JP2014125422A - Oxide sintered body, oxide sintered body sputtering target and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high quality and high yield IGZO sputtering target suitable for an oxide semiconductor film use by improving variation of property of an IGZO thin film and improving generation of cracks during target manufacturing and sputtering which are problems especially for large scale sputtering target for oxide semiconductor film.SOLUTION: There is provided an oxide sintered body containing at least In, Ga and Zn, having a homologous crystal structure represented by InGaZnOand a diffraction intensity ratio I1/I2 of 0.85 to 1.25, where I1 is a diffraction intensity at 30.3° to 30.9° of an incident angle in X-ray diffraction (2θ) and I2 is diffraction intensity at 31.1° to 31.5°.

Description

  The present invention relates to an oxide semiconductor film sputtering target (IGZO target) mainly composed of indium, gallium, zinc, and oxygen.

  An oxide (IGZO) containing indium oxide-gallium oxide-zinc oxide or an oxide semiconductor film containing these oxides as a main component has an advantage that the mobility is higher than that of an amorphous silicon film, and an organic EL in which high mobility is required. Application is progressing as a TFT device application.

  The formation of the IGZO thin film is generally performed by a sputtering method using an IGZO sintered body because a large area can be easily obtained and a high performance film can be obtained. In particular, in recent years, the commercialization of IGZO semiconductor films has progressed dramatically, and the demand for large-scale sputtering targets for mass production has increased. However, variations in the characteristics of IGZO thin films generated when these large targets are used, and large targets The production yield reduction of the above, and the problem of cracking during sputtering are prominent.

  Variation in IGZO thin film characteristics is a problem in which the elemental composition ratio of In, Ga, and Zn in an IGZO thin film formed by a sputtering method fluctuates as the target usage rate increases. Has been pointed out. For this reason, variations in TFT characteristics occur, causing quality defects. Patent Document 1 has already pointed out that the thin film composition tends to fluctuate when a plurality of crystal phases exist in the sintered body. However, in practice, even a target composed only of a homologous single-phase structure has a problem of composition variation, and in particular, variation in characteristics in a mass production process using a large target.

  Regarding the problem of cracking of the sintered body, the crystal structure of the IGZO sintered body often includes a homologous crystal structure having a highly anisotropic layered structure, and the strength of such a sintered body is a conventional oxide. There is a problem that it is extremely low compared to the target. For this reason, the problem of the crack generation at the time of target manufacture and the problem of the target crack have occurred by the thermal stress generated at the time of sputtering. Further, the problem of target cracking tends to occur more easily because the generated stress increases as the size of the sintered body increases.

As a method for improving the strength of the IGZO sintered body, Patent Document 2 shows that the bending strength is increased to 58 MPa by using a crystal layer containing a spinel structure. In Patent Document 3, a bending strength of 14.3 kg / mm ² (about 140 MPa) is obtained by using a crystal phase including a spinel structure and a bixbite. However, since these methods limit the composition of the IGZO film, the composition ratios of In, Ga, and Zn in the IGZO sintered body cannot be determined as appropriate in order to optimize the film characteristics. As mentioned above, since the problem of fluctuations in the composition of the thin film has been pointed out in the sintered body containing a plurality of crystal phases, a method for increasing the strength of the sintered body regardless of the composition ratio of the sintered body has been desired. . In particular, in the case of a composition ratio having only a homologous crystal structure, since the strength is remarkably low, improvement of the strength of the sintered body is strongly desired.

  In addition, it is known that increasing the density of the sintered body is effective as a method for improving the strength of the sintered body. However, since the IGZO sintered body grows relatively quickly, pores (bubbles) However, it is difficult to obtain a high-density sintered body. In Patent Document 4, a sintered body having a density of 98% is obtained with a sintering holding time of 20 hours or longer. However, since the crystal growth of the sintered body is promoted, the particle size becomes as large as 7 μm or more, and there is no description of the strength of the sintered body, but generally the strength of the sintered body when the particle size grows in this way. Is low. In particular, in the case of a sintered body having only a layered structure such as a homologous structure, the strength is likely to further decrease.

International Publication No. 2009/157535 Pamphlet JP 2008-163441 A International Publication No. 2011/040028 Pamphlet International Publication No. 2009/157535 Pamphlet

  An object of the present invention is to improve the characteristic variation of an IGZO thin film, which is a problem of a large-sized sputtering target for an oxide semiconductor film, and to improve the generation of cracks during target production and sputtering. An object of the present invention is to provide an IGZO sputtering target having a high quality and a high yield that is optimum for the application.

As a result of intensive investigations, the inventors of the present invention have determined that sputtering is achieved by controlling the incident intensity (2θ) diffraction intensity ratio in X-ray diffraction in a sintered body having a homologous crystal structure represented by InGaZnO _4. It has been found that the composition fluctuation in the IGZO thin film after the film can be suppressed. Furthermore, in the manufacture of large-size targets required for mass production apparatuses, the present inventors have found the effect of improving the production yield and improving the generation of cracks during sputtering, and have completed the present invention.

