Hybrid piezoelectric mems resonators for application in bio-chemical sensing

MEMS resonator exhibits extraordinary high sensitivity when used as bio-chemical sensor for detecting weight of specimen, adsorption of molecules or cells, etc. by resonant frequency shift, in which piezoelectric transduction is effective to reduce driving voltage as well as power consumption for portable applications. However, sensitivity of pizeoelectric MEMS resonator is deteriorated by piezoelectric film and complicated resonant structure due to its large energy dissipation and residual stress. This paper reviews and summerizes our recent developed several piezoelectric MEMS resonators, including cantilever actuated by PZT thin film and detected by piezoresistive gauge, beam resonator actuated by PZT thin film and detected by electrostatic sensor, disk/ring resonator actuated and detected by PZT thin film, for the pursuit of high quality-factor (Q-factor), high resonant frequency, and thus better device sensitivity. The detailed device structures were presented in this paper, and the performance of each device was evaluated, investigated, and listed for comparisons. Our experimental results clearly demonstrated that by seperating the PZT thin film from the resonant strcuture or by modulating the resonant mode through novel structure design, preferred high Q-factor were achieved with reasonably high resonent frequency. According to above results, the advantageous and weaknesses of those devices were discussed for application as bio-chemical sensors.