Demonstration for integrating capacitive pressure sensors with read-out circuitry on stainless steel substrate

Capacitive pressure sensors have lots of potential for commercial applications. However, successful commercial exploitation of highly miniaturized capacitive sensors is often inhibited by the presence of parasitic effects such as environmental noise and parasitic capacitances. Therefore, to alleviate the problems encountered in the capacitive pressure sensor approach, it is important to integrate the sensors and the circuitry as directly as possible. This paper builds on preliminary work reported previously by us [Sens. Actuators A 101 (2002) 231] and focuses on direct integration of read-out circuitry with microfabricated microsensors. These capacitive pressure sensors with three-candidate diaphragm materials (Kapton polyimide film, stainless steel, and titanium) are demonstrated the integration with read-out circuitry on stainless steel substrate. Several approaches for the demonstration of integration have been taken and their various degrees of successes are examined. As the final stage of this study, a commercially available MS3110 Universal Capacitive Read-out IC from Microsensors Inc. in its un-packaged, die-type was used. This chip in its die-form was integrated via wirebonding to the microfabricated sensors. The sensors that are tested using the IC have only the metal diaphragms of stainless steel. The measured value of relative voltage change is 2.85% over the applied pressure range from 0 to 75 kPa. This sensor contains a gap of 21 mum and has a sensitivity of 0.92 mV/kpa. (C) 2004 Elsevier B.V. All rights reserved.