TWI519627B - Etching liquid composition for transparent conductive film - Google Patents

Description

Etching liquid composition for transparent conductive film

The present invention relates to an etching liquid composition for a transparent conductive film used in a liquid crystal display (LCD) or an electroluminescence display (ELD) display element or the like.

Examples of the transparent conductive film used in a liquid crystal display or an electroluminescence display element or the like include indium tin oxide (ITO), indium zinc oxide (IZO), indium oxide, tin oxide, zinc oxide, and the like, wherein the ITO film and IZO films are widely used. As a method of patterning a transparent conductive film, a usual method is to form a transparent conductive film by sputtering or the like on a substrate such as glass, and then form a photoresist pattern by photolithography, and then use a transparent conductive film. Etching to form an electrode pattern.

As an etching solution for a transparent conductive film, an etching solution containing (1) aqueous solution of ferric chloride, (2) aqueous solution of iodic acid, (3) aqueous solution of phosphoric acid, and (4) mixed solution of hydrochloric acid and nitric acid (aqua regia) have been proposed. And (5) a component of dissolved indium oxide such as an aqueous oxalic acid solution.

In the ITO film, a polycrystalline ITO film which is excellent in basic characteristics as a transparent conductive film, such as a resistance or a transmittance, has been used. However, in recent years, it has been required to increase the size, high definition, and high performance of display elements. As a transparent conductive film that satisfies these requirements, an amorphous ITO film or an IZO film is used as the processing precision is improved, the temperature of the process is lowered, and the surface flatness is improved.

An etch liquid of a transparent conductive film such as an amorphous ITO film or an IZO film is widely used because it is inexpensive and has excellent stability, and has a practical etching rate and little damage to Al wiring. However, when the transparent conductive film is etched using an aqueous oxalic acid solution, there is a problem that crystals of indium oxalate are easily precipitated.

In general, since the etching liquid is used in an etching apparatus and is repeatedly circulated, when the transparent conductive film is etched using an etching solution containing oxalic acid, the crystal of indium oxalate is easily precipitated because the concentration of indium in the etching liquid increases. Once precipitated, it crystallizes as a core and forms coarse crystals, which adhere to the device. As a result, there is a problem that the operation of the device is poor, the mesh of the filter is clogged, or the substrate is damaged.

Since indium oxalate has a salt which is relatively insoluble, it is difficult to redissolve in an etching solution, and it is also difficult to dissolve in water. Therefore, in order to remove the crystals precipitated in the apparatus, only the etching liquid in the apparatus is removed, and it is removed by manual work or by some means such as dissolution of the chemical solution, but this causes production. Reduced quantity and increased cost. Also, filters that are clogged with mesh can be removed by some means or have to be renewed, but this also results in reduced throughput and increased costs. As described above, when etching using a transparent conductive film containing an etchant liquid of oxalic acid, crystals of indium oxalate are easily precipitated, which is a major problem.

The countermeasure against this problem is a component in which indium oxide is used in a solution other than the above-mentioned oxalic acid. However, the aqueous solution of iron chloride has a large amount of side etching and has a drawback of containing Fe which adversely affects the semiconductor. Further, the aqueous iodic acid solution is not only easy to dissociate but lacks stability, and has an expensive disadvantage. Further, the phosphoric acid aqueous solution dampens the Al wiring and has a drawback that the etching residue is likely to occur. Further, the hydrochloric acid-nitric acid mixed liquid (Aqua regia) has a remarkable change with time, and has a drawback that it is difficult to convey the process and is difficult to transport.

Further, when a transparent conductive film such as an amorphous ITO film or an IZO film is etched using an etching solution containing oxalic acid as a main component, there is a problem that etching residue is likely to occur.

As a method for solving this problem, the present inventors have proposed to disclose an etchant composition for an ITO film (Patent Document 1) which contains oxalic acid and is selected from a polysulfonic acid compound and a polyoxyethylene-polyoxypropylene block copolymer. One or two or more compounds of the group consisting of the substances. Further, an etchant composition for an ITO film containing oxalic acid, an aminocarboxylic acid or triethanolamine has been proposed (Patent Document 2); an etchant for an amorphous ITO film containing oxalic acid and a carboxylic acid (Patent Document 3) An etchant liquid composition containing a perfluoroalkyl group-containing phosphate salt, oxalic acid and water, and an etchant composition for an IZO film (Patent Document 4) and an ITO film and an IZO film containing an oxalic acid and a fluorine-based surfactant In the liquid composition (Patent Document 5), etc., the etching liquid containing oxalic acid has a practical etching rate and has an effect of suppressing etching residue, but the problem of crystal precipitation of the indium oxalate is not fully recognized. It is still an unresolved state.

