KR101343503B1 - Etchant for patterning of zinc oxide thin film and method of fabricating liquid crystal display device using the same - Google Patents

Abstract

The etching solution for patterning the zinc oxide thin film of the present invention and a method of manufacturing a liquid crystal display device using the same are excellent in etching properties and controllable etching characteristics depending on the deposition temperature in wet etching of the zinc oxide thin film, which is one of the transparent conductive oxides. To provide an organic acid-based etching solution having a rate, it is composed of 0.02 ~ 2M aqueous formic acid and 0.0008 ~ 4M citric acid aqueous solution deposited zinc oxide system deposited at 80 ~ 250 ℃ and 25 ~ 80 ℃, respectively The transparent conductive film is etched to form a predetermined pattern.

Zinc oxide thin film, organic acid-based etchant, liquid crystal display

Description

ETCHANT FOR PATTERNING OF ZINC OXIDE THIN FILM AND METHOD OF FABRICATING LIQUID CRYSTAL DISPLAY DEVICE USING THE SAME}

The present invention relates to an etchant for patterning a zinc oxide thin film and a method of manufacturing a liquid crystal display device using the same, and more particularly, to an organic acid-based etchant for wet etching a zinc oxide thin film, which is one of transparent conductive oxides, and a liquid crystal using the same. A method for manufacturing a display device.

In recent years, there has been a growing interest in information display and a demand for a portable information medium has increased, and a lightweight flat panel display (FPD) that replaces a cathode ray tube (CRT) And research and commercialization are being carried out. Particularly, among such flat panel display devices, a liquid crystal display (LCD) is an apparatus for displaying an image using the optical anisotropy of a liquid crystal, and is excellent in resolution, color display and picture quality and is actively applied to a notebook or a desktop monitor have.

The liquid crystal display comprises a color filter substrate, an array substrate, and a liquid crystal layer formed between the color filter substrate and the array substrate.

Hereinafter, the structure of a typical liquid crystal display device will be described in detail with reference to FIG.

1 is an exploded perspective view schematically showing a general liquid crystal display device.

As shown in the figure, the liquid crystal display comprises a color filter substrate 5, an array substrate 10, and a liquid crystal layer (not shown) formed between the color filter substrate 5 and the array substrate 10 30).

The color filter substrate 5 includes a color filter C composed of a plurality of sub-color filters 7 implementing colors of red (R), green (G) and blue (B) A black matrix 6 for separating the sub-color filters 7 from each other and shielding light transmitted through the liquid crystal layer 30 and a transparent common electrode for applying a voltage to the liquid crystal layer 30 8).

In addition, the array substrate 10 may be arranged vertically and horizontally to define a plurality of gate lines 16 and data lines 17 and a plurality of gate lines 16 and data lines 17 that define a plurality of pixel regions P. A thin film transistor T, which is a switching element formed in an intersection region, and a transparent pixel electrode 18 formed on the pixel region P.

The color filter substrate 5 and the array substrate 10 configured as described above are joined to face each other by sealants (not shown) formed on the outer side of the image display area to form a liquid crystal display panel. 5) and the array substrate 10 are bonded through a bonding key (not shown) formed in the color filter substrate 5 or the array substrate 10.

In order to manufacture most flat panel display devices including the liquid crystal display device, a plurality of thin film deposition and mask processes, that is, photolithography processes are required.

The photolithography process is a series of processes in which a pattern drawn on a mask is transferred onto a substrate on which a thin film is deposited to form a desired pattern as one of photolithography processes. The photoresist is applied, aligned and exposed, developed, and etched as follows. It consists of many complex processes such as processes.

First, a photoresist as a photosensitive material is applied onto a thin film to form a predetermined pattern, and then the photomask on which the pattern is formed is aligned and an exposure process is performed. In this case, the photomask to be used is composed of a predetermined transmission region and a blocking region, and light passing through the transmission region chemically changes the photoresist.

The chemical change of the photoresist varies depending on the type of photoresist. The positive type photoresist is changed to a property in which the lighted part is dissolved by the developer, and the negative type photoresist is opposite to the developer. Change to a property that does not dissolve. Here, the case of using the positive type photoresist is described as an example.

When the exposed portion of the photoresist is removed by using a developing solution, a predetermined photoresist pattern is formed on the thin film.

Thereafter, the thin film is etched in the form of the photoresist pattern, and the remaining photoresist pattern is removed to form a thin film pattern having a predetermined shape.

In this case, when forming the pixel electrode and the common electrode in the manufacturing process of the liquid crystal display device, a thin film made of a material having high electrical conductivity and transparent optical characteristics is required. Currently, indium tin oxide based on indium oxide is used. Transparent conducting oxides (TCO), such as (Indium Tin Oxide; ITO) and Indium Zinc Oxide (IZO), are widely used as materials for transparent conductive films.

