KR100579511B1 - Etchant for forming metal line and fabrication method for metal line using the same - Google Patents

Abstract

The present invention, in etching a metal line consisting of a double layer of aluminum alloy and molybdenum, nitric acid (HNO ₃ ), iron nitrate (Fe (NO ₃ ) ₃ ), perchloric acid (HClO ₄ ), ammonium fluoride (NH ₄ F) By applying an etchant including an etchant to etch a metal line consisting of a double layer of aluminum alloy and molybdenum in one wet etching, the process is shortened and a metal line having a good profile is formed.

Nitric acid, iron nitrate, perchloric acid, sulfuric acid, ammonium fluoride, etchant, wet etching

Description

Etchant for forming metal wiring and metal wiring forming method using same {ETCHANT FOR FORMING METAL LINE AND FABRICATION METHOD FOR METAL LINE USING THE SAME}

1A to 1D are flowcharts showing a process of forming a gate line in a conventional liquid crystal display device.

2A to 2B are cross-sectional views illustrating etching patterns of a conventional gate line.

3 is an electron micrograph showing a profile of a gate line using a conventional gate metal etchant.

Figure 4 is an electron micrograph showing the profile of the gate line formed by applying the etchant of the present invention.

5a to 5d is a process flowchart of forming a metal wiring by applying the etchant of the present invention.

******** Explanation of symbols for the main parts of the drawings *********

1,501: substrate 2,502: aluminum alloy layer

3,503: molybdenum layer 4,504: mask

506: gate line

The present invention relates to an etchant used for the manufacture of a liquid crystal display device and a liquid crystal display device manufacturing method using the etchant, in particular an etchant used in the process of forming a gate line of the liquid crystal display device. The present invention relates to a method for developing and manufacturing a liquid crystal display device using the same.

Liquid crystal display devices (LCDs) are the most popular image display devices today. In particular, a TFT liquid crystal display device mainly using a thin film transistor (TFT) as a switching element for representing a pixel is widely used.

The TFT liquid crystal display element is formed by having a TFT array substrate in which TFTs serving as switching elements are arranged in a matrix form, and a color filter substrate including a color filter, facing the TFT array substrate. Further, liquid crystal is filled between the TFT array substrate and the color filter substrate.

In particular, since the TFT array substrate of the liquid crystal display device is a unit pixel of the liquid crystal display device by the thin film transistor, the process of forming the TFT array substrate occupies an important part of the process of forming the TFT liquid crystal display device. do.

 Typically, the process of forming a TFT array substrate includes forming a gate electrode, forming a gate insulating film on the gate electrode, forming a semiconductor layer on the gate insulating film, and source / drain electrodes on the semiconductor layer. And forming a data line, forming a protective film on the data line, and forming a pixel electrode on the protective film.

In particular, the process of forming the gate wiring and the gate electrode is a process of forming a gate line and a gate electrode pattern by depositing a gate metal on a transparent substrate and applying a photolithography process.

A process of forming the gate line and the gate electrode will be described in detail with reference to FIGS. 1A to 1D.

First, as shown in FIG. 1A, a gate metal 2 such as a copper alloy or an aluminum alloy is deposited on a substrate 1 by a sputtering method.

The sputtering method is a method in which inert gas ion particles accelerated by an electric field hit a target and scatter the target material to deposit on a substrate. Usually, a metal thin film is deposited by the sputtering method.

Copper alloys or aluminum alloys are mainly used as gate metals. Especially, aluminum (Al) alloys and molybdenum (Mo) alloys have excellent electrical conductivity and improve electrical bonding characteristics between the gate metal and the pad portion for supplying the gate signal. Bilayer is mainly used.

After the gate metal is formed on the substrate, the gate metal is patterned to form gate lines and gate electrodes.

As shown in FIG. 1B, the photosensitive film 3 is coated on the entire surface of the substrate on which the gate metal is deposited by a spin coating method or the like. Next, exposure is performed by applying the mask 4 in which the pattern of the gate line was formed.

The photoresist film is a polymer whose bonding structure changes when exposed to light such as ultraviolet rays, and forms a pattern on the gate metal by using properties that are removed or maintained in the photoresist film development process by the light that is exposed.

