JPH0961851A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal display device which increases the capacity value of storage capacitors and improves the opening rate of pixels by solving the problem that the opening rate of the pixels is sacrificed in order to increase the capacity value of the storage capacitors. SOLUTION: An insulating film 101 is formed at about 300 to 500nm on a quartz substrate 1 and is patterned (a). A polycrystalline silicon layer is formed and is patterned to form semiconductor layers 102 (b). The entire surface is subjected to thermal oxidation to form a thermally oxidized film 103 (c). A polycrystalline silicon layer to constitute a second semiconductor layer is formed over the entire surface and is then patterned to form gate electrodes 5 and the storage capacitors 104. The flanks of the semiconductor layers are assured as the regions for the storage capacitors and the capacity value of the storage capacitors is increased.

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 represented by an active matrix type liquid crystal panel or the like. More specifically, the method of forming a storage capacitor formed in the liquid crystal display device is improved to improve the pixel aperture ratio. The present invention relates to a liquid crystal display device that is improved.

[0002]

2. Description of the Related Art In recent years, along with the widespread use of devices with a liquid crystal display device represented by a VTR with a built-in camera and a liquid crystal projector, there has been an increasing demand for higher performance of the liquid crystal display device. Is progressing. With respect to higher resolution and higher performance of a liquid crystal display device, it is effective to secure a sufficient storage capacity and reduce the storage capacity region to improve the pixel aperture ratio. The present invention relates to a storage capacitor of a liquid crystal display device, which will be described below with reference to specific examples.

A manufacturing process of a conventional liquid crystal display device will be described with reference to FIGS. 2A to 2D are process cross-sectional views for explaining a first half process of a conventional liquid crystal display device.

An active matrix type liquid crystal display device having transparent electrodes arranged in a matrix and switching elements for individually controlling the transparent electrodes has an insulating transparent substrate such as a quartz substrate for its driving substrate. Multiple thin film transistors (hereinafter, simply referred to as "TF
T)) is formed. An example of the fabrication will be described below.

In FIG. 2A, for example, a polycrystalline silicon layer to be a semiconductor layer is formed on a cleaned quartz substrate 1 by LP-CVD (Low Pressure Chemical Vapor Deposition) or the like, and then heat treated or the like. Grow crystal grains. After patterning this by a photolithography technique, a p-type impurity boron B or the like is ion-implanted into the entire surface at a low concentration to form a semiconductor layer 2 of a polycrystalline silicon layer.

Next, thermal oxidation is performed to form a thermal oxide film 3 on the entire surface of the semiconductor layer 2. The thermal oxide film 3 serves as a gate insulating film and a storage capacitor insulating film of the TFT to be formed thereafter ((b) of the same figure).

Turning to FIG. 1C, an n-type impurity is implanted into a portion which will be a storage capacitor to form one electrode 4 of the storage capacitor. Further, after forming a polycrystalline silicon layer serving as a second semiconductor layer on the entire surface, patterning is performed by using a photolithography technique to form a gate electrode 5 and a storage capacitor 6 (which serves as the other electrode of the storage capacitor) by the polycrystalline silicon layer ) Is formed. Then, using the gate electrode 5 as a mask, n-type impurities are ion-implanted into the semiconductor layer 2 to secure the source region 7 and the drain region 8.

In FIG. 1D, an interlayer insulating film 9 such as a thick phosphorous silica gate glass is formed on the entire surface by a CVD method or the like to prevent a short circuit with an upper wiring, and a signal line to be formed next is formed. A contact hole for opening the connection is opened.

Then, for example, Al-1% Si, which is generally used as a wiring material, is formed on the entire surface by a sputtering method and patterned to form a signal line 10 of an Al layer (see FIG. e)).

Next, the latter half process of this embodiment will be described with reference to FIG. 3A to 3D are process cross-sectional views for explaining the latter half process of the conventional liquid crystal display device.

After the above first half process is completed, a second interlayer insulating film 11 to be an interlayer insulating film is formed by, for example, the CVD method (FIG. 3A), and a thin film is formed on the second interlayer insulating film 11 for improving the performance of the TFT. The plasma SiN film 12 is formed by the plasma CVD method. After that, ITO (Indium-Tin Oxid)
e) A contact hole for connecting to the film is opened by etching ((b) of the same figure).

