JPH04177810A - Manufacture of thin film capacitor - Google Patents

Abstract

PURPOSE:To make it possible to obtain a high-performance and high--reliability thin film capacitor while a humidity resistance is ensured and low-cost aliminium electrodes are used by a method wherein the aluminium electrodes are used and plasma emission is performed on the surfaces of the electrodes. CONSTITUTION:Internal electrodes 2 and a thin film dielectrode film 3 are alternately stacked on an insulating substrate 1 to support an element thereon and a protective film 4 is formed on the electrode 2. These electrodes 2 respectively include a part which is not covered with the film 4 and external electrodes 5 are respectively formed on the extension of the electrodes 2 formed on both end parts of the substrate 1. After aluminium electrodes which are used as the electrodes 2 and formed, plasma is emitted on the aluminium electrodes and the surfaces of the aluminium electrodes are made to react to the plasma gas to modify into surfaces having a humidity resistance. Thereby, while the low-cost aluminium electrodes are used, a thin film capacitor, which is superior in humidity resistance, is high in performance and is highly reliable, is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for manufacturing high performance and reliable thin film capacitors.

BACKGROUND OF THE INVENTION In recent years, with the rapid downsizing and increasing performance of electronic devices, there has been a growing demand for electronic components to be downsized, have higher performance, and lower costs. In particular, the environment in which electronic devices are used has become harsher, and the reliability required of electronic components has become higher. Under these circumstances, the capacitor industry is also working to develop more reliable capacitors.

A conventional thin film capacitor is composed of an element part made of an internal electrode and a dielectric, a substrate that directs the element part, an external electrode connected to the element part, and a film that protects the element. Aluminum electrodes, which have been considered as electrode materials for such thin film capacitors, have not been able to sufficiently ensure moisture resistance. Therefore, as a means to ensure moisture resistance, (1) a metal with strong corrosion resistance (such as a noble metal) is used as the electrode material.

(2) Prevent water from entering the element by providing an exterior cover.

The above two points have been conventionally performed.

Problems to be Solved by the Invention However, when a metal with strong moisture resistance such as Ni or NiCr is used as an electrode material, such metal has a high surface resistance and a dielectric loss (tan δ) as a capacitor.
It is known that in addition to increasing the insulation resistance, even a small amount of water intrusion can lower the insulation resistance. Furthermore, although it is possible to improve moisture resistance by using a noble metal or the like, this becomes a major impediment to cost reduction.

In addition, resin is generally used as the exterior to prevent water from entering the element portion, but there is a problem that the resin itself absorbs moisture, resulting in insufficient sealing performance and high reliability. Furthermore, since the connection between the internal and external electrodes is not sealed with a protective film, aluminum electrodes are susceptible to moisture absorption, making it impossible to create highly reliable thin film capacitors.

An object of the present invention is to realize a method for manufacturing a high-performance, highly reliable thin film capacitor that uses inexpensive aluminum electrodes and has excellent moisture resistance.

Means for Solving the Problems In order to achieve the above object, the present invention provides a method for manufacturing a thin film capacitor in which thin film dielectrics and aluminum electrodes are alternately stacked using a dry process. The aluminum electrode is irradiated with plasma every time.

Working aluminum electrodes usually have a very small amount of natural oxide film formed on their surface when forming a thin film, but this alone cannot ensure moisture resistance. Therefore, by irradiating the aluminum electrode with plasma after forming the aluminum electrode, the surface of the aluminum electrode reacts with the plasma gas and is modified into a moisture-resistant surface. That is, when the plasma generating gas is nitrogen, the surface is nitrided, and when the plasma generating gas is oxygen, it is oxidized. In either case, a sufficient passive structure is formed on the surface of the aluminum electrode to ensure moisture resistance.

In the present invention, aluminum used as an electrode material has good electrical conductivity and is used as an internal electrode of electronic components. Therefore, a highly reliable thin film capacitor using aluminum electrodes can be obtained. Regarding plasma generation, the effect obtained is the same whether high frequency discharge or direct current discharge is used.

EXAMPLE Hereinafter, an example of the thin film capacitor of the present invention will be described with reference to the drawings.

FIG. 1 is an example of the configuration of a cross-sectional view of a general thin film capacitor. In this figure, internal electrodes 2 and thin film dielectrics 3 are alternately stacked on an insulating substrate 1 that supports an element, and a protective film 4 is further formed thereon. Further, the internal electrode 2 includes a portion not covered with the protective film 4, and the external electrode 5 is formed on an extension of the internal electrode 2 formed at both ends of the insulating substrate 1. Here, as the insulating substrate 1, an inorganic material such as alumina can be used as long as it can withstand high temperatures during surface mounting and is inexpensive.

As a dry process for forming the internal electrodes 2, a vacuum evaporation method, a sputtering method, etc. can be used. Further, as a dry process for forming the thin film dielectric 3, it is possible to use a vapor deposition polymerization method, a plasma CVD method, a sputtering method, or the like. As the material used for the thin film dielectric 3, either inorganic or organic materials can be used. For example, materials that can be formed by vapor deposition polymerization include polyimide,
Examples include polyamide, polyurea, and polyurethane. Materials that can be formed using the plasma CVD method include silicon,
Examples include oxides such as titanium, nitrides, and oxynitrides. Further, a plasma CVD method or the like is used to form the protective film 4, and silicon oxide, nitride, or oxynitride is formed.

Next, in order to clarify the present invention, six types of specific manufacturing methods were carried out by changing various manufacturing conditions, and as a comparative example, thin film capacitors were manufactured using a conventional manufacturing method, and the characteristics of the capacitors were measured over time. A comparative study was conducted.

Six specific embodiments based on the present invention and conventional examples will be described below.

