JPH04112514A - Semiconductor ceramic capacitor of grain-boundary insulation type - Google Patents

Abstract

PURPOSE:To obtain this capacitor by a method wherein a sintering-promoting additive, a semiconductor-promoting additive and a grain-boundary depletion- layer forming agent, in respectively prescribed quantities, are added to a perovskite-type oxide composed mainly of SrTiO3, this mixture is baked and a diffusion treatment is executed in an oxidizing atmosphere. CONSTITUTION:The following are added to and mixed with a perovskite-type oxide composed mainly of strontium titanate (SrTiO3): 0.1 to 5.0wt.% of a sintering-promoting additive; 0.05 to 2.0wt.% of a semiconductor-promoting additive Nb2O5; and 0.1 to 5.0wt.% of a grain-boundary depletion-layer forming agent composed of Sr1-x-yBaxCay(Cu1/3Ta2/3)O3 (where x<=0.3, y<=0.3 and 0<=x+y<=0.6). This mixture is pressurized and molded. Then, the mixture is baked at 1250 to 1500 deg.C in a reducing atmosphere which contains hydrogen. The surface of its baked substance is coated with a grain-boundary diffusing substance which contains bismuth oxide (Bi2O3). A heat treatment is executed at 850 to 1200 deg.C in an oxidizing atmosphere. Electrodes are formed. Thereby, a large element whose characteristic is good can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a grain boundary insulated semiconductor ceramic capacitor, and more particularly to a laminated grain boundary insulated semiconductor ceramic capacitor.

Conventional technology It has been known that by insulating the grain boundaries of this type of ceramic oxide semiconductor, it is possible to obtain a capacitor body with a much larger effective dielectric constant than conventional ceramic dielectrics. It is being For example, 5rTiO:+
The main component is Nb:! 0. and T i O:
! A I20: Copper oxide (CuO) and bismuth oxide (Bi203) are diffused into the grain boundaries of a polycrystalline magnetic semiconductor formed by adding an IS i 02-based mixture, molding, and sintering. In a grain boundary insulated semiconductor capacitor obtained by forming a depletion layer at the boundary, insulating the grain boundary, and forming an electrode, the boost breakdown voltage is 1200 V/mm, and the insulation resistance is approximately I.
A large effective dielectric constant of 20.000 to 100.000 is obtained while maintaining insulation properties of 105 MΩ/country. Note that here, Cub, which is a diffusion substance,
Regarding the role of BizO3, CuO forms an electron trap center in the grain boundaries of the sintered body, and traps electrons in the crystal grains of the n-type semiconductor crystal near the grain boundaries. It acts to form a depletion layer in which there are no electrons near the grain boundaries. A grain boundary insulated semiconductor ceramic capacitor forms a capacitor by storing charge on both sides of the depletion layer thus formed. On the other hand, B
i2O3 is known as a good conductor of oxygen, along with ZrO2, etc., and exists at grain boundaries, and functions to transport oxygen from the outside to the inside of the sintered body by diffusion, and to supply oxygen necessary for forming a grain boundary depletion layer.

However, in contrast to these bulk type capacitors, there is a strong demand for lamination even in grain boundary insulated semiconductor ceramic capacitors.

Problems to be Solved by the Invention However, in order to obtain a large capacitance, grain boundary insulated semiconductor ceramic capacitors obtained by such conventional manufacturing methods are made by making the crystal grains in the sintered body as large as possible and using paste. Bi2O, CuO, etc. are diffused into the inside of the sintered body by coating bismuth oxide containing copper oxide in the form of bismuth oxide, etc., around the sintered body obtained by firing at high temperature, and then applying heat treatment. However, since the spacing between the electrodes of laminated ceramics becomes narrower, the grain size of the crystal grains in the sintered body must be controlled.

In addition, in devices manufactured using conventional methods, CuO and the like are less likely to diffuse during the process than B12Q3, etc. Therefore, characteristics tend to vary, and thicker devices are not sufficiently oxidized to the inside. Since it is difficult to diffuse copper or the like, there are problems such as restrictions on the size of the element.

