Oxide sinter and method for producing the same, and sputtering target

Abstract

The oxide sintered body of the present application contains a tin element, a tantalum element, and a niobium element. The area ratio of the hole portion per unit area in the cross-sectional observation of the oxide sintered body is 1% or less. The maximum equivalent circle diameter of the hole portion in the cross-sectional observation of the oxide sintered body is 20 μm or less. The maximum Feret diameter of the hole portion in the cross-sectional observation of the oxide sintered body is 50 μm or less. The relative density of the oxide sintered body determined based on the Archimedes method is 99.6% or more is appropriate. The bending strength of the oxide sintered body determined according to JIS R1601 is 180 MPa or more is appropriate.

Description

Technical Field

[0001] This invention relates to oxide sintered bodies and methods for manufacturing the same. Additionally, this invention relates to sputtering targets formed from oxide sintered bodies. Background Technology

[0002] Tin oxide-based transparent conductive films are widely used in display devices such as liquid crystal displays, plasma displays, and organic EL displays. Sputtering is one known method for forming tin oxide-based transparent conductive films. However, in the formation of conductive films using sputtering, the presence of numerous pinholes and other defects in the sputtering target can lead to abnormal discharges, particle generation, target breakage, and crack formation.

[0003] To prevent abnormal discharges during sputtering, the applicant first proposed a method for manufacturing a sputtering target by preparing an unsintered molded body containing Nb2O5 and Ta2O5 as the main component, and sintering the molded body at 1550°C to 1650°C (see Patent Document 1). For the same purpose, the applicant first proposed a sputtering target containing Ta2O5, Nb2O5, SnO2 as a balance, and unavoidable impurities (see Patent Document 2).

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2007-131891

[0007] Patent Document 2: Japanese Patent Application Publication No. 2008-248278 Summary of the Invention

[0008] According to the technology described in Patent Documents 1 and 2, abnormal discharge and target breakage during sputtering can be suppressed. However, display devices using tin oxide-based transparent conductive films require further performance improvements, and the quality of the tin oxide-based transparent conductive films also needs to be further improved. Therefore, for sputtering targets used in manufacturing tin oxide-based transparent conductive films, high-quality sputtering targets with reduced abnormal discharge and target breakage during sputtering compared to the past are also required.

[0009] Therefore, the object of the present invention is to provide an oxide sintered body with few defects such as pinholes, which is not prone to abnormal discharge or cracking when used as a sputtering target, as well as a method for manufacturing the same and a sputtering target.

[0010] The present invention solves the aforementioned problems by providing an oxide sintered body containing tin, tantalum, and niobium.

[0011] In the cross-sectional observation of the aforementioned oxide sintered body, the area ratio of the pores per unit area is less than 1%.

[0012] In addition, the present invention provides a sputtering target formed from the aforementioned oxide sintered body.

[0013] Furthermore, the present invention provides a method for manufacturing an oxide sintered body, which is as follows:

[0014] Tin oxide paste, tantalum oxide paste, and niobium oxide paste were prepared separately and individually.

[0015] The aforementioned slurries are mixed to prepare a mixed slurry.

[0016] The aforementioned mixed slurry is then used in a spray drying process to produce granules.

[0017] The aforementioned granules are used to manufacture shaped bodies.

[0018] The aforementioned shaped body is sintered, wherein,

[0019] The aforementioned tin oxide slurry, tantalum oxide slurry, and niobium oxide slurry are each pre-contained with a dispersant. Detailed Implementation

[0020] The present invention will now be described based on its preferred embodiments. The present invention relates to oxide sintered bodies and sputtering targets using the same.

[0021] The oxide sintered body of the present invention is a sintered body of multiple metal oxides. Specifically, the oxide sintered body of the present invention contains tin (hereinafter referred to as "Sn"), tantalum (hereinafter referred to as "Ta"), and niobium (hereinafter referred to as "Nb") as metals. These metal elements exist in the sintered body in the state of oxides of each metal, or in the sintered body in the state of composite oxides selected from at least two of these three metal elements.

[0022] As described in Patent Document 1 above, SnO2 is a difficult-to-sinter material, making it difficult to manufacture dense sintered bodies containing SnO2 until now. Consequently, known SnO2-containing sintered bodies tend to produce pores as defects. In contrast, one characteristic of the oxide sintered body of the present invention is that the presence of pores is extremely reduced. Pores are defects 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 refers to the surface obtained by cutting the oxide sintered body using a prescribed method.

[0023] A pore is an opening in the cross-section that extends into the interior of the oxide sintered body. A pore includes both through holes and bottom holes. In this specification, a pore refers to a defect of an acceptable size when the cross-section of the oxide sintered body is observed under a microscope at 200x magnification (viewing field: 445.3 μm × 634.6 μm).

[0024] The presence of pores in the oxide sintered body of the present invention is preferably extremely low, such that the area ratio of pores per unit area in a cross-sectional view of the oxide sintered body (hereinafter also referred to as "pore area ratio") is 1% or less. Because the presence of pores is so low, when the oxide sintered body of the present invention is used, for example, as a sputtering target, abnormal discharge during sputtering is effectively suppressed. Furthermore, the generation of particles during sputtering, the occurrence of fractures and cracks in the target material, are effectively prevented. From the viewpoint of further maximizing these advantages, the pore area ratio is more preferably 0.9% or less, more preferably 0.8% or less, even more preferably 0.7% or less, particularly preferably 0.6% or less, and especially preferably 0.5% or less. The closer the value of the pore area ratio is to zero, the more preferred it is. From this perspective, the area ratio of the aperture is preferably more than 0% and less than 1%, more preferably more than 0.02% and less than 0.9%, further preferably more than 0.04% and less than 0.8%, even more preferably more than 0.06% and less than 0.7%, particularly preferably more than 0.08% and less than 0.6%, and especially preferably more than 0.1% and less than 0.5%.

