JP3076704B2 - Liquid crystal display device and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device characterized by the structure of an extraction electrode of the liquid crystal display device, and a method of manufacturing the same.

[0002]

2. Description of the Related Art A conventional liquid crystal display device in which thin film transistors (TFTs) and pixel electrodes are arranged in an array to drive liquid crystals in a dot matrix will be described. FIG. 5 is a plan view showing the configuration of the mounting electrode portion of the liquid crystal display device. The extraction electrode 1a is a TA connected to the gate electrode 1 of the TFT.
It is an electrode for B film connection.

A method for manufacturing a liquid crystal display device including such an extraction electrode 1a and a TFT will be described. FIG. 6 is a process chart showing a method for manufacturing the extraction electrode 1a.

As shown in FIG. 6A, as a first step, an undercoat film 3 of, for example, SiO ₂ or TaOx (x is an integer) is formed on the entire surface of a glass substrate 2 as an insulating transparent substrate. I do. Next, as a second step, an Al film or an Al alloy film is pattern-formed as a first metal film at a position to be the extraction electrode 1a.

As a third step, a gate insulating film 4 of, for example, SiNx (x is an integer) is formed on the entire surface. Then, a TFT is formed in a portion (not shown) as a fourth step. That is, a silicon semiconductor layer and an interlayer insulating film for channel protection are formed, and the channel protection film on the gate electrode is patterned. Next, after forming an n ⁺ silicon film as a fifth step, the n ⁺ silicon film and the silicon semiconductor layer are patterned. As a sixth step, as a pixel electrode, for example, IT
A transparent conductive film of O is formed and patterned. Then, as a seventh step, a second metal film serving as a source / drain electrode is patterned.

Next, as an eighth step, as shown in FIG. 6B, a SiNx film is formed as an insulating protective film 5. Thus, a two-layer SiNx film is formed as a gate insulating film 4 and an insulating protective film 5 on the extraction electrode 1a. In addition, TFT
A similar insulating protective film 5 is also formed on the extraction electrode on the source side.

Finally, as a ninth step, a resist 6 is applied on the insulating protective film 5 to form a pattern. At this time, as shown in FIG. 6C, portions of the gate insulating film 4 and the insulating protective film 5 other than those protected by the resist 6 are removed by dry etching of SF ₆ gas. By doing so, the extraction electrode 1a is exposed.

[0008]

In order to form a mounting electrode in the pattern formation in the ninth step, as a first method, a plurality of extraction electrodes 1a are collectively collected, and a gate insulating film 4 and an insulating protection film are formed over a wide range. There is a method of opening the film 5.
As a second method, there is a method of partially opening the gate insulating film 4 and the insulating protective film 5 for each extraction electrode 1a.

The first method can be performed by simple mask alignment.
Since most of the SiNx film around the extraction electrode 1a is removed by etching, the cross-sectional structure of the processed extraction electrode 1a becomes convex. 5 indicates an opening 7 of the insulating protection film (BP) 5. TA is applied to the extraction electrode 1a of the opening 7.
The B film 8 is connected by, for example, thermocompression bonding. When the thus manufactured liquid crystal display device is subjected to a reliability test (wet and wet test) under high temperature and high humidity, Al disappearance is observed at the exposed portions of the extraction electrode 1a indicated by arrows A and B. FIG.
(D) is a cross-sectional view of the extraction electrode 1a subjected to a wet test.
In the portion indicated by C in this drawing, a considerable amount of Al in the extraction electrode 1a has disappeared.

On the other hand, FIG. 7 is a plan view showing the result of a humidity test of the extraction electrode 1a formed by the second method. In this method, an opening 9 is formed in the SiNx on the extraction electrode 1a by opening a window. Therefore, the sectional structure of the extraction electrode 1a is concave. The TAB film 8 is connected through the opening 9. In this case, since the periphery of the extraction electrode 1a is covered with the insulating protective film 5, there is a disadvantage that a fine mask alignment must be performed. However, as a result of performing a test in moisture on the extraction electrode 1a, it was found that the disappearance of Al subsided at the exposed portion of Al, and Al under the insulating protective film 5 remained. Therefore, complete disconnection of the extraction electrode 1 does not occur.

