JPH0450818A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To improve the yield of this display device which incorporates a peripheral circuit by setting a distance between a signal circuit and a picture element part larger than a distance between a scanning circuit and the picture element part. CONSTITUTION:A distance d2 between a signal side circuit 4 and a picture element part 2 in a peripheral circuit is set larger than a distance d1 between a scanning side circuit 3 and the picture element part 2. In this regard, d2>=900mum, and d1>=600mum are desirable. In this case, as for the signal side circuit 4 and the picture element part 2, allowable temperatures for manufacture are different from each other and between both of them, a sudden temperature gradient is generated. In order to soften the influence of this temperature difference, the signal side circuit 4 must be separated from the picture element part 2 with >=900mum large distance. On the other hand, a temperature difference for manufacture between the scanning side circuit 3 and the picture element part 2 is low, therefore, it is allowable that a distance between them is >=600mum. In such a manner, the yield of a display device which incorporates the peripheral circuit can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a display device using liquid crystal, and particularly to a display device in which a scanning side circuit and a signal side circuit are formed on the same substrate as the display device.

[Conventional technology]

Display devices using liquid crystals are moving toward larger screens and higher definition, with the former requiring larger substrates themselves, and the latter requiring smaller pixel dimensions and finer processing dimensions.

Both the larger screen size and higher definition of display devices have increased the technical difficulty of manufacturing display devices and caused a significant drop in yield. Conventionally, as a method to make the manufacturing of display devices as easy as possible and at the same time increase the yield, it has been proposed to provide redundancy in the structure (Japanese Patent Laid-Open No. 57-49997).
(2) Methods such as not using the peripheral area of the substrate have been taken. In particular, when trying to reduce the cost by incorporating a drive circuit in the periphery of a display device as in JP-A-59-1.0988, defects in the peripheral circuit become line defects in the display. Improving the yield is a very important issue. Although the above-mentioned conventional technology is mainly used for the display section (pixel section) of a display device, it is also used to improve the yield of peripheral circuits. However, compared to the pixel section, the peripheral circuit section generally has to be formed using a high-temperature process, and high yields are not necessarily achieved. Unexamined Japanese Patent Publication 1986
No. 223788 attempts to form a scanning side circuit using amorphous silicon and a signal side circuit using polycrystalline silicon in order to improve the characteristics of peripheral circuits built into a display device. However, no consideration is given to improving the yield of the entire display device. Special application 1986-200
In order to improve the yield of display devices with built-in peripheral circuits, No. 96 devises a process in which the silicon film is separated by a photo process before laser annealing, but does not consider the structure of the display device.

[Problem to be solved by the invention]

As described above, in the above-mentioned conventional technology, although individual studies have been made such as improving the yield of the pixel area and improving the yield of the peripheral circuit area, improvements in yield that take into account the difference between the peripheral circuit area and the pixel area have been carried out. Furthermore, it is necessary to sufficiently consider measures to improve the yield of display devices with built-in peripheral circuits, such as measures to improve the yield by taking into account the effects on the display device configuration caused by differences between the pixel section, scanning side circuit, and signal side circuit. It wasn't.

An object of the present invention is to provide a structure and configuration of a display device for improving the yield of a display device incorporating a peripheral circuit, and to achieve a reduction in price and higher definition of the display device.

[Means to solve the problem]

In the present invention, the distance d2 between the signal side circuit in the peripheral circuit and the pixel section is made larger than the distance d1 between the scanning side circuit and the pixel section (dz>dl), or d2≧900 μm.
+ d 1≧500 μm.

[Effect]

The invention works as follows. Generally, when comparing a scanning side circuit and a signal side circuit, the signal side circuit is required to operate at about an order of magnitude higher speed. Therefore, the carrier mobility in the transistors constituting the signal circuit must be about one order of magnitude higher than that on the scanning side. In other words, the crystallinity in the active region of the transistor, which is usually made of polycrystalline silicon, must be much higher than that in the scanning side. Therefore, the signal side circuit must be manufactured at a high temperature of approximately 900'C or higher. On the other hand, transistors in the display section are generally constructed using amorphous silicon in many cases. Amorphous silicon is formed at a temperature of 300° C. or lower, and if the temperature is raised to 300° C. or higher after the film is formed, hydrogen in the film will be removed and transistor characteristics will deteriorate. That is, the signal side circuit and the pixel portion have different allowable manufacturing temperatures, and a sharp temperature gradient occurs between the two.

In order to alleviate the influence of this temperature difference, the signal side circuit must be separated from the pixel portion by a large distance.

