JP2022159633A - Igzo sintered body, manufacturing method thereof, and sputtering target - Google Patents

Abstract

To provide an IGZO sintered body having high density and deflective strength and less breakage when used as a sputtering target, and a manufacturing method thereof.SOLUTION: Disclosed is an oxide sintered body involving In, Ga, and Zn, wherein the sintered body is characterized by having a homologous crystal structure represented by InGaZnO4 and having a carbon content in the sintered body of 0.005 wt.% or under, a crystal grain size of 5 μm or under, and a relative density of the sintered body of 98% or over.SELECTED DRAWING: Figure 1

Description

The present invention relates to a sputtering target used for forming an In--Ga--Zn--O (IGZO) semiconductor thin film composed of indium, gallium, zinc and oxygen used in a thin film transistor (TFT), and a method for producing the same.

In recent years, various flat panel displays (FPDs) such as organic electroluminescence (EL) and flexible displays have been proposed, and TFTs capable of forming thin films at low temperatures and having relatively high mobility are desired. An IGZO semiconductor thin film can be formed at a lower temperature than a crystalline silicon thin film and has a higher mobility than an amorphous silicon thin film. 2). In addition, since the IGZO film has visible transparency, it is used in a wide variety of applications such as switching elements such as liquid crystal display elements and drive circuit elements. For such applications, a thin film material having as high a transmittance as possible is desired.

A sputtering method is used for the formation of these IGZO thin films because it is easy to increase the area and obtain a high-performance film. In general, an IGZO sintered compact is used as a target for both flat-plate sputtering targets and cylindrical sputtering targets. As IGZO sintered bodies, those having a homologous crystal structure with a layered structure are mainly used. When the stress concentrates on a specific portion, there is a problem that the target tends to crack due to the stress.

As a method for improving the strength of the IGZO sintered body, Patent Document 3 discloses increasing the bending strength to 58 MPa by using a crystal phase containing a spinel structure. Further, in Patent Document 4, a bending strength of 14.3 kg/mm ² (about 140 MPa) is obtained by using a crystal phase containing a spinel structure and a bixbite. However, since the composition of the IGZO film is limited by these methods, the composition ratio of In, Ga, and Zn in the IGZO sintered body cannot be determined appropriately for optimizing the film characteristics. A method for increasing the strength of a sintered body without depending on the composition ratio of the body has been desired. In particular, in the case of a composition ratio that results in only a homologous crystal structure, the strength of the sintered body is remarkably low.

It is known that increasing the density of the sintered body is effective as a method of improving the strength of the sintered body. It is difficult to obtain a high-density sintered body because it tends to remain inside the compact. In Patent Document 5, a sintered body with a density of 98% is obtained by setting the sintering holding time to 20 hours or longer. However, since the crystal growth of the sintered body is promoted, the grain size increases to 7 μm or more. strength is low. In particular, in the case of a sintered body having only a layered structure such as a homologous structure, the strength tends to be further reduced.

In addition, a method of adding impurities to a sintered body to improve its properties is also known. The resistance (bulk resistance) of the IGZO film is reduced to less than 1×10 ⁻³ Ω·cm to reduce arcing. Not an effective method.

JP-A-2000-044236 JP-A-2004-103957 JP 2008-163441 A Patent International Publication No. 2011/040028 Patent International Publication No. 2009/157535 Patent WO2008/072486 Patent International Publication No. 2009/157535

An object of the present invention is to provide an IGZO sintered body containing few impurities, having high density and bending strength, and hardly cracking even when used as a sputtering target, and a method for producing the same.

As a result of extensive studies, the present inventors have found that a sintered body having a homologous crystal structure represented by InGaZnO has a carbon content of 0.005 wt% or less, a crystal grain size of ₅ μm or less, and is sintered. The relative density of the body is 98% or more to increase the bending strength, and even a large sintered body does not crack during grinding, and it can be used as a cylindrical sputtering target that can be applied with high power. The inventors have found that a sputtering target exhibiting excellent high-power durability without cracking even when the target is subjected to pressure has been found, and the present invention has been completed.

