JPH03292701A - Non-linear resistance element - Google Patents

Abstract

PURPOSE:To prevent generation of film exfoliation when a microscopic work is conducted, to make it possible to use a wiring material adaptable to the formation of a large area element, and to prevent the deterioration of display characteristics caused by the delay of a data signal by a method wherein an oxidizable metal oxide film, which is different from the upper and lower metal, is used for a non-linear resistor. CONSTITUTION:The title resistance element is composed of four sections consisting of a lower electrodes 3, a non-linear resistor 4, an upper electrode 5 and a picture element electrode 6; the resistance element is constructed in such a manner that a piece of low resistance metal, having excellent workability can be used for the lower electrode, and that the use of a piece of metal of low resistance and low stress such as the high melting point metals of Cr, Ti, Mo and the like or aluminum can be made possible. It is unnecessary to use chemically-formed metal for a data line, and wiring material suitable for liquid crystal display can arbitrarily be selected. Also, a film of large area uniformly formed on the whole surface of a substrate can be obtained, and its display characteristics can also be made uniform.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a nonlinear resistance element used as a switching element of an active matrix liquid crystal display.

[Conventional technology]

One type of nonlinear resistance element is a structure that uses an anodic oxide film as a nonlinear resistance element.As shown in Figure 3, such a conventional structure uses a data line that becomes the lower electrode 3, and The device has a three-part structure including a nonlinear resistor made of an anodized TaOx film 7 on the surface, and an upper mold 8i5 made of Cr or the like placed above the nonlinear resistor to intersect with the lower electrode 3.

In the figure, 1 is a glass substrate, 2 is a sputtered Ta
Ox film 6 is a pixel electrode. A Ta anodic oxide film with such an element structure is widely used as a nonlinear resistor, and elements using this are already on the market for small TVs.
It has been put in for use. As described above, in the conventional structure, the anodic oxide film, which is a nonlinear resistor, is always an oxide of the same metal as the lower electrode.

On the other hand, SiN formed by CVD method or sputtering method
In a structure using .

[Problem to be solved by the invention]

When a nonlinear resistance element is used as a switching element in a liquid crystal display, as the area of the element becomes larger, the reliability of the wiring material becomes more dependent on the display characteristics. In other words, issues to be solved include wiring resistance, adhesion to the glass substrate, and heat resistance. When using a Ta anodic oxide film, which is currently widely used, as a nonlinear resistor, the specific resistance of the Ta sputtered film is high, and when wiring is performed over a large area, display defects may occur due to an increase in wiring resistance. This may occur, and it is necessary to take measures to reduce this wiring resistance.

Further, Ta has a drawback that it has poor adhesion to a glass substrate, and when microfabrication is performed, the film may peel off. Therefore, in order to improve the adhesion, sputtered TaOx is deposited on the glass substrate, or the sputtered Ta film is thermally oxidized to produce TaOx.
An element structure is required in which x is formed and Ta is deposited thereon.

Therefore, in the structure of the present invention, a metal that has good adhesion to glass and is an excellent low-resistance wiring material is arbitrarily selected for the lower electrode, thereby providing a structure in which fine processing is performed precisely and display defects are eliminated. There is a particular thing.

On the other hand, in nonlinear resistance elements using SiNx or 5iCx manufactured by the CVD method or the Suba-Shita method as a nonlinear resistor, metals suitable for the wiring material can be used as the wiring material, but It is extremely difficult to form these films with uniform thickness and composition. for that,
It becomes difficult to obtain uniform device characteristics over a large area, resulting in variations in display characteristics. Therefore, the structure of the present invention uses an anodic oxide film that can obtain a uniform nonlinear resistor in the plane regardless of the substrate size, and provides uniform display characteristics.

As described above, in the element structure of the present invention, a material can be arbitrarily selected for the lower electrode in consideration of adhesion with glass and specific resistance, and a uniform nonlinear resistor can be provided over a large area.

Further, in the manufacturing process, the etching process of Ta or TaOx, which is difficult to microfabricate, can be omitted, and the device can be completed by simply machining the upper and lower metal parts sandwiching the nonlinear resistor.

[Means to solve the problem]

The present invention is characterized in that, in a nonlinear resistance element in which a nonlinear resistor is sandwiched between metals, an oxide film of an oxidizable metal different from the above-mentioned upper and lower metals is used for the nonlinear resistor.