As shown in FIG. 1C, after the photosensitive film 3 is exposed, a photosensitive film developing process is performed to selectively remove the exposed photosensitive film. After the above process, the photosensitive film 5 having the pattern of the gate line remains on the substrate, and the etching process is performed by applying the photosensitive film 5 as a mask.

As a result, as in FIG. 1D, the gate metal 2 is etched through the etching process and the gate line 6 is formed.

The etching method of the gate metal 2 includes a wet etching method and a dry etching method. Wet etching is a method of oxidizing and removing a gate metal in a chemical solution, and dry etching is a process of removing a gate metal by irradiating ions in a plasma state onto the gate metal.

Wet etching has anisotropic etching characteristics with uniform etching rates according to the etching direction, and dry etching has anisotropic etching characteristics with different etching rates depending on the etching direction.

Many thin films are formed on the gate line. In order to prevent disconnection of the thin film to be formed, the shape of the gate line needs to be tapered to reduce the step difference of the thin film formed on the gate line. Therefore, in order to form the gate line into a tapered shape, wet etching which mainly exhibits isotropic etching characteristics is used for etching the gate line.

The wetted gate line uses a double layer of aluminum alloy and molybdenum as the gate metal to improve ohmic contact characteristics even though it is tapered. Ethoxy phosphate (H ₃ PO ₄ ), nitric acid (HNO ₃ ), and acetic acid (CH ₃ COOH In the prior art using a mixed solution of), the aluminum alloy layer and the molybdenum layer have different etching rates in the etchant, so that the tapered shape is deformed.

2A to 2B show a gate line using a double layer of an aluminum alloy layer and a molybdenum layer as a gate metal and a mixture of phosphoric acid (H ₃ PO ₄ ), nitric acid (HNO ₃ ), and acetic acid (CH ₃ COOH) as an etchant. It is a figure which shows roughly the method of etching.

FIG. 2A illustrates an aluminum alloy layer 21 and a molybdenum layer 22 etched in different shapes by different etching rates. At this time, the phosphoric acid and the aluminum alloy layer 21 in the etchant react to etch the aluminum alloy layer 21 and the nitric acid and the molybdenum layer 22 react to etch the molybdenum layer 22. However, the reactivity of the aluminum alloy layer 21 and phosphoric acid is greater than that of the molybdenum layer 22 and nitric acid, and as shown in FIG. 2A, the molybdenum layer 22 remaining on the aluminum alloy layer 21 after etching is removed. It is formed larger than the etched aluminum alloy layer 21.

Therefore, the wet etched molybdenum layer 22 must be etched once again by dry etching to form a complete taper formation. The molybdenum layer 22 is tapered like the aluminum alloy layer 21 through dry etching. In FIG. 2B, the molybdenum layer 22 tapered through dry etching is stacked with the aluminum alloy layer 21.

After etching, the photoresist remaining on the substrate is removed and a gate line is formed through a cleaning process.

In summary, the gate line forming process may include depositing a gate metal on a substrate, performing a photolithography process on the gate metal to form a photoresist pattern, and wet etching the photoresist pattern as a mask. It may be divided into a step, further dry etching the wet gate metal, a photoresist removing step, and a cleaning step.

In the TFT array substrate manufacturing process using a double layer of aluminum alloy layer and molybdenum layer as the gate line, wet etching is performed to etch the aluminum alloy when conventional etchant is used, and dry etching process is used to etch the molybdenum layer. This leads to a cost increase because of the process delay problem that must be performed separately and the equipment for dry etching.

In addition, since the pattern of the gate line by the conventional etchant has a large tapered side inclination angle, it may cause a short circuit when forming a thin film on the gate line.

3 is an electron micrograph of a gate line etched using a conventional etchant. As shown in the figure, it can be seen that the profile of the gate line has a large slope.

Since the profile of the gate line is sensitive to the short circuit of various thin films formed on the gate line, it is important to smooth the profile of the gate line in order to prevent disconnection.

