JPS60124112A - Surface elastic wave element - Google Patents

Abstract

PURPOSE:To obtain highly efficient characteristics by forming an SiO2 film and a ZnO film on a silicon substrate cut at its (110) surface and also forming electrodes on the ZnO film to propagate surface elastic waves in the [001] axial direction of the silicon substrate. CONSTITUTION:The SiO2 film 12 having film thickness h2 is formed on the silicon substrate 11 cut at a surface almost equivalent to the (110) surfacce and the ZnO film 13 having film thickness h1 is formed on the film 12 so that a surface almost equivalent to a (0001) surface is parallel with the cut surface of said silicon substrate 11. Then, input electrodes 14 and output electrodes 15 consisting of comb line electrodes are formed on the film 13. When Sezawa waves are propagated in the direction almost equivalent to the [001] axial direction of the silicon substrate through said structure, characteristics having a high electromechanical coupling coefficient K are obtained. If the silicon substrate 11 is used as the substrate for an integrated circuit in common, a small-sized and high density element will be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a surface acoustic wave device that operates efficiently and is constructed of 141 ln.

Recently, various surface acoustic wave devices that utilize surface acoustic waves that propagate along the surface of an elastic body have been actively developed. The reasons for this are, firstly, that the @wI speed of surface acoustic waves is about 10 times the t magnetic wave speed, which allows for smaller devices and higher retention.

Second, surface acoustic waves can tap signals from any location on the transmission path that propagates on the surface of a material, and third, because surface acoustic waves concentrate energy on the surface of a material, it is possible to tap signals from any location on the surface of a material. Interaction with the carrier of the device,
Or it can be applied to devices that utilize nonlinear effects due to high energy density.

Fourthly, since IC technology can be used in the manufacturing technology mentioned above,
Combination 1. The actual state of new elements can be expected 2.
etc.

Figures 1 and 2 show the structure of a conventional surface acoustic wave device. 3 is a piezoelectric thin film made of zinc oxide (ZnO), whose surface is approximately equicurved to the 00017 plane, and is cut on a plane substantially equivalent to the (110) plane. The comb-shaped electrodes 4.5 are formed parallel to the cut surface and are provided on the lithium dioxate substrate 1 and the acid 11 on the zinc film 3 so as to intersect with each other. 4 is used as a manual electrode, and 5 is used as an output electrode.

Here, the surface acoustic wave excited from the manual electrode 4 propagates through the surface of the lithium niobate group IJii 1 or the surface of the zinc oxide film 3 and is extracted from the output '1IHk5.

In these Izo-zukuri, the surface 'j' in the first section I
When propagating using Rayleigh waves as LL waves.

Frost a, which is an important indicator for device characteristics 2. ! Mechanical connection Vd
Since the square value of K is about 5.5% and Ia is small, this advantage Y? However, on the other hand, since the substrate is composed of a monomorphic material, the mechanical coupling fermentation 1 (or the direction of the substrate crystal axis or 6) 3. There is a drawback that the direction of propagation of the surface acoustic waves is fixed.

In this point part 2 figure, when using Sezawa e as a surface acoustic wave and propagating in a direction almost equivalent to the C00L) axis direction of the silicon substrate 2, the film thickness b1 of the zinc oxide film 3 can be calculated by analysis. By setting the value to be I<, the property can be made more flexible.

In addition, it is possible to obtain a mechanical coupling coefficient of 1 (1) which is thicker than the structure shown in FIG.
By selecting = 8000 (ω is the angular frequency of the surface acoustic wave), K can be approximately 586%.

However, in this structure, the zinc oxide film 3 is formed by spunter technology, etc., but as mentioned above, in order to obtain the optimum characteristics, it is necessary to form the film relatively thick, which increases costs in terms of productivity. However, it is desirable to have a structure in which a mechanical coupling coefficient K as large as possible can be obtained with a film thickness as small as possible.

