KR20000017470A - ITO etchant composition - Google Patents

Abstract

PURPOSE: An indium tin oxide (In2O3-SnO2, ITO) etching composition is provided, which the stability of the etching solution is improved, the frequency of the generation of fume is reduced, and the side etching is minimized. CONSTITUTION: The ITO etching composition comprises a solution of oxalic acid and its salt in a range of 1.5 g per 1 L to the saturation concentration at the temperature using the solution. The salt is preferably ammonium oxalate. The composition can further include persulfates such as ammonium persulfate, sodium persulfate and potassium persulfate in amount of 1-250 g per 1 L, and/or a surfactant such as sodium dihexylsulfonate in amount of 0.1-20 g per 1 L. Also the ITO etching composition comprises a solution of aluminium chloride in a range of 5.5 wt% to the saturation concentration at the temperature using the solution, and a surfactant in amount of 0.1-20 g per 1 L or a reducing agent such as L-ascorbic acid in amount of 0.5-100 g per 1 L. This composition can further include persulfates in amount of 1-250 g per 1 L.

Description

Itio etchant composition

The present invention relates to an ITO (Indium Tin Oxide (In ₂ O ₃ -SnO ₂ ; hereinafter referred to as "ITO") etching composition. More specifically, the present invention is laminated on various electronic component substrates are used as a transparent electrode The present invention relates to an etching composition capable of effectively etching ITO which is an oxide of indium and tin.

ITO is an oxide of indium and tin in which In ₂ O ₃ and SnO ₂ are mixed at an appropriate ratio. Generally, ITO is laminated on a glass substrate by sputtering or the like, coated on the photoresist, and patterned through exposure and development. After forming, the ITO is etched to form a transparent electrode.

ITO film has excellent chemical resistance and is difficult to be etched by chemical reactions. Conventional etching solutions include aqua regia (HCl + HNO ₃ + H ₂ O), ferric chloride (FeCl ₃ + HCl) and HBr or HI 3 I am using kind.

In the case of aqua regia, the etching solution is inexpensive, but the amount of side etching on the pattern sidewall is large, and hydrochloric acid and nitric acid are volatilized after forming the etching solution. In the case of ferric chloride-based, too, hydrochloric acid is the main etching solution, as in aqua regia, and the variation of the components is the same as that of aqua regia. HBr or HI system has a large etching rate and low side etching amount, but the price is high and the toxicity and corrosiveness is high, so the application to the mass production line is limited.

In addition, in the case of conventional ITO etchant, all of them have a strong chemical activity, so that during the wet etching of ITO, other parts such as Al, Mo, and alloy films of which are less resistant to chemicals are eroded, and an electronic component that requires the use of multiple multilayer films (eg ; TFT-LCD) has many limitations in the selection of the material forming the other film. In other words, a high selectivity with a large difference in etching rate for each material is required. Conventional etching liquids interfere with Al films, Mo films, or alloy films thereof that adjoin or support the ITO film at the time of etching.

Furthermore, the conventional etchant has a fume property, which not only causes a problem of the air environment due to the fume, but also causes an increase of equipment cost and a safety operation problem, and the composition composition of the composition solution is so severe that the etching reproducibility is caused. Difficult to get. In addition, when the temperature of the etching solution is increased, the generation of fume and the compositional variation of the composition solution are intensified. Therefore, in order to ensure reproducibility, the composition of the fumeable etching solution must be frequently replaced or replenished with the fresh solution, thereby increasing the wastewater treatment amount.

Accordingly, an object of the present invention is to improve the selectivity with other films and the reproductivity of the etching process and minimize the generation of fumes when etching ITO stacked on an electronic component substrate or the like, It is to provide a stable etching solution with low toxicity and corrosion.

In order to achieve the above object of the present invention, the present invention provides a composition for etching ITO consisting of an aqueous solution comprising a range of oxalic acid and its salt from 1.5 g per liter of water to the saturation concentration at the temperature of use of the aqueous solution.

