WO2023032456A1

WO2023032456A1 - Oxide sintered body, production method for same, and sputtering target material

Info

Publication number: WO2023032456A1
Application number: PCT/JP2022/026468
Authority: WO
Inventors: 功児深川
Original assignee: 三井金属鉱業株式会社
Priority date: 2021-09-01
Filing date: 2022-07-01
Publication date: 2023-03-09
Also published as: JP7480439B2; CN117529574A; JP2024083640A; JP7557648B2; KR20240046818A; JPWO2023032456A1; TW202323220A

Abstract

This oxide sintered body includes tin, tantalum, and niobium. The area fraction of pores per unit area of the oxide sintered body as observed in cross-section is no more than 1%. The maximum circle equivalent diameter of the pores of the oxide sintered body as observed in cross-section is no more than 20 μm. The maximum Feret diameter of the pores of the oxide sintered body as observed in cross-section is no more than 50 μm. The relative density of the oxide sintered body as measured by the Archimedes method is preferably at least 99.6%. The flexural strength of the oxide sintered body as measured in accordance with JIS R1601 is preferably at least 180 MPa.

Description

Oxide sintered body, method for producing the same, and sputtering target material

The present invention relates to an oxide sintered body and a method for producing the same. The present invention also relates to a sputtering target material comprising an oxide sintered body.

　Tin oxide-based transparent conductive films are used in a wide range of applications, including display devices such as liquid crystal displays, plasma displays, and organic EL. Sputtering is known as one of means for forming a tin oxide-based transparent conductive film. In the formation of a conductive film using sputtering, if there are many defects such as pinholes in the sputtering target material, it becomes a factor in the occurrence of abnormal discharge during sputtering, resulting in the generation of particles during sputtering, cracking of the target material, and the like. It also contributes to the generation of cracks.

For the purpose of preventing abnormal discharge from occurring during sputtering, the present applicant previously prepared an unsintered compact containing SnO ₂ as a main component and containing Nb ₂ O ₅ and Ta ₂ O ₅ . , proposed a method for manufacturing a sputtering target in which the compact is sintered at 1550°C to 1650°C (see Patent Document 1). For a similar purpose, the present applicant previously proposed a sputtering target containing Ta ₂ O ₅ , Nb ₂ O ₅ , SnO ₂ as the balance, and unavoidable impurities (see Patent Document 2).

JP 2007-131891 A JP 2008-248278 A

According to the techniques described in Patent Documents 1 and 2, it is possible to suppress abnormal discharge during sputtering and cracking of the target material. However, display devices using tin oxide-based transparent conductive films are required to have further improved performance, and even higher quality tin oxide-based transparent conductive films are required. Therefore, a sputtering target material used for producing a tin oxide-based transparent conductive film is also required to have a high quality in which abnormal discharge during sputtering and cracking of the target material are reduced as compared with the conventional ones.
Accordingly, an object of the present invention is to provide an oxide sintered body that has few defects such as pinholes and is less prone to abnormal discharge and cracking when used as a sputtering target material, a method for producing the same, and a sputtering target material.

The present invention is an oxide sintered body containing a tin element, a tantalum element and a niobium element,
The above problem is solved by providing an oxide sintered body having an area ratio of pores per unit area of 1% or less in cross-sectional observation of the oxide sintered body.

The present invention also provides a sputtering target material comprising the above oxide sintered body.

Further, the present invention separately prepares a tin oxide slurry, a tantalum oxide slurry and a niobium oxide slurry,
Mixing the respective slurries to prepare a mixed slurry,
The mixed slurry is subjected to a spray drying method to produce granules,
Producing a compact using the granules,
A method for producing an oxide sintered body, in which the compact is sintered,
A method for producing an oxide sintered body is provided in which a dispersant is added to each of the tin oxide slurry, the tantalum oxide slurry, and the niobium oxide slurry.

The present invention will be described below based on its preferred embodiments. The present invention relates to an oxide sintered body and a sputtering target material using the same.
The oxide sintered body of the present invention is a sintered body of multiple kinds of metal oxides. Specifically, the oxide sintered body of the present invention includes, as metals, a tin element (hereinafter also simply referred to as “Sn”), a tantalum element (hereinafter also simply referred to as “Ta”), and a niobium element (hereinafter also referred to as “Ta”). Also simply referred to as “Nb”). These metal elements are present in the sintered compact in the form of oxides of the respective metals, or in the form of composite oxides of at least two metal elements selected from these three metal elements. present in the body.

