Micromechanical ring resonators with a 2D phononic crystal support for mechanical robustness and providing mask misalignment tolerance

This paper reports on the design of ring-type electrostatically transduced bulk acoustic wave resonators designed for increased shock and vibration resistance. This was achieved through a 2D Phononic Crystal (PnC) support. The PnC is designed to operate in its bandgap so that it acts as a non-propagating medium, hereby achieving simultaneously a mechanically strong and acoustically well-confined support. We manufactured SiGe-resonators at 137.8MHz with a Q-factor of around 17,000. Another feature of this design is the process tolerance of the Q-factor (within 5%) and the resonance frequency towards mask misalignment (<7µm) for the center support.