Transport In MOSFETs Research Articles

An Improved Model for Quasi-Ballistic Transport in MOSFETs

We have already presented a compact model for FETs operating in the quasi-ballistic regime [1] . However, this model suffers from two important problems: 1) the profile for charge density along the channel is not correctly accounted for and 2) current is not conserved throughout the channel. In this brief, we propose improvement, which does away with these inaccuracies.

Deterministic simulation of transport in MOSFETs by coupling Wigner, Poisson and Schrödinger equations

AbstractIn this paper, we present a new simulation approach for quantum transport in short and thin MOSFET channels which is based on a deterministic resolution of 1D Wigner Transport Equation and its couplings with 2D Poisson and 1D Schrödinger equations. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Ballistic/quasi-ballistic transport in nanoscale transistor

The current voltage characteristics of the silicon ballistic MOSFETs are introduced and discussed. They are derived by considering the current capacity through the bottleneck point in the channel, and they provide a simple measure of the performance limit. The performance of experimental nanoscale bulk MOSFETs are compared with the ideal ballistic limit. It was shown that the performance degradation due to carrier scattering amounts to several to several tens percent in recent nanoscale MOSFETs. Quasi-ballistic transport in MOSFETs was also analyzed by a simple approach based on the transmission viewpoint. Channel-length reduction was found to yield consistent improvement of the ballisticity. Considerable performance degradation, however, was still found to persist even in 10-nm MOSFETs. The role of each carrier scattering mechanism is analyzed. It is shown that elastic scattering degrades the performance, but the inelastic energy relaxation improves the performance of the MOSFET.

Donor activation and damage in Si–SiO2 from low-dose, low-energy ion implantation studied via electrical transport in MOSFETs

Using silicon MOSFETs with thin (5 nm) thermally grown SiO2 gate dielectrics, we characterize the density of electrically active traps at low temperature after 16 keV phosphorus ion implantation through the oxide. We find that, after rapid thermal annealing at 1000 °C for 5 s, each implanted P ion contributes an additional 0.08 ± 0.03 electrically active traps, whilst no increase in the number of traps is seen for comparable silicon implants. This result shows that the additional traps are ionized P donors, and not damage due to the implantation process. We also find, using the room temperature threshold voltage shift, that the electrical activation of donors at an implant density of 2 × 1012 cm−2 is ∼100%.

3-D granular Monte Carlo simulation of silicon n-MOSFETs

A 3-D ensemble Monte Carlo (EMC) simulation with granular doping is implemented and simulations on a 50 nm channel length n-MOSFET are compared with results from 2- and 3-D simulations with continuous doping profiles. Granular simulations treat ionized acceptors in the channel discretely and the electron-ion interaction is calculated with a particle–particle–particle–mesh (P 3M) algorithm. Steady-state results for the electric field and electron velocities along the oxide interface are compared under strong inversion. Preliminary results indicate that 3-D Coulomb and granular effects in the channel have limited impact on transport in MOSFETs in the strong inversion case, but that the P 3M–EMC method shows promise for evaluating short-range effects including carrier–ion and carrier–carrier effects in subthreshold conditions where the impact of granularity should be larger.

Computer aided analysis of carrier energy transport in mosfets

The two-dimensional numerical simulation of energy transport for MOSFETs is presented, in which the effect of generation, recombination and temperature gradient of carriers on the characteristics of devices are considered. An improved mobility model is also proposed. The numerical results of micron and submicron MOSFETs show that the present model fits experiment very well.

A physics based analytical MOSFET model with accurate field dependent mobility

A new approach to the modeling of short-channel MOSFETs in the triode region is proposed. A system of equations for an accurate quasi-1-D-formulation of the current transport in MOSFETs is presented. A highly accurate description of the local normal effective field-dependent surface mobility is included. The mobility degradation due to the parallel field is modeled by a hyperbolic formula for P-channel and by Jaggi's expression for N-channel MOSFETs. The mobility models are examined by comparing with several experimental data. The system includes a precise modeling of the inversion layer charge and surface potential, and it is valid in both weak and strong inversion. Using novel approaches an approximate solution in the triode region is derived analytically. The obtained expressions for the current are explicit. An error analysis of the analytical current models is carried out by comparing with a numerical solution of the starting quasi-1-D-formulation. As a result of the error analysis the simplest final expression for the drain current is proposed. Some further extensions of the model are noted.

Experimental study of hot carriers in small size Si-MOSFETs

Hot carrier effects in Si-MOSFETs cause serious reliability problems in VLSI circuits. While most of them have been investigated empirically, it is also important to clarify the microscopic degradation mechanism. In addition, there are other effects which can affect the device characteristics significantly and can be used to study hot carrier transport in MOSFETs. In this paper, several experimental studies associated with hot carrier effects in MOSFETs are reviewed. In particularly, hot electron energy effects are discussed, such as velocity overshoot and photo-emission in MOSFETs, and technological efforts to overcome the degradation problem in actual devices are reviewed briefly.