Novel CMOS two-dimensional integrated gas flow sensor

A two-dimensional integrated gas flow sensor with on-chip pre-amplifying circuits is demonstrated. The sensor is fabricated by standard CMOS (complementary mental oxide semiconductor) process and post processing anisotropic etching technology. The sensor, which uses four aluminum/p-type polysilicon thermopiles as sensing elements and four polysilicon resistors as heaters respectively, is based on a thin floating membrane composed of the sandwich dielectric layers. The principle of operation is based on the heat transfer from the four heaters to the gas and the detection of the flow-induced temperature gradients in the two directions by the four thermopiles, integrated at four sides of the heaters in this chip. The flow-induced temperature gradients provide information about the magnitude and direction over the full range of 360 degree(s) of the gas flow. When compared to an aluminum/p-type silicon flow sensor of similar dimension, this new structure possesses a much higher sensitivity, and an improved offset and time response behavior.