Study of ISFET sensitivity to pH variations using Silvaco TCAD

Abstract

Chemical sensors are increasingly used in healthcare because of their small size, durability, low resistance, and quick reaction time. This research aims to develop a pH biosensor utilizing an ion-sensitive field-effect transistor (ISFET) simulated with Silvaco technology computer-aided design (TCAD) software. The pH range of operation for the ISFET is 2 to 12. Sensitivity was evaluated based on the critical pH value and threshold voltage (V_th) parameters across different gate channel lengths (250 nm, 200 nm, and 50 nm) and sensing membrane thicknesses (3 nm, 10 nm, and 20 nm). The sensitivity of different materials to pH levels was measured. Titanium dioxide (TiO₂) had the highest sensitivity at 57.98 mV/pH, followed by hafnium (IV) oxide (HfO₂) at 57.46 mV/pH, tantalum pentoxide (Ta₂O₅) at 57.36 mV/pH, aluminium oxide (Al₂O₃) at 55.05 mV/pH, and silicon nitride (Si₃N₄) at 54.75 mV/pH. Notably, TiO₂ with a 200 nm gate channel length and a 3 nm sensing membrane thickness demonstrated the highest sensitivity. These findings highlight the potential of ISFETs, particularly those with TiO₂ sensing membranes, as robust and precise pH monitoring platforms in the biomedical industry.