JPH04335617A - Active matrix substrate - Google Patents

Abstract

PURPOSE:To provide the active matrix substrate which is equipped with an additional capacitor with a large capacity value and has a large aperture rate. CONSTITUTION:An additional capacity electrode 17 is formed on an insulating substrate 1 and a gate insulating film 4 is formed thereupon. A 1st picture element electrode 11a is formed on the gate insulating film 4 and the additional capacity 19 is formed between the additional capacity electrode 17 and 1st picture element electrode 11a. An inter-layer insulating film 10 is formed covering the 1st picture element electrode 11a and a TFT 13 connected thereto and a 2nd picture element electrode 11b is formed on the inter-layer insulating film 10. The 2nd picture element electrode 11b is connected to the drain electrode 8 of the TFT 13 thorugh a contact hole 12 formed in the inter-layer insulating film 10. The 2nd picture element electrode 11b overlaps with a gate bus electric conductor and a source bus electric conductor connected to the TFT 13 across the inter-layer insulating film 10.

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 a matrix type display device in combination with a display medium such as a liquid crystal.

0002

2. Description of the Related Art Active matrix display devices have advantages such as high contrast and no restrictions on the number of picture elements. Therefore, active matrix substrates used in active matrix display devices are being actively researched. However, active matrix substrates have a complicated structure, have low light utilization efficiency (aperture ratio), and have the drawbacks of dark display screens.

0003

[Problems to be Solved by the Invention] FIG. 6 shows a partial plan view of an active matrix substrate that solves these drawbacks.
FIG. 7 shows a cross-sectional view taken along line BB in FIG. 6. This active matrix substrate includes an insulating substrate 1 made of glass or the like,
A thin film transistor (hereinafter referred to as "TFT") formed on the substrate 1
) 13. As shown in Figure 6, T
The gate electrode 2 of the FT 13 is connected to the gate bus wiring 3, and the source electrode 6 of the TFT 13 is connected to the source bus wiring 7. The picture element electrode 11 is connected to the drain electrode 8 of the TFT 13, and is connected to the gate bus wiring 3 and the source bus wiring 7.
It is also superimposed on top. Further, an additional capacitor electrode 17 faces the picture element electrode 11 with a gate electrode 4 and an interlayer insulating film 14, which will be described later, in between. Picture element electrode 11 and additional capacitance electrode 17
An additional capacitor 19 is formed between the two. Additional capacitance electrode 17 is connected to additional capacitance wiring 18 .

As described above, the structure of the active matrix substrate in which the picture element electrode 11 is formed so as to overlap the gate bus wiring 3 and the source bus wiring 7 is particularly effective for increasing the aperture ratio of a reflective display device. It is.

A method of manufacturing the active matrix substrate shown in FIGS. 6 and 7 is shown in FIGS. 8 and 9. First, a gate bus wiring 3 and a gate electrode 2 made of Ta, Cr, etc. are formed on an insulating substrate 1 made of glass or the like. Next, ITO (I
An additional capacitor electrode 17 and an additional capacitor wiring 18 made of a transparent conductive film such as ndium tin oxide are formed. Next, a gate insulating film 4 made of SiNx, SiOx, etc.
, contact layers 9 made of an n+ type amorphous silicon (hereinafter referred to as "a-Si") layer doped with P (phosphorus), and a semiconductor layer 5 made of an a-Si layer. Next, a source electrode 6 made of Mo, Ti, Al, etc.
, drain electrode 8, and source bus wiring 7 are formed (
Figure 8). Through the above steps, the TFT 13 is completed.

Next, an interlayer insulating film 10 made of polyimide, acrylic resin, etc. is formed on the entire surface of the substrate 1, and a contact hole 12 is formed in a portion of the interlayer insulating film 10 corresponding to the drain electrode 8 (FIG. 9). . Furthermore, the ITO film is attached to the substrate 1.
The picture element electrode 11 is formed and patterned on the entire upper surface.
(Figure 7). Thereby, the picture element electrode 11 is electrically connected to the drain electrode 8 of the TFT 13 via the contact hole 12. Furthermore, as described above, the picture element electrode 11
An additional capacitor 19 is formed between the additional capacitor electrode 17 and the additional capacitor electrode 17 .

In such an active matrix substrate, a gate-on signal is applied to the gate electrode 2 connected to each picture element electrode 11, and an image signal is written from the source electrode 6 to the picture element electrode 11 via the drain electrode 8. It will be done. next,
The written image signal is held for one frame from when the gate-off signal is output to the gate electrode 2 until the next gate-on signal is applied. The additional capacitor 19 formed between the picture element electrode 11 and the additional capacitor electrode 17 functions to hold this image signal.

