A servo-controlled capacitive pressure sensor using a capped-cylinder structure microfabricated by a three-mask process

A silicon-micromachined servo-controlled capacitive pressure sensor is described. The use of a capped-cylinder shape with pick-off electrodes external to a sealed cavity permits this device to be fabricated in only three masking steps. Device behavior is evaluated experimentally and by finite element analysis. A fabricated device with 2 mm diameter, 9.7 [micro]m structural thickness and 10 [micro]m cavity height provides a measured sensitivity of 0.516 V/kPa over a dynamic range of 20-100 kPa gauge pressure, with a nonlinearity of Index Terms--Dissolved wafer process, liquid encapsulation, pressure sensor, servo-controller.