# US 10,873,311 B2 · Acoustic resonators with reduced loss characteristics and methods of manufacturing same > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,873,311 B2 - Document ID: US10873311B2 - Status: Granted - Kind: B2 - Application number: 15/894,021 - Filed: 2018-02-12 - Published: 2018-08-16 - Granted: 2020-12-22 - Earliest claimed: 2017-02-15 - Assignees: Skyworks Solutions, Inc. - Applicants: Skyworks Solutions, Inc. - Inventors: Yoshiaki Ando; Satoshi Niwa; Hiroyuki Nakamura - Web page: https://patentgrep.com/patent/US10873311B2 ## CPC - H03H 9/02086: {Means for compensation or elimination of undesirable effects} - H03H 3/02: for the manufacture of piezoelectric or electrostrictive resonators or networks (H03H3/08 takes precedence) - H03H 9/1014: {the enclosure being defined by a frame built on a substrate and a cap, the frame having no mechanical contact with the BAW device} - H03H 9/13: for networks consisting of piezoelectric or electrostrictive materials (for networks using surface acoustic waves H03H9/145) - H03H 9/205: having multiple resonators (crystal tuning forks H03H9/21) - H03H 9/54: comprising resonators of piezoelectric or electrostrictive material (comprising resonators using surface acoustic waves H03H9/64) - H03H 9/587: {Air-gaps} - H03H 9/605: {consisting of a ladder configuration} - H03H 9/706: {Duplexers} - H04B 1/40: Circuits - H03H: IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS (waveguides, resonators, lines or other devices of the waveguide type H01P) - H04B: TRANSMISSION ## Abstract An acoustic resonator that prevents a radio frequency (RF) signal from being coupled to a cap substrate. An electronic device includes a first substrate (device substrate) of piezoelectric material having a top surface on which an electronic circuit including a film bulk acoustic resonator is formed, a second substrate (cap substrate) of low-resistivity material, a bottom surface of which is disposed opposing the top surface of the first substrate, and a side wall disposed between the top surface of the first substrate and the bottom surface of the second substrate. The side wall defines a cavity together with the top surface of the first substrate and the bottom surface of the second substrate, the cavity internally including the electronic circuit. A thin film of high-resistivity material is formed on at least a portion of the bottom surface of the second substrate to prevent an RF signal emitted from the electronic circuit from being coupled to the second substrate. ## Claims ### Claim 1 An electronic device comprising: a first substrate having a top surface on which an electronic circuit including a bulk acoustic wave (BAW) resonator is formed, the first substrate being formed of piezoelectric material; a second substrate having a bottom surface disposed opposing the top surface of the first substrate, the second substrate being formed of high-resistivity material to prevent a radio frequency (RF) signal emitted by the electronic circuit from being coupled to the second substrate; and a side wall disposed between and in contact with the top surface of the first substrate and the bottom surface of the second substrate, the side wall defining a cavity together with the top surface of the first substrate and the bottom surface of the second substrate, the cavity internally including the electronic circuit, the side wall including a first side wall and a second sidewall sequentially stacked and bonded by transient liquid phase bonding, the first side wall formed of gold-tin (Au—Sn) alloy and the second side wall formed of tin-copper (Sn—Cu) alloy. ### Claim 2 (depends on 1) A duplexer comprising: a reception filter configured to allow a first frequency to pass through; and a transmission filter configured to allow a second frequency to pass through, at least one of the reception filter and the transmission filter being the electronic device of claim 1. ### Claim 3 (depends on 2) A communication device comprising the duplexer of claim 2. ### Claim 4 (depends on 3) The communication device of claim 3 wherein the communication device is a mobile phone. ### Claim 5 (depends on 1) The electronic device of claim 1 further comprising a column disposed between the top surface of the first substrate and the bottom surface of the second substrate. ### Claim 6 (depends on 5) The electronic device of claim 5 wherein the column is formed of metal. ### Claim 7 (depends on 5) The electronic device of claim 5 wherein the first substrate includes a via extending through a through-hole between the top surface of the first substrate and a bottom surface of the first substrate and connecting the electronic circuit to an external electrode formed on the bottom surface of the first substrate, the column being disposed immediately above the via. ### Claim 8 (depends on 1) The electronic device of claim 1 wherein the high-resistivity material forming the second substrate includes at least one of silicon dioxide (SiO2) and aluminum oxide (Al2O3). ### Claim 9 (depends on 1) The electronic device of claim 1 wherein the piezoelectric material forming the first substrate includes at least one of aluminum nitride (AlN) and zinc oxide (ZnO). ### Claim 10 (depends on 1) The electronic device of claim 1 wherein the BAW resonator includes at least one of a film bulk acoustic resonator (FBAR) and a solidly mounted resonator (SMR). ### Claim 11 (depends on 1) The electronic device of claim 1 wherein a ground line of the electronic circuit is connected to the side wall. ### Claim 12 (depends on 1) A diplexer comprising: a first reception filter configured to receive a signal of a first frequency band; and a second reception filter configured to receive a signal of a second frequency band different from the first frequency band, at least one of the first reception filter and the second reception filter being the electronic device of claim 1. ### Claim 13 An electronic device comprising: a first substrate having a top surface on which an electronic circuit including a bulk acoustic wave (BAW) resonator is formed, the first substrate