JPH07191348A - Manufacture of liquid crystal display device - Google Patents

Abstract

PURPOSE:To manufacture an LCD which secures desired electrostatic capacity, increases the optical numerical aperture of a pixel and is improved in the brightness and contrast of an image. CONSTITUTION:A TFT 13 and an auxiliary capacitor 12 is formed on a transparent substrate 1 by forming a gate electrode 2 and an electrode 3 for the auxiliary capacitor on the transparent electrode 1, forming an inter-layer insulating film 4 on the transparent substrate where the gate electrode and the electrode for the auxiliary capacitor are formed, making an insulating film 4b for the capacitor on the electrode for the auxiliary capacitor thin by etching, providing a semiconductor layer 7 on the inter-layer (gate) insulating film 4a on the gate electrode, providing a pixel electrode 6 on the surfaces of the inter-layer insulating film 4 and insulating film 4b for the capacitor, and-providing a source electrode 10 and a drain electrode 11 on the semiconductor layer 7.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a liquid crystal display device. More specifically, it is an active matrix type using a thin film transistor element or the like as a switching element, and a high-definition liquid crystal display device can be provided without lowering the aperture ratio even for a high-definition liquid crystal display device with an increased number of pixels. The present invention relates to a method of manufacturing a liquid crystal display device.

[0002]

2. Description of the Related Art Conventionally, a thin film transistor (hereinafter referred to as a TFT
2), an active matrix type liquid crystal display device (hereinafter, referred to as LCD) using an element or the like is provided in order to apply a voltage to each pixel of the liquid crystal layer 51 as shown in FIG.
The pixel electrode is switched by the FT element 52, and the short-time voltage application is repeated in each row or column for a short time. Therefore, a voltage is applied to the liquid crystal layer 51 even after the applied voltage is turned off. Need to be kept. Therefore, the auxiliary capacitance 53 for holding the electric charge is provided. When the liquid crystal layer 51 itself is used as an auxiliary capacitor,
The capacitance is small and the holding operation is insufficient, and parasitic capacitance is generated, which adversely affects the displayed image. Therefore, an auxiliary capacitor 53 is provided separately from the liquid crystal layer 51.
In the figure, 54 is a gate line connecting the gate electrodes of the TFTs of the pixels arranged in the horizontal direction, 55 is a source line connecting the source electrodes of the TFTs of the pixels arranged in the vertical direction,
56 is a common electrode. In the auxiliary capacitor 53, (a) of FIG.
As shown in FIG. 3, there are two types, that is, a storage capacitor that is uniquely provided in the central portion of the pixel electrode, and an additional capacitor that shares a part of the gate line as shown in FIG.

As shown in FIGS. 3 (a) and 3 (b), the additional capacitance 53a having one electrode of the electrode film 58a connected to the gate line 54a is arranged at the end of the pixel, so that the opening of the pixel is opened. Although the rate can be increased, on the other hand, since capacitance is added to the gate line, there is a drawback that wiring delay increases and responsiveness decreases.

On the other hand, as shown in FIGS. 4A and 4B, a storage capacitor 53b in which an electrode film 58b is provided on a dedicated connection line 59 in addition to the gate line 54 has a poor aperture ratio, line
Since it does not affect 54, it becomes easier to ensure display uniformity.

For example, the TFT and the auxiliary capacitance portion of the LCD shown in FIGS. 4 (a) and 4 (b) are manufactured as follows.

First, a transparent insulating substrate 67a made of glass or the like is provided with A
1, a gate electrode 60 made of a metal such as Cr, a storage capacitor 53
After forming the electrode 58b for b, the gate insulating film 65 made of SiN _x , SiO _x or the like is formed. Next, a semiconductor film 62 made of amorphous silicon or polysilicon is provided on the gate insulating film 65 above the gate electrode 60. Then, the display pixel electrode 57 is formed on the surface of the gate insulating film 65.
And a source region 61a made of amorphous silicon doped with a high impurity on the semiconductor layer 62,
A source electrode 61 and a drain electrode 63 made of the same material as the gate electrode 60 are provided through the drain region 63a, and a passivation film 66 is provided on the surface thereof. In addition, 68 is an electrode of the opposing transparent substrate 67b.

[0007]

In the above-described conventional LCD manufacturing method, it is necessary to reduce the pixel size in accordance with the finer and finer dot matrix, and the auxiliary capacitance requires a constant value. The ratio of the area of the auxiliary capacitor 53 to the area of the pixel electrode 57 is high regardless of the type of the capacitor 53. As a result, there is a problem that the aperture ratio relatively decreases, and the brightness and contrast of the displayed image decrease.

