JP3257864B2 - Manufacturing method of capacitor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a method for manufacturing a capacitor .
More particularly, the present invention relates to a method for manufacturing a capacitor which is capable of efficiently manufacturing a small and lightweight capacitor having a large capacitance.

[0002]

2. Description of the Related Art With the miniaturization of electronic equipment, the component density of electronic equipment has increased, and the number of electronic parts housed per unit volume has increased significantly. Devices related to physical phenomena at the interface, such as transistors and diodes, have been extremely miniaturized due to advances in integrated circuit technology.However, capacitors have the property that the capacitance is proportional to the electrode area. However, it is not easy to reduce the size without reducing the capacitance. In particular, the fact is that the miniaturization of capacitors having a capacitance of 1 μF or more has been delayed.

There are three main methods for reducing the size of a capacitor without lowering the capacitance as described below.

First, as a first method, there is a method of increasing the dielectric constant of a dielectric. As a material having a large dielectric constant, for example, there is a perovskite ferroelectric represented by BaTiO ₃ . As a capacitor using a high-permittivity material having a dielectric constant of several thousands or more, for example, a multilayer ceramic capacitor formed by laminating a dielectric layer made of a high-permittivity material and an internal electrode layer has already been put into practical use. This multilayer ceramic capacitor usually mixes a powder material of a high dielectric constant material with an organic binder or the like to form a slurry, forms the slurry into a film, forms a dielectric layer (film), and places the dielectric layer inside. It is manufactured by firing at a high temperature after alternately laminating with the electrode layers. Therefore, as an internal electrode material, it is necessary to use expensive noble metals such as silver and palladium which are hardly oxidized in the firing step, and the cost is high because high temperature firing requires a lot of energy,
There is a problem that the manufacturing process is complicated. Further, the thickness of the dielectric layer formed by forming the slurry into a film as described above is about 10 μm, and from the viewpoint of thinning the dielectric layer described below, it is possible to make the dielectric layer sufficiently thin. There is a problem that can not be.

As a second method, there is a method of increasing the surface area of the electrode. Examples of the capacitor according to this method include an electrolytic capacitor and an electric double layer capacitor. However, electrolytic capacitors such as aluminum electrolytic capacitors and tantalum electrolytic capacitors have problems in that they have a limited life, have poor frequency characteristics, a large dielectric loss tangent, and are polar. Further, although the electric double layer capacitor can reduce the volume per capacitance, it has a problem that it is vulnerable to impact and uses a low voltage because it contains an electrolytic solution.

Further, as a third method, there is a method of making the thickness of the electrode and the dielectric extremely thin. Reducing the thickness of the dielectric does not only reduce the volume occupied by the dielectric but also contributes to miniaturization, but also has the effect of increasing the capacitance by reducing the distance between the electrodes if the electrode area is the same. is there. Ta ₂ O ₅ is used as a thin film capacitor by this method.
There is an oxide thin film formed by vapor phase method such as vapor deposition and sputtering. However, the dielectric constant of a material such as Ta ₂ O ₅ used in this method is usually several tens, and a large-capacity capacitor has not been realized.

A ferroelectric such as BaTiO ₃ is made of Ta ₂
Attempts have been made to reduce the thickness by a vapor phase method similar to that of O _5, but it is not easy to control the atmosphere and composition to prevent the formation of a semiconductor during the formation of the thin film, and the crystallinity is poor and the ferroelectricity is insufficient. Because it is difficult to express
Large capacitors have not yet been obtained.
Furthermore, regarding the thinning of ferroelectrics, the technology of multilayering, which is an advantage of ceramic capacitors, or the technology of forming thin films on the surface of a large-area substrate, which is an advantage of electrolytic capacitors and electric double-layer capacitors, is also extremely insufficient. It has to be said that practical use involves many problems.

[0008] The present invention is intended to solve the above problems, and an object thereof is to provide a method for producing small and lightweight, yet capacitor <br/> capacitors capacitance is greater.

