JP2697112B2 - Method for manufacturing reduction-reoxidation type semiconductor porcelain element - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a reduced re-oxidation type semiconductor ceramic element used for an electric circuit and an electronic circuit.

2. Description of the Related Art Conventionally, as a reduction-reoxidation type semiconductor porcelain element, for example, a high-resistance re-oxidation layer is formed on the surface of a disk-shaped semiconductor porcelain, or a high-resistance re-oxidation layer is formed on a grain boundary of the disk-shaped semiconductor porcelain. Is formed as a dielectric material, and electrodes are formed on opposing surfaces, and are in practical use. This type of reduced-reoxidation type semiconductor porcelain element has a relatively small size, provides a large capacitance, is non-polar, has good heat resistance and frequency characteristics, has low leakage current, and is relatively inexpensive. And is widely and generally used.

Problems to be Solved by the Invention In recent years, electronic components used in electronic devices tend to be miniaturized and made into chips, but the capacitance per unit area of the above-mentioned reduced re-oxidation type semiconductor porcelain element is at most as small as possible. 30
It is about 0 (nF / cm ² ), and there is a problem that the shape becomes large when trying to obtain a large capacitance of about 1 μF. In order to solve this problem, a disk-shaped reduction / reoxidation type semiconductor ceramic in which an ohmic electrode is formed on one surface and a non-ohmic electrode is formed on the opposite surface has been proposed. The reduction-reoxidation type semiconductor porcelain element having such a structure is 1.5 to 2.0 times the capacitance of the element having a non-ohmic electrode formed on both surfaces of the disk-shaped reduction-reoxidation type semiconductor porcelain. However, in order to manufacture an element with this structure, the porcelain is reduced and fired and re-oxidized, and then the high-resistance oxide layer formed on the surface of the semiconductor porcelain is removed on only one surface. To expose the semiconductor portion. Means for removing the high-resistance oxide layer include lapping, sand blasting, and laser processing, but in any case, lacks mass productivity and has not been put to practical use. Also, when molding a disc-shaped reduced reoxidation type semiconductor material, a convex portion is provided on one surface in advance, and after reducing and reoxidizing, the convex portion is mechanically removed to remove the semiconductor portion. Although a method of exposing is proposed, a high-resistance oxide layer to be removed has a thickness of about 30 to 100 μm, and a method of mechanical removal, such as sand paper, file, lap polishing, sand blasting, laser processing, etc., is not suitable for mass production. There was a problem that it could not be practically used.

The present invention solves the above-described problem. After reducing and firing the porcelain and re-oxidizing the porcelain, a mechanical method is used to remove the high-resistance oxide layer formed on the surface of the semiconductor porcelain. It is an object of the present invention to provide a method capable of easily producing a large amount by removing an oxide layer without removing the oxide layer.

Means for Solving the Problems In order to solve this problem, according to the present invention, a reduced-reoxidation type semiconductor ceramic material is used as a main component, which is molded, debindered, reduced and fired, and then converted into a semiconductor in the main component. One of the surfaces of the fired body is reoxidized so that one surface of the fired body is buried in a substance (oxygen diffusion retarding substance) containing a substance that promotes the conversion of the main component into a semiconductor more than the content of the promotion substance. .

In this way, a semiconductor (oxygen diffusion retardant) containing a larger amount of the substance that promotes the conversion of the main component into a semiconductor than the content of the semiconductor conversion promoting substance in the main component has a higher content. Since diffusion of oxygen is slower than that of the main component due to the chemical substance, oxygen is hardly diffused up to the surface of the reduced reoxidation type semiconductor porcelain in contact with such a substance, and a high resistance layer is hardly formed. . Therefore, there is no high-resistance layer on the surface in contact with a substance (oxygen diffusion retarding substance) containing a substance that promotes the conversion of the main component into a semiconductor more than the content of the semiconductor conversion promoting substance in the main component. A high resistance layer is formed only on the surface of the element, and the capacitance is significantly increased as compared with a case where a high resistance oxide layer is present on both surfaces of the element. Further, when the particle diameter of a substance (oxygen diffusion retardant) containing a large amount of a substance that promotes semiconductivity of the main component is greater than 100 μm or more than the content of the semiconductivity promoting substance in the main component, the content of the substance may be reduced. Baking while keeping the fired body in contact with a substance (oxygen diffusion retarding substance) having a small number of contact points and containing a substance that promotes the conversion of the main component into a semiconductor more than the content of the semiconductor conversion promoting substance in the main component Even so, the two can be easily separated.

