JPH09186543A - Electrode structure for surface acoustic wave element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrode structure improving the manufacture yield without causing local short-circuit by cutting off an end of an apex angle of common bus bars or reflectors adjacent to each other. SOLUTION: An angle of apex angle ends 3, 4 of adjacent parts of common bus bars 1, 2 is selected to be an obtuse angle. Through the constitution above, the positions of the apex angle ends 3, 4 of common bus bars 1, 2 of IDT electrodes adjacent to each other are parted from each other. Thus, no local short-circuit due to defective etching is caused between the apex angle ends 3, 4 of the common bus bars 1, 2 adjacent to each other. As a result the yield of a SAW filter is improved and the manufacture cost is reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrode structure of a surface acoustic wave device, and more particularly to an electrode structure of a surface acoustic wave device for preventing a common bus bar of adjacent IDT electrodes and a reflector from being short-circuited.

[0002]

2. Description of the Related Art In recent years, a surface acoustic wave (SAW) element has been widely used as a filter or a resonator in a high frequency region of VHF to UHF band. As shown in FIG. 4, for example, a general structure of a SAW filter is a comb-teeth shape called an interdigital transducer (IDT) on a piezoelectric substrate 5 made of quartz, lithium tantalate, lithium niobate, lithium tetraborate or the like. No. 2 (in the example shown in the figure, the IDT electrodes are two reference numerals 6 and 7) and, if necessary, reflectors 8 and 9 are provided on both sides of the IDT electrode.

The IDT electrode and the reflector of the surface acoustic wave device are generally formed by a photolithography technique. As shown in the flowchart of FIG. 5, a metal thin film is formed on the piezoelectric substrate by a thin film forming technique such as vacuum deposition or sputtering of a metal such as aluminum, gold, silver, nickel, chromium, copper, or an alloy ( Step 1), apply photoresist (Step 2),
The desired I for the photoresist through the photomask
The pattern of the DT electrode and the reflector is exposed and developed (steps 3 and 4), the metal thin film is etched with an acid or the like based on the photoresist pattern (step 5), and then the photoresist is stripped (step 5). Step 6) The method is general.

The photoresist is classified into a positive type and a negative type. In the positive type, the photoresist is exposed to light when exposed, and the exposed photoresist disappears when developed, and the photoresist is not exposed to light. The remaining portion functions as a mask in the etching process of the metal thin film. It is the opposite of the negative type, in which the photoresist which is exposed to light remains by exposure. Generally, a positive photoresist is often used.

FIG. 6 is an enlarged view of the portion shown in FIG. 4A.
It is the person who showed the adjacent part of the electrode. As shown in the figure, conventionally, the common bus bars 10 and 1 of the IDT electrodes adjacent to each other are provided.
The angles θ1 and θ2 of the apex angle end portions 12 and 13 of No. 1 are equal to 90 ° (right angle).

[0006]

However, FIG.
When the SAW filter having the structure as shown in FIG. 6 is manufactured by the photolithography technique, the common bus bar 1 of the IDT electrodes 6 and 7 adjacent to each other as shown in FIG.
The metal thin film remains in the gap between the apex angle end portions 12 and 13 of 0 and 11 due to insufficient etching of the metal thin film and the local short circuit portion 14 is generated.

That is, since the adjacent IDT electrodes are electrically connected as described above, it becomes impossible to obtain proper characteristics as a SAW filter, resulting in defective characteristics of the manufactured SAW filter, and improving the manufacturing yield. However, there was a drawback that it became a very serious hindrance factor.

The present invention has been made in order to eliminate the drawbacks of the electrode structure of the surface acoustic wave device as described above, in which a local short circuit occurs at the apex end of the common bus bar of the adjacent IDT electrodes. It is an object of the present invention to provide an electrode structure of a surface acoustic wave device that does not occur and has a significantly improved manufacturing yield.

[0009]

To achieve the above object, an electrode structure of a surface acoustic wave device according to the present invention comprises a desired number of IDT electrodes in which electrode fingers are connected to common bus bars separated from each other on a piezoelectric substrate. In the electrode structure of the surface acoustic wave element having a reflector provided as necessary, the common busbars or reflectors separated from each other are cut off at the apex end portions of the respective common busbars or reflectors adjacent to each other. By doing so, the electrode structure of the surface acoustic wave element in which a local short circuit does not occur at the apex angle end portion of the common bus bar of the IDT electrode, and particularly, the apex angle end portion of the common bus bar or the reflector is formed. This is an electrode structure of a surface acoustic wave device having the same effect by making the shape to be cut off obtuse or curved.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the drawings showing an embodiment.

FIG. 1 is a SAW showing a first embodiment of the present invention.
FIG. 6 is an electrode structure diagram of a filter, showing an enlarged view of a common bus bar of adjacent IDT electrodes formed on a piezoelectric substrate. Reference numerals 1 and 2 denote common bus bars that are adjacent to each other, and the angles θ1 and θ2 of the apex angle end portions 3 and 4 of the adjacent portions of the common bus bar are obtuse angles, that is,

[0012]

[Equation 1]

It is configured so that

According to the above-mentioned configuration, the adjacent IDTs
The positions of the apex end portions of the common busbars of the electrodes are distant from each other, and even if the SAW filter is manufactured by the conventional photolithography manufacturing process, a local area due to a defective etching is generated between the apex end portions of the adjacent common busbars. No short circuit will occur. Therefore, the manufacturing yield of the SAW filter can be improved, and the manufacturing cost can be reduced.

