One-port active polysilicon resonant microstructures

Abstract

Microsensors based on resonant structures are attractive because of their wide dynamic range, high sensitivity, and frequency shift output. In this paper we discuss theoretical and experimental charateristics of a two-terminal, or one-port, resonant microstructure. An equivalent circuit model that is useful for design and analysis of these devices is presented. This model is verified by experimental measurements, with a worst case error between between model and experimental parameters of 30%. We also describe a process for integrating polysilicon resonant microstructures with onchip NMOS circuitry. A novel feature of this process is the use of rapid thermal annealing (RTA) for strain-relief of the ion-implanted phosphorus-doped polysilicon. The RTA-strain-relieved polysilicon has a Young's modulus of 0.9~1012 dynes/cm2 and residual strain of 0.002% as measured by resonant frequency techniques. This low value of strain indicates that RTA is a useful strain-relief technique.

Micromechanical Mixer-Filters (“Mixlers”)

“…Mixer conditions differ from those of previous work [8] in that the beam is subjected to not only the dc-bias voltage , but also to the large off-resonance ac voltage , both of which influence its resonance frequency by generating electrical stiffnesses [8]- [11]. As such, the expression for the resonance frequency for a clamped-clamped beam with both I/O and frequency tuning electrodes, and under the mixer conditions of Fig.…”

VHF free-free beam high-Q micromechanical resonators

“…The electrical operation of this structure is very similar to that of previous clamped-clamped beam resonators [6]- [9], in that a dc-bias voltage applied to the resonator structure is required to amplify -derived force components at the frequency of , and the detected output current is generated by the action of across the time-varying (at resonance) electrode-to-resonator capacitor : . Note that, unlike many of its two-port predecessors, this device is a one-port device, so its output current must be taken directly off the resonator structure [9]. To allow sensing of the output current from the resonator structure while also applying the dc-bias , a bias tee consisting of the inductor and coupling capacitor is utilized.…”

Fault Detection Considerations in Silicon Based MEMS Resonators by Observing Changes in Dynamic Behaviour

“…U=U DC +U AC is applied to the resonator, where U DC serves for two the purposes: The one is that the resonator does not oscillate at twice the fundamental resonance frequency [12]. It further is directly effective on the transduction.…”