TW201942088A - Oxide sintered body, sputtering target and transparent conductive film - Google Patents

Abstract

An oxide sintered body according to one of the embodiments of the present invention is an oxide sintered body containing indium, niobium, tin and oxygen, which contains indium in an amount of 90.0 mass% or more in terms of In2O3, niobium in an amount of 3.5 to 6.5 mass% in terms of Nb2O5, and tin in an amount of 0.5 to 2 mass% in terms of SnO2.

Description

Oxide sintered body, sputtering target and transparent conductive film

Embodiments disclosed in the present invention relate to an oxide sintered body, a sputtered film, and a transparent conductive film.

In the past, a sputtering target for a transparent conductive film is known, which is made of ITO (Indium Tin Oxide, indium tin oxide), added with niobium, etc., and is used to improve the transparency in the purple region (for example, the wavelength of 400 nm). A person who forms a conductive film (for example, refer to Patent Document 1).

[Prior technical literature] [Patent Literature]

Patent Document 1: International Publication No. 2011/052375

However, the transparent conductive film formed by the conventional sputtering target still has room for improvement in transmittance in a short wavelength region such as an ultraviolet region (for example, a wavelength of 300 nm) or a purple region (for example, a wavelength of 400 nm). .

The state of this embodiment is based on the above circumstances The inventor's goal is to provide an oxide sintered body, which can improve the transmittance of a short-wavelength region such as an ultraviolet region or a purple region in a transparent conductive film formed using a sputtering target.

The same oxide sintered body of this embodiment contains indium, niobium, tin, and oxygen, and contains 90.0% by mass or more of the above indium in terms of In ₂ O _{3 and} 3.5 to 6.5 in terms of Nb ₂ O ₅ The aforementioned niobium by mass contains 0.5 to 2 mass% of the aforementioned tin in terms of SnO ₂ .

According to the state of this embodiment, the transmittance of the short-wavelength region such as the ultraviolet region or the purple region of the formed transparent conductive film can be improved.

FIG. 1 is a graph showing the wavelength dependence of the transmittance before heat treatment of the transparent conductive films of Example 2 and Comparative Examples 1 and 4.

FIG. 2 is a graph showing the wavelength dependence of the transmittance of the transparent conductive films of Example 2 and Comparative Examples 1 and 4 after heat treatment.

Hereinafter, embodiments of the oxide sintered body, the sputtering target, and the transparent conductive film disclosed in the present invention will be described with reference to the accompanying drawings. The present invention is not limited to the embodiments described below.

The oxide sintering system of the embodiment contains indium (In), niobium (Nb), tin (Sn), and oxygen (O), and can be used as a sputtering target. The oxide sintered body of the embodiment contains 90.0% by mass or more of indium in terms of In ₂ O ₃ , 3.5 to 6.5% by mass of niobium in terms of Nb ₂ O ₅ , and 0.5 to 2 mass in terms of SnO ₂ . % Of tin. That is, the oxide sintering system of the embodiment contains indium as a main component, and niobium, tin, and oxygen as other components.

Thereby, the transmittance of the transparent conductive film formed by using the oxide sintered body as a sputtering target in a short wavelength region such as an ultraviolet region or a purple region can be improved.

The transparent conductive film of the embodiment contains indium, niobium, tin, and oxygen, and contains 90.0% by mass or more of indium in terms of In ₂ O _{3 and} 3.5 to 6.5% by mass of niobium in terms of Nb ₂ O ₅ . In terms of SnO ₂ , it contains 0.5 to 2% by mass of tin. That is, the transparent conductive film of the embodiment contains indium as a main component, and niobium, tin, and oxygen as other components.

Thereby, the transmittance of the transparent conductive film in a short-wavelength region such as an ultraviolet region or a purple region can be improved. Therefore, according to the embodiment, for example, when the transparent conductive film is applied to a transparent electrode of a solar cell, the light (that is, ultraviolet rays) incident on the ultraviolet light region of the solar cell can also be used for power generation, so the sun can be improved. The luminous efficiency of the battery.

The oxide sintered body of the embodiment contains 90.0% by mass or more of indium in terms of In ₂ O ₃ . Accordingly, when the oxide sintered body is used as a transparent conductive film formed by a sputtering target, the conductivity and transmittance can be favorably maintained.

