JPS62257716A - Thin film capacitor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to the improvement of dielectric materials for capacitors, for example, aromatic thin films such as polyamide thin films formed by the Langmuir-Prodgett method (hereinafter simply referred to as "LB method"). The present invention relates to technology for small-sized, large-capacity thin-film capacitors that can be formed on integrated substrates, using the same as the dielectric material of capacitors.

Conventional technology As a conventional capacitor technology, for example, Japanese Patent Application Laid-Open No. 54-55
There is a technique disclosed in Japanese Patent No. 68.

This technology relates to a capacitor formed on an insulating substrate such as a hybrid integrated circuit, and its structure is as follows. That is, a first conductive layer formed as a transmission line on an insulating substrate, and a part of this first conductive layer, or a first conductive layer formed on this and a part of the insulating substrate. A capacitor was formed by a second conductive layer electrically insulated by an insulating member.

The insulating member is formed of silicon oxide (sio2), tantalum oxide (T'zOs), or other inorganic or organic insulating materials by vapor deposition, printing, oxidation, or the like.

Problems to be Solved by the Invention The above-mentioned conventional techniques relate to dielectrics of capacitors.

However, when forming a small capacitor with a large capacity using such dielectric technology, it has reached its limit due to the following problems.

1] Conventional dielectrics have a low dielectric strength E (V/υ), and in order to obtain the desired withstand voltage, it is necessary to increase the thickness t (A"l) of the dielectric.

For example, silicon oxide (sio2) is used as a conventional dielectric.
Tantalum oxide (7ato, ), titanium oxide (Tie,
), alumina (At203), etc., but the dielectric strength voltage E (V/CIN) of all of them is 10' (V/α
] is required.

[2] Conventional dielectrics have a thickness t(
Since X) is thick, the capacitance C(F) of the capacitor cannot be increased.

The capacitance CICF) of the capacitor is the dielectric constant ε(
F/cm], the area of the electrode plates is S Ccd], and the distance between the opposing electrode plates is dCelI], then C is calculated by the well-known formula.
−ε(S/d).

Therefore, it is obvious that the capacitance 0 (F) of the capacitor is approximately inversely proportional to the thickness t (ffi') of the dielectric.

[3] Conventional dielectrics have sparse surfaces, and their dielectric strength decreases due to uneven surfaces and defects. Therefore, in order to compensate for the defective state and obtain a stable capacitor, it was necessary to adopt a dielectric layered structure. For example, tantalum oxide (Ta, O
, ) include mangaf oxide (Mn02), silicon oxide (Si
n, ) Also, a dielectric material was formed by laminating chromium (N1cr) or the like.

Means for Solving the Problems The present invention solves the above-mentioned problems and provides the following technology.

That is, the present invention provides a thin film capacitor characterized in that it is constructed by alternately combining an aromatic thin film and a conductive member into a plurality of layers, and the aromatic thin film is made of polyamide formed by imidizing polyamic acid. Provided is a thin film capacitor made of a thin film, the aromatic thin film is a thin film formed by an LE method, and the conductive member is a thin film capacitor made of a conductive film. provides a thin film capacitor consisting of a conductor formed on an integrated substrate.

For production The present invention will be explained in detail using the above-mentioned means.

As mentioned above, the aromatic thin film of the thin film capacitor of the present invention is made of a polyamide thin film formed by the T, B method, for example. Because it is a thin film with a thickness equal to the length of the chain, it forms an extremely uniform surface with no uneven surfaces.
In addition, an extremely thin and thin insulating layer is formed.

In addition, when the aromatic thin film is a polyimide thin film, it inherits the basic properties of polyimide resin, and therefore has excellent heat resistance and mechanical strength, and is chemically stable. Because it is an ultra-thin, uniform film, it has high voltage resistance.

As a result of experiments conducted on the polyimide thin film, the following was confirmed.

That is, an aluminum electrode was deposited on a slide glass using a sample piece, a polyimide thin film formed by the LB method was adhered thereon, and an aluminum electrode was further deposited thereon.

External wiring was connected to each of the null electrodes of the sample pieces thus prepared, and the applied voltage was gradually increased to measure the dielectric strength E, and data of 10' (V/-) was obtained. This value was compared to the maximum value of about 106 (V, mm) in conventional insulating materials, and an exceptional effect could be demonstrated. The reason why this exceptional dielectric strength voltage was obtained is considered to be due to the thickness and uniformity of the polyimide thin film.

In other words, the thickness of the monomolecular film of the polyimide thin film has been confirmed to be around 4 [x] as a result of measurement, and the thickness is related to the structure of the aromatic ring of polyimide, and the thickness is related to the structure of the aromatic ring of polyimide. An ultra-thin film with an extremely uniform surface is formed. In addition, since the molecules that make up the polyimide thin film form an array structure, they are strongly bonded to each other and are strong, and molecular defects are less likely to occur, so pinholes are also less likely to occur. Confirmed.

