Elastic wave device

Patent metadata

Field	Value
Publication number	US-2016352304-A1
Application number	US-201615233016-A
Country	US
Kind code	A1
Filing date	Aug 10, 2016
Priority date	Mar 14, 2014
Publication date	Dec 1, 2016
Grant date	—

Abstract

An elastic wave device includes a first IDT electrode on a first main surface of a LiNbO 3 substrate, and a second IDT electrode on a second main surface thereof. The application of alternating voltages with reversed phases to each other to the first and second IDT electrodes excites plate waves in which SH waves in a high order mode predominate. The elastic wave device uses the plate waves in the high order mode in which the SH waves predominate.

First claim

What is claimed is:

1 . An elastic wave device comprising:
a LiNbO 3 substrate including a first main surface and a second main surface on an opposite side of the first main surface; a first IDT electrode provided on the first main surface of the LiNbO 3 substrate; and a second IDT electrode provided on the second main surface of the LiNbO 3 substrate so as to be opposed to the first IDT electrode across the LiNbO 3 substrate; wherein a plate wave in a high order mode in which an SH wave predominates is excited in the LiNbO 3 substrate as an elastic wave in response to alternating voltages of reversed phases to each other being applied to the first IDT electrode and the second IDT electrode.

2 . The elastic wave device according to claim 1 , wherein in Euler angles (Φ, θ, ψ) of the LiNbO 3 substrate, Φ=0±5°, ψ=0±5°, and θ is about 72° or more and about 97° or less.

3 . The elastic wave device according to claim 1 , wherein a thickness of the LiNbO 3 substrate is about 0.05λ or more and about 0.52λ or less, and λ represents a wavelength determined by a pitch of electrode fingers of the first and second IDT electrodes.

4 . The elastic wave device according to claim 1 , wherein a duty of each of the first and second IDT electrodes is about 0.15 or more and about 0.77 or less.

5 . The elastic wave device according to claim 1 , wherein the first and second IDT electrodes each include an electrode film made of Al or an alloy having Al as a main constituent, and a film thickness of each of the electrode films is about 0.035λ or less, and λ represents a wavelength determined by a pitch of electrode fingers of the first and second IDT electrodes.

6 . The elastic wave device according to claim 1 , wherein the first and second IDT electrodes each include a multilayer structure including an Al film and another metal film.

7 . The elastic wave device according to claim 1 , wherein a fractional bandwidth of the elastic wave device is 17% or more.

8 . The elastic wave device according to claim 1 , wherein a fractional bandwidth of the elastic wave device is 20% or more.

9 . An elastic wave device comprising:
a LiNbO 3 substrate including a first main surface and a second main surface on an opposite side of the first main surface; an IDT electrode provided on the first main surface of the LiNbO 3 substrate; and an electrode film provided on the second main surface of the LiNbO 3 substrate so as to occupy an entire area enclosed with outer edges of the IDT electrode in a plan view from a side of the first main surface; wherein a plate wave in a high order mode in which an SH wave predominates is excited in the LiNbO 3 substrate as an elastic wave in response to an alternating voltage being applied to the IDT electrode.

10 . The elastic wave device according to claim 9 , wherein in Euler angles (Φ, θ, ψ) of the LiNbO 3 substrate, Φ=0±5°, ψ=0±5°, and θ is about 68° or more and about 96° or less.

11 . The elastic wave device according to claim 9 , wherein a thickness of the LiNbO 3 substrate is about 0.05λ or more and about 0.18λ or less, and λ represents a wavelength determined by a pitch of electrode fingers of the IDT electrode.

12 . The elastic wave device according to claim 9 , wherein a duty of the IDT electrode is about 0.1 or more and about 0.68 or less.

13 . The elastic wave device according to claim 9 , wherein the IDT electrode includes an electrode film made of Al or an alloy having Al as a main constituent, and a film thickness of the electrode film is about 0.022λ or less, and λ represents a wavelength determined by a pitch of electrode fingers of the IDT electrode.

14 . The elastic wave device according to claim 9 , wherein the electrode film defines a floating electrode.

15 . The elastic wave device according to claim 9 , wherein the first and second IDT electrodes each include a multilayer structure including an Al film and another metal film.

16 . The elastic wave device according to claim 9 , wherein the electrode film is made of one of Ti, Au, Ni, Cr, and a conductive compound including one of ZnO and ITO.

17 . The elastic wave device according to claim 9 , wherein a fractional bandwidth of the elastic wave device is 17% or more.

18 . The elastic wave device according to claim 9 , wherein a fractional bandwidth of the elastic wave device is 20% or more.

19 . The elastic wave device according to claim 9 , wherein a thickness of the LiNbO 3 substrate is about 0.07λ or more and about 0.16λ or less, and λ represents a wavelength determined by a pitch of electrode fingers of the IDT electrode.

Assignees

• Murata Manufacturing Co

Inventors

• Kadota Michio
• Kimura Tetsuya
• Hashimoto Kenya
• Tanaka Shuji

Classifications

• H03H9/14538 Primary

  Formation · CPC title

• H03H9/02559

  of lithium niobate or lithium-tantalate substrates · CPC title

• H03H9/02228

  Guided bulk acoustic wave devices or Lamb wave devices having interdigital transducers situated in parallel planes on either side of a piezoelectric layer · CPC title