JPS6015130B2 - Voltage nonlinear resistor and its manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a voltage nonlinear resistor with extremely low rise voltage and a method for manufacturing the same.

In recent years, semiconductor elements have come to be widely used in various electrical and electronic devices. However, these semiconductor devices are generally susceptible to surges (abnormal overvoltage). Therefore,
When semiconductor devices are used in circuits where surges occur, either one of two methods is used: select one with a high withstand voltage, or use a surge absorber to protect against surges. The latter method is usually used because the former method of surge protection is not sufficient and is also expensive. Conventionally, as these surge protection elements, a Zn○ varistor is known, which is obtained by adding a certain amount of additives such as Bi203, Co203, Mn02, etc. to Zn0 and phosphorizing it.

Zn0 varistors are stable against surges and exhibit excellent surge protection ability. However, Zn○ burrs utilize the non-ohmic nature of the grain boundaries of the sintered body, and therefore it is difficult to obtain one for low pressure use. That is, since the rising voltage is proportional to the number of grain boundaries inserted in series between the electrodes, the thickness of the element must be reduced in order to obtain a low rising voltage. However, since the particle size of Zn0 particles ranges from several Am to loAm, if you want to obtain one for low pressure, the thickness needs to be less than several hundreds of meters, but due to mechanical strength, such It is extremely difficult to obtain thin ones. Therefore, nothing that can be used to protect devices that operate at several volts, such as ICs and semiconductor devices, has yet to be obtained. The present invention solves the problems of conventional varistors and realizes a voltage nonlinear resistor with particularly low rise voltage.

Examples thereof will be described in detail below.

FIG. 1 shows the basic structure of a device according to the invention. In the figure, 1 is Zn○ or Z containing additives.
2 is a cobalt oxide or manganese oxide layer, 3 is a ZnO layer containing ZnO or an additive, and 4 and 5 are electrodes. With such a configuration, Schottky barriers 6 and 7 are formed on the Zn○ layer side at the interface between the Zn○ layer and the cobalt oxide or manganese oxide layer, so a voltage is applied using the electrode 4 as an anode. In this case, the Schottky barrier 6 is biased in the reverse direction, and in the case where the electrode 5 is used as an anode, the Schottky barrier 7 is biased in the reverse direction. An element exhibiting symmetrical voltage nonlinearity in which current suddenly begins to flow can be obtained. Example 1 Zn○ containing Zn○ powder or additives shown in Table 1
The powder is molded into a shape with a diameter of 12 mm and a thickness of 1 mm using a normal molding method.
5 side, and this molded body was fired in air at 1250° C. for 2 hours.

Both sides of the obtained sintered body were polished, and one side in particular was mirror polished using alumina powder. after that,
After thorough cleaning with an organic solvent, a cobalt oxide sputtered film was formed on the substrate surface of the mirror-polished Zn○ sintered body using a high-frequency sputtering device. Then, a Znq film was formed thereon by sputtering using a target having the same composition as the substrate. Thereafter, AI vapor-deposited electrodes were provided on both sides of the device, and the electrical characteristics thereof were measured. For each element, the voltage non-linearity index a in the range of 0.1 mA to lmA (however, a is defined as 1 = (V/C) a) and the rising voltage (terminal when a current of lmA/V is applied) voltage). As is clear from Table 1, especially Co20
3. The characteristics of the element containing Mn02, AI203, and Ca203 are good.

Table 1 Example 2 Manganese oxide (2 in M ) was sputtered.

A sputtered film having the same composition as the substrate 1 was provided on the shavings by the same method as in Example 1, and electrodes were attached to both sides. Table 2 shows the electrical characteristics of each element. As can be seen from the table, devices with similar characteristics can be obtained using manganese oxide. Table 2 Example 3 AI was vacuum-deposited on a glass substrate, and a Zn○ sputtered film was formed on this AI-deposited film.