However, since the gate insulating film 4 and the interlayer insulating film 10 are present between the picture element electrode 11 and the additional capacitor electrode 17 that constitute the additional capacitor 19, the additional capacitor 19 is The capacitance due to the capacitance due to the capacitance due to the interlayer insulating film 10 and the capacitance due to the interlayer insulating film 10 are arranged in series, and the capacitance value of the additional capacitance 19 becomes small. Therefore, in a display device using this active matrix substrate, a reduction in image quality such as a reduction in contrast occurs.

The present invention is intended to solve these problems, and an object of the present invention is to provide an active matrix substrate that is provided with an additional capacitance having a large capacitance value and has a large aperture ratio.

0010

[Means for Solving the Problems] The active matrix substrate of the present invention includes an additional capacitor electrode formed on an insulating substrate, an insulating film formed on the additional capacitor electrode, and an insulating film formed on the additional capacitor electrode. a switching element having a first picture element electrode facing each other across a film, an output terminal connected to the first picture element electrode, and an interlayer insulating film formed on the switching element and the first picture element electrode; , has a contact hole formed in the interlayer insulating film, and a second picture element electrode electrically connected to the output terminal of the switching element via the contact hole, thereby achieving the above-mentioned effect. The purpose is achieved.

[0011] Furthermore, the display device may further include a scanning line connected to the switching element, and the second picture element electrode may be superimposed on the scanning line.

[0012] Furthermore, the display device may further include a signal line connected to the switching element, and the second picture element electrode may be superimposed on the signal line.

[0013]

[Function] In the active matrix substrate of the present invention, additional capacitance is formed between the additional capacitance electrode on the substrate and the first picture element electrode that faces the additional capacitance electrode with an insulating film interposed therebetween. The capacitance value of can be increased. Further, the output terminal of the switching element is connected to the first picture element electrode, and a contact hole is formed in the interlayer insulating film formed on the first picture element electrode and the switching element. A second picture element electrode is formed on the interlayer insulating film, and the second picture element electrode is connected to the output terminal of the switching element via a contact hole. Therefore, since the second picture element electrode can be formed to overlap the scanning line and/or signal line connected to the switching element with the interlayer insulating film in between, it is possible to improve the aperture ratio of the substrate.

[0014]

[Examples] Examples of the present invention will be described below. FIG. 2 shows a plan view of an example of the active matrix substrate of this example, and FIG. 1 shows a cross-sectional view taken along line A--A in FIG. The active matrix substrate of this embodiment includes an insulating substrate 1 made of glass or the like, and a TFT 13 formed on the substrate 1. As shown in FIG. 2, the gate electrode 2 of the TFT 13 is connected to the gate bus wiring 3, and the source electrode 6 of the TFT 13 is connected to the source bus wiring 7. The picture element electrode 11 includes a first picture element electrode 11a in the lower layer, and a second picture element electrode 11a superimposed on the first picture element electrode 11a with a gate insulating film, which will be described later, in between.
It consists of a picture element electrode 11b. The first picture element electrode 11a and the second
The picture element electrodes 11b are both connected to the drain electrode 8 of the TFT 13, and the second picture element electrode 11b is also overlapped on the gate bus wiring 3 and the source bus wiring 7. Further, an additional capacitance electrode 17 is provided on the first picture element electrode 11a with the gate electrode 4 in between.
are facing each other. First picture element electrode 11a and additional capacitance electrode 1
An additional capacitor 19 is formed between the capacitor 7 and the capacitor 7. Additional capacitance electrode 17 is connected to additional capacitance wiring 18 .

A method of manufacturing the active matrix substrate shown in FIGS. 1 and 2 is shown in FIGS. 3 to 5. The active matrix substrate of this example will be explained according to the manufacturing process. First, a Ta metal film with a thickness of 300 nm is formed on an insulating substrate 1 made of glass by sputtering, and this metal film is patterned by photolithography and etching to form gate bus wiring 3 and gate electrode 2. Form. Next, an ITO film with a thickness of 80 nm is formed by sputtering, and patterned by photolithography and etching to form additional capacitor electrode 17 and additional capacitor wiring 18. Next, plasma CVD
A gate insulating film 4 made of SiNx with a thickness of 400 nm and a 100 nm thick a
-Si layer and n+ type a- which will later become contact layers 9, 9
and the Si layer are successively formed in this order. Next, n+ type a
-Si layer and a-Si layer are patterned to form contact layers 9, 9 and semiconductor layer 5.