The present invention solves these problems, namely:
The grain size of the crystal grains in the sintered body is small and well-aligned, and it is not necessary to apply and diffuse a grain boundary depletion layer forming agent such as copper oxide, but simply apply a grain boundary diffusion substance such as bismuth oxide. The objective is to obtain large elements with good characteristics simply by performing heat treatment and diffusion in air.

Means for Solving the Problems In order to solve the above problems, the present invention adds 0.1 to 5.0 wt% of a sintering accelerating additive to a perovskite oxide mainly composed of 5rT103. agent Nb2O
5 to 0.05 to 2.0 wt%, and S rl-1-y
Adding 0.1 to 5.0 wt% of a grain boundary depletion layer forming agent consisting of BaXcay (Cu+3Ta23)O3 (X≦0.3.y≦0.3.0≦X+y≦0.6),
After mixing, printing, and molding, the materials are sintered at high temperatures to become a semiconductor, and then subjected to a diffusion treatment of bismuth oxide or the like at 850 to 1200° C. in an oxidizing atmosphere to obtain a grain boundary insulated semiconductor ceramic capacitor.

Effect With this configuration, the perovskite type oxide mainly composed of 5rTiO3 and the grain boundary depletion layer forming agent S r 1
-x-yB axCay (Cu I 3T a23)
O = is reacted with Nb2O5, an additive for promoting semiconducting, to form a solid solution, and during the cooling process during firing, oxides containing copper are precipitated at the grain boundaries, and the bismuth oxide that has diffused into the grain boundaries is diffused. The oxygen that has arrived at this process further oxidizes grain boundary substances such as copper, forming electron trap centers at the grain boundaries, and forming depletion layers along the grain boundaries within the low-resistance semiconductor crystal formed by reduction. . The depletion layer obtained in this way has good insulating properties, and charges can be stored on both sides of the depletion layer, resulting in a high-quality capacitor. That is, according to the present invention, it is possible to easily obtain an excellent grain boundary insulated semiconductor ceramic capacitor without requiring the conventional process of applying and diffusing CuO or the like after semiconductor formation.

EXAMPLE Hereinafter, a grain boundary insulated semiconductor ceramic capacitor according to an example of the present invention will be described with reference to tables and drawings.

(Example 1) Titanyl strontium oxalate (SrTiO(C204)
Strontium titanate (SrTiO:+) obtained by thermal decomposition of 2.4H20) was added with a sintering accelerator, Tieney Al.
2O3SiO: (20:35:45wt% ratio) 0.0
5 to 6.0 wt%, 0°0 of semiconductor formation accelerator Nb2O5
2 to 3.0 wt%, grain boundary depletion layer forming agent S r (Cu
0.05 to 6.0 wt% of 0.03 to 0.03 was added, mixed well, and then calcined at 900°C. After wet pulverization, it is dried, granulated, molded, sintered at 1400°C in the air, wet pulverized again, made into a paste using a resin and an organic solvent, and printed alternately with platinum paste for electrodes.
After hydrogen reduction at 1300° C. and application of bismuth oxide, heat treatment was performed at 950° C. in the air, electrodes were adjusted, and electrical properties were measured. The measurement results are shown in Table 1. In addition, the sintering accelerator TiO2Al2O35i02 (20+35:45i
t% ratio) is commercially available T i 02. A I2O3,S
The powder of i02 was weighed and mixed at a weight ratio of 2015:45, calcined at 1200°C, and pulverized. Grain boundary depletion layer forming agent Sr (Cu+:+Ta=3)O
3 is commercially available S rCCF+ Cub, Ta2C);
were mixed, calcined at 900°C, and pulverized.

