KR100796483B1 - Method For Fabricating Liquid Crystal Display Device - Google Patents

Abstract

The present invention relates to a method for manufacturing a liquid crystal display device that prevents damage of the molybdenum wiring layer by ITO etchant by applying an aqueous solution of hydrochloric acid from which nitric acid has been removed. Forming a gate insulating film on the entire surface including the first wiring layer, forming a second wiring layer on the gate insulating film, forming a protective film on the entire surface including the second wiring layer, and forming a protective film on the protective film. Forming a pixel electrode by a photolithography process using a HCl aqueous solution of HCl etchant having a concentration of% to 24%, and forming a liquid crystal layer between the first substrate and the second substrate facing the first substrate. It features.

ITO etchant, molybdenum, disconnection defect

Description

Method for manufacturing liquid crystal display device {Method For Fabricating Liquid Crystal Display Device}

1 is a plan view of a general liquid crystal display device.

FIG. 2 is a cross-sectional view taken along the line AA ′ of FIG. 1; FIG.

3A to 3E are cross-sectional views illustrating a method of manufacturing a liquid crystal display device according to the present invention.

Figure 4 is a graph showing the ITO etching ratio according to the concentration and temperature of HCl etchant.

5 is a graph showing the change over time of the concentration of HCl etchant at 45 ℃.

* Explanation of symbols on the main parts of the drawings

110: first substrate 111: gate wiring

111a: gate electrode 111c: gate pad

112 gate insulating film 113 semiconductor layer

114: ohmic contact layer 115: data wiring

115a: source electrode 115b: drain electrode

115c: data pad 117: protective film

118a, 118b, 118c: first, second and third contact holes
119a: pixel electrode

119b: transparent conductive film for gate pad                 

119c: Transparent conductive film for data pad

120: photoresist

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device (LCD), and more particularly to a method for manufacturing a liquid crystal display device for preventing disconnection of a wiring layer made of molybdenum.

In general, the gate wiring and the data wiring of the liquid crystal display device are required to suppress signal delay and disconnection as a means for transmitting a scan signal and a data signal, respectively.

Therefore, the material used as the wiring layer is preferably a metal such as aluminum, aluminum alloy, molybdenum, copper, etc. having a low resistivity of 15 μΩcm or less. Among them, it is preferable to use an aluminum or aluminum alloy having a very low resistivity to prevent signal delay. It is common. Here, the aluminum alloy contains about 5% of transition metals such as chromium (Cr), tantalum (Ta), titanium (Ti), tungsten (W), and molybdenum (Mo) in aluminum (Al).

However, aluminum has a disadvantage in that its physical properties are weak and that the contact portion is oxidized by oxygen in the ITO upon contact with the ITO, resulting in an increase in the electrical resistance value.

Accordingly, molybdenum, which has a specific resistance of about 12 to 14 mu OMEGA cm, has no bad contact characteristics with ITO, and can be used as a single film wiring, has been used.                         

When molybdenum is used as a wiring, the etchant used for wet etching is an etchant used to etch aluminum or an aluminum alloy, for example, HNO3 / H3PO4 / CH3COOH / H2O, wherein HNO3 is 8-14%. It is preferable.

Hereinafter, a method of manufacturing a liquid crystal display device according to the prior art will be described with reference to the accompanying drawings.

1 is a plan view of a general liquid crystal display device, and FIG. 2 is a cross-sectional view illustrating a cutting line AA ′ of FIG. 1.

In general, a liquid crystal display device includes a color filter substrate on which a color filter layer for color expression is formed, a thin film transistor array substrate on which a thin film transistor and a pixel electrode are formed in each pixel in which a plurality of wirings are arranged in a matrix form. And the components of the liquid crystal layer formed between the two substrates opposed to each other.

The thin film transistor array substrate may be divided into an active region and a pad portion region. The pad portion region may include a gate pad and a data pad extending from gate lines and data lines of the active region and connected to a driving circuit. It divides the data input signal supplied from the signal according to its control signal and delivers it to each pixel.

Referring to FIGS. 1 and 2, a method of manufacturing a thin film transistor array substrate is described. First, a metal is deposited on a glass substrate 10 by sputtering, and then patterned to form a gate wiring 11, a gate electrode 11a, and a gate. A gate pattern made of the pad 11c is formed. As the metal, aluminum, aluminum alloy, chromium or molybdenum may be used.

Next, a silicon nitride, which is an inorganic material having good insulation voltage characteristics, is deposited on the entire surface including the gate pattern by PECVD to form a gate insulating film 12, and polycrystalline silicon (a) is formed on the gate insulating film 12 on the gate electrode 11a. -Si) and n + a-Si doped with impurities are sequentially deposited to form the semiconductor layer 13 and the ohmic contact layer 14.

