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

Abstract

The present disclosure addresses the problem of providing: a sintered body containing indium, gallium, zinc, and oxygen, the sintered body having an IGZO homologous crystal phase as a main phase and suppressing the occurrence of cracks; and a method for manufacturing said sintered body. This sintered body contains indium, gallium, zinc, and oxygen, has an IGZO homologous crystal phase as a main phase, has a total crack length of 0.1 μm or less per 1 μm2, and has a volume resistivity of 10 mΩ・cm or less.

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] In sintered bodies containing indium, gallium, zinc, and oxygen, a homologous crystalline phase is likely to form, and because the homologous crystalline phase has a layered structure, shear forces are generated, which can easily cause cracks to form within the crystal grains.

[0006] In view of the above problems, an object of the present disclosure is to provide a sintered body containing indium, gallium, zinc, and oxygen, in which a homologous crystalline phase is the main phase and in which the occurrence of cracks is suppressed, and a method for manufacturing the same.

[0007] In order to solve the above problems, the present inventors conducted extensive research and discovered that by devising a manufacturing method, etc., it is possible to obtain a sintered body in which the homologous crystalline phase is the main phase and in which the occurrence of cracks is suppressed.

[0008] That is, the gist of the present disclosure is as follows: [1] A sintered body containing indium, gallium, zinc, and oxygen, which has an IGZO homologous crystalline phase as a main phase, and has cracks with a total length of 1 μm. ２ [1] A sintered body having an average crystal grain size of 0.05 μm or less and a volume resistivity of 10 mΩ cm or less. [2] The sintered body according to [1], having an average crystal grain size of 3 μm or less. [3] The sintered body according to [1] or [2], having a volume resistivity of 5 mΩ cm or less. [4] The sintered body according to any one of [1] to [3], having a coefficient of variation of volume resistivity of 10% or less. [5] The sintered body according to [1] to [3], having a coefficient of variation of volume resistivity of 10% or less. [6] The sintered body according to [1] to [3], having a coefficient of variation of volume resistivity of 10% or less. [7] The sintered body according to [1] to [3], having a coefficient of variation of volume resistivity of 10% or less. [8] The sintered body according to [1] to [3], having a coefficient of variation of volume resistivity of 10% or less. [9] The sintered body according to [1] to [3], having a coefficient of variation of volume resistivity of 10% or less.

[10] The sintered body according to

[10] , having a coefficient of variation of volume resistivity of 10% or less.

[11] The sintered body according to

[11] to

[12] , having a coefficient of variation of volume resistivity of 10% or less.

[12] The sintered body according to

[12] , having a coefficient of variation of volume resistivity of 10% or less.

[13] The sintered body according to

[13] , having a coefficient of variation of volume resistivity of 10% or less.

[14] The sintered body according to

[14] , having a coefficient of variation of volume resistivity of 10% or less.

[15] The sintered body according to [15 ｍａｘ The largest diffraction peak intensity among the normalized XRD diffraction peak intensities of the other crystalline phases excluding the IGZO homologous phase is defined as Q ｍａｘ When the XRD diffraction peak intensity ratio (P ｍａｘ / Q ｍａｘ ) is 3 or more. [6] The sintered body according to any one of [1] to [5], which has a relative density of 95% or more. [7] The sintered body according to any one of [1] to [6], which has a flexural strength of 200 MPa or more. [8] The sintered body according to any one of [1] to [7], which has a composition in the following ranges in atomic ratio: 0.11≦In / (In+Ga+Zn)≦0.40 (1) 0.11≦Ga / (In+Ga+Zn)≦0.40 (2) 0.20≦Zn / (In+Ga+Zn)≦0.78 (3) [9] A sputtering target composed of the sintered body according to any one of [1] to [8].

[10] The area of ​​the sputtering surface is 176 cm ２

[11] The method for producing a sintered body according to any one of [1] to [8], further comprising the step of: ２ O３ Powder, Ga ２ O ３ The powder and ZnO powder were mixed, and the resulting mixed powder was sintered in a vacuum or inert gas atmosphere at a maximum sintering temperature of 1000 to 1150°C and a pressing pressure of 150 kgf / cm ２ A method for producing a sintered body by hot pressing under the above conditions.

[12] In the temperature range from 900°C to the maximum sintering temperature, the pressing pressure is 125 kgf / cm ２ The method for producing a sintered body according to

[11] above.