As described in the above-mentioned Patent Document 1, it has been difficult to produce a dense sintered body containing SnO ₂ because SnO ₂ is a difficult-to-sinter substance. Due to this, conventionally known sintered bodies containing SnO ₂ tend to have holes, which are defect sites. On the other hand, the oxide sintered body of the present invention is characterized in that the presence of pores is extremely reduced. The pore is a defect site observed in the cross section of the oxide sintered body of the present invention. In the present specification, the cross section of the oxide sintered body is a surface obtained by cutting the oxide sintered body by a predetermined means.
The hole is open in cross section and extends toward the inside of the oxide sintered body. A hole includes both a through hole and a bottomed hole. As used herein, the term “pore” refers to a defect site of a size that can be observed when the cross section of the oxide sintered body is observed under a microscope at a magnification of 200 (observation field: 445.3 μm × 634.6 μm). is.

The degree of presence of pores in the oxide sintered body of the present invention is preferably the area ratio of pores per unit area (hereinafter also referred to as "pore area ratio") in cross-sectional observation of the oxide sintered body. is as low as 1% or less. Due to such a low degree of existence of the holes, when the oxide sintered body of the present invention is used as, for example, a sputtering target material, abnormal discharge is effectively generated during sputtering. Suppressed. In addition, the generation of particles during sputtering and the generation of cracks in the target material can be effectively prevented. From the viewpoint of making these advantages more remarkable, the pore area ratio is more preferably 0.9% or less, even more preferably 0.8% or less, and 0.7% or less. is still more preferable, particularly preferably 0.6% or less, and particularly preferably 0.5% or less. The closer the pore area ratio is to zero, the better. From this viewpoint, the hole area ratio is preferably more than 0% and 1% or less, more preferably 0.02% or more and 0.9% or less, and 0.04% or more and 0.8% or less. more preferably 0.06% or more and 0.7% or less, even more preferably 0.08% or more and 0.6% or less, particularly preferably 0.1% or more and 0.5% The following are particularly preferred.
A method for measuring the pore area ratio will be described in Examples described later. Also, a technique for reducing the hole area ratio to the above value or less will be described later.

One of the characteristics of the oxide sintered body of the present invention is that, when a hole is observed in its cross section, the size of the hole is suppressed. Specifically, the maximum equivalent circle diameter of the pores in the observation of the cross section of the oxide sintered body is as small as 20 μm or less. By suppressing the size of the holes in this way, the oxide sintered body of the present invention effectively suppresses the occurrence of abnormal discharge during sputtering when it is used as a sputtering target material, for example. be done. In addition, the generation of particles during sputtering and the generation of cracks in the target material can be effectively prevented. From the viewpoint of making these advantages more remarkable, the maximum equivalent circle diameter of the hole is more preferably 18 μm or less, even more preferably 16 μm or less, even more preferably 15 μm or less, and 13 μm. It is particularly preferably 12 μm or less, particularly preferably 12 μm or less. The closer the maximum equivalent circle diameter of the hole is to zero, the better. From this point of view, the maximum equivalent circle diameter of the hole is preferably more than 0 μm and 20 μm or less, more preferably 1 μm or more and 18 μm or less, even more preferably 2 μm or more and 16 μm or less, and 3 μm or more and 15 μm or less. It is even more preferable to be 4 μm or more and 13 μm or less, and particularly preferably 5 μm or more and 12 μm or less.
A method for measuring the maximum equivalent circle diameter of the hole will be described in Examples described later. Also, a technique for reducing the maximum equivalent circle diameter of the hole to the above value or less will be described later.

In addition to the maximum equivalent circle diameter of the pores being equal to or less than the value described above, the oxide sintered body of the present invention has an extremely small maximum Feret diameter of 50 μm or less. The Feret diameter is the size of a rectangle that circumscribes the object to be measured. Even by setting the maximum Feret diameter of the hole to the above-mentioned value or less, the oxide sintered body of the present invention effectively prevents abnormal discharge from occurring during sputtering when it is used, for example, as a sputtering target material. suppressed by In addition, the generation of particles during sputtering and the generation of cracks in the target material can be effectively prevented. From the viewpoint of making these advantages more remarkable, the maximum Feret diameter of the hole is more preferably 45 μm or less, even more preferably 40 μm or less, even more preferably 35 μm or less, and 30 μm or less. is particularly preferred, 28 µm or less is particularly preferred, and 26 µm or less is most preferred. The closer the maximum Feret diameter of the hole to zero, the better. From this point of view, the maximum Feret diameter of the pore is preferably more than 0 μm and 50 μm or less, more preferably 2 μm or more and 45 μm or less, even more preferably 3 μm or more and 40 μm or less, and 4 μm or more and 35 μm or less. 6 μm or more and 30 μm or less is particularly preferable, 8 μm or more and 28 μm or less is particularly preferable, and 10 μm or more and 26 μm or less is most preferable.
A method for measuring the maximum Feret diameter of the pore will be described in Examples described later. Also, a technique for reducing the maximum Feret diameter of the hole to the above value or less will be described later.

The oxide sintered body of the present invention preferably satisfies at least one of the above-described (i) hole area ratio, (ii) maximum equivalent circle diameter, and (iii) maximum Feret diameter, and (i) More preferably, a combination of at least two of -(iii) is satisfied, and more preferably all of (i)-(iii) are satisfied.