That is, according to the present invention, a composite oxide having a perovskite structure, which is a high dielectric constant material, is uniformly formed on a large-area electrode surface having an arbitrary shape under favorable crystallinity. Capable of small and large capacitance
And a method of manufacturing a capacitor capable of obtaining the above.

[0010]

In order to achieve the above object, a method of manufacturing a capacitor according to the present invention comprises the steps of :
Titanium (Ti) metal film formed on the surface of the metal base
And a dielectric film formed on the surface of the titanium metal film,
A conductive film formed on the surface of the dielectric film, and the conductive film
One of the external electrodes and the metal substrate or
A core having the other external electrode which is in conduction with the titanium metal film;
A method of manufacturing a capacitor, comprising: (a) forming a groove or a hole in a surface to increase a surface area, and forming a metal substrate having a titanium metal film formed on at least a part of a surface thereof by using calcium (Ca), strontium ( At least one element selected from the group consisting of Sr), barium (Ba), lead (Pb), titanium (Ti), and zirconium (Zr) in an amount of 0.1 mol / l or more;
immersed in a treatment aqueous solution having a pH of 13 or more ,
A current is passed between any of the electrodes disposed therein and the metal substrate.
Hydrothermal treatment at a temperature of 50 ° C. or higher while performing electrolytic treatment, thereby forming a dielectric film on the surface of the titanium metal film by the general formula: XYO ₃ (where X = Ca, Sr, B
a, Pb, forming a Y = Ti, perovskite complex oxide film represented by Zr), forming a conductive film on the surface of the (b) the perovskite-type composite oxide film, (c) characterized by comprising the step of forming the other external electrode conducting with one external electrode and the metal substrate or the titanium metal film formed on the surface to conduct with the conductive film.

[0011]

In the method of manufacturing a capacitor according to the present invention,
By forming grooves or holes in the surface to increase the surface area, a metal substrate having a titanium metal film formed on at least a part of the surface is made of Ca, Sr, Ba, Pb, Ti,
Immersed in a treatment aqueous solution containing at least one selected from the group consisting of Zr , and disposed in the treatment aqueous solution.
By applying a current between any electrode and the metal substrate,
Hydrothermal treatment is performed while applying a treatment to the surface of the titanium metal film as a dielectric film of the general formula: XYO ₃ (where X = C
a, Sr, Ba, Pb, Y = Ti, Zr) to form a perovskite-type composite oxide film .
Therefore, a complex oxide having a perovskite structure, which is a high dielectric constant material, is easily and reliably formed on the surface of a titanium metal film formed on the surface of a metal substrate having a large area and an arbitrary shape. It is possible to efficiently manufacture a small-sized capacitor having a large capacitance at a low cost.

Further, a core manufactured by the method of the present invention is used.
In the capacitor, a titanium metal film is formed on the surface.
A dielectric film is formed on a metal substrate having a large surface area.
Furthermore, a structure in which a conductor film (electrode) is formed on this dielectric film
The size of the metal substrate
Increase the area of the dielectric film and the area of the conductor film (electrode).
To achieve high capacitance.
Becomes possible.

[0013]

Embodiments Hereinafter, embodiments of the present invention will be described.
The features of the invention will be described in more detail.

First, Cu metal having a purity of 99.5% or more is
As shown in FIG. 2, length (L) is 3.0 mm and width (W) is 2.
It was shaped into a chip having a height of 0 mm and a height (H) of 2.0 mm .

Then, as shown in FIG. 3, a groove 1 (width (G) 50 μm, depth (D) 1.00 mm, pitch (two adjacent two A metal substrate (Cu metal substrate) A was prepared by forming (distance between grooves 1) (P) 50 μm).

Then, in order to remove minute processing scratches on the surface of the metal substrate A, the metal substrate A is put into a treatment liquid (90 parts by weight of distilled water + 20 parts by weight of phosphoric acid),
Using a Cu plate as a cathode, electrolytic polishing was performed at 5 V for 10 seconds.

Next, the entire surface of the metal substrate A including the inner surface of the groove 1 is formed to a thickness of 1.0 μm by the method described below.
An m-thick Ti plating film (Ti metal film) 2 was formed. (FIG. 4).