[0025] The method for measuring the orifice area ratio will be described in the examples described later. Additionally, methods for achieving an orifice area ratio below the aforementioned value will also be described later.

[0026] One of the features of the oxide sintered body of the present invention is that the size of the pores is suppressed when the cross-section of the pores is observed. Specifically, the maximum equivalent circle diameter of the pores in the cross-section of the oxide sintered body is extremely small, less than 20 μm. By suppressing the size of the pores in this way, the oxide sintered body of the present invention effectively suppresses abnormal discharge during sputtering when used, for example, as a sputtering target. In addition, the generation of particles during sputtering, the breakage of the target material, and cracks are effectively prevented. From the viewpoint of further emphasizing these advantages, the maximum equivalent circle diameter of the pores is more preferably less than 18 μm, more preferably less than 16 μm, even more preferably less than 15 μm, particularly preferably less than 13 μm, and especially preferably less than 12 μm. The closer the maximum equivalent circle diameter of the pores is to zero, the more preferred. From this perspective, the maximum equivalent circle diameter of the hole is preferably greater than 0 μm and less than 20 μm, more preferably greater than 1 μm and less than 18 μm, further preferably greater than 2 μm and less than 16 μm, even more preferably greater than 3 μm and less than 15 μm, particularly preferably greater than 4 μm and less than 13 μm, and especially preferably greater than 5 μm and less than 12 μm.

[0027] The method for determining the maximum equivalent circle diameter of the hole will be described in the embodiments described later. Furthermore, the method for ensuring that the maximum equivalent circle diameter of the hole is below the aforementioned value will also be described later.

[0028] In addition to the maximum equivalent circle diameter of the orifice being below the aforementioned value, the maximum Freette diameter of the orifice in the oxide sintered body of the present invention is extremely small, being 50 μm or less. The Freette diameter refers to the dimension of the rectangle circumscribed by the object being measured. By setting the maximum Freette diameter of the orifice below the aforementioned value, the oxide sintered body of the present invention effectively suppresses abnormal discharge during sputtering when used, for example, as a sputtering target. Furthermore, the generation of particles during sputtering, the occurrence of fractures and cracks in the target material, are effectively prevented. From the viewpoint of further emphasizing these advantages, the maximum Freette diameter of the orifice is more preferably 45 μm or less, more preferably 40 μm or less, even more preferably 35 μm or less, particularly preferably 30 μm or less, especially preferably 28 μm or less, and most preferably 26 μm or less. The closer the maximum Freette diameter of the orifice is to zero, the more preferred it is. From this perspective, the maximum Ferrette diameter of the aperture is preferably greater than 0 μm and less than 50 μm, more preferably greater than 2 μm and less than 45 μm, further preferably greater than 3 μm and less than 40 μm, even more preferably greater than 4 μm and less than 35 μm, particularly preferably greater than 6 μm and less than 30 μm, especially preferably greater than 8 μm and less than 28 μm, and most preferably greater than 10 μm and less than 26 μm.

[0029] The method for determining the maximum Ferrette diameter of the hole will be described in the examples described later. Furthermore, the method for ensuring that the maximum Ferrette diameter of the hole is below the aforementioned value will also be described later.

[0030] The oxide sintered body of the present invention preferably satisfies at least one of (i) pore area ratio, (ii) maximum equivalent circle diameter and (iii) maximum Ferrette diameter, more preferably a combination of at least two of (i)-(iii), and even more preferably all of (i)-(iii).

[0031] The oxide sintered body of the present invention is also characterized by a high relative density, in addition to the above-described (i)-(iii). 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, when used, for example, as a sputtering target and sputtered using that target, can suppress abnormal discharge during sputtering, and is therefore preferred. From this viewpoint, the relative density of the oxide sintered body of the present invention is more preferably 99.8% or more, further preferably 100.0% or more, even more preferably 100.2% or more, and particularly preferably 100.3% or more. There is no particular limitation on the upper limit of the relative density, but it is preferably 105% or less, more preferably 104% or less, further preferably 103% or less, and even 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 later. The relative density is determined according to the Archimedes method. The specific determination method is described in the examples described later.

[0032] The oxide sintered body of the present invention is also characterized by high strength. Specifically, the oxide sintered body of the present invention exhibits a flexural strength preferably of 180 MPa or higher. By exhibiting such high flexural strength, when the oxide sintered body of the present invention is used, for example, as a sputtering target and sputtered using that target, the target is less prone to cracking or breakage even if an abnormal discharge occurs accidentally during sputtering, which is therefore preferable. From this viewpoint, the flexural strength of the oxide sintered body of the present invention is more preferably 190 MPa or higher, further preferably 200 MPa or higher, even more preferably 210 MPa or higher, particularly preferably 220 MPa or higher, especially preferably 230 MPa or higher, and most preferably 240 MPa or higher. There is no particular limitation on the upper limit of the flexural strength, but it is preferably 300 MPa or lower, more preferably 290 MPa or lower, further preferably 280 MPa or lower, and even more preferably 270 MPa or lower. The oxide sintered body of the present invention having this flexural strength is suitably manufactured by the method described later. The flexural strength is measured according to JIS R1601. The specific measurement methods are described in the examples described later.