In FIG. 1C, the flattening film 1 is used for the purpose of suppressing the occurrence of irregular alignment (alignment defect) of the liquid crystal.
3 is formed by coating with a spin coater or the like.

Further, after depositing an ITO film by, for example, a sputtering process, the ITO film is patterned to form a transparent electrode 14 for a liquid crystal display device. The transparent electrode 14 has a shape separated for each pixel. Finally, heat treatment is performed to lower the specific resistance of the ITO film and improve the characteristics of the TFT, thus ending the manufacturing process of the drive substrate of the conventional liquid crystal display device (FIG. 3D).

By the way, the capacitance value of the above-mentioned storage capacitor 6 is proportional to the junction area with the semiconductor layer 2 of polycrystalline silicon shown in FIG. Therefore,
In order to increase the capacitance value of the storage capacitor in the conventional liquid crystal display device, it is necessary to increase the junction area. However, if the junction area is increased to increase the capacitance value, the pixel aperture ratio of the liquid crystal display device is sacrificed.

[0015]

An object of the present invention is that the capacitance value of the storage capacitor is proportional to the junction area with the underlying polycrystalline silicon semiconductor layer. Another object of the present invention is to provide a liquid crystal display device which solves the problem that the pixel aperture ratio is sacrificed, increases the capacitance value of the storage capacitor, and improves the pixel aperture ratio.

[0016]

In order to solve the problems of the above-mentioned conventional liquid crystal display device, the following means were taken. That is, in a liquid crystal display device including a thin film transistor arranged in a matrix on a substrate and a drive substrate having a storage capacitor having the same semiconductor layer as the thin film transistor as one electrode, at least 1 layer is formed below the semiconductor layer. Two convex insulating films are formed, and the above-mentioned semiconductor layer, the interlayer insulating film thereon, and the second semiconductor layer are further formed on the convex insulating film and the thin film transistor. It Then, the storage capacitor is three-dimensionally configured by the semiconductor layer formed on the convex insulating film serving as one electrode of the storage capacitor and the second semiconductor layer serving as the other electrode, and the region of the storage capacitor is expanded. Then, the capacitance value is increased.

According to the liquid crystal display device of the present invention, the storage capacitor is three-dimensionally constructed by one or more convex insulating films formed under the semiconductor layer, and the capacitance value of the storage capacitor is increased. Therefore, the display quality of the liquid crystal display device can be improved by ensuring a sufficient write signal for the liquid crystal display device.

In the liquid crystal display device according to the second aspect of the present invention, the pixel area ratio is improved by reducing the planar formation region of the storage capacitor by the storage capacitor having such a configuration.

Therefore, for example, if the capacitance value of the storage capacitor is made constant, the planar formation region of the storage capacitor can be reduced, so that the pixel aperture ratio of the liquid crystal display device can be improved.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of a liquid crystal display device of the present invention will be described below with reference to FIG. In the following description, only the manufacturing process of the characteristic part of the present invention will be described, and the description of the same parts as the manufacturing process of the conventional liquid crystal display device will be omitted. Further, the same parts as those in the manufacturing process of the conventional liquid crystal display device are designated by the same reference numerals.

First, the structure of the liquid crystal display device of the present invention will be described with reference to FIG. FIG. 1 is a process sectional view for explaining a manufacturing process of a characteristic portion of a liquid crystal display device of the present invention.

In FIG. 1A, the cleaned quartz substrate 1
Etc., the insulating film 101, which is a characteristic part of the present invention, has a film thickness of, for example, 300 to 5 having a film thickness similar to that of the second semiconductor layer described later.
It is formed by a CVD method or the like so as to have a thickness of 00 nm. After that, the insulating film 101 is patterned by a photolithography technique to be formed as a base of the polycrystalline silicon layer.

Similarly, after the polycrystalline silicon layer is formed by the CVD method, the polycrystalline silicon layer is patterned by the photolithography technique to form the semiconductor layer 102 of the polycrystalline silicon layer (FIG. 2B).

Next, the entire surface of the semiconductor layer 102 is thermally oxidized to form a thermal oxide film 103. This thermal oxide film 103
Serves as a gate insulating film of a TFT and an insulating film of a storage capacitor formed thereafter ((c) of the same figure).

