FABRICATION OF A MICRO CATALYTIC GAS SENSOR USING THIN-FILM PROCESS AND SI ANISOTROPIC ETCHING TECHNIQUES

A new micro catalytic gas sensor for detecting inflammable gases was f abricated on a Si wafer by thin film deposition and Si anisotropic etc hing. The size of the fabricated sensor was 3.25 x 2.20 mm(2). The sen sor was designed to consist of a catalyst with high surface area and a heater with high temperature coefficient of resistance (TCR) in order to acquire high sensitivity to gases of interest. The TCR of the sens or was found to be 3844 ppm degrees C-1. Sensitivities to methane and butane gases were 2.2 mV 1000 ppm(-1) and 8.9 mV 1000 ppm(-1), respect ively. The optimum applied Wheatstone bridge power was varied in the r ange from 350 to 400 mW, being much smaller than those of commercial p ellistors. It was also found that sensitivities to methane and butane gas were decreased by increasing humidity. (C) 1997 Elsevier Science S .A. All rights reserved.