JPS6015129B2 - Voltage nonlinear resistor and its manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a high voltage non-conducting resistor 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 that generate surges, either one of two methods is used: select one with a high withstand voltage, or use a surge absorber to protect against surges. . Usually, the former method of surge protection is not sufficient and is also expensive, so the latter method is used. Conventionally, as these surge protection elements, Zn○ B
A Zn0 varistor obtained by adding and sintering a certain amount of additives such as i203, Co203, Mn02, etc. is known.

Zn○ varistors are stable against surges and exhibit excellent surge protection capabilities. However, the Zn○ varistor utilizes the non-ohmic nature of the grain boundaries of the bran compact, 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, in order to obtain a low rising voltage, the thickness of the element must be reduced. However, the particle size of ZnO particles ranges from several m2 to 1 m in Europe and France, so if you want to obtain one for low pressure, the thickness needs to be several hundred rms or less, but due to mechanical strength, It is extremely difficult to obtain such a thin material. Therefore, suitable varistors for protecting semiconductor devices such as integrated circuits have not been available. 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 a Zn○ layer containing Zn○ or an additive, 2 is an MO layer containing M0 (where M is Ba, Sr, or Pb) or an additive, and 3 is a Zn○ layer containing Zn○ or an additive. , 4 and 5 are electrodes. With this configuration, the Schottky barriers 6 and 7 are formed on the Zn○ layer side at the interface between the Zn○ layer and the MO layer, so when a voltage is applied using the electrode 4 as an anode, the Schottky barriers are When the barrier 6 is biased in the opposite direction and the electrode 5 is used as the anode, the Schottky barrier 7 will be reverse biased, and current will not flow until a certain voltage value, but the current will suddenly start flowing from a certain voltage value. A device exhibiting symmetrical voltage nonlinearity is obtained. Example 1 A powder of Z shown in Table 1 or Zn○ powder containing additives was molded into a diameter of 12 mm and a thickness of 1.5 mm using a normal molding method, and this molded body was heated at 1250°C for 2 hours. It was baked in air for an hour.

Both sides of the obtained cord body were polished, and one side in particular was mirror polished using alumina powder. after that,
After thoroughly cleaning with an organic solvent, a high-frequency sputtering device is used to deposit a layer of light on the substrate surface of the mirror-polished Zn○ burnt striped body.
A sputtered film was formed. Next, Z is deposited on the substrate by sputtering using a target having the same composition as the substrate.
An n○ film was formed. 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 and rise voltage (terminal voltage when rudder current flows through lmA/c) in the region of 0.1 to lmA/ground are shown. As is clear from Table 1, especially Co20
3. The characteristics of the element containing Mn02, AI203, and Ga203 are good. Table 1 Example 2 On a Zn0 sintered body substrate obtained in the same manner as in Example 1, M
However, M is a step, Sr, or Pb) film or an MO film containing various additives was provided by sputtering.

Furthermore, a sputtered film having the same composition as the substrate 1 was provided thereon by the same method as in Example 1, and electrodes were attached to both surfaces. Table 2 shows the electrical characteristics of each element. As can be seen from the table, characteristics can be improved by further adding Co203 and Mn02 to MO. 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, M○ having the composition shown in Table 3 (however, M
A Ba, Sr, or Pb) film or an MO main component 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 Zno film, 9
is M○ (where M is mother, Sr, or Pb) or M
A film whose main component is O, 10 is a Zn◯ film, 11 is an electrode provided on the glass substrate 13 side, and 12 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 scale bodies mainly composed of Zn○,
A disk-shaped Zn◯ single crystal with a diameter of 2 sails and a thickness of 0.3 willows, one main surface of which was mirror-polished, was used as a substrate.

The mirror-like surface of this substrate was coated with M○(
(M is Ba, Sr, or Pb) or a film containing MO as a main component and a Zn◯ film were sequentially formed by sputtering, and then the 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.

Even if a single phase of M○ (where M is mother, Pb, or Sr) is used for layer 2 in FIG.
Adding n02 improves the characteristics. This is considered to be because the added additive forms trap surface levels in the MO sputtered film and at the interface with Zn◯. Therefore, for the effect of the amount of additive in the MO, Example 2
As mentioned above, the explanation focused on the effect of sputtering on the Zn○ knee body, but some of the effects are shown in Tables 3 and 4, regardless of whether the ZnQ substrate side is a sputtered film or a single crystal. As shown in Table 2, the same effect can be obtained when Co203 is 0.1 to 40 mol% and Mn02 is 0.
．． Improvement effects are seen in the range of 1 to 40 mol%. Also, among the additives added to the Zn0 side, Co203, Mn0
No. 2 forms traps in the surface level 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 Zn○, and thereby the height and inside of the Schottky barrier can be controlled. Therefore, Example 1
As shown in ~3, 0.05~3 mol% to Zn0 layer
Co203, 0.05-3 mol% Mn02, 0.0
Addition of 1 to 0.1 mol% of N203, 0.001 to 0.1 mol% of Ga203 is an effective method for improving the voltage nonlinearity index. It is clear from the principle that these additives are valid when Zn◯ single crystal is used. M0 (where M is B) as described in Examples 1 to 4
The MO main component layer containing a, Sr, or Pb) or an additive was mainly produced with a thickness of 500 to 1000A, but even if it is formed thinner than 500A,
Similar characteristics were obtained even when the thickness was formed thicker than 0△. The Zn○ sputtered films containing Zn○ or additives in Examples 1 to 4 were mainly produced with a thickness of 5,000 to 10,000 Å, but in principle, a thickness sufficient to form a Schottky barrier (300 Å ) or above is sufficient. When a sintered body is used for the Zn◯ substrate portion, a sintered body with a large area can be easily manufactured at low cost, so a device with a large area, that is, one with a large surge current can be easily manufactured.

