JPH0262021A - Manufacture of semiconductor porcelain substrate of grain boundary insulation type - Google Patents

Abstract

PURPOSE:To incorporate a capacitor whose characteristic is good and whose cross capacitance is reduced sharply by a method wherein a component for low permittivity is supplied to a molded substance composed of a high-permittivity component so as to partition a plurality of regions and a grain boundary is insulated. CONSTITUTION:A molded substance 4 composed of a high-permittivity composition with a permittivity of 1500 or higher is obtained by an extrusion molding method. The main surface of the molded substance 4 is coated with a paste 5 which is obtained by adding ethyl cellulose, a solvent or the like to a component for low permittivity use or a composition for low permittivity use. This assembly is baked temporarily in the air at 600 to 1200 deg.C. During this process, the component for low permittivity use or the composition for low permittivity use in the coated paste 1 is diffused at the inside of the molded substance 4; a semiconductor porcelain substrate 6 is produced. In order to insulate a grain boundary, the substrate 6 is immersed io a suspension; after that, it is baked in the air at 1100 to 1300 deg.C. A part coated with the paste 5 becomes a low-permittivity porcelain 2; a remaining part becomes a high-permittivity porcelain 1. Thereby, it is possible to incorporate a capacitor whose characteristic is good and whose cross capacitance is reduced sharply.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention is directed to a grain boundary method that has two or more types of dielectric constants and can be used for various electronic circuit boards or substrates containing a plurality of capacitors. The present invention relates to a method for manufacturing an insulated semiconductor ceramic substrate.

(Conventional technology) In recent years, there has been an active movement toward miniaturization of electronic devices.

Among these, the ceramic substrate has a conductive circuit, a resistor, etc. formed by a thick film method or a thin film method on its surface, and further has chip-shaped capacitors, inductances, etc. mounted thereon. However, since the role of this board is simply to mount the electronic components, it is, so to speak, a space in terms of electrical functionality, and by moving some of the electronic components into this space, that is, into the board , attempts are being made to further reduce the size. As a specific example, a technique has been proposed in which a capacitor is built into a substrate and miniaturized by multilayering dielectric sheets.

(Problems to be Solved by the Invention) However, the type of capacitor-embedded substrate made of multilayered dielectric sheets is made up of multiple layers by alternately laminating dielectric sheets and electrode materials, which makes the process complicated and Since the capacitance between the built-in capacitors (hereinafter referred to as cross capacitance) is large, there is a problem in that signal leakage cannot be ignored. That is, it has conventionally been difficult to form a capacitor-embedded substrate in a state in which a plurality of capacitors are sufficiently electrically isolated from each other in a simple manner.

It is an object of the present invention to connect a plurality of capacitors made of grain-boundary insulated semiconductor porcelain with a high dielectric constant to a state in which they are sufficiently electrically isolated from each other, without a decrease in mechanical strength, and without shape distortion. It is an object of the present invention to provide a method for manufacturing a ceramic substrate that can be incorporated in a ceramic substrate.

(Means for Solving the Problems) The present invention, as a first step. At least one component for low dielectric constant selected from the group consisting of Can, SrO and BaO is applied on the main surface of a molded body made of a high dielectric constant composition containing SrTiO3 as a main component and a valence control agent. Or 55.0 to 99.9 mol% of at least one component selected from the group consisting of Cab, SrO and BaO
and 45.1 to 0.1 mol% of at least one component selected from the group consisting of 5ill□, TiO□, MnO□, CuO and ZnO, in which a plurality of regions Grain boundary insulated semiconductor porcelain, characterized in that: as a second step, the low dielectric constant component is diffused into the molded body; and as a third step, grain boundaries are insulated. The present invention relates to a manufacturing method.

Note that although all of the components constituting the low dielectric constant component and the low dielectric constant composition are described as oxides, carbonates thereof are also included.

In a preferred embodiment of the method according to the invention, the diffusion is carried out by calcination. In this case, there is an advantage that no special process is required for diffusion, and diffusion can be achieved during the firing process normally required for manufacturing grain boundary insulated ceramic substrates.

"Low dielectric constant component" or "low dielectric constant composition" here
shall mean a component or composition added to convert a high dielectric constant molded body to a low dielectric constant. Furthermore, the term "composition" includes compounds in addition to mixtures.

The invention will now be explained by way of example with reference to the drawings.

FIG. 1 is a cross-sectional view of a grain-boundary insulated semiconductor ceramic substrate having two types of permittivity manufactured by the method of the present invention, and FIG. 2 is a cross-sectional view of the ceramic substrate of FIG. FIG. 2 is a cross-sectional view of a ceramic substrate with a built-in capacitor. In FIGS. 1 and 2, 1 is a high dielectric constant region used as a capacitor, 2 is a low dielectric constant region for reducing the capacitance between built-in capacitors, and 3 is an electrode of the capacitor. 6 is a grain boundary insulated semiconductor ceramic substrate.