The present invention has been made in order to solve such a problem, and an LCD in which a desired capacitance is ensured and at the same time the optical aperture ratio of each pixel is increased and the brightness and contrast of an image are improved is provided. The purpose is to provide a manufacturing method.

[0009]

The LCD manufacturing method of the present invention is a liquid crystal display in which a liquid crystal layer is sandwiched between two transparent substrates, and a thin film transistor and an auxiliary capacitor are provided on the liquid crystal layer side of one transparent substrate. A method of manufacturing a device, comprising: (a) forming a gate electrode and an electrode for the auxiliary capacitance on the transparent substrate; and (b) forming the gate electrode and the electrode for the auxiliary capacitance. An interlayer insulating film is formed on the formed transparent substrate, and (c) a portion of the interlayer insulating film laminated on the auxiliary capacitance electrode is thinned by etching, and (d) on the gate electrode. A semiconductor layer is provided through the interlayer insulating film, (e) a pixel electrode is provided on the surface of the interlayer insulating film, and a drain electrode and a source electrode are provided on the semiconductor layer. To.

[0010]

According to the LCD manufacturing method of the present invention, in order to reduce the film thickness of the insulating film of the auxiliary capacitance, it is possible to form the auxiliary capacitance of the same conventional capacitance and reduce the auxiliary capacitance area from the conventional one. it can. That is, since the auxiliary capacitance area can be reduced, the aperture ratio can be improved, and as a result, the LCD can be improved.
It is possible to cope with higher definition and higher definition.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A method for manufacturing an LCD of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a process of forming a TFT and an auxiliary capacitor on a transparent substrate in a method of manufacturing a liquid crystal display device of the present invention.

First, as shown in FIG. 1A, a metal film such as Cr or Al is provided on the transparent substrate 1 made of glass or polyester film by a sputtering method or the like.
The gate electrode 2 and the auxiliary capacitance electrode 3 are formed by patterning.

Next, the gate electrode 2 and the auxiliary capacitance electrode 3
An interlayer insulating film 4 made of silicon nitride, silicon oxide, or the like is formed on the transparent substrate 1 on which the film has been formed to a thickness of 0.4 to 0.6 μm by, for example, the CVD method.

Next, as shown in FIG. 1B, a photoresist film 5 is provided on the interlayer insulating film 4, and an upper portion of the auxiliary capacitance electrode 3 is opened. After that, Figure 1 (c)
As shown in FIG. 2, the patterned photoresist film 5 is used as a mask to form the interlayer insulating film 4 on the auxiliary capacitance electrode 3.
Is etched and thinned to a thickness of 0.3 to 0.5 μm. This etching may be wet etching using a hydrofluoric acid solution or dry etching such as reactive ion etching (RIE).

Generally, the capacitance C of the auxiliary capacitance is proportional to the area S of the electrodes on both sides of the dielectric film and the dielectric constant ε of the dielectric film,
Since it is inversely proportional to the distance d between the electrodes (C = εS / d), if the thickness d of the interlayer insulating film 4 is halved, the target capacitance can be obtained even if the electrode area of the capacitor is halved. be able to. Therefore, the thinner the interlayer insulating film 4 is, the smaller the electrode area can be made. However, if it is too thin, the withstand voltage between both electrodes is lowered, so that the thickness is preferably about 0.3 to 0.5 μm. After that, the photoresist film 5 is removed by oxygen plasma or the like.

Next, a semiconductor layer 7 made of amorphous silicon or the like is formed on the gate insulating film 4a, and a source region 8 and a drain region 9 made of amorphous silicon containing impurities of, for example, n ^{+ type} conductivity are formed on both sides of the semiconductor layer 7. Form. Then, the IT is formed on the interlayer insulating film 4 so as to be connected to the drain region 9 and sandwich the capacitor insulating film 4b of the auxiliary capacitor with the auxiliary capacitor electrode 3.
A pixel electrode (represented by an ITO film) 6 made of O, SnO ₂ , In ₂ O ₃ or the like and serving as a drive electrode of each pixel is formed. As a result, the auxiliary capacitance 12 having the interlayer insulating film 4 as a dielectric is formed.
Is formed. Then, electrically between the source region 8 and the source line (not shown) and between the drain region 9 and the pixel electrode 6 by a source electrode 10 and a drain electrode 11 made of aluminum or the like formed by a sputtering method or the like, electrically. Connecting. (See FIG. 1 (d)). On this surface, a passivation film made of silicon nitride or silicon oxide, an alignment film (not shown) made of polyimide or the like is further provided.

