Analysis of CMOS Extended-Gate Field-Effect Transistor With On-Chip Window Based on Uricase/RuO2 Sensing Film

In this study, the extended-gate field-effect transistor (EGFET) with an on-chip sensing window under the TSMC 0.18{\mu }\text{m} 1P6M (one poly and six metals) CMOS process technology was fabricated as a biosensor. The sensing window was composed of six metal layers and functionalized with the ruthenium dioxide (RuO 2 ) thin film and uricase for uric acid detection. The RuO 2 thin film was deposited on the top metal layer of the sensing window using the radio frequency (RF) sputtering system. The silver probe was employed as a reference electrode to provide a voltage to the test solution with a micro-volume of 0.5 {\mu }\text{L} . The properties of the EGFET for uric acid detection were investigated through the semiconductor parameter analyzer. The EGFET had a voltage and the current sensitivity of 8.63 mV/(mg/dL) and 0.17 ( {\mu }\text{A} ) ^{1/2} /(mg/dL), respectively. The device worked with a supply voltage lower than 1.8V. Based on the results, the fabrication of the miniaturized biosensor device was a success. Due to its advantages such as the use of low voltage and its simple fabrication process, it could help realize the development of a wearable biosensor.