JPH0677083A - Thin film capacitor and manufacture thereof - Google Patents

Abstract

PURPOSE:To realize a method of manufacturing a thin film capacitor which is applicable to a micro electronic circuit, of which characteristics are large in capacity, small in size, and excellent in frequency. CONSTITUTION:An electrode 2, dielectric layers 3 and 4, and a counter electrode 5 are successively laminated on a substrate 1 for the formation of a thin film capacitor, where the dielectric layers 3 and 4 different from each other in dielectric constant and frequency characteristics are provided. In a method where a thin film capacitor is manufactured, as dielectric bodies different from each other in dielectric constant and frequency characteristics are arranged, a first dielectric layer 3 is laminated on the electrode 2 in film form, and a second dielectric layer 4 is provided through such a manner that a part of the electrode 2 is oxidized through an anodizing process after the first dielectric layer 3 is laminated on the electrode 2 to turn into an oxide insulator which serves as the second dielectric layer 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a capacitor used in a small electronic circuit, and more particularly to a thin film capacitor having high heat resistance, large capacity and excellent frequency characteristics. In particular, it is used for electronic devices that require small size, high density, and high speed.

[0002]

2. Description of the Related Art In recent years, in the field of consumer equipment, expansion of microwave communication of several GHz such as cellular radio, and further miniaturization and speeding up of electronic equipment such as computers and workstations have been rapidly advanced. There is. It is common to insert a bypass capacitor between the power supply and the ground in order to stabilize the power supply in a high frequency circuit and to eliminate switching noise in an integrated circuit. This bypass capacitor is required to have a large capacity with excellent frequency characteristics.

A barium titanate-based ceramic capacitor is often used as the bypass capacitor which requires a large capacity. However, at low frequencies, a barium titanate-based chip capacitor having a large capacitance starts to deteriorate in characteristics due to its high dielectric constant due to dielectric dispersion in a high frequency region, and its capacitance begins to decrease, and the capacitance is almost lost at 400 MHz. This is Sumitomo Electric 13th 1989
No. 5, pp. 178-184. On the other hand, the tantalum oxide capacitor does not decrease in capacitance even in the high frequency region.

Therefore, in the bypass capacitor as described above, a capacitor having a large capacity and poor frequency characteristics, such as a barium titanate ceramic capacitor, and a capacitor having a small capacity and good frequency characteristics, such as a tantalum oxide capacitor, are electrically connected. When connected in parallel in parallel, a small-capacity capacitor with good frequency characteristics operates for noise consisting of high-frequency components, and a large-capacity capacitor with poor frequency characteristics operates for noise consisting of low-frequency components. It is effective for cutting.

[0005]

In the above-mentioned prior art, although effective for noise cutting, capacitors having different characteristics are separately arranged in the circuit and used. No consideration has been given to making it an element, and the number of parts has increased, the circuit configuration has become complicated, and there have been problems with circuit miniaturization, circuit maintenance, and circuit reliability. The present invention has been made in order to solve the above-mentioned problems of the prior art, and an object of the present invention is to provide a thin film capacitor having a large capacity, a small size, and good frequency characteristics, and a method for manufacturing the same.

[0006]

In order to achieve the above object, a thin film capacitor according to the present invention has a structure in which an electrode, a dielectric layer and a counter electrode are sequentially laminated on a substrate. In the above, the dielectric layer is made of a plurality of different materials, and at least some of these dielectrics are arranged in parallel.

The electrodes are tantalum, tantalum nitride,
It is composed of a plurality of materials selected from materials that form an oxide insulating layer by being oxidized, including titanium and aluminum. Furthermore, the dielectric layer composed of a plurality of different materials uses one of the dielectric materials as a ferroelectric having a perovskite structure.
Further, the dielectric layer composed of a plurality of different materials is one in which the dielectric material is an oxide insulator. Further, in order to achieve the above object, the structure of the method for manufacturing a thin film capacitor according to the present invention is a method for manufacturing a thin film capacitor having a plurality of different dielectric layers,
The first dielectric is deposited on the electrode and laminated, and the second dielectric is the oxide dielectric obtained by oxidizing a part of the electrode after the lamination is used as the second dielectric. . This oxide insulator is formed by using the anodic oxidation method.

