JP2544367B2 - Thin film transistor liquid crystal display - Google Patents

Description

The present invention relates to an active matrix type thin film transistor (TFT) liquid crystal display device.

[Conventional technology]

In the TFT liquid crystal display device, a plurality of minute pixel electrodes are arranged in a matrix and each pixel electrode is switched by a TFT formed of a MOS transistor provided corresponding to each pixel electrode. Therefore, as shown in the circuit configuration of FIG.
Of the gate electrode G as a gate line G, and one of the source / drain electrodes as a source / drain line SD extending in orthogonal directions, and these are used as control lines for vertical scanning and horizontal scanning. In the figure, LVS is a vertical scanning circuit and LHS is a horizontal scanning circuit.

A liquid crystal display device of this type is disclosed in
58-199323.

[Problems to be solved by the invention]

In such a TFT liquid crystal display device, when one of the source / drain electrodes connected to the source / drain line is short-circuited with the gate electrode, the signal of the source / drain line flows into the gate electrode through the source / drain electrode. Become. Therefore, not only an image defect occurs in the pixel portion where the gate electrode and the source / drain electrode are short-circuited, but also all the pixel portions in the horizontal direction connected to this gate line become image defects, and linear image defects occur in the entire display. There is a problem.

Therefore, in this liquid crystal display device, a defect in only one pixel becomes a linear defect and causes the entire display device to be defective, resulting in a significant decrease in the manufacturing yield of products.

It is an object of the present invention to provide a TFT liquid crystal display device in which generation of linear image defects is prevented and the product yield is improved even when a gate electrode and a source / drain electrode are short-circuited.

[Means for solving problems]

The liquid crystal display device of the present invention is configured such that a source / drain electrode and a source / drain line are electrically separated from each other, and
A source / drain electrode and a source / drain line are capacitively coupled via a capacitor electrode formed near T.

[Action]

In this TFT liquid crystal display device, since the source / drain electrodes and the source / drain lines are capacitively coupled, in normal AC driving, both are electrically connected to enable normal operation, while the gate electrode and Even when the source and drain electrodes are short-circuited, it is possible to prevent signal leakage to the gate electrodes of other pixels, prevent linear image defects, and improve product yield.

〔Example〕

 The present invention will be described below with reference to embodiments shown in the drawings.

FIG. 1 is a partial plan view of an embodiment of the present invention, and FIG. 2 is an enlarged sectional view taken along the line AA of FIG.

As shown in the figure, after a chromium film is sputtered on the glass substrate 1 for 1000 Å, the gate electrode 2 and the gate line 3 integrally with the gate electrode 2 are formed into a required pattern by photolithography. At this time, the capacitor electrode 4 is simultaneously formed in a position adjacent to the gate electrode. Insulating film 5 on this
Then, a silicon nitride film is formed by the 3000Å CVD method.

An amorphous silicon thin film is formed on this as a semiconductor thin film layer by the CVD method to a thickness of 3000 Å. Then, a resist island pattern is formed by photolithography, and then an amorphous silicon layer and a semiconductor thin film layer 6 that is an island pattern are formed by dry etching.

Chromium film is sputtered on this 600 Å, aluminum film is sputtered 3,000 Å, and then source / drain electrodes 7 and 8 are formed in the required pattern by photolithography, and at the same time separated from these source / drain electrodes. Then, the source / drain lines 9 are patterned.

In this case, the source / drain electrodes 8 and the source / drain lines 9 are 5 μ in the lateral direction with the capacitor electrodes 4 respectively.
The source / drain electrode 8 and the capacitor electrode 4 and the source / drain line 9 and the capacitor electrode 4 are capacitively coupled to each other, and as a result, the source / drain electrode 8 is formed. And the source / drain line 9 are capacitively coupled to each other via the capacitor electrode 4. Here, the capacitance between the source / drain electrode 8 and the source / drain line 9 is about 0.1 p.
It is F and the resistance is 6 × 10 ¹² Ω.

