High field effect of a new tip type CMOS MEMS gas sensor

A new proposed gas sensor was built to achieve high field with the tip type electrode in a standard CMOS process. The increase of electric field will enhance the chemical reaction rate dramatically. Beyond the conventional chemical sensors with heating power to achieve a high sensitivity, we proposed a total new sensing mechanism with the short distance of electrodes which includes the different distance between electrodes with even higher sensitivity than before without any heating. To form the sensing material SnO₂, we first formed the material Fe₃O₄ with 0.86g FeCl₂ + 1.4g FeCl₃ using in 40ml H₂O at 80°C, and SnO₂ solution is mixed at SnO₂:Fe₃O₄ = 3:1. After the micromachining of CMOS gas sensor, a spin-on of sensing material and the subsequent process of wire-bond were performed. The samples with several electric fields were under test and verified inside a CO gas chamber with the tip type electrode. With careful investigation of measurement results, it shows the proposed configuration with tip electrode sensor reaches the higher sensitivity with the higher electric field, while the normalized sensitivity rises from 107.6 %/ppm to 388 %/ppm under the applied electric field from 1.67 V/μm to 8.33 V/μm. Experimental measurement shows the research is available for CO sensor with high sensitivity under high electric field.