KR102816464B1 - Oxide sintered body and its manufacturing method and sputtering target material - Google Patents

Abstract

The oxide sintered body of the present invention contains tin elements, tantalum elements, and niobium elements. The area ratio of pores per unit area in cross-sectional observation of the oxide sintered body is 1% or less. The maximum equivalent circle diameter of pores in cross-sectional observation of the oxide sintered body is 20 µm or less. The maximum ferret diameter of pores in cross-sectional observation of the oxide sintered body is 50 µm or less. It is preferable that the relative density of the oxide sintered body measured based on the Archimedes method is 99.6% or more. It is preferable that the rupture strength of the oxide sintered body measured in accordance with JIS R1601 is 180 MPa or more.

Description

Oxide sintered body and its manufacturing method and sputtering target material

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

Tin oxide transparent conductive films are widely used in display devices such as liquid crystal displays, plasma displays, and organic EL. Sputtering is known as one of the means for forming tin oxide transparent conductive films. In forming a conductive film using sputtering, if there are many defects such as pinholes in the sputtering target material, this can cause abnormal discharge during sputtering, and can cause particles to be generated during sputtering or cracks or crazing in the target material.

For the purpose of preventing abnormal discharge from occurring during sputtering, the present applicant first proposed a method for manufacturing a sputtering target, which comprises preparing an unsintered molded body containing SnO ₂ as a main component, Nb ₂ O ₅ and Ta ₂ O ₅ , and sintering the molded body at 1550° C. to 1650° C. (see Patent Document 1). For the same purpose, the present applicant first proposed a sputtering target containing Ta ₂ O ₅ , Nb ₂ O ₅ , SnO ₂ as a remainder, and unavoidable impurities (see Patent Document 2).

Japanese Patent Publication No. 2007-131891 Japanese Patent Publication No. 2008-248278

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 in which a tin oxide-based transparent conductive film is used are required to have further improved performance, and the tin oxide-based transparent conductive film is also required to have higher quality. Accordingly, a sputtering target material used for manufacturing a tin oxide-based transparent conductive film is also required to have higher quality with reduced occurrence of abnormal discharge during sputtering and cracking of the target material than before.

Accordingly, the present invention provides an oxide sintered body having fewer defects such as pinholes and being less likely to cause abnormal discharge or cracks when used as a sputtering target material, a method for manufacturing the same, and a sputtering target material.

The present invention is an oxide sintered body containing tin elements, tantalum elements and niobium elements,

The above problem was solved by providing an oxide sintered body having a pore area ratio per unit area of 1% or less in cross-sectional observation of the oxide sintered body.

In addition, the present invention provides a sputtering target material including the above-described oxide sintered body.

In addition, the present invention separately prepares a slurry of tin oxide, a slurry of tantalum oxide, and a slurry of niobium oxide,

Mix the above slurries to prepare a mixed slurry,

The above mixed slurry is subjected to a spray drying method to produce a granular product,

A molded body is manufactured using the above assembly,

A method for manufacturing an oxide sintered body by sintering the above-mentioned molded body,

A method for producing an oxide sintered body is provided, wherein a dispersant is contained in each of the slurry of the above tin oxide, the slurry of the above tantalum oxide, and the slurry of the above niobium oxide.

Hereinafter, the present invention will be described 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 a plurality of types of metal oxides. Specifically, the oxide sintered body of the present invention contains tin element (hereinafter also simply referred to as “Sn”), tantalum element (hereinafter also simply referred to as “Ta”), and niobium element (hereinafter also simply referred to as “Nb”) as metals. These metal elements exist in the sintered body in the state of oxides of the respective metals, or exist in the sintered body in the state of composite oxides of at least two types of metal elements selected from these three types of metal elements.

As described in the above-mentioned patent document 1, since SnO ₂ is a material that is difficult to sinter, it has been difficult to produce a dense sintered body containing SnO ₂ up to now. As a result, sintered bodies containing SnO ₂ known up to now have been prone to having pores, which are defective parts. In contrast, the oxide sintered body of the present invention has one of the characteristics in that the presence of pores is extremely reduced. The pores are defective parts observed in the cross-section of the oxide sintered body of the present invention. In this 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 portion is open in the cross section and extends toward the inside of the oxide sintered body. The hole portion includes both sides of a perforated hole and a hole having a bottom. In this specification, the hole portion is a defect portion having a size that is confirmed to exist when the cross section of the oxide sintered body is observed under a microscope at a magnification of 200 times (field of view: 445.3 ㎛ × 634.6 ㎛).

The degree of the presence of pores in the oxide sintered body of the present invention is such that the area ratio of pores per unit area in a cross-sectional observation of the oxide sintered body (hereinafter also referred to as the “pore area ratio”) is preferably extremely low, such as 1% or less. Due to the low degree of the presence of pores, when the oxide sintered body of the present invention is used as, for example, a sputtering target material, abnormal discharge is effectively suppressed from occurring during sputtering. Furthermore, the occurrence of particles during sputtering or the occurrence of cracks or breaks in the target material is effectively prevented. From the viewpoint of making these advantages even more remarkable, the pore area ratio is more preferably 0.9% or less, further preferably 0.8% or less, further preferably 0.7% or less, particularly preferably 0.6% or less, and particularly preferably 0.5% or less. The closer the value of the pore area ratio is to zero, the more preferable it is. From this viewpoint, the pore area ratio is preferably greater than 0% and less than or equal to 1%, more preferably greater than or equal to 0.02% and less than or equal to 0.9%, still more preferably greater than or equal to 0.04% and less than or equal to 0.8%, still more preferably greater than or equal to 0.06% and less than or equal to 0.7%, particularly preferably greater than or equal to 0.08% and less than or equal to 0.6%, and particularly preferably greater than or equal to 0.1% and less than or equal to 0.5%.

