Gas sensing can be achieved by fingerprinting the ionization characteristics of distinct species. In this study, the
fabrication of a miniaturized gas ionization sensor using polyimide as sacrificial layer is reported. The sensor consists of
two planar metallic electrodes with a gap spacing obtained by the polyimide under-etching. This known sacrificial layer
has the advantage besides a high planarization factor, to be CMOS compatible. Furthermore, its chemical resistance up to
high temperatures, high resistance to radiation from both electrons and neutrons, and low outgassing are of primary
importance to avoid interferences with the ionization gas sensing. A suspended micro-bridge with dimensions 20 μm
width and 220 μm length has been developed and released by using etching holes in the membrane. The ionization
characteristics of air at controlled temperature, humidity and pressure (21°C, 40% humidity and 1 atm) have been
obtained during non-destructive electrical characterizations, with a breakdown voltage of 350 V for a 6 μm gap. The
growth of metallic nanowires templated in ion track-etched polyimide on the electrode is envisioned in order to enhance
the ionization field and to reduce the required measurement power of the sensor.
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