The above object of the present invention may be achieved by an ITO etching composition composed of an aqueous solution containing aluminum chloride ranging from 5.5% by weight to the saturated concentration at its use temperature.

The aqueous solution of oxalic acid and salts thereof and the aqueous aluminum chloride solution may further include persulfate.

If necessary, the aqueous solution of oxalic acid and salts thereof and the aqueous aluminum chloride solution may further include 0.01 to 2% by weight of a surfactant.

According to the present invention, it is possible to minimize the stability of the etching solution and the generation of fumes (fume) to improve the air environment problems, and to minimize the side etching to implement a fine pattern.

Hereinafter, the present invention will be described in detail.

The first composition of the present invention contains, as a main component, an aqueous solution containing oxalic acid or a salt thereof.

Oxalic acid and its salts are powerful reducing agents, and the aqueous solution of this oxalic acid is very stable so that the cell has little change in composition when stored in a cold dark for at least one year.

Oxalic acid and its salts are generally used as members for reducing oxides by using reducing properties.

The oxalic acid aqueous solution decomposes when irradiated with light, raises the temperature, or is mixed with other substances to generate a reducing substance and to reduce metal oxides. The reaction at this time is as follows.

H ₂ C ₂ O ₄ = HCOOH + 2CO ₂ + CO + H ₂ O (1)

H ₂ C ₂ O ₄ = CO ₂ + CO + H ₂ O (2)

The generated reducing material CO reacts with ITO as shown in the following reaction formula to etch the ITO film.

In ₂ O ₃ + 3CO = 2In + 3CO ₂ (3)

SnO ₂ + 2CO = Sn + 2CO ₂ (4)

If the oxalic acid is less than 1.5 g per liter of water, the etching rate of ITO is slow and not preferable. If the oxalic acid exceeds the saturation concentration, the oxalic acid crystal is precipitated, which is not preferable. Thus, the concentration of oxalic acid is from 1.5 g to saturated concentration, preferably from 2 to 350 g, per liter of water.

Generally, oxalic acid is preferably used as an etching solution because of its strong reducing power, but since oxalate is also decomposed into oxalic acid in an aqueous solution, it can be used as an etching solution in an aqueous state. As such oxalate, it is preferable to use a nonmetal oxalate such as ammonium oxalate.

Persulfate acts as a homogeneous oxidant as an aqueous solution, and the reaction in aqueous solution is expressed as follows.

S ₂ O ₈ ^2- + 2e- = 2SO ₄ ² -E = 2.01v (5)

S ₂ O ₈ ^2- + 2H ₂ O = 2SO ₄ ^2- + O ₂ + 4H ⁺ (6)

In addition, when the temperature of the aqueous solution rises, the following reaction occurs in part.

S ₂ O ₈ ^2- + 4H ₂ O = 2SO ₄ ^2- + H ₂ O ₂ + 2H ⁺ (7)

ITO is a complex oxide, and oxalic acid and its salts play a major role in reducing the film quality by reducing it, and by adding persulfate, it plays a role of reducing by generating hydrogen ions as shown in Equation (7). It is considered to improve the reducing action. That is, due to the nature of the film to be removed by reduction, the reaction of redox is complex in the system and the reacting materials react with each other organically to determine that etching is performed.

Persulfate is not preferred if less than 1g per liter of water is not enough reducing action, if it exceeds 250g it is not preferred because there is no further reducing effect. Therefore, the amount of persulfate used is 1 to 250 g, preferably 5 to 150 g per liter of aqueous solution.

Examples of the persulfate that can be used in the present invention include ammonium persulfate, sodium persulfate and potassium persulfate, and it is particularly preferable to use ammonium persulfate.

The ITO etching solution composition according to the present invention may further include a surfactant. The surfactant increases the penetration force of the etching liquid by lowering the surface tension of the etching liquid, thereby facilitating the penetration of the etching liquid between the photoresist of the fine pattern. In addition, the surfactants allow the reactant material to be easily released from the substrate and also serve to shorten the etching time by increasing the wettability of the substrate surface to be treated.

