Volume 1, Number 2, 1998, 107 - 126


Recent Advances On The Deposition And Characterization Of The
Sno2 Sol-Gel Derived Thin Layers For Gas Sensing Applications.

C. Cobianu
National Institute of Microtechnology
PO Box 27-17, 77550, Bucharest, Romania

Recent progresses in the field of synthesis and structural characterization of SnO2 sol-gel derived thin films for integrated gas sensing microdevices are presented. Undoped and Sb/Pt doped SnO2 sol-gel layers are prepared for the first from tin (IV) ethoxide and deposited over different types of substrates including porous silicon (PS). Composition and structural investigations of the SnO2 thin films have described the evolution of the Sn-O-Sn chemical bonds during film consolidation (as shown by IR), capability of the SnO2 to penetrate in the pores of PS (as revealed by XTEM, EDXS, RBS, AFM) and the crystalline structure (ED and XRD) of the layer. A simple, IC compatible, SnO2 -based test structure has been used to evaluate the hydrogen sensitivity which presented a maximum at an operating temperature of 400 oC. A low power consumption test structure for gas sensing applications was technologically designed and its thermal regime was simulated by means of 3D finite element "COSMOS" program. The initial predictions indicate that an input power of only 30 mW is enough to obtain 400oC on the suspended dielectric membrane used as a substrate for gas detection.