The TCO is a general term for the electrically conductive metal oxide having light transmittance, and is defined as a material having a transmittance of 80% or more and a conductivity of 10 ⁻³ / Ωcm or less in the region of 400 nm to 700 nm. Until now, TCO has been used as an important material in flat panel display devices including liquid crystal displays, plasma display panels (PDPs), organic light emitting diodes (OLEDs), and the like. As one of the most widely used TCO, ITO has many advantages such as high visible light transmittance and low electrical resistance. However, there is a shortage of resources due to increased consumption of indium, and thus, there is a need to develop alternative materials that can supplement the problem by overlapping price problems and environmental problems caused by indium toxicity.

Zinc oxide doped with gallium (Ga) or aluminum (Al) doped ZIO has been attracting attention because the dual component is cheap and has a high possibility of popularization due to abundant resources.

Patterning of the transparent conductive film is performed through the photolithography process described above, and the etching method may be classified into dry etching, which is usually performed in a vacuum process, and wet etching, which is performed at normal pressure using a solution. Wet etching has the advantage of being inexpensive because it can be processed at atmospheric pressure compared to dry etching, but it requires a knowledge of the relationship between the reactants because it is a chemical reaction method.

In particular, the zinc oxide-based TCO has a problem that it is difficult to apply the existing wet etching technology of the existing ITO because it is highly reactive to the acid solution. In addition, since the zinc oxide thin film deposited at room temperature for plastic substrate application is obtained in an amorphous form, the etching rate is expected to be faster. In addition to the problem of etching rate, there is a need for technology to control problems caused by different ITO wet etching and reaction mechanisms, and it is important to establish a base technology that can control the development and development of new etchant.

Examples of conventional ITO etchant include aqua regia (HCl + HNO ₃ + H ₂ O), ferric chloride hydrochloride (FeCl ₃ + HCl), HBr or HI system, but a low cost and relatively less toxic aqua regia Etching liquids as main components have been used.

FIG. 2 is a scanning electron microscope (SEM) photograph showing an etching result of a zinc oxide thin film by a general inorganic acid-based etching solution, and diluted with 1/20 of an aqueous solution containing aqua regia used as a main component. The result of etching was carried out without stirring while the temperature was maintained.

As shown in the figure, when the commercialized ITO etchant was diluted to etch by 1/20, the etching shape, that is, the profile is relatively good, but the edges of the pattern are rough and the etching rate is very fast.

As such, the conventional wet etching of ITO uses an inorganic acid-based strong acid and an aqueous solution in which several acids are mixed at a constant ratio. However, even if diluted due to the high reactivity of the zinc oxide acid has a problem that the etching rate is faster than ITO. Because of this phenomenon, it is difficult to determine the exact etching completion time of the pattern required in the device. In particular, the finer the pattern, the greater the problem of loss of line width when the etching completion point is not accurately controlled.

Therefore, it is required to develop an etching composition that can control the etching rate at a controllable level and at the same time, there is no uniformity of the etching shape and no product.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide an etching solution for securing a controllable etching rate and high quality etching shape as a wet etching technique of a zinc oxide thin film, and a method of manufacturing a liquid crystal display device using the same.

Other objects and features of the present invention will be described in the following description of the invention and claims.

In order to achieve the above object, the etching solution for patterning the zinc oxide thin film of the present invention is characterized by etching the zinc oxide-based transparent conductive film deposited at 80 ~ 250 ℃ consisting of an aqueous solution of formic acid of 0.02 ~ 2M.

Another etching solution for the patterning of the zinc oxide thin film of the present invention is characterized by etching the zinc oxide-based transparent conductive film deposited at 25 ~ 80 ℃ consisting of an aqueous solution of 0.0008 ~ 4M citric acid.

In the manufacturing method of the liquid crystal display device of the present invention, a step of depositing a zinc oxide transparent conductive film on a first substrate at 80 ~ 250 ℃ and etching the zinc oxide transparent conductive film with a formic acid solution of 0.02 ~ 2M to a predetermined pixel electrode. Forming a thin film transistor on the first substrate, including forming the thin film transistor; And bonding the first substrate and the second substrate to each other.

According to another aspect of the present invention, there is provided a method of depositing a zinc oxide transparent conductive film on a first substrate at 25 ° C. to 80 ° C., and etching the zinc oxide transparent conductive film with an aqueous 0.0008-4 m citric acid solution. Forming a thin film transistor on the first substrate, including forming a thin film transistor; And bonding the first substrate and the second substrate to each other.

As described above, the etching liquid for patterning the zinc oxide thin film according to the present invention and the manufacturing method of the liquid crystal display device using the same have high quality such as sidewall angle, uniform pattern edge shape, residual material and product suppression. It shows the etching characteristics and provides the effect of patterning the zinc oxide thin film at a controllable etching rate.

