Sintered body, sputtering target, and method for producing sintered body

Abstract

The present invention addresses the problem of providing: an IGZO sintered body which contains indium, gallium, zinc, and oxygen and has a small crystal grain size and a high density; and a method for producing the sintered body. The present invention specifically provides a sintered body which contains indium, gallium, zinc, and oxygen and has an average crystal grain size of 2 μm or less and a relative density of 97% or more.

Description

Sintered body, sputtering target, and method for producing sintered body

[0001] The present disclosure relates to a sintered body, a sputtering target, and a method for producing a sintered body.

[0002] Thin films of oxides (also called IGZO) composed of indium (In), gallium (Ga), zinc (Zn), and oxygen (O) have attracted attention as transparent conductive films and oxide semiconductors. IGZO thin films have the advantage of higher mobility than amorphous silicon (a-Si), and are gradually being used as display driver elements (TFTs) (Patent Documents 1 to 3). Since mobility tends to increase with increasing In content, active research has been conducted on regions with a high In content (high In content) (Patent Document 4). Crystallinity tends to improve with increasing Zn content (Patent Document 5).

[0003] IGZO thin films are usually formed using a sputtering target made of an IGZO sintered body. Since layered homologous crystal phases are generated in IGZO sintered bodies, which tend to cause grain growth, it has been proposed to suppress grain growth by microwave sintering (Patent Document 6). Patent Document 7 describes that particles can be reduced by forming a sintered body having two or more types of homologous crystal phases.

[0004] JP 2008-163441 A JP 2008-163442 A WO 2009 / 142289 A JP 2011-106003 A JP 2017-145510 A JP 2014-040348 A WO 2009 / 142289

[0005] When manufacturing an IGZO sintered body containing indium, gallium, zinc, and oxygen, it is necessary to suppress grain growth to prevent cracks from occurring. However, if sintering is performed at a low temperature to suppress grain growth, sintering does not proceed sufficiently, resulting in a problem that the relative density of the sintered body is not sufficiently high. In view of the above problem, an object of the present disclosure is to provide an IGZO sintered body containing indium, gallium, zinc, and oxygen, which has a small crystal grain size and high density, and a method for manufacturing the same.

[0006] In order to solve the above problems, the present inventors have conducted extensive research and have found that by devising a method for producing a sintered body containing indium, gallium, zinc, and oxygen, a sintered body having a small crystal grain size and high density can be obtained.

[0007] That is, the gist of the present disclosure is as follows. [1] A sintered body containing indium, gallium, zinc, and oxygen, having an average crystal grain size of 2 μm or less and a relative density of 97% or more. [2] The sintered body containing indium, gallium, zinc, and oxygen, as set forth in [1], having a pore ratio of 3% or less. [3] The sintered body containing indium, gallium, zinc, and oxygen, as set forth in [1], having a pore ratio of 2% or less. [4] The sintered body as set forth in any one of [1] to [3], having a flexural strength of 200 MPa or more. [5] The sintered body as set forth in any one of [1] to [4], having an in-plane coefficient of variation of volume resistivity of 10% or less. [6] The sintered body as set forth in any one of [1] to [5], having a volume resistivity of 10 mΩ cm or less. [7] The sintered body according to any one of [1] to [6], wherein the atomic ratios of the elements contained in the sintered body are In, Ga, and Zn, respectively, satisfy 0.41≦Ga / (In+Ga+Zn)≦0.90 and / or 0.21≦Zn / (In+Ga+Zn)≦0.70. [8] The sintered body according to any one of [1] to [7], wherein the atomic ratios of the elements contained in the sintered body are In, Ga, and Zn, respectively, satisfy 0.41≦In / (In+Ga+Zn)≦0.90. [9] A sputtering target comprising the sintered body according to any one of [1] to [8].

[10] A sputtering target having an area of ​​176 cm ２ The sputtering target according to [9] above.

