comparative Example 1) In Comparative Example 1, the firing temperature was changed to 1400°C, but the same manufacturing method as in Example 1 was performed to obtain the oxide sintered body of Comparative Example 1.

[0076] (Comparative Example 2) In Comparative Example 2, the firing temperature was changed to 1530°C, and the same manufacturing method as in Example 1 was performed to obtain the oxide sintered body of Comparative Example 2.

[0077] (Comparative Example 3) Ga₂O₃ powder (median diameter D50 of 1.5 μm) and ZnO powder (median diameter D50 of 0.8 μm) were weighed at a ratio of Ga₂O₃:ZnO = 1:1 (atomic ratio of Ga to Zn: Ga:Zn = 2:1). Water was used as the dispersion medium, and a grinding medium (ZrO₂ balls) was used to mix the powders in a ball mill for 6 hours to obtain a Ga₂O₃-ZnO mixed powder slurry. Next, the obtained Ga₂O₃-ZnO mixed powder slurry was spray-dried to obtain Ga₂O₃-ZnO granulated powder. Then, the obtained Ga₂O₃-ZnO granulated powder was placed in an alumina crucible and pre-calcined at 900°C for 5 hours in an atmospheric environment to obtain a pre-calcined powder containing crystalline Ga₂ZnO₄.

[0078] The obtained pre-calcined powder (containing crystalline Ga2ZnO4) and In2O3 powder (median diameter D50 of 0.6 μm) were weighed at a ratio of Ga2ZnO4:In2O3 = 2:1 (atomic ratio of In to Ga to Zn = 1:2:1). Water was used as the dispersion medium, and ZrO2 balls were used as the pulverizing medium. The mixture was then milled for 6 hours to obtain a Ga2ZnO4-In2O3 mixed powder slurry. Next, the obtained Ga2ZnO4-In2O3 mixed powder slurry was spray-dried to obtain Ga2ZnO4-In2O3 granulated powder.

[0079] The Ga2ZnO4-In2O3 granulated powder obtained in this way was subjected to a surface pressure of 0.5 tf / cm. 2 Under these conditions, the material is pressed and formed; furthermore, the surface pressure is 1.5 tf / cm. 2 CIP molding is performed under certain conditions to obtain a molded body.

[0080] Next, the obtained molded body was fired in an atmospheric environment at a firing temperature of 1450°C, a firing time of 10 hours, a heating rate of 300°C / h, and a cooling rate of 50°C / h to obtain a fired body. Then, the obtained fired body was machined to a width of 210 mm × a length of 710 mm × a thickness of 6 mm to obtain the oxide sintered body of Comparative Example 3. Furthermore, the machining was performed using a #170 grinding stone. In addition, the In₂O₃ powder, Ga₂O₃ powder, and ZnO powder used in Comparative Example 3 were the same as those used in Example 1.

[0081] (Comparative Example 4) In Comparative Example 4, the firing temperature was changed to 1500°C, and the same manufacturing method as Comparative Example 3 was performed to obtain the oxide sintered body of Comparative Example 4.

[0082] (Comparative Example 5) In2O3 powder (median diameter D50 of 0.6 μm), Ga2O3 powder (median diameter D50 of 1.5 μm), and ZnO powder (median diameter D50 of 0.8 μm) were weighed according to the mixing ratio of each powder, with the atomic ratio of In to Ga to Zn being In:Ga:Zn = 1:2:1. The powders were placed in a pot and dry-mixed for 24 hours using a ball mill with a grinding medium (ZrO2 balls) to obtain a mixed raw material powder.

[0083] The obtained mixed raw material powder was placed in an alumina crucible and pre-fired at a pre-fired temperature of 900°C for 5 hours in an atmospheric environment to obtain a pre-fired powder containing crystalline Ga2ZnO4.

[0084] Next, add 0.2% by mass of acrylic emulsion binder relative to the pre-fired powder as a binder, 0.6% by mass of ammonium polycarboxylate relative to the pre-fired powder as a dispersant, and 20% by mass of water relative to the pre-fired powder as a dispersion medium to the pot. Then, use a grinding medium (ZrO2 balls) to ball mill and mix for 24 hours to obtain a slurry mixture.

[0085] The mixture slurry obtained in this way is fed into an aluminum mold, and the dispersion medium is drained to obtain a shaped body.

[0086] Next, the resulting molded body was fired in an atmospheric environment at a firing temperature of 1430°C, a firing time of 10 hours, a heating rate of 300°C / h, and a cooling rate of 50°C / h to obtain a fired body. Then, the obtained fired body was machined to a width of 210 mm × a length of 710 mm × a thickness of 6 mm to obtain the oxide sintered body of Comparative Example 5. Furthermore, the machining was performed using a #170 grinding stone.

