bluuebunny/crossref_metadata_2025_split huggingface dataset:
Simulation of Alkali Migration in β′′-Alumina Under Ion Bombardment
Authors: D’Ajello Paulo C.T. , Pasa André A. 
Published: April 2011

ABSTRACTAmong the different effects induced by ion implantation into dielectric solids, the enhancement of the ionic mobility is the most important regarding practical applications. We simulated the Na migration in a super-ionic conductor, sodium β″-alumina, irradiated with Ar (E=200 keV) at room temperature. A theoretical model to describe the electric field originated in the bombarded region near the surface was developed. The model emphasizes the relation between the electric field and the energy deposited by the ions in the ionization process.
Point Defect-Based Modeling of Transient Diffusion of Boron Implanted in Silicon Along Random and Channeling Directions
Authors: Jäger H. U. 
Published: April 2011

ABSTRACTA point defect-based model, which has been developed to describe diffusion and electrical activation of boron in crystalline silicon during post-implantation annealing, is used to simulate the anomalous diffusion of boron implanted into silicon along the random and [100] channeling directions. The model predictions are compared to data measured by Chu et al.
A New Local Electronic Stopping Model for the Monte Carlo Simulation of Arsenic Ion Implantation into (100) Single-Crystal Silicon
Authors: Yang S.-H. , Morris S. , Tian S. , Parab K. , Tasch A. F. , Echenique P. M. , Capaz R. , Joannopoulos J. 
Published: April 2011

ABSTRACTIn this paper is reported the development and implementation of a new local electronic stopping model for arsenic ion implantation into single-crystal silicon. Monte Carlo binary collision (MCBC) models are appropriate for studying channeling effects since it is possible to include the crystal structure in the simulators. One major inadequacy of existing MCBC codes is that the electronic stopping of implanted ions is not accurately and physically accounted for, although it is absolutely necessary for predicting the channeling tails of the profiles. In order to address this need, we have developed a new electronic stopping power model using a directionally dependent electronic density (to account for valence bonding) and an electronic stopping power based on the density functional approach. This new model has been implemented in the MCBC code, UT-MARLOWE The predictions of UT-MARLOWE with this new model are in very good agreement with experimentally-measured secondary ion mass spectroscopy (SIMS) profiles for both on-axis and off-axis arsenic implants in the energy range of 15-180 keV.
Conformality and Composition of Films Deposited at Low Pressures
Authors: Cale Timothy S. 
Published: April 2011

ABSTRACTConformality limitations and film composition variations inside features for films deposited at low pressures are explained using examples of studies which combine transport and reaction simulations of deposition processes with experimental work. In the first example, the use of film profile information to decide between two kinetic models for the low pressure chemical vapor deposition (LPCVD) of SiO2 from tetraethoxysilane (TEOS) is described. In the second example, a simple but useful model for the plasma enhanced chemical vapor deposition (PECVD) of silicon dioxide from TEOS/oxygen mixtures (PETEOS) is discussed. In the third example, composition profiles in sputter deposited (PVD) Ti-W films are explained in terms of titanium re-emission. Combined simulation and experimental studies of film profiles and composition profiles in features is a valuable tool in efforts to arrive at useful kinetic and transport models.
The Influence of Strain Energy Minimization on Abnormal Grain Growth in Copper Thin Films
Authors: Zielinski E. M. , Vinci R. P. , Bravman J. C. 
Published: April 2011

AbstractSputtered Cu films on Si, Al and Cu substrates were thermally cycled to 300 °C at a rate of 6 °/min, which induced an applied thermal strain that was compressive, tensile and zero, respectively. Microstructural characterization of the annealed films revealed abnormal (100) grain growth in the films on Al and Si, but not Cu substrates. In addition, symmetric x-ray diffraction scans demonstrated that the films in which abnormal grain growth was observed were primarily (100) in orientation. In contrast, the Cu film on a Cu substrate was largely randomly oriented after cycling, with a small degree of (111) preferred orientation. These results are consistent with a strain energy driving force for abnormal grain growth, which predicts that the growth should occur in compression, as on the Si substrate, or in tension, as on the Al substrate, but not when there is no applied thermal strain, as on the Cu substrate.
Finite Element Analysis of Electromigration and Stress Induced Diffusion in Deformable Solids
Authors: Bower A.F. , Freund L.B. 
Published: April 2011