Therefore, the time constant of the source / drain electrode 8 and the source / drain line 9 is 0.6 seconds, and if a signal having a pulse width longer than this time constant is applied to the source / drain line 9, the source / drain line 9 and the source / drain line 9 are Drain electrode 8
Can be electrically conducted.

A pixel electrode 10 is in contact with the source / drain electrode 7. Further, 11 is a protective film.

Therefore, according to the configuration of this embodiment, if a signal having a pulse width longer than the time constant is applied to the source / drain line 9 as described above, it can be supplied to the source / drain electrode 8 equivalently. Therefore, similarly to the conventional TFT liquid crystal display device, the TFT can be driven to realize the charge and discharge of the pixel electrode 10 to polarize the liquid crystal molecules and display the pixel.

However, on the other hand, since the source / drain electrode 8 and the source / drain line 9 are DC-separated, even if the gate electrode 2 and the source / drain electrode 8 are partially short-circuited, the signal of the source / drain line 9 is Does not continue to flow into the gate electrode 2 and the gate line 3, and it is possible to prevent the generation of a linear image defect including other pixels connected to the gate electrode 2.

3 to 5 show other embodiments of the present invention, respectively, and the same parts as those in FIGS. 1 and 2 are designated by the same reference numerals.

FIG. 3 shows a structure in which the source / drain electrodes 8 and the source / drain lines 9 are formed after the amorphous silicon 6 is patterned. In this structure, the source / drain electrodes 8 and the source / drain lines 9 are formed. The amorphous silicon 6 does not exist on the lower side, and the source / drain electrode 8 and the source / drain line 9 are capacitively coupled directly via the capacitor electrode 4.

In the structure shown in FIG. 4, a further metal layer is formed on the protective film 11 to make it conductive to the source / drain electrode 8, and this is arranged so as to face the source / drain line 9 to form the capacitor electrode 4. It was done.

The structure shown in FIG. 5 is the same as that shown in FIG. 4, and in this case, the amorphous silicon 6, the source / drain electrodes 8 and the source / drain electrodes 9 are simultaneously patterned.

〔The invention's effect〕

As described above, the TFT liquid crystal display device of the present invention is configured such that the source / drain electrode and the source / drain line are electrically separated from each other, and the source / drain electrode is formed via the capacitor electrode formed near the TFT. Since the source and drain lines are capacitively coupled to each other, normal AC drive allows them to be electrically connected to enable normal operation, while other factors may occur even if the gate electrode and source / drain electrodes are short-circuited. It is possible to prevent signal leakage to the gate electrode of the pixel of (1), prevent linear image defects, and improve product yield.

[Brief description of drawings]

FIG. 1 is a plan view of an essential part of an embodiment of the present invention, FIG. 2 is an enlarged sectional view taken along the line AA of FIG. 1, and FIGS. 3 to 5 are enlarged sectional views of different embodiments. FIG. 6 is a circuit configuration diagram. 1 ... Glass substrate, 2 ... Gate electrode, 3 ... Gate line, 4 ... Capacitor electrode, 5 ... Insulating layer, 6 ... Amorphous silicon, 7,8 ... Source / drain electrodes,
9 ... Source / drain line, 10 ... Pixel electrode, 11 ... Protective film.

Claims (3)

(57) [Claims] 1. A source / drain electrode of a thin film transistor formed corresponding to a pixel electrode, and a source / drain line to which a signal to be supplied to the source / drain electrode is applied are formed separately. A thin film transistor liquid crystal display device, wherein the source / drain electrodes and the source / drain lines are capacitively coupled via a capacitor electrode formed in the vicinity of the thin film transistor. 2. The capacitor electrode is composed of a metal layer disposed adjacent to the gate electrode, and a part of the metal layer is disposed to face the source / drain electrode and the source / drain line with an insulating film interposed therebetween. A thin film transistor liquid crystal display device according to item 1. 3. The thin film transistor liquid crystal display device according to claim 1, wherein the capacitor electrode is formed of a metal film that conducts to the source / drain electrodes, and is arranged so as to face the source / drain lines with an insulating film interposed therebetween. .