2-DIMENSIONAL INTEGRATED GAS-FLOW SENSORS BY CMOS IC TECHNOLOGY

Two integrated thermal gas flow sensors have been developed for the si multaneous measurement of the velocity and the direction of gas flow. The sensors were fabricated using a commercial CMOS process followed b y silicon micromachining. The first sensor consists of two crossed die lectric 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 t he two components of the velocity of gas flows. In contrast to previou s 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, respe ctively. Gas flow direction measurements with average errors of 1.7 de grees and 0.6 degrees, respectively, are achieved. We also demonstrate gas flow velocity and direction measurements using the rear of the me mbrane devices, which opens new perspectives for the packaging of inte grated flow sensors. In this configuration a sensitivity of 0.67 V W-1 (m/s)(-1) and an angular resolution of 3.1 degrees were obtained.