Aspects of the present invention are as follows.
(1) An oxide sintered body containing In, Ga, and Zn, having a homologous crystal structure represented by _InGaZnO4 , and having a carbon content of 0.005 wt% or less in the sintered body, A sintered body having a grain size of 5 μm or less and a relative density of 98% or more.
(2) The sintered body according to (1), which has a bending strength of 150 MPa or more.
(3) The sintered body according to (1) or (2), wherein the target surface area is 200 cm ² or more and the shape is a flat plate.
(4) The sintered body according to (1) or (2), wherein the target surface area is 486 cm ² or more and the shape is cylindrical.
(5) A sputtering target using the sintered body according to any one of (1) to (4) as a target material.
(6) A compact obtained by mixing raw material powders containing In, Ga, and Zn with a hydrocarbon-based compound content of 0.6% or less, filling the mold, and molding by cold isostatic pressing. A method of manufacturing a sintered body using Molding using a molding die having a bottom plate provided in contact and having a structure in which the formwork members constituting the knockdown formwork can be moved in accordance with the expansion of the molded body that occurs when the pressure is reduced after the completion of pressurization. and firing the obtained molded body.
(7) A mold is used in which a bottom plate provided in contact with the knockdown form cannot move along the inner surface of the knockdown form (6). The method for producing a sintered body according to 1.
(8) The method for producing a sintered body according to (6) or (7), wherein the bottom plate is made of a material that undergoes less compression deformation than the upper punch.
(9) The method for producing a sintered body according to any one of (6) to (8), characterized in that the molded body is fired using electromagnetic wave heating.

The present invention will be described in detail below.

The IGZO sintered body of the present invention is a sintered body containing indium, gallium, zinc and oxygen and having a homologous crystal structure represented by InGaZnO ₄ . The term “sintered body having a homologous crystal structure represented by InGaZnO ₄ ” as used in the present invention means that the X-ray diffraction pattern matches the diffraction pattern of InGaZnO ₄ and does not contain peaks not attributed to the diffraction pattern of InGaZnO 4 . means.

According to the present invention, the carbon content in the IGZO sintered body having a homologous crystal structure represented by _InGaZnO4 is 0.005 wt% or less, the crystal grain size is 5 μm or less, and the sintered body When the relative density is 98% or more, the IGZO sintered body has high bending strength and less cracks even when used as a sputtering target.

The carbon content of the IGZO sintered body of the present invention is 0.005 wt% or less, preferably 0.003 wt% or less, more preferably 0.001 wt% or less. By doing so, it is possible to reduce the occurrence of cracks originating from carbon.

The grain size of the IGZO sintered body of the present invention is 5 μm or less, preferably 4.5 μm or less, more preferably 4 μm or less. It is preferably 0.1 μm or more, particularly preferably 1 μm or more. The smaller the crystal grain size of the sintered body is, the smaller the crystal grain size is, the better, because when the sintered body is used as a sputtering target, the elements are uniformly ejected from the target.

The IGZO sintered body of the present invention has a relative density of 98% or more, preferably 99% or more. If a sintered body with a relative density of less than 98% is used as a target, abnormal discharge may easily occur during sputtering, and particles generated by abnormal discharge may deteriorate the quality of the film and reduce the yield. because there is

Furthermore, in the IGZO sintered body of the present invention, the ratio of the number of pores existing at the grain boundaries to the number of pores existing within the crystal grains (the number of pores at the grain boundaries/the number of pores within the crystal grains) is 0.5 or more. is preferably When the IGZO sintered body has a homologous crystal structure, it has a layered structure within the crystal grains. This layered structure can be easily confirmed by etching the mirror-polished surface of the sintered body. There are many. Therefore, the presence of pores in the crystal grains becomes a source of fracture and significantly reduces the strength of the sintered body. Therefore, it is better to reduce the number of pores existing in the grain, and the ratio of the pores existing in the grain boundary to the pores in the grain (the number of pores in the grain boundary / the number of pores in the grain) can effectively increase the strength of the sintered body. The ratio of pores existing at grain boundaries and within grains (number of pores at grain boundaries/number of pores within grains) is preferably 0.5 or more, more preferably 1 or more, and still more preferably 3 or more. .

The bending strength of the IGZO sintered body of the present invention is preferably 150 MPa or more. If the strength of the sintered body is high, cracks are less likely to occur even during grinding, and the productivity is high because the yield is high. Furthermore, even when used in a cylindrical sputtering target to which high power is applied during sputtering, cracking is less likely to occur. In addition, in the present invention, the bending strength was measured according to the three-point bending test of JISR1601.

The IGZO sintered body of the present invention has a target surface area of 200 cm ² or more, preferably 400 cm ² or more, more preferably 600 cm ² or more, and particularly preferably 1200 cm ² or more. , cylindrical. In particular, it is preferable that the target surface area is 1302 cm ² or more and the shape is a flat plate or the target surface area is 486 cm ² or more and the shape is a cylinder.

In addition, the ratio of indium, gallium and zinc in the IGZO sintered body of the present invention is not particularly limited as long as it is a composition that produces a homologous crystal structure represented by _InGaZnO4 . :Zn=1:1:1.

