Chemically Sensitive Field-Effect Sensors for Polar Molecular Detection

The chemically sensitive field-effect sensors were made with simplified silicon chip technology, and its fabrication processing flow was designed based on the metal gate CMOS technology employing only 6 pattern masks. The sensors were measured as field modulation resistors since they were made in its depletion mode. When the selected polar molecules as the analyte polymer were coated on the gate area of sensor instead of the gate metal using self-assembly techniques, the work function and charge distribution in gate dielectric film will be changed, although there is no direct interaction between the semiconductor surface and the analyte polymer, however the electric field in the surface channel was modified since the presence of the analyte polymer, so the channel conductivity is changed according to the self-assembled polar molecules. For our sensors being made, the milliampere magnitude response of conducting currents for each polar molecule was measured with clearly detective sensitivity. For sensors with different sensing area of W/L=50, 100, 150, the average slope which can be extracted from the measured I-V curves is 0.36mA, 0.70mA, 1.22mA/per unit of carbon for alkyl-acid; 0.38mA, 0.66mA, 1.12mA/per unit of carbon for alkyl-alcohol; -0.21mA, -0.36mA, -0.44mA/per unit of carbon for alkyl-amine, respectively.