JPH04265945A - Active matrix substrate - Google Patents

Abstract

PURPOSE:To offer the active matrix substrate which is so structured that short circuit is hardly generated between a picture element electrode and an additional capacity electrode which constitute additional capacitance. CONSTITUTION:The picture element electrode 19 is formed on a protection film 20 formed on the entire surface of a substrate 11 while covering a TFT 1 and then connected to the drain electrode 18 of the TFT 1 electrically through a contact hole 26. In this constitution, the picture element electrode 19 is not formed on a gate insulating film 15 where a source bus conductor is formed, and the gate insulating film 15 and protection film 20 are sandwiched between the additional capacitance electrode 14 and picture element electrode 19 which constitute additional capacitance. The picture element electrode and additional capacitance electrode are hardly short-circuited and the picture element electrode can be formed without being restrained by the source bus conductor. The area of the picture element electrode can be increased.

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 constructing 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 method has been used in display devices using display media such as liquid crystals. 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 regular intervals on an insulating substrate, and source bus lines 4 are arranged in parallel orthogonal to the gate bus lines 5. A thin film transistor (hereinafter referred to as "TFT") is located 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 wiring 5, and the source electrode of the TFT 1 is connected to the source bus wiring 4. A picture element capacitor 2 formed between the picture element electrode and the counter electrode, and an additional capacitor 3 formed between the picture element electrode and the additional capacitor electrode are connected to the drain electrode of the TFT 1.

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 from the source bus wiring 4 to the TFT 1 in the on state, and this video signal is stored in the pixel capacitor 2 and the additional capacitor 3 for display. The additional capacitor 3 functions to hold the video signal stored in the pixel capacitor 2 for one frame until the next video signal is input.

FIG. 6 shows a plan view of an active matrix substrate used in such a display device. A-A in Figure 6
A cross-sectional view of this display device along a line is shown in FIG. In this display device, a gate bus wiring 5 and an additional capacitance wiring 13 are formed on an insulating substrate 11 using a sputtering method or the like and an etching method, and the upper surface of the gate bus wiring 5 is anodized on the gate bus wiring 5. By doing so, an anodic oxide film 25 is formed. On the additional capacitor wiring 13, an additional capacitor electrode 14 made of a transparent conductive film is patterned. Furthermore, 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 wiring 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. Through the above steps, TFT1 is completed.

A picture element electrode 19 made of a transparent conductive film is patterned on the gate insulating film 15 , and the end of the picture element electrode 19 is electrically connected to the drain electrode 18 . Further, the picture element electrode 19 is also superimposed on the additional capacitance electrode 14,
The aforementioned gate insulating film 15 is sandwiched between the picture element electrode 19 and the additional capacitance electrode 14. The additional capacitor 3 is formed between the additional capacitor electrode 14 and the picture element electrode 19. TF
A protective film 20 is formed on the entire surface of the substrate 11, covering T1, the picture element electrode 19, and the additional capacitor 3. A counter electrode 22 and a black stripe 23 for shielding light are formed on a substrate 21 facing the substrate 11. Substrates 11 and 21
A liquid crystal layer 24 is sealed in between, completing a liquid crystal display device.

[0006]

In the active matrix substrate used in such a conventional display device, a short circuit may occur between the picture element electrode 19 and the additional capacitance electrode 14. If such a short circuit occurs, pixel defects will occur on the display screen.

The present invention solves these problems, and an object of the present invention is to provide an active electrode having a structure in which short circuits are unlikely to occur between the picture element electrode and the additional capacitor electrode that constitute the additional capacitor. An object of the present invention is to provide a matrix substrate.

[0008]

[Means for Solving the Problems] The active matrix substrate of the present invention has pixel electrodes arranged in a matrix on an insulating substrate and an additional capacitor for forming an additional capacitance between the pixel electrodes. An active matrix substrate having an electrode and an additional capacitor wiring electrically connecting the additional capacitor electrodes, the active matrix substrate having a first insulating film and a second insulating film between the picture element electrode and the additional capacitor electrode. An insulating film is sandwiched therebetween, thereby achieving the above object.

[0009] Furthermore, the device may further include a thin film transistor, and the first insulating film may be a gate insulating film of the thin film transistor.

[0010] The invention further includes a protective film covering the thin film transistor, wherein the second insulating film is the protective film, and the picture element electrode is connected to the thin film transistor through a contact hole formed in the second insulating film. It can be configured to be connected to a thin film transistor.

[0011]

[Examples] Examples of the present invention will be described below.