The IGZO sintered body of the present invention may contain metal impurities such as iron in addition to carbon, and the content of the metal impurities is preferably 50 ppm or less, more preferably 30 ppm or less, and particularly preferably 20 ppm or less.

Next, the method for producing the IGZO sintered body of the present invention will be described.

In the method for producing an IGZO sintered body of the present invention, raw material powders containing In, Ga, and Zn are mixed (raw material mixing step), filled in a mold, and cold isostatically pressed to form a compact. A manufacturing method for a sintered body using a collapsible form comprising a plurality of form members, an upper punch provided movably along the inner surface of the collapsible form, and contacting the collapsible form Molding using a mold having a bottom plate provided at the end of pressurization and having a structure in which the formwork members constituting the knockdown formwork can move in accordance with the expansion of the molded body that occurs when the pressure is reduced after the end of pressurization ( molding step) and firing the obtained compact (firing step). Each step will be described in detail below.

(1) Raw material mixing step The raw material powder is not particularly limited, and for example, it is possible to use metal salt powder such as indium, gallium, zinc chloride, nitrate, carbonate, etc. Considering ease of handling, Oxide powders are preferred.

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

The composition of these raw materials is not particularly limited as long as it has a composition that produces a homologous crystal structure represented by _InGaZnO4 , and the composition is In:Ga:Zn = 1:1:1 in terms of the atomic ratio of the metal elements. is preferred.

If the raw material powder has a large crystallite size, it may be locally heated during firing, resulting in cracking or abnormal grain growth. When the crystallite size of the raw material powders is larger than 60 nm, it is possible to grind the raw material powders in advance before mixing them, or to grind them simultaneously during powder treatment during mixing. Since pulverization and mixing of the raw material powder are often performed using the same apparatus, it is preferable to perform pulverization and mixing at the same time in consideration of simplification of the manufacturing process.

The method of pulverizing and mixing these powders is not particularly limited, and includes dry and wet media stirring mills using balls and beads of zirconia, alumina, nylon resin, etc., and medialess vessel rotating and mechanical stirring types. and pulverization and mixing methods such as an airflow method are exemplified. Specific examples include ball mills, bead mills, attritors, vibration mills, planetary mills, jet mills, and twin-screw planetary stirring mixers. Among them, if hydrocarbon impurities from the container or grinding media are mixed in, they will remain during sintering. Therefore, it is preferable to use a dry or wet grinding and mixing method using a ceramic container and ceramic media, and more preferably a wet method. A mixture of types is preferred.

Even if the crystallite size is reduced by pulverization, the presence of aggregates of the powder may not sufficiently increase the density after firing. The particle size of the powder is preferably 1.0 μm or less, more preferably 0.1 to 1.0 μm as an average particle size measured by a laser diffraction/scattering method. Moreover, the specific surface area of the powder measured by the BET method is preferably 11 m ² /g or more, more preferably 12 m ² /g or more. By doing so, it is possible to obtain a sintered body with small sintered particles and high sintered density. When wet method ball mills, bead mills, attritors, vibration mills, planetary mills, jet mills, etc. are used, it is necessary to dry the slurry after pulverization. Although the drying method is not particularly limited, for example, filter drying, fluidized bed drying, spray drying and the like can be exemplified.

In the case of using a powder other than the oxide powder or in the case of forming InGaZnO ₄ in advance to facilitate firing, calcination can be performed at 900 to 1200° C. after mixing. When calcined powder is used, it is preferably pulverized to an average particle size of 1.0 μm or less, more preferably 0.1 to 1.0 μm. In the molding process, it is preferable not to add molding aids such as polyvinyl alcohol, acrylic polymers, methyl cellulose, waxes, and hydrocarbon compounds such as oleic acid to the raw material powder as much as possible. It is preferable to use the minimum amount of hydrocarbon-based compound as a dispersant necessary for slurrying, and it is more preferable not to use a dispersant.

The content of the hydrocarbon compound in the raw material powder is preferably 0.6 wt% or less, more preferably 0.3 wt% or less, still more preferably 0.2 wt% or less, still more preferably 0.1 wt% or less, especially , it is more preferable that the raw material powder does not contain a hydrocarbon-based compound.