AbstractWith a view to analyzing failure mechanisms in interconnects, we have developed a finite element method that may be used to compute the effects of diffusion and deformation in an electrically conducting, deformable solid. The analysis accounts for large changes in the shape of the solid due to surface diffusion, grain boundary diffusion, and elastic or inelastic deformation within the grains. To illustrate the capabilities of the method, we have analyzed void migration and collapse due to current induced surface diffusion; the drift of a strip of conducting solid on a substrate; and have calculated intergranular stresses and plastic deformation induced by electromigration in a passivated, polycrystalline interconnect line.
The Effect of Cluster Interactions on Electromigration Induced Stress Evolution in Confined Metal Lines
Authors: Brown D.D. , Sanchez J.E. , Besser P.R. , Korhonen M.A. , Li C.-Y. 
Published: April 2011

AbstractIn near-bamboo interconnect lines used in advanced integrated circuits, electromigration flux divergences occur at the intersection between polycrystalline cluster segments (where grain boundaries offer a fast diffusion path), and bamboo segments (where there are no grain boundaries along the line length). For confined, passivated metal interconnects, these flux divergences are linked to the evolution of significant mechanical stresses in the metal. A quasisteady state stress distribution builds up relatively quickly in the cluster segments and remains unchanged until there is significant diffusion into the bamboo segments. The stress profile of a given cluster then becomes dependent on neighboring clusters as well as the diffusivity and flux in the separating bamboo segments. Previous analyses of electromigration failure in interconnect lines have focused on the distribution of cluster lengths and the stress build up in isolated cluster segments. In this paper, we show that the bamboo length distribution can strongly affect the interaction between clusters and the evolution of stresses in a near-bamboo interconnect during electromigration. We present simulation results, using a ratio of cluster to bamboo diffusivity Dc/Db=100, which show greater interactions and larger maximum stresses in cluster segments as the average bamboo segment length decreases and as the bamboo segment length distribution widens.
Study of Diffusion Barrier Performance in MOCVD TiN by Transmission Electron Microscopy
Authors: Lee Hoojeong , Sinclair Robert , Roberts Bruce , Jackson Robert 
Published: April 2011

AbstractThe diffusion barrier performances of MOCVD TiN films with different thicknesses and various contact layers are compared by both ex situ and in situ TEM experiments. MOCVD TiN films grown at 425°C and 10 torr without a titanium underlayer show a semi-columnar structure while films grown with a titanium layer are columnar. It is found that the former has better diffusion barrier performance for Al metallization in Si contact holes. In addition, it is found the MOCVD TiN films combined with a TiSi2 contact layer are stable up to 600°C.
Material Properties of Coherent Tin Films
Authors: Ngan Ken 
Published: April 2011

AbstractIn this paper, material properties of low pressure, metallic mode Coherent TiN and poison mode Coherent TiN have been examined. The material properties include resistivity, crystal orientation, stress, lattice spacing, density, texture, atomic composition, bonding, roughness, hydrogen content, and grain size. Various analytical tools have been used to analyze the TiN films.
Grain Boundary Grooving as the Mechanism of the Blech Electromigration in Interconnects
Authors: Glickman E.E. , Klinger L.M. 
Published: April 2011

