# US 12,119,807 B2 · Transversely-excited film bulk acoustic resonator matrix filters with split die sub-filters > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 12,119,807 B2 - Document ID: US12119807B2 - Status: Granted - Kind: B2 - Application number: 17/940,925 - Filed: 2022-09-08 - Published: 2023-01-05 - Granted: 2024-10-15 - Earliest claimed: 2020-10-05 - Assignees: Murata Manufacturing Co., Ltd. - Applicants: Murata Manufacturing Co., Ltd. - Inventors: Andrew Guyette; Neal Fenzi; Greg Dyer; Sean McHugh - Web page: https://patentgrep.com/patent/US12119807B2 ## CPC - H03H 9/205: having multiple resonators (crystal tuning forks H03H9/21) - H03H 3/02: for the manufacture of piezoelectric or electrostrictive resonators or networks (H03H3/08 takes precedence) - H03H 9/02031: {consisting of ceramic} - H03H 9/02157: {Dimensional parameters, e.g. ratio between two dimension parameters, length, width or thickness} - 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 9/13: for networks consisting of piezoelectric or electrostrictive materials (for networks using surface acoustic waves H03H9/145) - H03H 9/17: having a single resonator (crystal tuning forks H03H9/21) - H03H 9/174: {Membranes} - H03H 9/542: {including passive elements (H03H9/545 takes precedence)} - H03H 9/545: {including active elements} - H03H 9/564: {implemented with thin-film techniques} - H03H 9/568: {consisting of a ladder configuration} - H03H 2003/023: {the resonators or networks being of the membrane type} - H03H: IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS (waveguides, resonators, lines or other devices of the waveguide type H01P) ## Abstract A radio frequency filter includes at least a first sub-filter and a second sub-filter connected in parallel between a first port and a second port. Each of the sub-filters has a piezoelectric plate having front and back surfaces, the back surface attached to a substrate, and portions of the piezoelectric plate forming diaphragms spanning respective cavities in the substrate. A conductor pattern is formed on the front surface of the plate, the conductor pattern includes interdigital transducers (IDTs) of a respective plurality of resonators, with interleaved fingers of each IDT disposed on a respective diaphragm of the plurality of diaphragms. A thickness of the portions of the piezoelectric plate of the first sub-filter is different from a thickness of the portions of the piezoelectric plate of the second sub-filter. ## Claims ### Claim 1 A method of forming a radio frequency filter, comprising: connecting a first sub-filter and a second sub-filter in parallel between a first port and a second port, wherein connecting each of the first and second sub-filters comprises: forming a first portion of at least one piezoelectric plate to have a thickness that is different than a thickness of a second portion of the at least one piezoelectric plate; bonding the at least one piezoelectric plate to a surface of at least one substrate, at least the first and second portions of the at least one piezoelectric plate forming respective diaphragms over respective cavities; and forming a conductor pattern on only one surface of the piezoelectric plate and not an opposing surface of the piezoelectric plate, the conductor pattern including a plurality of interdigital transducers (IDTs) of a respective plurality of resonators, interleaved fingers of each IDT on the respective diaphragms, wherein the first sub-filter is formed on the first portion of the at least one piezoelectric plate and the second sub-filter is formed on the second portion of the at least one piezoelectric plate. ### Claim 2 (depends on 1) The method of claim 1, wherein the at least one piezoelectric plate is a single piezoelectric plate for both the first sub-filter and the second sub-filter. ### Claim 3 (depends on 1) The method of claim 1, wherein the at least one piezoelectric plate comprises a plurality of piezoelectric plates with a first piezoelectric plate of the first sub-filter being a different piezoelectric plate than the piezoelectric plate of the second sub-filter. ### Claim 4 (depends on 1) The method of claim 1, wherein the at least one substrate is a single substrate for both the first sub-filter and the second sub-filter. ### Claim 5 (depends on 1) The method of claim 1, wherein: the first and second portions and first and second IDTs of the plurality of IDTs are configured such that radio frequency signals applied to the first and second IDTs excite primary shear acoustic modes in the first and second portions of the at least one piezoelectric plate forming the respective diaphragms over the respective cavities; and the thicknesses of the first and second portions are selected to tune the primary shear acoustic modes in the first and second portions. ### Claim 6 (depends on 1) The method of claim 1, further forming a third sub-filter in parallel between the first port and the second port, with the third sub-filter being formed on a third first portion of the at least one piezoelectric plate that has a thickness different than the thickness of the first portion and the second portion. ### Claim 7 (depends on 6) The method of claim 6, wherein the thickness of the at least one piezoelectric plate portion of the first sub-filter is a thickness of between 720 nm and 740 nm extending between a front surface and a back surface of the at least one piezoelectric plate of the first sub-filter; wherein the thickness of the at least one piezoelectric plate portion of the second sub-filter is a thickness of between 752 nm and 772 nm extending between front surface and back surface of the at least one piezoelectric plate portion of the second sub-filter; and wherein the thickness of the piezoelectric plate of the third sub-filter is a thickness of between 734 nm and 754 nm extending between front surface and back surface of the at least one piezoelectric plate of the third sub-filter. ### Claim 8 (depends on 6) The method of claim 6, wherein connecting each of the first, second and third sub-filters further comprises: connecting three resonators in series between the first port and the second port; and connecting two coupling capacitors between ground and a respective node between two of the resonators of the sub-filter. ### Claim 9 (depends on 8) The method of claim 8, further comprising: connecting a first low-edge resonator, from the plurality of resonators, between the first port and ground; connecting a second low-edge resonator, from the plurality of resonators, between the second port and ground; wherein respective resonance frequencies of the first and second low-edge resonators