The method for measuring the hole area ratio is described in the examples described below. In addition, a method for making the hole area ratio less than the above-described value is also described below.

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 hole in the cross-section observation of the oxide sintered body is an extremely small 20 μm or less. Since the size of the hole is suppressed in this way, when the oxide sintered body of the present invention is used as, for example, a sputtering target material, abnormal discharge is effectively suppressed from occurring during sputtering. Furthermore, the generation of particles during sputtering and the generation of cracks or cracks in the target material are effectively prevented. From the viewpoint of making these advantages even more remarkable, the maximum equivalent circle diameter of the hole is more preferably 18 μm or less, further preferably 16 μm or less, further preferably 15 μm or less, particularly preferably 13 μm or less, and particularly preferably 12 μm or less. The closer the maximum equivalent circle diameter of the hole is to zero, the more preferable it is. From this viewpoint, the maximum equivalent circle diameter of the hole is preferably greater than 0 µm and less than or equal to 20 µm, more preferably greater than or equal to 1 µm and less than or equal to 18 µm, still more preferably greater than or equal to 2 µm and less than or equal to 16 µm, still more preferably greater than or equal to 3 µm and less than or equal to 15 µm, particularly preferably greater than or equal to 4 µm and less than or equal to 13 µm, and particularly preferably greater than or equal to 5 µm and less than or equal to 12 µm.

The method for measuring the maximum equivalent circular diameter of the hole is described in the examples described below. In addition, a method for making the maximum equivalent circular diameter of the hole less than or equal to the above-described value is also described below.

In addition to the maximum equivalent circle diameter of the hole being equal to or less than the above-mentioned value, the oxide sintered body of the present invention has an extremely small maximum ferret diameter of the hole being equal to or less than 50 µm. The ferret diameter is the size of a rectangle circumscribed to a measurement target. By setting the maximum ferret diameter of the hole to equal to or less than the above-mentioned value, the oxide sintered body of the present invention effectively suppresses abnormal discharge from occurring during sputtering when it is used as, for example, a sputtering target material. Furthermore, the generation of particles during sputtering and the generation of cracks or cracks in the target material are effectively prevented. From the viewpoint of making these advantages even more remarkable, the maximum ferret diameter of the hole is more preferably equal to or less than 45 µm, further preferably equal to or less than 40 µm, further preferably equal to or less than 35 µm, particularly preferably equal to or less than 30 µm, particularly preferably equal to or less than 28 µm, and most preferably equal to or less than 26 µm. The closer the maximum ferret diameter of the hole is to zero, the more preferable it is. From this viewpoint, the maximum ferret diameter of the hole is preferably more than 0 µm and less than or equal to 50 µm, more preferably 2 µm or more and less than or equal to 45 µm, still more preferably 3 µm or more and less than or equal to 40 µm, still more preferably 4 µm or more and less than or equal to 35 µm, particularly preferably 6 µm or more and less than or equal to 30 µm, particularly more preferably 8 µm or more and less than or equal to 28 µm, and most preferably 10 µm or more and less than or equal to 26 µm.

The method for measuring the maximum ferret diameter of the hole is described in the examples described below. In addition, a method for making the maximum ferret diameter of the hole less than or equal to the above-described value is also described below.

It is preferable that the oxide sintered body of the present invention satisfies at least one of the above-described (i) pore area ratio, (ii) maximum circle equivalent diameter, and (iii) maximum Feret diameter, more preferably satisfies a combination of at least two of (i)-(iii), and still more preferably satisfies all of (i)-(iii).

The oxide sintered body of the present invention is characterized by, in addition to the above-described (i)-(iii), also having a high relative density. Specifically, the oxide sintered body of the present invention preferably exhibits a high value of 99.6% or more in its relative density. By exhibiting such a high relative density, the oxide sintered body of the present invention is preferable because, when it is used as, for example, a sputtering target material and sputtering is performed using the target material, it is possible to suppress abnormal discharge during sputtering. From this viewpoint, the oxide sintered body of the present invention more preferably has a relative density of 99.8% or more, still more preferably 100.0% or more, still more preferably 100.2% or more, and particularly preferably 100.3% or more. The upper limit of the relative density is not particularly limited, but is preferably 105% or less, more preferably 104% or less, still more preferably 103% or less, and still more preferably 102% or less. The oxide sintered body of the present invention having such a relative density is suitably manufactured by the method described below. The relative density is measured according to the Archimedes method. A specific measurement method is described in the examples described below.