(2) Forming process As the forming method, it is possible to appropriately select a forming method capable of forming the raw material powder (calcined mixed powder when calcined) into the desired shape. A method for manufacturing a sintered body using a molded body formed by the A molding having a bottom plate provided in contact with a collapsible formwork, and having a structure in which the formwork members constituting the collapsible formwork can be moved in accordance with the expansion of the molded body that occurs when the pressure is reduced after the completion of pressurization. use the mold. In addition, it is preferable that the bottom plate is configured so as not to be able to move along the inner surface of the knockdown formwork. In addition, the bottom plate or the lower punch is preferably made of a material that undergoes less compression deformation than the upper punch. Particularly, the bottom plate or the lower punch is made of metal, and the upper punch is made of resin. preferable.

The molding die is a molding die for producing a compact by filling the raw material powder in the molding die and compressing it. The mold for compression molding is characterized in that it has a structure capable of isotropically releasing the pressure substantially isotropically with respect to the molding when the pressure is reduced after the completion of the pressurization. In addition, when molding is performed with the plate surface of the formed body horizontal, the force due to the weight of the formed body and the weight of the upper punch acts on the formed body. Since the area of is large, the pressure due to these forces can be neglected.

Further, in the mold of the present invention, at least a part of the formwork members constituting the knockdown formwork engages with the ends of the adjacent formwork members, and under pressure during molding, the knockdown formwork It is preferable to have a structure at the end portion for limiting the shape of the opening of the raw material powder filling chamber formed by to not be smaller than a predetermined size. In the present invention, the raw material powder filling chamber means the space formed by the inner surface of the knockdown mold, the bottom surface of the upper punch, and the upper surface of the bottom plate (or lower punch). The cross-sectional shape on the plane parallel to the bottom surface of is referred to as the opening shape of the raw powder filling chamber or the opening shape of the prefabricated formwork.

Further, the surfaces of the bottom plate and the upper punch that come into contact with the raw material powder may each be composed of one flat surface, and the bottom plate is composed of a plurality of mutually movable bottom plate constituting members, and is in contact with the raw material powder of the bottom plate. The surface may have at least one recess. Similarly, the upper punch may be composed of a plurality of mutually movable upper punch constituent members, and may have at least one concave portion on the surface of the upper punch that is in contact with the raw material powder.

The molding pressure is not particularly limited as long as the molded body does not cause cracks or the like and can be handled, and it is preferable to increase the molding density as much as possible. Therefore, the CIP pressure in cold isostatic press (CIP) molding is preferably 1 ton/cm ² or more, more preferably 2 ton/cm ² or more, and particularly preferably 2 to 3 ton/cm ² in order to obtain a sufficient consolidation effect. .

(3) Firing Step Next, the molded body obtained is fired. At the time of firing, it is preferable to use electromagnetic wave heating, and as the firing furnace to be used, various firing furnaces such as batch type, continuous type, and hybrid type with external heating type can be used.

In the case of external heating such as an electric furnace generally used for sintering ceramic materials, sintering progresses from the outer surface of the sintered body. In particular, in a material such as IGZO, which has a high crystal growth rate, pores are likely to be incorporated into the crystal grains (inside the grains), making it difficult to obtain a high-density and uniform sintered body. Furthermore, in the layered and anisotropic crystal structure of IGZO, when primary particles grow, the anisotropy causes gaps between crystal particles (grain boundaries), and pores tend to aggregate to form large pores. Therefore, it is difficult to obtain a sintered body having a high density and a fine structure by external heating such as an electric furnace, particularly for a material such as IGZO, which has anisotropic crystal grain growth. The primary particles referred to here refer to particle diameters observed after cross-sectional polishing and etching of the sintered body.

On the other hand, in the case of self-heating by electromagnetic wave heating, the sintered body itself is heated from the inside, sintering proceeds uniformly from the center of the sintered body in the state of open pores, and the pores are discharged outside the sintered body. Ideal sintering is possible. In addition, even if the sintered body is heated rapidly by electromagnetic waves, the sintered body is heated by self-heating from within itself. Therefore, even large-sized products have little temperature distribution, are less likely to crack during firing, and are evenly heated by self-heating. Therefore, the holding time of firing can be shortened, and the growth of crystal grains can be suppressed.

However, unlike external heating, self-heating by electromagnetic wave heating cannot be applied to any material, and the easiness of heating depends on the electromagnetic wave absorption characteristics of the material to be heated. The electromagnetic wave absorption property is better for a substance with a larger dielectric loss, and a substance with a smaller dielectric loss does not absorb electromagnetic waves and cannot be heated by electromagnetic waves. Although the dielectric loss is determined by each material, the dielectric loss has temperature dependence, and depending on the material, the electromagnetic wave absorption characteristics may vary greatly depending on the temperature. When materials with different electromagnetic wave absorption characteristics coexist, the parts with good absorption characteristics are locally heated, and the parts with poor absorption characteristics are not heated. It causes abnormal grain growth. Therefore, when substances with different electromagnetic wave absorption characteristics coexist, it is difficult to obtain a uniform sintered body without cracks.

