JP2800958B2 - 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 a structure of an active matrix substrate for a display device which performs high-density display by arranging picture element electrodes for display in a matrix.
The present invention relates to an active matrix substrate that performs display by applying a drive signal to a display pixel electrode via a switching element.

[0002]

2. Description of the Related Art In a liquid crystal display device, an EL display device, and a plasma display device, a display pattern is formed on a screen by selecting display pixels arranged in a matrix and performing light modulation. . In the case where the display picture elements are selected and the light modulation is performed, an active picture element in which each picture element is arranged so as to be light-modulated by an independent picture element electrode and a switching element is connected to each picture element electrode is used. The matrix driving method has been put to practical use for a liquid crystal television, a word processor, a terminal display of a computer, and the like because a high contrast display is possible. As a switching element for selectively driving a pixel electrode, a TFT (Thin Fi
lm Transistor) element, MIM (metal-insulating film-metal)
Devices, MOS transistor devices, diodes, varistors and the like are generally used. Each pixel electrode in the active matrix substrate has a counter electrode opposed to each other with a display medium such as a liquid crystal, an EL light emitting layer, or a plasma light emitter interposed therebetween, and by switching a voltage applied to each pixel electrode, The display medium interposed therebetween is optically modulated, and the optical modulation is visually recognized as a display pattern.

FIG. 7 shows an example of a conventional active matrix substrate. FIG. 8 is a sectional view taken along line EE in FIG. As shown in the drawing, in the active matrix substrate 50 of this conventional example, a plurality of scanning lines (gate bus lines) 60 and a plurality of signal lines (source bus lines) 70 are formed on a glass substrate 52 which is an insulating substrate. The gate insulating films 62 (see FIG. 8) intersect at right angles so as to form a lattice. Each scanning line 60 and each signal line 7
Pixel electrodes 90 are arranged in respective rectangular regions surrounded by zeros. TFTs 80 as switching elements are provided at the corners in each region. The TFT 80 is electrically connected to each of the pixel electrodes 90 in the region where the TFT 80 is provided, and one scanning line 60 and one signal line 70 adjacent to each of the pixel electrodes 90. Have been. A branch line 61 branches from the scanning line 60 toward the pixel electrode 90.
The position near the tip of the TFT is the TFT as the switching element
The gate electrode 80 is used.

The signal line 70 has a two-layer structure of a lower layer 71 and an upper layer 73 made of a material different from that of the lower layer 71 and made of the same conductive film as the pixel electrode 90.

[0005] Such an active matrix substrate 50
Then, after patterning the lower layer 71 in the signal line 70, the conductor film forming the pixel electrode 90 is changed to the scanning line 60,
The upper layer 73 is formed by patterning while leaving the lower layer 71 on the signal line 70.

The lower layer 71 of the signal line 70 may be disconnected for some reason during the manufacturing process of the active matrix substrate. However, since the signal line 70 has the two-layer structure, even when the lower layer 71 is disconnected, the upper layer 73 of the conductive film is formed thereon, so that the signal line 70 is electrically There is no possibility of disconnection, and it can function as a signal line. In the case where the signal line has a single-layer structure, if the signal line for supplying a signal to the pixel electrode is disconnected for some reason in the manufacturing process, a signal to be originally supplied is not input before the disconnected portion. As a result, it is recognized as a line defect on the display device. Such a line defect significantly impairs the quality of the display device and becomes a serious problem from the viewpoint of product yield. However, as described above, disconnection of the signal line 70 is prevented by forming the signal line 70 in a two-layer structure.

[0007]

In such an active matrix substrate, as the upper layer 73 of the signal line 70, a transparent conductive material (ITO or SnO2) constituting the picture element electrode 90 is used.
Etc.) are used. Such a transparent conductive material is usually not extremely low in resistance, and thus is useful as a measure against disconnection of the scanning line 60 and the signal line 70. However, when the size of the insulating substrate 52 is increased in order to increase the size of the display device, the scanning lines 60 and the signal lines 70 also become longer, so that signal delay becomes a problem. Since the signal delay depends on the resistance and capacitance of the scanning line 60 and the signal line 70, the scanning line 60
As a material of the signal line 70, a material having a lower resistance is desired.

The present invention has been made to solve the above-mentioned problems of the prior art. It is an object of the present invention to further improve the effect of preventing defects due to disconnection of a signal line and to reduce the resistance of a scanning line and a signal line. Another object of the present invention is to provide a higher quality active matrix substrate.

[0009]

An active matrix substrate according to the present invention comprises: an insulating substrate; a plurality of scanning lines and a plurality of signals provided on the insulating substrate so as to be arranged in a grid pattern at right angles to each other. a line, and the pixel electrodes arranged respectively in a region surrounded by the scanning lines and the signal lines, the one scanning line and one signal line adjacent to each picture element electrode and each pixel electrode An active matrix substrate including switching elements electrically connected to each other, and having a width wider than the signal line below the signal line except for an intersection with the scanning line via at least one insulating film. are formed on, the signal through a through hole formed in the insulating film
Route electrically has a connection to a conductive film, the conductive film is low
A layer different from the pixel electrode via at least one insulating film
, Which achieves the above-mentioned object.

