Numerical simulation of ISFET structures for biosensing devices with TCAD tools

Abstract

BackgroundIon Sensitive Field Effect Transistors (ISFETs) are one of the primitive structures for the fabrication of biosensors (BioFETs). Aiming at the optimization of the design and fabrication processes of BioFETs, the correlation between technological parameters and device electrical response can be obtained by means of an electrical device-level simulation. In this work we present a numerical simulation approach to the study of ISFET structures for bio-sensing devices (BioFET) using Synopsys Sentaurus Technology Computer-Aided Design (TCAD) tools.MethodsThe properties of a custom-defined material were modified in order to reproduce the electrolyte behavior. In particular, the parameters of an intrinsic semiconductor material have been set in order to reproduce an electrolyte solution.By replacing the electrolyte solution with an intrinsic semiconductor, the electrostatic solution of the electrolyte region can therefore be calculated by solving the semiconductor equation within this region.ResultsThe electrostatic behaviour (transfer characteristics) of a general BioFET structure has been simulated when the captured target number increases from 1 to 10. The ID current as a function of the VDS voltage for different positions of a single charged block and for different values of the reference electrode have been calculated.The electrical potential distribution along the electrolyte-insulator-semiconductor structure has been evaluated for different molar concentrations of the electrolyte solution.ConclusionsWe presented a numerical simulation approach to the study of Ion-Sensitive Field Effect Transistor (ISFET) structures for biosensing devices (BioFETs) using the Synopsys Sentaurus Technology Computer-Aided Design (TCAD) tools.A powerful framework for the design and optimization of biosensor has been devised, thus helping in reducing technology development time and cost. The main finding of the analysis of a general reference BioFET shows that there is no linear relationship between the number of charges and the current modulation. Actually, there is a strong position dependent effect: targets localized near the source region are most effective with respect to targets localized near the drain region. In general, even randomly distributed targets are more efficient with respect to locally grouped targets on the current modulation. Moreover, for the device at hand, a small positive biasing of the electrolyte solution, providing that the transistor goes on, will result in a greater enhancement of the current levels, still retaining a good sensitivity but greatly simplifying the operations of a real device.

Dynamic behaviour of the silica-water-bio electrical double layer in the presence of a divalent electrolyte

“…Finally, for nanowire BioFETs, with small cross sections in the semiconducting region, and a correspondingly high sensitivity, the spatial variation of the field is crucial in understanding the response rather than a smeared out average approximation of the behaviour of an artificial one-dimensional system. 3,98,99 The spatial variation in the electric field at the surface of the silica was investigated for the control system (''0 mM'') and is shown in Fig. 12.…”

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.…”

“…In this work, we will focus on the structures where the electrolyte is present, and specically on the modelling of the interaction between the electrolyte ions and the target molecules attached to the sensing interface. The BioFET simulation has been so far carried out using either commercial TCAD simulators, [20][21][22][23] which are not purpose-designed to include the electrolyte effects, or ad hoc soware. [24][25][26] In particular, TCAD simulators make coarse approximations to model the effect of the electrolyte and biomolecules.…”

Modeling of carbon nanotube ISFETs with high‐κ gate dielectrics for biosensing applications

“…Referring to modeling of ISFET, many physical models have been developed in SPICE (Simulation Program with Integrated Circuit Emphasis) with the modifications over MOSFET models . However, such SPICE models are not exact as electrochemistry involved in the device is not included in the device model .…”

“…12 Referring to modeling of ISFET, many physical models have been developed in SPICE (Simulation Program with Integrated Circuit Emphasis) with the modifications over MOSFET models. [13][14][15][16][17][18][19][20][21][22][23] However, such SPICE models are not exact as electrochemistry involved in the device is not included in the device model. 24 Grattarola et al 25 have developed a physico-chemical model for SPICE simulation but was mostly for Si-based ISFET.…”