Shaoyan Di

Subthreshold Behavior Models for Nanoscale Short-Channel Junctionless Cylindrical Surrounding-Gate MOSFETs

With the exact solution of the 2-D Poissons equation in cylindrical coordinates, analytical subthreshold behavior models for junctionless cylindrical surrounding-gate (JLCSG) MOSFETs are developed. Using these analytical models, subthreshold characteristics of JLCSG MOSFETs are investigated in terms of channel electrostatic potential distribution, subthreshold current, and subthreshold slope (SS). It is shown that the electrostatic potential distribution, subthreshold current, and SS predicted by the analytical models are in close agreement with 3-D numerical simulation results without the need of any fitting parameters. These analytical models not only provide useful physical insight into the subthreshold behaviors, but also offer basic design guideline for the nanoscale JLCSG MOSFETs.

Calibration of drift-diffusion model in quasi-ballistic transport region for FinFETs

In the past few years, conventional digital IC technologies have developed rapidly and the device structures have shrunk down to the quasi-ballistic region which strongly affects the device characteristics. The usage of the steady-state transport model and the parameters of the drift-diffusion (DD) method may not correctly model the performance of these devices, including the velocity distributions of the carriers. Several previous studies have suggested modifying the transport parameters of the DD model to continue using it in the quasi-ballistic region. In this paper, a Monte Carlo (MC) simulator is used to calibrate the transport parameters of the DD model for silicon FinFETs. The device features obtained via the parameter-calibrated DD model fit well with the MC simulator. The trends of the calibration factors are also investigated for varying drain voltage, gate voltage, fin width and gate length.

Impact of crystal orientation and surface scattering on DG-MOSFETs in quasi-ballistic region

The characteristics of nano scale n-type double gate MOSFETs with (100) and (110) surfaces are studied using 3D full band ensemble Monte Carlo simulator. The anisotropic surface scattering mechanism is investigated. The (100) case is sensitive to the gate voltage more than the (110) case. The impact of crystal orientation and surface scattering on transport features mainly reflects in the carrier velocity distribution. The electron transport features with (100) direction are greater than that with (110) direction, but are more likely to be affected by the surface scattering.

Comprehensive Investigation of Multi-traps Induced Degradation in HfO2 Based nMOSFETs with Interfacial Layer by 3D-KMC Method

This paper investigates trap-induced degradation in nmosfets with HfO2 gate dielectric by three-dimensional Kinetic Monte Carlo method. Multiple microscopic mechanisms including trapping/detrapping, traps coupling, and trap generation/recombination are considered in simulation. The impacts of interfacial layer (IL) SiOx on positive bias temperature instability (PBTI) and trap-assisted tunneling (TAT) are comprehensively investigated. PBTI characteristics show the variations of power laws with time, and power laws are greatly affected by stress condition, trap density, and dielectric thickness. Therefore, impressionable power laws make much complexion in lifetime prediction. Meanwhile, it is found that IL markedly reduces PBTI effects. Significantly, TAT currents of fresh devices increase with IL thickening in the same effective oxide thickness (EOT), whereas TAT currents after stress decrease with IL thickening in a specific range. It can be concluded that the IL in the proper range of thickness can effectively suppress PBTI and TAT currents.

Insight into PBTI in InGaAs nanowire FETs with Al 2 O 3 and LaAlO 3 gate dielectrics

The traps induced degradation of the Al<inf>2</inf>O<inf>3</inf> and LaAlO<inf>3</inf> based InGaAs nanowire FETs are investigated by 3D Kinetic Monte-Carlo (KMC) method considering trap coupling and trap generation. The measurement time constants of the defect in Al<inf>2</inf>O<inf>3</inf> and positive bias temperature instability (PBTI) can be well interpreted by consideration with metastable state. The power law of threshold shift can be greatly affected by the stress. Different from traps in Al<inf>2</inf>O<inf>3</inf>, oxygen vacancies and interstitial Aluminum ions in LaAlO<inf>3</inf> have important roles in PBTI. Simulated results indicate that Al<inf>2</inf>O<inf>3</inf> have better PBTI and recovery than that of LaAlO<inf>3</inf>.