If the particle diameter of the oxygen diffusion retarding substance is relatively small, less than 100 μm, it is difficult for oxygen to directly contact the surface of the sintered body, and it is difficult to form a high resistance layer.

The same effect can be obtained by using a non-ohmic electrode or an ohmic electrode as the type of electrode, but the ohmic electrode provides better characteristics. Also, one surface of the sintered body is buried in a substance (oxygen diffusion retarding substance) containing a substance that promotes the conversion of the main component into a semiconductor more than the content of the semiconductor conversion promoting substance in the main component. By forming an ohmic electrode on the fired surface,
Since the semiconductor portion of the element and the ohmic electrode are in direct contact with each other, no barrier is formed at the electrode interface. Also, one surface of the sintered body is buried in a substance (oxygen diffusion retarding substance) containing a substance that promotes the conversion of the main component into a semiconductor more than the content of the semiconductor conversion promoting substance in the main component. Since the dielectric layer is exposed on the surface opposite to the fired surface, the same effect can be obtained with an ohmic electrode or a non-ohmic electrode.However, in the case of an ohmic electrode, deterioration of characteristics such as a decrease in dielectric constant is caused. In the case of a non-ohmic electrode, there is a decrease in the dielectric constant, but it is possible to improve characteristics such as an increase in dielectric strength with a barrier formed at the electrode interface.

Examples Hereinafter, the present invention will be described specifically with reference to examples.

(Example 1) First, SrTiO ₃ (99.5 mol%), Nb ₂ O ₅ (0.2 mol%), CuO
(0.3 mol%), and weigh with a ball mill etc.
After wet mixing with Hr and drying, 10 wt% of organic binder such as polyvinyl alcohol is added and granulated.
Formed into a disc at 10φ × 1t (mm), press pressure 1t / cm ² ,
After firing (removing binder) at 1200 ℃, 2Hr in air,
Calcination is performed at 1350 ° C. and 4 hours in a reducing atmosphere of N ₂ : H ₂ = 9: 1.
Next, an oxygen diffusion retarding substance [for example, SrTiO ₃ (99.2 mol
%) And Nb ₂ O ₅ (0.8 mol%) in powder form with various compositions and particle diameters as shown in Table 1 below, spread over a porcelain sheath, and fired on it One side of the disk is down, and that side is, for example, SrTiO ₃ (99.2 mol%) and Nb ₂
Arrange them one by one so as to be completely buried in the mixed powder of O ₅ (0.8 mol%), and heat-treat at 1010 ° C., 8Hr in air to perform reoxidation. Next, an electrode paste such as Ag is applied to the surface of the opposing disc by screen printing or the like, and the
The electrodes are formed by firing at 10 ° C for 10 minutes, the lead wires are attached by soldering or the like, and the exterior resin is applied. The characteristics of the device thus obtained are also shown in Table 1 below.

FIG. 1 shows an outline of the manufacturing process in the present invention.