In the high dielectric constant region 1 used as a capacitor,
The dielectric constant is preferably 15,000 or more. In this case, even if the thickness of the ceramic changes, it is possible to form a capacitor with a capacitance of 1000 pF or more, and many types of capacitors among the commonly used ceramic chip capacitors can be formed in ceramic. be able to.

Furthermore, the ceramic constituting the capacitor is required to have good performance in terms of not only dielectric constant but also dielectric loss (tan δ) and temperature characteristics. As something that satisfies them, S
Grain boundary insulated semiconductor porcelain whose main component is rTiO3 is known.

The constituent components of grain boundary insulated semiconductor porcelain mainly composed of SrTiO3 include Y2O,, Nb, O, Ta2Us, W
At least one valence control agent selected from the group consisting of oxides of lanthanum series elements including O, 1, and a203 is used. Furthermore, to obtain a high dielectric constant,
It is necessary to increase the crystal grain size of porcelain, and for this purpose, appropriate additives are also added.

IAnO,,Cub, 5in2. Additives such as Zr0z are examples.

On the other hand, in order to adjust the temperature characteristics, dielectric constant, dielectric loss, etc. of the main component SrT i03,
It is also possible to slightly change the ratio of Sr to T1 from 1:1 or to replace a portion of Sr with Ca and Ba.

In order to separate the high dielectric constant region having the above-mentioned composition into a plurality of regions, a low dielectric constant region 2 is provided in the substrate as shown in FIG. 1. Refer to and explain.

First, as a first step: 1) A molded body 4 made of a high dielectric constant composition having a dielectric constant of 15,000 or more is obtained by an extrusion method, a doctor blade method, or the like.

2) As shown in FIG. 3, the above-mentioned low dielectric constant component or low dielectric composition is applied to a predetermined portion of the main surface (preferably both the front and back surfaces) of the formed body 4, and ethyl cellulose is added thereto. , a solvent and the like are added to form a paste 5. In this case, the paste application width is 0.1 m.
The diameter is required to be l11 or more, preferably 0.2 mm or more.

Then, as a second step: 3) Calcinate at 600 to 1200° C. in the atmosphere to remove the binder component in the molded body and the coating paste.

4) This calcined body is placed in a reducing atmosphere such as a mixed gas of hydrogen and nitrogen, a mixed gas of hydrogen and argon, or nitrogen,
1320-14 in a neutral atmosphere such as argon
Sintering is performed at 50° C. to obtain semiconductor porcelain. Also, in this process,
The low dielectric constant component or the low dielectric constant composition in the applied paste 5 diffuses into the molded body to form a semiconductor ceramic substrate 6 (see FIG. 4).

After that, as a third step; 5) In order to insulate the crystal grain boundaries of this semiconductor porcelain, for example, the double-layer ratio is 81□03/CIJO/ethyl alcohol-0.
,710,3/10 or PbO/ethyl alcohol-
After soaking in a 1/10 suspension or the like, it is fired at 1100°C to 1300°C in the air. As a result, the part to which the paste 5 is applied becomes the low-permittivity porcelain 2, and the remaining part becomes the high-permittivity porcelain 1. In this way, a grain boundary insulated semiconductor ceramic substrate 6 consisting of the high dielectric constant ceramic 1 and the low dielectric constant ceramic 2 is obtained.

Note that Ag, Au, AI, Ni, Cu, 2n may be added to the main surface of the grain boundary insulated semiconductor ceramic substrate 6 as desired.
, By baking the electrode 3 such as Ag-Pd,
A capacitor can be formed.

Note that the reduction in dielectric constant can be confirmed by measuring the capacitance between adjacent capacitors, that is, the cross capacitance.

Further, the strength of the ceramic substrate obtained by the method of the present invention as a substrate is significantly higher than that in the case of only a high dielectric constant region.

As described above, the method of the present invention makes it possible to incorporate a capacitor with good capacitor characteristics and a significant reduction in cross capacitance, and to manufacture a substrate with good mechanical strength.

(Function) At least one low dielectric constant component selected from the group consisting of Cab, SrO and BaO, or Cab applied on a predetermined surface of a molded body forming a high dielectric constant porcelain after grain boundary insulation. , 55.0 to 99.9 mol% of at least one component selected from the group consisting of SrO and BaO, and Sin□, Tin2. MnO7, CuO and Zn
At least one component selected from the group consisting of 45.0
-0.1 mol% of the composition for low dielectric constant,
This will be explained below.

