bluuebunny/crossref_metadata_2025_split huggingface dataset:
Coupled Stress Evolution in Polygranular Clusters and Bamboo Segments in Near-Bamboo Interconnects
Authors: Knowlton B. D. , Clement J. J. , Frank R. I. , Thompson C. V. 
Published: April 2011

AbstractElectromigration-induced failure of near-bamboo interconnects depends strongly on the number and lengths of both polygranular clusters and bamboo segments in a line. We have used numerical techniques to calculate the stress profile as a function of position and time for near-bamboo lines with a variety of microstructures. Our results show that coupling of stress profiles between nearby clusters can affect the time to reach a pre-defined critical, or failure, stress. The degree of coupling depends both on the spacing between clusters and the ratio of the diffusivities between polygranular and single crystal regions. Electromigration failure is therefore sensitive to the distribution and lengths of bamboo segments, and the likelihood of long polygranular clusters coinciding with adjacent short bamboo segments.
Real-Time Tem Studies of Electromigration in Submicron Aluminum Runners
Authors: Riege S. P. , Hunt A. W. , Prybyla J. A. 
Published: April 2011

AbstractDirect real-time observations of electromigration (EM) in submicron Al interconnects were made using a special sample-stage which allowed TEM observations to be recorded while simultaneously heating and passing current through the sample. The samples consisted of 4000 Å thick Al(0.5wt%Cu) patterned over a TEM-transparent window into five runners in parallel, with linewidths 0.2, 0.3, 0.5, 0.8, and 1.0 μm. Both passivated and unpassivated samples were examined. A current density of 2 x 106A/cm2 was used with temperatures ranging from 200 - 350°C. The experiments were done using constant voltage testing, and we used a special sample design which dramatically minimized Joule-heating. Our approach has allowed us to directly observe voids form, grow, migrate, pin, fail a runner, and heal, all with respect to the detailed local microstructure of the runners.
Mechanism of Electromigration Failure in Al Thin Film Interconnects Containing Sc
Authors: Kim Choong-Un , Kang S. H. , Génin F.Y. , Morris J. W. 
Published: April 2011

AbstractIn order to understand the role of Sc on electromigration (EM) failure, Al interconnects with 0.1 and 0.3 wt.% Sc were tested as a function of post-pattern annealing time. In response to the evolution of the line structure, the statistics of lifetime evolved. While the addition of Sc greatly reduces the rate of evolution of the failure statistics because the grain growth rate decreases, the MTF variation was found to be very similar to that of pure Al. These observations seem to show that Sc has little influence on the kinetics of Al EM; however, it has some influence on the EM resistance of the line since it is an efficient grain refiner. Unlike Cu in Al, Sc does not seem to migrate, which may explain its lack of influence on the kinetics of Al EM.
Circuit Reliability Simulation
Authors: Hu Chenming 
Published: April 2011

AbstractIn designing a complex circuit, designers make a large number of circuit simulations, design changes and optimizations and can predict the circuit's performance reasonably accurately before committing it to silicon. It would be unthinkable to bypass detailed circuit simulation and optimization and rely on simple design rules and the testing of finished IC's to discover errors or to find out if the performance of the circuit meet specifications. Yet, this is basically the way IC reliability is treated today. A logical alternative is to predict circuit reliability at the circuit design stage through reliability simulation.Reliability simulator BERT is used to illustrate the physical models and approaches used to simulate the hot electron effect, oxide time-dependent breakdown, electromigration, bipolar transistor gain degradation, and radiation effects. The goal is to make circuit reliability simulation a part of the IC design process.
Influence of Film Thickness and Capping Layer on the Mechanical Properties of Copper Films
Authors: Keller R.-M. , Kuschke W.-M. , Kretschmann A. , Bader S. , Vinci R.P. , Arzt E. 
Published: April 2011

AbstractSubstrate curvature and X-ray technique were used to study the mechanical properties of Cu films. Stress-temperature curves were measured using both methods. An additional analysis of the X-ray peak width allows us to estimate grain size and dislocation density as a function of temperature. It can be shown that a capping layer changes the mechanical properties of a Cu film strongly and that in capped films dislocation processes seem to be more important than diffusion at high temperatures.
The Effect of Cu Distribution on Post-Patterning Grain Growth and Reliability of Al-1%Cu Interconnects
Authors: Knowlton B. D. , Frank R. I. , Thompson C. V. 
Published: April 2011

