Parylene-Coated Piezoelectrically-Actuated Silicon Disc Resonators for Liquid-Phase Sensing

摘要

In this work a novel surface treatment is applied to thin-film piezoelectric-on-silicon disc resonators that enables liquid phase operation of the resonator while maintaining a high quality factor (Q). By coating the backside and the surrounding trenches of the resonator with Parylene-C, a biocompatible insulation layer is formed that completely avoids the penetration of liquid into small gaps while enabling the surface functionalization for various sensing purposes. The effect of viscous damping on different vibration modes of the disc resonator is investigated and a high order contour mode is identified at 17.2 MHz which exhibits the least drop in the quality factor (Q) when operated in liquid media. A record Q of 440 is measured for this resonance mode in water, corresponding to a ~55% reduction from the Q measured in air. Such high Q values in water facilitate implementation of high resolution liquid-phase mass sensors for biomedical or industrial applications.