Sintered oxide

Abstract

The oxide sintered body according to the present invention contains In, Ga, and Zn and contains an In2Ga2ZnO7 crystal phase and a Ga2ZnO4 crystal phase, the oxide sintered body having a relative density of more than 100.0% and a Zr content of 100 ppm by mass or less.

Description

[Technical Field]

[0001] The present invention relates to an oxide sintered body containing an In-Ga-Zn based composite oxide. [Background technology]

[0002] In the technical field of thin film transistors (hereinafter referred to as "TFTs") used in display devices such as flat panel displays (hereinafter referred to as "FPDs"), as FPDs become more highly functional, oxide semiconductors, such as In-Ga-Zn composite oxides (hereinafter referred to as "IGZO") as shown in Patent Documents 1 and 2, are increasingly being put to practical use in place of conventional amorphous silicon.

[0003] In recent years, oxide semiconductors have become popular due to their high mobility (>10 cm 2 It has the excellent feature of being able to achieve both high voltage (V / Vs) and extremely low off-leakage current (<10-22A / μm), and is expected to be used as a channel material for vertical FETs that can be integrated with Si-CMOS LSIs and highly integrated using BEOL compatible processes in the semiconductor manufacturing process. Along with these expectations, the required properties for sputtering targets for depositing oxide semiconductor films are also increasing. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-105124 [Patent Document 2] Japanese Patent Application Laid-Open No. 2011-195406 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the oxide sintered bodies disclosed in Patent Documents 1 and 2 were produced by first producing Ga2ZnO4 powder by mixing Ga2O3 powder and ZnO powder and calcining the mixture, then pulverizing the Ga2ZnO4 powder and mixing it with In2O3 powder, which resulted in problems such as insufficient sintering of the oxide sintered body and a lack of density.Furthermore, because Ga2ZnO4 powder is very hard, when it is mixed with In2O3 powder, the ZrO2 used as the pulverizing media for pulverizing the Ga2ZnO4 powder is scraped off, resulting in the sintered body containing a large amount of impurities, including Zr.

[0006] In view of the above problems, the present invention provides an oxide sintered body having a high relative density and a significantly reduced content of impurities including Zr. [Means for solving the problem]

[0007] The oxide sintered body of the present invention, which has been made to solve the above problems, is an oxide sintered body containing In, Ga, and Zn elements, and is characterized by including an InGaZnO crystalline phase and a GaZnO crystalline phase, having a relative density of more than 100.0%, and having a Zr content of 100 mass ppm or less. The oxide sintered body of the present invention is an oxide sintered body containing In, Ga, and Zn elements, and includes an In2Ga2ZnO7 crystalline phase and a Ga2ZnO4 crystalline phase. The oxide sintered body has a relative density of more than 100.0% and a Zr content of 100 mass ppm or less, thereby achieving a high relative density and a significantly reduced content of impurities including Zr.

[0008] The oxide sintered body of the present invention is an oxide sintered body containing In element, Ga element, and Zn element.

[0009] Furthermore, the oxide sintered body of the present invention and a sputtering target material made using the same have an In2Ga2ZnO7 crystalline phase and a Ga2ZnO4 crystalline phase. The oxide sintered body of the present invention has a mottled mixture of the In2Ga2ZnO7 crystalline phase and the Ga2ZnO4 crystalline phase. Figure 2 is an SEM image of the surface of the oxide sintered body of the present invention observed using a scanning electron microscope. The black region (A in Figure 2) indicates the Ga2ZnO4 crystalline phase, and the whitish region (B in Figure 2) indicates the In2Ga2ZnO7 crystalline phase.

[0010] The SEM image shown in Fig. 2 can be taken as follows. The cut surface obtained by cutting the oxide sintered body of the present invention is polished in stages using emery paper #180, #400, #800, #1000, and #2000, and finally buffed to a mirror finish. The mirror-finished cut surface is then thermally etched at 1100°C for 1 hour and observed using a scanning electron microscope (SU3500, manufactured by Hitachi High-Technologies Corporation), and an SEM image showing the grain boundaries of the cut surface is taken.

[0011] The In2Ga2ZnO7 phase and the Ga2ZnO4 phase contained in the oxide sintered body of the present invention and in the sputtering target material made using the oxide sintered body can be confirmed by identifying peaks obtained by powder X-ray diffraction. Specifically, the X-ray diffraction measurement is carried out according to the following powder X-ray diffraction measurement conditions.

