JPH06289423A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To improve a yield by plural TFT structures and to prevent the lowering in opening rate by providing the display device with drain lines between pixel columns, diagonally forming the parts between rows and arranging the TFTs at both ends of these diagonal parts. CONSTITUTION:The drain lines 21 are provided to extend vertically between the columns of the pixels and are formed diagonally in the parts between the rows so as to have the shapes to connect the columns of the rows adjacent to each other by a deviation in half pitch in the row direction to each other. The gate lines 12 intersect with each other in the diagonal parts of the drain lines 21, bend diagonally downward at the points diagonally above the parts near the intersected points thereof and intersect with the drain lines 21 at 90 deg.. Further, the gate lines 12 are extended in parallel with the diagonal parts in the lower parts of the drain lines and both ends of the diagonal parts are integrated to gate electrodes 11 of the TFTs. Display electrodes 19 are disposed in the regions enclosed along the gate lines 12 an the drain lines 21 and are commonly connected to source electrodes 22 of the two TFTs.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a triangle type liquid crystal display device capable of achieving a high yield by providing two TFTs per pixel while avoiding a reduction in aperture ratio.

[0002]

2. Description of the Related Art In recent years, active matrix type liquid crystal display devices have been widely put into practical use because of their advantages such as small size, thin shape and low energy consumption. Particularly, a triangle type in which pixels are arranged in a triangle shape is used in AV equipment and the like. Conventionally, liquid crystal display devices have a problem of low yield. In particular, there is a structure in which a plurality of TFTs are provided in one pixel as a method of relieving defects due to defective TFTs.
For example, Japanese Patent Application No. 3-267686 shows an example of a liquid crystal display device having a 2TFT structure. An example of a conventional liquid crystal display device will be described below with reference to FIGS. 2, 3 and 5. 2 is a plan view, and FIG. 3 is a sectional view taken along the line AA ′ of FIG. Since the drawing numbers in FIG. 3 are also used in this embodiment, those in parentheses are used. Further, FIG. 5 is a plan view. As shown in FIG. 5, display electrodes (59) indicated by dotted lines are arranged in a triangle shape, and gate lines (52) indicated by alternate long and short dash lines extend between rows in the lateral direction of the figure. It is located there. Further, the drain line (61) extends in the vertical direction of the drawing between the columns of the display electrodes (59) as indicated by the solid line, but in the odd and even rows, the display electrodes (59). Since the positions of the lines are shifted from each other by a half pitch, the drain line (61) connects between the columns of the odd-numbered display electrodes (59) and between the columns of the even-numbered display electrodes (59). Lateral direction, that is, the gate line (52)
It has a flat shape. Then, two TFTs (63) and (64) are provided in the portion where the gate line (52) and the drain line (61) are parallel to each other.

Subsequently, the structure of one pixel of the conventional liquid crystal display device will be described with reference to FIGS. 2 and 3. First, on the insulating substrate (50), the gate electrode (5
1), the gate line (5) integrated with the gate electrode (51)
2), the auxiliary capacitance electrode (53), and the auxiliary capacitance electrode (5
An auxiliary capacitance line (54) integral with 3) is provided. Then, a gate insulating film (5
5) is provided, and an a-Si layer (56), a semiconductor protective film (57), and an N ⁺ a-Si layer (in the portion corresponding to the gate electrode (51) on the gate insulating film (55). 5
8), drain electrode (60), and source electrode (62)
Is provided, and a TFT is formed together with the gate electrode (51) and the gate insulating film (55).

Further, a drain line (61) integrated with the drain electrode (60) is provided in a direction perpendicular to the gate line (52) in the shape described above. The display electrode (59) is formed so as to be electrically connected to the source electrode (62).
Further, although omitted in the drawing, a final passivation film is provided below the alignment film and, if necessary, the alignment film to form a TFT substrate.

Finally, a conventional liquid crystal display device is obtained by injecting a liquid crystal between the counter substrate provided with the light shielding film, the counter electrode and the alignment film while being bonded to the TFT substrate.