[0009] According to the present disclosure, it is possible to provide a sintered body and a sputtering target that contain indium, gallium, zinc, and oxygen, have a homologous crystal phase as the main phase, and suppress the occurrence of cracks.

[0010] This is an image analysis diagram (for reference) used when analyzing cracks. This is an image (for reference) of a sintered body (single phase) after binarization processing.

[0011] 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.

[0012] The sintered body according to the embodiment of the present disclosure contains indium, gallium, zinc, and oxygen. A sintered body having such a composition is sometimes 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 a-Si.

[0013] 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 caused to collide 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.

[0014] IGZO sputtering targets are made from sintered bodies obtained by sintering raw material powders. During sintering, the raw material oxides containing In, Ga, and Zn react to form a homologous crystalline phase. While the homologous crystalline phase is a stable phase, its layered structure makes it susceptible to shear forces, resulting in cracks. Cracks can cause arcing during sputtering and can also cause target cracking during high-power sputtering, so it is desirable to minimize them.

[0015] The IGZO sintered body according to this embodiment has an IGZO homologous phase as its main phase. The IGZO homologous phase is (In, Ga) ２ O ３ (ZnO) ｍ It is a homologous crystalline phase (m = 0.5 or an integer of 1 to 20) represented by, in particular, (In, Ga) ２ O ３ (ZnO) ｍ In addition to the IGZO homologous phase, the IGZO sintered body also contains ZnGa ２ O ４ Phase, In ２ O ３ Phase, β-GaInO ３ Phase, In ２ Zn ７ O １０ Crystalline phases such as crystalline phases may be present.

[0016] The IGZO sintered body was analyzed by XRD (X-ray diffraction method), and each crystalline phase was identified by ICSD (Crystal Structure Database). The largest XRD diffraction peak intensity among the normalized XRD diffraction peak intensities of the IGZO homologous phase was determined as P. ｍａｘThe largest XRD diffraction peak intensity among the normalized XRD diffraction peak intensities of the other crystalline phases excluding the IGZO homologous phase is Q ｍａｘ When the XRD diffraction peak intensity ratio (P ｍａｘ / Q ｍａｘ ) is at least 1, it is determined that the IGZO homologous crystal phase is the main phase.

[0017] The normalized XRD diffraction peak intensity refers to the XRD diffraction peak intensity obtained by subtracting the "background intensity" from the XRD diffraction peak intensity of each crystalline phase (crystal plane), where the average intensity at X-ray diffraction angles 2θ = 40° to 41° is defined as the "background intensity." If a peak derived from a crystalline phase exists within the above angle range, a range of Δ2θ = 1°, where no peak derived from a crystalline phase exists, is selected from the range of 2θ = 20° to 50°, and the average intensity thereof is used as the background. If the X-ray diffraction peak intensity after normalization is 0 (zero) or less, the diffraction peak intensity is considered to be zero.

[0018] A thin film in a composition range in which the IGZO homologous crystalline phase is the main phase exhibits excellent properties as a channel layer of a TFT, such as high mobility and low carrier concentration. ｍａｘ / Q ｍａｘ ) is more preferably 3 or more, even more preferably 5 or more, and particularly preferably 10 or more. ｍａｘ / Q ｍａｘ ) is at least 1, In, Ga, and Zn can be substituted with other elements as necessary.

[0019] Cracks can cause arcing during sputtering and can also cause cracks or fissures in the sputtering target, so it is desirable to reduce them as much as possible. In the IGZO sintered body according to this embodiment, the total length of the cracks is 1 μm. ２ This makes it possible to prevent adverse effects of cracks during sputtering and to prevent the target from cracking or breaking. Preferably, the total length of the cracks is 1 μm or less. ２The total length of the cracks is preferably 0.03 μm or less, more preferably 0.02 μm or less. ２ The average particle size is 0.000 μm or more.

[0020] In this embodiment, the average crystal grain size of the sintered body is preferably 3 μm or less. The IGZO homologous phase is prone to grain growth, and as the crystal grains become coarse, cracks are more likely to occur. Furthermore, as described above, when the layered IGZO homologous phase is the main phase, cracks are likely to occur due to shear force, but the occurrence of cracks can be suppressed by reducing the grain size. Furthermore, since grain growth also leads to a decrease in flexural strength, it is preferable that the crystal grain size is fine. Preferably, the average crystal grain size is 2 μm or less.

