US-12620959-B2 - Film bulk acoustic wave resonators and filters with transverse mode suppression

Abstract

A film bulk acoustic wave resonator (FBAR) is disclosed with raised and recessed frame portions formed in a top electrode. The FBAR can include a substrate, a piezoelectric film supported to oscillate in a direction opposite to a main surface of the substrate, and a pair of top and bottom electrodes formed respectively on top and bottom surfaces of the film. The recessed frame portion and the raised frame portion can be formed to extend adjacent to each other along a periphery of an active region of the film oscillating during an operation of the film on a top surface of the top electrode.

Inventors

• Gong Bin Tang
• Ousmane I Barry
• Hiroyuki Nakamura

Assignees

• SKYWORKS SOLUTIONS, INC.

Dates

Publication Date

20260505

Application Date

20220929

Claims (18)

1. 1 . A film bulk acoustic wave resonator comprising: a substrate; a piezoelectric film supported to oscillate above a main surface of the substrate, the piezoelectric film including a recessed frame portion and a raised frame portion extending adjacent to each other along a periphery of an active area of the film, the raised frame portion spaced from a central portion of the active area by the recessed frame portion; and a pair of top and bottom electrodes formed respectively on top and bottom surfaces of the film, the top electrode including a recessed frame portion and a raised frame portion extending adjacent to each other along the periphery of the active area of the film, the active area oscillating during an operation of the film, the recessed frame portion and raised frame portion of the top electrode above the recessed frame portion and raised frame portion of the piezoelectric film, respectively.
2. 2 . The film bulk acoustic wave resonator of claim 1 wherein the recessed frame portion is formed along an inner periphery of the raised frame portion.
3. 3 . The film bulk acoustic wave resonator of claim 1 wherein the top electrode includes an inner portion within the periphery of the recessed frame portion, a top surface of the recessed frame portion is recessed from a top surface of the raised frame portion by a first distance, and the top surface of the recessed frame portion is recessed from a top surface of the inner portion by a second distance less than the first distance.
4. 4 . The film bulk acoustic wave resonator of claim 1 wherein the recessed frame portion has a first width and the raised frame portion has a second width different than the first width.
5. 5 . The film bulk acoustic wave resonator of claim 4 wherein the second width is greater than the first width.
6. 6 . The film bulk acoustic wave resonator of claim 1 wherein a cavity resides between the active area of the piezoelectric film and the substrate.
7. 7 . A film bulk acoustic wave filter comprising: a plurality of film bulk acoustic wave resonators configured to filter a radio frequency signal, at least one of the plurality of film bulk acoustic wave resonators including a substrate, a piezoelectric film supported to oscillate above main surface of the substrate, the piezoelectric film including a recessed frame portion and a raised frame portion extending adjacent to each other along a periphery of an active area of the film, the raised frame portion spaced from a central portion of the active area by the recessed frame portion, and a pair of top and bottom electrodes formed respectively on top and bottom surfaces of the film, the top electrode including a recessed frame portion and a raised frame portion extending along the periphery of the active area of the film, the active area oscillating during an operation of the film, the recessed frame portion and raised frame portion of the top electrode above the recessed frame portion and raised frame portion of the piezoelectric film, respectively.
8. 8 . The film bulk acoustic wave filter of claim 7 wherein the recessed frame portion is formed along an inner periphery of the raised frame portion.
9. 9 . The film bulk acoustic wave filter of claim 7 wherein the top electrode includes an inner portion within the periphery of the recessed frame portion, a top surface of the recessed frame portion is recessed from a top surface of the raised frame portion by a first distance, and the top surface of the recessed frame portion is recessed from a top surface of the inner portion by a second distance less than the first distance.
10. 10 . The film bulk acoustic wave resonator of claim 7 wherein the recessed frame portion has a first width and the raised frame portion has a second width different than the first width.
11. 11 . The film bulk acoustic wave resonator of claim 10 wherein the second width is greater than the first width.
12. 12 . The film bulk acoustic wave resonator of claim 1 wherein a cavity resides between the active area of the piezoelectric film and the substrate.
13. 13 . A film bulk acoustic wave filter assembly comprising: a first film bulk acoustic wave filter coupled to a common node; and a second film bulk acoustic wave filter coupled to the common node, at least one of the first film bulk acoustic wave filter and the second film bulk acoustic wave filter including a plurality of film bulk acoustic wave resonators to filter a radio frequency signal, at least one of the plurality of film bulk acoustic wave resonators including a substrate, a piezoelectric film supported to oscillate above a main surface of the substrate, the piezoelectric film including a recessed frame portion and a raised frame portion extending adjacent to each other along a periphery of an active area of the film, the raised frame portion spaced from a central portion of the active area by the recessed frame portion, and a pair of top and bottom electrodes formed respectively on top and bottom surfaces of the film, the top electrode including a recessed frame portion and a raised frame portion extending along the periphery of the active area of the film, the active area oscillating during an operation of the film, the recessed frame portion being formed along an inner periphery of the raised frame portion, the recessed frame portion and raised frame portion of the top electrode above the recessed frame portion and raised frame portion of the piezoelectric film, respectively.
14. 14 . A wireless communication device comprising: an antenna; and a multiplexer coupled to the antenna, the multiplexer including a plurality of filters coupled to a common node and arranged to filter a radio frequency signal, the plurality of filters including a film bulk acoustic wave filter, the film bulk acoustic wave filter including a plurality of film bulk acoustic wave resonators, at least one of the plurality of film bulk acoustic wave resonators including a substrate, a piezoelectric film supported to oscillate above a main surface of the substrate, the piezoelectric film including a recessed frame portion and a raised frame portion extending adjacent to each other along a periphery of an active area of the film, the raised frame portion spaced from a central portion of the active area by the recessed frame portion, and a pair of top and bottom electrodes formed respectively on top and bottom surfaces of the film, the top electrode including a recessed frame portion and a raised frame portion extending adjacent to each other along the periphery of the active area of the film, the active area oscillating during an operation of the film, the recessed frame portion and raised frame portion of the top electrode above the recessed frame portion and raised frame portion of the piezoelectric film, respectively.
15. 15 . The wireless communication device of claim 14 wherein the recessed frame portion is formed along an inner periphery of the raised frame portion.
16. 16 . The wireless communication device of claim 14 wherein the top electrode includes an inner portion within the periphery of the recessed frame portion, a top surface of the recessed frame portion is recessed from a top surface of the raised frame portion by a first distance, and the top surface of the recessed frame portion is recessed from a top surface of the inner portion by a second distance less than the first distance.
17. 17 . The wireless communication device of claim 14 wherein the recessed frame portion has a first width and the raised frame portion has a second width different than the first width.
18. 18 . A bulk acoustic wave resonator comprising: a substrate; a piezoelectric layer on the substrate, the piezoelectric layer including a recessed frame portion and a raised frame portion extending adjacent to each other along a periphery of an active region of the piezoelectric layer, the raised frame portion spaced from a central portion of the active region by the recessed frame portion; and first and second electrodes on opposing sides of the piezoelectric layer, the first electrode including a recessed frame portion and a raised frame portion formed along the periphery of the active region of the bulk acoustic wave resonator, the recessed frame portion and raised frame portion of the first electrode above the recessed frame portion and raised frame portion of the piezoelectric layer, respectively, the second electrode being disposed opposite to the substrate via a cavity.

