Using ultrathin polyimide films, a highly sensitive polyimide
humidity sensor has been realized with the highest sensitivity
of 3.4 pF/%RH for thinnest (300 Å) devices. The output of the
devices are very linear with a nonlinearity of less than a few
percent RH. The sensors survive the anodic bonding process
with a very high yield. The stability of the sensor in medium humidity
environments (50%RH) has been evaluated for 10 days
and the sensor is found to drift less than 3%RH during this time
at 37 C. Cycling tests for the sensor show a hysteresis which
is less than 1.75% RH for a 1200 Å device at 37 C and 50%
RH. Scaling the device in area is possible at the expense of reduced
sensitivity