Oxide sintered body

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

Sintered oxide

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

[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 been developed with 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 (<10-22 A / 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 a BEOL compatible process in the semiconductor manufacturing process. Along with these expectations, the required properties of sputtering targets for depositing oxide semiconductor films are also increasing.

[0004] JP 2014-105124 A JP 2011-195406 A

[0005] However, the oxide sintered bodies disclosed in Patent Documents 1 and 2 do not contain Ga. ２ O ３ Ga powder and ZnO powder are mixed and calcined to obtain Ga ２ ZnO ４ After the powder is produced, the Ga ２ ZnO ４ The powder was crushed and ２ O ３ When the oxide sintered body is manufactured by mixing it with Ga powder, the sintering does not proceed sufficiently, and the density does not increase. ２ ZnO ４ The powder is very hard, so ２ O ３ When mixed with the powder, Ga ２ ZnO ４ ZrO, which is a grinding medium for grinding powder ２There was also the problem that the surface was scraped off and that a large amount of impurities including Zr was contained.

[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.

[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, ２ Ga ２ ZnO ７ The crystalline phase and Ga ２ ZnO ４ The oxide sintered body of the present invention is an oxide sintered body containing In, Ga, and Zn elements, and is characterized by comprising a crystalline phase, a relative density of more than 100.0%, and a Zr content of 100 mass ppm or less. ２ Ga ２ ZnO ７ The crystalline phase and Ga ２ ZnO ４ The crystalline phase has a relative density of more than 100.0% and a Zr content of 100 mass ppm or less, so that the relative density is high and the content of impurities including Zr can be significantly reduced.

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

[0009] The oxide sintered body of the present invention and the sputtering target material made using the same are also ２ Ga ２ ZnO ７ The crystalline phase and Ga ２ ZnO ４ The oxide sintered body of the present invention has an In crystal phase. ２ Ga ２ ZnO ７ The crystalline phase and Ga ２ ZnO ４ 2 is an SEM image of the surface of the oxide sintered body of the present invention observed using a scanning electron microscope, and the black area (A in FIG. 2) is Ga. ２ ZnO ４The whitish area (B in Figure 2) shows the crystalline phase. ２ Ga ２ ZnO ７ Shows 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 oxide sintered body of the present invention and the In contained in the sputtering target material made using the same are also ２ Ga ２ ZnO ７ phase and Ga ２ ZnO ４ The phase can be confirmed by identifying the peaks obtained by powder X-ray diffraction. Specifically, 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: 40 kV; Tube current: 30 mA; Scan speed: 5 deg / min; Step: 0.02 deg; Scan range: 2θ = 20 degrees to 80 degrees; X-ray analysis software: PDXL2 Version 2.1.3.6

[0013] As a result of X-ray diffraction measurement, In ２ Ga ２ ZnO ７ If the X-ray diffraction pattern matches the X-ray diffraction pattern of ICDD (International Centre for Diffraction Data) card No. 38-1097 corresponding to the crystal structure of the phase, the oxide sintered body of the present invention is determined to contain In. ２ Ga ２ ZnO ７ It can be confirmed that the Ga phase is included. ２ ZnO ４If the X-ray diffraction pattern matches the X-ray diffraction pattern of ICDD card No. 38-1240 corresponding to the crystal structure of the Ga phase, the oxide sintered body of the present invention is ２ ZnO ４ It can be confirmed that the phase is included.

[0014] Furthermore, it is preferable that the relative density of the oxide sintered body of the present invention and the sputtering target material made using the same exceeds 100.0% in order to reduce the number of arcing occurrences during sputtering. This is because an improvement in the 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 occurrences. 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]

[0017] (C in the formula １ ~C ｉ indicates the content (mass%) of the constituent substances in the target material, and ρ １ ~ρ ｉ is C １ ~C ｉThe density (g / cm) of each constituent material corresponding to ３ ) indicates.