In the IGZO sintered body of the present invention, when the raw materials are blended so as to have a composition of In:Ga:Zn=1:1:1 in terms of the atomic ratio of the metal elements, indium oxide, gallium oxide, and zinc oxide are used as raw materials. When used, indium oxide is a substance that easily self-heats with good electromagnetic wave absorption characteristics from low temperature to high temperature near room temperature, but gallium oxide is a substance that has poor electromagnetic wave absorption characteristics and is difficult to self-heat, and zinc oxide is a low-temperature region. is a substance that shows temperature dependence, in which the electromagnetic wave absorption characteristics are poor and the electromagnetic wave absorption characteristics improve when the temperature exceeds a specific temperature. That is, IGZO is a composite material system in which materials with completely different electromagnetic wave absorption characteristics coexist, and when subjected to electromagnetic wave heating as described above, local heating causes cracks and abnormal grain growth, resulting in uniform sintering. It is a material that is difficult to obtain.

However, in the firing of the IGZO sintered body having only the homologous crystal structure represented by _InGaZnO4 , by preparing the powder so that the crystallite diameter obtained from the X-ray diffraction of the raw material powder is 60 nm or less, cracking even under electromagnetic wave heating It becomes possible to obtain a uniform sintered body without In the case of a composite raw material in which a plurality of raw materials are mixed, the crystallite diameter obtained from the X-ray diffraction of the raw material powder referred to in this application is calculated separately from the X-ray diffraction peak derived from the crystal structure of each raw material. It is the maximum value when

Heating using electromagnetic waves causes the dipoles inside the material to vibrate, rotate, collide, and friction due to the absorbed electromagnetic waves, and the material is heated by self-heating. In other words, although self-heating occurs inside the crystal grains, the amount of heat generated is determined by the size of the crystal grains. It is possible to suppress the temperature distribution due to the difference in self-heating. This makes it possible to obtain a uniform sintered body without cracks even in IGZO in which materials with different electromagnetic wave absorption properties coexist.

The IGZO sintered body of the present invention is heated by electromagnetic waves and is uniformly heated by self-heating. It is possible to suppress grain growth and obtain a high-density, high-strength sintered body.

As the electromagnetic waves used in the present invention, continuous or pulsed microwaves such as 2.45 GHz, millimeter waves such as 28 GHz, or submillimeter waves generated from magnetrons or gyrotrons can be used. The frequency of the electromagnetic waves can be selected appropriately according to the electromagnetic wave absorption characteristics of the object to be fired, but considering the economic efficiency such as the cost of the oscillator, microwaves of 2.45 GHz are preferable.

In the case of sintering by electromagnetic waves, the compact is placed on a setter and surrounded by heat insulating material. At this time, it is also possible to install an isothermal heat barrier inside the heat insulating material. Materials having heat resistance at the firing temperature may be selected for the material of the setter and the isothermal heat barrier, such as alumina, mullite, zirconia, and SiC.

The rate of temperature increase during firing is not particularly limited, and in order to obtain a high-strength sintered body, the rate is preferably 20 to 600°C/hour, preferably 100 to 600°C/hour, more preferably 300 to 600°C/hour. time, more preferably 400 to 600° C./hour. Since sintering by electromagnetic waves is heating by self-heating, the temperature distribution in the sintered material is small, and even if a large-sized sintered material is heated at a high rate of temperature rise, cracking is extremely rare. In the case of a molded body containing water or a hydrocarbon-based compound, especially a large-sized molded body, when the water or binder components evaporate, the molded body may crack due to rapid volume expansion. Therefore, in a temperature range where moisture and binder components volatilize, for example, a temperature range of 100 to 400° C., it is preferable to set the heating rate to 20 to 100° C./hour.

The firing temperature is preferably 1300°C to 1500°C. Within this temperature range, the obtained sintered body has a sufficiently homologous crystal structure of InGaZnO ₄ .

The holding time at the firing temperature is not particularly limited, and is preferably within 5 hours. Moreover, the temperature drop rate is preferably 250° C./hour or more, preferably 300° C./hour or more, from the firing temperature to 1100° C. By lowering the temperature in this temperature range at 250° C./hour or more, the amount of oxygen taken into the surface of the sintered body can be reduced, and it is possible to suppress color unevenness on the surface of the sintered body. In other temperature ranges, the cooling rate is not particularly limited, and can be appropriately determined in consideration of the capacity of the sintering furnace, the size and shape of the sintered body, the susceptibility to cracking, and the like.

