JPH09312543A - Surface acoustic wave element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the propagation loss by generating a film of a silicon dioxide onto a non-piezoelectric substrate, propagating a surface acoustic wave through the film, and employing the technology to remove dirts on the non- piezoelectric substrate. SOLUTION: A silicon dioxide film 2 is produced as a dielectric material on a substrate 1 made of glass or ceramics except quartz. Interdigital electrodes 3 are placed apart on the surface of the film 2 and the electrodes 3 are covered by a zinc oxide film 4 as a piezoelectric film. Concretely the silicon oxide film 2 whose film thickness is 13.5μm is produced over the one side of the substrate 1 made of a Pylex(R) glass by the sputtering method. The interdigital electrodes 3, 3 are placed on the film 2 apart by an interval of 38.4mm, and the electrodes 3, 3 are covered with the zinc oxide film 4 whose thickness of 2μm by the sputtering method. Furthermore, aluminum-made opposed electrodes whose film thickness is 0.1μm are formed on them. Through the constitution above, the propagation loss of the silicon dioxide is smaller than that of the substrate 1 made of glass or ceramics.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface acoustic wave device in which silicon dioxide constituting a dielectric film is combined with a non-piezoelectric film substrate such as glass, ceramic metal or plastic.

[0002]

2. Description of the Related Art A surface acoustic wave device that allows signals to easily enter and exit along a surface acoustic wave propagation path is used for an intermediate frequency filter, an oscillator, a resonator, and the like of a television, and is disclosed in Japanese Patent Laid-Open No. 5-90860. As can be seen from Fig. 3, it is composed of a piezoelectric body that excites surface acoustic waves, a comb-shaped electrode on the piezoelectric body that applies an electric signal, and an insulating layer in which the propagation speed of elastic waves is higher than that of the piezoelectric layer. A representative piezoelectric material is Japanese Patent Publication Sho 61
(Si) as disclosed in Japanese Patent Laid-Open No. 35716.
Zinc oxide (ZnO) as a piezoelectric film is formed on the substrate, and silicon dioxide (Si) as a dielectric film is formed on the zinc oxide layer.
O ₂ ) and a comb-shaped electrode are arranged.

A window wiping device disclosed in Japanese Patent Application Laid-Open No. 4-15146 is disclosed in which the surface acoustic wave device is used in a vehicle, for example, in a windshield of a vehicle. Japanese Patent Application Laid-Open No. 7-223512 discloses a vehicle mirror device used as a vehicle side mirror.

[0004]

[Patent Document 1] Japanese Unexamined Patent Publication No. 5-90
In the device disclosed in Japanese Patent No. 860, a diamond layer is provided on a substrate, and a comb-shaped electrode is provided on the diamond layer, which is expensive because the diamond layer is provided on the substrate. What is disclosed in Japanese Patent Publication No. 61-35716 is
This is an application of surface acoustic waves to electronic devices, and IC
The device is a common substrate, and a silicon substrate is used for this element. However, the silicon substrate is generally expensive, which leads to an increase in cost. on the other hand,
As an application of surface acoustic waves to a vehicle, Japanese Laid-Open Patent Publication No. 4-1
Although Japanese Patent Laid-Open No. 5146 and Japanese Patent Application Laid-Open No. 7-223512 are disclosed, in this device, since the surface acoustic wave propagates on the glass surface, a large power is required to generate the surface acoustic wave and the glass is used. Since surface acoustic waves propagate on the surface, the propagation loss becomes large. Therefore, an object of the present invention is to solve the above-mentioned disadvantages of the related art.

[0005]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention is basically a dioxide provided on a non-piezoelectric substrate such as glass (excluding quartz glass), ceramics, metal or plastic. A technical means of forming a silicon film, propagating surface acoustic waves through the silicon dioxide film, and removing dirt and water droplets on a non-piezoelectric substrate such as glass is used.

Specifically, the present invention provides a substrate made of any one of glass, ceramics, metal, and plastic, a silicon dioxide film formed on the substrate, and a silicon dioxide film or a substrate. There is provided a surface acoustic wave device including a comb-shaped electrode separated from each other and a zinc oxide film covering the electrode.

According to the present invention, a silicon dioxide film is formed on a substrate, and this silicon dioxide film is used as a medium for transmitting surface acoustic waves to reduce propagation loss, thereby generating surface acoustic waves with a small power. Further, the surface acoustic wave device functions to remove raindrops and the like by using the substrate as a window glass of a vehicle or a front plate of a mirror. Furthermore, since the substrate is made of glass, ceramics, metal, or plastic, the silicon dioxide film has less propagation loss than the substrate, and the efficiency is further improved.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. The surface acoustic wave device produces a silicon dioxide film 2 as a dielectric on a substrate 1 made of glass other than quartz, ceramics, metal plastic, or the like. A comb-shaped electrode 3 which is spaced apart from the surface of the silicon dioxide film 2 is arranged, and this is covered with a zinc oxide film 4 as a piezoelectric film.

