ELASTIC WAVE DEVICE AND METHOD FOR MANUFACTURING THE SAME

• US 20130285768A1
• Filed: 06/18/2013
• Published: 10/31/2013
• Est. Priority Date: 12/24/2010
• Status: Active Grant

• Current Assignee: Murata Manufacturing Co Limited
• Original Assignee: Murata Manufacturing Co Limited
• Inventors: KANDO, Hajime, WATANABE, Munehisa, IWAMOTO, Hideki, KIDO, Syunsuke
• Granted Patent: US 9,431,996 B2
• Time in Patent Office: Days
• US Class Current: 333/193
• CPC Class Codes: H03H 2003/023 the resonators or networks being of the membrane type
• CPC Class Codes: H03H 2003/027 the resonators or networks being of the microelectro-mechanical [MEMS] type
• CPC Class Codes: H03H 3/02 for the manufacture of piezoelectric or electrostrictive resonators or networks H03H3/08 takes precedence
• CPC Class Codes: H03H 3/04 for obtaining desired frequency or temperature coefficient
• CPC Class Codes: H03H 3/08 for the manufacture of resonators or networks using surface acoustic waves
• CPC Class Codes: H03H 3/10 for obtaining desired frequency or temperature coefficient
• CPC Class Codes: H03H 9/0222 of interface-acoustic, boundary, pseudo-acoustic or Stonely wave devices
• CPC Class Codes: H03H 9/02574 of combined substrates, multilayered substrates, piezoelectrical layers on not-piezoelectrical substrate
• CPC Class Codes: H03H 9/02834 of temperature influence cut angles H03H9/02543
• CPC Class Codes: H03H 9/54 comprising resonators of piezoelectric or electrostrictive material H03H9/64 takes precedence
• CPC Class Codes: H10N 30/01 Manufacture or treatment
• CPC Class Codes: H10N 30/80 Constructional details
• CPC Class Codes: H10N 30/85 Piezoelectric or electrostrictive active materials
• CPC Class Codes: H10N 30/87 Electrodes or interconnections, e.g. leads or terminals
• CPC Class Codes: H10N 30/877 Conductive materials in general H01B1/00
• CPC Class Codes: Y10T 29/42 Piezoelectric device making
• CPC Class Codes: Y10T 29/49005 Acoustic transducer
• CPC Class Codes: Y10T 29/49155 Manufacturing circuit on or in base

Abstract

An elastic wave device includes a supporting substrate, a high-acoustic-velocity film stacked on the supporting substrate and in which an acoustic velocity of a bulk wave propagating therein is higher than an acoustic velocity of an elastic wave propagating in a piezoelectric film, a low-acoustic-velocity film stacked on the high-acoustic-velocity film and in which an acoustic velocity of a bulk wave propagating therein is lower than an acoustic velocity of a bulk wave propagating in the piezoelectric film, the piezoelectric film is stacked on the low-acoustic-velocity film, and an IDT electrode stacked on a surface of the piezoelectric film.

Claims

1. An elastic wave device including a piezoelectric film, the elastic wave device comprising:

a high-acoustic-velocity supporting substrate in which an acoustic velocity of a bulk wave propagating therein is higher than an acoustic velocity of an elastic wave propagating in the piezoelectric film;

a low-acoustic-velocity film stacked on the high-acoustic-velocity supporting substrate, in which an acoustic velocity of a bulk wave propagating therein is lower than an acoustic velocity of a bulk wave propagating in the piezoelectric film;

the piezoelectric film stacked on the low-acoustic-velocity film; and

an IDT electrode disposed on a surface of the piezoelectric film.

2. The elastic wave device according to claim 1, wherein a portion of energy of an elastic wave propagating in the piezoelectric film is distributed into the low-acoustic-velocity film and the high-acoustic-velocity supporting substrate.

5. The elastic wave device according to claim 1, wherein the low-acoustic-velocity film is composed of silicon oxide or a film containing as a major component silicon oxide.

6. The elastic wave device according to claim 1, wherein a thickness of the piezoelectric film is about 1.5λ

or less, where λ

is a wavelength of an elastic wave determined by an electrode period of the IDT electrode.

7. The elastic wave device according to of claim 1, wherein a thickness of the piezoelectric film is in a range of about 0.05λ

to about 0.5λ

, where λ

is a wavelength of an elastic wave determined by an electrode period of the IDT electrode.

8. The elastic wave device according to claim 1, wherein a thickness of the low-acoustic-velocity film is about 2λ

or less, where λ

is a wavelength of an elastic wave determined by an electrode period of the IDT electrode.