Using this as a substrate, a cobalt oxide or manganese oxide film and a Zn0 film having the same composition as the above sputtered film were formed by sputtering, and electrodes were further provided thereon. The structure of the obtained device is shown in FIG. In the figure, 8 is a Zn○ film,
9 is cobalt oxide or manganese oxide film, 10 is Zn
○Membrane, 1 1 is an electrode provided on the glass substrate 13 side, 1
2 is the other electrode. The electrical characteristics of the device thus obtained are shown in Table 3.

It can be seen that good characteristics were obtained in this case as well.
Table 3 Example 4 Instead of Zn○ or a sintered body containing Zn○ as the main component,
A disk-shaped Zn◯ single crystal with a diameter of 2 willows and a thickness of 0.3 ribs with one main surface polished to a mirror finish was used as a substrate.

After a mirror-like surface of this substrate, a cobalt oxide or manganese oxide film, and a ZnO film were sequentially formed by sputtering, electrodes were formed by vapor deposition. Table 4 shows its electrical characteristics. As can be seen from the Examples in Table 4 and above, the element having the basic structure shown in FIG. 1 exhibits significant voltage nonlinearity.

Also, among the additives added to the Zn○ side, Co203, Mn0
No. 2 forms traps in the surface states of the interface and in the Schottky barrier depletion layer formed at the interface, and is effective in improving characteristics.

Furthermore, AI203 and Ga203 have a function of lowering the specific resistance of Zn02, and thereby the height and inside of the Schottky barrier can be controlled. Therefore, as shown in Examples 1 to 3, 0.05 to 3 mol% Co203, 0.05 to 3 mol% Mn02,0 to the Zn○ layer
．． 01-0.1 mol% N203, 0.001-0.1
Addition of mol% Ga203 is an effective method for improving the voltage nonlinearity index. It is clear from the principle that these additives can also be applied when a Zn◯ single crystal is used. The cobalt oxide or manganese oxide layers described in Examples 1 to 4 were mainly produced with a thickness of 500 to 1000A, but even if formed thinner than 500A,
Further, similar characteristics were obtained even when the thickness was formed thicker than 1000A. 5000 to 10000A for Zn○ or Zn○ sputtered films containing additives in Examples 1 to 4
Although the thickness of the film was mainly made as follows, in principle, any thickness sufficient to form a Schottky barrier (approximately 300 A) or more may be sufficient.

When a sintered body is used for the Zn◯ substrate portion, a large-area sintered body can be easily manufactured at low cost, and therefore a large-area element, that is, one with a large surge current can be easily manufactured.

Furthermore, it is extremely easy to dope the ZNO side with an additive for improving properties. On the other hand, when a sputtered film is also used on the Zn○ substrate side, the Zn0 layer is thin and has low resistance, so it is possible to obtain an element with even lower voltage at a large current.

Furthermore, when a single crystal is used as Zn◯, there are fewer defects on the bonding surface, so it is possible to obtain an element with long-term stability and stability against repeated surges.

However, in either method, it is possible to obtain an element that exhibits voltage non-linearity and has a low rise voltage.

For comparison, the characteristics of a sintered Zn○ varistor using Zn○ were measured.

This dovetail type Zn○ varistor is made of Zn○ with Bi203 (0.
5 mol%), Co203 (0.5 mol%), Mn. 2(
0.5 mol%), Ti.

After adding Cr203 (1.0 mol%) and Cr203 (0.5 mol%) and mixing thoroughly, it was molded into a piece with a diameter of 12 ribs and a thickness of 1.5 mm, baked at 1350°C for 2 hours, and then Both sides are polished and aluminum sprayed electrodes are provided.

The rising voltage of this element is 30V per skin, and the limit to which it can be made thinner by polishing is 0.5V due to mechanical strength.
4 side, and therefore the limit of the rising voltage was 12V.
In any case, the atmosphere during sputtering may be an inert gas atmosphere such as argon, or an atmosphere in which about 50% of the atmosphere is replaced with oxygen gas. The resistance value of the sputtered film can be controlled by the amount of oxygen gas replaced. The sintered body mainly composed of ZnO or Zn○ used in Examples 1 and 2 was Zn○ powder or Zn○ powder.
○ By adding additives to the powder and mixing well, adding an appropriate amount of organic binder to the resulting mixed powder, molding it into a disk, and then firing it in air at 100 to 1400 qo. can get. A suitable firing time is 1 hour to 5 hours. In addition, although glass was used for the substrate in Example 3, it is not necessary to be limited to glass, and stable materials that can withstand heat generation during sputtering, such as an alumina sintered substrate or a magnesia sintered substrate, may be used. .

