Thermal Analysis and Characterization of a High Q Film Bulk Acoustic Resonator (FBAR) as Biosensers in Liquids

This paper presents the thermal analysis and characterization of a zinc oxide (ZnO) based film bulk acoustic resonator (FBAR) having a high quality factor (Q) in liquid environments for biosensing applications. Q of up to 120, an improvement of at least 8times greater than state-of-the-art devices in liquids, are achieved by integrating microfluidic channels with heights comparable to the acoustic wavelength in FBAR. In order to achieve temperature stability in the highly sensitive FBAR sensor, we analyze sources of thermal effects and characterize FBAR in a Pierce oscillator. Measurements show a temperature coefficient of oscillation frequency (TCF) of -112 ppm/K for the uncompensated circuit. We show that this thermal drift can be reduced to less than 1 ppm/K by applying a properly chosen bias to the oscillator, which suggests the possibility of a feedback approach to achieve thermal stability.