A low cost high sensitivity CMOS MEMS gas sensor

A CMOS micromachined gas with advantages of CMOS standard process and high sensitivity is presented in this paper. The proposed gas sensor was built with array of floating membranes and serially connected over an etched cavity. Finger type electrodes are built for sensing the resistance of coated sensor material. A proposed highly integrated multi-layer structure of electrodes is formed with metal/via layers in series to derive a lower and stable resistance of sensing material. The micro heater of n-type polysilicon with 4.2 kΩ is situated beneath each active area of the membrane to obtain a stable working temperature with an 120μW power consumption. The sensing material SnO₂ was deposited onto the electrodes after sol-gel formation. Furthermore, the samples are fabricated by TSMC 0.35μm 2P4M CMOS process which is provided by CIC with outstanding strong structures and high sensing performance with the minimum CO concentration under 4ppm. The experimental measurement shows the research is applicable for a low cost CO sensor with enough sensitivity.