JP2006196200A - Transparent electrode and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a transparent electrode that does not use indium, which is superior in alkaline resistance and wet heating stability, and moreover, is also superior in etching characteristics. <P>SOLUTION: This transparent electrode has zinc oxide and tin oxide as the main components, and has a taper angle of an electrode end part being 30 to 89°. The ratio of zinc atom (Zn/(Zn+Sn), the atomic ratio), with respect to the total amount of the zinc atom and the tin atom in this transparent electrode, is preferably in the range of 0.5 to 0.85. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a transparent electrode used for a thin display or the like. More specifically, the present invention relates to a transparent electrode mainly composed of zinc oxide and tin oxide and having an electrode end tapered, and a method for manufacturing the electrode.

  A liquid crystal display device is considered promising among thin displays because of its features such as low power consumption and easy full color, and in recent years, development relating to enlargement of the display screen has been active. In particular, an active matrix liquid crystal flat panel display in which α-Si thin film transistors (TFTs) or p-Si TFTs are arranged in a matrix as a switching element for each pixel and is driven has a high definition of 800 × 600 pixels or more. Since it does not deteriorate the contrast ratio even if it is performed, it has attracted attention as a flat display for high-performance color display.

  In such an active matrix liquid crystal flat display, a transparent electrode such as indium oxide-tin oxide (ITO) is often used as a pixel electrode, and an Al-based alloy thin film is often used as a gate electrode and source / drain electrodes. This is because ITO has a low sheet resistance and high transmittance, and Al can be easily patterned and has low resistance and high adhesion.

Here, a configuration example of the TFT substrate will be described. FIG. 3 shows a cross section in the vicinity of the α-Si TFT at the stage where the pixel electrode pattern formation is completed in the manufacturing process of the liquid crystal flat display.
In FIG. 3, a gate electrode pattern 22 is formed on a translucent glass substrate 21, and then a SiN gate insulating film 23, an α-Si: H (i) film 24, and a channel protective film 25 are formed by plasma CVD. Then, the α-Si: H (n) film 26 is continuously formed to form a desired shape pattern. Further, a metal film mainly composed of Al is deposited by a vacuum evaporation method or a sputtering method, and a source electrode pattern 27 and a drain electrode pattern 28 are formed by a photolithography technique, thereby completing an α-Si TFT element portion. In this example, a protective film 30 is formed.

An ITO film is deposited thereon by a sputtering method to form a pixel electrode pattern 29 electrically connected to the source electrode 27 by a photolithography technique. The reason why the ITO film is deposited after the Al film is that the electrical contact characteristics between the α-Si: H film and the source and drain electrodes are not deteriorated.
Al is inexpensive and has a low specific resistance, and is an indispensable material in terms of preventing deterioration in display performance of a liquid crystal display due to increased resistance of gate and source / drain electrode wiring.

In the manufacturing process, after formation of the source and drain electrode patterns mainly composed of Al, when the ITO pixel electrode pattern processed in HCl-HNO 3 _-H 2 _O based etching solution, Al pattern eluting with machining end point The problem that occurred frequently.
This is because Al originally has a property of being dissolved in an HCl-HNO ₃ —H ₂ O-based etching solution which is an ITO etching solution. HNO ₃ in the etching solution is added to form a thin Al oxide film on the Al surface to prevent the elution of Al, but the etching time of the ITO film is long, or the Al film mixed during Al deposition If there are defective parts such as impurities and foreign matters, it is considered that the effect of oxidizing Al by HNO ₃ does not sufficiently act due to the local battery reaction. In addition, when Al and ITO are immersed in a 2.38 wt% aqueous solution of tetramethylammonium hydroxide (TMAH), which is a resist developer, in a state where Al and ITO are electrically bonded, there is also a problem that Al is eluted by a battery reaction. .

To prevent dissolution of such Al, an ITO film by an amorphous, it has been disclosed to increase the ITO / Al etching rate ratio _HCl-HNO 3 -H ₂ O-based etchant (For example, refer to Patent Document 1).
However, since an etching solution of ITO film HCl-HNO 3 _-H 2 _O system even in the amorphous, elution of Al is not fully prevented, realizing a high-definition liquid crystal display could not.

  With regard to this problem, patterning of Al electrodes, transparent electrodes made of indium oxide-zinc oxide, and pixel electrodes on the source / drain electrode pattern is facilitated by using an oxalic acid-based etching solution. Has been proposed (see, for example, Patent Document 2).