[0033] The oxide sintered body of the present invention has a low volume resistivity, which is preferable from the viewpoint that DC sputtering can be easily performed when using the oxide sintered body as a sputtering target. From this viewpoint, the volume resistivity of the oxide sintered body is preferably 10 Ω·cm or less. The volume resistivity was measured using a Loresta HP MCP-T410 (TYPE ESP, a 4-probe cascade probe) manufactured by Mitsubishi Chemical Corporation in AUTO RANGE mode. The measurement sites were set at a total of 5 locations, including the center and four corners of the oxide sintered body, and the arithmetic mean of the measured values ​​was taken as the volume resistivity of the sintered body.

[0034] The oxide sintered body of the present invention, as described above, contains Sn, Ta, and Nb as metallic elements. The oxide sintered body of the present invention contains SnO2 as a main component and Ta2O5 and Nb2O5 as secondary components, which is preferable from the viewpoint of improving the properties of the transparent conductive film formed from this oxide sintered body. From the viewpoint of further maximizing this advantage, the total amount of Ta2O5 and Nb2O5 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, more preferably 4.0% by mass or more and 8.0% by mass or less, and even more preferably 5.0% by mass or more and 7.0% by mass or less.

[0035] From the viewpoints of improving the properties of the transparent conductive film formed from the oxide sintered body and improving the sintering density of the oxide sintered body, the ratio of Ta2O5 to Nb2O5 in the oxide sintered body of the present invention, expressed as the mass ratio of Nb2O5 / Ta2O5, is preferably 0.15 or more and 0.90 or less, more preferably 0.15 or more and 0.60 or less, further preferably 0.16 or more and 0.43 or less, and even more preferably 0.17 or more and 0.33 or less.

[0036] For the specific ratio of Sn, Ta and Nb in the oxide sintered body of the present invention, Sn is preferably 80% or more and less than 100% by mass when converted to SnO2, Ta is preferably more than 0% by mass and less than 10% by mass when converted to Ta2O5, and Nb is preferably more than 0% by mass and less than 10% by mass when converted to Nb2O5.

[0037] Furthermore, Sn, when converted to SnO2, is preferably 88% or more and 98.85% or less by mass; Ta, when converted to Ta2O5, is preferably 1% or more and 8% or less by mass; and Nb, when converted to Nb2O5, is preferably 0.15% or more and 4% or less by mass.

[0038] In particular, Sn, when converted to SnO2, is preferably 90% or more and 96.5% or less by mass; Ta, when converted to Ta2O5, is preferably 3% or more and 7% or less by mass; and Nb, when converted to Nb2O5, is preferably 0.5% or more and 3% or less by mass.

[0039] By including Sn, Ta, and Nb in this ratio in the oxide sintered body of the present invention, the properties of the transparent conductive film formed from the oxide sintered body are improved, and therefore preferred.

[0040] It should be noted that the ratios of SnO2, Ta2O5, and Nb2O5 are values ​​based on the mass of the amounts of unavoidable impurities contained in the oxide sintered body.

[0041] Next, a suitable manufacturing method for the oxide sintered body of the present invention will be described. The oxide sintered body of the present invention is manufactured by sintering raw material powder. Tin oxide powder, tantalum oxide powder, and niobium oxide powder are used as raw material powders. SnO2 powder is preferably used as the tin oxide powder. Ta2O5 powder is preferably used as the tantalum oxide powder. Nb2O5 powder is preferably used as the niobium oxide powder.

[0042] The ratio of each oxide powder used is preferably adjusted so that the ratio of SnO2, Ta2O5 and Nb2O5 contained in the target oxide sintered body is within the above-mentioned range.

[0043] From the viewpoint of ensuring sufficient dispersibility of the dispersion medium, the particle size of each oxide powder is expressed as the cumulative particle size D50 at 50% of the cumulative volume obtained by laser diffraction scattering particle size distribution determination method, 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 even more preferably 0.5 μm or more and 0.9 μm or less.

[0044] In this manufacturing method, the inventors' research has shown that individually preparing slurries of each oxide powder, mixing the slurries, and adjusting the mixed slurry is advantageous from the viewpoint of being able to smoothly manufacture oxide sintered bodies in which the formation of pores is suppressed. This step will be described in detail below.

[0045] First, slurries of each oxide powder are prepared individually. As the dispersion medium used in the preparation of the slurry, a liquid capable of dispersing each oxide powder can be used. Examples of such dispersion media include water and various organic solvents. For example, ethanol can be used as an organic solvent. Among these dispersion media, water is preferred from the viewpoints of economy and ease of handling.

[0046] If the ratio of the dispersion medium in the slurry to the mass of the oxide powder is set to 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, and even more preferably 35% by mass or more and 55% by mass or less, the oxide powder will be sufficiently dispersed in the dispersion medium.

[0047] Regarding the concentration of oxide powder in the slurry of each oxide powder, considering the dispersibility of the oxide powder to the dispersion medium, it is preferably set to 58% by mass or more and 84% by mass or less, more preferably 62% by mass or more and 77% by mass or less, and even more preferably 64% by mass or more and 74% by mass or less.

