Characterization and optimization of Ion-Sensitive Field Effect Transistor (ISFET) with different gate dielectric and thickness

Abstract

The ion-sensitive field effect transistor (ISFET) is one of the emerging chemical sensors with advantages in miniaturization, low-cost manufacture and short response time. Previous studies primarily focused on the types of gate dielectric materials of ISFET and their respective sensitivity in terms of gate voltage. This paper will analyze the effect of the gate dielectric materials and their respective thickness on pH sensing. To achieve this, an ISFET model is developed using COMSOL Multiphysics software. Gate dielectric plays a significant role as sensing film, which has a binding site to detect the ions present in the electrolyte solution. Therefore, gate dielectric materials and their thickness are critical in determining the sensing performance of ISFET. In this study, Y2O3, Ta2O5, HfO2 and TiO2 with 20 nm, 30 nm and 40 nm thicknesses are used as gate dielectric materials. The simulation uses an electrolyte solution with pH values of 3, 7 and 11. The sensitivity of ISFET is determined in terms of the reference voltage and drain current. The ISFET with the highest voltage sensitivity is obtained with TiO2 as the gate dielectric material at 20nm thickness, which shows a sensitivity of 56.25 mV/pH and 22.62 mA/pH, respectively.