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To overcome limitations of the classic drift-diffusion model, several higher-order transport models such as Stratton’s energy-balance model and Bløtekjær’s hydrodynamic model have been proposed. While for the drift-diffusion model the only transport parameter to be modeled correctly is the carrier mobility, there are many more significant parameters in higher-order models which cannot be directly...
The fundamentally sound non-Equilibrium Green’s function (NEGF) approach provides the theoretical basis for NEMO 1-D as the first nanoelectronic TCAD tool. Effects of quantum charging, bandstructure and incoherent scattering from alloy disorder, interface roughness, acoustic phonons, and polar optical phonons are modeled. Engineers and experimentalists who desire a black-box design tool as well as...
Recent papers on advanced semiconductor devices adopt a model called density-gradient correction, in which the standard electric potential acting on the carriers is modified by a non-linear term involving the carrier concentration and its second derivatives. When applied to cases where quantum effects are not negligible, the modified model improves the results with respect to the standard approach...
In this paper, we investigated the quantization in the MOSFET inversion layer by solving the Schrödinger EQuation (SEQ) in the momentum space according to the 3D Full Band (FB) structure of silicon. For the first time, we explain the dependence of the eigenvalues on the momentum k in the plane of transport and discuss its periodicity. Furthermore, we discuss the solution of the SEQ around the energy...
In this paper, we have carried out a numerical simulation of FinFETs. The model is based on ID non-equilibrium Green’s function (NEGF) along the channel and 2-D Schrödinger equation in the confined cross section and provides insights into the performance of FinFETs with ultra small channel cross section. The simulation results of FinFETs show normal I—V characteristics with great potential in scalability...
We study the calculation of quasi-bound states in nMOS inversion channels and their impact on direct tunneling currents through the dielectric layer. For typical device parameters, the gate leakage in inversion is dominated by this tunneling component. However, a strong inaccuracy arises, if the eigenvalues of the closed system are used for the quasi-bound state tunneling current. We propose simple...
We report studies of quantum transport in double gate Si MOSFETs (DG MOSFETs) based upon a full-2D tight-binding Green’s function method. As a result, it is found that the I—V characteristics is quite different when a realistic band structure with 6 valleys is taken into account compared with the case of isotropic effective mass. More importantly, it is also found that the carriers flow not only in...
Several models for B diffusion in Si1-x Gex have been proposed [1, 2]. In order to help discriminate between the models, an experiment was performed. Preamorphized Si wafers were implanted with varying doses of Ge, followed by a B implant. Samples were annealed at several temperatures. Ge implanted samples showed an increase in the B profile peak magnitude with anneal time, as well as its shift towards...
Stress effects on dopant diffusion and activation are of critical interest in current and future CMOS devices. Since experiments are very difficult to perform, we utilized ab-initio calculations to predict the effect of stress on B solubility. We find strongly enhanced solubility under compressive biaxial stress, whereas tensile biaxial stress leads to a reduction. In contrast to other work the enhancement/reduction...
SiGe has been utilized for aggressive CMOS technologies development recently and there are many literatures talking about the advantages brought by it. However, few publications discuss the impacts from both mechanical strain and Ge doping on boron diffusion. Moreover these effects have mostly been studied at low boron concentrations and with long high temperature anneals. They are not the possible...
Following the developement of a unified diffusion model valid for all usual dopants in SiGe layers [1], considering the effect of carbone diffusion on point defects concentrations extends the application of our model to strained SiGeC layers. Using a new SIMS methodology, the study of As intrinsic diffusion in SiGe and SiGeC layers is performed, at low concentration and under equilibrium annealing...
Indium (In) diffusion and dose-loss in silicon is modeled in a continuum simulator. The model includes the large segregation of In to End of Range (EOR) defects, and the dissolution of these defects resulting in dose-loss of In at the surface. The models developed are successfully applied to predict state of the art (90 nm) transistor performance.
We performed a theoretical analysis of the stress and surface orientation effects on inversion carrier mobility modulation using a quantum mechanical carrier transport simulator that incorporates intra-valley acoustic phonons, inter-valley optical phonons, surface roughness, and impurity scattering mechanisms. The eigenstates of the inversion carrier were calculated using a pseudo-potential method...
With the advent of novel device structures that can be easily fabricated outside of the traditional (100) plane, it may be advantageous to change the crystal orientation to optimize CMOS circuit performance. The use of alternative surface orientations enhances hole mobility while degrading electron mobility. By optimizing the surface orientation, up to a 15% improvement in gate delay can be expected...
Layout dependent stress induced effects on current drivability of 90nm node CMOS devices have been modeled by both performing stress modeling in process simulation and device simulation with stress dependent mobility model. It has been demonstrated that dependence of drive current of both n- and p-MOSFETs on source/drain size is successfully modeled. In addition, with this procedure, the performance...
In this work, we simulated the long channel Ge-buried channel PMOSFETs by using driftdiffusion equation and calibrated the commonly used silicon mobility model to take buried channel hole mobility enhancement into account. 2D simulations were performed to study the channel design space for strained Ge buried channel PMOSFETs and two different buried channel structures were proposed to control short...
The retention time characteristics in DRAM cells are strongly influenced by various leakage mechanisms near the storage node junction. In this work, we present a full three-dimensional analysis of stress distributions in and around the active area of high-density memory cells. We use a combination of high-resolution metrology analysis and 3D numerical modeling to provide quantitative estimates. Since...
We developed a method for optimizing strain to reduce gate leakage current in metal-oxide-semiconductor (MOS) transistors by using first-principles calculations. This method was used to investigate the possibility of decreasing gate leakage current by controlling the strain on gate dielectric materials. We found that compressive strain decreases drastically the leakage current through silicon oxynitride...
A simulation study has been performed on CMOS-compatible, thin-SOI, silicon-base, vertical bipolar transistors as a potential solution for cost-effective SOI BiCMOS. These transistors have a virtual collector, which is an inversion layer created by the substrate bias. Device performance is suitable for mixed-signal applications, and scales well with design rules and SOI thickness.
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