JPH02189523A - Electrooptical device - Google Patents

Abstract

PURPOSE:To enhance the stability of picture element electrodes and switching elements while maintaining the high light transmittance and electrical conductivity of the picture element electrodes by constituting the picture elements on a substrate of 2 layers of thin films. CONSTITUTION:The picture element electrodes are made into two-layered structures in which the 1st layer 2 on the substrate 1 side is made of the layer 2 essentially consisting of indium oxide to obtain the high electrical conductivity and the light transmittance. The 2nd layer 3 having the boundary with the film deposited on the picture element electrodes 5 is made of the layer 3 essen tially consisting of tin oxide to obtain the high chemical stability. The picture element electrodes which have the advantages of the two layers in combination are obtd. in this way and the display grade and reliability of the electrooptical device are enhanced by using these picture element electrodes for the electrooptical device.

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention relates to a large number of pixels used in display springs of measuring instruments, instrument panels of transportation means, personal computer image display devices, liquid crystal shutters for printers, etc. The present invention relates to an electro-optical device having a number.

[Summary of the invention]

This invention provides an electro-optical device with a matrix structure having a large number of pixels, by increasing the chemical stability of the transparent electrode material that is the pixel and by increasing the reliability of the switching element connected to the pixel. The quality has been improved.

[Conventional technology]

2. Description of the Related Art As small and lightweight electro-optical devices, electro-optical devices using materials having an electro-optic effect, such as electrochromism and liquid crystal, have been put into practical use. In recent years, with the aim of increasing the information content of this type of electro-optical device, three-terminal active matrix liquid crystal display devices using TPT thin film transistors, etc., and two-terminal active matrix liquid crystal display devices in which a nonlinear resistance element is provided in series with each liquid crystal pixel have been developed. is in the spotlight.

For example, a two-terminal active matrix liquid crystal panel that uses silicon nitride as a nonlinear resistance switching element material,
Proc, of the 6th International
ionalDisplay Conference p
p., 72-74 (1986). Second
The figure is a longitudinal cross-sectional view of the same, and its structure is such that a liquid crystal is held between a substrate 8 having a counter electrode 7 and a substrate 1 having a nonlinear resistance element 41 formed thereon. The lower substrate in this figure is manufactured through the following steps.

First, ITO (indium tin oxide 9), which is mainly composed of indium oxide and added with tin, is deposited on the glass substrate 1 and patterned to form the pixel electrode IO. Next, a silicon nitride film 4 and a metal that will become the wiring electrode 5 are deposited and patterned.

[Problem to be solved by the invention]

In order to obtain good display quality with this type of LCD panel,
It is desired that the pixel electrode 10 has a high transmittance to visible light, and from that point of view indium oxide is preferable. When deposited using a growth method, it is damaged by ions, radicals, etc.

Specifically, indium is reduced and diffused into silicon nitride, reducing the reliability of switching elements, and silicon nitride grows in island shapes, making it impossible to obtain the initial characteristics of switching elements. There was a point. From the viewpoint of chemical stability, tin oxide or its fluoride can be considered, but tin oxide is difficult to etch for patterning, has low light transmittance,
Furthermore, it had the disadvantage of low electrical conductivity.

ITO has properties intermediate between indium oxide and tin oxide, and depending on the composition ratio of indium and tin, a material with properties close to the required properties is selected. was difficult to obtain.

Therefore, the purpose of this invention is to provide a pixel electrode with a structure that has high light transmittance, high conductivity, and is chemically stable, thereby improving the display quality of electro-optical devices and increasing reliability. .

[Means to solve the problem]

In order to solve the above problems, the present invention has a two-layer structure for the pixel electrode, and the first layer on the substrate side is a layer containing indium oxide as a main component to obtain high conductivity and light transmittance. The second layer, which is in contact with the film deposited on the electrode, has high chemical stability by making the layer mainly composed of tin oxide.

(Function) By taking the above measures, a pixel electrode that combines the advantages of both layers is obtained, and by using this in an electro-optical device, its display quality and reliability are improved.

〔Example〕

An embodiment of the present invention will be described based on FIG.

The general structure is almost the same as the conventional example shown in Figure 2, and the pixel electrode IO
is different from the conventional example.

The lower substrate in FIG. 1 is manufactured through the following steps. Indium tin oxide 2 is deposited on a glass substrate 1. Setting the film thickness is a trade-off between light transmittance and electrical resistance, but it is usually 100 to 1000. The molar ratio of tin to indium (Sn/In) is O-1/2.

If the tin ratio becomes larger than this, the light transmittance and electrical conductivity will decrease. Indium oxide, which does not contain tin, may be used, but
The smaller the tin ratio, the lower the chemical stability.

Next, a layer 3 having two main components of tin oxide is deposited on the indium tin oxide 2. The first role of tin oxide 3 is to protect the underlying indium tin oxide 2 from damage when silicon nitride 4 is deposited thereon. From this point of view, the film thickness should be at least 10 Å.The second role is to prevent the indium atoms in the indium tin oxide 2 from diffusing into the silicon nitride 4, which occurs during the heating process, driving the electro-optical device, etc. It is. This effect is also effective when the film thickness is 10 Å or more. On the other hand, if the tin oxide layer 3 is too thick, the light transmittance will decrease and etching for patterning the pixel electrode will become difficult. Considering the above circumstances, it is desirable that the film thickness of ~His tin 3 be 500 Å or less.

In this example, the film thickness of the indium tin oxide 2 is set to 3
00 people, and the film thickness of tin oxide 3 was 50 people.

Indium tin oxide or tin oxide can be produced by a CVD method, a vacuum evaporation method, an ionization evaporation method, a sputtering method, or the like.

The chemical stability of tin oxide 3 can be further enhanced by containing fluorine. In addition, 10
Annealing at 0° C. or higher was also effective in increasing chemical stability.

When a 2#a active matrix liquid crystal electro-optical device using silicon nitride as shown in FIG. 1 was fabricated using a two-layer pixel electrode according to the present invention, no abnormal growth of silicon nitride occurred. , the changes in the current-voltage characteristics of the two-terminal element due to driving are significantly reduced compared to the case of using the conventional single-layer indium tin oxide shown in Figure 2, and sufficient transmittance and electrical conductivity are achieved. It was possible to easily carry out processes such as etching.

〔Effect of the invention〕

As described above, according to the electro-optical device using the pixel electrode according to the present invention, the stability of the pixel electrode and the switching element is increased while maintaining the high light transmittance and high conductivity of the pixel electrode. It has an excellent effect of improving the display quality of an electro-optical device, and particularly improving its reliability.

[Brief explanation of the drawing]

FIG. 1 is a vertical cross-sectional view of a liquid crystal electro-optical device in which the first layer of a transparent pixel electrode is made of indium tin oxide 2 and the second layer is made of tin oxide 3, and FIG. 2 shows a conventional transparent pixel electrode made of indium tin oxide. FIG. 2 is a longitudinal cross-sectional view of a liquid crystal electro-optical device made of a single layer of tin. 1, 8...Substrate 2...First layer 3...2nd N Applicant: Seiko Electronics Co., Ltd.

Claims (1)

[Claims] Two opposing substrates, a layer of material having an electro-optic effect sandwiched between the substrates, a large number of pixels and electrodes formed on the inner surface of the first substrate, and a number of pixels and electrodes formed on the inner surface of the second substrate. In an electro-optical device, each pixel of the first substrate is made of a two-layer thin film, and the first layer of the thin film on the substrate side is An electro-optical device comprising indium and oxygen as main components, and a second thin film on the side of the layer of material having an electro-optic effect comprising tin and oxygen as main components.