[0021] The sintered body according to this embodiment has a volume resistivity of 10 mΩ·cm or less. The lower the volume resistivity of a sputtering target made of an IGZO sintered body, the more stable the sputtering becomes. Since IGZO homologous crystal phases tend to grow grains, the use of "microwave sintering" to suppress grain growth has been investigated. However, this sintering method makes it difficult to obtain a sintered body with low resistance. According to the present disclosure, a sintered body with low resistance can be obtained while suppressing grain growth. The volume resistivity is more preferably 5 mΩ·cm or less, and even more preferably 1 mΩ·cm or less.

[0022] The sintered body according to this embodiment preferably has an in-plane coefficient of variation of volume resistivity of 10% or less. In a sputtering target made of an IGZO sintered body, the smaller the coefficient of variation of volume resistivity, the more stable the sputtering becomes. As described above, the IGZO homologous phase has the property of being prone to grain growth, but in conventional manufacturing methods, suppressing grain growth causes fluctuations in volume resistivity and its variation. According to the present disclosure, it is possible to suppress grain growth while keeping the coefficient of variation of volume resistivity small. More preferably, it is 5% or less.

[0023] The coefficient of variation of the volume resistivity is calculated from the following formula: Coefficient of variation (CV) [%] = (standard deviation) / (arithmetic mean value) × 100. The measurement points and number of measurement points for the volume resistivity are calculated by dividing the area of ​​the sintered body into 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 in the above formula, the maximum number of measurable points is measured.

[0024] The sintered body according to this embodiment preferably has a relative density of 95% or more. The higher the relative density of a sputtering target made of an IGZO sintered body, the more effectively it can suppress the generation of particles and the like during sputtering. Since IGZO homologous crystal phases tend to cause grain growth, lowering the sintering temperature to suppress grain growth has been studied. However, it is difficult to obtain a high-density sintered body with this low-temperature sintering. According to the present disclosure, a high-density sintered body can be obtained while suppressing grain growth. The relative density is more preferably 97% or more, and even more preferably 98% or more.

[0025] The sintered body according to this embodiment preferably has a bending strength of 200 MPa or more. In particular, when an IGZO homologous crystal phase is present, there is a problem that cracks occur due to grain growth, which makes it easy for bending strength to decrease. According to the present disclosure, grain growth can be suppressed, so that the occurrence of cracks can be suppressed and the decrease in bending strength can be suppressed. More preferably, it is 230 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.

[0026] The sintered body according to this embodiment contains indium, gallium, and zinc, and the content of each element is not particularly limited. However, in order to form an IGZO homologous phase as the main phase, it is preferable that the content ratios of indium, gallium, and zinc satisfy the following formulas (1) to (3). In the formulas below, In, Ga, and Zn represent the atomic ratios of each element contained in the sintered body. Furthermore, other elements may be added or substituted as necessary. 0.11≦In / (In+Ga+Zn)≦0.40 (1) 0.11≦Ga / (In+Ga+Zn)≦0.40 (2) 0.20≦Zn / (In+Ga+Zn)≦0.78 (3) More preferably, the following formulas (4) to (6) are satisfied. 0.15≦In / (In+Ga+Zn)≦0.35 (4) 0.15≦Ga / (In+Ga+Zn)≦0.35 (5) 0.20≦Zn / (In+Ga+Zn)≦0.70 (6)

[0027] 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 flat plate, a rectangular flat 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 is 176 cm ２ It is preferable that the diameter of the sputtered surface is 150 mm or more. In the case of HIP (hot isostatic pressing) sintering or SPS (spark plasma sintering), the area is 176 cm ２ It is difficult to increase the size to 150 mm or more in diameter.

[0028] 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.

[0029] (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.

[0030] (2. Mixing and Grinding Step) The raw material powders are weighed out to achieve 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, as it has high efficiency in breaking down agglomerates in a short time and also provides a good dispersion state of additives. After pulverization, the median diameter (D50): 0.1 to 1.0 μm, specific surface area: 10.0 to 30.0 m ２ / g.

[0031] (3. Sintering Step) Next, the mixed 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. Furthermore, 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 uniform films.

