Resonant Inc.
TRANSVERSELY-EXCITED FILM BULK ACOUSTIC RESONATOR WITH A BONDING LAYER AND AN ETCH-STOP LAYER

Abstract:

Acoustic resonator devices and methods are disclosed. An acoustic resonator device includes a substrate having a surface and a single-crystal piezoelectric plate having front and back surfaces. A bonding layer is formed on the surface of the substrate. An etch-stop layer is sandwiched between the bonding layer and the back surface of the single crystal piezoelectric plate. A portion of the single crystal piezoelectric plate and the etch-stop layer, but not the bonding layer, forms a diaphragm spanning a cavity in the substrate. An interdigital transducer (IDT) is formed on the front surface of the single-crystal piezoelectric plate with interleaved fingers of the IDT disposed on the diaphragm. The etch-stop layer is impervious to an etch process used to form the cavity.