JP2714270B2 - Liquid crystal display - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device, and more particularly to a liquid crystal display device capable of preventing a short circuit between a display electrode and an auxiliary capacitance electrode and a disconnection of the display electrode.

[0002]

2. Description of the Related Art In general, development and mass production of liquid crystal display devices are being actively promoted mainly for color TVs.

[0003] As a detailed explanation of these technical trends, there is "Flat Panel Display 1991" issued by Nikkei BP. Among them, liquid crystal display devices having various structures are disclosed. Here, an active matrix liquid crystal display device using a TFT will be described below.

This active matrix liquid crystal display device has, for example, a configuration as shown in FIG. First, there is a transparent insulating substrate, for example, a glass substrate (51). On the glass substrate (51), a gate (52) and an auxiliary capacitance electrode (53), which are components of the TFT, are formed, for example, by Mo-.
It is formed of a Ta alloy or the like. Furthermore, the whole surface is SiNx
Is formed. Subsequently, an amorphous silicon film (55) and an N ⁺ type amorphous silicon film (56) are laminated on the SiNx film (54) corresponding to the gate (52). A semiconductor protective film (57) is provided between (55) and (56). Subsequently, on the N ⁺ type amorphous silicon film (56), a source electrode (58) and a drain electrode (59) are provided, for example, as a laminate of Mo and Al. Further, the SiNx film (54) corresponding to the auxiliary capacitance electrode (53)
A display electrode (60) made of, for example, ITO is provided thereon, and is electrically connected to the source electrode (58).

On the other hand, although not shown, a glass substrate is provided to face the glass substrate (51), and a counter electrode is provided on the glass substrate. Further, a liquid crystal is injected between the pair of glass substrates to form a liquid crystal display device.

A plan view of the apparatus will be described with reference to FIG. FIG. 4 substantially corresponds to the line BB in FIG. First, the gate line (61) is shown by a dashed line,
It extends left and right with respect to the paper surface. A wide portion is provided in one region of the gate line (61), and this region corresponds to the gate (52). The auxiliary capacitance electrode (5
3) is also indicated by a dashed line, and the display electrode (6)
0) Below, it is provided in the shape of the letter H. In addition, an auxiliary capacitance line (62) is provided to connect to an adjacent auxiliary capacitance electrode (53). The drain line (63) integrally formed with the drain electrode (59) extends zigzag in the vertical direction with respect to the plane of the paper because the display electrodes (60) form a triangle structure in a set of three. Have been.

[0007]

In the above configuration,
Si is provided between the auxiliary capacitance electrode (53) and the display electrode (60).
Although the Nx film (54) is provided, both electrodes (53) and (60) are formed due to adhesion of dust in the process of forming the film (54), a defect in the step cover of the auxiliary capacitance electrode (53), and the like.
In some cases, a short-circuit phenomenon occurred between them.

Further, depending on the thickness of the auxiliary capacitance electrode (53), the display electrode (6) provided on the SiNX film (54) may be used.
0) cannot completely cover the steps of the SiNX film (54) as described above, and the edge of the auxiliary capacitance electrode (53)
In some cases, the display electrode (60) which should be electrically integrated was separated into a plurality of regions.
For this reason, the potential of the source electrode (58) is not applied to all the regions, and a display defect may occur.

[0009]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and has at least a part of a step formed on a part of a display electrode (11) from a high place to a low place of the step. The problem is solved by providing a metal layer (15) extending integrally with the metal layer.

A TFT is provided between the gate insulating film (7) formed on the auxiliary capacitance electrode (4) and the display electrode (11).
(2) of the same material as the semiconductor active layer (8)
0), a layer (21) of the same material as the semiconductor protective film (10) covering the surface of the semiconductor active layer (8) corresponding to the channel of the TFT, and a layer of the same material as the semiconductor contact layer (9) constituting the TFT ( 22) are stacked, and the display electrode (1) is stacked.
A metal layer (15) integrally extended from at least a part of the step to a part of the step formed at a part of the step (1).
This can be solved by providing

As shown in FIG. 1, the display electrode (11) corresponding to the auxiliary capacitance electrode (4) has a step due to the thickness of the auxiliary capacitance electrode (4). Since cracks and the like mainly occur in the region corresponding to the edge of the auxiliary capacitance electrode (4), if the metal layer (15) is provided from a high place to a low place with the crack as a boundary, the display electrode (11) The potential can be applied uniformly over all regions.