[0032] In the present disclosure, sintering is performed in a vacuum or in an inert gas (argon, nitrogen, etc.) atmosphere from the viewpoint of generating oxygen deficiency in the sintered body and reducing the volume resistivity. From the viewpoint of suppressing the sublimation of ZnO, sintering in an inert gas atmosphere is preferable to a vacuum. On the other hand, when sintering in an inert gas atmosphere without pressure (atmospheric pressure), In ２ O ３ and Ga ２ O ３ Therefore, pressure sintering, which can suppress reduction to some extent, is preferred, and hot press sintering is particularly preferred from the viewpoint of productivity.

[0033] (3-1. Sintering Temperature) The maximum sintering temperature in the sintering process is set to 1000°C to 1150°C. Conventionally, sintering was performed at 1400 to 1600°C, but by setting the temperature to 1150°C or less, grain growth can be suppressed and bending strength can be improved. If the maximum sintering temperature is set too high, the In ２ O ３ or Ga ２ O ３ However, since there is a risk of reaction with carbon, which is a sintering equipment component, and reduction, the maximum sintering temperature is set to 1150°C or less. On the other hand, if the maximum sintering temperature is set too low, the density of the sintered body will not increase, so the maximum sintering temperature is set to 1000°C or more.

[0034] (3-2. Pressing pressure) The pressing pressure at the maximum sintering temperature during pressure sintering is 150 kgf / cm ２ When sintered in a vacuum or inert gas atmosphere, In ２ O ３ or Ga ２ O３ may be reduced, but 150 kgf / cm ２ By performing hot pressing at a pressure of 400 kgf / cm or more, reduction can be suppressed. There is no particular upper limit to the pressure, but considering the strength of the members used in the hot pressing, a pressure of 400 kgf / cm is preferred. ２ It is preferable to do the following:

[0035] (3-3. Sintering Holding Time) The holding time at the maximum sintering temperature can be 2 to 50 hours. By controlling the holding time within this range, it is possible to increase the density of the sintered body while maintaining productivity.

[0036] (3-4. Heating Rate) In the temperature range from 700°C to the maximum sintering temperature, the heating rate is preferably 0.1 to 5.0°C / min, and more preferably 0.3 to 3.0°C / min. In the above-mentioned predetermined temperature range, a heating rate exceeding 5.0°C / min is undesirable from the viewpoint of process stability during mass production, and a heating rate of less than 0.1°C / min is undesirable from the viewpoint of reduced productivity. However, the heating rate outside the above-mentioned predetermined temperature range is not limited, and any heating rate can be adopted.

[0037] (3-5. Reduction measures) In the temperature range of 900°C or higher, the pressing pressure should be 125 kgf / cm during heating, temperature maintenance, and temperature reduction. ２ In the temperature range of 900°C or higher, the pressing pressure is preferably 125 kgf / cm ２ In the following state, ２ O ３ , Ga ２ O ３ may react with the carbon in the sintered part and be reduced, causing a decrease in density, compositional deviation, and damage to the part.

[0038] (3-6. Temperature Decreasing Rate) In the temperature range from the maximum sintering temperature to 600°C, the temperature decreasing rate is preferably 10°C / min or less. By setting the temperature decreasing rate to 10°C / min or less, cracking of the sintered body due to thermal stress can be suppressed. Here, the temperature range in which the temperature decreasing rate is 10°C / min or less is set to 600°C or higher because sintered bodies at 600°C or higher are prone to large thermal stress when decreasing in temperature. However, the temperature decreasing rate outside the above-mentioned predetermined temperature range is not particularly limited, and any temperature decreasing rate can be adopted.

[0039] Furthermore, if pressure is applied continuously at temperatures below 600°C, internal stress will build up, causing cracks in the sintered body. Therefore, when the temperature is lowered to 600°C or below, the pressure should be kept at 50 kgf / cm. ２ Hereinafter, it is particularly preferable not to apply any pressing pressure.

[0040] (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 for use as needed.

[0041] 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.

[0042] The evaluation methods used in the examples and comparative examples are as follows. Since sputtering targets are processed by grinding, polishing, etc., the surface of the sintered body after polishing is in substantially the same state as the sputtering surface of the sputtering target. Various evaluations were also performed on a representative portion (sample) of the sintered body. If the various physical properties of a representative sample fall within the ranges of the present disclosure, the sintered body is encompassed by the present invention. In other words, even if a unique, exceptional, or partial sample that is not representative of the sintered body is measured and falls outside the range of the present disclosure, if the various physical properties of the representative sample fall within the ranges of the present disclosure, the sintered body is encompassed by the present invention as long as it exhibits the effects of the present invention.