The oxide sintered body of the present invention is also characterized by its high strength. Specifically, the oxide sintered body of the present invention preferably exhibits a high value of the transverse rupture strength of 180 MPa or more. By exhibiting such a high transverse rupture strength, the oxide sintered body of the present invention is preferably such that, when it is used as, for example, a sputtering target material and sputtering is performed using the target material, even if an abnormal discharge occurs unintentionally during sputtering, cracks or breaks are unlikely to occur in the target material, which is preferable. From this viewpoint, the oxide sintered body of the present invention more preferably has a transverse rupture strength of 190 MPa or more, further preferably 200 MPa or more, further preferably 210 MPa or more, particularly preferably 220 MPa or more, particularly preferably 230 MPa or more, and most preferably 240 MPa or more. The upper limit of the flexural strength is not particularly limited, but is preferably 300 MPa or less, more preferably 290 MPa or less, still more preferably 280 MPa or less, and still more preferably 270 MPa or less. The oxide sintered body of the present invention having such a flexural strength is suitably manufactured by the method described below. The flexural strength is measured in accordance with JIS R1601. A specific measuring method is described in the examples described below.

The oxide sintered body of the present invention is preferably one having a low bulk resistivity, because this enables easy DC sputtering when the oxide sintered body is used as a sputtering target material. From this viewpoint, the bulk resistivity of the oxide sintered body is preferably 10Ω·cm or less. The bulk resistivity is measured in AUTO RANGE mode using Loresta (registered trademark) HP MCP-T410 (serial 4-probe probe TYPE ESP) manufactured by Mitsubishi Chemical Corporation. The measurement points are a total of five points, including the center and four corners of the oxide sintered body, and the arithmetic mean of each measurement value is taken as the bulk resistivity of the sintered body.

The oxide sintered body of the present invention, as described above, contains Sn, Ta, and Nb as metal elements. It is preferable that 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 secondary components, from the viewpoint of improving the properties of a transparent conductive film formed from the oxide sintered body. From the viewpoint of making this advantage even more remarkable, the total amount of Ta ₂ O ₅ and Nb ₂ O ₅ in the oxide sintered body is preferably 1.15 mass% or more and 12.0 mass% or less, more preferably 3.5 mass% or more and 10 mass% or less, still more preferably 4.0 mass% or more and 8.0 mass% or less, and still more preferably 5.0 mass% or more and 7.0 mass% or less.

The ratio of Ta ₂ O ₅ and Nb ₂ O ₅ in the oxide sintered body of the present invention is, from the viewpoint of improving the properties of a transparent conductive film formed from the oxide sintered body and improving the sintering density of the oxide sintered body, expressed as a mass ratio of Nb ₂ O ₅ /Ta ₂ O ₅ , preferably 0.15 or more and 0.90 or less, more preferably 0.15 or more and 0.60 or less, still more preferably 0.16 or more and 0.43 or less, and still 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 mass% or more and less than 100 mass% in terms of SnO ₂ , preferably 0 mass% or more and 10 mass% or less in terms of Ta ₂ O ₅ , and preferably 0 mass% or more and 10 mass% or less in terms of Nb ₂ O ₅ .

In addition, it is preferable that Sn is 88 mass% or more and 98.85 mass% or less in terms of SnO ₂ , Ta is preferably 1 mass% or more and 8 mass% or less in terms of Ta ₂ O ₅ , and Nb is preferably 0.15 mass% or more and 4 mass% or less in terms of Nb ₂ O ₅ .

In particular, it is preferable that Sn is 90 mass% or more and 96.5 mass% or less in terms of SnO ₂ , Ta is preferably 3 mass% or more and 7 mass% or less in terms of Ta ₂ O ₅ , and Nb is preferably 0.5 mass% or more and 3 mass% or less in terms of Nb ₂ O ₅ .

Since the oxide sintered body of the present invention contains Sn, Ta and Nb in this ratio, the properties of a transparent conductive film formed from the oxide sintered body are improved, which is preferable.

In addition, the ratios of SnO ₂ , Ta ₂ O ₅ , and Nb ₂ O ₅ are values based on mass, including the amount of inevitable impurities contained in the oxide sintered body.

Next, a suitable 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 powders. As the raw material powders, tin oxide powder, tantalum oxide powder, and niobium oxide powder are used. As the tin oxide powder, it is preferable to use SnO ₂ powder. As the tantalum oxide powder, it is preferable to use Ta ₂ O ₅ powder. As the niobium oxide powder, it is preferable to use Nb ₂ O ₅ powder.

It is preferable that the usage ratio of each oxide powder be adjusted so that the ratios of SnO ₂ , Ta ₂ O ₅ and Nb ₂ O ₅ included in the target oxide sintered body are within the above-described range.

From the viewpoint of ensuring sufficient dispersibility in a dispersion medium, the particle size of each oxide powder is preferably 0.3 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, as expressed by the volume cumulative particle size D50 at a cumulative volume of 50% by volume by a laser diffraction scattering particle size distribution measurement method.

In the present manufacturing method, it has been found through examination by the inventors that it is advantageous to prepare slurries of each oxide powder separately and mix the slurries to adjust the mixed slurry, in that it enables smooth manufacturing of an oxide sintered body in which the occurrence of pores is suppressed. Hereinafter, this procedure will be described in detail.