Aspects of the present invention are as follows.
(1) An oxide sintered body containing at least In, Ga and Zn, having a homologous crystal structure represented by InGaZnO ₄ , and having an incident angle (2θ) in X-ray diffraction of 30.3 ° to When the diffraction intensity at 30.9 ° is I1, and the diffraction intensity at 31.1 ° to 31.5 ° is I2, the diffraction intensity ratio I1 / I2 is 0.85 or more and 1.25 or less. Oxide sintered body.
(2) The oxide sintered body according to (1), wherein the number of microcracks having a length of 3 μm or more existing in the range of 60 μm × 80 μm in the oxide sintered body is 20 or less. .
(3) The oxide sintered body according to (1) or (2), which has a flat plate shape with an area of the target surface of 1302 cm 2 or more, or a cylindrical shape with an area of the target surface of 486 cm 2 or more. .
(4) The oxide sintered body according to (1) to (3), wherein the bending strength of the oxide sintered body is 100 MPa or more.
(5) A sputtering target using the oxide sintered body according to (1) to (4) described above as a target material.
(6) The sputtering target according to (5), wherein the composition fluctuation rate of the zinc element in the IGZO thin film formed by sputtering is less than 5%.
(7) In an oxide sintered body containing at least In, Ga, and Zn and having a homologous crystal structure represented by InGaZnO ₄ , the oxide powder of each element is wet The mixed powder obtained by media mill treatment has a specific surface area of 12.0 to 15.0 m ² / g and an average particle size of 0.35 to 0.45 μm, and the zinc oxide crystallites in the mixed powder The method for producing an oxide sintered body according to any one of (1) to (4), wherein a mixed powder having a diameter of 60 nm or less is used.
(8) In the mixed powder, the volume expansion coefficient in the temperature range of 300 to 750 ° C. is 2.1% or less, and the volume expansion coefficient in the temperature range of 1000 to 1200 ° C. is 4.2% or less. The method for producing an oxide sintered body according to (7), wherein:

  Hereinafter, the present invention will be described in detail.

The oxide sintered body of the present invention is a sintered body that includes at least indium, gallium, zinc, and oxygen and has a homologous crystal structure represented by InGaZnO ₄ . The “sintered body having a homologous crystal structure represented by InGaZnO ₄ ” referred to in the present invention refers to a sintered body having an X-ray diffraction pattern including a peak that matches the diffraction pattern of InGaZnO ₄ . Further, the "sintered body having only homologous crystal structure represented by InGaZnO _4" is referred to in the present invention, X-ray diffraction pattern is consistent with the diffraction pattern of InGaZnO _4, the peaks that are not attributable to the diffraction pattern of InGaZnO ₄ It means not included.

  According to the present invention, when the incident angle (2θ) in X-ray diffraction is I1, the diffraction intensity at 30.3 ° to 30.9 ° is I1, and the diffraction intensity at 31.1 ° to 31.5 ° is I2, When the diffraction intensity ratio I1 / I2 is 0.85 or more and 1.25 or less, the composition fluctuation phenomenon of the sputtering thin film is suppressed, and an IGZO sintered body with less generation of cracks during target production and sputtering is obtained. .

In the oxide sintered body of the present invention, the incident angle (2θ) in X-ray diffraction is I1 when the incident angle (2θ) is 30.3 ° to 30.9 °, and the diffraction intensity when 31.1 ° to 31.5 °. When I2, the diffraction intensity ratio I1 / I2 is 0.85 or more and 1.25 or less. More preferably, the diffraction intensity ratio I1 / I2 is 0.90 or more and 1.10 or less. The increase in the diffraction intensity ratio I1 / I2 indicates that the growth of the InGaZnO ₄ crystal phase in the C-axis direction is selectively advanced. The present inventors have found that when the growth of crystal grains in the C-axis direction exceeds a certain level, a large amount of layered microcracks are likely to enter the crystal grains, and the value of the diffraction intensity ratio is set to a certain value or less. By doing so, we succeeded in obtaining a sintered body with few microcracks. On the other hand, when the diffraction intensity ratio is less than 0.85, it is difficult to obtain a desired sintered body density, which leads to a decrease in strength and abnormal discharge during sputtering.

In the oxide sintered body of the present invention, the number of microcracks having a length of 3 μm or more existing in the range of 60 μm × 80 μm of the sintered body is preferably 20 or less, and more preferably 10 or less. preferable. More preferably, the crack does not have a length of 15 μm or more. The present inventors conducted a detailed cause investigation on the composition fluctuation phenomenon of the IGZO sputtered film. In order to obtain a high-density IGZO sintered body, it is necessary to fire a molded body made of a raw material at a sufficiently high temperature. However, in general, the homologous crystal structure represented by InGaZnO ₄ is present inside the high-density IGZO sintered body, and there is a specific layered microcrack. When this microcrack increases, the composition variation of the thin film becomes more prominent. It has been found. That is, a sintered body having many microcracks adsorbs and contains moisture in the internal crack layer by contact with moisture in the atmosphere and a cleaning liquid in the target cleaning process. When forming a film using such a target, the zinc atoms knocked out of the target are scattered by water molecules, and the film adhesion rate of zinc atoms is extremely reduced, resulting in the compositional variation of the IGZO film. It was.

  Furthermore, the open pore ratio of the oxide sintered body of the present invention is preferably 0.2% or less, more preferably 0.15% or less, and further preferably 0.10% or less. Open pores refer to voids (holes or cracks) that have an open path to the resurface of the sintered body, and not only when the voids open directly to the surface of the sintered body, but also other voids. It refers to a void that is open to the surface while passing through. The open pore ratio refers to the ratio of the open pore volume to the total volume of the sintered body volume and the open pore volume. When open pores are present in a certain ratio or more, moisture from the atmosphere or the like is adsorbed inside the sintered body, which causes variation of each elemental composition in the IGZO film, and therefore it is preferable to reduce it as much as possible.

  The bending strength of the oxide sintered body of the present invention is preferably 100 MPa or more, and more preferably 150 MPa or more. If the strength of the oxide sintered body is high, cracks are less likely to occur during grinding, and the yield is high, so the productivity is good. Furthermore, even when used for a cylindrical sputtering target in which high power is applied during sputtering, the problem of cracking is unlikely to occur.

Incidentally, indium oxide sintered body, gallium and zinc ratio is not particularly limited as long as the composition containing a homologous crystal structure represented by InGaZnO _4, having only the homologous crystal structure represented by InGaZnO ₄ Sintered bodies are particularly suitable because of the great effect of the present invention.

  Next, the manufacturing method of the oxide sintered body of the present invention will be described for each step.

