KR100321227B1 - Etchant for electrode of TFT LCD - Google Patents

Abstract

The present invention provides Mo / Al (Al-Nd) / Mo triple layer, which is a metal wiring material for gate, source, and drain electrodes, which constitutes a TFT (Thin Film Transitor) of a liquid crystal display device. The present invention relates to an etching solution for obtaining a desired pattern by coating and exposing a photoresist.

The composition ratio of the etchant of the present invention is composed of phosphoric acid (50 ~ 80wt.%) + Nitric acid (0.5 ~ 10wt.%) + Acetic acid (2 ~ 15wt.%) + Oxidation regulator (0.1 ~ 10wt.%) The oxidation regulator is preferably HClO ₄ or HlO ₄ , and the composition ratio of the oxidation regulator is actually 1 to 6 wt.%, And the remaining portion of the etching liquid composition is composed of water (H ₂ O).

Description

Etching liquid for electrode of liquid crystal display device {Etchant for electrode of TFT LCD}

The present invention provides Mo / Al (Al-Nd) / Mo triple layer, which is a metal wiring material for gate, source, and drain electrodes, which constitutes a TFT (Thin Film Transitor) of a liquid crystal display device. The present invention relates to an etching solution for obtaining a desired pattern by coating and exposing a photoresist.

Conventionally, Mo / Al (Al-Nd) / Mo triple film is mixed with wet etching and dry etching using a regular Al monolayer etching solution consisting of phosphoric acid + nitric acid + acetic acid + water, or is disclosed in Korean Patent Publication No. 1999-0066167. As described above, a mixed pattern of chlorine (Cl ₂ ) + argon (Ar) + oxygen (O ₂ ) was dry-etched in a vacuum atmosphere to prepare a desired pattern.

In the case of dry etching, an etching process is performed in an expensive vacuum equipment, followed by an ashing process using an oxygen plasma to remove partially cured photoresist on the surface during the etching process, followed by removal of residual photoresist. Since the process steps are complicated such as stripping process and separate cleaning process, the wet etching partly mixed with the dry etching process after wet etching and dry etching only the part that does not have the desired pattern. In most cases, the process is applied.

In general, the Mo / Al (Al-Nd) / Mo triple layer, which is a metal interconnect for the gate, source, and drain electrodes of the TFT of the liquid crystal display, is etched with a conventional etchant including phosphoric acid, nitric acid, acetic acid, and water. 3 A pattern is manufactured in the same form, but as shown in FIG. 1, the Al (Al-Nd) layer, which is a middle layer of the triple layer, is often over-etched than the Mo layer, which is the upper and lower layers.

This phenomenon is caused by Al (E = -1.66V), which is a metal whose electrodepotential base is electrochemically when two metals are in contact with each other in an aqueous solution, to promote dissolution. Noble metal, Mo (E = -0.20V), is protected as a negative electrode and is interpreted as a galvanic corrosion phenomenon by a local cell (Local Cell or Galvanic Cell) which is relatively delayed in dissolution (electrochemical etching). do.

Due to such local erosion, if the patterns of the gate, source and drain electrodes are not uniformly formed, it becomes difficult to realize high resolution and vivid color of the image of the liquid crystal display.

The technical problem to be achieved by the present invention is to use Mo / of the gate, source and drain electrodes constituting the TFT of the liquid crystal display using an etchant added with an additional oxidation regulator to a conventional etchant consisting of a composition of phosphoric acid + nitric acid + acetic acid + water. An object of the present invention is to provide a method of collectively wet etching an Al (Al-Nd) / Mo triple layer in a uniform pattern.

FIG. 1 is a photograph showing observation of a triple layer cross section of Mo / Al (Al-Nd) / Mo, which is a port resist, a gate, a source, and a drain electrode material after a wet etching process using an existing etching solution. FIG.

FIG. 2 is a photograph showing observation of a triple layer cross section of Mo / Al (Al-Nd) / Mo, which is a pot resist, a gate, a source, and a drain electrode material, after a batch wet etching process using an etchant of the present invention; FIG.

FIG. 3 is a photograph showing observation of a triple layer cross section of Mo / Al (Al-Nd) / Mo, which is a pot resist, a gate, a source, and a drain electrode material after a batch wet etching process using an etchant of the present invention. FIG.

The present invention provides an additional oxidation modifier to the composition of phosphoric acid + nitric acid + acetic acid + water, which is a conventional etching solution used in a conventional etching process, to obtain a Mo / Al (Al-Nd) / Mo triple layer having a uniform profile. It is added so that a batch wet etching of Mo / Al (Al-Nd) / Mo triple layer is performed.

When the wet etching was performed by adding the oxidation regulator to the existing etching solution, taper etching with a uniform inclination angle of Mo / Al (Al-Nd) / Mo was obtained.

This phenomenon with respect to the reaction mechanism, such as the formula (1) occurring in the cathode portion of the local cell _{^{Al → Al 3 + + 3e -}} --------------- ( formula 1)

An additional oxidation regulator is added to form a passivation oxide film partially on the surface of the Al (Al-Nd) metal film, which is a cathode in which the reaction of Equation 1 generally proceeds, thereby reducing the etching rate. The role of the oxidizing regulator is called annodic corrosion inhibitor.

