A Three-Dimensional Integrated Micro Calorimetric Flow Sensor in CMOS MEMS Technology

This article presents a 3-D integrated molybdenum (Mo) thermoresistive microcalorimetric flow sensor in a 0.18-μm CMOS MEMS technology. The sensor consists of a MEMS structure which is fabricated inside a sealed microchannel and a constant temperature control circuit implemented on the CMOS wafer. The MEMS structure and the CMOS circuit are 3-D integrated at the wafer level. For the N2 gas flow, the proposed flow sensor achieves a high sensitivity of 0.71 mV/(m/s) and a wide bidirectional detection ability of -26-26 m/s. Moreover, an equivalent circuit model is proposed in this article, which depicts the nonlinear output/overheated temperature (V
_out
/ΔT
_h
) sensor response to the input gas flow. This model would be an efficient tool for the design and optimization of high-performance system-on-chip calorimetric flow sensors.