Page 64 - MEMS Mechanical Sensors

3.2 Simulation and Design Tools 53

ANSYS

Capacitive Pressure Sensor

Figure 3.12 Element plot of one-quarter of a capacitive pressure sensor diaphragm.

1
Nodal Solution ANSYS
Step = 1 Apr 16 2002
Sub=1 16:19:01
Time=1
Sint (avg)
Dmx = .113E-04
Smn = 432866
Smx = .165E+09

Z
Y MN
X

432866 .371E+08 .737E+08 .110E+09 .147E+09
.188E+08 .554E+08 .920E+09 .129E+09 .165E+09
µ
Chip / Borofloat 33/ Solder (50 m) / Steel diaphragm assembly
Figure 3.13 Finite element stress contour plot of a pressurized steel diaphragm.

diaphragm of a capacitive silicon pressure sensor [13]. The diaphragm was defined
by anisotropically etched double corrugations designed in such a way that as the
diaphragm deflects with applied pressure, it remains flat and parallel to the fixed
electrode. This simplifies the linearization of the sensor output by removing the