The oxide sintered body of the present invention is characterized by high relative density in addition to (i)-(iii) described above. Specifically, the oxide sintered body of the present invention preferably exhibits a high relative density of 99.6% or more. By exhibiting such a high relative density, the oxide sintered body of the present invention can be used as, for example, a sputtering target material, and when sputtering is performed using the target material, abnormal discharge during sputtering can be suppressed. Therefore, it is preferable. From this point of view, the relative density of the oxide sintered body of the present invention is more preferably 99.8% or more, more preferably 100.0% or more, and more preferably 100.2% or more. Even more preferably, it is particularly preferably 100.3% or more. Although the upper limit of the relative density is not particularly limited, it is preferably 105% or less, more preferably 104% or less, even more preferably 103% or less, and even more preferably 102% or less. preferable. The oxide sintered body of the present invention having such a relative density is preferably produced by the method described below. Relative density is measured according to the Archimedes method. A specific measuring method will be described in Examples described later.

The oxide sintered body of the present invention is also characterized by high strength. Specifically, the oxide sintered body of the present invention preferably exhibits a high bending strength of 180 MPa or more. By exhibiting such a high bending strength, the oxide sintered body of the present invention is used as a sputtering target material, for example, and when sputtering is performed with the target material, abnormal discharge occurs unintentionally during sputtering. However, it is preferable because the target material is less likely to be broken or cracked. From this point of view, the flexural strength of the oxide sintered body of the present invention is more preferably 190 MPa or more, more preferably 200 MPa or more, even more preferably 210 MPa or more, and 220 MPa or more. is particularly preferred, 230 MPa or higher is particularly preferred, and 240 MPa or higher is most preferred. Although the upper limit of the bending strength is not particularly limited, it is preferably 300 MPa or less, more preferably 290 MPa or less, even more preferably 280 MPa or less, and even more preferably 270 MPa or less. The oxide sintered body of the present invention having such bending strength is preferably produced by the method described below. The bending strength is measured according to JIS R1601. A specific measuring method will be described in Examples described later.

The oxide sintered body of the present invention preferably has a low bulk resistivity because DC sputtering can be easily performed when the oxide sintered body is used as a sputtering target material. From this point of view, the bulk resistivity of the oxide sintered body is preferably 10 Ω·cm or less. Bulk resistivity is measured in AUTO RANGE mode using Loresta (registered trademark) HP MCP-T410 (series 4-probe probe TYPE ESP) manufactured by Mitsubishi Chemical Corporation. Measurement points are five points in total, near the center and four corners of the oxide sintered body, and the arithmetic mean value of each measured value is taken as the bulk resistivity of the sintered body.

As described above, the oxide sintered body of the present invention contains Sn, Ta and Nb as metal elements. The oxide sintered body of the present invention contains SnO ₂ as a main component and Ta ₂ O ₅ and Nb ₂ O ₅ as subcomponents. It is preferable from the point of improvement. From the viewpoint of making this advantage more remarkable, the total amount of Ta ₂ O ₅ and Nb ₂ O ₅ in the oxide sintered body is preferably 1.15% by mass or more and 12.0% by mass or less. , More preferably 3.5% by mass or more and 10% by mass or less, even more preferably 4.0% by mass or more and 8.0% by mass or less, and 5.0% by mass or more and 7.0% by mass or less It is even more preferred to have

The ratio of Ta ₂ O ₅ and Nb ₂ O ₅ in the oxide sintered body of the present invention improves the characteristics of the transparent conductive film formed from the oxide sintered body, and the oxide sintered body From the viewpoint of improving the sintered density, the mass ratio of Nb ₂ O ₅ /Ta ₂ O ₅ is preferably 0.15 or more and 0.90 or less, and 0.15 or more and 0.60 or less. is more preferably 0.16 or more and 0.43 or less, and even more preferably 0.17 or more and 0.33 or less.

The specific ratio of Sn, Ta, and Nb in the oxide sintered body of the present invention is preferably 80% by mass or more and less than 100% by mass in terms of SnO ₂ , and Ta is Ta ₂ O ₅ It is preferably more than 0% by mass and 10% by mass or less in terms of conversion, and preferably more than 0% by mass and 10% by mass or less in terms of Nb ₂ O ₅ .
Furthermore, Sn is preferably 88% by mass or more and 98.85% by mass or less in terms of SnO ₂ , Ta is preferably 1% by mass or more and 8% by mass or less in terms of Ta ₂ O ₅ , and Nb is Nb ₂ It is preferably 0.15% by mass or more and 4% by mass or less in terms of _O5 .
In particular, Sn is preferably 90% by mass or more and 96.5% by mass or less in terms of SnO ₂ , Ta is preferably 3% by mass or more and 7% by mass or less in terms of Ta ₂ O ₅ , and Nb is Nb ₂ It is preferably 0.5% by mass or more and 3% by mass or less in terms of _O5 .
It is preferable that the oxide sintered body of the present invention contain Sn, Ta and Nb in this proportion, because the properties of the transparent conductive film formed from the oxide sintered body are improved.
The proportions of SnO ₂ , Ta ₂ O ₅ and Nb ₂ O ₅ are values based on mass including the amount of unavoidable impurities contained in the oxide sintered body.

