JP5776563B2 - Transparent film, method for producing the same, and sputtering target for forming transparent film - Google Patents

Description

  The present invention relates to a gas barrier layer used for electronic paper such as a liquid crystal display element, an electroluminescence display element, an electrophoretic display element, and a toner display element, a film type solar cell, and the like, and a transparent electrode layer of a thin film solar cell using a compound semiconductor The present invention relates to a zinc oxide-based transparent film that is used as a gas barrier layer of the present invention, a manufacturing method thereof, and a sputtering target for forming a transparent film.

  Conventionally, a gas barrier layer used for electronic paper such as a liquid crystal display element, an electroluminescence display element, an electrophoretic display element, a toner display element, a film type solar cell, and the like, and a thin film solar cell using a compound semiconductor (for example, CIGS (Cu-- As a gas barrier layer on a transparent electrode layer of an (In-Ga-Se) solar cell), a technique for producing a transparent oxide film by a sputtering method is known.

  For example, Patent Document 1 contains tin oxide and at least one additive element selected from the group consisting of Si, Ge, and Al. The additive element is based on the total content of the additive element and Sn. It is contained at a ratio of 15 atomic% to 63 atomic%, and the composition of the crystal phase includes at least one of a metal phase of the additive element, an oxide phase of the additive element, and a composite oxide phase of the additive element and Sn. Using the oxide sintered body in which the oxide phase of the additive element and the composite oxide phase of the additive element and Sn are dispersed with an average particle size of 50 μm or less as a sputtering target, A method of forming a transparent oxide film on the surface of a resin film substrate by a sputtering method using a pulsing method has been proposed.

  The transparent oxide film obtained by this method is a transparent oxide film containing tin oxide and at least one additional element selected from the group consisting of Si, Ge, and Al. It is included in a ratio of 15 atomic% to 63 atomic% with respect to the total of the additive element and Sn, and is an amorphous film.

Patent Document 2 discloses that at least one mixed thin film layer mainly composed of a mixture of ZnS and SiO ₂ is formed on one or both surfaces of a polymer film substrate, and a resin is formed on the mixed thin film layer. A gas barrier film in which at least one layer is laminated is described. This mixed thin film layer is formed by sputtering with a high frequency applied using a sputtering target which is a mixed sintered material formed of ZnS and SiO ₂ .

JP 2007-290916 A JP 2010-208072 A

The following problems remain in the conventional technology.
That is, in the target described in Patent Document 1, a large amount of nodules is generated at the time of sputtering, and it takes time to clean the apparatus. Therefore, a transparent oxide film having excellent gas barrier properties other than tin oxide is desired. Has been.
In addition, the gas barrier film described in Patent Document 2 is manufactured by sputtering with a high frequency applied. However, in order to form a film at a higher speed, the gas barrier film needs to be a film that can be formed by DC sputtering.

  The present invention has been made in view of the above-mentioned problems, and provides a zinc oxide-based transparent film having a good gas barrier property and capable of being formed by DC sputtering, a method for producing the same, and a sputtering target for forming a transparent film. For the purpose.

The present inventors have found that when SiO ₂ is contained in an AZO (Al-Zn-O: Aluminum doped Zinc Oxide) film, the film becomes amorphous and gas barrier properties are improved. Therefore, research was conducted to form a ZnO—SiO ₂ —Al ₂ O ₃ film as a transparent oxide film by sputtering. In this research, it was found that a transparent film having flexibility and high gas barrier performance can be obtained by performing DC sputtering using a sputtering target containing ZnS in a specific range.

  Therefore, the present invention has been obtained from the above findings, and the following configuration has been adopted in order to solve the above problems. That is, the transparent film of the first invention comprises 0.3 to 6.0 at% of at least one metal element selected from the group of Al, Ga and In, 6.0 to 27.0 at% of Si, It is characterized by containing 11.0 to 32.5 at% of Zn and 0.5 to 5.0 at% of S, the balance being a component composition composed of O and inevitable impurities, and being amorphous.

  In this transparent film, at least one metal element selected from the group of Al, Ga, and In is 0.3 to 6.0 at%, Si is 6.0 to 27.0 at%, and Zn is 11.0 to 32.5 at%, S is contained in 0.5 to 5.0 at%, the remainder has a component composition consisting of O and inevitable impurities, and is amorphous, so high film flexibility and gas barrier properties (for example, , Water vapor barrier properties). Furthermore, a high average transmittance is obtained in the wavelength region of 400 to 750 nm, and the film has good transparency.