Referring to FIG. 3D, an n-type impurity is injected into a portion which will be a storage capacitor to form one electrode 4 of the storage capacitor. Further, after forming a polycrystalline silicon layer serving as a second semiconductor layer on the entire surface, patterning is performed using a photolithography technique to form the gate electrode 5 and the storage capacitor 104 of the present invention by the polycrystalline silicon layer. Then, using the gate electrode 5 as a mask, n-type impurities are ion-implanted into the semiconductor layer 2 to secure the source region 7 and the drain region 8. The following process is the same as that of the conventional liquid crystal display device, and the description thereof is omitted because it is redundant. This makes it possible to secure the side surface of the semiconductor layer 102 as a region of the storage capacitor and increase the capacitance value of the storage capacitor. Alternatively, it is possible to improve the pixel aperture ratio of the liquid crystal display device by reducing the planar formation region of the storage capacitor while keeping the capacitance value as it is. By improving the pixel aperture ratio,
A high-brightness liquid crystal display device can be constructed.

On the other hand, a black matrix and a color filter (in the case of a color liquid crystal) are opposed to such a driving substrate.
The counter substrate (not shown) on which is formed a predetermined gap (several μ
The liquid crystal composition is sandwiched in these gaps so that they are opposed to each other. A liquid crystal display device is configured by integrally laminating polarizing plates on both surfaces of these substrates.

The operation of the liquid crystal display device of the present invention having such a configuration will be briefly described. Although not shown in the drawings, the liquid crystal display device of the present invention takes in various control signals and video signals from an external IC. The fetched video signal controls the video voltage of each pixel by the TFT and supplies it to the storage capacitor and the transparent electrode. This image voltage causes the liquid crystal composition to be twisted in the voltage application direction so as to be inverted, and information is displayed on the liquid crystal display device of the present invention by utilizing the optical rotatory power of the liquid crystal composition. According to the liquid crystal display device of the present invention, since a sufficient storage capacity is secured, it becomes possible to display information suitable for a VTR with a built-in camera and a liquid crystal projector having a high contrast ratio.

The present invention is not limited to the above embodiment, and various embodiments can be adopted. For example, although the example in which one convex insulating film is formed is illustrated in the present embodiment, it is also possible to further improve the capacitance value of the storage capacitor by forming a plurality of convex insulating films. The present invention is not limited to the number of convex insulations formed. Needless to say, the present invention can be developed into various forms without being limited to the above-described embodiments.

[0029]

As described above, according to the liquid crystal display device of the present invention, the storage capacitor is three-dimensionally configured by at least one convex insulating film formed under the semiconductor layer,
The capacitance value of the storage capacitor is increased by utilizing the side surface of the semiconductor layer. Therefore, a sufficient write signal for the liquid crystal display device can be secured, and the display quality of the liquid crystal display device can be improved. Further, if the capacitance value of the storage capacitor is fixed, the planar formation region of the storage capacitor can be reduced, so that the pixel aperture ratio of the liquid crystal display device can be improved.

[Brief description of drawings]

FIG. 1 is a process sectional view for explaining a manufacturing process of a characteristic part of a liquid crystal display device of the present invention.

FIG. 2 is a process cross-sectional view for explaining a first half process of a conventional liquid crystal display device.

FIG. 3 is a process cross-sectional view for explaining a latter half process of a conventional liquid crystal display device.

[Explanation of symbols]

 1 quartz substrate 2, 102 semiconductor layer 3, 103 thermal oxide film 4 one electrode of storage capacitor 5 gate electrode 6 storage capacitor 7 source region 8 drain region 9 interlayer insulating film 10 signal line 11 second interlayer insulating film 12 plasma SiN film 13 flattening film 14 transparent electrode 101 insulating film 104 storage capacitor of the present invention

Claims (2)

[Claims] 1. A liquid crystal display device comprising: a thin film transistor arranged in a matrix on a substrate; and a driving substrate having a storage capacitor having the same semiconductor layer as the thin film transistor as one electrode. At least one convex insulating film is formed, and on the convex insulating film and the thin film transistor,
The semiconductor layer, an interlayer insulating film on the semiconductor layer, and a second semiconductor layer on the interlayer insulating film; the semiconductor layer formed on the convex insulating film; and the second semiconductor. The storage capacitor is three-dimensionally configured by layers and
A liquid crystal display device, wherein a region of the storage capacitor is expanded to increase a capacitance value. 2. The liquid crystal display device according to claim 1, wherein the storage capacitor reduces a planar formation region of the storage capacitor to improve a pixel aperture ratio.