Next, a preferred method for producing the oxide sintered body of the present invention will be described. The oxide sintered body of the present invention is produced by sintering raw material powder. Tin oxide powder, tantalum oxide powder and niobium oxide powder are used as the raw material powder. SnO ₂ powder is preferably used as the tin oxide powder. Ta ₂ O ₅ powder is preferably used as the tantalum oxide powder. Nb ₂ O ₅ powder is preferably used as the niobium oxide powder.
The ratio of each oxide powder to be used is preferably adjusted so that the ratio of SnO ₂ , Ta ₂ O ₅ and Nb ₂ O ₅ contained in the target oxide sintered body is within the range described above.

From the viewpoint of ensuring sufficient dispersibility in a dispersion medium, the particle size of each oxide powder is expressed as a volume cumulative particle size D50 at a cumulative volume of 50% by volume measured by a laser diffraction scattering particle size distribution measurement method, and is 0.00. It is preferably 3 μm or more and 1.2 μm or less, more preferably 0.4 μm or more and 1.1 μm or less, and still more preferably 0.5 μm or more and 0.9 μm or less.

In this production method, slurries of the respective oxide powders are separately prepared, and the slurries are mixed to prepare a mixed slurry, thereby successfully producing an oxide sintered body in which the generation of pores is suppressed. As a result of investigations by the present inventors, it was found that it is advantageous in terms of obtaining. This procedure will be described in detail below.
First, slurries of each oxide powder are separately prepared. A liquid capable of dispersing each oxide powder can be used as a dispersion medium for preparing the slurry. Examples of such dispersion media include water and various organic solvents. As an organic solvent, for example, ethanol can be used. Among these dispersion media, it is preferable to use water from the viewpoint of economy and ease of handling.
The proportion of the dispersion medium in the slurry is preferably 20% by mass or more and 70% by mass or less, more preferably 30% by mass or more and 60% by mass or less, still more preferably 35% by mass or more and 55% by mass or less, relative to the mass of the oxide powder. The oxide powder is sufficiently dispersed in the dispersion medium when the following settings are made.

Considering the dispersibility of the oxide powder in the dispersion medium, the concentration of the oxide powder in the slurry of each oxide powder is preferably 58% by mass or more and 84% by mass or less, and 62% by mass or more and 77% by mass. % or less, more preferably 64 mass % or more and 74 mass % or less.
From the viewpoint of enhancing the dispersibility of each oxide powder contained in the slurry, it is preferable to blend a dispersant into each slurry. As the dispersant, an appropriate one can be used according to the type of oxide powder. polycarboxylates such as ammonium polycarboxylates, sodium polycarboxylates and polycarboxylate amine salts; quaternary cationic polymers; nonionic surfactants such as polyalkylene glycols; and cations such as quaternary ammonium salts. system surfactants and the like can be used. These dispersants can be used singly or in combination of two or more. Among these dispersants, it is preferable to use polycarboxylates because of the high dispersibility of the oxide powder, and it is particularly preferable to use ammonium polycarboxylates.
The type of dispersant to be blended in each slurry may be the same or different.

The concentration of the dispersant to be mixed in each slurry is appropriately selected according to the concentration and type of oxide powder contained in the slurry. The concentration of the dispersant in the slurry is preferably 0.01% by mass or more and 0.04% by mass or less, more preferably 0.015% by mass or more and 0.035% by mass or less, more preferably 0.035% by mass or less, relative to the mass of the oxide powder. When is set to 0.02% by mass or more and 0.03% by mass or less, satisfactory dispersibility is exhibited. The concentration of dispersant in each slurry may be the same or different.

Each slurry may contain a binder. By blending the binder, the strength of the granules can be moderated when the granules are obtained using the mixed slurry described later. As the binder, for example, various organic polymer materials can be used. Examples of organic polymer materials that can be used include polyvinyl alcohol and acrylic emulsion binders.
The concentration of the binder compounded in each slurry is appropriately selected according to the concentration and type of oxide powder contained in the slurry. The concentration of the binder in the slurry is preferably 0.2% by mass or more and 0.8% by mass or less, more preferably 0.3% by mass or more and 0.7% by mass or less, more preferably 0.7% by mass or less, relative to the mass of the oxide powder. is set to 0.4% by mass or more and 0.6% by mass or less, the strength of the granules can be made moderate. The binder concentration in each slurry may be the same or different.

Preparation of the slurry is done by mixing each component that makes up the slurry. For mixing, it is preferable to use a media mill such as a ball mill or a bead mill because the oxide powder can be sufficiently dispersed in the dispersion medium.