[11] A method for producing a sintered body by hot pressing a metal member capable of forming a metal oxide having a higher standard Gibbs energy of formation at the maximum sintering temperature than the raw material powder, placed between the sintering device member and the raw material powder.

[12] A method for producing a sintered body according to

[11] , wherein the maximum sintering temperature is equal to or higher than the temperature at which the standard Gibbs energy of formation of the raw material powder and the standard Gibbs energy of formation of the sintering device member intersect in the Ellingham diagram.

[13] A method for producing a sintered body according to

[12] , wherein weight loss due to hot pressing is 5% or less.

[0008] According to the present disclosure, it is possible to provide a sintered body and a sputtering target that contain indium, gallium, zinc, and oxygen, and that have a small average crystal grain size and high density.

[0009] Photographs of the structure of a sintered body (two or more phases) and image analysis diagrams (for reference). Images of a sintered body (two or more phases) before and after binarization processing (for reference). Photographs of the structure of a sintered body (single phase) and image analysis diagrams (for reference). Images of a sintered body (single phase) before and after binarization processing (for reference).

[0010] Below, the present disclosure will be described with reference to specific embodiments, but each configuration and their combinations in each embodiment are merely examples, and additions, omissions, substitutions, and other modifications of configurations are possible as appropriate within the scope that does not deviate from the gist of the present disclosure.

[0011] The sintered body according to an embodiment of the present disclosure (sometimes referred to as the sintered body according to the present embodiment) contains indium, gallium, zinc, and oxygen. A sintered body having such a composition may be referred to as an IGZO sintered body. IGZO is an abbreviation derived from the initials of the constituent elements indium (In), gallium (Ga), zinc (Zn), and oxygen (O). IGZO thin films are used as transparent conductive films and oxide semiconductors, and are used as driving elements (TFTs) for displays and the like due to their excellent properties, such as higher mobility than amorphous Si.

[0012] An IGZO thin film can usually be formed by sputtering. A sputtering target made of an IGZO sintered body (sometimes referred to as an IGZO sputtering target) is placed in a vacuum chamber, and argon ions generated by glow discharge are collided with the sputtering target at high speed, causing the ejected atoms to be deposited on an opposing glass substrate or the like, thereby forming a thin film having approximately the same composition as the sputtering target.

[0013] The sintered body according to the embodiment of the present disclosure has an average crystal grain size of 2 μm or less. By making the crystal grains finer, it is possible to suppress particle generation during sputtering. Furthermore, the particles are more likely to be dispersed uniformly, enabling uniform film formation by sputtering. The average crystal grain size is preferably 1.5 μm or less, and more preferably 1 μm or less.

[0014] The sintered body according to this embodiment has a relative density of 97% or more. The higher the relative density of a sputtering target made of an IGZO sintered body, the more particles can be suppressed during sputtering. Since a fine crystal structure is required for an IGZO sintered body, sintering at a low temperature, which can suppress grain growth, is preferable. However, it is difficult to obtain a high-density sintered body with this low-temperature sintering. However, according to the manufacturing method disclosed below, it is possible to obtain a high-density sintered body while suppressing grain growth. The relative density is preferably 98% or more, and more preferably 99% or more.

[0015] In the sintered body according to this embodiment, the pore ratio is preferably 3% or less. If pores are present in the sputtering target, particles are generated from the pores during sputtering, so it is preferable to reduce the pores as much as possible. The pore ratio is more preferably 2% or less, and particularly preferably 1% or less.

[0016] The sintered body according to this embodiment preferably has a bending strength of 200 MPa or more. According to the present disclosure, grain growth can be suppressed, so that a decrease in bending strength can be suppressed. More preferably, it is 220 MPa or more. In particular, by increasing the strength of the sintered body, cracks during sputtering can be suppressed, and sputtering can be performed at high power.