[0018] Incidentally, Ti, since hardly reduced in an aqueous solution, in this embodiment, using an apparatus as shown in FIG. 13
The metal substrate A in the alkali metal halide melt.
The surface was plated with Ti.

In applying Ti plating to the metal substrate A,
Te, first, placed in a carbon crucible 16 and lithium fluoride (LiF) an equimolar mixture of potassium fluoride (KF), was melted by heating it to 500 ° C., K ₂ T
iF ₆ was added to prepare a melt 17 containing 0.5 mol% of TiF ₆ ^2-ions.

Next, platinum (Pt) plates 18 and 19 having a platinum (Pt) wire 20 connected thereto, and a platinum (Pt) wire 21
Is immersed in the melt 17 and the external potentiostat 2
2 was connected.

Then, while maintaining the temperature of the melt 17 at 500 ° C., the platinum plate 18 is used as a working electrode, the platinum plate 19 is used as a counter electrode, the platinum wire 21 is used as a reference electrode, and the potential of the working electrode 18 is +2.0 V. by subjecting (vs.K ⁺ / K) and the electrolysis for 10 minutes, was reduced TiF ₆ ^2-ions in the melt 17 to TiF ₆ ^3- ions. The reference of the potential was the redox potential of K ⁺ / K in the melt 17.

Thereafter, the temperature of the melt 17 is raised to 700 ° C., and a metal substrate (Cu metal substrate) A having a Cu wire 23 connected thereon is immersed in the melt 17 instead of the platinum plate 18.
The working electrode was connected to the potentiostat 22. Then, by applying the potential of ⁺ 0.4V (vs.K + / K) as the electrolytic treatment for 2 minutes, the thickness of 1.0μ to TiF ₆ ^3- ions are reduced to Ti metal on the entire surface of the metal substrate A
An m-thick Ti plating film 2 (FIG. 4) was formed. It should be noted that under the conditions described here, Ti is applied at a speed of 0.5 μm / min.
The plating film 2 could be formed.

The thickness of the entire surface of the Ti plating film 2 is
A 0.2 μm BaTiO ₃ film 3 was formed (FIG. 5). What
The formation of the BaTiO ₃ film 3 on the Ti plating film 2 is as follows.
Using the apparatus shown in FIG.
went.

First, a beaker made of fluororesin (Teflon)
9, a 0.5 mol / l Ba (O 2
H) ₂ aqueous solution, pH 14.2 using NaOH aqueous solution.
Add the aqueous solution adjusted to 5.

Then, the metal substrate is placed in the treatment aqueous solution 10.
(Cu metal substrate) A and platinum plate 13
From the external power supply 15 to the metal base A and the platinum plate 13
A pair of fluoroplastic so that power can be supplied
The coated platinum wire 14 is connected to the titanium metal substrate A and
And a platinum plate 13. Then, the entire beaker 9
It is set in the autoclave 12 and sealed.

In this state, the temperature is raised to 150 ° C.
While maintaining this temperature for 0 minutes and performing the hydrothermal treatment,
Directly between the metal base A and the platinum plate 13 (that is, between the electrodes)
By applying a constant voltage electrolytic treatment by applying a current of 10 V,
A dielectric film (BaTiO ₃ polycrystal ) is formed on the surface of the Ti plating film 2.
Film).

Next, the hydrothermally treated and electrolytically treated
After the ultrasonic cleaning of the tin metal substrate A sufficiently in distilled water,
Dry at 120 ° C. for 60 minutes. With this method, the metal base
1.0 μm thick BaTiO on the entire surface of body A _Three Polycrystalline film
Could be formed. In addition, this BaTiO _Three Polycrystalline
The film thickness is measured directly within the field of view of a scanning electron microscope.
Was. The crystallinity was confirmed by a thin film X-ray diffraction method.

[0028] Then, as shown in FIG.
_Three A low-viscosity silver paste is applied to the part of the film 3 excluding the part 4
Apply and bake it at about 600 ° C.
A film (electrode) 5 was formed.

