3D Multi-Subband Ensemble Monte Carlo Simulator of FinFETs and nanowire transistors

In this paper we present the development of a 3D Multi Subband Ensemble Monte Carlo (3DMSB-EMC) tool targeting the simulation of nanoscaled FinFETs and nanowire transistors. In order to deliver computational efficiency, we have developed a self-consistent framework that couples a MSB- EMC transport engine for a 1D electron gas with a 3DPoisson- 2DSchro ̈dinger solver. Here we use a FinFET with a physical channel length of 15nm as an example to demonstrate the appli- cability and highlight the benefits of the simulation framework. A comparison of the 3DMSB-EMC with Non-Equilibrium Green’s Functions (NEGFs) in the ballistic limit is used to verify and validate our approach

Random Discrete Dopant Induced Variability in Negative Capacitance Transistors

In this work we investigate the impact of random discrete dopants (RDD) induced statistical variability in ferroelectric negative capacitance field effect transistors (NCFETs). We couple the 3D `atomistic' statistical device simulator GARAND with the Landau - Khalatnikov equation of the ferroelectric for this study. We found that the negative capacitance effect provided by the ferroelectric layer can lead to suppression of the RDD induced variability in the threshold voltage (Vt), OFF-current (IOFF), and ON-current (ION). This immunity to RDD induced variability increases with increase in the ferroelectric thickness

Physical Simulation of Si-Based Resistive Random-Access Memory Devices

We present a newly-developed three-dimensional (3D) physical simulator suitable for the study of resistive random-access memory (RRAM) devices. We explore the switching behavior of Si-rich silica (SiOx) RRAM structures, whose operation has been successfully demonstrated experimentally at ambient conditions [1]. The simulator couples self-consistently a simulation of oxygen ion and electron transport to a self-heating model and the `atomistic' simulator GARAND. The electro-thermal simulation model provides many advantages compared to the classical phenomenological models based on the resistor breaker network. The simulator is validated with respect to experimental data and captures successfully the memristive behavior of the simulated SiOx RRAMs, by reconstructing the conductive filament formation and destruction phenomena in the 3D space. The simulation framework is useful for exploring the little-known physics of SiOx RRAMs, and providing efficient designs, in terms of performance, variability and reliability, for both memory devices and circuits

REVIEW ON QUERCUS DALECHAMPII TEN. AND QUERCUS PETRAEA (MATTUSCHKA) LIEBL. IN THE VEGETATION OF BULGARIA

Quercus dalechampii Ten. and Quercus petraea (Mattuschka) Liebl. have close taxonomical features, ecological requirements and phytocenological characteristics. Quercus dalechampii is wide spread in Bulgarian mountains up to 1500 m. Q. petraea does not make communities, but takes part in the communities of Q. dalechampii as single individuals. The aim of this review is to show taxonomical differences and some ecological and phytocenological characteristics of these two similar species

Does a Nanowire Transistor Follow the Golden Ratio? A 2D Poisson-Schrödinger/3D Monte Carlo Simulation Study

In this work, we observed the signatures of isotropic charge distributions showing the same attributes as the golden ratio (Phi) described in art and architecture, we also present a simulation study of ultra-scaled n-type silicon nanowire transistors (NWT) for the 5nm CMOS application. Our results reveal that the amount of mobile charge in the channel is determined by the device geometry and could also be related to the golden ratio (Phi). We also established a link between the main device characteristics, such as a drive and leakage current, and cross-sectional shape and dimensions of the device. We discussed the correlation between the main Figure of Merit (FoM) and the device variability and reliability

Self-consistent physical modeling of SiOx-based RRAM structures

We apply a unique three-dimensional (3D) physics-based atomistic simulator to study silicon-rich (SiOx, x<;2) resistive switching nonvolatile memory (RRAM) devices. We couple self-consistently a simulation of ion and electron transport to the `atomistic' simulator GARAND and a self-heating model to explore the switching processes in these structures. The simulation model is more advanced than other available phenomenological models based on the resistor breaker network. The simulator is calibrated with experimental data, and reconstructs accurately the formation and rupture of the conductive filament in the 3D space. We demonstrate how the simulator is useful for exploring the little-known physics of these promising devices, and show that switching is an intrinsic property of the SiOx layer. In general, the simulation framework is useful for providing efficient designs, in terms of performance, variability and reliability, for memory devices and circuits. The simulator validity is not limited to SiOx-based devices, and can be used to study other promising RRAM systems based, e.g., on transition metal oxides

Simulation study of vertically stacked lateral Si nanowires transistors for 5 nm CMOS applications

In this paper we present a simulation study of vertically stacked lateral nanowires transistors (NWTs), which may have applications at 5nm CMOS technology. Our simulation approach is based on a collection of simulation techniques to capture the complexity in such ultra-scaled devices. Initially, we used drift-diffusion methodology with activated Poisson-Schrodinger quantum corrections to accurately capture the quantum confinement in the cross-section of the device. Ensemble Monte Carlo simulations are used to accurately evaluate the drive current capturing the complexity of the carrier transport in the NWTs. We compared the current flow in single, double, and triple vertically stacked lateral NWTs with and without contact resistance. The results presented here suggest a consistent link between channel strain and device performance. Furthermore, we propose a device structure for the 5nm CMOS technology node that meets the required industry scaling projection. We also consider the interplay between various sources of statistical variability and reliability in this work

3D Multi-Subband Ensemble Monte Carlo Simulator of FinFETs and nanowire transistors

In this paper we present the development of a 3D Multi Subband Ensemble Monte Carlo (3DMSB-EMC) tool targeting the simulation of nanoscaled FinFETs and nanowire transistors. In order to deliver computational efficiency, we have developed a self-consistent framework that couples a MSB- EMC transport engine for a 1D electron gas with a 3DPoisson- 2DSchro ̈dinger solver. Here we use a FinFET with a physical channel length of 15nm as an example to demonstrate the appli- cability and highlight the benefits of the simulation framework. A comparison of the 3DMSB-EMC with Non-Equilibrium Green’s Functions (NEGFs) in the ballistic limit is used to verify and validate our approach

A Hierarchical Model for CNT and Cu-CNT Composite Interconnects: From Density Functional Theory to Circuit-Level Simulations

No abstract available

Interaction Between Precisely Placed Dopants and Interface Roughness in Silicon Nanowire Transistors: Full 3-D NEGF Simulation Study

In this work, we report a theoretical study based on quantum transport simulations that show the impact of the surface roughness on the performance of ultimately scaled gate-all-around silicon nanowire transistors (SNWT) with precisely positioned dopants designed for digital circuit applications. Due to strong inhomogeneity of the self-consistent electrostatic potential, a full 3-D real-space Non Equilibrium Green's Function (NEGF) formalism is used. The individual dopants and the profile of the channel surface roughness act as localized scatters and, hence, the impact on the electron transport is directly correlated to the combined effect of position of the single dopants and surface roughness shape. As a result, a large variation in the IOFF and ION and modest variation of the subthreshold slope are observed in the ID-VG characteristics when comparing devices without surface roughness. The variations of the current-voltage characteristics are analyzed with reference to the behaviour of the transmission coefficients, electron potential and electron concentration along the length of the device. Our calculations provide guidance for a future development of the next generation components with sub-10 nm dimensions for the semiconductor industry