[0087] Then, for the oxide sintered bodies obtained in Examples 1-4 and Comparative Examples 1-5, the following physical properties were measured. The measured physical property values ​​and the methods used to measure them are shown below, and the measurement results are displayed in [the table / document / etc.]. Figure 1 .

[0088] <Elemental Analysis> Nitric acid, perchloric acid, and hydrogen peroxide are added to the sample as needed, and the sample is heated to decompose it into a solution. The concentrations of each element (In, Ga, Zn, and Zr) are measured using an ICP emission spectrometer (Agilent Technologies: 720 ICP-OES).

[0089] Relative density The relative densities of the oxide sintered bodies in Examples 1-4 and Comparative Examples 1-5 were measured according to Archimedes' method. Specifically, the relative density ρ (g / cm³) of the target material was calculated by dividing the air mass of the target material by its volume (mass of the target material in water / specific gravity of water at the measurement temperature) relative to the theoretical density ρ based on the above formula (X). 3 The percentage value of ) is used as the relative density (unit: %).

[0090] <Crystal Size Measurement> The grain size, i.e., the area equivalent circle diameter, of the In2Ga2ZnO7 and Ga2ZnO4 phases was measured from SEM images of the oxide sintered bodies of Examples 1-4 and Comparative Examples 1-5 obtained using a scanning electron microscope. Specifically, the cut surfaces obtained by cutting the oxide sintered bodies of Examples 1-4 and Comparative Examples 1-5 were ground in stages using diamond sandpaper #180, #400, #800, #1000, and #2000, and finally polished to a mirror finish. Next, the mirror-finished cut surfaces were subjected to thermal etching at 1100°C for 1 hour, and observed using a scanning electron microscope (SU3500, manufactured by Hitachi High-Tech Corporation). BSE-COMP images of 10 fields of view with a magnification of 1000x and a range of 87.5μm × 125μm were randomly captured to obtain SEM images of 10 fields of view.

[0091] Furthermore, using ImageJ image processing software, the obtained SEM images were plotted along the grain boundaries of the In2Ga2ZnO7 phase. After all plotting was completed, particle analysis was performed to obtain the area of ​​each particle. Then, the area equivalent circle diameter was calculated from the area of ​​each particle. This operation was then performed on SEM images with 10 fields of view, and the average of the calculated area equivalent circle diameters of all particles was taken as the area equivalent circle diameter of the In2Ga2ZnO7 phase. Next, using ImageJ image processing software, the obtained SEM images were plotted along the grain boundaries of the Ga2ZnO4 phase, and particle analysis was performed in the same way. The area equivalent circle diameter was calculated from the area of ​​each particle. This operation was then performed on SEM images with 10 fields of view, and the average of the calculated area equivalent circle diameters of all particles was taken as the area equivalent circle diameter of the Ga2ZnO4 phase.

[0092] <Specification of Crystallized Phases Using X-ray Diffraction> The specific crystal phases of the oxide sintered bodies in Examples 1-4 and Comparative Examples 1-5 were determined by X-ray diffraction using Rigaku Corporation's SmartLab (registered trademark) and measured under the powder X-ray diffraction measurement conditions described above.

[0093] <Flexural Strength> Using an Autograph (registered trademark) AGS-500B manufactured by Shimadzu Corporation, the flexural strength of the oxide sintered bodies of Examples 1-4 and Comparative Examples 1-5 was measured according to JIS standard: JIS-R-1601 (Test Method for Flexural Strength of Precision Ceramics). Specifically, test pieces (over 36 mm in length, 4.0 mm in width, and 3.0 mm in thickness) cut from the oxide sintered bodies were used, and the flexural strength was measured according to the three-point flexural strength measurement method of JIS-R-1601 (Test Method for Flexural Strength of Precision Ceramics).

[0094] <Pinhole area ratio> The pinhole area ratio of the oxide sintered bodies in Examples 1-4 and Comparative Examples 1-5 was measured by evaluating the crystalline phase on the surface of the oxide sintered bodies using a scanning electron microscope. Specifically, the cut surfaces of the oxide sintered bodies were progressively ground using diamond sandpaper (#180, #400, #800, #1000, and #2000), and finally polished to a mirror finish. Then, for the mirror-finished cut surfaces, BSE-COMP images of 10 fields of view with a magnification of 1000x and a range of 87.5μm × 125μm were randomly captured using a scanning electron microscope (SU3500, manufactured by Hitachi High-Tech Corporation) to obtain SEM images of 10 fields of view.

