Drift Behavior Analysis of ISFET Models Using COMSOL Multiphysics

The Ion-Sensitive Field Effect Transistor (ISFET) has been used for ion concentration detection, with applications spanning biomedicine, environmental monitoring, and agriculture. A challenge that affects the accuracy and reliability of ISFETs is temporal drift. In this paper, we explore the ISFET structure in-depth, focusing on the factors causing temporal drift. Our study employs the COMSOL Multiphysics environment to construct a comprehensive ISFET model that follows the specifications of a commercially available device. Through simulation, we added the behavior of ions in the electrolyte domain and their influence on the device's threshold voltage. Notably, temporal drift, primarily resulting from ion movements and alterations in surface potential, modulates the ISFET's threshold voltage. By understanding these dynamics, illustrated in our macro model, we aim to enhance ISFET designs that exhibit reduced drift, ensuring more stable and accurate ion concentration measurements over time.