JP2003306676A - Etching agent for transparent electroconductive film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an etching agent enabling an amorphous ITO film to be etched under a mild condition without causing etching residue at all. <P>SOLUTION: The etching agent comprises an aqueous solution containing oxalic acid and a carboxylic acid. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an etching agent used for wet etching a transparent conductive film made of amorphous ITO (indium tin oxide) used as a pixel electrode in a liquid crystal display or the like.

[0002]

2. Description of the Related Art Transparent conductive films such as ITO films are
It has been widely used in the field of electronic devices such as antistatic films, heat-reflecting films, photoelectric conversion elements and transparent electrodes of various flat panel displays. In particular, recently, with the spread of notebook PCs, small TVs, portable information terminals, and the like, the demand for liquid crystal displays (LCDs) is increasing. A transparent conductive film such as an ITO film is used as a display electrode of a pixel in the field of flat panel displays, and the display electrode is formed by etching of photolithography. Liquid crystal display (LCD), especially TFT-LCD
In the field, a polycrystalline ITO film has been conventionally used, but as the substrate size increases, it becomes more difficult to make the polycrystalline ITO film uniform. As a method of forming the above-mentioned display electrode, a photoresist is applied on a transparent conductive film, and after exposure and development, an etching agent is used with the photoresist as a mask, and after etching, the remaining photoresist is peeled off. Formed. Ferric chloride / hydrochloric acid aqueous solution, iodic acid aqueous solution, phosphoric acid aqueous solution, hydrochloric acid / nitric acid aqueous solution (aqua regia), etc. have been used as the etching agent for the transparent conductive film such as the polycrystalline ITO film. It is difficult to perform patterning with high processing accuracy because corrosion of Al or the like occurs during patterning and selective etching proceeds from grain boundaries.

For the above reasons, the size of the board is increased,
With the increase in size of TFT panels, the increase in definition, the use of Al wiring, and the like, there is an increasing demand for an etchant capable of performing etching with high processing accuracy as a pixel display electrode. In order to solve these problems, recently, a transparent conductive film made of amorphous ITO (hereinafter referred to as an amorphous ITO film) is used, and the amorphous ITO film is wet-etched with a weak acid, especially an oxalic acid aqueous solution. Is advocated by. However, there is a problem that an etching residue is generated when the amorphous ITO film is wet-etched using an oxalic acid aqueous solution, and an etching agent that does not generate this etching residue is desired.

[0004]

An object of the present invention is to produce no etching residue when wet etching an amorphous ITO film with an aqueous oxalic acid solution as described above in the prior art, and An object is to provide an etching agent that can perform etching under mild conditions.

[0005]

Means for Solving the Problems The inventors of the present invention have conducted extensive studies to solve the above-mentioned problems, and as a result, an aqueous solution containing oxalic acid and a carboxylic acid was found to be It was completed based on the finding that it was possible to perform etching under mild conditions and no residue was generated.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention is described in detail below.
The concentration of oxalic acid used in the present invention is 0.01-10.
Weight% is preferable. If it is 0.01% by weight or less, the etching rate is slow, and if it is 10% by weight or more, the etching rate does not improve, which is not a good idea.

Specific examples of the carboxylic acid that can be used in the etching agent according to the present invention include those described below, but the carboxylic acid is not particularly limited thereto. (1) As a carboxylic acid having one carboxyl group,
Formic acid, acetic acid, propionic acid, lactic acid, butyric acid, valeric acid, gluconic acid, pivalic acid, glycolic acid, salicylic acid, crotonic acid, etc. (2) As a carboxylic acid having two carboxyl groups,
Tartaric acid, fumaric acid, malic acid, succinic acid, adipic acid,
Maleic acid, diglycolic acid, malonic acid, phthalic acid, phthalonic acid, glutaric acid, dioxyfumaric acid, dioxymaleic acid, oxaloacetic acid, dioxybutenedioic acid, etc. (3) As a carboxylic acid having three carboxyl groups,
Citric acid, propanetricarboxylic acid, hemimellitic acid, trimellitic acid, trimesic acid, oxalosuccinic acid, etc. (4) As a carboxylic acid having four carboxyl groups,
Planeic acid, melophanoic acid, pyromellitic acid, etc. Further, salts of the above carboxylic acids can also be used. The carboxylic acids and salts thereof may be used alone or in combination of two or more, and the preferred concentration is 0.0001 to 10% by weight.