First, slurries of each oxide powder are prepared separately. As a dispersion medium used in preparing the slurry, a liquid capable of dispersing each oxide powder can be used. Examples of such dispersion mediums include water and various organic solvents. As an organic solvent, ethanol, etc. can be used, for example. Among these dispersion mediums, water is preferably used from the viewpoints of economy and ease of handling.

When the ratio of the dispersion medium in the slurry is set to preferably 20 mass% or more and 70 mass% or less, more preferably 30 mass% or more and 60 mass% or less, and still more preferably 35 mass% or more and 55 mass% or less, with respect to the mass of the oxide powder, the oxide powder is sufficiently dispersed in the dispersion medium.

The concentration of the oxide powder in the slurry of each oxide powder is preferably 58 mass% or more and 84 mass% or less, more preferably 62 mass% or more and 77 mass% or less, and still more preferably 64 mass% or more and 74 mass% or less, taking into consideration the dispersibility of the oxide powder in the dispersion medium.

From the viewpoint of improving the dispersibility of each oxide powder included in the slurry, it is preferable to mix a dispersant into each slurry. As the dispersant, an appropriate one can be used depending on the type of oxide powder. For example, polycarboxylic acid salts such as ammonium polycarboxylate, sodium polycarboxylate, and polycarboxylic acid amine salt; quaternary cationic polymers; nonionic surfactants such as polyalkylene glycol; and cationic surfactants such as quaternary ammonium salts can be used. One type of these dispersants can be used alone, or two or more types can be used in combination. Among these dispersants, it is preferable to use a polycarboxylic acid salt because the dispersibility of the oxide powder is high, and it is particularly preferable to use ammonium polycarboxylate.

The type of dispersant mixed in each slurry may be the same or different.

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

A binder may be mixed into each slurry. By mixing a binder, when an assembly is obtained using the mixed slurry described below, the strength of the assembly can be made appropriate. As the binder, for example, various organic polymer materials can be used. As the organic polymer material, for example, polyvinyl alcohol, acrylic emulsion binder, etc. can be used.

The concentration of the binder mixed in each slurry is appropriately selected depending on the concentration and type of the oxide powder contained in the slurry. When the concentration of the binder in the slurry is set to preferably 0.2 mass% or more and 0.8 mass% or less, more preferably 0.3 mass% or more and 0.7 mass% or less, and still more preferably 0.4 mass% or more and 0.6 mass% or less, based on the mass of the oxide powder, the strength of the assembly can be appropriate. The concentration of the binder in each slurry may be the same or different.

The preparation of the slurry is carried out by mixing each component that constitutes the slurry. For mixing, it is preferable to use a media mill device such as a ball mill or a bead mill, because it can sufficiently disperse the oxide powder in the dispersion medium.

After preparing each slurry in the above sequence, each slurry is then mixed to prepare a mixed slurry. It is preferable that the mixing ratio of each slurry be adjusted so that the ratios of SnO ₂ , Ta ₂ O ₅ and Nb ₂ O ₅ included in the target oxide sintered body are within the above-described range.

In order to obtain a mixed slurry by mixing each slurry, it is preferable to use a media mill device such as a ball mill or a bead mill, but the present invention is not limited to this method.

There are advantages to preparing a slurry of each oxide powder and mixing each slurry to obtain a mixed slurry, as described below.

In the present manufacturing method, as described later, it is preferable to obtain a granule by a spray drying method using a mixed slurry. In order to smoothly perform the spray drying method, it is advantageous to increase the amount of a dispersant mixed in the mixed slurry to lower the viscosity of the mixed slurry. However, if the amount of the dispersant mixed in is increased, the granule obtained by the spray drying method tends to be hard and difficult to crush. When such a granule is used to compression mold a molded body for producing an oxide sintered body, a defective part is likely to occur in the molded body due to the fact that the granule is difficult to crush during the compression process. When such a molded body is fired, the obtained sintered body does not become dense, and a defective part occurs.

On the other hand, if the amount of dispersant mixed into the mixed slurry is reduced for the purpose of making the assembly easy to crush, the viscosity of the mixed slurry tends to increase, which makes it difficult to manufacture an assembly with a tailored shape. If such an assembly is used to compression mold a molded body, defective parts are likely to occur in the molded body, and furthermore, the sintered body does not become dense, resulting in defective parts.

In contrast, the inventors of the present invention have found that by mixing a dispersant into a slurry of each oxide powder and mixing the slurries to obtain a mixed slurry, even if the amount of the dispersant added is small, an increase in the viscosity of the mixed slurry can be suppressed, and a mixed slurry with good dispersibility can be obtained. A sintered body manufactured using such a mixed slurry becomes dense with the occurrence of defective portions suppressed.

There are other advantages to preparing slurries of each oxide powder and mixing each slurry to obtain a mixed slurry, which are described below.

