JP2001135149A - Zinc oxide-based transparent electrode - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a transparent electrode using a zinc oxide-based material featured by high plasma resistance and low cost and having a reduced specific resistance and improved other characteristics including thermal oxidation resistance, as compared with a transparent electrode composed only of zinc oxide. SOLUTION: This transparent electrode comprises a zinc oxide layer containing at least two elements selected from group III of the periodic table, such as aluminum or gallium. Assuming that any specified two types of at least two elements are an additional element 1 and an additional element 2, respectively, the concentration of the additional element 1 on one surface or in the vicinity of the zinc oxide layer is higher than the concentration of the additional element 2, and the concentration of the additional element 2 on the opposite face to or in the vicinity of the zinc oxide layer is higher than the concentration of the additional element 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a transparent electrode used for a photovoltaic element, a thin film transistor and the like.

[0002]

2. Description of the Related Art Conventionally, tin oxide-based materials have been widely used as transparent electrodes used as electrodes for electronic devices such as photovoltaic elements and thin film transistors. Such an electrode for an electronic device has a function of transmitting light,
Further, it is desired that the electric resistance is small because it is used as an electrode. The above-mentioned tin oxide-based materials are preferably used because they are excellent in transparency and electric resistance characteristics.

As an attempt to further reduce the electrical resistance of a transparent electrode material, an indium tin oxide (hereinafter, also referred to as ITO) -based material obtained by adding tin to indium oxide has been widely used. I have.

[0004] However, although the tin oxide-based transparent electrode and the indium tin oxide-based transparent electrode certainly show excellent characteristics in terms of transparency and electric resistance, they are exposed to hydrogen plasma in a manufacturing process for manufacturing a device. At this time, tin and indium are reduced and deposited, and there is a problem that device performance is deteriorated. In addition, indium was said to be scarce in resources and had a problem in production cost. Therefore, in recent years, zinc oxide-based materials have been proposed and manufactured as inexpensive materials having high plasma resistance.

A transparent electrode using each of the above-mentioned materials is generally formed on a base material or a base layer, and the manufacturing method thereof is a vacuum evaporation method, a sputtering method, and a chemical vapor deposition method (hereinafter, referred to as a chemical vapor deposition method). The precursor is converted by a method such as a vapor deposition method such as a CVD method), a spray method, or a method including applying a solution containing a compound to be a precursor of each of the above materials to a substrate, and then heating the substrate in an oxidizing atmosphere. A solution coating method or the like for forming a layer made of each material is used. Among these, the vacuum evaporation method and the sputtering method are particularly preferably used from the viewpoint of producing a high-performance transparent electrode.

Meanwhile, in the case of a transparent electrode made of a transparent conductive film of zinc oxide, the first electrode of the periodic table must be used to improve the electrode characteristics.
It is known that Group III elements are added into the matrix. In general, it is known that a zinc oxide film to which a Group III element of the periodic table is added has different characteristics depending on the type of the element to be added. For example, when aluminum is added, the specific resistance is known to decrease. (JP-A-7-249
316). It is also reported that a zinc oxide film to which gallium is added has excellent heat resistance in an oxidizing atmosphere. Further, it seems that the zinc oxide film to which a Group III element of the periodic table other than aluminum and gallium is added also has characteristics.

[0007]

However, when different Group III elements of the periodic table are simultaneously added to the zinc oxide layer so that they are evenly distributed, the transparency and electric conductivity of the transparent electrode can be reduced. Due to the relationship, there is an upper limit to the total amount of Group III elements in the periodic table, so that the effect of each additive element cannot be sufficiently exerted, or the effect of each other is offset, and each element is added. The characteristics obtained when independently added could not be added.
For example, a transparent electrode obtained when aluminum and gallium are simultaneously added to the zinc oxide layer so that they are uniformly distributed, compared to a case where aluminum is independently added,
The specific resistance increases.

The present invention provides a zinc oxide-based transparent electrode to which at least two elements selected from Group III of the periodic table are added, and has a plurality of characteristics that are exhibited when each element is added alone. It is an object of the present invention to provide a zinc oxide-based transparent electrode having the same.