[0095] Next, using Pictbear (manufactured by Fenrir), the area occupied by pinholes with an equivalent circle diameter of 0.1 μm or larger in each SEM image was depicted and filled with color. Then, particle analysis software (manufactured by Sumitomo Metal Technology Co., Ltd.: Particle Analysis Version 3.0) was used to identify the SEM image after the pinhole filling and binarize it. At this point, the conversion value was set to use μm units to represent 1 pixel. Then, the area of ​​the pinholes and the whole were calculated separately using the particle analysis software, and the percentage of pinholes relative to the whole was obtained as the area ratio. Finally, the average of the area ratios obtained from SEM images of every 10 fields of view was taken as the pinhole area ratio in the oxide sintered body.

[0096] <Electric Arc Evaluation> Using the oxide sintered bodies of Examples 1-4 and Comparative Examples 1-5, sputtering was performed under the following sputtering conditions, and the number of arc occurrences was measured.

[0097] =Sputtering Conditions= • Equipment: DC magnetron sputtering unit, cryogenic pump for exhaust system, rotary pump • Achieved vacuum level: 3×10 -6 [Pa] Sputtering pressure: 0.4 Pa Oxygen partial pressure: 1×10 -3 [Pa] • Duration of electrical force application: 2W / cm 2 • Duration: 10 hours The number of arc occurrences was measured using an arc counter (model: μArc Moniter MAM Genesis MAM data collector Ver. 2.02 (manufactured by LANDMARK TECHNOLOGY) and evaluated as follows.

[0098] A: Very few (less than 200 times) B: Few (more than 200 times but less than 250 times) C: Slightly more (more than 250 times but less than 300 times) D: A lot (more than 300 times) like Figure 1 As shown, if the relative density of the oxide sintered body in Examples 1 to 4 is greater than 100.0%, the number of electric arcs can be suppressed.

[0099] The Zr content of the oxide sintered bodies in Examples 1-4 is less than 100 ppm by mass, thus reducing the content of Zr-containing impurities. Furthermore, if the Zr content of the oxide sintered bodies in Examples 1-3 is less than 1 ppm by mass, the number of electric arcs occurring is particularly low.

[0100] If the pinhole area ratio of the oxide sintered body in Examples 1 to 4 is less than 0.7%, the number of electric arcs can be suppressed.

[0101] If the flexural strength of the oxide sintered body in Examples 1 to 4 is 150 MPa or higher, the number of electric arcs can be suppressed.

[0102] The oxide sintered bodies of Examples 1-4 and Comparative Examples 1-5 were confirmed by X-ray diffraction measurements to be composed of two crystalline phases: the In2Ga2ZnO7 phase and the Ga2ZnO4 phase.

[0103] In addition to the configuration of each invention or embodiment, the inventions disclosed in this specification, within their applicable scope, also include: those that modify some of the above-described configurations to other configurations disclosed in this specification and specify them; those that add other configurations disclosed in this specification to the above-described configurations and specify them; or those that delete some of the above-described configurations and specify them within the limits of obtaining some of the effects, forming a higher-level conceptualization.

[0104] Industrial availability The oxide sintered body of the present invention has a high relative density and significantly reduces the content of Zr-containing impurities, making it suitable as a sputtering target. Furthermore, compared to conventional sputtering targets, the oxide sintered body of the present invention can suppress arcing, thus reducing the production of defective products. This enables sustainable management, efficient utilization, and decarbonization (carbon neutralization) of natural resources.

Claims

1. An oxide sintered body comprising In, Ga, and Zn elements, characterized in that, It contains In2Ga2ZnO7 crystalline phase and Ga2ZnO4 crystalline phase. Relative density greater than 100.0%, The Zr content is below 100 ppm by mass.

2. The oxide sintered body as described in claim 1, wherein, The pinhole area ratio is less than 0.7%.

3. The oxide sintered body as described in claim 1 or 2, wherein, The atomic ratio of In, Ga, and Zn elements satisfies the following formula: 0.15<In / (In+Ga+Zn)<0.35, 0.4<Ga / (In+Ga+Zn)<0.6, 0.15<Zn / (In+Ga+Zn)<0.

35.

4. The oxide sintered body as described in claim 1 or 2, wherein, The relative density is 100.5% or higher.

5. The oxide sintered body as described in claim 1 or 2, wherein, The relative density is 101.0% or higher.

6. The oxide sintered body as described in claim 1 or 2, wherein, The Zr content in the oxide sintered body is below 50 ppm by mass.

7. The oxide sintered body as described in claim 1 or 2, wherein, The Zr content in the oxide sintered body is less than 1 ppm by mass.

8. The oxide sintered body as described in claim 1 or 2, wherein, The flexural strength of the oxide sintered body is above 150 MPa.

9. A sputtering target, characterized in that, It comprises the oxide sintered body as described in claim 1 or 2.

10. A method for manufacturing a membrane, characterized in that, Using the sputtering target as described in claim 9, a thin film is formed on a substrate by sputtering.

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