ELASTIC WAVE ELEMENT

• US 20140001919A1
• Filed: 03/05/2012
• Published: 01/02/2014
• Est. Priority Date: 03/22/2011
• Status: Active Grant

• Current Assignee: Skyworks Filter Solutions Japan Co., Ltd. (Skyworks Solutions Incorporated)
• Original Assignee: Panasonic Corporation (Panasonic Holdings Corporation)
• Inventors: Nakamura, Hiroyuki, Tsurunari, Tetsuya, Fujiwara, Joji, Nakanishi, Hidekazu, Komatsu, Tomoya
• Granted Patent: US 9,136,458 B2
• Time in Patent Office: Days
• US Class Current: 310/313.B
• CPC Class Codes: H03H 9/02818 Means for compensation or elimination of undesirable effects
• CPC Class Codes: H03H 9/02992 Details of bus bars, contact pads or other electrical connections for finger electrodes
• CPC Class Codes: H03H 9/25 Constructional features of resonators using surface acoustic waves devices for manipulating acoustic surface waves in general G10K11/36
• CPC Class Codes: H10N 30/87 Electrodes or interconnections, e.g. leads or terminals

Abstract

An elastic wave element includes a piezoelectric substrate, an IDT electrode, and a first dielectric film. The IDT electrode includes a first bus bar electrode, a second bus bar electrode, first electrode fingers, and second electrode fingers. The piezoelectric substrate includes a bus bar electrode region, an alternately disposed region, and an intermediate region. The first dielectric film is formed in at least a part of the intermediate region, and formed of a medium in which acoustic velocity of a transverse wave propagating in the first dielectric film is lower than acoustic velocity of a main elastic wave in the alternately disposed region.

Claims

1. An elastic wave element comprising:

a piezoelectric substrate; and

an IDT electrode that is provided in contact with the piezoelectric substrate,

wherein the IDT electrode includes;

a first bus bar electrode;

a second bus bar electrode facing the first bus bar electrode;

first electrode fingers extending from the first bus bar electrode toward the second bus bar electrode; and

second electrode fingers extending from the second bus bar electrode toward the first bus bar electrode, and

the piezoelectric substrate includes;

a bus bar electrode region including any one of the first bus bar electrode and the second bus bar electrode;

an alternately disposed region including the first electrode fingers and the second electrode fingers which are alternately disposed; and

an intermediate region including any one of the first electrode fingers and the second electrode fingers, and

wherein a first dielectric film is formed in at least a part of the intermediate region, and the first dielectric film is formed from a medium in which acoustic velocity of a transverse wave propagating in the first dielectric film is lower than acoustic velocity of a main elastic wave of the alternately disposed region.

2. The elastic wave element of claim 1, wherein the piezoelectric substrate is a lithium tantalate substrate.

3. The elastic wave element of claim 1, wherein the piezoelectric substrate has negative anisotropy index γ

in a propagation direction of the main elastic wave.

4. The elastic wave element of claim 1, wherein the first dielectric film is made of tantalum oxide having a film thickness of 0.001λ

or more and 0.1λ

or less where λ

indicates a wavelength of the main elastic wave.

5. The elastic wave element of claim 1, wherein the first dielectric film is formed in the bus bar electrode region.

6. The elastic wave element of claim 1,

wherein the IDT electrode further includes first dummy electrodes extending from the first bus bar electrode toward the second bus bar electrode, and second dummy electrodes extending from the second bus bar electrode toward the first bus bar electrode,

a dummy electrode region is further formed between the bus bar electrode region and the intermediate region, in which any one of the first dummy electrodes and the first electrode fingers and the second dummy electrodes and the second electrode fingers is formed, and

the first dielectric film is formed also in the dummy electrode region.

7. The elastic wave element of claim 1, wherein the first dielectric film extends to a part of the alternately disposed region.

8. The elastic wave element of claim 1, wherein an end portion of the first dielectric film in an extending direction of the first and second electrode fingers has a tapered shape in which a film thickness of the first dielectric film is gradually reduced in a direction from the bus bar electrode region toward the alternately disposed region.

9. The elastic wave element of claim 1, wherein the first dielectric film extends to the alternately disposed region, and a thickness of the first dielectric film in the alternately disposed region is smaller than a thickness of the first dielectric film in the intermediate region.

10. The elastic wave element of claim 1, wherein a height from an upper surface of the piezoelectric substrate to an upper surface of the first dielectric film in the alternately disposed region is lower than a height from the upper surface of the piezoelectric substrate to the upper surface of the first dielectric film in the intermediate region.

11. The elastic wave element of claim 1, wherein a third dielectric film is further provided in the alternately disposed region, and the third dielectric film is formed from a medium in which acoustic velocity of a transverse wave propagating in the third dielectric film is higher than acoustic velocity of a transverse wave propagating in the first dielectric film.

12. The elastic wave element of claim 1, wherein a fourth dielectric film is formed between the first dielectric film and the IDT electrode.

13. An elastic wave element comprising:

a piezoelectric substrate; and

an IDT electrode that is provided in contact with the piezoelectric substrate,

wherein the IDT electrode includes;

a first bus bar electrode;

a second bus bar electrode facing the first bus bar electrode;

first electrode fingers extending from the first bus bar electrode toward the second bus bar electrode; and

second electrode fingers extending from the second bus bar electrode toward the first bus bar electrode, and

the piezoelectric substrate includes;

a bus bar electrode region including any one of the first bus bar electrode and the second bus bar electrode;

an alternately disposed region including the first electrode fingers and the second electrode fingers which are alternately disposed; and

an intermediate region including any one of the first electrode fingers and the second electrode fingers, and

wherein a second dielectric film is formed in at least a part of the alternately disposed region, the second dielectric film formed from a medium in which acoustic velocity of a transverse wave propagating in the second dielectric film is higher than acoustic velocity of a main elastic wave in the intermediate region.

14. The elastic wave element of claim 13, wherein the piezoelectric substrate is a lithium tantalate substrate.

15. The elastic wave element of claim 13, wherein the second dielectric film is formed from silicon nitride having a film thickness of 0.05λ

or more and 1λ

or less, where λ

indicates a wavelength of the main elastic wave.

16. The elastic wave element of claim 13, wherein the second dielectric film is formed from aluminum nitride having a film thickness of 0.001λ

or more and 0.1λ

or less where λ

indicates a wavelength of the main elastic wave.

17. The elastic wave element of claim 15, wherein the second dielectric film extends to a part of the intermediate region.

18. The elastic wave element of claim 13, wherein an end portion of the second dielectric film in an extending direction of the first and second electrode fingers has a tapered shape in which a film thickness of the second dielectric film is gradually reduced in a direction from the alternately disposed region to the bus bar electrode region.

19. The elastic wave element of claim 13, wherein the second dielectric film extends to the intermediate region, and a thickness of the second dielectric film in the alternately disposed region is larger than a thickness of the second dielectric film in the intermediate region.

20. The elastic wave element of claim 13, wherein a height from an upper surface of the piezoelectric substrate to an upper surface of the second dielectric film in the alternately disposed region is higher than a height from an upper surface of the piezoelectric substrate to an upper surface of the second dielectric film in the intermediate region.