Hereinafter, exemplary embodiments of an etching solution for patterning a zinc oxide thin film and a method of manufacturing a liquid crystal display using the same according to the present invention will be described in detail with reference to the accompanying drawings.

ITO's conventional etching solution is inorganic acid-based, and strong acid with high hydrogen ion concentration is used. On the other hand, zinc oxide has a high etching rate because of its high reactivity to strong acids, and a very high etching rate means that it is difficult to secure a minimum process time. In fact, even if the concentration of inorganic acid is lowered to satisfy the etching rate of 50 nm / min or less required in the process, the etching rate is still high.

Accordingly, the present invention has been applied to the etching of zinc oxide thin films using a weak acid-based organic acid having a low acid dissociation constant. As a result, an organic acid-based etchant having excellent etching characteristics and a controllable etching rate is proposed. In particular, the organic acid-based etchant of the present invention was an acid capable of dissociating into hydronium ions (H ₃ O ⁺ ) in an aqueous solution, and citric acid and formic acid aqueous solutions were used. Has different properties in different zinc oxide thin films.

In order to use zinc oxide as a transparent electrode, a process of depositing a thin film is required. Generally, sputtering, e-beam evaporation, thermal evaporation, and pulse laser deposition are performed. Physical Vapor Deposition (PVD) methods, such as Laser Deposition (PLD), and Chemicals such as Plasma Enhanced Chemical Vapor Deposition (PECVD) and Metal Organic Chemical Vapor Deposition (MOCVD) There is a vapor deposition method.

At this time, in the embodiment of the present invention, the composition was searched by changing the ratio of gallium to the zinc oxide target at 3 to 7 wt%, and showed the lowest resistance and the high transmittance at about 5.3 wt%. In addition, the thickness of the zinc oxide thin film used in the embodiment of the present invention is 10nm ~ 1㎛, for example, about 150nm used as an electrode of a general liquid crystal display device, in this case, argon (Ar) gas injection rate, process as the deposition conditions Zinc oxide thin films were deposited at high temperature (80 to 250 ° C.), for example, at 200 ° C. and at room temperature (25 to 80 ° C.) at 50 sccm, 5 to 8 mTorr, and 150 W, respectively. However, the present invention is not limited to the above-described thickness and deposition conditions of the zinc oxide thin film, which is merely one example.

3A to 3C are scanning electron microscope (SEM) photographs showing etching results of a polycrystalline zinc oxide thin film by an organic acid-based etching solution according to an embodiment of the present invention.

3A, 3B and 3C illustrate polycrystalline zinc oxide thin films formed by oxalic acid ((COOH) ₂ ), citric acid (C ₆ H ₈ O ₇ ) and formic acid (CH ₂ O ₂ ), respectively. SEM photograph showing the etching result.

For reference, a polycrystalline zinc oxide thin film is deposited on a glass substrate by a sputtering method, for example, a zinc oxide thin film having a thickness of about 150 nm or a gallium doped zinc oxide thin film at a substrate temperature of 80 to 250 ° C, for example, 200 ° C. After the formation, the photoresist pattern was formed using a photolithography process.

At this time, the oxalic acid, citric acid and formic acid, for example, contained about 150ml in a 250ml beaker in the form of an aqueous solution, and the specimen was cut to 70mm × 70mm and mounted on a support made of Teflon to proceed with etching.

In this case, the organic acid-based aqueous solution contains 0.0001 to 0.01 wt% of hydrochloric acid (HCl), nitric acid (HNO ₃ ), acetic acid (CH ₃ COOH), phosphoric acid (H ₃ PO ₄ ), and ferric chloride (FeCl). ₃ ) may further include an additive, and the zinc oxide thin film may further include an additive such as gallium or aluminum of 0.001 to 10% by weight.

In addition, the concentration of the acid aqueous solution is, for example, 0.004 to 4M, preferably 0.02 to 2M, more preferably 0.02M for formic acid, 0.0002 to 6M, preferably 0.0008 to 4M, more preferably for citric acid. Preferably, 0.02M was wet-etched in a temperature range of 20 to 80 ° C, preferably 30 to 60 ° C. Etching was performed in an oven where the temperature was maintained and immediately etched in distilled water to stop the etching. The profile of the etched specimen was examined using SEM, and the etch rate was calculated by measuring the step using a meter as a profile.

As described above, a weak acid based solution having a low degree of ionization is required to secure a high quality etching shape and a controllable etching rate. Organic acids generally belong to weak acids. The well-known etching solution is oxalic acid solution. The solution showed a slow etch rate in ITO etching but a suitable rate in zinc oxide, so it could be used as a suitable etch solution. However, as shown in FIGS. 3A and 3B, when the etching completion of the oxalic acid and the citric acid is observed, the expansion of the pores is remarkable, and it can be seen that the hole is covered with the photoresist pattern. This is the reason why the sidewall shape of the surface becomes rough. This is not suitable for device formation, and many cavities are generated in the pattern corner and the step is unclear.

