FABRICATION AND MODELING OF CMOS MICROBRIDGE GAS-FLOW SENSORS

We report the fabrication, characterization and modelling of an integrated thermoresistive microbridge gas-flow sensor. It is produced using industrial standard CMOS technology followed by a single maskless post-processing etching step. The sensor principle consists in measuring flow-induced temperature modulations on a heated microbridge by means of integrated polysilicon thermoresistors. Typical values of the flow sensitivity are about 2.5 mV/(m/s) in the linear range. For a quantitative description of the sensor function, an analytical two-dimensional model has been formulated, which in particular takes into account the heat-exchange mechanism between sensor and gas along the surface of the sensor element. We obtain analytical expressions for the output signal resulting from the gas flow; these fit the measured sensor response and, thus, may be used to optimize the sensor design.