(1) Raw material mixing step The raw material powder is not particularly limited. For example, metal salt powders such as indium, gallium, zinc chloride, nitrate, carbonate, etc. can be used. Oxide powder is then preferred.

  The purity of each raw material powder is preferably 99.9% or more, more preferably 99.99% or more. This is because if the purity is low, the impurities contained may adversely affect the TFT formed by the sputtering target using the IGZO sintered body of the present invention.

The blending of these raw materials is not particularly limited because the effects of the present application can be obtained as long as the composition produces a homologous crystal structure represented by InGaZnO ₄ . The specific surface area and average particle diameter of each raw material powder are important for obtaining a powder having the physical properties necessary for the present invention by the subsequent pulverization / mixing process. In the present application, the specific surface area of indium oxide is 10.0 to 13.0 m ² / g and the average particle size is 0.9 to 1.3 μm, the specific surface area of gallium oxide is 10.0 to 17.0 m ² / g and the average It is preferable to use as a raw material a powder having a particle size of 1.8 to 2.5 μm, a specific surface area of zinc oxide of 3.0 to 15.0 m ² / g, and an average particle size of 0.2 to 1.5 μm. Regarding the zinc oxide raw material, the desired physical properties are more easily obtained by using a powder having a specific surface area of 10.0 to 13.0 m ² / g and an average particle size of 0.20 to 0.35 μm. Is particularly preferred.

Next, these raw material powders are pulverized and mixed. In the present invention, it is particularly important to obtain a mixed powder having desired physical properties by performing an appropriate treatment in the pulverization / mixing. In the present invention, it is most preferable to use a wet processing method which is excellent in mixing and grinding ability. Specifically, wet bead mill pulverization / mixing using zirconia beads is preferable. By performing appropriate wet bead mill grinding / mixing, the powder after grinding / mixing has a specific surface area of 12.0-15.0 m ² / g and an average particle size of 0.35-0.45 μm, It is extremely important in the present application to obtain a raw material powder satisfying that the crystallite diameter of zinc oxide in the mixed powder after treatment is 60 nm or less. The specific surface area of the powder after pulverization and mixing is more preferably in the range of 12.5 to 14.5 m ² / g. By adjusting to these physical property ranges, the activity of the raw material powder is remarkably improved, and the sintering reactivity in the firing step is remarkably improved. In addition to being able to be densified at a lower temperature and in a shorter time than before, selective grain growth in the C-axis direction of InGaZnO ₄ homologous crystal particles is suppressed, and the generation of microcracks in the sintered body is suppressed. It becomes possible to do.

  In addition to the above, the powder after the treatment is 2.1% or less in the temperature range of 300 to 750 ° C. and 4.2% or less in the temperature range of 1000 to 1200 ° C. of the molded body produced from the powder. It is preferable that It is more preferably 1.3% or less in the temperature range of 300 to 750 ° C., 2.5% or less in the temperature range of 1000 ° C. to 1200 ° C., and 0.08 in the temperature range of 300 to 750 ° C. % Or less, and more preferably 0.13% or less in the temperature range of 1000 ° C. to 1200 ° C.

The volume expansion coefficient in the present application is an index mainly showing the uniform mixing property of each raw material powder. When the dispersion state of each raw material in the mixed powder is not appropriate, severe volume expansion occurs in the process of forming InGaZnO _{4 in} the firing step, which causes firing cracks. By setting it in the above range, the risk of firing cracks of a large-sized target is greatly reduced even at a relatively high rate of temperature increase.

  In order to obtain an IGZO mixed raw material satisfying the above physical properties, it is necessary to perform treatment under appropriate bead mill apparatus pulverization / mixing conditions. For example, when processing 25 kg of powder in a bead mill apparatus having a mill volume of 2 L, it is preferable to carry out under the following conditions.

  The solid content concentration in the slurry is 30% to 70%, more preferably 40% to 55%. If the solid content concentration becomes too high, the processing ability is lowered, and desired powder physical properties cannot be obtained. In particular, zinc oxide tends to cause an increase in viscosity and greatly impairs the mixing property with other raw materials, so it is important to adjust it within an appropriate range. On the other hand, if the solid content concentration in the slurry is too low, the treatment amount itself is reduced, which is not preferable.

  As the grinding media, zirconia beads having high grinding ability are used, and the bead diameter is in the range of φ0.2 mm to φ0.4 mm. The total amount of beads charged into the mill is in the range of 5.0 to 6.5 kg, and the bead filling rate relative to the mill volume is in the range of 75 to 85%.

  The slurry temperature also needs to be strictly controlled, and the mill inlet slurry temperature must be controlled to 15 ° C. or lower, preferably 12 ° C. or lower, and constantly controlled so that the slurry temperature at the mill outlet is 21 ° C. or lower. . Since the slurry temperature rapidly rises due to the milling process, it is preferable to provide the slurry tank with an appropriate cooling mechanism.

  The type of the dispersant is not particularly limited. In particular, it is necessary to suppress the change in the slurry viscosity of the zinc oxide powder within a certain range. For this reason, the slurry pH is adjusted to be in the vicinity of the neutral region of 5-9. When the amount of the dispersant added is large, the strength of the powder granule after spray drying becomes too high, which leads to a decrease in strength of the molded product and causes fire cracking of the molded product. For this reason, it is necessary to make addition amount smaller than general addition amount, 0.9 wt% or less is preferable, and 0.7 wt% or less is more preferable.

  It is efficient to supply the slurry into the mill from 0.6 L / min to 1.5 L / min up to 1 to 2 passes with a heavy load on the mill, and from 1.5 L / min to 3.1 L / min thereafter. This is preferable because the process proceeds to the above and the number of passes can be reduced. If the number of passes increases excessively, impurities from the inner wall of the mill cause contamination of the sputtered thin film TFT, which is not preferable.