[0043] (Composition Analysis) The composition of the sintered body was analyzed using the following device: Device: SPS3500DD manufactured by SII Method: ICP-OES (Inductively Coupled Plasma Optical Emission Spectroscopy)

[0044] (Analysis of Crystalline Phase) Analysis of the crystalline phase was performed using the following equipment. Principle: X-ray diffraction method Equipment: Rigaku Ultima IV Tube: Cu-Kα ray Tube voltage: 40 kV Tube current: 30 mA Measurement method: 2θ-θ reflection method Measurement range (2θ): 20 to 90° Scan speed: 8° / min Sampling interval: 0.02° Divergence slit: 1° Divergence vertical limiting slit: 10 mm Scattering slit: 8 mm Receiving slit: open state Goniometer: sample horizontal type Sample measurement location: sputtered surface side

[0045] (Regarding cracks) The cross sections (planes parallel to the plane corresponding to the sputtered surface) of the center and end (3 cm inside from the outer periphery) of the sintered body were observed using a backscattered electron image (magnification: 2000x) of an FE-EPMA (field emission electron probe microanalyzer), and an arbitrary number of images were taken. Apparatus used: JXA-8500 (JEOL) Acceleration voltage: 15.0 kV Beam current: 2.0 × 10 －８

[0046] 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). Note that in the backscattered electron image, heavier elements are displayed in brighter colors, and lighter elements are displayed in darker colors.

[0047] For single-phase tissue, the brightness (n ｍａｘ ) is 160≦n ｍａｘ ≦180 and frequency is n ｍａｘ The darkest brightness (n １／１０ ) is n ｍａｘ −20≦n １／１０ ≦n ｍａｘ We selected three images with a value of -15. １／１０ -n ｄｅｆ = 5 ｄｅｆ Set n ｄｅｆ The following is in black, ｄｅｆ The images were binarized so that higher brightness was white (see Figure 2). To distinguish them from pores, black areas with a long side / short side of 3 or more were considered cracks, and their lengths were measured. The total length of the lines divided by the area of ​​the field of view was calculated as 1 μm. ２ The crack length per unit is 1 μm for three sheets. ２ The average crack length per test piece was taken as the total crack length.

[0048] In the case of a structure in which multiple crystalline phases exist, 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 are arbitrarily selected, where the brightness (n2) of the part corresponding to the phase with the lowest ratio of the phase is 115≦n2≦135. Among the brightnesses where the frequency is 1 / 10 or more of the frequency of n2, the darkest brightness is defined as n １／１０ Let n １／１０ -n ｄｅｆ = 5ｄｅｆ Set n ｄｅｆ The following is in black, ｄｅｆ The higher brightness is binarized to white. To distinguish from pores, black areas with a long side / short side of 3 or more are considered cracks, and their lengths are measured. The total length of the lines divided by the area of ​​the field of view is defined as 1 μm. ２ The crack length per unit area of ​​the three sheets is taken as the crack length, and the average of the crack lengths per unit area of ​​the three sheets is taken as the total crack length.

[0049] (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 structural photograph of the mirror-polished sample surface was taken in five fields of view at a magnification of 5000 times using a scanning electron microscope (SEM). 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. Then, the crystal grain size was calculated for each of the five fields of view using the above formula, and the arithmetic average value of the five fields of view was taken as the average crystal grain size. However, when the number of particles intersected by each straight line in the field of view was less than 10, a magnification of 2000 or 1000 was used. The equipment used and measurement conditions were as follows: Equipment used: JXA-8500F (JEOL) Acceleration voltage: 15.0 kV Beam current: 5.0 × 10 ―８ A

[0050] (Volume Resistivity) The surface of a sintered body with a diameter of 180 mm was polished, and the volume resistivity was measured at 13 random points on the polished surface spaced at intervals of 5.0 cm or more, and the arithmetic mean value and standard deviation of the 13 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)

[0051] (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)

[0052] (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.