[0009]

Means for Solving the Problems The present inventors have made intensive studies to solve the above-mentioned problems. As a result, when a zinc oxide film is actually applied as a transparent electrode of an element or the like, certain properties such as heat resistance in an oxidizing atmosphere are necessarily required over the entire layer of the zinc oxide film. Instead, it has been found that it is sufficient to have only the vicinity of the surface directly in contact with the oxidizing atmosphere. Then, as a result of further study, they found a method of controlling the type and concentration of the added element of the Group III element in the periodic table in the film thickness direction, and found that the two types of Group III elements in the periodic table were different from each other. The present invention succeeded in forming an unevenly distributed zinc oxide film, and completed the present invention.

That is, the present invention relates to a zinc oxide-based transparent electrode comprising a zinc oxide layer containing at least two kinds of elements selected from Group III of the periodic table. Of the zinc oxide layer, the concentration of the additional element 1 on one surface of the zinc oxide layer or in the vicinity thereof is equal to the additional element 2.
A zinc oxide-based transparent electrode, wherein the concentration of the additional element 2 is higher than the concentration of the additional element 1 on the surface opposite to or near the surface of the zinc oxide layer or the vicinity thereof. is there.

In the transparent electrode of the present invention, the additive element 1 and the additive element 2 added to the zinc oxide layer are not uniformly dispersed. The concentration of the element 1 is higher than the concentration of the additional element 2, and the concentration of the additional element 2 is higher than the concentration of the additional element 1 on the surface on the opposite side or in the vicinity thereof. For this reason, on each surface of the zinc oxide layer or in the vicinity thereof, a high addition concentration of the periodic table III
The effect of the addition of group elements is effectively exhibited.

For example, when the zinc oxide-based transparent electrode of the present invention is used for a photovoltaic element, the zinc oxide layer has a high aluminum concentration near the interface with the substrate and a high zinc oxide concentration near the upper surface. By forming the film, a transparent electrode having a feature that a portion in contact with the underlying layer has a low resistance and an upper layer is resistant to thermal oxidation can be obtained. When such a transparent electrode is used, when the substrate is heated at the time of forming the photovoltaic element, it is possible to perform preliminary heating in the atmosphere or in an environment with a low degree of vacuum. Can be greatly reduced.

The zinc oxide-based transparent electrode of the present invention also includes a transparent electrode comprising a zinc oxide layer having a two-layer structure in which two zinc oxide films each having a different group III additive element added thereto are laminated. However, according to the present invention, the concentration of the additive element 1 and the additive element 2 in the zinc oxide layer gradually decreases from the surface where the respective additive elements are present at a high concentration or the vicinity thereof to the opposite surface or the vicinity thereof. The transparent electrode is characterized in that the possibility of introducing a defect into the zinc oxide layer at the time of manufacture is low, so that its characteristics are reproducible and stable.

Another aspect of the present invention is an electronic device having the zinc oxide-based transparent electrode of the present invention. The electronic device of the present invention has the economical advantages of using a zinc oxide-based material and, as seen in the above-described example of the photovoltaic element, has a short production time and is produced on an industrial scale. It has the feature of being suitable for

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION The transparent electrode of the present invention
It is formed of a zinc oxide layer to which at least two elements selected from group III elements (hereinafter, also simply referred to as group III elements), that is, boron, aluminum, gallium, indium, or thallium are added. By including two or more kinds of Group III elements, it becomes possible to simultaneously exert an addition effect corresponding to the Group III element to be added. The combination of the two or more Group 3 elements may be appropriately determined according to the purpose. However, when it is desired to reduce the specific resistance of the zinc oxide layer and improve heat resistance in an acidic atmosphere, at least aluminum and Preferably, gallium is added.

The amount of the Group III element added to the zinc oxide layer is not particularly limited, but from the viewpoint of the conductivity and transparency of the zinc oxide layer, the total amount of the Group III element relative to the total number of zinc atoms in the zinc oxide layer is considered. Preferably, the atomic weight is from about 0.5 atomic% to about 12 atomic%. In general, when the addition amount of all Group 3 elements (as defined above) is less than 0.5 at% and more than 12 at%, the specific resistance tends to increase, and in the latter case, the zinc oxide layer Also tends to be less transparent.