On the contrary, referring to FIG. 3C, it can be seen that the etching by formic acid of 0.02M shows a uniform shape of the pattern edge and the sidewall angel has a characteristic close to vertical with about 111 °. In addition, it can be seen that formic acid exhibits excellent etching behavior in the case of a polycrystalline zinc oxide thin film etched at an appropriate etching rate of about 67 nm / min and deposited at 200 ° C.

As described above, the polycrystalline zinc oxide thin film deposited at 200 ° C. forms a cavity in most organic acids. In the case of an acid having a large cavity, the polycrystalline zinc oxide thin film also affects the shape of the pattern and forms an opaque shape. In the case of formic acid, the cavity is generated, but because of its small size, the formic acid has a small effect on the pattern, thereby showing the best pattern shape.

On the other hand, the zinc oxide thin film deposited at room temperature (about 25 ~ 80 ℃) has a disadvantage of higher resistivity and lower transmittance than when deposited at high temperature, but there is an advantage that can be used plastic substrates that are susceptible to heat.

4A to 4C are SEM photographs showing etching results of an amorphous zinc oxide thin film by an organic acid-based etching solution according to an embodiment of the present invention. 5 is a SEM photograph showing a pattern cross section of an amorphous zinc oxide thin film etched with citric acid shown in FIG. 4C.

4A, 4B and 4C are SEM photographs showing etching results of amorphous zinc oxide thin films by oxalic acid, formic acid and citric acid, respectively.

As described above, the organic acid-based aqueous solution contains 0.0001 to 0.01 wt% of hydrochloric acid (HCl), nitric acid (HNO ₃ ), acetic acid (CH ₃ COOH), phosphoric acid (H ₃ PO ₄ ) and ferric chloride based on the total weight. An additive such as (FeCl ₃ ) may be further included, and the zinc oxide thin film may further include an additive such as gallium or aluminum in an amount of 0.001 to 10% by weight.

In addition, the concentration of the acid aqueous solution is, for example, 0.004 to 4M, preferably 0.02 to 2M, more preferably 0.02M for formic acid, 0.0002 to 6M, preferably 0.0008 to 4M, more preferably for citric acid. Preferably, 0.02M was wet-etched in a temperature range of 20 to 80 ° C, preferably 30 to 60 ° C. Etching was performed in an oven maintained at a temperature, and the etching was stopped by washing in distilled water immediately after etching. The profile of the etched specimen was examined using SEM, and the etch rate was calculated by measuring the step using a meter as a profile.

As illustrated in FIG. 4A, when the amorphous zinc oxide thin film deposited at room temperature using 0.02 M of oxalic acid is etched, it can be seen that the pattern is damaged due to a plurality of generated particles.

In addition, in the case of etching with formic acid of 0.02M, the pattern edge shows a uniform shape as shown in FIG. 4B, but there is a problem in that residual material remains on the substrate surface.

4C and 5, when etched with 0.02M citric acid, no cavities are generated unlike etching of the zinc oxide thin film deposited at 200 ° C., and uniform pattern shape and side angle are excellent at about 97 °. Characteristics.

As described above, the amorphous zinc oxide thin film deposited at room temperature has an even pattern since no cavity is generated in any acid. However, oxalic acid shows a result that the pattern is damaged by the generated particles, it can be seen that formic acid has a problem that remains around the pattern.

Hereinafter, a method of manufacturing a liquid crystal display using an etchant for patterning a zinc oxide thin film having the above characteristics will be described in detail with reference to the accompanying drawings.

As described above, in order to manufacture most flat panel display devices including liquid crystal display devices, a plurality of photolithography processes are required, and the etching of the zinc oxide thin film used as the transparent conductive film of the flat panel display device is described in the embodiments of the present invention. According to the organic acid-based etchant.

FIG. 6 is a plan view schematically illustrating a portion of an array substrate of a liquid crystal display according to a first exemplary embodiment of the present invention. In an actual liquid crystal display, although N gate lines and M data lines cross each other, MxN pixels exist. For simplicity of explanation, one pixel is shown in the drawing.

As shown in the figure, a gate line 116 and a data line 117 are formed on the array substrate 110 according to the first embodiment of the present invention, which are arranged vertically and horizontally on the array substrate 110 to define a pixel region. have. A thin film transistor, which is a switching element, is formed in the intersection region of the gate line 116 and the data line 117. A common electrode of the color filter substrate (not shown) is connected to the thin film transistor And a pixel electrode 118 for driving a liquid crystal (not shown) is formed.

Although not shown in the drawing, a gate pad electrode and a data pad electrode electrically connected to the gate line 116 and the data line 117 are formed in the edge region of the array substrate 110. The scan signal and the data signal applied from the driving circuit unit are transferred to the gate line 116 and the data line 117, respectively.

