JP2702294B2 - Active matrix substrate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an active matrix substrate for forming an active matrix display device in combination with a display medium such as a liquid crystal.

[0002]

2. Description of the Related Art Conventionally, an active matrix system has been used for a display device using a display medium such as a liquid crystal. FIG. 5 shows an equivalent circuit diagram of a conventional active matrix display device. In this display device, gate bus lines 5 are arranged in parallel at equal intervals on an insulating substrate, and source bus lines 4 are arranged in parallel with the gate bus lines 5 at right angles.
A thin film transistor (hereinafter, referred to as “TFT”) is provided near each intersection of the gate bus wiring 5 and the source bus wiring 4.
1) is formed. The gate electrode of the TFT 1 is connected to the gate bus line 5, and the source electrode of the TFT 1 is connected to the source bus line 4. The drain electrode of the TFT 1 is connected to a pixel capacitor 2 formed between the pixel electrode and the counter electrode, and an additional capacitor 3 formed between the pixel electrode and the additional capacitor electrode.

In this display device, when one gate bus line 5 is selected, the TFT 1 connected to the selected gate bus line 5 is turned on. A video signal is input to the TFT 1 in the ON state from the source bus wiring 4, and the video signal is accumulated in the pixel capacitor 2 and the additional capacitor 3, and display is performed. The additional capacitor 3 converts the video signal stored in the pixel capacitor 2 into one until the next video signal is input.
Plays the function of holding during the frame.

FIG. 6 is a plan view of an active matrix substrate used in such a display device. P in FIG. 6 - P
A sectional view of this display device along the line is shown in FIG. In this display device, the gate bus line 5 and the additional capacitance line 13 are formed on the insulating substrate 11 by using a sputtering method or the like and an etching method, and the upper surface of the gate bus line 5 is anodized on the gate bus line 5. Thus, an anodic oxide film 25 is formed. An additional capacitance electrode 14 made of a transparent conductive film is pattern-formed on the additional capacitance wiring 13. Further, a gate insulating film 15 is formed on the entire surface of the substrate 11 covering the additional capacitance electrode 14 and the anodic oxide film 25. A channel layer 16 made of amorphous silicon (hereinafter referred to as “a-Si”) is formed above the gate bus line 5 on the gate insulating film 15, and a source electrode 17 and a drain are formed on both sides of the channel layer 16. Electrode 1
8 are formed respectively. Thus, the TFT 1 is completed.

A pixel electrode 19 made of a transparent conductive film is patterned on the gate insulating film 15, and an end of the pixel electrode 19 is electrically connected to the drain electrode 18. The pixel electrode 19 is also superimposed on the additional capacitance electrode 14,
The gate insulating film 15 described above is interposed between the pixel electrode 19 and the additional capacitance electrode 14. The additional capacitance 3 is formed between the additional capacitance electrode 14 and the picture element electrode 19. TF
A protective film 20 is formed on the entire surface of the substrate 11 so as to cover the T1, the pixel electrode 19, and the additional capacitance 3. On a substrate 21 facing the substrate 11, a counter electrode 22 and a light-shielding black stripe 23 are formed. Substrates 11 and 21
A liquid crystal layer 24 is sealed between the layers, and a liquid crystal display device is completed.

[0006]

An active matrix substrate used in such a conventional display device has an additional problem.
In the region where the capacitance is the pixel electrode 19, the additional capacitance
Since it is composed of two layers with the quantity wiring 13, the step is high.
Therefore, when the gate insulating film 15 is formed,
At the step 14, the gate insulating film 15 becomes thin, and a short circuit may occur between the pixel electrode 19 and the additional capacitance electrode 14. When such a short circuit occurs, a picture element defect occurs on the display screen.

The present invention has been made to solve such a problem, and an object of the present invention is to provide a storage device in which the additional capacitance is in the area of the pixel electrode.
In the case of a two-layer structure of an additional capacitance electrode and an additional capacitance line.
In any case, an object of the present invention is to provide an active matrix substrate having a structure in which a short circuit hardly occurs between a picture element electrode and an additional capacitance electrode.

