PROCEEDINGS ARTICLE | December 30, 2008
Proc. SPIE. 7268, Smart Structures, Devices, and Systems IV
KEYWORDS: Microelectromechanical systems, Resonators, Imaging systems, Scanning electron microscopy, Transducers, Measurement devices, Phonons, Acoustics, Motion measurement, Network security
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.