In addition, as mentioned above, dielectric breakdown is generally caused by the avalanche effect, that is, carriers subjected to a strong electric field cause a smearing phenomenon, and the flow of carriers increases one after another like a snow avalanche, growing into a large current flow and causing dielectric breakdown. It is said to cause

However, it has been confirmed that the thickness of the polyimide thin film in the present invention is around 4 [X], and at this thickness, even if there is movement of carriers due to tunneling effect etc. It is thought that it will not cause an avalanche.

In other words, according to the experimental results, the above-mentioned dielectric strength voltage E was able to obtain the exceptional value of approximately 10' (V15) because the polyimide thin film has uniformity, has no pinholes, and is strong. Furthermore, it is thought that this was possible because the thickness of the thin film was extremely thin.

Hereinafter, five embodiments of the present invention will be described in detail with reference to the accompanying drawings.

First Embodiment FIGS. 1 and 2 are partial sectional views of a preferred first embodiment of the present invention.

Reference numeral 1 denotes a first conductive member, which is made of, for example, a metal film such as aluminum or chrome.

Reference numeral 2 is an aromatic thin film, for example a polyimide thin film, and the polyimide thin film 2 formed by the LB method is adhered to the surface of the first conductive member 1.

Here, a method for forming the polyimide thin film 2 using the LB method described above and a process for attaching the polyimide thin film 2 to the first conductive member 1 will be explained.

First, in the second step, the polyamic acid synthesized in the first step was diluted with DMAc-benzene in the same ratio, and a solution of dimethylhexadecylamine at the same concentration in the same solvent was mixed in a ratio of 1:2 to form a polyamide. An acid long chain derivative film 2' (not shown) is made. Next, the first conductive member 1 is immersed in the solution in which the polyamic acid long chain derivative film 2' is floating.
is applied to the surface of the first conductive member 1, and then acetic anhydride:
A polyimide thin film 2 is formed on the surface of the first conductive member 1 by immersing it in a solvent containing a mixture of pyridine and benzene at a ratio of 11:3 for about 12 hours.

In addition, the upper surface of the polyamic acid long chain derivative film 2' floating on the liquid surface exhibits hydrophobicity, and the lower surface facing the liquid exhibits hydrophilicity, so that the orientation of each molecule is regularly aligned in the same direction. The polyimide thin [2
The monomolecular film made of polyimide thin film 2 also has a regular arrangement structure, and has a uniform thickness determined by the aromatic ring structure of the polyimide thin film 2, and is coated on the surface of the first conductive member 1. It will be worn.

A slight oxide film layer is previously formed on the surface of the fourteenth electrically conductive member 1, and the polyimide thin film 2 is adhered to this oxide film layer.

Furthermore, if the polyamic acid long chain derivative film 2' of the first conductive member 1 is repeatedly dipped into and taken out from the floating solution, the polyimide thin film 2 will have a thickness proportional to the number of repetitions. It is formed.

However, the uniformity of the polyimide thin film 2 is not affected.

Next, in FIG. 1, 3 is a second conductive member, and the second conductive member 3 is passed through the process by the above-mentioned LB method, and then the second conductive member 3 is
It is formed on a polyimide thin film 2 deposited on the surface of a conductive member 1, and processes such as sputtering or vacuum deposition of metal such as aluminum, plating process, or printing process with metal paste are used. It was formed using

In addition, it can be seen that in the structure shown in FIG. 1, one side of the polyimide thin film 2 is held between the first conductive member 1 and the second conductive member 3.

Then, the first terminal 4 is fixed to the first conductive member 1, and the second terminal 5 is fixed to the second conductive member 2.
A conventional electrolytic capacitor, that is, a cylindrical capacitor 7, is formed by appropriately insulating the capacitor and placing it in an aluminum case 6. However, since the dielectric is formed from the polyimide thin film 2, it is non-polar.

Second Embodiment FIGS. 5 and 4 show the configuration of a second preferred embodiment of the present invention, in which the technology of the present invention is applied to a capacitor array.

In FIG. 3, 8 is a substrate made of silicon (Sl), and 9 is a silicon oxide (SIO) formed on the substrate 8 by thermal oxidation or reactive sputtering.
), 10 is a first conductive member formed on the insulating layer 9, 11 is a polyimide thin film as an aromatic thin film, and 12 is a second conductive member formed on the polyimide thin film 11. It is. In addition, the first conductive member 10 and the second conductive member 12 are formed by a method such as photoetching or sputtering using a metal mask, and the polyimide thin film 11 is formed by forming the first conductive member 10 and the insulating layer by the LB method. 9 and is formed by partially removing it by photo-etching, beam irradiation, etc.

