JPS6242574A - Nonlinear resistance element and manufacture of the same - Google Patents

Abstract

PURPOSE:To obtain a nonlinear resistance element which has a conductive switching function by attaching a lead electrode to a thin film of a mixture of manganese oxide, tin oxide and iron oxide. CONSTITUTION:2-Ethyl hexanates, which are easy to be formed into a film, are employed as compounds of Mn, Sn and Fe and these compounds are applied by spin-coating with methyl isobutyl keton as solvent to the surface of a glass substrate 1 on which an Au thin film electrode 4 is provided. The substrate is then baked in the atmosphere at 550 deg.C for 60min to form an activation layer 2 and an Au thin film electrode 3 is formed. With this constitution, a nonlinear resistance element, which has switching characteristics with a threshold voltage Vth, a threshold current Ith, a holding voltage Vh and a holding current Ih, can be obtained with high productivity and at a low cost.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to nonlinear resistive elements with functions such as conductive switching.

BACKGROUND OF THE INVENTION A nonlinear resistance element that performs conductive switching is known as an OvONIc element, and uses an amorphous semiconductor mainly composed of chalcogen elements as its material. It is also known that similar electrical properties are found in transition metal oxides, such as hematite, magnetite, nickel ferrite, nickel zinc ferrite, and nickel oxide. These conventional nonlinear resistance elements use materials in the form of thin films or sintered bodies, but it is advantageous to construct them with thin films from the viewpoint of low threshold voltage, and they exhibit relatively stable characteristics. Most amorphous semiconductor devices are of the thin film type.

The basic structure of this is shown in FIGS. 2 and 3.

In the figure, 1 is the base, 2 is the active layer, and 3.4
is an electrode.

The film thus formed can be divided into a sandwich type (FIG. 2) in which the film is used in the thickness direction, and a planar type (FIG. 3) in which the film is used in the surface direction. In either case, the active layer is usually formed by vacuum evaporation or sputtering.

Problems to be Solved by the Invention As mentioned above, in conventional nonlinear resistance elements exhibiting switching characteristics, the active layer is formed by a vacuum method.
This is not a disadvantage in terms of manufacturing yield or productivity, but it is necessary to accommodate this for reasons such as higher costs for applications that require devices to be constructed on very large substrates. I can't do it.

An object of the present invention is to provide a nonlinear resistance element having switching characteristics that solves these problems and a method for manufacturing the same, and to enable these elements to be manufactured with high productivity and at low cost.

Means for Solving the Problems In order to achieve the above object, the present invention adopts a method of coating a solution of a metal compound and thermal decomposition to form an active layer. As a metal compound, it dissolves in an appropriate solvent,
It only needs to form a film when the solution is applied and dries.
For example, inorganic acid salts such as nitrates, organic acid salts such as acetates,
Complexes and organic metals with an alkyl group attached to the metal can be used. Although there are many metal compounds that can be used to form thin films using this method, the inventors discovered a mixture of manganese oxide, tin oxide, and iron oxide as a compound that exhibits switching properties, and used this for the active layer.

The mixture thin film of functional manganese oxide, tin oxide and iron oxide is
It can be easily obtained by mixing and dissolving a compound of manganese, tin, and iron in a solvent, coating the mixture on a substrate, and thermally decomposing the mixture. At this time, by appropriately considering the combination of compound and solvent, a very stable solution can be obtained and can be stored as an ink for a long period of time. By introducing such a formation method, methods such as dipping, spraying, and printing can be used, so that a uniform film can be manufactured over a large area with high productivity and at low cost.

In addition, the thin film obtained by pyrolysis exhibits switching characteristics in which the threshold voltage and sustaining current change depending on the film thickness, distance between electrodes, composition, etc., and the stability of these characteristics is very good.

Example The present invention will be explained below with reference to Examples.

(Example 1) In order to make the sandwich type element shown in FIG.
A coating solution for forming a thin film of a mixture of manganese oxide, tin oxide and iron oxide was prepared with the composition shown in the table. manganese,
As a compound of tin and iron, 2-
Ethylhexanoate was used, and methyl isobutyl keto y'6 was used as the solvent. These coating solutions were spin-coded onto a glass substrate on which a thin gold film was formed as an electrode, dried at room temperature, and fired in air at 550'C for 60 minutes to form an active layer. A thin film was formed. When the knee V characteristics of these elements are measured with a curve tracer when voltage is applied, the I-
A V curve is obtained. The measurement results are shown in Table 1. In this table, vth (threshold voltage) and
Threshold current), vh (maintaining voltage), and h (maintaining current) are shown as numerical values. These values are all values when swept at a frequency of 5ol-IZ. The thickness of the active layer was measured by etching a part of this thin film to form a step and using a contact type surface roughness meter.