[0018] The oxide sintered body of the present invention and the sputtering target material made using the same are composed of In. ２ O ３ , Ga ２ O ３ , ZnO, for example, as follows: C １ : In of oxide sintered body or target material ２ O ３ Mass% of ρ １ :In ２ O ３ Density (7.18 g / cm ３ ) C ２ : Ga of oxide sintered body or target material ２ O ３ Mass% of ρ ２ : Ga ２ O ３ Density (5.95 g / cm ３ ) C ３ ρ: mass% of ZnO in the oxide sintered body or target material ３ : Density of ZnO (5.60 g / cm ３ ) can be applied to equation (X) to calculate the theoretical density ρ.

[0019] In addition, the above-mentioned In ２ O ３ %, by mass of Ga ２ O ３ The mass % of ZnO and the mass % of ZnO can be determined from the analysis results 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, still 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 the sintered body by heating to form a solution, and then using an ICP optical emission spectrometer (manufactured by Agilent Technologies: 720 ICP-OES).

[0022] The oxide sintered body of the present invention is also characterized in that it has a pinhole area ratio of 0.7% or less. When the oxide sintered body of the present invention has a pinhole area ratio of 0.7% or less, it is preferable that it be used as a sputtering target material in terms of forming a high-quality thin film. Furthermore, the oxide sintered body of the present invention more preferably has 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, BSE-COMP images of the mirror-finished cut surface are taken at random in 10 fields of view at a magnification of 1000 times and within an area of ​​87.5 μm × 125 μm using a scanning electron microscope (SU3500, manufactured by Hitachi High-Technologies Corporation), to obtain SEM images of 10 fields of view.

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

[0026] Thereafter, the areas of the pinholes and the entire surface area are calculated using particle analysis software, and the percentage of the pinholes relative to the entire surface area 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 defined as the pinhole area ratio in the oxide sintered body of the present invention.

[0027] In addition, the In contained in the oxide sintered body of the present invention ２ Ga ２ ZnO ７ The average grain size of the In phase is preferably 6.0 μm or less in terms of increasing the bending strength. ２ Ga ２ ZnO ７ The average particle size of the In 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. ２ Ga ２ ZnO ７ The average particle size of the phase is preferably 1.0 μm or more, more preferably 2.0 μm or more, and particularly preferably 3.0 μm or more.

[0028] In contained in the oxide sintered body of the present invention２ Ga ２ ZnO ７ The average grain size of the phase, that is, the diameter of an equivalent circle per 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 of 10 fields of view within a range of 87.5 μm × 125 μm at 1000x magnification are randomly taken, and SEM images of 10 fields of view are obtained.

[0030] The obtained SEM images were analyzed using the image processing software ImageJ. ２ Ga ２ ZnO ７ Plotting was performed along the grain boundaries of the phase, and 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 obtained. This was performed on SEM images of 10 fields of view, and the average value of the calculated area-equivalent circle diameter of all particles was calculated as In ２ Ga ２ ZnO ７ The area of ​​the phase is the equivalent circle diameter.

[0031] In addition, Ga contained in the oxide sintered body of the present invention ２ ZnO ４ The average grain size of the Ga phase is preferably 1.0 μm or more and 4.5 μm or less in terms of reducing abnormal discharge. ２ ZnO ４ The average particle size is 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] Ga contained in the oxide sintered body of the present invention ２ ZnO ４ The average grain size of the phase, i.e., the diameter of the circle equivalent to the area of ​​the In ２ Ga ２ ZnO ７As with the average grain size of the phase, it can be calculated by image processing of an SEM image taken using a scanning electron microscope.

[0033] Specifically, the obtained SEM image was processed using image processing software ImageJ. ２ ZnO ４ After all the drawings were 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 performed on 10 SEM images, and the average value of the calculated area-equivalent circle diameters of all the particles was used as the Ga ２ ZnO ４ The area of ​​the phase is the equivalent circle diameter.

[0034] 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 formulae: 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 has the In element, Ga element, and Zn element atomic ratios satisfying all of the above three formulae, thereby providing the oxide sintered body of the present invention with a low content of In. ２ Ga ２ ZnO ７ phase and Ga ２ ZnO ４ This is preferable because the phases are contained in an optimum ratio.

