Taeyoung Won

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.

17.2: Invited Paper: Improved PVA Mode with High Transmittance and Aperture Ratio

In this paper, we propose a cell structure which has high aperture ratio and transmittance with chevron-shaped electrode. As an exemplary cell, we selected PVA (Patterned Vertical Alignment) mode. Optical transmittance and aperture ratio were calculated with 3D-FEM numerical solver, TechWiz LCD, which is commercially available. The simulation results exhibited 4.8% improvement in aperture ratio and 11.3 % improvement in optical transmission.

Ferroelectric Properties of MBi4Ti4O15 (M = Sr, Pb, Ca) Thin Films

Among the ferroelectric bismuth layered perovskites belonging to Aurivillius family, the MBi4Ti4O15 (MBT15, M = Sr, Ca, Pb) thin films have been fabricated by a chemical solution deposition technique, and their structures and ferroelectric properties were investigated in this work. The SrBi4Ti4O15 (SBT15) film fabricated on IrO2 presented the highest remanent polarization (Pr) among the films in this series. It demonstrated a saturated hysteresis loop at 5 V with Pr of 19 μ C/cm2 and coercive field (Ps) of 116 kV/cm. The PbBi4Ti4O15 (PBT15) thin films were selectively controlled in c-axis and off-c-axis orientation on Pt layer by adjusting the annealing condition. The off-c-axis oriented PbBi4Ti4O15 film demonstrated considerably higher Pr (8.7 μ C/cm2) than that of c-axis oriented film (3.7 μ C/cm2). Regardless of grain orientation, however, PBT15 films were not fatigued up to 1010 cycles under 9V application. The CaBi4Ti4O15 (CBT15) thin films were also produced on Pt and IrO2 electrode, respectively, by controlling the annealing condition. The CBT15 film on IrO2 presented higher Pr (∼10.8 μ C/cm2) than that of film (∼ 6.7 μ C/cm2) on Pt. † Present address: Samsung Advanced Institute of Technology, P.O. Box 111, Suwon 440-600, Korea

Two-Dimensional Quantum Mechanical Modeling for Multiple-Channel FinFET

In this paper, we report our preliminary study on the 2D quantum-mechanical modeling of multiple-channel FET through solving the coupled Poisson-Schrodinger equations for a multiple-channel FET structure in a self-consistent manner. Our simulation revealed that the drain current driving capability as well as the transconductance for multiple-channel FETs was tremendously improved when compared to FinFETs. The simulation results also revealed that the short-channel effects are more effectively suppressed with comparison to the conventional FinFETs

Two-Dimensional Quantum-Mechanical Modeling and Simulation of Strained-Si Fin Field Effect Transistor (FinFET) on SiGe-On-Insulator

A strained-Si fin field effect transistor (SSFinFET) on SiGe-on-insulator is modeled and using two-dimensional Schrodinger and Poisson equations quantum-mechanically simulated in a self-consistent manner. The quantum electron concentration in an SS fin is then obtained using a two-dimensional Schrodinger equation. The field-dependent mobility in SS fin is calculated using the doping-dependent mobility which considered strain and velocity overshoot effects. These effects give rise to an enhancement in the drain current of SSFinFET by up to 25% compared with the conventional FinFET using relaxed Si-on-insulator (RSFinFET). For the gate length 1.5 times longer than fin width, the drain induced barrier lowering (DIBL) and subthreshold swing are below 0.1 V/V and 60 mV/dec, respectively, regardless of whether Si-fin experiences a strain. These results indicate that the ratio of gate length to fin width should be above approximately 1.5 to suppress short channel effects and DIBL in both SSFinFET and RSFinFET.

MODELING AND SIMULATION OF PARASITIC CAPACITANCES FOR ACTIVE MATRIX LIQUID CRYSTAL DISPLAYS (AMLCDs)

In this paper, we present a compact approach for modeling a parasitic capacitance in active matrix liquid crystal displays (AMLCDs) as a function of voltage applied at pixel electrodes. The director distribution as well as the potential distribution is estimated from a three-dimensional finite element method (FEM), while the parasitic capacitance within a liquid crystal cell is calculated with an energy moment method. Furthermore, we applied our proposed approach on the VA (vertical alignment) mode LC cell with a chevron-type electrode structure in order to understand the dynamic behavior of the cell.

Optical characteristics of organic green-light-emitting devices: Finite element approach

In this paper, we report our theoretical study on the electrical and optical properties of organic light-emitting-diode (OLED) devices based on the green emitter tris(8-hydroxyquinolinato)aluminum (Alq3). The electrical analysis of the bilayer structure has been carried out in order to identify and understand the behavior of carriers. After investigating the behavior of carriers, we devised a bottom mirror between the anode and the substrate to improve the luminance efficiency. Using the bottom mirror as the distributed Bragg reflector (DBR), we could attain an improvement of 17% in emission efficiency and sharper emission characteristics. Also, we found that the chromaticity of the device varies with the geometry of the bottom mirror.

Finite Element Method (FEM) Study on Space Charge Effects in Organic Light Emitting Diodes (OLED)

In this paper, we present a finite element method (FEM) study on the space charge effects in organic light emitting diodes. The physical model covers all the key physical processes in OLEDs, namely charge injection, transport and recombination, exciton diffusion, transfer and decay as well as light coupling, and thin-film-optics. The exciton model includes generation, diffusion, and energy transfer as well as annihilation. We assumed that the light emission originates from oscillation which thus is embodied as exciton in a stack of multilayer. We discuss the accumulation of charges at internal interfaces and their signature in the transient response as well as the electric field distribution. We also report our investigation on the influence of the insertion of the emission layer (EML) in the bilayer structure.

High‐Side nLDMOS Design for Ensuring Over‐100 V Breakdown Voltages

We propose a novel n‐channel LDMOSFET(Lateral Double‐diffused Metal Oxide Semiconductor Field Effect Transistor) structure with a breakdown voltage over 100 V under the thermal budget for the conventional 0.35μm BCD process. We varied the gap between the DEEP N‐WELL and the center of the source for optimization and the doping concentration under the surface by the NADjusT‐layer in an effort to obtain high breakdown voltage and simultaneously the low specific on‐resistance. The proposed High‐Side n‐channel LDMOS exhibits BVdss of 110 V and the specific on‐resistance of 2.20 mΩcm2.

Numerical simulation of on thermal nanoimprint lithography (NIL) process

Nanoimprint lithography (NIL) relies on a direct mechanical deformation of the resist material and can therefore achieve resolutions beyond the limitations which are set by a light diffraction or a beam scattering. In addition, NIL is expected to realize a low cost and high-throughput production. In this work, we modeled the NIL process and employed commercially available software, COMSOL Multi-physics, for the implementation of our model. In this paper, we report the stress distribution of the polymer deformation process on the imprinting pressure.