Wael Fikry

Implementation of hot-carrier reliability simulation in Eldo

The implementation of all components of hot-carrier reliability simulation in Eldo is described in this paper. A repetitive simulation scheme has been adopted to ensure accurate prediction of the circuit-level degradation process under dynamic operating conditions. Two approaches for modeling the degraded MOS transistor have been implemented, namely, the parameter fitting method and a newly proposed /spl Delta/I/sub d/ model. The new model overcomes the discontinuity and subthreshold invalidity of the existing models. The model has proven high accuracy for two well known foundries on their 0.25 /spl mu/m technologies. Simulation is results on some direct applications like inverters and ring oscillator circuits are also presented in this paper.

Rapid and efficient method for numerical quantum mechanical simulation of gate-all-around nanowire transistors

In this paper, we propose a 2D numerical quantum simulator for silicon gate-all-around (GAA) nanowire transistors with cylindrical cross-section within the effective mass approximation. The Hamiltonian is expanded in the uncoupled mode space and the nonequilibrium Greens function (NEGF) formalism is adopted to calculate the electron density and current. An approximated isotropic effective mass is used in conjunction with optimizing the flatband voltage (VFB) as a fitting parameter. Verification of the results is done through a comparison with those obtained from a published 3D simulator and excellent agreement is achieved.

Compact model for short and ultra thin symmetric double gate

In this paper we propose a new model based on an analytical model for undoped symmetric double gate MOSFETs introduced by Chenming Hu et al. The proposed model targets to include the quantum confinement and the most important short channel effects. The new model results were compared with a device simulator results to validate the proposed modifications. The proposed model introduces low fitting error reaches to 1% for ultra thin and short channel double gate transistors.

Compact model for ballistic MOSFET-like carbon nanotube field-effect transistors

In this work, a compact model for MOSFET-like ballistic carbon nanotube field-effect transistors (CNFETs) is presented. The model is based on calculating the charge and surface potential on the top of the barrier between source and drain using closed-form analytical formulae. The formula for the surface potential is obtained by merging two simplified expressions obtained in two extreme cases (very low and very high gate bias). Two fitting parameters are introduced whose values are extracted by best fitting model results with numerically calculated ones. The model has a continuous derivative and thus it is SPICE-compatible. Accuracy of the model is compared to previous analytical model presented in the literature with numerical results taken as a reference. Proposed model proves to give less relative error over a wide range of gate biases, and for a drain bias up to 0.5 V. In addition, the model enables the calculation of quantum and gate capacitance analytically reproducing the negative capacitance behaviour known in CNFETs.

A new semi-empirical model for funneling assisted drain currents due to single events

We present a new semi-empirical model for the funneling-assisted currents due to single events. It is then used to predict the collected charge due to the funneling process. Comparison with previously published simulated data using ISE CAD tools has shown that the relative error in the collected charge prediction is of about 0.8%. This model can be used for circuit simulations in space applications.

Staggered mode MEMS gyroscope

This paper presents a novel design concept of a MEMS gyroscope comprising a sense mode with a staggered frequency response. Considering a two-degree of freedom sense-mode structure, the bandwidth is enhanced by more than 40%. A post-fabrication electrostatic tuning mechanism based on two tuning electrodes is proposed to achieve resonance frequency trimming. The concept is applied on the design and analysis of fully decoupled gyroscope based on the SOI MUMPS process and operating around a resonance frequency of 5 kHz. The concept is extendable for multi-degree of freedom for wider bandwidth extension.

Simulation of Quantum Ballistic Transport in FinFETs

Quantum effects play a vital role in determining the transistor characteristics of FinFET devices. Quantum confinement, coherent ballistic transport, and quantum mechanical tunneling are a few examples. The nonequilibrium Green’s function formalism (NEGF) provides a rigorous description of quantum transport in nanoscale devices. Depending on the chosen space for representation of the wave function, real-space and mode-space representations are widely used. In this chapter, the basic tools involved in the NEGF simulation of the quantum ballistic transport in FinFETs are provided. The different techniques applied in either the real- or the mode-space representations are discussed. In this chapter, a comparison of the NEGF methods in the real-space representation considers the recursive Green’s function method, the Gauss elimination method, and the contact block reduction method and then highlights the computational efficiency of these methods. A comparison between the fully coupled, the partially coupled and the uncoupled methods in the mode-space representation is also given considering their accuracy and computational efficiency.

Partial-Coupled Mode Space for quantum transport simulation in nanoscale double-gate MOSFETs

A novel computationally efficient approach for simulation of quantum transport in nanoscale devices is proposed. The idea is based on partial coupling between the modes of the nanoscale device. The proposed approach, termed Partial-Coupled Mode Space (PCMS), is applied to the double-gate MOSFETs and device targets from the ITRS roadmap were simulated. A Comparison with the fully Coupled-Mode Space (CMS) was carried out. The PCMS reduces more than 65 % of the computational burden while an accuracy of better than 0.1 % and 0.01 % is maintained in the device charge and terminal current respectively.

Series resistance and carrier tunneling of compact model for double gate nanoscale transistors

In this paper we enhance the published model of Abo-Elhadeed et al. based on an analytical model for undoped symmetric double gate MOSFETs introduced by Chenming Hu et al. Our proposed model includes the effects of the source/drain series resistances on the drain current and the effects of the gate tunneling current. The new model results were compared with a device simulator results to validate the proposed modifications. These effects improved the behavior of basic model of Abo-Elhadeed and enabled us to bring down the fitting error from 25% for Hus model and 19% for the original Abo-Elhadeeds model to 5% only.

Analytical model for ballistic MOSFET-like carbon nanotube field-effect transistors

An analytical model is developed for the carrier density in MOSFET-like carbon nanotube field-effect transistors in terms of surface potential. This model is based on approximating the density of states with delta function in addition to a constant value. The model has a continuous derivative and contains two fitting parameters, which are determined by best fitting with numerical results. The fitting parameters are found to depend on the subband minima and this dependence is modeled by simple quadrature formula. The model is compared to two previous analytical models with numerical results are taken as a reference and found to have less relative error. In addition, the drain current is extracted using the proposed model at various bias values. The results for current are verified by comparison with self-consistent numerical results of FETToy simulator available on the NanoHub.