[0035] It is more preferable that In / (In+Ga+Zn) be in the range of 0.17<In / (In+Ga+Zn)<0.33, and it is even more preferable that 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 ratios of In, Ga, and Zn in the oxide sintered body of the present invention can be measured by measuring the concentrations of In, Ga, and Zn 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 also characterized by having 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. Since the sputtering target material of the present invention includes the oxide sintered body of the present invention described above, the number of arcing occurrences can be significantly reduced, thereby further suppressing particle generation and enabling high-quality oxide semiconductor films to be formed with a high yield. Furthermore, the incorporation of impurities containing Zr into 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 material In ２ O ３ Powder, Ga ２ O ３The powder and ZnO powder are weighed, placed in a pot, pulverized and mixed, and an organic additive and a dispersion medium are added to obtain a mixture slurry. Examples of the organic additive include known binders and dispersants. The dispersion medium is not particularly limited, and may be selected from water, alcohol, etc. depending on the application.

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

[0044] Specifically, the dry grinding is carried out by adding In ２ O ３ Powder, Ga ２ O ３ powder, and ZnO powder, and Ga as a grinding medium. ２ ZnO ４ The pot was mixed with ball mill to produce In ２ O ３ Powder, Ga ２ O ３ The powder and ZnO powder are dry-milled.

[0045] The dry-ground In in the pot ２ O ３ Powder, Ga ２ O ３ The mixture containing the powder and ZnO powder was separated from the GZO media using a filter, and the dry-milled In ２ O ３ Powder, Ga ２ O ３ A mixture containing the powder and ZnO powder is obtained.

[0046] Then, in a separate pot, dry-ground In ２ O ３ Powder, Ga ２ O ３ The powder, ZnO powder, organic additives (e.g., dispersants), and dispersion media (e.g., water) are added to the pot, and GZO media are added as grinding media. The pot is then mixed to form a slurry. ２ O ３ Powder, Ga ２O ３ Alternatively, the powder and the mixture containing the ZnO powder may be left in the pot, and an organic additive (e.g., a dispersant) and a dispersion medium (e.g., water) may be added to the pot containing the dry-milled mixture, and the mixture may be mixed to form a slurry.

[0047] On the other hand, wet grinding is carried out by adding In ２ O ３ Powder, Ga ２ O ３ In powder, ZnO powder, organic additives (e.g., dispersants), and dispersion media (e.g., water) are added, and GZO media are added as grinding media. The pot is mixed in a ball mill to produce In ２ O ３ Powder, Ga ２ O ３ The powder and ZnO powder are wet-milled.

[0048] The wet-ground In in the pot ２ O ３ Powder, Ga ２ O ３ The mixed slurry containing the powder and ZnO powder is filtered using a filter to separate it from the GZO media, thereby obtaining the mixed slurry.

[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 compact is fired to obtain a fired body. ２ Ga ２ ZnO ７ phase and Ga ２ ZnO ４ When the sintering temperature of the compact is more than 1400°C and less than 1530°C, an oxide sintered body having high density and high strength can be obtained. The obtained sintered body is then cut into a 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 raw material In ２ O ３ Powder, Ga ２ O ３ The process of pulverizing and mixing the powder and ZnO powder to obtain a mixture slurry is the same as the above-mentioned filtration-type molding method, and therefore 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. ２ Ga ２ ZnO ７ phase and Ga ２ ZnO ４ When the sintering temperature of the compact is more than 1400°C and less than 1530°C, an oxide sintered body having high density and high strength can be obtained. The obtained sintered body is then cut into a desired shape to obtain the oxide sintered body of the present invention.

[0055] The method for producing an oxide sintered body of the present invention described above is ２ O ３ The powder and ZnO powder were pulverized, mixed, and calcined to form a crystalline Ga ２ ZnO ４ Since the step of forming a calcined body consisting of ２ ZnO ４ is not present, and ZrO ２ Even if a grinding medium made of ZrO is used, the content of impurities including Zr in the obtained oxide sintered body of the present invention can be significantly reduced. ２ Instead of grinding media consisting of Ga ２ ZnO ４By using a grinding medium made of the above, 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 film manufacturing method 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 forming a thin film on a substrate by sputtering using the sputtering target material of the present invention, a high-quality thin film can be formed 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 means "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 means "preferably larger than X" or "preferably smaller than Y".

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

[0061] 1 is a list of 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. 2 is an SEM image of the surface of an oxide sintered body according to the present invention, observed using a scanning electron microscope.