FIG. 3(a) shows the influence of the distance between the signal side circuit and the pixel on the yield. Here, an excimer laser with a wavelength of 308 nm was used to irradiate energy of 320 mJ/ali. This energy has an annealing effect equivalent to thermal annealing at 900°C. The film thickness is 2,500 people. The yield of a display device refers to the pixel portion TP adjacent to the peripheral circuit.
It can be considered as the yield of T. As the distance between the signal side circuit and the pixel section increases, the yield improves, and when this distance becomes 90%
It can be seen that when the thickness is 0 μm or more, the yield of the pixel portion TPT is about 100%. That is, it is desirable that the distance between the signal side circuit and the pixel section is 900 μm or more. On the other hand, the scanning side circuit is not required to operate as fast as the signal side circuit, and therefore a temperature of about 600° C. for forming the polycrystalline silicon constituting the transistor is sufficient. In other words, the manufacturing temperature difference between the scanning side circuit and the pixel section is only about 3°C, and there is no need for a large distance between the signal side circuit and the pixel section. FIG. 3(b) shows the influence of the distance between the scanning side circuit and the pixel section on the yield of the display device. It can be seen that as the distance between the two increases, the yield improves, and when this distance becomes 600 μm or more, a yield of about 100% can be obtained. That is, it is sufficient that the distance between the scanning side circuit and the pixel section is 600 μm or more. Here, the excimer laser has 240mJ/al! energy was used. This energy is as effective as a 600'C thermal anneal.

By the way, since display devices are generally horizontally long,
Comparing the distance from the center of the display substrate to the scanning side circuit and the distance from the center of the display substrate to the signal side circuit, the former is larger. Therefore, the yield of the scanning side circuit itself is often lower than the yield of the signal side circuit, and there is an urgent need to increase the yield of the former. For this reason, the scanning side circuit needs to be placed as close to the pixel area as possible. That is, the distance between the scanning side circuit and the pixel section needs to be smaller than the distance between the signal side circuit and the pixel section.

In addition to the above-mentioned effects on manufacturing the display device, there is a problem of heat generation in the peripheral circuits. That is, since power consumption is relatively large, especially in the signal side circuit, the temperature of some parts of the circuit becomes high. Therefore, if the signal side circuit and the pixel section are brought close to each other, the life of the liquid crystal in the pixel section will be shortened. This problem can be ignored if the distance between the two is set to 900 μm or more, as described above.

On the other hand, the power consumption of the scanning side circuit is not as large as that of the signal side circuit, so the amount of heat generated is also less than tJ, and it is sufficient that the distance between the scanning side and the pixel section is 600 μm or more.

As described above, the above distance restriction also arises from the problem of heat generation in the peripheral circuit section.

Here, the distance between the scanning side circuit and the signal side circuit and the pixel section refers to the distance between the pixel section and the silicon in the active area of the transistor that makes up the peripheral circuit in the line where they are directly connected by wiring. It refers to the shortest distance between the active region of the transistor and the silicon. If the distance to the pixel portion is not constant among the many lines of the scanning side circuit or the signal side circuit, the distance of the lines that make up the majority among them is important. Usually, this can be approximated by the average distance in each of the scanning side circuit and the signal side circuit. Note that heat from the peripheral circuit section to the pixel section is mainly transmitted through the glass surface, so it does not depend on the thickness of the glass substrate.

Furthermore, it is hardly affected by the type (component) of the glass substrate.

According to the present invention, the peripheral circuit can be formed on the liquid crystal substrate in the same process as the pixel portion TPT, so there is no layer between high-density wiring lines, and the pixel size can be reduced.

Therefore, high-definition display is possible.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG. As the glass substrate 1, a 12-inch diagonal glass substrate (strain temperature of about 600°C) is used.9 First, a Cr gate electrode 5 is formed by sputtering, and then a SiN gate insulating film 6 is formed.
The film and amorphous silicon film (J layer) 7 are subjected to plasma CV
Form by method D.

The film thicknesses are 3000A and 2500A, respectively. Next, the peripheral circuit forming portion shown in FIG. 1 is laser annealed using a XeCQ excimer laser (wavelength: 308 nm) to convert amorphous silicon into polycrystalline silicon. The laser irradiation intensity is 240 mJ/a for the scanning side circuit section 3.
l, the signal side circuit section 4 is 320 mJ/aj.

This energy has the same effect on silicon films as thermal annealing at temperatures of about 900° C. and about 600° C., respectively. Next, a phosphorus-doped amorphous silicon film (n middle layer) source 8. is formed by plasma CVD.
Deposit Tren 9. After forming the island region of the transistor by a photo process, a wiring Or@polar film source electrode 10° and a train electrode 1 are formed by sputtering. Next, the sauce 8. Form a train 9 area. after that,
A transparent electrode of ITO [transparent electrode 13 is formed and patterned by a photo process. Next, a SiN passivation film 12 is formed for passivation by plasma CVD.

Next, the liquid crystal 15 is sealed between the polarizing plate 16 and another glass substrate 1 provided with the color filter 14 to complete the display device. The number of peripheral circuits in this display device is 640 on the scanning side and 1440 on the signal side. In this display device, the distance d2 between the pixel section and the signal side circuit is 950 μm, and the distance between the pixel section and the scanning side circuit is 11i.
dt is 600 μm. It can be seen that the yield of TPT in the pixel portion of this display device is about 100%, which is much better than the yield of about 80% or less when the present invention is not used.