The present invention has been made in view of such a conventional problem. Even when the extraction electrode is left in a high-temperature and high-humidity environment, the loss of the metal film at the junction with the TAB film is prevented. It is a first object of the present invention to provide a liquid crystal display device that does not cause the problem and that simplifies mask alignment of an extraction electrode portion and that has improved reliability of a mounting electrode, and further realizes a method of manufacturing the liquid crystal display device. This is a second object.

[0012]

According to the first aspect of the present invention, there is provided a thin film transistor arranged in an array on an insulating transparent substrate, a liquid crystal cell driven by the thin film transistor, and a gate for inputting a driving signal of the thin film transistor. A liquid crystal display device comprising: an electrode connected to an external circuit to supply a drive signal to a gate electrode of the thin film transistor; and an extraction electrode formed of A1 or an Al alloy. A water-resistant transparent conductive film formed via a gate insulating film is provided.

According to the invention of claim 2 of the present application, there is provided a step of forming an undercoat film of SiO ₂ or TaOx (x is an integer) on an insulating transparent substrate; Forming a first metal film to be an extraction electrode, and forming a gate insulating film of SiNx (x is an integer) on the upper surface of the gate electrode and the extraction electrode, and on the upper surface of the undercoat film on which the gate electrode and the extraction electrode are not mounted. Forming, forming a silicon semiconductor layer and a channel protective layer on the upper surface of the gate insulating film formed on the gate electrode, and patterning; forming a pixel electrode on the gate insulating film; A step of forming a transparent conductive film on the gate insulating film formed on the electrode and patterning the conductive film, and a step of forming a source / drain on at least the upper surface of the channel protective layer and the pixel electrode. A step of forming a second metal film to be an in-electrode and performing patterning; a step of forming an insulating protective film on at least the uppermost surfaces of the source / drain electrodes and the extraction electrode; Patterning the insulating protective film and leaving the transparent conductive film and the gate insulating film integrally on the outer peripheral portion of the extraction electrode.

[0014]

According to the first aspect of the present invention having such a feature, the metal film portion of the extraction electrode is connected to an external circuit and receives a driving signal of the thin film transistor. The outer periphery of the metal film is formed of a water-resistant gate insulating film and a transparent conductive film. Therefore, even if the liquid crystal display device is under high humidity, the metal film of the extraction electrode is protected by the transparent conductive film and the gate insulating film, and corrosion does not occur over the entire surface.

According to the invention of claim 2 of the present application, in the first step of the liquid crystal display device, the Si is placed on the insulating transparent substrate.
An undercoat film of O ₂ or TaOx is formed. Next, a first metal film partly serving as an extraction electrode is formed on the undercoat film. Then, a gate insulating film of SiNx is formed on the undercoat film and the first metal film. Further, a transparent conductive film is formed on the extraction electrode at a position to be a gate insulating film and a pixel electrode. Further, a Si semiconductor layer and a channel protection layer are formed at a position where a thin film transistor to be connected to the extraction electrode is formed. In the last step, patterning is performed so that the transparent conductive film and the gate insulating film remain integrally on the outer peripheral portion of the extraction electrode. When the TAB film is thermocompression-bonded to the extraction electrode, even if moisture penetrates into the first metal film in contact with the TAB film, the corroded area does not progress to the outer peripheral portion of the extraction electrode. For this reason, a connection excellent in moisture resistance can be obtained.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A liquid crystal display device and a method of manufacturing the same according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view showing the entire configuration of the liquid crystal display device of the present embodiment. FIGS. 2 and 3 are explanatory views of the manufacturing process of the liquid crystal display device centering on the extraction electrodes of the present embodiment. FIG. 4 is a plan view showing the configuration of the extraction electrode portion of this embodiment. The same parts as those in the conventional example are denoted by the same reference numerals, and description thereof will be omitted.