At least one metal element selected from the group of Al, Ga and In is added to the sputtering target as a dopant to ZnO in order to enable DC sputtering during sputtering film formation. It is included as a group element.
The reason for setting the content of at least one metal element selected from the group of Al, Ga, and In to 0.3 to 6.0 at% is that the composition for obtaining a film of less than 0.3 at% is used. This is because the set sputtering target has insufficient conductivity, and DC sputtering cannot be performed. In the sputtering target set to a composition for obtaining a film exceeding 6.0 at%, a group III element and Zn contain a composite oxide. As a result, abnormal discharge occurs frequently and stable DC sputtering cannot be performed.

The Si has an effect of improving the gas barrier property by making the film amorphous and reducing the path of water vapor and gas.
The reason why the Si content is 6.0 to 27.0 at% is that when the Si content is less than 6.0 at%, the film is crystallized and gas barrier properties are deteriorated, which exceeds 27.0 at%. This is because a sputtering target set to have a composition for obtaining a film has a large amount of Si, resulting in low conductivity and DC sputtering cannot be performed.

S, as ZnS, has the effect of improving the gas barrier properties by increasing the flexibility of the film and suppressing the generation of cracks that can serve as a path for water vapor and gas.
The reason why the content of S is in the above range is that if it is less than the lower limit value, the gas barrier property is lowered due to mechanical deformation of the film. If the upper limit value is exceeded, 400 to 750 nm. This is because the visible light transmittance in the wavelength region is lowered.

  The reason why the Zn content is in the above range is that if the Al content is less than the lower limit, the amount of Al and Si added in the film exceeds the upper limit, and if the upper limit is exceeded, Al, This is because the Si addition amount falls below the lower limit.

  In the transparent film of the second invention, Al is 1.5 to 6.0 at%, Si is 6.0 to 27.0 at%, Zn is 11.0 to 32.5 at%, and S is 0.5 to 5. It contains 0 at%, the remainder has a composition composed of O and inevitable impurities, and has an average transmittance of 85% or more in the visible light region at a wavelength of 400 to 750 nm at a thickness of 100 nm and is amorphous. Features.

In the second aspect of the invention, Al is added to the sputtering target as a dopant to ZnO in order to enable DC sputtering at the time of sputtering film formation. However, since Al and Si coexist in the film, the gas barrier property is improved. To express.
The reason why the Al content is set to 1.5 to 6.0 at% is that the effect of improving the gas barrier property due to coexistence with Si is reduced in a film of less than 1.5 at%, which exceeds 6.0 at%. This is because in a sputtering target set to a composition for obtaining a film, Al and Zn form a composite oxide, abnormal discharge occurs frequently, and stable DC sputtering cannot be performed.

In the first or second invention, the transparent film of the third invention is characterized by having a thickness of 100 nm or more and a water vapor transmission rate of 0.03 g / (m ² · day) or less.
That is, since this transparent film has a thickness of 100 nm or more and a water vapor transmission rate of 0.03 g / (m ² · day) or less, a gas barrier formed on a resin film substrate used in electronic paper or solar cells. Suitable as a layer.

The sputtering target for forming a transparent film according to the fourth aspect of the present invention includes 0.3 to 3.5 at% of at least one metal element selected from the group of Al, Ga, and In, and 5.5 to 14.0 at of Si. %, Zn 25.0 to 40.5 at%, S 1.0 to 6.0 at%, the balance being a sintered body having a component composition consisting of O and inevitable impurities .
That is, by using this transparent film forming sputtering target, high transmittance in the visible light region can be obtained and a transparent film having high film flexibility and gas barrier properties can be stably obtained. .

  The component composition of the sputtering target for forming a transparent film is a composition adjusted so that a film having the composition described in the first or second invention can be obtained, and a sputtering target outside this composition range is used. If it is used, a transparent film having the composition shown in the first or second invention cannot be obtained.

  A method for producing a transparent film of a fifth invention is a method for producing a transparent film according to the first to third inventions, wherein at least one metal element selected from the group of Al, Ga, In is used. Contains 0.3 to 3.5 at%, Si 5.5 to 14.0 at%, Zn 25.0 to 40.5 at%, S 1.0 to 6.0 at%, the balance being O and inevitable Using a sputtering target made of a sintered body having a component composition made of impurities, sputtering was performed by applying a direct current in at least one of an inert gas atmosphere containing oxygen and a heated substrate. DC sputtering).