[0053] (Example 1) In ２ O ３ Powder, Ga ２ O ３Powder and ZnO powder were prepared, weighed, mixed, and pulverized to obtain a desired composition. ５０ : 0.64μm, specific surface area: 11.7m ２ Next, this mixed powder was filled into a carbon die and sintered in an argon atmosphere at a maximum sintering temperature of 1150°C and a press pressure of 250 kgf / cm. ２ The temperature was increased from 700°C to the maximum sintering temperature at a rate of 3°C / min, and the temperature was decreased from the maximum sintering temperature to 600°C at a rate of 5°C / min.

[0054] The physical properties of the sintered body obtained in Example 1 were measured, and the total length of the cracks was found to be 0.002 μm / μm. ２ The sintered body had an average crystal grain size of 1.2 μm, a relative density of 98.6%, a volume resistivity of 0.6 mΩ·cm, a coefficient of variation of the volume resistivity of 4.7%, and a bending strength of 262.6 MPa, which were satisfactory results. ４ The main phase was the IGZO homologous crystal phase. The results are shown in Table 1.

[0055]

[0056] (Example 2) A sintered body was produced using the same production method and production conditions as in Example 1, except for the composition. As a result of measuring the physical properties of the sintered body obtained in Example 2, it was found that the total length of the cracks was 0.019 μm / μm. ２ The sintered body had an average crystal grain size of 1.6 μm, a relative density of 99.1%, a volume resistivity of 0.6 mΩ·cm, a coefficient of variation of the volume resistivity of 8.3%, and a bending strength of 241.3 MPa, which were all satisfactory results. ２ O ５ The main phase was an IGZO homologous crystal phase.

[0057] (Example 3) A sintered body was produced using the same production method and production conditions as in Example 1, except for the composition. The physical properties of the sintered body obtained in Example 3 were measured, and the crack length was found to be 0.010 μm / μm. ２The sintered body had an average crystal grain size of 1.3 μm, a relative density of 98.7%, a volume resistivity of 0.8 mΩ·cm, a coefficient of variation of the volume resistivity of 2.8%, and a bending strength of 260.0 MPa, which were satisfactory results. ４ O ７ The main phase was an IGZO homologous crystal phase.

[0058] (Example 4) A sintered body was produced using the same production method and production conditions as in Example 1, except for the composition. As a result of measuring the physical properties of the sintered body obtained in Example 3, it was found that the total length of the cracks was 0.003 μm / μm. ２ The sintered body had an IGZO homologous crystal phase of InGaZn3O6 as the main phase, and had an InGaZn3O6 homogeneous crystal phase as the main phase. ２ Zn ７ O １０ Phases were present.

[0059] (Comparative Example 1) In ２ O ３ Powder, Ga ２ O ３ Powder and ZnO powder were prepared, weighed, mixed, and pulverized to obtain the desired composition shown in Table 1. ５０ : 0.64μm, specific surface area: 11.7m ２ Next, this mixed powder was filled into a die, and then pressed under a pressure of 785 kfg / cm. ２ , uniaxial molding with a holding time of 1 minute, and then pressing pressure: 1795 kgf / cm ２ The obtained compact was subjected to atmospheric sintering in an oxygen atmosphere at a maximum sintering temperature of 1350°C for a holding time of 20 hours to produce a sintered body having a diameter of 180 mm. The physical properties of the sintered body obtained in Comparative Example 1 were measured, and the total crack length was found to be 0.111 μm / μm. ２ The average crystal grain size was 8.3 μm, the volume resistivity was 70 mΩ·cm, and the bending strength was 77.1 MPa, and the desired results were not obtained. ４ The IGZO homologous crystal phase was the main phase.

[0060] (Comparative Example 2) In ２ O ３ Powder, Ga ２ O ３ Powder and ZnO powder were prepared, weighed, mixed, and pulverized to obtain the desired composition shown in Table 1. ５０ : 0.24μm, specific surface area: 11.45m ２ Next, this mixed powder was filled into a die, and then pressed under a pressure of 785 kfg / cm. ２ , uniaxial molding with a holding time of 1 minute, and then pressing pressure: 1795 kgf / cm ２ The obtained compact was subjected to atmospheric sintering at a maximum sintering temperature of 1400°C for a holding time of 20 hours in the atmosphere to produce a sintered body having a diameter of 180 mm. The physical properties of the sintered body obtained in Comparative Example 2 were measured and the total crack length was found to be 0.118 μm / μm. ２ The average crystal grain size was 8.3 μm, the volume resistivity was 41.7 mΩ·cm, and the coefficient of variation of the volume resistivity was 13.29%, and the desired results were not obtained. ２ O ５ The IGZO homologous crystal phase was the main phase.