As described above, an etchant capable of forming a gate line by one wet etching in a gate line forming step using a double layer of an aluminum alloy layer and a molybdenum layer during forming a liquid crystal display device is described. It aims to provide. In addition, by applying the etchant to form a gate line is to improve the profile of the gate line to improve the disconnection defect that may occur in the process of forming a thin film on the gate line.

In addition, the gate line may be formed by only one wet etching in the gate line forming process, and thus, the process may be shortened.

The etchant of the present invention is characterized in that it comprises nitric acid (HNO ₃ ), iron nitrate (Fe (NO ₃ ) ₃ ), perchloric acid (HClO ₄ ), ammonium fluoride (NH ₄ F). In addition, forming the gate line by applying the etchant may include forming a gate metal on a substrate; Etching the gate metal by applying an etchant comprising nitric acid (HNO ₃ ), iron nitrate (Fe (NO ₃ ) ₃ ), perchloric acid (HClO ₄ ), and ammonium fluoride (NH ₄ F) It features. In addition, the process of manufacturing a TFT array substrate by applying the etchant comprises the steps of forming an aluminum alloy on the substrate, forming a molybdenum alloy on the aluminum alloy and nitric acid (HNO ₃ ), iron nitrate (Fe (NO _{3 3} ) a gate line forming step comprising etching a double layer of the aluminum alloy and molybdenum with an etchant comprising perchloric acid (HClO ₄ ) and ammonium fluoride (NH ₄ F), and forming a gate insulating film on the gate line. Forming a semiconductor layer on the gate insulating film, forming a source and a drain electrode on the semiconductor layer, forming a protective film on the source and the drain electrode, and forming a pixel electrode. It is characterized by including.

 The present invention provides a new etchant for etching a metal. Hereinafter, the present invention will be described in detail.

The etchant of the present invention used for etching the gate metal is formed including nitric acid (HNO ₃ ), iron nitrate (Fe (NO ₃ ) ₃ ), perchloric acid (HClO ₄ ), ammonium fluoride (NH ₄ F) , The weight ratio of nitric acid (HNO ₃ ), iron nitrate (Fe (NO ₃ ) ₃ ), perchloric acid (HClO ₄ ), ammonium fluoride (NH ₄ F) is about 7-12 wt%, 2-4 wt%, 1-4 wt It is characterized in that the%, 0.1 ~ 2.0wt%.

The process in which the constituents of the etchant of the present invention reacts with and etches with the double layer of the aluminum alloy layer and the molybdenum layer constituting the gate line will be described through a reaction scheme.

Scheme 1

The molybdenum layer constituting the gate metal reacts with nitric acid in the etchant component of the present invention.

2Mo → 2Mo ³⁺ + 6e ^-

_{^{2H + + 6e - → 3H 2}} (H + is condensed in nitric acid (HNO ₃₎₎

2Mo + 2H ⁺ → 2Mo ³ + + 3H ₂

As in the above reaction scheme, the molybdenum layer is removed by oxidation and reduction with nitric acid. That is, molybdenum is oxidized and removed while hydrogen ions condensed in nitric acid are reduced.

Scheme 2

The aluminum alloy layer in the gate metal is removed by reaction with aluminum and iron nitride (Fe (NO ₃ ) ₃ ) in the etchant of the present invention.

Al → Al ³⁺ + 3e ^-

^{3Fe 3+ 3e - → 3Fe 2+ (} Fe 3+ is condensed in the quality of iron oxide _{(Fe (NO 3) 3)} )

Al + 3Fe ³⁺ → Al ³⁺ + 3 Fe ²⁺

According to the above reaction scheme, the aluminum layer is removed by oxidation and reduction with iron nitride (Fe (NO ₃ ) ₃ ) in the etchant. That is, the aluminum alloy is oxidized and removed while iron condensed in the iron nitride is reduced.

In addition, perchloric acid (HClO ₄ ) in the etchant of the present invention lowers the pH of the etchant and serves to create an environment so that the etching reaction is active, ammonium fluoride (NH ₄ F) gate during the etching process It prevents adsorption of etched particles on the surface of the metal and prevents re-adsorption of oxidized molybdenum ions. In particular, perchloric acid is the more contains a significant sansogi hydrochloric acid as a strong acid than hydrochloric acid represents a strong acid perchloric acid (HClO ₄₎ instead of the sulfuric acid (H ₂ SO ₄₎ or hypochlorous acid (HClO), chlorite (HCl _2), acid ( HCl0 ₃ ) and the like can be used.