If the amount of the surfactant is less than 0.1 g per liter of water, the effect of lowering the surface tension is small, which is not preferable. If the amount of the surfactant is more than 20 g, the surfactant activity is not increased, and there is a concern that it may interfere with the reducing effect. Accordingly, the amount of the surfactant used is 0.1 to 20 g, preferably 0.5 to 5 g, per liter of the aqueous solution.

As a surfactant which can be used by this invention, the salt of alkyl sulfonic acids like sodium dihexyl sulfonate is mentioned.

The ITO etching solution mainly containing the aqueous solution of oxalic acid and salts thereof does not contain any halogen compounds, which is advantageous in terms of environment.

According to another aspect of the present invention, there is provided a composition for etching ITO having aluminum chloride and a surfactant, which are chlorides of nonferrous metals, as a main component.

The reaction scheme of the aqueous solution of AlCl ₃ and In ₂ O ₃ and SnO ₂ is as follows.

In ₂ O ₃ + AlCl ₃ = In ₂ Cl ₃ + 1/2 Al ₂ O ₃ + 3/2 O ₂ (1)

SnO ₂ + AlCl ₃ = SnCl ₂ + 1/2 Al ₂ O ₃ + 1/2 O ₂ (2)

According to the experiments of the present inventors, it was found that the above-described etching of the ITO film was not sufficient with aluminum chloride alone, and it could be applied to the ITO etching process when a surfactant or a reducing agent was added as an auxiliary agent.

If the amount of the aluminum chloride used is less than 80 g per liter of water, the etching rate of ITO is slow, which is not preferable. If the concentration of the aluminum chloride is exceeded, aluminum chloride crystals are precipitated, which is not preferable. Therefore, the amount of aluminum chloride used is 80 to saturation concentration, preferably 100 g to 350 g, per liter of water.

It is preferable that the ITO etching liquid composition which has aqueous aluminum chloride as a main component contains surfactant as a main component. At this time, the usage-amount of surfactant is 0.1-20g, Preferably, it is 0.5-5g per liter of aqueous solution.

At this time, the addition of persulfate can improve the etching rate. The amount of persulfate used is 1 to 250 g, preferably 5 to 150 g per liter of aqueous solution. Persulfates are the same as described above.

According to another aspect of the present invention, there is provided an ITO etching liquid composition composed of aluminum chloride and an organic acid capable of acting as a reducing agent.

The aluminum chloride is as described above. Examples of the organic acid as a reducing agent that can be used in the present invention include oxalic acid, L-ascorbic acid, and the like.

Generally, the film quality used for TFT-LCD (Thin Film Transistor-Liquid crystal Display) is composed of Al and Mo or their alloys, a-Si, poly-Si, SiNx, SiO ₂ , Cr, ITO film. Therefore, in the case of Al and Mo or their alloys as the lower gate wiring or the source and drain wiring during the etching of ITO, there is a fear that the wiring will be short.

Conventionally known etching compositions contain chlorine ions, fluorine ions, cyan ions, etc., which are mostly halogen elements, thereby invading metal wiring. To overcome this, in some cases, a thick metal film is formed.

As in the present invention, when an aqueous solution of oxalic acid and its salt is used as the ITO etching solution, Al, Mo, or alloys thereof, which are components of adjacent or supporting films, are hardly impaired.

Aluminum chloride used in the present invention is in the form of a non-natural salt such as hydrochloric acid, so that it is dissolved in water and used in the form of an aqueous solution, so there is little generation of fume.

In order to promote the etching reaction of the etching solution according to the present invention, it is preferable to perform an etching process by increasing the etching temperature at the time of etching. The etching temperature is from room temperature to the boiling temperature of the etching liquid, preferably from 35 ° C to 85 ° C.

The etching solution according to the present invention may be performed by a method such as an immersion method, a spray method, a water flow method, an ultrasonic method, etc. to perform an etching process. Not only these methods but also other methods can be used to etch the ITO film using the etching solution according to the present invention.

