Micromachined differential temperature gas flow sensor with on-chip readout electronics

A micromachined gas flow sensor with on-chip readout electronics has been fabricated. It is made up of a suspended polysilicon heater placed between two poly n+/Al thermopiles located on SiO2 cantilever beams upstream and downstream with respect to the gas flow direction. In constant heating power mode, the temperature asymmetry around the heater is converted into the output signal. Response times smaller than 1.5 ms and sensitivity of about 3.5 μV/SCCM have been obtained