After each slurry is prepared by the above procedure, each slurry is then mixed to prepare a mixed slurry. The mixing ratio of each slurry is preferably adjusted so that the ratio of SnO ₂ , Ta ₂ O ₅ and Nb ₂ O ₅ contained in the target oxide sintered body is within the range described above.
In order to mix the slurries to obtain a mixed slurry, it is preferable to use a media mill such as a ball mill or bead mill, but the method is not limited to this method.

The advantages of preparing a slurry of each oxide powder and mixing the slurries to obtain a mixed slurry are as follows.
In this production method, as described later, it is preferable to use a mixed slurry and obtain granules by a spray drying method. In order to carry out the spray drying method smoothly, it is advantageous to reduce the viscosity of the mixed slurry by increasing the amount of the dispersant blended into the mixed slurry. However, when the content of the dispersant is increased, the granules obtained by the spray drying method tend to be hard and difficult to crush. When such granules are used to compression-mold a molded body for producing an oxide sintered body, the granules are less likely to be crushed during the compression process, resulting in defects in the molded body. easier. When such a molded body is fired, the resulting sintered body is not dense and has defects.
On the other hand, when the amount of the dispersant mixed in the mixed slurry is reduced for the purpose of making the granules easily crushable, the viscosity of the mixed slurry tends to increase, resulting in uniform-shaped granules. becomes difficult to manufacture. When a compact is compression-molded using such granules, defects are likely to occur in the compact, and the sintered compact will not be dense, resulting in defects. .
On the other hand, by adding a dispersant to the slurry of each oxide powder and mixing the slurries to obtain a mixed slurry, it is possible to suppress the increase in the viscosity of the mixed slurry even if the amount of the dispersant is reduced. As a result of investigations by the present inventors, it was found that a mixed slurry having good dispersibility can be obtained. A sintered body manufactured using such a mixed slurry is dense in which the generation of defective portions is suppressed.

Preparing a slurry of each oxide powder and mixing the slurries to obtain a mixed slurry has another advantage as described below.
In the conventional technology, for example, the technology described in the above-mentioned Patent Documents 1 and 2, when producing an oxide sintered body containing a plurality of metal elements, the oxide powder of each metal element is collectively used as a dispersion medium. A slurry was prepared by dispersing. When the slurry was prepared by this method, the dispersant contained in the slurry preferentially acted on a specific oxide, and it was found that there was a difference in the dispersibility of the oxides in the dispersion medium. This was found out as a result of examination by the inventor. If there is a difference in dispersibility, the state of the oxide powder in the granules produced from the slurry, for example, the degree of crumbability, becomes uneven, and as a result, the finally obtained oxide sintered product becomes uneven. There is an inconvenience that holes are likely to occur in the body. The reason for the difference in dispersibility is that the interaction between the dispersant and each oxide powder differs depending on the type of oxide powder. Therefore, in this production method, in order to prevent differences in dispersibility in the dispersion medium between oxides, instead of dispersing each oxide powder in the dispersion medium at once, each oxide powder is A method of dispersing them separately in a dispersion medium and blending a dispersant with the dispersion medium at that time is employed. By adopting this method, the dispersing agent reliably acts on each oxide powder, so that it becomes difficult to cause a difference in the dispersibility of each oxide powder in the mixed slurry.

After the mixed slurry is prepared, the mixed slurry is subjected to a spray drying method to produce granules. In the granulation by the spray drying method, the particle diameter represented by the volume cumulative particle diameter D50 at the cumulative volume of 50% by volume measured by the laser diffraction scattering particle size distribution measurement method is 30 μm or more and 60 μm or less, particularly 35 μm or more and 55 μm or less, especially 40 μm or more and 50 μm. It is preferable to produce the following granules from the viewpoint of ease of crushing of the granules. The fact that the granules are easily crushed is advantageous in that when the granules are used to produce an oxide sintered body, pores are less likely to occur. The volume cumulative particle size D50 of the granules is the particle size measured without ultrasonic dispersion treatment.

After the granules are obtained, the granules are filled into a mold to produce a compact. For molding, a cold press method such as cold isostatic pressing can be employed. The pressure during molding is preferably set to 600 kg/cm ² or more and 1200 kg/cm ² or less from the viewpoint of obtaining a dense molded body.
After obtaining the molded article, the molded article may be subjected to a degreasing step, if necessary. By subjecting the molded body to the degreasing process, organic substances contained in the molded body, such as dispersants and binders, can be removed. The degreasing step is performed by heating the compact to, for example, 500° C. or higher and 900° C. or lower in an air atmosphere.