(Margin below) Table 1 As is clear from Table 1, the sintering accelerator T i 02-A 1203-3 i O:!
0.1 to 5.0 wt% of Nb2O5, 0.05 to 2.0 wt% of Nb2O5, a grain boundary depletion layer forming agent, 5r (Cu
+, +Ta, 3) O3 is 0.1 to 5. This material obtained by firing with Owt% added saponide exhibits extremely excellent dielectric properties and can be used as a capacitor. That is, as a result of microscopic observation, the particle size of the fine particles of the sintered body was well aligned, with a diameter of 2.0~
At 4.0 μm, the dielectric loss was 1.0% or less and the apparent dielectric constant was 2.000 or more. Other measurements were taken of the temperature coefficient of capacitance, insulation resistance, boosted breakdown voltage 1 equivalent series resistance, etc., and satisfactory values were obtained. In addition, the sintering accelerator is 5
% or more, the sintered bodies deform and adhere to each other, making it impractical.

FIG. 1 shows a grain boundary insulated semiconductor ceramic capacitor according to a first embodiment of the present invention. In FIG. 1, 11 is a grain boundary insulated semiconductor ceramic, 12 is an electrode, and 13 is a lead wire.

(Example 2) Tio2-MgO-3io2 system (
For example, 30:30.40wt% ratio), T i 02
Mn0-3i02 series (e.g. 10:50:40
wt% ratio), CaO-Mg0-A 1203-3 i
o: system (e.g. 30.10:15:45wt% ratio), T
iO2Al2O35i02 series (e.g. 2035:45w
t% ratio), ZnO-Nb20s-S i O- system (e.g. 50:45:5 wt% ratio), ZrO2Mn0-3i0
0.05 to 5.0 wt% of a sintering accelerator selected from two systems (for example, 10:55:35 wt% ratio), 0.4 wt% of a semiconductor accelerator Nb2O5, and a grain boundary depletion layer forming agent Sr.
(Cu+.3T a273) 03 was added in an amount of 2.0 wt%, mixed well, and then calcined at 9008C. After wet pulverization, drying, granulation, and molding yield 95% nitrogen and 5% hydrogen.
After baking at 1380° C. in a reducing atmosphere consisting of 10%, bismuth oxide was applied and heat treated at 950° C. in the air to form electrodes and the electrical properties were measured. The measurement results are shown in Table 2.

Note that the sintering accelerator is, for example, TiO2MgO-8102.
The system (30:30:40wt% ratio) was commercially available T
i O2, MgO, S io2 powder at 30.3040
They were weighed and mixed at a weight ratio of , calcined at 1200°C, and pulverized. Furthermore, the grain boundary depletion layer forming agent is commercially available Src
O3, Cub, and Ta205 were mixed, calcined at 900°C, and pulverized.

(Margin below) As is clear from Table 2, 5rTiO:+ has T10
2~1g0-3in: Nato sintering accelerator 0.1~5
．． 0 wt%, semiconductor accelerator Nb, ○, or 0.4 wt%
This material obtained by adding 2.0 wt % of a grain boundary depletion layer forming agent and firing the material exhibits extremely excellent dielectric properties and can be used as a capacitor. That is, as a result of microscopic observation, the particle size of the fine particles of the sintered body is well matched depending on the composition.2.
In the range of 0 to 4.0 μm, the dielectric loss was 1.0% or less and the apparent dielectric constant was 2.000 or more. Other measurements were taken of the temperature coefficient of capacitance, insulation resistance, and boosted breakdown voltage 5 equivalent series resistance, and satisfactory values were obtained. Incidentally, if the sintering accelerator exceeds 5%, the sintered bodies deform and adhere to each other, making it impractical.

(Example 3) A sintering accelerator based on Tio2-MgO-Si○2 (for example, 30.30:40 wt% ratio) was added to commercially available industrial strontium titanate (SrTiO3).
．． 0 wt%, semiconducting accelerator N b 20 s, Q, 5
wt%, grain boundary depletion layer forming agent S ro, a B ao, +
Ca.

((:u, 3Ta23) Os, S ro
, +Bao :+Caa, :+(CLI 1.3
T a = 3) 0.05-6.0 wt% of 03 was added,
After mixing well, the mixture was calcined at 900°C. After wet pulverization, it is dried, granulated, molded, and fired at 1380°C in a reducing atmosphere consisting of 95% nitrogen and 5% hydrogen. After coating with bismuth oxide, it is heat-treated at 950°C in the air to form an electrode. The electrical properties were measured. The measurement results are shown in Table 3.

