KR102218814B1 - Sintered compact, sputtering target and method for producing sintered compact - Google Patents

Abstract

(Problem) A method for producing a sintered body, a sputtering target, and a sintered body capable of effectively reducing bulk resistance and suppressing the occurrence of abnormal discharge while having an appropriate mechanical strength is provided.
(Solution means) The sintered body of the present invention is a sintered body of an oxide containing In, Ga, and Zn, and is 0.317 <In/(In + Ga + Zn) ≤ 0.350, 0.317 <Ga/(In + Ga + Zn) ≤ 0.350 , And 0.317<Zn/(In+Ga+Zn)≦0.350, a bulk resistance value of 15 mΩcm or more and 25 mΩcm or less, and a break strength of 40 MPa or more and less than 50 MPa.

Description

Sintered compact, sputtering target, and manufacturing method of sintered compact {SINTERED COMPACT, SPUTTERING TARGET AND METHOD FOR PRODUCING SINTERED COMPACT}

The present invention relates to a method for producing a sintered body, a sputtering target and a sintered body, which can be called IGZO, which is suitable for use in the production of various display devices, etc., and provides a technique capable of effectively suppressing abnormal discharge during sputtering. Is to suggest.

In manufacturing a liquid crystal display (LCD), electroluminescence (EL), and other various display device electrodes, and film electrodes such as touch panels and electronic papers mounted on a personal computer or word processor, etc., by sputtering, glass Alternatively, a transparent conductive film made of a metal composite oxide is formed on a film-forming substrate such as plastic.

As a sputtering target used for such sputtering, there is an IGZO sputtering target made of an oxide sintered body containing In, Ga, and Zn and having a homologous structure of InGaZnO ₄ (InGaO ₃ (ZnO)). Since the IGZO sputtering target can form a visible transmissive IGZO film by sputtering using it, it is widely used in the manufacture of the display device and the like.

Examples of the technology relating to this kind of IGZO sputtering target include those described in Patent Documents 1 to 3.

In Patent Document 1, in a sputtering target containing a compound represented by InGaZnO ₄ as a main component, it is proposed that a metal element having a positive tetravalence or higher is contained from 100 ppm to 10,000 ppm with respect to all metal elements in the sputtering target. According to this sputtering target, it is considered that the occurrence of abnormal discharge during sputtering can be suppressed by adding a metal element having a positive tetravalence or higher in a predetermined amount.

In Patent Document 2, as a sputtering target including an oxide sintered body, the oxide sintered body is made of a compound having only a homogeneous crystal structure represented by InGaO ₃ (ZnO), and the peak between 2θ = 62 to 63 degrees in X-ray diffraction is It is 3% or less of the maximum peak of InGaO ₃ (ZnO), and the atomic ratio excluding oxygen satisfies the following formula: Ga/(In + Zn + Ga) ≤ 0.26. As a sputtering target, the surface of the sputtering target is 10 points A sputtering target in which the ratio of the maximum value of the bulk resistance/the minimum value of the bulk resistance value is within 10 is described. As a result, it is believed that there is little change in the characteristics of the thin film transistor, the transistor characteristics are improved, the bulk resistance is uniform, and the variation in the film formation speed at the time of film formation becomes small.

In Patent Document 3, as an IGZO sintered body with high density and rupture strength and less cracking even when used for a sputtering target, as an oxide sintered body containing In, Ga and Zn, it has only a homogeneous crystal structure represented by InGaZnO _4, and a sintered body The grain size of the sintered body is 5 μm or less, and the relative density of the sintered body is 98% or more, and the ratio of the number of pores (pores) present in the grain boundary of the sintered body and the number of pores (pores) present in the grain boundary (pores at the grain boundary It is described that the number/number of pores in the crystal grain) is 0.5 or more.