  The peripheral speed of the mill is set in the range of 5.5 m / sec to 9.5 m / sec, and more preferably in the range of 6.0 m / sec to 8.0 m / sec. Depending on the processing batch, the slurry viscosity may increase due to some factor even under the same conditions. In this case, the amount of the dispersant is appropriately added within the above range, and the slurry viscosity is always set to 3000 mPa · s. It is important to keep the processing stable.

  In consideration of the above conditions, a mixed powder having desired physical property values can be obtained by performing pulverization treatment by circulating for 5 to 20 passes, more preferably 5 to 15 passes. If the number of passes is insufficient, it not only causes firing cracks but also makes it difficult to obtain a high-density sintered body. In order to obtain a high-density body, high-temperature or long-time firing is required, and microcracks are likely to be generated inside as in the case of a conventional IGZO sintered body. On the other hand, when the number of passes increases and the specific surface area is excessively increased or the average particle size is decreased, the bulk density of the powder is decreased, which causes a decrease in yield due to a decrease in moldability and a re-use of the powder. As a result of the progress of aggregation, it becomes difficult to obtain a high-density sintered body. Also in this case, since it is necessary to perform baking at a high temperature or for a long time in order to obtain a high-density sintered body, micro cracks are likely to be generated inside as in the conventional IGZO.

  The state of the final powder when the wet mixing process is performed is not particularly limited. In a wet molding method such as cast molding, the slurry can be used as it is. However, in the case of dry molding, it is desirable to use a granulated powder with high powder fluidity and uniform compact density. The granulation method is not particularly limited, and spray granulation, fluidized bed granulation, rolling granulation, stirring granulation, and the like can be used. In particular, it is desirable to use spray granulation which is easy to operate and can be processed in large quantities.

(2) Molding step Next, this powder is molded. Here, dry molding using a dry powder will be described as an example. The pressing pressure can be appropriately changed depending on the physical properties of the powder used, but is generally 100 to 500 kg / cm ² . The molding pressure is not particularly limited as long as it does not generate cracks and can be handled. Moreover, it is preferable to perform cold isostatic pressing (CIP) in order to further increase the molding density after press molding. The CIP pressure can also be appropriately changed depending on the powder physical properties to be used, but a range of 1000 to 3500 kg / cm ² is common.

(3) Firing step Subsequently, the firing step is performed. As the firing method, various methods such as atmospheric pressure sintering and pressure sintering can be used. In the present invention, from the viewpoint of suppressing grain growth in the C-axis direction in InGaZnO ₄ homologous crystal grains, it is preferable to raise the temperature at a relatively high rate of temperature increase. Specifically, it is 20-600 degreeC / hour, Preferably it is 100-600 degreeC / hour, More preferably, it is 200-600 degreeC / hour, More preferably, it is 300-600 degreeC / hour. For this reason, it is more effective to perform firing using an electromagnetic wave firing furnace capable of rapid heating firing. When the temperature range of 300 to 750 ° C. and 1000 to 1200 ° C. is increased at a temperature increase rate of 200 ° C./hour or more, the volume expansion coefficient of the powder after bead mill pulverization / mixing is 300 to 750 ° C. From the viewpoint of preventing firing cracks of the large target, it is preferable to use a mixed powder of 1.3% or less in the temperature range of 2.5% or less and 2.5% or less in the temperature range of 1000 to 1200 ° C.

The holding temperature is preferably 1350 ° C to 1450 ° C. If the temperature is too high, the crystal grain growth of InGaZnO ₄ proceeds rapidly, firing cracks occur due to strength reduction due to abnormal grain growth, and the yield decreases. On the other hand, if the holding temperature is too low, the densification does not proceed, so that a high-density sintered body cannot be obtained, which causes an increase in arcing during sputtering.

The holding time at the above temperature is 3 hours or less, preferably 5 minutes or more and 60 minutes or less. When the holding time is long, selective grain growth in the C-axis direction of InGaZnO ₄ homologous crystal grains tends to proceed, and microcracks are generated inside the sintered body, which is not preferable. If the holding time is short, sufficient sintering will not proceed and problems such as low density and density unevenness will occur, so a certain holding time is required, but the mixed powder in the present invention has a high holding time with an extremely short holding time. It is possible to obtain a sintered body that is densified and has no density unevenness even when firing a large target.

  The temperature lowering speed is appropriately selected at a speed that does not cause cracking due to thermal shock. In a general resistance heating electric furnace, cooling is performed at a temperature of 300 ° C./h or less, for example. The atmosphere during firing is not particularly limited, but is preferably an air or oxygen atmosphere in order to suppress zinc sublimation.

(4) Targeting process The obtained sintered body is formed into a desired shape such as a plate shape, a circular shape, or a cylindrical shape by using a machining machine such as a surface grinder, a cylindrical grinder, a lathe, a cutting machine, or a machining center. To grind. Furthermore, a sputtering target using the sintered body of the present invention as a target material is obtained by bonding (bonding) a backing plate made of oxygen-free copper, titanium, or the like to the backing tube or backing tube using indium solder or the like as necessary. Can do.

The size of the sintered body is not particularly limited, but since the sintered body according to the present invention has high strength, a large target can be manufactured. In the case of a flat-plate-type sputtering target, a large-sized sintered body having a length of 310 mm × width of 420 mm (target surface area 1302 cm ² ) or more can be produced. In the case of a cylindrical sputtering target, a large-sized sintered body having an outer diameter of 91 mmΦ × 170 mm (target surface area 486 cm ² ) or more can be produced. In addition, the area of the target surface said here means the area of the sintered compact surface by the side of sputtering. In the case of a multi-divided target composed of a plurality of sintered bodies, the area of the surface of the sintered body on the side to be sputtered in each sintered body is the largest and the area of the target surface in the multi-divided target To do.