In conventional technologies, for example, the technologies described in the above-described Patent Documents 1 and 2, when producing an oxide sintered body containing a plurality of metal elements, the oxide powders of each metal element are dispersed all at once in a dispersion medium to prepare a slurry. As a result of the inventors' examination, it has been found that when a slurry is prepared by this method, the dispersant mixed in the slurry acts preferentially on a specific oxide, and a difference in the dispersibility between the oxides with respect to the dispersion medium occurs. If a difference in dispersibility occurs, the state of the oxide powder in the granulated body produced from the slurry, for example, the degree of susceptibility to crushing, becomes uneven, and as a result, there is a problem in that pores easily occur in the oxide sintered body finally obtained. The reason why a difference in dispersibility occurs is that the interaction between the dispersant and each oxide powder differs depending on the type of oxide powder. Therefore, in this manufacturing method, in order to prevent the occurrence of differences in dispersibility among oxides in the dispersion medium, instead of dispersing each oxide powder in the dispersion medium all at once, a method is adopted in which each oxide powder is dispersed separately in the dispersion medium and a dispersant is then mixed into the dispersion medium. By adopting this method, the dispersant acts reliably on each oxide powder, so it is difficult for differences in the dispersibility of each oxide powder in the mixed slurry to occur.

When a mixed slurry is prepared, the mixed slurry is subjected to a spray drying method to manufacture a granule. In granulation by the spray drying method, it is preferable to manufacture a granule having a particle size expressed as a volume cumulative particle size D50 at a cumulative volume of 50% by volume by a laser diffraction scattering particle size distribution measuring method of 30 µm or more and 60 µm or less, particularly 35 µm or more and 55 µm or less, particularly 40 µm or more and 50 µm or less, from the viewpoint of ease of crushing of the granule. The ease of crushing of the granule is advantageous in that it makes it difficult for pores to form when manufacturing an oxide sintered body using the granule. In addition, the volume cumulative particle size D50 of the granule is a particle size measured without performing ultrasonic dispersion treatment.

When the assembly is obtained, the assembly is filled into a mold to produce a molded body. For molding, a cold press method such as cold isostatic pressing can be used, for example. It is preferable to set the pressure during molding to 600 kg/cm ² or more and 1,200 kg/cm ² or less in order to obtain a dense molded body.

Once the molded body is obtained, the molded body may be subjected to a degreasing process as needed. By subjecting the molded body to a degreasing process, organic substances contained in the molded body, such as a dispersant or a binder, can be removed. The degreasing process is performed by heating the molded body to, for example, 500°C or higher and 900°C or lower in an air atmosphere.

When a molded body is obtained in this way, it is next fired. The firing of the molded body 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 more and 1700°C or less, more preferably 1520°C or more and 1680°C or less, and still more preferably 1550°C or more and 1650°C or less. The firing time is preferably 1 hour or more and 100 hours or less, more preferably 2 hours or more and 50 hours or less, and still more preferably 3 hours or more and 30 hours or less. The heating rate and the cooling rate 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 still more preferably 20°C/hour or more and 100°C/hour or less.

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

The oxide sintered body thus obtained can be processed into a predetermined dimension by grinding or the like to become a sputtering target material. The sputtering target material obtained is bonded to a backing plate to obtain a sputtering target. As the backing plate, for example, stainless steel, copper, titanium, etc. can be used. For bonding the target material and the backing plate, for example, a low-melting-point solder such as indium can be used.

The sputtering target obtained in this manner is suitably used for the production of a sputtered film, for example, a transparent conductive film. The sputtered film formed using this sputtering target can have the same composition as the sputtering target material. The resistivity of the sputtered film is preferably a low resistance of 9 mΩ·cm or less.

Example

Hereinafter, the present invention will be described in more detail by examples. However, the scope of the present invention is not limited to these examples.

〔Example 1〕

SnO ₂ powder having a particle size D50 of 0.7 μm, Ta ₂ O ₅ powder having a particle size D50 of 0.6 μm, and Nb ₂ O ₅ powder having a particle size D50 of 0.9 μm were prepared. The particle size D50 was measured using a particle size distribution measuring device MT3300EXII manufactured by Microtrack Bell Co., Ltd. Water was used as the dispersion medium. The refractive index of the measured substance was 2.20.

Each oxide powder was placed separately in a pot, and 0.5 mass% of polyvinyl alcohol, 0.02 mass% of ammonium polycarboxylate, and 50 mass% of water were added based on the mass of each oxide powder, and mixed using a ball mill for 20 hours to prepare each slurry.

Each prepared slurry was 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 device, and a spray drying method was performed under the conditions of an atomizer rotation speed of 14,000 rpm, an inlet temperature of 200°C, and an outlet temperature of 80°C to obtain a granulated product. The particle size D50 of the granulated product was 45 μm.

The obtained assembly was filled into a 158 mm × 640 mm mold and press-molded at a pressure of 800 kg/cm ² to obtain a molded body. The obtained molded body was heated at 750° C. for 6 hours in an air atmosphere to degrease.

A sintered body was produced by firing the molded body after degreasing. The 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 heating rate of 50°C/h, and a cooling rate of 50°C/h.

The sintered body thus obtained was cut and processed to obtain an oxide sintered body measuring 100 mm in width, 240 mm in length, 8 mm in thickness, and having a surface roughness Ra of 1.0 ㎛. A #170 grinding wheel was used for cutting.

〔Examples 2 and 3〕

For the sum of SnO ₂ powder, Ta ₂ O ₅ powder, and Nb ₂ O ₅ powder, each powder was mixed so that the ratio of each powder was as shown in Table 1 below. Except for this, an oxide sintered body was obtained in the same manner as Example 1.