In Patent Document 4, as an oxide sintered body composed of indium (In), gallium (Ga), zinc (Zn), oxygen (O) and inevitable impurities, an IGZO sintered body having a break strength of 50 MPa or more and a bulk resistance of 100 mΩcm or less It is described.

Japanese Patent Publication No. 5244327 Japanese Patent Publication No. 5928856 Japanese Patent Publication No. 5904056 International Publication No. 2016/136611

By the way, in the above-described sputtering target, in order to suppress abnormal discharge during sputtering, it is effective to reduce the bulk resistance of the IGZO sintered body.

As a method of lowering the bulk resistance of the IGZO sintered body, it is considered to increase the heating temperature when the raw material powder is molded into a predetermined shape and then heated to sinter. However, if the heating temperature is increased by simply changing the heating temperature, The crystal grain size of the sintered body increases. In this case, as a result of lowering the mechanical strength of the sintered body, there is a problem that cracks occur during sputtering.

The IGZO sintered body described in Patent Literature 4 has a low bulk resistance, but has a somewhat low transverse strength (see Table 1).

On the other hand, if the breaking strength is too high, the thermal shock damage resistance coefficient becomes small, and there is another problem that there is a possibility that cracks may occur in the target due to thermal stress generated in the target during sputtering.

The present invention aims to solve such a problem encountered in the prior art, and its object is to effectively reduce bulk resistance while maintaining appropriate mechanical strength, thereby suppressing the occurrence of abnormal discharge. It is to provide a method for producing a sintered compact, a sputtering target, and a sintered compact.

When manufacturing the sintered body, the inventors change the atmosphere during sintering from the conventional oxygen atmosphere to the atmosphere or nitrogen atmosphere, and set the oxygen partial pressure to a predetermined oxygen partial pressure, and then, by heating at a predetermined temperature range, It was found that the breaking strength was secured and the bulk resistance was further effectively lowered.

Under such knowledge, the sintered body of the present invention is a sintered body of an oxide containing In, Ga and Zn, and is 0.317 <In/(In + Ga + Zn) ≤ 0.350, 0.317 <Ga/(In + Ga + Zn) ≤ It satisfies the relationship of 0.350, and 0.317 <Zn/(In + Ga + Zn) ≤ 0.350, the bulk resistance value is 15 mΩcm or more and 25 mΩcm or less, and the break strength is 40 MPa or more and less than 50 MPa.

It is preferable that the sintered compact of the present invention has an average crystal grain size of 15 µm or more and 20 µm or less.

In addition, in the SEM image of the cross section of the sintered body, the sintered body of the present invention has a minimum inclusion circle diameter of 3 µm or less and a diameter of 0.5 µm or more within an observation field of 90 µm × 120 µm. It is preferable that the number of pores contained in the circle is 50 to 100.

In addition, it is preferable that the sintered compact of the present invention has a relative density of 99% or more.

The sputtering target of the present invention is provided with any of the sintered bodies described above.

In the method for producing a sintered body of the present invention, each oxide powder of In, Ga, and Zn is 0.317 <In/(In + Ga + Zn) ≤ 0.350, 0.317 <Ga/(In + Ga + Zn) ≤ 0.350, and, Mixing so as to satisfy the relationship of 0.317 <Zn/(In + Ga + Zn) ≤ 0.350, the powder is molded, and the molded article obtained therefrom is 1450° C. to 1510° C. in an atmosphere or nitrogen atmosphere having an oxygen partial pressure of 20% or less. It is heated at a temperature of 5 to 20 hours.

In the method for producing a sintered body of the present invention, it is preferable that the time to be maintained at the temperature during heating is 10 to 20 hours.

Moreover, in the manufacturing method of a sintered body of this invention, it is preferable to set the said temperature at the time of heating to 1460 degreeC-1490 degreeC.

Moreover, in the manufacturing method of the sintered body of this invention, it is preferable to perform heating in an electric furnace.

