JP5761528B2 - Transparent oxide film, method for producing the same, and oxide sputtering target - 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 oxide film having excellent gas barrier properties, a method for producing the same, and an oxide sputtering target.

  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. An oxide sintered body in which an oxide phase of the additive element and a composite oxide phase of the additive element and Sn are dispersed with an average particle size of 50 μm or less is used as a sputtering target, and direct current 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 contained at a ratio of 15 atomic% to 63 atomic% with respect to the total of the additive element and Sn, is an amorphous film, and has a refractive index of 1.90 or less at a wavelength of 633 nm.

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 that 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-described problems, and an object thereof is to provide a zinc oxide-based transparent oxide film having a low refractive index and good gas barrier properties, a method for producing the same, and an oxide sputtering target. To do.

The present inventors have found that when SiO ₂ or MgO is contained in an AZO (Al-Zn-O: Aluminum doped Zinc Oxide) film, the film becomes amorphous and the gas barrier property is improved. Therefore, research was conducted to form a ZnO—SiO ₂ —MgO—Al ₂ O ₃ based film as a transparent oxide film by sputtering. In this research, it was found that a transparent film having a low refractive index and a high gas barrier performance can be obtained by setting the atmosphere during sputtering film formation or the temperature of the substrate to a specific condition.

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 oxide film according to the first invention contains 3 to 13 at% Al, 21 to 59 at% Si, and 10 to 48 at% Mg with respect to the total amount of metal components, with the balance being Zn and inevitable. It is an oxide having a component composition consisting of impurities, the refractive index average value in the visible light region of wavelength 400 to 750 nm is 1.9 or less, and the transmittance average value in the visible light region is 90% or more It is characterized by being amorphous.
That is, this transparent oxide film contains 3 to 13 at% Al, 21 to 59 at% Si, and 10 to 48 at% Mg with respect to the total metal component amount, with the balance being Zn and inevitable impurities. A refractive index average value in a visible light region having a wavelength of 400 to 750 nm is 1.9 or less, a transmittance average value in the visible light region is 90% or more, and amorphous. Therefore, it has a low refractive index and a high transmittance in the visible light region and has a high gas barrier property (for example, a water vapor barrier property).

The transparent oxide film according to the second invention is characterized in that, in the first invention, the water vapor transmission rate is 0.03 g / (m ² · day) or less.
That is, in this transparent oxide film, since the water vapor transmission rate is 0.03 g / (m ² · day) or less, the water vapor barrier property is high. Therefore, the transparent oxide film is laminated on the resin film substrate used for electronic paper and solar cells. It is suitable for a gas barrier layer.

The oxide sputtering target according to the third invention is a sputtering target for producing the transparent oxide film of either the first or second invention, and Al is 3 to 3 with respect to the total metal component amount. It is characterized by comprising an oxide sintered body containing 8 at%, Si of 11 to 27 at%, Mg of 5 to 18 at%, and the balance of Zn and inevitable impurities.
That is, this oxide sputtering target contains 3 to 8 at% Al, 11 to 27 at% Si, and 5 to 18 at% Mg with respect to the total metal component amount, with the balance being Zn and inevitable impurities. Therefore, the transparent oxide film of the present invention can be stably formed by DC sputtering with high conductivity.

A method for producing a transparent oxide film according to a fourth invention is a method for producing a transparent oxide film according to any one of the first and second inventions, using the oxide sputtering target of the third invention, Sputtering is performed by supplying a direct current in at least one of an inert gas atmosphere containing oxygen and a state in which the substrate is heated.
That is, in this method for producing a transparent oxide film, the transparency of the formed transparent oxide film is improved in at least one of an inert gas atmosphere containing oxygen and a state in which the substrate is heated. , The refractive index decreases. In addition, since the film is formed at a high speed by DC sputtering, it is denser and has better barrier properties than the film formed by RF sputtering.

Here, the reason for limiting the content ratio of the metal component elements in the transparent oxide film and the oxide sputtering target of the present invention as described above is as follows.
Al:
Al is added to the sputtering target as a dopant to ZnO to enable DC sputtering, and is contained in the film as a result of sputtering film formation. If the Al content is less than the above content range, the target will not have sufficient conductivity and DC sputtering will not be possible. Moreover, when there is more Al than the said content range, Zn and a complex oxide will be formed, crystallinity will become high, and gas barrier property will fall.

