JPH06265938A - Liquid crystal display device and its production - Google Patents

Abstract

PURPOSE:To provide the process for production of the image display device which can realize good electrical connection between pixel electrodes and semiconductor films simply by adding a simple stage and the image display device which realizes multiple pixels and higher fineness. CONSTITUTION:TFTs 13 having source connecting ends 11 consisting of the semiconductor films 9 are formed by combining thin-film materials on a transparent insulating substrate and the pixel electrodes 7 consisting of transparent conductive films are so formed as to come into contact with these source connecting terminals 11. Contact parts 11 which come into contact with the source connecting ends 11 by averting parts 17 relating to display of the pixel electrodes 7 are selectively exposed to hydrogen plasma to form the compsn. of the contact parts 11 so as to have the oxygen content lower than the oxygen content of the compsn. of the parts 17 relating to the display, by which the contact resistance of the contact parts 11 is suppressed while the transparency of the parts 17 relating to the display is maintained. The good electrical contact is thus obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image display device,
In particular, the present invention relates to an image display device in which a pixel electrode for display is formed of a transparent conductive film and a manufacturing method thereof.

[0002]

2. Description of the Related Art Generally, a CRT has been used as an image display device.
Although a display device using a liquid crystal display device is used, as an image display device capable of further miniaturization and thinning, for example, a flat panel image using a plasma display panel or an electroluminescent panel including a liquid crystal display device. Display devices are receiving attention.

Among them, the liquid crystal display device is widely used as a display device such as a television or a graphic display due to its features such as thin shape and low power consumption. Among the liquid crystal display devices, an active matrix type liquid crystal display device using a thin film transistor (TFT) as a switching element is excellent in high-speed response and suitable for high definition display screen. It is attracting attention as a device that realizes high image quality, large size, and color image formation.

The display element portion of this active matrix type liquid crystal display device is generally an active element array substrate provided with a switching active element such as a TFT and a pixel electrode connected thereto, and an active element array substrate opposed thereto. A main part is composed of a counter substrate having counter electrodes formed thereon, a liquid crystal composition sandwiched between these substrates, and a polarizing plate attached to the outer surface side of each substrate. .

Also in the simple matrix type liquid crystal display device, the scanning electrodes and the signal electrodes arranged in a row are pixel electrodes made of a transparent conductive film such as ITO (indium tin oxide film). Is also connected to a drive circuit having a switching element or the like for controlling voltage application.

Also in the plasma display panel and the electroluminescent panel described above, a pixel electrode formed of a transparent conductive film is generally used in a portion related to image display in many cases. Also in this case, the pixel electrode is generally connected to a drive circuit having a switching element or the like for controlling voltage application. In recent years, it has been actively practiced to form a drive circuit integrally with the panel in the peripheral portion of the panel, and the drive circuit is often formed of TFTs.

It is necessary to directly or indirectly connect the connection terminal of the TFT used as the active element or the driving circuit as described above and the pixel electrode to obtain electrical conduction. For example, in the case of the above liquid crystal display device, the source portion of the active layer formed of the semiconductor film of the TFT is directly connected to the pixel electrode through the contact hole, but the electrical connection is good. Must. If the electrical connection is poor, the operating characteristics of the TFT will not be fully exhibited, and as a result, the display quality of the liquid crystal display device will be low. In particular, in recent years, there has been a growing demand for multi-pixel and high-definition image display devices. For example, in the case of a liquid crystal display device, the number of pixels is remarkably increased, and a higher frequency voltage waveform tends to be used. Yes,
In addition, since the element size of TFTs and the line width of scan electrodes tend to be further miniaturized, it is increasingly important to improve the electrical connection between the semiconductor film and pixel electrodes as described above. Become.

[0008]

However, the connection between the pixel electrode according to the prior art and the semiconductor film such as a-Si of the TFT is generally directly connected, and the contact resistance at the interface is obstructed. Therefore, it is difficult to obtain a good electrical connection. As a result, it is not possible to apply a high-frequency voltage waveform, and it is difficult to realize high-definition, multi-pixel (so-called multi-digit display) image display.