Note that the sintering accelerator is, for example, T i 02-MgO-8
For the iO2 system (30:30:40wt% ratio), commercially available TiO2MgO, SiO□ powder was mixed with 3030.40%
They were weighed and mixed at a weight ratio of , calcined at 1200°C, and pulverized. Furthermore, the grain boundary depletion layer forming agent is commercially available SrCO
3, BaCO3, CaC0: + , Cu0T a,, O
s was mixed, calcined at 900°C, and pulverized.

(Margins below) As is clear from Table 3, 3.0 wt % of sintering accelerator such as Ti O: -MgO-5i O2 and semiconducting accelerator were added to S r T IO:I. Nb2O5 is Q, 5w
This material, which is obtained by adding 0.1 to 5.0 wt% of grain boundary depletion layer forming agent and firing, exhibits excellent dielectric properties and can be used as a capacitor. That is, as a result of microscopic observation, the fine particles of the sintered body were found to have a uniform particle size of 2 to 4 μm for each composition, a dielectric loss of 1.0% or less, and an apparent dielectric constant of 2.000 or more. We measured the temperature coefficient of its low capacitance, insulation resistance boost breakdown voltage, 7 equivalent series resistance, etc., and found satisfactory values. In addition, the sintering accelerator is 5
% or more, the sintered bodies deform and adhere to each other, making it impractical.

Effects of the Invention As described above, according to the present invention, 0.1 to 5.0 wt% of a sintering accelerating additive is added to a perovskite-type oxide whose main component is strontium titanate (SrTiO3). The agent Nb2O5 is 0.05 to 2. Owt%,
and S r 1−x−yB a=Cay(CU+ 3
T a2 :]) Owl (Tatashi, X≦0.3.y
≦0.3.0≦x+y≦06). After adding Qwt%, mixing and pressure molding, it is fired at 1250 to 1500°C in a reducing atmosphere containing hydrogen, and bismuth oxide (Bi20
．． 85% in an oxidizing atmosphere.
By performing heat treatment at 0 to 1200°C to form an electrode, or by forming an electrode, 5rTiO
: A perovskite type oxide mainly composed of
r+-1-A B axCay (Cut/3Ta2/3
)O:] (However, X≦0.3.y≦0.3.0≦
Grain boundary depletion layer forming agent consisting of 0.1~
5. Owt% reaction and solid solution, then 0.1 to 5.0 wt% of the sintering accelerator additive and 0.05 to 2.0 wt% of the semiconductor accelerator Nb2O5, mixed and pressure molded. After that, 1250~1 in a reducing atmosphere containing hydrogen.
It is fired at 500°C, a grain boundary diffusion substance containing Bi2O5 is applied to the surface of the fired product, and 850-12
By performing heat treatment at 00°C to form an electrode, or by adding 0.1 to 5.0 wt of a sintering accelerating additive to a perovskite oxide whose main component is SrTiO3.
%, 0.05 to 2.0 wt% of the semiconducting accelerating additive, and 5rl-x-y B a x Ca y (Cu+,
3Ta2z:+ )03 (However, X≦0.3゜y≦
0.3, 0≦x+y≦0.6) 0.1 to 5.0 wt% of grain boundary depletion layer forming agent is added, mixed and pressure molded, and then pre-sintered at 1250 to 1500°C in the atmosphere. Then, after reduction at 850 to 1400°C in a reducing atmosphere containing hydrogen, a grain boundary diffusion substance containing Bi2O3 is applied to the surface of the sintered body, and heat treatment is performed at 850 to 1200°C in an oxidizing atmosphere to form an electrode. By forming this, it is possible to obtain a grain boundary insulated semiconductor ceramic capacitor with good characteristics.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing a grain boundary insulated semiconductor ceramic capacitor according to an embodiment of the present invention. 11... Grain boundary insulation type semiconductor ceramics, 12
... Electrode, 13 ... Lead wire. t Lamix 1z-electrode 13...su, -d wire

