JPH07142288A - Method of manufacturing multilayer thin film capacitor - Google Patents

Abstract

(57) [Summary] [Purpose] Only one electrode is exposed at the electrode extraction end face by a simple method. [Structure] On the electrode extraction end surface side of one electrode 2, only the end portion of the other electrode 4 is partially etched, and on the electrode extraction end surface side of the other electrode 4, only the end portion of one electrode 2 is partly etched. Etching.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a laminated thin film capacitor in which electrodes and dielectrics are alternately laminated.

[0002]

2. Description of the Related Art In order to support high-density mounting on a printed circuit board, a chip which can be surface-mounted in the field of capacitors has been sought, and among them, a multilayer ceramic capacitor and a thin film capacitor have been started as a chip type from an early stage.

An example of a method of manufacturing a chip-type ceramic capacitor will be described. First, a dielectric material prepared by mixing a lead-based or barium titanate-based material with a suitable binder is mixed into a slurry.

Next, this slurry is screen-printed on a predetermined substrate and dried, and then the electrodes are screen-printed and dried. This is repeated a predetermined number of times to form a multilayer structure.
As another method, there is also a case where a slurry is formed into a green sheet, and an electrode is printed on the green sheet, which is laminated and pressure-bonded to form a multilayer structure.

Then, cut into a desired chip size,
The binder is removed and baked, and finally the external electrodes are coated and baked, and the external electrodes are plated to improve solderability.

Thin film capacitors are made of silicon, alumina,
A physical film forming method such as sputtering or vapor deposition on a substrate such as glass or sapphire or MOCVD (Meta)
lOxide Chemical Vapor Dep
The film is formed by sandwiching the dielectric film between the electrode films by a chemical biofilm method such as the oscillating method), and in the case of a laminated type, this is repeated to form a multilayer structure.

[0007]

Ceramic capacitors have a tendency to be further made into chips, smaller in size and larger in capacity in the future. In order to increase the capacitance, the dielectric film may be thinned according to the following equation.

C (F) = 8.85 × 10 ⁻¹² εS (m
² ) / D (m) where F is the capacitance of the capacitor, ε is the relative permittivity, S is the area of the electrodes facing each other across the dielectric, and D is the thickness of the dielectric.

However, in order to reduce the thickness of the dielectric film of the ceramic capacitor, there are many difficult technical points in terms of making the dielectric material fine particles and making the particle diameter uniform, and making a thin green sheet. However, at present, there is no mass production of a ceramic multilayer capacitor having a dielectric film thickness of 5 μm or less.

Further, since the firing process is performed, the internal electrodes need not be oxidized at the firing temperature (1000 ° C. or higher), and the precious metal is inevitably used, which is expensive.

On the other hand, the thin film capacitor has an advantage that the thickness of the dielectric can be set to several μm or less.
For example, JP-A-60-94716 and JP-A-3-20
As proposed in Japanese Patent Publication No. 0307, in order to secure electrical insulation between electrodes and dielectrics which are alternately laminated and electrodes facing each other, wet etching is performed every time a film is formed on the dielectrics and electrodes. It is necessary to devise the film formation of the electrode by masking.

That is, when the electrodes are stacked with the dielectric material sandwiched therebetween, the electrodes are alternately displaced by several hundreds of μm in the direction of the electrode extraction end face, and when the external electrodes are attached to the electrode extraction end face in the subsequent step, two external electrodes are attached. It is necessary to prevent conduction between the electrodes.

However, every time wet etching is performed, a high vacuum such as sputtering or vapor deposition must be broken, which requires a long time, which is not preferable.

There is also a method of avoiding this and performing masking in a high vacuum, but this requires the mask to be moved with an accuracy of several hundreds of μm as described above, which causes considerable technical difficulties. . These technical challenges become more difficult as the size of the capacitors decreases.

[0015]

The present invention has been made to solve the problems of the above-mentioned multilayer thin film capacitor, and its structural feature is that one electrode and the other electrode are placed between them. In a laminated thin-film capacitor in which dielectrics are alternately laminated, the electrode lead-out end faces are exposed at different side faces facing each other, and external electrodes are formed on each of them, the electrode lead-out end face side of one of the electrodes is Only the end portion of the other electrode is partially etched, and only the end portion of the one electrode is partially etched on the electrode lead-out end surface side of the other electrode so that the electrode lead-out end surface of each electrode faces each other. A method of manufacturing a multilayer thin film capacitor, characterized in that it is exposed on different side surfaces.