AbstractWe present a new approach to understand the mechanism of "homogeneous", or Blech electromigration (EM). This phenomenon describes macroscopically homogeneous displacement of the up-wind edge of thin film lines in microelectronic devices and is responsible for openings at contact windows, "vias" and other sites of perfect diffusion flux divergence.Our SEM, EPMA and EM drift velocity experiments have revealed the gradual transition from the microscopically homogeneous EM displacement to the highly nonhomogeneous mode wherein copious islands of residual material remain behind the drifting cathode edge of aluminum stripes. The transition is shown to occur due to an increase in either the current density, j, or in the stripe length, 1. The latter case suggests, that the transition results from the growth of the net grain boundary (GB) diffusion flux, I=le-Ib ,where Ie∝j and 1b∝1/1 are the EM flux and stress-gradient-driven back flux, respectively.Based upon recent progress in the theory of GB grooving under "external" GB fluxes, with surface diffusion acting as the healing mechanism, grooves' propagation along the line and their merging is considered to be the micromechanism of the "homogeneous" EM. In terms of the simple model described, the transition from the slow receding of the cathode butt edge slightly wrinkled by shallow grooves (A-regime of EM) to the fast extension and merging of slot -like grooves (B-regime) accounts for the transition observed in EM mode, while in both regimes the EM displacement velocity, V, is presumed to represent the groove propagation rate.The theory developed reduces to Blech formulae for V for the truly homogeneous A-regime and predicts quite different EM kinetics for the B-regime of microscopically nonhomogeneous EM. The latter is expected to dominate for films loaded by high current density with large grains and low surface diffusion.The dependence obtained for the residual mass left behind the drifted edge vs the displacement velocity, V, for unpassivated aluminum stripes of various lengths, loaded by j=2-106 A/cm2 at 548K provides a good evidence in support of a new approach.
On the Role of Surface Diffusion in Stress Relaxation During Electromigration
Authors: Klinger L.M. , Levin L. , Glickman E.E. 
Published: April 2011

AbstractWe report on the role of surface diffusion involved in relaxation of electromigration (EM) induced compressive stresses in relation to hillock growth and EM behavior of interconnects. Two competing mechanisms of EM stress relaxation by material transport onto the surface are considered. The first is hillocking by threshold diffusional creep (TCH), with rather large blocks of material (grains or group of grains) involved in plastic flow. The second mechanism, atomic diffusion hillocking (ADH), is presumed to be a nonthreshold one, and represents atomic grain boundary (GB) diffusion stimulated by the hydrostatic stress gradient in the direction normal to the film surface. The latter process involves surface diffusion because GB diffusional flux onto the surface must be coupled with the flux of redistribution of the atoms over the surface. If ADH acts rapidly, this should prevent the build-up of the matter at the down-wind (anode) end of the stripe, and thus, eliminate the Blech EM threshold resulting from the stress-gradient along the stripe. The question as to whether GB diffusion capable of transporting atoms pushed by electron wind along the stripe is also effective in relieving compressive stress by GB migration of the surplus atoms in the normal direction, has remained open up to now. The problem is especially acute for short or/and narrow lines separated into short polycrystalline segments, where the Blech threshold effects are critical to EM reliability.We derived the main features of the EM behavior in drift velocity test geometry assuming that both TCH and ADH are operative. The result can be compared with available and future experimental observations in order to reveal if and when the ADH mechanism with surface diffusion involved works.
Stress-Voiding and Electromigration in Multilevel Interconnects
Authors: Korhonen M.A. , Liu Tao , Brown D.D. , Li C.-Y. 
Published: April 2011

AbstractStress-voiding and electromigration have become urgent reliability concerns at the decrease of interconnect dimensions to submicron size. Severe stress voiding may arise in multilevel metallizations, particularly at contact and via regimes where the thermal stresses are highest. Via and contact structures with the attached refractory layers usually block entirely the electromigration flux; hence, EM voids are likely to form here. In this paper we first model the migration of atoms due to gradients in composition, stress, and electric potential. We seek a formulation in the spirit of irreversible thermodynamics, i.e. without reference to any specific micromechanisms of diffusion. We then apply the general developments to predict the stress evolution and void growth in Al based interconnect lines confined between entirely blocking Wstuds. We also analyze the effects of Cu depletion at vias, either by interfacial or grain boundary diffusion, on the stress evolution and void growth. Finally we demonstrate that the change in the line resistance due to void growth will display apparent incubation times even if the void grows linearly with time.
An Effect of Dopants on Contact Electromigration
Authors: Kim Eungsoo , Cho Kyungwon , Jang Hyungwoo , Lim Soonkwon 
Published: April 2011