[0017] The sintered body according to this embodiment preferably has an in-plane coefficient of variation of volume resistivity of 10% or less. The smaller the in-plane coefficient of variation of volume resistivity, the more improved the stability of discharge during sputtering. It is more preferably 5% or less. The coefficient of variation of volume resistivity is calculated using the following formula: Coefficient of variation (CV) [%] = (standard deviation) / (arithmetic mean value) × 100. The measurement locations and number of measurement points for volume resistivity are calculated by dividing the area of ​​the sintered body by S cm ２ When the perimeter length is L cm, the distance between the measurement points is (L １／２ ) / 1.5 (cm) or more, and the number of measurement points is set to the smallest number (positive number) equal to or greater than the number calculated from 3 × S / L, and the volume resistivity at each measurement point is measured, and the arithmetic mean value and standard deviation are calculated. Note that if it is not possible to take the number of measurement points specified by the above formula, the interval specified by the above formula is used, and the maximum number of measurable points is measured.

[0018] The sintered body according to this embodiment preferably has a volume resistivity of 10 mΩ cm or less. A high volume resistivity makes arcing more likely to occur, generating particles during sputtering, so it is preferable that the resistance be as low as possible. The volume resistivity is preferably 5 mΩ cm or less, and more preferably 3 mΩ cm or less.

[0019] The sintered body according to this embodiment contains indium (In), gallium (Ga), and zinc (Zn). The respective contents are not particularly limited, but if high mobility characteristics are required, it is preferable that the In content satisfy formula (1). Furthermore, if electronic stability is required, it is preferable that the Ga content satisfy formula (2). Furthermore, if structural stability is required, it is preferable that the Zn content satisfy formula (3). 0.41≦In / (In+Ga+Zn)≦0.90 (1) 0.41≦Ga / (In+Ga+Zn)≦0.90 (2) 0.21≦Zn / (In+Ga+Zn)≦0.70 (3) In these formulas, In, Ga, and Zn represent the atomic ratios of the indium, gallium, and zinc elements contained in the sintered body. Furthermore, other elements may be added or substituted as necessary.

[0020] The sintered body of this embodiment can be used as a PVD (physical vapor deposition) material, and can be used, for example, as a sputtering target, a vacuum deposition material, an ion plating material, etc. When used as a sputtering target, it can be formed into a disk-shaped plate, a rectangular plate, or a cylindrical shape, and can be bonded to a backing plate with a bonding material. When used as a sputtering target, its thickness can be 20 mm or less, preferably 3.0 to 15 mm, and more preferably 3.0 to 12 mm. The area of ​​the sputtered surface (sputtering surface) is 176 cm ２ or more, or preferably has a diameter of 150 mm or more.

[0021] A method for producing a sintered body, particularly a sputtering target, according to this embodiment will be described. However, the following production conditions are not limited to the disclosed range, and it is clear that some omissions and modifications may be made. In addition, detailed descriptions of well-known production steps and processing operations will be omitted to avoid unnecessarily obscuring the disclosed production method.

[0022] (1. Raw Material Powder) As the raw material powder, indium oxide (In ２ O ３ ) powder, gallium oxide (Ga ２ O ３ ) powder and zinc oxide (ZnO) powder are prepared. ２ O ３ The powder has a median diameter (D50): 0.5 to 3.0 μm and a specific surface area: 4.0 to 10 m ２ / g, and Ga ２ O ３ The powder has a median diameter (D50): 0.5 to 4.0 μm and a specific surface area: 6.0 to 30 m ２ / g, and the ZnO powder has a median diameter (D50): 0.1 to 2.0 μm and a specific surface area: 2.0 to 20 m ２ It is preferable to use raw material powder having a purity of 99.9% by mass or more. The raw material powder may be calcined.

[0023] (2. Mixing and pulverization step) The raw material powders are weighed to have the desired composition ratio (content ratio of the sintered body), and mixed and pulverized. There are various pulverization methods depending on the desired particle size and the material to be pulverized, and wet or dry ball mills, vibration mills, bead mills, etc. can be used. To obtain uniform and fine crystal particles, a bead mill mixing method is preferred, which has high efficiency in breaking down agglomerates in a short time and also provides a good dispersion state of additives. The median diameter (D ５０ ): 0.1 to 1.0 μm, specific surface area: 10.0 to 30.0 m ２ / g.

