gas

Carmen Moldovan (a), Sebastian Sosin (a), Oana Nedelcu (a), Ulrike Kaufmann (b), Hans-Joachim Ritzhaupt-Kleissl (b),
Stefan Dimov (c), Petko Petkov (c), Robert Dorey (d), Katrin Persson (e), David Gomez (f), Per Johander(g)
a National Institute for R&D in Microtechnologies, Erou Iancu Nicolae 32 B, Bucharest 077190, Romania
b Forschungszentrum Karlsruhe, Institut für Materialforschung III, P.O. Box 3640, 76021 Karlsruhe, Germany ;
c Manufacturing Engineering and Multidisciplinary Technology Centre, Cardiff University;
d Nanotechnology Group, Cranfield University, Cranfield, Bedfordshire, UK;
e IMEGO, Arvid Hedvalls Backe 4, SE 411 33 Goteborg, Sweden;
f Fundacion Tekniker
g IVF - Industrial Research and Development Corporation; Argongatan 30, S431 53 Molndal, Sweden

Abstract

The paper presents the development of a novel suspended membrane resistive gas sensor on a ceramic substrate. The sensor is designed and simulated to be fabricated by combining laser milling techniques, conductive ceramic technology, thin film technology, and semiconductor metal oxides. Trenches are created in the alumina substrate in order to define the geometry of the heater using laser processing of the substrate. The heater is completed by filling the trenches with conductive ceramic paste and then baking to remove the solvent from the paste. The next step consists of polishing the surface to obtain a surface roughness small enough for thin film technology. A dielectric (SiO2 or ceramic) material is then deposited, acting as hot plate and also as electrical isolation between the heater and sensing electrode. The sensing electrode consists of an interdigitated resistor made of Au or Pt with thickness in the range of 2000 -3000 Å. The gas sensitive layer (SnO2) is deposited by screen printing or spinning. When heated it react with gas molecules and changes its resistivity, thereby acting as a sensor. The final step involves releasing the sensor, enabling it to be suspended on four bridges, to minimise the dissipation of the heat in the substrate.