SnO2/Pt microsensors fabricated on micromachined Si (100) substrate suitable for silicon processing

Using standard photolithography process, thin film SnO₂-based gas sensors were fabricated on Si₃N₄ membrane for detection of CO and H₂. The sensing material with a thickness of 400nm was spin-coated using a sol-gel deposition technique. Platinum was added by deposition of various thicknesses of Pt using an RF sputtering unit onto the spin-coated films after preannealing process. 2% chemically Pt doped sensors were prepared adding appropriate amount of H₂Cl₆Pt.6H₂O to the sol-gel solution. Conductivity measurements of the sensors annealed at different temperatures have been carried out in dry air and in presence of various concentrations of CO and H₂. The Pt-doped sensor prepared by the method of sputter-deposited platinum onto the SnO₂ surface exhibited a high sensitivity for selective detection of H₂. However, the chemically doped sensors showed a considerable high response to CO at a temperature around 170°C. The selectivity of the sensing material was studied toward different reducing gases. SEM and XRD analyses were used to investigate the surface morphology and crystallinity of SnO₂ films after annealing at different temperatures.