[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) In ２ O ３ Powder (median diameter D50 is 0.6 μm), Ga ２ O ３ In powder (median diameter D50 1.5 μm) and ZnO powder (median diameter D50 0.8 μm) were weighed 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 (GZO media), they were dry mixed in a ball mill 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 an 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 dispersion medium, and 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 obtained 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 grinding media was ZrO ２ The oxide sintered body according to Example 4 was obtained by carrying out the same manufacturing method as in Example 1, except that the firing temperature was changed to 1450°C.

[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) Ga ２ O ３ powder (median diameter D50 is 1.5 μm) and ZnO powder (median diameter D50 is 0.8 μm) were mixed with Ga ２ O ３ The Ga and Zn were weighed so that the atomic ratio of Ga to Zn was 1:1 (Ga:Zn=2:1), and the mixture was dispersed in water using grinding media (ZrO ２ The mixture was milled and mixed for 6 hours using a ball mill. ２ O ３ A Ga—ZnO mixed powder slurry was obtained. ２ O３ The Ga-ZnO mixed powder slurry was dried using a spray dryer. ２ O ３ Ga-ZnO granulated powder was obtained. ２ O ３ The ZnO granulated 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 crystalline Ga. ２ ZnO ４ A calcined powder containing

[0074] The calcined powder obtained (crystalline Ga ２ ZnO ４ ) and In ２ O ３ powder (median diameter D50 is 0.6 μm) and Ga ２ ZnO ４ :In ２ O ３ The atomic ratio of In, Ga, and Zn was 1:2:1 (In:Ga:Zn=1:2:1), and the mixture was dispersed in water as a dispersion medium and crushed with ZrO ２ The mixture was milled and mixed for 6 hours using a ball mill. ２ ZnO ４ -In ２ O ３ A mixed powder slurry was obtained. ２ ZnO ４ -In ２ O ３ The mixed powder slurry was dried using a spray dryer to obtain Ga ２ ZnO ４ -In ２ O ３ A granulated powder was obtained.

[0075] The Ga thus obtained ２ ZnO ４ -In ２ O ３ The granulated powder was pressed at a pressure of 0.5 tf / cm ２ and a surface pressure of 1.5 tf / cm ２ A compact was obtained by CIP molding under the conditions of

[0076] Next, the obtained compact was fired in an air atmosphere at a firing temperature of 1450°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 3. A #170 grindstone was used for the cutting. The In used in Comparative Example 3 ２ O ３ Powder, Ga ２ O ３ The powder and ZnO powder 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) In ２ O ３ Powder (median diameter D50 is 0.6 μm), Ga ２ O ３ The powder (median diameter D50 is 1.5 μm) and ZnO powder (median diameter D50 is 0.8 μm) were weighed 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 were placed in a pot. ２ The mixture was dry mixed in a ball mill using a ball mill (using a ball mill) for 24 hours to be pulverized and mixed, 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 crystalline Ga. ２ ZnO ４ A calcined powder containing

[0080] Next, 0.2% by mass of acrylic emulsion binder based on the calcined powder was added to the pot as a binder, 0.6% by mass of ammonium polycarboxylate based on the calcined powder as a dispersant, and 20% by mass of water based on the calcined powder as a dispersion medium. ２ The mixture was mixed in a ball mill using a ball mill (ball mill) for 24 hours to obtain a mixed 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 obtained 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 stone 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 measurement methods for the physical property values ​​are shown below, and the measurement results are shown in FIG.

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

[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] <Crystalline Grain Size Measurement> 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, the grain size of In ２ Ga ２ ZnO ７ phase, and Ga ２ ZnO ４The crystal grain size of the phase, i.e., the diameter of an equivalent circle in area, was measured. 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 in stages using emery paper #180, #400, #800, #1000, and #2000, and finally buffed 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-Technologies Corporation). BSE-COMP images were taken at 1000x magnification in a range of 87.5 μm × 125 μm in 10 random fields of view, and SEM images of the 10 fields of view were obtained.

