A micromachined tunable resonator fabricated by the CMOS post-process of etching silicon dioxide

This work investigates the fabrication of a micromechanical tunable resonator using the commercial 0.35 mu m complementary metal oxide semiconductor (CMOS) process and the post-process of only one maskless wet etching. The post-process has advantages of easy execution and low cost. The post-process employs an etchant (silox vapox III) to etch the silicon dioxide layer to release the suspended structures of the resonator. The tunable resonator comprises a driving unit, a tuning unit and a sensing unit. The resonant frequency of the resonator can be tuned using a dc-biased electrostatic comb of linearly varied finger-length. Experimental results show that the resonant frequency of the resonator is about 4.8 kHz, and it has a frequency-tuning range of 6.8% at the tuning voltage of 0-25 V.