[0024] (3. Sintering Process) Next, the mixed and pulverized raw material powder is sintered. Conventionally, sintering has been performed in air or an oxygen gas atmosphere at approximately 1400 to 1600°C. However, as the sintering temperature increases, grain growth occurs, resulting in a decrease in flexural strength. In addition, the volume resistivity increases, which can lead to abnormal discharges and particle generation during sputtering, making stable sputtering difficult. Stabilizing sputtering is particularly important when using larger targets and attempting to form a uniform film.

[0025] In the manufacturing method of the present disclosure, pressure sintering is preferred from the viewpoint of increasing the relative density at a relatively low temperature. Regarding the atmosphere during sintering, sintering is preferably performed under an inert gas atmosphere rather than a vacuum from the viewpoint of suppressing the sublimation of ZnO. Furthermore, when sintering is performed under an inert gas atmosphere without pressure (atmospheric pressure), In ２ O ３ and Ga ２ O ３ Therefore, pressure sintering is preferred from the viewpoint of being able to suppress reduction to some extent, and hot press sintering is particularly preferred from the viewpoint of productivity.

[0026] (3-1. Metallic Member) When hot press sintering is performed, the raw material powder may react with the carbon of the sintering device member and be reduced. However, the manufacturing method of the present disclosure prevents reduction by the sintering device member by placing a metallic member between the sintering device member and the raw material powder, making high-temperature hot press sintering possible. This method is not particularly limited by the type or composition of the raw material powder, and is applicable as long as it is reduced by the sintering device member. On the other hand, depending on the type of metallic member, the metallic member itself may reduce the raw material powder, so it is necessary to use a metallic material that can form a metal oxide with a higher standard Gibbs energy of formation at the highest sintering temperature than the raw material powder. For example, if the raw material powder is In ２ O ３ and Ga ２ O ３ In this case, metal members such as Mo, Ni, Co, etc. can be used.

[0027] As described above, the manufacturing method according to this embodiment is to prevent a reduction reaction during sintering by placing a metal member between the sintering device member and the target raw material. This prevents the target raw material (In) from being reduced by the sintering device member (carbon). ２ O ３ , Ga ２ O ３ , ZnO raw material powder), especially In ２ O ３ It is possible to prevent the reduction of In. ２ O ３ When the weight loss ([weight of raw material powder before sintering] - [weight of sintered body]) / [mixed powder before sintering] x 100), which is an index of reduction, exceeds 5% (in this case, In ２ O ３ Therefore, the weight loss due to hot pressing should be 5% or less, and more preferably 3% or less.

[0028] (3-2. Maximum sintering temperature) The maximum sintering temperature can be set to a temperature or higher where the standard Gibbs energy of formation of the raw material powder and the standard Gibbs energy of formation of the sintering device components intersect in the Ellingham diagram. On the other hand, the maximum sintering temperature is set to a temperature or lower than the melting point of the raw material powder. ２ O３ and Ga ２ O ３ In this case, the sintering temperature is preferably 1160° C. to 1300° C. If the maximum sintering temperature is less than 1160° C., pores may remain in the sintered body, whereas if the maximum sintering temperature is too high, grain growth occurs, leading to a decrease in the strength of the sintered body.

[0029] (3-3. Pressing pressure) The pressing pressure in the pressure sintering is 150 kgf / cm ２ It is preferable that the pressing pressure is 150 kgf / cm or more. ２ If the pressure is less than this, the density of the sintered body may decrease. Although there is no particular upper limit, it is recommended to use a pressure of 400 kgf / cm2 or less in consideration of the strength of the members used in the hot press. ２ It is preferable to have the following:

[0030] (3-4. Sintering Holding Time) The holding time at the maximum sintering temperature is preferably within 3 hours. A shorter holding time is preferable because it increases productivity, but if the holding time is too short, it becomes difficult to obtain a high-density sintered body. As described above, the manufacturing method of the present disclosure enables sintering at a relatively high temperature, and therefore the holding time can be shortened accordingly, making it possible to significantly improve productivity.