Thus, the polyimide thin film 11 is sandwiched between the first conductive member 10 and the second conductive member 12 to form a capacitor. Then, by connecting the terminals 13 to the first conductive member 10 and the second conductive member 12, a capacitor array shown in FIG. 4 is formed.

Fifth Embodiment FIG. 5 shows the configuration of a third preferred embodiment of the present invention, in which the technology of the present invention is applied to an integrated circuit. The third embodiment is similar to the second embodiment, but the difference is that the substrate 8 is formed of a semiconductor element having an n-shade region and a p-shade region.

Specifically, the substrate 8 is, for example, a p-type substrate with an n-shade region formed by diffusion or ion implantation;
An insulating layer 9 made of silicon oxide (Si02) or the like is formed on the upper surface, and is partially etched away by photo-etching, a first conductive member 10 is partially formed by photo-etching, and a polyimide thin film 11 is deposited. , and further a second conductive member 1
2 and connect the terminals 13 to form an integrated circuit having a capacitor therein.

In addition, in the second and third embodiments described above, if it is desired to increase the capacitance of the capacitor, the first conductive member 1
0. It is possible to increase the capacitance of the capacitor by alternately performing the steps of forming the polyimide thin IJ 11 and the second conductive member 12 and stacking them. Further, the present invention is not limited to the above-described embodiments, but includes various embodiments.

For example, the film capacitor shown in the first embodiment can be applied to forming a capacitor on a flexible substrate, and the
Capacitors constructed as shown in the embodiments and the third embodiment can be applied to circuits in which the substrate is made of a glass plate and the conductive member is made of a transparent electrode.

Effects of the Invention As explained in detail above, the present invention uses an aromatic thin film such as a polyimide thin film formed by imidizing polyamic acid formed by the LB method etc. as a dielectric material and sandwiching it between conductive members. A feature is that a thin film capacitor is formed by alternately combining multiple layers.

Therefore, the following effects are achieved.

(a) The aromatic thin film in the present invention, particularly the polyimide thin film formed by the LB method, has a dielectric strength E of about 10
'(v/c+++'), and the dielectric thickness t(Z) is approximately 106 [■/e
II+] The thickness can be reduced to about 1/1 to 0 times.

('b) As mentioned above, the thickness t(X) of the dielectric material made of polyimide thin film etc. can be made approximately 1/100 times thinner than that of the conventional dielectric material, and the capacitor capacitance t C
(') can be increased by a factor of 100 compared to that of the prior art. This becomes effective when forming a capacitor on an integrated substrate.

In other words, for example, when forming a capacitor with the same capacity as a conventional capacitor, the area occupied by the capacitor can be increased to approximately 1/100 times, and it is also possible to mount a capacitor internally, which previously could only be mounted outside the integrated circuit board. can do.

(c) In addition, the polyimide thin film formed by the LB method has an extremely uniform surface because each of its constituent molecules forms an array structure, and the molecules that are adjacent to each other are strongly bonded to each other. Because of this, molecular defects are less likely to occur, and therefore pinholes are less likely to exist.

(a) In addition, when the aromatic thin film is composed of a polyimide thin film, it inherits the basic properties of polyimide resin, and therefore has excellent heat resistance and mechanical strength, and is a chemically stable dielectric material. can be formed.

(e) The present invention has many excellent effects as described above,
Therefore, it is suitable for forming a small, large-capacity, non-polar thin film capacitor.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing a first preferred embodiment of the present invention. FIG. 2 is a perspective view of what is shown in FIG. 1 wound and assembled into a cylindrical capacitor. FIG. 3 is a perspective view showing a second preferred embodiment of the present invention. FIG. 4 is an electrical circuit diagram of what is shown in FIG. FIG. 5 is a sectional view showing a third preferred embodiment of the present invention. FIG. 3 is a sectional view showing another preferred embodiment of the present invention. 1.10...First conductive member, 2.11...
・・Polyimide thin film as aromatic thin film, 3.12−・
...Second conductive member, 8...Substrate, 9...
...Insulating layer. Above Figure 1 Figure 2/Figure 3

Claims (5)

[Claims] (1) A thin film capacitor characterized in that it is constructed by alternately combining an aromatic thin film and a conductive member into a plurality of layers. (2) The thin film capacitor according to claim 1, wherein the aromatic thin film is a polyamide thin film formed by imidizing polyamic acid. (3) The thin film capacitor according to claim 1 or 2, wherein the aromatic thin film is a thin film formed by a Langmuir-Prodgett method. (4) The thin film capacitor according to claim 1, 2, or 3, wherein the conductive member is made of a conductive film. (5) The thin film capacitor according to claim 1, 2, or 3, wherein the conductive member is a combination of a plurality of conductors formed on an integrated substrate.