JPH10282907A - Electrode substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an electrode substrate free from trouble in the connection of electrodes in spite of low electrical resistance and high moisture resistance by varying the concn. of indium or tin in the thickness direction of multiple oxide thin films. SOLUTION: The multiple oxide thin films 15 to 18 on at least one side where a silver alloy thin film 12 is held consists of two layers varying in the concn. of the indium or tin and are so disposed that the concn. of the indium or tin of the multiple oxide 15, 18 on the outermost layers not in contact with the silver alloy thin film 12 is made higher. The conductive film formed on the electrode substrate 10 is usable as a transparent electrode having high transmittance by forming the thinner film thickness of the silver alloy thin film 12 held by the multiple oxides 15 to 18. Conversely, the conductive film is usable as a reflection electrode having high reflectivity by forming the thicker film thickness of the silver alloy thin film 12. The reflection electrode is usable as the electrode of a liquid crystal display device of a reflection type and electroluminescence(EL).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an output display device such as a liquid crystal display device or a plasma display device, or an input / output display device for directly inputting from a display screen.
Alternatively, the present invention relates to a substrate provided with a transparent electrode or an electrode substrate provided with a reflective electrode, which is used for a solar cell or the like.

[0002]

2. Description of the Related Art An electrode substrate in which a transparent electrode in the form of an electrode that transmits visible light is provided on a substrate such as a glass or plastic film is used as a display electrode for various display devices (display screens) such as a liquid crystal display device. It is widely used for input / output electrodes and the like that can be directly input from the display screen of this display device.

[0003] The use of a reflective electrode as one light-reflective electrode opposite to a transparent electrode in a reflective liquid crystal display device is being studied. As a transparent electrode,
A thin film of ITO, which is a mixed oxide obtained by adding tin oxide to indium oxide, is widely used, and its specific resistance is about 2 × 10 ⁻⁴ Ω · cm. In addition, if the ITO film is
At 00 nm, the sheet resistance is 10 Ω / □.

[0004] In recent years, a slightly better-performing ITO has begun to be marketed, but its sheet resistance is 300 nm in thickness and about 5 Ω.
/ □, and the specific resistance is about 1.5 × 10 ⁻⁴ Ω · cm.

On the other hand, in 1982, the 7th
In the ICVM, as a heat ray reflection film, an ITO thin film or an indium oxide thin film (IO thin film) on the front and back surfaces of a silver thin film
Have been proposed. This three-layer transparent conductive film has a resistance of about 5Ω /
It has a low sheet resistance of about □, and is expected to be applied to the transparent electrode by making use of its high conductivity.

In recent years, in the above display devices and input / output devices, it has been required to display a fine screen by increasing the pixel density, and accordingly, the transparent electrode pattern has been required to be fine. , For example, 100 μm
It is required that the terminal portions of the transparent electrode be formed at a pitch of the order.

In a liquid crystal display device in which a liquid crystal driving IC is directly connected to a substrate (COG method), there is a portion where the wiring is a thin line having a width of 20 to 50 μm. There is a demand for a high degree of suitability for etching and high conductivity (low resistivity).

[0008] On the other hand, there is a demand for a larger display screen. For such a large screen, a transparent electrode with a dense pattern as described above is formed,
Moreover, in order to be able to apply a sufficient drive voltage to the liquid crystal, it was necessary to apply a transparent electrode having a high conductivity of 4.5Ω / □ or less as the transparent electrode.

In addition to this, in a simple matrix driving type liquid crystal display device using an STN liquid crystal or the like, one
In the case of performing multi-gradation display of 6 or more gradations, a lower sheet resistance of 3Ω / □ or less is required.

However, the transparent electrode having the three-layer structure proposed in the 7th ICVM also has a maximum of 5Ω.
There was a problem that only a sheet resistance of about // could be obtained, and sufficient conductivity could not be secured. It can be said that by increasing the thickness of the silver thin film of the transparent electrode having the three-layer structure to, for example, about 16 to 18 nm, the sheet resistance can be reduced to about 3Ω / □. However, when the thickness of the silver thin film is increased, the visible light transmittance (especially the visible light transmittance on the long wavelength side of about 610 nm) decreases to about 75%, and the function as a transparent electrode is impaired. A problem arises.

Further, in the transparent electrode having a three-layer structure, that is, in a laminated structure of ITO and a silver thin film, a reaction easily occurs in the presence of moisture, and particularly, aggregation of silver and destruction of the ITO are prevented around the interface. Easy to bring. as a result,
It easily causes a spot-like defect that can be easily visually recognized, and has a defect that a display defect and a disconnection of the transparent electrode occur.

