PROCEEDINGS ARTICLE | February 15, 2012
Proc. SPIE. 8250, Reliability, Packaging, Testing, and Characterization of MEMS/MOEMS and Nanodevices XI
KEYWORDS: Microelectromechanical systems, Actuators, LabVIEW, Particles, Scanning electron microscopy, Capacitance, Humidity, Computer aided design, Adhesives, Plasma
A MEMS tribogauge was used for on-chip and in-situ characterization of nano-tribological phenomena
(stiction, friction, and wear of coated polysilicon surfaces). The device was fabricated using the SUMMiT-V
process. Measurements were made on sidewall surfaces on the polysilicon-3 layer. The device consists of two
orthogonally positioned comb-drive assemblies that are used for both actuation and sensing. One assembly is used to
apply a normal load (Fn) to contacting surface, while the other induces a tangential load (FT). Precise position
control is tracked by employing a LabVIEW controlled AD7747 capacitance sense mechanism. The resolution of
the characterization apparatus is ±10nm.
Three MEMS tribogauge devices are tested; two of them have a chemisorbed layer of self-assembled
monolayer (SAM) coatings and one with no SAM coating. The two types of SAM coatings are FOTS and 'Sandia
vapor-SAM' (SVSAM). The tribogauge with no FSAM coating is either UV-Ozone or 'air plasma' treated to
remove organic contaminants leaving behind -OH bonds on top of the MEMS surface (native oxide, SiO2).
Characterization using the tribogauge for each coating type includes: measurement of baseline stiction force [see manuscript], static and dynamic coefficient of friction [see manuscript], induced stiction force
calculated after specific load cycles [see manuscript]. Experiments showed that the induced stiction force
increases in proportion to the increase in the number of load cycles, indicating degradation of the FSAM coating and
topographical changes to the interacting surfaces. The UV-Ozone /air plasma treated pristine tribogauge was used to
measure the stiction force of the device with no SAM coating [see manuscript].