9. The elastic wave device according to claim 1, wherein the piezoelectric film is composed of single-crystal lithium tantalate with Euler angles (0±

5°

, θ

, ψ

), and the Euler angles (0±

5°

, θ

, ψ

) are located in any one of a plurality of regions R1 shown in FIG. 17.

10. The elastic wave device according to claim 9, wherein the Euler angles (0±

5°

, θ

, ψ

) of the piezoelectric film are located in any one of a plurality of regions R2 shown in FIG. 18.

11. The elastic wave device according to claim 1, wherein a coefficient of linear expansion of the supporting substrate is lower than that of the piezoelectric film.

12. The elastic wave device according to claim 1, wherein a specific acoustic impedance of the low-acoustic-velocity film is lower than that of the piezoelectric film.

13. The elastic wave device according to claim 1, wherein a dielectric film is disposed on the piezoelectric film and the IDT electrode, and a surface acoustic wave propagates in the piezoelectric film.

14. The elastic wave device according to claim 1, wherein a dielectric film is disposed on the piezoelectric film and the IDT electrode, and a boundary acoustic wave propagates along a boundary between the piezoelectric film and the dielectric film.

15. The elastic wave device according to claim 1, wherein at least one of an adhesion layer, an underlying film, a low-acoustic-velocity layer, and a high-acoustic-velocity layer is disposed in at least one of boundaries between the piezoelectric film, the low-acoustic-velocity film, the high-acoustic-velocity film, and the supporting substrate.

3. An elastic wave device including a piezoelectric film, the elastic wave device comprising:

a supporting substrate;

a high-acoustic-velocity film disposed on the supporting substrate, in which an acoustic velocity of a bulk wave propagating therein is higher than an acoustic velocity of an elastic wave propagating in the piezoelectric film;

a low-acoustic-velocity film stacked on the high-acoustic-velocity film, in which an acoustic velocity of a bulk wave propagating therein is lower than an acoustic velocity of a bulk wave propagating in the piezoelectric film;

the piezoelectric film stacked on the low-acoustic-velocity film; and

an IDT electrode disposed on a surface of the piezoelectric film.

4. The elastic wave device according to claim 3, wherein a portion of energy of an elastic wave propagating in the piezoelectric film is distributed into the low-acoustic-velocity film and the high-acoustic-velocity film.

16. A method for manufacturing an elastic wave device comprising:

a step of preparing a supporting substrate;

a step of forming a high-acoustic-velocity film, in which an acoustic velocity of a bulk wave propagating therein is higher than an acoustic velocity of an elastic wave propagating in a piezoelectric, on the supporting substrate;

a step of forming a low-acoustic-velocity film, in which an acoustic velocity of a bulk wave propagating therein is lower than an acoustic velocity of a bulk wave propagating in a piezoelectric, on the high-acoustic-velocity film;

a step of forming a piezoelectric layer on the low-acoustic-velocity film; and

a step of forming an IDT electrode on a surface of the piezoelectric layer.

17. The method for manufacturing an elastic wave device according to claim 16, wherein the steps of forming the high-acoustic-velocity film, the low-acoustic-velocity film, and the piezoelectric layer on the supporting substrate include:

(a) a step of performing ion implantation from a surface of a piezoelectric substrate having a larger thickness than that of the piezoelectric layer;

(b) a step of forming the low-acoustic-velocity film on the surface of the piezoelectric substrate on which the ion implantation has been performed;

(c) a step of forming the high-acoustic-velocity film on a surface of the low-acoustic-velocity film, opposite to the piezoelectric substrate side of the low-acoustic-velocity film;

(d) a step of bonding the supporting substrate to a surface of the high-acoustic-velocity film, opposite to the surface on which the low-acoustic-velocity film is stacked; and

(e) a step of, while heating the piezoelectric substrate, separating a piezoelectric film, at a high concentration ion-implanted region of the piezoelectric substrate in which the implanted ion concentration is highest, from a remaining portion of the piezoelectric substrate such that the piezoelectric film remains on a low-acoustic-velocity film side.

18. The method for manufacturing an elastic wave device according to claim 17, further comprising a step of, after separating the remaining portion of the piezoelectric substrate, heating the piezoelectric film disposed on the low-acoustic-velocity film to recover piezoelectricity.

19. The method for manufacturing an elastic wave device according to claim 16, further comprising a step of, prior to bonding the supporting substrate, performing mirror finishing on the surface of the high-acoustic-velocity film, opposite to the low-acoustic-velocity film side of the high-acoustic-velocity film.