  The thickness of the target is not particularly limited, but is preferably 4 mm or more and 15 mm or less. If it is thinner than 4 mm, the target utilization is low and not economical. On the other hand, when the thickness is larger than 15 mm, the sintered body becomes heavy, and thus handling equipment or the like is required in the targeting step.

In the present invention, an oxide sintered body containing at least In, Ga, and Zn, having a homologous crystal structure represented by InGaZnO ₄ , and an incident angle (X-ray diffraction) in the oxide sintered body ( By controlling the diffraction intensity ratio of 2θ), the problem of composition variation of the IGZO thin film is improved, the strength of the sintered body is improved, the yield of large target production is improved, and cracking during sputtering is suppressed. Is possible.

4 is a microcrack observation photograph of a sintered body test piece shown in Example 2. FIG. The numbers in the photographs indicate the observed microcracks. 4 is a microcrack observation photograph of a sintered body test piece shown in Comparative Example 2.

Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to the methods described herein. The main measurement conditions in this example are as described below.
(1) Density of sintered body In accordance with JIS R 1634, the bulk density is calculated from the volume and dry weight of the sintered body calculated by Equation (1) by the Archimedes method, and this is divided by the theoretical density. Relative density.
Sintered body volume = (weight of hydrate-weight of water) / density of water (1)
The theoretical density (d) of the sintered body is determined by converting In, Ga, and Zn in the sintered body into oxides, respectively, indium oxide, gallium oxide, and zinc oxide. , B (g), c (g) and their respective true densities of 7.18 (g / cm ³ ), 5.95 (g / cm ³ ), 5.67 (g / cm ³ ), 2) Calculated from the arithmetic mean as in the equation.
d = (a + b + c) / ((a / 7.18) + (b / 5.95) + (c / 5.67)) (2)
(2) Open pore ratio It calculated by the equation (4) from the sintered body volume calculated by the Archimedes method and the open pore volume calculated by the equation (3).
Open pore volume = (wet weight-dry weight) / density of water (3)
Open pore rate =
(Open pore volume / (sintered body volume + open pore volume)) × 100 (%) (4)
(3) Crystallite diameter The X-ray diffraction pattern of the mixed powder was measured under the following conditions, and the crystallite diameter was calculated from the Scherrer equation using the obtained 102 peaks of zinc oxide.
Scanning method: Step scan method (FT method)
X-ray source: CUKα
Power: 40kV, 40mA
Step width: 0.01 °
Measurement range: Zinc oxide (102 peak) 46.8 ° ≦ 2θ ≦ 48.2 °
(4) X-ray diffraction measurement An arbitrary 10 places after grinding 0.5 mm or more from the outermost surface were sampled, and an X-ray diffraction pattern in the range of 2θ = 20 to 70 ° of the mirror-polished sintered body sample was as follows. And was compared with a diffraction pattern of InGaZnO ₄ (see Materials Data Inc. JADE7 (ver. 7j) File No. 00-038-1104).
Scanning method: Step scan method (FT method)
X-ray source: CuKα
Power: 40kV, 40mA
Step width: 0.02 °
(5) Observation of microcracks Sampling is performed at 10 arbitrary positions after grinding 0.5 mm or more from the outermost surface. In order to prevent the occurrence of cracks in the mechanical polishing stage, an observation surface was created by a cross-sectional ion milling method (apparatus: cross section polisher IB-09020CP manufactured by JEOL), and then a conductive coating (osmium coating) was applied to the observation surface. Later, observations were made.
Equipment: FE-SEM (JSM-7600F made by JEOL)
Acceleration voltage: 10 kV (magnification: 1500 times)
Detector: Backscattered electron detector measurement method: Counts the number of cracks having a length of 3 μm or more in an arbitrary region of 60 μm × 80 μm. When it is recognized that the end of the crack is connected to the end of one or more other cracks, they are combined and counted as one. When it is recognized that two or more cracks intersect, each is counted independently.
(6) Fracture strength A sample having the following dimensions was cut out from the sintered body after grinding 0.5 mm or more from the outermost surface, and measured according to JIS R 1601.
Test method: 3-point bending test fulcrum distance: 30 mm
Sample size: 3 x 4 x 40 mm
Head speed: 0.5 mm / min
(7) Volume expansion coefficient In this invention, the volume expansion of the molded object which generate | occur | produces at the time of temperature rising is defined as a volume expansion coefficient. The volume expansion coefficient in the present invention is a value calculated by the following procedure. A sample having a diameter of 28 to 30 mm and a thickness of 6 to 8 mm after cold isostatic pressing (CIP) at 2000 kg / cm ² is used as a measurement sample. Firing is performed at a predetermined firing temperature T by a general atmospheric pressure firing method. The volume expansion coefficient is calculated as α = (L−L ₀ ) / L ₀ × 100 (%) from the diameter L of the sintered body at the firing temperature T with the diameter before firing as L ₀ . The firing conditions are such that the temperature rise rate and the temperature fall rate are both 100 ° C./h, the holding time at the temperature T is 1 hour, and the atmosphere is fired in an air atmosphere. By changing the firing temperature T in steps of 20 ° C., plotting the volume expansion coefficient at each firing temperature T and performing smoothing, a volume expansion coefficient profile in a predetermined temperature range is obtained.
(8) Average particle diameter (D50)
Measuring device: Laser diffraction particle size distribution measuring device (Salazu-7100, manufactured by Shimadzu Corporation)
Measurement method: 0.3 to 0.5 g of the weighed raw material powder is put into 30 ml of a sodium hexametaphosphate solution (0.2%), and measured after being dispersed for 1 minute at an output of 200 W with an ultrasonic disperser.

