High Performance SOI-CMOS Wall Shear Stress Sensors

Here we present for the first time, a novel silicon on insulator (SOI) complementary metal oxide semiconductor (CMOS) MEMS thermal shear stress sensor for turbulent flow measurements based on aluminum hot-film as a sensing element. These devices have been fabricated using commercial 1 mum SOI-CMOS process followed by a deep reactive ion etch (DRIE) back-etch step, offering low cost and the option of circuit integration. The sensors have a good spatial resolution (size 130 mum times 130 mum) and a very efficient thermal isolation (due to their location on a 500 mum times 500 mum, low thermal conductivity silicon oxide membrane). Results show that these sensors have a high temperature coefficient of resistance (TCR) (0.319%/degC), a low power consumption (below 10 mW for 100degC temperature rise) and a high reproducibility within a wafer and from wafer to wafer. In constant temperature (CT) mode, the sensors exhibit an average sensitivity of 22 mV/Pa in a wall shear stress range of 0-1.5 Pa and an ultra-short time constant of only 17 mus, which corresponds to a high cut-off frequency of 39 kHz.