JPH06302879A - Current-voltage nonlinear element and its manufacturing method - Google Patents

Abstract

PURPOSE:To obtain a voltage-current nonlinear element having a uniform film thickness and film quality over a large area. CONSTITUTION:A current-voltage nonlinear element is structured by successively laminating a lower electrode film 2, an insulation film 3, and and upper electrode film 4 on an insulation substrate 1. After a species of metal organic solution or more selected from bismuth(Bi) or titanium(Ti) or yttrium(Y) are applied on the lower electrode film, the insulation film, and the upper electrode film, they are burnt to form a metal or a metal oxide.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a current-voltage non-linear element used for a switch element such as a liquid crystal display and a method for manufacturing the same.

[0002]

2. Description of the Related Art Liquid crystal displays have come into widespread use as display devices in place of CRTs with the spread of information processing devices such as word processors and personal computers. This liquid crystal display has a simple matrix system and an active matrix system. The former can be manufactured at low cost because it uses a glass substrate on which only electrodes are formed, but the display quality is poor due to crosstalk.
On the other hand, in the active matrix system, a thin film transistor is provided for each pixel in order to solve this crosstalk problem. For this reason, the active matrix method has a high display quality, but since the thin film transistor is provided, the process is complicated and the cost is high.

To solve this, for example, SID198
0 MI as shown in Digest (p.200)
An M (Metal-Insulator-Metal) element has been devised. This is one of the non-linear elements whose current-voltage characteristics are non-linear and can be manufactured by a simpler process than a thin film transistor, so that it has an advantage of high yield and low cost. FIG. 3 shows a cross section of the MIM element. In this MIM element, a tantalum (Ta) electrode film 11 is provided on a glass substrate 1 and its surface is oxidized to tantalum oxide film (Ta).
₂ O ₅ ) 12 is formed, and a transparent electrode (Cr / ITO) 13 is further formed on a part of it to form an element.
In the manufacturing method, the tantalum (Ta) electrode film 11 is deposited on the glass substrate 1 by a sputtering method or the like. Next Ta
The surface of the electrode film 11 is anodized to form an insulating film 12 of tantalum oxide (Ta ₂ O ₅ ) on the surface. Then, Cr / ITO is deposited thereon by a sputtering method or the like to form C
The r / ITO electrode film 13 is formed.

[0004]

[Problems to be Solved by the Invention] However, MIM
Also in the element, the Ta electrode film and the Cr / ITO electrode film are manufactured by a manufacturing method using a vacuum device such as a sputtering method. Since such a thin film process has a large number of steps due to the laminated structure, and it is difficult to control the inflow method and pressure of multiple gases, it is possible to produce a thin film over a large area or to maintain uniform film quality over a large area. In addition to the difficulty, there is a problem in that the equipment cost of a film forming apparatus such as a sputtering apparatus or a vacuum vapor deposition apparatus is high, and the running cost is high, so that the cost of a thin film to be formed is high.

Further, in the MIM element, since the overlapping of the respective films of the taper portion of the Ta electrode film 11 shown in FIG. 3 functions as the MIM element, the manufacturing process control such as the processing of the Ta electrode film into a tapered shape is strict. There was a problem. The present invention is to solve the above-mentioned conventional problems, and an object thereof is to obtain a current-voltage nonlinear element having a uniform film thickness and film quality over a large area. Furthermore, the present invention is an IC
An object of the present invention is to obtain a thin film current-voltage nonlinear element which can be applied to a circuit or a display, has a simple laminated structure, and is inexpensive and highly productive.
In addition, it is an object of the present invention to provide a method for manufacturing the above current-voltage nonlinear element.

[0006]

The current-voltage non-linear element of the present invention is a thin-film current-voltage non-linear element made of a metal or a metal oxide by thermally decomposing a metal organic substance using a thick film process which is inexpensive to manufacture. Let it form.

[0007]

The thin film current-voltage nonlinear element of the present invention can be applied to an IC circuit or a display, and the thin film current-voltage nonlinear element is manufactured by a thick film process. However, even in the thick film process, unlike the conventional paste in which crystal particles are kneaded, the film formation method by the thermal decomposition of the metal organic solution is used, so that the current of the thin film that can be applied to IC circuits and displays is used. A voltage non-linear element can be formed. In addition, the current-voltage nonlinear element of the present method is very versatile and highly productive because it can be easily performed compared with a film formed by a conventional thin film process using a vacuum device such as adjustment of film thickness and composition ratio of constituent elements.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG. On a glass substrate 1, indium octylate and tin octylate were weighed so that the atomic ratio of indium to tin was 1: 0.1, and the mixed weight of indium octylate and tin octylate was adjusted to 10. On the other hand, a paste in which abietic acid serving as a solvent is mixed at a ratio of 3 is printed by using, for example, a screen printing method, and then baked at 700 ° C. in the air to be a lower electrode 2 having a thickness of 0.1 to 0.2 μm. To form. A solution of bismuth octylate diluted with xylene to a viscosity of about 30 to 100 cPs was spin-coated at 3000 rpm for 20 seconds and then baked at 700 ° C. in the atmosphere to form a bismuth oxide (Bi ₂ O ₃ ) insulating film 3. Form. The thickness of the insulating film at this time is about 40 nm
Is. The film thickness of the insulating film has a great influence on the current-voltage nonlinear characteristic, and if it is too thick, the nonlinear characteristic is not exhibited. It is desirable that the thickness of this insulating film be 100 nm or less.
˜50 nm is preferred. Then, after a metalloorganic gold paste is printed on the upper layer of the insulating film 3 to a thickness of about 0.2 μm by using, for example, a screen printing method,
The upper electrode 4 is formed by firing.