That is, the gate line 116 and the data line 117 extend toward the driving circuit part and are connected to the corresponding gate pad line and the data pad line, respectively, and the gate pad line and the data pad line are the gate pad line and the data pad line. Scan signals and data signals are applied from the driving circuit unit through gate pad electrodes and data pad electrodes electrically connected to the lines, respectively.

The thin film transistor is electrically connected to the pixel electrode 118 through a gate electrode 121 connected to the gate line 116, a source electrode 122 connected to the data line 117, and a contact hole 140. The drain electrode 123 is formed. The thin film transistor includes an active pattern (not shown) which forms a conductive channel between the source electrode 122 and the drain electrode 123 by a gate voltage supplied to the gate electrode 121 .

At this time, a part of the gate line 116 located at the previous stage overlaps a part of the pixel electrode 118 above the gate insulating film (not shown) with a protective film (not shown) therebetween to form a storage capacitor Cst ). The storage capacitor Cst keeps the voltage applied to the liquid crystal capacitor constant until the next signal comes in. That is, the pixel electrode 118 of the array substrate 110 forms a liquid crystal capacitor together with the common electrode of the color filter substrate. In general, the voltage applied to the liquid crystal capacitor is not maintained until the next signal is input and is leaked. Disappear. Therefore, in order to maintain the applied voltage, the storage capacitor Cst needs to be connected to the liquid crystal capacitor.

The storage capacitor Cst has effects such as stabilization of gray scale display and reduction of flicker and afterimage in addition to signal retention.

In the liquid crystal display according to the first exemplary embodiment of the present invention configured as described above, when the pixel electrode of the array substrate is formed of a zinc oxide thin film, the above-described organic acid may be used in wet etching of the zinc oxide thin film. Based citric acid or formic acid is used, which will be described in detail by the following method of manufacturing a liquid crystal display.

7A to 7E are cross-sectional views sequentially illustrating a manufacturing process along line AA ′ of the array substrate illustrated in FIG. 6.

As shown in FIG. 7A, the gate electrode 121 and the gate line (not shown) formed of the first conductive layer are formed on the array substrate 110 made of a transparent insulating material such as glass.

In this case, the gate electrode 121 and the gate line according to the first embodiment of the present invention are selectively patterned through a photolithography process (first mask process) after depositing a first conductive film on the entire surface of the array substrate 110. To form.

The first conductive layer may be formed of aluminum (Al), aluminum alloy (Al alloy), tungsten (W), copper (Cu), chromium (Cr), molybdenum (Mo), or the like. Low resistance opaque conductive materials can be used. The first conductive layer may have a multi-layer structure in which two or more low resistance conductive materials are stacked.

Next, as shown in FIG. 7B, a gate insulating film 115a, an amorphous silicon thin film, and an n + amorphous silicon thin film are deposited on the entire surface of the array substrate 110 on which the gate electrode 121 and the gate line are formed, and then photolithography. The active pattern 124 formed of the amorphous silicon thin film is formed on the array substrate 110 by selectively removing the amorphous silicon thin film and the n + amorphous silicon thin film through a process (second mask process).

At this time, an n + amorphous silicon thin film pattern 125 formed of the n + amorphous silicon thin film and patterned in the same manner as the active pattern 124 remains on the active pattern 124.

Next, as shown in FIG. 7C, a second conductive film is formed on the entire surface of the array substrate 110 on which the active pattern 124 is formed, and then selectively patterned using a photolithography process (third mask process). A source electrode 122, a drain electrode 123, and a data line (not shown) formed of the second conductive layer are formed on the active pattern 124. In this case, the n + amorphous silicon thin film pattern formed on the active pattern 124 is removed through the third mask process, and the ohmic − is separated between the active pattern 124 and the source / drain electrodes 122 and 123. An ohmic contact layer 125n for ohmic contact is formed.

In this case, the source electrode 122, the drain electrode 123, and the data line may include aluminum (Al), aluminum alloy (Al alloy), tungsten (W), copper (Cu), chromium (Cr), molybdenum (Mo), and the like. The same conductive material may be used to form a single layer, and may be formed in a multi-layered structure in the same manner as the above-described gate wiring.

Here, the first embodiment of the present invention has been described in the case where the active pattern 124, the source electrode 122 and the drain electrode 123 is formed through two mask processes, for example, but the present invention is The active pattern 124, the source electrode 122, and the drain electrode 123 may be formed through a single mask process by using a diffraction mask.

Next, as shown in FIG. 7D, the passivation layer 115b is formed on the entire surface of the array substrate 110 on which the source electrode 122, the drain electrode 123, and the data line are formed. Thereafter, the protective film 115b is selectively patterned using a photolithography process (a fourth mask process) to form a contact hole 140 exposing a portion of the drain electrode 123.