  Incidentally, indium oxide-tin oxide (ITO) and indium oxide-zinc oxide (IZO), which are generally used as transparent electrodes, both have indium oxide as a main component. In recent years, demand for indium has been increasing rapidly for thin display applications, and the price has been rising. For this reason, there exists a problem that the price of the sputtering target used in order to produce a transparent electrode also rises.

For this reason, a zinc oxide-based transparent conductive film that does not use indium oxide and a tin oxide-based transparent conductive film have been proposed (see, for example, Non-Patent Document 1).
However, it is known that a zinc oxide film is not practical because it is weak against acid and alkali solutions due to its nature. In addition, in zinc oxide film formation, zinc oxide in the vicinity of the substrate has low crystallinity and the surface of the transparent conductive film has high crystallinity. Therefore, in the etching process, the film in the vicinity of the substrate is etched from the surface. There is a problem that the etched electrode becomes an inverted trapezoid (undercut).

On the other hand, tin oxide has a problem that it is difficult to etch even aqua regia (a mixed acid of nitric acid and hydrochloric acid), which is a strong acid, because chemical stability is too strong.
JP 63-184726 A Japanese Patent Application Laid-Open No. 11-264995 Japan Society for the Promotion of Science Transparent Oxide Optical and Electronic Materials 166th Edition: Transparent Conductive Film Technology, Ohmsha (1999)

  The present invention has been made in view of the above-described problems, and an object thereof is to provide a transparent electrode that does not use indium, has excellent alkali resistance and wet heat stability, and has excellent etching properties.

The inventors of the present invention have made extensive studies to solve the above problems, and found that the above problems can be solved by forming a transparent electrode using a sputtering target made of zinc oxide / tin oxide. Completed.
According to the present invention, the following transparent electrode and the manufacturing method thereof can be provided.

1. A transparent electrode mainly composed of zinc oxide and tin oxide and having a taper angle of 30 to 89 degrees at the electrode end.
2. 2. The transparent electrode according to 1, wherein the ratio of zinc atoms to the total amount of zinc atoms and tin atoms in the transparent electrode (Zn / (Zn + Sn), atomic ratio) is 0.5 to 0.85.
3. A method of etching a transparent conductive film mainly composed of zinc oxide and tin oxide using an aqueous oxalic acid solution.
4). 4. The etching method according to 3, wherein the concentration of oxalic acid in the oxalic acid aqueous solution is 1 wt% to 10 wt%.

5. The process of forming the transparent conductive film which has as a main component the zinc oxide and tin oxide whose ratio (Zn / (Zn + Sn), atomic ratio) of a zinc atom with respect to the total amount of a zinc atom and a tin atom is 0.5-0.85. And a step of patterning the transparent conductive film using an aqueous solution having an oxalic acid concentration of 1 wt% to 10 wt% as an etchant and etching the etchant at a temperature in the range of 20 to 50 ° C. Of manufacturing transparent electrode.

Since the transparent electrode of the present invention does not use indium, it is inexpensive regardless of the price fluctuation of indium. By using zinc oxide / tin oxide having a specific composition, the electrode can be made excellent in alkali resistance and moist heat resistance.
Further, by using a specific etching solution, it is possible to prevent the end of the electrode from becoming an inverted trapezoid, and it is possible to obtain an electrode controlled to have a constant taper angle.

Hereinafter, the transparent electrode of the present invention will be specifically described.
FIG. 1 is a cross-sectional view of the transparent electrode of the present invention.
The transparent electrode 11 of the present invention is formed on the substrate 10, mainly composed of zinc oxide and tin oxide, and has a taper angle (α) of 30 to 89 degrees at the electrode end.
“Mainly composed of zinc oxide and tin oxide” means that the proportion (atomic ratio) of zinc and tin oxide in the transparent electrode is 51% or more. In the present invention, the proportion of the oxide is preferably 75% or more, particularly preferably 90% or more.

Zinc and tin oxide forms include zinc oxide such as ZnO, tin oxide such as SnO ₂ and SnO, and complex oxides between zinc oxide and tin oxide such as ZnSnO ₃ and Zn ₂ SnO ₄ . Although there is a form, an amorphous form is preferable.
This amorphous transparent conductive film has excellent etching characteristics not found in zinc oxide-based transparent conductive films and tin oxide-based transparent conductive films. That is, unlike a zinc oxide-based transparent conductive film, the electrode end after etching is unlikely to have an inverted trapezoidal shape, and the etching characteristics are not as bad as a tin oxide-based transparent conductive film.