Example 1 After forming aluminum with a thickness of 0.1 μm as internal electrodes by an electron beam method on an alumina substrate whose surface of the substrate except for both ends was covered with glass with a thickness of 20 μm, plasma irradiation was performed. Nitrogen was used as the plasma generation gas, plasma generation was performed at a frequency of 13.56 MHz, and the plasma generation pressure was 0.1 torr. After plasma irradiation, an aromatic voluria film with a thickness of 0.2 μm was formed as a thin film dielectric by vapor deposition polymerization. Thereafter, 10 layers of aluminum electrodes and thin film dielectrics were stacked alternately. Note that the plasma irradiation described above was performed each time after forming the aluminum electrode.

Next, a silicon nitride film having a thickness of 2 μm was formed as a protective film by plasma CVD. Furthermore, an external electrode made of a copper alloy was formed using a low-pressure plasma spraying method to obtain a thin film capacitor.

Example 2 After forming an aluminum electrode in the same manner as in Example 1 on the same alumina substrate as in Example 1, plasma irradiation was performed. Nitrogen is used as the plasma generation gas, plasma generation is performed at a frequency of 2.45 GHz, and the plasma generation pressure is 0.2 to
It was set as rr. Thin film dielectric.

A protective film and external electrodes were formed in the same manner as in Example 1 to obtain a thin film capacitor.

Example 3 After forming an aluminum electrode in the same manner as in Example 1 on the same alumina substrate as in Example 1, plasma irradiation was performed. Nitrogen is used as the plasma generation gas, plasma generation is performed at a frequency of 400KHz, and the plasma generation pressure is 0.3torr.
It was set as r. A thin film dielectric, a protective film, and an external electrode were formed in the same manner as in Example 1 to obtain a thin film capacitor.

Example 4 After forming an aluminum electrode in the same manner as in Example 1 on the same alumina substrate as in Example 1, plasma irradiation was performed. Nitrogen was used as the plasma generation gas, plasma generation was performed by direct current discharge, and the plasma generation pressure was 0.1 torr.

A thin film dielectric, a protective film, and an external electrode were formed in the same manner as in Example 1 to obtain a thin film capacitor.

Example 5 After forming an aluminum electrode in the same manner as in Example 1 on the same alumina substrate as in Example 1, plasma irradiation was performed. Oxygen was used as the plasma generation gas, plasma generation was performed at a frequency of 13, 56 MHz, and the plasma generation pressure was Q.
, 1 torr. A thin film dielectric, a protective film, and an external electrode were formed in the same manner as in Example 1 to obtain a thin film capacitor.

Example 6 After forming an aluminum electrode in the same manner as in Example 1 on the same alumina substrate as in Example 1, plasma irradiation was performed. A mixed gas of nitrogen and oxygen with a mixture ratio of 4:1 was used as the plasma generating gas, plasma generation was performed at a frequency of 13.56 MHz, and the plasma generation pressure was 0.2 Torr.

A thin film dielectric, a protective film, and an external electrode were formed in the same manner as in Example 1 to obtain a thin film capacitor.

Comparative Example 1 After aluminum electrodes were formed in the same manner as in Example 1 on the same alumina substrate as in Example 1, they were stacked alternately with thin film dielectrics without plasma irradiation. A thin film dielectric, a protective film, and an external electrode were formed in the same manner as in Example 1 to obtain a thin film capacitor.

The thin film capacitors of Examples 1 to 6 and Comparative Example 1 were subjected to a humidity test (temperature = 60°C, humidity 9:5%RH).
, applied voltage: 25 VDC, test time: 1000 h). The results are shown in FIG.

In the thin film capacitor of Comparative Example 1, corrosion occurred from the portion of the aluminum electrode surface not covered with the protective film after 100 hours, resulting in deterioration of dielectric loss. Furthermore, as time progressed, the corrosion progressed to the element facing portion, resulting in oven failure. For Examples 1 to 6, the characteristics (capacitance) of the capacitor before the test.

dielectric loss, insulation resistance).

That is, the moisture resistance is improved regardless of whether the irradiated plasma is a high frequency discharge or a direct current discharge. Regarding the plasma generating gas, the same effect can be obtained whether nitrogen, oxygen or a mixture thereof is used.

Effects of the Invention As is clear from the above explanation, according to the present invention, by using an aluminum electrode and irradiating the electrode surface with plasma, it is possible to ensure moisture resistance, and it is possible to use an inexpensive aluminum electrode. However, it is possible to obtain a thin film capacitor with high performance and high reliability.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a general thin film capacitor, and FIG. 2 is a graph of characteristics over time of a thin film capacitor manufactured by the manufacturing method of the present invention and a thin film capacitor manufactured by a conventional manufacturing method. 1...Insulating substrate, 2...Internal electrode, 3
... Thin film dielectric, 4... Protective film, 5.
...External electrode. Name of agent: Patent attorney Haruaki Koebi and 2 others / ---2
Matchmaking search 2-m-internal @drawing 3-*M diden Ei 4 ・-protection organ 5--1 external electric 2 camphor 1st figure

Claims (4)

[Claims] (1) A thin film capacitor manufacturing method in which thin film dielectrics and aluminum electrodes are alternately stacked using a dry process, which is characterized in that the aluminum electrodes are irradiated with plasma each time after forming the aluminum electrodes. manufacturing method. (2) The method for manufacturing a thin film capacitor according to claim (1), wherein the plasma generating gas is nitrogen, oxygen, or a mixed gas thereof. (3) The method for manufacturing a thin film capacitor according to claim (1) or (2), wherein the plasma is generated by high-frequency discharge. (4) The method for manufacturing a thin film capacitor according to claim (1) or (2), wherein the plasma is generated by direct current discharge.