Fabrication of Integrated Dual Type Sensor to Detect Harmful Exhaust Gas and Offensive Odor for Automotive Application

摘要

A dual silicon micro gas sensor device was fabricated using nano sized SnO{sub}2 thin films which had good sensitivities to CO and combustible gases, or to H{sub}2S gas for air quality sensors of automotive application. The integrated dual sensor, which can detect harmful reducing gases, and offensive odors simultaneously with simple integrated structure and low power consumption, was fabricated by MEMS silicon process. The silicon substrate was back etched for thermal isolation of sensing element area after Si{sub}3N{sub}4 layer was deposited on the both side of polished silicon wafer. Thin SnO{sub}2 thin film was deposited by RF magnetron sputtering, and then a thin tin metal layer between 1000 and 2000 A thick was oxidized between 600 and 800℃ by thermal oxidation to make nano sized and porous gas sensing film. The gas sensing layers such as SnO{sub}2, SnO{sub}2(Pt) and SnO{sub}2(+CuO) were patterned by a metal shadow mask for simple fabrication process on the silicon substrate. The sensing elements of the micro gas sensors, SnO{sub}2(+Pt) and SnO{sub}2(CuO) showed good selectivity to CO gas among reducing gases and good sensitivity to H{sub}2S, separately.