SnO2 sol–gel derived thin films for integrated gas sensors

Abstract In this paper, we present for the first time the compatibility of sol–gel method for SnO 2 thin film preparation with the silicon technology for integrated gas sensor microfabrication. An integrated circuit (IC) compatible test structure of medium power consumption equipped with boron-doped silicon heater and Au/W metallization is developed. The acid composition of the (liquid) sol phase, the thermal budget of sensing layer structuring, selective wet etching of SnO 2 sensing film, thickness uniformity and step coverage of SnO 2 sol–gel films are fitted with the requirement of above test structure where metal layer is deposited before SnO 2 film. Nanometric grain sizes of undoped and antimony doped polycrystalline SnO 2 films are obtained, as revealed by XRD investigations. The AFM measurements of SnO 2 thin films deposited on existing Au/W metallization shown the excellent step coverage and morphology of SnO 2 films used for gas sensing applications. Low temperature gas sensing properties of our SnO 2 sol–gel derived thin films in reducing (CH 4 , CH 3 COOH) and oxidizing (NO 2 ) are preliminary reported by using our integrated test structure.