The auxiliary capacitance electrode (4) and the display electrode (1)
Short-circuit with 1) occurs from the surface of the gate insulating film (7), from the surface of the gate insulating film (7), to the layer (20) of the same material as the semiconductor active layer (8), the layer (21) of the same material as the semiconductor protective film (10), and If layers (22) of the same material as in 9) are sequentially laminated,
At least the pinholes generated in the respective layers do not match, and the pinholes generated in series between the electrodes (4) and (11) are eliminated.

However, the three layers (20), (21),
Due to (22), the above-mentioned cracks are more likely to occur, but by providing the metal layer (15), display defects due to the cracks can be eliminated.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The construction of the present invention will be described below with reference to FIGS. FIG. 2 is a sectional view substantially corresponding to the line BB in FIG.

Referring to FIG. 2, there is a transparent insulating substrate (1). This substrate (1) is made of, for example, glass.

On the glass substrate (1), a gate (2), a gate line (3) integral with the gate, an auxiliary capacitance electrode (4) and an auxiliary capacitance line (5) integral with the auxiliary capacitance electrode (4) are provided. Is provided. Here, the auxiliary capacitance electrode (4) in FIG. 2 indicates the lower right end of the letter H in FIG.
These (2), (3), (4), and (5) are made of Cr in the present embodiment, but may be made of, for example, Ta, TaMo,
Cr-Cu (containing a small amount of Fe) may be used.

Referring to FIG. 1, the gate (2) and the gate line (3) extend in the direction transverse to the plane of the drawing with dashed lines, and are formed slightly wider only in the TFT forming region. On the other hand, the auxiliary capacitance electrode (4) is formed in a shape of an H in a dashed line, and an auxiliary capacitance line (5) is provided to connect the auxiliary capacitance electrodes (4) provided adjacently on the left and right. ing.

Although not shown in the drawings, a gate terminal and an auxiliary capacitance terminal are provided around the glass substrate (1). The auxiliary capacitance line (5) is connected.

Next, the gate (2), the gate line (3),
There is a gate insulating film (7) covering the auxiliary capacitance electrode (4) and the auxiliary capacitance line (5). This film is formed by plasma CVD
It is a SiNx film formed by a method. Here, SiNx
Instead of a film, a SiO ₂ film may be used, or these two films may be stacked. When the SiNx film or the SiO ₂ film is used alone, the film forming process may be divided into two processes to form a two-layer structure.

Next, a gate insulating film corresponding to the TFT
(7) An amorphous silicon active layer (a-S
i-layer) (8) and amorphous silicon contact
Layer (N⁺a-Si layer) (9) is laminated
A-Si layer (8) corresponding to ⁺a-Si layer (9)
Between them, a semiconductor protective film (10) made of a SiNx film is provided.
Is provided. This semiconductor protective film (10) is made of N⁺a
A-Si layer when etching the Si layer (9)
(8) The etching is prevented, and further, the gate insulating film
(7) a-Si layer (8) and SiNx film (10)
By continuously forming TFT switching characteristics
Has the function of improving.

Referring to FIG. 1, an a-Si layer (8) is provided slightly wider than the gate (2) constituting the TFT and in a square shape shown by a dotted line and a solid line. The semiconductor protective film (10) is provided in the center of the gate (2) in a square shape shown by a solid line. Further, an N ⁺ a-Si layer (9)
Are provided in regions hatched by oblique lines.

On the other hand, the display electrode (11) is made of ITO and is shown by a dotted line in FIG. This display electrode (1
1) is arranged in a triangle structure in order to display RGB on three display electrodes (11).

Further, N ⁺ a- corresponding to the source of the TFT
N ⁺ a-S corresponding to a source electrode (12) extending from the Si layer (9) to the display electrode (11) and a drain of the TFT.
A drain line (14) integral with the drain electrode (13) extending from the i-layer (9) to the drain terminal is provided. Since the display electrode (11) has a triangle structure, the drain line (14) extends zigzag in the vertical direction with respect to the paper surface. In this embodiment, the electrodes (12), (13), and (14) are made of Al.
Although made of -Mo, other metals may be used.