[0031] (4. Finishing) The sintered body obtained through the above sintering process can be processed into a desired shape using a processing machine such as a surface grinder, a cylindrical grinder, or a machining device, as needed. There are no particular restrictions on the shape of the sputtering target, and it can be a flat disk, a rectangle, a cylinder, or the like. Furthermore, the sputtering target can be bonded to a backing plate as needed.

[0032] The following description will be given based on examples and comparative examples. Note that these examples are merely examples and are not intended to limit the scope of the present invention. That is, the present invention is limited only by the scope of the claims, and includes various modifications other than the examples included in this disclosure.

[0033] The evaluation methods used in the examples and comparative examples are as follows: (Composition analysis) The composition of the sintered body was analyzed using the following device: Device: SPS3500DD manufactured by SII Corporation Method: ICP-OES (inductively coupled plasma optical emission spectroscopy)

[0034] (Regarding relative density) The relative density was calculated using the following formula: Relative density (%) = Archimedes density / Calculated density × 100 Archimedes density: The top and bottom surfaces of the sintered body were ground to a thickness of 1 mm, and the outer peripheral surface was ground to a thickness of 5 mm to prepare a measurement sample, and the Archimedes density was calculated using the Archimedes method. Calculated density: The sintered body was subjected to a component analysis, and the oxide mass ratio (mass%) was calculated by converting the atomic ratio (at%) of In, Ga, and Zn to the total of 100 at% of the constituent elements In, Ga, and Zn. ２ O ３ , Ga ２ O ３ The calculated density was calculated using the theoretical density of ZnO. ３ )=(W1+W2+W3) / (W1 / d1+W2 / d2+W3 / d3) W1:In ２ O ３ Mass ratio (mass%) of W2:Ga ２ O ３ Mass ratio (mass%) of W3: Mass ratio of ZnO (mass%) Theoretical density: d1: 7.18 g / cm ３ (In ２ O ３ theoretical density) d2: 5.95 g / cm ３ (Ga ２ O ３ Theoretical density) d3: 5.61 g / cm ３ (Theoretical density of ZnO)

[0035] (Regarding the average crystal grain size) A sample for observation was cut out from the sintered body, and the surface of the cut out sample (the surface corresponding to the sputtered surface) was mirror-polished. A secondary electron image of the mirror-polished sample surface was taken using a scanning electron microscope (SEM) at a magnification of 5000x in five fields of view. Next, three lines (hereinafter referred to as lines 1, 2, and 3) were drawn on the photographed image so that the number of crystal grains crossed by each line was 10 or more. The length of each line and the number of intersections with the grain boundaries were determined. The grain boundaries at the start and end points of the lines were not included. Based on the measured length of the lines and the number of intersections, the crystal grain size in one field of view was calculated using the following formula: Crystal grain size in one field of view = (length of line 1 / number of intersections between line 1 and grain boundaries + length of line 2 / number of intersections between line 2 and grain boundaries + length of line 3 / number of intersections between line 3 and grain boundaries) ÷ 3. The grain size was calculated using the above formula for five fields of view, and the arithmetic average of the five fields of view was used as the average crystal grain size of the sintered body. However, when the number of particles intersected by each straight line in the field of view was less than 10, magnifications of 2000x and 1000x were used. The equipment used and measurement conditions were as follows: Equipment used: JXA-8500F (JEOL) Acceleration voltage: 15.0 kV Beam current: 2.0 x 10 －８ A