That is, in this method for producing a transparent film, since a sputtering target made of a sintered body having the above component composition is used, DC sputtering can be performed, and the substrate is heated in an inert gas atmosphere containing oxygen. Since sputtering is performed by applying a direct current in at least one of the states of the state, an amorphous transparent film (ZnS—SiO ₂ —ZnO—Al ₂ O ₃ / Ga ₂ O ₃ / In ₂ O is used. ₃ films) can be formed. Therefore, according to the manufacturing method of the present invention, an amorphous transparent film having a high gas barrier property can be formed by DC sputtering. Note that the transparency of the film is improved by performing DC sputtering while the substrate is heated or performing DC sputtering in an inert gas atmosphere containing oxygen. In addition, a film formed by DC sputtering at a high speed is denser than a film formed by RF sputtering and has excellent barrier properties.

The present invention has the following effects.
That is, according to the transparent film of the present invention, at least one metal element selected from the group of Al, Ga, and In is 0.3 to 6.0 at%, and Si is 6.0 to 27.0 at%. , Containing 11.0 to 32.5 at% of Zn, 0.5 to 5.0 at% of S, the balance being a component composition consisting of O and inevitable impurities, visible light having a wavelength of 400 to 750 nm at a thickness of 100 nm Since the average transmittance in the region is 85% or more and is amorphous, a high transmittance can be obtained in the visible light region and the film has high flexibility and gas barrier properties.
Further, according to the method for producing a transparent film according to the present invention, since a sputtering target made of a sintered body having the above component composition is used, DC sputtering can be performed and further in an inert gas atmosphere containing oxygen. Since sputtering is performed by applying a direct current in at least one environment in which the substrate is heated, an amorphous transparent film (ZnS—SiO ₂ —ZnO—Al ₂ O ₃ / Ga ₂ O is used. ₃ / In ₂ O ₃ film). Therefore, according to the manufacturing method of the present invention, it is possible to form a transparent film having high transparency, amorphous, and high gas barrier properties by DC sputtering.
Therefore, by adopting the transparent film of the present invention for gas barrier layers such as electronic paper and solar cells, the required high transparency and high gas barrier properties can be obtained. It is possible to produce a solar cell with good conversion efficiency.

It is a flowchart which shows the manufacturing process of the sputtering target used in one Embodiment of the transparent film which concerns on this invention, its manufacturing method, and the sputtering target for transparent film formation.

  Hereinafter, an embodiment of a transparent film, a manufacturing method thereof, and a sputtering target for forming a transparent film according to the present invention will be described with reference to FIG.

The transparent film of the present embodiment is a film used as a gas barrier layer for the above-described applications, and contains at least one metal element selected from the group of Al, Ga, and In at 0.3 to 6.0 at%. And a component composition comprising Si of 6.0 to 27.0 at%, Zn of 11.0 to 32.5 at%, S of 0.5 to 5.0 at%, the balance being O and inevitable impurities The transmittance average value in the visible light region with a wavelength of 400 to 750 nm at a thickness of 100 nm is 85% or more and is amorphous. The transparent film has a thickness of 100 nm or more and a water vapor transmission rate of 0.03 g / (m ² · day) or less.
The water vapor transmission rate is measured by the Mocon method in accordance with JIS standard K7129 method.

  Moreover, the manufacturing method of the transparent film of this embodiment is 0.3-3.5at% of at least 1 or more types of metal elements chosen from the group of Al, Ga, In, and 5.5-14.0at of Si. %, Zn 25.0-40.5 at%, S containing 1.0-6.0 at%, the remainder using a sputtering target consisting of a sintered body having a component composition consisting of O and inevitable impurities, Sputtering (DC sputtering) is performed by applying a direct current in an atmosphere of an inert gas containing oxygen and / or in an environment where the substrate is heated.

At this time, the resin film base material is used as the substrate, and the heating temperature of the substrate is set in the range of 100 to 200 ° C. The oxygen partial pressure: O ₂ / (Ar + O ₂ ) with respect to the whole atmosphere gas of oxygen and inert gas is set to 0.05 or more and 0.2 or less.