[0010]

[0011]

[0012]

According to the active matrix substrate of the present invention, the signal
Formed underneath the wires, the signal wires and through holes
Is electrically connected to a pixel electrode via an insulating film.
They are arranged in different layers. Therefore, the conductive film and the pixel electrode
Is not short-circuited with the
Can be close to the electrode formation area, affecting the aperture ratio
Form conductive film as large as possible without giving
It becomes possible. Therefore, the formation area of the signal line is limited.
Even if it is, the conductive film formed wider than the signal line
Is electrically connected to signal lines by through holes to reduce resistance
Wiring. Further, in the active matrix substrate of the present invention, even when a signal line is disconnected for some reason, a signal transmitted by the signal line is:
A conductive film laminated below the signal line via an insulating film,
Since the signal is transmitted through the through hole formed in the insulating film, there is no possibility that a line defect due to disconnection of the signal line occurs. By selecting a low-resistance material for the conductive film, the resistance of the signal line can be reduced.

[0013]

Embodiments of the present invention will be described below. In the active matrix substrate of the present invention, as shown in FIG. 1, a plurality of scanning lines (gate bus lines) 10 and a plurality of signal lines (source bus lines) 20 are formed in a grid on a glass substrate 2 which is an insulating substrate. As shown in FIG. Pixel electrodes 40 are arranged in respective rectangular regions surrounded by the scanning lines 10 and the signal lines 20. A branch line 11 extending from the scanning line 10 toward the pixel electrode 40 is branched at a corner in a region where each of the pixel electrodes 40 is arranged. The TFTs 30 as switching elements are formed at the corners of each region so that is a gate electrode of each TFT 30. Each of the TFTs 30 has a corresponding one of the pixel electrodes 40 in the region where the TFT 30 is formed, and each of the pixel electrodes 40.
Are also electrically connected to the signal lines 20 adjacent to each other.

Under the signal line 20, the conductive film 21 is laminated with the signal line 20 with the gate insulating film 12 interposed therebetween, except for a portion intersecting the scanning line 10 as shown in the figure. Is provided. The conductive film 21 extends along the signal line 20 different from the vicinity of the position where the TFT 30 is provided in the rectangular region where the pixel electrodes 40 are provided and the corner where the TFT 30 is provided in that region. In the vicinity of the corner, part of the gate insulating film 12 on the conductive film 21 is removed by etching, and two through holes 22 are formed.
Is formed, and the signal line 2 laminated on the conductive film 21 is formed.
0 is electrically connected through each through hole 22. In the active matrix substrate having such a configuration, it is possible to relieve the disconnection of the signal line 20, and
It is possible to reduce the overall resistance of the signal line 20.

A procedure for manufacturing the active matrix substrate having such a configuration will be described. First, the scanning lines 10 are formed on a glass substrate 2 which is an insulating substrate. On the surface of the glass substrate 2, an insulating film such as Ta2O5 may be formed as a base coat film. Next, Al, which is a conductive material having a relatively low resistance, is laminated in a strip shape on the glass substrate 2 by a sputtering method, and is patterned to form a conductive film 21.
Was formed. As the conductive film 21, instead of Al, M
A low-resistance conductive material such as o or Ta may be used. Thereafter, Ta is similarly laminated using a sputtering method,
The scanning lines 10 are formed by patterning.
Further, the SiNx film is formed by a plasma CVD method to a thickness of 300 nm.
The gate insulating film 12 is formed by laminating about nm. The insulating properties may be further improved by anodizing the scanning lines 10.

Subsequently, as shown in FIG.
1. An etching stopper layer 42 is continuously formed on the gate insulating film 12 by using a plasma CVD method. The semiconductor layer 41 is intrinsic semiconductor amorphous silicon (hereinafter referred to as a-Si), and the etching stopper layer 42 is SiNx, which is the same as the gate insulating film 12. The thickness of the semiconductor layer 41 is 60 nm, and the thickness of the etching stopper layer 42 is 2 nm.
00 nm. The etching stopper layer 42 of SiNx has a predetermined shape by patterning.

Next, as shown in FIG. 2, the signal line 20 and the conductive film 2 are formed on the gate insulating film 12 laminated on the conductive film 21.
Through holes 22 for electrically connecting the through holes 1 are formed through a patterning step and an etching step.
Subsequently, as shown in FIG. 3, an n ⁺ -type amorphous silicon layer to which phosphorus is added (hereinafter, referred to as a-Sin ⁺ ) is laminated with a thickness of 80 nm by a plasma CVD method and patterned to form a contact layer. 43 and 44 are formed. Next, Ti is formed on the entire surface of the glass substrate 2 as a source conductor by sputtering.
The signal line 20, the source electrode 31, and the drain electrode 32 were formed by patterning. Signal line 20
Are electrically connected to the conductive film 21 through the through holes 22. Source electrode 31 or drain electrode 32
The ohmic contact with the semiconductor layer 41 is improved by the contact layers 43 and 44. Note that a metal layer of Al, Cr, Mo, or the like may be used instead of Ti.