The present invention has been made to address the above-mentioned problems.

A silicon substrate cut with a plane almost equivalent to the (110) plane, a silicon dioxide film formed on the substrate, and a curved plane almost equivalent to the (0001) plane on the silicon dioxide film. The silicon substrate includes a constant zinc oxide film formed parallel to the cut surface of the silicon substrate, and an electrode formed on the zinc oxide film.
) It is an object of the present invention to provide a surface acoustic wave element configured to propagate surface acoustic waves in a direction substantially equivalent to the axial direction, thereby eliminating the conventional drawbacks. Embodiments of the present invention will be explained below with reference to the drawings. 〇 Figure 3 shows a cross-sectional view of a surface acoustic wave device according to the present invention. A substrate 12 is formed on the silicon substrate 11 and is made of silicon dioxide (5iOz
) film, 13 is (000
1) A zinc oxide film having a thickness of 111 mm and formed so that a surface substantially equivalent to the surface thereof is parallel to the cut surface of the silicon substrate 11; input and output electrodes consisting of type electrodes;
Reference numeral 16 denotes a conductive film formed between the zinc oxide film 13 and the silicon dioxide film 12, and the film thickness is preferably infinitely small.
[1@14.15] It is desirable to be formed so as to be located directly below at least the crossing width portion.

The above structure (ZnO(0001)/5i02/Si (
110) For a surface acoustic wave device (abbreviated as 001:]), a silicon substrate 1 is fabricated using Sezawa waves as surface acoustic waves.
By propagating in a direction almost equivalent to the (001) axis direction of 1, characteristic curves as shown in FIGS. 4 and 5 can be obtained. In FIG. h2
The thickness of is indicated by ωh2 (ω is the angular frequency), and the vertical axis indicates the square value K of the electromechanical coupling coefficient iK in percentage. In Fig. 5, the axis is the thickness of the zinc oxide film, which is indicated by ωh (ω is the angular frequency).

The vertical axis represents the square value of the electromechanical coupling coefficient iK expressed as a 'Y percentage. In Figure 4, when ωh1 is set to 7000, the ωh2 ratio changes (preferably 126 to 1
Figure 5 shows the change in I when ωhl is changed (preferably within the range of 4200 to 15000) with ωh2 = looO. It shows.

Figures 4 and 518! ! As is clear from J, the thickness h1 of the zinc oxide film 13 and the thickness h2 of the silicon dioxide film 12 are ω11z=7000 and ωh2=100, respectively.
By adding 0 to the maximum value at point A, 2=5.8
I got 9%, my friend.

The above value is the value obtained by iU in the conventional structure shown in Fig. 2 (K″′=
5.86%, ωhl = 8000), and the film thickness 111 of zinc oxide 13 is larger than that of silicon dioxide [
By interposing 12, the conventional ωJ = 8000
can be reduced from ωhl = 7000.

This makes it possible to reduce costs in terms of production.

In addition, by adjusting the thickness h1 of the zinc oxide film 13 and the thickness h2 of the silicon dioxide film 12 variously within the above-mentioned ranges, a surface acoustic wave device with greater flexibility than the conventional structure in terms of 1% resistance can be obtained. It can be realized.

Note that the cut surface of the silicon substrate IJ is approximately equivalent to the (110) plane, the zinc oxide film 13 is approximately equivalent to the (0001) plane, and the propagation axis of the silicon substrate 11 is approximately equivalent to the (001) axis direction. Although the explanation has been given by taking the example of the case shown in FIG.

FIG. 6 shows a row applied to a conformer element as an embodiment of the present invention, in which 17 is a gate electrode provided between the manual electrode 14 on the zinc oxide film 13 and the outputs 'i and i415. It is.

In this structure, since the conductive layer 1ii416 is provided as is, the silicon substrate 11. It is possible to utilize the electric potential generated within the silicon dioxide film 12 and the zinc oxide film 13.