The composition according to the present invention is based on the use in the form of an aqueous solution, the medium can be stored and transported in the form of a powder separately, dissolved and used immediately before use. In addition, if necessary during use, a medium may be further added to extend the life of the prescription liquid.

Example

Although the present invention will be described in detail with reference to the following examples, these examples do not limit the scope of the present invention.

In the specimens used in the following Examples and Comparative Examples, a specimen in which an ITO film was laminated at a thickness of 500 mm by sputtering on a bare glass for 0.7 mm thickness LCD was used. In the following examples, commercially available ammonium oxalate monohydrate was used as ammonium oxalate, and commercially available aluminum chloride hexahydrate was used as aluminum chloride.

Examples 1-7

An aqueous solution in which oxalic acid was dissolved was prepared at a concentration as shown in Table 1 below.

Etch Rate Measurement

A 0.7 mm thick bare glass substrate was prepared with a 500 μm thick ITO film. Using the aqueous solution of Examples 1-7, the specimens were deposited at temperatures of 60 ° C. and 80 ° C. to measure the time taken until the ITO membrane was completely etched.

The measurement results are shown in Table 1 below.

As can be seen from Table 1, the higher the concentration of oxalic acid and the higher the temperature, the higher the etching rate and the faster the etching treatment rate of the ITO film.

When the aqueous solution of Example 5 was selected and the temperature was raised to 100 ° C. and the treatment time thereof was measured, the etching treatment time of the ITO film was 1 minute.

Examples 8-16

An etching composition was prepared by adding L-ascorbic acid to the aqueous solution of Example 4 (oxalic acid aqueous solution having a concentration of 150 g / l) as shown in Table 2 below.

Etch Rate Measurement

As described above, a specimen in which an ITO film was laminated on a 0.7 mm thick LCD glass panel was prepared. Using the aqueous solution of Examples 8-16, the specimens were deposited at temperatures of 60 ° C. and 80 ° C. to measure the time taken until the ITO membrane was completely etched. The measurement results are shown in Table 2 below.

As can be seen in Table 2, the etching rate of Example 5, which is an aqueous solution of 150 g / l content of oxalic acid alone, was 15 and 8.5 minutes at 60 ° C. and 80 ° C., but the etching rate was increased by adding L-ascorbic acid as a reducing agent. Significantly improved.

Examples 17-22

As shown in Table 3 below, oxalic acid and ammonium persulfate were mixed at a weight ratio of 1: 1, and then dissolved in an aqueous solution to prepare an etching solution.

Etch Rate Measurement

As described above, a specimen in which an ITO film was laminated on a 0.7 mm thick LCD glass panel was prepared. Using the aqueous solution of Examples 17-22, the specimens were deposited at a temperature of 60 ° C. and the time taken until the ITO membrane was completely etched was measured. The measurement results are shown in Table 3 below.

As can be seen in Table 3, the ammonium persulfate does not directly participate in the reaction, but it can be seen that the etching rate of the etching solution is improved until the content of oxalic acid is 100 g / l.

Examples 23-27

As shown in Table 4, oxalic acid and 35% -H ₂ O ₂ were mixed at a weight ratio of 1: 1, and then dissolved in an aqueous solution to prepare an etching solution.

Etch Rate Measurement

As described above, a specimen in which an ITO film was laminated on a 0.7 mm thick LCD glass panel was prepared. Using the aqueous solution of Examples 23-27, the specimen was deposited at a temperature of 60 ° C to measure the time taken until the ITO membrane was completely etched. The measurement results are shown in Table 4 below.

* Note 1) Not applicable to etching process

As can be seen in Table 4, when H ₂ O ₂ is added to oxalic acid, the etching rate is inhibited at low concentrations, but the etching rate of the etching solution is improved when the content of oxalic acid is 150 g / l or more. Compared with the use of persulfate as in Example 17-22 above, it can be seen that it is not suitable as an ITO etching solution at low concentrations, but can be used as an ITO etching solution at high concentrations.

