Resonant Inc.
FILTER USING TRANSVERSELY-EXCITED FILM BULK ACOUSTIC RESONATORS WITH TWO FREQUENCY SETTING LAYERS

Abstract:

Acoustic filters and methods are disclosed. A piezoelectric is attached to a substrate, portions of the piezoelectric plate forming one or more diaphragms spanning respective cavities in the substrate. A conductor pattern is formed on a front surface of the piezoelectric plate, the conductor pattern including a plurality of interdigital transducers (IDTs) of a plurality of resonators, interleaved fingers of each of the plurality of IDTs disposed on a respective diaphragm of the one or more diaphragms. A first frequency setting dielectric layer having a first thickness is disposed over the fingers of the IDTs of a first subset of the plurality of resonators. A second frequency setting dielectric layer having a second thickness greater than the first thickness is disposed over the fingers of the IDTs of a second subset of the plurality of resonators, wherein the first subset and the second subset are not identical.