In addition, the oxide sintered body according to the embodiment preferably contains 91.5 to 96.0% by mass of indium, more preferably 92.5 to 95.0% by mass, and even more preferably 93.6 to 94.4% by mass in terms of In ₂ O ₃ . .

The oxide sintered body of the embodiment preferably contains 4.0 to 6.0 mass% of niobium when converted into Nb ₂ O _{5 and} 0.5 to 2 mass% of tin when converted into SnO ₂ . Thereby, when this oxide sintered body is used as a transparent conductive film formed by a sputtering target, electrical conductivity can be favorably maintained.

The oxide sintered body of the embodiment more preferably contains 4.5 to 5.5% by mass of niobium when converted into Nb ₂ O _{5 and} 0.5 to 2% by mass of tin when converted into SnO ₂ , and more preferably Nb _It contains 4.8 to 5.2% by mass of niobium in terms of ₂ O _{5 and} 0.8 to 1.2% by mass of tin in terms of SnO ₂ .

The transparent conductive film of the embodiment contains 90.0% by mass or more of indium in terms of In ₂ O ₃ . Thereby, the conductivity and transmittance of the transparent conductive film can be favorably maintained.

In addition, the transparent conductive film according to the embodiment preferably contains 91.5 to 96.0% by mass of indium, more preferably 92.5 to 95.0% by mass, and even more preferably 93.6 to 94.4% by mass in terms of In ₂ O ₃ .

The transparent conductive film of the embodiment preferably contains 4.0 to 6.0 mass% of niobium when converted into Nb ₂ O _{5 and} 0.5 to 2 mass% of tin when converted into SnO ₂ . Thereby, the conductivity of the transparent conductive film can be favorably maintained.

Furthermore, the transparent conductive film of the embodiment more preferably contains 4.5 to 5.5 mass% of niobium when converted into Nb ₂ O _{5 and} 0.5 to 2 mass% of tin when converted into SnO ₂ , and more preferably Nb ₂ O ₅ contains 4.8 to 5.2 mass% of niobium, and SnO ₂ contains 0.8 to 1.2 mass% of tin.

The oxide sintered body and the transparent conductive film of the embodiment are more preferably composed of indium as a main component and niobium, tin, and oxygen as other components.

The oxide sintered body and the transparent conductive film of the embodiment may contain inevitable impurities derived from raw materials and the like. Examples of the unavoidable impurities in the oxide sintered body according to the embodiment include Fe, Cr, Ni, Si, W, and Zr. The content of each of these is generally 100 ppm or less.

The specific resistance of the oxide sintered body of the embodiment is preferably 7.0 × 10 ^-4 Ω. cm or less. Accordingly, when the oxide sintered body is used as a sputtering target, sputtering using an inexpensive DC power source can be performed, and the film forming speed can be increased.

The specific resistance of the oxide sintered body of the embodiment is more preferably 5.0 × 10 ^-4 Ω. cm or less, and more preferably 4.0 × 10 ^-4 Ω. cm or less, and more preferably 3.0 × 10 ^-4 Ω. cm or less.

The relative density of the oxide sintered body of the embodiment is 95% or more. Thereby, when this oxide sintered body is used as a sputtering target, the discharge state of DC sputtering can be stabilized. The oxide sintered body of the embodiment preferably has a relative density of 97% or more, and more preferably has a relative density of 99% or more.

When the relative density is 95% or more, when the oxide sintered body is used as a sputtering target, the voids in the sputtering target can be reduced and it becomes easy. Prevent the intrusion of gas components in the atmosphere. Also, during sputtering, abnormal discharges from the voids and cracking of the sputtering target are unlikely to occur.

In the transparent conductive film of the embodiment, the transmittance at a wavelength of 300 nm is preferably 52% or more, more preferably 55% or more, still more preferably 58% or more, and still more preferably 60% or more.

<Each manufacturing step of oxide sputtering target>

The oxide sputtering target according to the embodiment can be produced, for example, by the following method. First, the raw material powder is mixed. The raw material powder is usually In ₂ O ₃ powder, Nb ₂ O ₅ powder, and SnO ₂ powder. The average particle diameter of each raw material powder is preferably 5 μm or less, and the average particle size difference of each raw material powder is preferably 2 μm or less. In addition, the average particle diameter of the raw material powder is a volume cumulative diameter D ₅₀ at a cumulative volume of 50% by volume measured by a laser diffraction scattering particle size distribution measurement method.

