JP2000002886A - Manufacture of liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To decrease steps of a photomechanical process in manufacture of a liquid crystal display, to improve throughput and to reduce a manufacturing cost. SOLUTION: In the manufacturing process, a protective film 12 is formed with a transparent insulating film such as silicon nitride, silicon oxide or the like on a substrate on which thin film transistors are formed, and besides, an alignment film 13 composed of polyimide or the like is formed by a method such as screen printing or transferring in a region other than terminal parts. Succeedingly, using the alignment film 13 as a mask, the protective film 12 on terminal parts is wet-etched by using liquid chemicals such as hydrofluoric acid or the like. Subsequently rubbing is done as it is, and the substrate is stuck with a counter substrate and the liquid crystal display is manufactured with filling of liquid crystal. Following this method, steps of the photomechanical process such as resist coating, exposure, developing or the like conventionally conducted for protective film forming and a resist-stripping step can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an active matrix type liquid crystal display device.

[0002]

2. Description of the Related Art FIG. 6 is a diagram showing a process flow from the formation of a protective film to the rubbing of a conventional liquid crystal display device. In a conventional active matrix type liquid crystal display device, a protective film is formed on the outermost surface of a thin film transistor integrated device (hereinafter, referred to as a thin film transistor array) substrate by a photolithography process using a resist, and then the pixels of the thin film transistor array substrate are formed. An alignment film made of an organic material such as polyimide is formed on the portion thus formed by screen printing or the like, and the liquid crystal molecules are aligned by rubbing with a cloth such as cotton, rayon, polyester, or nylon.

[0003]

In the production of the liquid crystal display device as described above, improvement of the throughput is an important problem for reducing the production cost. In particular, in the manufacture of a thin film transistor array substrate, usually 5 to 8 photoengraving steps are performed. Reducing the number of photoengraving steps greatly contributes to an improvement in throughput.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has been made to reduce the number of photoengraving steps in the production of a liquid crystal display device, improve the throughput,
The purpose is to reduce the manufacturing cost.

[0005]

According to the present invention, there is provided a method of manufacturing a liquid crystal display device, comprising: a switching element including a thin film transistor; a thin film transistor array substrate having a display element controlled via the switching element;
A method of manufacturing a liquid crystal display device including a counter substrate that sandwiches liquid crystal between the thin film transistor array substrate and
A step of forming a protective film made of a transparent insulating film on the substrate on which the thin film transistor is formed, and screen-printing or transferring an alignment film made of polyimide or the like to a region excluding terminals provided on the periphery of the substrate; And a step of etching the protective film on the terminal portion using the alignment film as a mask.

The etching of the protective film is performed by wet etching using a chemical solution containing hydrofluoric acid or hot phosphoric acid as a main component. The etching of the protective film is performed by dry etching. Further, the orientation film is formed in advance to have a thickness that is reduced by dry etching.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a plan view showing the structure of one pixel of a thin film transistor array substrate manufactured in Embodiment 1 of the present invention, and FIG. 2 is a cross-sectional view showing a method for manufacturing the thin film transistor array substrate in this embodiment. 1 shows a cross-sectional structure of a part indicated by AA and a mounting terminal part. In the figure, 1 is a glass substrate which is a transparent insulating substrate, 2 is a gate electrode and a gate wiring formed on the glass substrate 1, 3 is a common wiring provided on the gate electrode 2 via a gate insulating film 4. A semiconductor layer comprising an amorphous silicon film (hereinafter referred to as an a-Si film) 5 and an amorphous silicon film (hereinafter referred to as an n ⁺ -a-Si film) 6 doped with impurities such as phosphorus;
The thin film transistor 14 is composed of the source electrode 9 and the drain electrode 10 connected to the semiconductor layer.
Reference numeral 7 denotes a pixel electrode made of a transparent conductive film such as ITO connected to the drain electrode 10 of the thin film transistor 14;
Is a terminal electrode, 11 is a contact hole, 12 is a protective film made of a transparent insulating film such as silicon nitride, silicon oxide, or the like.
Reference numeral 3 denotes an alignment film made of polyimide or the like. The liquid crystal display device manufactured in the present embodiment has a structure in which a thin film transistor array substrate having a switching element including a thin film transistor 14 and a pixel electrode 7 which is a display element controlled via the switching element, and the thin film transistor array substrate And a counter substrate (not shown) sandwiching liquid crystal.

A method for manufacturing a thin film transistor array substrate according to the present embodiment will be described with reference to FIG. First, a gate electrode and a gate wiring 2 and a common wiring 3 are formed on a glass substrate 1.
To Cr, Al, Mo, Ta, Cu, Al-Cu, Al
-A transparent material such as Si-Cu, Ti, W alone or an alloy thereof, or ITO or the like is formed in a single layer or a laminated structure with a thickness of about 0.03 μm to 0.6 μm (see FIG. )). The gate electrode and the gate wiring 2
In the present embodiment, as an etching method for forming the common wiring 3, taper etching with a trapezoidal cross section has been described as an example, but an etching method with a rectangular cross section may be used. Next, the gate insulating film 4, a-Si
The film 5, n ⁺ -a-Si film 6 sequentially deposited, after photolithography, etching the a-Si film 5 and the n ⁺ -a-Si film 6 is patterned into an island shape (FIG. 2 ( b)). The gate insulating film 4 is formed of a single layer or a stacked structure of silicon nitride, silicon oxide, an oxide film of a gate electrode material, or the like. Also, as a material instead of the n ⁺ -a-Si film 6 doped with an impurity such as phosphorus, microcrystal silicon or the like doped with an impurity such as phosphorus may be used.

