JPH03268401A - Voltage non-linearity resistive element - Google Patents

Abstract

PURPOSE:To stably obtain a voltage non-linearity resistive element with a high non-linearity by using a low-priced NiO as a metallic oxide layer. CONSTITUTION:Nickel(Ni) is formed as a first electrode layer 2 by about 0.5mum thick on a glass substrate 1 by vapor deposition. Then, an oxide layer 3 composed of ZnO layer or a layer mainly consisting of ZnO is formed by about 1.0mum thick by a sputtering process with ZnO sintered body as a target. Subsequently, a metallic oxide layer 4 composed of NiO layer or a layer mainly consisting of NiO is similary formed by about 1.0mum thick with NiO sintered body as a target. Aluminum(Al) is formed as a second electrode layer 5 by about 0.5mum thick on this metallic oxide layer 4 by vapor deposition. When voltage is applied in the normal direction to the first and second electrode layers 2 and 5, electric current begins to abruptly flow through a potential barrier 3a if the barrier exceeds a certain voltage 50 that an asymmetrical voltage non-linearity is shown. Thus, it is possible to stably obtain a varistor with a high non-linearity.

Description

[Detailed description of the invention] [Object of the invention] (Industrial application field) The present invention is a means for protecting relay contacts, protecting semiconductor elements such as ICs and LSIs against static electricity, and absorbing discharges in color television cathode ray tube circuits. This invention relates to improvements in voltage nonlinear resistance elements used as such.

(Prior art) Conventional voltage nonlinear resistance element (hereinafter referred to as varistor)
For example, a structure as shown in Japanese Patent Publication No. 59-10042 is known. As shown in FIG. 4, this structure consists of a first electrode layer 11 formed on a substrate 10 and a ZnO layer or a layer mainly composed of ZnO formed on the first electrode layer 11. A metal oxide layer 13 consisting of a Bi2O3 layer or a layer mainly composed of Bi2O formed on the oxide layer 12, and a second electrode layer 14 formed thereon. There is. A potential barrier 12a is formed at the interface between the oxide layer 12 and the metal oxide layer 13,
The varistor voltage is determined by this potential barrier 12a.

In the structure shown in FIG. 4, when a positive voltage is applied to the first electrode layer 11 with respect to the second electrode layer 14, the potential barrier 12a is reverse biased, and no current flows until a certain voltage is reached. It is known that voltage nonlinearity (nonlinear coefficient α is around 20) is exhibited, in which current suddenly starts flowing from a certain voltage value.

(Problems to be Solved by the Invention) However, in conventional varistors, it is said that it is difficult to form a layer whose main component is a Bi2O3 layer or a B1□03 layer used as a metal oxide layer with good reproducibility. There's a problem. In other words, in order to manufacture varistors with high nonlinearity, it is necessary to form resistivity with good reproducibility, but to do this, the oxygen content in the film must be controlled with high precision. . However, this requires extremely precise film formation conditions, making it difficult to achieve.

The present invention has been made in response to the above-mentioned problems.
The purpose of this invention is to stably provide a voltage nonlinear resistance element with high nonlinearity by using inexpensive NiO as a metal oxide layer.

[Structure of the Invention] (Means for Solving the Problems) In order to achieve the above object, the present invention provides a first electrode layer formed on a substrate and a ZnO layer formed on the first electrode layer.
an oxide layer consisting of a layer or a layer mainly composed of ZnO, a metal oxide layer consisting of a NiO layer or a layer mainly composed of NiO formed on the oxide layer, and at least on this metal oxide layer. The device is characterized by having a second electrode layer formed thereon.

(Function) By configuring the metal oxide layer from a NiO layer or a layer containing NiO as a main component, these NiO layers, etc. can have good resistivity reproducibility (formation) without requiring very precise film formation conditions. Therefore, conventional Bi2O, layer or B
A varistor with high nonlinearity can be stably provided compared to the case where the layer is composed of a layer containing i2O3 as a main component.

(Example) The present invention will be described in detail below with reference to the drawings.

FIG. 1 is a sectional view showing a first embodiment of the voltage nonlinear resistance element (varistor) of the present invention, where 1 is glass, alumina (
A first electrode layer 2 made of Ni or the like is formed on the substrate 1. The first electrode layer 2 is made of Ni or the like. Further, on this first electrode layer 2, an oxide layer 3 consisting of a ZnO layer or a layer mainly composed of ZnO is formed, and further on this oxide layer 3, a NiO layer or a layer mainly composed of NiO is formed. A metal oxide layer 4 is formed. A second electrode layer 5 is formed on the metal oxide layer 4 and is made of AI, Au, or the like. A bias voltage is applied between the second electrode layer 5 and the first electrode layer 2. Further, a potential barrier 3a is formed at the interface between the oxide layer 3 and the gold member oxide layer 4.

Next, a method for manufacturing the varistor of this embodiment will be explained.