[0012]

DISCLOSURE OF THE INVENTION The present inventors have proposed an ITO
To solve the problem of low moisture resistance, which was a problem in the laminated structure of silver and silver thin films, the technology shown in Japanese Patent Application No. 7-88797 was proposed. In the art, that is, in order to improve moisture resistance and transmittance, the mixed oxide is a mixed oxide obtained by adding cerium oxide or the like to indium oxide, and, in a silver alloy, a silver alloy obtained by adding copper or the like to silver. With this technique, a transparent conductive film having high moisture resistance can be obtained.

In the configuration according to the present technology, it is necessary to add cerium oxide, for example, in an amount of about 10 to 40% in order to improve moisture resistance and transmittance. However, in a configuration in which a thin film of a silver alloy is sandwiched by a mixed oxide obtained by adding a large amount of cerium oxide to indium oxide, the conductivity of the oxide thin film as the mixed oxide is greatly reduced.

As a result, the surface resistance of the drive electrode of the liquid crystal display device is increased, and the electrical connection to TAB (a film obtained by processing a copper wiring pattern on a polyimide film) or the like is extremely unstable. .

The present invention has been made in view of the above problems, and an object of the present invention is to provide an electrode substrate which has low resistance and high moisture resistance and has no inconvenience in electrode connection. Where you do it.

[0016]

Means for Solving the Problems The present inventors have made intensive studies to solve the above problems, and as a result,
As means for solving the above-mentioned problems, an oxide layer having high conductivity is provided on a surface side to be electrically connected to TAB or the like, and a high moisture resistance is provided on a surface side in contact with the silver alloy thin film. It is proposed to provide an oxide layer of the above. More specifically, the composition ratio of indium oxide or tin oxide, which has high conductivity, is set low for the oxide on the side in contact with the silver alloy thin film, and high for the oxide on the outside.

That is, according to the first aspect of the present invention, there is provided an electrode substrate provided with a conductive film having a structure in which a silver alloy thin film is sandwiched between mixed oxide thin films based on indium oxide or tin oxide. It is characterized in that the concentration of indium or tin differs in the thickness direction of the oxide thin film.

According to a second aspect of the present invention, at least one of the mixed oxide thin films sandwiching the silver alloy thin film is composed of two layers having different indium or tin concentrations, and is not in contact with the silver alloy thin film. The mixed oxide of the outermost layer is arranged so as to increase the concentration of indium or tin.

The conductive film formed on the electrode substrate of the present invention can be used as a transparent electrode having a high transmittance by forming the silver alloy thin film sandwiched between the mixed oxides to be thin. Conversely, by forming the silver alloy thin film to be thick, it can be used as a reflective electrode having a high reflectance. The reflective electrode can be used as a reflective liquid crystal display device or an electrode of electroluminescence (EL). It is possible.

That is, the invention of claim 3 relates to the transparent electrode, and is characterized in that the thickness of the silver alloy thin film is in the range of 7 to 25 nm. The invention of claim 4 relates to the reflection electrode, and is characterized in that the thickness of the silver alloy thin film is in the range of 50 to 200 nm.

The thickness of the silver alloy thin film is 7 nm as a transparent electrode.
If it is less than 1, the silver alloy thin film becomes a discontinuous film, and it is difficult to become a continuous and uniform film. In addition, a transparent electrode having poor optical characteristics and conductivity is obtained. Further, when the thickness of the silver alloy thin film is 25 nm, a transparent electrode having a transmittance of about 80% at a light wavelength of 550 nm is obtained.

The silver alloy thin film is used as a reflective electrode.
Although the film may be formed to have a thickness exceeding 200 nm, even if the thickness is set to exceed 200 nm, the light reflectance does not become higher than this, so that it is not necessary to set the thickness to exceed 200 nm.

When the silver alloy thin film is formed of a silver alloy obtained by adding a noble metal such as gold, copper, palladium, or platinum to silver, the reliability of the three conductive films sandwiching the silver alloy thin film with the mixed oxide is improved. Can be improved. For example, when the amount of the noble metal added is 5 at% (atomic percent) or less, the three-layered conductive film can be used without significantly affecting the light transmittance (or light reflectance) and conductivity of the conductive film. , High reliability and high adhesion to the substrate.

That is, the invention according to claim 5 is characterized in that the silver alloy thin film is a silver alloy obtained by adding at least one of gold, copper, palladium, and platinum to silver.

In order to further improve the adhesion to the oxide, the silver alloy contains a small amount of a metal such as indium, tin, aluminum, magnesium or the like, or a transition metal such as nickel (for example, 2 at% or less). ) May be added.

