US-20260128727-A1 - ACOUSTIC WAVE DEVICE

US20260128727A1US 20260128727 A1US20260128727 A1US 20260128727A1US-20260128727-A1

Abstract

An acoustic wave device includes a support including a support substrate with a thickness direction in a first direction, a piezoelectric layer on the support, and resonators each including a functional electrode provided to the piezoelectric layer. The support is provided with a hollow portion at a position overlapping at least a portion of each of the resonators in plan view in the first direction. The resonators include a first resonator and a second resonator adjacent to each other. A through hole reaching the hollow portion is provided to the piezoelectric layer between the first resonator and the second resonator.

Inventors

Tetsuya Kimura
Hisashi Yamazaki
Katsumi Suzuki

Assignees

MURATA MANUFACTURING CO., LTD.

Dates

Publication Date: 20260507
Application Date: 20251230

Claims (20)

1 . An acoustic wave device comprising: a support including a support substrate with a thickness direction in a first direction; a piezoelectric layer provided on the support; and a plurality of resonators each including a functional electrode provided to the piezoelectric layer; wherein the support is provided with a hollow portion at a position overlapping at least a portion of each of the plurality of resonators in plan view in the first direction; the plurality of resonators include a first resonator and a second resonator adjacent to each other; each of the functional electrodes includes one or more first electrode fingers and one or more second electrode fingers that overlap one another when viewed in a third direction; a through hole is provided to the piezoelectric layer between the first resonator and the second resonator; and the through hole is closer to the second resonator than to the first resonator in the third direction.
2 . The acoustic wave device according to claim 1 , wherein the first resonator and the second resonator are provided on the piezoelectric layer.
3 . The acoustic wave device according to claim 1 , wherein the through hole includes a first through hole and a second through hole provided between the first resonator and the second resonator.
4 . The acoustic wave device according to claim 3 , wherein an opening area of the first through hole is different from an opening area of the second through hole in plan view in the first direction.
5 . The acoustic wave device according to claim 3 , wherein the first through hole and the second through hole are provided at positions not overlapping each other when viewed in a direction in which the first resonator and the second resonator are adjacent to each other.
6 . The acoustic wave device according to claim 3 , wherein the first through hole and the second through hole are provided at positions overlapping each other when viewed in a direction in which the first resonator and the second resonator are adjacent to each other.
7 . The acoustic wave device according to claim 1 , wherein the hollow portion includes a first hollow portion provided at a position overlapping at least a portion of the first resonator in plan view in the first direction and a second hollow portion provided at a position overlapping at least a portion of the second resonator in plan view in the first direction; and the first hollow portion and the second hollow portion are partitioned by a portion of the support.
8 . The acoustic wave device according to claim 1 , wherein the hollow portion is a single hollow portion provided at a position overlapping at least a portion of the first resonator and of the second resonator in plan view in the first direction.
9 . The acoustic wave device according to claim 1 , wherein a total number of the through holes is an even number.
10 . The acoustic wave device according to claim 9 , wherein the number of the through holes provided on one side of an imaginary partition line partitioning between the first resonator and the second resonator is equal to the number of the through holes provided on another side of the imaginary partition line.
11 . The acoustic wave device according to claim 9 , wherein the hollow portion includes a plurality of hollow portions provided between the support and the piezoelectric layer at positions overlapping at least portions of the respective resonators in plan view in the first direction; the acoustic wave device further includes an extended passage provided to the support and establishing communication between at least two hollow portions out of the plurality of hollow portions; the extended passage is provided at a position not overlapping the plurality of hollow portions in plan view in the first direction; and the through holes include a through hole that extends through the piezoelectric layer at a position overlapping the extended passage in plan view in the first direction.
12 . The acoustic wave device according to claim 11 , wherein the extended passage includes a channel that connects a plurality of the hollow portions provided at positions overlapping the plurality of resonators being adjacent to each other in plan view in the first direction.
13 . The acoustic wave device according to claim 1 , wherein each of the functional electrodes further includes a first busbar, a second busbar opposed to the first busbar, the one or more first electrode fingers provided to the first busbar and extending toward the second busbar, and the one or more second electrode fingers provided to the second busbar and extending toward the first busbar; the one or more first electrode fingers and the one or more second electrode fingers extend in a second direction intersecting with the first direction, and overlap one another when viewed in the third direction being orthogonal to the second direction; and the through hole is located between a first imaginary line passing through a tip end or tip ends of the one or more first electrode fingers and a second imaginary line passing through a tip end or tip ends of the one or more second electrode fingers in plan view in the first direction.
14 . The acoustic wave device according to claim 13 , wherein a third through hole reaching the hollow portion is provided to the first resonator on a side opposite to a side being adjacent to the second resonator; a fourth through hole reaching the hollow portion is provided to the second resonator on a side opposite to a side being adjacent to the first resonator; and the third through hole and the fourth through hole are provided between the first imaginary line and the second imaginary line in plan view in the first direction.
15 . The acoustic wave device according to claim 13 , wherein a thickness of the piezoelectric layer is less than or equal to 2p in a case where p is a center-to-center distance between a first electrode finger and a second electrode finger being adjacent to each other out of the one or more first electrode fingers and the one or more second electrode fingers.
16 . The acoustic wave device according to claim 1 , wherein the acoustic wave device is configured to be capable of using a bulk wave in a thickness-shear mode.
17 . The acoustic wave device according to claim 13 , wherein d/p is less than or equal to about 0.5 in a case where d is a film thickness of the piezoelectric layer and p is a center-to-center distance between electrode fingers being adjacent to each other out of the one or more first electrode fingers and the one or more second electrode fingers.
18 . The acoustic wave device according to claim 17 , wherein d/p is less than or equal to about 0.24.
19 . The acoustic wave device according to claim 1 , wherein the functional electrodes each include the one or more first electrode fingers extending in a second direction intersecting with the first direction and the one or more second electrode fingers extending in the second direction and opposed to any of the one or more first electrode fingers in the third direction being orthogonal to the second direction, and MR≤about 1.75(d/p)+0.075 is satisfied when a region where the one or more first electrode fingers and the adjacent one or more second electrode fingers overlap each other when viewed in a direction in which the electrode fingers are opposed to each other is an excitation region, and MR is a metallization ratio of the one or more first electrode fingers and the one or more second electrode fingers relative to the excitation region.
20 . The acoustic wave device according to claim 1 , wherein the acoustic wave device is structured to generate a plate wave.