〔Comparative Example 1〕

SnO ₂ powder, Ta ₂ O ₅ powder, and Nb ₂ O ₅ powder were prepared similarly to Example 1.

Each powder was weighed so that SnO ₂ was 94 mass%, Ta ₂ O ₅ was 5 mass%, and Nb ₂ O ₅ was 1 mass% of the total of each powder, and dry mixed for 21 hours.

A 4 mass% polyvinyl alcohol aqueous solution was added at 6 mass% to the mixed powder. The polyvinyl alcohol and the mixed powder were mixed using a mortar, and the mixture was passed through a 5.5 mesh sieve to obtain a mixed powder for molding.

Except for these, an oxide sintered body was obtained in the same manner as in Example 1.

〔Comparative Example 2〕

SnO ₂ powder, Ta ₂ O ₅ powder, and Nb ₂ O ₅ powder were prepared similarly to Example 1.

All the powders were placed in a pot, and 0.5 mass% of polyvinyl alcohol, 0.02 mass% of ammonium polycarboxylate, and 50 mass% of water were added based on the total amount of the powders, and mixed using a ball mill for 20 hours to prepare a mixed slurry. The proportion of each powder in the mixed slurry was such that SnO ₂ was 94 mass%, Ta ₂ O ₅ was 5 mass%, and Nb ₂ O ₅ was 1 mass% based on 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 mass% of polycarboxylic acid ammonium, a dispersant used in Example 2, was increased to 0.05 mass%. Aside from this, an oxide sintered body was obtained in the same manner as in Example 2.

〔evaluation〕

For the oxide sintered bodies obtained in the examples and comparative examples, the pore area ratio, maximum equivalent circle diameter, maximum Feret diameter, relative density, and transverse tensile strength were measured by the following methods.

In addition, sputtering targets were manufactured using the oxide sintered bodies obtained in the examples and comparative examples, and the degree of occurrence of abnormal discharge and the degree of occurrence of cracks in the target when sputtering was performed using the target were evaluated by the following methods.

The results above are shown in Table 1 below.

(Pore area ratio, maximum equivalent circle diameter and maximum ferret diameter)

(1) Preparation of cross-section of oxide sintered body

The cut surface obtained by cutting the oxide sintered body was polished step by step using emery #180, #400, #800, #1000, and #2000, and finally buffed to finish it into a hard surface.

(2) Measurement of hole area ratio, maximum equivalent circle diameter and maximum ferret diameter

For the cross-section of the oxide sintered body, a BSE-COMP image (hereinafter also referred to as “SEM image”) in the range of 445.3 μm × 634.6 μm at a magnification of 200x was photographed using a scanning electron microscope (SU3500, manufactured by Hitachi High-Technologies, Inc.). The SEM image was traced using particle analysis software (“Particle Analysis Version 3.0,” manufactured by Sumitomo Kinzoku Technology Co., Ltd.) and imaged using a scanner. This image was binarized. At this time, the conversion value was set so that 1 pixel was displayed in units of μm.

Next, the area and the total area of all the holes captured on the SEM were calculated. The percentage value of the total area of the holes relative to the field of view (445.3 ㎛ × 634.6 ㎛) was calculated. The arithmetic mean value of the measured percentages for 10 other SEM images was calculated, and this arithmetic mean value was used as the hole area ratio in the present invention.

In addition, the equivalent circular diameter of the hole was calculated based on the measured area of the hole in the process of obtaining the hole area ratio. Among all the equivalent circular diameters measured for the other 10 SEM images, the maximum value was taken as the maximum equivalent circular diameter of the hole.

Separately from the above manipulations, the horizontal Feret diameter (㎛) was calculated based on the total number of pixels in the horizontal direction for all the holes captured on the SEM image, and the vertical Feret diameter (㎛) was calculated based on the total number of pixels in the vertical direction. Among all the horizontal Feret diameters and vertical Feret diameters measured for the other 10 SEM images, the maximum value was taken as the maximum Feret diameter of the hole.

〔Relative density〕

The relative density was measured based on the Archimedes method. Specifically, the air mass of the oxide sintered body was divided by the volume (the mass of the sintered body in water/the specific gravity of water at the measurement temperature), and the value as a percentage of the theoretical density ρ (g/cm ³ ) based on the following equation (1) was taken as the relative density (unit: %).

ρ={(C ₁ /100)/ρ ₁ +(C ₂ /100)/ρ ₂ +(C ₃ /100)/ρ ₃ } ^-1 (1)

In equation (1), C ₁ to C ₃ represent the content (mass%) of the constituent substances of the target material, respectively, and ρ ₁ to ρ ₃ represent the density (g/cm ³ ) of each constituent substance corresponding to C ₁ to C ₃ .

In the case of the present invention, the content (mass%) of the constituent materials of the target material is considered to be SnO ₂ , Ta ₂ O ₅ , Nb ₂ O ₅ , for example.

C1: Mass% of SnO ₂ in target material

ρ1: Density of SnO ₂ (6.95 g/cm ³ )

C2: Mass% _{of Ta2O5} in target material

ρ2: Density of Ta ₂ O ₅ (8.74 g/cm ³ )

C3: Mass% of Nb ₂ O ₅ in target material

ρ3: Density of Nb ₂ O ₅ (4.47 g/cm ³ )

By applying to equation (1), the theoretical density ρ can be calculated.