The above carboxylic acid and its salt have a concentration of 0.
If it is 0001% by weight or less, a residue is generated during etching, and if it is 10% by weight or more, the etching rate of the amorphous ITO film may decrease or may not sufficiently dissolve.
Not preferable.

The use concentration of the present invention is from room temperature to 90 ° C., and the use time is about 0.1 to 30 minutes. In addition to the amorphous ITO film, the present invention can be preferably used for wet etching of IZO (indium-zinc oxide) film and the like.

[0010]

【Example】

Example 1 In the substrate shown in FIG. 1, an insulating film 2 made of SiN is formed on a glass substrate 1, an amorphous ITO film 3 is further formed, and the amorphous ITO film is formed on the amorphous ITO film. This is a state after applying a resist and developing. 2. Using the substrate shown in FIG.
An aqueous solution containing 4% by weight of oxalic acid and 0.2% by weight of lactic acid was used, etching was performed at 40 ° C. for 2 minutes to wash with water, and then the resist 4 was removed with a basic resist remover, followed by washing with water. As a result of observing the surface with a dried SEM (electron microscope), the amorphous ITO was satisfactorily etched and no residue was observed.

Example 2 The substrate used in Example 1 was etched at 40 ° C. for 2 minutes using a cleaning solution which was an aqueous solution containing 3.4% by weight of oxalic acid and 0.2% by weight of formic acid, and washed with water. After that, the resist was further stripped with a basic resist stripping solution, washed with water, and dried. As a result of SEM observation, the amorphous ITO film was well etched, and no residue was observed at all.

Comparative Example 1 The substrate used in Example 1 was etched by washing with an aqueous solution containing 3.4% by weight of oxalic acid at 40 ° C. for 2 minutes and then dried. Further, the resist was stripped with a basic resist stripping solution, followed by washing with water, and as a result of SEM observation, the amorphous ITO film was etched, but many residues 5 were observed as shown in FIG.

Comparative Example 2 The substrate used in Example 1 was etched at 40 ° C. for 2 minutes using an aqueous solution containing 0.2% by weight of lactic acid.
After washing with water, the resist was further stripped with a basic resist stripping solution, followed by washing with water and drying. As a result of SEM observation, amorphous IT
The O film was hardly etched.

Comparative Example 3 The substrate used in Example 1 was etched at 40 ° C. for 2 minutes using an aqueous solution containing 0.2% by weight of formic acid.
After washing with water, the resist was further stripped with a basic resist stripping solution, followed by washing with water and drying. As a result of SEM observation, amorphous IT
The O film was hardly etched.

Example 3 An aqueous solution containing 3.4% by weight of oxalic acid and 0.2% by weight of propionic acid was used, and the substrate used in Example 1 was changed to 4%.
Etching was carried out for 2 minutes at 0 ° C., and after washing with water, the resist was further stripped with a basic resist stripping solution, followed by washing with water and drying. As a result of SEM observation, the amorphous ITO film was well etched, and no residue was observed at all.

Example 4 The substrate used in Example 1 was etched at 40 ° C. for 2 minutes using an aqueous solution containing 3.4% by weight of oxalic acid and 5% by weight of formic acid, washed with water, and then made basic. The resist was stripped with a resist stripper, washed with water, and dried. As a result of SEM observation, the amorphous ITO film was well etched, and no residue was observed at all.

