Fabrication and calibration of a gas sensor based on chemically vapor deposited WO3 films on silicon substrates Application to H-2 sensing

The electrical resistance of low pressure chemically vapor deposited (LPCVD ) WO3 films exhibits reversible changes when gases, such as hydrogen, are p resent in their environment. Within the frame of this work, WO3 films activ ated with some gold monolayers were integrated, together with a polysilicon hearer and two temperature-sensing resistors, on the same silicon substrat e. For the fabrication, processes typically used in the manufacturing of si licon-based integrated circuits were used. After fabrication, dies with dim ensions of 5 mm x 5 mm have been packed and wire-bonded in classic dual in- line (DIL) packages. The temperature-sensing resistors were calibrated by e xternal heating and monitoring their electrical resistance. Devices were te sted in H-2 and were found to be sensitive to concentrations down to 100 pp m. Sensitivity was dependent on temperature and H-2 concentration. The maxi mum sensitivity (approximately 50%) was observed at temperatures around 120 degreesC. (C) 2001 Elsevier Science B.V. All rights reserved.