Description

CROSS REFERENCE TO RELATED APPLICATIONS This application claims the benefit of priority to Provisional Application Nos. 63/168,297 and 63/168,329 filed on Mar. 31, 2021, and is a Continuation Application of PCT Application No. PCT/JP2022/014500 filed on Mar. 25, 2022. The entire contents of each application are hereby incorporated herein by reference. BACKGROUND OF THE INVENTION 1. Field of the Invention The present disclosure relates to an acoustic wave device including a piezoelectric layer. 2. Description of the Related Art For example, International Publication No. 2016/147687 discloses an acoustic wave device that includes a support substrate, a thin film, a piezoelectric substrate, and an IDT electrode. An upper surface of the support substrate is provided with a recess. The thin film is disposed on the support substrate. The piezoelectric substrate includes a first principal surface and a second principal surface opposed to the first principal surface, and the first principal surface side is disposed on the thin film. The IDT electrode is provided on the second principal surface of the piezoelectric substrate. A hollow surrounded by the support substrate and at least the thin film out of the thin film and the piezoelectric substrate is formed. The thin film is provided in a region on the first principal surface of the piezoelectric substrate, which is a region joined to the support substrate with the thin film interposed therebetween, and in a region of at least a portion of a region above the hollow. SUMMARY OF THE INVENTION In recent years, there has been a demand for an acoustic wave device which is capable of reducing or preventing deterioration of characteristics. Preferred embodiments of the present invention provide acoustic wave devices each capable of reducing or preventing deterioration of characteristics. An acoustic wave device according to an aspect of a preferred embodiment of the present invention includes a support including a support substrate with a thickness direction in a first direction, a piezoelectric layer provided on the support, and a plurality of resonators each including a functional electrode provided to the piezoelectric layer. The support is provided with a hollow portion at a position overlapping at least a portion of each of the plurality of resonators in plan view in the first direction. The plurality of resonators include a first resonator and a second resonator adjacent to each other. A through hole reaching the hollow portion is provided to the piezoelectric layer between the first resonator and the second resonator. According to preferred embodiments of the present disclosure, it is possible to provide acoustic wave devices each capable of reducing or preventing deterioration of characteristics. The above and other elements, features, steps, characteristics and advantages of the present invention will become more apparent from the following detailed description of the preferred embodiments with reference to the attached drawings. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1A is a schematic perspective view showing the appearance of an acoustic wave device according to first and second aspects of preferred embodiments of the present invention. FIG. 1B is a plan view showing an electrode structure on a piezoelectric layer. FIG. 2 is a cross-sectional view of a portion along line A-A in FIG. 1A. FIG. 3A is a schematic elevational cross-sectional view for explaining a Lamb wave that propagates in a piezoelectric film of an acoustic wave device of the related art. FIG. 3B is a schematic elevational cross-sectional view for explaining a wave in an acoustic wave device according to a preferred embodiment of the present invention. FIG. 4 is a schematic diagram showing a bulk wave in a case where a voltage which renders a voltage at a second electrode higher than that at a first electrode is applied between the first electrode and the second electrode. FIG. 5 is a graph showing resonance characteristics of an acoustic wave device according to a first preferred embodiment of the present invention. FIG. 6 is a graph showing a relation between d/2p and a fractional bandwidth as a resonator of the acoustic wave device. FIG. 7 is a plan view of another acoustic wave device according to the first preferred embodiment of the present invention. FIG. 8 is a reference graph showing an example of resonance characteristics of the acoustic wave device. FIG. 9 is a graph showing a relation between a fractional bandwidth in a case of forming numerous acoustic wave resonators and an amount of phase rotation of impedance of spurious normalized at 180 degrees as a magnitude of the spurious. FIG. 10 is a graph showing a relation among d/2p, a metallization ratio MR, and the fractional bandwidth. FIG. 11 is a graph showing a map of the fractional bandwidths relative to Euler angles (0°, θ, ψ) of LiNbO3 when d/p is infinitesimally brought close to 0. FIG. 12 is a partially cutaway perspective vie