The method for producing the sputtering target includes at least one kind of Al ₂ O ₃ powder, Ga ₂ O ₃ powder, or In ₂ O ₃ powder, SiO ₂ powder, ZnO powder, and ZnS powder. In contrast, at least one metal element selected from the group of Al, Ga, and In is 0.3 to 3.5 at%, Si is 5.5 to 14.0 at%, and Zn is 25.0 to 40.%. 5 at%, S is contained in 1.0 to 6.0 at%, and the remaining powder is composed of O and inevitable impurities, and the mixed powder is sintered. This sintering can be realized by using normal pressure, hot pressing, or HIP method.

If described in detail an example of the above process, for example, as shown in FIG. 1, first, a purity of 99.9% or more _Al 2 _{O 3} powder, _Ga 2 _{O 3} powder or _In 2 _{O 3} powder of at least one or more of The powder, the SiO ₂ powder, the ZnO powder, and the ZnS powder are weighed so as to be in the above content range, and pulverized and mixed by a wet ball mill to produce a mixed powder. For example, each powder obtained by weighing and zirconia balls are placed in a poly container (polyethylene pot) and wet-mixed for a predetermined time in a ball mill apparatus to obtain a mixed powder. For example, alcohol is used as the solvent.

Next, the obtained mixed powder is dried, granulated by sieving, and further vacuum-dried, and then hot-pressed in a vacuum at a pressure of 200 kgf / cm ² at, for example, 1200 ° C. for 5 hours to obtain a sintered body. .
The hot-pressed sintered body is usually machined to a target shape using electrical discharge machining, cutting or grinding, and the processed target is In or soldered to Cu or SUS (stainless steel) or others. Bonding to a backing plate made of metal (for example, Mo) and subjecting to sputtering.

In order to DC sputter the transparent film of this embodiment using this sputtering target, the sputtering target is set in a magnetron sputtering apparatus, and the sputtering gas partial pressure is set at a predetermined input power, ultimate vacuum, and sputtering pressure. The film is formed on the resin film substrate under the condition that O ₂ / (Ar + O ₂ ) is in the range of 0.05 to 0.2 and the substrate heating is 100 ° C. to 200 ° C.

Thus, in the transparent film of the present embodiment, at least one metal element selected from the group of Al, Ga, and In is 0.3 to 6.0 at%, Si is 6.0 to 27.0 at%, Visible light region having a wavelength composition of 400 to 750 nm at a thickness of 100 nm, containing 11.0 to 32.5 at% of Zn, 0.5 to 5.0 at% of S, the balance being O and inevitable impurities The average transmittance of the film is 85% or more and is amorphous, so that high transmittance can be obtained in the visible light region, and high film flexibility and gas barrier properties (for example, water vapor barrier properties). ing.
In particular, since the water vapor transmission rate is 0.03 g / (m ² · day) or less, it is suitable as a gas barrier layer formed on a resin film substrate used in electronic paper and solar cells.

Further, in this method for producing a transparent film, since a sputtering target made of a sintered body having the above component composition is used, DC sputtering is possible, and the substrate is heated in an inert gas atmosphere containing oxygen. Since sputtering is performed by applying a direct current in at least one of the states of the state, an amorphous transparent film (ZnS—SiO ₂ —ZnO—Al ₂ O ₃ / Ga ₂ O ₃ / In ₂ O is used. ₃ films) can be formed. Therefore, according to the manufacturing method of the present invention, an amorphous transparent film having a high gas barrier property can be formed by DC sputtering. Note that the transparency of the film is improved by performing DC sputtering while the substrate is heated or performing DC sputtering in an inert gas atmosphere containing oxygen.

In addition, since the heating temperature of the board | substrate at the time of a sputtering is set in the range of 100-200 degreeC, it is sufficient as a gas barrier layer employ | adopted with an electronic paper or a solar cell, suppressing the heat influence to the resin film base material to form into a film. A transparent film having excellent transparency can be obtained.
Furthermore, since the oxygen partial pressure with respect to the whole atmosphere gas of oxygen and inert gas is set to 0.05 or more, a transparent film having sufficient transparency as a gas barrier layer employed in electronic paper and solar cells can be obtained. can get.

  The result evaluated about the Example of the transparent film produced based on the said this embodiment is demonstrated below with reference to Tables 1-3.

