JPH0770431B2 - Method of manufacturing thin film capacitor - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a thin film capacitor having excellent withstand voltage characteristics.

2. Description of the Related Art A typical structure of a conventional thin film capacitor is shown in FIG.
1 is an alumina ceramic substrate, 2 is a metal layer made of thin chromium formed by vacuum evaporation, 3 is a metal layer made of gold also formed by vacuum evaporation, 5 is a silicon oxide layer formed by chemical vapor deposition, 6 Is a thin chromium metal layer formed by vacuum evaporation, and 7 is a gold metal layer similarly formed by vacuum evaporation.

A typical manufacturing method of this structure is as follows:
An electrode is formed by vacuum evaporation, etc., a dielectric thin film such as silicon oxide is deposited on it by a method such as chemical vapor deposition (CVD), and an electrode is also formed on it by a method such as vacuum evaporation. That is.

Problems to be Solved by the Invention However, in the conventional method based on such a simple manufacturing method, as shown in FIG. 3, the unevenness of the ceramic surface used for the substrate is directly formed on the electrode. , Reflected in the dielectric film. On the surface of a ceramic substrate, unlike single crystals, it is difficult to avoid voids, and it is possible to have thousands of Angstroms to several μm.
It is very common to have irregularities of m, and even a mirror-polished surface has irregularities of hundreds to thousands of angstroms.
However, in the case of a thin film capacitor, the thickness of the dielectric film is several thousand angstroms to several μm, and the unevenness on the surface of the ceramic substrate greatly affects the uniformity with respect to this thickness. Above all, the withstand voltage characteristics are greatly affected.

The present invention has been made in view of the above points, and an object of the present invention is to provide a method of manufacturing a thin film capacitor having excellent withstand voltage characteristics even when a ceramic substrate having a surface with some irregularities is used.

Means for Solving the Problems In order to solve the above problems, the present invention forms an electrode on a ceramic substrate, and then applies a substance that easily changes into silicon oxide by heat treatment dispersed in a solvent, and heat treatment After removing the solvent by the method and changing this substance to silicon oxide, a silicon oxide layer is formed, and then silane (SiH ₄ ) and oxygen are reacted on the substrate by chemical vapor deposition. A thin film capacitor having excellent withstand voltage characteristics is provided by depositing a silicon oxide layer on and forming an electrode thereon.

Action The present invention improves the withstand voltage characteristics of the thin film capacitor by the above-described manufacturing method.

Example An example of a method for manufacturing a thin film capacitor of the present invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment of a structure in which the thin film capacitor of the present invention is integrated and formed on an alumina substrate. In FIG. 1, 1 is an alumina ceramic substrate, 2
Is a thin chromium metal layer formed by vacuum deposition,
3 is a metal layer made of gold also formed by vacuum vapor deposition,
4 is a silicon oxide layer formed by a coating heat treatment method, 5 is a silicon oxide layer formed by a chemical vapor deposition method, 6 is a metal layer made of thin chromium formed by vacuum vapor deposition, and 7 is a gold layer also formed by vacuum vapor deposition. Is a metal layer.

The thickness of each layer is the alumina ceramic substrate 1 in this embodiment.
Is 635 μm, chromium layer 2 is 100 Å, gold 3 is 3000 Å, silicon oxide layer 4 is 1000 Å, silicon oxide layer 5 is 1 μm, chromium layer 6
Is 100Å and metal 7 is 3000Å.

Next, a method of manufacturing the device of this example will be described. First, the chromium layer 2 and the gold layer 3 are formed on the alumina ceramic substrate 1 by vacuum vapor deposition to have a predetermined thickness. Since these metal layers are thin, if the substrate has irregularities, it is formed by tracing it as it is. The chromium layer 2 and the gold layer 3 serve as the lower electrode of the thin film capacitor. Next, a photoresist mask is formed by an ordinary photolithography method, and the chromium and gold layers other than necessary portions are removed by wet etching using this photoresist mask. Next, a solution of alkylsilanol (RSi (OH) ₃ ; R is an alkyl group) dissolved in alcohol is applied. Since this is in the form of a solution, even if there is a large dent in the lower electrode formed on the ceramic substrate and in a shape tracing the same, the entire lower part is flattened. This is shown in FIG. FIG. 2 is an enlarged view of a part of the structure of FIG. 1 so that the unevenness of the substrate surface can be seen well. In FIG. 2, 1 is an alumina ceramic substrate, 2 is a metal layer made of thin chromium formed by vacuum evaporation, 3 is a metal layer made of gold similarly formed by vacuum evaporation, and 4 is a silicon oxide formed by a coating heat treatment method. Layers 5 are silicon oxide layers formed by chemical vapor deposition, 6 is a thin chromium metal layer formed by vacuum evaporation, and 7 is a metal layer also formed by vacuum evaporation of gold. As can be seen from FIG. 2, by inserting the layer 4 formed by the coating heat treatment, the unevenness of the substrate disappears in this layer.