FIG. 1 shows a sectional view of a liquid crystal display device using an embodiment of the active matrix substrate of the present invention. Figure 1
FIG. 2 shows a plan view of the active matrix substrate constituting the display device. FIG. 1 is a cross-sectional view of a display device using the active matrix substrate of FIG. 2, taken along line A--A in FIG. Moreover, the manufacturing process of the active matrix substrate of FIG. 2 is shown in FIGS. 3(a) to 3(d).

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

Furthermore, additional capacitance electrode 14 and anodic oxide film 2
A gate insulating film 15, which is a first insulating film, is formed on the entire surface of the substrate 11, covering the gate insulating film 5. A channel layer 16 made of a-Si is formed above the gate bus wiring 5 on the gate insulating film 15 (FIG. 3(b)), and a source electrode 17 and a drain electrode 18 are formed on both sides of the channel layer 16. (FIG. 3(c)). The source electrode 17 and drain electrode 18 are patterned simultaneously with the source bus wiring. The source electrode 17, drain electrode 18, and source bus wiring are made of metal such as Ta, Mo, and Al. Through the above steps, TFT1 is completed.

Next, a protective film 20, which is a second insulating film, is formed over 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. Furthermore, a transparent conductive film is formed on the entire surface of the protective film 20, and is patterned into the shape of the picture element electrode 19 shown in FIG. 2 (FIG. 3(d)). In this embodiment, the picture element electrode 19 is formed to have a larger area than the conventional example shown in FIG. 6, and as shown in FIG. is formed. Even if the area of the picture element electrode 19 is increased in this way, the picture element electrode 19 and the source bus wiring 4 are electrically separated by the protective film 20. Further, the end of the picture element electrode 19 is also formed on the contact hole 26, so that the picture element electrode 19 is connected to the drain electrode 18 through the contact hole 26.
electrically connected via. Furthermore, the picture element electrode 19
is also superimposed on the additional capacitor electrode 14, and the aforementioned gate insulating film 15 and protective film 20 are sandwiched between the picture element electrode 19 and the additional capacitor electrode 14. The additional capacitor 3 is formed between the additional capacitor electrode 14 and the picture element electrode 19. Through the above steps, the active matrix substrate of this example is completed.

A counter electrode 22 and a black stripe 23 for shielding light are formed on a substrate 21 facing the substrate 11. A liquid crystal layer 24 is sealed between the substrates 11 and 21, and a liquid crystal display device is completed. The equivalent circuit diagram of this liquid crystal display device is similar to FIG. 5 described above.

In the active matrix substrate of this embodiment, two insulating films, the gate insulating film 15 and the protective film 20, are formed between the pixel electrode 19 and the additional capacitance electrode 14, so that the pixel electrode 19 and the additional capacitance electrode 14 are less likely to be short-circuited.

Furthermore, 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 example. For comparison, FIG. 8 shows an opening of a display device using the substrate of FIG. 6 described above. In FIGS. 6 and 8, the portions that are not shaded are openings. Each opening is defined by the opening of the black stripe 23 formed on the counter substrate 21. The opening of the black stripe 23 is designed in consideration of positional deviation when 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 picture element electrode 19 is large, the area of the opening of the black stripe 23 can also be made large. From a comparison between FIGS. 6 and 8, it can be seen that the aperture ratio of the display device using the active matrix substrate of this example is larger than that of the conventional display device.

[0019]

[Effects of the Invention] In the active matrix substrate of the present invention, a two-layer insulating film is formed between the picture element electrode and the additional capacitance electrode that constitute the additional capacitance, so the connection between the picture element electrode and the additional capacitance electrode is Short circuits are less likely to occur between the two.

[Brief explanation of the drawing]

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

FIG. 2 is a plan view of an active matrix substrate constituting the active matrix display device of FIG. 1;

3 is a diagram showing 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.

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 sectional view of an active matrix display device using the active matrix substrate of FIG. 6. FIG.

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

[Explanation of symbols]

1 TFT 2 Pixel capacity 3 Additional capacity 4 Source bus wiring 5 Gate bus wiring 11, 21 Insulating substrate 13 Additional capacitance wiring 14 Additional capacitance electrode 15 Gate insulation film 16 Channel layer 17 Source electrode 18 Drain electrode 19 Picture element electrode 20 Protective film 22 Counter electrode 23 Black stripe 24 Liquid crystal layer

Claims (1)

[Claims] 1. Picture element electrodes arranged in a matrix on an insulating substrate, an additional capacitance electrode for forming an additional capacitance between the picture element electrodes, and an electrical connection between the additional capacitance electrodes. an active matrix substrate having an additional capacitance wiring for connection, the active matrix substrate having a first connection between the picture element electrode and the additional capacitance electrode;
an active matrix substrate in which an insulating film and a second insulating film are sandwiched.