# US 2017/0256701 A1 · Piezoelectric device and production method for piezoelectric device > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2017/0256701 A1 - Document ID: US20170256701A1 - Status: Published application - Kind: A1 - Application number: 15/600,828 - Filed: 2017-05-22 - Published: 2017-09-07 - Earliest claimed: 2014-12-08 - Assignees: Murata Manufacturing Co., Ltd. - Applicants: Murata Manufacturing Co., Ltd. - Inventors: Yutaka KISHIMOTO - Web page: https://patentgrep.com/patent/US20170256701A1 ## CPC - H10N 30/082: by etching, e.g. lithography - H03H 3/02: for the manufacture of piezoelectric or electrostrictive resonators or networks (H03H3/08 takes precedence) - H03H 3/08: for the manufacture of resonators or networks using surface acoustic waves - 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 9/25: Constructional features of resonators using surface acoustic waves {(devices for manipulating acoustic surface waves in general G10K11/36)} - H10N 30/05: Manufacture of multilayered piezoelectric or electrostrictive devices, or parts thereof, e.g. by stacking piezoelectric bodies and electrodes - H10N 30/086: by polishing or grinding - H10N 30/202: {using longitudinal or thickness displacement combined with bending, shear or torsion displacement} - H10N 30/704: {based on piezoelectric or electrostrictive films or coatings} - H03H 2003/021: {the resonators or networks being of the air-gap type} - H10N: ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR - H03H: IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS (waveguides, resonators, lines or other devices of the waveguide type H01P) ## Abstract A piezoelectric resonator includes a piezoelectric thin film including a functional conductor, a fixing layer provided on a principal surface of the piezoelectric thin film to define a void that overlaps a functional portion region, and a support substrate on a principal surface of the fixing layer. A sacrificial layer is provided on a principal surface of a piezoelectric substrate and the fixing layer is provided on the principal surface of the piezoelectric substrate to cover the sacrificial layer. The support substrate is attached to a surface of the fixing layer and the piezoelectric thin film is peeled from the piezoelectric substrate. The functional conductor is provided on the piezoelectric thin film, a through hole is provided in the piezoelectric thin film to straddle a boundary between the fixing layer and the sacrificial layer, and the sacrificial layer is removed by wet etching using the through hole to form the void. ## Claims ### Claim 1 A piezoelectric device comprising: a piezoelectric film including a through hole provided in a thickness direction; a functional conductor provided on the piezoelectric film; a fixing layer provided on a principal surface of the piezoelectric film such that a void overlaps a region where the functional conductor is provided in plan view; and a support substrate provided on a first principal surface of the fixing layer, the first principal surface being opposite to a second principal surface of the fixing layer which is a principal surface of the piezoelectric film side; wherein the fixing layer includes a step provided in an inner wall surface of the fixing layer at a position overlapping the through hole in plan view. ### Claim 2 (depends on 1) The piezoelectric device according to claim 1, wherein the step is provided at a position between the second principal surface and a bottom of the fixing layer, in a direction of a thickness of the fixing layer; and an angle of inclination of the step is different from an angle of inclination of the inner wall surface except for the step, in a cross-sectional view. ### Claim 3 (depends on 1) The piezoelectric device according to claim 1, wherein the functional conductor includes functional conductors disposed to define an interdigital transducer. ### Claim 4 (depends on 3) The piezoelectric device according to claim 3, wherein the multiple functional conductors are electrically connected to wiring conductors provided on a front surface of the piezoelectric film. ### Claim 5 (depends on 4) The piezoelectric device according to claim 4, wherein the wiring conductors are provided on the front surface of the piezoelectric film to not overlap the void. ### Claim 6 (depends on 4) The piezoelectric device according to claim 4, wherein the multiple functional conductors and the wiring conductors are made of Al, Cu, or Au. ### Claim 7 (depends on 1) The piezoelectric device according to claim 1, wherein a plurality of the through holes are provided. ### Claim 8 (depends on 7) The piezoelectric device according to claim 7, wherein the plurality of the through holes are provided at an outermost boundary of a periphery of the void. ### Claim 9 (depends on 1) The piezoelectric device according to claim 1, wherein the step is located at an off-center position in the through hole. ### Claim 10 A production method for a piezoelectric device including a piezoelectric film including a functional conductor provided thereon, a fixing layer provided on a principal surface of the piezoelectric film such that a void overlaps a region where the functional conductor is provided in plan view, and a support substrate provided on a principal surface of the fixing layer opposite to the piezoelectric film, the production method comprising the steps of: forming a sacrificial layer on a principal surface of a piezoelectric substrate; forming the fixing layer on the principal surface of the piezoelectric substrate to cover the sacrificial layer; attaching the support substrate to a surface of the fixing layer opposite to the piezoelectric substrate; forming the piezoelectric film from the piezoelectric substrate; forming the functional conductor on the piezoelectric film; forming a through hole in the piezoelectric film by performing a dry etching at positions on the piezoelectric film straddling a boundary between the fixing layer and the sacrificial layer in plan view to define a step in an inner wall surface of the fixing layer; and removing the sacrificial layer by wet etching using the through hole, to form the void. ### Claim 11 (depends on 10) The production method for a piezoelectric device according to claim 10, further comprising a step of determining whether the step has been formed before the wet etching is performed. ### Claim 12 (depends on 11) The production method for a piezoelectric device according to claim 11, wherein the process of forming the through hole including performing the wet etching after the step has been determined. ### Claim 13 (depends on 10) The production method for a piezoelectric device according to claim 10, wherein the step is defined at a position between the principal surface and a bottom of the fixing layer, in a direction of a thickness of the fixing layer; and an angle of inclination of the step is different from an angle of the inner wall surface except for portions below the step, in a cross-sectional view. ### Claim 14 (depends on 10) The production method for a piezoelectric device according to claim 10, wherein the functional conductor includes multiple functional conductors disposed to define an interdigital transducer. ### Claim 15 (depends on 14) The production method for a piezoelectric device according to claim 14, wherein the multiple functional conductors are electrically connected to wiring conductors formed on a front surface of the piezoelectric film. ### Claim 16 (depends on 15) The production method for a piezoelectric device according to claim 15, wherein the wiring conductors are formed on the front surface of the piezoelectric film to not overlap the void. ### Claim 17 (depends on 14) The production method for a piezoelectric device according to claim 14, wherein the multiple functional conductors and the wiring conductors are formed of Al, Cu, or Au. ### Claim 18 (depends on 10) The production method for a piezoelectric device according to claim 10, wherein a plurality of the through holes are formed. ### Claim 19 (depends on 18) The production method for a piezoelectric device according to claim 18, wherein the plurality of the through holes are provided at an outermost boundary of a periphery of the void. ### Claim 20 (depends on 10) The production method for a piezoelectric device according to claim 10, wherein the step is formed at an off-center position in the through hole.