In this case, each of the electrodes is formed of a different conductive material, and on the electrode extraction end face side of the one electrode, the other electrode dissolves, but the same electrode does not dissolve. The end portion of the other electrode is etched, and the one electrode is dissolved on the electrode extraction end face side of the other electrode, but the other electrode is not dissolved. The end portion of the one electrode is etched by a second etchant. Preferably.

Here, various combinations of the material of each electrode and the first and second etchants are conceivable. For example, it is selected from a combination of a metal that is easily dissolved in a specific acid but is difficult to be dissolved in another acid and the acid. However, the following combinations can be exemplified.

One electrode (first etchant) Other electrode (second etchant) Palladium (nitric acid) Iron (hydrochloric acid or sulfuric acid) Palladium (nitric acid) Zinc (hydrochloric acid or sulfuric acid) Palladium (nitric acid) Chromium (hydrochloric acid or sulfuric acid) Nickel (Nitric acid) Aluminum (hydrochloric acid or sulfuric acid) Silver (nitric acid) Iron (hydrochloric acid or sulfuric acid) Silver (nitric acid) Aluminum (hydrochloric acid or sulfuric acid) Silver (nitric acid) Zinc (hydrochloric acid or sulfuric acid) Silver (nitric acid) Chromium (hydrochloric acid) Copper (nitric acid) ) Aluminum (hydrochloric acid or sulfuric acid) Molybdenum (nitric acid) Aluminum (hydrochloric acid or sulfuric acid) Lead (nitric acid) Aluminum (hydrochloric acid or sulfuric acid) Molybdenum (nitric acid) Zinc (hydrochloric acid or sulfuric acid) Molybdenum (nitric acid) Chromium (hydrochloric acid or sulfuric acid) Lead (nitric acid) ) Chromium (hydrochloric acid or sulfuric acid) It is preferable conductors of which are formed by physical or chemical deposition method.

[0019]

According to the above construction, by etching one end face side with an etchant which dissolves one electrode but not the other electrode, only the other electrode remains on the end face side. Also, by etching the other end face side with an etchant that does not melt one electrode but melts the other electrode, only one electrode remains on that end face side, so it is equivalent to shifting the position of the electrode. The effect is obtained, and when the external electrodes are attached, their electrical insulation is secured.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the accompanying drawings. The method of laminating the electrode and the dielectric may be either a method by screen printing, a pressure bonding of a green sheet, or a physical or chemical film forming method. Here, the case of the sputtering method will be described.

First, a desired dielectric and two types of electrodes different from a desired dielectric are prepared as a sputtering target, and the sputtering apparatus is set so that a film can be formed from an arbitrary target with a shutter or the like.

Next, as shown in FIG. 1, a substrate 1 made of silicon, glass, alumina, sapphire, or the like.
Is placed at a predetermined portion of the sputtering apparatus, and the temperature of the substrate 1 is maintained at a temperature at which film formation is good.

Then, one electrode 2 is formed on the substrate 1 by the sputtering method, and the dielectric 3 is formed on the electrode 2.
Is also formed by sputtering. Then, the other electrode 4 is sputter-deposited on the same dielectric 3, and the dielectric 3 is further sputter-deposited thereon (first step).

By repeating the first step and laminating the dielectric 3 and the electrodes 2 and 4 in a desired number,
A thin film laminated body 5 of the dielectric 3 and the electrodes 2 and 4 is produced on the substrate 1 (second step).

In this way, the substrate 1 on which the thin film laminate 5 is formed is removed from the sputtering apparatus and cut into a desired size (third step).

FIG. 2 shows this cut chip-shaped capacitor element 5a.
The end portion of the other electrode 4 is etched in the etching tank 6 of FIG.

That is, an etchant 6a in which the other electrode 4 is melted but the one electrode 2 is not melted is stored in the etching bath 6, and one side surface side of the capacitor element 5a is dipped in the etchant 6a. Then, only the electrode 4 is slightly etched (fourth step).

