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

Thin-film sensors based on tungsten trioxide (WO3) were manufactured o n oxidized 100 mm silicon wafers using standard silicon processing tec hnology with 2 to 4 lithography steps. Reactive sputtering together wi th plasma etching for film patterning was used to manufacture the WO3- sensing films. Electron microscopic studies together with X-ray diffra ction and Rutherford back scattering (RBS) measurements were used for the characterization of the properties of the sputtered WO3-sensing fi lms. Response characteristics of the sensors were tested in the labora tory using a computer-controlled testing facility. After some prelimin ary test results, the sensor structure was modified. The H2S response properties of the final sensors were studied both in dry and wet synth etic air with different amount of humidity. Several different operatio nal parameters related to the response and recovery times and to the i nterfering effects of CO, CH4, NO and NO2 were also tested.