[0061] (Comparative Example 3) In ２ O ３ Powder, Ga ２ O ３ Powder and ZnO powder were prepared, weighed, mixed, and pulverized to obtain the desired composition shown in Table 1. ５０ : 0.64μm, specific surface area: 11.7m ２ After filling this mixed powder into a die, a pressing pressure of 785 kfg / cm was applied. ２ , uniaxial molding with a holding time of 1 minute, and then pressing pressure: 1795 kgf / cm ２ CIP molding was performed with a holding time of 1 minute. The obtained molded body 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 with a diameter of 30 mm. Cracks occurred in the sintered body obtained in Comparative Example 3. This is thought to be because high temperatures were applied to parts of the sintered body during sintering, causing large temperature variations within the sintered body.

[0062] In addition, since it was not possible to obtain samples of sufficient size for the sintered body obtained in Comparative Example 3, it was not possible to measure the XRD, bending strength, and coefficient of variation of volume resistivity. The volume resistivity varied greatly, reaching 11 mΩ·cm in low areas, but exceeding the upper limit of measurement in high areas. When the grain size was measured in areas with low volume resistivity, the average crystal grain size was 3.55 μm and the total length of the cracks was 0.052 μm, which was not the desired result. It is believed that the short sintering time of microwave sintering caused large temperature variations within the sintered body, resulting in non-uniform volume resistivity and grain size.

[0063] (Comparative Example 4) A sintered body was produced using the same production method and conditions as in Example 1, except for the composition and sintering temperature. The physical properties of the sintered body obtained in Comparative Example 4 were measured, and the result was InGaZnO ４ In addition to the IGZO homologous crystal phase, ２ O ３ phases were present and the desired results were not obtained.

[0064] 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.

[0065] According to the present disclosure, it is possible to provide a sintered body containing indium, gallium, zinc, and oxygen, which has an IGZO homologous crystalline phase as a main phase and in which the occurrence of cracks is suppressed, and a method for manufacturing the same. The sintered body and 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, with an IGZO homologous crystalline phase as the main phase, and with a total crack length of 1 μm. ２ The sintered body has a particle size of 0.05 μm or less per particle and a volume resistivity of 10 mΩ·cm or less.

2. The sintered body according to claim 1, wherein the average crystal grain size is 3 μm or less.

3. The sintered body according to claim 1, having a volume resistivity of 5 mΩ·cm or less.

4. The sintered body according to claim 1, wherein the coefficient of variation of the volume resistivity is within 10%.

5. The largest XRD diffraction peak intensity among the normalized XRD diffraction peak intensities of the IGZO homologous phase is defined as P ｍａｘ The largest XRD diffraction peak intensity among the normalized XRD diffraction peak intensities of the other crystalline phases excluding the IGZO homologous phase is defined as Q ｍａｘ When the XRD diffraction peak intensity ratio (P ｍａｘ / Q ｍａｘ 2. The sintered body according to claim 1, wherein the number of sintered bodies is 3 or more.

6. The sintered body according to claim 1, which has a relative density of 95% or more.

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

8. The sintered body according to claim 1, wherein the composition is in the following ranges in atomic ratio: 0.11≦In / (In+Ga+Zn)≦0.40 (1) 0.11≦Ga / (In+Ga+Zn)≦0.40 (2) 0.20≦Zn / (In+Ga+Zn)≦0.78 (3) 9. A sputtering target comprising the sintered body according to any one of claims 1 to 8.

10. The area of ​​the sputtered surface is 176 cm ２ 10. The sputtering target according to claim 9, wherein the diameter of the sputtering surface is 150 mm or more.

11. A method for producing a sintered body according to any one of claims 1 to 8, comprising the steps of: ２ O ３ Powder, Ga ２ O ３ The powder and ZnO powder were mixed, and the resulting mixed powder was sintered in a vacuum or inert gas atmosphere at a maximum sintering temperature of 1000 to 1150°C and a pressing pressure of 150 kgf / cm ２ A method for producing a sintered body by hot pressing under the above conditions.

12. Press pressure is 125 kgf / cm in the temperature range from 900°C to the maximum sintering temperature. ２ The method for producing a sintered body according to claim 11 .

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