KR20040005456A - Etchant composition for amorphous ito - Google Patents

Abstract

PURPOSE: A composition of amorphous ITO etch solution is provided to reduce the environmental pollution due to harmful materials by controlling the etch speed using the variation of temperature and the amount of addition. CONSTITUTION: A composition of amorphous ITO etch solution includes an oxalic acid of 0.5 to 8 weight percent, an inorganic acid of 0.1 to 5 weight percent, an oxidation addition of 0.1 to 5 weight percent, a surface active agent of 1 to 1000ppm, and water of the remaining weight percent of 100 weight percent. The inorganic acid is formed by combining hydrogen with acid radical including nonmetal such as chlorine, sulfur, nitrogen, and phosphorus. The inorganic acid is selected from a group including hydrochloric acid, sulfuric acid, nitric acid, and phosphoric acid.

Description

Amorphous ITO etchant composition ETCHANT COMPOSITION FOR AMORPHOUS ITO

The present invention relates to a novel etchant composition used for wet etching a metal film in a semiconductor device, and more particularly to an etchant composition for etching an amorphous indium-tin-oxide (ITO) film constituting a pixel electrode of a liquid crystal display device. It is about.

The ITO film constituting the pixel electrode of the liquid crystal display device is widely used because it has excellent conductivity, good chemical thermal stability, and good pattern processability. ITO is electrically insulating in the visible region, but free electrons are generated in the visible region when it is shifted from the stoichiometric composition due to lack of oxygen or determined by the introduction of impurities (tin ions). In general, after 300 ~ 500 ℃ heat treatment, the resistance of ITO (1.7 ~ 2.0 X 10-4 Ωcm) is increased 2.5 ~ 3 times. However, the thermal stability is slightly inferior, but as the film thickness increases, the rate of increase after the heat treatment of the resistance tends to decrease. Evaporation film has the advantage that the etching rate by the acid is fast, the fine pattern processing is relatively easy in the ITO film.

The process of forming the metal wiring on the substrate in the semiconductor device is generally composed of a metal film forming process by sputtering, a photoresist forming process in a selective region by photoresist coating, exposure and development, and an etching process. And washing processes before and after individual unit processes. The etching process refers to a process of leaving a metal film in a selective region using a photoresist mask, and typically, a dry etching using a plasma or the like, or a wet etching using an etching solution is used.

In such a semiconductor device, an ITO film constituting a pixel electrode of a liquid crystal display device of a thin film transistor-liquid crystal display (TFT-LCD) can be divided into crystalline and amorphous ITO films in the order of annealing. In the case of the crystalline ITO membrane which was annealed first, an etchant such as ferric chloride or aqua regia was used. Since ferric chloride and aqua regia are used at high temperatures, the amount of evaporation of the etchant is high, and thus harmful substances contained in the etchant contaminate the working environment. Korean Patent No. 2000-65954, which improves these disadvantages and improves the etching process, deposits an ITO film in an amorphous state in which it is not annealed, and then forms a pattern of the ITO film with an oxalic acid etchant. After etching, the ITO film is annealed to undergo a crystallization step. In addition, Korean Patent Publication No. 2000-17470 discloses the addition of a salt to oxalic acid as an additive to improve the performance of the etchant, such as minimizing the stability of the etchant and the evaporation of the etchant.

Oxalic acid etchant does not damage the lower layer of Cr, Al, Mo, etc., and it can maintain the etching speed about twice as fast as that of 80 ℃ even without heating the temperature of the etchant. Hazardous substances from evaporation could reduce the contamination of the work environment.

However, while the etching rate is determined only by the temperature, when an etchant prepared only with oxalic acid is used for ITO etching, residues tend to occur around the pattern.

Accordingly, the present inventors have intensively studied to solve such problems, and have developed an etching solution in which a small amount of an inorganic acid and an oxidizing aid are added to the conventional oxalic acid etching solution. Inorganic acid is used in addition to the existing crystalline ITO etchant, but because the harmful substances due to equipment corrosion and evaporation of the etchant contaminates the working environment, an etchant prepared only with oxalic acid was used. However, a small amount was added in order to obtain a stable etching rate, which is an advantage of the inorganic acid system, and an oxidizing aid was added to solve the problem of residue that is likely to occur in etching using only oxalic acid by increasing the oxidation power of the etching solution.