First, a glass substrate, for example, is prepared as the substrate 1, and a first electrode layer 2 is formed on this substrate 1 by 0.5 μm of Ni by vapor deposition.
It is formed to a thickness of about m. Next, using the ZnO sintered body as a target, an oxide layer 3 consisting of a ZnO layer or a layer mainly composed of ZnO is formed to a thickness of about 1.0 μm by sputtering, and then the same process is performed using the NiO sintered body as a target. Next, a metal oxide layer 4 made of a NiO layer or a layer mainly composed of NiO is formed to a thickness of about 1.0 μm by sputtering. Next, a second electrode layer 5 is formed on the metal oxide layer 4.
1 is formed to a thickness of about 0.5 μm by a vapor deposition method.

In the varistor of FIG. 1 manufactured in this way,
When a voltage is applied to the first electrode layer 2 in the positive direction with respect to the second electrode layer 5, the potential barrier 3a is biased in the opposite direction, and when a certain voltage is exceeded, a current suddenly flows out, resulting in an asymmetrical voltage. It begins to show nonlinearity.

The following table shows the values of the nonlinear coefficient α and the varistor voltage v1 mA obtained when the film thicknesses of the oxide layer 3 and the metal oxide layer 4 were changed.

(Margin below) In either case, practically excellent characteristics can be obtained.

Moreover, according to this embodiment, the N used as the metal oxide layer 4
The iO layer or the layer mainly composed of NiO has no dependence on the thickness of the NiO layer compared to the conventionally used Bi2O3 layer or layer mainly composed of B12O3, and can stably obtain high nonlinearity. be able to.

FIG. 2 shows a second embodiment of the present invention, and shows a structure in which a second oxide layer 6 is formed on a metal oxide layer 4. In FIG. This second oxide layer 6 is made of a ZnO layer or a layer containing ZnO as a main component similarly to the first oxide layer 3, and is similarly formed by the sputtering method. This also creates a potential barrier 6 at the interface between the second oxide layer 6 and the metal oxide layer 4.
a is formed, and this potential barrier 6a is biased in the opposite direction when a voltage is applied to the second electrode layer 5 in the positive direction with respect to the first electrode layer 2, and when a certain voltage is exceeded, the current suddenly increases. begins to flow.

Therefore, according to the second embodiment, in addition to obtaining the same effect as the first embodiment, the two electrode layers 2 and 5 can be Potential barriers 3a, 6
Since either a is reverse biased, an element exhibiting symmetrical voltage nonlinearity in both directions is obtained.

FIG. 3 shows a third embodiment of the present invention, in which a second metal oxide layer 7 is formed on the second oxide layer 6 in the structure shown in FIG. This shows a structure in which a third oxide layer 8 is formed on an oxide layer 7. This second
Like the first metal oxide layer 4, the oxide layer 7 is made of a NiO layer or a layer containing NiO as a main component, and is similarly formed by sputtering. The third oxide layer 8 is the first and second oxide layer 8.
Like the oxide layers 3 and 6, it is made of a ZnO layer or a layer containing ZnO as a main component, and is similarly formed by sputtering. Further, as a result, a potential barrier 8a is formed at the interface between the third oxide layer 8 and the second metal oxide layer 7, and this potential barrier 8a is applied to the second electrode layer 5 with respect to the first electrode layer 2. If a voltage is applied in the positive direction, it will be biased in the reverse direction. Further, a potential barrier 6b is formed at the interface between the second oxide layer 6 and the second metal oxide layer 7, and acts in the same manner as the potential barrier 8a. Therefore, the third embodiment also provides the same effects as the first and second embodiments. Further, in the structure of this third embodiment, potential barriers are formed at four locations, so that fine adjustment of the varistor voltage is possible by controlling each of these potential barriers.

Furthermore, it is possible to repeatedly stack oxide layers and metal oxide layers.

[Effects of the Invention] As described above, according to the present invention, the metal oxide layer formed in contact with the oxide layer is composed of a NiO layer or a layer mainly composed of NiO, so that non-linear It is possible to stably obtain high quality varistors.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing a first embodiment of a voltage nonlinear resistance element of the present invention, FIG. 2 is a cross-sectional view showing a second embodiment of the present invention, and FIG. FIG. 4 is a sectional view of a conventional example. 1.--Substrate, 2.-First electrode layer, 3a,
6a, 6b, 8a, ...potential barrier, 3.6
．． 8... Oxide layer (ZnO layer or layer containing ZnO as a main component), 4.7...
・Metal oxide layer (N i 0 layer or layer mainly composed of NiO), 5...
-Second electrode layer.

Claims (1)

[Claims] A first electrode layer formed on a substrate, an oxide layer formed on the first electrode layer consisting of a ZnO layer or a layer containing ZnO as a main component, and a NiO layer formed on the oxide layer. Alternatively, a voltage nonlinear resistance element comprising a metal oxide layer made of a layer containing NiO as a main component, and a second electrode layer formed at least on the metal oxide layer.