According to the present invention, it is possible to obtain a sintered body having an appropriate transverse strength and sufficiently reduced bulk resistance. Therefore, when sputtering is performed using this as a sputtering target, the occurrence of abnormal discharge can be effectively suppressed.

Hereinafter, an embodiment of the present invention will be described in detail.

The sintered body of one embodiment of the present invention is a sintered body containing an oxide composed of In, Ga, and Zn, and is 0.317 <In/(In + Ga + Zn) ≤ 0.350, 0.317 <Ga/(In + Ga + Zn) ≤ 0.350, and, 0.317 <Zn / (In + Ga + Zn) is an amount that satisfies the relationship of ≤ 0.350, which contains In, Ga and Zn, and has a bulk resistance value of 15 mΩcm or more and 25 mΩcm or less, The strength is 40 MPa or more and less than 50 MPa.

(Furtherance)

The sintered body is composed of In, Ga, Zn and O, In, Ga, and Zn are 0.317 <In/(In + Ga + Zn) ≤ 0.350, 0.317 <Ga/(In + Ga + Zn) ≤ 0.350, and, It is included in an amount satisfying the relationship of 0.317 <Zn/(In + Ga + Zn) ≤ 0.350. This can be confirmed by analysis of ICP-MS, ICP-OES, XRF, etc.

If the composition of In, Ga, and Zn is greatly deviated from 1:1, a phase other than IGZO (111), such as an In ₂ O ₃ phase or ZnGa ₂ O ₄ phase, is generated, resulting in abnormal discharge during sputtering. There is a fear that it may be the cause of.

Therefore, In, Ga and Zn in the sintered body is 0.317 <In/(In + Ga + Zn) ≤ 0.350, 0.317 <Ga/(In + Ga + Zn) ≤ 0.350, and, 0.317 <Zn/(In + Ga + It is still more preferable to satisfy Zn) ≤ 0.350.

(Bulk resistance)

In a sintered compact for a sputtering target, bulk resistance is a very important characteristic. In other words, if the bulk resistance is too high, it is necessary to use an expensive RF power supply rather than a low-cost DC power supply in order to prevent abnormal discharge during sputtering, and the film formation rate during sputtering of the RF power supply is significantly lowered, resulting in productivity. This is because it gets worse.

Therefore, in this embodiment, the bulk resistance value of the sintered body is 15 mΩcm or more and 25 mΩcm or less. With such a low bulk resistance value, abnormal discharge during sputtering when used as a sputtering target can be effectively suppressed. In other words, when the bulk resistance value exceeds 25 mΩcm, abnormal discharge tends to occur during sputtering. In addition, in the case of the composition range of In, Ga, and Zn described above, it is considered that the bulk resistance value is usually 15 mΩcm or more. Therefore, when the composition of In, Ga, and Zn is in the above range, inevitably, the bulk resistance value is often 15 mΩcm or more.

The measurement of the bulk resistance value was carried out by grinding the surface of the sintered body about 1 mm to 3 mm with a grinding material having a particle size of #80, and then grinding the surface of the sintered body with a grinding material having a particle size of #400 specified in JIS R 6001 (1998). Accordingly, it can be carried out based on the four-probe method described in JIS R 1637 on the surface finished with a grinding thickness of 0.2 mm or more. The measurement points of the bulk resistance value are taken as three points on the grinding surface, and the average value of the measurement values at these measurement points is adopted.

(Section strength)

The fracture strength of the sintered body is 40 MPa or more and less than 50 MPa. By adjusting the temperature and atmosphere at the time of sintering, it is possible to ensure the strength in this range while making it a low bulk resistance value as described above.

When the sintered body has a fracture strength of less than 40 MPa, the possibility of occurrence of cracks during sputtering increases due to the low strength.

On the other hand, when the cross section strength is 50 MPa or more, the thermal shock damage resistance coefficient becomes small, and there is a possibility that a crack may occur in the target due to thermal stress generated in the target during sputtering. This will be described in detail as follows.

