Design fabrication and test of micromachined-silicon capacitive gas sensors with integrated readout

In 1985 Gerd Binnig and Calvin F. Quate from Stanford and Christopher Gerber from IBM (Zurich) designed the Atomic Force Microscope (AFM), since then a big interest arose around one of its main components; micromachined cantilevers. During all these years, authors have employed these tiny devices to sense multiple physical and chemical parameters through diverse transduction principles. Micromachined cantilevers offer many different transduction mechanisms: force sensing, bimetallic effect, mass loading, medium viscoelasticity, thermogravimetry, stress sensing, and more. Along with all these transduction mechanisms, a great variety of detection methods can be employed with cantilever-based sensors as for example: optical detection, resonance frequency measurement, piezoelectric integrated resistors, etc. The design and fabrication process of a micromachined Silicon capacitive gas sensor are described in this paper. Design and testing of the interface circuitry are also shown with preliminary results.