The main reason for making it difficult to obtain a good electrical connection between the pixel electrode and the semiconductor film is a semiconductor film (for example, a silicon thin film such as a-Si).
It may be due to the natural oxide film formed on the surface of the above, or due to the formation of a PN junction-like energy band at the contact interface.

To solve this problem, a method has been devised to reduce the above contact resistance by inserting a metal film typified by aluminum (Al) between the pixel electrode and the semiconductor film. Has been done. Besides Al, an alloy of indium and tin has been proposed as the metal film to be used.

However, in such a method, after forming a metal film typified by aluminum (Al) described above, the metal film is patterned with high precision by a photolithography process using a resist or the like to form a pixel electrode. Since it is necessary to add a series of steps of forming a very fine pattern with high accuracy in the connection portion with the semiconductor film and completely removing the resist, the manufacturing process becomes complicated and the cost increases. . In addition, there is a problem that the probability of impurities being mixed between the connection surfaces becomes high, the electrical characteristics become unstable, and the reliability decreases.

As described above, in the conventional technique, it is difficult to obtain a good electrical connection due to the contact resistance at the connection interface between the pixel electrode and the semiconductor film such as a-Si of the TFT. There was a problem that was. As a result, it is difficult to apply a high-frequency voltage waveform, and it has been difficult to realize high-definition and multi-pixel display.

The present invention has been made to solve such a problem, and an object thereof is to realize an electrically good connection between a pixel electrode and a semiconductor film only by adding a simple process. An object of the present invention is to provide a method of manufacturing an image display device capable of achieving the above, and an image display device that realizes a large number of pixels and high definition by the manufacturing method.

[0014]

In order to solve the above problems, an image display device of the present invention comprises a semiconductor material formed by combining a pixel electrode formed of a transparent conductive film containing oxygen in its composition and a thin film. And a thin film switching element that has a connection end that is connected to the pixel electrode and performs switching of voltage application to the pixel electrode, the pixel electrode being connected to the connection end. It is characterized in that the transparent conductive film in the contact portion is a transparent conductive film having a composition with an oxygen content lower than that of the composition of the transparent conductive film in the portion related to the display of the pixel electrode.

Further, in the method of manufacturing an image display device of the present invention, a thin film switching element having a connection end made of a semiconductor material is formed on an insulating substrate by combining thin films, and a transparent conductive film is brought into contact with the connection end. Forming a pixel electrode made of, and selectively exposing a contact portion of the pixel electrode, which is in contact with the connection end, at least in a portion related to the display of the pixel electrode, to a hydrogen plasma, thereby forming a transparent conductive film of the contact portion. The composition is characterized in that it has a lower oxygen content than the oxygen content of the composition of the transparent conductive film in the portion related to the display of the pixel electrode.

[0016]

Function: Hydrogen plasma treatment is selectively applied to the connection portion of the pixel electrode that is in contact with the connection end made of a semiconductor material to reduce oxygen from the composition of the transparent conductive film in that portion. Generally, the pixel electrode is formed of a transparent conductive film having a composition of a metal component such as indium or tin such as ITO and oxygen, but the oxygen content rate of the contact portion of such a transparent conductive film is lowered to relatively reduce the oxygen content. By improving the metal component content and changing the composition to one rich in metal component, the contact state between the contact portion and the connection end of the semiconductor film can be improved.

However, generally, when the oxygen content of the transparent conductive film such as ITO is lowered, the metal content becomes relatively high and the transparency (light transmittance) is lowered. That is, if the above-mentioned hydrogen plasma treatment is applied to the entire pixel electrode, the light transmittance is lowered even in the portion related to the image display, and the inconvenience that the display contrast characteristics and the like are lowered.

Therefore, according to the present invention, the display portion of the pixel electrode which needs to retain transparency is covered with a resist or the like to avoid the influence of the hydrogen plasma treatment, while the contact is exposed while avoiding the covering. Hydrogen plasma treatment is selectively applied only to the part. In this way, it is possible to obtain a good electrical connection by sufficiently suppressing the contact resistance in the contact portion while maintaining the transparency for displaying an image in the portion related to the display of the pixel electrode.

