Fabrication and characterization of micro-gas sensor for nitrogen oxides gas detection

WO3-based thin film micro-gas sensor was fabricated and the NOx gas sensing as well as electrical properties have been investigated. To obtain the optimal heat distribution, the structure of micro-hot plate was designed from the result of finite element simulation and was prepared by backside etching with KOH solution. cro-hot plate was made out of N/O/N diaphragm with the thickness of 0.6 μm and area of 1.5×1.5 mm2. The power consumption to maintain the device temperature of 300°C was about 60 mW. WO3 thin film was thermally evaporated on micro-diaphragm. The film exhibited a fast response to NO2 gas and the relationship between sensitivity and NO2 concentration showed good linearity in the gas concentration range of 0–30 ppm NO2. The sensitivity of micro-gas sensor to NOx was correlated with the microstructure of the thin film.