Si:
Si, together with Mg, has the effect of improving the gas barrier properties by reducing the crystallinity of the film and reducing the path of water vapor and gas. When Si is less than the above content range, the crystallinity of the film is increased, the gas barrier property is lowered, and the refractive index is increased. Further, if Si is more than the above content range, a complex oxide is formed with Zn, the crystallinity is increased, the gas barrier property is lowered, and it is necessary for sputtering a film having a desired composition. Therefore, the amount of Si in the target is increased, the conductivity is lowered, and DC sputtering cannot be performed.

Mg:
Mg, together with Si, has the effect of improving the gas barrier properties by reducing the crystallinity of the film and reducing the path of water vapor and gas. When Mg is less than the above content range, the crystallinity of the film is increased, and the gas barrier property is lowered. On the other hand, if Mg is more than the above content range, a complex oxide is formed with Al and Zn, the crystallinity is increased, the gas barrier property is lowered, and a film having a desired composition is formed by sputtering. As a result, the amount of Mg required for the target increases, the conductivity becomes low, and DC sputtering cannot be performed.

The present invention has the following effects.
That is, according to the transparent oxide film of the present invention, the oxide having a component composition containing Al, Si, Mg within the above range with the balance being Zn and inevitable impurities with respect to the total amount of metal components. Thus, it has a low refractive index and a high transmittance in the visible light region and is amorphous, and thus has a high gas barrier property.
Further, according to the oxide sputtering target according to the present invention, the oxide having a component composition containing Al, Si, Mg within the above range with the balance being Zn and inevitable impurities with respect to the total metal component amount. Since it consists of a sintered body, the transparent oxide film of the present invention can be stably formed by DC sputtering with high conductivity.
Furthermore, according to the method for producing a transparent oxide film according to the present invention, DC sputtering can be performed using the oxide sputtering target, and at least in an inert gas atmosphere containing oxygen and a state in which the substrate is heated. Since sputtering is performed by applying a direct current under one environment, a transparent oxide film having the above composition with high transparency can be formed.
Therefore, by adopting the transparent oxide film of the present invention for gas barrier layers such as electronic paper and solar cells, the required high transparency, low refractive index and high gas barrier properties can be obtained, and it has high reliability and is visible. High-performance electronic paper, solar cells with good conversion efficiency, and the like can be manufactured.

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

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

The transparent oxide film of the present embodiment is a film used as a gas barrier layer for the above-described applications, and Al is 3 to 13 at%, Si is 21 to 59 at%, and Mg is 10 with respect to the total amount of metal components. It is an oxide having a component composition of ˜48 at%, with the balance being Zn and inevitable impurities. Further, this transparent oxide film has a refractive index average value in a visible light region of a wavelength of 400 to 750 nm of 1.9 or less, a transmittance average value in the visible light region of 90% or more, It is crystalline. The transparent oxide film preferably has 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 oxide sputtering target for producing the transparent oxide film of the present embodiment contains 3 to 8 at% Al, 11 to 27 at% Si, and 5 to 18 at% Mg with respect to the total amount of metal components. The balance is made of an oxide sintered body having a component composition composed of Zn and inevitable impurities.
Furthermore, the method for producing a transparent oxide film of the present embodiment uses the above-described oxide sputtering target to generate a direct current in an inert gas atmosphere containing oxygen and in at least one environment where the substrate is heated. Input and sputtering (DC sputtering).

  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. Further, the partial pressure of oxygen 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 oxide sputtering target includes a step of weighing and mixing Al ₂ O ₃ powder, MgO powder, SiO ₂ powder and ZnO powder, and a step of sintering the mixed powder. have. This sintering can be realized by using a normal pressure sintering method, HP, or HIP method.
If described in detail an example of the above process, for example, as shown in FIG. 1, first made a purity of 99.9% or more _Al 2 _{O 3} powder and MgO powder and SiO ₂ powder and ZnO powder as the content range The obtained powder and zirconia balls are put in a poly container (polyethylene pot) and wet-mixed for a predetermined time in a ball mill device to obtain a mixed powder. For example, alcohol is used as the solvent.