The atmosphere during firing is not particularly limited, and air or oxygen atmosphere is preferable in order to suppress the sublimation of zinc. Further, for the purpose of suppressing color unevenness on the surface of the sintered body and lowering the specific resistance of the sintered body, a non-oxidizing atmosphere such as nitrogen may be used when the temperature is lowered from the firing temperature.

The obtained sintered body can be ground into a desired shape such as a plate, circle, or cylinder using a machine such as a surface grinder, cylindrical grinder, lathe, cutting machine, or machining center. can. Furthermore, if necessary, a sputtering target using the sintered body of the present invention as a target material can be obtained by bonding to a backing plate or backing tube made of oxygen-free copper, titanium, or the like using indium solder or the like. can be done.

The size of the sintered body is not particularly limited, and since the sintered body according to the present invention has high strength, it is possible to manufacture a large-sized target. In the case of a flat sputtering target, a large sintered body of 100 mm long×200 mm wide (target surface area 200 cm ² ) or more can be produced. The larger the size of the sintered body, the higher the production efficiency. The area is preferably 400 cm ² or more, more preferably 1200 cm ² or more. In the case of a cylindrical sputtering target, a large sintered body having an outer diameter of 91 mmΦ×170 mm (target surface area of 486 cm ² ) or more can be produced. The area of the target surface referred to here means the area of the surface of the sintered body on the sputtering side. In the case of a multi-divided target composed of a plurality of sintered bodies, the area of the target surface of the multi-divided target is the area of the surface of the sintered body on the sputtering side that is the largest among the sintered bodies. do.

Moreover, the thickness of the target is not particularly limited, and is preferably 4 mm or more and 15 mm or less. If the thickness is less than 4 mm, the target utilization rate is low and it is not economical. Further, if the thickness is more than 15 mm, the weight of the sintered body becomes heavy, so handling equipment or the like is required in the targeting process.

The surface roughness of the target is not particularly limited, and the surface roughness (Ra) is preferably 1 μm or more because it takes a long time to reduce the surface roughness and is not economical.

In the present invention, an IGZO sintered body having only a homologous crystal structure represented by InGaZnO ₄ can be obtained as a sintered body having high density and high strength. When such a sintered body is used as a planar sputtering target or a cylindrical sputtering target, it is possible to manufacture a high-quality target with less cracking and less abnormal discharge (arcing). Moreover, since the strength of the sintered body is high, the sintered body can be easily processed, and a large-sized target can be produced with a high yield.

FIG. 5 is a diagram showing the relationship between the bending strength and the pore number ratio (grain boundary/intragranular) of the IGZO sintered bodies obtained in Example 3 and Comparative Example 3; BRIEF DESCRIPTION OF THE DRAWINGS It is a perspective view which shows typically exploded an example of the shaping|molding die of this invention. 1 is a sectional view (side view) showing an exploded example of a mold of the present invention; FIG. 1 is a cross-sectional view (side view) showing an example of a mold of the present invention; FIG. FIG. 3 is a schematic exploded perspective view of another example of the mold of the present invention.

EXAMPLES The present invention will be described in more detail with reference to examples below, but the present invention is not limited to these examples. In addition, each measurement in the present Example was performed as follows.

(1) Density of sintered body The relative density of the sintered body was obtained by measuring the bulk density by the Archimedes method in accordance with JISR1634 and dividing it by the true density. The true density of the sintered body was 6.38 g/cm ³ (see Materials Data Inc. JADE7 (ver.7j) File No. 00-038-1104) calculated from the X-ray diffraction crystal lattice.

(2) Crystallite Size The X-ray diffraction pattern in the range including the main peak of each raw material powder was measured, and the crystallite size was calculated from the X-ray diffraction peak by Scherrer's formula. In the case of a composite raw material obtained by mixing a plurality of raw materials, it was calculated from the peak with the maximum intensity among the X-ray diffraction peaks attributed to the crystal structure of each raw material.
(Measurement conditions for X-ray diffraction test)
Scanning method: Step scan method (FT method)
X-ray source: CUKα
Power: 40kV, 40mA
Step width: 0.01°
(3) X-ray diffraction measurement The X-ray diffraction pattern of the mirror-polished sintered body sample in the range of 2θ = 20 to 70 ° was measured, and the diffraction pattern of InGaZnO ₄ (X-ray diffraction analysis software JADE 7 of Rigaku Co., Ltd.) was measured. .0 database No: 01-070-3626).
(Measurement conditions for X-ray diffraction test)
Scanning method: Step scan method (FT method)
X-ray source: CUKα
Power: 40kV, 40mA
Step width: 0.02°
(4) Average Primary Particle Size A mirror-polished and etched sintered body sample was observed with a scanning electron microscope, and the primary particle size was measured by the diameter method from the obtained sintered body structure image. At least three arbitrary points were observed, 300 or more particles were measured, and the 50% particle size was taken as the average primary particle size.
(Etching conditions)
Solution: 3N hydrochloric acid
Temperature: 50°C
Time: 70 to 80 seconds (scanning electron microscope measurement conditions)
Accelerating voltage: 40kV, 40mA
(5) Number of Pores In the same manner as in (4), the number of pores existing at grain boundaries and within grains was measured from the micrograph of the obtained sintered body. At least three arbitrary points were observed and 500 or more pores were measured.