As described above, the total amount of gold, copper, palladium, and platinum added to silver is within a range that does not affect the optical characteristics (light transmittance or light reflectance) or conductivity.
6 at% (atomic percent) or less is desirable. In addition, since gold is completely dissolved in silver, even if it is added up to about 20 at%, it does not significantly affect the optical characteristics. The effect of adding these noble metals to silver starts to be seen even with a small amount of about 0.3 at%, but from the viewpoint of improving moisture resistance,
0.5at% or more is preferable, and low sheet resistance (high conductivity)
In order to ensure the above, each is preferably 3 at% or less.

In the three-layer conductive film sandwiching the silver alloy thin film, the base material of the mixed oxide on both sides of the silver alloy thin film is preferably indium oxide or tin oxide which is a good conductor. Zinc oxide may be used as the base material, but the former two are preferred because they are inferior in acid resistance and alkali resistance.

In order to improve the moisture resistance of the three-layered conductive film, oxides of high melting point transition metals such as Ti, Zr, Hf, Nb, Ta, and Cr, and oxidation of lanthanum-based metals such as Ce are used. It is preferable to add a substance, an oxide of a semimetal such as Bi, Ge, or Si to the base material. Among them, particularly, addition of cerium oxide (CeO ₂ ) to a substrate is preferable because it has both high chemical resistance and high refractive index. In other words, the invention of claim 6 is characterized in that the mixed oxide thin film contains cerium oxide, and the mixed oxide thin film contains cerium oxide to have a high refractive index, thereby providing a transparent electrode. The transmittance can be improved.

The base material of indium oxide or tin oxide may be a mixed oxide thin film to which the above-mentioned metal oxide is added in addition to cerium oxide.

When cerium oxide is added to indium oxide as a substrate, the ratio of cerium in the substrate is 1 to 50 atm.
% (Atomic percent), and particularly preferably 3 to 40 at%. That is, if cerium oxide is added to the substrate in an amount exceeding 40 at%, cracks are likely to be generated in the target in the processing of the sputtering target used for forming the mixed oxide thin film.

The ratio of cerium oxide in the base material was determined by the following (Equation 1), and was obtained by calculating (C) in (Equation 1).
The descriptions of (e element) and (In element) are the atomic percentage (at) of the cerium element and the indium element, respectively.
%), And both have no count of oxygen element.

[0032]

(Equation 1)

The electrode substrate of the present invention can be used as a transmission type or reflection type display device electrode substrate. For example, when used as a reflective display device electrode substrate,
The substrate on which the electrodes are formed may be a transparent substrate such as glass or plastic, or a transparent or opaque substrate colored in another color such as white or black. further,
The substrate itself is an electric circuit, a solar cell, or amorphous silicon, polysilicon, MIM (diode element)
Or a substrate having an optical function such as a polarizing element, a diffraction grating, a light scattering film, a λ / 4 plate, or a retardation film. Further, a substrate on which a color filter is formed in advance may be used.

The conductive film having a three-layer structure according to the present invention has a low resistance, so that the TFT (thin film transistor) or the MIM
It can be used for signal lines and bus lines of elements such as (diode elements) and can also be used as these pixel electrodes.

[0035]

Embodiments of the present invention will be described below in detail with reference to the drawings.

<Embodiment 1> As shown in FIG. 1, a transmission electrode substrate 14 according to the present embodiment (Embodiment 1) is made of a tin oxide base material sequentially laminated on a glass substrate 10 having a thickness of 0.7 mm. The first layer mixed oxide 15 (thickness 34 nm) and the second layer mixed oxide 16 (thickness 34 nm)
8 nm), a silver alloy thin film 12 (film thickness 16 nm), a third layer mixed oxide 17 (film thickness 8 nm), and a fourth layer mixed oxide 18 (film thickness 37
nm) constitutes the main part.

Here, the first-layer mixed oxide 15 and the third-layer mixed oxide 17 of the present embodiment (Example 1) are formed by adding tin oxide as a base material to tin oxide.
Indium oxide is added. In other words, the composition of tin oxide rich (the amount of tin oxide is large) in which the content of tin is 99 at% (atomic percent) and the content of indium is 1 at% (atomic percent) in terms of metal tin and metal indium (the oxygen element is assumed to be no count). And In this (Example 1), indium oxide was added to the mixed oxide at 1 at%, but another dopant such as antimony oxide may be added in a required amount.