Example 2 First, SrTiO ₃ (99.5 mol%), Nb ₂ O ₅ (0.2 mol%), CuO
(0.3 mol%), and weigh with a ball mill etc.
After wet mixing with Hr and drying, 10 wt% of organic binder such as polyvinyl alcohol is added and granulated.
Formed into a disc at 10φ × 1t (mm), press pressure 1t / cm ² ,
After firing at 1100 ° C and 4Hr in air (debinding),
Calcination is performed at 1450 ° C. and 3 hours in a reducing atmosphere of N ₂ : H ₂ = 9: 1.
Next, an oxygen diffusion retarding substance [for example, SrTiO ₃ (99.2 mol
%) And Nb ₂ O ₅ (0.8 mol%) were powdered with various compositions and particle diameters as shown in Table 2 below, spread over a porcelain sheath, and then fired. One side of the disk is down, and that side is, for example, SrTiO ₃ (99.2 mol%) and Nb ₂
One by one so as to be completely buried in the mixed powder of O ₅ (0.8 mol%), and heat-treated at 1030 ° C. and 6 hours in air to perform re-oxidation. Next, an electrode paste such as Ag is applied to the surface of the opposing disc by screen printing or the like, and the
The electrodes are formed by firing at 10 ° C for 10 minutes, the lead wires are attached by soldering or the like, and the exterior resin is applied. The characteristics of the device thus obtained are also shown in Table 2 below.

Here, substances that promote the conversion of the main component into a semiconductor include Nb ₂ O ₅ , Ta ₂ O ₅ , WO ₃ , La ₂ O ₃ , CeO ₂ , Nd ₂ O ₃ , Pr ₆ O ₁₁ , Dy ₂ O ₃ ,
It was confirmed that a similar effect can be obtained with at least one of Y ₂ O ₃ , Sm ₂ O ₃ , GeO ₂ , and Eu ₂ O ₃ .
Examples of the substance (oxygen diffusion retardant) containing a substance that promotes the conversion of the main component into a semiconductor more than the content of the semiconductor conversion promoting substance in the main component include Nb ₂ O ₅ , Ta ₂ O ₅ , and WO. ₃ , La ₂ O
₃ , at least one of CeO ₂ , Nd ₂ O ₃ , Pr ₆ O ₁₁ , Dy ₂ O ₃ , Y ₂ O ₃ , Sm ₂ O ₃ , GeO ₂ , Eu ₂ O ₃ and SrTiO ₃ , BaTiO ₃ , CaTiO ₃ , M
It has been confirmed that the same effect can be obtained with a mixture or compound with at least one of gTiO ₃ . In addition, the content of the semiconducting substance in a substance (oxygen diffusion retardant) containing a substance that promotes semiconductivity of the main component is larger than the content of the semiconducting substance in the main component, It was confirmed that the effect was higher when the content was larger than the content of the substance that promotes the formation of a semiconductor, but the effect was higher as the difference in the content was larger.

The evaluation of the capacitance and tan δ was performed at 1 KHz. Although this embodiment shows only the composition of the SrTiO ₃ system, BaTiO _3, to CaTiO _3, or whatever if reduction reoxidation type semiconductor ceramic material, such as MgTiO _3, also additives It was confirmed that the same effect could be obtained regardless of the type. Regarding the type of electrode, the same effect can be obtained with a non-ohmic electrode or an ohmic electrode, but the ohmic electrode has better characteristics.
Further, one surface of the molded body is buried in a substance (oxygen diffusion retarding substance) containing a substance that promotes the conversion of the main component into a semiconductor more than the content of the semiconductor conversion promoting substance in the main component. By forming an ohmic electrode on the fired surface, the semiconductor portion of the element and the ohmic electrode are in direct contact, and no barrier is formed at the electrode interface, so that deterioration in characteristics such as a decrease in dielectric constant is eliminated.
In addition, firing is performed such that one surface of the molded body is buried in a substance (oxygen diffusion retarding substance) containing a substance that promotes the conversion of the main component into a semiconductor more than the content of the semiconductor conversion promoting substance in the main component. Since the dielectric layer is exposed on the opposite side of the surface, the same effect can be obtained with an ohmic electrode or a non-ohmic electrode, but in the case of an ohmic electrode, there is no deterioration in characteristics such as a decrease in dielectric constant. In the case of a non-ohmic electrode, the dielectric constant is reduced, but the barrier formed at the electrode interface can improve characteristics such as an increase in dielectric strength. Further, the obtained characteristics are shown only for the capacitance and tan δ, but it was confirmed that the same effect can be obtained with the varistor characteristics.
As an example, the above Table 1 shows the surge withstand capability (the electric charge value when a change in the voltage applied to both ends of the element when a current of 1 mA flows through the element after a predetermined current flows becomes ± 10%).