are adjacent to a lower edge of a passband of the filter. ### Claim 10 (depends on 9) The method of claim 9, wherein: two of the resonators of each sub-filter are symmetrical in response; the low-edge resonators have the same response; each of the coupling capacitors is a metal-insulator-metal capacitor; and the sub-filters and the low-edge resonators form a matrix filter having a contiguous passband formed by passbands of the sub-filters; and a center frequency of a passband of each sub-filter is different from a center frequency of any other sub-filter. ### Claim 11 (depends on 6) The method of claim 6, wherein: the thickness of the at least one piezoelectric plate of the first sub-filter is thinner than the thickness of the at least one piezoelectric plate of the second sub-filter; and the thickness of the at least one piezoelectric plate of the second sub-filter is thinner than the thickness of the at least one piezoelectric plate of the third sub-filter. ### Claim 12 A method of forming a radio frequency filter, comprising: connecting a first sub-filter and a second sub-filter in parallel between a first port and a second port, wherein connecting the first sub-filter comprises: bonding a first piezoelectric plate to a first substrate first portions of the first piezoelectric plate forming a first plurality of diaphragms over respective first cavities; and forming a first conductor pattern on the first piezoelectric plate, the first conductor pattern including a first plurality of interdigital transducers (IDTs) of a first respective plurality of resonators, first interleaved fingers of each IDT on a first respective diaphragm of the first plurality of diaphragms, wherein connecting the second sub-filters comprises: bonding a second piezoelectric to a second substrate second portions of the second piezoelectric plate forming a second plurality of diaphragms over respective second cavities; and forming a second conductor pattern on the first piezoelectric plate, the second conductor pattern including a second plurality of interdigital transducers (IDTs) of a second respective plurality of resonators, second interleaved fingers of each IDT on a second respective diaphragm of the second plurality of diaphragms, wherein a thickness of the first portions of the first piezoelectric plate is thicker than a thickness of the second portions of the second piezoelectric plate, and wherein the first substrate is different than the second substrate. ### Claim 13 (depends on 12) The method of claim 12, wherein the first piezoelectric plate is a same piezoelectric plate as the second piezoelectric plate. ### Claim 14 (depends on 12) The method of claim 12, wherein the first piezoelectric plate is a different piezoelectric plate than the second piezoelectric plate. ### Claim 15 (depends on 12) The method of claim 12, wherein: the first and second portions and the first and second IDTs are configured such that radio frequency signals applied to the first and second IDTs excite primary shear acoustic modes in the first and second portions of the first and second piezoelectric plates; and the thicknesses of the first and second portions are selected to tune the primary shear acoustic modes in the first and second portions. ### Claim 16 (depends on 12) The method of claim 12, wherein connecting each of the first and second sub-filters further comprises: connecting three resonators in series between the first port and the second port; connecting each of two coupling capacitors between ground and a respective node between two of the resonators of the sub-filter; connecting a first low-edge resonator, from the plurality of resonators, between the first port and ground; connecting a second low-edge resonator, from the plurality of resonators, between the second port and ground; wherein respective resonance frequencies of the first and second low-edge resonators are adjacent to a lower edge of a passband of the filter. ### Claim 17 A method of forming radio frequency filter, comprising: connecting a first sub-filter, a second sub-filter and a third sub-filter in parallel between a first port and a second port, wherein connecting each of the first, second and third sub-filters comprises: bonding at least one piezoelectric plate to at least one substrate, portions of the at least one piezoelectric plate forming a plurality of diaphragms over respective cavities; and forming a conductor pattern on only one surface of the at least one piezoelectric plate and not an opposing surface of the piezoelectric plate, the conductor pattern including a plurality of interdigital transducers (IDTs) of a respective plurality of resonators, interleaved fingers of each IDT disposed on a respective diaphragm of the plurality of diaphragms; wherein a thickness of the portion of the at least one piezoelectric plate of the first sub-filter is different from a thickness of the respective portions of the at least one piezoelectric plate of the second and third sub-filter, and wherein the thickness of the portion of the at least one piezoelectric plate of the second sub-filter is different from the thickness of the portion of the at least one piezoelectric plate of the third sub-filter. ### Claim 18 (depends on 17) The method of claim 17, wherein the at least one piezoelectric plate comprises a plurality of piezoelectric plates and the respective piezoelectric plate of the first sub-filter is a different piezoelectric plate than the respective piezoelectric plate of the second sub-filter and the third sub-filter, and wherein the respective piezoelectric plate of the second sub-filter is different than the respective piezoelectric plate of the third sub-filter. ### Claim 19 (depends on 18) The method of claim 18, wherein the at least one substrate comprises a plurality of substrates and the respective substrate of the first sub-filter different than the respective substrate of each of the second sub-filter and the third sub-filter, and wherein the respective substrate of the second sub-filter is different than the respective substrate of the third sub-filter. ### Claim 20 (depends on 17) The method of claim 17, wherein: the respective portions of the at least one piezoelectric plate and the IDTs of the first, second and third sub-filter are configured such that radio frequency signals applied to the IDTs excite primary shear acoustic modes in the respective portions of the at least one piezoelectric plate; and the thicknesses of the respective portions of the at least one piezoelectric plate of the first, second and third sub-filters are selected to tune the primary shear acoustic modes in the respective portions.