Additionally, the mass% of _SnO2 , the mass% _{of Ta2O5} , and _the mass% of _Nb2O5 can be obtained from the analysis results of each element of the target material by ICP-OES analysis.

〔Intensity of resistance〕

An Autograph (registered trademark) AGS-500B from Shimadzu Seisakusho was used. A sample piece (overall length 36 mm or more, width 4.0 mm, thickness 3.0 mm) cut from an oxide sintered body was used, and the measurement was performed according to the three-point bending strength measurement method of JIS R1601.

〔The occurrence of abnormal discharge and the degree of target crack occurrence〕

A sputtering target was manufactured using the oxide sintered body obtained in the examples and comparative examples, and the target was installed in a DC magnetron sputtering device to perform sputtering. The sputtering conditions are as follows.

· Vacuum level reached: 3×10 ^-6 Pa

· Sputtering pressure: 0.4Pa

· Oxygen partial pressure: 1×10 ^-3 Pa

· Input power time: 2W/ ^cm2

· Time: 25 hours

The number of arcings that occurred during sputtering under the above conditions was measured using an arcing counter attached to the power supply. As an arcing counter, μArc Moniter MAM Genesis MAM Data Collector Ver. 2.02 (manufactured by LANDMARK TECHNOLOGY) was used. The evaluation criteria are as follows.

A: Arcing count less than 5 times

B: Arcing frequency is 5 or more but less than 30 times

C: Arcing count is 30 or more

During sputtering under the above conditions, whether cracks occurred in the target was also evaluated by visual observation.

[Table 1]

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, it can be seen that abnormal discharge is less likely to occur during sputtering and cracks in the target are less likely to occur compared to when the oxide sintered body obtained in the comparative example is used as a sputtering target material.

In contrast, in Comparative Example 1, where a molded body for sintering was manufactured without using a spray drying method, the molded body could not be made dense, and many pores were formed in the oxide sintered body manufactured from the molded body.

In addition, in Comparative Example 2, where slurry was not prepared for each raw material powder, the assembly became non-uniform, the molded body could not be made dense, and many pores were generated in the oxide sintered body manufactured from the molded body.

In Comparative Example 3, where the amount of dispersant was increased compared to Comparative Example 2, the assembly became uniform, but since it was hard and difficult to crush, the molded body could not be made dense, and many pores were generated in the oxide sintered body manufactured from the molded body.

According to the present invention, an oxide sintered body having a small number of holes or, even when holes are present, a small size thereof, which makes it difficult for abnormal discharge or cracks to occur when used as a sputtering target material, a method for producing the same, and a sputtering target material 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 or cracks during sputtering, compared to the case where a conventional oxide sintered body is used, so that the occurrence of extra defective products can be suppressed, and further, the occurrence of waste can be reduced. In other words, it becomes possible to reduce the energy cost for disposing of such waste. This leads to achieving sustainable management and efficient use of natural resources, and decarbonization (carbon neutrality).

Claims (22)