The developed amorphous ITO membrane etchant can be controlled not only by the etching rate but also by the amount of inorganic acid, compared to the conventional etching solution. Therefore, the harmful substances by the etching liquid evaporation reduce the contamination of the working environment. In addition, it is possible to solve the problem of the pattern portion residues that are likely to occur in the etching liquid containing oxalic acid as a main component.

Figure 1 shows (a) a scanning electron micrograph of the unetched surface, (b) a scanning electron micrograph of the etched surface.

Figure 2 shows a scanning electron micrograph of the surface after the etching process by the etching solution prepared in (a), Comparative Example 1, (b) shows a scanning electron micrograph of the surface after the etching process by the etchant prepared in Example 1 will be.

FIG. 3 shows a scanning electron micrograph of the pattern part residue of (a) Comparative Example 1, and (b) the scanning electron microscope picture of the pattern part residue of Example 1;

As a means for realizing the present invention, there is provided an amorphous ITO membrane etchant composition containing oxalic acid, an inorganic acid, an oxidizing aid, a surfactant, and water.

More specifically, 0.5 to 8% by weight of oxalic acid relative to the total weight of the total composition; 0.1-5% by weight of inorganic acid; 0.1 to 5% by weight of an oxidizing aid; An amorphous ITO membrane etchant composition is provided comprising 1 to 1000 ppm of surfactant and water such that the total weight of the composition is 100% by weight.

Hereinafter, the present invention will be described in more detail.

The etchant composition according to the present invention is an etchant for etching an amorphous ITO membrane.

Oxalic acid used in the amorphous ITO membrane etchant composition of the present invention utilizes a dihydrate form having a purity of at least 99.5%.

The inorganic acid used in the amorphous ITO membrane etching liquid composition of the present invention is an acid produced by the combination of an acid group containing a nonmetal such as chlorine, sulfur, nitrogen, or phosphorus with hydrogen, such as hydrochloric acid, sulfuric acid, nitric acid or phosphoric acid.

Oxidation aids used in the amorphous ITO membrane etchant composition of the present invention are various salts containing active oxygen, such as oxone (potassium monopersulfate), K ₂ S ₂ O ₈ , Na ₂ S ₂ O ₈ , (NH ₄ ) ₂ S ₂ O ₈ and H ₂ O ₂ .

Surfactants used in the amorphous ITO membrane etching liquid composition of the present invention are ionized in an aqueous solution, and the main agent of the active agent is ammonium fluoroalkyl sulfonate as an anion.

The amorphous ITO membrane etchant composition of the present invention is diluted with water so that the total weight of this composition is 100% by weight.

Most of the amorphous ITO membrane etchant composition of the present invention is composed of water, and the oxalic acid, inorganic acid, oxidizing aid, and surfactant are essentially contained, and additionally, additives such as metal ion disintegrants, corrosion inhibitors, and pH adjusting agents are necessary. can do.

The amorphous ITO membrane etchant composition of the present invention contains oxalic acid, inorganic acid, oxidizing aid, surfactant, and water, or the composition ratio of oxalic acid / inorganic acid / oxidizing aid / surfactant except water is 0.5 to 8 wt% / 0.1 to 5 wt% When% / 0.1 to 5% by weight / 1 to 1000 ppm, the etching rate of the amorphous ITO membrane can be controlled by changing the content at a constant temperature (Table 1), and the evaporation amount of the etchant is reduced because it is used at a lower temperature. . Therefore, it is possible to prevent the harmful substances due to the evaporation of the etchant contaminate the working environment. In addition, the pattern part residue that appeared in the existing oxalic acid etchant or oxalic acid / inorganic acid etchant did not appear due to the addition of the oxidizing aid.

In Table 1 of Examples of the present invention, Comparative Example 1 is a case where the ITO membrane is etched using only oxalic acid as disclosed in the above-described Korean Patent No. 2000-65954. Examples 1 to 6 show the results of experiment by adding an inorganic acid and an oxidizing aid to oxalic acid. As shown in Table 1, various etching rates were shown depending on the amount of the additive. As the amount of inorganic acid increases, the etching rate of amorphous ITO film increases. However, when the inorganic acid exceeds 5% by weight, the device corrosion phenomenon should be considered rather than the increase of the etching rate. The addition of the oxidizing aid is to effectively solve the residue around the pattern. However, when the oxidizing aid is used in excess of 5% by weight, not only the residue is removed but also the etching of the micropattern causes a short circuit in the data line.

