# US 7,745,975 B2 · Piezoelectric thin film resonator, piezoelectric thin film resonator filter and manufacturing method thereof > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 7,745,975 B2 - Document ID: US7745975B2 - Status: Granted - Kind: B2 - Application number: 11/704,995 - Filed: 2007-02-12 - Published: 2008-07-17 - Granted: 2010-06-29 - Earliest claimed: 2007-01-15 - Assignees: Hitachi Media Electronics Co., Ltd. - Inventors: Kengo Asai; Hisanori Matsumoto; Atsushi Isobe - Web page: https://patentgrep.com/patent/US7745975B2 ## CPC - H03H 9/175: {Acoustic mirrors} - H03H 3/04: for obtaining desired frequency or temperature coefficient - H03H 9/02149: {of ageing changes of characteristics, e.g. electro-acousto-migration} - H03H 9/173: {Air-gaps} - H03H 9/174: {Membranes} - H03H 9/21: Crystal tuning forks - H03H 9/706: {Duplexers} - H03H 2003/021: {the resonators or networks being of the air-gap type} - H03H 2003/023: {the resonators or networks being of the membrane type} - H03H 2003/025: {the resonators or networks comprising an acoustic mirror} - H03H 2003/026: {the resonators or networks being of the tuning fork type} - Y10T 29/42: Piezoelectric device making - H03H: IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS (waveguides, resonators, lines or other devices of the waveguide type H01P) - Y10T: TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION ## Abstract A piezoelectric thin film resonator includes: a piezoelectric thin film; a laminated structure which includes a first metal electrode film and a second metal electrode film that interpose at least a part of the piezoelectric thin film, and which is formed on a substrate; and an acoustic insulating layer which is formed on the substrate at a position corresponding to the laminated structure, wherein the first metal electrode film is formed on the substrate and the second metal electrode film is formed on the first metal electrode film while sandwiching the piezoelectric thin film, and a protection film laminated on the second metal electrode film is provided so as to cover the second metal electrode film. ## Claims ### Claim 1 A piezoelectric thin film resonator comprising: a substrate; a laminated structure including first metal electrode film formed in a vacuum, a piezoelectric thin film formed on the first metal electrode film and a second metal electrode film formed on the piezoelectric thin film, the laminated structure being formed on the substrate; an acoustic insulating layer formed on the substrate at a position corresponding to the laminated structure, and a protection film formed on the second metal electrode film wherein an interface between the protection film and the second metal electrode film has a concentration of at least one of oxygen and hydrogen that is less than 1.E+21 atoms/cc. ### Claim 2 (depends on 1) The piezoelectric thin film resonator according to claim 1, wherein plane shapes of the piezoelectric thin film and the second metal electrode film are substantially the same, and wherein the protection film is formed on an upper surface of the second metal electrode film so as to cover the whole surface of an area where the laminated structure substantially functions as a resonator. ### Claim 3 (depends on 2) The piezoelectric thin film resonator according to claim 2, further comprising: an electrode pad connected with the second metal electrode film is provided, wherein the substantially whole upper surface of the second metal electrode film is covered with the protection film and the electrode pad. ### Claim 4 (depends on 1) The piezoelectric thin film resonator according to claim 1, wherein the second metal electrode film comes into contact with the protection film through an interface. ### Claim 5 (depends on 4) The piezoelectric thin film resonator according to claim 4, wherein the piezoelectric thin film resonator is a piezoelectric thin film bulk acoustic wave resonator, wherein the piezoelectric thin film resonator further comprises: a support film formed on the acoustic insulating layer, and wherein the laminated structure is provided on the support film. ### Claim 6 (depends on 4) The piezoelectric thin film resonator according to claim 4, wherein the piezoelectric thin film resonator is a thin film tuning-fork-shape distorting oscillator, wherein the piezoelectric thin film resonator further comprises: a support film formed on the acoustic insulating layer is provided, and wherein the laminated structure is provided on the support film. ### Claim 7 (depends on 4) The piezoelectric thin film resonator according to claim 4, wherein the acoustic insulating layer is formed on the substrate at a position corresponding to the laminated structure, and wherein the acoustic insulating layer is a Bragg reflection layer in which low acoustic impedance layers and high acoustic impedance layers are alternately laminated. ### Claim 8 (depends on 4) The piezoelectric thin film resonator according to claim 4, wherein the acoustic insulating layer is formed on the substrate at a position corresponding to the laminated structure, and wherein the acoustic insulating layer is a cavity formed in the substrate. ### Claim 9 (depends on 1) The piezoelectric thin film resonator according to claim 1, wherein the protection film contains silicon dioxide, and has a thickness of 50 nm to 600 nm. ### Claim 10 (depends on 1) The piezoelectric thin film resonator according to claim 1, wherein the protection film contains aluminum nitride, and has a thickness of 50 nm to 600 nm. ### Claim 11 (depends on 1) The piezoelectric thin film resonator according to claim 1, wherein the laminated structure is comprised of two laminated structures laminated above and below, and wherein the protection film is formed on an upper surface of the second metal electrode film in the upper laminated structure. ### Claim 12 A piezoelectric thin film bulk acoustic wave resonator filter comprising: a substrate; and a plurality of piezoelectric thin film bulk acoustic wave resonators provided on the substrate, wherein at least one piezoelectric thin film bulk acoustic wave resonator includes: a laminated structure including a first metal electrode film formed in a vacuum, a piezoelectric thin film formed on the first metal electrode film and a second metal electrode film formed on the piezoelectric thin film, the laminated structure being formed on the substrate; an acoustic insulating layer formed on the substrate at a position corresponding to the laminated structure, and a protection film formed on the second metal electrode film wherein an interface between the protection film and the second metal electrode film has a concentration of at least one of oxygen and hydrogen that is less than 1.E+21 atoms/cc. ### Claim 13 (depends on 12) The piezoelectric thin film bulk acoustic wave resonator filter according to claim 12, wherein the protection film contains silicon dioxide. ### Claim 14 (depends on 12) The piezoelectric thin film bulk acoustic wave resonator filter according to claim 12, wherein the protection film contains aluminum nitride. ### Claim 15 (depends on 12) The piezoelectric thin film bulk acoustic wave resonator filter according to claim 12, wherein the second metal electrode film comes into contact with the protection film through an interface. ### Claim 16 (depends on 15) The piezoelectric thin film bulk acoustic wave resonator filter according to claim 15, further comprising: a plurality of first piezoelectric thin film bulk acoustic wave resonators which are series-connected; and a plurality of second piezoelectric thin film bulk acoustic wave resonators which are parallel-connected, wherein at least one piezoelectric thin film bulk acoustic wave resonator includes a first electrode pad connected with the first metal electrode film and a second electrode pad connected with the second metal electrode film, and wherein the substantially whole upper surface of the second metal electrode film is covered with the protection film and the second electrode pad.