  In the transparent electrode of the present invention, the taper angle of the electrode end is 30 to 89 degrees. When the taper angle is smaller than 30 degrees, the distance between the electrode edge portions becomes long, and when the liquid crystal or the organic EL is driven, the contrast between the pixel peripheral portion and the inside may be different. When the taper angle exceeds 89 degrees, electrode cracking or peeling occurs at the edge, and in the case of liquid crystal, the alignment film may be defective, or in the case of organic EL, the counter electrode may be disconnected.

  The thickness of the transparent conductive film (transparent electrode) is preferably 5 to 300 nm, more preferably 20 to 150 nm, and particularly preferably 30 to 80 nm. If the film thickness is less than 5 nm, the resistance value may be too high, and if it exceeds 300 nm, the taper angle of the electrode end after etching may not be within 30 to 89 degrees.

In the present invention, since the transparent conductive film mainly composed of zinc oxide and tin oxide described above is used, the taper angle of the transparent electrode can be controlled. The taper angle is controlled, for example, by adjusting the concentration of the oxalic acid aqueous solution that is an etching agent. Specifically, in order to reduce the taper angle, the concentration of the oxalic acid aqueous solution is adjusted to be low. Conversely, to increase the taper angle, the concentration of the oxalic acid aqueous solution is adjusted to be high.
The transparent conductive film mainly composed of zinc oxide / tin oxide is preferably an amorphous film. If it is not an amorphous film, it is difficult to control the taper angle, and it may not be possible to keep it within 30 to 89 degrees.

In the present invention, the ratio of zinc atoms to the total amount of zinc atoms and tin atoms in the transparent electrode (Zn / (Zn + Sn), atomic ratio) is preferably 0.5 to 0.85. When Zn / (Zn + Sn) is larger than 0.85, it becomes difficult to control when etching with an aqueous oxalic acid solution, the taper angle of the electrode end becomes 90 degrees or more, the side etching becomes too large, and the electrode becomes thin. There is a risk of breakage. In addition, the contact resistance between the transparent electrode and the anisotropic conductive film (ACF) connecting the external circuit may increase, or the contact resistance with the ACF may increase in the durability test (high temperature, high humidity).
On the other hand, when Zn / (Zn + Sn) is less than 0.5, the etching rate with oxalic acid decreases, and etching may not be possible. Preferably, Zn / (Zn + Sn) is 0.5 to 0.8, and more preferably 0.7 to 0.8.
The atomic ratio (Zn / (Zn + Sn), atomic ratio) is a value measured by an ICP (high frequency inductively coupled plasma) analysis method.

  The transparent electrode of the present invention can be produced by etching and patterning a transparent conductive film composed of an amorphous conductive oxide mainly composed of zinc oxide and tin oxide. Hereinafter, description will be given with reference to the drawings.

FIG. 2 is a diagram showing a manufacturing process of the transparent electrode of the present invention. The manufacturing process mainly includes formation of a transparent conductive film (FIG. 2A), formation of a resist film (FIG. 2B), patterning of the resist film (FIG. 2C), and etching of the transparent conductive film (FIG. 2). 2 (d)).
(1) Formation of transparent conductive film A transparent conductive film 11 ′ is formed on a substrate 10 on which a transparent electrode is to be formed.
As the substrate 10, a transparent resin plate such as a glass plate, polysulfone, or polycarbonate that is a transparent substrate can be used.
Examples of the method for forming the transparent conductive film 11 ′ include a vapor deposition method, a sputtering method, a CVD method, a spray method, and a dipping method. Of these, sputtering is preferably used.
Specifically, a sputtering target prepared and sintered using zinc oxide and tin oxide as main raw materials may be used. In order to make the formed transparent conductive film 11 ′ an amorphous transparent conductive film, the substrate temperature during sputtering is adjusted to 300 ° C. or less, or hydrogen is added to the sputtering gas during sputtering (10 vol% or less). )do it.
Thus, by making the transparent conductive film 11 ′ amorphous, it becomes possible to easily etch with an aqueous oxalic acid solution.

(2) Formation of transparent electrode Subsequently, the transparent conductive film is etched and patterned into a desired electrode pattern. Patterning can be performed by a method usually used in the technical field, for example, photolithography. That is, a resist film 12 is formed on the transparent conductive film 11 ′ (FIG. 2B), and the resist film 12 is patterned by exposure and development (FIG. 2C). Thereafter, the transparent conductive film 11 ′ is etched using an etchant to form a desired pattern. Finally, the resist film 12 remaining on the transparent electrode 11 is removed using a stripping solution (FIG. 2D) to form a transparent electrode (FIG. 2E).