In this way, TFTs, auxiliary capacitors and pixel electrodes are formed at once in a matrix, and a plurality of display panels are formed on a large transparent substrate at one time to form one transparent substrate. An electrode film, an alignment film and the like are formed on the other transparent substrate, and the transparent film and the transparent film are attached to each other by a sealant layer so that the alignment film sides of the two transparent substrates face each other, and cut for each display panel. After that, a liquid crystal material is filled between both transparent substrates, and a polarizing plate is provided on both outer sides of the transparent substrate to form a liquid crystal display panel. A light source such as a backlight and a drive circuit are connected to the LCD.
become.

In the LCD manufacturing method of the present invention, as described above, the gate insulating film 4a of the TFT 13 for each pixel and the auxiliary capacitance are formed.
It is characterized in that after forming the capacitor insulating film 4b for 12 in the same process, only the capacitor insulating film 4b is thinned by etching to form the auxiliary capacitor 12 capable of obtaining a large capacitance in a small area. That is, the gate insulating film 4
a requires a film thickness of 0.4 μm or more for the purpose of preventing dielectric breakdown, whereas the capacitor insulating film 4b of the auxiliary capacitance 12 has a large area, it may be about 0.3 μm. Etching the insulating film is not considered. However, with the high definition and high quality of the liquid crystal display device, the area of the non-display area TFT or the auxiliary capacitance portion is reduced to make the pixel smaller and increase the scanning lines, and display each pixel. It is required to maintain a high aperture ratio without decreasing the area ratio.
Regarding the TFT, there is a limit to the reduction of the area, and the aperture ratio is improved by reducing the area of the auxiliary capacitance. In this case, using a material having a large dielectric constant for the capacitor insulating film of the auxiliary capacitor is also effective in reducing the area of the auxiliary capacitor, but deposits a material having a large dielectric constant on a large substrate. Due to this difficulty, the present inventors sought to improve the aperture ratio by thinning the insulating film on the storage capacitor.

According to the present invention, the thickness of the insulating film for capacitors can be reduced.
As a result of reducing the area of the auxiliary capacitance by 25% from 0.4 μm to 0.3 μm, the aperture ratio could be improved by 12%.

[0020]

According to the LCD manufacturing method of the present invention, it is possible to simultaneously secure the aperture ratio of the pixel and the capacity of the auxiliary capacitor, so that the liquid crystal display of low power consumption, high definition and high quality can be obtained. You can get an image. Therefore, it can be applied to a high-definition high-definition television which has been developed and put into practical use in recent years, and the aperture ratio is improved and the brightness and the contrast are improved even in a normal liquid crystal display device.

[Brief description of drawings]

FIG. 1 is a sectional explanatory view showing an embodiment of a manufacturing process of an LCD of the present invention.

FIG. 2 is an equivalent circuit diagram showing an example of an LCD having a TFT.

3A and 3B are diagrams showing an example of a conventional LCD, in which FIG. 3A is an explanatory plan view and FIG. 3B is an explanatory sectional view thereof.

FIG. 4 is a diagram showing another example of a conventional LCD, in which (a) is a plan view and (b) is a cross-sectional view thereof.

[Explanation of symbols]

 1 transparent substrate 2 gate electrode 3 auxiliary capacitance electrode 4 interlayer insulating film 5 photoresist film 6 pixel electrode 7 semiconductor layer 10 source electrode 11 drain electrode 12 auxiliary capacitance 13 TFT

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Makoto Takamura, 21 Mizozaki-cho, Saiin, Ukyo-ku, Kyoto ROHM Co., Ltd.

Claims (1)

[Claims] 1. A method of manufacturing a liquid crystal display device, wherein a liquid crystal layer is sandwiched between two transparent substrates, and a thin film transistor and an auxiliary capacitance are provided on one of the transparent substrates on the liquid crystal layer side. Formation of
(A) forming a gate electrode and an electrode for the auxiliary capacitance on the transparent substrate, and (b) forming an interlayer insulating film on the transparent substrate on which the gate electrode and the electrode for the auxiliary capacitance are formed,
(C) A portion of the interlayer insulating film laminated on the auxiliary capacitance electrode is thinned by etching, (d) a semiconductor layer is provided on the gate electrode via the interlayer insulating film, (e) ) A method for manufacturing a liquid crystal display device, comprising forming a pixel electrode on the surface of the interlayer insulating film and further providing a drain electrode and a source electrode on the semiconductor layer.