Micromachining of silicon substrate and ultrathin Si3N4 membrane technologies for the fabrication of integrated thin film gas sensors

A fabrication technology suitable for the realization of the substrate for thin film gas sensors operating at high temperatures is presented. A very thin silicon nitride membrane is obtained by micromachining of silicon. A heating resistor and the relevant temperature sensor are realised in the middle of the membrane. Apassivation film is deposited between the sensing layer and these components to achieve electrical insulation. Results of computer simulations and experimental investigations carried out on realised microstructures are presented.