Piezoelectric resonator, filter and electronic component using the same

• US 20050023932A1
• Filed: 07/29/2004
• Published: 02/03/2005
• Est. Priority Date: 07/31/2003
• Status: Active Grant

• Current Assignee: Snaptrack Incorporated (Qualcomm, Inc.)
• Original Assignee: TDK Corporation
• Inventors: Inoue, Kenji, Saitou, Hisatoshi
• Granted Patent: US 7,348,714 B2
• Time in Patent Office: Days
• US Class Current: 310/327
• CPC Class Codes: H03H 9/02102 of temperature influence cutting angles H03H9/02015
• CPC Class Codes: H03H 9/174 Membranes
• CPC Class Codes: H03H 9/175 Acoustic mirrors

Abstract

A piezoelectric resonator includes; a lower electrode 24 formed on a substrate 11; a piezoelectric film 23 formed on the lower electrode 24; an upper electrode 25 formed on the piezoelectric film 23 and obtaining, in collaboration with the lower electrode 24, a signal having a predetermined resonance frequency by a propagation of a bulk acoustic wave inside the piezoelectric film 23; and an acoustic multilayer reflective film 28 including an SiO₂ film 28a having a predetermined acoustic impedance and an AIN film 28b having an acoustic impedance higher than the SiO₂ film 28a, and reflecting the bulk acoustic wave, the SiO₂ film 28a and the AIN film 28b being alternately stacked on the upper electrode 25, and the SiO₂ film 28a being in contact with the upper electrode 25.

Claims

1. A piezoelectric resonator comprising:

a first electrode film formed on a substrate;

a piezoelectric film formed on the first electrode film;

a second electrode film formed on the piezoelectric film and obtaining, in collaboration with the first electrode film, a signal having a predetermined resonance frequency by a propagation of a bulk acoustic wave inside the piezoelectric film; and

an acoustic multilayer reflective film including a first acoustic film having a predetermined acoustic impedance and a second acoustic film having an acoustic impedance higher than the first acoustic film, and reflecting the bulk acoustic wave,

the first acoustic film and the second acoustic film being alternately stacked on the second electrode film, and the first acoustic film being in contact with the second electrode film.

2. The piezoelectric resonator as claimed in claim 1, wherein the first acoustic film is made of SiO₂.

3. The piezoelectric resonator as claimed in claim 1, wherein the second acoustic film is made of AIN or ZnO.

4. The piezoelectric resonator as claimed in claim 1, wherein assuming that the wavelength of the bulk acoustic wave is λ

, the thickness of the first acoustic film is 0.125 λ

or more.

5. The piezoelectric resonator as claimed in claim 1, wherein assuming that the wavelength of the bulk acoustic wave is λ

, the thickness of the first acoustic film falls within the range of 0.18 λ

to 0.225 λ

, and that of the second acoustic film falls within the range of 0.05 λ

to 0.225 λ

.

6. The piezoelectric resonator as claimed in claim 1, wherein assuming that the wavelength of the bulk acoustic wave is λ

, the thickness of the first acoustic film falls within the range of 0.275 λ

to 0.34 λ

, and that of the second acoustic film falls within the range of 0.05 λ

to 0.225 λ

.

7. The piezoelectric resonator as claimed in claim 1, wherein assuming that the wavelength of the bulk acoustic wave is λ

, the thickness of the first acoustic film falls within the range of 0.18 λ

to 0.225 λ

, and that of the second acoustic film falls within the range of 0.275 λ

to 0.35 λ

.

8. The piezoelectric resonator as claimed in claim 1, further comprising:

a third electrode film formed on the acoustic multilayer reflective film;

a piezoelectric film formed on the third electrode film; and

a fourth electrode film formed on the piezoelectric film and obtaining, in collaboration with the third electrode film, a signal having a predetermined resonance frequency by a propagation of a bulk acoustic wave inside the piezoelectric film.

9. The piezoelectric resonator as claimed in claim 1, wherein the piezoelectric resonator is an SMR-type piezoelectric resonator or a diaphragm-type piezoelectric resonator.

10. A filter comprising the piezoelectric resonator as claimed in claim 1.

11. An electronic component comprising the piezoelectric resonator as claimed in claim 1.

12. An electronic component comprising the filter as claimed in claim 10.

13. The electronic component as claimed in claim 11, wherein the piezoelectric resonator is mounted on a substrate and sealed with a resin.

14. The electronic component as claimed in claim 12, wherein the filter is mounted on a substrate and sealed with a resin.