JPH06160912A - Liquid crystal display device and its production - Google Patents

Abstract

PURPOSE:To provide the liquid crystal display device which can be easily produced at a low cost by decreasing production stages as compared with heretofore and the process for production of the device. CONSTITUTION:An array substrate 12 of the liquid crystal display has signal electrodes 20 and MIM elements 24 connected to pixel electrodes 22. The MIM elements 24 have a first metallic layer 24a and a second metallic layer 24b contg. oxygen and these metallic layers are formed partly in overlap. The first and second metallic layers 24a, 24b are heat treated, by which the contact part of the first metallic layer 24a in contact with the second metallic layer 24b in the overlapped part is oxidized by the oxygen component diffused form the second metallic layer 24b and a metal oxide layer 24c is formed between the first and second metallic layers.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a liquid crystal display device, and more particularly to
The present invention relates to a liquid crystal display device using a non-linear resistance element including a metal layer-insulating layer-metal layer (hereinafter referred to as MIM) as a switching element and a method for manufacturing the same.

[0002]

2. Description of the Related Art In recent years, liquid crystal display devices have been used for displaying large-capacity information such as personal computers, word processors, terminal equipment for office automation, and image display for TV, and higher image quality is required. It has become. Although various types of switching elements used in liquid crystal display devices are known, a two-terminal non-linear resistance element having a simple structure and easy to manufacture, and among them, MIM has been put into practical use at present. An element is mentioned.

The structure of the MIM element will be described according to the manufacturing process of this element. First, a Ta film is formed on a glass substrate by a thin film forming method such as a sputtering method or a vacuum evaporation method, and patterned by a photolithography method. This allows
The wiring and the electrode on one side of the MIM element are formed on the glass substrate. Next, the Ta film is formed by, for example, an anodizing method in an aqueous citric acid solution to form an oxide film that acts as an insulating layer of the MIM element. Further, a MIM element is completed by forming a Cr film as an electrode on the other side of the MIM element by a thin film forming / processing method. Then, a transparent electrode for image display is formed so as to be in contact with the Cr film of the MIM element. The basic manufacturing technology as described above is disclosed in Japanese Examined Patent Publication No. 55-16.
1273, and an improved technique thereof is disclosed in Japanese Patent Laid-Open No. 58-58.
-178320 and the like.

[0004]

The conventional MIM element is
As described in JP-A-55-161273, it is necessary to form a thin film and photolithography three times in order to pattern the MIM element and the transparent electrode for image display. Therefore, the liquid crystal display device using the MIM element is superior in performance to the conventional simple matrix type device, but the manufacturing process is complicated and the production efficiency is poor. In addition, each of these MIM elements has a structure in which a plurality of layers are laminated on a substrate, and there are problems such as breakage and leakage of each layer during lamination, and it is difficult to manufacture a highly reliable element. .

The present invention has been made in view of the above circumstances, and an object thereof is a liquid crystal display device which can be manufactured easily and at low cost by reducing the manufacturing process as compared with the conventional method, and the manufacturing thereof. To provide a method.

[0006]

In order to achieve the above object, according to the present invention, the structure of a non-linear resistance element used in a liquid crystal display device and its manufacturing method are simplified.
That is, according to the liquid crystal display device of the present invention, the nonlinear resistance element formed on the one substrate is formed with the first metal layer and the first metal layer partially overlapping each other, and the oxygen component And a second metal layer including the oxide metal layer, the oxide layer acting as an insulator layer is formed only in an overlapping portion between the first metal layer and the second metal layer.

Further, according to the manufacturing method of the present invention, first, both the first and second metal layers are formed so as to partially overlap each other. After that, the first and second metal layers are heat-treated to form an oxide layer (insulator layer) between the metal layers in the overlapping portion.

[0008]

When the first metal layer and the second metal layer containing an oxygen component are formed so as to partially overlap with each other and these metal layers are heat-treated, the first and second metal layers are in contact with each other. part,
That is, in the overlapping portion, the oxygen component of the second metal layer diffuses into the first metal layer to form a metal oxide layer. Ta film as first metal layer and ITO as second metal layer
According to the experiment in which the (indium / tin oxide) film is overlapped, oxygen in ITO oxidizes Ta in the overlapping portion, and IT
Oxygen is released on the O side, so that a metal oxide film is formed between the Ta film and the ITO film. Then, since oxygen on the ITO side escapes when the metal oxide film is formed, the characteristics of the non-linear resistance element as an electrode are rather improved, and good non-linear current-voltage characteristics can be obtained.