[0048] From the viewpoint of improving the dispersibility of the various oxide powders contained in the slurry, it is preferable to incorporate a dispersant into each slurry. As a dispersant, an appropriate dispersant can be used depending on the type of oxide powder. For example, polycarboxylate salts such as ammonium polycarboxylate, sodium polycarboxylate, and amine polycarboxylate; quaternary cationic polymers; nonionic surfactants such as polyalkylene glycol; and cationic surfactants such as quaternary ammonium salts can be used. These dispersants can be used alone or in combination of two or more. Among these dispersants, polycarboxylate salts are preferred due to their high dispersibility of oxide powders, and ammonium polycarboxylate is particularly preferred.

[0049] The types of dispersants used in the various slurries can be the same or different.

[0050] The concentration of the dispersant in each slurry is appropriately selected based on the concentration and type of oxide powder contained in the slurry. Satisfactory dispersibility is achieved when the concentration of the dispersant in the slurry relative to the mass of the oxide powder 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, and even more preferably 0.02% by mass or more and 0.03% by mass or less. The concentration of the dispersant in each slurry can be the same or different.

[0051] Binders can be mixed into each slurry. By mixing the binder, the strength of the granules obtained using the mixed slurry described later can be made suitable. Various organic polymer materials can be used as binders, for example. Examples of organic polymer materials include polyvinyl alcohol and acrylic emulsion binders.

[0052] The concentration of the binder mixed in each slurry is appropriately selected based on the concentration and type of oxide powder contained in the slurry. If the concentration of the binder in the slurry relative to the mass of the oxide powder 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, and even more preferably 0.4% by mass or more and 0.6% by mass or less, the strength of the granules can be suitable. The concentration of the binder in each slurry can be the same or different.

[0053] The slurry is prepared by mixing the various components that make up the slurry. Mixing is preferably performed using media milling equipment such as ball mills or bead mills, from the viewpoint of being able to fully disperse the oxide powder in the dispersion medium.

[0054] After preparing each slurry through the above steps, the slurries are then mixed to prepare a mixed slurry. The mixing ratio of each slurry is preferably adjusted so that the ratio of SnO2, Ta2O5 and Nb2O5 contained in the target oxide sinter is within the above-mentioned range.

[0055] To mix the various slurries to obtain a mixed slurry, media milling devices such as ball mills or bead mills are preferred, but not limited to this method.

[0056] Preparing slurries of various oxide powders and mixing the slurries to obtain a mixed slurry has the following advantages.

[0057] In this manufacturing method, as described below, it is preferable to use a mixed slurry and obtain granules by spray drying. To facilitate spray drying, it is advantageous to increase the amount of dispersant mixed in the slurry to reduce its viscosity. However, if the amount of dispersant is increased, the granules obtained by spray drying tend to be hard and difficult to crush. If such granules are used to compress a molded body for manufacturing oxide sintered bodies, defects are easily generated in the molded body because the granules are difficult to crush during compression. If such a molded body is fired, the resulting sintered body will not be dense and will not have defects.

[0058] On the other hand, if the amount of dispersant in the mixed slurry is reduced to make the granules easier to crush, there is a tendency for the viscosity of the mixed slurry to increase, which makes it difficult to produce granules with uniform shape. If such granules are used to compress the molded body, defects are still likely to be generated in the molded body, resulting in a non-dense sintered body with defects.

[0059] In contrast, the inventors' research has shown that by mixing the slurries of various oxide powders with a dispersant to obtain a mixed slurry, even with a reduced amount of dispersant, the viscosity increase of the mixed slurry can be suppressed, resulting in a well-dispersed mixed slurry. Sintered bodies manufactured using this mixed slurry are dense sintered bodies where the formation of defects is suppressed.

[0060] Preparing slurries of various oxide powders and mixing the various slurries to obtain a mixed slurry also has the following other advantages.

[0061] In existing technologies, such as those described in Patent Documents 1 and 2, when manufacturing oxide sintered bodies containing multiple metal elements, the oxide powders of each metal element are dispersed together in a dispersion medium to prepare a slurry. The inventors' research has shown that if this method is used to prepare the slurry, the dispersant mixed in the slurry preferentially acts on specific oxides, resulting in differences in the dispersibility of the dispersion medium between the oxides. These differences in dispersibility lead to unevenness in the state of the oxide powders in the granulated slurry, such as their ease of crushing, resulting in the potential for pores to form in the final oxide sintered body. The reason for these differences in dispersibility is that the interaction between the dispersant and each oxide powder varies depending on the type of oxide powder. Therefore, in this manufacturing method, to prevent differences in the dispersibility of the dispersion medium between oxides, instead of dispersing each oxide powder together in the dispersion medium, a method is employed where each oxide powder is individually dispersed in the dispersion medium, and the dispersant is mixed into the dispersion medium at this time. By employing this method, the dispersant effectively acts on each oxide powder, thus minimizing differences in the dispersibility of the oxide powders in the mixed slurry.