[0006]

In the conventional liquid crystal display device having the 2-TFT structure described above, both of the two TFTs are often defective and defective, resulting in a low yield. In particular, when an oxide film is formed on the surface of a-Si (56) (the portion indicated by B in FIG. 3) and the surface of the N ⁺ a-Si layer (58) (the portion indicated by A in FIG. 3), the drain of the TFT The electric conduction between the channels or / and the source / channel may be cut off, and the TFT may not operate.

The a-Si layer (56) and the N ⁺ a-Si layer (58) are obtained by growing and forming each on the entire surface of the substrate by plasma CVD, and then etching away the region except the active region of the TFT. , A-Si and N ⁺ a-Si have an oxide film on the film surface after growth. Normally, this oxide film is removed by etching, but it may not be completely removed for some reason and may remain partially. When a TFT is formed in a region where an oxide film remains (hereinafter referred to as an oxide film region), a drain-channel or / and a source-channel is formed.
Electrical conduction is cut off between the channels, and the TFT becomes inoperative. As is apparent from FIG. 2, in the conventional liquid crystal display device, since two TFTs are provided in close proximity to each other, the two TFTs are often formed in the oxide film region, and the number of point defects increases. It was

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and a drain line is arranged in a shape in which a portion between pixel rows is slanted, and TFTs are provided at both ends of this slanted portion. The solution is to place.

[0009]

In the virtual isosceles right triangle formed by the conventional L-shaped portion of the drain line and the slanted portion of the present invention, the conventional TFT has both ends of one of two sides sandwiching the right angle of the right isosceles triangle. However, in the present invention, the distance between the two TFTs is √2 times because it is at both ends of the hypotenuse of the isosceles right triangle in the present invention. Comparing FIG. 5 of the conventional example and FIG. 4 which is the embodiment of the present invention, it is clear that FIG.
It can be seen that the FT separation distance is increasing.

If the two TFTs are separated from each other, TF
The possibility that both of the positions where T is formed is included in the oxide film region is reduced, and at least one TFT can operate normally outside the oxide film region, and the point defects are reduced. Further, by making the L-shaped portion of the drain line oblique, the drain line becomes shorter than in the prior art, and the total area of the drain line occupying the substrate decreases, so that the display region expands correspondingly and the aperture ratio improves. It will be.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to FIGS.
And FIG. 4 will be described. Since FIG. 3 is shared with the conventional example, the figure numbers used are those without parentheses. FIG. 4 shows a positional relationship between pixels and wirings on a TFT substrate of a liquid crystal display device. The pixels are arranged in a triangular shape with respect to each other. For example, for pixels in odd rows, the upper right corner of conventional rectangular pixels is cut off obliquely, and for pixels in even rows, upper left corner. Has an obliquely cut shape.

Drain line (21) shown in solid lines
Are provided so as to extend in the vertical direction of the figure between the columns of pixels, but are formed diagonally in the portion between the rows unlike the conventional example, and are shifted by a half pitch in the row direction so as to be adjacent to each other. The shape connects the rows. Further, the gate line (12) indicated by the alternate long and short dash line intersects at an oblique portion of the drain line (21), but at a point diagonally above and near the intersection, the gate line (12) is bent diagonally downward and 90 degrees. Cross at °. Further, below the drain line (21), the drain line (21) is extended in parallel with the diagonal portion of the drain line (21), and both ends of the diagonal portion are TFTs (23) (24).
Of the gate electrode (11). Upper TF
The gate electrode (11) of T (23) remains a part of the main line of the gate line (12).

The display electrode (19) shown by a dotted line is provided in a region surrounded by the gate line (12) and the drain line (21) and is commonly connected to the source electrodes (22) of the two TFTs. Has been done. Subsequently, a structure of one pixel will be described with reference to FIGS. 1 and 3 together with a manufacturing method. 1 is a plan view, and FIG. 3 is AA ′ of FIG.
It is sectional drawing which follows the line. First, a transparent insulating substrate (1
0), for example, Cr is sputtered to a film thickness of 1500 Å to form a pattern, and the gate line (1
2), the gate electrode (11) which is a part of the gate line (12), the auxiliary capacitance electrode (13), the auxiliary capacitance electrode (1
3) to form an auxiliary capacitance line (14) integrated with the same. Next, plasma CVD of 4000 Å SiNx or SiO ₂
To form a gate insulating film (15). The gate insulating film (15) is made of SiNx or SiO to prevent short circuit.
₂ is divided into _two layers, or the lower layer is SiO ₂ and the upper layer is S
It may be a two-layer insulating film of iNx.

