Characterisation and stabilisation of Pt/TaSix/SiO2/SiC gas sensor

In this work the electrical characterisation as well as the chemical and structural analysis of MOS devices with Pt/TaSix catalytic gates fabricated on 6H-SiC substrates for their use as gas sensors is presented. Layers obtained under different conditions have been deposited on Si wafers in order to learn about the mechanisms of formation of the different layers constituting the gate area. The electrical characterisation of the devices as a function of the operating temperature and in the presence of gases CO, NO2 and C3H8 has been performed. Annealing the MOS capacitors in C3H8 ambient during some hours has been found necessary for their electrical stabilisation and for their activation as gas sensors. The maximum response obtained to 1000 ppm of CO is 80 mV at 250 °C and to 10 ppm of NO2 is 71 mV at 310 °C. On the other hand, the tunnel MOS diodes, which have been annealed at 700 °C in air during 3 min, show worse sensitivity to both gases. The same annealing made on capacitors is now under study for the diodes.