[0062] After preparing the mixed slurry, the mixed slurry is subjected to spray drying to produce granules. In the spray drying granulation process, it is preferable to produce granules with a particle size of 30 μm or more and 60 μm or less, particularly 35 μm or more and 55 μm or less, and particularly 40 μm or more and 50 μm or less, expressed as the volumetric particle size D50 at 50% of the cumulative volume obtained by laser diffraction scattering particle size distribution determination, from the viewpoint that the granules are easily crushable. The ease of crushing the granules is advantageous from the viewpoint that it reduces the formation of pores when using these granules to manufacture oxide sintered bodies. It should be noted that the volumetric particle size D50 in the granules is the particle size measured without ultrasonic dispersion treatment.

[0063] After obtaining the granules, the granules are filled into a mold to form a shaped body. Forming can be achieved, for example, by cold pressing or cold isostatic pressing. The forming pressure is set at 600 kg / cm². 2 Above and 1200kg / cm 2The following is a preferred option from the viewpoint of obtaining a dense shaped body.

[0064] After obtaining the molded body, it can be fed into a degreasing process as needed. By feeding the molded body into the degreasing process, organic matter, such as dispersants and binders, contained in the molded body can be removed. The degreasing process is carried out by heating the molded body, for example, to a temperature above 500°C and below 900°C in an atmospheric atmosphere.

[0065] After obtaining the shaped body, it is then fired. Firing of the shaped body can typically be carried out in an oxygen-containing atmosphere. Firing in an atmospheric atmosphere is particularly 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 even more preferably 1550°C or higher and 1650°C or lower. The firing time is preferably 1 hour or higher and 100 hours or lower, more preferably 2 hours or higher and 50 hours or lower, and even more preferably 3 hours or higher and 30 hours or lower. The heating rate and cooling rate are preferably each independently 5°C / hour or higher and 500°C / hour or lower, more preferably 10°C / hour or higher and 200°C / hour or lower, and even more preferably 20°C / hour or higher and 100°C / hour or lower.

[0066] 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, a small maximum equivalent circle diameter, and a small maximum Freette diameter.

[0067] The resulting oxide sintered body can be machined to specified dimensions using processes such as grinding to form a sputtering target. By bonding the obtained sputtering target to a backing plate, a sputtering target is obtained. For example, stainless steel, copper, and titanium can be used as the backing plate. The bonding between the target and the backing plate can be achieved, for example, using low-melting-point solder such as indium.

[0068] The sputtering target thus obtained is suitable for the manufacture of sputtered films, such as transparent conductive films. 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 low, below 9 mΩ·cm.

[0069] Example

[0070] The present invention will be described in more detail below through embodiments. However, the scope of the present invention is not limited to the above embodiments.

[0071] [Example 1]

[0072] Prepare SnO2 powder with a particle size D50 of 0.7 μm, Ta2O5 powder with a particle size D50 of 0.6 μm, and Nb2O5 powder with a particle size D50 of 0.9 μm. The particle size D50 was measured using a MicrotracBEL Corp. MT3300EXII particle size distribution analyzer. Water was used as the dispersion medium. The refractive index of the measured substances was set to 2.20.

[0073] Each oxide powder was individually added to a tank, and 0.5% by mass of polyvinyl alcohol, 0.02% by mass of ammonium polycarboxylate and 50% by mass of water were added relative to the mass of each oxide powder. The mixture was then mixed using a ball mill for 20 hours to prepare the slurry.

[0074] The prepared slurries were mixed and then milled in a ball mill for 60 minutes to obtain a mixed slurry. The mixing ratio of each slurry relative to the total amount of each powder was 96.5% by mass for SnO2, 3.0% by mass for Ta2O5, and 0.5% by mass for Nb2O5.

[0075] The mixed slurry was fed into a spray drying unit, and spray drying was carried out under the conditions of atomizer speed of 14000 rpm, inlet temperature of 200℃, and outlet temperature of 80℃ to obtain granules. The particle size D50 of the granules was 45 μm.

[0076] The obtained granules were filled into a 158mm × 640mm mold and subjected to a pressure of 800kg / cm³. 2 The molded body is obtained by pressing under pressure. The molded body is then degreased by heating at 750°C for 6 hours in an atmospheric atmosphere.

[0077] The degreased molded body is calcined to produce a sintered body. The calcination is carried out in an atmosphere with an oxygen concentration of 20 vol%, a calcination temperature of 1600℃, a calcination time of 8 hours, a heating rate of 50℃ / h, and a cooling rate of 50℃ / h.

[0078] The sintered body thus obtained was machined to obtain an oxide sintered body with 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 grinding wheel was used for machining.

[0079] [Examples 2 and 3]

[0080] The powders were mixed in the manner shown in Table 1 below, with the ratio of each powder relative to the total SnO2 powder, Ta2O5 powder, and Nb2O5 powder. Otherwise, an oxide sintered body was obtained in the same manner as in Example 1.

[0081] [Comparative Example 1]

[0082] Prepare SnO2 powder, Ta2O5 powder and Nb2O5 powder as in Example 1.

[0083] Each powder was weighed with SnO2 at 94% by mass, Ta2O5 at 5% by mass, and Nb2O5 at 1% by mass relative to the total amount of each powder, and then dry-mixed for 21 hours.

[0084] Add 6% by mass of a 4% by mass aqueous solution of polyvinyl alcohol relative to the mixed powder. After mixing the polyvinyl alcohol and the mixed powder using a mortar, pass the mixture through a 5.5 mesh sieve to obtain a mixed powder for molding.

[0085] In addition, oxide sintered bodies were obtained in the same manner as in Example 1.