The zinc oxide layer to which the group 3 element is added,
There is no particular limitation as long as it is a layered material substantially made of zinc oxide. Here, zinc oxide may be any oxide of zinc, and zinc and oxygen need not necessarily be stoichiometrically bonded. Also, the crystal structure is not particularly limited, and may be a single crystal, polycrystal or other crystalline or amorphous material, or a mixture thereof. Further, the thickness of the zinc oxide layer is not particularly limited, either, but from the viewpoint of specific resistance and transparency, 10 to 10,000 nm (0.01 to 10 μm).
m), especially 30 to 5000 nm (0.03 to 5 μm). Further, the shape may be a flat plate shape having a substantially uniform thickness, or a layered material having irregularities on the bottom surface, the top surface, or both. For example, when a zinc oxide layer formed in advance by a vapor deposition method or the like on a substrate on which a concavo-convex structure is formed is used, a transparent electrode having excellent light confinement characteristics is obtained.

The above-mentioned zinc oxide layer may contain an element such as carbon and nitrogen in addition to the group 3 element as long as the performance as a transparent electrode is not adversely affected.

In the transparent electrode of the present invention, in the zinc oxide layer constituting the transparent electrode, any two of the at least two kinds of Group 3 elements are defined as the additional element 1 and the additional element 2, respectively. In some cases, the concentration of the additional element 1 on one surface of the zinc oxide layer or in the vicinity thereof is higher than the concentration of the additional element 2 and the addition of the zinc oxide layer on the surface on the opposite side to or near the surface of the zinc oxide layer or the vicinity thereof. The concentration of element 2 needs to be higher than the concentration of additive element 1.

By satisfying such conditions, the effect of adding the additional element 1 and the additional element 2 can be maintained without canceling the effect.
In each portion of the zinc oxide layer in which each additive element exists at a high concentration (predominantly), it is possible to effectively exert the effect of adding the dominant additive element. Here, the vicinity is a region having a depth of several nm to several tens nm from the surface as a guide.

For example, in the case of a transparent electrode formed on a substrate, aluminum and gallium are respectively selected as the additive element 1 and the additive element 2, and the aluminum concentration at or near the interface of the zinc oxide layer with the substrate is determined. By setting the gallium concentration higher than the gallium concentration and the zinc oxide layer having the gallium concentration at or near the surface opposite to the zinc oxide layer higher than the aluminum concentration, the resistance at the interface with the base material or the vicinity thereof is particularly low, and the atmosphere A transparent electrode having a characteristic of high resistance to thermal oxidation can be obtained on a surface that can be in contact with a gas or in the vicinity thereof.

The transparent electrode is used for forming an element by stacking a semiconductor layer or the like on the upper surface of a transparent electrode formed on a substrate while heating the substrate, as in the case of manufacturing a photovoltaic element. Since the portion in contact with the atmospheric gas has high thermal oxidation resistance, it can be heated in the atmosphere where an oxidizing gas such as oxygen is present or in an environment with a low degree of vacuum. For this reason, for example, preheating can be performed while the inside of the reactor is evacuated, and the total device manufacturing time can be greatly reduced.

The concentration of the additional element 1 on “one surface of the zinc oxide layer or its vicinity” where the concentration of the additional element 1 is higher than the concentration of the additional element 2 is not particularly limited. 0.3 to 12 atomic%, especially 1 to
Preferably it is 7 atomic%. The concentration of the additional element 2 on the surface or in the vicinity thereof is not particularly limited as long as it is lower than the concentration of the additional element 1. However, from the viewpoint that the addition effect of the additional element 1 is effectively exhibited, the concentration of the additional element 2 is 50%.
Hereinafter, it is particularly preferable that the content be 30% or less. For the same reason, the concentration of the additional element 2 in the “surface opposite to the zinc oxide layer or in the vicinity thereof” in which the concentration of the additional element 2 is higher than the concentration of the additional element 1 is determined by the number of zinc atoms in the surface or in the vicinity thereof. Is preferably 0.3 to 12 atomic%, particularly 1 to 7 atomic%, and the concentration of the additional element 1 on the surface is 50% or less, particularly 30% or less of the additional element 2. It is suitable.