[0012] = Powder X-ray diffraction measurement conditions = ·Radiation source: CuKα radiation Tube voltage: 40kV ·Tube current: 30mA Scan speed: 5deg / min Step: 0.02deg Scan range: 2θ=20°~80° X-ray analysis software: PDXL2 Version 2.1.3.6

[0013] If the X-ray diffraction pattern matches the X-ray diffraction pattern of ICDD (International Centre for Diffraction Data) card No. 38-1097, which corresponds to the crystal structure of the In2Ga2ZnO7 phase, it can be confirmed that the oxide sintered compact of the present invention contains the In2Ga2ZnO7 phase.If the X-ray diffraction pattern matches the X-ray diffraction pattern of ICDD card No. 38-1240, which corresponds to the crystal structure of the Ga2ZnO4 phase, it can be confirmed that the oxide sintered compact of the present invention contains the Ga2ZnO4 phase.

[0014] Furthermore, it is preferable that the oxide sintered body of the present invention and the sputtering target material made using the same have a relative density of more than 100.0% in order to reduce the number of arcing events during sputtering. This is because an improved relative density reduces the volume resistivity of the oxide sintered body and the sputtering target material made using the same, thereby suppressing charge concentration during sputtering. Furthermore, the formation of high-potential areas due to charge concentration and low-potential areas due to charge non-concentration during sputtering is suppressed, making it difficult for discharge from high-potential areas to low-potential areas to occur, thereby reducing the number of arcing events. The relative density of the oxide sintered body of the present invention is more preferably 100.5% or more, even more preferably 101.0% or more, particularly preferably 101.5% or more, even more particularly preferably 102.0% or more, even particularly preferably 102.5% or more, and even particularly preferably 103.0% or more. The upper limit of the relative density is not particularly limited, but is, for example, 105.0% or less.

[0015] Here, the relative density of the oxide sintered body of the present invention and the sputtering target material made using the same is measured based on Archimedes' method. Specifically, the mass of the target material in air is divided by the volume (mass of the target material in water / specific gravity of water at the measurement temperature) to obtain the theoretical density ρ (g / cm) based on the following formula (X): 3 The percentage of the density (unit: %) is the relative density.

[0016]

number

[0017] (C1~C in the formula i indicates the content (mass%) of the constituent substances of the target material, and ρ1 to ρ i is C1~C i The density of each constituent material (g / cm 3 ) indicates.

[0018] The oxide sintered body of the present invention and the constituent materials of the sputtering target material using the same are considered to be In2O3, Ga2O3, and ZnO, and for example, C1: mass% of In2O3 in oxide sintered body or target material ρ1: Density of In2O3 (7.18 g / cm 3 ) C2: mass% of Ga2O3 in the oxide sintered body or target material ρ2: density of Ga2O3 (5.95 g / cm 3 ) C3: mass% of ZnO in oxide sintered body or target material ρ3: Density of ZnO (5.60 g / cm 3 ) By applying this to equation (X), the theoretical density ρ can be calculated.

[0019] The above-mentioned mass % of In2O3, mass % of Ga2O3, and mass % of ZnO can be determined from the results of analysis of each element of the oxide sintered body or sputtering target material by ICP-OES analysis.

[0020] 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, and this is preferable. Furthermore, the Zr content in the oxide sintered body of the present invention is more preferably 50 ppm by mass or less, even more preferably 30 ppm by mass or less, particularly preferably 20 ppm by mass or less, more particularly preferably 10 ppm by mass or less, even more particularly preferably 5 ppm by mass or less, also particularly preferably 2 ppm by mass or less, even more particularly preferably 1 ppm by mass or less, and even more particularly preferably less than 1 ppm by mass.

[0021] Here, the Zr content in the oxide sintered body of the present invention can be measured by adding nitric acid, perchloric acid, or hydrogen peroxide to the sintered body as needed, decomposing it by heating to form a solution, and then using an ICP optical emission spectrometer (Agilent Technologies: 720 ICP-OES) to measure the Zr concentration.

[0022] The oxide sintered body of the present invention is characterized in that the pinhole area ratio is 0.7% or less. The oxide sintered body of the present invention is preferably a sputtering target material having a pinhole area ratio of 0.7% or less, in terms of forming a high-quality thin film. Furthermore, the oxide sintered body of the present invention is more preferably a pinhole area ratio of 0.6% or less, even more preferably 0.5% or less, particularly preferably 0.4% or less, and even more particularly preferably 0.3% or less. The lower limit of the pinhole area ratio is not particularly limited, but is, for example, 0.01% or more.

[0023] Here, the pinhole area ratio can be measured as follows: The pinhole area ratio is measured by evaluating the crystalline phase of the surface of the oxide sintered body of the present invention using a scanning electron microscope (SEM).