Next, a pixel electrode 7 and a terminal electrode 8 are formed using a transparent conductive film such as ITO (FIG. 2C). next,
After forming the contact holes 11 in the terminal portions, the source electrode, the source wiring 9, and the drain electrode 10 are simultaneously formed, and then the n ⁺ -a-Si film 6 in the channel portion is removed (FIG. 2D). The source electrode and the source wiring 9 and the drain electrode 10 are made of Cr, Al, Mo, Ta, Cu, Al-Cu,
A single layer or a laminated structure of a transparent material such as Al—Si—Cu, Ti, W alone or an alloy thereof, or ITO is formed. Next, a protective film 12 made of a transparent insulating film such as silicon nitride or silicon oxide is formed, and an alignment film 13 such as polyimide is screen-printed or transferred to a region other than a terminal portion provided on a peripheral portion of the substrate. (FIG. 2 (e)). Note that the alignment film 13 may be formed by using a photosensitive organic material and exposing and developing the terminals in a lump using a large-sized exposure device or the like.

Next, using the alignment film 13 as a mask, the protection film 12 on the terminal portion is etched by wet etching using a chemical solution containing hydrofluoric acid or hot phosphoric acid as a main component (FIG. 2 ( f)). The etchant used at this time is a chemical that does not etch ITO. In this embodiment, the etching of the protective film 12 is performed by wet etching. However, SF ₆ , CF ₄ ,
Dry etching using a gas mainly containing CCl ₄ , HF, CHF ₃ or the like may be used. In that case, while selecting a gas which is hard to etch the alignment film 13,
The alignment film 13 is formed in advance to have a thickness that is reduced by dry etching. Next, rubbing is performed as it is, bonded to a counter substrate, and liquid crystal is injected to manufacture a liquid crystal display device.

FIG. 3 is a diagram showing a process flow from formation of a protective film to rubbing of the liquid crystal display device in the present embodiment. According to the present embodiment, the processes indicated by oblique lines in FIG. 6, that is, photolithography processes such as resist coating, exposure and development, and resist removal processes are reduced in comparison with the conventional flow shown in FIG. As a result, the production throughput of the liquid crystal display device is improved, and the production cost is reduced.

Embodiment 2 FIG. In the first embodiment, an example in which the present invention is applied to a twisted nematic liquid crystal display device in which an electric field is formed in the vertical direction with respect to the substrate direction has been described. An example in which the present invention is applied to a liquid crystal display device of a type in which an electric field is formed in a lateral direction, which is characterized by having a wide width, will be described. FIG. 4 is a plan view showing a structure of one pixel of a thin film transistor array substrate manufactured in Embodiment 2 of the present invention, and FIG. 5 is a cross-sectional view showing a method of manufacturing the thin film transistor array substrate in this embodiment. 4 shows a cross-sectional structure of a portion indicated by AA and a mounting terminal portion. In the figure, reference numeral 15 denotes a counter electrode.
The liquid crystal is driven by generating an electric field between them. In the drawings, the same or corresponding parts have the same reference characters allotted, and description thereof will not be repeated.

A method for manufacturing a thin film transistor array substrate according to the present embodiment will be described with reference to FIG. First, a gate electrode and a gate wiring 2 and a common wiring 3 are formed on a glass substrate 1.
And the counter electrode 15 is made of Cr, Al, Mo, Ta, Cu,
Al-Cu, Al-Si-Cu, Ti, W alone or an alloy thereof, or a transparent material such as ITO in a single layer or a laminated structure, and has a thickness of 0.03 μm to 0.6 μm.
m (FIG. 5A). As an etching method for forming the gate electrode and the gate wiring 2, the common wiring 3, and the counter electrode 15, in this embodiment, taper etching having a trapezoidal cross section has been described as an example.
An etching method with a rectangular cross section may be used. Next, the gate insulating film 4, the a-Si film 5, and n ⁺ -a-
After continuously depositing a Si film 6 and performing photolithography, a-Si
The film 5 and the n ⁺ -a-Si film 6 are etched and patterned into an island shape (FIG. 5B). As a material of the gate insulating film 4, a single layer or a stacked structure of silicon nitride, silicon oxide, an oxide film of a gate electrode material, or the like is formed. Further, n ⁺ -a-Si doped with impurities such as phosphorus
As a material instead of the film 6, microcrystal silicon or the like doped with an impurity such as phosphorus may be used.