(6) Bending strength Measured according to JISR1601.
(Measurement conditions for bending strength)
Test method: 3-point bending test Distance between fulcrums: 30 mm
Sample size: 3 x 4 x 40mm
Head speed: 0.5mm/min
(7) Carbon content measurement The carbon content in the sintered body was measured using a carbon content analyzer (manufactured by LECO).

(Examples 1 to 3)
Indium oxide powder, gallium oxide powder, and zinc oxide powder with a purity of 99.99% or more were weighed so that the atomic ratio of the metal elements was In:Ga:Zn=1:1:1. The weighed powder was slurried with pure water, and in a state where the slurry concentration was 50 wt%, zirconia beads of 0.3 mmφ were used to change the number of wet bead mill treatments, and three types of slurries of Examples 1 to 3 were prepared. got At this time, a dispersant (DISPEX (registered trademark) AA 4040/manufactured by BASF) was appropriately added so that the slurry viscosity was 1000 ps or less. The amount added was 0.1 to 0.2 wt % with respect to the total amount of indium oxide, gallium oxide and zinc oxide powder. Next, the slurries subjected to these pulverization treatments were granulated and dried using a spray dryer to obtain raw material powders. Table 1 shows the number of pulverization treatments and the results of measurements such as the crystallite size calculated from the X-ray diffraction of the obtained powder.

Using these powders, a compact of 30 mm×30 mm×10 mmt was produced by a mold press at a pressure of 300 kg/cm ² and then CIP-treated at a pressure of 2 ton/cm ² .

Next, this molded body was placed on an alumina setter in a microwave firing furnace (frequency = 2.45 GHz) and fired under the following conditions to obtain a sintered body.
(Firing conditions)
Firing temperature: 1400°C
Holding time: 1 hour Heating rate: 300°C/hour Atmosphere: Atmospheric cooling rate: 300°C/hour (from 1400°C to 1100°C)
Table 1 shows the results of sintering cracking, relative density, and X-ray diffraction of the obtained sintered body.

(Comparative example 1)
A sintered body was obtained in the same manner as in Example 1, except that the pulverization treatment was performed once with a wet bead mill. Table 1 shows the measurement results of the crystallite size calculated from the X-ray diffraction of the obtained powder, the state of sintering cracks of the obtained sintered body, the relative density, the X-ray diffraction measurement results, and the like.

(Comparative example 2)
The raw material powder was weighed in the same manner as in Example 1, and the weighed powder and iron-cored nylon balls with a diameter of 15 mm were placed in a polyethylene pot and mixed by a dry ball mill for 24 hours to prepare a mixed powder. Table 1 shows the measurement results of the crystallite size calculated from the X-ray diffraction of the obtained powder.

Next, this powder was molded and fired in the same manner as in Example 1. Table 1 shows the results of measurement of the sintered body obtained, such as the state of sintering cracks, relative density, and X-ray diffraction. It was not possible to mix uniformly, and nylon and polyethylene were mixed and the amount of carbon increased.

(Examples 4 to 8)
Using the powder of Example 2, the size of the compact is 120 mm × 210 mm × 10 mm
t (equivalent to a sputtering surface area of 252 cm ² ), and when producing a flat plate-shaped compact, a mold having a size (Fig. 2) that allows the above compact to be obtained is used, and powder is filled in the portion 5, After placing the upper punch 1 and the cushioning material 6, the whole was vacuum-packaged and pressurized at a pressure of 2 ton/cm 2 by a CIP device to obtain a compact. Five types of sintered bodies were obtained in the same manner as in Example 1, except that the microwave firing conditions were partially changed. Table 2 shows the sintering conditions and the measurement results of relative density, crystal grain size, pore number ratio (grain boundary/grain), bending strength, X-ray diffraction, etc. of the obtained sintered body.

