Low Acoustic Loss Butterfly Lamb Wave Resonator

This study reports a novel AlN Lamb wave resonator (LWR) with anti-resonance quality factor (Q
_a
) as high as 4,021 for the first time, indicating an ultra-low acoustic loss. Conventionally, resonance quality factor (Q
_r
) is widely studied and used for various comparisons. However, it's unconvincing and inconclusive since Q
_r
is always dominated by the routing resistance (R
_s
) which heavily relies on the thick metal re-wiring and probing pad. Instead, Q
_a
is a much better indicator for its independence of R
_s
and precise representation of the acoustic loss. Besides, it predicts quality factors closer to Q
_max
of Bode Q-curve in the IDT-excited devices.A butterfly-shape resonance cavity, theoretically predicted to suppress the transverse spurious mode and reduce the anchor loss, have been applied to the AlN LWR and experimentally shown to boost the Q
_a
by 2.3 times.