[0024] Specifically, the cut surface obtained by cutting the oxide sintered body of the present invention is polished in stages using emery paper #180, #400, #800, #1000, and #2000, and finally buffed to a mirror finish. Then, using a scanning electron microscope (SU3500, manufactured by Hitachi High-Technologies Corporation), BSE-COMP images of the mirror-finished cut surface are randomly taken in 10 fields of view within an area of 87.5 μm × 125 μm at 1000x magnification, to obtain SEM images of 10 fields of view.

[0025] Next, the area of each SEM image occupied by pinholes with a circle-equivalent diameter of 0.1 μm or more is drawn and color-filled using Pictbear (Fenrir). Furthermore, using particle analysis software (Sumitomo Metal Technology Co., Ltd.: Particle Analysis Version 3.0), the SEM image with the pinholes filled in is recognized and binarized. At this time, the conversion value is set so that one pixel is displayed in μm units.

[0026] Then, the pinhole and total areas are calculated using particle analysis software, and the percentage of pinholes relative to the total is determined as the area ratio. The average value of the area ratios obtained for each of the 10 fields of view of the SEM images is taken as the pinhole area ratio in the oxide sintered body of the present invention.

[0027] Furthermore, 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 in terms of high bending strength. The average particle size of the In2Ga2ZnO7 phase is more preferably 5.5 μm or less, even more preferably 5.0 μm or less, particularly preferably 4.5 μm or less, even more particularly preferably 4.0 μm or less, and even more particularly preferably 3.5 μm or less. On the other hand, the average particle size of the In2Ga2ZnO7 phase is preferably 1.0 μm or more, more preferably 2.0 μm or more, and particularly preferably 3.0 μm or more.

[0028] The average particle size of the In2Ga2ZnO7 phase contained in the oxide sintered body of the present invention, that is, the diameter of an equivalent circle with respect to area, can be calculated by image processing of an SEM image taken using a scanning electron microscope.

[0029] Specifically, the cut surface obtained by cutting the oxide sintered body of the present invention is polished in stages using emery paper #180, #400, #800, #1000, and #2000, and finally buffed to a mirror finish. Next, the mirror-finished cut surface is thermally etched at 1100°C for 1 hour and observed using a scanning electron microscope (SU3500, manufactured by Hitachi High-Technologies Corporation). BSE-COMP images are randomly taken at 1000x magnification within a range of 87.5 μm × 125 μm to obtain SEM images for 10 fields of view.

[0030] The obtained SEM images were plotted along the grain boundaries of the In2Ga2ZnO7 phase using the image processing software ImageJ. After all plotting was completed, particle analysis was performed to obtain the area of each particle. The area-equivalent circle diameter was then calculated from the area of each particle. This was then performed on 10 SEM images, and the average value of the calculated equivalent circle diameters of all particles was taken as the equivalent circle diameter of the In2Ga2ZnO7 phase.

[0031] Furthermore, 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 in terms of reducing abnormal discharge, more preferably 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.

[0032] The average particle size of the Ga2ZnO4 phase contained in the oxide sintered body of the present invention, i.e., the area-equivalent circle diameter, can be calculated by image processing of an SEM image taken using a scanning electron microscope, similar to the average particle size of the In2Ga2ZnO7 phase.

[0033] Specifically, the obtained SEM image was drawn along the grain boundaries of the Ga2ZnO4 phase using the image processing software ImageJ. After all the drawings were completed, particle analysis was performed to obtain the area of each particle. Then, the equivalent circle diameter of the area was calculated from the area of each obtained particle. And this was carried out for the SEM images of 10 fields of view, and the average value of the equivalent circle diameters of all the calculated particles was taken as the equivalent circle diameter of the Ga2ZnO4 phase.

[0034] Further, the oxide sintered body of the present invention is characterized in that the atomic ratios of the In element, Ga element, and Zn element satisfy 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 The oxide sintered body of the present invention is preferable because the atomic ratios of the In element, Ga element, and Zn element satisfy all of the above three formulas, so that the In2Ga2ZnO7 phase and the Ga2ZnO4 phase are contained in an optimal ratio in the oxide sintered body of the present invention.

[0035] It is more preferable that In / (In + Ga + Zn) is 0.17 < In / (In + Ga + Zn) < 0.33, and further preferably 0.2 < In / (In + Ga + Zn) < 0.3.

[0036] Also, it is more preferable that Ga / (In + Ga + Zn) is 0.42 < Ga / (In + Ga + Zn) < 0.58, and further preferably 0.45 < Ga / (In + Ga + Zn) < 0.55.