Further, as an etching solution containing no oxalic acid, there is a proposal to disclose an amino group-containing sulfonic acid, a polyoxyethylene alkyl ether sulfate, a polyoxyethylene alkylphenyl ether sulfate or a polyoxyalkylene alkyl ether phosphate. An etchant for an amorphous ITO film composed of an aqueous solution (Patent Document 6) or the like contains an etchant containing no oxalic acid, and the crystal of indium oxalate is not precipitated, and it is considered to have an effect of preventing etching residue. Compared with an aqueous solution of oxalic acid, there is a problem that the etching rate is slow and the production amount is lowered.

As described above, when the original etching liquid in which the inorganic acid which dissolves indium oxide other than oxalic acid is used as a main component, the etching property and the stability of the etching liquid have significant problems in use, and there is no problem. It is comparable to an excellent etching solution which is superior to an etching solution containing oxalic acid as a main component. Further, in the case of an etching solution containing oxalic acid as a main component, an etching liquid capable of maintaining excellent characteristics and capable of suppressing crystal precipitation of indium oxalate does not exist.

Therefore, as an etching solution using oxalic acid as a main component, it is used for the crystallization of the transparent conductive film containing indium during the etching process, and the current state of the art is that only the etching liquid after use is filtered by a nanofiltration membrane to be regenerated. The method of the device, the periodic maintenance of the device, and the device structure in which the crystal structure is not easily precipitated (Patent Document 7 and Non-Patent Document 1).

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2002-164332

[Patent Document 2] Japanese Patent Laid-Open Publication No. 2002-033304

[Patent Document 3] Japanese Patent Laid-Open Publication No. 2003-306676

[Patent Document 4] Japanese Patent Laid-Open Publication No. 2005-116542

[Patent Document 5] Japanese Patent Laid-Open Publication No. 2005-244083

[Patent Document 6] Japanese Laid-Open Patent Publication No. 2002-367974

[Patent Document 7] Japanese Patent Laid-Open Publication No. 2006-013158

[Non-Patent Document 1] The first edition of December 17, 2007, and the Information Technology Corporation issued the "Recent Collection of Transparent Conductive Films", pp. 556-557.

Therefore, the object of the present invention is to provide an etching liquid composition for a transparent conductive film, and to prevent crystallization of indium oxalate by etching the transparent conductive film such as amorphous ITO or IZO used in a liquid crystal display or the like. It helps to increase production and reduce costs.

In order to solve the problem, the present inventors have found that an etching liquid composition for a transparent conductive film containing oxalic acid and a basic compound has excellent characteristics of an etching liquid containing oxalic acid as a main component and can suppress oxalic acid. The present invention was completed by crystallizing the indium and further studying the results.

That is, the present invention relates to an etching liquid composition for a transparent conductive film containing oxalic acid and a basic compound (excluding triethanolamine).

Further, the present invention relates to the etching liquid composition for a transparent conductive film, wherein the basic compound is selected from the group consisting of a fourth-order ammonium hydroxide, an alkali metal hydroxide, and an alkanolamine (except for triethanolamine). And one or more of the group consisting of hydroxylamines.

Further, the present invention relates to the etching liquid composition for a transparent conductive film described above, wherein the pH is from 1.1 to 5.0.

Further, the present invention relates to the etching liquid composition for a transparent conductive film, which further comprises a compound selected from the group consisting of a polysulfonic acid compound, a polyoxyethylene-polyoxypropylene block copolymer, and a sulfonate type anionic surfactant. One or two or more compounds of the group.

Furthermore, the present invention relates to the etchant composition for a transparent conductive film, which further contains one or more kinds of water-soluble polymers.

Moreover, the present invention relates to an etching liquid composition for a transparent conductive film which is used for etching a transparent conductive film containing indium oxide.

Moreover, the present invention relates to a method of etching a transparent conductive film using the etching liquid composition for a transparent conductive film.

