Development of tin oxide material by screen-printing technology for micro-machined gas sensors

Screen-printing technology is a low-cost production process that enables to deposit sensing elements for gas sensors, mainly on ceramic substrates. This study is focused on the optimization of inks composition in order to improve the performance of sensors regarding electrical and adhesion properties, on ceramic or smooth substrates like Si-based wafers. It has been demonstrated that it is possible to replace the inorganic vehicles and mineral binders contained in conventional inks by a tin oxide gel. New ink was developed by addition of a SnO2 gel to a commercial SnO2 powder. The gel allows to control the theological properties for ink deposition. Its decomposition at low temperature (250-300 degreesC) to form SnO2 during annealing reinforces the mechanical adhesion of the thick layer on the substrate. As there is no more glassy binder in the ink, the conductance strongly increases. Moreover, the annealing temperatures required for new inks can be lowered contrary to conventional inks, which enhances the compatibility with the microelectronics process regarding the maximum temperatures that wafers can withstand. (C) 2003 Elsevier Science B.V. All rights reserved.