A Fully-Integrated, Single-Element CMOS Anemometer

Miniaturized flow rate sensors are increasingly utilized for in situ gas and liquid sensing, where small size, low cost, and robust operation are critical. Many flow rate sensors utilize two sensor elements, a heater, and a downstream temperature sensor, for measurement of mass flow rate. In this article, a single-element flow rate sensor architecture is presented, in which the sensor element and measurement electronics are integrated into a silicon complementary metaloxide semiconductor (CMOS) integrated circuit (IC) substrate. The architecture uses a single, resistive transducer element defined in top-metal CMOS layers, which requires no postfabrication or postprocessing. The design is implemented in a general purpose 0.18 μm CMOS process, and a two-phase control and measurement scheme is used to alternately heat and cool the sensor. Experimental results demonstrate the feasibility of the fully integrated CMOS anemometer for measuring air flow rate, and the complete sensor occupies less than 0.065 mm2 IC chip area.