In the present invention, it is preferable to use an aqueous oxalic acid solution as an etching solution. When an acid other than oxalic acid is used, the etching power increases, so that Al used in the TFT may be dissolved.
The concentration of oxalic acid in the oxalic acid aqueous solution is preferably 1 wt% to 10 wt%. If the oxalic acid concentration is less than 1 wt%, the etching rate is slow and impractical, and if it exceeds 10 wt%, oxalate crystals may precipitate. More preferably, they are 2 wt%-7 wt%, Especially preferably, they are 2 wt%-5 wt%.

  The use temperature of the etchant during etching is preferably 20 to 50 ° C. If it is less than 20 ° C., the etching rate is slow and impractical, and if it exceeds 50 ° C., the concentration of the oxalic acid aqueous solution may fluctuate due to evaporation of moisture. Preferably it is 25 to 45 degreeC, More preferably, it is 30 to 45 degreeC.

  As the resist developer, an aqueous solution of tetramethylammonium hydroxide (TMAH) is preferably used. If an alkali component other than TMAH is used, the resist pattern may be displaced or dissolved, which may cause a serious problem in etching. In addition, when Al and the transparent conductive film are electrically bonded, battery reaction may occur when they come into contact with the electrolyte solution, which may require attention.

  The concentration of TMAH is preferably 1 to 5 wt%. If it is less than 1 wt%, resist development failure may occur, and the formed transparent electrode is easily short-circuited. Further, when the concentration exceeds 5 wt%, the resist pattern may be thinned or peeled off, and the electrode pattern may be thinned or disconnected. Preferably, it is 2 to 4 wt%.

It is preferable to use an ethanolamine amine as the resist stripping solution. Examples of ethanolamine-based amines include monoethanolamine, diethanolamine, and triethanolamine, and diethanolamine is preferably used. Further, an aqueous solution may be used, but a mixed solution with a polar solvent can also be used. Examples of such polar solvents include DMF, DMSO, NMP and the like.
The concentration of ethanolamine amine in the resist stripping solution is preferably 10 wt% to 60 wt%, and particularly preferably 20 wt% to 40 wt%.
Note that it is not preferable to use an inorganic alkali such as NaOH or KOH as the stripping solution because the surface of the electrode may be dissolved and uneven.

The carrier (charge) mobility of the transparent electrode thus formed is preferably 10 cm ² / V · SEC or more. More preferably, it is 20 cm ² / V · SEC or more. In the case of a TFT drive LCD, if it is less than 10 cm ² / V · SEC, the response speed may become slow and the image quality of the liquid crystal may be degraded. The specific resistance should be low, but in the case of TFT driving, the distance from the TFT element to the LCD driving electrode end is very short, so there is no problem as long as it is on the order of 10 ⁻² Ωcm.
The carrier mobility is measured by the Hall measurement method (Fandia Poe method).

In the transparent electrode of the present invention, a third metal can be added within a range that does not affect the carrier mobility. As the third metal, for example, a metal oxide having a small refractive index can be added for the purpose of improving the transmittance. Typical examples of these include MgO, B ₂ O ₃ , Ga ₂ O ₃ , GeO _{2 and the} like.
In addition, an oxide having a small specific resistance can be added for the purpose of reducing the specific resistance of the transparent electrode. Typical examples of these include rhenium oxide, iridium oxide, and ruthenium oxide. However, these heavy metal oxides may be colored, and attention should be paid to the amount added, so they are added in a range that does not affect the transmittance.

Hereinafter, the present invention will be described more specifically with reference to examples.
Example 1
(1) Production of Sputtering Target Zinc oxide powder (manufactured by Hakusui Tec Co., Ltd.) having an average particle size of 1 μm or less and tin oxide powder (manufactured by Mitsubishi Materials) having an average particle size of 1 μm or less are Zn / (Zn + Sn) = 0.79 formulated so that the ratio (atomic ratio) were placed in a resin pot, and further adding pure water and subjected to wet ball mill mixing using a hard ZrO ₂ ball mill. The mixing time was 20 hours.
The obtained mixed slurry was taken out, filtered, dried and granulated.
The granulated product was molded by a cold isostatic press while applying a pressure of 294 MPa (3 t / cm ² ).

