A parallel plate capacitor with four silicon support beams is shown below. (a)
The top plate has area of 1×1 mm2. Calculate the capacitance values for two distances
between the electrode plates: 2 and 0.5 ?m. The medium is air.(b) The four support
beams are each 500 ?m long, 5 ?m wide, and 0.3 ?m in thickness. What is the
force constant Km experienced by the parallel plate capacitor? (diagram not drawn to
scale).
(b) If the support beams becomes 0.25 mm long (i.e. half as long as before), which of
the following statement would be correct?
(1) The pull-in voltage would increase by four times
(2) The plate would pull in when the displacement of the beam exceeds xo/6 instead.
(3) The electric force constant (ke) at the pull-in point will be increased by 8 times.
(4) The resonant frequency of the device will decrease.