If the zinc oxide layer constituting the transparent electrode of the present invention has the above-mentioned concentration relationship between the additive element 1 and the additive element 2 on both surfaces or in the vicinity thereof, each zinc oxide layer in the intermediate layer is provided. The concentration relationship of the elements (in other words, the concentration distribution of each additive element) is not particularly limited.

For example, a zinc oxide layer containing only the additional element 1 is formed by a vapor deposition method using a composite oxide of zinc and the additional element 1 as a target, and the zinc oxide layer containing the composite oxide of zinc and the additional element 2 is formed thereon by a vapor deposition method. A method of laminating a zinc oxide layer containing only the additional element 2 by the above method. In this method, a zinc oxide layer substantially containing only the other group 3 element (the additional element 3) is formed between both layers in the same manner. Can also. And the like. (The concentration of the additive element 2 on one surface of the zinc oxide layer or in the vicinity thereof is substantially 0, and the concentration of the additive element 1 on the opposite surface or in the vicinity thereof is substantially zero. As in the case of the transparent electrode of the present invention, the concentration distribution of the additive element in the thickness direction of the zinc oxide layer changes abruptly or discontinuously from a certain thickness. Good, as in the zinc oxide layer manufactured by the manufacturing method described in detail later, the concentration of each additional element, from the surface where each element is present at a high concentration or its vicinity to the opposite surface or its vicinity The density distribution may be such that the density gradually decreases (gradually decreases). However, it is preferable to have the latter concentration distribution from the viewpoint that defects and the like are hardly introduced at the time of production and stable transparent electrode performance is exhibited.

In the latter case, from the viewpoint of effectively exhibiting the effect of addition of the additional elements 1 and 2, the ratio of the total of the additional elements 1 and 2 to the total group 3 elements to be added. Is preferably at least 80 atomic%, particularly preferably at least 90 atomic%. The ratio of the total addition amount of each of the additional element 1 and the additional element 2 is 0.5 to 2, particularly 0.8 to 0.8, in the atomic ratio of the additional element 2 to the additional element 1.
It is preferably 1.5. In addition, additive elements 1 and 2
When other Group 3 elements are added, the concentration distribution of these elements is not particularly limited.

The method for producing the transparent electrode of the present invention is not particularly limited, but it can be suitably produced by the following method.

That is, after forming the thin film layer containing the additional element 1 on the substrate, when forming the zinc oxide layer on the thin film layer, the process of forming the zinc oxide layer or the formation of the zinc oxide layer Thereafter, a treatment is performed to diffuse the additional element 1 contained in the thin film layer into the formed zinc oxide layer, and further, a thin film comprising the additional element 2 is formed on the zinc oxide layer thus formed. A layer can be suitably manufactured by forming a layer and then performing a treatment of diffusing the additional element 2 contained in the thin film layer into the zinc oxide layer.

In the preferred manufacturing method, first, a thin film layer containing the additive element 1 is formed on a substrate. Here, the substrate is not particularly limited as long as it is a material on which a thin film layer and a zinc oxide film can be formed. Suitable substrates include various transparent substrates such as quartz glass and blue plate glass, monocrystalline silicon, polycrystalline silicon, amorphous silicon, various metals, heat-resistant polymers, and other transparent conductors, and a laminate of these materials. Laminated base material.

The thin film layer containing the additive element 1 formed on the substrate by the preferable manufacturing method is not necessarily a thin film layer.
It does not need to be composed only of other elements, and may contain other elements as long as the performance (characteristics) of the finally obtained transparent electrode is not adversely affected. Such elements include other Group 3 elements, oxygen, zinc, nitrogen, carbon, and the like. However, from the viewpoint of particularly improving the characteristics of the finally obtained transparent electrode, it is preferable that the transparent electrode does not contain an element other than the additional element 1 and oxygen.

Although the thickness of the thin film layer is not particularly limited,
From the viewpoint of light transmittance, 2 to 300 nm, particularly 5 to 100 n
m is preferred.

