JPH052192A - Matrix array substrate and manufacturing method thereof - Google Patents

Abstract

(57) [Summary] [Object] The present invention provides a matrix array substrate and a method of manufacturing the same, in which a large ON / OFF ratio of current can be obtained and the contrast is significantly increased to obtain a good large screen display. The purpose is to provide. A matrix array substrate according to the present invention is formed by crystallizing an insulator layer of a non-linear resistance element 5 having a three-layer structure of metal layer 2-insulator layer 3-metal layer 4, and the manufacturing method thereof is as follows.
When the insulating layer is formed by anodizing the metal layer 2, the temperature of the chemical conversion solution is set to 1 ° C. or higher and 10 ° C. or lower, and the above object can be achieved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a matrix array substrate using a non-linear resistance element having a three-layer structure of metal layer-insulator layer-metal layer 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 relatively simple, such as clocks, calculators, and measuring instruments, to personal computers, word processors, and terminal equipment for office automation.
It has been used for displaying large-capacity information such as TV image display.

As a driving method in this type of liquid crystal display device, a simple multiplex driving method has been generally adopted for a word processor used as a two-gradation display product. However, a liquid crystal display device is required to have a larger screen, higher resolution, and higher definition, and a driving method for improving the contrast ratio, which has been a drawback of the multiplex driving method up to now, is
Various things are done. One of them directly switches and drives each pixel, and uses a thin film transistor or a non-linear resistance element as a switching element. Among them, the non-linear resistance element basically has two terminals as compared with three terminals of the thin film transistor, and therefore has a simple structure and is easy to manufacture. Therefore, improvement in manufacturing yield can be expected,
There is an advantage of cost reduction.

Such a non-linear resistance element is composed of a diode type formed by using a material similar to that of a thin film transistor, a varistor type using zinc oxide, a metal layer sandwiching an insulator between electrodes, and an insulation layer. A body layer-metal layer (MIM) mold and a mold using a semiconductive layer between metal electrodes have been developed. Of these, the MIM type has the simplest structure.
At present, it is already in practical use. Now, FIG. 1 is a cross-sectional view showing an example of one pixel portion of a matrix array substrate having a conventional MIM type non-linear resistance element, which will be described according to the manufacturing process.

First, a Ta film 2 is formed on a glass substrate 1 by a thin film forming method such as a sputtering method or a vacuum evaporation method,
The patterning is performed by a photo-etching method. As a result, the wiring (data line) and one first metal layer of the nonlinear resistance element integrated with the wiring can be obtained. Next, the Ta film 2 is anodized in an aqueous citric acid solution to form an oxide film 3 that constitutes an insulator layer of the nonlinear resistance element. In this case, the temperature of the chemical conversion liquid is around room temperature, and the oxide film 3 formed under these conditions is amorphous. Then, the Cr film 4 is formed as the other second metal layer of the nonlinear resistance element by the thin film forming / processing method, whereby the nonlinear resistance element 5 is completed. Further, the transparent electrode 6 for image display may be formed so as to be connected to the Cr film 4. Such a basic manufacturing technique is disclosed in JP-B-55-161273, and an improved technique thereof is disclosed in JP-A-58-178320.

[0006]

Generally, in a liquid crystal display device using a non-linear resistance element having a three-layer structure of a metal layer-insulator layer-metal layer, the liquid crystal is turned on / off due to the non-linearity of the element.
Since it is turned off, its current-voltage characteristic is required to be rapid, and the ON / OFF ratio is at least 10 ⁵ It is known that some degree is necessary. However, the ON / OFF ratio of the nonlinear resistance element formed by the conventional manufacturing method is 10 ³ ~
10 ⁴ Only the characteristic of was obtained. Therefore, attempts were made to change the metal material or the element structure in order to make the characteristics rapid, but the characteristics did not improve remarkably. Therefore, in a large-screen display, the contrast (ratio of light transmittance when ON / OFF in a single pixel) is about 40, crosstalk is likely to occur, and image quality is poor.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a matrix array substrate and a method of manufacturing the same which can obtain a good large screen display with a significantly high contrast.

[0008]

According to the present invention, a plurality of display pixels and a non-linear resistance element having a three-layer structure of a metal layer-insulator layer-metal layer electrically connected to each of the display pixels are formed on a substrate. In the matrix array substrate, the insulator layer is crystallized.