Thereafter, molybdenum is deposited and patterned on the gate insulating layer 12 to form a data pattern including the data line 15, the source / drain electrodes 15a and 15b, and the data pad 15c. At this time, the ohmic contact layer 14 acts as an etch stop layer when patterning the source / drain electrodes 15a and 15b.

In the above description, the gate wiring 11 and the data wiring 15 cross each other to define a pixel, and the gate electrode 11a, the gate insulating layer 12, the semiconductor layer 13, the ohmic contact layer 14, and the source The laminated film of the / drain electrodes 15a and 15b forms a thin film transistor.

Subsequently, a protective film 17 is formed by applying BCB (Benzocyclobutene) having a low dielectric constant, an acrylic resin, or the like on the entire surface including the data pattern, and the drain electrode 15b, the gate pad 11c, and the data pad 15c. The gate insulating layer 12 or the protective layer 17 is removed to expose a predetermined portion to form contact holes 18a, 18b, and 18c.

After the deposition of ITO, which is a transparent conductive material, on the entire surface including the passivation layer 17, the pixel electrode 19a is connected to the drain electrode 15b through the contact holes 18a, 18b, and 18c by applying a photolithography process. ), A gate pad transparent conductive film 19b connected to the gate pad 11c, and a data pad transparent conductive film 19c connected to the data pad 15c.

In order to etch the ITO, an etchant containing hydrochloric acid (HCl) and nitric acid (HNO3) is wet-etched, wherein nitric acid in the etchant forms molybdenum through the path 20 by pinholes or cracks in the protective film. The gate pattern or data pattern is oxidized.

That is, the conventional manufacturing method of the liquid crystal display device as described above has the following problems.

In case of using ITO etchant mixed with nitric acid for patterning pixel electrode or transparent conductive film for pads, if there is a pinhole in the lower protective layer or foreign substance that can be an penetration route of etchant, The molybdenum wiring layer is oxidized.

Accordingly, disconnection defects occur in the wiring layer formed of molybdenum material, the electrode of the thin film transistor, and the pad metal layer, and the reliability of the device is lowered.

The present invention has been made to solve the above problems, and to provide a method for manufacturing a liquid crystal display device that prevents the damage of the molybdenum wiring layer by the ITO etchant by applying an aqueous solution of hydrochloric acid removed nitric acid as an ITO etchant. have.

A method of manufacturing a liquid crystal display device of the present invention for achieving the above object comprises the steps of forming a first wiring layer on a first substrate, forming a gate insulating film on the entire surface including the first wiring layer, the gate Forming a second wiring layer on the insulating film, forming a protective film on the entire surface including the second wiring layer, and using a photolithography process using an aqueous HCl solution, an HCl etchant having a concentration of 15% to 24% on the protective film. Forming a pixel electrode, and forming a liquid crystal layer between the first substrate and the second substrate facing the first substrate.

The present invention is characterized in that molybdenum is easily applied as a wiring material by providing an etchant that removes nitric acid, which causes molybdenum oxidation, in the conventional ITO etchant.

In particular, in order to prevent a sudden change in concentration of the etchant according to the temperature change, it is characterized by using a 20% HCl aqueous solution in which the mixture of HCl and H2O forms an azeotropic point as an etchant.

Hereinafter, a method of manufacturing a liquid crystal display device according to the present invention will be described in detail with reference to the accompanying drawings.

3A to 3E are cross-sectional views illustrating a method of manufacturing a liquid crystal display device according to an exemplary embodiment of the present invention. The following description relates to a thin film transistor array substrate for a liquid crystal display device.

First, as shown in FIG. 3A, molybdenum is deposited on the glass substrate 110 by sputtering, and then patterned to form a plurality of gate wires (not shown) in a row, and at the same time, a gate electrode that is a branch of the gate wires ( 111 and a gate pad (not shown) for connecting to an external driving circuit at the end of the gate wiring. In this case, in addition to the molybdenum, aluminum, aluminum alloy, copper, chromium, and the like may also be used.

Next, silicon nitride, which is an inorganic material having good insulation voltage characteristics, is deposited on the entire surface including the gate pattern by PECVD to form a gate insulating layer 112, and polycrystalline silicon is formed on the gate insulating layer 112 on the gate electrode 111a. (a-Si) and n + a-Si doped with impurities are sequentially deposited and patterned to form a semiconductor layer 113 and an ohmic contact layer 114 used as channels of the thin film transistor, respectively.

Next, as shown in FIG. 3B, a molybdenum metal film is deposited on the entire surface including the ohmic contact layer 114 by a sputtering method, and then patterned to cross the gate wiring to define pixels, and the semiconductor layer 113. Source and drain electrodes 115a and 115b respectively positioned on both sides of the data line 115 and a data pad 115c connected to an external driving circuit at the end of the data line are formed. The ohmic contact layer 114 between the source electrode and the drain electrode is simultaneously etched when the source / drain electrodes 115a and 115b are patterned.