As shown in FIG. 7E, after the third conductive film is deposited on the entire surface of the array substrate 110 on which the protective film 115b is formed, the contact is selectively patterned using a photolithography process (a fifth mask process). The pixel electrode 118 electrically connected to the drain electrode 123 is formed through the hole 140.

In this case, the third conductive layer may be, for example, a zinc oxide-based transparent conductive layer doped with gallium or aluminum to form the pixel electrode 118, and may be formed by chemical vapor deposition such as physical vapor deposition or plasma chemical vapor deposition. It can be formed to a thickness of about 10nm ~ 1㎛ using vapor deposition.

The zinc oxide-based transparent conductive film can be used as a substitute for ITO because it can compensate for resource shortage due to increased consumption of indium, increase in price, and environmental problems due to toxicity of indium.

In this case, when the zinc oxide-based thin film is deposited at a substrate temperature of 80 to 250 ° C., for example, 200 ° C., the wet etching may be performed at a temperature range of 20 ° C. to 80 ° C. using an aqueous 0.02 ~ 2 M formic acid solution.

When the zinc oxide thin film is deposited at room temperature of 25 to 80 ° C., wet etching may be performed at a temperature ranging from 20 ° C. to 80 ° C. using 0.0008-4 M citric acid solution.

In this case, the organic acid-based aqueous solution may further include an additive such as 0.0001 to 0.01 wt% of hydrochloric acid, nitric acid, acetic acid, phosphoric acid, and ferric chloride, based on the total weight, and the zinc oxide thin film may include 0.001-10. Additives such as gallium or aluminum by weight may be included.

On the other hand, the liquid crystal display according to the first embodiment of the present invention has been described using a twisted nematic (TN) method for driving the nematic liquid crystal molecules in a vertical direction with respect to the substrate as an example However, the present invention is not limited thereto.

The present invention can also be applied to an in-plane switching (IPS) type liquid crystal display device in which the liquid crystal molecules are driven in a horizontal direction with respect to the substrate to improve the viewing angle to 170 degrees or more.

8 is a plan view schematically illustrating a portion of an array substrate of a liquid crystal display according to a second exemplary embodiment of the present invention, in which a fringe field formed between the pixel electrode and the common electrode is positioned on the pixel region and the common electrode through the slit. A portion of an array substrate of a Fringe Field Switching (FFS) liquid crystal display device which implements an image by driving liquid crystal molecules is illustrated.

In the fringe field type liquid crystal display, as the common electrode is formed at the lower side while the liquid crystal molecules are horizontally aligned, and the pixel electrode is formed at the upper side, an electric field is generated in the horizontal and vertical directions so that the liquid crystal molecules are twisted. It is tilted and driven.

However, the present invention is not limited to the fringe field type liquid crystal display device, and the present invention can be applied to a general transverse electric field type liquid crystal display device.

As shown in the drawing, in the array substrate 210 of the fringe field type liquid crystal display according to the second embodiment of the present invention, a gate line 216 arranged vertically and horizontally on the transparent array substrate 210 defines a pixel region. ) And a data line 217, and a thin film transistor, which is a switching element, is formed at an intersection of the gate line 216 and the data line 217.

The thin film transistor includes a gate electrode 221 connected to the gate line 216, a source electrode 222 connected to the data line 217, and a drain electrode 223 connected to the pixel electrode 218. In addition, the thin film transistor is formed by a gate insulating film (not shown) for insulation between the gate electrode 221 and the source / drain electrodes 222 and 223 and a gate voltage supplied to the gate electrode 221. An active pattern (not shown) forming a conductive channel between the 222 and the drain electrode 223 is included.

A box-shaped common electrode 208 and a pixel electrode 218 are formed in the pixel area, and the pixel electrode 218 together with the common electrode 208 generates the fringe field together with the pixel electrode ( 218 includes a plurality of slits 218s.

In this case, the pixel electrode 218 is electrically connected to the drain electrode 223 through a contact hole 240 formed in a passivation layer (not shown), and the common electrode 208 is connected to the gate line 216. It is connected to the common line 208l arranged in parallel.

The liquid crystal display according to the second exemplary embodiment of the present invention configured as described above has the above-described method according to the deposition temperature in wet etching the zinc oxide thin film when the common electrode and the pixel electrode of the array substrate are formed of the zinc oxide thin film. One organic acid-based citric acid or formic acid is used, which will be described in detail by the following method of manufacturing a liquid crystal display.

9A to 9F are cross-sectional views sequentially illustrating a manufacturing process along line BB ′ of the array substrate illustrated in FIG. 8.

As shown in FIG. 9A, a gate electrode 221 made of a conductive metal material, a common line 28l, and a gate line (not shown) are formed on the array substrate 210 using a photolithography process (first mask process). To form.

