Acoustic wave device, filter, and multiplexer

Patent metadata

Field	Value
Publication number	US-10700662-B2
Application number	US-201816198284-A
Country	US
Kind code	B2
Filing date	Nov 21, 2018
Priority date	Dec 28, 2017
Publication date	Jun 30, 2020
Grant date	Jun 30, 2020

Abstract

An acoustic wave device includes: a piezoelectric substrate; and a pair of comb-shaped electrodes that is located on the piezoelectric substrate, includes a metal film, and excites a surface acoustic wave, the metal film being mainly composed of a metal having a melting point equal to or higher than a melting point of Pt, the metal film having a first region in which a crystal grain has a columnar shape and a second region that is located on and/or under the first region in a stacking direction and has less crystallinity than the first region or has an amorphous structure.

First claim

What is claimed is:

1. An acoustic wave device comprising:
a piezoelectric substrate; and
a pair of comb-shaped electrodes that is located on the piezoelectric substrate, includes a metal film, and excites a surface acoustic wave, the metal film being mainly composed of a metal having a melting point equal to or higher than a melting point of Pt, the metal film having a first region in which a crystal grain has a columnar shape and a second region that is located on and/or under the first region in a stacking direction and has less crystallinity than the first region or has an amorphous structure.

2. The acoustic wave device according to claim 1 , wherein
when a cross-section is observed with an electron microscope, a ratio of a number of crystal grains having a columnar shape to a number of crystal grains in the first region is 50% or greater.

3. The acoustic wave device according to claim 1 , wherein
the second region is located between the first region and the piezoelectric substrate.

4. The acoustic wave device according to claim 3 , wherein
the second region is in contact with the piezoelectric substrate.

5. The acoustic wave device according to claim 3 , further comprising
an intermediate film that is located between the piezoelectric substrate and the second region, and is mainly composed of a metal having a lower density than Pt.

6. The acoustic wave device according to claim 1 , wherein
the second region has an amorphous structure.

7. The acoustic wave device according to claim 1 , wherein
a thickness of the first region in the stacking direction is greater than a thickness of the second region in the stacking direction.

8. The acoustic wave device according to claim 7 , wherein
the thickness of the second region in the stacking direction is equal to or greater than one-fifth of the thickness of the first region in the stacking direction.

9. The acoustic wave device according to claim 7 , wherein
the thickness of the second region in the stacking direction is equal to or greater than one-tenth of the thickness of the first region in the stacking direction.

10. The acoustic wave device according to claim 1 , wherein
the metal film is mainly composed of at least one of Mo, Ir, Pt, Re, Rh, Ru, Ta, and W.

11. The acoustic wave device according to claim 1 , wherein
the metal film is a Mo film.

12. A filter comprising:
an acoustic wave device including:
a piezoelectric substrate, and
a pair of comb-shaped electrodes that is located on the piezoelectric substrate, includes a metal film, and excites a surface acoustic wave, the metal film being mainly composed of a metal having a melting point equal to or higher than a melting point of Pt, the metal film having a first region in which a crystal grain has a columnar shape and a second region that is located on and/or under the first region in a stacking direction and has less crystallinity than the first region or has an amorphous structure.

13. A multiplexer comprising:
a filter including an acoustic wave device, wherein
the acoustic wave device includes:
a piezoelectric substrate, and
a pair of comb-shaped electrodes that is located on the piezoelectric substrate, includes a metal film, and excites a surface acoustic wave, the metal film being mainly composed of a metal having a melting point equal to or higher than a melting point of Pt, the metal film having a first region in which a crystal grain has a columnar shape and a second region that is located on and/or under the first region in a stacking direction and has less crystallinity than the first region or has an amorphous structure.

Assignees

• Taiyo Yuden Kk

Inventors

• Miura Shinpei
• Imasu Satoshi
• Matsuda Takashi
• Iwaki Masafumi

Classifications

• H10N30/877

  Conductive materials · CPC title

• H03H9/02929

  of ageing changes of characteristics, e.g. electro-acousto-migration · CPC title

• H03H9/02826

  of adherence · CPC title

• H03H9/6436

  having one acoustic track only · CPC title

• H03H9/14541 Primary

  Multilayer finger or busbar electrode · CPC title