Physical Model of Temporary Current Instability in Ion- Selective Field-Effect Transistors With Silicon Oxide/Nitride Dielectric Layers

Abstract

The work is devoted to the study of the instability (drift) of the threshold voltage of p-channel ion selective field- effect transistors (ISFET) with an induced channel, caused by the long-term effect of a negative voltage applied to the channel section of the transistor through a double- layer dielectric SiO2/Si3N4. Based on the obtained experimental data, a physical model of the observed instability is proposed, according to which it is caused by the process of accumulation of an unbalanced positive charge in the near-surface layer of silicon nitride. The mechanisms of Pool–Frenkel superbarrier ionization and multiphonon ionization of deep centers are involved in the quantitative calculation of model parameters. Design and technological improvements are outlined that can improve the stability of ISFET sensors for long-term continuous measurements in solutions.