[0086] [Comparative Example 2]

[0087] Prepare SnO2 powder, Ta2O5 powder and Nb2O5 powder as in Example 1.

[0088] All powders were added to a container, along with 0.5% by mass of polyvinyl alcohol, 0.02% by mass of ammonium polycarboxylate, and 50% by mass of water relative to the total powder amount. The mixture was then prepared by ball milling for 20 hours. The ratio of each powder in the slurry relative to the total powder amount was 94% by mass of SnO2, 5% by mass of Ta2O5, and 1% by mass of Nb2O5. Otherwise, an oxide sintered body was obtained in the same manner as in Example 1.

[0089] [Comparative Example 3]

[0090] In this comparative example, the concentration of ammonium polycarboxylate, which was used as a dispersant in Example 2, was increased from 0.02% by mass to 0.05% by mass. Otherwise, the oxide sintered body was obtained in the same manner as in Example 2.

[0091] [evaluate]

[0092] For the oxide sintered bodies obtained in the examples and comparative examples, the pore area ratio, maximum equivalent circle diameter, maximum Freret diameter, relative density, and flexural strength were determined using the following methods.

[0093] In addition, sputtering targets were fabricated using the oxide sintered bodies obtained in the examples and comparative examples, and the degree of abnormal discharge and the degree of target breakage during sputtering were evaluated using the following methods.

[0094] The results are shown in Table 1 below.

[0095] [Aperture area ratio, maximum equivalent circle diameter, and maximum Ferrette diameter]

[0096] (1) Preparation of cross-section of oxide sintered body

[0097] The cut surface obtained by cutting the oxide sintered body is ground in stages using sandpaper of #180, #400, #800, #1000, and #2000, and finally polished to achieve a mirror finish.

[0098] (2) Determination of pore area ratio, maximum equivalent circle diameter and maximum Ferrette diameter

[0099] For the cross-section of the oxide sintered body, a BSE-COMP image (hereinafter referred to as "SEM image") with a magnification of 200x and a range of 445.3 μm × 634.6 μm was captured using a scanning electron microscope (SU3500, Hitachi High-Technologies Corporation). The SEM image was scanned using particle analysis software ("Particle Analysis Version 3.0", Sumitomo Metal Technology Inc.), and image recognition was performed using the scanner. The image was then binarized. At this point, a conversion value was set using μm units, with each pixel as the unit of measurement.

[0100] Next, all the holes projected onto the SEM image are considered as objects, and their areas and the sum of their areas are calculated. The percentage of the sum of the hole areas relative to the field of view area (445.3 μm × 634.6 μm) is calculated. The arithmetic mean of the percentages measured using 10 different SEM images as objects is calculated, and this arithmetic mean is taken as the hole area ratio in this invention.

[0101] In addition, based on the area of ​​the hole measured during the calculation of the hole area ratio, the equivalent circle diameter of the hole was calculated. The maximum value among all equivalent circle diameters measured from 10 different SEM images was taken as the maximum equivalent circle diameter of the hole.

[0102] Unlike the above operations, this method treats all holes mapped onto the SEM image as objects, calculates the horizontal Ferrette diameter (μm) based on the total number of pixels in the horizontal direction, and calculates the vertical Ferrette diameter (μm) based on the total number of pixels in the vertical direction. The maximum value among all horizontal and vertical Ferrette diameters measured from 10 different SEM images is taken as the maximum Ferrette diameter of the hole.

[0103] [Relative density]

[0104] Relative density is determined based on the Archimedes method. Specifically, the air mass of the oxide sintered body is divided by its volume (mass of the sintered body in water / specific gravity of water at the measurement temperature) relative to the theoretical density ρ (g / cm³) based on the following equation (1). 3 The percentage value of ) is taken as the relative density (unit: %).

[0105] ρ={(C1 / 100) / ρ1+(C2 / 100) / ρ2+(C3 / 100) / ρ3} -1 (1)

[0106] In formula (1), C1 to C3 represent the content (mass%) of each constituent substance of the target material, and ρ1 to ρ3 represent the density (g / cm³) of each constituent substance corresponding to C1 to C3. 3 ).

[0107] In the case of this invention, the content (mass%) of the constituent substances of the target material is considered to be SnO2, Ta2O5, and Nb2O5, for example, ...

[0108] C1: Mass % of SnO2 from the target material

[0109] ρ1: Density of SnO2 (6.95 g / cm³) 3 )

[0110] C2: Mass % of Ta2O5 in the target material

[0111] ρ2: Density of Ta2O5 (8.74 g / cm³) 3 )

[0112] C3: Mass % of Nb2O5 in the target material

[0113] ρ3: Density of Nb₂O₅ (4.47 g / cm³) 3 )

[0114] Applying to equation (1), the theoretical density ρ can be calculated.

[0115] It should be noted that the mass percentages of SnO2, Ta2O5, and Nb2O5 can be determined from the elemental analysis results of the target material obtained by ICP-OES analysis.

[0116] [Flexural Strength]

[0117] The universal testing machine (Autograph) AGS-500B (registered trademark) manufactured by Shimadzu Corporation was used. A specimen (over 36 mm in length, 4.0 mm in width, and 3.0 mm in thickness) cut from an oxide sintered body was used as the test subject, and the flexural strength was measured according to the three-point bending strength determination method of JIS R1601.