The example shown in FIG. 2 is a surface acoustic wave device having a structure in which a comb-shaped electrode 3 and a zinc oxide film 4 are directly arranged on a substrate 1 and a silicon dioxide film 2 is filled between the zinc oxide films 4. Is.

[0010]

Example 1 An example of the surface acoustic wave device shown in FIG. 1 will be described. A silicon dioxide film 2 having a film thickness of 13.5 μm was formed on the entire surface of one side of the Pyrex glass substrate 1 by the sputtering method. On this silicon dioxide film 2, comb-shaped electrodes 3 and 3 spaced apart by 38.4 mm (the line width and the gap of the electrodes are both 15
μm, the number of logarithms is 114, and the cross width is 3 mm), and the electrodes 3, 3 are covered with zinc oxide films 4, 4 of 2 μm by sputtering. Further, an aluminum counter electrode having a film thickness of 0.1 μm was formed thereon. The insertion loss of the surface acoustic wave device according to this example was 24.2 dB.

[0011]

Example 2 An example of the surface acoustic wave device shown in FIG. 2 will be described. The comb-shaped electrodes 3 and 3 (both electrode and gap are 20
μm, a logarithm of 114 pairs, and a cross width of 3 mm made of aluminum) and a zinc oxide film 4 or 4 having a film thickness of 2 μm formed by the sputtering method, and a film thickness of 7.2 μ formed by the sputtering method between the zinc oxide films 4 and 4.
m silicon dioxide film 2 was formed. The counter electrode was opposed to the electrodes 3 and 3. The insertion loss of the surface acoustic wave device according to this example was 28.5 dB.

[0012]

[Comparative Example] In the example of FIG. 1, a zinc oxide film is used in place of the silicon dioxide film (dimensions are the same as in Example 1).
Has an insertion loss of 32.6 dB.

Third Embodiment FIG. 3 shows a cross section of a side mirror used in an automobile. The mirror assembly 5 has a structure in which a holder 9 supports a front plate 6 of Pyrex glass having a silicon dioxide film 2 on the front surface and a chromium film 7 which is a reflective material on the back surface, and its periphery is supported by the first embodiment. The same surface acoustic wave element 8 (however, the substrate is the front plate 6) was fixed to the edge of the front plate 6. Electricity was applied to measure the degree of removal of water drops on the front plate 6, but the water drops were completely removed except for a part of the edge of the front plate 6. The energization was a high frequency voltage having a frequency of 50.68 MHz and an amplitude of 20V. In this case, the surface acoustic wave generated from the surface acoustic wave element 8 by the applied voltage is propagated to the mirror surface (silicon dioxide film surface). In other words, the principle that water drops are removed is
When the energy of the surface acoustic wave is input to the water droplet attached to the mirror surface, the water droplet is excited. The water droplets thus excited tend to move with respect to the mirror surface, and the water droplets flow, scatter, or are atomized.By holding the surface acoustic waves in a vertical state so that they are above the mirror, Surface acoustic waves are propagated vertically from the upper side to the lower side of the mirror, and the movement of the water droplet on the mirror surface is affected by the weight of the water droplet, and even with a small power, the water droplet is completely removed from the mirror surface. . Instead of the zinc oxide film, aluminum nitride, lead zirconate titanate, or the like can be used.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a surface acoustic wave device according to an example of the present invention.

FIG. 2 is a sectional view of a surface acoustic wave device according to another example of the present invention.

FIG. 3 is a cross-sectional view of a mirror device.

[Explanation of symbols]

 1 substrate 2 silicon dioxide film 3 electrode 4 zinc oxide 5 side mirror 6 front plate 8 surface acoustic wave device

Claims (3)

[Claims] 1. A silicon dioxide film generated on a substrate for transmitting a surface acoustic wave, a comb-shaped electrode disposed on the silicon dioxide film or the substrate for generating the surface acoustic wave, and covering the comb-shaped electrode. A surface acoustic wave device including a zinc oxide film. 2. The surface acoustic wave device according to claim 1, wherein the substrate is a window glass of an automobile or a front plate of a mirror. 3. The surface acoustic wave device according to claim 1, wherein the substrate is made of glass, ceramics, metal, or plastic.