This molded body was sintered as follows.
In the sintering furnace, sintering was performed at 1500 ° C. for 5 hours in an atmosphere in which oxygen was introduced at a rate of 5 L / min per furnace inner volume of 0.1 m ³ . At this time, the temperature was increased up to 1000 ° C. at 1 ° C./min and 1000 to 1500 ° C. at 3 ° C./min. Thereafter, the introduction of oxygen was stopped, and the temperature was decreased from 1500 ° C. to 1300 ° C. at 10 ° C./min. And in the atmosphere which introduce | transduces argon gas at the rate of 10 L / min per furnace internal volume 0.1m < ³ >, 1300 degreeC was hold | maintained for 3 hours, Then, it stood to cool. Thereby, a zinc oxide / tin oxide-containing sintered body having a relative density of 90% or more was obtained.

The sputter surface of the obtained sintered body was polished with a cup grindstone, processed to a diameter of 100 mm and a thickness of 5 mm, and a backing plate was bonded using an indium alloy to produce a sputtering target (sintered body target 1). The density of this target was 5.72 g / cm ³ .

In addition, in the target, it is preferable that tin oxide is dispersed, and in particular, it is substituted and dissolved in the zinc site of zinc oxide. That is, the form in which Sn is contained in the target may be a form dispersed in the form of tin oxide such as SnO ₂ and SnO, but the composite oxidation between zinc oxide and tin oxide such as ZnSnO ₃ and Zn ₂ SnO ₄ is possible. In the form of a product, a form dispersed in the zinc oxide sintered body is preferable. This is because, when Sn is dispersed at the atomic level in the zinc oxide sintered body, the discharge is stabilized in sputtering and the resulting transparent conductive thin film has a low resistance.

The average diameter of the crystal particles determined by the mapping image processing of Sn atoms of EPMA (X-ray microanalyzer) of the sintered compact target 1 was 3.87 μm. Moreover, the bulk resistance (specific resistance) of the target 1 was 360 Ωcm, and a target capable of stable RF sputtering was obtained.
Table 1 shows the properties of the sintered compact target.

(2) Production of transparent conductive film The sintered compact target 1 was mounted on a sputtering apparatus. A glass substrate (thickness: 1.1 mm) is moved into the apparatus, the ultimate vacuum is 5 × 10 ⁻⁴ Pa, the deposition pressure is 0.1 Pa, the substrate temperature is 200 ° C., and a transparent conductive film (thickness) is formed on the substrate. 100 nm).
The specific resistance, carrier mobility and light transmittance of this transparent conductive film were evaluated. The specific resistance and the carrier (charge) mobility were obtained by Hall measurement. The light transmittance was measured with respect to a light beam having a wavelength of 550 nm with a spectrophotometer.
The measurement results are shown in Table 2.

(3) Preparation of transparent electrode On the transparent conductive film of the substrate with a transparent conductive film prepared in (2), a resist film was formed by spin coating using a resist solution (manufactured by Fuji Hunt, HPR204).
Next, the resist film was exposed and developed using a resist mask having a predetermined pattern. As the developer, a 2.8 wt% aqueous solution of tetramethylammonium hydroxide (TMAH) was used.

Next, this substrate was treated with an aqueous oxalic acid solution as an etching solution, whereby the transparent conductive film was etched and the transparent electrode was patterned. The conditions at this time were such that the concentration of the oxalic acid aqueous solution was 3.5 wt%, the temperature was 30 ° C., and etching was performed by dipping.
The etching rate under these conditions was evaluated.
The etching rate was also evaluated when the use temperature of the oxalic acid aqueous solution was 40 ° C., and when the concentration of the oxalic acid aqueous solution was 5.0 wt% and the use temperature was 35 ° C.
The results are shown in Table 3.

Finally, the resist film remaining on the transparent electrode was removed using a DMSO solution of diethanolamine (30 wt%) as a stripping solution. The conditions at this time were immersion at 40 ° C. for 1 minute.
Thus, a substrate on which transparent electrodes (width 90 μm, pitch 110 μm) were formed was produced.
The taper angle of the electrode end portion of the obtained transparent electrode was measured by SEM observation. The results are shown in Table 3.

Example 2-5 Comparative Example 1-2
Implementation was performed except that zinc oxide powder having an average particle diameter of 1 μm or less and tin oxide powder having an average particle diameter of 1 μm or less were used as raw material powders and the ratio of zinc atoms to tin atoms was as shown in Table 1. A sputtering target was produced in the same manner as in Example 1, and a substrate on which a transparent electrode was formed was produced using this sputtering target.
The sputtering target had a diameter of 152 mm and a thickness of 5 mm.
Properties of the sputtering target and evaluation results of the transparent electrode are shown in Table 1-3.