First, as shown in FIG. 1 and FIG.
As a step, an undercoat film 3 of SiO ₂ or TaOx (x is an integer) is formed on the entire surface of a glass substrate 2 as an insulating transparent substrate. As a second step, an Al film or an Al alloy film is formed as a first metal film on the undercoat film 3, and the gate electrode 1 and its extraction electrode 1a are formed by patterning.

Next, as shown in FIG. 2A, as a third step, a gate insulating film 4 is formed on the entire surface as in the conventional example.
Then, as shown in the TFT portion of FIG. 1, a silicon semiconductor layer 10 and an interlayer insulating film for a channel protective film are formed on the gate electrode 1. In the fourth step, the channel protective film 11 on the gate electrode 1 is patterned. Further, an n ⁺ silicon film is formed as a fifth step, and the n ⁺ silicon film and the silicon semiconductor layer 10 are patterned for forming a TFT in a later step.

Next, as shown in FIG. 1 and the pixel electrode portion of FIG. 2 and FIG. 2B, the gate insulating film 4 on the position to become the pixel electrode 12 and the lead electrode 1a which is led out as a sixth step. An ITO transparent conductive film 12a is formed thereon.
Then, as shown in FIG. 2C and FIG.
Patterning is performed so that 2a remains on the outer peripheral portion of the extraction electrode 1a. At this time, the transparent conductive film 12a of the pixel electrode portion shown in FIG. 1 is simultaneously patterned to form the pixel electrode 12.

As a seventh step, as shown in the TFT section and the pixel electrode section in FIG. 1, Ti and Al are pattern-formed as the second metal film 13 to be the source / drain electrodes of the TFT. Further, as shown in FIG. 3D, an SiNx is formed as an insulating protective film 5 as an eighth step. As a result, the transparent conductive film 12a is formed on the outer peripheral portion of the extraction electrode 1a via the gate insulating film 4, and the insulating protective film 5 is further formed thereon. In the center of the extraction electrode 1a, Si
An Nx gate insulating film 4 and an insulating protective film 5 are formed.

Finally, as a ninth step, a resist 6 is formed on a specific portion of the insulating protective film 5. Then, dry etching is performed using the resist 6 as a mask to pattern-form the insulating protective film 5 and the gate insulating film 4. That is, as shown in FIG. 4, an opening 7 is provided in a portion where a plurality of extraction electrodes 1a are adjacent. As a result, as shown in FIG. 3E, the insulating protective film 5 and the gate insulating film 4 formed at the center and the periphery of the extraction electrode 1a are respectively removed. As a result, the extraction electrode 1a
, The frame-shaped transparent conductive film 1 via the gate insulating film 4
2a is exposed, and the cross-sectional shape of the extraction electrode 1a becomes concave.

In order to evaluate the extraction electrode 1a formed as described above, a high-temperature and high-humidity humidity test was performed. As a result, the cross-sectional shape of the extraction electrode 1a along the line XX changed as shown in FIG. 3 (f), and the disappearance of Al in the extraction electrode 1a resulted in calming only in the central portion, and Al in the outer peripheral portion remained.

As shown in FIG. 4, a TAB film 8 was attached to the extraction electrode 1a obtained in this example by thermocompression bonding, and a wet test was performed. In this case, as shown by the hatched portion in FIG. 4, it was found that the frame-shaped transparent conductive film 12a plays a role of a protective film and serves as a stopper for elimination of Al. Therefore, disconnection of the extraction electrode 1a does not occur, and the opening 7 is formed using a simple mask.
Can be easily joined.

In the present embodiment, the shape of the transparent conductive film 12a to be left in the extraction electrode portion is frame-shaped, but may be L-shaped or U-shaped, and the effect can be achieved. In forming the source / drain metal film, a gate insulating film was provided as an underlayer.
Any interlayer insulating film may be used as long as it is the same SiNx film as the insulating protective film.

