# US 9,520,855 B2 · Bulk acoustic wave resonators having doped piezoelectric material and frame elements > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 9,520,855 B2 - Document ID: US9520855B2 - Status: Granted - Kind: B2 - Application number: 14/190,361 - Filed: 2014-02-26 - Published: 2015-08-27 - Granted: 2016-12-13 - Earliest claimed: 2014-02-26 - Assignees: Avago Technologies General IP (Singapore) Pte. Ltd. - Applicants: Avago Technologies General IP (Singapore) Pte. Ltd. - Inventors: Chris Feng; John Choy; Phil Nikkel; Kevin J. Grannen; Tina L. Lamers - Web page: https://patentgrep.com/patent/US9520855B2 ## CPC - H03H 9/02031: {consisting of ceramic} - H03H 9/02118: {of lateral leakage between adjacent resonators} - H03H 9/132: {characterized by a particular shape} - H03H 9/172: {Means for mounting on a substrate, i.e. means constituting the material interface confining the waves to a volume} - H03H 9/173: {Air-gaps} - H03H 9/175: {Acoustic mirrors} - H03H 9/562: {comprising a ceramic piezoelectric layer} - H03H: IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS (waveguides, resonators, lines or other devices of the waveguide type H01P) ## Abstract A bulk acoustic wave (BAW) resonator includes a first electrode; a second electrode; and a piezoelectric layer disposed between the first and second electrodes. The piezoelectric layer includes a piezoelectric material doped with at least one rare earth element. In an embodiment, the BAW resonator includes a recessed frame element disposed over a surface of at least one of the first and second electrodes. In another embodiment, the BAW resonator includes a raised frame element disposed over a surface of at least one of the first and second electrodes. In yet another embodiment, the BAW resonator includes both the raised and recessed frame elements. ## Claims ### Claim 1 A bulk acoustic wave (BAW) resonator comprising: a first electrode; a second electrode; a piezoelectric layer disposed between the first and second electrodes, the piezoelectric layer comprising a piezoelectric material doped with two or more rare earth elements incorporated into a crystal lattice of the piezoelectric material; and a recessed frame element disposed over a surface of at least one of the first and second electrodes. ### Claim 2 (depends on 1) A BAW resonator as claimed in claim 1, wherein the recessed frame element is disposed along a periphery of the second electrode. ### Claim 3 (depends on 1) A BAW resonator as claimed in claim 1, wherein the recessed frame element is disposed within the first electrode and directly opposes a periphery of the second electrode. ### Claim 4 (depends on 1) A BAW resonator as claimed in claim 1, wherein the recessed frame element is integrated into the one of the first and second electrodes. ### Claim 5 (depends on 1) A BAW resonator as claimed in claim 1, further comprising a reflective element disposed beneath the first electrode, the second electrode and the piezoelectric layer, wherein an overlap of the reflective element, the first electrode, the second electrode and the piezoelectric layer defines an active area of the BAW resonator. ### Claim 6 (depends on 5) A BAW resonator as claimed in claim 5, wherein the reflective element comprises a cavity disposed in a substrate over which the first electrode, the second electrode and the piezoelectric layer are disposed. ### Claim 7 (depends on 5) A BAW resonator as claimed in claim 5, wherein the reflective element comprises a plurality of layers having alternating high acoustic impedance and low acoustic impedance. ### Claim 8 (depends on 1) A BAW resonator as claimed in claim 1, wherein the piezoelectric material comprises aluminum nitride (AlN). ### Claim 9 (depends on 8) A BAW resonator as claimed in claim 8, wherein the two or more rare earth elements comprise scandium (Sc). ### Claim 10 (depends on 1) A BAW resonator as claimed in claim 1, wherein the two or more rare earth elements comprise scandium (Sc) and erbium (Er). ### Claim 11 (depends on 10) A BAW resonator as claimed in claim 10, wherein the two or more rare earth elements further comprise yttrium (Y). ### Claim 12 (depends on 1) A BAW resonator as claimed in claim 1, further comprising a raised frame element disposed over a surface of at least one of the first and second electrodes. ### Claim 13 (depends on 12) A BAW resonator as claimed in claim 12, wherein the piezoelectric material comprises aluminum nitride (AlN). ### Claim 14 (depends on 13) A BAW resonator as claimed in claim 13, wherein the two or more rare earth elements comprise scandium (Sc). ### Claim 15 (depends on 13) A BAW resonator as claimed in claim 13, wherein the two or more rare earth elements comprise scandium (Sc) and erbium (Er). ### Claim 16 (depends on 15) A BAW resonator as claimed in claim 15, wherein the two or more rare earth elements comprise yttrium (Y). ### Claim 17 A bulk acoustic wave (BAW) resonator comprising: a first electrode; a second electrode; a piezoelectric layer disposed between the first and second electrodes, the piezoelectric layer comprising a piezoelectric material doped with two or more rare earth elements incorporated into a crystal lattice of the piezoelectric material; and a raised frame element disposed over a surface of at least one of the first and second electrodes. ### Claim 18 (depends on 17) A BAW resonator as claimed in claim 17, wherein the raised frame element is disposed along a periphery of the second electrode. ### Claim 19 (depends on 17) A BAW resonator as claimed in claim 17, wherein the raised frame element is disposed within the first electrode and directly opposes a periphery of the second electrode. ### Claim 20 (depends on 17) A BAW resonator as claimed in claim 17, wherein the raised frame element is integrated into the one of the first and the second electrodes. ### Claim 21 (depends on 17) A BAW resonator as claimed in claim 17, further comprising a reflective element disposed beneath the first electrode, the second electrode and the piezoelectric layer, wherein an overlap of the reflective element, the first electrode, the second electrode and the piezoelectric layer defines an active area of the BAW resonator. ### Claim 22 (depends on 21) A BAW resonator as claimed in claim 21, wherein the reflective element comprises a cavity disposed in a substrate over which the first electrode, the second electrode and the piezoelectric layer are disposed. ### Claim 23 (depends on 21) A BAW resonator as claimed in claim 21, wherein the reflective element comprises a plurality of layers having alternating high acoustic impedance and low acoustic impedance. ### Claim 24 (depends on 17) A BAW resonator as claimed in claim 17, wherein the piezoelectric material comprises aluminum nitride (AlN). ### Claim 25 (depends on 24) A BAW resonator as claimed in claim 24, wherein the two or more rare earth elements comprise scandium (Sc). ### Claim 26 (depends on 17) A BAW resonator as claimed in claim 17, wherein the two or more rare earth elements comprise scandium (Sc) and erbium (Er). ### Claim 27 (depends on 26) A BAW resonator as claimed in claim 26, wherein the two or more rare earth elements further comprise yttrium (Y).