Elastic wave device and method for manufacturing the same

Patent metadata

Field	Value
Publication number	US-9780759-B2
Application number	US-201313920344-A
Country	US
Kind code	B2
Filing date	Jun 18, 2013
Priority date	Dec 24, 2010
Publication date	Oct 3, 2017
Grant date	Oct 3, 2017

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 SiO 2 , and the high-acoustic-impedance layers are made of at least one material selected from the group consisting of W, LiTaO 3 , Al 2 O 3 , AlN, LiNbO 3 , SiN, and ZnO.

First claim

What is claimed is:

1. An elastic wave device 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;
the low-acoustic-impedance layer is made of SiO 2 , and the high-acoustic-impedance layer is made of at least one material selected from the group consisting of W, LiTaO 3 , AI 2 O 3 , AIN, LiNbO 3 , SiN, and ZnO;
the piezoelectric layer is made of LiNbO 3 or LiTaO 3 ;
Euler Angles of the LiNbO 3 of the piezoelectric layer are (0, 20, 0) to (0, 50, 0), (90, 90, 25) to (90, 90, 44), or (0, 95, 0) to (0, 132, 0); or
Euler Angles of the LiTaO 3 of the piezoelectric layer are (0, 12, 0) to (0, 48, 0), (90, 90, 13) to (90, 90, 36), or (0, 100, 0) to (0, 134, 0).

2. 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 LiTaO 3 , AI 2 O 3 , AIN, LiNbO 3 , SiN, and ZnO.

3. 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.

4. The method for manufacturing an elastic wave device according to claim 3 , 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.

5. The method for manufacturing an elastic wave device according to claim 3 , 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.

6. 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.

7. 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.

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

9. The elastic wave device according to claim 8 , wherein the reflectors are made of at least one of Al, Cu, Pt, Au, Ti, Ni, Cr, Ag, W, Mo, Ta.

10. 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.

11. The elastic wave device according to claim 1 , further comprising at least one insulating film made of SiO 2 , SiN, or AI 2 O 3 disposed on the IDT electrode.

12. The method for manufacturing an elastic wave device according to claim 3 , 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.

13. The method for manufacturing an elastic wave device according to claim 3 , further comprising forming reflectors such that the IDS electrode is disposed between the reflectors to define a one-port elastic wave resonator.

14. The method for manufacturing an elastic wave device according to claim 13 , wherein the reflectors are made of at least one of Al, Cu, Pt, Au, Ti, Ni, Cr, Ag, W, Mo, Ta.

15. The method for manufacturing an elastic wave device according to claim 3 , further comprising forming one of a temperature compensation film, a protection film, and a frequency adjustment film on the IDT electrode.

16. The method for manufacturing an elastic wave device according to claim 3 , further comprising forming at least one insulating film made of SiO 2 , SiN, or AI 2 O 3 on the IDT electrode.

17. The elastic wave device according to claim 1 , wherein
the elastic wave device is configured to propagate A 1 , S 0 , or SH 0 mode plate waves;
the A l plate waves are anti-symmetric mode Lamb waves having one node in the thickness direction of the piezoelectric layer;
the S 0 mode plate waves are symmetric mode Lamb waves having no node in the thickness direction of the piezoelectric layer;
the SH 0 mode waves are shear horizontal waves having no node in the thickness direction of the piezoelectric layer; and
the Euler Angles of the LiNbO 3 or LiTaO 3 of the piezoelectric layer fall within a range specified in Table 1:

TABLE 1

Piezoelectric material

Mode
LiNbO 3
LiTaO 3

A 1
(0, 20, 0) to (0, 50, 0)
(0, 12, 0) to (0, 48, 0)

S 0
(90, 90, 25) to (90, 90, 44)
(90, 90, 13) to (90, 90, 36)

SH 0
 (0, 95, 0) to (0, 132, 0)
(0, 100, 0) to (0, 134, 0).

18. The elastic wave device according to claim 17 , wherein the high-impedance layer is made of at least one material selected from the group consisting of LiTaO 3 , AI 2 O 3 , AIN, LiNbO 3 , SiN, and ZnO.

Assignees

• Murata Manufacturing Co

Inventors

• Kimura Tetsuya
• Ogami Takashi
• Daimon Katsuya

Classifications

• Y10T29/42

  Piezoelectric device making · CPC title

• H03H9/02535 Primary

  of surface acoustic wave devices · CPC title

• H03H3/02

  for the manufacture of piezoelectric or electrostrictive resonators or networks (H03H3/08 takes precedence) · CPC title

• H03H9/02574

  of combined substrates, multilayered substrates, piezoelectrical layers on not-piezoelectrical substrate · CPC title

• H03H9/02228 Primary

  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