JPH0324710A - Capacitor and manufacture thereof - Google Patents

Abstract

PURPOSE:To easily manufacture a capacitor having high withstand voltage and large capacitance by piling up Si substrates respectively provided with silicon-oxide layers on both surfaces upon another with internal electrodes in between and, at the same time, forming gap spaces on one sides of the electrodes. CONSTITUTION:After dielectric films 6 are formed of a silicon oxide on upper and lower surfaces of a plurality of Si substrates 4, the substrates 4 are piled up upon another with internal electrodes 8 in between and one end face of each Si substrate 4 is coated with insulating members 10. The first external electrode 14 is connected to the end faces of the electrodes 8 on which the members 10 are formed and the second external electrode 16 is connected to the end faces of the substrates 4 opposite to the members 10. Then gap spaces 9 are formed between the electrode 16 and end faces of the electrodes 8. The silicon oxide forming the dielectric films 6 is compact and high in withstand voltage, the withstand voltage of the films 6 is improved. Moreover, since the substrates 4 are piled up, the capacitance of this capacitor is multiplied and, since the gap spaces 9 are formed on one sides of the electrodes 8, the electrode connecting process can be carried out easily. Therefore, a capacitor having large capacitance and high withstand voltage can be manufactured easily.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates to a capacitor having a large capacitance and excellent voltage resistance, particularly a multilayer capacitor.

TECHNICAL BACKGROUND OF THE INVENTION One type of capacitor is a thin film capacitor made of a dielectric film. In this structure, a lower electrode, a dielectric film, and an upper electrode are laminated in this order on a substrate.

In such thin film capacitors, the capacitance is proportional to the permittivity of the dielectric film and inversely proportional to the thickness of the dielectric film. Therefore, in order to increase the capacitance, a material with a high permittivity must be used or a dielectric material All you have to do is make the film thinner. Generally, materials with a high dielectric constant have a large change in dielectric constant with temperature, so in a thin film capacitor using such a material as a dielectric film, the capacitance of the capacitor varies greatly with changes in temperature.

Therefore, it is conceivable to use a material with a small temperature coefficient as the dielectric thin film and reduce the thickness of the dielectric film in order to improve its capacity. However, in such cases, a satisfactory capacitance cannot be obtained unless the thickness of the dielectric is made sufficiently thin. Moreover, when the dielectric film is thin like this, there is a problem in that the withstand voltage becomes small due to unevenness or foreign matter in the underlying layer.

Furthermore, in conventional thin film capacitors, the lower electrode and dielectric film are laminated in this order on the substrate, so the lower electrode is also exposed to high temperature when the dielectric film is fired, resulting in excellent heat resistance. It was necessary to use an electrode such as PT. Moreover, when such a heat-resistant electrode is used, an adhesive layer is required between the electrode and the substrate, making the electrode manufacturing process complicated and costly.

It is known that a silicon oxide layer obtained by thermally oxidizing the surface of a Si substrate is used as a capacitor in integrated circuits, but the capacitance is insufficient, and silicon oxide layers are used to improve capacitance. When the film thickness of the layer is made thinner, there is a problem in that the withstand voltage property decreases.

In addition, as shown in FIG. 3, in order to increase the capacitance, a plurality of ceramic sheets 22 made of dielectric material are used.
A ceramic multilayer capacitor 20 is also known in which the capacitors are laminated with internal electrodes 24 arranged alternately on the left and right sides, and the internal electrodes 24 of every other layer are connected by separate external electrodes 26 and 26.

Under these circumstances, the present inventors are developing a capacitor that can increase the capacitance by laminating Si substrates with a dielectric film formed on the surface, but the Compared to the case of stacking sheets 22, when stacking Si substrates on which dielectric films are formed, Si
Since the substrate also functions as an internal electrode, it was not possible to construct a capacitor with a laminated structure as shown in FIG.