The method for forming the thin film layer is not particularly limited, and a known method such as a vapor deposition method, a printing method, a spraying method and the like can be employed. Among these methods, it is preferable to use an evaporation method from the viewpoint of obtaining a high-purity thin film having a controlled thickness.

In the preferred manufacturing method, a zinc oxide layer is formed on the thin film layer formed as described above. The method for forming the zinc oxide layer is not particularly limited, and a known method such as a vapor deposition method such as a vacuum deposition method, a sputtering method, and a chemical vapor deposition method (CVD method), a spray method, and a solution coating method may be used. Applicable. In the vacuum deposition method and the sputtering method, a zinc oxide sintered body is used as a target, and the deposition may be performed in the same manner as in a normal method. In the CVD method, a normal plasma CVD method using a raw material gas containing dimethyl zinc (DME) or the like is used. It may be performed by the method. In the case of performing a solution coating method, a solution containing a zinc oxide precursor such as zinc alkoxide, or a suspension of zinc oxide fine particles is applied,
The conversion can be suitably carried out by converting the precursor into zinc oxide by firing and simultaneously burning off the hydrocarbon component or sintering the zinc oxide fine particles. As such a suspension, there is a commercially available suspension, and it is preferable to use such a commercially available product.

Among these methods, the vacuum evaporation method and the sputtering method are particularly preferably employed because a zinc oxide layer having a small electric resistance can be produced.

In the preferred manufacturing method, during or after the formation of the zinc oxide layer, the additional element 1 is diffused from the thin film layer in contact with the zinc oxide layer. When the zinc oxide layer is formed by a solution coating method, the additional element 1 may diffuse into the precursor before being converted into zinc oxide.

The method for diffusing the additional element 1 into the zinc oxide layer is not particularly limited, but it is preferable to perform heat treatment. That is, when the above diffusion is performed during the formation of the zinc oxide layer, the diffusion may be performed by heating the substrate and the thin film layer during the formation of the zinc oxide. The heat treatment may be performed on the stacked body.

Vacuum evaporation, sputtering or CVD
When the zinc oxide layer is formed by a vapor deposition method such as the method, the substrate is heated to 50 to 600C, preferably 100 to 450C.
It is common practice to perform evaporation by heating to a temperature of about 50 ° C. to about 600 ° C. in the solution coating method. At this time, the diffusion of the additional element 1 occurs. When a sufficient amount of the additional element 1 is not introduced only by diffusion in the process, it is preferable to perform a heat treatment after the formation of the zinc oxide layer.

The conditions for the heat treatment may be appropriately determined according to the kind of the additive element 1 and the amount to be introduced, the thickness of the thin film layer, the method for forming the zinc oxide layer, the thickness of the zinc oxide layer, and the like. The heating temperature is 50 to 600 ° C., and the heating time is about 10 to 600 minutes. As a heating method, a known method such as a method of heating with a heater embedded in a holder for installing a transparent electrode in a manufacturing process or a method of heating with an infrared lamp is used without particular limitation.

It should be noted that the temperature of the heat treatment may be restricted in some cases. For example, when a transparent electrode is formed on the surface of the uppermost layer of a substrate on which an element has already been formed, the heat treatment temperature is preferably set to less than 400 ° C. so as not to adversely affect the performance of the element.

The conditions such as the type of the additive element 1, the thickness of the thin film layer, the method of forming the zinc oxide layer, and the thickness of the zinc oxide layer are fixed, and the heat treatment conditions during the formation of the zinc oxide layer or after the formation of the zinc oxide layer The relationship between the heat treatment conditions and the concentration and concentration distribution of the additional element 1 in the obtained zinc oxide layer is checked in advance, and the amount of the additional element 1 and the concentration distribution are controlled by controlling the heat treatment conditions. Can be controlled. In this case, since the additional element 1 is added to the zinc oxide layer by diffusion, the additional element 1 depends on the heat treatment conditions.
Usually decreases gradually toward the center of the zinc oxide layer.