[0019]

1 is a plan view showing the structure of an image display device according to the present invention and its sectional view taken along the line AA '(b), FIG.
FIG. 4 is a diagram showing a manufacturing method thereof. For simplification of the drawings, FIGS. 1 and 2 show mainly the vicinity of the contact portion between the pixel electrode and the semiconductor film, which is a characteristic portion of the present invention. Further, for simplification of description, the structure in the vicinity of such a contact portion and the manufacturing process thereof will be mainly described below in detail.

The image display device according to the present invention comprises a plurality of scanning wirings 3 and a plurality of signal wirings 5 arranged in a row so as to intersect with each other on the transparent insulating substrate 1, and a transparent conductive film containing oxygen in its composition. A pixel electrode 7 formed of a certain ITO (indium tin oxide film) and a source connection end 11 formed by combining a thin film and formed of a semiconductor film 9 are provided, and the source connection end 11 is connected to the pixel electrode 7 7 is a liquid crystal display device having a TFT 13 for switching the voltage applied to the pixel electrode 7, and the composition of the transparent conductive film of the contact portion 15 connected to the source connection end 11 of the pixel electrode 7 is for displaying the pixel electrode 7. The oxygen content is set to be lower than the oxygen content of the transparent conductive film of the portion 17.

A protective film 19 is formed so as to cover almost the entire surface of the TFT array substrate on which the pixel electrodes 7 and the TFTs 13 are formed. Although illustration is omitted, the TFT array substrate and the counter substrate on which the counter electrode is formed are arranged so as to face each other with a gap substantially parallel to each other with a sealing material in the same manner as in a general method for manufacturing a liquid crystal display device. A main part of this liquid crystal display device is constituted by sealing and forming an empty cell, and injecting and sandwiching the liquid crystal composition into the cell.

In the present embodiment, the oxygen content in the composition of the transparent conductive film of the contact portion 15 of the pixel electrode 7 is set to about 60% or less, which is lower than the oxygen content of the display portion 17. . The preferable value of the oxygen content of the composition of the contact portion 15 of the pixel electrode 7 is theoretically 0%. Reducing the oxygen content means that the oxygen content is reduced. The content (ratio) of the metal component will increase. Therefore, from the viewpoint of the above effect, the oxygen content may be set to about 60% or less, which is a value lower than the oxygen content of the display portion 17.

Next, a method of manufacturing the image display device according to the present invention will be described. As shown in FIG. 2A, a silicon thin film such as a-Si is formed on the transparent insulating substrate 1 and patterned to form a semiconductor film 9 as a so-called active layer.

Subsequently, as shown in FIG. 2B, the insulating film 2
1 is formed. The insulating film 21 may be formed, for example, by oxidizing the surface of the semiconductor film 9 or may be formed by depositing another silicon oxide film (SiO _x ) by CVD or the like. Then, the insulating film 21 at the position where the source connection end 11 is to be formed is removed by etching to form a contact hole, and the semiconductor film 9 covered under the contact hole is formed.
The surface of is exposed to obtain the source connection end 11 of the TFT 13.

Then, as shown in FIG. 2C, an ITO film is formed by a sputtering method to form a transparent conductive film so as to cover the insulating film 21 and the exposed source connection end 11, and the transparent conductive film is formed, for example. The pixel electrode 7 is formed by patterning by etching. At this time, the electrical connection at the interface between the source connection end 11 of the semiconductor film 9 and the contact portion 15 of the pixel electrode 7 that is in contact therewith is not yet satisfactory.