Next, as shown in FIG. 3, the capacitor element 5a is reversed so that the side surface opposite to the above is the second side surface.
It is immersed in the etching tank 7 of FIG. Contrary to the above, an etchant 7a that melts one electrode 2 but does not melt the other electrode 4 is stored in the etching tank 7, whereby only the electrode 2 is slightly etched (fifth). Process).

In this way, the electrode lead-out end face of one electrode 2 is exposed on one side face side of the capacitor element 5a, and the electrode lead-out end face of the other electrode 4 is exposed on the other side face side of the same capacitor element 5a. As exposed, the external electrodes 8 and 9 are formed so as to cover the exposed portions on each side surface, as shown in FIG. 4 (sixth step). In this case, the external electrodes 8 and 9 may be formed by a normal coating and baking method, or may be formed by sputtering or vapor deposition.

Example 1 A glass plate 30 cm square and 2 mm thick was used as a substrate. The film forming method was a high frequency sputtering method in an Ar atmosphere. Dielectric material is (Ba _0.5 S
r _0.5 ) TiO ₃ , and Ni and Al were used as targets for the internal electrode materials. The substrate is 500 ° C
Heated to.

The above glass substrate was attached to a holder of a sputtering device (not shown), and sputtering was performed with Ni as a target to form a Ni electrode with a thickness of about 100 nm.

Next, as a dielectric (Ba _0.5 Sr
_0.5 ) TiO ₃ was deposited to a thickness of about 200 nm, and an Al electrode was deposited thereon to a thickness of about 100 nm. Then, again (Ba _0.5 Sr _0.5 ) TiO ₃ was formed into a film with a thickness of about 200 nm.

The above steps were repeated again to produce a thin film laminate having three dielectric layers sandwiched between electrodes. The uppermost dielectric layer is provided as a protective film for preventing the internal electrodes from being exposed.

The substrate on which the film had been formed as described above was taken out from the sputtering apparatus, and about 3,800 4.5 mm × 3.2 mm square chips were cut out.

Then, one side surface of the chip was immersed in hydrochloric acid to melt the end portion of the Al electrode and then washed. Next, the other side surface side of the chip was immersed in nitric acid to melt the end portion of the Ni electrode and then washed.

After that, an external electrode was formed on each side surface of the chip where the Al electrode and the Ni electrode were exposed by a known method, and the capacitance was measured and found to be 1 μF.

[0037]

As described above, according to the present invention,
When exposing only one electrode to the electrode extraction end face of the chip type multilayer thin film capacitor, it is not necessary to control the position of the mask with an accuracy of several hundreds of μm as in the conventional case, and the film is continuously formed in a high vacuum. In addition to the above, the process can be simplified.

[Brief description of drawings]

FIG. 1 is a sectional view showing a thin film laminated body as an intermediate product of a laminated thin film capacitor according to the present invention.

FIG. 2 is a schematic diagram for explaining a state in which an end portion of one electrode is etched.

FIG. 3 is a schematic diagram for explaining a state in which the end portion of the other electrode is etched.

FIG. 4 is a sectional view showing a laminated thin film capacitor as a final product to which external electrodes are attached.

[Explanation of symbols]

 1 substrate 2, 4 electrode 3 dielectric 6a, 7a etchant 8, 9 external electrode

Claims (3)

[Claims] 1. One electrode and the other electrode are alternately laminated with a dielectric interposed between them, the electrode lead-out end faces are exposed on different side faces facing each other, and external electrodes are formed on each of them. In the multilayer thin film capacitor consisting of the above, only one end of the other electrode is partially etched on the electrode extraction end face side of the one electrode, and the one electrode end is formed on the electrode extraction end face side of the other electrode. A method of manufacturing a multilayer thin film capacitor, wherein only the portions are partially etched so that the electrode extraction end faces of the respective electrodes are exposed on different side faces facing each other. 2. Each of the electrodes is made of a different conductive material, and on the electrode extraction end face side of the one electrode, the other electrode dissolves but the same electrode does not dissolve. Etching the end of the electrode and etching the end of the one electrode with a second etchant that dissolves the one electrode but does not dissolve the other electrode on the electrode extraction end face side of the other electrode. The method of manufacturing a multilayer thin film capacitor according to claim 1. 3. The electrode and the dielectric are formed by a physical or chemical film forming method.
Alternatively, the method of manufacturing the multilayer thin film capacitor described in 2.