FIG. 2 shows a current-voltage curve of the current-voltage nonlinear element (ITO-Bi ₂ O ₃ -Au) according to the present invention. From this graph, it can be seen that the nonlinearity is similar to the MIM characteristic explained by the Poole-Frenkel effect.

In this embodiment, indium / tin and gold are used as the metal element forming the electrode, but the present invention is not limited to this, and zinc / aluminum or platinum can be used. Although bismuth is used as the metal element forming the insulating film, similar effects can be expected by using tantalum (Ta), titanium (Ti), yttrium (Y), or the like. Further, a usual method such as screen printing can be used in the step of thick film, and a method such as spin coating or dip can be used in the step of thin film.

The metal organics used in this process are:
It is not particularly limited as long as it contains an organic ligand complex, but specific organic ligands include octylic acid, benzoic acid, naphthenic acid, lauric acid, stearic acid, abietic acid, cabric acid, myristic acid. , Carboxylic acids such as palmitic acid, linoleic acid and oleic acid, β-diketones such as acetylacetone, carbamic acid and the like can be used. The metal organic material is dissolved in a solvent and applied to a heat-resistant substrate to form a film. As the solvent, petroleum-based solvents, mineral spirits, turpentine oil, benzene, alcohol-based solvents, carbitol-based, toluene-based solvents are used. , An organic solvent such as cellosolve can be selected according to the metal organic substance.

When the metal organic substance is difficult to dissolve in the solvent, a suitable amount of a ligand that forms an addition complex such as trioctylphosphine oxide (TOPO), tributyl phosphate (TBD) or amines is added, if necessary. To do. Further, the metal organic material solution may be applied as it is, but it is preferable to adjust the viscosity by adding a thickener or a diluent depending on the application method. As the thickener, for example, rosin, abietic acid, cellulose, acrylic resin or the like can be used, and as the diluent, α-terpineol, butyl carbitol acetate or the like can be used. The viscosity of the solution is preferably 1000 cPs or less in the case of the spin coating method and 3000 to 5000 cPs in the case of the screen printing method. Needless to say, the film thickness of the thin film obtained by coating and baking once can be freely selected by changing the viscosity of the solution within the range according to the coating method.

The substrate used in the present invention is not particularly limited as long as it does not deform or change phase even when heated to 600 ° C. or higher. For example, a barium borosilicate glass substrate, a quartz glass substrate, an alumina substrate or the like is used. , Used according to its purpose. The viscosity-adjusted paste is applied to the substrate by a screen printing method or a spin coating method, and the temperature at which the metal organic material decomposes and disappears in the coating film formed of the organic material solution of the target metal (usually 450 to 6
Baking at 00 ° C. is desirable. The heating method for firing is not particularly limited as long as the heat resistant substrate can be heated to a predetermined temperature. Specifically, a belt-type firing furnace or the like can be used.

The element size can also be reduced to the level of 10 microns by a technique such as photolithography, which makes it possible to manufacture a current-voltage nonlinear element which can be applied to an IC circuit, a display, etc., at a low cost like a thick film. . However, if the density is about 4 line / mm,
Since direct patterning can be performed by screen printing without photolithographic etching, a current-voltage nonlinear element can be manufactured without using any photomask. It goes without saying that this is a great merit because not only the mask manufacturing cost but also the cost for the photolithography etching step is reduced.

[0015]

As described above, the method for manufacturing a thin film current-voltage nonlinear element according to the present invention does not require expensive vacuum equipment used for thin film growth methods such as vacuum deposition method, sputtering method and CVD method. Since the operation can be performed with a simple operation and a device, the manufacturing cost can be reduced, and since the operation is performed under normal pressure, the manufacturing process can be continuous and the productivity can be improved. Furthermore, the structure is a simple laminated structure, and unlike the conventional MIM element, it does not require the difficult process of processing the pole film into a tapered shape.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing the structure of an example of a non-linear element according to the present invention.

FIG. 2 is a diagram showing current-voltage characteristics of a non-linear element according to the present invention.

FIG. 3 is a sectional view showing the structure of a conventional MIM element.

[Explanation of symbols]

1 glass substrate, 2 lower electrode, 3 insulating film, 4
Upper electrode, 11 electrode film, 12 Ta ₂ O ₅ insulating film, 13 Cr / ITO electrode film.

Claims (4)

[Claims] 1. A current-voltage nonlinear element comprising a lower electrode film, an insulating film, and an upper electrode film sequentially laminated on an insulating substrate, wherein the lower electrode film, the insulating film, and the upper electrode film are made of a metal organic compound solution. A current-voltage non-linear element, which is a metal or a metal oxide formed by coating and then baking. 2. The insulating film is a metal oxide formed by applying and baking one or more metal organic compound solutions selected from bismuth (Bi), titanium (Ti), or yttrium (Y). The current-voltage nonlinear element according to claim 1, wherein 3. The current-voltage nonlinear element according to claim 1, wherein the insulating film is a metal oxide having a film thickness of 100 nm or less. 4. A method of manufacturing a current-voltage non-linear element comprising a lower electrode film, an insulating film, and an upper electrode film sequentially laminated on an insulating substrate, wherein a metal organic solution is applied on the insulating substrate and then baked. And a lower electrode film forming step of forming a lower electrode film, and bismuth (Bi) or titanium (T) on the lower electrode film.
i) or an insulating film forming step of applying at least one metal organic solution selected from yttrium (Y) and then baking to form an insulating film; and applying the metal organic solution on the insulating film and baking. And an upper electrode film forming step of forming an upper electrode film, the manufacturing method of the current-voltage non-linear element.