Next, a second embodiment of the present invention is shown in FIG.

In this embodiment, a pixel driving T in a pixel adjacent to a peripheral circuit is used.
A PT is installed at a position within a pixel in contact with the intersection of two sides away from the scanning side circuit and the signal side circuit. In the case of this example, since the pixel size is large at 1 mm x 111111, by arranging the TPTs in this way, it is possible to achieve dl > 600 μ without intentionally separating the peripheral circuit section and the pixel section.
The condition m, dz>900am is satisfied.

〔Effect of the invention〕

According to the present invention, there is an effect of improving the yield of display devices incorporating peripheral circuits, and as a result, it is possible to reduce the price of the display devices. Furthermore, high-definition display is possible.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of a display device according to an embodiment of the present invention. Figure 2 is a cross-sectional view of the thin film transistor used in Figure 1, Figure 3 (a) is a diagram showing the effect of the distance between the signal side circuit and the pixel on yield, and Figure 3 (b) is the scanning side circuit and pixel. FIG. 4 is a schematic cross-sectional view of a liquid crystal display device according to an embodiment of the present invention, and FIG. 5 is a diagram showing the effect of distance on yield.
FIG. 3 is a configuration diagram of a liquid crystal display device according to another embodiment of the present invention. 1...Glass substrate, 2...Pixel section (display section), 3.
...Scanning side circuit section, 4...Signal side circuit section, 5...Gate electrode, 6...Gate insulating film, 7...Silicon film (i layer), 8...Source, 9...・Drain, 10...
- Source electrode, 11... Drain electrode, 12... Passivation film, 13... Transparent electrode, 14... Color filter, 15 Figure A Figure 2 Figure 4 Town τ Road TFT Image S TFT Figure 3 0 300 600 ? 0D1200 r! ;
DOI Rogo 1j1110t and white fish, d2 (
pm) / on the front l! The distance between I and the fish, cll (μm
) Figure

Claims (1)

[Claims] 1. A liquid crystal sealed between transparent substrates, a transparent electrode for driving the liquid crystal, and a voltage applied to this electrode,
In a display device incorporating a thin film element formed in each pixel and a peripheral circuit formed by a thin film transistor formed on the same substrate for driving the thin film element of each pixel,
A liquid crystal display device characterized in that the distance between a signal circuit on a substrate and a pixel section is greater than the distance between a scanning circuit on a substrate and a pixel section. 2. The liquid crystal display device according to claim 1, wherein at least one of the scanning side circuit and the signal side circuit is formed using a laser annealing method. 3. The liquid crystal display device according to claim 2, wherein glass is used as the substrate. 4. The liquid crystal display device according to claim 1, wherein the transistors in the pixel section are made of amorphous silicon, and the transistors in the signal side and scanning side circuit sections are made of polycrystalline silicon. 5. The liquid crystal display device according to claim 1, wherein the signal side circuit section is irradiated with a laser having a higher energy than the scanning side circuit section. 6. A liquid crystal display device according to claim 1, characterized in that the crystallinity of the signal side circuit part active layer is improved more than the crystallinity of the scanning side circuit part. 7. Claim 1 is characterized in that the pixel driving thin film transistor in the pixel adjacent to the peripheral circuit is installed in contact with at least one side of the pixel that is remote from the scanning side circuit and the signal side circuit. LCD display device. 8. A liquid crystal sealed between transparent substrates, a transparent electrode for driving the liquid crystal, and a voltage applied to this electrode,
In a display device incorporating a thin film element formed in each pixel and a peripheral circuit formed by a thin film transistor formed on the same substrate for driving the thin film element of each pixel,
A liquid crystal display device characterized in that the distance between a signal circuit on a substrate and a pixel section is 900 μm or more. 9. The liquid crystal display device according to claim 8, wherein the distance between the scanning side circuit and the pixel portion is 600 μm or more. 10. The liquid crystal display device according to claim 9, wherein at least one of the scanning side circuit and the signal side circuit is formed using a laser annealing method. 11. The liquid crystal display device according to claim 10, wherein glass is used as the substrate. 12. A liquid crystal display device according to claim 8, wherein the transistors in the pixel section are made of amorphous silicon, and the transistors in the signal side and scanning side circuit sections are made of polycrystalline silicon. 13. The liquid crystal display device according to claim 8, wherein the signal side circuit section is irradiated with a laser beam having a higher energy than the scanning side circuit section. 14. A liquid crystal display device according to claim 8, characterized in that the crystallinity of the signal side circuit part active layer is improved more than the crystallinity of the scanning side circuit part. 15. Claim 8 is characterized in that the pixel driving thin film transistor in the pixel adjacent to the peripheral circuit is installed in contact with at least one side of the side away from the scanning side circuit and the signal side circuit at a position within the pixel. LCD display device.