JPH052191A - Production of matrix substrate - Google Patents

Abstract

PURPOSE:To provide the process for production of the matrix array substrate with which a uniform display free from unequalness is obtainable in spite of a large-screen display. CONSTITUTION:An insulator layer 3 is formed by anodizing a 1st metallic layer 2 and the current density at the time of anodizing the 1st metallic layer 2 is set at 0.1 to 0.8mA/cm<2> at the time of forming plural display picture elements and nonlinear resistance elements 5 having three-layered structures consisting of the 1st metallic layer-insulator layer-2nd metallic layer respectively electrically connected to these elements.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing 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.

[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 a liquid crystal display device of this type, 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 so far, 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 a diode type formed by using the same material as that of a thin film transistor, a varistor type using zinc oxide, a metal layer sandwiching an insulating material between electrodes-insulation. 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 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 a 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 the photo-etching method. Thereby, 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 solution of citric acid to form an oxide film 3 forming an insulator layer of the nonlinear resistance element. In this case, the temperature of the chemical conversion liquid is around room temperature and the current density is 1.0 mA /
cm ² Is. 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. Furthermore,
The transparent electrode 6 for image display may be formed so as to be connected to the Cr film 4. Such a basic manufacturing technology is Japanese Patent Publication Sho 55
No. 161273, and an improved technique thereof is disclosed in Japanese Patent Laid-Open No. 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, it is required that the current-voltage characteristics of the device be uniform within the screen. However, in recent years, liquid crystal display devices have become larger, and when a panel is created under the conventional conditions,
The current-voltage characteristics have a distribution in the plane, which causes display unevenness, which is a problem.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for manufacturing a matrix array substrate capable of obtaining a uniform display even in a large-screen display.

[0008]

The present invention provides a non-linear resistance element having a three-layer structure of a plurality of display pixels and a first metal layer-insulator layer-second metal layer electrically connected to each of them. In the method for manufacturing a matrix array substrate in which the insulating layer is formed by anodizing the first metal layer when forming the first metal layer on the substrate, the current density when anodizing the first metal layer is 0.1-0.8 mA / cm ² The method of manufacturing a matrix array substrate set in step 1.

[0009]

In general, in the case of a non-linear resistance element, an oxide film which is an insulating layer has a great influence on the element characteristics. As a method of forming this oxide film, the first film having a small thickness distribution and good workability is used. The anodic oxidation method of the metal layer is used. For anodic oxidation, a concentration of 0.01 to 0.
An aqueous citric acid solution having a temperature of about 1 wt% at room temperature is used.
Current density is 1.0 mA / cm ² Is. When a large-screen display was manufactured under these conditions, display unevenness occurred.

The cause of this unevenness can be considered as follows. Since the method of anodic oxidation for forming an oxide film on the first metal layer is a method of forming a uniform film thickness over the surface, it is considered that this unevenness is caused by some distribution in the film quality. In other words, as the display becomes larger and finer, the wiring becomes thinner and the resistance becomes higher. In the part where the wiring resistance is high, the oxide film does not grow in the initial stage of anodic oxidation, and the film in the part where the wiring resistance is low grows and becomes the insulator. Therefore, the growth rate of the oxide film is different between the portion where the wiring resistance is low and the portion where the wiring resistance is high among the one wiring of the first metal layer. It is considered that this difference is linked to the difference in characteristics.

In order to reduce the voltage drop between the wirings, the set current value for anodic oxidation may be reduced. On the other hand, if the set current value is too small, the processing time becomes long, so from this viewpoint, the smaller the current value is, the better. Therefore, an experiment was conducted to obtain an appropriate current density.

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. At this time, the current density per Ta film area is 0.1, 0.5, 0.8, 1.0, 1.5,
2.0 mA / cm ² And the conditions were changed (0.1 mA / cm
² If the current density is lower than that, the anodic oxidation takes too long, resulting in poor productivity). On top of these insulator layers,
A Cr film is formed as the second metal layer, and a desired pattern is formed by the same method as that for the Ta film to complete the nonlinear resistance element.

The current-voltage characteristics of each non-linear resistance element thus formed were measured. The element exhibits non-linear characteristics of high resistance (OFF) at low voltage and low resistance (ON) at high voltage. Therefore, FIG. 2 shows a result of summarizing the in-plane distribution of the current value at the voltage of 5 V in the OFF state. Current density is 1.0 mA / cm ² It has been found that a large distribution of current values occurs when the above is reached.

Therefore, in order to obtain a good display without unevenness even on a large screen, the current density is 0.8 mA / cm ²
In the present invention, the current density when anodizing the first metal layer is 0.1 to 0.8 mA / cm.
² Is set to. As a result, even on a large-screen display, it was possible to obtain a uniform display without unevenness.

[0015]

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, the current density is set to 0.1 to 0.8 mA / c.
m ² Range, for example, 0.1 mA / cm ² And perform anodic oxidation. As the chemical conversion solution, a citric acid aqueous solution of about 0.01 to 0.1% is used. 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 (insulator layer) 3 uniform. Next, on the oxide film 3 formed as described above, the Cr film 4 as the second metal layer is formed to a thickness of 1500 angstrom. A resist pattern is formed again, 17 g of ceric ammonium nitrate and 5 cc of perchloric acid are added to 10 cc of water.
Etching is performed using a solution dissolved in the ratio of 2 to form a pattern of the second metal layer, and the non-linear resistance element 5 is obtained.
Finally, the transparent electrode 6 is formed into a film, and etching is performed using a liquid in which equal amounts of hydrochloric acid, nitric acid and water are mixed 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 nonlinear resistance element 5 is formed, and the liquid crystal is aligned by rubbing. The same process 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 the liquid crystal is injected by holding the liquid crystal 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 two substrates, and a liquid crystal cell is formed. Then, the polarizing plate may be arranged outside the liquid crystal cell with the polarization axis twisted by about 90 °. With the above method,
Diagonal 12 inches, pixel pitch 210 μm, number of pixels 115
A large liquid crystal display device having 2 × 900 dots was produced.

The display characteristics of the matrix array substrate thus manufactured were measured, and the relationship between the current density at the time of anodic oxidation and the driving voltage distribution at 25 points in the plane is shown in FIG.
And the display results are shown in Table 1 below.

[0021]

[Table 1] Current density is 1.0 mA / cm ² In the above cases, the driving voltage difference becomes 2 V or more, and at this time, it can be seen from Table 1 that display unevenness occurs.

[0022]

According to the present invention, the insulator layer is formed by anodizing the first metal layer, and the current density at this time is 0.1 to 0.8 mA / cm ^2. Since it is set to, it is possible to obtain a uniform display even on a large-screen display.

[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 non-linear resistance element in the matrix array substrate of the present invention and the conventional example.

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

[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 (1)

[Claims] 1. A plurality of display pixels and electrically connected to each of them.
Three layers of connected first metal layer-insulator layer-second metal layer
When forming a non-linear resistance element having a structure on a substrate,
By anodizing the first metal layer, the above-mentioned insulator layer is formed.
In the method of manufacturing a matrix array substrate to be formed,
The current density when anodizing the first metal layer is 0.1.
~ 0.8 mA / cm² Is set to
A method for manufacturing a matrix array substrate.