Furthermore, in the examples, vacuum-deposited AI electrodes were used as electrodes, but as can be seen from the above explanation, the electrode material does not have to be limited to AI as long as it is an ohmic electrode, and its formation is not by vapor deposition but by thermal spraying. A method such as baking may also be used.

The Bi203-based sputtering target containing the various additives described in Example 2 can be produced by conventional ceramic techniques.

The same applies to the ZnO-based sputtering targets containing various additives described in Examples 1 to 4. That is, cobalt oxide or manganese oxide or Zn
○Alternatively, thoroughly mix Zn0 and additives in powder form,
After molding into a predetermined shape, it may be fired in air. In the case of a sintered body whose main component is Zn○, it is 10,000 to 1.
It is desirable to fire at a temperature of 40,000 ℃. A suitable firing time is 1 hour to 5 hours. As described in detail above, the present invention applies thin film forming technology by sputtering and can provide a voltage nonlinear resistance element with new characteristics.

[Brief explanation of the drawing]

FIG. 1 is a basic structural diagram of one embodiment of a voltage nonlinear resistor according to the present invention, and FIG. 2 is a structural diagram of another embodiment. 1, 3... ZnO or a layer containing it as the main component,
2...Cobalt oxide or manganese oxide layer, 4,5...
...Electrode, 6,7... Schottky barrier, 8,1
0...ZnO or a film containing it as the main component,
9...Cobalt oxide or manganese oxide film, 1
1, 12...electrode, 13...glass substrate. Momme 1 figure 2

Claims (1)

[Scope of Claims] 1. First and second regions containing at least ZnO and a third region containing at least cobalt oxide or manganese oxide, and the first region is on one side of the third region. The voltage nonlinear resistor is characterized in that the second region is in contact with the other side, and electrodes are provided on each of the first and second other regions. 2 The first and second regions contain at least Co,
One or more of Mn, Al, and Ga is converted into Co_2O_3 form for cobalt from 0.05 to 3
mol%, for manganese 0.05 to 3 mol% in the form of MnO_2, for aluminum Al_2
0.001 to 0.1 mol% in terms of O_5 form, 0.00 mol% in terms of Ga_2O_3 for gallium
The voltage nonlinear resistor according to claim 1, characterized in that the voltage nonlinear resistor contains 1 to 0.1 mol%. 3. The voltage nonlinear resistor according to claim 1, wherein the first region is a polycrystalline sintered body. 4. The voltage nonlinear resistor according to claim 1, wherein the first region is a sputtered film. 5. The voltage nonlinear resistor according to claim 1, wherein the first region is a single crystal. 6. On one side of ZnO or a substrate mainly composed of ZnO, in an atmosphere containing an inert gas or oxygen gas,
A film containing cobalt oxide or manganese oxide or cobalt oxide or manganese oxide as a main component is formed by a sputtering method, and further, by a sputtering method in an atmosphere containing an inert gas or oxygen gas,
A method for manufacturing a voltage nonlinear resistor, which comprises forming a ZnO film or a film containing ZnO as a main component, and further providing an electrode thereon. 7 ZnO powder or ZnO containing additives as a substrate
Manufacture of a voltage nonlinear resistor according to claim 6, characterized in that a sintered body obtained by granulating and molding powder and firing in air at 1000° to 1400°C is used. Method. 8. The voltage according to claim 6, characterized in that the substrate is formed by forming an electrode film on a heat-resistant substrate and further forming a ZnO film containing ZnO or an additive thereon. Method of manufacturing non-linear resistors. 9. The method of manufacturing a voltage nonlinear resistor according to claim 6, characterized in that a ZnO single crystal is used as the substrate.