Therefore, as shown in FIG. 2D, a resist 23 having a high covering property against hydrogen plasma, such as a photoresist, is formed to expose the contact portion 15 of the pixel electrode 7 and other pixels. The display-related portion 17 of the electrode 7 is covered, and the portion exposed from the resist 23, that is, the contact portion 15 of the pixel electrode 7 is exposed to oxygen plasma. In this way, the contact portion 1 of the pixel electrode 7 that comes into contact with the source connection end 11 made of the semiconductor film 9
5 is selectively subjected to hydrogen plasma treatment to reduce oxygen from the transparent conductive film of the contact portion 15. Generally, the pixel electrode 7 is formed of a transparent conductive film having a composition of a metal component such as indium or tin such as ITO and oxygen, but the oxygen content rate of the contact portion 15 is reduced to 60% or less and relatively. By improving the metal component content rate and changing the composition to a composition rich in metal component, the electrical connection state between the contact portion 15 and the source connection end 11 of the semiconductor film 9 can be improved. At this time, the hydrogen plasma treatment can be more effectively promoted by heating. In general, when ITO is deposited by a sputtering method to form a transparent conductive film, heat treatment (baking) is performed to stabilize the film quality. Therefore, performing the heat treatment in addition to the hydrogen plasma treatment has good process compatibility with the conventional ITO formation process, and the hydrogen plasma treatment and the heat treatment can be performed at one time to prevent the manufacturing process from becoming complicated. Therefore, it is preferable.
Alternatively, the hydrogen plasma treatment may be performed after heat treatment (baking) of the transparent conductive film or before heat treatment (baking).

As the resist 23, a photolithography resist used in a general TFT manufacturing process may be used. Alternatively, the resist 23 can be freely patterned and functions as a resist against hydrogen plasma. However, a material having a covering property for preventing hydrogen from penetrating into the semiconductor film 9 covered thereunder can be preferably used.

After the hydrogen plasma treatment is performed as described above, the resist 23 is peeled off. However, this resist 2
3 may be left as it is without peeling. A resist material may be used so that the resist 23 is hardly adversely affected in the subsequent steps.

In the above embodiments, the embodiments in which the present invention is applied to the liquid crystal display device have been described, but the application of the present invention is not limited to this. In addition to the above, the present invention is applicable to any image display device using a transparent conductive film such as ITO having oxygen and metal components as a pixel electrode in a plasma display device or an electroluminescent display device. Can be applied.

Further, in the above embodiments, the case where the present invention is applied to the active matrix type liquid crystal display device has been described in detail, but the present invention is not limited to this. In addition to this, for example, a driving circuit is provided around the transparent insulating substrate in a TF
It can also be applied to the case of integrally forming with T and connecting the connection end made of the semiconductor film and the contact portion of the pixel electrode made of the transparent conductive film.

In addition, it goes without saying that various changes can be made to the material for forming each part of the image display device of the present invention without departing from the scope of the present invention.

[0032]

As clearly described in the above detailed description, according to the present invention, it is possible to realize an electrically good connection between the pixel electrode and the semiconductor film by adding a simple process. It is possible to provide a method for manufacturing a display device and an image display device that realizes a large number of pixels and high definition.

[Brief description of drawings]

FIG. 1 is a plan view and a cross-sectional view showing a structure of an image display device of the present invention.

FIG. 2 is a diagram showing a method for manufacturing an image display device of the present invention.

[Explanation of symbols]

1 ... Transparent insulating substrate, 3 ... Scan wiring, 5 ... Signal wiring, 7 ...
Pixel electrode, 9 ... Semiconductor film, 11 ... Source connection, 13 ... T
FT, 15 ... Contact part, 17 ... Portion related to display of pixel electrode, 19 ... Protective film, 21 ... Insulating film, 23 ... Resist

Claims (2)

[Claims] 1. A pixel electrode formed by combining a thin film and a pixel electrode formed of a transparent conductive film containing oxygen in the composition, and having a connection end made of a semiconductor material, the connection end being connected to the pixel electrode In an image display device having a thin film switching element that performs switching of voltage application to electrodes, a transparent conductive film of a contact portion of the pixel electrode connected to the connection end is a transparent conductive film of a portion related to display of the pixel electrode. An image display device comprising a transparent conductive film having a composition with an oxygen content lower than that of the composition of the film. 2. A thin film switching element having a connection end made of a semiconductor material is formed on an insulating substrate by combining thin films, and a pixel electrode made of a transparent conductive film is formed so that at least a part of the connection end contacts the connection end. The contact portion of the pixel electrode contacting the connection end is selectively exposed to hydrogen plasma while avoiding the display portion of the pixel electrode, and the composition of the transparent conductive film of the contact portion is changed to display the pixel electrode. The method for producing an image display device, wherein the oxygen content is lower than the oxygen content of the composition of the transparent conductive film in the portion related to.