The mixing ratio of each raw material powder can be appropriately determined so that the oxide sintered body becomes a desired constituent element ratio.

Since each raw material powder generally exhibits agglomeration, it is preferred to pulverize before mixing, or to pulverize while mixing.

There is no particular limitation on the method of pulverizing or mixing the raw materials. For example, the raw material powder can be put into a bottle and pulverized or mixed with a ball mill.

The obtained mixed powder can be directly shaped into a shaped body and sintered, but a binder can be added to the mixed powder to form the shaped body as needed. The binder can be a binder used when a shaped body is produced in a known powder metallurgy method, such as polyvinyl alcohol, an acrylic latex binder, and the like. In addition, it can also be prepared by adding a dispersion medium to the mixed powder. The slurry is spray-dried to produce particles, and the particles are formed.

For the forming method, a method adopted in the conventional powder metallurgy method can be used, such as cold pressing or CIP (Cold Isostatic Pressing).

In addition, the mixed powder may be temporarily pressed to produce a temporarily formed body, and then the pulverized powder obtained after pulverizing may be formally pressed to produce a formed body.

In addition, a molded body may be produced using a wet molding method such as a slip casting method. The relative density of the formed body is usually 50 to 75%.

Next, the obtained formed body is fired to produce a sintered body. The sintering furnace for producing the sintered body is not particularly limited, and a sintering furnace that can be used when producing a ceramic sintered body can be used.

The firing temperature is preferably 1300 ° C to 1600 ° C, and more preferably 1400 ° C to 1600 ° C. The higher the sintering temperature, the higher the density of the sintered body can be obtained. On the other hand, from the viewpoint of suppressing the enlargement of the sintered body structure to prevent cracking, it is preferable to control the temperature below the above temperature.

The holding time at this firing temperature is preferably 3 to 30 hours, and more preferably 5 to 20 hours. When the holding time is within the above range, a high-density sintered body can be obtained. From the viewpoint of high density and prevention of cracking, the temperature rising rate is preferably 100 to 500 ° C / h. The firing environment is preferably an oxygen environment.

Next, the obtained sintered body is subjected to cutting processing. This cutting process is performed using a plane grinder or the like. The table after cutting The surface roughness Ra can be appropriately controlled by selecting the size of the abrasive grains of the grindstone used in the cutting process.

A sintered body after cutting is bonded to a base material to produce a sputtering target. The material of the substrate can be appropriately selected from stainless steel, copper, or titanium. As the bonding material, a low melting point solder such as indium can be used.

(Example)

[Example 1]

An In ₂ O ₃ powder having an average particle diameter of 0.7 μm, an Nb ₂ O ₅ powder having an average particle diameter of 1.2 μm, and an SnO ₂ powder having an average particle diameter of 0.9 μm were subjected to a ball mill dry process in a bottle by using zirconia balls. Mix to prepare a mixed powder.

The average particle diameter of the raw material powder was measured using a particle size distribution measuring device HRA manufactured by Nikkiso Co., Ltd. In this measurement, water was used as the solvent, and the refractive index of the measurement substance was 2.20.

In addition, when preparing the mixed powder, it was prepared such that indium was 94.5% by mass in terms of In ₂ O ₃ , niobium was 5.0% by mass in terms of Nb ₂ O ₅ , and tin was 0.5% by mass in terms of SnO ₂ . Each raw material powder.

Next, 6% by mass of polyvinyl alcohol diluted to 4% by mass was added to the mixed powder, and the polyvinyl alcohol was sufficiently applied to the powder using a mortar, and passed through a 5-mesh screen. Next, the obtained powder was temporarily pressed under the condition of 200 kg / cm ² , and the obtained temporarily formed body was pulverized in a mortar. Next, the obtained pulverized powder was filled in a mold for pressurization, and formed at a pressurization pressure of 1 t / cm ² for 60 seconds to obtain a formed body.

Next, the formed body is fired to form a sintered body. The firing was performed in an oxygen flow environment in which oxygen was passed through the furnace at 10 L / min, and was performed at a firing temperature of 1550 ° C, a firing time of 9 hours, a heating rate of 350 ° C / h, and a cooling rate of 100 ° C / h.

Next, the obtained sintered body was subjected to cutting processing to obtain an oxide sintered body having a surface roughness Ra of 1.0 μm and a width of 210 mm × a length of 710 mm × a thickness of 6 mm. In this cutting process, a # 170 grindstone was used.