[0008]

An active matrix substrate according to the present invention comprises picture element electrodes arranged in a matrix on an insulating substrate, and a thin film transistor electrically connected to the picture element electrodes.
An active matrix substrate having a transistor, an additional capacitance electrode for forming an additional capacitance between the pixel electrode, and an additional capacitance line for electrically connecting the additional capacitance electrode, The electrode and the additional capacitance line are stacked in the pixel electrode region, and the stacked additional capacitance electrode and the additional capacitance line are disposed between the pixel electrode and the first insulating film and the second insulating film. Sandwiching the membrane , and the first
The insulating film is a gate insulating film of the thin film transistor;
The second insulating film is a protective film covering the thin film transistor.
Accordingly, the above object is achieved.

According to the above configuration, the additional capacitance is connected to the pixel electrode.
The region is composed of two layers of additional capacitance electrode and additional capacitance wiring
Even in this case, two layers are provided between the pixel electrode and the additional capacitance electrode.
Since the insulation film is sandwiched, high insulation is maintained and short-circuit is suppressed.
Is controlled. Also, on the protective film that covers the thin film transistor
The pixel electrode is connected to the source
The bus wiring is electrically separated by a protective film,
Form elementary electrodes without being restricted by source bus wiring
be able to. Therefore, the area of the pixel electrode must be sufficiently large.
Thus, the aperture ratio can be increased.

[0010]

[0011]

Embodiments of the present invention will be described below.

FIG. 1 is a sectional view of a liquid crystal display using one embodiment of the active matrix substrate of the present invention. FIG.
FIG. 2 is a plan view of an active matrix substrate included in the display device of FIG. FIG. 1 is a cross-sectional view of a display device using the active matrix substrate of FIG. 2 along the line AA in FIG. FIGS. 3A to 3D show a manufacturing process of the active matrix substrate of FIG.

This embodiment will be described according to the manufacturing process. First, a metal film of Ta, Mo, or the like was formed on an insulating substrate 11 of glass or the like by using a sputtering method, and the metal film was etched to form a gate bus line 5 and an additional capacitance line 13. Part of the gate bus line 5 functions as a gate electrode of the TFT 1 to be formed later. An anodized film 25 is formed on gate bus line 5 by anodizing the surface of gate bus line 5.
Next, ITO (Indium tin oxidizer) is placed on the additional capacitance line 13.
The additional capacitance electrode 14 made of a transparent conductive film such as e) is patterned (FIG. 3A).

Further, the additional capacitance electrode 14 and the anodic oxide film 2
5, a gate insulating film 15 as a first insulating film is formed on the entire surface of the substrate 11. A channel layer 16 made of a-Si is formed above the gate bus line 5 on the gate insulating film 15 (FIG. 3B), and a source electrode 17 and a drain electrode 18 are formed on both sides of the channel layer 16. Each is formed (FIG. 3C). The source electrode 17 and the drain electrode 18 are patterned simultaneously with the source bus wiring. The source electrode 17, the drain electrode 18, and the source bus wiring are made of metal such as Ta, Mo, and Al. Thus, the TFT 1 is completed.

Next, a protective film 20 as a second insulating film is formed on the entire surface of the substrate 11 on which the TFT 1 is formed.
Next, a contact hole 26 is formed in the protective film 20 on the drain electrode 18. Further, a transparent conductive film is formed on the entire surface of the protective film 20, and is patterned into the shape of the pixel electrode 19 shown in FIG. 2 (FIG. 3D). In the present embodiment, the picture element electrode 19 is formed with a larger area than the conventional example shown in FIG. 6, and as shown in FIG. 2, the picture element electrode 19 and the source bus wiring 4 are in contact with each other in plan view. Is formed. Even if the area of the picture element electrode 19 is increased, the picture element electrode 19 and the source bus line 4 are electrically separated by the protective film 20. The end of the pixel electrode 19 is also formed on the contact hole 26,
The pixel electrode 19 is provided in the contact hole 2 in the drain electrode 18.
6 are electrically connected. Furthermore, the picture element electrode 1
9 is also superimposed on the additional capacitance electrode 14, and between the pixel electrode 19 and the additional capacitance electrode 14, the gate insulating film 15 described above is formed.
And the protective film 20 are sandwiched. The additional capacitance 3 is formed between the additional capacitance electrode 14 and the picture element electrode 19. As described above, the active matrix substrate of this embodiment is completed.

