JPS6118282B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method of manufacturing a dielectric material that can provide a high insulation resistance and control the dielectric constant. Methods for obtaining amorphous dielectrics from crystalline dielectric materials such as BaTiO ₃ , PbTiO ₃ , and LiNbO ₃ include methods of melting a crystalline high dielectric constant material and dropping it onto a saucer made of copper, aluminum, etc.; An amorphous dielectric is formed on a substrate by ejecting a molten crystalline high-permittivity material from a nozzle onto a rotating disk made of copper, aluminum, etc. and rapidly cooling it, or by depositing a dielectric compound by vapor deposition, electrodeposition, sputtering, etc. There are ways to do this. Amorphous dielectrics obtained by these methods have fewer pinholes and fewer pinholes than ordinary polycrystalline dielectrics.
It is characterized by extremely high insulation resistance because there are almost no pores. For this reason, it has a sufficiently high dielectric breakdown voltage even when it is as thin as 5 to 20 μm. For example, when this amorphous dielectric is used in a laminated capacitor, the thickness of each layer of the laminate can be made as thin as 10 μm or less. It has many advantages, such as miniaturization and improved reliability. The purpose of this invention is to provide a method for controlling the permittivity of an amorphous dielectric material having the above-mentioned characteristics. heated amorphous dielectric material at 300 to 1100℃
0.01 to 5.0 in an amorphous dielectric.
This method is characterized by growing dielectric crystals having a grain size of μm. Crystalline dielectric materials for obtaining amorphous dielectrics include BaTiO ₃ , PbTiO ₃ , LiNbO 3 , SrTiO ₃ , LiTaO _{3 ,} Pb(Ti,Zr)O ₃ , Pb
(Zn _1/3 Nb _2/3 ) Perovskite type or composite perovskite type such as O ₃ , Ba ₂ Nb ₂ O ₇ ,
Pyrochlore types such as Ca ₂ Nb ₂ O ₇ ,
Bismuth layered types such as Bi ₄ Ti ₃ O ₁₂ , KxWO ₃
(0.43≦×≦0.51), the main component is tungsten bronze type materials such as PbNb ₂ O ₆ . Of course, these main components can contain other elements to improve their properties. In addition, in order to obtain a high-quality amorphous dielectric material with a uniform surface condition and no internal voids, B ₂ O ₃ , PbO, Bi ₂ O ₃ , SiO ₂ , Al ₂ O ₃ ,
Glass formers such as SnO ₂ and Sb ₂ O ₃ may be included. Furthermore, the temperature at which the amorphous dielectric is heat treated is
The reason why we chose 300 to 1100℃ is because the temperature at which these dielectrics transition from amorphous to crystalline (crystalization temperature) is
This is because it exists within this temperature range. Specifically, at temperatures below 300°C, the size of the crystal grains obtained by transitioning from amorphous to crystalline is small, less than 0.01 μm, and since the ratio of crystal grains to the total volume is small, the dielectric constant is small. This is because it exhibits properties as an amorphous dielectric. On the other hand, if the temperature exceeds 1100°C, crystallization progresses too much and almost no amorphous portion remains, resulting in the occurrence of cracks. For example, _LiNbO3 is 450℃,
BaTiO ₃ and PbTiO ₃ are between 800 and 900°C. However, for amorphous dielectrics with low melting points, crystallization progresses too much at temperatures lower than 1100℃.
Occurrence of cracks is observed. Therefore, such amorphous dielectrics are heat treated at temperatures lower than 1100°C. Furthermore, the reason why the grain size of the dielectric crystal in the amorphous dielectric material is set to 0.01 to 5.0 μm is that the grain size is 0.01 μm.
This is because if the grain size is less than 5.0 m, the crystalline part in the sample is too small in terms of volume ratio, and the amorphous nature becomes dominant and the crystalline nature does not appear.
If it exceeds .mu.m, the structural change from amorphous to crystalline during heat treatment will be large, causing cracks in the sample and making it unusable. Methods for obtaining an amorphous dielectric from a crystalline dielectric material include a method of rapidly cooling a molten crystalline dielectric material, vapor deposition, electrodeposition, and sputtering, any of which may be used. This invention will be described in detail below with reference to Examples. FIG. 1 shows a manufacturing apparatus for obtaining an amorphous dielectric material from a crystalline dielectric material. In the figure, 1 is a vacuum chamber, and a rotating body 2 is installed inside the vacuum chamber 1. The rotating body 2 is made of a material having good heat conductivity, such as copper, and is connected to a motor 3 for driving it. This motor 3 has a maximum rotation speed of about 30,000 rpm, and the speed can be varied. 4 is a fixed base on which the motor 3 is installed, and a nozzle 5 for storing a crystalline dielectric material is installed directly above the rotating body 2 so as to be movable up and down.
6 is a pipe for injecting the crystalline dielectric material into the nozzle 5; Further, 7 is a pipe for injecting gas to jet the molten crystalline dielectric material from the nozzle 5. 8 is nozzle 5
The nozzle 5 is connected to the rotating body 2 by a cylinder that moves up and down.
Adjust the distance to place it directly above. A vacuum bellow 9 expands and contracts in accordance with the vertical movement of the nozzle 5, and seals the space between the vacuum chamber 1 and the nozzle 5.
10 is a heater, which is arranged around the tip of the nozzle 5, and heats the nozzle 5 at a temperature of, for example, 1250 to 1300°C.
is heated to melt the crystalline dielectric material housed within the nozzle 5. 11 is a thermocouple placed near the tip of the nozzle 5; 12 is a shutter;
The shutter 12 is rotatably disposed between the nozzle 5 and the nozzle 5, and the shutter 12 is placed in the closed position before spouting the molten crystalline dielectric material from the nozzle 5 to prevent the rotating body 2 from being heated. 13 is integrally attached to a rotating shaft 14 that rotates the shutter 12 using a magnet. 15 is an exhaust port of the vacuum chamber 1 and is connected to an exhaust system. 16 is a collection port for the amorphous dielectric material produced by this apparatus. If the crystalline dielectric material is non-magnetic and does not contain ferromagnetic oxides, this material should be stored in the nozzle 5 before the nozzle 5 is installed in the vacuum chamber 1, or the nozzle 5 should be heated After heating at 10, this material is introduced through pipe 6. Further, when the crystalline dielectric substance is a mixture with a ferromagnetic oxide, in addition to the above-mentioned arrangement, placing the magnet 13 close to or in contact with the nozzle 5 helps in passing this mixture. When a molten crystalline dielectric material is ejected from the nozzle 5 and rapidly cooled on the rotating surface of the rotating body 2 to obtain an amorphous dielectric material, the vacuum chamber 1 may be a natural atmosphere under atmospheric pressure. In order to obtain a dielectric thin body, it is sufficient to reduce the pressure in the vacuum chamber 1 and manufacture it under low pressure. Furthermore, to prevent peroxidation, the inside of vacuum chamber 1 should be
An inert atmosphere such as N ₂ or Ar may be used. Next, specific examples will be described. 0.5 to 1.0 g of a powder sample having the composition ratio shown in Table 1 was placed in the nozzle 5, and the sample was melted at a temperature of 1300°C or higher. Next, the molten sample was ejected onto a rotating body 2 with a diameter of 30 cm rotating at 2000 rpm using Ar gas having an ejection pressure of 1 atm to obtain a thin plate-like amorphous dielectric. For these amorphous dielectrics, the dielectric constant (εr), resistivity (ο), and breakdown voltage (B.
DV) was measured and the results are shown in Table 1. The size of the obtained sample is 3mm x 4mm x 10μ.
m, more than 99% by volume was in an amorphous state. Next, the dielectric constant and particle size of the amorphous dielectric thus obtained were measured while changing the heat treatment temperature. The heat treatment time was 60 minutes each. Table 2 shows the measurement results. The temperature at the time of measurement is
It is 25℃.