Manufacture of the Example of this invention was performed on condition of the following.
First, Al ₂ O ₃ powder, Ga ₂ O ₃ powder or In ₂ O ₃ powder, SiO ₂ powder, ZnO powder and ZnS powder with a purity of 99.9% or more are weighed so as to have the composition ratio shown in Table 1. Then, the obtained powder and its 4 times amount (weight ratio) zirconia ball (diameter 5 mm) are put into a 10 L plastic container (polyethylene pot), wet-mixed for 48 hours in a ball mill apparatus, and mixed powder did. In addition, alcohol was used for the solvent.

Next, the obtained mixed powder was dried and then vacuum hot pressed at 1200 ° C. for 5 hours at a pressure of 200 kgf / cm ^{2 to} obtain a sintered body.
The sintered body thus hot pressed was machined into a target shape (diameter 125 mm, thickness 10 mm), and the processed one was bonded to a backing plate made of oxygen-free copper. A sputtering target was produced.

Further, these sputtering targets were set in a magnetron sputtering apparatus, and the power source: DC, input power: 500 W, ultimate vacuum: 1 × 10 ⁻⁴ Pa, sputtering gas partial pressure (the whole atmosphere gas of oxygen and inert gas Oxygen gas partial pressure with respect to: O ₂ / (Ar + O ₂ ) 0.05 to 0.2, sputtering pressure: 0.67 Pa, substrate heating at 100 ° C. to 200 ° C., glass for transmittance measurement A transparent film having a film thickness of 100 nm was formed on a substrate (Corning # 1737 length: 20 mm × width: 20 mm, thickness: 0.7 mm).

  Further, a transparent film having a thickness of 100 nm was formed on a PET film (length: 100 mm × width: 100 mm, thickness 120 μm) for measuring water vapor transmission rate. Furthermore, after measuring the water vapor permeability immediately after film formation, the film was repeatedly bent and deformed by a cylindrical mandrel bending tester. Water vapor permeability measurement was performed again on the deformed membrane.

  In addition, as a transparent film of a comparative example, the composition of the sputtering target was adjusted under the conditions shown in Table 1, and the composition of Al in the transparent film was outside the range of 0.3 to 6.0 at% (Comparative Example 1 2), the composition of Si in the transparent film outside the range of 6.0 to 27.0 at% (Comparative Examples 3 and 4), and the composition of S in the transparent film of 0.5 to 5. Those outside the 0 at% range (Comparative Examples 5 and 6) were produced in the same manner as in the above Examples.

When the film compositions of the transparent films of Examples and Comparative Examples of the present invention thus prepared were measured by ICP emission analysis, each metal component relative to all metal components was as shown in Table 2.
Moreover, the resistivity of each sputtering target used for the Example and comparative example of this invention was measured by the four-terminal method using Mitsubishi Chemical Corporation Loresta GP.

Table 3 shows the results of X-ray diffraction (XRD) analysis of the transparent films of Examples and Comparative Examples of the present invention and the presence or absence of crystal peaks.
Furthermore, the water vapor transmission rate (water vapor barrier property) was measured based on JIS standard K7129 method using the Mocon method and using PERMATRAN-WMODEL 3/33 manufactured by mocon. The measured results are shown in Table 3.

  Moreover, the water vapor barrier property after performing a deformation | transformation process with respect to a transparent film was evaluated. In this evaluation, a cylindrical mandrel bending tester (type I) conforming to JIS 5600-5-1 was used for bending deformation of the sputtered single-layer film (transparent films of Examples and Comparative Examples of the present invention). The mandrel used had a diameter of 20 mm, and was bent and deformed so that the film-forming surface was outside when the film was folded. This deformation was repeated until the cumulative number reached 50. And about each sputtered film (transparent film of the Example of this invention, and a comparative example) after a bending deformation test, the value of the water-vapor-permeation rate was obtained again using the said measuring method. The results are also shown in Table 3.