OBJECTS OF THE INVENTION The present invention was made in view of the above circumstances, and an object of the present invention is to provide a capacitor having a large capacitance and excellent voltage resistance, and a method for manufacturing the same.

Summary of the Invention In order to achieve the above object, a capacitor according to the present invention includes a plurality of Si substrates and a dielectric film made of silicon oxide formed on the front and back surfaces of each Si substrate, Thirty-one substrates on which the dielectric film is formed are stacked in the film thickness direction via internal electrodes, one end surface of each Si substrate is covered with an insulating member, and the side covered with the insulating member is A first external electrode is connected to one side end surface of each internal electrode, and a first external electrode is connected to one side end surface of each Si substrate not covered with an insulating member.
A second external electrode is connected thereto, and a gap space is formed between the second external electrode and the side end portion of the internal electrode.

In the present invention, it is preferable that the specific resistance of the Si substrate is 0.1 Ω·cm or less.

Since the present invention has an electrode structure in which a plurality of Si-based bases are electrically connected to each other to form part of the electrode, the lower electrode and the dielectric film are placed on the substrate in this order as in the conventional method. There is no need to stack layers, and there is no need to worry about deterioration of the lower electrode that may occur when firing the dielectric film. In addition, in the present invention, since silicon oxide formed on the front and back surfaces of the Si-based temporary is used as the dielectric film, the adhesion between the dielectric film and the Si substrate is improved, and cracks in the dielectric film can be prevented. It is possible to prevent this. Furthermore, although the silicon oxide film obtained by thermally oxidizing a Si substrate has a small dielectric constant of 4 or less, the film is dense and has a high withstand voltage, so that the withstand voltage property of the dielectric film is also improved. Furthermore, in the present invention, a silicon oxide film layer is provided not only on one side surface of the Si substrate but also on the back surface, and this is used as a dielectric film, and the silicon oxide layer is formed in this way. Since the Si substrates are laminated via internal electrodes, the capacitance is multiplied compared to the case where a dielectric film is formed on only one side of the Si substrates.

Further, the method for manufacturing a capacitor according to the present invention includes
Dielectric films made of silicon oxide are formed on the front and back surfaces of the i-substrate, and the Si substrates on which these dielectric films are formed are connected to each other such that an internal electrode is interposed between them, and one side of the internal electrode is interposed between the Si substrates. The Si substrates are laminated so that a gap is formed at the ends, one end surface of the Si substrate is coated with an insulating material by electrophoresis, and then one side of each Si substrate is coated with the insulating material. A first external electrode connecting these is formed on the end face, and each S1 on the side of the gap space formed at one end of the internal electrode is formed.
A feature is that a second external electrode is formed on one end surface of the substrate to connect each Si substrate.

According to the method for manufacturing a capacitor according to the present invention, a gap space is formed at one end of the internal electrode, and one end surface of the Si substrate is coated with an insulating member by electrophoresis. Therefore, the process of connecting each internal electrode with a common first external electrode becomes easy, and the process of connecting each Si substrate with a common second external electrode becomes easy. As an application of the electrophoresis method, there is Japanese Patent Application Laid-Open No. 17516/1983, which was used to insulate the end face of an electrostrictive element.

DETAILED DESCRIPTION OF THE INVENTION The capacitor according to the present invention will be specifically described below.

FIG. 1 is a sectional view showing one side of a capacitor according to the present invention;
FIG. 2 is a perspective view showing a method of manufacturing a capacitor according to the same embodiment.

As shown in FIG. 1, a capacitor 2 according to the present invention includes a plurality of Si substrates 4 and a dielectric film 6 formed on the front and back surfaces of each Si substrate 4. In the present invention, Si substrates 4 on which such dielectric films 6 are formed are stacked in the film thickness direction with internal electrodes 8 interposed therebetween.

The internal electrode 8 is a dielectric film 6 of the superimposed Si substrates 4.
is interposed between. Moreover, one end 8 of each internal electrode 8
A gap space 9 is formed in a.