[0008]

The function of each of the above technical means is as follows.
According to the present invention, in a thin-film capacitor in which an electrode, a dielectric layer, and a counter electrode are sequentially laminated on a substrate, the dielectric layer is made of a plurality of different materials, and at least a part of these dielectrics is used. Were arranged in parallel. That is, a plurality of dielectric materials having different relative permittivities and frequency characteristics are optimally combined and arranged in parallel, so that a capacitor having a dielectric layer made of a material having excellent frequency characteristics with respect to noise including a high frequency component is arranged. The noise is cut, and the noise having a low frequency component is effectively cut by the capacitor having a dielectric layer made of a material having a large relative dielectric constant. Further, according to the present invention, in a method of manufacturing a thin film capacitor having a plurality of different dielectric layers, a first dielectric is laminated on an electrode to form a film, and a second dielectric is formed after the lamination. Since a part of the electrode is applied as an oxide insulator and this oxide insulator is formed by the anodic oxidation method, the film formation time and area of the first dielectric are
For the second dielectric, oxidize area, oxidize time,
Regarding the anodizing method, by controlling the applied voltage, the capacitance ratio of each capacitor can be set arbitrarily and easily.
Moreover, it can be manufactured without increasing the number of steps. Further, the film thickness of the formed thin film capacitor can be set to only a few μm or less.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Each embodiment of the present invention will be described below with reference to FIGS. [Embodiment 1] FIGS. 1 (a), 1 (b), 1 (c), and 1 (d) are cross-sectional views of respective stages of a manufacturing process of a thin film capacitor according to an embodiment of the present invention, and FIGS. ), (C) and (d) are plan views corresponding to the respective steps of FIG. 1, FIG. 3 is an explanatory view of the anodizing device used in the embodiment of FIG. 1, and FIG. 4 is a view of the anodizing device of FIG. A diagram showing changes over time in voltage and current,
5 is an equivalent circuit diagram of the thin film capacitor of FIG. 1, and FIG. 6 is FIG.
FIG. 3 is a diagram showing the characteristics of frequency and capacity of the thin film capacitor of FIG.

The thin film capacitor of this embodiment according to the present invention is formed by sequentially laminating an electrode, a dielectric layer, and a counter electrode on a substrate, and a plurality of dielectrics having different relative dielectric constants and frequency characteristics are provided. Is provided. In the method of manufacturing a thin film capacitor of the present embodiment according to the present invention, since a plurality of dielectrics having different relative permittivity and frequency characteristics are arranged,
First, a first dielectric film is formed on an electrode and laminated, and a second dielectric film is formed by using an anodizing method for a part of the electrode after the lamination to form an oxide insulator. Of the dielectric material.

In FIG. 1, 1 is a silicon substrate, 2 is an electrode, 3 is a first dielectric layer, 4 is a second dielectric layer, and is an oxide insulator by an anodic oxidation method, and 5 is a counter electrode. Figure 2
In the figure, the same reference numerals as those in FIG. In FIG. 3, the same reference numerals as those in FIG. 1 are the same portions as those in FIG. 6 is a constant current source / constant voltage source, 7 is a cathode using a platinum electrode, and 8 is an electrolytic solution.

As shown in FIGS. 1 (a) and 2 (a), a tantalum film is formed on the silicon substrate 1 by the ion beam sputtering method to a film thickness of 5000 Å, which is used as the electrode 2. As shown in FIGS. 1B and 2B, the first dielectric 3 is formed on the surface of the electrode 2 by a reactive ion beam sputtering method.

[Equation 1] 5,000 Å is deposited. Next, FIG. 1 (c) and FIG. 2 (c)
As shown in FIG. 3, by anodizing the electrode 2 and a part of the first dielectric 3, a part of the electrode 2 becomes an oxide insulating film, which is used as a second dielectric 4.

FIG. 3 shows an apparatus used for this anodic oxidation. In the apparatus shown in FIG. 3, a platinum electrode is used as the cathode 7 and a 0.1% phosphoric acid solution is used as the electrolytic solution 8. In the initial stage of the reaction, as shown in the diagram showing the voltage-current characteristics of the anodizing device in FIG. 4, the oxidation reaction is promoted at a constant current to form an oxide film. After that, a constant voltage of 200 V is applied for 1 hour in order to continue the growth of the film.
By this anodic oxidation, a tantalum oxide film having a thickness of about 3000 Å can be obtained. Further, 2000 liters of tantalum is deposited to form a counter electrode 5. As shown in FIGS. 1D and 2D, a thin film capacitor in which different dielectrics 3 and 4 are arranged in parallel can be obtained.