Next, a film with a thickness of 200 nm is applied to the entire surface of this substrate.
A Mo metal layer of m is formed by a sputtering method, and this Mo metal layer is patterned to form the source electrode 6,
A drain electrode 8 and source bus wiring 7 are formed. Through the above steps, the TFT 13 is completed. Furthermore, an ITO film with a thickness of 100 nm is formed on the entire surface of the substrate 1, covering the TFT 13, and patterned to form the first picture element electrode 11a. In this embodiment, an additional capacitor 19 is formed between the first picture element electrode 11a and the additional capacitor electrode 17 (FIG. 3).

Next, the TFT 13 and the first picture element electrode 11a
An interlayer insulating film 10 made of a polyimide resin film or an acrylic resin film is applied to a thickness of 1 μm over the entire surface of the substrate 1 on which the film is formed (FIG. 4). Next, a contact hole 12 is formed in a portion of the interlayer insulating film 10 corresponding to the drain electrode 8 (
Figure 5). Furthermore, an interlayer insulating film 10 and a contact hole 1
An ITO film is formed on 2 and patterned to form a second picture element electrode 11b (FIG. 1). Thereby, the second picture element electrode 11b is connected to the drain electrode 8 of the TFT 13 via the contact hole 12 formed in the interlayer insulating film 10. Further, as shown in FIG. 2, the second picture element electrode 11b
is formed overlapping the gate bus wiring 3 and the source bus wiring 7 with an interlayer insulating film 10 in between.

In this embodiment, since only the relatively thin gate insulating film 4 is present between the additional capacitor electrode 17 and the first picture element electrode 11a constituting the additional capacitor 19, the additional capacitor 1
9 can be increased. Further, since the second picture element electrode 11b is formed to overlap the gate bus line 3 and the source bus line 7, the aperture ratio of this substrate can be increased.

In this embodiment, a TF is used as a switching element.
Although we have explained the case where T is used, other cases such as MI
It can also be applied to an active matrix substrate using M (Metal-Insulator-Metal) elements, diodes, varistors, and the like.

[0020]

[Effects of the Invention] In the active matrix substrate of the present invention, since the additional capacitor is formed between the additional capacitor electrode and the first picture element electrode which face each other with an insulating film in between, the capacitance value of the additional capacitor can be increased. be able to. Therefore, if a display device is constructed using the active matrix substrate of the present invention,
A high contrast display screen can be obtained. Further, since the picture element electrode has the second picture element electrode formed on the interlayer insulating film, the area of the picture element electrode can be increased, and the aperture ratio of the display device can be increased. Therefore, in a display device using the active matrix substrate of the present invention, a bright display screen can be obtained.

[Brief explanation of drawings]

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

FIG. 2 is a plan view of the substrate of FIG. 1;

3 is a cross-sectional view showing the manufacturing process of the active matrix substrate of FIGS. 1 and 2. FIG.

4 is a cross-sectional view showing the manufacturing process of the active matrix substrate of FIGS. 1 and 2. FIG.

5 is a cross-sectional view showing the manufacturing process of the active matrix substrate of FIGS. 1 and 2. FIG.

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

7 is a sectional view taken along line BB in FIG. 6. FIG.

8 is a diagram showing a manufacturing process of the active matrix substrate shown in FIGS. 6 and 7. FIG.

9 is a diagram showing a manufacturing process of the active matrix substrate shown in FIGS. 6 and 7. FIG.

[Explanation of symbols]

1 Insulating substrate 2 Gate electrode 3 Gate bus wiring 4 Gate insulating film 5 Semiconductor layer 6 Source electrode 7 Source bus wiring 8 Drain electrode 9 Contact layer 10 Interlayer insulation film 11 Picture element electrode 11a First picture element electrode 11b Second picture element electrode 12 Contact hole 13 TFT 17 Additional capacitance electrode 18 Additional capacitance wiring 19 Additional capacity

Claims (3)

[Claims] 1. An additional capacitor electrode formed on an insulating substrate, an insulating film formed on the additional capacitor electrode, and a first picture element electrode facing the additional capacitor electrode with the insulating film interposed therebetween. , a switching element having an output terminal connected to the first picture element electrode, an interlayer insulating film formed on the switching element and the first picture element electrode, and a contact hole formed in the interlayer insulating film. , a second picture element electrode electrically connected to the output terminal of the switching element via the contact hole. 2. An active matrix substrate further comprising a scanning line connected to the switching element, and the second picture element electrode is superimposed on the scanning line. 3. An active matrix substrate further comprising a signal line connected to the switching element, and the second picture element electrode is superimposed on the signal line.