Thereafter, a part (one end face) 6 of the metal substrate A
(FIG. 6) was treated with a treatment solution (85 parts by weight of distilled water + 10 parts of hydrofluoric acid).
Parts + nitric acid 5 parts by weight) for 30 seconds to etch
BaTiO _Three Film 3 and Ti plating film 2
Is removed, and as shown in FIG.
To form a capacitor element B,
Conductive film on end face opposite to end face 6 where metal base A is exposed
The measurement terminals 7, 7 were connected on the (electrode) 5 (FIG. 7).

The capacitor element manufactured as described above
B capacitance (frequency 1 kHz, applied voltage 1.0 Vrm
s), the capacitance was 0.155 μF
Met.

The capacitor obtained in the above embodiment
The capacitance value of the element is determined by forming a thin film of high dielectric constant material on a flat surface.
Table of electrode values of capacitor elements of Examples
It agrees with the value estimated from the calculated area with 98% accuracy
Was.

According to the method of this embodiment,
The surface of a metal substrate A having a titanium metal film formed on the surface
A 1.0 μm thick BaTiO ₃ polycrystalline film (dielectric
Film) could be formed efficiently. Such a short time
A uniform dielectric film can be formed between the inner surfaces of the grooves.
The reason for this was that the reaction in the liquid phase was used, and
And its reaction temperature is higher than the normal solution reaction temperature
by.

Further, since the hydrothermal treatment is performed while performing the electrolytic treatment, the formation speed of the dielectric film can be greatly improved as compared with the case without the electrolytic treatment. For example, in a method of forming a dielectric film without electrolytic treatment, it takes several hours to several tens of hours to grow the film to a thickness of 0.5 μm or more, whereas a dielectric film with electrolytic treatment is required. According to the method of forming the film, the film thickness is several μm.
The m order of the dielectric film can be formed at comparable time
become.

[0034] In this embodiment, as Ba ²⁺ ion source is used to Ba (OH) _2, Ba ²⁺ ion source
Is not limited to Ba (OH) ₂ , and other substances such as Ba salt can be used. As the alkali, not only NaOH but also KOH, LiOH and the like can be used.

In the above embodiment, the case where the groove is formed in the entire width of the metal substrate has been described. However, in the method of manufacturing a capacitor according to the present invention, the surface area of the metal substrate is
It is also possible to form holes to increase the power. Ma
There is no particular limitation on the shape , position, pitch, direction, and the like of the grooves and holes formed in the metal substrate , and various modifications and applications can be made within the scope of the invention. Therefore, for example, as shown in FIG. 8 , an elongated hole (through hole) 31 may be formed in the metal base A as shown in FIG. 8 , and further, as shown in FIG.
Groove 3 orthogonal to two directions of the longitudinal direction and the width direction
2, 33 can be formed to further increase the surface area of the metal substrate A.

[0036] In the case of forming a hole in the metal substrate A, it is also possible to form the through hole, and as shown in FIG. 10, forming a hole 34 having a bottom to the middle of the metal substrate A It is also possible. Further, as shown in FIG. 11 , it is also possible to form a plurality of through holes 35 , 36 , 37 in directions perpendicular to each other from three surfaces of the metal base A.

In the above embodiment, the metal substrate is made of Cu.
Although the description has been given of the case where the metal base made of metal is used, the material forming the metal base is not limited to Cu, but may be any of various metals that can be processed into the shape shown in the above embodiment. Materials can be used.

In the above-described embodiment, an example in which one external electrode that conducts to the conductor film (electrode) and the other external electrode that conducts to the metal substrate or the Ti metal film formed on the surface thereof is provided. Although not shown, these external electrodes
Conductive film and Ti formed on metal substrate or its surface
The conductive paste can be easily formed at an arbitrary position (for example, a position suitable for surface mounting) of the metal film by applying or baking a conductive paste. Note that a capacitor with a terminal can be configured by attaching a terminal (external electrode in a broad sense) instead of the external electrode.

