H2S RESPONSE OF WO3 THIN-FILM SENSORS MANUFACTURED BY SILICON PROCESSING TECHNOLOGY

Thin-film sensors based on tungsten trioxide (WO3) were manufactured on oxidized 100 mm silicon wafers using standard silicon processing technology with 2 to 4 lithography steps. Reactive sputtering together with plasma etching for film patterning was used to manufacture the WO3-sensing films. Electron microscopic studies together with X-ray diffraction and Rutherford back scattering (RBS) measurements were used for the characterization of the properties of the sputtered WO3-sensing films. Response characteristics of the sensors were tested in the laboratory using a computer-controlled testing facility. After some preliminary test results, the sensor structure was modified. The H2S response properties of the final sensors were studied both in dry and wet synthetic air with different amount of humidity. Several different operational parameters related to the response and recovery times and to the interfering effects of CO, CH4, NO and NO2 were also tested.