JPH0324706A - Capacitor - Google Patents

Abstract

PURPOSE:To increase the withstand voltage and capacitance of a capacitor and, at the same time, to simplify the manufacturing process of the capacitor by providing silicon-oxide films on both upper and lower surfaces of an Si substrate and forming lead-out electrodes in cap-like shapes so that the electrodes can be installed easily. CONSTITUTION:A capacitor is provided with an Si substrate 4, dielectric films 6 formed of a silicon oxide on the upper and lower surfaces of the substrate 4, electric parts 8 formed on the surfaces of the films 6, the cap-like first lead-out electrode 10 which electrically connects both electrode parts 8 to each other and does not come into contact with the substrate 4, and the cap-like second lead-out electrode 12 which is fitted to the side end section of the substrate 4. Since the silicon oxide forming the dielectric films 6 is compact and high in withstand voltage, the withstand voltage of this capacitor is improved. Moreover, since the films 6 are formed on both surfaces of the substrate 4, the capacitance of this capacitor is doubled as compared with the capacitor having the dielectric film on one surface only. In addition, the electrodes 10 and 12 can be installed easily, since they have cap-like shapes which can easily put on the side faces of this capacitor. Therefore, a capacitor having large capacitance and high withstand voltage can be manufactured easily.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a capacitor, particularly a thin film capacitor, which has a large capacitance, excellent voltage resistance, and is easy to manufacture.

TECHNICAL BACKGROUND OF THE INVENTION One type of capacitor is a thin film capacitor made of a dielectric thin film. In this structure, a lower layer 7{itM, 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 the 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 burnt out, so it has 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 an St substrate is used as a capacitor in integrated circuits, but as an individual capacitor, a film of silicon oxide layer is used to improve the capacitance. When the thickness was reduced, there was a problem in that the withstand voltage property decreased.

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 that has a large capacitance, excellent voltage resistance, and is easy to manufacture.

Summary of the Invention In order to achieve the above object, a capacitor according to the present invention includes a Si substrate, a dielectric film made of silicon oxide formed on the front and back surfaces of the Si substrate, and a dielectric film made of silicon oxide to cover the front and back surfaces of the Si substrate. an electrode portion formed on the surface of the dielectric film, and a cap-shaped first cap-shaped first electrode portion that sandwiches both electrode portions so as to electrically connect both electrode portions and not to contact the St substrate.
so as to sandwich the extraction electrode and both dielectric films formed on the front and back surfaces of the Si substrate not covered with the electrode portion,
Moreover, it is characterized by having a cap-shaped second extraction electrode attached to the side end of the St substrate so as to be electrically connected to the St substrate.

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

In the present invention, since the St substrate is used as a part of the electrode, there is no need to laminate the lower electrode and the dielectric film in this order on the substrate as in the conventional case, and when burning out the dielectric film, There is no need to worry about deterioration of the lower electrode, which may occur. In addition, in the present invention, since silicon oxide formed on the front and back surfaces of the St substrate is used as the dielectric film, the adhesion between the dielectric film and the St substrate is improved, and cracks in the dielectric film are 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 surface of the Si substrate but also on the back surface, and this is used as a dielectric film.
The capacitance is doubled compared to when a dielectric film is formed on only one side.

Furthermore, in the present invention, the dielectric film is formed by thermally oxidizing the front and back surfaces of the 81 substrate, so it is extremely easy to form the dielectric film. Furthermore, the extraction electrode can be easily installed by simply fitting the metal cap. Therefore, the capacitor according to the present invention can be manufactured extremely easily, and the manufacturing cost can also be reduced.

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

FIG. 1 is a sectional view showing an example of a capacitor according to the present invention;
FIG. 2 is a front view showing a method of manufacturing a capacitor according to the same embodiment.

As shown in FIG. 1, the capacitor 2 according to the present invention has S
It has an i-substrate 4 and a dielectric film 6 formed on the front and back surfaces of the St substrate 4. Electrode portions 8 are provided on the surface of the dielectric film 6 so as to cover almost the entire surface of the dielectric film 6.
, 8 are provided. In order to electrically connect these electrode portions 8, 8, a cap-shaped first extraction electrode 10 is provided to sandwich both electrode portions. However, since a gap space 11 is provided between the cap-shaped first extraction electrode 10 and the Si substrate 4, there is no electrical connection between them. Cap-shaped second extraction electrode 12
are adapted to sandwich the portions of the surface of the dielectric film 6 that are not covered by the electrode portions 8, 8. Furthermore, the second extraction electrode 12 is electrically connected to the St substrate 4 via an electrode portion 8C provided in advance within the second extraction electrode 12.

The dielectric film 6 is made of silicon oxide, preferably St.
Obtained by thermally oxidizing the substrate. 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
It is 0 μm, more preferably 100λ to 5 μm. Note that although silicon oxide is mainly composed of SIO2, it may also contain SiO or the like.

As the electrode portions 8, 8c, A g −, Cu %
Electrodes such as A u -, AllSPt, Pd, etc. can be used. As a means for forming the electrode portion 8, a sputtering method, a vapor deposition method, a paste coating, etc. are used. Electrode 8
Preferably, c is preformed into the cap by paste application.