Further, according to the present invention, a plurality of display pixels and a first metal layer-insulator layer-second electrically connected to each of the display pixels are provided.
In the method of manufacturing a matrix array substrate, wherein the non-linear resistance element having a three-layer structure of the metal layer is formed on the substrate by anodizing the first metal layer, the insulator layer is formed. In the method for producing a matrix array substrate, the temperature of the chemical conversion solution when anodizing the metal layer is set to 1 ° C. or higher and 10 ° C. or lower.

[0010]

In general, as a method of forming the insulating layer of the non-linear resistance element, an anodic oxidation method having a small film thickness distribution and good workability is used. Usually, the concentration is 0.0 as a chemical conversion solution.
An aqueous citric acid solution having a temperature of about 1 to 0.1 wt% at room temperature is used. Since the current-voltage characteristics of the non-linear resistance element are greatly affected by the insulator layer, attention was paid to the conditions of anodic oxidation, and as a result of various studies, the current-voltage characteristics of the non-linear resistance element changed when the temperature of the chemical conversion solution was changed. It turned out to have a big influence. The experiment was performed as follows.

First, a Ta film is formed by a sputtering method, and a desired pattern is formed by a photo-etching method. Next, anodic oxidation is performed, where the temperature of the chemical conversion solution is set to 1,
Experiments were carried out with the temperature changed to 3, 5, 10, 20, 30, 50, 70 ° C. (a temperature lower than 1 ° C. is not preferable because the glass surface is frozen). On top of these insulator layers,
A Cr film is formed, a desired pattern is formed by the same method as that for the Ta film, and the nonlinear resistance element is completed.

FIG. 2 shows the result of measurement of the current-voltage characteristic of each non-linear resistance element thus formed. (A) in the figure, when the temperature of the chemical conversion liquid is 1, 3, 5, 10 ° C,
(B) shows the characteristics at 20 ° C, and (c) shows the characteristics at 50 ° C. It was found that by lowering the temperature of the chemical conversion solution, the agility can be improved as compared with the conventional condition of around room temperature. In order to investigate the cause, X-ray diffraction of the anodic oxide film was carried out, and it was found that the high temperature one was amorphous and the low temperature one was crystallized at room temperature.
The crystallinity was high at ℃. In Fig. 4 (a) 5 ° C,
(B) A part of the X-ray diffraction chart at 20 ° C. and (c) 50 ° C. is shown. Then, in (a), the crystal peak of the underlying Ta film is
The peak of TaOx is clearly observed in the vicinity of
It can be seen that neither the (b), (c) blots, nor the peaks can be observed, and it is amorphous.

Therefore, the present invention is characterized in that the insulating layer of the non-linear resistance element is crystallized, and the temperature of the chemical conversion solution is set when the insulating layer is formed by anodizing the metal layer in manufacturing. Is set to 1 ° C or higher and 10 ° C or lower. As a result, the ON / OFF ratio of the current can be made large, so that the contrast is significantly increased and a good large screen display can be obtained.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings. The matrix array substrate according to the present invention is also constructed as shown in FIG. 1 similarly to the conventional example, and will be described according to the manufacturing process.

First, for example, a glass substrate 1 having a thickness of 300
A Ta film 3 of 0 angstrom is formed by a sputtering method using Ar gas. In this case, Nb or Mo
It may be a film formed by a sputtering method using Ta or N ₂ gas in which a small amount of is mixed. Next, a desired pattern is formed by a photo-etching method to obtain a wiring (data line) and a first metal layer of the non-linear resistance element integrated with the wiring.

In the above case, in order to form a desired pattern by the photo-etching method, a resist is coated on the entire surface, then exposed to light using a mask and developed to form a resist pattern.
Form Then, the Ta film 3 is etched in the plasma in which CF ₄ gas and O ₂ gas are mixed in a ratio of 1: 2 by the chemical dry etching method, and then the resist is peeled off.

Next, anodic oxidation is carried out with the temperature of the chemical conversion solution in the range of 1 to 10 ° C., for example 5 ° C. At this time, it is desirable to stir the solution in order to keep the temperature of the chemical conversion solution constant and to make the growth of the oxide film 3 uniform.
Thus, an insulator layer is obtained on the first metal layer.