In this embodiment, as shown in FIGS. 1 and 2 , the display electrode is formed so as to extend across the edge line of the auxiliary capacitance electrode (4) and to be formed by the thickness of the auxiliary capacitance electrode (4). A metal layer (15) formed so as to extend from the high part of (11) to the low part of the step part on both sides bordering this high part is provided at five places on the display electrode (11). Is provided. This metal layer (15) is made of the same material as the source electrode (12) and the drain electrode (13), and is formed simultaneously with the source and drain electrodes (12, 13). In particular, as shown in FIG. 1, at five predetermined positions of the auxiliary capacitance electrode (4) having an H shape, the auxiliary capacitance electrode (4) is formed so as to always cross the edge line of the auxiliary capacitance electrode (4). I have. In particular, the metal layer (15) extends from a point on the auxiliary capacitance electrode (4) to a region on both sides divided by the auxiliary capacitance electrode (4) across the edge line of the auxiliary capacitance electrode (4). Each is connected.
In the present embodiment, for example, the H-shaped horizontal bar portion of the auxiliary capacitance electrode (4) is formed so as to connect between vertically divided regions in the figure. Therefore, the display electrode (15) is disconnected due to a step at the edge of the auxiliary capacitance electrode (4).
2) The voltage for driving the liquid crystal is not applied to a region farther from the region, or the stepped portion has a high resistance, and the applied voltage is different on both sides of the stepped portion. Such a problem can be prevented.

Although not shown below, the upper layer is provided with an alignment film made of, for example, polyimide or the like. on the other hand,
An opposing glass substrate paired with the glass substrate (1) is provided. On the opposing glass substrate, a light-shielding film is provided at a position corresponding to the TFT and an opposing electrode is provided. Further, the above-mentioned alignment film is provided.

Further, a spacer is provided between the pair of glass substrates, the periphery is sealed with a sealing material, and liquid crystal is injected from the injection hole to obtain the present device.

Next, another embodiment will be described with reference to FIG.

In this embodiment, a short circuit between the auxiliary capacitance electrode (4) and the display electrode (11) is prevented, and a deterioration in display characteristics due to a crack is also prevented. Since the configuration is almost the same as that of FIG. 1, only different portions will be described here.

Between the display electrode (11) and the lower gate insulating film (7), a TFT a, which is a feature of the present invention, is provided.
-The first interlayer (2) made of the same film as the Si layer (8);
0), a second interlayer (21) made of the same SiNx as the semiconductor protective film (10), and a third interlayer (22) made of the same film as the N + a-Si layer (9). These first, second and third interlayer layers (20), (21) and (22)
Are formed simultaneously with the TFT a-Si layer (8), the semiconductor protective film (10), and the N + a-Si layer (9).

The first, second and third interlayer layers (2
Since (0), (21) and (22) are interposed between the display electrode (11) and the gate insulating film (7) in the region above the auxiliary capacitance electrode (4), even if the gate insulating film Even if there is a pinhole in (7), a short circuit between the display electrode (11) and the auxiliary capacitance electrode (4) is prevented.

Incidentally, the second interlayer (21) made of SiNx functions as a dielectric constituting a capacitor depending on the configuration, but the first interlayer (20) made of a-Si and the N + a- Since the first interlayer layer (20) and the third layer (22) are in contact with each other while being completely wrapped by the third interlayer layer (22) made of Si, no capacitance is formed. Since this device is used after being irradiated with light, a
The first interlayer (20) made of -Si is excited by this light and functions as a normal electrode.

Therefore, the second interlayer (21) is completely shielded at one potential, does not constitute a capacitor, and further has the display electrode (11), the third interlayer (22), 2
The first interlayer layer (20) and the first interlayer layer (21) are integrated to function as an upper electrode of the auxiliary capacitance.

Referring to FIG. 3, two dashed-dotted lines and three dashed-dotted lines are shown outside and inside the storage capacitor electrode (4) shown by dashed-dotted lines. The region indicated by the arrows indicates the first interlayer layer (20) and the third interlayer layer (22), and the region surrounded by the inner line is the second interlayer layer (21). At least one of the first interlayer layer (20), the second interlayer layer (21) and the third interlayer layer (22) completely covers the storage capacitor electrode (4) in plan view. It is shaped to cover.

With the above configuration, a short circuit between the auxiliary capacitance electrode (4) and the display electrode (11) can be prevented. However, unlike the embodiment of FIG. 1, between the electrodes (4) and (11) there is a first interlayer (20), a second interlayer (21) and a third interlayer (22). Is added, the step on the base of the display electrode (11) is further increased.