As described in the above scheme, the gate line composed of the double layer of the aluminum alloy layer and the molybdenum layer is removed by reacting with nitric acid (HNO ₃ ) and iron nitride (Fe (NO ₃ ) ₃ ) in the etchant component of the present invention.

At this time, since the etching rate of the aluminum alloy layer and the molybdenum layer is removed by reacting with the etchant is similar, the gate line is etched into a complete taper shape by one wet etching.

In addition, when the gate line is formed by applying the etchant of the present invention, the profile of the gate line is improved so that the profile of the tapered gate line has a gentle lateral inclination angle. The profile of the gate line is a very important process for preventing a short circuit in the deposition process of the thin film formed on the gate line. As the lateral inclination angle of the profile is gentle, disconnection defects can be prevented.

4 shows an electron micrograph of a gate line having an improved profile as a result of using the etchant of the present invention. As shown in FIG. 4, it can be seen that the inclination angle of the side profile of the tapered gate line is about 45 degrees, which is improved compared to the profile inclination angle of the conventional gate line, 70 to 80 degrees.

Next, the process of forming a gate line formed of a double layer of aluminum alloy and molybdenum by applying the etchant of the present invention will be described.

The gate line forming process may include preparing a substrate, forming an aluminum alloy layer on the substrate, forming a molybdenum layer on the aluminum alloy layer, and applying the etchant to a double layer of aluminum and molybdenum to etch the same. And cleaning the substrate on which the gate line is formed.

 A process of forming a gate line using the etchant will be described in detail with reference to FIG. 5.

As shown in Fig. 5A, an aluminum alloy layer 502 and a molybdenum layer 503 are successively deposited on the transparent substrate 501 by the sputtering method, and the aluminum alloy has excellent electrical conductivity and a low cost gate. However, the aluminum alloy may be formed of the aluminum oxide layer 503 as described above due to a problem in that the pixel electrode material and the ohmic contact property are not good in the pad portion to which the gate signal is applied. It is further formed on the alloy layer 502. Molybdenum has good ohmic contact properties with the pixel electrode material.

Next, as shown in FIG. 5B, a photosensitive film 504 is formed on the molybdenum layer 503. The photoresist film 504 is a polymer whose chemical composition is changed by irradiated light, and thus, a polymer capable of producing a predetermined pattern is a positive type in which a region to which light is irradiated is removed and a negative type in which a region to which light is irradiated remains. There is this.

The negative type or positive type photosensitive film can be selected and used in some cases, and the present embodiment exemplifies the positive type.

After the photosensitive film 504 is applied, an exposure process is performed by applying a mask 505 including a gate line and a gate electrode pattern as shown in FIG. 5B. As a result of the exposure process, the chemical structure is changed in a form that can be removed in the development process to the area irradiated with light.

After the exposure process is performed, the development process is performed by passing the substrate through a bath in which a developer is stored. As a result of the developing process, the photoresist film remains on the molybdenum layer 503 in a predetermined pattern.

Next, as shown in Figure 5c, by applying the patterned photosensitive film 504a as a mask to pass the substrate into the bath containing the etchant of the present invention by passing the bilayer of molybdenum and aluminum in one wet etching Form a pattern.

In the conventional method, two etching processes, wet etching and dry etching, have to be performed to etch the aluminum alloy and molybdenum layers. However, when the etchant of the present invention is used, the double layer of molybdenum and aluminum alloy is effectively patterned with one wet etching. Ning can.

Next, a cleaning process is performed to remove foreign matter remaining in the patterned gate line to form the gate line 506.

Although not shown in FIG. 5, after the gate line is formed, a process of forming a gate insulating film, forming a semiconductor layer composed of an amorphous silicon layer and a high concentration n-doped layer, and forming a source, a drain electrode, and a data line on the semiconductor layer The TFT array substrate may be formed by performing a TFT forming process including a process, a process of forming a protective film, and a process of forming a pixel electrode.

