Ohseob Kwon

Nanoscale Device Modeling and Simulation: Fin Field-Effect Transistor (FinFET)

The device performance of nanoscale fin field-effect transistor (FinFET) was investigated by numerically solving coupled Poisson-Schrodinger equations in a self-consistent manner. The number of fins was varied in order to optimize the current driving capability of FinFET. The simulation results were compared with the experimental results in order to verify the validity of the proposed quantum mechanical approach. Device optimization was theoretically performed in order to suppress the short-channel effect in terms of subthreshold swing, threshold voltage roll-off, and drain-induced barrier lowering. Quantum mechanical simulation results were also compared with the results from the classical approach in order to understand the influence of electron confinement. Our simulation results indicate that quantum mechanical simulation is essential for the realistic optimization of the FinFET structure.

A mesh generation algorithm for complex geometry [semiconductor process modelling]

A mesh generation algorithm for a curved surface is proposed to investigate a complex structure on a semiconductor substrate. This algorithm relies on the advancing front method with scattered data interpolation through a NURBS (nonuniform rational B-spline) surface. This algorithm has been applied to a cell-based simulation and a level set simulation. The NURBS mesh according to our algorithm excellently represented the surface evolution of the topography.

Molecular Dynamics Calculation for Low-Energy Ion Implantation Process with Dynamic Annealing Effect

In this paper, we present a molecular dynamics (MD) study on a low-energy ion implantation process for nanoscale CMOS (Complementary Metal Oxide Semiconductor) processes. To model the profiles of interstitials and vacancies, the recoil interaction approximation (RIA) was employed, while the kinetic Monte Carlo (KMC) approach was used for modeling the dynamic annealing effect between cascades. The simulation results performed for as-implanted boron profiles were compared with the results of the binary collision approximation (BCA) calculation by UT-MARLOWE as well as with the experimental SIMS data. The simulation revealed that the dynamic annealing effect between cascades is essential for the accurate estimation of defect distribution as well as as-implanted ion distribution. The dynamic annealing effect was carefully investigated for a case of boron implantation with an ion implantation energy of 2 keV, doses of 1×1014 ions/cm2 and 1×1015 ions/cm2, and a dose rate of 1×1012 ions/cm2s.

Molecular Dynamics (MD) Calculation for Low-energy Ion Implantation Process with Dynamic Annealing Effect

In this paper, we report a molecular dynamics (MD) simulation on the ion implantation for nano-scale CMOS devices with ultra-shallow junctions. In order to model the profile of ion distribution in nanometer scale, the molecular dynamics with a damage model has been employed with the Kinetic Monte Carlo (KMC) diffusion model used for the dynamic annealing between cascades. The concentration distribution of dopants during the ion implantation was calculated using the interaction potentials between atoms [1,2] from MD calculation.

Process and device simulation based on atomistic and quantum mechanical approach in the regime of sub-50 nm gate length

In this paper, we report simulation methods based on atomistic approach for sub-50 nm gate length. Molecular dynamics (MD) is implemented for the ion implantation process to form ultra-shallow junctions. And then, the diffusion process is simulated by using kinetic Monte Carlo (KMC) with the damages and dopants distribution from ion implantation in MD. A device simulation is performed by using profiles from the results of KMC. As an exemplary case, we demonstrate FinFET of 20nm physical gate length.

Nano-scale device modeling and simulation: FinFET

In this paper, two-dimensional quantum mechanical simulation of FinFET is reported. Current-voltage characteristics are compared with the experimental data. Device optimization has been performed in order to suppress the short-channel effect inculating the subthreshhold swing, threshold voltage rool-off, drain induced barrier lowering (DIBL). The QM simulation is compared with the classical approach in the order to understand the influenece of the electron confinement effect.

P-98: Modeling of Anchoring Strength upon the Fringe-Field Switching

In this paper, we report the influence of surface anchoring strength on the optical switching behavior. As a test vehicle, we have chosen the LC cell structure having the fringe-field switching(FFS) layer. The director distribution is calculated by using three dimensional finite difference method(FDM), while the surface director has a various anchoring strength. Moreover the optical analysis is performed by 2×2 extended Johns method. According to our result, the lower transmission intensity is obtained with the same voltage in the weak anchoring.

50.1: Comparison of Numerical Methods for Analysis of Liquid Crystal Cell: In-Plane Switching

In this paper, we present the comparison of numerical methods, the finite element method (FEM) and the finite difference method (FDM), for the analysis of liquid crystal cell. In this work, In-plane switching (IPS) mode is chosen as a test vehicle. The electrical and optical characteristics of the cell structure are simulated by two type of the numerical solver which is using each numerical scheme. Especially, we report our work in the view of CPU time and the result of simulation. Furthermore, we report the adaptability to other applications having non-rectangular structure, such as chevron-type patterned vertical alignment (PVA) mode.

Level Set Modeling of Profile Evolution during Deposition Process

In this paper, we report three-dimensional modeling of the sputter deposition process for ULSI interconnects. The numerical method in this work is based upon the level-set scheme for accurately tracking the moving boundaries of the deposited profiles. A new approach is proposed in an effort to reduce thecalculating CPU time during the calculating step of the deposition rate. Our simulation incorporates three-dimensional direct and/or indirect flux distributions and shadow-effects as well as the dependence of sticking coefficient that affects not only the thickness of film at different position but also the initiation of the creation of a void. In this work, we present several numerical examples for copper deposition process, which include L-shaped trenches and contact holes with different aspect ratios.

A Full-Wave Analysis for Multi-Level Interconnects Using FDTD-PML method

FDTD(finite difference time domain) method is a 3-D full-wave numerical algorithm for solving various electromagnetic phenomena and interaction problems. PML(perfectly matched layer) method is very efficient for absorbing the electromagnetic waves and then for solving unbounded problems. This paper deals with the application of FDTD-PML technique to the solution of wave-structure interaction problems. It is shown that the excited Gaussian pulses were propagated along the multi-level interconnect metal line as the increase of time and the interaction phenomena occurred. The absorbing effectiveness of PML as a function of the time step is also demonstrated.