# US 12,009,798 B2 · Transversely-excited film bulk acoustic resonators with electrodes having irregular hexagon cross-sectional shapes > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 12,009,798 B2 - Document ID: US12009798B2 - Status: Granted - Kind: B2 - Application number: 17/242,062 - Filed: 2021-04-27 - Published: 2021-08-26 - Granted: 2024-06-11 - Earliest claimed: 2018-06-15 - Assignees: Murata Manufacturing Co., Ltd. - Applicants: Murata Manufacturing Co., Ltd. - Inventors: Viktor Plesski; Julius Koskela - Web page: https://patentgrep.com/patent/US12009798B2 ## CPC - H03H 9/02157: {Dimensional parameters, e.g. ratio between two dimension parameters, length, width or thickness} - H03H 9/02338: {Suspension means} - H03H 3/04: for obtaining desired frequency or temperature coefficient - H03H 9/02228: {Guided bulk acoustic wave devices or Lamb wave devices having interdigital transducers situated in parallel planes on either side of a piezoelectric layer} - H03H 9/02559: {of lithium niobate or lithium-tantalate substrates} - H03H 9/132: {characterized by a particular shape} - H03H 9/174: {Membranes} - H03H 9/175: {Acoustic mirrors} - H03H 9/547: {Notch filters, e.g. notch BAW or thin film resonator filters} - H03H 3/02: for the manufacture of piezoelectric or electrostrictive resonators or networks (H03H3/08 takes precedence) - H03H 9/568: {consisting of a ladder configuration} - H03H 2003/023: {the resonators or networks being of the membrane type} - H03H 2003/025: {the resonators or networks comprising an acoustic mirror} - H03H: IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS (waveguides, resonators, lines or other devices of the waveguide type H01P) ## Abstract Acoustic resonators and filter devices, and method of making acoustic resonators and filter devices. An acoustic resonator includes a substrate having a surface and a piezoelectric plate having front and back surfaces, the back surface attached to the surface of the substrate except for a portion of the piezoelectric plate forming a diaphragm that spans a cavity in the substrate. An interdigital transducer (IDT) is formed on the front surface of the piezoelectric plate such that interleaved fingers of the IDT are disposed on the diaphragm. The interleaved fingers have an irregular hexagon cross-sectional shape. ## Claims ### Claim 1 An acoustic resonator device comprising: a substrate having a surface; a piezoelectric plate having front and back surfaces, the back surface attached to the surface of the substrate except for a portion of the piezoelectric plate forming a diaphragm that spans a cavity in the substrate; and an interdigital transducer (IDT) formed on the front surface of the piezoelectric plate, wherein interleaved fingers of the IDT are disposed on the diaphragm and configured such that a radio frequency signal applied to the IDT excites a primary shear acoustic mode in the diaphragm, and wherein the interleaved fingers have an irregular hexagon cross-sectional shape. ### Claim 2 (depends on 1) The device of claim 1, wherein the irregular hexagon cross-sectional shape comprises: a lower layer comprising three sides of the irregular hexagon cross-sectional shape that is adjacent the diaphragm; and an upper layer comprising the other three sides of the irregular hexagon cross-sectional shape that is over the lower layer opposite the diaphragm. ### Claim 3 (depends on 2) The device of claim 2, wherein a thickness of the upper layer is greater than a thickness of the lower layer. ### Claim 4 (depends on 3) The device of claim 3, wherein the thickness of the lower layer is in a range from 5% to 40% of a thickness of the diaphragm, and the thickness of the upper layer is in a range from 25% to 75% of the thickness of the diaphragm. ### Claim 5 (depends on 2) The device of claim 2, wherein the lower layer comprises a different material than the upper layer. ### Claim 6 (depends on 2) The device of claim 2, wherein the lower layer is titanium, platinum or molybdenum. ### Claim 7 (depends on 2) The device of claim 2, wherein a sidewall of the upper layer is at an angle in a range from 70 degrees to 90 degrees to the diaphragm. ### Claim 8 (depends on 2) The device of claim 2, wherein a sidewall of the lower layer is at an angle in a range from 90 degrees to 120 degrees to the diaphragm. ### Claim 9 A filter device comprising: a substrate having a surface; a piezoelectric plate having front and back surfaces, the back surface attached to the surface of the substrate, portions of the piezoelectric plate forming one or more diaphragms spanning respective cavities in the substrate; and a conductor pattern formed on the front surface, the conductor pattern including a plurality of interdigital transducers (IDTs) of a respective plurality of acoustic resonators, interleaved fingers of each of the plurality of IDTs disposed on one of the one or more diaphragms, the piezoelectric plate and all of the IDTs configured such that respective radio frequency signals applied to each IDT excite respective shear primary acoustic modes in the respective diaphragm, wherein the interleaved fingers have an irregular hexagon cross-sectional shape. ### Claim 10 (depends on 9) The device of claim 9, wherein the irregular hexagon cross-sectional shape comprises: a lower layer comprising three sides of the irregular hexagon cross-sectional shape that is adjacent a respective one of the one or more diaphragms; and an upper layer comprising the other three sides of the irregular hexagon cross-sectional shape that is over the lower layer opposite the respective one of the one or more diaphragms. ### Claim 11 (depends on 10) The device of claim 10, wherein a thickness of the upper layer is greater than a thickness of the lower layer. ### Claim 12 (depends on 11) The device of claim 11, wherein the thickness of the lower layer is in a range from 5% to 40% of a thickness of a respective one of the one or more diaphragms, and the thickness of the upper layer is in a range from 25% to 75% of the thickness of the respective one of the diaphragm. ### Claim 13 (depends on 10) The device of claim 10, wherein the lower layer comprises a different material than the upper layer. ### Claim 14 (depends on 10) The device of claim 10, wherein the lower layer is titanium. ### Claim 15 (depends on 10) The device of claim 10, wherein a sidewall of the upper layer is at an angle in a range from 70 degrees to 90 degrees to the respective one of the one or more diaphragms. ### Claim 16 (depends on 10) The device of claim 10, wherein a sidewall of the lower layer is at an angle in a range from 90 degrees to 120 degrees to the respective one of the one or more diaphragms. ### Claim 17 (depends on 9) The device of claim 9, wherein the plurality of acoustic resonators comprises at least one first acoustic resonator and at least one second acoustic resonator, wherein a front side dielectric layer is deposited over the at least one first acoustic resonator and not deposited over the at least one second acoustic resonator. ### Claim 18 A method of fabricating an acoustic resonator device, comprising: bonding a piezoelectric plate to a substrate; forming a cavity in the substrate, before or after bonding the piezoelectric plate to the substrate, such that a portion of the piezoelectric plate forms a diaphragm spanning the cavity; and forming an interdigital transducer (IDT) on the front surface of the piezoelectric plate such that interleaved fingers of the IDT are disposed on the diaphragm, the IDT configured to excite a shear primary acoustic mode in the diaphragm in response to a radio frequency signal applied to the IDT, wherein the interleaved fingers have an irregular hexagon cross-sectional shape.