Next, after drying the obtained mixed powder, it is 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 press temperature is preferably in the range of 1100 to 1250 ° C., the time is preferably in the range of 1 to 10 hours, and the pressure is preferably in the range of 100 to 400 kgf / cm ² .
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 oxide film of this embodiment using this sputtering target, the sputtering target is set in a magnetron sputtering apparatus, the input power density is 0.8 to 12 W / cm ² , and the ultimate vacuum is set. 5 × 10 ⁻⁴ Pa or less, sputtering pressure is 0.3 to 20 Pa, sputtering gas partial pressure is in the range of O ₂ / (Ar + O ₂ ) of 0.05 to 0.2, and substrate heating temperature is 100 to 200 ° C. Under certain conditions, a film is formed on a resin film substrate.

As described above, the transparent oxide film of this embodiment contains 3 to 13 at% Al, 21 to 59 at% Si, and 10 to 48 at% Mg with respect to the total amount of metal components, with the balance being Zn and inevitable impurities. It is an oxide having a component composition of the above, and has a low refractive index and a high transmittance in the visible light region and is amorphous, and thus has a high gas barrier property.
In particular, since the water vapor transmission rate is 0.03 g / (m ² · day) or less, the water vapor barrier property is high, so it is suitable for a gas barrier layer or the like laminated on a resin film substrate used for electronic paper or solar cells. is there.

  In addition, the oxide sputtering target for producing this transparent oxide film contains 3 to 8 at% Al, 11 to 27 at% Si, and 5 to 18 at% Mg with respect to the total amount of metal components, and the balance. Is made of an oxide sintered body having a component composition composed of Zn and inevitable impurities, so that the transparent oxide film of the present invention can be stably formed by DC sputtering with high conductivity.

  Furthermore, in the method for producing the transparent oxide film, a direct current is applied in an inert gas atmosphere containing oxygen and in an environment in which the substrate is heated using the oxide sputtering target. Since sputtering is performed, the transparency of the formed transparent oxide film is improved.

In addition, since the heating temperature of the substrate is set in the range of 100 to 200 ° C., it is sufficiently transparent as a gas barrier layer employed in electronic paper and solar cells while suppressing the thermal effect on the resin film substrate to be formed. And a transparent oxide film having a low refractive index.
Furthermore, since the partial pressure of oxygen with respect to the whole atmospheric gas of oxygen and inert gas is set to 0.05 or more, sufficient transparency and a low refractive index as a gas barrier layer employed in electronic paper and solar cells A transparent oxide film having

  The result evaluated about the Example of the transparent oxide film and oxide sputtering target which were produced based on the said this embodiment is demonstrated below.

Manufacture of the Example of this invention was performed on condition of the following.
First, Al ₂ O ₃ powder (4N, D ₅₀ = 0.2 μm), MgO powder (3N, D ₅₀ = 0.4 μm), and SiO ₂ powder (3N, D ₅₀ =) so as to have the composition ratio shown in Table 1. 5 μm) and ZnO powder (4N, D ₅₀ = 1 μm), and the resulting powder and 4 times its weight (weight ratio) zirconia balls (balls with a diameter of 5 mm) are placed in a 10 L polycontainer (polyethylene pot). ) And wet mixed in a ball mill device for 48 hours to obtain a mixed powder. In addition, alcohol was used for the solvent.
Here, for example, D ₅₀ = 1 μm indicates that the particle size of 50% of the particles in the powder is 1 μm or less.

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 is machined into a target shape (diameter 125 mm, thickness 10 mm), and the processed one is bonded to a backing plate made of oxygen-free copper. A sputtering target was produced.

Furthermore, 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 (of oxygen and inert gas (Ar) Refractive index under the condition that the partial pressure of oxygen with respect to the whole atmospheric gas: O ₂ / (Ar + O ₂ )) is 0.05 or more and 0.2 or less, the sputtering pressure is 0.67 Pa, and the substrate heating is 100 ° C. to 200 ° C. In addition, a film thickness of 100 nm is formed on a glass substrate (Corning # 1737 length: 20 mm × width: 20 mm, thickness: 0.7 mm) for measuring transmittance, and a PET film (length: 100 mm × for measuring water vapor transmittance). An attempt was made to form a transparent film having a thickness of 100 nm on a width of 100 mm and a thickness of 120 μm.