AbstractThe reliability of Al-Cu interconnects is a strong function of both grain structure and the Cu content and distribution. Because pre-patteming and post-patterning grain growth are affected by the presence of Al2Cu precipitates, the effects of grain structure and Cu distribution are interrelated. We have studied the effect of Al2Cu precipitate spacing on interconnect reliability independent of grain size effects. This was accomplished by varying the thermal history of the continuous films to produce samples with identical grain structures, but different precipitate spacings. The precipitate spacing in continuous films was varied by an order of magnitude, from 2.6 μm to 25. pm. Lines were then patterned from each sample and tested. Lifetime testing results show that the reliability of lines with smaller precipitate spacings can be roughly an order of magnitude higher than that of lines with a larger precipitate spacing. We have also qualitatively studied the effects of Cu distribution on post-patterning grain growth. We found that precipitates retard post-patterning grain evolution, leading to reduced reliability. These results suggest strategies for developing thermal histories which will lead to optimal reliability.
Failure in Tungsten-Filled Via Structures
Authors: Clement J. J. , Lloyd J. R. , Thompson C. V. 
Published: April 2011

AbstractFailure of the tungsten-filled via interconnect structure is modelled. Two mechanisms contributing to void growth are considered: relief of stress due to differential thermal expansion, and electromigration. A self-limiting void volume is predicted, resulting in a self-limiting resistance increase which is a function of structure geometry and the void morphology. The relative contributions of the two mechanisms change significantly as the temperature and current density are reduced from accelerated test conditions, affecting the extrapolation of test results to service conditions. Modified procedures for extrapolating lifetimes are discussed, as well as suggested process changes to improve reliability.
The Effect of Post W-Etchback Cleaning Treatments and Implementation of Refractory Metal Buffer Layers on the Electromigration Performance of TiN/AlCu/TiN/Ti Metallization Systems
Authors: Roede Henk , Gounelle Catherine , Giroux François , Doedel Wim 
Published: April 2011

AbstractTiN/Ti films employed as glue layers for a blanket/etchback W plug technology show a significant surface contamination after the W-etchback process. An Al film deposited directly on a contaminated TiN/Ti underlayer exhibits a very weak texture, increasing the susceptibility to electromigration. Reliability tests confirm that the electromigration performance of a TiN/AlCu/TiN/Ti metallization system with a W plug technology, is significantly inferior to interconnecs that do not employ this plug technology. To improve the electromigration performance of this metallization system, several TiN surface cleaning treatments were evaluated. Also, the impact of the implementation of refractory metal buffer layers, before Al deposition was investigated. Analysis was performed by means of several surface analysis techniques, Al texture measurements and wafer-level reliability tests. It has been demonstrated that the contamination needs to be removed completely, or to be covered by a refractory buffer layer in order to restore the Al texture and to recover the proper electromigration resistance.
Effect of Via Etch Profile and Barrier Metal on Electromigration Performance of W-Filled Via Structure in TiN/AlCu/TiN Metallization
Authors: Ting Larry M. , Dixit G. , Jain M. , Littau K. A. , Tran H. , Chang M. , Sdsfha A. 
Published: April 2011

AbstractIn this study, we have evaluated electromigration performance of W-plug vias, fabricated with process variations in via hole etching as well as in via barrier deposition, on a TiN(barrier)/AlCu/TiN metallization system. We found that via etch profile scheme as well as deposition conformity for via barrier can significantly affect W-plug via lifetimes. The results indicate that the quality of contact with AlCu layer of bottom level metal is a critical factor in determining via lifetime. Precise control of via etching or by use of conformal via barrier to ensure a good barrier between W-plug and the AlCu of bottom level metal is essential for achieving reliable via structures.
Reliability Issues with Mixed-Signal CMOS Technology
Authors: Lahri Rajeeva , Chen Hung-Sheng , Zhao Ji , Gadepally Kamesh , Teng C.S. 
Published: April 2011