[0118] [The generation of abnormal discharge and the extent of target breakage]

[0119] A sputtering target was fabricated using the oxide sintered body obtained in the examples and comparative examples, and the target was mounted in a DC magnetron sputtering apparatus for sputtering. The sputtering conditions are as described below.

[0120] • Achieve vacuum level: 3×10-6 Pa

[0121] Sputtering pressure: 0.4 Pa

[0122] Oxygen partial pressure: 1×10 -3 Pa

[0123] • Time to apply electrical energy: 2W / cm² 2

[0124] • Duration: 25 hours

[0125] The number of arcs generated during sputtering under the aforementioned conditions was measured using an arc counter attached to the power supply. The arc counter used was a μArc Moniter MAM Genesis MAM data collector (DATACOLLECTOR) Ver. 2.02 (manufactured by LANDMARK TECHNOLOGY). The evaluation criteria are as follows.

[0126] A: The number of arcs is less than 5.

[0127] B: The number of arcs fired is more than 5 but less than 30.

[0128] C: The number of arc strikes is more than 30.

[0129] During sputtering under the aforementioned conditions, visual observation is used to simultaneously evaluate whether cracks occur on the target.

[0130] [Table 1]

[0131]

[0132] As shown in Table 1, if the oxide sintered body obtained in each embodiment is used as the sputtering target, compared with the case where the oxide sintered body obtained in the comparative example is used as the sputtering target, abnormal discharge is less likely to occur during sputtering, and target breakage is less likely to occur.

[0133] In contrast, in Comparative Example 1, which does not use spray drying to manufacture the molded body for sintering, the molded body cannot be made dense, and many pores are generated in the oxide sintered body manufactured from the molded body.

[0134] In addition, in Comparative Example 2, where no slurry was prepared separately for the raw material powder, the granules were uneven and the molded body could not be made dense, resulting in many pores in the oxide sintered body manufactured from the molded body.

[0135] In Comparative Example 3, where the amount of dispersant increased compared to Comparative Example 2, although the granules were uniform, they were hard and difficult to crush, thus failing to make the molded body dense, resulting in many pores in the oxide sintered body manufactured from the molded body.

[0136] Industrial availability

[0137] According to the present invention, an oxide sintered body with few or small or even if holes are present is provided, which is not prone to abnormal discharge or cracking when used as a sputtering target, as well as a method for manufacturing the same and a sputtering target.

[0138] When sputtering is performed using the oxide sintered body of the present invention, compared with the use of conventional oxide sintered bodies, abnormal discharge and cracking during sputtering can be suppressed while film formation occurs, thus suppressing the generation of excess defective products and reducing waste generation. In other words, the energy costs of disposing of such waste can be reduced. This achieves sustainable management and effective utilization of natural resources, as well as decarbonization (carbon neutralization).

Claims

1. An oxide sintered body containing tin, tantalum, and niobium. In cross-sectional observation of the oxide sintered body, the area ratio of pores per unit area is less than 1%, wherein, The area ratio of the orifice was determined in the following manner: The cut surfaces obtained by cutting the oxide sintered body are subjected to staged grinding using sandpaper of grits #180, #400, #800, #1000, and #2000, and finally polished to achieve a mirror finish. For the cross-section of the oxide sintered body, a BSE-COMP image with a magnification of 200x and a range of 445.3μm × 634.6μm was captured using a scanning electron microscope. The BSE-COMP image was scanned using particle analysis software and image recognition was performed using a scanner. The image was then binarized, and a conversion value was set using μm units, with each pixel as the unit. Next, all the apertures projected onto the BSE-COMP image are taken as objects, and their areas and the sum of their areas are calculated. The percentage of the sum of the aperture areas relative to the field of view area is calculated, and the arithmetic mean of the percentages measured using 10 different BSE-COMP images as objects is calculated. This arithmetic mean is taken as the aperture area ratio.

2. An oxide sintered body containing tin, tantalum, and niobium. The maximum equivalent circle diameter of the pores in the cross-sectional observation of the oxide sintered body is less than 20 μm, wherein, The maximum equivalent circle diameter of the hole is determined in the following manner: The cut surfaces obtained by cutting the oxide sintered body are subjected to staged grinding using sandpaper of grits #180, #400, #800, #1000, and #2000, and finally polished to achieve a mirror finish. For the cross-section of the oxide sintered body, a BSE-COMP image with a magnification of 200x and a range of 445.3μm × 634.6μm was captured using a scanning electron microscope. The BSE-COMP image was scanned using particle analysis software and image recognition was performed using a scanner. The image was then binarized, and a conversion value was set using μm units, with each pixel as the unit. Next, all holes mapped onto the BSE-COMP image are taken as objects, and their areas are calculated. Based on these areas, the equivalent circle diameter of the holes is calculated. The maximum value among all equivalent circle diameters measured using 10 different BSE-COMP images as objects is taken as the maximum equivalent circle diameter of the holes.