  In addition, as a sputtering target and a transparent oxide film of a comparative example, on the conditions shown in Table 1, what set the target composition and the film composition outside the scope of the present invention (comparative examples 1 to 6) was the same as the above example. Produced. That is, as the transparent oxide film of the comparative example, the composition of the sputtering target was adjusted, and the composition of Al in the transparent oxide film was outside the range of 3 to 13 at% (Comparative Examples 1 and 2), and transparent oxidation The Si composition in the physical film was outside the range of 21 to 59 at% (Comparative Examples 3 and 4), and the Mg composition in the transparent oxide film was out of the range of 10 to 48 at% (Comparative Example) 5 and 6) and those in which the film-forming conditions were set outside the scope of the present invention (Comparative Example 7) were produced in the same manner as in the above Examples.

Regarding the transparent oxide films of Examples and Comparative Examples of the present invention thus prepared, the film composition was measured by ICP emission analysis. As a result, each metal component with respect to all metal components was as shown in Table 1. When the film was analyzed by EPMA, it was confirmed that oxygen was uniformly distributed throughout the entire structure and each metal element was present as an oxide in the film.
Table 1 shows the results of X-ray diffraction (XRD) analysis of the transparent oxide films of Examples and Comparative Examples of the present invention and the presence or absence of crystal peaks.

The refractive index of each transparent oxide film obtained was measured with a spectroscopic ellipsometer (UVISEL NIR manufactured by HORIBA Jobin Yvon), and the transmittance was measured with a spectrophotometer (V-550 manufactured by JASCO Corporation). The measured results are shown in Table 1.
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 1.

As a result of these evaluations, in Comparative Example 1, the electric resistance value of the target was too high and DC sputtering could not be performed.
In Comparative Example 2, a complex oxide (ZnAl ₂ O ₄ ) structure was formed on the target, abnormal discharge was frequently generated, and DC sputtering could not be performed. Therefore, when RF sputtering was performed, a complex oxide phase was deposited on the film and a water vapor barrier was formed. The nature was bad.

In Comparative Example 3, the amount of Si added is small and the refractive index is high. Moreover, since the coarse crystal precipitated and the amorphous structure collapsed, the water vapor barrier property was poor.
In Comparative Example 4, since the electric resistance of the target was too high and DC sputtering could not be performed, when RF sputtering was performed, composite oxide (Zn ₂ SiO ₄ ) was deposited, and the water vapor barrier property was poor.
In Comparative Example 5, since the amount of Mg added is small, the crystallinity of the film is high, coarse particles are precipitated, and the water vapor barrier property is lowered.
In 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, composite oxide (ZnMgO ₂ ) was deposited, and the water vapor barrier property was poor.
In Comparative Example 7, the sputter deposition conditions of the present invention are not met. Even when the sputtering target of the present invention is used, oxygen vacancies remain in the film unless substrate heating and oxygen addition are performed, so that the refractive index in the visible light region is high and the visible light transmittance is low.

On the other hand, in all examples of the present invention, no crystal peak was observed by XRD, and the water vapor transmission rate was 0.03 g / (m ² · day) or less, and the water vapor barrier property was high. doing. In any of the examples, the refractive index in the visible light region having a wavelength of 400 to 750 nm is 1.9 or less and the transmittance in the visible light region is as high as 90% or more, and has a low refractive index and a high transmittance. The film which has is obtained.

In order to use the oxide 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 × It is preferable that 10 ¹ 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 embodiments and examples, and various modifications can be made without departing from the spirit of the present invention.

Claims (4)

  It is an oxide having a component composition containing 3 to 13 at% Al, 21 to 59 at% Si, 10 to 48 at% Mg, and the balance consisting of Zn and inevitable impurities with respect to the total amount of metal components. Transparent having a refractive index average value in a visible light region of 400 to 750 nm of 1.9 or less, a transmittance average value in the visible light region of 90% or more, and amorphous. Oxide film. The transparent oxide film according to claim 1,
A transparent oxide film having a water vapor transmission rate of 0.03 g / (m ² · day) or less. A sputtering target for producing the transparent oxide film according to claim 1 or 2,
From an oxide sintered body having a component composition containing 3 to 8 at% Al, 11 to 27 at% Si, 5 to 18 at% Mg, and the balance consisting of Zn and inevitable impurities with respect to the total amount of metal components An oxide sputtering target. A method for producing the transparent oxide film according to claim 1, comprising:
Using the oxide sputtering target according to claim 3, sputtering is performed by applying a direct current in at least one of an inert gas atmosphere containing oxygen and a state in which the substrate is heated. A method for producing a transparent oxide film.

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