Evaluation 1
About the board | substrate with a transparent electrode produced in the said Example 1-5 and Comparative Example 1-2, the connection test by the TCP method (Tape Carrier Package) was done, and connection stability was evaluated.
The TCP connection substrate was stored in an environment of 60 ° C. and 90% RH, and the change in connection resistance with time was observed. The results are shown in Table 4.

Evaluation 2
On a glass substrate, a pure Al sputtering target is mounted in a sputtering apparatus, and the ultimate vacuum is 5 × 10 ⁻⁴ Pa, the deposition pressure is 0.1 Pa, the substrate temperature is room temperature, and an Al thin film ( (Thickness 200 nm) was formed.
10% of the area of the obtained glass substrate was sealed with Kapton tape. A thin film having a thickness of 100 nm was formed on this substrate at room temperature using the sputtering targets prepared in the above-described examples and comparative examples. Thereafter, the Kapton tape was peeled off to produce a laminated film-attached glass substrate in which the Al film was partially exposed.
As a reference example, a glass substrate with a laminated film in which an ITO thin film was formed on an Al film was also produced.

  These laminated film-attached glass substrates were immersed in a 2.4 wt% aqueous solution of TMAH (20 ° C.) for 2 minutes, and dissolution of the Al film was observed. The results are shown in Table 5.

  Even when a glass substrate on which only a pure Al film was formed was immersed in this aqueous solution, dissolution of the Al layer was not observed. Therefore, in the case where dissolution of Al was observed in this evaluation, it was confirmed that a battery reaction occurred due to the laminated structure of Al / transparent conductive film.

Evaluation 3
The glass with a thin film of 100 nm obtained in Example 1 was added with 10 vol% of water to a mixed solution of 30 vol% of diethanolamine and 70 vol% of dimethyl sulfoxide (DMSO) as a resist remover, and 5 ° C. at 45 ° C. Immerse for a minute. Thereafter, the surface of the thin film was observed with a scanning electron microscope (SEM). As a result, unevenness and surface roughness were not observed.
On the other hand, as a result of performing the same operation using the glass with a thin film of 100 nm obtained in Comparative Example 1, unevenness and roughness of the surface were observed on the surface of the thin film, which is not suitable as an electrode for liquid crystal or organic EL. It was confirmed that there was.

Evaluation 4
In the substrate in which the transparent conductive film and the Al film of each example described above were laminated on the glass substrate, the transparent conductive film and the Al film were each formed in a thin line shape with a line width of 50 μm so that the Al thin line and the transparent conductive thin line were orthogonal to each other. (The intersection of both thin wires is in a laminated state). The contact resistance of the laminated interface was measured (Kelvin probe method). The results are shown in Table 6.

  The transparent electrode of the present invention is inexpensive because it does not use indium. In addition, the etching characteristics are good, and the electrode end can be tapered. Therefore, it is suitable as a transparent electrode used for thin displays such as liquid crystal display devices, organic electroluminescence display devices, and plasma displays.

It is sectional drawing of the transparent electrode of this invention. It is a figure which shows the manufacturing process of the transparent electrode of this invention. It is a figure which shows an example of a TFT substrate.

Explanation of symbols

10 Substrate 11 Transparent electrode 11 'Transparent conductive film 12 Resist film

Claims (5)

  A transparent electrode mainly composed of zinc oxide and tin oxide and having a taper angle of 30 to 89 degrees at the electrode end.   2. The transparent electrode according to claim 1, wherein the ratio of zinc atoms to the total amount of zinc atoms and tin atoms in the transparent electrode (Zn / (Zn + Sn), atomic ratio) is 0.5 to 0.85.   A method of etching a transparent conductive film mainly composed of zinc oxide and tin oxide using an aqueous oxalic acid solution.   The etching method according to claim 3, wherein a concentration of oxalic acid in the oxalic acid aqueous solution is 1 wt% to 10 wt%. The process of forming the transparent conductive film which has as a main component the zinc oxide and tin oxide whose ratio (Zn / (Zn + Sn), atomic ratio) of a zinc atom with respect to the total amount of a zinc atom and a tin atom is 0.5-0.85. When,
Etching and patterning the transparent conductive film using an aqueous solution having an oxalic acid concentration of 1 wt% to 10 wt% as an etchant in a temperature range of 20 to 50 ° C .;
The manufacturing method of the transparent electrode of Claim 2 which has these.

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