Transduction of High-Frequency Micromechanical Resonators Using Depletion Forces in p-n Diodes

We present in this paper the design and fabrication of a homogeneous silicon micromechanical resonator actuated using forces acting on the immobile charge in the depletion region of a symmetrically doped p-n diode. The proposed resonator combines the high quality factor Q of air-gap-transduced resonators with the frequency-scaling benefits of internal dielectrically transduced resonators. Using this transduction method, we demonstrate a thickness-longitudinal-mode micromechanical resonator with Q~18000 at a resonant frequency of 3.72 GHz at room temperature, yielding an f ·Q product of 6.69 × 10¹³ Hz, which is the highest reported value for a silicon micromechanical resonator to date.