[0036] (Regarding pore ratio) A sample for observation (20 mm x 20 mm, thickness: 7 mm) was cut out from the center of the sintered body, and the surface of the cut out sample (the surface corresponding to the sputtered surface) was mirror-polished. A backscattered electron image of the mirror-polished sample surface was taken with a scanning electron microscope (SEM) at a magnification of 2000 times (100 μm x 100 μm). At this time, the total number of pixels in the image was set to 750,000 or more. The equipment used and measurement conditions were as follows. Equipment used: JXA-8500 (JEOL) Acceleration voltage: 15.0 kV Beam current: 2.0 x 10 ―８ A Total number of pixels: 1,209,600 pixels (horizontal: 1,280, vertical: 945)

[0037] The captured images were analyzed using ImageJ (image processing software). A reference diagram for ImageJ analysis is shown in Figure 1 (left: SEM micrograph, right: ImageJ image analysis diagram). As shown in Figure 1, analysis using ImageJ makes it possible to count the frequency (vertical axis) of the brightness (horizontal axis) of the captured image: n (range = 0 to 255).

[0038] For structures with two or more crystalline phases, the brightest crystalline phase (In ２ O ３ The brightness (n1) at which the frequency of the portion corresponding to the darkest crystalline phase (In phase) is highest is 200≦n1≦220. ２ O ３ Three images were randomly selected so that the brightness (n2) at which the frequency of the portion corresponding to the "phase with a low ratio of the phase" was at its maximum was 115≦n2≦135. Since accurate measurement was not possible with images that contained blown-out highlights, images with a frequency of less than 1000 when the brightness n was 250 to 255 were selected.

[0039] Next, the three selected images were converted to 8-bit display using ImageJ, and then binarized using the threshold function. The minimum threshold value was set to 0, and the maximum threshold value was set to a range of 10 to 100, so that only pores were displayed in black. Figure 2 shows reference images before (left) and after (right) binarization. Note that for IGZO sintered bodies, a maximum threshold value can be set so that the interior of the crystal grains is not displayed in black, and only the pores at the grain boundaries are displayed in black.

[0040] The number of black parts counted from the obtained binarized image (A ｐｏｒｅ ) and the count of the white part (A ｂｕｌｋ The pore ratio was calculated using the following formula, and the arithmetic mean value of the three images was used. (Pore ratio) = A ｐｏｒｅ / (A ｐｏｒｅ +A ｂｕｌｋ ) x 100 [%]

[0041] For single-phase structures, as shown in Figure 3, the brightness (n ｍａｘ ) is 140≦n ｍａｘ ≦160 and frequency is nｍａｘ The darkest brightness (n ｈａｌｆ ) is n ｍａｘ −10≦n ｈａｌｆ ≦n ｍａｘ Three images with a value of -5 were selected. Since accurate measurement is not possible with images that have blown-out highlights, images with a value of An<1000 when the brightness n is between 250 and 255 were selected.

[0042] The three selected images are binarized using ImageJ in the same way as in the case where two or more crystalline phases are present, as shown in Figure 4. From the obtained binarized images, the count number of black areas (A ｐｏｒｅ ) and the count of the white part (A ｂｕｌｋ The pore ratio was calculated using the following formula, and the arithmetic mean value of the three images was used. (Pore ratio) = A ｐｏｒｅ / (A ｐｏｒｅ +A ｂｕｌｋ ) x 100 [%]

[0043] (Volume Resistivity) The surface of a sintered body with a diameter of 160 mm was polished, and the volume resistivity was measured at 12 random points on the polished surface spaced at least 4.7 cm apart, and the arithmetic mean value and standard deviation of the 12 points were calculated. The following equipment was used for the measurement. Equipment: Resistivity Meter Σ-5+ manufactured by NPS Co., Ltd. Method: Constant current application method Method: DC 4-probe method Measurement temperature: Room temperature (20 to 25°C)

[0044] (Regarding flexural strength) A sample was cut out from the sintered body, and the surface of the cut sample (the surface corresponding to the sputtered surface) was polished. The flexural strength of the polished surface was measured in accordance with JIS R 1601: 2008. Test method: Three-point bending test Support distance: 30 mm Sample size: 3 × 4 × 40 mm Head speed: 0.5 mm / min The number of test pieces was 10, and the average value was calculated.

