Reliability testing of MEMS resonators has grown significantly in importance since these devices moved into high
volume production. In line with this development, we present an automated phonon detection-based test setup, which
utilizes a piezoelectric transducer to translate resonator mechanical motion into voltage, for investigating the long-term
frequency stability of clamped-clamped beam resonators. The automated test system we have developed is able to
continuously actuate up to four devices and characterize them every 30 minutes to monitor resonance frequency f0 and
Q-factor changes resultant from long-term actuation. The surface temperature of the devices is also carefully monitored
and the temperature data is used to compensate for the f0 variations caused by temperature fluctuations. The compensated
f0 measurements obtained over time can be used to determine the frequency drift of the resonators. Q-factor degradation
and variations in resonator in-plane displacement can also be detected by our system. The test system was used to
monitor the behaviour of a 168.502 kHz resonator over a 225-hour operating period. The device was actuated in its linear
mode at 29 ±1.0 °C and ~10-1 Pa. It showed an f0 shift of -1.092 Hz/day with Q-factor remaining at ~27,000 throughout.
Resonator displacement was also consistent over the actuation period.
In this work, three useful techniques for dynamic motion characterization of MEMS devices are presented, namely
network analyzer, acoustic phonon detection and stroboscopic SEM techniques. Proof-of-concept experiments using an
MEMS electrostatic resonator reveal reliable and consistent measurement results from the three techniques. The network
analyzer characterization technique is most widely used in practice due to its convenience, high sensitivity and high
speed. The second acoustic phonon technique features non-invasive and package level testing, but it is still an indirect
characterization method, like the network analyzer. In acoustic phonon detection, mechanical waves (phonons) generated
by the actuated MEMS device are used as the coupling mechanism through which information on the dynamic
mechanical state of the device can be obtained. The third stroboscopic SEM technique is capable of directly measuring
the device motion, but its throughput is low and hence not suitable for high volume testing. The stroboscopic SEM
imaging system is based on time-gated sampling of the analogue secondary electron (SE) signal. Unlike conventional
SEM, stroboscopic SEM is able to detect the actual position of the structure at a specific point in time by taking a
time-gated sample of the SEM SE signal at a specific phase of the structure's motion.
Nonlinear behavior of a capacitively driven and sensed micromechanical free-free beam resonator is characterized,
modeled and experimentally verified in this paper. Both the mechanical and electrostatic nonlinear effects are included in
the resonator model. Instead of using the FEM tools which introduces uncertainties to the simulation process, an
alternative semi-analytic method is proposed to identify the resonator parameters from just a few preliminary testing
results. A 615kHz free-free beam resonator was designed, fabricated and studied. From the experimental results, it is
observed that the nonlinear effects in the free-free beam always shift the resonant peak of the beam to a higher frequency
under nonlinear vibration. In order to validate the proposed modeling approach, a nonlinear model was constructed based
on the experimentally extracted parameters and numerically solved in MATLAB. The simulation results were compared
with the experimental data, showing that the measured large-signal frequency domain response can be accurately
reproduced by simulation. Although this work focused on the free-free beam resonator, the proposed modeling approach
is not specific to flexural designs, but is valid for all types of electrostatic resonators. Such a method to predict nonlinear
effects of microresonators will be especially useful for MEMS oscillator and filter applications.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.