(Preparation of mixed powder by bead mill treatment)
15.0 kg of indium oxide powder, gallium oxide powder, and zinc oxide powder having a purity of 99.99% or more were weighed so that In: Ga: Zn = 1: 1: 1 in terms of atomic ratio of metal elements. The weighed powder was slurried with 10 kg of pure water, and 90 g (0.6 wt%) of a polyacrylate dispersant was added to prepare a slurry having a solid content concentration of 60%. A bead mill with an internal volume of 2.5 L is filled with 80% φ0.3 mm zirconia beads, and the slurry is circulated through the mill at a mill peripheral speed of 7.5 m / sec and a slurry supply rate of 2.5 L / min. Processed. Furthermore, by controlling the temperature of the slurry supply tank within the range of 10 ° C. to 12 ° C. and the temperature of the slurry outlet within the range of 18 ° C. to 20 ° C. Different mixed powders were prepared. Then, after the obtained slurry was spray-dried, a sample for measuring the volume expansion coefficient was prepared, and the volume expansion coefficient was measured by the method described above. Table 1 shows the properties of the mixed powder according to the number of passes.

（実施例１）
成形型に条件１の混合粉末をタッピングしながら充填し、２ｔｏｎ／ｃｍ^２の圧力でＣＩＰ処理して平板型成形体を３枚と円筒型成形体を３個得た。次にこの成形体を抵抗加熱型の電気炉にセットし、アルミナ製のセッターの上に設置して、下記条件にて焼成し、概寸：縦４２０ｍｍ×横３１０ｍｍ×厚さ６ｍｍの平板型焼結体（ターゲット面の面積：１３０２ｃｍ^２）３枚と、外径９１ｍｍ×高さ１７０ｍｍ×厚さ７ｍｍ（ターゲット面の面積：４８６ｃｍ^２）の円筒型焼結体を３個得た。
（焼成条件）
焼成温度：１３７５℃
保持時間：３０分
昇温速度：３００℃〜７５０℃ ２００℃／ｈ
１０００℃〜１２００℃ ２００℃／ｈ
その他の昇温領域 ２００℃／ｈ
雰囲気 ：大気
降温速度：３００℃／ｈ（１４００℃から４００℃の間）
得られた焼結体の相対密度を測定した結果、相対密度の平均は９８．７％であり、焼成割れを目視で観察した結果、平板型の焼結体には割れは認められなかった。円筒型の焼結体においては、３個中１個に僅かなクラックが発生していた。得られた平板型の焼結体の内１枚について、微小クラック本数、Ｘ線ピーク強度比、オープンポア率、抗折強度を測定した結果を表２に示す。

Example 1
The mixed powder of Condition 1 was filled in the mold while tapping, and CIP treatment was performed at a pressure of ² ton / cm ² to obtain three flat mold bodies and three cylindrical mold bodies. Next, this compact is set in a resistance heating type electric furnace, placed on an alumina setter, and fired under the following conditions. The approximate dimensions are 420 mm x 310 mm x 6 mm thick Three pieces of the sintered body (the area of the target surface: 1302 cm ² ) and three cylindrical sintered bodies having an outer diameter of 91 mm × height of 170 mm × thickness of 7 mm (target surface area: 486 cm ² ) were obtained.
(Baking conditions)
Firing temperature: 1375 ° C
Holding time: 30 minutes Temperature rising rate: 300 ° C to 750 ° C 200 ° C / h
1000 ° C to 1200 ° C 200 ° C / h
Other temperature rising range 200 ℃ / h
Atmosphere: Air cooling rate: 300 ° C / h (between 1400 ° C and 400 ° C)
As a result of measuring the relative density of the obtained sintered body, the average of the relative density was 98.7%. As a result of visually observing the fired cracks, no cracks were observed in the flat plate-type sintered body. In the cylindrical sintered body, a slight crack occurred in one of the three. Table 2 shows the results of measuring the number of microcracks, the X-ray peak intensity ratio, the open pore ratio, and the bending strength of one of the obtained flat plate-type sintered bodies.

Next, the obtained flat plate-shaped sintered body was processed to 101.6 mmΦ × 6 mmt, and then bonded to an oxygen-free copper backing plate with indium solder to obtain a sputtering target. Using this target, sputtering was performed under the following conditions to form an IGZO film on the glass substrate.
(Sputtering conditions)
Gas: Argon, oxygen (10%)
Pressure: 0.3Pa
Power supply: DC
Input power: 500 W (5.3 W / cm ² )
Target rotation: 5rpm
(Evaluation method of thin film fluctuation)
In order to evaluate the change over time of composition variation, Seiko Instruments Inc. ICP (inductive) was used for the IGZO thin film formed at a target usage rate of 10% between 0% (initial) and 100% (life end). The In: Ga: Zn ratio in the thin film was measured using a combined argon plasma) emission spectrometer and an ICP mass spectrometer manufactured by PerkinElmer. From the average value [Zn] ave (mol%), the maximum value [Zn] max (mol%) and the minimum value [Zn] min (mol%) of the obtained analysis results, the composition fluctuation rate is calculated from the following formula (5). Calculated.
Composition variation rate (%) = ([Zn] max− [Zn] min) / [Zn] ave × 100 (%)
... (5)
The calculated composition variation rate was less than 5%, and no significant thin film composition variation was observed.