[0045] (Example 1) In ２ O ３ Powder, Ga ２ O ３ Powder and ZnO powder were prepared, weighed and mixed to obtain the desired composition shown in Table 1, and then the median diameter D５０ :0.64μm, specific surface area: 11.7m ２ The powder was then pulverized to a density of 1 / g. Next, the pulverized raw material powder was filled into a carbon die. At this time, in order to prevent the raw material powder from coming into contact with the carbon die and being reduced during sintering, a metal member was placed at the location where the raw material powder came into contact with the carbon die. Then, the powder was sintered in an argon atmosphere at a maximum sintering temperature of 1250°C and a press pressure of 250 kgf / cm. ２ A sintered body was produced by hot press sintering with a holding time of 1 hour. The physical properties of the sintered body obtained in Example 1 were measured, and the results were good: an average crystal grain size of 1.60 μm, a relative density of 100.2%, a volume resistivity of 0.70 mΩ cm, a coefficient of variation of volume resistivity of 4.3%, a pore fraction of 1.20%, a weight loss of 1.3%, and a flexural strength of 291 MPa.

[0046]

[0047] (Examples 2 to 8) In ２ O ３ Powder, Ga ２ O ３ Powder and ZnO powder were prepared, weighed, and mixed to obtain the desired composition shown in Table 1, and then pulverized under the same conditions as in Example 1. Next, the pulverized raw material powder was filled into a carbon die, a metal member was placed at the location where the raw material powder contacted the carbon die, and hot press sintering was carried out under the same conditions as in Example 1 to produce a sintered body. In Examples 2 and 3, unlike Example 1, the maximum sintering temperature was 1200°C, but the other conditions were the same. Measurement of the physical properties of the sintered bodies obtained in Examples 2 to 8 showed good results, with an average crystal grain size of 2 μm or less and a relative density of 97% or more.

[0048] (Comparative Example 1) In ２ O ３ Powder, Ga ２ O ３ Powder and ZnO powder were prepared, weighed and mixed to obtain the desired composition shown in Table 1, and then pulverized under the same conditions as in Example 1. Next, the pulverized raw material powder was filled into a die, and then pressed under a pressure of 785 kfg / cm. ２, holding time: 1 minute, uniaxial molding, then press pressure: 1795 kgf / cm ２ A green body was produced by CIP molding with a holding time of 1 minute. The green body was then subjected to atmospheric sintering in an oxygen atmosphere at a maximum sintering temperature of 1400°C and a holding time of 20 hours to produce a sintered body. Measurement of the physical properties of the sintered body produced in Comparative Example 1 revealed that the average crystal grain size was 8.3 μm, which was not the desired result.

[0049] (Comparative Example 2) In ２ O ３ Powder, Ga ２ O ３ Powder and ZnO powder were prepared, weighed, and mixed to obtain the desired composition shown in Table 1, and then pulverized under the same conditions as in Example 1. Next, a compact was produced from the pulverized raw material powder under the same conditions as in Comparative Example 1, and this compact was subjected to microwave sintering in air at a maximum sintering temperature of 1400°C and a holding time of 30 minutes to produce a sintered body. Cracks occurred in the sintered body obtained in Comparative Example 2. This is thought to be due to the high temperature applied to part of the sintered body during sintering, resulting in large temperature variations within the sintered body. Measurement of the physical properties of the sintered body obtained in Comparative Example 2 revealed a relative density of 87.7%, which was not the desired result.

[0050] For the sintered body obtained in Comparative Example 2, the coefficient of variation of volume resistivity and flexural strength could not be measured because a sample of sufficient size could not be obtained. The volume resistivity varied widely, reaching 11.00 mΩ·cm at the low end, but exceeding the upper limit of measurement at the high end. The average crystal grain size was 3.55 μm, but the grain size also varied widely, ranging from 2.49 μm at the low end to 5.12 μm at the high end. The pore ratio also varied widely, ranging from 1.28% at the low end to 17.88% at the high end. Because microwave sintering has a short sintering time, it is believed that this resulted in large temperature variations within the sintered body, resulting in nonuniform volume resistivity, density, and grain size.

