Science and Technology of MEMS/NEMS Resonators: Si vs. Diamond Platform Materials

Having recently been demonstrated at frequencies over 1GHz with measured Q's>10,0001(-6), MEMS/NEMS resonators in silicon, SiC and CVD diamond structural materials have great potential for enabling resonant mass sensing down to zeptogram resolution as well as on-chip high-Q passives needed in wireless communication systems for frequency generation, translation and filtering. However, the acceptance of such devices for RF applications in present-day transceivers has been hindered so far by several remaining issues, including: (1) a frequency range lower than 5 GHz, (2) higher motional impedances than normally exhibited by macroscopic high-Q resonators, (3) limited linearity and power handling ability, and (4) insufficient frequency repeatability and stability. This paper reviews several material-centric strategies for alleviating the aforementioned issues. Given that resonance frequency is generally proportional to the acoustic velocity while energy dissipation and Q is also a strong function of the material properties, several device-oriented and system-level performance-enhancing technologies will be discussed. Both capacitively-transduced and piezoelectrically-transduced resonators will be discussed with a particular emphasis on the employment of transducers with improved electromechanical coupling coefficient as the device-level method for lowering the motional impedance.