Furthermore, we applied a sawtooth wave of ±1 sV to these devices at 5-channel to examine the stability of their characteristics. Even after
No fluctuation of more than 5 degrees was observed, and the stability of the properties was considered to be sufficient for practical use.

(Hereinafter referred to as "Kinshiro") (Example 2) Using a coating liquid having the same composition as in Example 1, a sandwich-type element was constructed by replacing the electrode with a tin-doped indium oxide thin film. The manufacturing method except for the electrodes is exactly the same as in Example 1. When these IV characteristics were measured using a curve tracer, an I-7 curve as shown in FIG. 1 was similarly obtained, and the results are shown in Table 2. The sample cases in the table correspond to those in Table 1, and the same positives indicate that the active layer was formed using the same coating solution. Sweep frequency is 50
It is Hz. From this table, it can be seen that almost the same results as in Example 1 were obtained, although there were some variations.

Further, stability tests similar to those in Example 1 were conducted, and it was confirmed that the characteristics were stable even after switching approximately 4 million times or more.

(Example 3) A thin gold film was formed on a glass substrate, a part of this thin film was ethoched to create a gap of several tens of microns in width, the gold thin film separated by this was used as an electrode, and the example was applied on top of this. An active layer was formed using the same coating solution as in Example 1. The formation conditions are the same as in Example 1. In this way, the planar type element shown in FIG. 3 was produced. When a DC voltage is applied to these and the knee V characteristics are measured, the first
An I-7 curve as shown in the figure was obtained. The results are shown in Table 3. Similarly, the sample position corresponds to the positive part of Example 1. It can be seen that the threshold voltage increases in response to the larger inter-electrode spacing compared to the sandwich type element. It was confirmed that the stability of the properties in these cases was sufficient for practical use.

(Hereinafter referred to as gold and white) Table 2 Table 3 (Example 4) A stainless steel wire with a diameter of 1 ff was immersed in the coating solution of No. 8 of Example 1, pulled up at a rate of about 5 txx/sea, and then dried. A thin film of a mixture of manganese oxide, tin oxide and iron oxide was formed on the surface of the stainless steel wire by heating and baking at 60°C for 90 minutes, and a silver electrode was further formed on the surface of this film to construct an element. In this case, at a sweep frequency of 60, vth is 12.5V1"th is 0.3mm, and vh is 9mm.
．． Switching characteristics similar to those of Examples 1 to 3 with 2V and Ih of 4.8 mm were observed.

In Examples 1 to 4, the firing temperature was set at 500 to 550'C in view of the heat resistance of the substrate and electrode materials used. However, when using a heat resistant substrate such as alumina, The temperature can be raised up to the heat-resistant temperature of the substrate.

Regarding the compounds to be used, any inorganic acid salts such as nitrates and sulfates, organic acid salts such as acetates, complex salts, metal alkoxides, etc., which can be dissolved in an appropriate solvent, can be used without any problem. Further, as the electrode material, metals other than those used in this embodiment such as copper, aluminum, and zinc, conductive oxides such as cadmium stannate and antimony-doped tin oxide, or carbon can also be used.

Effects of the Invention As described above, the nonlinear resistance element of the present invention consists of a thin film of a mixture of manganese oxide, tin oxide, and iron oxide, and an electrode for taking electrical leads from the thin film. A mixture thin film is formed by applying a solution of a manganese compound, a tin compound, and an iron compound mixed and dissolved in a solvent onto a substrate, drying it, and then heating and baking it in the air to improve the switching characteristics. It has great practical utility in that it can provide a nonlinear resistance element with high productivity and at low cost, and can be easily manufactured even over a large area.

[Brief explanation of drawings]

FIG. 1 is a current-voltage characteristic diagram of the nonlinear resistance element of the present invention,
FIG. 2 is a sectional view showing the structure of a Sandinch type nonlinear resistance element, and FIG. 3 is a sectional view showing the structure of a planar type nonlinear resistance element. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure ■ Current

Claims (2)

[Claims] (1) A nonlinear resistance element comprising a thin film of a mixture of manganese oxide, tin oxide, and iron oxide, and an electrode for taking electrical leads from this thin film, and having conductive switching characteristics. (2) A solution of a manganese compound, a tin compound, and an iron compound mixed and dissolved in a solvent is applied onto the substrate, and after drying,
A method for manufacturing a nonlinear resistance element, comprising forming a thin film of a mixture of manganese oxide, tin oxide, and iron oxide by heating and baking.