Example 5 The substrate used in Example 1 was prepared by using an aqueous solution containing 3.4% by weight of oxalic acid and 0.2% by weight of malonic acid.
After etching at 2 ° C. for 2 minutes and washing with water, the resist 4 was stripped off with a basic resist stripping solution, washed with water and dried. As a result of SEM observation, the amorphous ITO film was well etched, and no residue was observed at all.

Example 6 The substrate used in Example 1 was etched at 40 ° C. for 2 minutes using an aqueous solution containing 3.4% by weight of oxalic acid and 0.2% by weight of diglycolic acid, and washed with water. After further removing the resist with a basic resist remover, it was washed with water and dried. As a result of SEM observation, the amorphous ITO film was well etched, and no residue was observed at all.

Example 7 The substrate used in Example 1 was prepared by using an aqueous solution containing 3.4% by weight of oxalic acid and 2.0% by weight of malonic acid.
Etching was performed at 2 ° C. for 2 minutes, and after washing with water, the resist was peeled off with a basic resist stripping solution, followed by washing with water and drying.
As a result of SEM observation, the amorphous ITO film was well etched, and no residue was observed at all.

Example 8 The substrate used in Example 1 was treated at 40 ° C. using an aqueous solution containing 1.0% by weight of oxalic acid and 0.2% by weight of citric acid.
After performing etching for 2 minutes and washing with water, the resist was stripped with a basic resist stripping solution, washed with water, and dried. SE
As a result of M observation, the amorphous ITO3 was etched well, and no residue was observed at all.

Example 9 The substrate used in Example 1 was etched at 40 ° C. for 2 minutes using an aqueous solution containing 5.5% by weight of oxalic acid and 2% by weight of citric acid, washed with water, and then made basic. The resist was stripped with a resist stripper, washed with water, and dried. As a result of SEM observation, the amorphous ITO film was well etched, and no residue was observed at all.

Comparative Example 4 Example 1 using an aqueous solution containing 2% by weight of citric acid.
The substrate used in 1. was etched at 40 ° C. for 2 minutes, washed with water, and the resist 4 was further stripped with a basic resist stripping solution, washed with water, and dried. As a result of SEM observation, amorphous IT
The O film was hardly etched.

Example 10 40% of the substrate used in Example 1 was prepared by using an aqueous solution containing 5.5% by weight of oxalic acid and 0.2% by weight of pyromellitic acid.
Etching was carried out at 2 ° C. for 2 minutes, and after washing with water, the resist was further stripped with a basic resist stripping solution, followed by washing with water and drying.
As a result of SEM observation, the amorphous ITO film was well etched, and no residue was observed at all.

[0025]

INDUSTRIAL APPLICABILITY As described above, the etching composition of the present invention exhibits an excellent effect that no residue is observed after etching the amorphous ITO film.

[Brief description of drawings]

FIG. 1 shows a state after an insulating film made of SiN is formed on a glass substrate, an amorphous ITO film is further formed, a resist is applied on the amorphous ITO film, and development is performed. It is sectional drawing shown.

FIG. 2 is obtained by etching the substrate of FIG. 1 with an aqueous solution containing 3.4% by weight of oxalic acid at 40 ° C. for 2 minutes and washing with water,
FIG. 4 is a cross-sectional view showing a state in which the resist is dried, and the resist is peeled off with a basic resist peeling liquid and then washed with water.

[Explanation of symbols]

1 glass substrate, 2 SiN insulating film, 3 amorphous ITO film, 4
Resist, 5 residues

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Minoru Takakawa             Niigata City Niigata City Tayuhama Niiwari 182 Mitsubishi Mitsubishi             Gas Chemical Co., Ltd. Niigata Research Center

Claims (2)

[Claims] 1. An etching agent for a transparent conductive film, which is an aqueous solution containing oxalic acid and a carboxylic acid. 2. The etching agent according to claim 1, wherein the transparent conductive film is made of amorphous indium tin oxide.