Resonant Inc.
Transversely-excited film bulk acoustic resonator using pre-formed cavities

Abstract:

Acoustic resonator devices and filters are disclosed. An acoustic resonator device includes a substrate having a surface, wherein the surface comprises an etched cavity, and a single-crystal piezoelectric plate having parallel front and back surfaces, the back surface attached to the surface of the substrate except for a portion of the piezoelectric plate forming a diaphragm that spans the cavity. An interdigital transducer (IDT) is formed on the front surface of the single-crystal piezoelectric plate, wherein interleaved fingers of the IDT are aligned with the cavity such that the interleaved fingers are disposed on the diaphragm. The IDT is configured to excite a primary acoustic mode in the diaphragm in response to a radio frequency signal applied to the IDT. The substrate further includes an alignment pattern that is separate from resonator cavities to facilitate alignment of the piezoelectric plate and the interleaved fingers, the alignment pattern comprising a trench.