JPH08195641A - Electrode structure of surface acoustic wave element - Google Patents

Abstract

PURPOSE: To greatly improve the yield by reducing a local short circuit between end parts of adjacent parts of mutually separated bus bars for the removal of a defect that the electrode structure of the surface acoustic wave element has. CONSTITUTION: Of the surface acoustic wave element equipped with plural IDT groups coupled with the mutually separated bus bars 1 and 2 on a piezoelectric substrate, the end parts 3 and 4 of the adjacent parts of the mutually separated bus bars 1 and 2 are shifted in position from each other at right angles of the propagation direction of a surface acoustic wave. Further, the end parts 3 and 4 of at least the adjacent parts of the mutually separated bus bars are made different in width. Namely, the vertical angle parts 3 and 4 of the adjacent parts of the bus bars are kept away from each other to remove a resolution defect that an electrode pattern has.

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 capable of preventing a short circuit between adjacent bus bars.

[0002]

2. Description of the Related Art In recent years, a surface acoustic wave (SAW) element has been widely used as an element such as a filter or a resonator in a high frequency region of VHF to UHF band. For example, as shown in FIG. 8, a general structure of a SAW filter is such that comb-shaped electrodes called interdigital transducers (IDTs) 6 and 7 are provided on a piezoelectric substrate 5 made of crystal, lithium tantalate, lithium niobate, or the like. The reflectors 8 and 9 are provided on both sides of the reflectors if necessary.

FIG. 9 is an enlarged view of the portion shown in FIG. 8A. In the conventional technique, in a SAW filter including a plurality of IDT groups connected to the bus bars 10 and 11 separated from each other,
The positions of the ends of the adjacent portions of the bus bars separated from each other are arranged such that the apex angles 13 and 14 of them are closest to each other without being displaced in the direction perpendicular to the surface wave propagation direction 12.

However, in the structure shown in FIG. 9, the metal of the portion remains because of the problem that the etching of the metal is insufficient at the ends of the adjacent portions of the bus bars separated from each other. As shown in FIG. 10, there is a problem that a local short circuit portion 15 occurs. For this reason, the defect rate has increased, which has been a very serious impeding factor in improving the yield.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in order to eliminate the drawbacks of the electrode structure of a surface acoustic wave device as described above, and it is possible to prevent local short circuit at the ends of adjacent parts of bus bars separated from each other. It is an object of the present invention to provide an electrode structure of a surface acoustic wave device which is extremely reduced and which has a significantly improved yield.

[0006]

SUMMARY OF THE INVENTION To achieve the above object, in the present invention, a surface acoustic wave device having a plurality of IDT groups connected to bus bars separated from each other on a piezoelectric substrate is separated from each other. It is characterized in that the positions of at least the ends of the adjacent portions of the bus bar are offset from each other in a direction perpendicular to the surface wave propagation direction. Further, the width of at least the end portions of at least adjacent portions of the bus bars separated from each other is different. In short, the resolution of the electrode pattern is removed by arranging the apex portions of the adjacent bus bars separated from each other.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail based on illustrated embodiments.

FIG. 1 is a SAW showing a first embodiment of the present invention.
It is a principal part electrode structural drawing of a filter, and expands only the adjacent part of the separated bus bar. Reference numerals 1 and 2 denote bus bars separated from each other. In the embodiment shown in this figure, the adjacent portions of the bus bars are offset from each other in the direction perpendicular to the surface wave propagation direction. With this configuration, it has been confirmed by experiments that the positions of the apex portions 3 and 4 of the adjacent portions are moved away from each other, and a short circuit does not occur even in the conventional manufacturing process.

FIG. 2 is a diagram showing a second embodiment of the present invention. As is clear from the figure, the widths of the bus bars adjacent to each other are different from each other. The same effect as that shown in FIG. 1 has been confirmed.

FIG. 3 is a diagram showing a third embodiment of the present invention, in which the width of one of the adjacent portions of the bus bar is partially reduced in the direction perpendicular to the surface wave propagation direction so that the apex angle portions of each other are reduced. The width is partially different so as to keep away from each other.

FIG. 4 is a view showing a fourth embodiment of the present invention, in which the width of one of the adjacent portions of the bus bar is partially increased in the direction perpendicular to the surface wave propagation direction, and the apex angle of each other is increased. The width is partially different so that the parts are separated.

FIG. 5 is a diagram showing a fifth embodiment of the present invention, in which one width of the adjacent portion of the bus bar is partially reduced in a direction perpendicular to the surface wave propagation direction and the other width is reduced. By partially increasing the width in the direction perpendicular to the surface wave propagation direction, the widths are partially different so that the apex angles of the parts are separated from each other. In this example, the synergistic effect of the third and fourth embodiments can be expected, and the probability of a short circuit can be further reduced.

FIG. 6 is a diagram showing a sixth embodiment of the present invention, in which the widths of both adjacent portions of the bus bar are partially reduced in the direction perpendicular to the surface wave propagation direction so as to be apex of each other. The width is partially different so that the corners are moved away.

FIG. 7 is a diagram showing a seventh embodiment of the present invention, in which the widths of both adjacent portions of the bus bar are partially increased in the direction perpendicular to the surface wave propagation direction, and the widths of the adjacent portions are increased. The width is partially different so that the apex part can be distanced.

In short, it is sufficient to move away the apex angle portion of the adjacent portion of the bus bar, which can greatly reduce the probability of occurrence of local short circuit even in the conventional manufacturing process. Further, providing the bus bar with the concave portion and the convex portion at the minimum portion has almost no effect on the characteristics of the SAW filter.

The above-mentioned electrode structure is not limited to the SAW filter, but can be applied to a surface acoustic wave element such as a SAW resonator.

Further, the electrode structure of the surface acoustic wave element is not always necessary, and vibrations of piezoelectric resonators and filters by bulk waves, and multimode filters such as high frequency fundamental wave monolithic crystal filters (HFF-MCF) are also possible. It may be the electrode structure of the device.

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 accommodating the vibrating device and the like.

[0020]

Since the present invention is configured as described above, it exerts a remarkable effect in eliminating the defects of the electrode structure of the surface acoustic wave element without deteriorating the characteristics of the surface acoustic wave element. To do.

[Brief description of drawings]

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

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

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

FIG. 4 is a schematic view of an electrode structure of essential parts showing a fourth embodiment according to the present invention.

FIG. 5 is an electrode structure diagram of a main part showing a fifth embodiment according to the present invention.

FIG. 6 is an electrode structure diagram of a main part showing a sixth embodiment according to the present invention.

FIG. 7 is an electrode structure diagram of a main part showing a seventh embodiment according to the present invention.

FIG. 8 is a diagram showing a general configuration of a surface acoustic wave element.

FIG. 9 is an enlarged view of part A.

FIG. 10 is a diagram showing a local short circuit portion generated in the conventional technique.

[Explanation of symbols]

 1, 2, 10, 11 ... Busbar 3, 4, 13, 14 ... Busbar apex 5 ... Piezoelectric substrate 6, 7 ... Interdigital transducer 8, 9 ... Reflector 12 ... Surface wave propagation Direction 15: Local short circuit

Claims (2)

[Claims] 1. A surface acoustic wave device comprising a plurality of IDT groups connected to busbars separated from each other on a piezoelectric substrate, wherein surface wave propagation occurs at positions of at least end portions of the separated busbars. An electrode structure of a surface acoustic wave device, characterized in that they are offset from each other in a direction perpendicular to the direction. 2. The electrode structure for a surface acoustic wave device according to claim 1, wherein the widths of the ends of at least adjacent portions of the bus bars separated from each other are different.