Next, the picture element electrode 40 and ITO serving as an additional capacitance electrode are laminated by a sputtering method, and this is patterned to form the picture element electrode 40. At this time, like the conventional active matrix substrate, ITO may be formed on the signal line 20 in a stacked state. Then, a protective film layer 45 and an alignment film layer 46 are respectively laminated on the front surface of the glass substrate 2. Thereby, the active matrix substrate of the present invention is formed.

In the above embodiment, the conductive film 21 is formed of a material different from that of the scanning line 10. However, as shown in FIGS. 4 and 5, the conductive film 21 is formed on the glass substrate 2 by the same material as the scanning line 10. The film 21 may be formed. In this case, since the conductive film 21 is formed at the same time as the formation of the scanning line 10, the conductive film 21 is formed at the same time as in the above-described embodiment. A process for laminating materials is not required.

Further, the conductive film 21 may be formed of the same material as the scanning line 10, and the signal line 20 may be formed of the same material as the pixel electrode 40. In this case, the formation of the signal line 20 is also facilitated.

Further, as shown in FIG.
Gate insulating film 12 on each conductive film 21 located on the side of
Is etched over substantially the entire length of each conductive film 21 to form a through hole 22 over substantially the entire length of each conductive film 21, and the conductive film 21 and the signal line 20 may be connected through the through hole 22. .

Further, as shown in FIGS. 5 and 6, the conductive film 21 on the glass substrate 2 may be formed to have a larger width than the signal line 20 laminated thereon.

[0023]

According to the active matrix substrate of the present invention , the signal line and the through hole are formed below the signal line.
The conductive film electrically connected by the
Since it is arranged in a different layer from the pixel electrode, the conductive film and the pixel
Since there is no short circuit with the electrode,
It can be close to the pixel electrode formation area,
Form conductive film as large as possible without affecting
can do. Therefore, the formation area of the signal line is limited.
Even if it is, the conductive film formed wider than the signal line
Is electrically connected to signal lines by through holes to reduce resistance
Wiring. Further, in order to stacked conductive film to the signal lines through an insulating film, it was being electrically connected to the signal line via a through hole formed in the insulating film,
Even when the signal line is disconnected for some reason, the signal of the signal line is transmitted to the portion after the disconnection through the conductive film. as a result,
Disconnection of the signal line is saved. By using a low-resistance material for the conductive film, the electric resistance of the signal line can be reduced. Thus, a high-quality active matrix substrate can be obtained at a high yield. Further, by forming this conductive film simultaneously with the same material as the scanning line, the above object is achieved without increasing the film forming process.

[Brief description of the drawings]

FIG. 1 is a plan view showing one embodiment of the active matrix substrate of the present invention.

FIG. 2 is a sectional view taken along line AA of FIG. 1;

FIG. 3 is a sectional view taken along line FF of FIG. 1;

FIG. 4 is a plan view showing Embodiment 2 of the active matrix substrate of the present invention.

FIG. 5 is a plan view showing Embodiment 3 of the active matrix substrate of the present invention.

FIG. 6 is a sectional view taken along line DD in FIG. 5;

FIG. 7 is a plan view showing an example of a conventional active matrix substrate.

FIG. 8 is a sectional view taken along the line EE in FIG. 7;

[Explanation of symbols]

 Reference Signs List 1 active matrix substrate 2 glass substrate 10 scanning line 11 gate electrode 12 gate insulating film 20 signal line 21 conductive film 22 through hole 30 TFT 31 source electrode 32 drain electrode 40 picture element electrode 41 semiconductor layer 42 etching stopper layer 43, 44 contact layer 45 Protective film layer 46 Alignment film

──────────────────────────────────────────────────続 き Continued on the front page (72) Atsushi Ban, 22-22, Nagaike-cho, Abeno-ku, Osaka-shi, Osaka Prefecture Inside Sharp Corporation (72) Inventor Kiyoshi Nakazawa 22-22, Nagaike-cho, Abeno-ku, Osaka-shi, Osaka Sharp Corporation (72) Inventor: Yu Kajitani 22-22 Nagaikecho, Abeno-ku, Osaka-shi, Osaka Inside Sharp Corporation (56) References JP-A-1-134342 (JP, A) JP-A-3-122620 (JP, A) JP-A-60-66288 (JP, A) JP-A-63-136571 (JP, A) JP-A-63-253391 (JP, A) JP-A-1-266513 (JP, A) (58) (Int.Cl. ⁶ , DB name) G02F 1/136 500

Claims (1)

(57) [Claims] 1. An insulating substrate, a plurality of scanning lines and a plurality of signal lines provided orthogonally to each other in a grid pattern on the insulating substrate, and surrounded by each scanning line and each signal line. comprising: a picture element electrodes disposed respectively, and each pixel electrode and one electrically connected to the scan lines and one signal line is a switching element proximate to the respective picture element electrodes are within a region An active matrix substrate, which is formed wider than the signal line below the signal line except for an intersection with the scanning line via at least one insulating film, Through the through hole formed in the insulating film
It has a signal line electrically connected to the conductive film, conductive film
Is different from the pixel electrode via at least one insulating film.
Active matrix substrates arranged in different layers .