A counter electrode 22 and a light-shielding black stripe 23 are formed on a substrate 21 facing the substrate 11. A liquid crystal layer 24 is sealed between the substrates 11 and 21 to complete a liquid crystal display device. The equivalent circuit diagram of this liquid crystal display device is the same as that of FIG.

In the active matrix substrate of the present embodiment, since two insulating films of the gate insulating film 15 and the protective film 20 are formed between the picture element electrode 19 and the additional capacitance electrode 14, the picture element electrode Short-circuiting between 19 and the additional capacitance electrode 14 is unlikely to occur.

In this embodiment, as shown in FIG.
Since the picture element electrode 19 is formed so as to be in contact with the source bus wiring 4 in plan view, the aperture ratio of the display device using the active matrix substrate of this embodiment is large.
FIG. 4 shows an opening of a display device using the active matrix substrate of this embodiment. For comparison, FIG. 8 shows an opening of a display device using the above-described substrate of FIG. In FIGS. 6 and 8, the portions not shaded are openings. Each opening is defined by an opening of the black stripe 23 formed on the counter substrate 21. The opening of the black stripe 23 is formed in consideration of a displacement at the time of bonding the active matrix substrate and the counter substrate.
It is formed smaller than the picture element electrode 19. In this embodiment, since the area of the pixel electrode 19 is large, the area of the opening of the black stripe 23 can be increased. From a comparison between FIG. 6 and FIG. 8, it can be seen that the aperture ratio of the display device using the active matrix substrate of this embodiment is larger than that of the conventional display device.

[0019]

According to the active matrix substrate of the present invention, since the two-layer insulating film is formed between the picture element electrode forming the additional capacity and the additional capacity electrode, the additional capacity is formed in the area of the picture element electrode. Even in the case of the two-layer structure of the additional capacitance electrode and the additional capacitance wiring, a short circuit hardly occurs between the picture element electrode and the additional capacitance electrode. Also, on the thin film transistor
Since the pixel electrode is provided on the overlying protective film,
The element electrodes and the source bus wiring are electrically separated by a protective film
Pixel electrodes are restricted by source bus wiring.
It can be formed without any problem. Therefore, the surface of the pixel electrode
Product can be made sufficiently large to increase the aperture ratio.
It works.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of an active matrix display device using one embodiment of an active matrix substrate of the present invention.

FIG. 2 is a plan view of an active matrix substrate included in the active matrix display device of FIG.

FIG. 3 is a view illustrating a manufacturing process of the active matrix substrate of FIG. 2;

FIG. 4 is a plan view showing an opening of an active matrix display device using the active matrix substrate of FIG. 2;

FIG. 5 is an equivalent circuit diagram of the present invention and a conventional active matrix display device.

FIG. 6 is a plan view of a conventional active matrix substrate.

7 is a cross-sectional view of an active matrix display device using the active matrix substrate of FIG.

8 is a plan view showing an opening of the active matrix display device of FIG. 7;

[Explanation of symbols]

 Reference Signs List 1 TFT 2 picture element capacity 3 additional capacity 4 source bus wiring 5 gate bus wiring 11 and 21 insulating substrate 13 additional capacity wiring 14 additional capacity electrode 15 gate insulating film 16 channel layer 17 source electrode 18 drain electrode 19 picture element electrode 20 protection Film 22 counter electrode 23 black stripe 24 liquid crystal layer

Claims (1)

(57) [Claims] 1. A pixel electrode arranged in a matrix on an insulating substrate, and a thin film transistor electrically connected to the pixel electrode.
An active matrix substrate having a transistor, an additional capacitance electrode for forming an additional capacitance between the picture element electrode, and an additional capacitance wiring for electrically connecting the additional capacitance electrode, The electrode and the additional capacitance line are stacked in the pixel electrode region, and the stacked additional capacitance electrode and the additional capacitance line are disposed between the pixel electrode and the first insulating film and the second insulating film. A first insulating film interposed between the thin films;
A gate insulating film of the film transistor, wherein the second insulating film
Is an active matrix substrate which is a protective film covering the thin film transistor .