Next, as shown in FIG. 9B, an insulating film, an amorphous silicon thin film, and an n + amorphous silicon thin film are sequentially formed on the entire surface of the array substrate 210 on which the gate electrode 221, the common line 208l, and the gate line are formed. Deposit.

Thereafter, the insulating layer, the amorphous silicon thin film, and the n + amorphous silicon thin film are selectively patterned by using a photolithography process (second mask process) to form the amorphous silicon in the state where the gate insulating film 215a is interposed on the gate electrode 221. An active pattern 224 made of a thin film is formed.

In this case, an n + amorphous silicon thin film pattern 225 patterned in the same form as the active pattern 224 is formed on the active pattern 224.

Subsequently, as illustrated in FIG. 9C, a transparent conductive metal material is deposited on the entire surface of the array substrate 210 and then selectively patterned by using a photolithography process (third mask process). The common electrode 208 is electrically connected to the common line 208l.

In this case, the common electrode 208 may use a zinc oxide-based transparent conductive film doped with gallium or aluminum as described above. The zinc oxide thin film may have a substrate temperature of 80 to 250 ° C., for example, 200 ° C. In the case of deposition, wet etching may be performed in a temperature range of 20 to 80 ° C. using a formic acid solution of 0.02 to 2 M.

When the zinc oxide thin film is deposited at room temperature of 25 to 80 ° C., wet etching may be performed at a temperature ranging from 20 ° C. to 80 ° C. using 0.0008-4 M citric acid solution.

In this case, the organic acid-based aqueous solution may further include an additive such as 0.0001 to 0.01 wt% of hydrochloric acid, nitric acid, acetic acid, phosphoric acid, and ferric chloride, based on the total weight, and the zinc oxide thin film may include 0.001-10. Additives such as gallium or aluminum by weight may be included.

As illustrated in FIG. 9D, a conductive metal material is deposited on the entire surface of the array substrate 210 and then selectively patterned using a photolithography process (fourth mask process) to form a source on the active pattern 224. The electrode 222 and the drain electrode 223 are formed. In addition, a data line 217 defining a pixel region is formed along with the gate line through the fourth mask process.

In this case, the n + amorphous silicon thin film pattern formed on the active pattern 224 is removed between the active pattern 224 and the source / drain electrodes 222 and 223 by removing a predetermined region through the fourth mask process. The ohmic contact layer 225n to contact is formed.

Next, as shown in FIG. 9E, a protective film 215b is deposited on the entire surface of the array substrate 210 on which the source electrode 222, the drain electrode 223, and the data line 217 are formed, and then a photolithography process. Through the fifth mask process, a portion of the passivation layer 215b is removed to form a contact hole 240 exposing a portion of the drain electrode 223.

9F, a transparent conductive metal material is deposited on the entire surface of the array substrate 210 and then selectively patterned using a photolithography process (sixth mask process) through the contact hole 240. The pixel electrode 218 is electrically connected to the drain electrode 223. In this case, the pixel electrode 218 includes a plurality of slits 218s in the pixel electrode 218 to generate a fringe field together with the common electrode 208 under the pixel electrode 218.

In this case, the pixel electrode 218 may use a zinc oxide-based transparent conductive film doped with gallium or aluminum, like the common electrode 208 described above, and the zinc oxide-based thin film may be 80 to 250 ° C, for example, 200 ° C. When the deposition is performed at a substrate temperature of, the wet etching may be performed in a temperature range of 20 ° C. to 80 ° C. using a formic acid solution of 0.02 to 2 M.

When the zinc oxide thin film is deposited at room temperature of 25 to 80 ° C., wet etching may be performed at a temperature ranging from 20 ° C. to 80 ° C. using 0.0008-4 M citric acid solution.

In this case, the organic acid-based aqueous solution may further include an additive such as 0.0001 to 0.01 wt% of hydrochloric acid, nitric acid, acetic acid, phosphoric acid, and ferric chloride, based on the total weight, and the zinc oxide thin film may include 0.001-10. Additives such as gallium or aluminum by weight may be included.

The array substrate of the first and second embodiments of the present invention configured as described above is bonded to the color filter substrate by a sealant formed on the outer side of the image display area, wherein the thin film transistor and the gate are attached to the color filter substrate. A black matrix is formed to prevent light leakage into lines and data lines, and color filters are formed to realize colors of red, green, and blue.

At this time, the color filter substrate and the array substrate are bonded together through a covalent key formed on the color filter substrate or the array substrate.

The thin film transistors according to the first and second embodiments of the present invention have been described using a thin film transistor of a lower gate type in which a gate electrode is located below, but the present invention is not limited thereto. In addition to the top gate thin film transistor in which the gate electrode is positioned above, it is applicable to an etch stopper structure and a coplanar structure.

