Fabrication and testing of vertically-actuated polycrystalline SiC micromechanical resonators for MHz frequency applications

Vertically-actuated micromechanical resonators operating at MHz frequencies were fabricated from phosphorus-doped polycrystalline silicon carbide (poly-SiC) films. The films were deposited on thin polysilicon sacrificial layers by atmospheric pressure chemical vapor deposition (APCVD) and surface micromachined into structures using a lift-off patterning technique. The resonators were tested under high vacuum conditions using a transimpedance amplifier-based circuit. The measured resonant frequencies were consistent with what was expected based on device designs and material properties; however, the quality factors were much lower than expected. Equivalent circuit modeling suggested that the low quality factors were due to the electrical resistance of the beams, which was unexpectedly high.