Examples 28-31

An aqueous solution in which ammonium oxalate was dissolved was prepared at a concentration as shown in Table 5 below.

Etch Rate Measurement

As described above, a specimen in which an ITO film was laminated on a 0.7 mm thick LCD glass panel was prepared. The specimens were deposited at temperatures of 60 ° C., 80 ° C. and 100 ° C. using the aqueous solutions of Examples 28-31 to measure the time taken until the ITO membrane was completely etched. The measurement results are shown in Table 5 below.

* 1) Not applicable to etching process

From the table, it can be seen that the aqueous ammonium oxalic acid solution can be used as an ITO etchant at a temperature of about 70 ° C., while the etching effect is inferior.

Examples 32-34

An aqueous solution in which aluminum chloride and L-ascorbic acid were dissolved at a concentration as shown in Table 6 was prepared.

Etch Rate Measurement

As described above, a specimen in which an ITO film was laminated on a 0.7 mm thick LCD glass panel was prepared. Using the aqueous solution of Examples 32-34, the specimen was deposited at a temperature of 80 ° C. and the time taken until the ITO membrane was completely etched was measured. The measurement results are shown in Table 6 below.

Examples 35-36

An aqueous solution in which aluminum chloride and oxalic acid were dissolved at a concentration as shown in Table 7 was prepared.

Etch Rate Measurement

As described above, a specimen in which an ITO film was laminated on a 0.7 mm thick LCD glass panel was prepared. Using the aqueous solution of Examples 35-36, the specimens were deposited at a temperature of 80 ° C. and the time taken until the ITO membrane was completely etched was measured. The measurement results are shown in Table 7 below.

Comparative Example 1-6

An aqueous solution in which aluminum chloride was dissolved was prepared at a concentration as shown in Table 8 below.

Etch Rate Measurement

As described above, a specimen in which an ITO film was laminated on a 0.7 mm thick LCD glass panel was prepared. Using the aqueous solution of Comparative Example 1-6, the specimen was deposited at temperatures of 60 ° C., 80 ° C. and 100 ° C. to measure the time taken until the ITO membrane was completely etched. The measurement results are shown in Table 8 below.

As can be seen in Table 8, in the case of the etching solution using aluminum chloride alone, the etching rate is fast at a relatively high temperature and high concentration, but when the temperature and concentration are low, the etching rate is too slow, so that It was found to be unsuitable.

However, as shown in Table 7, in Comparative Example 4 of the aqueous solution of aluminum chloride alone of 150g / l content, the etching rate was 25 minutes at 80 ℃, it was found that the etching rate is significantly improved by adding L-ascorbic acid as a reducing agent Could.

Therefore, when adding a reducing agent, it turns out that an etching rate improves even in comparatively low temperature, and it can be used suitably as an ITO etching liquid.

Etch rate measurement at processing temperatures below 60 ° C

As described above, a specimen in which an ITO film was laminated on a 0.7 mm thick LCD glass panel was prepared. Using the aqueous solutions of Example 4 and Comparative Example 6, the specimens were deposited at temperatures of 55 ° C., 45 ° C. and 40 ° C. to measure the time taken until the ITO membrane was completely etched. The measurement results are shown in Table 8 below.

As can be seen from Table 9, the oxalic acid aqueous solution and the aluminum chloride aqueous solution have a significantly slower etching rate as the temperature is lower. In particular, an aqueous solution in which only aluminum chloride is dissolved alone is too slow to be suitable as an ITO etching solution. And it was found.

Saturated Dissolution of Oxalic Acid and Ammonium Oxalate at Constant Temperature and Etching Rate of Its Solution

Examples 38-39

Oxalic acid and ammonium oxalate were dissolved in an amount up to a saturation concentration at 80 ° C. as shown in Table 9 below to prepare an ITO etching solution.

Etch Rate Measurement

As described above, a specimen in which an ITO film was laminated on a 0.7 mm thick LCD glass panel was prepared. Using the aqueous solutions of Examples 35 and 36, the specimens were deposited at a temperature of 80 ° C. and the time taken until the ITO membrane was completely etched was measured. The measurement results are shown in Table 10 below.