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

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

[0039] The oxide sintered body of the present invention is characterized in that it has a bending strength of 150 MPa or more. The oxide sintered body of the present invention exhibits such high bending strength, which is preferable because when it is used as a sputtering target material for sputtering, even if an unintended abnormal discharge occurs during sputtering, the target material is less likely to break or crack. The oxide sintered body of the present invention preferably has a bending strength of 160 MPa or more, more preferably 165 MPa or more, and particularly preferably 170 MPa or more. The upper limit of the bending strength is not particularly limited, but is, for example, 250 MPa or less. A specific method for measuring bending strength will be described later.

[0040] The sputtering target material of the present invention is characterized by including the oxide sintered body of the present invention described above. The sputtering target material of the present invention contains the oxide sintered body of the present invention described above, and therefore the occurrence of arcing can be significantly reduced, thereby further suppressing the generation of particles and enabling the deposition of a high-quality oxide semiconductor film with a high yield. In addition, the inclusion of impurities including Zr in the oxide semiconductor film can be significantly reduced.

[0041] As an example of the method for producing the oxide sintered body of the present invention, a filtration molding method will be described below.

[0042] First, the raw materials In2O3 powder, Ga2O3 powder, and ZnO powder are weighed and placed in a pot. They are then pulverized and mixed, and organic additives and a dispersion medium are added to obtain a mixture slurry. Examples of organic additives include known binders and dispersants. The dispersion medium is not particularly limited, and can be selected from water, alcohol, and the like depending on the application.

[0043] Here, the method of pulverizing and mixing may be dry pulverization or wet pulverization.

[0044] Specifically, in the dry grinding, In2O3 powder, Ga2O3 powder, and ZnO powder, along with Ga2ZnO4 balls (hereinafter referred to as GZO media) as grinding media, are placed in a pot, and the pot is mixed in a ball mill to dry grind the In2O3 powder, Ga2O3 powder, and ZnO powder.

[0045] The mixture containing the dry-milled In2O3 powder, Ga2O3 powder, and ZnO powder in the pot is separated from the GZO media using a filter, and the mixture containing the dry-milled In2O3 powder, Ga2O3 powder, and ZnO powder is obtained.

[0046] Then, the dry-milled In2O3 powder, Ga2O3 powder, and ZnO powder, along with an organic additive (e.g., a dispersant), and a dispersion medium (e.g., water) are placed in yet another pot, and GZO media is added as a grinding medium. The pot is then mixed to form a slurry. Alternatively, instead of removing the mixture containing the dry-milled In2O3 powder, Ga2O3 powder, and ZnO powder from the pot, an organic additive (e.g., a dispersant) and a dispersion medium (e.g., water) can be added to the pot containing the dry-milled mixture and mixed to form a slurry.

[0047] On the other hand, in wet milling, In2O3 powder, Ga2O3 powder, ZnO powder, organic additives (e.g., dispersant), and dispersion medium (e.g., water) are placed in a pot, GZO media is further added as milling media, and the pot is mixed using a ball mill to wet mill the In2O3 powder, Ga2O3 powder, and ZnO powder.

[0048] The mixture slurry containing the wet-milled In2O3 powder, Ga2O3 powder, and ZnO powder in the pot is filtered using a filter to separate it from the GZO media, and the mixture slurry is obtained.

[0049] The mixture slurry thus obtained is poured into a mold, and the dispersion medium is removed to obtain a molded body. Examples of the mold include a metal mold, a gypsum mold, and a resin mold.

[0050] The resulting molded body is fired to obtain a fired body. When the molded body is fired, an In2Ga2ZnO7 phase and a Ga2ZnO4 phase are formed. When the firing temperature of the molded body is higher than 1400°C and lower than 1530°C, a high-density, high-strength oxide sintered body can be obtained. The resulting fired body is then cut into any desired shape to obtain the oxide sintered body of the present invention.

[0051] As another example of the method for producing an oxide sintered body of the present invention, a CIP molding method will be described below.

[0052] First, the process of pulverizing and mixing the raw materials In2O3 powder, Ga2O3 powder, and ZnO powder to obtain a mixture slurry is the same as the process of the filtration molding method described above, so a description thereof will be omitted.

[0053] The resulting mixture slurry is spray-dried as described above to obtain a dry powder, which is then filled into a mold and compacted under pressure to obtain a molded body.

[0054] Next, the obtained compact is fired to obtain a fired body. When the compact is fired, In2Ga2ZnO7 phase and Ga2ZnO4 phase are formed. When the firing temperature of the compact is more than 1400°C and less than 1530°C, an oxide sintered body with high density and high strength can be obtained. Then, the obtained fired body is cut into any shape to obtain the oxide sintered body of the present invention.

