MEMS gas sensor of resistive type for detection of hydrogen sulfide down to low concentrations

The technological route to manufacture a resistive-type MEMS gas sensor for low analyte concentration detection is proposed and the main characteristics of the device are demonstrated. MEMS consists of a silicon substrate with nickel interdigital electrodes acting as a microheater, on top of which a thin (100 nm) gas-sensitive layer of nickel oxide (NiO) is deposited. The silicon substrate is etched from the back side of the device to achieve a membrane of about 50 microns. The operating temperature of the sensitive layer in measurement mode is 130–205 °C. The proposed device shows the effect of introducing hydrogen sulfide in a gas mixture from 1 to 100 ppm on the conductivity of the sensing layer.