It can be seen from Table 9 that oxalic acid and ammonium oxalate exhibit excellent etching rates even when they are saturated solutions and can be used as ITO etchant.

Comparative Example 7

A conventional aqua regia ITO etchant was prepared by mixing 35% -HCl: 65% -HNO3: deionized water (D.I.W) in a volume ratio of 53: 7: 40.

Comparative Example 8

FeCl 3: 35% -HCl: 65% -HNO 3: Deionized water (D.I.W) was mixed in a weight ratio of 20: 50: 2: 28 to prepare a conventional ferric chloride ITO etching solution.

Examples 40 and 41

0.1 wt% of sodium dihexyl sulfosuccinate as a surfactant was added to the aqueous solutions of Example 30 and Comparative Example 5 to prepare an ITO etching solution.

Measurement of line width reduction in etching solution

In order to measure the line width reduction amount of the etching solution, 500 Å of ITO film was laminated on a 0.7 mm thick bare glass. A specimen was prepared by forming a photoresist pattern having a line width of 5 μm on the ITO film. The prepared specimens were deposited using the ITO etchant of Comparative Examples 7 and 8, and Examples 3, 19, 40, and 41 described above under the temperature and time conditions as shown in Table 10 to etch the ITO film. In order to measure the line width of these specimens, photoresist was removed with acetone and the line width of ITO was measured.

The etching liquids of Comparative Examples 7 and 8, which are conventional etching liquids, were treated at 40 ° C., which is a general treatment temperature applied in a mass production line, due to the fact that fumes are generated at room temperature and the composition of the liquid changes.

The etching liquids according to Examples 3, 19, 40, and 41 were treated at a temperature of 60 ° C. or higher in consideration of the etching rate since the fume generation and the liquid composition fluctuation were not severe even when the treatment temperature was 60 ° C. or higher.

The line width and etching treatment time of the formed ITO pattern were measured, and the results are shown in Table 11 below.

As can be seen from the above table, the line width of the conventional etching solution ranged from 4.72 to 4.76 µm and 4.76 to 4.80 µm in the etching solution according to the present invention.

In consideration of the industrial application of large-area LCD manufacturing, the etching was performed for an additional 2 minutes after the etching was completed, and the line width thereof was measured. As a result, the conventional etching solution ranges from 4.20 to 4.26 μm and the etching solution according to the present invention. Was 4.68 to 4.74 mu m, which was much better than the conventional etching solution.

The etching time is generally faster than that of the conventional etching solution according to the present invention. However, the conventional etching solution has a disadvantage in that a spray method must be employed for uniformity of substrate etching. However, the etching solution according to the present invention can be processed at once by putting several to several dozen panels in a cassette, so the treatment time of the etching solution is not an important problem. It can be seen that the etching solution according to the present invention is better in this respect because the most important purpose of the etching process is to minimize the circuit line width and profile the circuit pattern after etching.

In addition, by selecting and using an appropriate photoresist in consideration of the etching rate, it is possible to appropriately adjust the treatment concentration and the treatment temperature.

Furthermore, in the treatment of a large-area substrate, the time for contacting the etchant may not be the same as the entire substrate, and thus the etching time needs to be extended to completely etch the portions other than the pattern covered with the photoresist over the entire surface. . In consideration of this, as a result of increasing the etching time by 2 minutes, the reduction rate of the line width was very large in the conventional etching solution as shown in the above table. Thus, the conventional etching solution was found to be difficult to implement a fine line width.

Selectivity comparison test of etching solution

Different film quality by etching solution in Comparative Examples 7-8, Examples 3, 19, 40, and 41 (Al-Nb lamination thickness 2500Å, Mo-W; lamination thickness 5000Å, Cr; 1500Å, a-Si; 1500Å, SiNx 3000 dl) was prepared and immersed in each etching solution for a certain time at a constant temperature. The etching amount was checked for each specimen to compare selectivity. The results are shown in Table 12 below.