The reason why the crystal of indium oxalate is easily precipitated is considered to be a low solubility of indium in an aqueous oxalic acid solution. According to the investigation by the present inventors, it is clear that the amount of indium dissolved in the aqueous oxalic acid solution is about 300 ppm, and the crystal of indium oxalate is easily precipitated at a concentration higher than the above. That is, it is considered that the increase in the amount of indium dissolved in the aqueous oxalic acid solution is related to the inhibition of crystal precipitation of indium oxalate.

The reason why the etchant composition for a transparent conductive film of the present invention can suppress the crystallization of indium oxalate by containing a basic compound is not clear, but it is considered to be relative to indium as the pH in the liquid becomes higher. Since oxalic acid is more likely to form a complex with an OH group or an amine or a fourth-order ammonium, the formation of indium oxalate can be suppressed, and as a result, the amount of indium dissolved can be increased.

According to the etching liquid composition for a transparent conductive film of the present invention, since the crystallization of indium oxalate can be suppressed during the etching process of the transparent conductive film, the liquid life of the etching liquid can be extended, and the operation for removing the crystal can be reduced. Increase production and reduce costs.

Hereinafter, the present invention will be described in detail. The transparent conductive film of the present invention is a transparent conductive film made of indium tin oxide (ITO), indium zinc oxide (IZO), or indium oxide, and particularly a transparent conductive film made of amorphous ITO and an IZO film. Further, the etching liquid composition for a transparent conductive film of the present invention is an etching liquid composition used in an etching process of the transparent conductive film in a process such as a liquid crystal display or an electroluminescence display.

The concentration of the oxalic acid to be used in the etching liquid composition of the present invention is appropriately determined in consideration of the etching rate, and the oxalic acid crystal is not precipitated, and is preferably 0.1 to 10% by weight, and preferably 0.3 to 0.3% by weight. More preferably, 8 wt% is particularly preferably 0.5 to 6 wt%. When the concentration of oxalic acid is low, the etching rate is lowered, and when the concentration of oxalic acid is high, the crystal of oxalic acid tends to precipitate. When the concentration of oxalic acid is within the above range, a practical etching rate can be obtained without crystallization of oxalic acid. The possibility of preservative or barriers to delivery is preferred.

The basic compound used in the etching liquid composition of the present invention is selected in consideration of the amount of indium dissolved, the etching rate, etc., and the etching liquid composition of the present invention is characterized in that the etching rate is decreased when a basic compound is added. Smaller, and the balance between the amount of indium dissolved and the etching rate is particularly important. The basic compound used in the etching liquid composition of the present invention typically includes a fourth-order ammonium hydroxide, an alkali metal hydroxide, an alkanolamine (except triethanolamine), and a hydroxyl group. Amines, etc.

Specifically, examples of the fourth-order ammonium hydroxide include tetramethylammonium hydroxide, tetraethylammonium hydroxide, and choline.

Further, examples of the alkali metal hydroxide include sodium hydroxide and potassium hydroxide.

Further, examples of the alkanolamines include monoalkanolamines, dialkanolamines, and trialkanolamines other than triethanolamine. Examples of the monoalkanolamines include monoethanolamine, 2-methylaminoethanol, 2-ethylaminoethanol, 2-(2-aminoethoxy)ethanol, and 1-amino-2-propane. Alcohol, monopropanolamine, dimethylaminoethanol, and the like. Further, examples of the dialkanolamines include diethanolamine, N-methyldiethanolamine, dibutanolamine, and the like. Among the above-mentioned alkanolamines, from the viewpoints of the amount of indium dissolved, the etching rate, and the like, preferred are monoalkanolamines, dialkanolamines, and the like, and more preferably monoalkanolamines and the like. It is particularly preferable to be monoethanolamine or the like.

Further, examples of the hydroxylamines include hydroxylamine, N-hydroxylamine, N,N-dimethylhydroxylamine, N,N-diethylhydroxylamine, hydroxylamine sulfate, and hydroxylamine hydrochloride. A hydroxylamine etc. are preferable.

In addition, these basic compounds may be contained in one type or two or more types depending on the use.