As is clear from the above description, according to the method of the present invention, the conventional method had to use a mechanical method to remove the high-resistance oxide layer formed on the surface of the semiconductor porcelain. What was lacking in the fired body was a substance (oxygen diffusion retarding substance) containing a substance that promotes the conversion of the main component into a semiconductor more than the content of the semiconductor conversion promoting substance in the main component during reoxidation. Since the formation of a high-resistance oxide layer can be suppressed by simply filling one surface so that it is buried, an electrode can be formed directly on the semiconductor part without using a mechanical method, and compared with a conventional device. Since the capacitance can be increased, small-sized and large-capacity reduced-re-oxidation type semiconductor ceramic devices can be easily mass-produced. When the oxygen diffusion retardant is less than 100 μm, it is effective to increase the capacity.

[Brief description of the drawings]

FIG. 1 is a view showing a schematic manufacturing process in a method for manufacturing a reduced re-oxidation type semiconductor ceramic device according to one embodiment of the present invention.

Claims (8)

(57) [Claims] 1. A reduced-reoxidation type semiconductor porcelain material comprising a main component, which is formed, debindered, reduced and fired to form a fired body. A re-oxidation type semiconductor ceramic device characterized in that one of the surfaces of the fired body is re-oxidized so as to be buried in a substance (oxygen diffusion retarding substance) containing a large amount of a substance which promotes the conversion of a component into a semiconductor. Method. 2. A substance (oxygen diffusion retarding substance) having a particle diameter of 100 μm or more is used as a substance (oxygen diffusion retarding substance) containing a substance that promotes the conversion of the main component into a semiconductor more than the content of the semiconductor conversion promoting substance in the main component. The method for producing a reduced re-oxidized semiconductor ceramic device according to claim 1. 3. A substance (oxygen diffusion retarding substance) having a particle diameter of less than 100 μm as a substance (oxygen diffusion retarding substance) containing a substance that promotes the formation of a semiconductor as a main component more than the content of the semiconductor conversion promoting substance in the main component. The method for producing a reduced re-oxidized semiconductor ceramic device according to claim 1. 4. The substance which promotes the conversion of a main component into a semiconductor is Nb ₂ O
_{5, Ta 2 O 5, WO} 3, La 2 O 3, CeO 2, Nd 2 O 3, Pr 6 O 11, Dy 2 O 3, Y 2 O 3, Sm 2
_{2. The method according} to claim 1, wherein at least one of O ₃ , GeO ₂ , and Eu ₂ O ₃ is used. 5. A substance (oxygen diffusion retarding substance) containing a substance that promotes the conversion of the main component into a semiconductor more than the content of the semiconductor conversion promoting substance in the main component is Nb ₂ O ₅ , Ta ₂ O ₅ , WO ₃ , La ₂ O ₃ , Ce
O ₂ , Nd ₂ O ₃ , Pr ₆ O ₁₁ , Dy ₂ O ₃ , Y ₂ O ₃ , Sm ₂ O ₃ , GeO ₂ , Eu ₂ O ₃ , and at least one of SrTiO ₃ , BaTiO ₃ , CaTiO ₃ , MgTiO
_{2. The} method of claim 1, wherein the mixture is a compound or a compound with at least one of the three. 6. One surface of the fired body is buried in a substance (oxygen diffusion retarding substance) containing a substance that promotes the conversion of the main component into a semiconductor more than the content of the semiconductor conversion promoting substance in the main component. 2. The method according to claim 1, wherein an ohmic electrode is formed on the fired surface. 7. The method according to claim 1, wherein ohmic electrodes are formed on both surfaces of the fired body. 8. One surface of the fired body is buried in a substance (oxygen diffusion retarding substance) containing a substance that promotes the conversion of the main component into a semiconductor more than the content of the semiconductor conversion promoting substance in the main component. 2. The method according to claim 1, wherein a non-ohmic electrode is formed on the surface opposite to the surface fired.