[0025]

As described above, according to the first aspect of the present invention, the gate insulating film and the transparent conductive film having excellent moisture resistance are arranged around the gate extraction electrode. Therefore, the metal film is less likely to be corroded in moisture, and even if the liquid crystal display device is used for a long time by being connected to an external circuit via the TAB film, disconnection of the extraction electrode is eliminated.

According to the invention of claim 2 of the present application, since the process of forming the extraction electrode and the process of manufacturing the thin film transistor for driving the liquid crystal cell are common, only a part of the conventional manufacturing process of the thin film transistor is changed. Thus, an extraction electrode having excellent moisture resistance can be manufactured. In addition, the mask alignment of the extraction electrode portion is simplified, and the effect of simplifying the manufacturing process of the liquid crystal display device is obtained.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating an overall configuration of a liquid crystal display device according to an embodiment of the present invention.

FIG. 2 is a process chart (1) showing a method for manufacturing a liquid crystal display device centering on an extraction electrode according to an embodiment of the present invention.

FIG. 3 is a process diagram (part 2) illustrating the method for manufacturing the liquid crystal display device centering on the extraction electrode in the present embodiment.

FIG. 4 is a plan view showing an extraction electrode portion of the liquid crystal display device of the present embodiment.

FIG. 5 is a process chart showing a conventional method for manufacturing a liquid crystal display device centering on an extraction electrode.

FIG. 6 is a plan view showing a lead electrode portion of a liquid crystal display device of a conventional example (part 1).

FIG. 7 is a plan view showing an extraction electrode portion of a liquid crystal display device of a conventional example (part 2).

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Gate electrode 1a Leader electrode 2 Glass substrate 3 Undercoat film 4 Gate insulating film 5 Insulating protective film 6 Resist 7,9 Opening 8 TAB film 10 Silicon semiconductor layer 11 Channel protective film 12 Pixel electrode 12a Transparent conductive film 13 Second Metal film

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-3-64737 (JP, A) JP-A-1-281432 (JP, A) JP-A-62-125330 (JP, A) (58) Investigation Field (Int.Cl. ⁷ , DB name) G02F 1/1368 G02F 1/1343 G02F 1/1345

Claims (2)

(57) [Claims] 1. A thin film transistor arranged in an array on an insulating transparent substrate, a liquid crystal cell driven by the thin film transistor, a gate electrode for inputting a driving signal of the thin film transistor, and the thin film transistor connected to an external circuit. A drive signal to the gate electrode of the thin film transistor, and an extraction electrode formed of Al or an Al alloy. A water-resistant display formed on the outer periphery of the extraction electrode via a gate insulating film of the thin film transistor. A liquid crystal display device provided with a transparent conductive film having a characteristic. 2. An insulating transparent substrate comprising SiO ₂ or TaO
forming an undercoat film of x (x is an integer); forming a first metal film partially serving as a gate electrode and an extraction electrode on an upper surface of the undercoat film; Forming a gate insulating film of SiNx (x is an integer) on the upper surface of the extraction electrode and the upper surface of the undercoat film on which the gate electrode and the extraction electrode are not mounted; and the gate formed on the gate electrode. A step of forming a silicon semiconductor layer and a channel protective layer on the upper surface of the insulating film and performing patterning; and a position to be a pixel electrode on the gate insulating film, and on the gate insulating film formed on the extraction electrode. Forming a transparent conductive film and patterning each of the transparent conductive films, and forming a source / drain electrode on at least the upper surface of the channel protective layer and the pixel electrode. Forming a metal film, and patterning at least an uppermost surface of the source / drain electrode and the extraction electrode; and forming an insulating protection film on the extraction electrode. Performing a patterning of a protective film, and leaving the transparent conductive film and the gate insulating film integrally on an outer peripheral portion of the extraction electrode.