In particular, when the source, drain and data lines are made of the same material as the metal wiring, the etchant may be applied to the process of forming the source and drain electrodes.

As described above, aluminum alloy and molybdenum are applied by applying an etchant including nitric acid (HNO ₃ ), iron nitrate (Fe (NO ₃ ) ₃ ), perchloric acid (HClO ₄ ), and ammonium fluoride (NH ₄ F). By effectively removing the metal line consisting of the double layer of through a single wet etching, the process can be shortened to increase the yield. In forming the gate line composed of the double layer of aluminum alloy and molybdenum, the tapered shape having a smooth inclination angle The gate line can be formed to improve the occurrence of disconnection when the film is formed on the gate line. The present invention also prevents the plasma ions from colliding with the thin film to perform the etching on the substrate. It can be etched effectively without leaving an etch mark on it.

Claims (10)

Weight ratio of 7-12 wt% nitric acid (HNO ₃ ), 2-4 wt% iron nitrate (Fe (NO ₃ ) ₃ ), 1-4 wt% perchloric acid (HClO ₄ ), 0.1-2.0 wt% ammonium fluoride ( Etchant comprising NH ₄ F). delete The weight ratio of the nitric acid (HNO ₃ ), iron nitrate (Fe (NO ₃ ) ₃ ), perchloric acid (HClO ₄ ), ammonium fluoride (NH ₄ F) is 10wt%, 3wt%, 3wt% Etchant, characterized in that 0.4wt%. The method of claim 1, wherein the perchloric acid (HClO ₄₎ instead of the sulfuric acid (H ₂ SO _4), hypochlorous acid (HClO), hypochlorite etchant comprises a (HCl _2), or acid (HCl0 ₃₎ . Forming a metal layer in which aluminum and molybdenum are laminated on the substrate; The metal layer was composed of 7-12 wt% of nitric acid (HNO ₃ ), 2-4 wt% of iron nitrate (Fe (NO ₃ ) ₃ ), 1-4 wt% of perchloric acid (HClO ₄ ), and 0.1-2.0 wt% of And etching by applying an etchant comprising ammonium fluoride (NH ₄ F). The method of claim 5, wherein forming the metal layer comprises: forming an aluminum alloy; Forming a molybdenum layer on the aluminum alloy layer. The method of claim 5, further comprising: forming a photoresist film on the metal layer; Exposing on the photosensitive film; And developing the photosensitive film. Forming a metal layer in which aluminum and molybdenum are laminated on the substrate; The metal layer was composed of 7-12 wt% of nitric acid (HNO ₃ ), 2-4 wt% of iron nitrate (Fe (NO ₃ ) ₃ ), 1-4 wt% of perchloric acid (HClO ₄ ), and 0.1-2.0 wt% of Forming a gate electrode by applying an etchant containing ammonium fluoride (NH ₄ F) Forming a gate insulating layer on the gate line; Forming a semiconductor layer on the gate insulating layer; Forming a source and a drain electrode on the semiconductor layer; And forming a pixel electrode on the source and drain electrodes. The etchant of claim 8, wherein the source and drain electrode forming steps include nitric acid (HNO ₃ ), iron nitrate (Fe (NO ₃ ) ₃ ), perchloric acid (HClO ₄ ), and ammonium fluoride (NH ₄ F). Liquid crystal display device manufacturing method characterized in that made by applying. Forming a metal layer on the substrate; Etching the metal layer to form a gate electrode; Forming a gate insulating layer on the gate line; Forming a semiconductor layer on the gate insulating layer; On the semiconductor layer, a weight ratio of 7-12 wt% nitric acid (HNO ₃ ), 2-4 wt% iron nitride (Fe (NO ₃ ) ₃ ), 1-4 wt% perchloric acid (HClO ₄ ), 0.1-2.0 wt% Applying an etchant comprising phosphorus ammonium fluoride (NH ₄ F) to form a source, drain electrode; And forming a pixel electrode on the source and drain electrodes.

Images