Further, the second layer mixed oxide 16 and the fourth layer mixed oxide 18 are obtained by converting cerium oxide and gallium oxide to tin oxide base material in terms of metal element (oxygen element is not counted). Tin 80at%, Cerium 10at%, Gallium 10
It was a mixed oxide having a composition of at%. Furthermore, silver alloy thin film 12
Was a silver alloy having a composition of 97 at% silver, 2 at% gold, and 1 at% copper.

Next, the five-layered transparent electrode 11 is
It was formed by the following manufacturing process. That is,
First, a negative resist pattern was formed on the cleaned surface of the glass substrate 10 (the surface on which the transparent electrode 11 is to be formed in FIG. 1) by a usual photolithography technique.

Next, the first layer mixed oxide, the second layer mixed oxide, the silver alloy thin film, the third layer mixed oxide, the fourth layer mixed oxide,
A layered mixed oxide was deposited. In forming each layer, the amount of oxygen gas introduced into the apparatus was adjusted to form a film.

Next, the glass substrate 10 was taken out of the sputtering apparatus, and the entire surface of the resist pattern was irradiated with ultraviolet light. Then, the resist pattern was removed using an organic alkali-based film remover to form a transparent electrode 11 pattern. Thereafter, the glass substrate 10 was subjected to a heat treatment at 220 ° C. for 1 hour to form an electrode substrate 14.

The electrode substrate 14 thus obtained has a sheet resistance of about 3 Ω / □ and a specific resistance calculated at a total film thickness of 103 nm of about 3.1 × 10 ⁻⁵ Ω · cm, which means that it has extremely good conductivity. I understood. The light transmittance at a wavelength of 550 nm was about 94%.

A film (having 480 wiring portions) called a TAB in which a copper wiring pattern is formed on a polyimide film is applied to a transparent electrode on the electrode substrate 14 of the present embodiment (Example 1). When a mounting test was performed through an anisotropic conductive film in which metal fine particles were dispersed, no conduction failure was observed at 480 wiring portions, and good electrical connection was obtained.

Comparative Example 1 Next, for comparison with the above (Example 1), an electrode substrate 34 was formed as shown in FIG. At that time, cerium oxide and gallium oxide were added to tin oxide as a base material, 80 at% tin, 10 at% cerium, gallium
It was added so as to have a composition of 10 at% and used as a mixed oxide. Using the mixed oxide described above, a glass substrate 30 having a thickness of 0.7 mm was manufactured in substantially the same manufacturing process as in (Example 1).
A three-layered transparent electrode 31 is formed on the mixed oxide layer 36 (film thickness 42 nm), the silver alloy thin film 32 (film thickness 16 nm), and the mixed oxide layer 37 (film thickness 45 nm) in this order. The electrode substrate 34 of this example (Comparative Example 1) was formed.

As in the above (Example 1), (Comparative Example 1)
When a mounting test was performed using TAB on the electrode substrate 34, 225 conduction failures, which were nearly half of the 480 wiring connections, occurred.

<Embodiment 2> As shown in FIG. 2, the reflection type electrode substrate 24 according to the present embodiment (Embodiment 2) is composed of a first layer mixed layer on a glass substrate 20 having a thickness of 0.7 mm. Oxide 25
(Film thickness 20 nm), silver alloy thin film 22 (film thickness 120 nm), second layer mixed oxide 27 (film thickness 10 nm), third layer mixed oxide 28
(Film thickness 65 nm) constitutes the main part.

Here, the first layer mixed oxide 25 and the second layer mixed oxide 27 are obtained by adding cerium oxide, tin oxide and titanium oxide to indium oxide as a base material. The composition of the mixed oxide is expressed as atomic percentage in terms of metal element (oxygen element is assumed to be no count), with indium at 76.5 at%, cerium at 20 at%, tin at 3 at%, and titanium at 0.5 at%, respectively. is there. In addition, cerium oxide, tin oxide, and titanium oxide are also added to the third layer mixed oxide 28 containing indium oxide as a base material, and the composition of the mixed oxide is defined as an atomic percent in terms of a metal element (the oxygen element is no Count), respectively, indium 92.5
at%, cerium 5at%, tin 3at%, titanium 0.5at%.

Next, the four-layer reflective electrode 21 was formed by the following manufacturing process. First, after cleaning the surface of the cleaned glass substrate 20 with an organic alkali-based surfactant and water, the glass substrate 20 is housed in a vacuum chamber (sputtering apparatus) and subjected to a plasma treatment called reverse sputtering.
Further, the surface was cleaned. Next, the first layer mixed oxide, the silver alloy thin film, the second layer mixed oxide, and the third layer mixed oxide are removed from the glass substrate 20 by a sputtering method without removing the glass substrate 20 from the vacuum chamber and without heating. Films were sequentially laminated on the substrate 20.