It is important that the oxidation of the first metal layer and the reduction of the second metal layer be caused at the overlapping portion.
For example, in the case where after forming a Ta film, heat treatment is performed in the atmosphere to oxidize the entire surface of the Ta film, and then ITO is overlaid,
It is difficult to obtain an MIM element having good symmetry characteristics.

According to the present application having the above-described structure, it is possible to reduce the number of manufacturing steps of the MIM element without impairing the non-linear characteristic, and to provide the liquid crystal display device and the manufacturing method thereof which can be easily and inexpensively manufactured. Can be provided.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A matrix array type liquid crystal display device and a method of manufacturing the same according to embodiments of the present invention will be described in detail below with reference to the drawings.

As shown in FIGS. 1 and 2, the liquid crystal display device includes an array substrate 12 having a glass substrate 10, an opposed substrate 14 opposed to and held at a predetermined distance from the array substrate, and these substrates. A liquid crystal layer 16 enclosed between
Is equipped with.

The array substrate 12 has a large number of signal electrodes 20 formed of Ta formed on the upper surface of the glass substrate 10 and extending in parallel to each other, and a large number of ITO electrodes arranged along the respective signal electrodes at predetermined intervals. Transparent pixel electrode 22
And have. Each pixel electrode 22 has a MIM element 24.
It is connected to the corresponding signal electrode 20 via.

Each MIM element 24 has a first metal layer 24a formed by projecting a part of the signal electrode 20 toward the pixel electrode 22 side and a part of the corresponding pixel electrode 22 projecting toward the signal electrode side. And a second metal layer 24b formed by
The second metal layer is formed such that a part thereof overlaps the first metal layer. Then, as shown in FIG. 3, in the overlapping portion 25 of the first metal layer 24a and the second metal layer 24b, the metal oxide layer 2 as an insulator layer is provided between these metal layers.
4c is formed. The metal oxide layer 24c is formed by oxidizing the surface portion of the first metal layer 24a in contact with the second metal layer 24b in the overlapping portion 24. As a result, the MIM element 24 having the structure of metal layer-insulator layer-metal layer is formed. Further, on the upper surface of the glass substrate 10, the signal electrode 20, the MIM element 24,
An alignment film 26 made of polyimide resin is formed so as to overlap with the pixel electrode 22.

On the other hand, the counter substrate 14 is provided with a glass substrate 28, and a large number of transparent scanning electrodes 30 made of ITO are formed on the inner surface of the glass substrate 28 in parallel with each other and extend in a direction orthogonal to the signal electrodes 20. ing. In addition, the counter substrate 1
On the inner surface of 4, an alignment film 32 made of polyimide resin is formed so as to overlap the scanning electrode 30.

The liquid crystal display device configured as described above is
It is manufactured by the following steps. First, as shown in FIG. 1, for example, a glass substrate 10 having a thickness of 1.1 mm and having an alkali protective film of SiO2 (not shown) on its surface
A Ta film with a thickness of 00 angstrom is formed by sputtering. Photoexposure, development using a photosensitive resist,
The Ta film is patterned by an etching process. T
The etching of the a film is performed by chemical dry etching using CF4 and O2 in equal amounts using the photosensitive resist pattern as a mask. As a result, T on the glass substrate 10
The signal electrode 20 made of a and the first metal layer 24a for forming the MIM element, which is made of a protrusion protruding from the signal line, are formed.

After that, a transparent conductive film made of ITO is formed on the glass substrate 10 by a sputtering method. A photosensitive resist is applied over the entire surface of the transparent conductive film, and then exposed using a photomask and developed to form a resist pattern. Subsequently, water, hydrochloric acid, and nitric acid were mixed in a ratio (volume ratio) of 1: 1: 0.1, and the ITO pixel electrode 22 having the same resist pattern as the resist pattern was formed using an etching solution heated to 30 ° C.
Then, a second metal layer 24b made of an ITO protrusion protruding from the pixel electrode is formed. At that time, the second metal layer 24b
Is formed so that a part thereof overlaps with the first metal layer 24a. Subsequently, the glass substrate 10 is heated at 350 to 450 ° C. for 1 hour, so that the first metal layer 24 a and the second metal layer 24 a are heated.
Of the Ta layer and the I layer at the overlapping portion 25 with the metal layer 24b of
A Ta oxide layer 24c having a thickness of 500 Å is formed at the boundary with the TO layer.

The formation of such a metal oxide layer 24c is based on the following principle. That is, as shown in FIG. 3, the second metal layer 24 is heated in the overlapping portion 25 by being heated.
The oxygen component in b diffuses into the first metal layer 24a, and the contact portion of the first metal layer 24a in contact with the second metal layer 24b is oxidized to form a metal oxide layer (TaOx) 24c. In addition, in the overlapping portion 25, the first metal layer 24a
Oxygen escapes and is reduced at the contact portion of the second metal layer 24 that comes into contact with. As a result, the MIM element 24 exhibiting good switching characteristics is formed.