In the preferred manufacturing method, another thin film layer further containing the additional element 2 is formed on the zinc oxide layer in which the additional element 1 is diffused from the underlying thin film layer,
The additional element 2 in the another thin film layer is diffused into the zinc oxide layer. At this time, another method of forming a thin film layer and a method of diffusing the additional element 2 may be performed according to a method of forming a thin film including the additional element 1 and a method of diffusing the additional element 1. In addition, the transparent electrode of the present invention manufactured in this way is expected to also function as a light control coating film.

Hereinafter, a method for producing the transparent electrode of the present invention by a sputtering method among the preferred production methods will be described in more detail with reference to the drawings.

FIG. 1 is a schematic view of a typical sputtering apparatus B which can be used in the preferred manufacturing method. In addition,
The apparatus is shown as an example and is not particularly limited. The sputtering apparatus B shown in FIG. 1 mainly includes each of the reaction vessels 1a to 1c, vacuum pumps 9a to 9c, plasma sources 7a to 7c, and gas supply devices 5a to 5c communicating with each reaction vessel. By sputtering using a different target in each reactor, for example, a thin film comprising the additional element 1 (eg, aluminum) in 1a, a zinc oxide thin film in 1b, and an additional element 2 (eg, gallium) in 1c Each thin film layer and a zinc oxide layer can be formed like a thin film.

In each of the reaction vessels 1a to 1c, there are provided a substrate mounting section 2a to 2c to which substrate heaters 11a to 11c are mounted, and high-frequency application electrodes 3a to 3c to which various targets 10a to 10c can be mounted. The high-frequency applying electrodes 3a to 3c are matched with matching circuits 6a to 6c.
Are connected to the plasma generation sources 7a to 7c via the.
Further, in each of the reaction vessels 1a to 1c, argon as a sputtering gas can be supplied from gas supply ports 4a to 4c through a gas supply device (5a to 5c) having a gas flow controller or the like. Pressure regulator 8a
-8c and vacuum pumps 9a-9c can be maintained at a constant pressure lower than the atmospheric pressure. Further, gate devices 12a to 12c are provided between the respective reaction vessels, and the base material A (the substrate or the transparent electrode in the manufacturing process) can be used without opening the reaction vessel to the atmosphere using the sample moving jig 13. It can be moved.

In order to manufacture a transparent electrode, first, a substrate such as a glass substrate is set on the base member mounting portion 2a of the reaction vessel 1a, and the substrate is evacuated to about 1 × 10 ^-6 Torr by a vacuum pump. Heater 11 embedded in base material installation part 2a
a to raise the substrate temperature to a predetermined temperature of room temperature to 600 ° C., preferably 100 ° C. to 450 ° C. by applying a current to
Argon, which is a sputtering gas, is passed through a flow controller 5a,
The gas is supplied from the gas supply port 4a into the reaction vessel. Then, a high-frequency plasma is generated by applying a high frequency to the high-frequency application electrode 3a from the high-frequency application power supply 7a, and a thin metal layer made of aluminum is formed on the substrate by, for example, sputtering an aluminum target 10a. The reaction pressure is appropriately set depending on the sputtering conditions.
The range is from mTorr to 5 Torr. Especially 1mTorr
r to 100 mTorr is preferred. The power output of the power supply for plasma generation is also set as appropriate according to the sputtering conditions. A general output range is about 10 W to 3 KW, and particularly preferably 50 W to 2 KW.

Thereafter, the substrate A is moved to the reaction vessel 1b, and the substrate is heated at 50 to 600 ° C., preferably 100 to 45 ° C.
Zinc oxide target 1 while heating to a predetermined temperature of 0 ° C.
Ob is sputtered to form a zinc oxide layer and to diffuse aluminum into the zinc oxide layer.

After the zinc oxide layer is further formed, the substrate A is moved to the reaction vessel 1c,
Is used to perform sputtering in the same manner as in the case of the reactor 1a to form a gallium-containing thin film layer. At this time, when the substrate is heated, gallium may diffuse into the zinc oxide layer during the formation of the thin film layer.

After the gallium-containing thin film layer is formed in this manner, the gallium may be further diffused by heating to 100 to 600 ° C.

