Effects of geometric parameters and limits of application of microelectronic capacitive pressure sensors

The static response of microelectronic capacitive pressure sensors with a fine silicon rectangular membrane or square membrane is studied in the low distortion limit. The response represented by the variation of the capacity with the pressure, presents two parts: a nearly linear part corresponding to values of PN lower than 0,6 (unity) and second highly non linear part for PN higher than 0,6(unity). To improve the linearity, we studied sensors with fixed armatures of different geometries. We show that reduction of the surface of the fixed armature involves a loss of sensitivity but a gain in linearity. On the other hand the extension of the open part of this armature increases the linearity but decreases considerably the sensitivity.