Self-polarized capacitive silicon micromechanical resonators via charge trapping

We present for the first time a charge trapping technique as a viable passive biasing mechanism for capacitive silicon micromechanical resonators. Potential wells are created on the surface of the microresonator to trap charges for mimicking a polarization voltage (V_p) of 8 V. With no externally applied V_p, the resonance peak of a 20 μm thick silicon bulk acoustic resonator (SiBAR) with 50 nm transduction air-gaps comes up by ~25 dB from the noise floor. An insertion loss (I.L.) of 30.7 dB and a quality factor (Q) of 59,000 has been measured in vacuum at a resonance frequency of 104.81 MHz.