Integrated Micro-Heater Solid State Based NO2 Gas Sensors with Enhanced Response

Wednesday, 27 May 2015: 09:45
Continental Room C (Hilton Chicago)


Microelectromechanical systems (MEMS) based integrated gas sensors offer many potential advantages for sensing applications including low power consumption, low fabrication cost, high quality, and reliability. A conductance type gas sensor system can be implemented in a cost effective manner using MEMS technology. In the present work an effort has been made to develop highly sensitive gas sensors for trace level detection of NO2 gas. SnO2 thin film was deposited by RF sputtering technique under 30% O2 and 70% Ar in the reactive gas mixture using a metallic tin (Sn) target at an optimized deposition pressure of 16 mTorr. Bare SnO2 thin film based gas sensor showed a very high sensitivity of ~1.4x104 towards 10 ppm of NO2 gas at a low operating temperature of 100 oC, but with very slow response and recovery times of ~4 min. and ~33min. respectively. Platinum micro-heater has been fabricated using micromachining technique on silicon dioxide membrane of about 1.8 mm thickness which provided improved thermal isolation of the active area. This mircrohotplate has been integrated with the SnO2 based gas sensor for the fast detection of 1 ppm NO2 gas. The temperature of mircrohotplate could be controlled by varying the applied dc voltage. The microhoheater has obtained a maximum temperature of ~800 oC at a dc voltage of 3 V. The SnO2 sensor based on MEMS structure exhibits the maximum sensing response of about 56 towards 1 ppm of NO2 gas at an operating temperature of 70 oC. Thus to attain an operating temperature of 70 oC, the power consumption of MEMS sensor was found to be about 1.2 mW. The studies indicate that the fabricated NO2 gas sensor having integrated micro-heater and SiO2 membrane can be utilized efficiently for the fabrication of a commercial gas sensor with low power consumption.