When sputtering is performed using a sputtering target, the surface to be sputtered is heated in response to Ar ions. In contrast, since the backing plate to which the sputtering target is attached is water-cooled, a temperature distribution occurs in the sputtering target, and thermal stress is generated. As an index of the strength against such thermal stress (thermal shock), there are a thermal shock resistance coefficient (R) and a thermal shock damage resistance coefficient (R''). When the temperature difference generated in the sputtering target is ΔT, the Young's modulus of the sputtering target is E, the coefficient of thermal expansion is α, the Poisson's ratio is ν, and the term strength is σf, the thermal shock resistance coefficient (R) and the thermal shock damage resistance coefficient (R'') are respectively. It is represented by the following equation.

R = (1-ν)/(Eα)σf

R'' = E/{(1-ν)σf ² }

The thermal shock resistance coefficient (R) is an index indicating the difficulty of occurrence of cracks when heat is applied, and the thermal shock damage resistance coefficient (R'') is an index indicating the difficulty of the development of the generated cracks. It will not crack well.

Here, the Young's modulus (E) and the modulus strength (σf) generally have a substantially proportional relationship, and when the modulus strength (σf) is large, the Young's modulus (E) also tends to be large. The thermal shock resistance coefficient R does not change very much, since even if the modulus of strength (?f) increases, the Young's modulus E also increases in proportion to it. However, since σf of the denominator acts as a power of 2 in the thermal shock damage resistance coefficient R'', the crack is less prone to progress when the term break strength σf is somewhat smaller.

The transverse strength of the sintered body is measured as follows. A test piece in the shape of a square rod is cut out from the sintered body, the surface is polished with a grindstone of #80 in the length direction of the test piece, and then polished with a grindstone of #400 in the lengthwise direction, and finally, width 4 mm and thickness Ten test pieces of 3 mm and length 50 mm were prepared. At this time, the surface roughness of the test piece was measured with a surface roughness meter SJ-301 manufactured by Mitsutoyo Co., Ltd., and polishing was performed so that the surface roughness Ra was 1 µm to 3 µm. The test piece is subjected to a cross-section strength test by a three-point bending test in accordance with the measurement method of JIS R 1601:2008. The cross-section strength test shall conform to JIS R 1601:2008 except for the surface roughness (Ra) of the test piece.

(Average grain size)

It is preferable that the average crystal grain size of the sintered body is 15 µm or more and 20 µm or less from the viewpoint of sufficiently reliably securing the required strength. If the average grain size is less than 15 µm, sintering does not sufficiently proceed, and pores remain in the sintered body, causing a decrease in strength, and there is a fear that cracks may occur during sputtering. In addition, when stress acts on the IGZO sintered body to lead to fracture, cracking at the grain boundary is dominant, and cracks are more likely to occur at the grain boundary and the fracture strength decreases, so when the average grain size exceeds 20 µm. In addition, there is a fear that the strength of the breakdown may be significantly reduced.

From this point of view, it is more preferable that the average grain size of the sintered body is 17 µm or more and 18 µm or less.

In order to measure the average crystal grain size, a total of 5 points are collected from the vicinity of the center of the sintered body and the locations at the four corners to obtain a sample. For each sample, a 300 times SEM image is taken on an arbitrary surface of the target cross section, and five straight lines are drawn on the captured image, and the length at which each straight line crosses the crystal grains is taken as the cord length, and these cord lengths The average value of is calculated and it is set as the crystal grain size.

(Number of pores)

When the atmosphere at the time of sintering is made into air or nitrogen atmosphere when manufacturing the sintered body, pores (vacations) may be generated in the sintered body. About this pore, in the SEM (scanning electron microscope) image of the cross section of the sintered body, the size of each pore was evaluated as the diameter of the smallest inclusion circle containing the pore within an observation field of 90 μm × 120 μm, While measuring the diameter of the minimum inclusion circle of the largest pore in the observation field, the number of pores whose diameter is 0.5 µm or more is counted.

