A TCAD-Based Methodology to Model the Site-Binding Charge at ISFET/Electrolyte Interfaces

Abstract

We propose a new approach to describe in commercial TCAD the chemical reactions that occur at dielectric/electrolyte interface and make the ion sensitive FET (ISFET) sensitive to pH. The accuracy of the proposed method is successfully verified against the available experimental data.\ud We demonstrate the usefulness of the method by performing, for the first time in a commercial TCAD environment, a full 2-D analysis of ISFET operation, and a comparison between threshold voltage and drain current differential sensitivities in the linear and saturation regimes. The method paves the way to accurate\ud and efficient ISFET modeling with standard TCAD tools

An innovative ion sensitive device based on side‐contacted field effect diode

“…To mimic electrolyte, we have utilized similarity between anions/ cations in a solution and electrons/holes in a semiconductor, respectively. Thus, the electrolyte has been modeled as an intrinsic semiconductor [21,23] : A symmetric monovalent electrolyte (1:1) can be map as an undoped semiconductor with zero bandgap, relative permittivity of water, and effective density of states as:…”

“…By changing pH of the solution, surface charge, which has been introduced by equilibrium reactions alternates and cause changes in drain current, make it possible to track pH changes. Surface charge density at the electrolyte/insulator interface can be calculated as [21] :…”

“…Interface traps with some modifications are utilized to model surface charge density and mapped the surface charge caused by site-binding in a solution. [21,25] We can define surface traps in such way to form the same charge as Eq. (4).…”

“…To scrutinize and examine the performance of this device, we have developed a platform on a TCAD tool to model electrolyte behavior among different pHs and interactions between the electrolyte and the insulator. [21] Results show more sensitivity and a different trend against geometrical parameter changes.…”

Assessment of three electrolyte–molecule electrostatic interaction models for 2D material based BioFETs

“…3,[15][16][17] Indeed, several 2D material-based BioFETs have already been successfully fabricated 2,3,[16][17][18][19] and their operating principles are subject of intense research. [20][21][22][23][24][25][26] This growing interest in the design of new and highly sensitive biosensors based on 2D materials is driven by a myriad of practical applications with an expected huge impact from a technological and economical point of view.…”