[0039]

As described above, according to the method for manufacturing a capacitor of the present invention, a groove or a hole is formed to increase the surface area, and a metal substrate having a titanium metal film formed on the surface is subjected to electrolytic treatment. While performing hydrothermal treatment
A perovskite-type composite oxide film is formed as a dielectric film on the surface of the titanium metal film, and a conductor film (electrode) is formed on the surface of the perovskite-type composite oxide film. A complex oxide having a perovskite structure, a high dielectric constant material, can be uniformly formed on the surface of a titanium metal film of a large-area metal substrate with good crystallinity under good crystallinity ing to. Therefore,
A capacitor that is small, lightweight, and has a large capacitance can be manufactured without requiring a particularly large manufacturing cost.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a capacitor element according to an embodiment of the present invention.

FIG. 2 is a perspective view showing a metal chip (metal substrate) as a starting material of the capacitor according to one embodiment of the present invention.

FIG. 3 is a perspective view showing a metal base on which a groove is formed.

FIG. 4 is a perspective view showing the metal base in a state where a Ti plating film is formed on the surface.

FIG. 5 is a perspective view showing a metal base in a state where a dielectric film is formed on the surface.

FIG. 6 is a perspective view showing a metal base in a state where a conductor film (electrode) is formed on a portion other than a part of the dielectric film.

FIG. 7 is a perspective view showing a state in which a measuring terminal is attached to the capacitor element according to one embodiment of the present invention.

FIG. 8 shows a hole in a metal substrate in another embodiment of the present invention .
It is a perspective view which shows the example of formation of.

FIG. 9 shows a metal substrate according to still another embodiment of the present invention .
It is a perspective view which shows the example of formation of the groove | channel to the side.

FIG. 10 shows a metal substrate according to still another embodiment of the present invention .
It is a perspective view which shows the example of formation of a hole in a body.

FIG. 11 shows a metal group according to still another embodiment of the present invention .
It is a perspective view which shows the example of formation of a hole in a body.

FIG. 12 shows a method of hydrothermal treatment according to an embodiment of the present invention .
FIG.

FIG. 13 shows T used in the embodiment of the present invention .
It is a figure showing composition of an i plating device.

[Explanation of symbols]

A metal substrate 1 grooves 2 Ti plating film 3 dielectric film (Ba TiO ₃ film) 5 conductor film (electrode) 7 pin (measuring terminal) 10 processing solution 13 platinum plate (electrode)

Continued on the front page (72) Inventor Kunisaburo Banno 2-26-10 Tenjin, Nagaokakyo-shi, Kyoto, Japan Murata Manufacturing Co., Ltd. (72) Inventor Masahiro Yoshimura 1-12-12 Teraonaka, Ayase-shi, Kanagawa Prefecture 56 References JP-A-59-8321 (JP, A) JP-A-3-162584 (JP, A) JP-A-59-39726 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name ) H01G 4/00-4/10 H01G 4/14-4/42

Claims (1)

(57) [Claims] A metal substrate formed on a surface of the metal substrate;
Titanium metal film and a surface of the titanium metal film
And a dielectric film formed on the surface of the dielectric film.
Conductive film, and one external electrode and
And the other conductive with the metal substrate or the titanium metal film
And a method for manufacturing a capacitor having external electrodes.
Te, (a) with increasing the surface area by forming grooves or holes on the surface, at least a part forming a titanium metal film metallic substrate surface, calcium (Ca), strontium (Sr), barium (Ba ), At least one element selected from the group consisting of elements consisting of lead (Pb), titanium (Ti) and zirconium (Zr) in an amount of 0.1 mol / l or more;
immersed in a treatment aqueous solution having a pH of 13 or more ,
A current is passed between any of the electrodes disposed therein and the metal substrate.
Hydrothermal treatment at a temperature of 50 ° C. or more while performing electrolytic treatment, thereby forming a dielectric film on the surface of the titanium metal film by the general formula: XYO ₃ (where X = Ca, Sr, B
a, Pb, forming a Y = Ti, perovskite complex oxide film represented by Zr), forming a conductive film on the surface of the (b) the perovskite-type composite oxide film, (c) method for producing a capacitor characterized by comprising the step of forming the other external electrode conducting with one external electrode and the metal substrate or the titanium metal film formed on the surface to conduct with the conductive film.