In the observation field, if the diameter of the minimum inclusion circle of the largest pore is 3 μm or less, and the number of such pores is 50 to 100, the occurrence of abnormal discharge during sputtering can be more effectively suppressed. . If pores with a diameter of the minimum inclusion circle exceeding 3 µm are present in the observation field, there is a fear that abnormal discharges increase, which may hinder mass production. Therefore, the diameter of the smallest inclusion circle of the largest pore in the observation field is more preferably 2 µm or less, still more preferably 1 µm or less. In addition, when the number of pores is too large, there is a concern that the probability of occurrence of abnormal discharge during sputtering increases, and the effect of suppressing abnormal discharge by lowering the bulk resistance value may be attenuated.

It is preferable that the diameter of the minimum inclusion circle of the largest pore and the number of pores in which the diameter of the smallest inclusion circle is 0.5 µm or more satisfy the above-described regulations within an arbitrary observation field of an arbitrary cross section of the sintered body. .

(density)

It is preferable that the density of the sintered body is 99% or more, particularly 99.5% or more. This is because when the density is low, there is a concern that the strength of the sintered body may decrease or abnormal discharge during sputtering may be caused. The density is generally 100% or less.

Here, the density is from the theoretical density in which the sintered body was regarded as an oxide of InGaZnO ₄ (InGaO ₃ (ZnO)) and the density of the sintered body measured by the Archimedes method, and the relative density = (density measured by Archimedes method) ÷ (theoretical density) It can be calculated by the formula of x 100 (%). Here, 6.357 g/cm 3, which is the density calculated based on the lattice constant of IGZO 111 of JCPDS card No. 01-070-3625, is used as the theoretical density.

In addition, this density is based on the theoretical density when it is assumed that the sintered body is made of InGaZnO ₄ , and the true value of the density of the target sintered body is sometimes higher than the theoretical density, so the density referred to here is 100% There may be cases exceeding.

(Manufacturing method)

The sintered compact as described above can be manufactured by the method described below.

First, indium oxide powder, gallium oxide powder, and zinc oxide powder were prepared from 0.317 <In/(In + Ga + Zn) ≤ 0.350, 0.317 <Ga/(In + Ga + Zn) ≤ 0.350, and, 0.317 <Zn/( In + Ga + Zn) ≤ 0.350, and mixed in a ratio satisfying the relationship, and this is used as a raw material powder. The purity of each oxide powder is preferably 99.9% or more, more preferably 99.99% or more.

The raw material powder is wet mixed and pulverized by a bead mill to obtain a slurry. It is preferable that the average particle diameter (D50) of the raw material powder is 1 µm or less, preferably 0.5 µm or less. This average particle diameter can be measured according to JIS R 1619.

Next, assembling is performed. This is to improve the flowability of the raw material powder and to make the filling situation at the time of press molding sufficiently good. PVA (polyvinyl alcohol) serving as a binder is mixed in a ratio of 100 to 200 cc per 1 kg of slurry, and the granulator inlet temperature is 200 to 250°C, the outlet temperature is 100 to 150°C, and the disc rotation speed is 8000 to 10000 rpm. To assemble.

Next, the granulated powder is press-molded to obtain a molded body. The granulated powder is filled into a mold having a predetermined size, and a molded article is obtained by uniaxial pressing under the conditions of a surface pressure of 40 to 100 MPa and holding for 1 to 3 minutes. If the surface pressure is less than 40 MPa, a molded article having a sufficient density cannot be obtained. On the other hand, even if the surface pressure is more than 100 MPa, the density of the molded article is saturated and does not rise easily, so no more surface pressure is required.