(Example 2)
Using the mixed powder of Condition 2, three flat plate molded bodies and three cylindrical molded bodies were obtained in the same manner as in Example 1. Next, this compact is set in a resistance heating type electric furnace, placed on an alumina setter, and fired under the following conditions. The approximate dimensions are 420 mm x 310 mm x 6 mm thick Three pieces of the sintered body (the area of the target surface: 1302 cm ² ) and three cylindrical sintered bodies having an outer diameter of 91 mm × height of 170 mm × thickness of 7 mm (target surface area: 486 cm ² ) were obtained.
(Baking conditions)
Firing temperature: 1375 ° C
Holding time: 10 minutes Temperature rising rate: 300 ° C. to 750 ° C. 200 ° C./h
1000 ° C to 1200 ° C 200 ° C / h
Other temperature rising range 200 ℃ / h
Atmosphere: Air cooling rate: 300 ° C / h (between 1400 ° C and 400 ° C)
As a result of measuring the relative density of the obtained sintered body, the average of the relative density was 98.8%. As a result of visually observing the fired cracks, no cracks were observed in the flat plate-type sintered body. In the cylindrical sintered body, a slight crack occurred in one of the three. Table 2 shows the results of measuring the number of microcracks, the X-ray peak intensity ratio, the open pore ratio, and the bending strength of one of the obtained sintered bodies.

  Further, a sputtering target was prepared in the same manner as in Example 1, and the fluctuation of the thin film composition after the sputtering film formation was evaluated. As a result, the composition variation rate was less than 5%, and no significant thin film composition variation was observed.

(Example 3)
Using the mixed powder of Condition 2, three flat plate molded bodies and three cylindrical molded bodies were obtained in the same manner as in Example 1. Next, this compact is set in a resistance heating type electric furnace, placed on an alumina setter, and fired under the following conditions. The approximate dimensions are 420 mm x 310 mm x 6 mm thick Three pieces of the sintered body (the area of the target surface: 1302 cm ² ) and three cylindrical sintered bodies having an outer diameter of 91 mm × height of 170 mm × thickness of 7 mm (target surface area: 486 cm ² ) were obtained.
(Baking conditions)
Firing temperature: 1375 ° C
Holding time: 60 minutes Temperature rising rate: 300 ° C. to 750 ° C. 200 ° C./h
1000 ° C to 1200 ° C 200 ° C / h
Other temperature rising range 200 ℃ / h
Atmosphere: Air cooling rate: 300 ° C / h (between 1400 ° C and 400 ° C)
As a result of measuring the relative density of the obtained sintered body, the average of the relative density was 99.1%. As a result of visually observing the fired cracks, no cracks were observed in the flat plate-type sintered body. In the cylindrical sintered body, a slight crack occurred in one of the three. Table 2 shows the results of measuring the number of microcracks, the X-ray peak intensity ratio, the open pore ratio, and the bending strength of one of the obtained sintered bodies.

  Further, a sputtering target was prepared in the same manner as in Example 1, and the fluctuation of the thin film composition after the sputtering film formation was evaluated. As a result, the composition variation rate was less than 5%, and no significant thin film composition variation was observed.

Example 4
Using the mixed powder of condition 3, three plate-shaped molded bodies and three cylindrical molded bodies were obtained in the same manner as in Example 1. Next, this compact is set in a resistance heating type electric furnace, placed on an alumina setter, and fired under the following conditions. The approximate dimensions are 420 mm x 310 mm x 6 mm thick Three pieces of the sintered body (the area of the target surface: 1302 cm ² ) and three cylindrical sintered bodies having an outer diameter of 91 mm × height of 170 mm × thickness of 7 mm (target surface area: 486 cm ² ) were obtained.
(Baking conditions)
Firing temperature: 1375 ° C
Holding time: 30 minutes Temperature rising rate: 300 ° C to 750 ° C 200 ° C / h
1000 ° C to 1200 ° C 200 ° C / h
Other temperature rising range 200 ℃ / h
Atmosphere: Air cooling rate: 300 ° C / h (between 1400 ° C and 400 ° C)
As a result of measuring the relative density of the obtained sintered body, the average of the relative density was 99.2%. As a result of visually observing the fired cracks, no cracks were observed in the flat plate-type sintered body. In the cylindrical sintered body, a slight crack occurred in one of the three. Table 2 shows the results of measuring the number of microcracks, the X-ray peak intensity ratio, the open pore ratio, and the bending strength of one of the obtained sintered bodies.

  Further, a sputtering target was prepared in the same manner as in Example 1, and the fluctuation of the thin film composition after the sputtering film formation was evaluated. As a result, the composition variation rate was less than 5%, and no significant thin film composition variation was observed.

(Example 5)
Using the mixed powder of condition 4, three flat molded bodies and three cylindrical molded bodies were obtained in the same manner as in Example 1. Next, this compact is set in a resistance heating type electric furnace, placed on an alumina setter, and fired under the following conditions. The approximate dimensions are 420 mm x 310 mm x 6 mm thick Three pieces of the sintered body (the area of the target surface: 1302 cm ² ) and three cylindrical sintered bodies having an outer diameter of 91 mm × height of 170 mm × thickness of 7 mm (target surface area: 486 cm ² ) were obtained.
(Baking conditions)
Firing temperature: 1375 ° C
Holding time: 30 minutes Temperature rising rate: 300 ° C to 750 ° C 400 ° C / h
1000 ° C to 1200 ° C 400 ° C / h
Other temperature rising range 400 ℃ / h
Atmosphere: Air cooling rate: 300 ° C / h (between 1400 ° C and 400 ° C)
As a result of measuring the relative density of the obtained sintered body, the average of the relative density was 99.1%. As a result of visually observing the fired cracks, no cracks were observed in both the flat and cylindrical sintered bodies. . Table 2 shows the results of measuring the number of microcracks, the X-ray peak intensity ratio, the open pore ratio, and the bending strength of one of the obtained sintered bodies.

  Further, a sputtering target was prepared in the same manner as in Example 1, and the fluctuation of the thin film composition after the sputtering film formation was evaluated. As a result, the composition variation rate was less than 5%, and no significant thin film composition variation was observed.

