Integration by shadow mask process of ZnO:Ga sputtered layers onto microsensor platform for detection of sub-ppm acetaldehyde concentration

Micro-hotplates have been first prepared by using silicon microtechnologies onto a thin membrane, it was then possible to generate very fast temperature variations (from room temperature to 550 ° C in 25ms) and a rapid temperature cycled mode could be applied. A low cost and reliable stencil mask method has been developed and successfully tested during the integration of ZnO:Ga layer. The variation of the resistance of this 50 nm thick sensitive layer has been measured under 500 ppb of acetaldehyde (C 2 H 4 O). The very high response obtained was between 10 and 1000 depending on the working temperature.