JPS6084005A - Surface acoustic wave resonator - Google Patents

Abstract

PURPOSE:To attain ease of interval between reflecting gratings to a prescribed value even when a resonance frequency is increased and an exciting electrode and the reflecting gratings are etched on the same condition by preventing changing of a reflecting electrode due to an electric field of plural reflecting gratings and providing a removal part to a common electrode. CONSTITUTION:A surface acoustic wave resonator consists of comb line form exciting electrodes 12 meshed on one major plane of a piezoelectric substrate 11 made of LiTaO3, LiNbO3, crystal, or ceramics and the reflecting electrodes 13, 14 comprising common electrodes 132, 142 where lots of reflecting gratings 131, 141 and one ends of the reflecting gratings 131, 141 are led and connected mutually respectively at both sides of the exciting electrodes 12 at a prescribed interval. Since other common electrodes of the reflecting electrodes 13, 14 are removed entirely, the flowing of an etching solution through the tooth of the reflecting gratings 131, 141 to be etched is improved, the width of the reflecting graings 131, 141 or the like and an angle of a contact part between the piezoelectric substrate 11 and the reflecting gratings 131, 141 or the like is finished accurately.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a surface acoustic wave resonator, and more particularly to a surface acoustic wave resonator that can reduce the spacing between reflective electrode elements by a predetermined value 1 in the pattern etching process of a resonant electrode. It is related to the structure of

Since surface acoustic wave resonators have the advantage of being able to directly oscillate at a predetermined frequency, they have come to be widely used in, for example, F converters such as VT converters.

Next, an example of a surface acoustic wave resonator will be explained with reference to FIGS. 1 and 2.

That is, the conventional surface acoustic wave resonator is made of LiTa0. .

A comb-shaped excitation electrode (2) interlocks with each other on the main surface of a piezoelectric substrate (1) made of LiNbO3* crystal, ceramics, etc., and a large number of reflection gratings at predetermined intervals on both sides of the excitation electrode (2). (31) (4θ) and a reflective electrode (3) consisting of a pair of common electrodes (3,) (4,) that connect both ends of this reflective grating (3,) (4,) to each other.
(4) Consists of. This surface acoustic wave resonator uses the surface waves of the piezoelectric substrate (1) to reflect only the signal of a predetermined frequency applied between the terminals (2a) and (2b) of the excitation electrode (2) on both sides. Reflection grating (3) of electrode (3) (4)
, ) (4,) and fed back again to the excitation electrode (2), directly oscillating at the frequency of the room. In this case, the common electrode (3,) (4,
) are provided in order to prevent deterioration of the resonance characteristics caused by charging due to the electric field of the respective excitation gratings (31) and (41).

However, such a surface acoustic wave resonator is usually made of a thin substrate (1
) - A thin film of aluminum or the like is deposited on the entire surface by vapor deposition or other means, a photoresist film is provided, and then a predetermined portion of the photoresist film is photocured through a predetermined negative pattern. It is then formed by a so-called photo-etching method in which development, etching, and removal of the resist film are performed. However, in this etching process, the excitation electrode (
2) has one piece that protrudes alternately and interlocks with the other, allowing the etching solution to pass through easily. On the other hand, the reflective electrode (
3) In (4), the reflection grating (31) (41) and the common electrode (32) (4,) are etched.
3, ) (4t) The passage of etching solution between the respective parts becomes difficult. Therefore, the surface acoustic wave resonator requires precision in the width of the reflection gratings (3I) (4,), etc., and the angle of the contact part between the piezoelectric substrate (1) and the reflection gratings (3,) (4,), etc. It is extremely difficult to finish the excitation electrode (2) and the reflection grating (3,) (4,) simultaneously under the same etching conditions, and the resonant frequency of the surface acoustic wave resonator becomes high. As the spacing between (3,) and (4,) becomes narrower, various problems arise due to non-uniform etching.

The present invention was made in consideration of the various points of the conventional surface acoustic wave resonator mentioned above. The object of the present invention is to provide a surface acoustic wave resonator in which the interval between the two surfaces can be set to a predetermined value.

Next, one embodiment of the present invention will be explained with reference to FIG.

That is, the surface acoustic wave resonator of this example is made of LiTa0. .

A large number of reflective gratings are arranged at predetermined intervals on both sides of the interlocking comb-shaped excitation electrodes (1 and 2 excitation electrodes) on the whole surface of the piezoelectric substrate aυ made of L i NbO5 + crystal, ceramics, etc. (131) (141
) and this reflection grating (13+) (14θ) and a common electrode (13□) (142) whose ends are mutually lc-conducting.This surface acoustic wave resonator consists of an excitation electrode α Using surface waves of the piezoelectric substrate αυ, only a signal voltage of a predetermined frequency applied between the terminals (12a) and (12b) is applied to the reflection grating (t
al) (141) and fed back again to the excitation electrode Q, directly oscillating at a predetermined frequency.