[0055] The above-described method for producing an oxide sintered body of the present invention does not include a step of grinding, mixing, and calcining Ga2O3 powder and ZnO powder to form a calcined body made of crystalline Ga2ZnO4. Therefore, the calcined powder does not contain crystalline Ga2ZnO4, which has extremely hard properties, and even if grinding media made of ZrO2 are used, the content of impurities including Zr in the obtained oxide sintered body of the present invention can be significantly reduced. Furthermore, by using grinding media made of Ga2ZnO4 instead of grinding media made of ZrO2, the content of impurities including Zr in the obtained oxide sintered body of the present invention can be further reduced.

[0056] The sputtering target material of the present invention can be obtained by bonding the oxide sintered body of the present invention obtained by the above-mentioned method for producing an oxide sintered body of the present invention to a substrate. The substrate can be made of Cu, Al, Ti, or stainless steel. As the bonding material, a bonding material used for bonding conventional ITO target materials, such as In metal, can be used. The bonding method is also the same as the bonding method for conventional ITO target materials.

[0057] The method for producing a film of the present invention is characterized in that a thin film is formed on a substrate by sputtering using the sputtering target material of the present invention. By performing sputtering using the sputtering target material of the present invention to form a thin film on a substrate, it is possible to form a high quality thin film with a high yield.

[0058] Specifically, by performing sputtering using the sputtering target material of the present invention, a high-quality thin film, such as an oxide semiconductor film, can be formed on a substrate, such as a glass substrate, a resin substrate, or a silicon substrate.

[0059] In this specification, when "X to Y" (X and Y are any numbers) is expressed, unless otherwise specified, it means "X or more and Y or less," and also includes the meaning "preferably larger than X" or "preferably smaller than Y." Furthermore, when "X or more" (X is any number) or "Y or less" (Y is any number), it also includes the meaning "preferably larger than X" or "preferably smaller than Y." [Effects of the Invention]

[0060] The oxide sintered body of the present invention has a high relative density and the content of impurities including Zr is significantly reduced. [Brief explanation of the drawings]

[0061] [Figure 1] 1 is a table listing the physical property values and measurement results of oxide sintered bodies according to Examples 1 to 4 of the present invention and Comparative Examples 1 to 5. [Figure 2] 1 is an SEM image of the surface of an oxide sintered body according to the present invention, observed using a scanning electron microscope. BEST MODE FOR CARRYING OUT THE INVENTION

[0062] The oxide sintered body according to the embodiment of the present invention will be further described below with reference to the following examples. However, the present invention is not limited to the following examples.

[0063] Example 1 In2O3 powder (median diameter D50 of 0.6μm), Ga2O3 powder (median diameter D50 of 1.5μm), and ZnO powder (median diameter D50 of 0.8μm) were weighed out so that the atomic ratio of In, Ga, and Zn was In:Ga:Zn=1:2:1, placed in a pot, and ground and mixed in a ball mill using grinding media (GZO media) for 24 hours to obtain a mixed raw material powder. Note that after grinding and mixing, the mixed raw material powder was not calcined.

[0064] The median diameter D50 of each powder was measured using a particle size distribution analyzer MT3300EXII manufactured by Microtrackbell Co., Ltd. Water was used as the solvent for the measurement sample, and the refractive index of the measurement substance was set to 2.20.

[0065] Next, 0.2% by mass of acrylic emulsion binder relative to the mixed raw material powder was added to the pot 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 dispersant, and then the mixture was mixed in a ball mill using grinding media (GZO media) for 24 hours to obtain a mixed slurry.

[0066] The mixture slurry thus obtained was poured into an aluminum mold, the dispersion medium was drained, and a molded body was obtained.

[0067] Next, the obtained compact was fired in an air atmosphere at a firing temperature of 1410°C for 10 hours at a temperature increase rate of 300°C / h and a temperature decrease rate of 50°C / h to obtain a fired body. The fired body was then cut to a width of 210 mm, a length of 710 mm, and a thickness of 6 mm to obtain an oxide sintered body according to Example 1. A #170 grinding wheel was used for the cutting.

[0068] Example 2 In Example 2, the same manufacturing method as in Example 1 was carried out except that the firing temperature was changed to 1450° C., and an oxide sintered body according to Example 2 was obtained.

[0069] Example 3 In Example 3, the same manufacturing method as in Example 1 was carried out except that the firing temperature was changed to 1500° C., and an oxide sintered body according to Example 3 was obtained.