Next, molding is performed by CIP (cold isostatic pressing method). The molded article obtained above is vacuum-packed in double with vinyl, and CIP is carried out under conditions of a pressure of 150 to 400 MPa and holding for 1 to 3 minutes. If the pressure is less than 150 MPa, a sufficient effect of CIP cannot be obtained. On the other hand, even if a pressure of 400 MPa or more is applied, the density of the molded body will not be improved well beyond a certain value, so a surface pressure of 400 MPa or more is particularly required for production. It doesn't work.

After that, the molded body is heated and sintered in a furnace to obtain a sintered body.

In order to effectively lower the bulk resistance of the sintered body, the atmosphere at the time of heating for sintering is made into the atmosphere or nitrogen atmosphere, and the oxygen partial pressure is made into 20% or less. Thereby, oxygen vacancies occur in the sintered body, and many carriers are released, and a low bulk resistance of the sintered body can be realized. The oxygen partial pressure can be measured with an oxygen concentration meter.

In addition, heating for sintering is raised to a temperature within the range of 1450°C to 1510°C, and the temperature is maintained over 5 to 20 hours. By setting it as such conditions of temperature and time, oxygen is sufficiently released from the sintered body, and the bulk resistance is lowered due to oxygen vacancies. In addition, by controlling the crystal grain size in the appropriate range as described above, a decrease in mechanical strength is prevented. Therefore, in the sintered body, it is possible to achieve both satisfactory bulk resistance and strength at break as described above.

When the temperature at the time of heating is too low, the bulk resistance of the sintered body cannot be sufficiently reduced. On the other hand, when the temperature is too high, the bulk resistance of the sintered body decreases, but the crystal grain size increases, and therefore, The mechanical strength is lowered, and cracking occurs during sputtering.

In addition, when the heating time is too short, as a result of not generating sufficient oxygen defects in the sintered body, the bulk resistance value increases, and when the time is too long, the growth of crystal grains is excessively accelerated, resulting in a decrease in the strength of the sintered body. .

From the above point of view, the temperature at the time of sintering is preferably from 1450°C to 1510°C, particularly from 1460°C to 1490°C, and the time is preferably from 10 hours to 20 hours, particularly from 12 hours to 15 hours.

Although heating for sintering can be performed using various known furnaces, it is preferable to use an electric furnace that converts electric energy into thermal energy and heats it, and among them, an electric resistance furnace using Joule heat. If a furnace other than this is used, there is a possibility of causing a change in the properties of the sintered body.

As described above, a sintered body can be manufactured.

Then, a sputtering target can be obtained by grinding the outer surface of such a sintered body by a known method such as mechanical grinding or chemical grinding, and bonding the base material to a predetermined position of the sintered body.

Example

Next, the sintered compact of the present invention and the sputtering target were produced by trial, and the performance thereof was evaluated, and thus, the following description will be given. However, the description herein is for the purpose of mere illustration, and is not intended to be limited thereto.

Weigh and mix each oxide powder of In ₂ O ₃ , Ga ₂ O ₃ , and ZnO so that In: Ga: Zn = 1: 1: 1, add pure water, and put it into a bead mill to have an average particle diameter (D50) It mixed and pulverized until it became this 0.5 micrometers or less, and obtained the slurry of 30-50% of solid content. Next, PVA (polyvinyl alcohol) was mixed at a rate of 125 cc per kg of slurry, and dried and assembled with a spray dryer under the conditions of a granulator inlet temperature of 220°C, an outlet temperature of 120°C, and a disk rotation speed of 9000 rpm. I got a powder.

The granulated powder was filled with granulated powder in a mold having a predetermined size, and a surface pressure of 150 to 400 MPa was uniaxially pressed for 1 to 3 minutes to obtain a molded article. The molded body was vacuum-packed with vinyl in two layers, and a surface pressure of 300 MPa was pressed by CIP over 3 minutes, and the molded body thus obtained was heated and sintered under the conditions shown in Table 1 to obtain a sintered body.

