This study presents the fabrication and characterization of a micromechanical tunable in-plane resonator. The resonator is manufactured using the commercial 0.35 μm complementary metal oxide semiconductor (CMOS) process. The resonator is made of aluminum, and the sacrificial layer is silicon dioxide. The post-process involves only one maskless etching step using an etchant to remove the sacrificial layer. The resonator includes three parts: a driving part to provide a driving force, a sensing part that is used to detect a change in capacitance when the resonator is vibrating, and a tuning part that changes the resonant frequency of the resonator. The main advantages of the tunable resonator are a low driving voltage and compatibility with the CMOS process. The resonant frequency of the resonator can be changed upon applying a dc voltage to the tuning part. To reduce the driving voltage, the driving part is designed as comb-finger rows. Experimental results show that the resonator has a resonant frequency of about 183 kHz and a driving voltage of 10 V; the resonant frequency increases 14 kHz when a tuning voltage of 30 V is applied. The resonator has a maximum frequency-tuning ratio of 7.6%.
Keywords: CMOS-MEMS; Low driving voltage; Micromechanical tunable resonators.