COMSOL-Based Modeling and Simulation of ISFET pH Sensor Using Si02 Sensing Film

Abstract

The measurement of pH is an important routine practice in many chemical and biomedical applications. This work reports an Ion Sensitive Field Effect Transistors (ISFET) based pH sensor. The two-dimensional modeling of the sensor is performed in the COMSOL Multiphysics® v. 6.0 platform using its semiconductor module, electrostatics module, and transport of diluted species module. The binding of ions in Si02 results in induced charge carriers in the conducting channel of ISFET, which is controlled by the applied gate voltage for determining ion concentration. Here, the pH of water as the bulk electrolyte is measured by attaining the required gate voltage to achieve a certain drain current in ISFET. The sensor shows excellent sensitivities of 48.7 mV/pH and 41.3 mV/pH with linear detection ranges of pH 1–7 and 8–13, respectively. The excellent sensitivity and wide linear detection range can be attributed to the high concentration of surface sites in the Si02 sensing film and improved disassociation constants in the presence of the gate oxide in contact with the electrolyte. Finally, this sensor demonstrates its potential for real applications.