3D Simulation and I-V Compact Modeling of Nanopore Structure for DNA Sequencing

Abstract

Nanopore structure in solid-state device has been studied for faster DNA sequencing than optical method. The current-voltage behavior of the nanopore structure was not clearly understood. To clearly understand the internal physics of the nanopore structure, 3-dimensional (3-D) device simulation is required. In this case, 3-D simulator based on electrochemical models should be applied. This simulator is quite useful in designing and understanding the nanopore structure. However, this kind of simulator is now under developing and limited. Fortunately, due to the negative interface charge on the insulator surface and negative gate bias condition, the nanopore is filled with K+ ions which can be mimicked by p-type semiconductor, so we could simulate nanopore structure by conventional 3-D simulator, Sentaurus device. In this work, we report a method for simulating nanopore structure using conventional 3-D simulation tool to mimic the I-V behavior of the nanopore structure. We investigate how the nanopore structure really works. In the simulation, we use lightly doped silicon for ionic solvent where some parameters like electron affinity and dielectric constant are fitted to consider the ionic solvent. By using this method, we can simulate the I-V behavior of nanopore structure depending on the location and the size of the sphere shaped silicon oxide which is considered to be an indicator of a DNA base. In addition, we simulate an Ionic Field Effect Transistor (IFET) which has basically the nanopore structure, and show that the simulated curves follow sufficiently the I-V behavior of the measurement data. Furthermore, we modified simulation conditions of IFET structure to fit the simulated curves to measured curves. Some parameters, such as electron affinity, dielectric constant, and mobility of silicon are modified to mimic KCl solvent. We use p-type silicon with a concentration of 6.022×1016 cm-3 which has the same number of positive carrier (hole) with 10-4 M KCl solvent. We use constant mobility model, and gate electric field dependency of silicon mobility is modified. After all, we eliminated leakage current component and obtained simulated curves exact fitted with measured curves. We simulate an ionic field effect transistor (IFET) which has basically the nanopore structure, and show that the simulation result has quite similar to measurement data.