A chemical sensor design using a standard CMOS process

By integrating an electrochemical deposition process and a silicon chip manufacturing process, a chemical sensor based on a floating gate field-effect transistor was developed. The sensor was fabricated using the standard 0.35mum CMOS process with minimal post-processing. A pH-sensitive organic polymer was electrochemically deposited on the "pseudo" floating gate extension. This "pseudo" floating gate extension was an external area connected to the floating gate of the testing device. By monitoring the change of the current-voltage characteristics during exposure to the gas phase of the chemical aqueous solution, the sensor was shown to be feasible with a reasonable sensitivity.