Beyond Nernst Sensitivity of Ion Sensitive Field Effect Transistor based on Ultra-Thin Body Box FDSOI

Abstract

This paper reports an ultrahigh-sensitive ISFET sensor that is developed using TCAD model of the industrial 22-nm ultrathin body and buried oxide (UTBB) fully depleted silicon-on-insulator (FDSOI) transistors. The modeling method is exploited by changing the potential surface charge depending on the electrolyte pH change and investigating how will it cause the threshold voltage shift of ISFET device and other transfer characteristic parameters. The properties of a user-defined material offered by Silvaco are exploited to simulate the electrolyte behavior. The parameters of silicon semiconductor material (i.e., energy bandgap, permittivity, affinity, and density of states) are set to reconstruct an electrolyte solution. The electrostatic solution of the electrolyte area is investigated by giving a numerical solution for the semiconductor equation inside this area. On the other hand, the strong electrostatic coupling between the front gate and the back gate of FDSOI devices provide an intrinsic signal amplification feature for sensing applications. Utilizing a layer deposited Titanium dioxide (TiO2) as a pH sensing film, pH sensors having a sensitivity ∼1250 mV/pH is reported. The small sensing area and the FDSOI-based technology of the device make the sensors ideal for the IoT market.