A high-frequency (HF) micromechanical bandpass filter fabricated using the commercial 0.35 μm complementary metal oxide semiconductor (CMOS) process and the post-process has been investigated in this study. The area of the filter is about 150×200 μm 2 . The filter is composed of two resonators, which are joined by a coupling beam. Each resonator contains a membrane, four supported beams and two fixed electrodes, and the membrane is supported by four supported beams. The filter requires a post-process to etch the sacrificial layer, and to release the suspended structures. The post-process needs only one wet etching to etch silicon dioxide layer. The filter contains a sensing part and a driving part. When applying a driving voltage to the driving part, the sensing part generates a change in capacitance. The capacitance variation of the sensing part is converted into the output voltage by a sensing circuitry. Experiments show that the filter has a center frequency of about 39.6 MHz and a bandwidth of 330 kHz.
- Micromechanical filter