AbstractRecently, device reliability has been an important issue since the design rule is scaled down and complicated processing is involved. To improve the reliability, many problems should be solved. One of the problems in interconnection failure is short or open circuits at interconnection lines. Contact or via hole failure has been ignored while the metal line failure has been strongly studied by many researchers.In this study, electromigration (EM) phenomena at the submicron size of contact hole are presented with respect to the type of dopants, boron and arsenic, implanted by high dose. In both cases, the failure mode at the contact hole, the values of the activation energy and the mean-time-to-failure (MTTF) are much different. For example the value of MTTF in boron is lower than that in As. The contact failure by EM is analyzed by SEM micrographs, FIB micrographs, EM measurement. One of the interesting results is void formation at the interface between implanted surface and silicon dioxide film, which is located between contact holes. This fact indicates that the interface migration of Si is much faster than the self-diffusion of Si because the current path is mainly formed along the interface.
Analysis of the Mechanical Failure in a Multilayered Thin Film System Tested by Microtensile Loading
Authors: Marieb T. , Ignat M. , Fujimoto H. , Flinn P. 
Published: April 2011

AbstractMultilayered thin films were deposited on pure Al substrate test bars for in situ scanning electron microscope (SEM) microtensile deformation. The films consisted of a TiN layer covered by either SiO2 or W. Deformation of the samples showed that the TiN film dominated cracking events and caused cracking in the W to occur at lower critical stress values than previously reported. Crack deflections along the TiN-W interface were also seen. W film strain was measured by X-ray diffraction before and after testing to look at the effect of cracking and deformation on stress in this film.
Ligand Substitution Effect on Optical Properties in Conducting Tetraazaporphyrines
Authors: Guo Liqun , Ellis D. E. , Gubanova O. V. , Hoffman B. M. 
Published: April 2011

ABSTRACTSelf-consistent Density Functional calculations have been performed on a variety of planar conjugated Ni-centered macrocycles with a basic tetraazaporphyrinic core and dithiolene groups (PZ) or fused-benzo groups (PC). Theoretical energy diagrams, charge and spin distributions and densities of states have been obtained in order to understand the electronic structure modifications due to peripheral ligand substitution. The substituents role in altering electronic properties and charge distribution of the porphyrazine macrocycles has been used to interpret the observed variations in optical absorption profiles. In the Q-band (∼ 680 nm) region, a single peak is seen for high symmetry (D4h) macrocycles and a double peak for lower symmetry (D2h and C2v) systems. Calculated intensities and band splittings are compared in detail with qualitative molecular orbital models and experiment in the visible and UV regions. Predictions are made for the infrared absorption and semiconducting band gap.
Determination of Water Content and Resistivity of Perfluorosulfonic Acid Fuel Cell Membranes
Authors: Sen. Ashish , E.Leach Kevin , D.Varjian Richard 
Published: April 2011

ABSTRACTWater uptake and resistivity have been determined for Dupont's Nafion-115®and Dow membrane 800 EW while in contact with a water-saturated nitrogen atmosphere using Fourier transform near-infrared (NIR), and AC impedance four point techniques in the temperature range of 23°C to 100°C. Results show that at room temperature there is a significant increase in water content and a corresponding decrease in the electrical resistivity as the relative humidity increases from 0% to 100%. Results also indicate that there is a substantial decrease in water uptake from water vapor at 100°C relative to that at 23°C. The water content of Dow membrane is higher than Nafion-115 under all conditions tested. The water contents of Dow PFSA 800 EW and Nafion-115 membranes at about 92% R.H. and 23°C are approximately 25 wt% and 18 wt%, respectively. The corresponding water content values at 100°C are 10 wt% and 8 wt%, respectively. The resistivity of the membranes decreases sharply with the temperature up to 60°C, reaches a minimum near 80°C then increases up to 100°C. The Dow membrane has lower resistivity than Nafion-115 over the entire range.
Nickel-Metal Hydride Electric Vehicle Batteries Through Materials Science Advances
Authors: Venkatesan S. , Fetcenko M.A. , Corrigan D.A. , Gifford P.R. , Dhar S.K. , Ovshinsky S.R. 
Published: April 2011

Abstract:Proprietary, multicomponent hydrogen storage materials have been developed making use of the principles of disorder by atomic engineering of the short-range and intermediate -range order. These materials form the basis for Ovonic Nickel-Metal Hydride batteries which have emerged as the leading battery technology for electric vehicle applications. Ovonic Batteries have the highest volumetric energy density available extending the practical range of electric vehicles from under 100 miles to over 200 miles.
Structural Characterization of Carbon Materials Prepared at Low Temperature
Authors: Song Xiang-Yun , Chu Xi , Kinoshita Kimio 
Published: April 2011