Then, a-Si and SiNx are grown by plasma CVD to a film thickness of 1000Å and 2500Å respectively, and SiNx is patterned to form a semiconductor protective film (1
7) is formed. Further, plasma CVD of N ⁺ a-Si
After forming 500 Å with N, a ⁺ Si-a and a-Si are etched in the same pattern to form a ⁺ Si layer (16) and N ^+.
The a-Si layer (18) is used.

Next, ITO is sputtered and patterned to form a display electrode (19). Then, Mo was sputtered at 1000Å and Al was sputtered at 7,000Å to form a patterned drain line (21), the drain electrode (20) integrated with the drain line (21), and the display electrode (19). Forming a source electrode (22) having

Although not shown in the drawing, a final passivation film and an alignment film are provided, and the final passivation film and the alignment film are further bonded to a counter substrate having a light-shielding film, a counter electrode and an alignment film. The liquid crystal display device as an example is completed. The feature of the present invention is that the drain line (21) crosses rows (or columns) in an oblique direction with respect to rows (or columns), and two TFTs are provided at both ends of an oblique portion of the drain line (21). It is located at the position.

In the manufacturing process of the liquid crystal display device, a-Si and N ⁺ a-Si are plasma C respectively as described above.
Although it is grown by VD, it is exposed to the air
^An insulating SiO ₂ film is formed on the ⁺ a-Si film surface. Normally, SiO ₂ is removed by etching and the process proceeds to the next step, but SiO ₂ may remain for some reason. TF
If the position where T is formed is included in the region where the SiO ₂ film remains, the conduction between the drain and the channel or / and between the source and the channel is cut off by the SiO ₂ film, and the TFT malfunctions. Point defects will occur.

Further, a-Si and SiN are formed by plasma CVD.
x is continuously formed, and SiNx is patterned to form the semiconductor protective film (17). First cleaning, resist coating,
Although there are steps of etching, resist stripping, and second cleaning, especially in the second cleaning, sprayed water vapor may adhere to the substrate to form a SiO ₂ film. Further, when etching SiNx, the SiNx film may remain on the a-Si film. Further, the fine particles existing in the manufacturing apparatus may adhere to the substrate in the process of manufacturing, resulting in defective TFT. If the fine particles are oily and adhere before etching, a SiO ₂ film is also formed.

In any case, an unnecessary insulating region is formed on the surface of the substrate during manufacturing due to various causes, and if a TFT is formed in this region, the TFT becomes defective and leads to a point defect. Was there. Although it is possible to identify the cause of these defects and improve them, it is difficult to eliminate these defects at all. If the two TFTs are arranged apart from each other, even if one of the TFTs does not operate in the insulating region, the other TFT may operate normally outside the insulating region. Therefore, the occurrence rate of point defects is reduced and the yield is improved. In the conventional triangle type 2TFT structure, as can be seen from FIGS. 2 and 5, the two TFTs are arranged in a portion in which the gate line (52) and the drain line (61) are parallel and close to each other between the rows of the pixels. Therefore, the distance is limited to within half a pitch. That is, since the two TFTs are arranged extremely close to each other, both TFTs are often included in the above-mentioned insulating region.

