Two-dimensional integrated gas flow sensors by CMOS IC technology

Two integrated thermal gas flow sensors have been developed for the simultaneous measurement of the velocity and the direction of gas flow. The sensors were fabricated using a commercial CMOS process followed by silicon micromachining. The first sensor consists of two crossed dielectric microbridges, while the second device is based on a dielectric membrane. Both sensors contain integrated heaters and two orthogonal pairs of integrated thermopiles, which constitute a vector probe for the two components of the velocity of gas flows. In contrast to previous designs, the reported sensors show a linear output as a function of flow velocity, with sensitivities of 0.19 and 1.9 V W -1 m -1 s, respectively. Gas flow direction measurements with average errors of 1.7 degrees and 0.6 degrees , respectively, are achieved. We also demonstrate gas flow velocity and direction measurements using the rear of the membrane devices, which opens new perspectives for the packaging of integrated flow sensors. In this configuration a sensitivity of 0.67 V W -l (m/s) -l and an angular resolution of 3.1 degrees were obtained.