[Examples 2 to 7]

By the same method as in Example 1, an oxide sintered body was obtained. In addition, in Examples 2 to 7, when preparing the mixed powder, the content ratios of In, O, Nb, and Sn were converted to the content ratios shown in Table 1 when In ₂ O ₃ , Nb ₂ O _5, and SnO _{2 were} converted. Way to prepare each raw material powder.

[Comparative Examples 1 to 6]

By the same method as in Example 1, an oxide sintered body was obtained. In Comparative Examples 1 to 6, when preparing the mixed powder, the content ratios shown in Table 1 were converted to the content ratios of indium, niobium, and tin in terms of In ₂ O ₃ , Nb ₂ O _5, and SnO ₂ . Way to prepare each raw material powder.

In addition, in Examples 1 to 7 and Comparative Examples 1 to 6, the content ratios of the elements measured during the preparation of each raw material powder have been borrowed by ICP-AES (Inductively Coupled Plasma Atomic Emission Spectroscopy: inductively coupled plasma atomic emission). Spectroscopy) was confirmed to be equal to the content of each element in the obtained oxide sintered body.

Next, the obtained Examples 1 to 7 and comparison The oxide sintered bodies of Examples 1 to 6 were measured for relative density. This relative density was measured according to the Archimedes method.

Specifically, the air mass of the oxide sintered body is divided by the volume (mass in water of the sintered body / water specific gravity at the measurement temperature), and the value relative to the theoretical density ρ (g / cm ³ ) is used as the relative value. Density (unit:%).

The theoretical density ρ (g / cm ³ ) is calculated from the mass% and the density of the raw material powder used when producing the oxide sintered body. Specifically, it is calculated by the following formula.

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

In addition, C ₁ to C ₃ and ρ ₁ to ρ ₃ in the above formulas respectively represent the following values.

． C ₁ : mass% of In ₂ O ₃ powder used in production of oxide sintered body

． ρ ₁ : Density of In ₂ O ₃ (7.18g / cm ³ )

． C ₂ : mass% of Nb ₂ O ₅ powder used in production of oxide sintered body

． ρ ₂ : density of Nb ₂ O ₅ (4.47g / cm ³ )

． C ₃ : mass% of SnO ₂ powder used in manufacturing the oxide sintered body

． ρ ₃ : Density of SnO ₂ (6.95g / cm ³ )

Next, the oxide sintered bodies for sputtering targets of Examples 1 to 7 and Comparative Examples 1 to 6 obtained above were measured for specific resistance (bulk resistance), respectively.

Specifically, Loresta (registered trademark) HP MCP-T410 (tandem four-probe TYPE ESP) manufactured by Mitsubishi Chemical Corporation was used, and the probe was brought into contact with the surface of the oxide sintered body after processing. Measurements were performed in RANGE mode. The measurement locations were five locations near the center and four corners of the oxide sintered body, and the average value of each measurement value was used as the volume resistance value of the sintered body.

Here, Tables 1 show the measurement results of the content ratios, relative densities, and specific resistances (volume resistances) of the respective elements contained in the powders in Examples 1 to 7 and Comparative Examples 1 to 6.

It can be seen that the specific resistances of the oxide sintered bodies of Examples 1 to 7 are all 7.0 × 10 ^-4 Ω. cm or less. Therefore, according to the embodiment, when an oxide sintered body is used as a sputtering target, sputtering using an inexpensive DC power source can be performed, and the film forming speed can be increased.

Next, from Examples 1 to 7 and Comparative Examples 1 to 6 described above, For the oxide sintered body, sputtering targets of Examples 1 to 7 and Comparative Examples 1 to 6 were produced. This sputtering target is produced by using indium, which is a low melting point solder, as a bonding material, and bonding the obtained oxide sintered body to a copper base material.

Next, using the produced sputtering targets of Examples 1 to 7 and Comparative Examples 1 to 6, sputtering was performed to form a film under the following conditions, and a film having a thickness of 100 nm was formed.

． Film-forming device: EX-3013M (DC sputtering device) made by Vacuum Machinery Industry Co., Ltd.