After the layer 4 is formed by coating, it is heat-treated in the air at 300 to 600 ° C. to remove the solvent, change the alkylsilanol into silicon oxide, and form the silicon oxide layer 4. In this case, the silicon oxide has a disordered chemical bond.
SiO is connected in multiple layers and is generally (-SiO
It can be expressed as −) n and can be called silicon oxide in a broad sense. Here, the silicon oxide formed by the chemical vapor deposition method is mainly a polycrystal of silicon dioxide (SiO2), and in order to distinguish from this, the layer 4 formed by the coating heat treatment is expressed as a silicon oxide layer, The layer 5 formed by the vapor phase growth method,
It is expressed as a silicon oxide layer. Next, by reacting silane (SiH ₄ ) and oxygen on the substrate by chemical vapor deposition,
A silicon oxide layer 5 is formed. As described above, this is mainly a polycrystal of silicon dioxide (SiO2). Next, a photoresist mask is formed by a normal photolithography method, and the silicon oxide layer 4 and the silicon oxide layer 5 other than necessary portions are removed by wet etching using the photoresist mask,
Next, a chromium layer 6 and a gold layer 7 are formed by vacuum vapor deposition, a photoresist mask is formed by a normal photolithography method, and the chromium and gold layers other than necessary portions are removed by wet etching using this photoresist mask to form an upper electrode. To do.

With the structure of this embodiment, as can be seen from FIG. 2, a thin film capacitor having excellent withstand voltage characteristics can be obtained even if the substrate surface has some irregularities.

The capacitance of the thin film capacitor having the structure of the present embodiment is such that the silicon oxide layer 4 formed by the coating heat treatment method and the silicon oxide layer 5 formed by the chemical vapor deposition method are connected in series.
The dielectric constants of both are almost the same, which is 4. Therefore, the capacitance is determined by the total thickness of these dielectric layers.

As described above, according to the method of the present invention, it is possible to greatly improve the withstand voltage characteristics without impairing other characteristics.

The thin film capacitor obtained in this example exhibited good withstand voltage characteristics as expected. The surface roughness of the alumina ceramic substrate used was about 2000Å. The withstand voltage of a thin film capacitor formed only by chemical vapor deposition is about 1 x
While it was 10 ⁵ V / cm, the withstand voltage of this example was about 1 × 10 ⁷ V / cm, and the withstand voltage characteristic was improved about 100 times.

Although chromium and gold were used as the electrodes in this example,
It is clear that this forms only the counter electrode of the capacitor and is not limited to this material.

Further, in this embodiment, a specific value was used as the thickness of the electrode, but it is clear that the electrode only needs to have a thickness that effectively operates as an electrode.

Further, in this embodiment, the silicon oxide layer 4 and the silicon oxide layer 5 are
Although a specific value is used as the thickness of the above, the thickness is not limited to the specific value, as long as a predetermined capacitance can be obtained.

Also, if the entire dielectric layer is formed by coating and heat treatment, good withstand voltage characteristics can be obtained, but since this method is applied as a solution, a dense and dense film cannot be obtained. In addition, the method of changing from organic silicon (alkylsilanol) to inorganic silicon oxide does not yield a silicon oxide film mainly composed of silicon dioxide having a small number of lattice defects. Therefore, only a large dielectric loss (tan δ) is obtained. I can't. It is clear that increasing the dielectric loss (tan δ) is not desirable for capacitors. On the other hand, since the silicon oxide film formed by the chemical vapor deposition method is composed of a polycrystalline body mainly composed of silicon dioxide and having a small number of lattice defects, it exhibits a good dielectric loss (tan δ) characteristic. However, since it is deposited faithfully to the shape of the substrate surface, it does not contribute to flattening the unevenness of the substrate, and as described above, it is not possible to obtain an excellent withstand voltage characteristic.

Further, although alkylsilanol was used as the material for heat treatment for coating in this example, the purpose of the present invention is to flatten the surface irregularities by applying it in the form of a solution, and therefore it is limited to this material. It is obvious that any material may be used as long as it can be converted into silicon oxide after coating.

Further, although alumina ceramics is used as the substrate in this embodiment, the same effect of reducing the unevenness of the surface can be obtained by using a substrate made of other ceramic, single crystal, metal, etc., thereby improving the withstand voltage characteristics. It is clear that this can be achieved.

EFFECTS OF THE INVENTION As described above, the present invention flattens the unevenness on the ceramic substrate by taking advantage of the property that the solution flattens the unevenness, thereby forming a pinhole in a dielectric thin film formed on the unevenness. By reducing defects, the withstand voltage characteristics of the thin film capacitor are improved.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of the structure of the present invention, FIG. 2 is a partially enlarged view of the structure of FIG. 1, and FIG. 3 is a structural view of a conventional example. 1 ... Alumina ceramic substrate, 2 ... Chrome layer, 3 ...
... gold layer, 4 ... silicon oxide layer formed by coating heat treatment method, 5 ... silicon oxide layer formed by chemical vapor deposition, 6 ... chromium layer, 7 ... gold layer.

Claims (1)

[Claims] 1. After forming an electrode on a ceramic substrate, a solution substance which becomes a silicon oxide by heat treatment is applied on the electrode, and after the applied film is changed to a silicon oxide film by the heat treatment, the solution is formed on the electrode. A method of manufacturing a thin film capacitor, characterized in that SiH ₄ and oxygen are reacted with each other by chemical vapor deposition to deposit a silicon oxide film and an electrode is formed thereon.