Next, on the four-layer reflecting electrode 21,
After a resist pattern (positive pattern) in the shape of a reflective electrode was formed by photolithography, the exposed portions outside the pattern were etched with a sulfuric acid-nitric acid-based etchant. Next, after the resist was stripped, annealing (heat treatment) was performed at 220 ° C. for 1 hour to form a reflective electrode 24.

The area resistance of the thus obtained reflective electrode 21 was about 0.28 Ω / □. The specific resistance calculated assuming a total film thickness of 215 nm was 6.0 × 10 ⁻⁶ Ω · cm.

The reflection electrode 21 of the electrode substrate 24 of the second embodiment.
Using a film called TAB (having 480 wiring portions) in which a copper wiring pattern is formed and processed on a polyimide film, a mounting test is performed through an anisotropic conductive film in which fine nickel metal particles are dispersed. As a result, no conduction failure was observed at 480 wiring portions, and good electrical connection was obtained.

<Comparative Example 2> Next, for comparison with (Example 2), an electrode substrate 44 was formed as shown in FIG.
At that time, indium oxide as a base material, cerium oxide,
Titanium oxide was converted to metal element (oxygen element is assumed to be no count), indium 76.5at%, cerium 20
It was added as a composition of at%, tin 3 at%, and titanium 0.5 at%, and used as a mixed oxide. Using the mixed oxide described above, a first layer mixed oxide was formed on a glass substrate 40 having a thickness of 0.7 mm in substantially the same manufacturing process as in (Example 1).
46 (film thickness 20 nm), silver alloy thin film 42 (film thickness 120 nm), and second layer mixed oxide 47 (film thickness 75 nm) are sequentially laminated to form a three-layer transparent electrode 41. The electrode substrate 44 of this example (Comparative Example 2) was used.

In this (Comparative Example 2), a mounting test was performed using TAB in the same manner as in (Example 2) described above.
During the connection of 80 wires, 6 continuity failures occurred.

[0054]

According to the present invention, by increasing the composition ratio of a highly conductive oxide, the oxide on the electrode surface which is important for connection in mounting can be compared with a conventional transparent electrode called ITO. Thus, a conductive film having a good specific resistance of one or two digits can be obtained. That is, it is possible to provide an electrode substrate of a sufficient practical level having sufficient electrode mountability and high moisture resistance. Further, the electrode substrate of the present invention can be formed by selecting a substrate material and adjusting the thickness of the mixed oxide thin film and the silver alloy thin film to form an antireflection film, an electromagnetic wave shielding film, a transparent electrode for a solar cell, Thus, the present invention is practically excellent.

[0055]

[Brief description of the drawings]

FIG. 1 is an explanatory view showing one embodiment of an electrode substrate of the present invention.

FIG. 2 is an explanatory view showing another embodiment of the electrode substrate of the present invention.

FIG. 3 is an explanatory view showing an example of a conventional electrode substrate.

FIG. 4 is an explanatory view showing another example of a conventional electrode substrate.

[Explanation of symbols]

 10, 20, 30, 40 Substrate 11, 31 Transparent electrode 21, 41 Reflective electrode 14, 24, 34, 44 Electrode substrate 12, 22, 32, 42 Silver alloy thin film 15, 16, 17, 18 Mixed oxide 25, 27 , 28 Mixed oxides 36, 37, 46, 47 Mixed oxides

Claims (6)

[Claims] An electrode substrate provided with a conductive film having a structure in which a silver alloy thin film is sandwiched by a mixed oxide thin film based on indium oxide or tin oxide on a substrate, in a thickness direction of the mixed oxide thin film, An electrode substrate having a different concentration of indium or tin. 2. The mixed oxide thin film sandwiching the silver alloy thin film on at least one side is composed of two layers having different indium or tin concentrations, and the indium or tin concentration of the outermost mixed oxide is increased. The electrode substrate according to claim 1, wherein the electrode substrate is arranged as follows. 3. The electrode substrate according to claim 1, wherein the thickness of the silver alloy thin film is in a range of 7 to 25 nm. 4. The electrode substrate according to claim 1, wherein the thickness of the silver alloy thin film is in a range of 50 to 200 nm. 5. The electrode substrate according to claim 1, wherein the silver alloy thin film is a silver alloy obtained by adding at least one of gold, copper, palladium and platinum to silver. 6. The electrode substrate according to claim 1, wherein the mixed oxide thin film contains cerium oxide.