In addition, although the first and second embodiments of the present invention describe an amorphous silicon thin film transistor using an amorphous silicon thin film as an active pattern, the present invention is not limited thereto, and the present invention is not limited thereto. The present invention also applies to polycrystalline silicon thin film transistors using polycrystalline silicon thin films.

In addition, the etching solution for the patterning of the zinc oxide thin film of the present invention can be used in the process of manufacturing not only a liquid crystal display but also an organic light emitting display device or other flat panel display.

While a great many are described in the foregoing description, it should be construed as an example of preferred embodiments rather than limiting the scope of the invention. Therefore, the invention should not be construed as limited to the embodiments described, but should be determined by equivalents to the appended claims and the claims.

1 is an exploded perspective view schematically showing a general liquid crystal display device.

Figure 2 is a scanning electron microscope (Scanning Electron Microscope; SEM) photograph showing the results of etching the zinc oxide thin film by a common inorganic acid-based etching solution.

3A to 3C are SEM photographs showing etching results of a polycrystalline zinc oxide thin film by an organic acid-based etching solution according to an embodiment of the present invention.

4A to 4C are SEM photographs showing etching results of an amorphous zinc oxide thin film by an organic acid-based etching solution according to an embodiment of the present invention.

FIG. 5 is a SEM photograph showing a pattern cross section of an amorphous zinc oxide thin film etched with citric acid shown in FIG. 4C.

6 is a plan view schematically illustrating a portion of an array substrate of a liquid crystal display according to a first exemplary embodiment of the present invention.

7A to 7E are cross-sectional views sequentially illustrating a manufacturing process along line AA ′ of the array substrate illustrated in FIG. 6.

8 is a plan view schematically illustrating a portion of an array substrate of a liquid crystal display according to a second exemplary embodiment of the present invention.

9A to 9F are cross-sectional views sequentially illustrating a manufacturing process along the line BB ′ of the array substrate illustrated in FIG. 8.

DESCRIPTION OF REFERENCE NUMERALS

110,210: array substrate 116,216: gate line

117,217 data line 118,218 pixel electrode

121,221 gate electrode 122,222 source electrode

123,223 drain electrode 208 common electrode

218s: slit

Claims (14)

Etching liquid consisting of 0.02 ~ 2M aqueous formic acid solution to form a predetermined pattern by etching the zinc oxide-based transparent conductive film deposited at 80 ~ 250 ℃. Etching liquid consisting of 0.0008 ~ 4M citric acid aqueous solution to form a predetermined pattern by etching the zinc oxide-based transparent conductive film deposited at 25 ~ 80 ℃. The etchant according to any one of claims 1 and 2, wherein the aqueous solution has a concentration of 0.02M. The etchant according to any one of claims 1 to 2, further comprising 0.0001 to 0.01 wt% of hydrochloric acid, nitric acid, acetic acid, phosphoric acid or ferric chloride relative to the total weight. The etching solution according to any one of claims 1 to 2, wherein the zinc oxide transparent conductive film further comprises 0.001 to 10% by weight of gallium or aluminum. Depositing a zinc oxide transparent conductive film on a first substrate at 80 ° C. to 250 ° C. and etching the zinc oxide transparent conductive film with an aqueous 0.02˜2 M formic acid solution to form a predetermined pixel electrode. Forming a thin film transistor thereon; And And attaching the first substrate and the second substrate to each other. Depositing a zinc oxide transparent conductive film on a first substrate at 25 ° C. to 80 ° C. and etching the zinc oxide transparent conductive film with a 0.0008-4 M citric acid solution to form a predetermined pixel electrode. Forming a thin film transistor thereon; And And attaching the first substrate and the second substrate to each other. The method of manufacturing a liquid crystal display device according to any one of claims 6 to 7, wherein etching is performed at a temperature in the range of 20 to 80 ° C. The method of claim 8, wherein the aqueous solution is formed at a concentration of 0.02M. 10. The method of claim 8, further comprising 0.0001 to 0.01 wt% of hydrochloric acid, nitric acid, acetic acid, phosphoric acid, or ferric chloride relative to the total weight. The method of claim 8, wherein the zinc oxide-based transparent conductive film further comprises 0.001 to 10% by weight of gallium or aluminum. The method of claim 8, wherein the zinc oxide transparent conductive film is formed to a thickness of 10 nm to 1 μm. The method of claim 8, further comprising: depositing a zinc oxide-based transparent conductive film on the first substrate or the second substrate; And When the zinc oxide transparent conductive film is deposited at 80 to 250 ° C., the zinc oxide transparent conductive film is etched with 0.02 to 2 M of formic acid solution, and when the zinc oxide transparent conductive film is deposited at 25 to 80 ° C., 0.0008. And etching the zinc oxide-based transparent conductive film with a ~ 4M aqueous citric acid solution to form a predetermined common electrode. The method of claim 13, wherein the aqueous solution is formed at a concentration of 0.02M.

Images