JP2773479B2 - Grain boundary insulated semiconductor porcelain material and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a grain boundary insulated semiconductor porcelain material having an insulating layer formed at a grain boundary of a semiconductor porcelain and a method of manufacturing the same, and more particularly, to an electronic circuit mounted on communication equipment and audio equipment. And a method for manufacturing the same.

[0002]

2. Description of the Related Art A grain boundary insulated semiconductor porcelain capacitor is obtained by thermally diffusing a metal oxide or the like into a ceramic semiconductor crystal grain boundary to form an insulating layer and attaching electrodes to both surfaces of a semiconductor porcelain material. In general, since a thin grain boundary (insulating layer) of several nm is used, a small and large capacitance can be obtained.

At present, there are two main types of semiconductor porcelain materials used: barium titanate and strontium titanate. Barium titanate has a large capacitance due to the characteristics of barium titanate itself, but has a problem that its value is easily affected by temperature and frequency. On the other hand, strontium titanate has a smaller capacitance than barium titanate, but its value is hardly affected by temperature and frequency, furthermore, its dielectric loss is small, it is relatively easy to make a semiconductor, and the grain boundary is designed. There is an advantage that it is easy.

In recent years, especially electronic devices and electronic circuits are often used in a high frequency range, and are often used in harsh environments such as automobile parts, and have excellent high frequency characteristics and temperature characteristics. Highly reliable capacitors are required, and strontium titanate-based capacitors have been attracting attention.

However, a problem of the strontium titanate is that the breakdown voltage is lower than that of other types of capacitors.
000 V / mm, so the rated voltage is 200 W
It is suppressed around V. In order to increase the breakdown voltage, it is effective to reduce the load per grain boundary by increasing the number of crystal grains in the series direction. However, in this method, the thickness of the element increases, which is contrary to miniaturization. In addition, there was a problem that the material cost was high. In view of this, high dc breakdown voltage of a strontium titanate-based grain boundary insulating semiconductor ceramic capacitor has been studied.
In the publication, strontium titanate-based semiconductor porcelain
By adding a small amount of various auxiliaries to the raw material, the crystal grain size is reduced, the number of crystal grains in series is increased, and the breakdown voltage is improved.

[0006]

SUMMARY OF THE INVENTION
The strontium titanate-based grain boundary insulating semiconductor ceramic capacitor for high DC withstand voltage disclosed in Japanese Patent Application Laid-Open No. 1-63204 has a problem that the capacitance is small while the breakdown voltage value is improved.

The present invention has been made in view of the above problems, and has as its object to provide a grain boundary insulated semiconductor ceramic material having a large breakdown voltage and a large capacitance, and a method of manufacturing the same.

[0008]

In order to achieve the above-mentioned object, a high DC withstand voltage grain boundary insulating semiconductor porcelain according to the present invention is characterized in that the main component of the crystal grains is (Sr _1-xy Ca _X Mg _y ) Ti _1-z A _z O ₃ (where A represents one or two elements of Nb or Y, and X, Y and Z each represent 0.10 ≦ X
≦ 0.30, 0.05 ≦ Y ≦ 0.15, 0.002 ≦ Z
≦ 0.008) in a raw material mixture having a composition represented by the following formula:
It contains one or more of Co and Cs and a Bi element, and is characterized in that the average grain size of the crystal grains is in a range from 10 μm or more to less than 15 μm.

Further, the above-mentioned grain boundary insulating half according to the present invention.
The method of manufacturing a conductive porcelain material is to add one or two of Nb ₂ O ₅ or Y ₂ O ₃ to the main raw materials of SrCO ₃ , CaCO ₃ , MgO and TiO ₂ , calcine and then crush them. Then Al ₂
A sintering aid containing at least one of O ₃ , SiO _{2 and} H ₃ BO ₃ is added, and a semiconducting firing step is performed in a temperature range from 1400 ° C. to less than 1450 ° C. The obtained sintered body is coated with a diffusing agent containing at least one of CoO or Cs ₂ CO ₃ and a compound of Bi ₂ O ₃ , and thereafter is fired at grain boundary insulation.

[0010]

[Action] SrCO _3, CaCO _3, MgO, and Ti0 1 of the main raw material consisting of ₂ Nb ₂ 0 ₅ or Y ₂ 0 _3, two or added, and pulverized after calcination synthesis, then Al ₂ 0 _3, Si0 ₂ or with the addition of H ₃ B0 aid for sintering comprising at least one or more of the _3, subjected to a semiconductive firing step at a temperature ranging from 1400 ° C. to less than 1450 ° C., semiconductive C on the sintered body
Applying a diffusing agent containing at least one of oO or Cs ₂ CO ₃ and a compound of Bi ₂ O ₃ , and then performing grain boundary insulating firing to obtain the average particle size and standard deviation of the particle size , And the inside of the semiconductor ceramic material is formed in a series circuit with crystal grains having smaller and uniform grain sizes. As a result, a grain boundary insulating semiconductor ceramic material having a large breakdown voltage value and a large capacitance can be obtained.