Therefore, also in this embodiment, as shown in FIG. 3, metal layers (15) are provided at predetermined five places on the display electrode (11). In particular, in the present embodiment, the places where the display electrode (11) can be cracked by the steps of the base are not only the edges of the auxiliary capacitance electrode (4) but also the first, second and third interlayer layers. (20) (2
1) The same applies to the edge portion of (22). Therefore, as shown in FIG. 3, not only the edge of the auxiliary capacitance electrode (4) but also the outer two-dot chain line, that is, the edges of the first and second interlayer layers (20) and (21). As always, a metal layer (15) is provided.

As described above, cracks that occur in the display electrode (11) are likely to occur in the dashed line, two-dot chain line, and three-dot chain line portion in FIG. Furthermore, it is likely to occur at the end of the letter H. Therefore, in the present application, the metal layer (15) is provided at the four end portions wider than the region indicated by the two-dot chain line. It is provided on the horizontal line at the center of the letter H. This prevents the display electrode (11) from being separated into A and B shown in the figure due to cracks. Further, a metal layer (15) is provided integrally with the source electrode (12) and covers one of the four ends. This metal layer is different from the other three in that the source electrode (1
The potential of 2) can be directly applied.

[0037]

As is clear from the above description, cracks in the display electrode, which may be caused by the steps of the auxiliary capacitance electrode, degrade the display characteristics, but the metal layer can prevent the deterioration due to the crack.

Further, in order to prevent a short circuit between the auxiliary capacitance electrode and the display electrode, an a-Si layer, a SiNx film and an N ⁺
When the a-Si layer is laminated, the step is further increased and the crack generation rate is increased. However, since the display electrode is provided with the metal layer, the deterioration of the display characteristics due to the crack can be prevented.

[Brief description of the drawings]

FIG. 1 is a plan view of a liquid crystal display device of the present invention.

FIG. 2 is a sectional view taken along line BB of FIG.

FIG. 3 is a plan view of a liquid crystal display device for explaining another embodiment.

FIG. 4 is a sectional view of a conventional liquid crystal display device.

FIG. 5 is a plan view of a conventional liquid crystal display device.

[Description of Signs] (2) Gate (4) Storage capacitance electrode (11) Display electrode (15) Metal layer

Claims (5)

(57) [Claims] 1. A plurality of gate lines, a plurality of drain lines, and a plurality of auxiliary capacitance lines are formed on a transparent insulating substrate, and a TFT is provided at an intersection of the gate line and the drain line, and a display electrode connected to the TFT. And a liquid crystal display device in which an auxiliary capacitance electrode overlapped with the lower layer of the display electrode with an insulating film interposed is formed on the display electrode, above the auxiliary capacitance electrode,
At least above the edges on both sides of the auxiliary capacitance electrode.
A liquid crystal display device comprising a metal layer extending across the liquid crystal display. 2. The liquid crystal display device according to claim 1, wherein the metal layer is made of the same material as a drain electrode or a source electrode of the TFT. 3. A first interlayer made of the same material as a semiconductor active layer forming the TFT, between the insulating film and the display electrode in a region corresponding to a position above the storage capacitor electrode, A second interlayer layer of the same material as the semiconductor protective film covering the surface of the semiconductor active layer corresponding to the channel of
3. The liquid crystal display device according to claim 1 , wherein a third interlayer layer made of the same material as a semiconductor contact layer forming the TFT is interposed. 4. The second interlayer layer is narrower than the first interlayer layer below it and the third interlayer layer above it, and the first interlayer layer and the third interlayer layer are narrower. The liquid crystal display device according to claim 3, wherein the liquid crystal display device is included in an interlayer. 5. A first interlayer made of the same material as a semiconductor active layer constituting the TFT, between the insulating film and the display electrode in a region corresponding to a position above the storage capacitor electrode, and A second interlayer of the same material as the semiconductor protective film covering the surface of the semiconductor active layer corresponding to the channel of the TFT is interposed, and the second interlayer is smaller than the first interlayer below it. 3. The liquid crystal display device according to claim 1, wherein the width of the liquid crystal display device is reduced, and the liquid crystal display device is enclosed by the display electrode and the first interlayer layer located above the display layer. 4.