In the present invention, the portion between the rows (or the columns) of the drain line (21) is oblique, for example, at an angle of 45 ° with respect to the gate line direction, and the TFTs are arranged at both ends of this oblique portion. As mentioned in the above operation, the distance can be increased by √2 times, that is, 40% larger than the conventional one. As a structure that separates two TFTs,
According to the method disclosed in Japanese Utility Model Laid-Open No. 61-109487, it is possible to increase the number of wirings and dispose the TFTs at both ends of one side of the display electrode, but this causes a problem of reduction in aperture ratio. In general, a liquid crystal display device having a 2-TFT structure has a narrower display region and a lower aperture ratio than a 1-TFT, but in the structure of the present application, the conventional drain line (61) is L-shaped. Since the drain line (21) is shortened and the total area of the drain line (21) occupying the entire substrate is reduced by taking the portion obliquely, it is possible to prevent the reduction of the display area due to the 2TFT arrangement.

Further, using the method shown in FIGS. 8 (a) and 9 of JP-A-56-77887,
The maximum distance can be secured by arranging the TFT at a diagonal position of the display electrode. However, in this structure, T for relief is used.
The FT is shared with neighboring pixels and does not maintain a normal signal voltage, so it is an incomplete remedy.

In the present invention, the drain line (2
Due to the characteristic shape of 1), when the gate line is extended straight, the drain line (21) and the gate line (1
2) crosses diagonally, and the drain line (21)
Therefore, the area of the weight part of the gate line (12) may increase, and the occurrence rate of short circuit may increase. Therefore, the gate line (12) is slanted near the intersection so that the drain line (21) and the gate line (12) intersect each other at a right angle.

As a second embodiment, a part of the gate line (12) is enlarged in the upper part of the drawing as shown by the dotted line in FIG. 1, and the additional capacitance is obtained by the weight part with the display electrode (19). There is a structure in which the auxiliary capacitance electrode (13) and the auxiliary capacitance line (14) in the same layer as the gate electrode (11) and the gate line (12) are omitted instead. In this case, the gate line (12) is further extended downward from the lower TFT (shown by 24 in FIG. 4) of the two TFTs, and a new TFT is provided at the extended end. If formed, the two TFTs can have a larger distance than in the first embodiment.

In both the first and second embodiments, because of the characteristic shape of the drain line (21) of the present application, the same distance is taken between the two TFTs in the shape of the conventional drain line (21). The aperture ratio is improved as compared with the case.

[0025]

According to the present invention, the yield improvement due to the structure of a plurality of TFTs can be achieved, and the reduction of the aperture ratio, which is a drawback of the plurality of TFTs, can be prevented. Furthermore, it was possible to prevent an increase in short circuits at the weight parts of the drain line and the gate line.

[Brief description of drawings]

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

FIG. 2 is a plan view of a conventional liquid crystal display device.

FIG. 3 is a cross-sectional view taken along the line AA ′ of FIGS. 1 and 2.

FIG. 4 is a plan view of a liquid crystal display device that is an embodiment of the present invention.

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

[Explanation of symbols]

11 gate electrode 12 gate line 16 a-Si layer 18 N ⁺ a-Si layer 19 display electrode 20 drain electrode 21 drain line 22 source electrode 23, 24 TFT

Claims (2)

[Claims] 1. A plurality of gate lines provided on an insulating substrate, a plurality of drain lines provided so as to intersect the gate lines, a gate electrode integrated with the gate line, and a drain electrode integrated with the drain line. At least a drain electrode, a semiconductor layer provided on the upper layer of the gate electrode, and a source electrode provided on the opposite side of the drain electrode with the semiconductor layer in between, and arranged in a matrix on the insulating substrate. A liquid crystal display device having at least two TFTs arranged and a display electrode electrically connected to the source electrode, wherein the pixel is one structural unit composed of the gate line, the TFT, and the display electrode. Is one row (or one column)
Offset by half a pitch in the row (or column) direction, the gate lines are provided between the rows (or columns) of the pixels, the drain lines are provided between the columns (or rows) of the pixels, and A portion between rows (or columns) is provided obliquely to the row (or column) direction, TFTs are provided at both ends of the oblique portion, and the display electrode is surrounded along the gate line and the drain line. A liquid crystal display device, characterized in that the liquid crystal display device is provided in a separate region and is commonly connected to the two TFTs. 2. The liquid crystal display device according to claim 1, wherein the gate line has a shape intersecting the drain line at a right angle at an oblique portion of the drain line.