As is clear from the above, according to this investigation.

(110) A silicon substrate cut with a curved surface approximately equal to (110) ljii, a silicon dioxide film formed on this seven silicon substrate, and a silicon dioxide film formed on this silicon dioxide film (0001
) plane or parallel to the cut plane of the silicon substrate, and an electrode formed on the zinc oxide film.

Since the surface acoustic wave element is constructed so that it is drawn in a direction approximately equivalent to the [001] axis direction of the silicon substrate, the electrically-like mechanical coupling coefficient is large. The device can be operated efficiently.

In addition, according to the present invention, by using a 24-layer circuit common to multiplication circuits as a silicon substrate, it is possible to realize a compact and high-density element that integrates a functional element and a conductor element by utilizing integrated circuit technology. .

[Brief explanation of the drawing]

1 and 2 are sectional views showing the conventional method, 3 and 6 are sectional views showing the implementation of the present invention, and 4 and 5 are the results obtained by the present invention. FIG. DESCRIPTION OF SYMBOLS 11... Silicon substrate, 12... Divalent silicon film, 13... Zinc oxide film, 14... Manual electrode, 15.
... Output electrode, 16... Conductive film, 17... Gate electrode.乍Fig. 2, 3, Procedural Amendment (April 1980) - 3, Director General of the Patent Office, Aio Sugi, 1, Indication of the case, 1983 Patent Application No. 232445, 2, Name of the invention, Surface elasticity. Wave element 3 Relationship with the case of the person making the amendment Patent applicant address name (148) Clarion Co., Ltd. 4 agent 〒1
05 Address: Shiba 3-chome Building 5, 3-2-14 Shiba, Minato-ku, Tokyo
Detailed Description of the Invention Column 6: Contents of the Amendment (1) ``Since the exclusive electric film 16 is provided as is in lines 4 to 5 of page 10 of the specification of the present application'' is deleted. (21, same page, line 7, in place of 10) is corrected to ``without using''. (3) Same page, line 9, ``can be done'' is corrected to ``it is expected that the device will be realized.''

Claims (1)

[Claims] 1. A silicon substrate cut on a plane substantially equivalent to the (110) plane, a silicon dioxide film formed on this silicon substrate, and a silicon dioxide film cut on a plane substantially equivalent to the (0001) plane. A zinc oxide film formed such that an equivalent surface is parallel to the cut surface of the silicon substrate, and an electrode formed on the zinc oxide film are included.
i) A surface acoustic wave element configured to allow surface acoustic waves to propagate in a direction equivalent to the axial direction.
3. The surface acoustic wave device according to claim 194, wherein the crystal plane and its propagation axis have an inclination within 10” from the predetermined crystal plane and propagation axis direction. In the surface acoustic wave device according to claim 1 or 2, characterized in that Sezawa waves are used, the film thickness b3 of the zinc oxide film is 4200<ωhj<
15,000 (7,: where ω is the angular frequency of the surface acoustic wave). 5. The thickness h2 of the silicon dioxide film is 126<
The surface acoustic wave device according to any one of claims 1 to 4, characterized in that it belongs to the range of ωh2<10000 (where ω is the angular frequency of the surface acoustic wave). . 6. The surface acoustic wave device according to any one of claims 1 to 5, characterized in that a conductive film is interposed between the zinc oxide film and the silicon dioxide film. 7. The surface acoustic wave device according to any one of Claims 1JJ4 to 6, wherein the electrode has a comb-shaped structure.8. The surface acoustic wave element according to any one of claims 1 to 7, wherein the surface acoustic wave element is located directly below the width portion. 9. The surface acoustic wave device according to any one of claims 1 to 8, wherein the zinc oxide film is located directly below at least the reciprocal l1viI portion of the comb-shaped electrode. 10. The surface acoustic wave device according to claim 1, wherein the silicon substrate is a common substrate with an integrated circuit.