Next, the alignment film 26 made of a polyimide resin is applied, baked and rubbed on the MIM element forming surface of the array substrate 12 configured as described above to regulate the liquid crystal alignment direction. Further, the scanning electrode 30 made of ITO and the alignment film 32 made of polyimide resin are formed on the counter substrate by the same process as described above. And the alignment film 3
2 is rubbed in a direction twisted by about 90 ° with respect to the alignment film 26 of the array substrate 12.

The above-mentioned two types of substrates 12 and 14 are prepared, and the liquid crystal is injected by holding the liquid crystal molecules at a predetermined distance such that the direction of the major axis of the liquid crystal is twisted by about 90 ° between the two substrates. Make up a cell. Then, a polarizing plate (not shown) is arranged outside the liquid crystal cell, that is, outside the array substrate 12 and the counter substrate 14 with the polarization axis twisted by about 90 °. Thereby, the liquid crystal display device is completed.

FIG. 4 shows the current-voltage characteristics of the MIM element 24 of the liquid crystal display device constructed as described above.
From this figure, it can be seen that the MIM element 24 has sharp and non-linear characteristics comparable to those formed by the conventional photolithography three times.

As described above in detail, according to the liquid crystal display device and the manufacturing method configured as described above, the MIM element is formed only by forming the first and second metal layers 24a and 24b and then performing heat treatment. Therefore, compared with the conventional liquid crystal display device, thin film formation and photolithography steps can be reduced. Further, since the portion of the second metal layer that is in contact with the first metal layer is reduced during the heat treatment, it is possible to obtain a liquid crystal display device including an MIM element having good non-linear characteristics.

The present invention is not limited to the above-described embodiments, but can be variously modified within the scope of the present invention. For example, the first metal layer is not limited to Ta, but Al, T
Even when another metal such as i, W, Mo, or Nb is used, the same effect as above can be obtained.

In the above embodiment, the MIM element has the first metal layer formed on the glass substrate 10 and the first metal layer.
Although the second metal layer is formed by overlapping the second metal layer, the same effect can be obtained by forming the first metal layer by overlapping the second metal layer. .

[0025]

According to the present invention, it is possible to provide a liquid crystal display device including a non-linear resistance element having excellent non-linear characteristics and which can be manufactured easily and at low cost, and to provide a method for manufacturing the same. It is very effective in spreading.

[Brief description of drawings]

FIG. 1 is a plan view schematically showing a liquid crystal display device according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of the liquid crystal display device taken along line AA of FIG.

3 is a cross-sectional view of the MIM element portion taken along the line BB of FIG.

FIG. 4 is a characteristic diagram showing current-voltage characteristics of the MIM element of the liquid crystal display device according to the above-mentioned embodiment.

[Explanation of symbols]

10, 28 ... Glass substrate, 12 ... Array substrate, 14 ... Counter substrate, 16 ... Liquid crystal layer, 20 ... Signal electrode, 22 ... Pixel electrode, 24 ... MIM element, 24a ... First metal layer, 24b
... second metal layer, 24c ... oxide layer, 25 ... overlap portion.

Claims (2)

[Claims] 1. A liquid crystal display device comprising a pair of substrates each having an electrode and facing each other, a liquid crystal layer sandwiched between the substrates, and a nonlinear resistance element connected to the electrodes, The resistance element includes a first metal layer, a second metal layer formed to partially overlap with the first metal layer and containing oxygen, the first metal layer and the second metal layer. And a metal oxide layer formed between the first metal layer and the second metal layer in the overlapping portion with the second metal layer, the metal oxide layer being formed on the second metal layer in the overlapping portion. A liquid crystal display device, characterized in that the contact portion of the first metal layer in contact is oxidized by an oxygen component diffused from the second metal layer. 2. A method of manufacturing a liquid crystal display device, comprising: a pair of substrates each having an electrode and facing each other; a liquid crystal layer sandwiched between the substrates; and a non-linear resistance element connected to the electrodes. On one of the substrates, a first metal layer forming a nonlinear resistance element and a second metal layer containing oxygen are formed so as to partially overlap each other, and the first and second metal layers are formed. By the heat treatment, the first metal layer is oxidized by the oxygen component of the second metal layer in the overlapping portion of the first and second metal layers to form the first metal layer and the second metal layer. A method for manufacturing a liquid crystal display device, which comprises forming a metal oxide layer between the layers.