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Micromechanical voltage reference using the pull-in of a beam

Publication Type:

Journal Article


(IEEE) Transactions on Instrumentation and Measurement, Volume 50, Number 6, p.1504-1507 (2001)



bifurcation capacitive sensors electrostatic actuators finite element analysis mechanical stability micromachining microsensors semiconductor device models transfer standards voltage measurement 200 micron 9.1 to 9.5 V DC voltage reference bifurcati


The pull-in voltage of a single-side anchored freestanding beam, under
lateral deflection, has been investigated for application as a DC
voltage reference. Two sets of electrodes, along side the tip, are
used for parallel-plate type of electrostatic actuation of the 200
?m long beam in the plane of the wafer. Another set of buried electrodes
is aligned with the plate electrode at the free-standing tip and
is used as a differential capacitor for the simultaneous detection
of the displacement, with the purpose to determine the stability
border and thus the pull-in voltage. The single-end clamping ensures
that the pull-in voltage is insensitive to technology-induced stresses.
A 2D energy-based analytical model for the static pull-in is compared
with measurements. Bifurcation diagrams are computed numerically,
based on a local continuation method. Devices have been designed
and fabricated in an epi-poly process. Measurements are in agreement
with modeling and confirm a pull-in voltage in the 9.1-9.5 V range.
Reproducibility is limited by hysteresis and charging of the dielectric
layer in between the electrodes. The device can be operated in feedback
or as a seesaw, by using the two sets of electrodes


E. Cretu, L.A. Rocha, and R.F. Wolffenbuttel [2001] -