After the compact is obtained in this way, it is then fired. Firing of the compact can generally be carried out in an oxygen-containing atmosphere. In particular, firing in an air atmosphere is convenient. The firing temperature is preferably 1500° C. or higher and 1700° C. or lower, more preferably 1520° C. or higher and 1680° C. or lower, and still more preferably 1550° C. or higher and 1650° C. or lower. The firing time is preferably from 1 hour to 100 hours, more preferably from 2 hours to 50 hours, and even more preferably from 3 hours to 30 hours. The rate of temperature increase and the rate of temperature decrease are each independently preferably 5°C/hour or more and 500°C/hour or less, more preferably 10°C/hour or more and 200°C/hour or less, and 20°C/hour or more and 100°C. / hour or less is more preferable.

The oxide sintered body obtained by the above method is dense, and the formation of pores is suppressed. Therefore, the oxide sintered body has a low pore area ratio and a small maximum equivalent circle diameter and maximum Feret diameter.

The oxide sintered body thus obtained can be processed into a predetermined size by grinding or the like, and used as a sputtering target material. A sputtering target is obtained by joining the obtained sputtering target material to a backing plate. As the backing plate, for example, stainless steel, copper, titanium, or the like can be used. A low melting point solder such as indium can be used for joining the target material and the backing plate.
The sputtering target thus obtained is suitably used for producing a sputtered film such as a transparent conductive film. A sputtered film formed using this sputtering target can have the same composition as the sputtering target material. The specific resistivity of the sputtered film is preferably as low as 9 mΩ·cm or less.

The present invention will be described in more detail below with reference to examples. However, the scope of the invention is not limited to such examples.

[Example 1]
SnO ₂ powder with a particle size D50 of 0.7 μm, Ta ₂ O ₅ powder with a particle size D50 of 0.6 μm, and Nb ₂ O ₅ powder with a particle size D50 of 0.9 μm were prepared. The particle size D50 was measured using a particle size distribution analyzer MT3300EXII manufactured by Microtrack Bell Co., Ltd. Water was used as the dispersion medium. The refractive index of the substance to be measured was 2.20.
Each oxide powder is separately placed in a pot, and 0.5% by weight of polyvinyl alcohol, 0.02% by weight of ammonium polycarboxylate, and 50% by weight of water are added to the weight of each oxide powder. In addition, each slurry was prepared by mixing for 20 hours using a ball mill.
The prepared slurries were mixed and mixed for 60 minutes using a ball mill to obtain a mixed slurry. The mixing ratio of each slurry was such that SnO ₂ was 96.5 mass %, Ta ₂ O ₅ was 3.0 mass %, and Nb ₂ O ₅ was 0.5 mass % with respect to the total of each powder.

The mixed slurry was supplied to a spray drying apparatus, and spray drying was performed under the conditions of an atomizer rotation speed of 14000 rpm, an inlet temperature of 200°C and an outlet temperature of 80°C to obtain granules. The particle diameter D50 of the granules was 45 μm.
The obtained granules were filled in a mold of 158 mm×640 mm and press-molded at a pressure of 800 kg/cm ² to obtain a compact. The resulting compact was degreased by heating at 750° C. for 6 hours in an air atmosphere.
A sintered body was produced by sintering the molded body after degreasing. Firing was performed in an atmosphere with an oxygen concentration of 20 vol % at a firing temperature of 1600° C., a firing time of 8 hours, a temperature increase rate of 50° C./h, and a temperature decrease rate of 50° C./h.
The sintered body thus obtained was cut to obtain an oxide sintered body having a width of 100 mm, a length of 240 mm, a thickness of 8 mm, and a surface roughness Ra of 1.0 μm. A #170 whetstone was used for cutting.

[Examples 2 and 3]
Each powder was mixed so that the ratio of each powder to the total of SnO ₂ powder, Ta ₂ O ₅ powder, and Nb ₂ O ₅ powder is shown in Table 1 below. An oxide sintered body was obtained in the same manner as in Example 1 except for this.

[Comparative Example 1]
The same SnO ₂ powder, Ta ₂ O ₅ powder, and Nb ₂ O ₅ powder as in Example 1 were prepared.
Each powder was weighed to give 94% by weight _SnO2 , ₅ % by weight _Ta2O5 and ₁ % by weight _Nb2O5 based on the total weight of each powder and dry mixed for 21 hours.
6% by mass of a 4% by mass polyvinyl alcohol aqueous solution was added to the mixed powder. After the polyvinyl alcohol and the mixed powder were mixed using a mortar, the mixture was passed through a 5.5-mesh sieve to obtain a mixed powder for molding.
An oxide sintered body was obtained in the same manner as in Example 1 except for these.

[Comparative Example 2]
The same SnO ₂ powder, Ta ₂ O ₅ powder, and Nb ₂ O ₅ powder as in Example 1 were prepared.
Put all the powder in a pot, add 0.5% by weight of polyvinyl alcohol, 0.02% by weight of ammonium polycarboxylate, and 50% by weight of water to the total amount of powder, and add 20% by weight using a ball mill. A mixed slurry was prepared by mixing for a period of time. The ratio of each powder in the mixed slurry was such that SnO ₂ was 94% by mass, Ta ₂ O ₅ was 5% by mass, and Nb ₂ O ₅ was 1% by mass with respect to the total of each powder. An oxide sintered body was obtained in the same manner as in Example 1 except for this.

