Hydration Effect Analysis of Ion-Sensitive Field Effect Transistor

摘要

In this work, the drift of ISFET characteristics due to the hydration effect was studied. The ISFETs were fabricated using the standard NMOS process and the AgCl reference electrode was fabricated with the electrolysis method. The ISFET modeling was carried out in MATLAB to study the time variation of surface potential and the drain-source current. In addition, the surface morphology and dielectric constant of silicon dioxide were measured to study the hydration effect. It was found that the dielectric constant of the gate oxide increases exponentially with hydration time. The surface morphology studied with the atomic force microscope (AFM) showed no significant change after immersion in water. It is believed that the main cause of the drift is the hydration effect, which is due to the change in dielectric constant of the sensing material and a small number of surface binding sites that react slowly to a change in pH.