Silicon gas flow sensors using industrial CMOS and bipolar IC technology

Abstract

We report two silicon gas flow sensors fabricated by combining silicon micromachining with either standard CMOS or standard bipolar technology. Both sensors are based on the Seebeck effect. An integrated thermopile is placed on a free-standing cantilever beam and measures the temperature difference between the heated tip of the beam and the bulk silicon, which depends on the gas flow. For the CMOS sensor we report an output voltage sensitivity to the gas flow velocity of 1.78 V(m/s) −1/2 W −1 . The sensitivity of the bipolar sensor is 0.26 V (m/s) −1/2 W −1 .