The thus produced zinc oxide-based transparent electrode of the present invention can be suitably used as a transparent electrode for electronic devices such as photovoltaic elements and thin film transistors. When the zinc oxide-based transparent electrode of the present invention is applied to these electronic devices, a conventional method of manufacturing an electronic device can be applied as it is, except that the transparent electrode of the present invention is used. For example, when applied to a photovoltaic element such as a solar cell, a p-type semiconductor, an i-type semiconductor, and an n-type are formed on a transparent electrode of the present invention formed on a substrate by a plasma CVD method or the like. What is necessary is just to sequentially laminate | stack the silicon film which has a semiconductor property.

[0050]

EXAMPLES Hereinafter, the present invention will be described specifically with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples. In this embodiment, the transparent electrode is shown in FIG.
Was produced using the sputtering apparatus shown in FIG.

The zinc oxide layers obtained in the following examples and comparative examples were evaluated by the following methods (1) to (4).

(1) Transmittance of zinc oxide layer Visible region (400 nm to 800 nm) using a spectrophotometer
Was determined. The unit is shown in%.

(2) Resistivity of zinc oxide layer The resistivity was measured using a four-terminal resistance meter. The unit was expressed in Ω · cm.

(3) Thermal Oxidation Resistance of Zinc Oxide Layer The thermal oxidation resistance was evaluated by the change in specific resistance after heating and holding the zinc oxide layer formed on glass at 400 ° C. for about 1 hour in air. It can be said that those having a small increase in specific resistance after heat treatment have high thermal oxidation resistance.

(4) Concentration and Concentration Distribution of Group III Elements in Zinc Oxide Layer The concentration distribution of each additive element contained in the zinc oxide layer in the thickness direction was measured using a secondary ion detection mass spectrometer. . The measurement was performed while etching was performed, and the concentration was represented by an atomic standard (at.%) With respect to zinc.

It was evacuated to ⁶ Torr ^- [0056] Example 1 25mm × 25mm × 0.5mm (t ) in the glass substrate was set to a substrate holder of the sputtering device 1 of the apparatus 1 × 10. At this time, the glass substrate was heated to 300 ° C. by energizing a substrate heating heater embedded in the substrate holder. In this state, 10 sccm of argon gas was introduced into the sputtering apparatus, and the pressure in the apparatus was adjusted to 5 mTorr by a pressure regulator. After holding for about one hour so that heat was sufficiently transmitted to the surface of the glass substrate, 30 W of power was supplied to a high-frequency power application electrode provided with an aluminum target to generate argon gas plasma. Aluminum having a thickness of 30 nm was deposited on the substrate by sputtering for about 5 minutes. Thereafter, the substrate on which the aluminum was deposited was moved to the next reaction vessel equipped with the zinc oxide target using a sample moving jig without opening to the atmosphere. The substrate temperature was set to 300 ° C. by heating the substrate holder. In this state, 10 sccm of argon gas was introduced into the sputtering apparatus, and the pressure in the apparatus was adjusted to 50 mTorr by a pressure regulator. After holding for about one hour so that heat was sufficiently transmitted to the surface of the glass substrate, 50 W of power was supplied to a high frequency power application electrode provided with a zinc oxide target to generate argon gas plasma. Zinc oxide having a thickness of 1000 nm was deposited on the substrate by sputtering for about 30 minutes. Thereafter, the sample was moved to a reaction vessel in which a gallium oxide target was set by a sample moving jig without opening the sample to the atmosphere. The substrate temperature was set to 300 ° C. by heating the substrate holder. In this state,
Argon gas was introduced at 10 sccm into the sputtering apparatus, and the pressure inside the apparatus was adjusted to 5 mTorr by a pressure regulator. After holding for about one hour so that heat was sufficiently transmitted to the glass substrate surface, 30 W of high frequency power was supplied to a high frequency power application electrode provided with a gallium oxide target to generate argon gas plasma. 3 by sputtering for about 6 minutes
Gallium oxide with a thickness of 0 nm was deposited on the substrate. This state was maintained for about 1 hour, and then the heating of the sample was stopped. After confirming that the sample temperature had reached 100 ° C., the sample was taken out of the apparatus.