In order to suppress the phenomenon that dissolution (electrochemical etching) reaction is promoted in the anode where the electrode potential is relatively low due to local battery effect, the anode corrosion inhibitor is artificially added with various organic or inorganic compounds to change the active anode area. It serves to reduce the etching rate by reducing.

In the case of the present invention, since the oxidizing regulator was used, the added oxidizing regulator serves as an oxidizing inhibitor.

The quantitative measurement method when the oxidizing agent is added is expressed as a result of measuring the oxidation reduction potential for each etching liquid composition.

The oxidizing agent which can be added to the conventional etching solution may be H ₂ O ₂ , O ₂ , K ₂ Cr ₂ O ₇ , HClO, HClO ₂ , HClO ₃ , HlO _4, etc., but oxidizing agents of HClO ₄ and HlO ₄ are preferable.

In the case of adding HClO ₄ and HlO ₄ as an anode corrosion inhibitor to the conventional etching solution consisting of phosphoric acid + nitric acid + acetic acid + water, the results of measuring the redox potential as the main quantitative measurement indicators are shown in Tables 1 and 2.

Table 1. Redox potential when HClO ₄ is added

case HClO4 content (wt.%) Redox potential (V) One 0 1.03 2 One 1.05 3 2 1.06 4 3 1.07 5 4 1.07 6 5 1.07 7 6 1.08

Table 2. Redox potential when HlO ₄ is added

case HlO4 content (wt.%) Redox potential (V) One 0 1.03 2 One 1.2 3 2 1.3 4 3 1.4 5 4 1.4 6 5 1.5 7 6 1.5

Preferred etchant composition consists of phosphoric acid (50 to 80 wt.%), Nitric acid (0.5 to 10 wt.%), Acetic acid (2 to 15 wt.%) + HClO ₄ (1 to 6 wt.%) Or phosphoric acid (50 to 80 wt. %), Nitric acid (0.5 to 10 wt.%), Acetic acid (2 to 15 wt.%) + HlO 4 (1 to 6 wt.%), And the remainder of the composition of the etchant consists of water.

Example 1 Batch Etching of Mo / Al (Al-Nd) / Mo Triple Layer Using a Conventional Etching Solution

As a result of performing a wet etching process using a conventional etching solution consisting of phosphoric acid + nitric acid + acetic acid + water, the results of over-etching of the Al (Al-Nd) interlayer shown in FIG.

Example 2 Batch Etching of Mo / Al (Al-Nd) / Mo Triple Films When HClO _{4 Is} Added as Oxidation Inhibitor

HClO ₄ in a conventional etchant having a composition range of phosphoric acid (50 to 80 wt.%) + Nitric acid (0.5 to 10 wt.%) + Acetic acid (2 to 15 wt.%) + Water, as shown in Table 1 As a result of performing a batch wet etching process under the same conditions as in Example 1 with the addition of 7, as shown in FIG. 2, the Al (Al-Nd) interlayer was not overetched compared to the upper and lower Mo films. Etching results were observed.

Example 3 Batch Etching of Mo / Al (Al-Nd) / Mo Triple Films When HlO _{4 Is} Added as Oxidation Inhibitor

HlO ₄ in a conventional etchant having a composition range of phosphoric acid (50 to 80 wt.%) + Nitric acid (0.5 to 10 wt.%) + Acetic acid (2 to 15 wt.%) + Water, as shown in Table 2 As a result of performing a batch wet etching process under the same conditions as in Example 1 by adding a content of 7, as shown in FIG. 3, the Al (Al-Nd) interlayer was not overetched compared to the upper and lower Mo films. Etching results were observed.

Phosphoric acid (50 to 80 wt.%) + Nitric acid (0.5 to 10 wt) capable of collectively etching Mo / Al (Al-Nd) / Mo triple layer, which is a gate, source, and drain electrode of the TFT of the liquid crystal display according to the present invention. .%) Tapered etching is possible by using an etchant having a composition of acetic acid (2-15 wt.%) + HClO ₄ or HlO ₄ (1-6 wt.%) + Water. .

Claims (3)

In the etchant which wet-etches the Mo / Al (Al-Nd) / Mo triple layer which is the gate, the source, and the drain electrode which comprise the TFT of a liquid crystal display device collectively, An etchant for an electrode of a liquid crystal display device comprising phosphoric acid (50 to 80 wt.%) + Nitric acid (0.5 to 10 wt.%) + Acetic acid (2 to 15 wt.%) + HClO 4 (1 to 6 wt.%) + Water. In the etchant which wet-etches the Mo / Al (Al-Nd) / Mo triple layer which is the gate, the source, and the drain electrode which comprise the TFT of a liquid crystal display device collectively, An etchant for an electrode of a liquid crystal display device comprising phosphoric acid (50 to 80 wt.%) + Nitric acid (0.5 to 10 wt.%) + Acetic acid (2 to 15 wt.%) + HlO 4 (1 to 6 wt%) + water. The etchant for electrodes of a liquid crystal display device according to claim 1 or 2, wherein the redox potential of the etchant composition is represented by 0.5 to 1.6V.