[0070] Example 4 In Example 4, the same manufacturing method as in Example 1 was carried out except that the grinding media was changed to ZrO2 and the firing temperature was changed to 1450°C, and an oxide sintered body according to Example 4 was obtained.

[0071] (Comparative Example 1) In Comparative Example 1, the same manufacturing method as in Example 1 was carried out except that the firing temperature was changed to 1400° C., and an oxide sintered body according to Comparative Example 1 was obtained.

[0072] (Comparative Example 2) In Comparative Example 2, the same manufacturing method as in Example 1 was carried out except that the firing temperature was changed to 1530°C, and an oxide sintered body according to Comparative Example 2 was obtained.

[0073] (Comparative Example 3) Ga2O3 powder (median diameter D50: 1.5 μm) and ZnO powder (median diameter D50: 0.8 μm) were weighed to a Ga2O3:ZnO = 1:1 (Ga:Zn = 2:1 atomic ratio) and milled and mixed in a ball mill using water as a dispersion medium and ZrO2 balls for 6 hours to obtain a Ga2O3-ZnO mixed powder slurry. The resulting Ga2O3-ZnO mixed powder slurry was then dried using a spray dryer to obtain Ga2O3-ZnO granulated powder. The resulting Ga2O3-ZnO granulated powder was then placed in an alumina crucible and calcined in air at a calcination temperature of 900 °C for 5 hours to obtain a calcined powder containing crystalline Ga2ZnO4.

[0074] The obtained calcined powder (containing crystalline Ga2ZnO4) and In2O3 powder (median diameter D50 0.6 μm) were weighed so that Ga2ZnO4:In2O3 = 2:1 (atomic ratio of In, Ga, and Zn = In:Ga:Zn = 1:2:1), and were mixed and ground in a ball mill using water as a dispersion medium and grinding media (ZrO2 balls) for 6 hours to obtain a Ga2ZnO4-In2O3 mixed powder slurry. Next, the obtained Ga2ZnO4-In2O3 mixed powder slurry was dried using a spray dryer to obtain a Ga2ZnO4-In2O3 granulated powder.

[0075] The Ga2ZnO4-In2O3 granulated powder obtained in this way was placed under a surface pressure of 0.5 tf / cm 2 and press molding under the conditions of 1.5tf / cm 2 A green body was obtained by CIP molding under the conditions.

[0076] Next, the obtained compact was fired in an air atmosphere at a firing temperature of 1450°C for 10 hours at a heating rate of 300°C / h and a cooling rate of 50°C / h to obtain a fired body. The fired body was then cut to a width of 210 mm, a length of 710 mm, and a thickness of 6 mm to obtain an oxide sintered body according to Comparative Example 3. A #170 grindstone was used for the cutting. The In2O3 powder, Ga2O3 powder, and ZnO powder used in Comparative Example 3 were the same as those used in Example 1.

[0077] Comparative Example 4 In Comparative Example 4, the same manufacturing method as in Comparative Example 3 was carried out except that the firing temperature was changed to 1500° C., and an oxide sintered body according to Comparative Example 4 was obtained.

[0078] (Comparative Example 5) 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 out so that the mixing ratio of each powder was such that the atomic ratio of In, Ga, and Zn was In:Ga:Zn = 1:2:1, and placed in a pot. Using grinding media (ZrO2 balls), the powder was dry-mixed in a ball mill for 24 hours to grind and mix the powders, thereby obtaining a mixed raw material powder.

[0079] The obtained mixed raw material powder was placed in an alumina crucible and calcined in an air atmosphere at a calcination temperature of 900°C for 5 hours to obtain a calcined powder containing crystalline Ga2ZnO4.

[0080] Next, 0.2% by mass of acrylic emulsion binder relative to the calcined powder was added to the pot as a binder, 0.6% by mass of ammonium polycarboxylate relative to the calcined powder as a dispersant, and 20% by mass of water relative to the calcined powder as a dispersant.The mixture was then mixed in a ball mill using grinding media (ZrO2 balls) for 24 hours to obtain a mixture slurry.

[0081] The mixture slurry thus obtained was poured into an aluminum mold, the dispersion medium was drained, and a molded body was obtained.

[0082] Next, the obtained compact was fired in an air atmosphere at a firing temperature of 1430°C for 10 hours at a temperature increase rate of 300°C / h and a temperature decrease rate of 50°C / h to obtain a fired body. The fired body was then cut to a width of 210 mm, a length of 710 mm, and a thickness of 6 mm to obtain an oxide sintered body according to Comparative Example 5. A #170 grinding wheel was used for the cutting.

