US 11,901,873 B2
Transversely-excited film bulk acoustic resonator with partial BRAGG reflectors
Ventsislav Yantchev, Sofia (BG)
Assigned to MURATA MANUFACTURING CO., LTD., Nagaokakyo (JP)
Filed by Murata Manufacturing Co., Ltd., Nagaokakyo (JP)
Filed on Mar. 16, 2020, as Appl. No. 16/819,591.
Claims priority of provisional application 62/818,568, filed on Mar. 14, 2019.
Prior Publication US 2020/0295729 A1, Sep. 17, 2020
Int. Cl. H03H 9/02 (2006.01); H03H 9/17 (2006.01); H03H 9/205 (2006.01); H03H 9/64 (2006.01)
CPC H03H 9/02228 (2013.01) [H03H 9/02015 (2013.01); H03H 9/02559 (2013.01); H03H 9/02992 (2013.01); H03H 9/175 (2013.01); H03H 9/205 (2013.01); H03H 9/6406 (2013.01)] 14 Claims
OG exemplary drawing
 
1. An acoustic resonator device comprising:
a substrate having a surface;
a single-crystal piezoelectric plate attached to the surface of the substrate except for a portion of the piezoelectric plate forming a diaphragm that spans a cavity over the substrate in a thickness direction of the substrate that is orthogonal to the surface of the substrate;
an interdigital transducer (IDT) on a surface of the single-crystal piezoelectric plate such that interleaved fingers of the IDT are disposed on the diaphragm, the piezoelectric plate and the IDT configured such that a radio frequency signal applied to the IDT excites a primary shear acoustic mode in the diaphragm;
a back-side partial Bragg reflector on a back surface of the diaphragm, the back-side partial Bragg reflector consisting of a layer of low acoustic impedance dielectric material on the back surface of the diaphragm and a layer of high acoustic impedance dielectric material on the layer of low acoustic impedance dielectric material and opposite the diaphragm; and
a front-side partial Bragg reflector on a front surface of the diaphragm, with the front surface of the diaphragm opposing the back surface of the diaphragm, the front-side partial Bragg reflector consisting of a layer of low acoustic impedance dielectric material on the front surface of the diaphragm and a layer of high acoustic impedance dielectric material on the layer of low acoustic impedance dielectric material and opposite the diaphragm,
wherein each of the back-side partial Bragg reflector and the front-side partial Bragg reflector is structurally configured such that the respective reflectors do not reflect at least a portion of energy of an incident acoustic wave when the primary shear acoustic mode is excited in the diaphragm, and
wherein the primary shear acoustic mode is a bulk shear mode where acoustic energy propagates along a direction substantially orthogonal to the surface of the single-crystal piezoelectric plate and transverse to a direction of electric field created by the IDT.