being formed of piezoelectric material; a second substrate having a bottom surface disposed opposing the top surface of the first substrate, the second substrate being formed of low-resistivity material; a side wall disposed between the top surface of the first substrate and the bottom surface of the second substrate, the side wall defining a cavity together with the top surface of the first substrate and the bottom surface of the second substrate, the cavity internally including the electronic circuit; and a thin film of high-resistivity material entirely covering the bottom surface of the second substrate to prevent a radio frequency (RF) signal emitted by the electronic circuit from being coupled to the second substrate. ### Claim 14 (depends on 13) The electronic device of claim 13 wherein the side wall is formed of metal and connected to the second substrate via the thin film. ### Claim 15 (depends on 14) The electronic device of claim 14 wherein the side wall is formed by transient liquid phase bonding. ### Claim 16 (depends on 14) The electronic device of claim 14 wherein a ground line of the electronic circuit is connected to the side wall. ### Claim 17 (depends on 13) The electronic device of claim 13 further comprising a column disposed between the top surface of the first substrate and the bottom surface of the second substrate. ### Claim 18 (depends on 17) The electronic device of claim 17 wherein the column is formed of metal and connected to the second substrate via the thin film. ### Claim 19 (depends on 17) The electronic device of claim 17 wherein the first substrate includes a via extending through a through-hole between the top surface of the first substrate and a bottom surface of the first substrate and connecting the electronic circuit to an external electrode formed on the bottom surface of the first substrate, the column being disposed immediately above the via. ### Claim 20 (depends on 13) The electronic device of claim 13 wherein the low-resistivity material forming the second substrate includes silicon and the high-resistivity material forming the thin film includes at least one of silicon dioxide (SiO2) and aluminum oxide (Al2O3). ### Claim 21 (depends on 13) The electronic device of claim 13 wherein the piezoelectric material forming the first substrate includes at least one of aluminum nitride (AlN) and zinc oxide (ZnO). ### Claim 22 (depends on 13) The electronic device of claim 13 wherein the bulk acoustic wave resonator includes at least one of a film bulk acoustic resonator (FBAR) and a solidly mounted resonator (SMR). ### Claim 23 A method of manufacturing an electronic device, the method comprising: forming an electronic circuit including a bulk acoustic wave (BAW) resonator on a top surface of a first substrate formed of piezoelectric material; forming a thin film entirely covering a bottom surface of a second substrate formed of low-resistivity material, the thin film being formed of high-resistivity material to prevent a radio frequency (RF) signal emitted by the electronic circuit from being coupled to the second substrate; and forming a side wall between the top surface of the first substrate and the bottom surface of the second substrate, the side wall supporting the top surface of the first substrate and the bottom surface of the second substrate and defining a cavity internally including the electronic circuit together with the top surface of the first substrate and the bottom surface of the second substrate. ### Claim 24 (depends on 23) The method of claim 23 wherein the low-resistivity material forming the second substrate includes silicon and the high-resistivity material forming the thin film includes at least one of silicon dioxide (SiO2) and aluminum oxide (Al2O3). ### Claim 25 (depends on 23) The method of claim 23 wherein the piezoelectric material forming the first substrate includes at least one of aluminum nitride (AlN) and zinc oxide (ZnO). ### Claim 26 (depends on 23) The method of claim 23 wherein the bulk acoustic wave resonator includes at least one of a film bulk acoustic resonator (FBAR) and a solidly mounted resonator (SMR). ### Claim 27 (depends on 23) The method of claim 23 wherein the side wall is formed of metal and connected to the second substrate via the thin film. ### Claim 28 (depends on 23) The method of claim 23 wherein forming the side wall includes bonding a first side wall formed on the top surface of the first substrate with a second side wall formed on the bottom surface of the second substrate by transient liquid phase bonding. ### Claim 29 A method of manufacturing an electronic device, comprising: forming an electronic circuit on a top surface of a first substrate formed of piezoelectric material, the electronic circuit including a bulk acoustic wave (BAW) resonator; providing a second substrate formed of high-resistivity material to prevent a radio frequency (RF) signal emitted by the electronic circuit from being coupled to the second substrate; and forming a side wall between and in contact with the top surface of the first substrate and a bottom surface of the second substrate, the side wall defining a cavity together with the top surface of the first substrate and the bottom surface of the second substrate, the cavity internally including the electronic circuit, forming the side wall including bonding a first side wall formed on the top surface of the first substrate with a second side wall formed on the bottom surface of the second substrate by transient liquid phase bonding. ### Claim 30 (depends on 29) The method of claim 29 wherein the high-resistivity material forming the second substrate includes at least one of silicon dioxide (SiO2) and aluminum oxide (Al2O3). ### Claim 31 (depends on 29) The method of claim 29 wherein the piezoelectric material forming the first substrate includes at least one of aluminum nitride (AlN) and zinc oxide (ZnO). ### Claim 32 (depends on 29) The method of claim 29 wherein the bulk acoustic wave resonator includes at least one of a film bulk acoustic resonator (FBAR) and a solidly mounted resonator (SMR).