Collective dipole effects in ionic transport under electric fields

In the context of ionic transport in solids, the variation of a migration barrier height under electric fields is traditionally assumed to be equal to the classical electric work of a point charge that carries the transport charge. However, how reliable is this phenomenological model and how does it fare with respect to Modern Theory of Polarization? In this work, we show that such a classical picture does not hold in general as collective dipole effects may be critical. Such effects are unraveled by an appropriate polarization decomposition and by an expression that we derive, which defines the equivalent polarization-work charge. The equivalent polarization-work charge is not equal neither to the transported charge, nor to the Born effective charge of the migrating atom alone, but it is defined by the total polarization change at the transition state. Our findings are illustrated by oxygen charged defects in MgO and in SiO2

Advances, Challenges and Opportunities in 3D CMOS Sequential Integration

3D sequential integration enables the full use of the third dimension thanks to its high alignment performance. In this paper, we address the major challenges of 3D sequential integration: in particular, the control of molecular bonding allows us to obtain pristine quality top active layer. With the help of Solid Phase Epitaxy, we can match the performance of top FET, processed at low temperature (600°C), with the bottom FET devices. Finally, the development of a stable salicide enables to retain bottom performance after top FET processing. Overcoming these major technological issues offers a wide range of applications

Theoretical insights and experimental characterization of HfO 2 -based OxRRAMs operation

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An atomistic investigation of the impact of in-plane uniaxial stress during solid phase epitaxial regrowth

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A Link between CBRAM Performances and Material Microscopic Properties Based on Electrical Characterization and Atomistic Simulations

International audienceIn this paper, we investigate the link between various resistive memory (RRAM) electrical characteristics: endurance, window margin (WM), and retention. For this purpose, several RRAMs are characterized using various resistive layers and bottom electrodes. By focusing on one technology and optimizing programming conditions (current, voltage, and time), we establish a tradeoff between endurance and WM. Then, by changing memory stack, we demonstrate the correlation between endurance plus window marging improvement and retention degradation. Studying this last feature from a material point of view, we analyze different oxides by density functional theory. We realize a systematic review for possible exchanges of species between resistive layer and Cu-based top electrode and study their diffusion. This provides insights on conductive filament composition in different stacks. Combining previous experiments and simulations, we propose a link between memory characteristics and material microscopic parameters, through the ion energy migration barrier. Finally, we extract how endurance, WM, and retention are correlated to material properties and electrical parameters in order to choose the suitable material for a defined application using the RRAM technology

Insights in accesses optimization for nFET low temperature Fully Depleted Silicon On Insulator devices

session Annealing Technology S2-07International audienceThis work gives insights on the performance levers to optimize nFET Fully Depleted Silicon On Insulator sheet resistance with low temperature activation. Optimum dopant concentration, i.e clusterization limit for arsenic and phosphorus activated at 600°C has been extracted. This study shows that phosphorus appears to be the best candidate for nFET low temperature doping. Solid Phase Epitaxial Regrowth at 600°C enables to reach activation levels identical to the thermodynamic equilibrium at 1050°

Influence of device architecture on junction leakage in low-temperature process FDSOI MOSFETs

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Defect creation and Diffusion under electric fields from first-principles: the prototypical case of silicon dioxide

International audienceIn this paper we study the effect on the electric fields on the formation of bulk Frenkal Pairs and on the migration of oxygen interstitials, IO, and oxygen vacancies, VO, within the framework of Density Functional Theory and Modern Theory of Polarization. At typical OXRRAM field conditions, We show that a significant effect of the electric field is observed only for charged defect. Analyzing the polarization work, we found anomalously high polarization work, for the case of I −2 O , with respect to the classical picture of the electric work of an isolated point charge. This large difference has to be ascribed to collective contributions coming from the environment

Modeling study of the mobility in FDSOI devices with a focus on near-spacer-region

International audienceWe have studied the mobility in the FDSOI devices as a function of silicon thickness, doping, surface orientation and applying different back biases. This study is also done in the near-spacer-region that is partially inverted. Simulations have been obtained with a self-consistent Poisson-Schrödinger which provides a precise energy distribution of carriers and, allied to a Kubo-Greenwood carrier mobility solver, performs a quantum corrected drift diffusion (QCDD) model, capable of capturing non local effects on transport (tunneling) and mobility (influence of geometry)