(Example 9, Comparative Examples 3 and 4)
A compact was obtained in the same manner as in Example 1, except that the powder of Example 2 was used, the size of the compact was 120 mm×210 mm×10 mmt, and 1% polyvinyl alcohol was added as a binder to the raw materials. Next, this molded body was placed on an alumina setter in an electric furnace and fired under the following conditions except for the firing conditions shown in Table 2. Three kinds of Example 9 and Comparative Examples 3 and 4 A sintered body was obtained.
(Comparative Example 5)
Molding was carried out in the same manner as in Comparative Example 3, except that molding was performed without adding a binder.
(Firing conditions)
Atmosphere: Atmospheric cooling rate: 200°C/hour (from 1400°C to 1100°C)
Table 2 shows the measurement results of the relative density, crystal grain size, pore number ratio (grain boundary/grain), bending strength, X-ray diffraction, etc. of the obtained sintered body.

(Examples 10 to 13)
Sintered bodies were produced in the same manner as in Example 5, except that flat plate-shaped and cylindrical compacts of various sizes were produced. Next, in order to use these sintered bodies as targets, the flat sintered bodies were processed by a surface grinder, and the cylindrical sintered bodies were processed by a cylindrical grinder. No cracks were observed in the sintered body after working. Table 3 shows the sizes of the obtained sintered bodies and the presence or absence of cracks.

Among the produced sintered bodies, the cylindrical sintered bodies of Example 12 were each bonded to a titanium backing tube to form a target, then attached to a rotating cathode type sputtering apparatus, and the remaining thickness was 1 mm under the following conditions. Sputtering was performed. After that, the surface of the target was observed to confirm that no cracks occurred.
(Sputtering conditions)
Gas: Argon, Oxygen (10%)
Pressure: 0.3Pa
Power supply: DC
Input power: 1 kW (10.6 W/cm ² )
Target rotation: 5 rpm
(Comparative Examples 6 and 7)
Sintered bodies were produced in the same manner as in Comparative Example 3, except that flat plate-shaped and cylindrical compacts of various sizes were produced. Next, in order to use these sintered bodies as targets, the flat sintered bodies were processed by a surface grinder, and the cylindrical sintered bodies were processed by a cylindrical grinder. Table 3 shows the sizes of the obtained sintered bodies and the presence or absence of cracks.

Among the prepared sintered bodies, the cylindrical sintered body of Comparative Example 6 was bonded to a titanium backing tube to form a target, and then attached to a rotating cathode type sputtering apparatus under the same conditions as in Example 14. Sputtering was performed. After that, the surface of the target was observed, and it was confirmed that cracks occurred at the initial stage of sputtering (3 kWh).

Reference Signs List 1, 11 Upper punches 2, 12 Prefabricated forms 2a, 12a Formwork members 2b, 12b Formwork members 3, 13 Bottom plates 4, 14 Pedestal 5 Raw material powder 6 Cushioning materials 7, 8 Steps

Claims (9)

An oxide sintered body containing In, Ga, and Zn, having a homologous crystal structure represented by _InGaZnO4 , having a carbon content of 0.005 wt% or less in the sintered body, and having a crystal grain size is 5 µm or less, and the relative density of the sintered body is 98% or more. 2. The sintered body according to claim 1, which has a bending strength of 150 MPa or more. 3. The sintered body according to claim 1, wherein the target surface area is 200 cm< ² > or more and the shape is a flat plate. 3. The sintered body according to claim 1, wherein the target surface has an area of 486 cm ² or more and is cylindrical in shape. A sputtering target using the sintered body according to any one of claims 1 to 4 as a target material. Raw material powders containing In, Ga, and Zn with a hydrocarbon-based compound content of 0.6% or less are mixed, filled in a mold, and molded by cold isostatic pressing to use a compact. A method for manufacturing a sintered body, comprising: a collapsible form comprising a plurality of form members; an upper punch provided movably along an inner surface of the collapsible form; and a molding die having a structure in which the formwork members constituting the knockdown formwork can move in accordance with the expansion of the molded body that occurs when the pressure is reduced after pressurization is completed, and the 5. The method for producing a sintered body according to claim 1, wherein the molded body thus obtained is sintered. 7. The mold according to claim 6, wherein the bottom plate provided in contact with the knockdown formwork is configured so as not to be able to move along the inner surface of the knockdown formwork. A method for producing a sintered body. 8. The method for producing a sintered body according to claim 6, wherein the bottom plate is made of a material that undergoes less compression deformation than the upper punch. 9. The method for producing a sintered body according to any one of claims 6 to 8, wherein the molded body is fired using electromagnetic wave heating.

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