By adopting such a structure, the common electrode (13D (1
42) for each reflection grating (13+) (14
1) The conventional type and i can prevent charging due to electric field.
t has a similar effect. In addition, the surface acoustic wave resonator of one embodiment is manufactured by forming a thin film of aluminum or the like on one surface of the piezoelectric substrate αυ by means of one-sided Iζ vapor deposition, and providing a photoresist film. Afterwards, the portions of the photoresist film corresponding to the excitation electrode (13) Q4) are photocured through a predetermined negative pattern, and even if etching is performed, the excitation electrode (1
Similar to the iron, the other common electrode of the reflective electrodes a and σ is completely cut out, so the reflective grating (13
1) (141), it appears that the etching solution flows well between the parts. Therefore, the reflection grating (13,)
(141) etc. and the width of piezoelectric substrate (1) and reflection grating (1).
31) The angles of the contact parts such as (14+) are also precisely finished, and a surface acoustic wave resonator with extremely good characteristics can be obtained even if the excitation electrode α and the reflective electrode A (+41) are etched under the same etching conditions. It became possible.

Next, another embodiment of the present invention will be explained with reference to FIG.

That is, the surface acoustic wave resonator of the other embodiment has an excitation electrode (A) on a piezoelectric substrate Cυ, and a large number of reflection gratings (23 □) (24
1) and this reflection grating (23L) (24θ) A common type m (23t) (24z) having a missing part (23a) (24a) at one or both ends of the reflection grating (23□)
(241) Consisting of reflective electrodes (c) e4) provided alternately so that the etching solution can easily pass between them, and a predetermined frequency applied once between the terminals (22a) and (22b) of the excitation electrodes Q. Only the signal voltage is applied to the reflective electrodes C! on both sides using the surface waves of the substrate Cυ. 3) It is reflected by the reflection gratings (231) (241) of L24) and fed back to the excitation electrode (2) to directly oscillate at a predetermined frequency.

By having such a structure, the common electrode (232) (
Since ztJ is connected through the reflection grating (23θ (241)), an effect similar to that of the conventional one is created to prevent charging due to the electric field of the reflection grating (231) (24t). Therefore, during etching during the manufacturing process, the etching solution can flow well between the reflection gratings (23s) and (24s), allowing the excitation electrode (2) and the reflection electrode (c) (2) to be etched under the same etching conditions. However, it has become possible to obtain a surface acoustic wave resonator with extremely good characteristics.

With the above configuration, the surface acoustic wave resonator of the present invention prevents the plurality of reflective gratings of the reflective electrode from being charged by the electric field, and furthermore, the common electrode is provided with a cutout. Therefore, during etching during the manufacturing process, the passage of etching liquid between the reflection gratings is improved, and the width of the reflection gratings and the angle of the contact area of the piezoelectric substrate (reflection gratings, etc.) can be precisely finished. Therefore, even if the excitation electrode and the reflection electrode are etched under the same etching conditions, a surface acoustic wave resonator with extremely good characteristics can be obtained.

[Brief explanation of the drawing]

1 and 2 are diagrams showing a conventional surface acoustic wave resonator, in which FIG. 1 is a plan view, FIG. 2 is an enlarged plan view of main parts, and FIG.
This figure is a plan view showing one embodiment of the surface acoustic wave resonator of the present invention, and FIG. 4 is a plan view showing another embodiment of the surface acoustic wave resonator of the present invention. 1.11.21...Piezoelectric substrate 2 #12.22...
・Excitation electrode 3.4.13. L4.23.24...Reflecting electrode 31.41, 131114, 23□24. ...
Reflection grating 3□, 421132, 1421232, 242
...Common electrodes 23a, 24a...Deleted portion

Claims (3)

[Claims] (1) A piezoelectric substrate is provided with an excitation electrode on one surface thereof, and reflective electrodes disposed on both sides of the excitation electrode, and each of the reflective electrodes has a plurality of reflective gratings and both ends of the reflective grating. A surface acoustic wave resonator comprising a pair of common electrodes that are electrically connected to each other, the surface acoustic wave resonator having a cutout portion formed in the common electrode. (2) The surface acoustic wave resonator according to claim 1, wherein the deleted portion is the entire one common electrode. (3) The surface acoustic wave resonator according to claim 1, wherein the cutout portions are provided alternately on both common electrodes.