【table】

[Table] As is clear from Table 2, it was confirmed that the crystal grains increased as the temperature increased, and the dielectric constant also increased accordingly. In addition, sample number 6 is
There is a crack at 700℃, which means that the amount of glass former is large and the crystallization process has already finished in the low temperature range of 300 to 500℃, so there is no need to heat treat it at higher temperatures. do. Figure 2 shows the changes in the dielectric constant and the degree of growth of crystal grain size when sample No. 2 was heat treated at 900℃ for 30 to 120 minutes, and the crystal growth occurred throughout the sample. It was confirmed that the growth progressed as the heat treatment progressed. As is clear from the above examples, according to the present invention, by heat-treating amorphous dielectrics obtained by various methods, a dielectric having a desired dielectric constant and an extremely high breakdown voltage can be obtained. It is extremely useful as it can be used not only for multilayer capacitors but also for other capacitors.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram showing an example of an apparatus for obtaining an amorphous dielectric according to the present invention, and Figure 2 is a relationship between heat treatment time, dielectric constant, and crystal grain size of the amorphous dielectric obtained by the method of this invention. FIG.

Claims (1)

[Claims] 1. Heat treating an amorphous dielectric obtained from a crystalline dielectric substance at 300 to 1100°C to grow dielectric crystals having a grain size of 0.01 to 5.0 μm in the amorphous dielectric. A method for producing a dielectric material characterized by: 2. The method for producing a dielectric material according to claim 1, wherein the amorphous dielectric material is obtained by rapidly cooling a molten crystalline dielectric material. 3. The method for producing a dielectric material according to claim 1, wherein the amorphous dielectric material is obtained by any one of vapor deposition, electrodeposition, and sputtering of a crystalline dielectric material.