． Reaching vacuum degree: less than 1 × 10 ^-4 Pa

． Sputtering gas: Ar / O ₂ mixed gas

． Sputtering pressure: 0.4Pa

． O ₂ gas flow: 0 to _2.0 sccm

． Substrate: Glass substrate (EAGLE XG (registered trademark) by Corning)

． Substrate temperature: room temperature

． Sputtering power: 3W / cm ²

In addition, in Examples 1 to 7 and Comparative Examples 1 to 6, the content rate of each element in the oxide sintered body used for the sputtering target was confirmed by ICP-AES with the transparent conductive film formed. The content of each element is equal.

Next, a predetermined size was cut out from each glass substrate, and the cut glass substrates were measured for the transmittance of the transparent conductive films of Examples 1 to 7 and Comparative Examples 1 to 6 sputtered into a film. Wavelength dependence.

Furthermore, the cut glass substrate was heat-treated at 200 ° C for 1 hour in the air, and the penetration in the transparent conductive film after the heat treatment was also measured. The wavelength dependence of the rate. The measurement conditions of the wavelength dependency of the transmittance before and after the heat treatment are as follows.

． Measuring device: UV-NIR infrared spectrophotometer UH4150 made by Hitachi Advanced Technologies

． Scanning speed: 600nm / min

． Wavelength range: 200 to 2600nm

In the measurement of the transmittance of the transparent conductive film, a plain glass substrate on which no film formation has been performed is set on the device to measure the baseline, and then the transmittance of each film-forming sample is measured.

Figure 1 is a graph showing the wavelength dependence of the transmittance before heat treatment of the transparent conductive films of Example 2 and Comparative Examples 1 and 4, and Figure 2 is a chart showing the wavelength of the transmittance after heat treatment of the same transparent conductive film. Dependency chart. As shown in FIG. 1 and FIG. 2, by applying a predetermined heat treatment to the transparent conductive film formed by sputtering, the transmittance of the transparent conductive film can be improved as a whole.

Next, the specific resistance of each transparent conductive film subjected to heat treatment after film formation is measured. The specific resistance of this transparent conductive film was measured using a four-probe measuring instrument K-705RS made by Kyowa Riken.

Here, for the transparent conductive films of Examples 1 to 7 and Comparative Examples 1 to 6, the measurement results of the transmittance at the wavelengths of 300 nm, 400 nm, and 550 nm before and after the heat treatment, and the results of the specific resistance measurements after the heat treatment are shown.于 表 2。 In Table 2. The evaluation criteria for the specific resistance measurement shown in Table 2 are as follows.

A: The specific resistance is 4.5 × 10 ^-4 Ω. cm or less.

B: The specific resistance exceeds 4.5 × 10 ^-4 Ω. cm and 6.0 × 10 ^-4 Ω. cm or less.

C: Specific resistance exceeds 6.0 × 10 ^-4 Ω. cm.

The transparent conductive film after the heat treatment, will be In ₂ O ₃ equivalent, then indium oxide containing 90.0% by mass of, to Nb ₂ O ₅ equivalent words containing 3.5 to 6.5 mass% of niobium in terms of SnO ₂ then contains 0.5 to 2 As compared with Examples 1 to 7 having a mass% of tin and Comparative Examples 1 to 6 not containing niobium and tin at the content ratios, it is found that 90.0 mass% or more of indium and Nb are contained in terms of In ₂ O ₃ conversion. _It contains 3.5 to 6.5% by mass of niobium in terms of ₂ O _{5 and} 0.5 to 2% by mass of tin in terms of SnO ₂ to increase the transmittance in the ultraviolet region (wavelength 300 nm) to 52% or more.

In addition, the transparent conductive film after the heat treatment, as shown in Tables 2 and 2 in Examples 1 to 7, has not only the ultraviolet light region but also the visible light region (for example, a wavelength of 400 nm to 800 nm). 6 Penetration of equal or more. That is, in the embodiment, when the transparent conductive film is applied to a transparent electrode of a solar cell, light that has entered a wide range of wavelength regions of the solar cell can be used for power generation.

Therefore, according to the embodiment, the power generation efficiency of the solar cell using the transparent conductive film can be further improved.

Examples in which In ₂ O _{3 is} converted to contain 90.0% by mass or more of indium, Nb ₂ O _{5 is} converted to contain 4.0 to 6.0% by mass of niobium, and SnO _{2 is} converted to contain 0.5 to 2% by mass of tin. Comparing 1 to 3, 5, and 6 with Examples 4 and 7 that do not contain niobium at the content ratio, it can be seen that when converted to In ₂ O ₃ , 90.0% by mass or more of indium is contained, and when converted to Nb ₂ O ₅ It contains 4.0 to 6.0% by mass of niobium and 0.5 to 2% by mass of tin in terms of SnO ₂ , so that the conductivity of the transparent conductive film can be maintained well.