[Comparative Example 3]
In this comparative example, the concentration of 0.02% by mass of ammonium polycarboxylate, which is the dispersant used in Example 2, was increased to 0.05% by mass. An oxide sintered body was obtained in the same manner as in Example 2 except for this.

〔evaluation〕
The pore area ratio, maximum equivalent circle diameter, maximum Feret diameter, relative density, and bending strength of the oxide sintered bodies obtained in Examples and Comparative Examples were measured by the following methods.
In addition, a sputtering target was produced using the oxide sintered bodies obtained in Examples and Comparative Examples, and the degree of occurrence of abnormal discharge and cracking of the target when sputtering was performed using the target. The degree was evaluated by the following method.
The above results are shown in Table 1 below.

[Pore area ratio, maximum circle equivalent diameter and maximum Feret diameter]
(1) Preparation of cross section of oxide sintered body The cut surface obtained by cutting the oxide sintered body was stepwise using #180, #400, #800, #1000, and #2000 emery papers. Polished and finally buffed to a mirror finish.
(2) Measurement of hole area ratio, maximum circle equivalent diameter and maximum Feret diameter Using a scanning electron microscope (SU3500, manufactured by Hitachi High-Technologies Co., Ltd.) for the cross section of the oxide sintered body, 200 times magnification , 445.3 μm×634.6 μm BSE-COMP image (hereinafter also referred to as “SEM image”) was taken. Using particle analysis software (“Particle Analysis Version 3.0” manufactured by Sumitomo Metal Technology Co., Ltd.), the SEM image was traced and image recognition was performed with a scanner. This image was binarized. At this time, the conversion value was set so that one pixel was displayed in units of μm.
Next, the area and the sum of the areas were obtained for all the holes shown in the SEM image. The percentage value of the total area of the holes relative to the visual field area (445.3 μm×634.6 μm) was obtained. The arithmetic average value of the percentages measured for 10 different SEM images was obtained, and this arithmetic average value was defined as the pore area ratio in the present invention.
In addition, the equivalent circle diameter of the pore was calculated based on the area of the pore measured in the process of determining the area ratio of the pore. Among all equivalent circle diameters measured for ten different SEM images, the maximum value was taken as the maximum equivalent circle diameter of the hole.
Apart from the above operations, for all the holes in the SEM image, the horizontal Feret diameter (μm) is calculated based on the total number of pixels in the horizontal direction, and the vertical Feret diameter is calculated based on the total number of pixels in the vertical direction. (μm) was calculated. Among all horizontal Feret diameters and vertical Feret diameters measured for ten different SEM images, the maximum value was taken as the maximum Feret diameter of the hole.

[Relative density]
Relative density was measured based on the Archimedes method. Specifically, the air mass of the oxide sintered body is divided by the volume (the mass of the sintered body in water/the specific gravity of water at the measurement temperature), and the theoretical density ρ (g/cm ³ ) based on the following formula (1) The percentage value was defined as the relative density (unit: %).
ρ={(C ₁ /100)/ρ ₁ +(C ₂ /100)/ρ ₂ +(C ₃ /100)/ρ ₃ } ⁻¹ (1)
C ₁ _to C ₃ in _the formula (1) respectively indicate the content (% by mass) of the constituent substances of the target material, and ρ ₁ to ρ ₃ are the densities ( g/cm ³ ).
In the case of the present invention, the content (% by mass) of the constituent substances of the target material is considered to be SnO ₂ , Ta ₂ O ₅ and Nb ₂ O ₅ , for example C1: mass % of SnO ₂ in the target material
ρ1: Density of SnO ₂ (6.95 g/cm ³ )
C2: % by mass of Ta ₂ O ₅ in target material
ρ2: Density of Ta ₂ O ₅ (8.74 g/cm ³ )
C3: % by mass of Nb ₂ O ₅ in target material
ρ3: Density of Nb ₂ O ₅ (4.47 g/cm ³ )
is applied to equation (1), the theoretical density ρ can be calculated.
The mass % of SnO ₂ , the mass % of Ta ₂ O ₅ and the mass % of Nb ₂ O ₅ can be obtained from the analysis results of each element of the target material by ICP-OES analysis.

[Bending strength]
Autograph (registered trademark) AGS-500B manufactured by Shimadzu Corporation was used. A sample piece (length 36 mm or more, width 4.0 mm, thickness 3.0 mm) cut out from the oxide sintered body was measured according to the JIS R1601 three-point bending strength measurement method.