For each of the sintered compacts of Comparative Examples 1 to 5 and Examples 1 to 3, each of the density, average crystal grain size, bulk resistance value, transverse strength, and number of pores was measured by the method described above. The results are shown in Table 1.

Further, the sintered compact was subjected to grinding to a size of 5" x 20", and the substrate was bonded to this to prepare a sputtering target.

Using each sputtering target, a discharge test was performed under the conditions of room temperature, power 1.5 kW, pressure 0.6 Pa, and an Ar gas flow rate of 300 sccm, and the number of arcing (accumulative arcing frequency) up to the accumulated input power 160 Wh was measured. The results are also shown in Table 1.

In Examples 1 to 3, the sintering conditions were set to a temperature in the range of 1450°C to 1510°C while setting the sintering condition to an atmospheric atmosphere in which the oxygen partial pressure is 20% or less, so that the predetermined transverse strength and bulk resistance were sufficiently lowered, as a result. As, the number of arcing is relatively small.

In Comparative Example 1, when the sintering temperature was low and the atmosphere was an oxygen atmosphere, the bulk resistance was increased and the number of arcing was increased.

In Comparative Examples 2 to 4, the air atmosphere was set, but due to the low sintering temperature, the bulk resistance was slightly lowered to some extent, but the number of pores increased and the number of arcing increased due to the decrease in the oxygen partial pressure.

In Comparative Example 5, when the sintering temperature was too high, the result was insufficient in terms of breaking strength.

Therefore, according to the present invention, it was found that since the bulk resistance can be reduced while maintaining high transverse strength, abnormal discharge during sputtering can be effectively suppressed.

Claims (11)

As a sintered body of an oxide containing In, Ga, and Zn, 0.317 <In/(In + Ga + Zn) ≤ 0.350, 0.317 <Ga/(In + Ga + Zn) ≤ 0.350, and 0.317 <Zn/(In + Ga + Zn) ≤ 0.350, a sintered body having a bulk resistance value of 15 mΩcm or more and 25 mΩcm or less, and a transverse strength of 40 MPa or more and less than 50 MPa. The method of claim 1,
A sintered body having an average grain size of 15 µm or more and 20 µm or less. The method of claim 1,
In the SEM image of the cross-section of the sintered body, within the observation field of 90 µm × 120 µm, the diameter of the minimum inclusion circle of the largest pore is 3 µm or less, and the number of pores in the smallest inclusion circle having a diameter of 0.5 µm or more is , 50 to 100 sintered bodies. The method of claim 2,
In the SEM image of the cross-section of the sintered body, within the observation field of 90 µm × 120 µm, the diameter of the minimum inclusion circle of the largest pore is 3 µm or less, and the number of pores in the smallest inclusion circle having a diameter of 0.5 µm or more is , 50 to 100 sintered bodies. The method according to any one of claims 1 to 4,
A sintered body having a relative density of 99% or more. A sputtering target provided with the sintered body according to any one of claims 1 to 4. A sputtering target comprising the sintered body according to claim 5. In each oxide powder of In, Ga and Zn, 0.317 <In/(In + Ga + Zn) ≤ 0.350, 0.317 <Ga/(In + Ga + Zn) ≤ 0.350, and 0.317 <Zn/(In + Ga + Zn) is mixed so as to satisfy the relationship of ≤ 0.350, the powder is molded, and the molded article obtained therefrom is in an atmosphere or nitrogen atmosphere having an oxygen partial pressure of 20% or less at a temperature of 1450°C to 1510°C for 5 to 20 hours. A method for producing a sintered body by heating over. The method of claim 8,
A method for producing a sintered body, wherein the time to be maintained at the temperature during heating is 10 to 20 hours. The method of claim 8 or 9,
The method for producing a sintered body, wherein the temperature during heating is 1460°C to 1490°C. The method of claim 8 or 9,
A method for producing a sintered body in which heating is performed in an electric furnace.