Claims (5)

[Claims] (1) A perovskite type oxide whose main component is strontium titanate (SrTiO_3), 0.1 to 5.0 wt% of a sintering accelerating additive, and a semiconductor accelerating additive Nb_2
0.05 to 2.0 wt% O_5 and Sr_1_-
____−_yBa_xCa_y(Cu_1_/_3Ta
_2_/_3)O_3 (However, x≦0.3, y≦0.
3. Add 0.1 to 5.0 wt% of a grain boundary depletion layer forming agent consisting of 0≦x+y≦0.6), mix and pressure mold, and then at 1250 to 1500°C in a reducing atmosphere containing hydrogen. Bismuth oxide (Bi_2O_
3) is coated with a grain boundary diffusion substance containing 850%
A grain boundary insulated semiconductor ceramic capacitor whose electrodes are formed by heat treatment at ~1200°C. (2) The sintering accelerator additive is TiO_2-MgO-SiO_
2 system, TiO_2-MnO-SiO_2 system, CaO-M
gO-Al_2O_3-SiO_2 system, TiO_2-A
l_2O_3-SiO_2 system, ZnO-Nb_2O_5
The grain boundary insulated semiconductor ceramic capacitor according to claim 1, comprising a mixture selected from -SiO_2 series and ZrO_2-MnO-SiO_2 series. (3) Sr_1_-_x_-_yBa_xCa is added to the perovskite-type oxide mainly composed of SrTiO_3.
_y(Cu_1_/_3Ta_2_/_3)O_3 (however, x≦0.3, y≦0.3, 0≦x+y≦0.6)
0.1 to 5.0 wt% of the grain boundary depletion layer forming agent is reacted and dissolved in solid solution, and then 0.1 wt% of the sintering accelerating additive is added.
~5.0 wt% and 0.05 to 2.0 wt% of the semiconducting accelerator Nb_2O_5 are added, mixed and pressure molded, and then fired at 1250 to 1500°C in a reducing atmosphere containing hydrogen to obtain the fired product. A grain boundary insulated semiconductor ceramic capacitor is formed by applying a grain boundary diffusion substance containing Bi_2O_3 to the surface of the capacitor and heat-treating the surface at 850 to 1200°C in an oxidizing atmosphere to form electrodes. (4) Add 0.1 to 5.0 wt% of the sintering accelerator additive and 0.05 to 2.0 w of the semiconducting accelerator Nb_2O_5 to the perovskite oxide whose main component is SrTiO_3.
t%, and Sr_1_−_x_−_yBa_xCa_
0.1 to 5.0 wt% addition of grain boundary depletion layer forming agent consisting of y(Cu_1_/_3Ta_2_/_3)O_3 (x≦0.3, y≦0.3, 0≦x+y≦0.6) After mixing and pressure molding, it is heated to 1250 to 15
Calcined at 00°C and then heated at 850°C in a reducing atmosphere containing hydrogen.
After reduction at ~1400℃, Bi_2 is added to the surface of the sintered body.
A grain boundary diffusion substance containing O_3 is applied and 85% is applied in an oxidizing atmosphere.
A grain boundary insulated semiconductor ceramic capacitor whose electrodes are formed by heat treatment at 0 to 1200°C. (5) Add 0.1 to 5.0 wt % of a sintering accelerator additive and 0.05 to 2.0 w of a semiconductor accelerator additive Nb_2O_5 to a perovskite oxide whose main component is SrTiO_3.
t%, and Sr_1_−_x_−_yBa_xCa_
0.1 to 5.0 wt% addition of grain boundary depletion layer forming agent consisting of y(Cu_1_/_3Ta_2_/_3)O_3 (x≦0.3, y≦0.3, 0≦x+y≦0.6) mixed and made into a paste, and printed/printed alternately with the electrode paste.
After molding, it is fired in advance at 1250 to 1500°C in the air, and then at 850 to 1400°C in a reducing atmosphere containing hydrogen.
After reducing the sintered body in
A grain boundary insulated semiconductor ceramic capacitor heat-treated at ℃.