It is preferable that the St substrate 4 has a specific resistance of 0.1Ω·(7) or less. If the specific resistance of the St substrate itself is small,
This is because the St substrate 4 also functions as an electrode. Specifically, as the Si substrate 4, a silicon wafer or the like is used. As the silicon wafer, any type of commercial product such as non-doped type, P type, or N type can be used as is. The thickness of the substrate 4 is not particularly limited, but is preferably determined so that the resistance value does not become large as an electrode, and is preferably thick enough to impart appropriate rigidity to the entire capacitor. Specifically, it is preferable to have a thickness of 0.1+in+ 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 electrodes and dielectric film formed thereon also have a shape that follows the shape of the substrate.

The materials constituting the first extraction electrode 10 and the second extraction electrode 12 include Ag, CuSAu, A, Q, Pt, and Pt.
d etc. are exemplified. The thickness of these extraction electrodes 10.12 is not particularly limited, but preferably has a thickness of 0.1 μm to 50 μm. The shape of the extraction electrode is not necessarily limited to a U-shaped cross section, but may be rCJ-shaped or the like.

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

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

Thereafter, a metal paste that will become the electrodes 8.8 is applied to the front and back surfaces of the substrate 4 in a grid pattern, for example, as shown in FIG. Thereafter, the substrate 4 and the dielectric film 6 formed on the front and back surfaces of the substrate 4 are cut so that the cutting line 14 does not overlap at least one end of each electrode portion, thereby obtaining a chip having no extraction electrode.

Next, a chip is fitted into the recess of the cap-shaped first extraction electrode 10, and the electrode portions 8, 8 on the front and back surfaces are electrically connected. However, a gap space 11 is provided between the first extraction electrode 10 and the Si substrate 4, and the first extraction electrode 10 and the Si substrate 4 are provided with a gap space 11.
Make sure that it does not come into contact with the i-board 4. At the same time or after that, the electrode portion 8,
By fitting the portion not covered by 8 into the recess of the cap-shaped second extraction electrode 12, both dielectric films 6, 6 are sandwiched.

Note that when fitting the second extraction electrode 12, a metal paste that will become the electrode portion 8C is applied inside the recess of the second extraction electrode 12, so the second extraction electrode 12 and the St substrate 4 are
It comes to be electrically connected through the electrode 8C. In this way, 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, so that the capacitor capacity is improved and the withstand voltage characteristics are also improved.

Note that, in the present invention, the means for manufacturing the capacitor 2 is not limited to the above-mentioned embodiments, and can be modified in various ways.

Effects of the Invention As explained above, in the present invention, the silicon substrate is used as a part of the electrode, so there is no need to laminate the lower electrode and the dielectric film in this order on the substrate as in the conventional case. ,
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 and side end surfaces of the silicon substrate is used as the dielectric film, the adhesion between the dielectric film and the silicon substrate is improved, and the dielectric film is It is possible to prevent cracks and the like.

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 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 surface of the Si substrate but also on the back surface, and this is used as a dielectric film, so when a dielectric film is formed only on one side, The electric capacity is doubled compared to . Furthermore,
In the present invention, the formation of the dielectric film and the installation of the extraction electrode are easy, so the capacitor manufacturing process can be simplified and the cost can be reduced.

[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 Thickness 0 with specific resistance 0.01Ω・doped with sb
．． The St substrate was heat-treated for 20 minutes at 1000° C. in an oxygen atmosphere. Ag paste was applied to both sides of the plate by screen printing in a pattern of 3 mm x 4 squares as shown in FIG. Thereafter, the substrate 4 was cut into squares so that at least one end of each paste-like electrode was not crossed by the cutting line, thereby obtaining a chip body. Next, an aluminum cap was used as a first extraction electrode and placed over the end of the chip body, and the upper and lower electrode portions were electrically connected. On the other hand, inside Ag
An aluminum cap coated with paste was used as a second lead-out electrode and placed over the other end of the chip body, sandwiching the upper and lower dielectric films, and connecting to the St substrate to form a capacitor.

The characteristics of the thin film capacitor obtained in this way were evaluated by LCR.
The results measured using a meter are shown below.

The capacitance was 2.5 nF at a measurement frequency of 1 MHz, and the temperature coefficient of capacitance was 15 ppo+/°C from 80°C to -20°C. Also, when I measured the resistance value at constant voltage, it was LO at 20V.
It was more than GΩ.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an example of a thin film capacitor according to the present invention, and FIG. 2 is a front view showing a method of manufacturing the capacitor according to the same embodiment. 2nd Figure 2... Capacitor 4... St substrate 6... Dielectric film 8.80... Electrode portion 10... First
Extraction electrode 12...Second extraction electrode 14...Cutting line

Claims (1)

[Claims] 1) A Si substrate, a dielectric film made of silicon oxide formed on the front and back surfaces of the Si substrate, and an electrode portion formed on the surface of the dielectric film so as to cover the front and back surfaces of the Si substrate. a cap-shaped first extraction electrode that sandwiches both electrode portions so as to electrically connect the two electrode portions without contacting the Si substrate; A capacitor having a cap-shaped second lead-out electrode attached to a side end of a Si substrate so as to sandwich both dielectric films formed on the front and back surfaces and to be electrically connected to the Si substrate. 2) A capacitor characterized in that the specific resistance of the Si substrate is 0.1 Ω·cm or less.