The function of the thin film capacitor of this embodiment will be described with reference to the equivalent circuit of FIG. In FIG. 5, C1 is a capacitor section on which the first dielectric 3 is arranged, and C2 is a second dielectric 4
Is the capacitor section where The capacitance of the thin film capacitor composed of both C1 and C2 is C = C1 + C2. Further, in FIG. 6, the horizontal axis represents the frequency and the vertical axis represents the capacitance, and the combined capacitance C of the capacitors C1 and C2 having different frequency characteristics is shown. From this diagram, mainly in the low frequency region, C2 is C1 noise-cuts in the high-frequency region, and the noise-cut operation is performed well in all frequency regions. Further, in this example, by the above specific means, the film formation time and area for the first dielectric material, the area to be oxidized and the oxidation time for the second dielectric material, and the anodic oxidation method were used. By controlling the applied voltage, it is possible to obtain a capacitor that performs noise cutting operation in all frequency regions. Regarding the shape according to this embodiment, since the thin film capacitor has a thickness of only a few μm or less, it can be arranged under the IC chip, and the influence of the wiring can be removed and the consumer device can be used. It is possible to further downsize. The present embodiment shows an example, and the present invention is not limited to this, and many modes are conceivable. The ion beam sputtering method and the reactive ion beam sputtering method were used as the film forming method for the electrode 2 and the first dielectric material 3.
An RF sputtering method, a CVD method, or another vapor deposition method may be used.

Although tantalum is used as the electrode 2 in this embodiment, any material may be used as the material of the electrode 2 as long as it is a metal or conductor that can be used as the second dielectric by oxidation. . For example, titanium, aluminum,
Tantalum nitride can be used. Further, in this embodiment, PMN was used as the first dielectric, but any ferroelectric having a perovskite structure may be used.
Barium titanate or lead titanate may be used. Furthermore,
In the present embodiment, the anodic oxidation method was used as the oxidation method, but any method that can oxidize the conductor electrode can be applied. For example, a method of annealing at about 500 ° C. in an oxygen atmosphere or a method of irradiating with laser light in an oxygen atmosphere may be used. Furthermore, in this embodiment, the electrode 2
Was oxidized to obtain the second dielectric 4, but a sputtering method or a vapor deposition method may be used by using a mask.

[0016]

As described in detail above, according to the present invention, firstly, a thin film capacitor having a large capacity, a small size, and good frequency characteristics is provided by optimally combining different dielectrics. You can Also, secondly, first
By controlling the film thickness and effective area of the second dielectric and the second dielectric, a capacitor having characteristics suitable for the purpose can be obtained.

[Brief description of drawings]

FIG. 1 is a sectional view of each stage of a manufacturing process of a thin film capacitor according to an embodiment of the present invention.

FIG. 2 is a plan view of each stage of a manufacturing process of a thin film capacitor according to an embodiment of the present invention.

FIG. 3 is an explanatory view of an anodizing device used in the embodiment of FIG.

FIG. 4 is a diagram showing changes over time in voltage and current in the anodizing device of FIG.

5 is an equivalent circuit diagram of the thin film capacitor according to the embodiment of FIG.

6 is a frequency of the thin film capacitor according to the embodiment of FIG.
It is a diagram which shows the characteristic with capacity.

[Explanation of symbols]

 1 Silicon Substrate 2 Electrode 3 First Dielectric 4 Second Dielectric Anode Oxidation Oxidation Insulator 5 Counter Electrode 6 Constant Current Power Supply / Constant Voltage Power Supply 7 Platinum Electrode Cathode 8 Electrolyte

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Eiji Matsuzaki 292 Yoshida-cho, Totsuka-ku, Yokohama

Claims (6)

[Claims] 1. A thin film capacitor formed by sequentially laminating electrodes, a dielectric layer, and a counter electrode on a substrate, wherein the dielectric layers are composed of a plurality of different materials, and at least a part of these dielectrics is formed. A thin film capacitor, which is arranged in parallel. 2. The thin film according to claim 1, wherein the electrode is made of a plurality of materials including tantalum, tantalum nitride, titanium, and aluminum, which are selected from materials that form an oxide insulating layer by being oxidized. Capacitors. 3. The thin film capacitor according to claim 1, wherein the dielectric layer formed of a plurality of different materials is made of a ferroelectric material having a perovskite structure. 4. The thin film capacitor according to claim 1, wherein one of the dielectric layers made of a plurality of different materials is an oxide insulator. 5. A method of manufacturing a thin film capacitor having a plurality of different dielectric layers, wherein a first dielectric film is formed on an electrode and laminated, and a second dielectric is formed on the electrode after the lamination. A method of manufacturing a thin film capacitor, characterized in that an oxide insulator obtained by oxidizing a part of the above is used as the second dielectric. 6. The method for manufacturing a thin film capacitor according to claim 5, wherein the oxide insulator is formed by using an anodic oxidation method.