[0051] (Comparative Examples 3 and 4) In ２ O ３ Powder, Ga ２ O ３Powder and ZnO powder were prepared, weighed, and mixed to obtain the desired composition shown in Table 1, and then pulverized under the same conditions as in Example 1. Next, the pulverized raw material powder was filled into a carbon die, and hot-press sintering was performed under the same conditions as in Example 1 to produce a sintered body. However, in Comparative Examples 3 and 4, unlike Example 1, no metal member was provided to prevent reduction of the raw material powder, and the maximum sintering temperature was 1150°C in Comparative Example 3 and 1070°C in Comparative Example 4, but the other conditions were the same. Measurement of the physical properties of the sintered bodies obtained in Comparative Examples 3 and 4 revealed that both had low relative densities, and the desired results were not obtained.

[0052] According to the present disclosure, it is expected that particles generated during sputtering can be suppressed, potentially improving product yield. Improving product yield leads to a stable supply of products and reduced loss of metal raw materials, which are limited resources. Therefore, the present disclosure may contribute to Goal 9 of the United Nations-led Sustainable Development Goals (SDGs), "Build resilient infrastructure, promote inclusive and sustainable industrialization, and foster technological innovation," and Goal 12, "Ensure sustainable consumption and production patterns." The sintered body and sputtering target according to the present disclosure are useful for forming IZO thin films as transparent conductive films and oxide semiconductor films.

[0053] According to the present disclosure, it is possible to provide a sintered body and a sputtering target that contain indium, gallium, zinc, and oxygen, and that have a small average crystal grain size and high density. The sintered body and the sputtering target according to the present disclosure are useful for forming an IGZO thin film as a transparent conductive film or an oxide semiconductor film.

Claims

1. A sintered body containing indium, gallium, zinc, and oxygen, having an average crystal grain size of 2 μm or less and a relative density of 97% or more.

2. The sintered body according to claim 1, which contains indium, gallium, zinc, and oxygen and has a pore ratio of 3% or less.

3. The sintered body according to claim 1, which contains indium, gallium, zinc, and oxygen and has a pore ratio of 2% or less.

4. The sintered body according to claim 1, which has a bending strength of 200 MPa or more.

5. The sintered body according to claim 1, wherein the in-plane coefficient of variation of volume resistivity is 10% or less.

6. The sintered body according to claim 5, which has a volume resistivity of 10 mΩ·cm or less.

7. The sintered body according to claim 1, wherein the atomic ratios of the elements contained in the sintered body are In, Ga, and Zn, respectively, satisfy 0.41≦Ga / (In+Ga+Zn)≦0.90 and / or 0.21≦Zn / (In+Ga+Zn)≦0.

70.

8. The sintered body according to claim 1, wherein the atomic ratio of each element contained in the sintered body is In, Ga, and Zn satisfies 0.41≦In / (In+Ga+Zn)≦0.

90.

9. A sputtering target comprising the sintered body according to any one of claims 1 to 8.

10. The area of ​​the sputtering surface is 176 cm ２ The sputtering target according to claim 9 .

11. A method for producing a sintered body by hot pressing a metal member capable of forming a metal oxide having a higher standard Gibbs energy of formation at the highest sintering temperature than the raw material powder, which is placed between the sintering equipment member and the raw material powder.

12. A method for producing a sintered body according to claim 11, wherein the maximum sintering temperature is equal to or higher than the temperature at which the standard Gibbs energy of formation of the raw material powder intersects with the standard Gibbs energy of formation of the sintering equipment components in the Ellingham diagram.

13. The manufacturing method according to claim 11 or 12, wherein the weight loss due to hot pressing is 5% or less.

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