# US 2014/0152146 A1 · Elastic wave device and method for manufacturing the same

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- Number: US 2014/0152146 A1
- Document ID: US20140152146A1
- Status: Published application
- Kind: A1
- Application number: 13/920,344
- Filed: 2013-06-18
- Published: 2014-06-05
- Earliest claimed: 2010-12-24
- Assignees: Murata Manufacturing Co., Ltd.
- Applicants: Murata Manufacturing Co., Ltd.
- Inventors: Tetsuya KIMURA; Takashi OGAMI; Katsuya DAIMON
- Web page: https://patentgrep.com/patent/US20140152146A1

## CPC

- H03H 9/02535: {of surface acoustic wave devices}
- H03H 3/02: for the manufacture of piezoelectric or electrostrictive resonators or networks (H03H3/08 takes precedence)
- H03H 9/02228: {Guided bulk acoustic wave devices or Lamb wave devices having interdigital transducers situated in parallel planes on either side of a piezoelectric layer}
- H03H 9/02574: {of combined substrates, multilayered substrates, piezoelectrical layers on not-piezoelectrical substrate}
- H10N 30/8542: {Alkali metal based oxides, e.g. lithium, sodium or potassium niobates}
- Y10T 29/42: Piezoelectric device making
- H03H: IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS (waveguides, resonators, lines or other devices of the waveguide type H01P)
- H10N: ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- Y10T: TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION

## Abstract

An elastic wave device propagating plate waves includes a stack of an acoustic reflection layer, a piezoelectric layer, and IDT electrode on a supporting substrate. The piezoelectric layer is thinner than a period of fingers of the IDT electrode. The acoustic reflection layer includes low-acoustic-impedance layers and high-acoustic-impedance layers. The low-acoustic-impedance layers are made of SiO2, and the high-acoustic-impedance layers are made of at least one material selected from the group consisting of W, LiTaO3, Al2O3, AlN, LiNbO3, SiN, and ZnO.

## Claims

### Claim 1

An elastic wave device propagating plate waves, comprising:
a supporting substrate;
an acoustic reflection layer on the supporting substrate;
a piezoelectric layer on the acoustic reflection layer; and
an IDT electrode on an upper or lower surface of the piezoelectric layer, the piezoelectric layer being thinner than a period of fingers of the IDT electrode; wherein
the acoustic reflection layer includes a low-acoustic-impedance layer and a high-acoustic-impedance layer having a higher acoustic impedance than an acoustic impedance of the low-acoustic-impedance layer; and
the low-acoustic-impedance layer is made of SiO2, and the high-acoustic-impedance layer is made of at least one material selected from the group consisting of W, LiTaO3, Al2O3, AlN, LiNbO3, SiN, and ZnO.

### Claim 2 (depends on 1)

The elastic wave device according to claim 1, wherein the high-impedance layer is made of at least one material selected from the group consisting of LiTaO3, Al2O3, AlN, LiNbO3, SiN, and ZnO.

### Claim 3 (depends on 1)

The elastic wave device according to claim 1, wherein the piezoelectric layer is made of at least one material selected from the group consisting of LiTaO3, LiNbO3, ZnO, AlN, and quartz.

### Claim 4 (depends on 1)

The elastic wave device according to claim 1, wherein the piezoelectric layer is made of LiNbO3 or LiTaO3, and Euler Angles of the LiNbO3 or LiTaO3 fall within a range specified in Table 1 when an A1, S0, or SH0 mode is used:
TABLE 1
Piezoelectric material
Mode
LiNbO3
LiTaO3
A1
(0, 20, 0) to (0, 50, 0)
(0, 12, 0) to (0, 48, 0)
S0
(90, 90, 25) to (90, 90, 44)
(90, 90, 13) to (90, 90, 36)
SH0
(0, 95, 0) to (0, 132, 0)
(0, 100, 0) to (0, 134, 0)

### Claim 5 (depends on 1)

A method for manufacturing the elastic wave device according to claim 1, comprising:
forming the acoustic reflection layer on the supporting substrate;
putting the piezoelectric layer on the acoustic reflection layer; and
forming the IDT electrode on the piezoelectric layer.

### Claim 6 (depends on 5)

The method for manufacturing an elastic wave device according to claim 5, wherein the piezoelectric layer is formed on the acoustic reflection layer by bonding a piezoelectric layer onto the acoustic layer and making the piezoelectric layer thinner.

### Claim 7 (depends on 5)

The method for manufacturing an elastic wave device according to claim 5, wherein the piezoelectric layer is put on the acoustic reflection layer by producing the piezoelectric layer in a form of a film on the acoustic reflection layer.

### Claim 8 (depends on 1)

A method for manufacturing the elastic wave device according to claim 1, comprising:
forming the acoustic reflection layer on a piezoelectric body thicker than the piezoelectric layer;
bonding the supporting substrate to a surface of the acoustic reflection layer opposite to a surface on which the piezoelectric body is disposed;
making the piezoelectric body thinner; and
forming the IDT electrode on the piezoelectric layer.

### Claim 9 (depends on 1)

The elastic wave device according to claim 1, further comprising a plurality of the high-acoustic-impedance layers and a plurality of the low-acoustic-impedance layers alternatingly stacked on each other in a stacking direction.

### Claim 10 (depends on 1)

The elastic wave device according to claim 1, further comprising reflectors arranged such that the IDS electrode is disposed between the reflectors to define a one-port elastic wave resonator.

### Claim 11 (depends on 10)

The elastic wave device according to claim 10, wherein the reflectors are made of at least one of Al, Cu, Pt, Au, Ti, Ni, Cr, Ag, W, Mo, Ta.

### Claim 12 (depends on 1)

The elastic wave device according to claim 1, further comprising one of a temperature compensation film, a protection film, and a frequency adjustment film disposed on the IDT electrode.

### Claim 13 (depends on 1)

The elastic wave device according to claim 1, further comprising at least one insulating film made of SiO2, SiN, or Al2O3 disposed on the IDT electrode.

### Claim 14 (depends on 5)

The method for manufacturing an elastic wave device according to claim 5, further comprising forming a plurality of the high-acoustic-impedance layers and a plurality of the low-acoustic-impedance layers alternatingly stacked on each other in a stacking direction.

### Claim 15 (depends on 5)

The method for manufacturing an elastic wave device according to claim 5, further comprising forming reflectors such that the IDS electrode is disposed between the reflectors to define a one-port elastic wave resonator.

### Claim 16 (depends on 15)

The method for manufacturing an elastic wave device according to claim 15, wherein the reflectors are made of at least one of Al, Cu, Pt, Au, Ti, Ni, Cr, Ag, W, Mo, Ta.

### Claim 17 (depends on 5)

The method for manufacturing an elastic wave device according to claim 5, further comprising forming one of a temperature compensation film, a protection film, and a frequency adjustment film on the IDT electrode.

### Claim 18 (depends on 5)

The method for manufacturing an elastic wave device according to claim 5, further comprising forming at least one insulating film made of SiO2, SiN, or Al2O3 on the IDT electrode.