The concentration of the basic compound used in the etching liquid composition of the present invention is appropriately determined in consideration of the amount of indium dissolved, the crystal precipitation of indium oxalate, the pH of the etching liquid composition, the etching rate, and the like, and is 0.1 to 10 by weight. The % is preferably from 0.3 to 7% by weight, more preferably from 0.5 to 5% by weight. When the concentration of the basic compound is low, the crystal of indium oxalate is likely to be precipitated. When the concentration is high, the etching rate tends to decrease. When the concentration of the basic compound is within the above range, the effect of sufficiently preventing the precipitation of crystals of indium oxalate can be obtained. And practical etching speed is preferred.

The pH of the etching liquid composition of the present invention is appropriately determined in consideration of the amount of indium dissolved, the crystal precipitation of indium oxalate, the etching rate, and the like, and is preferably 1.1 to 5.0, more preferably 1.2 to 4.0, and 1.3 to 3.0. Very good. When the pH is low, the crystal of indium oxalate is likely to be precipitated, and when the pH is high, the etching rate tends to decrease. When the pH is in the above range, the effect of sufficiently preventing the crystal precipitation of indium oxalate and the practical etching rate can be obtained. Preferably.

In the etching liquid composition of the present invention, the pH of the composition of the present invention containing oxalic acid and a basic compound is compared with the pH of the composition having the same composition except for the basic compound, and the pH is increased by the addition of the basic compound. The amount of change ΔpH is appropriately determined in consideration of the amount of indium dissolved, the crystal precipitation of indium oxalate, the etching rate, and the like, and is appropriately adjusted by the type and concentration of the basic compound to be added.

The range of ΔpH is preferably from 0.1 to 4.0, more preferably from 0.3 to 3.0, and particularly preferably from 0.5 to 2.0. When ΔpH is small, crystals of indium oxalate are easily precipitated, and when ΔpH is large, the etching rate tends to decrease. When ΔpH is in the above range, it is preferable to obtain an effect of sufficiently preventing crystallization of indium oxalate from crystal precipitation and a practical etching rate. .

The etching rate of the etching liquid composition of the present invention is appropriately adjusted by the concentration of oxalic acid, the type and concentration of the basic compound, and the like in consideration of the treatment time and uniform etching.

Further, the etching liquid composition of the present invention can further contain a component for removing the etching residue without departing from the above effects. As a component used for such a purpose, a polysulfonic acid compound, a polyoxyethylene-polyoxypropylene block copolymer, a sulfonate type anionic surfactant, or the like is preferable.

Examples of the polysulfonic acid compound include a naphthalenesulfonic acid formaldehyde condensate and a salt thereof, polystyrenesulfonic acid and salts thereof, lignosulfonic acid and salts thereof, and the like. As a naphthalenesulfonic acid formaldehyde condensate and a salt thereof, specifically, Runox 1000C, 1500A, IONET D-2, Sanyo Levelon PHL (above, Toho Chemical Industry Co., Ltd.), LOMAR PWA-40 (made by SAN NOPCO Co., Ltd.), Demol Sales of trade names such as N (Kao Co., Ltd.), POLITY N-100K (LION Co., Ltd.), and Labelin FH-P (First Industrial Pharmaceutical Co., Ltd.). Specifically, the lignosulfonic acid and its salt are sold under the trade names of Sorpol 9047k (Toho Chemical Industry Co., Ltd.) and SunEkis (Japan Paper Chemical Co., Ltd.). Among these polysulfonic acid compounds, a metal containing sodium or the like is not suitable for use in the electronics industry, but it can be used by removing it by treatment with an ion exchange resin or the like.

The polyoxyethylene-polyoxypropylene block copolymer has various types depending on the ratio and molecular weight of polyoxyethylene to oxypropylene, and specifically, for example, NEWPOL PE series (Sanyo Chemical Industry Co., Ltd.), Epan series (first Sales of trade names such as Industrial Pharmaceuticals Co., Ltd.).

Examples of the sulfonate-type anionic surfactant include alkylbenzenesulfonate of dodecylbenzenesulfonic acid and salts thereof, salts thereof such as alkyl sulfate, and dialkyl esters of sulfosuccinate. And salts thereof, polyoxyethylene alkyl ether sulfonic acids and salts thereof, polyoxyethylene allyl ether sulfonic acids and salts thereof, and the like. Among them, polyoxyethylene alkyl ether sulfonic acid and its salt, polyoxyethylene allyl ether sulfonic acid and its salts are particularly preferred because of the low foaming, and the products are Newcol series (Japan Emulsifier Co., Ltd.). Name sales. Further, these compounds may be contained alone or in combination of two or more kinds depending on the use.