[Effect]

As wiring materials, high melting point metals C r , T i ,
Ni and Mo are widely used, and these are the result of taking into account their heat resistance and adhesion to glass.

By adopting the element structure of the present invention, there is no need to use only a chemically formed metal or a metal that forms a thermal oxide film for the lower wiring, so it can be used as a wiring material with good adhesion to glass, low resistance, and low stress. It becomes possible to use a suitable metal.

As a result, when microfabrication is performed during element formation, film peeling does not occur, wiring materials compatible with larger areas can be used, and display deterioration due to data signal delay can be prevented.

Furthermore, since the structure of the present invention uses an anodic oxide film that can form a uniform nonlinear resistor over a large area, it is possible to obtain a more uniform film than a film formed by sputtering or PCVD. It becomes possible. As a result, an element with uniform characteristics over a large area can be realized.

In addition, in the manufacturing process, this device structure, which uses a Ta anodic oxide film as the nonlinear resistor, can omit the etching process for Ta or TaOx, which is difficult to microfabricate over a large area, and Only metal processing is required, resulting in an element structure that is easy and suitable for mass production.

〔Example〕

Hereinafter, the present invention will be explained with reference to the drawings.

FIG. 1 is a sectional view of an embodiment of the present invention. The nonlinear resistance element of this embodiment includes a lower electrode 3, a nonlinear resistor 4, an upper electrode 8ii5. and pixel ti6.

In the element structure shown in 2, the nonlinear resistor 4 does not necessarily have to be the anodic oxide film of the lower electrode 3, and the structure is such that a metal with low resistance and good workability can be used for the lower electrode. For example, the lower electrode, which becomes the signal line, is made of high-melting point metals such as Cr and Ti, which are widely used as wiring materials.
, Mo, etc., or metals with low resistance and low stress such as Al can be used.

TaOx, which is obtained by anodizing Ta metal, is used for the nonlinear resistor, and a uniform film with a thickness of 400 to 100 OA is formed on the substrate surface. When Ta is anodized, 6.3 A of the lower metal is consumed for each anodizing voltage IV.
Since the oxide film is 16A, 400A of Ta metal is required to obtain an oxide film of 100A. In this device structure, if chemical metal remains, it may cause a short circuit between devices.
All chemical metals need to be oxidized.

Cr of the upper electrode is formed to intersect with the lower electrode,
This is an element structure that makes contact with the pixel electrode.

By adopting this structure, when the elements are placed in a large area and arranged into an array, the wiring resistance can be made from a material that can support a 20-inch class display screen, and it is possible to obtain uniform element characteristics, making it possible to The characteristics were improved.

FIG. 2 shows the current-voltage characteristics of the device structure of the present invention in comparison with a conventional device in which the lower electrode is anodized. From this figure, it can be seen that the present invention can obtain characteristics equivalent to the conventional one. In addition, with this device structure, thermal deterioration caused by thermal diffusion of oxygen in the anodic oxide film to the underlying metal could be prevented, and a device with excellent heat resistance was obtained.

〔Effect of the invention〕

Compared to conventional element structures, the nonlinear resistance element of the present invention has the effect that it is not necessary to use a chemically formed metal for the data lines, and that a wiring material suitable for a liquid crystal display can be arbitrarily selected. Furthermore, since an anodic oxide film is used for the nonlinear resistor instead of a deposited film such as a PCVD film or a sputtered film, a uniform film can be obtained over the entire large area of the substrate, and display characteristics can also be made uniform.

On the other hand, in terms of manufacturing, by using the structure of the present invention, there is no need to etch Ta, which is widely used as a chemical metal that becomes a nonlinear resistor, or its anodic oxide film TaOx, making it suitable for mass production. It becomes a structure.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing the structure of a nonlinear resistance element for explaining an embodiment of the present invention, and FIG. 2 is a voltage diagram showing the nonlinear resistance element obtained by the above embodiment in comparison with a conventional example. -Current characteristic diagram, FIG. 3 is a cross-sectional view showing the structure of a conventional nonlinear resistance element. 1... Glass substrate, 2... Sputtered TaOx film, 3
... lower electrode (scanning line), 4 ... nonlinear resistance element,
5... Upper electrode (data line), 6... Pixel electrode, 7
...Anodized T a Ox film. 5.

Claims (1)

[Claims] A nonlinear resistance element in which a nonlinear resistance element is sandwiched between metals, characterized in that the nonlinear resistance element uses an oxide film of an oxidizable metal different from the above-mentioned upper and lower metals.