One end surface 4a of each Si substrate 4 is covered with an insulating member 1o.

On the other end 8b of the internal electrode 8 on the side coated with the insulating member 10, a first external electrode 14 is inserted from above the insulating member 10 so as to electrically connect each internal electrode 8. It has been formed. Also, it is the side not covered with the insulating member 10,
One side end surface 4 of each Si substrate 4 on the side where the gap space 9 is formed
In b, a second external electrode 16 is formed to electrically connect each of the 31 substrates 4. In the present invention, the Si substrate 4
also functions as an internal electrode.

The dielectric film 6 is made of silicon oxide, preferably Si
It is obtained by thermally oxidizing the substrate 4.

However, the dielectric film 6 may be formed by other methods such as vapor deposition or sputtering.

The thickness of such dielectric film 6 is preferably 50λ to 1
0 μm1, more preferably 100 to 5 μm. Note that silicon oxide mainly consists of SiO2,
It may also contain SiO or the like.

As the internal electrode 8 and the first and second external electrodes 14 and 16, electrodes such as Ag, Cu, Au, /l 2 , PtsPd, etc. can be used. As means for forming the internal electrodes 8 and the first and second external electrodes 14 and 16 on the surface of the dielectric film 6 and the side surfaces of the laminate, a spatter method, a vapor deposition method, a paste coating, etc. are used. The thickness of the electrode 8 is 0.
It is preferable that it is 1 micrometer - 50 micrometers. Furthermore, the thickness of the external electrodes 14.16 is preferably 0.1 μm or more.

It is preferable that the Si substrate 4 has a specific resistance of 0.1 Ω·cm or less. If the specific resistance of the Si substrate itself is small, S
This is because the i-substrate 4 also functions as an internal electrode. Specifically, as the Si substrate 4, a silicon wafer or the like is used. The silicon wafer is non-doped, P
It is possible to use commercially available products of any type, such as type or N type, as they are. The thickness of the substrate 4 is not particularly limited, but it is preferable that it is determined so that the resistance value does not become large as an electrode, and it is also preferable that it has a thickness sufficient to impart appropriate rigidity to the entire capacitor. Specifically, it is preferable to have a thickness of 0.1 μm or more. The substrate 4 is not necessarily limited to a flat plate shape. When the substrate has a shape other than a flat plate, the dielectric film and electrode portion formed thereon also have a shape that follows the shape of the substrate.

Examples of the material constituting the insulating member 10 include glass, aluminum, epoxy resin, polyimide resin, and phenol resin. The means for forming these insulating members 10 on the Si substrate 4 or one end surface of the Si substrate 4 is preferably an electrophoresis method as described below, but is not limited to this, and may be formed by other means. Also good.

Next, a method for manufacturing the capacitor 2 according to the present invention will be explained.

First, a Si substrate 4 of a predetermined size is prepared, and this Si substrate 4 is heated under an oxidizing atmosphere. The heating temperature is preferably 300 to 1300°C, more preferably 700 to 110°C.
It is 0°C. The heating time is not particularly limited, but is preferably 3 minutes to 300 minutes, more preferably 10 minutes to 300 minutes.
The duration is 180 minutes. Through such heat treatment, Si
A dielectric film 6 made of a silicon oxide film having a predetermined thickness is formed on the front and back surfaces of the substrate 4 .

Thereafter, a paste-like electrode portion 8C, which will become the internal electrode 8, is placed on the surface of the dielectric film 6 of this substrate 4, for example, as shown in FIG. The coating is formed so that a gap space 9.11 is formed in the portion 8d. Next, a plurality of Si substrates 4 having paste-like electrode portions 8C formed on their surfaces are stacked one on top of the other and heated to integrate the pasted electrode portions 8C between the Si substrates 4. . Thereafter, it is cut into an appropriate size to prepare one block as shown in FIG.