ABSTRACTHigh-capacity carbon electrodes for rechageable lithium-ion batteries were prepared by carbonization of thermosetting resins such as phenol-formaldehyde at temperatures between 500°C and 600°C. Their structures were characterized by high resolution transmission electron microscopy, in-situ transmission electron microscopy and x-ray diffraction analysis. These studies suggest that the carbons consist predominantly of disorganized (amorphous) phase. However evidence was found in carbon containing nickel cobalt oxide for the presence of organized graphite-like regions of parallel and curved layer planes. These graphitized structure usually appear as agglomerate particles which are composed of many smaller (100-nm diameter) particles. The high degree of graphitization is attributed to catalytic graphitization that occurs in the presence of the metal oxide.
Lithium Intercalation in Porous Carbon Electrodes
Authors: Tran T. D. , Feikert J. , Pekala R. W. , Miller J. , Dunn B. 
Published: April 2011

ABSTRACTCarbons derived from the phase separation of polyacrylonitrile/solvent mixtures were investigated as lithium intercalation anodes for rechargeable lithium-ion batteries. The carbon electrodes have a bulk density of 0.35-0.5 g/cm3, relatively low surface areas (< 10 m2/g), and micron-size cells. Pyrolysis temperature influences the reversible lithium intercalation and the irreversible capacity (associated with the formation of the passivating layer). Carbon electrodes pyrolyzed at 600°C have first-cycle capacity as high as 550 mAh/g as well as large irreversible capacity, 440 mAh/g. Electrodes prepared at 1050°C have reversible capacities around 270 mAh/g with relatively lower capacity losses (120 mAh/g). Doping the organic precursors with phosphoric acid, prior to pyrolysis at 1050 C, leads to carbon electrodes with reversible capacities as high as 450 mAh/g. The capacity of doped carbon increased with increasing phosphorus concentration in the samples. The doped carbon anodes exhibited good cycleability and excellent coulombic efficiency. The electrochemical performance is related to morphology, chemical composition, and local structural order.
Influence of Precursor Chemistry on Phase Evolution and Stability Range in the Potassium-Beta Alumina System
Authors: Schäfer Günter W. , de Kroon Arnoud P. , Aldinger Fritz 
Published: April 2011

ABSTRACTThe beta alumina structures are known for their high ionic mobility within the lattice. This lead to the development of the Na-β”-alumina polycrystal as solid electolyte in Na/S and Na/NiCl2 batteries. The K-β”-alumina compound is a suitable precursor material to establish proton conducting materials by ion exchange. Tests with single crystal and polycrystalline samples showed the possible application in fuel cells operating between 150 - 250 °C.One of the main problems to be solved is the correlation between composition and phase evolution of either β- or β”-phase, another problem occuring during sintering is the high vapor pressure of the alkaline oxide. This leads to the decomposition of the highly conductive β”-alumina phase into β-alumina or corundum phases and lowers significantly the ionic conductivity.We investigated the beta alumina phase evolution using alumina raw materials with different crystallographic structure and grain size. The influence of initial alkaline content and dopant concentration on phase formation and phase stability under sintering conditions has been investigated. A refined phase diagram for Na- and K-beta aluminas will be presented.
Examination of Interact Roughening in Ion Irradiated Cu/Nb Films by Computer Simulation and by X-Ray Diffraction
Authors: Partyka P.J. , Averback R.S. , Robinson I.K. , Lee Y.S. , Flynn C.P. , Bellon P. 
Published: April 2011

AbstractInterfacial roughening during ion irradiation of an immiscible system is investigated by Monte Carlo computer simulation and by an x-ray diffraction technique called crystal truncation rod (CTR) analysis. In the simulations, ion flux and sample temperature are varied, and the system is allowed to evolve under irradiation until it reaches a steady state behavior. The observed behaviors are then sought experimentally in the Cu/Nb system implanted with 2 MeV Kr+ ions at different sample temperatures. Analysis of the roughness at the Cu interface is based upon the existence of a crystal truncation rod, which contains information on exactly how the crystal is terminated, or, in other words, the interfacial roughness. Rutherford backscattering spectrometry (RBS) is also used to study the intermixing of the Cu and Nb layers.