Next, the oxide film 3 formed as described above
A Cr film 4, which is a second metal layer, is formed thereon with a thickness of 1500 angstroms. After that, a resist pattern was formed again, and 17 g of ceric ammonium nitrate was added.
Etching is performed using a solution of 5 cc of perchloric acid dissolved in 10 cc of water to form a pattern of the second metal layer, and the nonlinear resistance element 5 is obtained. Finally, the transparent electrode 6 is formed into a film, and etching is performed using a liquid in which hydrochloric acid, nitric acid and water are mixed in equal amounts to form a pattern of pixel electrodes, whereby the matrix array substrate is completed. To form a liquid crystal display device using this matrix array substrate, for example, the following may be performed.

First, an alignment film made of a polyimide resin is applied and baked on the surface of the matrix array substrate on which the non-linear resistance element 5 is formed, and the liquid crystal is aligned by rubbing. Similar processing is performed on the counter substrate, and rubbing is performed in a direction twisted by about 90 ° from one liquid crystal display substrate. The above-mentioned two types of substrates are prepared, and liquid crystals are injected to form a liquid crystal cell by holding the substrates at a distance of 5 to 20 μm so that the major axis direction of the liquid crystal is twisted by about 90 ° between the substrates. Then, the polarizing plate may be arranged outside the liquid crystal cell with the polarization axis twisted by about 90 °.

A large-sized liquid crystal display device having a diagonal of 12 inches, a pixel pitch of 210 μm, and a number of pixels of 1152 × 900 dots was manufactured by the above method. Here, the measurement result of the display contrast when the temperature of the chemical conversion solution is 1, 3, 5, 10, 20, 30, 50, 70 ° C. is shown in FIG. Conventional example 2
It can be seen that when the temperature of the chemical conversion solution is lower than in the vicinity of 5 ° C., the contrast is high and a very good image can be obtained.

[0021]

According to the present invention, since the temperature of the chemical conversion solution for anodizing the first metal layer is set to 1 ° C. or higher and 10 ° C. or lower, a crystallized insulator layer is formed. Can be done.

As a result, the current-voltage characteristics of the non-linear resistance element became very rapid, and the ON / OFF ratio of the current could be increased. To obtain good image quality, it is necessary to make the OFF current sufficiently small, but in the characteristics of the conventional non-linear resistance element, the oxide film 3 must be made thick and
The current was so small that writing was insufficient.

However, since the nonlinear resistance element of the present invention can have a large ON / OFF ratio of current,
The FF current can be reduced, and at the same time sufficient O
It can take N current. Therefore, the contrast is significantly increased and a good large screen display can be obtained.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an example of a pixel portion of a matrix array substrate used for explaining an embodiment of the present invention and a conventional example.

FIG. 2 is a characteristic curve diagram showing current-voltage characteristics of a nonlinear resistance element in the matrix array substrate of the present invention and the conventional example.

FIG. 3 is a characteristic curve diagram comparing the display contrasts of liquid crystal display devices using the matrix array substrate of the present invention and the conventional example.

FIG. 4 is a characteristic curve diagram showing an analysis result relating to properties of an oxide film (insulator layer) of a nonlinear resistance element in the matrix array substrate of the present invention.

[Explanation of symbols]

1 ... Glass substrate, 2 ... Ta film (first metal layer), 3 ... Oxide film (insulator layer), 4 ... Cr film (second metal layer), 5 ...
Non-linear resistance element 6, transparent electrode.

Claims (2)

[Claims] 1. A matrix array substrate having a plurality of display pixels and a non-linear resistance element having a three-layer structure of a metal layer-insulator layer-metal layer electrically connected to each of the display pixels, formed on the substrate. A matrix array substrate in which the layers are crystallized. 2. When forming a plurality of display pixels and a non-linear resistance element having a three-layer structure of a first metal layer-insulator layer-second metal layer electrically connected to each of the display pixels on a substrate, A method of manufacturing a matrix array substrate, wherein the insulator layer is formed by anodizing the first metal layer,
The method for producing a matrix array substrate, wherein the temperature of the chemical conversion solution when anodizing the first metal layer is set to 1 ° C. or higher and 10 ° C. or lower.