Thereafter, after polishing the end surface 19a of one block on the side where the electrode portion 8C is not formed to remove the silicon oxide film, a temporary electrode 18 is formed with metal, paste, etc., and thereby the Si substrates 4 are connected to each other. Become electrically conductive.

Next, a resist film is provided on the side surface 19c of the block 19 on the side where the gap space 9 is formed, and this is soaked in waves used for electrophoresis to perform electrophoresis,
An insulating member 1o is formed on one end surface 4a of the Si substrate 4.

Electrophoresis is a technique in which a counter electrode plate and a sample are immersed in a liquid, a voltage is applied between them, and insulating particles in the liquid are charged and attached to the sample by an electric field.

In the present invention, the Si substrate 4 in block 19 serves as the sample.

In the present invention, in order to form an insulating member on one side end surface of the Si substrate 4, one temporary electrode 18 provided on the block 19
is used as a cathode, and a counter electrode immersed in the liquid together with one block is used as an anode, and a voltage can be applied between them. In this way, insulating particles in the liquid will be deposited on one side end surface of the Si substrate 4 that is not covered with the resist film, and each of the one side end surfaces will be covered with the first insulating member 10.

The thickness of the insulating member 1o formed by electrophoresis is preferably 0.1 μm to 100 μm, and more preferably 1 μm.
m to 100 μm. To make it as thick as this,
The voltage and time applied between the temporary electrode and the counter electrode are determined. The applied voltage is preferably 10 to 20
It is about 0V. In addition, the application time is preferably 1 minute to
It is 30 minutes.

An example of the wave used in the electrophoresis method is suspended IR& containing insulating particles that serve as an insulating member. Glass powder or the like can be used as the insulating particles. The suspension also contains a substance such as iodine that acts as an electrolyte, and is designed to positively charge insulating particles such as glass powder. A specific example of such a suspension is a mixture of ethanol containing insulating particles and an iodine-based ethanol solution.

According to such electrophoresis wide? & The insulating particles contained in it precipitate only on the part where the electric field is applied (the side end surface of the Si substrate) and not on other parts, so it conveniently forms a coating layer of the insulating member on the target part. can do.

After the insulating member 10 is shaped in this manner, the block 19 is cut in a direction perpendicular to the elongated direction to obtain chips of a predetermined size. Insulating member 10 in this chip
By applying a metal paste or the like to the side surfaces on which are formed the respective Si substrates 4 or the internal electrodes 8, the first
, second external electrodes 14 and 16 are formed, and the capacitor 2 is completely discharged.

In such a capacitor 2, the silicon oxide films formed on the front and back surfaces of the substrate 4 are used as the dielectric film 6, and the Si substrates 4 are overlapped, so that the capacitor capacity is improved and the durability is improved. Voltage characteristics are also improved.

In addition, in the present invention, the means for manufacturing the capacitor 2 is not limited to the above-described embodiment, and can be variously modified.

Effects of the Invention As explained above, the present invention has an electrode structure in which a plurality of Si substrates are electrically connected to each other to form a second electrode. There is no need to stack the dielectric film in this order, and there is no need to worry about deterioration of the lower electrode that may occur when burning the dielectric film.

In addition, in the present invention, since silicon oxide formed on the front and back surfaces of the silicon substrate is used as the dielectric film, the adhesion between the dielectric film and the silicon substrate is improved, and cracks in the dielectric film can be prevented. etc. can be prevented.

Furthermore, although the silicon oxide film obtained by thermally oxidizing a silicon substrate has a small dielectric constant of 4 or less, the film is dense and has a high withstand voltage, so the withstand voltage property of the dielectric film is also improved. Furthermore, in the present invention, a silicon oxide film layer is provided not only on one side surface of the Si substrate but also on the back surface, and this is used as a dielectric film, and the silicon oxide layer is formed in this way. Since the Si substrates are stacked via internal electrodes, the capacitance is several times higher than when a dielectric film is formed on only one side of the Si substrates.

