Coplanar Dual Gates Silicon-on-insulator based Ultra-sensitive Ion-Sensitive Field-Effect Transistors for Point-of-Care Biosensor platform

We proposed a silicon-on-insulator (SOI) based coplanar dual gate ion-sensitive field-effect transistor (Cop-DG-ISFET) pH sensor to improve the performance of conventional ISFET pH sensors. Cop-DG-ISFET employs coplanar dual gates consisting of a control gate (CG) and a sensing gate (SG) over the channel, and a floating gate (FG) under the channel. Since CG and SG are capacitively coupled to FG, both gates can be used to modulate FET channel conductance. As a result, this device can amplify the sensing signal according to the capacitive coupling ratio between FG and coplanar gates (CG or SG). Since the amplification factor can be adjusted by the capacitance ratio of SG and CG, the pH sensitivity is improved by reducing the CG area compared to the SG area. Moreover, we evaluated the stability of the device by measuring the hysteresis width and drift rate, and found the stability was improved when the sensitivity was taken into consideration. Therefore, the SOI-based Cop-DG-ISFET sensor is expected to be a promising point-of-care biosensor application platform with a simple structure and excellent sensitivity and stability.