In addition, the implementation of In ₂ O ₃ conversion contains 90.0 mass% or more of indium, Nb ₂ O ₅ conversion contains 4.5 to 5.5 mass% of niobium, and SnO ₂ conversion contains 0.5 to 2 mass% of tin. Comparing Examples 1 to 3 with Examples 4 to 7 that did not contain niobium at this content rate, it was found that 90.0% by mass or more of indium was contained in terms of In ₂ O _{3 and} 4.5 to ₄ in terms of Nb ₂ O ₅ 5.5% by mass of niobium and 0.5 to 2% by mass of tin in terms of SnO ₂ can increase the transmittance in the purple region (wavelength 400nm) to 93.2% or more.

Furthermore, those containing 90.0% by mass or more of indium in terms of In ₂ O ₃ , 4.8 to 5.2% by mass of niobium in terms of Nb ₂ O ₅ , and 0.8 to 1.2% by mass of tin in terms of SnO ₂ Comparing Example 2 with Examples 1, 3, and 7 that did not contain niobium and tin at this content ratio, it was found that 4.8 to 5.2% by mass of niobium was contained in terms of Nb ₂ O ₅ conversion, and it was contained in terms of SnO ₂ conversion. 0.8 to 1.2% by mass of tin increases the transmittance in the ultraviolet region (wavelength 300nm) to more than 61.4%, and increases the transmittance in the purple region (wavelength 400nm) to more than 94.6%.

As mentioned above, although embodiment of this invention was described, this invention is not limited to the said embodiment, Various changes can be made in the range which does not deviate from the meaning. For example, in the embodiment, an example in which a transparent conductive film is applied to a solar cell is disclosed, but a device to which the transparent conductive film of the embodiment can be applied is not limited to a solar cell.

For example, when the transparent conductive film of the embodiment is applied to a transparent electrode of an image display device such as a liquid crystal or an organic EL (electro-luminescence), the short-wavelength region such as an ultraviolet region or a purple region has high transmittance, so Improve luminous efficiency in the short wavelength region.

In addition, by applying the transparent conductive film of the embodiment to an optical antistatic film of an ultraviolet light source such as an ultraviolet lamp, the luminous efficiency in the ultraviolet region can be improved, and ultraviolet light can be stably emitted without generating static electricity.

In the embodiment, an example in which a sputtering target is produced using a plate-shaped oxide sintered body is disclosed. However, the shape of the oxide sintered body is not limited to a plate shape, and various shapes such as a cylindrical shape may be used.

More effects and modifications can be easily derived by the operator. Therefore, the broader aspects of the present invention are not limited to the specific details and representative embodiments shown and described above. Therefore, various changes can be made without departing from the spirit or scope of the overall invention concept as defined by the scope of the appended patent application and its equivalents.

Claims (7)

An oxide sintered body containing indium, niobium, tin, and oxygen, and containing 90.0 mass% or more of the aforementioned indium in terms of In ₂ O _{3 and} 3.5 to 6.5% by mass of the aforementioned niobium in terms of Nb ₂ O ₅ , The Sn content is 0.5 to 2% by mass in terms of SnO ₂ . The oxide sintered body described in item 1 of the scope of patent application contains 4.0 to 6.0% by mass of the aforementioned niobium when converted into Nb ₂ O ₅ . The oxide sintered body according to item 1 or 2 of the patent application scope has a specific resistance of 7.0 × 10 ^-4 Ω. cm or less. The relative density of the oxide sintered body as described in item 1 or 2 of the patent application range is 95% or more. A sputtering target is an oxide sintered body described in item 1 or 2 of the scope of patent application as a target. A transparent conductive film containing indium, niobium, tin, and oxygen, and containing 90.0% by mass or more of the aforementioned indium in terms of In ₂ O _{3 and} 3.5 to 6.5% by mass of the aforementioned niobium in terms of Nb ₂ O ₅ , based on In terms of SnO ₂ , the foregoing tin is contained in an amount of 0.5 to 2% by mass. The transparent conductive film according to item 6 of the scope of application for patent, has a transmittance of more than 52% at a wavelength of 300 nm.