A HIGH-SENSITIVITY CMOS GAS-FLOW SENSOR ON A THIN DIELECTRIC MEMBRANE

We report the first implementation of a double-polysilicon thermopile gas flow sensor in an industrial CMOS process. The sensor uses the Seebeck effect between n-doped and p-doped polysilicon as provided by the CMOS process. In order to prevent a pn-junction between the two materials the polysilicon lines are connected through aluminium contacts. Thermal isolation is achieved by placing the thermopile on a thin silicon dioxide membrane. Sensitivity with respect to nitrogen flow velocity and heating power is 0.36 mV/sccm/mW in the linear range, i.e. one order of magnitude better than our previous CMOS polysilicon/aluminium thermopile sensors (Sensors and Actuators A, 25-27 (1991) 577-581).