High-Q silicon fin bulk acoustic resonators for signal processing beyond the UHF

This paper reports, for the first time, on the silicon Fin Bulk Acoustic Resonator (FinBAR) technology that enables extreme scaling of integrated signal processing beyond the ultra-high-frequency (UHF) regime. High-aspect-ratio fins are etched in silicon substrate and covered by aluminum nitride films to enable efficient electromechanical transduction of bulk acoustic resonance modes with large coupling coefficient (k
_t
²
). The low phononic dissipation of single crystal silicon, along with suppression of piezoelectric charge redistribution loss in the sidewall transduction result in unprecedentedly high quality-factors (Q) in ultra-and super-high-frequency (SHF) regimes. A prototype FinBAR is presented operating in 3
^rd
and 9
^th
width-extensional modes at 2 GHz and 6 GHz, with Q of 4,800 and 2,300, and k
²
of %1.2 and %0.5, respectively. The resulting record f×Q of 1.4×10
¹³
, the large kt
²
×Q of 58, and lithographical frequency scalability demonstrate the potential of FinBARs to realize SHF acoustic processors for emerging 5G multi-frequency systems.