ZnO nanowires grown on SOI CMOS substrate for ethanol sensing

Santra, S.
Guha, P. K.
Ali, S. Z.
Hiralal, P.
Ünalan, Hüsnü Emrah
Covington, J. A.
Amaratunga, G. A. J.
Milne, W. I.
Gardner, J. W.
Udrea, F.
This paper reports on the integration of zinc oxide nanowires (ZnO NWs) with a silicon on insulator (SOI) CMOS (complementary metal oxide semiconductor) micro-hotplate for use as an alcohol sensor. The micro-hotplates consist of a silicon resistive micro-heater embedded within a membrane (composed of silicon oxide and silicon nitride, supported on a silicon substrate) and gold bump bonded aluminum electrodes that are used to make an ohmic contact with the sensing material. ZnO NWs were grown by a simple, low-cost hydrothermal method and characterised using SEM, XRD and photoluminiscence methods. The chemical sensitivity of the on-chip NWs to ethanol vapour (at different humidity levels) was characterised at two different temperatures namely, 300 degrees C and 400 degrees C (power consumption was 24 mW and 33 mW, respectively), and the sensitivity was found to be 0.1%/ppm (response 4.7 at 4363 ppm). These results show that ZnO NWs are a promising material for use as a CMOS ethanol gas sensor that offers low cost, low power consumption and integrated circuitry.