Modeling and simulation of isfet using tcad tool for various sensing films

Ion-Sensitive Field-Effect Transistor (ISFET) is a popular platform for chemical/biochemical sensing. The simulation of the typical Electrolyte-Insulator-Semiconductor structure using commercial TCAD simulators requires mapping of the chemical reactions taking place at the electrolyte-insulator interface to the Fermi-Dirac equations. This paper presents the modelling of ISFET pH sensor using Silvaco TCAD tool and an analysis of the effect of using different sensing films on the performance of the device has been performed. It is observed that the pH sensitivity of ISFET varies significantly with the sensing film deposited on the gate as well as the thickness of the sensing film. We provide a comparative study for Silicon Nitride, Aluminum Oxide and Silicon Dioxide used as sensing films. Output and transfer characteristics are obtained for these films for various pH values. It is observed that aluminum oxide gives better performance than silicon oxide and silicon nitride. The fabrication process of the device with aluminum oxide as the sensing film has been discussed and the effect of thickness of the film on device performance has been shown.