[Occurrence of abnormal discharge and degree of target cracking]
Sputtering targets were prepared using the oxide sintered bodies obtained in Examples and Comparative Examples, and the targets were attached to a DC magnetron sputtering apparatus to carry out sputtering. Sputtering conditions are as follows.
・Attainment vacuum: 3×10 ⁻⁶ Pa
・Sputtering pressure: 0.4 Pa
・ Oxygen partial pressure: 1 × 10 ^-3 Pa
・ Input power amount time: 2 W / cm ²
Time: 25 hours The number of times of arcing that occurred during sputtering under the above conditions was measured with an arcing counter attached to the power supply. As an arcing counter, μArc Monitor MAM Genesis MAM Data Collector Ver. 2.02 (manufactured by LANDMARK TECHNOLOGY) was used. Evaluation criteria are as follows.
A: less than 5 times of arcing B: more than 5 times less than 30 times of arcing C: more than 30 times of arcing During the sputtering under the above conditions, whether cracks occurred in the target by visual observation. It was also evaluated whether or not.

As is clear from the results shown in Table 1, when the oxide sintered body obtained in each example is used as a sputtering target material, the oxide sintered body obtained in the comparative example is used as a sputtering target material. In comparison, abnormal discharge is less likely to occur during sputtering, and target cracking is less likely to occur.
On the other hand, in Comparative Example 1 in which the compact for firing was produced without using the spray drying method, the compact could not be made dense, and the oxide sintered compact produced from the compact had many A hole has occurred.
In addition, in Comparative Example 2 in which a slurry was not prepared for each raw material powder, the granules became non-uniform and the compact could not be made dense, and the oxide sinter produced from the compact I have many holes in my body.
In Comparative Example 3, in which the amount of the dispersant was larger than that in Comparative Example 2, the granules were uniform, but were hard and hard to be crushed. A large number of holes were generated in the oxide sintered body produced from the molded body.

According to the present invention, an oxide sintered body that has few holes or has a small size even if there are holes, and is less likely to cause abnormal discharge or cracks when used as a sputtering target material. Methods of manufacture and sputtering target materials are provided.
When sputtering is performed using the oxide sintered body according to the present invention, it is possible to form a film while suppressing the occurrence of abnormal discharge and cracking during sputtering compared to the case of using a conventional oxide sintered body. is possible, it is possible to suppress the generation of extra defective products, and furthermore it is possible to reduce the generation of waste. That is, it becomes possible to reduce the energy cost in disposing of those wastes. This will lead to sustainable management and efficient use of natural resources, as well as achieving decarbonization (carbon neutrality).

Claims

An oxide sintered body containing a tin element, a tantalum element and a niobium element,
An oxide sintered body having an area ratio of pores per unit area of 1% or less in cross-sectional observation of the oxide sintered body.
An oxide sintered body containing a tin element, a tantalum element and a niobium element,
The oxide sintered body, wherein the maximum equivalent circle diameter of the pores is 20 μm or less in cross-sectional observation of the oxide sintered body.
An oxide sintered body containing a tin element, a tantalum element and a niobium element,
The oxide sintered body has a maximum Feret diameter of 50 μm or less in a hole when observed in cross section of the oxide sintered body.
An oxide sintered body containing a tin element, a tantalum element and a niobium element,
The area ratio of the pores per unit area in cross-sectional observation of the oxide sintered body is 1% or less,
The maximum circle equivalent diameter of the hole is 20 μm or less,
The oxide sintered body, wherein the maximum Feret diameter of the pores is 50 μm or less.
The oxide sintered body according to any one of claims 1 to 4, which has a relative density of 99.6% or more as measured by the Archimedes method.
The oxide sintered body according to any one of claims 1 to 4, which has a bending strength of 180 MPa or more as measured according to JIS R1601.
A tin element of 80% by mass or more and less than 100% by mass in terms of SnO 2 , a tantalum element in an amount of more than 0% by mass to 10% by mass or less in terms of Ta 2 O 5 , and more than 0% by mass to 10% by mass or less in terms of Nb 2 O 5 5. The oxide sintered body according to any one of claims 1 to 4, comprising a niobium element.
90% by mass or more and 96.5% by mass or less of tin in terms of SnO2 , 3% by mass or more and 7% by mass or less of tantalum in terms of Ta2O5 , and 0.5% by mass or more in terms of Nb2O5 5. The oxide sintered body according to any one of claims 1 to 4, containing 3% by mass or less of the niobium element.
A sputtering target material comprising the oxide sintered body according to any one of claims 1 to 4.
A sputtered film using the sputtering target material according to claim 9.
separately preparing a tin oxide slurry, a tantalum oxide slurry and a niobium oxide slurry;
Mixing the respective slurries to prepare a mixed slurry,
The mixed slurry is subjected to a spray drying method to produce granules,
Producing a compact using the granules,
A method for producing an oxide sintered body, in which the compact is sintered,
A method for producing an oxide sintered body, wherein a dispersing agent is added to each of the tin oxide slurry, the tantalum oxide slurry, and the niobium oxide slurry.
The production method according to claim 11, wherein the dispersant is a polycarboxylate.