[0087] Furthermore, the obtained SEM images were analyzed using the image processing software ImageJ. ２ Ga ２ ZnO ７ Drawing was performed along the grain boundaries of the phase, and after all the drawings 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 was performed for 10 SEM images, and the average value of the calculated area-equivalent circle diameter of all particles was calculated as In ２ Ga ２ ZnO ７ The area of ​​the Ga phase was calculated as the equivalent circle diameter. ２ ZnO ４ The grain boundaries of the Ga phase were plotted, and the area-equivalent circle diameter was calculated from the area of ​​each particle obtained by performing particle analysis in the same manner. This was then performed on SEM images of 10 fields of view, and the average value of the calculated area-equivalent circle diameters of all particles was calculated as the Ga ２ ZnO ４ The area of ​​the phase was taken as the equivalent circle diameter.

[0088] <Identification of Crystalline Phase by X-ray Diffraction> Identification of the crystalline phase by X-ray diffraction of the oxide sintered bodies according to Examples 1 to 4 and Comparative Examples 1 to 5 was performed using SmartLab (registered trademark) from Rigaku Corporation under the above-mentioned powder X-ray diffraction measurement conditions.

[0089] <Flexural 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, using test pieces (total length 36 mm or more, width 4.0 mm, thickness 3.0 mm) cut out from the oxide sintered bodies, the measurement was carried out in accordance with the three-point bending strength measurement method of JIS-R-1601 (Testing Method for Bending Strength of Fine Ceramics).

[0090] <Pinhole Area Ratio> The pinhole area ratio of the oxide sintered bodies according to Examples 1 to 4 and Comparative Examples 1 to 5 was 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 in stages 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 a range of 87.5 μm × 125 μm at 1000x magnification using a scanning electron microscope (SU3500, manufactured by Hitachi High-Technologies Corporation), and SEM images of the 10 fields of view were obtained.

[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 (manufactured by Fenrir Corporation). Furthermore, using particle analysis software (manufactured by Sumitomo Metal Technology Co., Ltd.: Particle Analysis Version 3.0), the SEM image with the filled-in pinholes was recognized and binarized. At this time, the conversion value was set so that one pixel was displayed in μm units. Then, the pinhole and total areas were calculated using the particle analysis software, and the percentage of pinholes relative to the total was determined as the area ratio. Then, the average value of the area ratios obtained for each of the 10 SEM images was taken as the pinhole area ratio in 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. Ultimate vacuum: 3 x 10 －６ [Pa] Sputtering pressure: 0.4 [Pa] Oxygen partial pressure: 1×10 －３ [Pa] ・Input power amount 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 (200 times or less) B: Few (more than 200 times and less than 250 times) C: Somewhat many (more than 250 times and less than 300 times) D: Very many (more than 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, and therefore it was possible to reduce the amount of impurities containing Zr. Furthermore, when the Zr content of the oxide sintered bodies according to Examples 1 to 3 was less than 1 mass ppm, the number of arcing occurrences 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] In the oxide sintered bodies according to Examples 1 to 4, when the bending strength was 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 found to contain a crystalline phase In ２ Ga ２ ZnO ７ phase, and Ga ２ ZnO ４ It was confirmed that the crystal consisted of two crystalline phases.

[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.

[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 the occurrence of 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, ２ G ２ ZnO ７ The crystalline phase and Ga ２ ZnO ４ A sintered oxide body comprising a crystalline phase, a relative density of more than 100.0%, and a Zr content of 100 ppm by mass or less.

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

3. The oxide sintered body according to claim 1 or 2, characterized in that the atomic ratios of the In element, the Ga element, and the Zn element satisfy the following formulas: 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 according to claim 1 or 2, characterized in that the relative density is 100.5% or more.

5. The oxide sintered body according to claim 1 or 2, characterized in that the relative density is 101.0% or more.

6. The oxide sintered body according to claim 1 or 2, characterized in that the Zr content in the oxide sintered body is 50 ppm by mass or less.

7. The oxide sintered body according to claim 1 or 2, characterized in that the Zr content in the oxide sintered body is less than 1 ppm by mass.

8. The oxide sintered body according to claim 1 or 2, characterized in that the oxide sintered body has a flexural strength of 150 MPa or more.

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

10. A method for producing a film, comprising the steps of: forming a thin film on a substrate by sputtering using the sputtering target material according to claim 9.

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