Further, according to the capacitor manufacturing method according to the present invention, one end surface of the Si substrate is coated with an insulating member by electrophoresis, and a gap space 9 is formed at one end of the internal electrode. The process of connecting each internal electrode with a common first external electrode becomes easy, and the process of connecting each Si substrate with a common second external electrode becomes easy.

[Examples] The present invention will be described below based on more specific examples, but the present invention is not limited to these examples.

Example 1 A 0.5 mm thick Si substrate doped with sb and having a specific resistance of 0.01 Ωcm was heated at 1000"C in an oxygen atmosphere.
Heat treatment was performed for 80 minutes. Next, the second end (symbol r8 shown in Figure 2)
Ag paste 8c was applied to the entire surface, leaving only 8 dJ), and the three sheets were stacked and dried by heating at 100° C. for 30 minutes. Cut this with a cutting saw, making sure that the part without Ag paste 8c is one end in the longitudinal direction.
One block was produced by cutting to a width of IIlm. The oxide film is removed by polishing the Si cross section at one longitudinal end where the Ag paste 8c is not attached, and then the Ag paste is applied to form the temporary electrode 18, and the three-layer Si substrate 4 connected. Next, a negative resist was applied to one of the side surfaces 19c parallel to the longitudinal direction, and the block 19 was immersed in a tube used for electrophoresis.

The liquid used in the electrophoresis method is zinc borosilicate glass powder (
(30 g), 290 ml of ethanol and 5% iodine ethanol (10 ml) were mixed. In this solution, electricity was applied using the Si substrate 4 as a cathode and the PT plate (not shown) as an anode. 15
A voltage of V was applied for 180 seconds. Next, after removing the resist with a resist stripping solution, the block was heated at 500° C. for 30 minutes.

After that, this block was cut at right angles in the longitudinal direction.
A chip of 8I1 square was obtained. Then, Ag paste was applied to the side surface on which the insulator was deposited and the side surface on the gap space 9 side, respectively, and dried to form two opposing external electrodes.

The results of measuring the characteristics of the capacitor thus obtained using an LCR meter are shown below.

The capacitance was 3 nF at a measurement frequency of 1 MHz, and the temperature coefficient of capacitance was 30 ppll/°C at a temperature of 80°C to -20°C. Also, when I measured the resistance value at constant voltage, IOC was found at 20V.
It was more than Ω.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing one side of a capacitor according to the present invention;
FIG. 2 is a perspective view showing a method of manufacturing a capacitor according to the same embodiment, and FIG. 3 is a sectional view of a conventional ceramic capacitor. 1

Claims (1)

[Claims] 1) It has a plurality of Si substrates and a dielectric film made of silicon oxide formed on the front and back surfaces of each Si substrate, and the Si substrate on which the dielectric film is formed is used as an internal electrode. are laminated in the film thickness direction with the Si substrates interposed therebetween, one end surface of each Si substrate is covered with an insulating member, and one end surface of each internal electrode on the side covered with the insulating member is coated with a first Si substrate. On one side end surface of each Si substrate to which the external electrode is connected and which is not covered with an insulating member, a second
A capacitor to which an external electrode is connected, and a gap space is formed between the second external electrode and the side end of the internal electrode. 2) A capacitor characterized in that the specific resistance of the Si substrate is 0.1 Ω·cm or less. 3) A dielectric film made of silicon oxide is formed on the front and back surfaces of a plurality of Si substrates, and the Si substrates on which the dielectric films are formed are separated so that an internal electrode is interposed between them. Laminated so that a gap space is formed at one end,
One side end surface of the Si substrate is coated with an insulating member by electrophoresis, and then a first external electrode is formed on one side end surface of each Si substrate on the side covered with the insulating member to connect them. . A method for manufacturing a capacitor, comprising: forming a second external electrode for connecting each Si substrate on one end surface of each Si substrate on the side of the gap formed at one end of the internal electrode.