As a result of measuring the resistance of the obtained sample, 8 × 1
0 ^-4 Ω · cm was obtained. In addition, as a result of measuring the aluminum concentration and the gallium concentration in the zinc oxide, the aluminum concentration near the glass substrate was about 2.5%, the gallium concentration was 0.5%, and the gallium concentration near the surface layer was about 2%. .8
% And the concentration of aluminum were 0.9%. The aluminum concentration and gallium concentration near the center of the zinc oxide film were 2% and 1.5%, respectively. The transmittance was 85% or more in the visible region. In addition, the product of the present invention is subjected to 40
After heating to 0 ° C. and holding for about 1 hour, the resistivity is 9 × 10
^-4 Ω · cm.

Comparative Example 1 In the same operation as in Example 1, a zinc oxide layer was formed directly on a glass substrate without forming an aluminum thin film.
Thereafter, without forming a thin film containing gallium and performing heat treatment, a zinc oxide layer having a thickness of 1000 nm to which a Group 3 element was not added was formed. The resistance of the obtained sample was measured and found to be 8 × 10 ⁴ Ω · cm.

Comparative Example 2 In the same manner as in Example 1, a zinc oxide layer containing only aluminum was formed on a glass substrate to a thickness of 1000 nm without forming a gallium-containing thin film and performing heat treatment. did. 7 × 1 as a result of measuring the resistance of the obtained sample
0 ^-4 Ω · cm was obtained. After heating this comparative product to 400 ° C. in air and holding it for about 1 hour, the resistivity is 2 × 10 ⁻³ Ω · c
m.

Comparative Example 3 In the same operation as in Example 1, a zinc oxide film having only gallium added was formed to a thickness of 1000 nm on a glass substrate without forming an aluminum thin film. As a result of measuring the resistance of the obtained sample, 1 × 10 ⁻³ Ω · cm was obtained. After heating this comparative product to 400 ° C. in air and holding it for about 1 hour, the resistivity was 2 × 10 ⁻³ Ω · cm.

[0061]

As to the zinc oxide-based transparent electrode, which is characterized by high plasma resistance and inexpensiveness, a technique of reducing the specific resistance by adding an element such as aluminum has been known. Effective techniques for improving other properties at the same time as reduction have not been known.

The present invention provides a zinc oxide-based transparent electrode in which not only the specific resistance but also other properties are improved at the same time. For example, by using the transparent electrode of the present invention having improved specific resistance and thermal oxidation resistance, it is possible to greatly reduce the manufacturing time of an element such as a photovoltaic element.

[Brief description of the drawings]

FIG. 1 is a schematic view of a typical sputtering apparatus that can be used when manufacturing the transparent electrode of the present invention.

[Explanation of symbols]

 1a to 1c: Reaction vessel 2a to 2c: Substrate installation part 3a to 3c: High frequency application electrode 4a to 4c: Gas supply port 5a to 5c: Flow rate controller 6a to 6c: Matching circuit 7a to 7c High-frequency power supply 8a to 8c Pressure regulator 9a to 9c Vacuum pump 10a to 10c Target 11a to 11c Substrate heater 12a to 12c Gate device 13: jig for moving sample A: base material B: sputtering device

Claims (3)

[Claims] 1. A zinc oxide-based transparent electrode comprising a zinc oxide layer containing at least two types of elements selected from Group III of the periodic table, wherein at least two specific elements of the at least two types of elements are selected. When the seeds are the additional element 1 and the additional element 2, respectively, the concentration of the additional element 1 on one surface of the zinc oxide layer or in the vicinity thereof is higher than the concentration of the additional element 2, and the surface of the zinc oxide layer or The concentration of the additive element 2 on the surface on the opposite side of the vicinity or the vicinity thereof is equal to
A zinc oxide-based transparent electrode characterized by having a concentration higher than that of the zinc oxide. 2. The concentration of the additional element 1 and the additional element 2 in the zinc oxide layer gradually decreases from a surface where each of the additional elements is present at a high concentration or its vicinity to a surface on the opposite side or its vicinity. The zinc oxide-based transparent electrode according to claim 1, wherein: 3. An electronic device having the zinc oxide-based transparent electrode according to claim 1.