The polysulfonic acid compound, the polyoxyethylene-polyoxypropylene block copolymer, and/or the sulfonate type anion interface used in the etching liquid composition of the present invention from the viewpoint of obtaining an effect of sufficiently removing the etching residue The concentration of the active agent is preferably 0.0001 to 10% by weight, particularly preferably 0.001 to 10% by weight.

Further, the etching liquid composition of the present invention can further contain a component for suppressing crystal precipitation of indium oxalate without departing from the above effects. As a component used for such a purpose, a water-soluble polymer having an effect of preventing scale is preferred.

Examples of the water-soluble polymer include polyacrylic acid, polymaleic acid, acrylic acid-maleic acid copolymer, acrylic acid-sulfonic acid copolymer, acrylic acid-styrene copolymer, and the like. Wait. Specifically, for example, it is sold under the trade names of Acalic series (Japan Catalyst Co., Ltd.), ARON series (East Asia Synthetic Co., Ltd.), and POLITY series (LION Co., Ltd.). Among these water-soluble polymers, a metal containing sodium or the like is not suitable for use in the electronics industry, but it can be used by removing it by treatment using an ion exchange resin or the like. These water-soluble polymers may be contained alone or in combination of two or more kinds depending on the use.

The concentration of the water-soluble polymer used in the etching liquid composition of the present invention is preferably 0.001 to 10% by weight, particularly preferably 0.01 to 10% by weight, from the viewpoint of obtaining an effect of sufficiently suppressing crystallization precipitation. . Further, the molecular weight of the water-soluble polymers is preferably from 200 to 100,000, particularly preferably from 500 to 10,000.

The etching liquid composition of the present invention can be used at room temperature or under heating, and can be appropriately set and used in such a manner that a desired etching rate and etching time can be obtained.

The etching method of the transparent conductive film using the etching liquid composition of the present invention includes a spraying process of supplying an etching liquid onto a substrate by a spray nozzle, and immersing the substrate directly in the etching liquid and shaking the substrate itself or The immersion treatment of the etching solution is stirred.

In the following, the present invention will be described in more detail by way of examples and comparative examples of the invention. However, the invention is not limited thereto, and various modifications can be made without departing from the scope of the invention.

[Examples]

(composition of etching solution)

The compositions of the etching liquids of the examples and comparative examples of the present invention are shown in Table 1.

TMAH: tetramethylammonium hydroxide

MEA: monoethanolamine

Demol N: sodium salt of naphthalenesulfonic acid formaldehyde condensate (made by Kao Corporation)

(Evaluation of solubility of indium)

In each of the etching liquids shown in Table 1, while adding a temperature to 50 ° C, indium oxide powder (average particle diameter: 1 μm, purity: 99.99%) was added so as to have a predetermined indium concentration, and stirred for 2 to 3 hours. . After visually confirming that the indium oxide powder was sufficiently dissolved, each etching solution was filtered using a 0.2 μm filter, and the filtrate was sealed in a container and left to stand in a thermostat set at 37 ° C, and visually confirmed whether or not crystallized at each predetermined time. Precipitate. Further, the pH of each etching solution was measured. Further, the amount of indium dissolved in the etching solution was calculated from the weight of the added indium, the capacity of the etching solution, and the change in the weight of the filter before and after the filtration. The results are shown in Table 2.

※Evaluation criteria for indium solubility

○: 168 hours (7 days) or more crystals were not precipitated.

×: Crystallization occurred within 24 hours (one day).

As shown in Table 2, in the case of the etching liquids of the comparative examples 1 to 5 which did not contain a basic compound, it was confirmed that the indium dissolved amount was small and crystallized and precipitated within 24 hours. In contrast, the etching solution containing the basic compound of Examples 1 to 13 of the present invention has a large amount of dissolved indium and does not cause crystal precipitation after 168 hours (7 days) or more, and the liquid stability is extremely excellent. As a result, it was found that increasing the amount of dissolved indium has an effect of suppressing crystallization of indium oxalate. In the etching liquid composition of the present invention, the balance between the amount of indium dissolved, the liquid stability, and the etching rate to be described later is particularly important.