As can be seen from the table above, in the case of aqua regia, which is a conventional etching solution, it can be seen that the Al-Nb and Mo-W are violated severely during the etching of ITO 500Å, and the etching solution according to the present invention does not invade Mo-W at all. Was confirmed.

In the etching solution of the present invention, the etching rate of Al-Nb was etched from 11% to 33%, thereby confirming a high selectivity.

In order to further increase the selectivity between the ITO film and Al-Nb, the two films were etched for 25 minutes at 45 ° C. in the etching solution of Example 4, whereby the ITO film was etched 100% and the Al-Nb film was etched 2%.

Comparative test of composition variation of etching solution

The etchant in Comparative Examples 7-8, Examples 3, 19, and 41, which are conventional aqua regia-based and ferric chloride-based etchant, and the etchant according to the present invention, were used. Each mL is charged in a beaker and the aqua regia and ferric chloride are measured at 40 ° C. in the operating conditions of the mass production line, and the prescription solution of the present invention is left at 60 ° C., which is a preferable treatment temperature, for measuring a time at which the ITO membrane is etched. It was. The results are shown in Table 13 below.

As can be seen from the above table, in the case of aqua regia and ferric chloride, which are conventional ITO etching solutions, the composition contains a large amount of hydrochloric acid, which plays a major role in etching of ITO, so that it is released into the atmosphere in the state of a fume, As the composition is changed, the time taken for etching is significantly different between the treatment of the composition liquid immediately and the etching time between the liquid which is left for a certain time. Etching liquid according to the present invention was confirmed that the composition of the liquid has little variation in the composition having a non-volatile characteristics. The smaller the variation of the composition of the etchant, the more reproducibility is secured, which is an important characteristic required for device manufacturing.

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Claims (15)

An composition for etching ITO comprising oxalic acid and its salt in an aqueous solution comprising a range from 1.5 g per liter of aqueous solution to a saturation concentration at the use temperature of the aqueous solution. The composition for etching ITO according to claim 1, wherein the oxalate is ammonium oxalate. The composition for etching ITO according to claim 1, further comprising 1 to 250 g of persulfate per liter of aqueous solution. The composition for etching ITO according to claim 3, wherein ammonium persulfate is used as the persulfate. The composition for etching ITO according to claim 1, further comprising 0.1 to 20 g of surfactant per liter of aqueous solution. The composition for etching ITO according to claim 5, wherein the surfactant is sodium dihexyl sulfosuccinate. The composition for etching ITO according to claim 1, further comprising an amount of the nonferrous metal chloride up to 50 g to a saturated concentration per liter of the aqueous solution. An aqueous solution containing a range from 0.1 wt% of oxalic acid to a saturation concentration at the use temperature of the aqueous solution; And ITO etching composition comprising 1 to 250 g / l persulfate dissolved in the aqueous solution. The composition for etching ITO according to claim 8, wherein ammonium persulfate is used as the persulfate. An aqueous solution containing a range from 0.1 wt% of oxalic acid to a saturation concentration at the use temperature of the aqueous solution; And ITO etching composition comprising 0.1 to 20g / l surfactant. The composition for etching ITO according to claim 10, wherein the surfactant is sodium dihexyl sulfosuccinate. An aqueous solution containing aluminum chloride ranging from 5.5% by weight to saturated concentration at its use temperature; And An ITO etching composition comprising 0.1 to 20 g of a surfactant dissolved in 1 liter of the aqueous solution. The composition for etching ITO according to claim 12, further comprising 1 to 250 g of persulfate per liter of aqueous solution. An aqueous solution containing aluminum chloride ranging from 5.5% by weight to saturated concentration at its use temperature; And A composition for etching ITO composed of 0.5 to 100 g of a reducing agent dissolved in 1 liter of the aqueous solution. The composition for etching ITO according to claim 14, wherein the reducing agent is L-ascorbic acid or oxalic acid.