Hereinafter, although an Example is given and this invention is demonstrated in detail, this invention is not limited only to a following example.

EXAMPLE

Comparative Example 1

A test piece was prepared in which an amorphous ITO membrane substrate was cut to 100 mm × 100 mm using a diamond knife. An etching solution in which water was added to 3.4 wt% of oxalic acid [(COOH) ₂ .2H ₂ O)] based on the total weight of the composition was prepared to be 10 kg. After the etching solution prepared in the spray etching method (KDNS, model name: ETCHER (TFT)) was added to warm the temperature to 37 ℃, the etching process was performed when the temperature reaches 37 ± 0.5 ℃. After the test piece was inserted and sprayed to carry out the above etching process, and then washed with deionized water, dried with a hot air dryer, the photoresist was removed using a photoresist stripper. After washing and drying, the result was evaluated by using a scanning electron microscope (SEM; manufactured by Hitachi, model: S-4700) for the degree of formation of etching, loss of critical dimension (CD), and etching residue. The results are shown in Table 1, FIG. 2 and FIG.

Examples 1-6

Oxalic acid, an inorganic acid, an oxidizing aid, a surfactant, and the remaining water are all contained, and the same procedure as in Comparative Example 1 is carried out except that an etchant prepared in the composition ratios shown in Table 1 is prepared. The results are shown in Table 1. Since the content of each component corresponds to the composition range of the amorphous ITO film etching liquid composition according to the present invention, the etching speed is fast and no residue was generated.

Comparative Examples 2 and 3

The same procedure as in Comparative Example 1 was carried out except that the etching solution formulated at the composition ratios shown in Table 1 was prepared. The results are shown in Table 1. In the case of the etching solution prepared in Comparative Example 2 or Comparative Example 3, in which the inorganic acid or the oxidizing aid was not added, the effect was lowered than the amorphous ITO membrane etching solution prepared in Examples 1 to 6.

Composition (wt%) (oxalic acid / inorganic acid / oxidizing aid / 100 ppm surfactant) Etching Temperature (℃) Etching time (second) Comparative Example 1 3.4 / 0/0 35 120 Example 1 3.4 / 0.5 / 0.1 35 71 Example 2 3.4 / 1.0 / 0.1 35 60 Example 3 3.4 / 5.0 / 0.1 35 45 Example 4 3.4 / 0.5 / 1.0 35 67 Example 5 3.4 / 1.0 / 1.0 35 58 Example 6 3.4 / 5.0 / 1.0 35 44 Comparative Example 2 3.4 / 0.5 / 0 35 72 Comparative Example 3 3.4 / 0 / 1.0 35 115

According to the present invention, the amorphous ITO membrane etchant can control the etching rate not only as the temperature change but also as the amount of the additive, compared to the conventional etchant. The inorganic acid is used as the additive, but the etching solution is easy to use at low temperatures. The evaporation amount of the etchant was reduced. Therefore, it is possible to reduce the contamination of the working environment by the harmful substances by the etching liquid evaporation. In addition, the addition of an oxidizing aid can solve the problem of the pattern periphery residue in the existing oxalic acid type etching solution.

Claims (4)

0.5-8% by weight of oxalic acid; 0.1-5% by weight of inorganic acid; 0.1 to 5% by weight of an oxidizing aid; An amorphous ITO etchant composition comprising 1 to 1000 ppm of surfactant and water so that the total weight of the composition is 100% by weight. [Claim 2] The inorganic acid according to claim 1, wherein the inorganic acid is an acid produced by combining an acid group containing a nonmetal such as chlorine, sulfur, nitrogen, phosphorus with hydrogen, and is selected from the group consisting of hydrochloric acid, sulfuric acid, nitric acid and phosphoric acid. Composition. The method of claim 1, wherein the oxidizing aid is a salt containing active oxygen, oxone (potassium monopersulfate), K ₂ S ₂ O ₈ , Na ₂ S ₂ O ₈ , (NH ₄ ) ₂ S ₂ O ₈ and H ₂ A composition, characterized in that selected from the group consisting of O ₂ . The composition according to claim 1, wherein the surfactant is ionized in an aqueous solution so that the main agent of the active agent is an ammonium fluoroalkyl sulfonate-based surfactant as an anion.