First, when these components or compositions for low dielectric constant are used as a coated article, a characteristic of the coated article is that the shrinkage rate after sintering does not change significantly depending on whether or not it is coated. As a result, the shape distortion of the sintered body is significantly reduced compared to, for example, when a mixture of Al2O3 and 5IO2 is applied, and excellent dimensional stability is obtained.

Cab, SrO are added to the molded body made of the high dielectric constant composition.
When at least one component selected from the group consisting of decreases to In other words, Can,
The presence of at least one component selected from the group consisting of SrO and BaO selectively converts the high dielectric constant composition into a low dielectric constant composition.

Next, at least one component selected from the group consisting of Cab, SrO and BaO is applied to a molded body made of a high dielectric constant composition, and then fired in air according to the usual process for grain boundary insulated semiconductor porcelain. After removing the binder, the coating material is diffused into the interior of the porcelain by firing in a neutral or reducing atmosphere, and the diffusion region is converted into a low dielectric constant region. However, the diffusion rate of Cab, SrQ, and BaO into the interior of the porcelain is relatively slow, so if the molded body (i.e., porcelain) is thick, the diffusion into the interior of the porcelain will be insufficient and the decrease in dielectric constant will slow down. do. In other words, applying at least one component selected from the group consisting of Cab, SrO, and BaO to the surface of the molded product is effective when the thickness of the molded product (i.e., porcelain) is not very thick, for example, when the thickness of the porcelain is 0.
．． 6ml! ! It is effective for the following degrees and below.

On the other hand, at least one component selected from the group consisting of Cab, SrO and BaO 55.0 to 99.9
Mol% and 5in2. Tie□, MnO□, CuO
When a low dielectric constant composition consisting of 45.0 to 0.1 mol% of at least one component selected from the group consisting of
The dielectric constant decreases significantly even if it exceeds Therefore, Sin,
, Tin, , MnO7, CuO and 2nO diffuse into the interior of the porcelain and have the effect of promoting the diffusion of [aO, SrO and BaO into the molded body.

Also, 5i02. Tin, MnO2, CuO, and ZnO have the effect of significantly improving the mechanical strength of the low dielectric constant region.

The reason for limiting the numerical value of the composition in the composition for low dielectric constant is as follows. SiO□, Tin□, MnO□, Cur
When at least one component selected from the group consisting of ZnO and ZnO exceeds 45.0 mol%, the conversion from high dielectric constant to low dielectric constant becomes slow, and the bending strength is Mechanical strength decreases significantly. On the contrary, 0.1
If it is less than mol%, the effect of promoting the diffusion of Can, SrO, and BaO into the interior of the porcelain will be reduced, and if the thickness of the porcelain is thick, the conversion from a high dielectric constant to a low dielectric constant will be markedly slow, and the mechanical This is not preferable because no improvement in strength will be recognized.

The required amount of coating varies depending on the thickness of the molded body, and the thicker it is, the more the amount of coating increases, but since the thickness of commonly used circuit porcelain substrates is up to 1.6 mm, it is necessary to apply 20 mg per coated area. A coating amount of / am2 or less is sufficient. 2
If it is applied in an amount exceeding 0 mg/0 m2, the mechanical strength will be significantly reduced, which is not preferable.

(Effects of the Invention) According to the method of the present invention, a ceramic substrate consisting of regions having two or more types of dielectric constants can be obtained, so that a plurality of capacitor parts can be incorporated in a state where they are sufficiently electrically isolated from each other. Therefore, it can greatly contribute to the miniaturization and performance improvement of circuit boards and, ultimately, electronic devices.

Furthermore, at least one component measured from the group consisting of Can, SrO and BaO and Sin, TiO2,
When MnO2゜CuO and at least one component selected from the group consisting of ZnO are used in combination, the region with a low dielectric constant due to diffusion has a higher mechanical strength than the high dielectric constant region, making it easier to manufacture. It is also possible to reduce the occurrence of defects such as damage during the process.

In addition, the shrinkage rate during sintering of the part where the low dielectric constant component or composition is applied and diffused, that is, the low dielectric constant region and the high dielectric constant region, is almost equal, so there is little distortion in shape and it is easy to process thick films. The positioning accuracy is also the same as that of a normal AI□03 board.

(Example) Next, the present invention will be explained with reference to Examples and Comparative Examples.