In addition, as shown in Comparative Examples 2 and 3, the concentration of oxalic acid was lowered, and even if the pH was 1.3 to 1.5, it was confirmed that crystals were precipitated, and it was found that there was no effect in simply raising the pH of the oxalic acid-containing etching solution. When it contains a basic compound, it is very effective for suppressing the crystal precipitation system of indium oxalate.

(Evaluation of etching speed)

The etchant as shown in Table 1 was heated to 40 ° C and will be at 800 A substrate having a photoresist pattern formed on the amorphous ITO film having a film thickness was immersed in the etching solution for 1 minute, washed with water, dried, and then peeled off, and the amount of etching was measured using a stylus film thickness gauge to calculate an etching rate. The results are shown in Table 3.

As shown in Table 3, it was found that the etching liquid containing the basic compound of Examples 1 to 13 of the present invention had a slightly smaller etching rate than the etching liquids of Comparative Examples 1 to 5 which did not contain the basic compound. However, the amorphous ITO film has a practically sufficient etching rate.

(residue removal evaluation)

The substrate on which the ITO film was formed on the glass substrate was etched by a time of 1.4 times the appropriate etching time calculated from the etching rate, and the residue after the etching was evaluated by electron microscope observation. In addition, a substrate obtained by forming a tantalum nitride (SiN) film on a glass substrate and further forming an ITO film is similarly etched and processed for 1.4 times of an appropriate etching time calculated from the etching rate to perform electrons. The residue after etching was evaluated by microscopic observation. The results are shown in Table 4.

* Evaluation criteria for residue removal

○: No residue was observed at all

×: The residue can be observed comprehensively.

As shown in Table 4, when the etching solution containing only oxalic acid of Comparative Example 1 was obtained, the residue was observed on both the glass substrate and the SiN film, and the oxalic acid and the alkali of Examples 12 and 13 were relatively The etching solution of the compound and the polysulfonic acid compound has the same residue-removability as the etching liquid containing the oxalic acid and the polysulfonic acid of the comparative example 5.

From the results of the above Tables 1 to 4, it is found that the etching solution composition of the present invention has a large indium dissolution amount and a very high liquid stability after dissolving indium, so that the effect of suppressing crystal precipitation of indium oxalate is excellent. .

Further, it was found that there is a practically sufficient etching rate equivalent to the previous etching liquid containing oxalic acid as a main component which does not contain a basic compound.

In addition, similarly to the etching liquid containing oxalic acid as a main component which does not contain a basic compound, it is possible to provide excellent residue removal property by adding a polysulfonic acid compound or the like.

[Industry use possibility]

According to the present invention, by using an etching liquid composition containing oxalic acid and a basic compound, a transparent conductive film such as ITO or IZO formed on a substrate such as glass is etched, and oxalic acid in the etching apparatus can be effectively suppressed. The precipitation of indium crystals can extend the liquid life of the etching liquid, and the operation for removing crystals and the frequency of exchange of the filter can be reduced, so that the production amount can be increased and the cost can be reduced. Therefore, it is particularly useful in the field of manufacturing technology such as a liquid crystal display or an electroluminescence display using a transparent conductive film such as an ITO film or an IZO film.

Claims (6)

An etchant composition for a transparent conductive film, which comprises oxalic acid and one or more basic compounds selected from the group consisting of alkali metal hydroxides, hydroxylamines, and cholines, and has a pH of 1.1~5.0. The etching liquid composition for a transparent conductive film according to claim 1, wherein the pH is from 1.3 to 3.0. The etchant composition for a transparent conductive film according to claim 1 or 2, further comprising an anion interface selected from the group consisting of a polysulfonic acid compound, a polyoxyethylene-polyoxypropylene block copolymer, and a sulfonate type. One or more compounds of the group consisting of active agents. The etchant composition for a transparent conductive film according to claim 1 or 2, further comprising one or more water-soluble polymers. The etching liquid composition for a transparent conductive film according to claim 1 or 2, which is used for etching a transparent conductive film containing indium oxide. An etching method for a transparent conductive film, which is an etching liquid composition for a transparent conductive film according to any one of claims 1 to 5.