[0083] The following physical properties were measured for the oxide sintered bodies obtained in Examples 1 to 4 and Comparative Examples 1 to 5. The measured physical property values and the methods for measuring the physical property values are shown below, and the measurement results are shown in FIG.

[0084] <Elemental analysis> Nitric acid, perchloric acid, and hydrogen peroxide were added to the sample as needed, and the sample was decomposed by heating to form a solution. The concentrations of each element (In, Ga, Zn, and Zr) were measured using an ICP optical emission spectrometer (Agilent Technologies: 720 ICP-OES).

[0085] <Relative density> The relative densities of the oxide sintered bodies according to Examples 1 to 4 and Comparative Examples 1 to 5 were measured based on the Archimedes method. Specifically, the mass of the target material in air was divided by the volume (mass of the target material in water / specific gravity of water at the measurement temperature) to obtain the theoretical density ρ (g / cm) based on the above formula (X). 3 The percentage of the density (unit: %) was taken as the relative density.

[0086] <Crystal grain size measurement> The crystal grain sizes, i.e., the area-equivalent circle diameters, of the In2Ga2ZnO7 and Ga2ZnO4 phases were measured from SEM images of the surfaces of the oxide sintered bodies according to Examples 1 to 4 and Comparative Examples 1 to 5 taken using a scanning electron microscope. Specifically, the cut surfaces obtained by cutting the oxide sintered bodies according to Examples 1 to 4 and Comparative Examples 1 to 5 were polished stepwise using emery paper #180, #400, #800, #1000, and #2000, and finally buffed to a mirror finish. Next, the mirror-finished cut surfaces were thermally etched at 1100°C for 1 hour and observed using a scanning electron microscope (SU3500, manufactured by Hitachi High-Technologies Corporation). BSE-COMP images were randomly taken at 1000x magnification within an area of 87.5 μm × 125 μm to obtain SEM images for the 10 fields of view.

[0087] Furthermore, the obtained SEM images were plotted along the grain boundaries of the In2Ga2ZnO7 phase using image processing software ImageJ. After all plotting was completed, particle analysis was performed to obtain the area of each particle. The equivalent circle diameter was then calculated from the obtained area of each particle. This was then performed on 10 SEM images, and the average value of the calculated equivalent circle diameters of all particles was taken as the equivalent circle diameter of the In2Ga2ZnO7 phase. Next, the obtained SEM images were plotted along the grain boundaries of the Ga2ZnO4 phase using image processing software ImageJ. Particle analysis was similarly performed on the obtained SEM images, and the equivalent circle diameter was calculated from the area of each particle. This was then performed on 10 SEM images, and the average value of the calculated equivalent circle diameters of all particles was taken as the equivalent circle diameter of the Ga2ZnO4 phase.

[0088] Identifying crystalline phases using X-ray diffraction The crystalline phases of the oxide sintered bodies according to Examples 1 to 4 and Comparative Examples 1 to 5 were identified by X-ray diffraction using SmartLab (registered trademark) manufactured by Rigaku Corporation under the above-mentioned powder X-ray diffraction measurement conditions.

[0089] <Diverse bending strength> The flexural strength of the oxide sintered bodies according to Examples 1 to 4 and Comparative Examples 1 to 5 was measured in accordance with JIS standard JIS-R-1601 (Testing method for bending strength of fine ceramics) using an Autograph (registered trademark) AGS-500B manufactured by Shimadzu Corporation. Specifically, the flexural strength was measured according to the three-point bending strength measurement method of JIS-R-1601 (Testing method for bending strength of fine ceramics) using test pieces (total length 36 mm or more, width 4.0 mm, thickness 3.0 mm) cut out from the oxide sintered bodies.

[0090] <Pinhole area ratio> The pinhole area ratios of the oxide sintered bodies according to Examples 1 to 4 and Comparative Examples 1 to 5 were measured by evaluating the crystalline phase of the surface of the oxide sintered body using a scanning electron microscope. Specifically, the cut surface obtained by cutting the oxide sintered body was polished stepwise using emery paper #180, #400, #800, #1000, and #2000, and finally buffed to a mirror finish. Then, BSE-COMP images of the mirror-finished cut surface were taken at random in 10 fields of view within an area of 87.5 μm × 125 μm at 1000x magnification using a scanning electron microscope (SU3500, manufactured by Hitachi High-Technologies Corporation), to obtain SEM images of the 10 fields of view.

