JPH01281436A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To prevent cracking of glass during the course of cooling and to improve yield by forming a nonlinear resistance element for switching of a MIM element the insulating film of which consists of the anodized film of Ta and annealing the anodized film of the Ta by an induction heating system. CONSTITUTION:The nonlinear resistance element for switching is the MIM (metal Insulator Metal) element the insulating film of which consists of the anodized film of the Ta. The anodized film of the Ta is annealed by the induction heating method. The annealing of the anodized film is thereby enabled and 2-5% fraction defective of glass crack is decreased to 0 without deterioration the current-voltage characteristics of the MIM nonlinear resistance element and without increasing the fluctuation in the characteristics thereof.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a liquid crystal display device, and more particularly to a nonlinear resistance two-terminal element for switching.

[Conventional technology]

MM, which is a nonlinear resistance two-terminal element for switching in active matrix liquid crystal display devices, utilizes the property that an insulating layer sandwiched between two electrodes allows current to flow in a high electric field, and the nonlinearity is a current-voltage characteristic. The mechanism is 5chottky and Pools-? This is explained by the renks1 mechanism, etc. A cross-sectional view of an example of these element structures is shown in FIG.

The simplest and most commonly implemented method is on a glass substrate.
ra is formed by sputtering and patterned by photolithography. Ta may be etched by dry etching or wet etching. Usually OF, -) 0. A dry etching method using etching gas is used. This buttered Ta film is anodized. 1% citric acid is often used as the solution for anodizing. After this anodization, ρ is annealed in an annealing furnace using a resistor in order to reduce variations in Q element characteristics.

This film becomes an insulating layer.

Thereafter, a layer of Or is formed by sputtering. This is also O
It is not limited to metal scraps, and other metal scraps may also be used. 'Or is also a must for photoringraphy! Buttering into shape. This forms the M element, and then the transparent conductive film that becomes the pixel electrode, generally made of Indium Tin 0 (TO).
xide) is sputtered, and this is also patterned into the required shape by well-known photolithography and etching. These element substrates are assembled into a liquid crystal panel.

[Problem to be solved by the invention]

However, in the conventional technology, the heat treatment method after anodizing
Even the glass substrate is heated. That is, due to the radiant convection of heat from the resistor, areas other than those originally desired to be annealed are also heated. Therefore, the temperature is 400℃ ~
Since the temperature was 500°C, there was a drawback that the glass substrate would break during cooling after being removed from the furnace. If it is cooled slowly in a furnace, it is assumed that the glass will break during cooling because it will be immediately released into the atmosphere.

The present invention proposes to heat only the element part and not the glass as much as possible, and aims to prevent the glass that is the substrate from breaking during cooling, and to improve the yield.

[Means to solve the problem]

It is equipped with a plurality of row electrodes and a plurality of column electrodes arranged on a counter substrate so as to intersect with these electrodes, and a nonlinear resistance element for switching and a liquid crystal are electrically connected to a pixel section formed in a matrix at the intersection of these two electrodes. In an active matrix type liquid crystal display device which is connected in series with the switching nonlinear resistance element, the insulating film of the switching nonlinear resistance element is made of an anodic oxide film of Ta. By trapping and annealing, the above-mentioned problems are solved.

〔Example〕

First, 5,000 layers of Ta were sputtered onto a glass substrate. The sputtering conditions may be the same as conventional methods. The process was carried out under RF sputtering conditions of A'r gas pressure of 10 μyaTorr and input power of 2 KW. Next, the resist was exposed and developed to a predetermined size, and Ta was dry etched. Dry etching is 0F4 (60%) + 0□ (40%) 550SOO
Etching was performed at a flow rate of M. Dry etching of Ta can be done by wet method, and the dry etching conditions are as follows:
Other conditions may also be used.

This panned Ta was immersed in 1% citric acid and oxidized by anodic oxidation. The final voltage was 35v. The thickness of this oxide film was measured with an elliplymeter and was approximately 5.
It was 00X.

Next, li! The extremely oxidized substrate was annealed using an induction heating method. The frequency used was 10KH2 and the time was 5 minutes. The test was carried out in the atmosphere, but N.

Inert gas such as gas, 0. An oxidizing gas may also be used. Immediately after heating, the glass substrate was taken out into the atmosphere. Although 100 glass substrates were flown using this method, there was no glass cracking. In an annealing furnace using a conventional resistor, approximately 2
Since the occurrence rate of cracking was ~5%, the 'r of the present invention
It became clear that the method of heating only the a-film was effective. The heating time is not limited to 5 minutes, and may be 1 minute or 60 minutes, but in consideration of workability and element balance, the heating time is 5 minutes.
It was set as 1 minute.

Next, Or[ was sputtered as in the conventional method.

The thickness was set to 1500. This Or was patterned with a resist to predetermined dimensions, and etched using MPM-E50 manufactured by Moroya Ink. Next, the pixel electrode was formed using sputtering, and using photolithography, sulfuric acid 20
% and a 20% aqueous solution of hydrochloric acid to a predetermined size.

When the current-voltage characteristics of the M element part of the M process of this example were measured, they were almost the same as the conventional current-voltage characteristics, the variation was the same as the conventional one, and there was no deterioration in image quality.

[Effects of the Invention] As described above, according to the present invention, the M nonlinear resistance A
(Child current) It is now possible to anneal the anodic oxide film without deteriorating the pressure characteristics or increasing the dispersion of the characteristics, reducing the glass cracking defect rate from 2 to 5% to 0. It became possible to do so.

[Brief explanation of the drawing]

FIG. 1 is an example of a cross-sectional view of the M element part of the M process used in the present invention, and is a diagram illustrating the present invention in order to make it easier to understand. 11...Substrate (transparent glass) 12...
・・・・・・Lower electrode (Ta) 13・・・・・・・・・
Insulating layer (TaOx) 1 4 ... ... ...
” Part 2 ηI right? 15・・・・・・Pixel electrode and above Applicant Seiko Epson Co., Ltd. Agent Patent attorney Kisanbe Meiki (1 other person) M1 time

Claims (1)

[Claims] It is equipped with a plurality of row electrodes and a plurality of column electrodes arranged on a counter substrate so as to intersect with these electrodes, and a nonlinear resistance element for switching and a liquid crystal are electrically connected to a pixel section formed in a matrix at the intersection of these two electrodes. In the active matrix liquid crystal display device, the insulating film of the switching nonlinear resistance element is an MIM (Metal Insulator Metal Insulator) made of an anodic oxide film of Ta.
) A liquid crystal display device characterized in that the Ta anodic oxide film of the element is annealed by an induction heating method.