The effect of the present invention has been confirmed by actually manufacturing the SAW filter which does not cause a local short circuit between the apex angle ends of the adjacent common bus bars by the electrode structure shown in the above-mentioned embodiment. In addition, when the end of the common bus bar of the IDT electrode has an obtuse angle, the common bus bar is configured to have a sufficient width, so that the electric resistance of the common bus bar is large. Moreover, there is no influence on the electrical characteristics of the SAW filter.

In the above-mentioned embodiment, the angles θ1 and θ2 are the same, but the angles θ1 and θ2 may be different. For example in Figure 2

[0017]

[Equation 2]

A second example of the above is shown. Also in this embodiment, similarly to the first embodiment, it is possible to prevent the occurrence of a local short circuit between adjacent common bus bars.

That is, since it is sufficient that the ends of the common busbars of the adjacent IDT electrodes are separated from each other, the angles θ1 and θ2 of the apex angle ends 3 and 4 of the adjacent portions of the common busbar are different from each other. ,

[0020]

(Equation 3)

It suffices to appropriately select from the angle range of

Although θ1 is set to 90 ° or more and θ2 is set to an angle exceeding 90 °, there is no problem even if they are reversed and θ1 is set to an angle exceeding 90 ° and θ2 is set to 90 ° or more. .

FIG. 3 is a diagram showing a third embodiment of the present invention. The feature of this embodiment is that the apex end portions 3 and 4 of the adjacent common bus bars 1 and 2 are formed in a curved shape (chamfered shape). Also in this embodiment, the effect that a short circuit does not occur at the apex end of the common bus bar is confirmed as in the first and second embodiments.

In short, by separating the apex angle end portions of the adjoining portions of the common busbars of the adjacent IDT electrodes from each other, the apex angle end portions of the common busbars can be formed at the apex angle end portions of the common busbar without changing the manufacturing process by the conventional photolithography technique. It is possible to realize a SAW filter in which a local short circuit does not occur. As described above, forming the common busbar sufficiently wide so that the shape of the apex angle end of the common busbar is obtuse or curved does not affect the characteristics of the surface acoustic wave element.

The above-described embodiment of the present invention is a SAW.
Although the electrode structure of the filter has been described, the present invention is not limited thereto and the present invention can be applied to a surface acoustic wave element including a SAW resonator or the like. Furthermore, although the shape of the ends of the adjacent IDT electrodes is described, the top of the reflector is prevented from causing a local short circuit between the apex end of the common bus bar and the apex end of the reflector. The present invention may be applied to the corner ends.

Further, the electrode structure of the surface acoustic wave element is not necessarily required, and piezoelectric resonators and filters by bulk waves and high frequency monolithic crystal filters (H
It may be an electrode structure of a vibration device such as a multi-mode filter such as FF-MCF).

In addition, the vibrating device does not necessarily have to be used, and may be applied to the electrode structure of a semiconductor device,
It may be applied to an electrode structure of a printed board having thin film metal wiring.

Further, it may be applied to an electrode structure such as a ceramic package having a thin film metal wiring for housing the above-mentioned vibrating device and the like.

[0029]

Since the present invention is configured as described above, the electrode structure of the surface acoustic wave device has the structure without deteriorating the characteristics of the surface acoustic wave device and without changing the manufacturing process. It is extremely effective in eliminating the drawback that a local short circuit occurs.

[Brief description of the drawings]

FIG. 1 is an electrode structure diagram showing a first embodiment of the present invention.

FIG. 2 is an electrode structure diagram showing a second embodiment example according to the present invention.

FIG. 3 is an electrode structure diagram showing a third embodiment of the present invention.

FIG. 4 is a diagram showing a general configuration of a surface acoustic wave element.

FIG. 5 is a diagram showing a flowchart of a manufacturing process of the surface acoustic wave element.

FIG. 6 is an enlarged view of an electrode structure of a conventional surface acoustic wave device.

FIG. 7 is a diagram showing that a local short-circuit portion is generated between the electrodes of the surface acoustic wave element.

[Explanation of symbols]

 1, 2, 10, 11, ... Common bus bar 3, 4, 12, 13 ... Common-vertical end of bus bar 5 ... Piezoelectric substrate 6, 7 ... IDT electrode 8, 9 ... Reflection Vessel 14 ··· Locally short-circuited part θ1, θ2 ···· Angle of top angle end

Claims (3)

[Claims] 1. An electrode structure of a surface acoustic wave device, comprising: a desired number of IDT electrodes in which electrode fingers are connected to a common bus bar separated from each other on a piezoelectric substrate; and a reflector provided as necessary. An electrode structure of a surface acoustic wave device, characterized in that a common bus bar or a reflector, which is adjacent to each other, is cut off at the apex angle end portions thereof. 2. The electrode structure of a surface acoustic wave device according to claim 1, wherein the shape of the common bus bar or the apex of the reflector cut off is obtuse. 3. The electrode structure of a surface acoustic wave device according to claim 1, wherein the shape in which the apex end of the common bus bar or the reflector is cut off is a curved shape.