Next, after a contact hole 11 of a terminal portion is formed, a source electrode and a source wiring 9 and a drain electrode 1 are formed.
0, the pixel electrode 7 is formed at the same time, and then the n ⁺ -a-Si film 6 in the channel portion is removed (FIG. 5C.) The source electrode and source wiring 9, the drain electrode 10, the pixel electrode 7
Are Cr, Al, Mo, Ta, Cu, Al-Cu, Al
-Si- Cu, Ti, W alone or an alloy thereof, or a transparent material such as ITO is formed in a single layer or a laminated structure. Next, a protective film 12 made of a transparent insulating film such as silicon nitride or silicon oxide is formed, and an orientation film 13 made of polyimide or the like is screen-printed or transferred to a region other than a terminal portion provided on a peripheral portion of the substrate. (FIG. 5D). Note that the alignment film 13 may be formed by using a photosensitive organic material and exposing and developing the terminals in a lump using a large-sized exposure device or the like.

Next, using the alignment film 13 as a mask, the protection film 12 on the terminal portion is etched by wet etching using a chemical solution containing hydrofluoric acid or hot phosphoric acid as a main component (FIG. 5 ( e)). Note that in this case, it is necessary to select a material that is not easily etched by an etchant as a material used for the terminal. Further, in the present embodiment, the etching of the protective film 12 is performed by wet etching. However, SF ₆ , CF ₄ , CCl ₄ , HF, C
Dry etching using a gas mainly containing HF ₃ or the like may be used. At this time, a gas that is difficult to etch the alignment film 13 is selected, and the thickness of the alignment film 13 that is reduced by dry etching is formed in advance. In this case, any metal material or ITO can be used for the terminal material. Next, rubbing is performed as it is, bonded to a counter substrate, and liquid crystal is injected to manufacture a liquid crystal display device.

In this embodiment, the terminal electrode 8 is formed using the same layer as the source electrode and the source wiring 9. However, the same layer as the gate electrode and the gate wiring 2 may be used. As in the terminal section of mode 1, I
TO or the like may be formed completely separately. According to the present embodiment, as in the first embodiment, the process flow from the formation of the protective film to the rubbing as shown in FIG. 3 is achieved, and the improvement of the manufacturing throughput and the reduction of the manufacturing cost are achieved.

[0017]

As described above, according to the present invention, the protective film on the terminal portion is etched by using the alignment film as a mask. The photolithography process such as exposure and development and the resist removal process can be reduced, the throughput of manufacturing the liquid crystal display device is improved, and the manufacturing cost is reduced.

[Brief description of the drawings]

FIG. 1 is a plan view showing one pixel of a thin film transistor array substrate included in a twisted nematic liquid crystal display device according to Embodiment 1 of the present invention.

FIG. 2 is a cross-sectional view illustrating the method for manufacturing the thin film transistor array substrate according to the first embodiment of the present invention.

FIG. 3 is a diagram showing a process flow from formation of a protective film to rubbing of the liquid crystal display device in Embodiments 1 and 2 of the present invention.

FIG. 4 is a plan view showing one pixel of a thin film transistor array substrate included in a liquid crystal display device of an in-plane switching mode according to a second embodiment of the present invention.

FIG. 5 is a cross-sectional view showing a method for manufacturing a thin film transistor array substrate according to Embodiment 2 of the present invention.

FIG. 6 is a view showing a process flow from formation of a protective film to rubbing of a conventional liquid crystal display device.

[Explanation of symbols]

1 glass substrate, 2 gate electrode and gate wiring, 3
Common wiring, 4 gate insulating film, 5 a-Si film, 6 n
⁺ -A-Si film, 7 pixel electrode, 8 terminal electrode, 9 source electrode and source wiring, 10 drain electrode, 11
Contact hole, 12 protective film, 13 alignment film, 14
Thin film transistor, 15 Counter electrode.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H090 HA03 HB08Y HC06 HC12 HD05 LA04 2H092 JA36 JA39 JA40 JA44 JB14 KA05 KA10 KA12 KA18 KB04 KB24 MA10 MA18 MA19 MA37 MA41 NA25 NA27 PA02 4J043 ZB23 4K057 DA20 DB11 DE08 DE02 DE06 WE07 WN01

Claims (4)

[Claims] 1. A liquid crystal display device comprising a thin film transistor array substrate having a switching element including a thin film transistor, a display element controlled via the switching element, and a counter substrate sandwiching liquid crystal between the thin film transistor array substrate. A method of forming a protective film made of a transparent insulating film on a substrate on which the thin film transistor is formed, and an alignment film made of polyimide or the like in a region excluding a terminal portion provided in a peripheral portion of the substrate. Forming a liquid crystal display device by a method such as screen printing or transfer, and a step of etching the protective film on the terminal portion using the alignment film as a mask. 2. The method according to claim 1, wherein the etching of the protective film is performed by wet etching using a chemical solution containing hydrofluoric acid or hot phosphoric acid as a main component. 3. The method according to claim 1, wherein the etching of the protective film is performed by dry etching. 4. The method for manufacturing a liquid crystal display device according to claim 3, wherein the alignment film is formed in advance so as to have a thickness reduced by dry etching.