It is also extremely easy to dope the Zn○ side with additives for improving properties. On the other hand, when a sputtered film is also used on the Zn◯ substrate side, the Zn◯ layer is thin and has low resistance, so that it is possible to obtain an element with even lower voltage in the case of 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 nonlinearity and has a low rise voltage.

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

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

2 (1.0 mol%) and Cr203 (0.5 mol%) were added, mixed thoroughly, and then molded into 12 diameter side and 1.5 ribs in thickness, fired at 1350 oo for 2 hours, and then both sides is polished and provided with an aluminum sprayed electrode.

The rising voltage of this element is 30V per leg, and the limit to which it can be made thinner by polishing is 0.4V due to mechanical strength.
Yanagi, 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 approximately 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 firing body mainly composed of ZnO or Zn○ used in Examples 1 and 2 was prepared by adding additive powder to Zn○ powder or Zn○ powder and mixing well, and to the obtained mixed powder, It is obtained by adding an appropriate amount of organic binder, molding it into a disk, and then firing it in air at 10,000 to 1,400 qC. A suitable firing time is 1 hour to 5 hours. Further, although glass was used for the substrate in Example 3, it is not necessary to be limited to glass, and a stable material that can withstand heat generation during sputtering, such as an alumina bonded substrate or a magnesia Akatsuki silk 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 Bj203-based sputtering target containing the various additives described in Example 2 can be made using conventional ceramic techniques.

The same applies to the ZnO-based sputtering tardets containing various additives described in Examples 1 to 4. That is, the additive and M○ (where M is Ba, Sr, or Pb) or Zn○ are thoroughly mixed in a powder state,
After molding into a predetermined shape, it may be fired in air. In the case of a sintered body whose main component is Zn0, it is 10,000 to 14
It is desirable to fire at 000C. Baking time is 1 hour~
5 hours is appropriate. As described in detail above, the present invention applies thin film forming technology by sputtering to 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 a main component,
2...M○ (M is Ba, Sr, or P
b) Or a layer containing it as the main component, 4, 5...
・Electrode, 6, 7... Schottky barrier, 8,
10...Zn○ or a film mainly composed of it, 9...M0 (where M is mother, Sr, or P
b) or a film containing it as a main component, 11, 12...
...Electrode, 13...Glass substrate. Figure 1 Figure 2

Claims (1)

[Scope of Claims] 1. A first and second region containing at least ZnO and a third region containing at least MO (where M is Ba, Sr, or Pb), one of the third regions The first region is in contact with one side, the second region is in contact with the other side, and electrodes are provided in each of the first and second other regions. Linear resistor. 2 The first and second regions contain at least Co,
One or more of Mn, Al, Ga, and 0.05 to 3 mol% of cobalt in the form of Co_2O_3
, for manganese, it is converted to MnO_2 form and is 0.0.
5-3 mol%, Al_2O_3 for aluminum
0.001 to 0.1 mol% in the form of , and 0.001 to 0 for gallium in the form of Ga_2O_3
．． The voltage nonlinear resistor according to claim 1, characterized in that the voltage nonlinear resistor contains 1 mol%. 3 The third region contains at least one of Co and Mn in the MO (where M is Ba, Sr, or Pb) and contains 0.1 to 40% of cobalt in the form of Co_2O_3.
2. The voltage nonlinear resistor according to claim 1, wherein the voltage nonlinear resistor contains 0.1 to 40 mol% of manganese in the form of MnO_2. 4. The voltage nonlinear resistor according to claim 1, wherein the first region is a polycrystalline sintered body. 5. The voltage nonlinear resistor according to claim 1, wherein the first region is a sputtered film. 6. The voltage nonlinear resistor according to claim 1, wherein the first region is a single crystal. 7 MO (where M is Ba, Sr,
or Pb) or MO as a main component,
Furthermore, ZnO or Zn is deposited on top of it by sputtering in an atmosphere containing inert gas or oxygen gas.
A method for manufacturing a voltage nonlinear resistor, comprising forming a film containing O as a main component, and further providing electrodes on the film and on a substrate. 8 ZnO containing ZnO powder or additives as a substrate
A method for manufacturing a voltage nonlinear resistor according to claim 7, characterized in that a sintered body obtained by granulating and molding powder and firing in air at 1000° to 1400°C is used. . 9. The voltage according to claim 7, 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. 10. The method of manufacturing a voltage nonlinear resistor according to claim 7, wherein a ZnO single crystal is used as the substrate.