Hereinafter, embodiments of a grain boundary insulating semiconductor ceramic material and a method of manufacturing the same according to the present invention will be described. SrCO ₃ , Ca
Nb ₂ O ₅ or Y ₂ O ₃ as raw material for CO ₃ , MgO and TiO ₂
One or two kinds selected from the above are added and blended to obtain a desired composition ratio. Formulation is the raw materials were weighed accurately, a proper amount of boulders, dispersing agent, together with the pure water in a pot mill carried out by mixing 24 hours. The mixed slurry-like raw material is dehydrated and dried, and is crushed. The crushed crushed powder is transferred into a baked crucible made of, for example, zirconia, and calcined at 1150 ° C. to form a ceramic. It is confirmed by X-ray diffraction, composition analysis and the like that the desired solid solution ceramic has been synthesized. After confirmation, after beating ceramic calcined synthesized and sieved using a sieve uniform powder 1.0 [mu] m before and after at least Al ₂
A sintering aid containing at least one selected from O ₃ , SiO _{2 and} H ₃ BO ₃ is added and mixed. Polyvinyl alcohol or the like is added as an organic binder to this, and it is molded in a disk shape using a metal mold so as to have a diameter of 10 mm and a thickness of 800 μm. The molded body is kept at 1000 ° C. for 2 hours to remove the organic binder. Next, the compact is filled in a firing crucible made of, for example, alumina and fired in a reducing atmosphere, and a ceramic is formed simultaneously with sintering of the ceramic. At this time, a thin plate made of zirconia is preferably laid on the lower side of the compact because the compact easily reacts with alumina. The firing in a reducing atmosphere is performed by firing in a mixed gas atmosphere having a hydrogen concentration of 1 to 15% and a nitrogen concentration of 85 to 99% within a temperature range of 1400 ° C. to less than 1450 ° C. for 4.0 hours. After sufficiently washing the obtained sintered body in an organic solvent (for example, acetone) and hot water, a diffusing agent containing CoO or Cs ₂ CO ₃ and Bi ₂ O ₃ is formed into a kneaded paste and applied to the surface of the sintered body. I do.

The coating amount is 10 to 20 m per 1 g of the sintered body.
g is sufficient. This is fired in the air at a temperature in the range of 1150 to 1250 ° C. for 1.0 to 2.0 hours to obtain a grain boundary insulating semiconductor ceramic material for high DC withstand voltage.

A commercially available silver base was printed on both sides of the semiconductor ceramic material, and electrodes were baked at 800 ° C. to obtain evaluation samples.

[0014]

[Sample Evaluation Method] The completed grain boundary insulating semiconductor ceramic material for high DC withstand voltage was evaluated as follows.

The measurement of the ceramic crystal grain size was performed by SEM observation. The average particle diameter and the standard deviation of the particle diameter (σ _n-1 ) in Table 1 below are values calculated by SEM observation for 30 pieces in each lot of each composition.

The electrical characteristics are apparent relative permittivity ε _app ,
The dielectric loss DF (%) was evaluated using an impedance analyzer, and the breakdown voltage BDV (V / mm) was evaluated using a DC variable voltage power supply. Apparent dielectric constant ε _app and dielectric loss DF are A
It is a value measured at C1 KHz and an applied voltage of 1 V. The breakdown voltage BDV is a value obtained by gradually increasing the DC voltage value applied between the electrodes, dividing the voltage at which the dielectric breakdown has occurred by the thickness of the element body, and converting the voltage per mm. The number of samples was 30 for each composition, and the numerical values of the electrical characteristics were their average values.

The breakdown voltage BDV (V / mm) is 3000 V /
mm, the apparent relative permittivity ε _app
Does not deteriorate and shows a value of 10,000 or more.

[0018]

[Table 1]

[0019]

[Table 1-2]

[0020]

[Table 1-3]

[0021]

[Table 1-4]

[0022]

According to the high DC breakdown voltage grain boundary insulated semiconductor porcelain material of the present invention, since the breakdown voltage value and the capacitance are both large, a highly reliable capacitor can be provided. Further, in the method for manufacturing a grain boundary insulated semiconductor porcelain according to the present invention, it is possible to provide a grain boundary insulated semiconductor porcelain excellent for high DC withstand voltage by a process substantially similar to a conventional process. .

[0023]

Claims (2)

(57) [Claims] The main component of the crystal grains is (Sr _1-xy Ca _x Mg _y ) Ti
_1-z A _z O ₃ (where A represents one or two elements of Nb or Y, and X, Y and Z each represent
0.10 ≦ X ≦ 0.30, 0.05 ≦ Y ≦ 0.15,
A sintered material of a raw material mixture having a composition represented by the following formula: 0.002 ≦ Z ≦ 0.008), wherein at least one of Co and Cs and a Bi element Wherein the average grain size of the crystal grains is in a range from 10 μm or more to less than 15 μm. Wherein the addition of SrCO _3, CaCO _3, 1 kind or two kinds of MgO and Ti0 Nb ₂ 0 ₅ in the main raw material consisting of ₂ or Y ₂ 0 _3, and pulverized after calcination synthesis, following Al ₂ O ₃ , Si 0 ₂
Or subjected to semiconductive firing step at a temperature range of additives to 1400 ° C. The sintering aid to less than 1450 ° C. comprising at least one or more of H ₃ B0 _3, the sintered body is sintered semiconductive CoO or one or more of Cs ₂ CO ₃ and Bi ₂ O ₃
2. The method for producing a grain boundary insulated semiconductor porcelain material according to claim 1, wherein a diffusing agent containing the above compound is applied, followed by baking with grain boundary insulation.