Lock-in driven quality factor enhancement with parasitic effect compensation of a self-actuated piezoelectric MEMS cantilever

Abstract

State of the art quality factor amplification for resonant MEMS cantilevers requires either complex electronics like highly sensitive analogue circuits or optical read-out to extract a resonance peak shaped feedback signal. In this investigation, a lock-in amplifier is used to extract the Q-control feedback signal which is proportional to the piezoelectric current. Due to influences related e.g. to the layered device architecture and fabrication intolerances of piezoelectric driven MEMS resonators the resonance peak shaped conductance can have an additional offset and a slope in the baseline as well as a dominant susceptance. All these parasitic effects are getting more dominant with higher frequencies by increasing the complex feedback signal. Hence, a higher lock-in input range has to be used leading in an inferior resolution when determining the real part. In this study, an approach for the compensation of these parasitic effects is presented, which gives the possibility to decrease the offset as well as the dominant suceptance leading to increased measurement sensitivity. Using this Q-factor enhancement technique this important device parameter was increased from 1766 to about 9679 in air.Index Terms-Quality factor enhancement, lock-in amplifier, compensation of parasitic effects, Q-control.

The impact of argon admixture on the c-axis oriented growth of direct current magnetron sputtered ScxAl1−xN thin films

“…Owing to properties, such as low permittivity, e r % 10, 1 high Curie temperature (T c ¼ 1150 C), 2 or high sound velocity (v $ 6000 m/s) (Ref. 3), c-axis tilted AlN has been employed for MEMS-based resonators, 4 energy harvesting systems, 5,6 ultrasonic transducers, 7 chemical sensors, 8 accelerometers, as well as for Film Bulk Acoustic Resonators (FBAR) used for duplexers in handheld communication. 9 The efficiency of these devices can be improved over those based on pure AlN thin films by increasing the piezoelectric constants of Sc x Al 1Àx N thin films.…”