First, for each comparative example, the above evaluation was as follows.
Comparative Example 1: Since the electric resistance value of the target was too high and DC sputtering could not be performed, when the film was formed by RF sputtering, the formed transparent film had a low water vapor barrier property.
Comparative Example 2: Since a complex oxide structure of ZnAl ₂ O ₄ was formed on the target, abnormal discharge occurred frequently, and DC sputtering could not be performed. When RF sputtering was performed, the formed transparent film was a complex oxide (ZnAl ₂ O ₄ ) was precipitated and the water vapor barrier property was low.
Comparative Example 3: The formed transparent film had a small amount of SiO ₂ added, coarse crystals were precipitated, the amorphous structure was destroyed, and the water vapor barrier property was low. Since the Si composition is lower than the range of the present invention, the Zn composition is higher than the range of the present invention.
Comparative Example 4: Since the electric resistance value of the target was too high and DC sputtering could not be performed, when RF sputtering was performed, the formed transparent film had a water vapor barrier property because a composite oxide (Zn ₂ SiO ₄ ) was deposited. It was low. Since the Si composition is higher than the range of the present invention, the Zn composition is lower than the range of the present invention.
Comparative Example 5: The formed transparent film had a high barrier property, but cracks were generated due to deformation, and the water vapor barrier property was lowered.
Comparative Example 6: Since the electric resistance value of the target was too high and DC sputtering could not be performed, when RF sputtering was performed, the formed transparent film had strong crystallinity and the water vapor barrier property was lowered. Moreover, the ratio of S (sulfur) was too high, and the visible light transmittance of the film was low.
Comparative Example 7: This comparative example is an example of a film that does not satisfy the sputtering film forming conditions of the present invention. Even when the sputtering target of the present invention was used, visible light transmittance was low because oxygen vacancies remained in the film unless substrate heating and oxygen addition were performed.

For each example of the present invention, the above evaluation was as follows.
That is, in all examples of the present invention, the target was conductive and could be DC sputtered. Further, when the sputtered film was evaluated, no crystal peak was observed in XRD. In addition, the water vapor transmission rate measured immediately after the film formation was 0.03 g / (m ² · day) or less, and the water vapor transmission rate did not change even after the deformation test. Further, the average transmittance in the wavelength region of 400 to 750 nm was 90% or more and was a transparent film.
In Examples 9, 11, 12, and 13, since there is no addition of Al or the amount of addition is small, the water vapor transmission rate is a high value in the examples of the present invention. Therefore, in order to obtain better gas barrier properties, the Al content is preferably 1.5 at% or more.
Thus, the transparent film of each Example of this invention is equipped with the film | membrane characteristic suitable as a gas barrier layer employ | adopted as an electronic paper or a solar cell.

In order to use the sputtering target of the present invention, relative density: 90% or more, surface roughness: Ra value 2 μm or less, Rz value 15 μm or less, particle size: 3 μm or less, electric resistance: 1.0 × 10 ¹ It is preferable that they are Ω · cm or less, metal impurity concentration: 0.1 atomic% or less, and bending strength: 120 MPa or more. Each of the above-described embodiments satisfies these conditions.
The technical scope of the present invention is not limited to the above-described embodiment and examples, and various modifications can be made without departing from the spirit of the present invention.

Claims (5)

At least one metal element selected from the group of Al, Ga, and In is 0.3 to 6.0 at%, Si is 6.0 to 27.0 at%, Zn is 11.0 to 32.5 at%, S contains 0.5 to 5.0 at%, the remainder has a component composition consisting of O and inevitable impurities,
A transparent film having an average transmittance of 85% or more in a visible light region having a wavelength of 400 to 750 nm at a thickness of 100 nm and being amorphous. It contains 1.5 to 6.0 at% of Al, 6.0 to 27.0 at% of Si, 11.0 to 32.5 at% of Zn, 0.5 to 5.0 at% of S, and the balance is O. And having a component composition consisting of inevitable impurities,
A transparent film having an average transmittance of 85% or more in a visible light region having a wavelength of 400 to 750 nm at a thickness of 100 nm and being amorphous. The transparent film according to claim 1 or 2,
A transparent film having a water vapor transmission rate at a thickness of 100 nm of 0.03 g / (m ² · day) or less.   At least one metal element selected from the group consisting of Al, Ga, and In is 0.3 to 3.5 at%, Si is 5.5 to 14.0 at%, Zn is 25.0 to 40.5 at%, 4. The composition according to claim 1, wherein S is contained in a sintered body containing 1.0 to 6.0 at% and the balance is composed of O and inevitable impurities. A sputtering target for forming a transparent film. A method for producing the transparent film according to any one of claims 1 to 3,
At least one metal element selected from the group consisting of Al, Ga, and In is 0.3 to 3.5 at%, Si is 5.5 to 14.0 at%, Zn is 25.0 to 40.5 at%, Using a sputtering target made of a sintered body having a component composition containing S in an amount of 1.0 to 6.0 at%, the balance being O and inevitable impurities, and in an inert gas atmosphere containing oxygen and the substrate A method for producing a transparent film, comprising sputtering by applying a direct current in at least one environment in a heated state.

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