Semiconducting Thin-Film Sensors for Detection of Polluting Gases and Floating Particles

Abstract

A micro sensor for polluting gases and organic floating particles has been developed. The sensor is composed of two parts: a sensing element and a micro heater. Both parts are fabricated using thin-film technology, IC fabrication, and a micromachining technique. The sensing film has a double-layered structure; the first layer is a Fe₂O₃-based thin-film and the second layer is a SnO₂-based thin-film. They are deposited by r.f. sputtering on a SiO₂/Al₂O₃/SiO₂ diaphragm formed on a Si substrate. A thin-film heater is also fabricated on a similar diaphragm on another Si substrate. The sensing element and the micro heater are placed in parallel at a distance of about 50μm. The sensor is sensitive to polluting gases such as NO_X, exhaust gases, cigarette smoke, and organic floating particles such as pollen.