Voltage-tunable piezoelectrically-transduced single-crystal silicon resonators on SOI substrate

This paper reports on a new class of high-Q single crystal silicon (SCS) resonators that are piezoelectrically actuated and sensed, and have voltage-tunable center frequencies. The resonating element is made out of the SCS device layer of a SOI wafer. In a unique manner, piezoelectric transduction was integrated with capacitive fine-tuning of the resonator center frequencies to compensate for any process variations. A quality factor of 6,200 was measured for the 1.7 MHz 1st resonance mode of a clamped-clamped beam resonator in 50 m Torr vacuum. A 200 μm long, 4.2 μm thick beam was operated in its higher order modes and demonstrated a Q of 5,300, 3,000, and 2,400 in its 3rd (3.3 MHz), 4th (4.9 MHz), and 5th (6.7 MHz) flexural modes, respectively. A 6 k Hz tuning range was measured for a 719 kHz resonator by applying a DC voltage in the range of 0-20 V.