Vibrating micromechanical resonators with solid dielectric capacitive transducer gaps
Yu-Wei Lin; Sheng-Shian Li; Yuan Xie; Zeying Ren; Nguyen, C.T.C.
Frequency Control Symposium and Exposition, 2005. Proceedings of the 2005 IEEE International
Volume , Issue , 29-31 Aug. 2005 Page(s):128 - 134
Digital Object Identifier 10.1109/FREQ.2005.1573914
Summary:VHF and UHF MEMS-based vibrating micromechanical resonators equipped with new solid dielectric (i.e., filled) capacitive transducer gaps to replace previously used air gaps have been demonstrated at 160 MHz, with Q's ~ 20,200 on par with those of air-gap resonators, and motional resistances (Rx's) more than 8times smaller at similar frequencies and bias conditions. This degree of motional resistance reduction comes about via not only the higher dielectric constant provided by a solid-filled electrode-to-resonator gap, but also by the ability to achieve smaller solid gaps than air gaps. These advantages with the right dielectric material may now allow capacitively-transduced resonators to match to the 50-377 Omega impedances expected by off-chip components (e.g., antennas) in many wireless applications without the need for high voltages. In addition to lower motional resistance, the use of filled-dielectric transducer gaps provides numerous other benefits over the air gap variety, since it (a) better stabilizes the resonator structure against shock and microphonics; (b) eliminates the possibility of particles getting into an electrode-to-resonator air gap, which poses a potential reliability issue; (c) greatly improves fabrication yield, by eliminating the difficult sacrificial release step needed for air gap devices; and (d) potentially allows larger micromechanical circuits (e.g., bandpass filters comprised of interlinked resonators) by stabilizing constituent resonators as the circuits they comprise grow in complexity
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