Each raw material was weighed out to give the composition shown in Table 1, pulverized and mixed in a wet ball mill for 12 hours, and dried. Next, after calcining in air at 1150℃ for 5 hours, it was heated to 18℃ in a wet ball mill.
Time crushed. After drying this mixture, methylcellulose was added and extrusion molded to obtain molded products having the thickness shown in Table 2. This molded body is 18.8mm x 12.5
It was punched out to a size of mm. As shown in FIG. 3, on both the front and back sides of the molded product, apply the ratio shown in the column of "Applied to the molded product" in Table 2, parallel to the short side of the molded product at the center position of the molded product 4. A paste consisting of the powder prepared in above, ethyl cellulose, and a solvent was mixed into a powder pot of 1.2 mm so that the powder had the value (mg/cm') shown in Table 2 per coated area of the molded body. It was applied in width. For comparison, a sample without coating was also prepared.

In order to remove the binder component, it was calcined at 900° C. for 2 hours in an atmosphere of air. Then 10% by volume hydrogen and 90% nitrogen
% by volume at 1400° C. for 4 hours to obtain semiconductor porcelain that had sintered and shrunk by about 20%, and the coating material was diffused into the interior of the porcelain. This semiconductor porcelain was soaked in a suspension of Bi2O,/CuO/ethyl alcohol in a weight ratio of 0.710.3/10.
An insulating layer was formed at the grain boundaries by firing in air at 0° C. for 30 minutes.

On both sides of the high dielectric constant region 1 used as the capacitor part of the semiconductor ceramic substrate 6 shown in FIG. 4 obtained in this way,
With the shape shown in Figure 5, A
g electrode 3 was baked.

Next, the capacitance (nf), apparent dielectric constant, tan δ (%), and rate of change in capacitance with temperature were measured as characteristics of the capacitor section. Note that the rate of change in capacitance with temperature is the rate of change in capacitance in a temperature range of -25°C to +85°C, which is determined based on the value of 25°C.

In addition, in order to determine the state of electrical separation of the capacitor part, the capacitance between electrodes located on the same plane (cross capacitance)
(pF) was measured.

In addition, the semiconductor ceramic substrate was cut along the lines A and B in Figure 4, a test piece with a width of 2 mm and a thickness of 15 mm was cut out, and the sample pieces were arranged as shown in Figure 6 and three points were cut out. A bending test was conducted to measure the bending strength.

In addition, with respect to the short side length of 12.5 mm of the molded body (18.8 mm x 12.5 mm), the corresponding length in the high dielectric constant region and low dielectric constant region of the fired ceramic substrate (mm x 4th (indicated by β1 and β2, respectively in the figure) were measured, and the shrinkage rate due to sintering was determined using the following formula.

The results of these measurements are shown in Table 2. In Table 2, * marks indicate comparative examples, and others indicate examples.

[Brief Description of the Drawings] Fig. 1 is a cross-sectional view of an example of a grain-boundary insulated semiconductor ceramic substrate manufactured by the method of the present invention, and Fig. 2 is a cross-sectional view of a capacitor-embedded ceramic substrate using the ceramic substrate of Fig. 1. Figure 3 is a perspective view showing a stage in which a low dielectric constant component or composition is supplied to a molded body in the method of the present invention, and Figure 4 is a perspective view showing a stage in which a low dielectric constant component or composition is supplied to a molded body in the method of the present invention. FIG. 5 is a perspective view of a part of the capacitor-embedded board of FIG. 2; FIG. 6 is a perspective view showing the arrangement of test pieces in a bending test. 1... High permittivity area (high permittivity porcelain, capacitor part)
2... Low dielectric constant region (low dielectric constant porcelain) 3... Electrode 4... Molded body (molded body made of high dielectric constant composition) 5.
...Paste (paste containing a component for low dielectric constant or a composition for low dielectric constant) 6... Grain boundary insulated semiconductor ceramic substrate A, B... Cutting line β1 when cutting out a test piece.
12... Length after sintering

Claims (3)

[Claims] 1. CaO
, SrO, and BaO, and supplying at least one component for low dielectric constant selected from the group consisting of , SrO, and BaO so as to define a plurality of regions, and diffusing the component for low dielectric constant into the inside of the molded body. A method for manufacturing a grain boundary insulated semiconductor ceramic substrate, comprising: insulating the grain boundaries, and then insulating the grain boundaries. 2. C on the main surface of the molded body made of the high dielectric constant composition.
55.0 to 99.9 mol% of at least one component selected from the group consisting of aO, SrO, and BaO and SiO
At least one component selected from the group consisting of _2, TiO_2, MnO_2, CuO and ZnO 45.0~
2. The method of claim 1, wherein the low dielectric constant composition comprising 0.1 mol % is provided so as to define a plurality of regions. 3. 3. The method according to claim 1, wherein said diffusion is performed by firing.