# US 2021/0281233 A1 · Bulk Acoustic Wave Filter and a Method of Frequency Tuning for Bulk Acoustic Wave Resonator of Bulk Acoustic Wave Filter > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2021/0281233 A1 - Document ID: US20210281233A1 - Status: Published application - Kind: A1 - Application number: 17/331,330 - Filed: 2021-05-26 - Published: 2021-09-09 - Earliest claimed: 2017-01-03 - Assignees: Win Semiconductors Corp. - Applicants: WIN Semiconductors Corp. - Inventors: CHIA-TA CHANG; CHUN-JU WEI; KUO-LUNG WENG - Web page: https://patentgrep.com/patent/US20210281233A1 ## CPC - H03H 3/02: for the manufacture of piezoelectric or electrostrictive resonators or networks (H03H3/08 takes precedence) - H03H 3/04: for obtaining desired frequency or temperature coefficient - H03H 9/587: {Air-gaps} - H03H 2003/021: {the resonators or networks being of the air-gap type} - H03H 2003/0442: {of a non-piezoelectric layer} - H03H 2009/02165: {Tuning} - H03H: IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS (waveguides, resonators, lines or other devices of the waveguide type H01P) ## Abstract A bulk acoustic wave filter comprises a substrate, an insulating layer disposed on the substrate and having a first cavity and a second cavity formed therein, a first bulk-acoustic-wave-resonance-structure disposed on the first cavity and a second bulk-acoustic-wave-resonance-structure disposed on the second cavity. The first bulk-acoustic-wave-resonance-structure comprises a first bottom electrode disposed on the first cavity, a first top electrode disposed on the first bottom electrode, a first piezoelectric layer portion sandwiched between the first top electrode and the first bottom electrode, and a first frequency tuning structure disposed between the first cavity and the first bottom electrode. The second bulk-acoustic-wave-resonance-structure comprises a second bottom electrode disposed on the second cavity, a second top electrode disposed on the second bottom electrode, a second piezoelectric layer portion sandwiched between the second top electrode and the second bottom electrode. ## Claims ### Claim 1 A bulk acoustic wave filter comprising: a substrate; an insulating layer disposed on the substrate, wherein the insulating layer has a first cavity and a second cavity formed therein; a first bulk acoustic wave resonance structure disposed on the first cavity, wherein the first bulk acoustic wave resonance structure comprises a first bottom electrode disposed on the first cavity, a first top electrode disposed on the first bottom electrode, a first piezoelectric layer portion sandwiched between the first top electrode and the first bottom electrode, and a first frequency tuning structure disposed between the first cavity and the first bottom electrode; and a second bulk acoustic wave resonance structure disposed on the second cavity, wherein the second bulk acoustic wave resonance structure comprises a second bottom electrode disposed on the second cavity, a second top electrode disposed on the second bottom electrode, a second piezoelectric layer portion sandwiched between the second top electrode and the second bottom electrode. ### Claim 2 (depends on 1) The bulk acoustic wave filter according to claim 1, wherein the second bulk acoustic wave resonance structure further comprises a second frequency tuning structure disposed between the second cavity and the second bottom electrode. ### Claim 3 (depends on 2) The bulk acoustic wave filter according to claim 2, wherein a thickness of the first frequency tuning structure is greater than a thickness of the second frequency tuning structure. ### Claim 4 (depends on 1) The bulk acoustic wave filter according to claim 1, wherein the substrate is a semiconductor substrate, and the insulating layer comprises silicon nitride, silicon oxide, polymer, or a combination thereof. ### Claim 5 (depends on 1) The bulk acoustic wave filter according to claim 1, wherein the substrate is a compound semiconductor substrate. ### Claim 6 (depends on 1) The bulk acoustic wave filter according to claim 1, wherein the first frequency tuning structure and the insulating layer are integrally formed. ### Claim 7 (depends on 1) The bulk acoustic wave filter according to claim 1, wherein the first frequency tuning structure and the insulating layer are made of a same material. ### Claim 8 (depends on 1) The bulk acoustic wave filter according to claim 1, wherein the first frequency tuning structure is made of an insulator. ### Claim 9 (depends on 8) The bulk acoustic wave filter according to claim 8, wherein the insulator comprises silicon nitride, silicon oxide, aluminium nitride, zinc oxide, or a combination thereof. ### Claim 10 (depends on 1) The bulk acoustic wave filter according to claim 1, wherein the first frequency tuning structure is made of a metal or an alloy. ### Claim 11 (depends on 1) The bulk acoustic wave filter according to claim 1, wherein the first frequency tuning structure is made of Ru, Ti, Mo, Pt, Au, Al, W, or a combination thereof. ### Claim 12 (depends on 1) The bulk acoustic wave filter according to claim 1, wherein the first frequency tuning structure and the first bottom electrode are made of a same material. ### Claim 13 (depends on 1) The bulk acoustic wave filter according to claim 1, wherein the first frequency tuning structure and the first bottom electrode are integrally formed. ### Claim 14 A bulk acoustic wave filter comprising: a substrate; an insulating layer formed on the substrate, wherein a first cavity and a second cavity are formed in the insulating layer, and the first cavity and the second cavity are defined by sidewalls of the insulating layer and a top surface of the substrate; a first bulk acoustic wave resonance structure formed on the first cavity, wherein the first bulk acoustic wave resonance structure comprises a first frequency tuning structure formed on the first cavity, a first bottom electrode formed on the first frequency tuning structure, a first piezoelectric layer portion formed on the first bottom electrode, and a first top electrode formed on the first piezoelectric layer portion; and a second bulk acoustic wave resonance structure formed on the second cavity, wherein the second bulk acoustic wave resonance structure comprises a second bottom electrode formed on the second cavity, a second piezoelectric layer portion formed on the second bottom electrode, and a second top electrode formed on the second piezoelectric layer portion. ### Claim 15 (depends on 14) The bulk acoustic wave filter according to claim 14, wherein a first spacing between the substrate and the first frequency tuning structure is less than a second spacing between the substrate and the second bottom electrode. ### Claim 16 (depends on 14) The bulk acoustic wave filter according to claim 14, wherein the second bulk acoustic wave resonance structure further comprises a second frequency tuning structure formed on the second cavity, wherein the second frequency tuning structure is between the second cavity and the second bottom electrode. ### Claim 17 (depends on 16) The bulk acoustic wave filter according to claim 16, wherein a first spacing between the substrate and the first frequency tuning structure is less than a second spacing between the substrate and the second frequency tuning structure. ### Claim 18 (depends on 16) The bulk acoustic wave filter according to claim 16, wherein the first frequency tuning structure and the second frequency tuning structure are made of a same material. ### Claim 19 (depends on 18) The bulk acoustic wave filter according to claim 18, wherein the first frequency tuning structure and the second frequency tuning structure are made of a metal or an alloy. ### Claim 20 (depends on 18) The bulk acoustic wave filter according to claim 18, wherein the first frequency tuning structure and the second frequency tuning structure are made of an insulator.