[0091] Next, the area occupied by pinholes with a circle-equivalent diameter of 0.1 μm or more in each SEM image was drawn and color-filled using Pictbear (Fenrir). Furthermore, particle analysis software (Sumitomo Metal Technology Co., Ltd.: Particle Analysis Version 3.0) was used to recognize and binarize the SEM images with the pinholes filled in. The conversion value was set so that one pixel was displayed in μm units. The particle analysis software then calculated the pinhole and total areas, and the percentage of pinholes relative to the total was calculated as the area ratio. The average area ratio obtained for each of the 10 SEM images was then used to determine the pinhole area ratio for the oxide sintered body.

[0092] Arcing evaluation Using the oxide sintered bodies according to Examples 1 to 4 and Comparative Examples 1 to 5, sputtering was carried out under the following sputtering conditions, and the number of times arcing occurred was measured.

[0093] =Sputtering conditions= Equipment: DC magnetron sputtering equipment, exhaust system cryopump, rotary pump ·Achieved vacuum level: 3×10 -6 [Pa] Sputtering pressure: 0.4 [Pa] Oxygen partial pressure: 1×10 -3 [Pa] ·Power input time: 2W / cm 2 Duration: 10 hours

[0094] The number of arcing occurrences was measured using an arcing counter (model: μArc Monitor MAM Genesis MAM Data Collector Ver. 2.02 (manufactured by LANDMARK TECHNOLOGY)) and evaluated as follows: A: Very few (less than 200 times) B: Low (more than 200 times but less than 250 times) C: Somewhat frequent (over 250 times but less than 300 times) D: Very many (over 300 times)

[0095] As shown in FIG. 1, the oxide sintered bodies according to Examples 1 to 4 were able to reduce the number of arcing occurrences when the relative density exceeded 100.0%.

[0096] The oxide sintered bodies according to Examples 1 to 4 had a Zr content of 100 mass ppm or less, which enabled the reduction of impurities containing Zr. Furthermore, the oxide sintered bodies according to Examples 1 to 3 had a Zr content of less than 1 mass ppm, and the occurrence of arcing was particularly low.

[0097] In the oxide sintered bodies according to Examples 1 to 4, when the pinhole area ratio was 0.7% or less, the number of occurrences of arcing could be reduced.

[0098] When the oxide sintered bodies according to Examples 1 to 4 had a bending strength of 150 MPa or more, the number of occurrences of arcing could be reduced.

[0099] The oxide sintered bodies according to Examples 1 to 4 and Comparative Examples 1 to 5 were confirmed to be composed of two crystalline phases, In2Ga2ZnO7 and Ga2ZnO4, from the results of X-ray diffraction measurements.

[0100] The inventions disclosed in this specification include, in addition to the configurations of each invention and embodiment, those specified by changing these partial configurations to other configurations disclosed in this specification, to the extent applicable, or those specified by adding other configurations disclosed in this specification to these configurations, or those specified as higher-level concepts specified by deleting these partial configurations to the extent that partial effects can be obtained. [Industrial Applicability]

[0101] The oxide sintered body according to the present invention has a high relative density and a significantly reduced content of impurities, including Zr, making it suitable as a sputtering target material. Furthermore, the oxide sintered body according to the present invention can suppress arcing compared to conventional sputtering targets, thereby reducing the occurrence of defective products. This leads to the sustainable management and efficient use of natural resources, and the achievement of decarbonization (carbon neutrality).

Claims

1. An oxide sintered body containing In, Ga, and Zn elements, the atomic ratio of the In element, the Ga element, and the Zn element 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 The peaks obtained by powder X-ray diffraction were identified and confirmed. ２ Ga ２ ZnO ７ The crystalline phase and Ga ２ ZnO ４ and a crystalline phase, The relative density, which is a percentage value of the theoretical density ρ (g / cm 3 ) based on the following formula (X), is more than 100.0%, An oxide sintered body having a Zr content of less than 1 ppm by mass. (In the formula, C 1 to C i respectively represent the content (mass %) of the constituent substances of the target material, and ρ 1 to ρ i respectively represent the density (g / cm 3 ) of the constituent substances corresponding to C 1 to C i .)

2. 2. The oxide sintered body according to claim 1, wherein the pinhole area ratio is 0.7% or less.

3. 3. The oxide sintered body according to claim 1, wherein the relative density is 100.5% or more.

4. 3. The oxide sintered body according to claim 1, wherein the relative density is 101.0% or more.

5. 3. The oxide sintered body according to claim 1, wherein the oxide sintered body has a bending strength of 150 MPa or more.

6. A sputtering target material comprising the oxide sintered body according to claim 1 or 2.

7. A method for producing a film, comprising sputtering the sputtering target material according to claim 6 to form a thin film on a substrate.

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