3. An oxide sintered body containing tin, tantalum, and niobium. The maximum Freette diameter of the pores in the cross-section of the oxide sintered body is less than 50 μm, wherein... The maximum Ferrette diameter of the orifice was determined in the following manner: The cut surfaces obtained by cutting the oxide sintered body are subjected to staged grinding using sandpaper of grits #180, #400, #800, #1000, and #2000, and finally polished to achieve a mirror finish. For the cross-section of the oxide sintered body, a BSE-COMP image with a magnification of 200x and a range of 445.3μm × 634.6μm was captured using a scanning electron microscope. The BSE-COMP image was scanned using particle analysis software and image recognition was performed using a scanner. The image was then binarized, and a conversion value was set using μm units, with each pixel as the unit. Next, taking all the holes projected onto the BSE-COMP image as objects, the horizontal Ferrette diameter (μm) was calculated based on the total number of pixels in the horizontal direction, and the vertical Ferrette diameter (μm) was calculated based on the total number of pixels in the vertical direction. The maximum value among all the horizontal and vertical Ferrette diameters measured using 10 different BSE-COMP images as objects was taken as the maximum Ferrette diameter of the hole.

4. An oxide sintered body containing tin, tantalum, and niobium. The area ratio of pores per unit area in the cross-sectional observation of the oxide sintered body is less than 1%. The maximum equivalent circle diameter of the hole is less than 20 μm. The maximum Ferrette diameter of the aperture is less than 50 μm. in, The area ratio of the orifice was determined in the following manner: The cut surfaces obtained by cutting the oxide sintered body are subjected to staged grinding using sandpaper of grits #180, #400, #800, #1000, and #2000, and finally polished to achieve a mirror finish. For the cross-section of the oxide sintered body, a BSE-COMP image with a magnification of 200x and a range of 445.3μm × 634.6μm was captured using a scanning electron microscope. The BSE-COMP image was scanned using particle analysis software and image recognition was performed using a scanner. The image was then binarized, and a conversion value was set using μm units, with each pixel as the unit. Next, all the holes projected onto the BSE-COMP image are taken as objects, and their areas and the sum of their areas are calculated. The percentage of the sum of the hole areas relative to the field of view area is calculated. The arithmetic mean of the percentages measured using 10 different BSE-COMP images as objects is calculated, and this arithmetic mean is taken as the area ratio of the holes. The maximum equivalent circle diameter of the hole is determined in the following manner: The cut surfaces obtained by cutting the oxide sintered body are subjected to staged grinding using sandpaper of grits #180, #400, #800, #1000, and #2000, and finally polished to achieve a mirror finish. For the cross-section of the oxide sintered body, a BSE-COMP image with a magnification of 200x and a range of 445.3μm × 634.6μm was captured using a scanning electron microscope. The BSE-COMP image was scanned using particle analysis software and image recognition was performed using a scanner. The image was then binarized, and a conversion value was set using μm units, with each pixel as the unit. Next, all holes mapped onto the BSE-COMP image are taken as objects, and their areas are calculated. Based on these areas, the equivalent circle diameter of the holes is calculated. The maximum value among all equivalent circle diameters measured using 10 different BSE-COMP images as objects is taken as the maximum equivalent circle diameter of the holes. The maximum Ferrette diameter of the orifice was determined in the following manner: The cut surfaces obtained by cutting the oxide sintered body are subjected to staged grinding using sandpaper of grits #180, #400, #800, #1000, and #2000, and finally polished to achieve a mirror finish. For the cross-section of the oxide sintered body, a BSE-COMP image with a magnification of 200x and a range of 445.3μm × 634.6μm was captured using a scanning electron microscope. The BSE-COMP image was scanned using particle analysis software and image recognition was performed using a scanner. The image was then binarized, and a conversion value was set using μm units, with each pixel as the unit. Next, taking all the holes projected onto the BSE-COMP image as objects, the horizontal Ferrette diameter (μm) was calculated based on the total number of pixels in the horizontal direction, and the vertical Ferrette diameter (μm) was calculated based on the total number of pixels in the vertical direction. The maximum value among all the horizontal and vertical Ferrette diameters measured using 10 different BSE-COMP images as objects was taken as the maximum Ferrette diameter of the hole.

5. The oxide sintered body according to any one of claims 1 to 4, wherein, The relative density, determined by the Archimedes method, is above 99.6%.

6. The oxide sintered body according to any one of claims 1 to 4, wherein, The flexural strength, as determined by JIS R1601, is above 180 MPa.

7. The oxide sintered body according to any one of claims 1 to 4, comprising 80% by mass and less than 100% by mass of tin (SnO2 equivalent), more than 0% by mass and less than 10% by mass of tantalum (Ta2O5 equivalent), and more than 0% by mass and less than 10% by mass of niobium (Nb2O5 equivalent).

8. The oxide sintered body according to any one of claims 1 to 4, comprising 90% by mass and 96.5% by mass of tin (based on SnO2), 3% by mass and 7% by mass of tantalum (based on Ta2O5), and 0.5% by mass and 3% by mass of niobium (based on Nb2O5).

9. A sputtering target formed from an oxide sintered body according to any one of claims 1 to 4.

10. A sputtering film using the sputtering target of claim 9.

11. A method for manufacturing an oxide sintered body according to any one of claims 1 to 8, comprising the following manufacturing method: Tin oxide paste, tantalum oxide paste, and niobium oxide paste were prepared separately and individually. The various slurries are mixed to prepare a mixed slurry. The mixed slurry is then subjected to spray drying to produce granules. The granules are used to manufacture shaped articles. The shaped body is sintered, wherein, The tin oxide slurry, the tantalum oxide slurry, and the niobium oxide slurry are each pre-contained with a dispersant.

12. The manufacturing method according to claim 11, wherein, The dispersant is a polycarboxylate.

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