Description

INCORPORATION BY REFERENCE TO ANY PRIORITY APPLICATIONS This application is based upon and claims the benefit of priority from U.S. Provisional Patent Application No. 63/251,510 filed on Oct. 1, 2021. Any applications for which a foreign or domestic priority claim is identified in the Application Data Sheet as filed with the present application are hereby incorporated by reference under 37 CFR 1.57. The entire contents of each of the above-listed items is hereby incorporated into this document by reference and made a part of this specification for all purposes, for all that each contains. BACKGROUND Technical Field Embodiments of this disclosure relate to film bulk acoustic wave resonators and filters used for radio frequency bandwidths to reduce a spurious mode. Description of Related Technology Acoustic wave devices such as bulk acoustic wave (BAW) devices can be used as components for filters in radio frequency electronic systems. For instance, filters in a radio frequency front end of a mobile phone can include acoustic wave filters. Two acoustic wave filters can be arranged as a duplexer. SUMMARY OF CERTAIN INVENTIVE ASPECTS A film bulk acoustic wave resonator of the present disclosure includes a substrate, a piezoelectric film supported to oscillate in a direction opposite to a main surface of the substrate, and a pair of top and bottom electrodes formed respectively on top and bottom surfaces of the film, where a recessed frame portion and a raised frame portion are formed to extend adjacent to each other along a periphery of an active area of the film oscillating during an operation of the film on a top surface of the top electrode and the recessed frame is formed along an inner periphery of the raised frame. The recessed frame portion may have a first width and a top surface of the recessed frame portion is recessed by a certain distance from the top surface of the top electrode. The raised frame may have a second width and a top surface of the raised frame is raised by a certain distance from the top surface of the top electrode. A film bulk acoustic wave resonator of the present disclosure includes a substrate, a piezoelectric film supported to oscillate in a direction opposite to a main surface of the substrate, and a pair of top and bottom electrodes formed respectively on top and bottom surfaces of the film, where a recessed frame portion and a raised frame portion are formed to extend adjacent to each other along a periphery of an active region of the film oscillating during an operation of the film on a top surface of the film and the recessed frame portion is formed along an inner periphery of the raised frame. The recessed frame portion may have a first width and a top surface of the recessed frame portion is recessed by a certain distance from the top surface of the film. The raised frame may have a second width and a top surface of the raised frame is raised by a certain distance from the top surface of the film. A film bulk acoustic wave filter of the present disclosure includes a plurality of film bulk acoustic wave resonators configured to filter a radio frequency signal, where at least one of the plurality of film bulk acoustic wave resonators includes a substrate, a piezoelectric film supported to oscillate in a direction opposite to a main surface of the substrate, and a pair of top and bottom electrodes formed respectively on top and bottom surfaces of the film. A recessed frame portion and a raised frame portion are formed to extend adjacent to each other along a periphery of an active region of the film oscillating during an operation of the film on a top surface of the top electrode and the recessed frame is formed along an inner periphery of the raised frame. Further, a film bulk acoustic wave filter of the present disclosure includes a plurality of film bulk acoustic wave resonators configured to filter a radio frequency signal, where at least one of the plurality of film bulk acoustic wave resonators includes a substrate, a piezoelectric film supported to oscillate in a direction to a main surface of the substrate, and a pair of top and bottom electrodes formed respectively on top and bottom surfaces of the film. A recessed frame portion and a raised frame portion are formed to extend adjacent to each other along a periphery of an active region of the film oscillating during an operation of the film on a top surface of the film and the recessed frame portion is formed along an inner periphery of the raised frame portion. The film bulk acoustic wave filter may include a ladder filter having a pass band in a radio frequency band. At least one of the film bulk acoustic wave resonators may be included in a series arm between an input node and an output node of the ladder filter. At least one of the film bulk acoustic wave resonators may be included in at least one of a plurality of parallel arms connecting a plurality of nodes between the film bulk acoustic wave resonators to a