A sintered oxide body containing tin elements, tantalum elements and niobium elements,
The area ratio of the pores per unit area in the cross-sectional observation of the above oxide sintered body is 1% or less,
A sputtering target material comprising an oxide sintered body having a tensile strength of 180 MPa or more as measured in accordance with JIS R1601. A sintered oxide body containing tin elements, tantalum elements and niobium elements,
The maximum equivalent circle diameter of the hole in the cross-section observation of the above oxide sintered body is 20㎛ or less,
A sputtering target material comprising an oxide sintered body having a tensile strength of 180 MPa or more as measured in accordance with JIS R1601. A sintered oxide body containing tin elements, tantalum elements and niobium elements,
The maximum ferret diameter of the hole in the cross-section observation of the above oxide sintered body is 50 ㎛ or less,
A sputtering target material comprising an oxide sintered body having a tensile strength of 180 MPa or more as measured in accordance with JIS R1601. A sintered oxide body containing tin elements, tantalum elements and niobium elements,
The area ratio of the pores per unit area in the cross-sectional observation of the above oxide sintered body is 1% or less,
The maximum equivalent diameter of the above hole is 20㎛ or less,
The maximum ferrule diameter of the above hole is 50㎛ or less,
A sputtering target material comprising an oxide sintered body having a tensile strength of 180 MPa or more as measured in accordance with JIS R1601. In any one of claims 1 to 4,
A sputtering target material comprising 80 mass% or more and less than 100 mass% of tin element in terms of SnO ₂ , 0 mass% or more and 10 mass% or less of tantalum element in terms of Ta ₂ O ₅ , and 0 mass% or more and 10 mass% or less of niobium element in terms of Nb ₂ O ₅ . In paragraph 5,
A sputtering target material comprising 90 mass% or more and 96.5 mass% or less of tin element in terms of SnO ₂ , 3 mass% or more and 7 mass% or less of tantalum element in terms of Ta ₂ O ₅ , and 0.5 mass% or more and 3 mass% or less of niobium element in terms of Nb ₂ O ₅ . In paragraph 5,
A sputtering target material, wherein the ratio of Ta ₂ O ₅ and Nb ₂ O ₅ , expressed as a mass ratio of Nb ₂ O ₅ /Ta ₂ O ₅ , is 0.15 or more and 0.90 or less. In paragraph 5,
A sputtering target material having a relative density of 99.6% or more as measured based on the Archimedes method. In any one of claims 1 to 4,
A sputtering target material having a bulk resistivity of 10Ω·cm or less. A method for manufacturing a sputtered film using a sputtering target material described in any one of claims 1 to 4. A method for manufacturing a sputtering target material as described in any one of claims 1 to 4,
A slurry of tin oxide, a slurry of tantalum oxide and a slurry of niobium oxide are prepared separately,
Mix the above slurries to prepare a mixed slurry,
An assembly is manufactured by subjecting the above mixed slurry to a spray drying method,
A molded body is manufactured using the above assembly,
A method for manufacturing a sputtering target material by sintering the above-mentioned molded body,
A method for manufacturing a sputtering target material, wherein each of the slurry of tin oxide, the slurry of tantalum oxide, and the slurry of niobium oxide contains a dispersant in an amount of 0.01 mass% or more and 0.04 mass% or less relative to the mass of oxide powder contained in the slurry of tin oxide, the slurry of tantalum oxide, and the slurry of niobium oxide. In Article 11,
A method for manufacturing a sputtering target material, wherein the dispersant is a polycarboxylic acid salt. A sintered oxide body containing tin elements, tantalum elements and niobium elements,
Containing 90 mass% or more and 96.5 mass% or less of tin element in terms of SnO ₂ , 3 mass% or more and 7 mass% or less of tantalum element in terms of Ta ₂ O ₅ , and 0.5 mass% or more and 3 mass% or less of niobium element in terms of Nb ₂ O ₅ .
The area ratio of the pores per unit area in the cross-sectional observation of the above oxide sintered body is 1% or less,
An oxide sintered body having a tensile strength of 180 MPa or more as measured according to JIS R1601. A sintered oxide body containing tin elements, tantalum elements and niobium elements,
Containing 90 mass% or more and 96.5 mass% or less of tin element in terms of SnO ₂ , 3 mass% or more and 7 mass% or less of tantalum element in terms of Ta ₂ O ₅ , and 0.5 mass% or more and 3 mass% or less of niobium element in terms of Nb ₂ O ₅ .
The maximum equivalent circle diameter of the hole in the cross-section observation of the above oxide sintered body is 20㎛ or less,
An oxide sintered body having a tensile strength of 180 MPa or more as measured according to JIS R1601. A sintered oxide body containing tin elements, tantalum elements and niobium elements,
Containing 90 mass% or more and 96.5 mass% or less of tin element in terms of SnO ₂ , 3 mass% or more and 7 mass% or less of tantalum element in terms of Ta ₂ O ₅ , and 0.5 mass% or more and 3 mass% or less of niobium element in terms of Nb ₂ O ₅ .
The maximum ferret diameter of the hole in the cross-section observation of the above oxide sintered body is 50 ㎛ or less,
An oxide sintered body having a tensile strength of 180 MPa or more as measured according to JIS R1601. A sintered oxide body containing tin elements, tantalum elements and niobium elements,
Containing 90 mass% or more and 96.5 mass% or less of tin element in terms of SnO ₂ , 3 mass% or more and 7 mass% or less of tantalum element in terms of Ta ₂ O ₅ , and 0.5 mass% or more and 3 mass% or less of niobium element in terms of Nb ₂ O ₅ .
The area ratio of the pores per unit area in the cross-sectional observation of the above oxide sintered body is 1% or less,
The maximum equivalent diameter of the above hole is 20㎛ or less,
The maximum ferrule diameter of the above hole is 50㎛ or less,
An oxide sintered body having a tensile strength of 180 MPa or more as measured according to JIS R1601. In any one of Articles 13 to 16,
An oxide sintered body, wherein the ratio of Ta ₂ O ₅ and Nb ₂ O ₅ , expressed as a mass ratio of Nb ₂ O ₅ /Ta ₂ O ₅ , is 0.15 or more and 0.90 or less. In any one of Articles 13 to 16,
An oxide sintered body having a relative density of 99.6% or more as measured based on the Archimedes method. In any one of Articles 13 to 16,
An oxide sintered body having a bulk resistivity of 10Ω·cm or less. A method for manufacturing a sputtering film using the oxide sintered body described in any one of claims 13 to 16 as a sputtering target material. A method for manufacturing an oxide sintered body according to any one of claims 13 to 16,
A slurry of tin oxide, a slurry of tantalum oxide and a slurry of niobium oxide are prepared separately,
Mix the above slurries to prepare a mixed slurry,
An assembly is manufactured by subjecting the above mixed slurry to a spray drying method,
A molded body is manufactured using the above assembly,
A method for manufacturing an oxide sintered body by sintering the above-mentioned molded body,
A method for producing an oxide sintered body, wherein a dispersant is contained in each of the slurry of tin oxide, the slurry of tantalum oxide, and the slurry of niobium oxide, in an amount of 0.01 mass% or more and 0.04 mass% or less relative to the mass of oxide powder contained in the slurry of tin oxide, the slurry of tantalum oxide, and the slurry of niobium oxide. In Article 21,
A method for producing an oxide sintered body, wherein the dispersant is a polycarboxylic acid salt.