(Comparative Example 1)
Three flat molded bodies were obtained in the same manner as in Example 1 using the mixed powder of Condition 5. Next, this compact is set in a resistance heating type electric furnace, placed on an alumina setter, and fired under the following conditions. The approximate dimensions are 420 mm x 310 mm x 6 mm thick Three sheets (area of target surface: 1302 cm ² ) were obtained.
(Baking conditions)
Firing temperature: 1375 ° C
Holding time: 30 minutes Temperature rising rate: 300 ° C to 750 ° C 200 ° C / h
1000 ° C to 1200 ° C 200 ° C / h
Other temperature rising range 200 ℃ / h
Atmosphere: Air cooling rate: 300 ° C / h (between 1400 ° C and 400 ° C)
As a result of measuring the relative density of the obtained sintered body, the average of the relative density was 96.6%, and as a result of visually observing the fired cracks, cracks occurred in two of the three sheets. Table 2 shows the results of measuring the number of microcracks, the X-ray peak intensity ratio, the open pore ratio, and the bending strength of one of the obtained sintered bodies.

  Further, a sputtering target was prepared in the same manner as in Example 1, and the fluctuation of the thin film composition after the sputtering film formation was evaluated. As a result, the composition fluctuation rate was 11.7%, and a clear thin film composition fluctuation was recognized.

(Comparative Example 2)
Using the mixed powder of Condition 5, three flat molded bodies and three cylindrical molded bodies were obtained in the same manner as in Example 1. Next, this compact is set in a resistance heating type electric furnace, placed on an alumina setter, and fired under the following conditions. The approximate dimensions are 420 mm x 310 mm x 6 mm thick Three pieces of the sintered body (the area of the target surface: 1302 cm ² ) and three cylindrical sintered bodies having an outer diameter of 91 mm × height of 170 mm × thickness of 7 mm (target surface area: 486 cm ² ) were obtained.
(Baking conditions)
Firing temperature: 1425 ° C
Holding time: 120 minutes Temperature rising rate: 300 ° C. to 750 ° C. 200 ° C./h
1000 ° C to 1200 ° C 200 ° C / h
Other temperature rising range 200 ℃ / h
Atmosphere: Air cooling rate: 300 ° C / h (between 1400 ° C and 400 ° C)
As a result of measuring the relative density of the obtained sintered body, the average of the relative density was 99.0%. As a result of visually observing the firing cracks, in the flat plate-type sintered body, two of the three were cylindrical. In the mold sintered body, cracks occurred in all three. Table 2 shows the results of measuring the number of microcracks, the X-ray peak intensity ratio, the open pore ratio, and the bending strength of one of the obtained sintered bodies.

  Further, a sputtering target was prepared in the same manner as in Example 1, and the fluctuation of the thin film composition after the sputtering film formation was evaluated. As a result, the composition fluctuation rate was 14.9%, and a clear thin film composition fluctuation was recognized.

(Comparative Example 3)
Three flat molded articles were obtained in the same manner as in Example 1 using the mixed powder of Condition 6. Next, this compact is set in a resistance heating type electric furnace, placed on an alumina setter, and fired under the following conditions. The approximate dimensions are 420 mm x 310 mm x 6 mm thick Three sheets (area of target surface: 1302 cm ² ) were obtained.
(Baking conditions)
Firing temperature: 1425 ° C
Holding time: 120 minutes Temperature rising rate: 300 ° C. to 750 ° C. 200 ° C./h
1000 ° C to 1200 ° C 200 ° C / h
Other temperature rising range 200 ℃ / h
Atmosphere: Air cooling rate: 300 ° C / h (between 1400 ° C and 400 ° C)
As a result of measuring the relative density of the obtained sintered body, the average of the relative density was 98.3%, and as a result of visually observing the fired cracks, cracks occurred in one of the three sheets. Table 2 shows the results of measuring the number of microcracks, the X-ray peak intensity ratio, the open pore ratio, and the bending strength of one of the obtained sintered bodies.

  Further, a sputtering target was prepared in the same manner as in Example 1, and the fluctuation of the thin film composition after the sputtering film formation was evaluated. As a result, the composition variation rate was 12.1%, and a clear thin film composition variation was observed.

Claims (8)

An oxide sintered body containing at least In, Ga, and Zn, has a homologous crystal structure represented by InGaZnO ₄ , and has an incident angle (2θ) in X-ray diffraction of 30.3 ° to 30.9. When the diffraction intensity at 1 ° is I1, and the diffraction intensity at 31.1 ° to 31.5 ° is I2, the diffraction intensity ratio I1 / I2 is 0.85 or more and 1.25 or less. Union.   2. The oxide sintered body according to claim 1, wherein the number of microcracks having a length of 3 μm or more existing in the range of 60 μm × 80 μm in the oxide sintered body is 20 or less. The oxide sintered body according to any one of claims 1-2 in which the area of the target surface of a flat plate shape is 1302Cm ² or more, or an area of the target surface is characterized by a cylindrical shape is 486cm ² or more .   The oxide sintered body according to any one of claims 1 to 3, wherein the bending strength of the oxide sintered body is 100 MPa or more.   A sputtering target using the oxide sintered body according to claim 1 as a target material.   6. The sputtering target according to claim 5, wherein the composition fluctuation rate of zinc element in the IGZO thin film formed by sputtering is less than 5%. In an oxide sintered body containing at least In, Ga, and Zn and having a homologous crystal structure represented by InGaZnO ₄ , an oxide powder of each element is subjected to a wet medium mill treatment. The specific surface area of the mixed powder obtained by the above is 12.0 to 15.0 m ² / g and the average particle size is in the range of 0.35 to 0.45 μm, and the crystallite diameter of zinc oxide in the mixed powder is 60 nm. The method for producing an oxide sintered body according to claim 1, wherein the following mixed powder is used.   In the mixed powder, a mixed powder having a volume expansion coefficient of 2.1% or less in a temperature region of 300 to 750 ° C. and a volume expansion coefficient of 4.2% or less in a temperature region of 1000 to 1200 ° C. is used. The method for producing an oxide sintered body according to claim 7, wherein:

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