In the above description, the stacked layers of the gate electrode 111a, the gate insulating layer 112, the semiconductor layer 113, the ohmic contact layer 114, and the source / drain electrodes 115a and 115b form a thin film transistor.

Subsequently, as shown in FIG. 3C, a protective film 117 is formed by coating or depositing BCB, which is a low dielectric constant, or silicon nitride, which is an inorganic material, on the entire surface including the data line 115, and forming a protective film 117. The first, second and third contact holes 118a, 118b, and 118c are removed by removing the gate insulating layer 112 or the protective layer 117 so that a predetermined portion of the pad (not shown) and the data pad 115c are exposed. Form. The gate pad removes the gate insulating film and the passivation layer to form a contact hole, and the data pad and the drain electrode remove the passivation layer to form a contact hole.

3D, a transparent conductive material ITO is deposited on the entire surface including the passivation layer 117 and the photoresist 120 is uniformly applied thereon, and then the photoresist 120 is patterned using a mask. do. Next, the ITO is patterned by wet etching using an HCl etchant using the patterned photoresist 120 as a mask, and then connected to the drain electrode 115b through the first contact hole 118a as shown in FIG. 3E. A pixel pad 119a, a gate pad transparent conductive film (not shown) connected to the gate pad 111c through the second contact hole 118b, and a data pad 115c through the third contact hole 118c. And a data pad transparent conductive film 119c to be connected to each other.

Thus, the ITO etchant of the present invention is characterized in that the aqueous HCl solution does not damage the molybdenum wiring layer.

However, in case of using HCl etchant, the etching rate is only about 50% compared to the case of using the conventional etchant. In order to solve this problem, the etching process requires more than twice the time or high temperature is applied. have. The former method is time consuming, so the latter method is more effective.

The detailed description through experimental data is as follows.

4 is a graph showing the ITO etching ratio according to the concentration and temperature of the HCl etchant, Figure 5 is a graph showing the change over time of the concentration of HCl etchant at 45 ℃.

First, the etch ratio is higher when using 20% HCl etchant than when using 15% HCl etchant, as shown in Figure 4, the etching ratio is higher in 45 ℃ HCl etchant than in 40 ℃ HCl etchant, 15 ℃ 45 The% HCl etchant shows an etch rate of 3.4 μs / sec and the 20% HCl etchant at 45 ° C. shows an etch rate of 6.7 μs / sec. This is not much different from the etching ratio when using a conventional HCl / HNO 3 etchant.

As such, when the high concentration of HCl etchant is used, the results of the experiment shows that the etching ratio is higher. However, when a high concentration of HCl etchant is applied, as shown in FIG. 5, since a rapid change in hydrochloric acid concentration occurs, the etchant must be exchanged to maintain a constant hydrochloric acid concentration, which is a major factor that lowers productivity. Becomes

Therefore, it is recommended to use 20% HCl etchant which has little change in concentration over time even at high temperatures.

Based on the above results, when the etching process is performed by selecting an HCl etchant having an appropriate concentration and temperature, a high etching ratio can be obtained without damaging the underlying molybdenum wiring layer.

The manufacturing method of the liquid crystal display device of the present invention as described above has the following effects.

First, by providing an ITO etchant which does not damage the molybdenum wiring layer, it is possible to form a wiring composed of low resistance and single film, and it is easy to apply molybdenum having good contact characteristics with ITO as the wiring material.

In particular, the yield decrease by the disconnection failure of the molybdenum wiring layer is prevented.

Second, HCl etchant using the property of forming an azeotropic point when mixing hydrochloric acid and water has little change in concentration with time, so it is unnecessary to replace the etchant frequently, thus improving productivity.

Claims (7)

Forming a first wiring layer on the first substrate; Forming a gate insulating film on the entire surface including the first wiring layer; Forming a second wiring layer on the gate insulating film; Forming a protective film on the entire surface including the second wiring layer; Forming a pixel electrode on the passivation layer by a photolithography process using an aqueous HCl solution, which is an HCl etchant having a concentration of 15% to 24%; And forming a liquid crystal layer between the first substrate and the second substrate opposing the first substrate. delete delete The method of claim 1, wherein the HCl etchant is 35 to 45 ℃. The method of claim 1, wherein the HCl etchant is a 20% HCl aqueous solution at 40 ° C. The method of claim 1, wherein the pixel electrode is formed using indium tin oxide (ITO). 2. The method of claim 1, wherein at least one of the first wiring layer and the second wiring layer is formed using molybdenum.

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