6533b85efe1ef96bd12c0579

RESEARCH PRODUCT

B7.3 - Field Effect SnO2 Nano-Thin Film Layer CMOS-Compatible

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description

The integration of metal oxide gas sensing layers into CMOS electronic still a challenge especially due to the high operating temperatures that do not comply with silicon transistor limits , even more critical, and metal oxide annealing temperatures. External electric fields will allow control over the energy levels of the sensing layer and thus over adsorption sensitivity, consequently the interaction between gas and sensitive layer is modulated. As the absorbed gas on the surface produces a band bending, it changes conduction paths allowing gas detection through resistance measurements. With this configuration, field switch offers fast desorption and thus handling of low temperature response times. Also electric fields may be useful to reduce annealing temperatures. In this paper some aspects as design, measurements and models are studied. 1. INTRODUCCTION: The conventional metal oxide gas sensors consist in a hybrid construction of a sensing element, discrete electronics and package. An integration of these sensors on CMOS technology stills a challenge due the high operation temperatures (up to 700° C), where the electronics can not operate anymore. Some observations of the high electric field leading to sensitivity changes in such devices and the knowledge of early semiconductor surface theory motivated our approach to use these effects for the possible control of a novel ultra thin film gas sensor. These external electric fields open the possibility of an electrical control of the energy levels (Fermi-level) and therefore gas sensitivity modulation on the metal-oxide surface, see Fig.1. Because of this fact, they are enabled to operate with relative low temperature (150° C ‐ 200° C) [1]-[9]. This approach enables the integration into CMOS technology together with the signal processing and information systems and eliminates the need for hybrid system setup.