Sensors and Actuators - Fachbereich Physik der Universität ...

Fortsetzung Beschleunigungssensoren
Kapazitive Messung
Alternative Bauweise:
Beschleunigungssensor nach Bauart der Feinwerktechnik (FWT) der Uni KL
In bulk micromachined capacitive acceleration sensors, the cantilever structure etch out
from Si is bonded between an upper and lower wafer or metallized glass substrates. An
acceleration perpendicular to the wafer surface moves the seismic mass out of its center
position. The displacement is detected by the top and bottom capacitors between the
wafers. A capacitive half bridge is generally used for signal pickup.
Silicon bulk micromachined acceleration sensor: aus Silizium gefertigter Beschleunigungssensor
In surface micromachined Si sensors movable polysilicon structures are etched out using
sacrificial layers. The seismic mass is suspended at the four corners by springs. The fingers
to both sides of the seismic mass as well as fingers attached to the wafer surface form a
capacitance for signal pickup. This capacitance is changed during acceleration. In contrast
to bulk micromachining, surface micomachining uses movements parallel to the wafer
surface.
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