AbstractIn a Mixed-Signal IC, both digital and analog circuits exist on the same chip. Analog circuit blocks require technology attributes like precise device matching, low parametric drifts and low noise. These requirements raise additional reliability issues, over and above the reliability concerns associated with digital circuits. CMOS device reliability for mixed-signal technologies can be enhanced by modifying device architecture and improving gate oxide integrity. Interconnect metallurgy plays an important role in determining electromigration related contact/via resistance change which may impact matching of devices and resistor pairs. Appropriate source/drain engineering, device design and utilizing nitrided gate oxide has been shown to produce extremely stable devices. This article will cover process architecture and material issues related with device stability and interconnect metallurgy issues related with contact/via stability, especially with W-Plugs.
Microscopic Measurements of Electromigration Damage Using Electrical Measurements
Authors: K Jones Brian 
Published: April 2011

AbstractContinuous measurements have been made of the changes in several electrical quantities of Al 4%Cu tracks during the lifetime under electromigration stress. The changes in resistance, second harmonic and the second harmonic delay have been used to determine the changes in the track cross-section, resistivity and temperature. During most of the lifetime the results are consistent with a linear increase in the microscopic damage occurring uniformly throughout the track. During the final phase of the life there is evidence of large void formation with subsequent healing. Considerable information can be obtained about these processes and the extent to which they are reversible. The observed events are compared with the changes which have been predicted by specific mechanisms.
Electromigration Induced Drift and Noise in a Single Aluminum Via
Authors: ALERS G. B. , OATES A. S. , BEVERLY N.L. 
Published: April 2011

AbstractWe have examined small changes in the resistance of a single aluminum via test structure with a resolution of 10-8 ohms. The via is roughly one cubic micron and contains a well defined TiN diffusion barrier. The high resolution of these resistance measurements allows the observation of atomic drift rates corresponding to roughly 100 atoms/second into and out of the well defined via structure. Resistance changes are observed with moderate current densities in the temperature range of 100°C to 200°C. We observe reversible increases and decreases in the resistance caused by the accumulation of atoms at the diffusion barrier within the via. Comparisons can be made to recent models for the transient electromigration induced vacancy drift. We are able to extract microscopic electromigration parameters as well as differentiate between copper and aluminum as the initial diffusing element.
The Influence of Thermal-Mechanical Effectson Resistance Changes During and After Electromigration Experiments
Authors: SCORZONI A. , DE MUNARI I. , STULENS H. , D'HAEGER V. 
Published: April 2011

AbstractThis paper is focused on the non-linear resistance behaviours often detected by means of high resolution resistometric methods both at the very beginning of an electromigration (EM) test, and after the high stressing current inducing EM is switched off. It is shown that temperature steps, always present at the beginning or after EM, are the triggering events for different, often reversible, physical phenomena contributing to resistance changes. Precipitation-dissolution of alloyed elements is perhaps the most important one, while other mechanisms, like the combined effect of hydrostatic stress relaxation and void volume change, should cancel out. These effects, however, don't exclude a possible simultaneous effect on the resistance of accumulation/relaxation of EM damage. Experimental results are collected by means of different, complementary techniques.
Hillock Formation in Tensile Loaded Films
Authors: Harris Karen E. , King Alexander H. 
Published: April 2011

AbstractWhile hillocks usually form to relieve compressive stresses in thin films resulting from electromigration or a difference in thermal expansion in the film and substrate, we have observed hillock formation in tensile-loaded films. We have used transmission electron microscopy to study hillocks which formed in free-standing gold thin films of 25nm nominal thickness. Grain growth during 150°C anneals reduced the grain boundary area and associated free volume, placing the films under tensile stress. While hillock formation could only increase this stress, large single crystal or polycrystalline hillocks with thicknesses up to three times the film thickness are observed after 400°C annealing, after long room temperature anneals, and during TEM observation. These observations suggest the operation of a hillock formation mechanism not explained by any existing hillock formation theories.
Yield Stress in Single Crystal and Polycrystalline Al Films
Authors: Traub A. , Volkert C. A. 
Published: April 2011

AbstractThe stresses in single crystal and polycrystalline Al films were determined by wafer curvature measurements during temperature cycling. Both elastic and plastic behavior was observed. The single crystal film exhibited anisotropic yield stresses indicating that dislocation glide is the dominant deformation mechanism. The polycrystalline film exhibited similar behavior, although without the anisotropy, indicating that it too deforms by dislocation glide. Unlike the single crystal film, the yield stress in the polycrystalline film varied depending on thermal and deformation history. These effects are attributed to the presence of grains and grain boundaries in the polycrystalline film.
Solution Synthesis and Characterization of Lithium Manganese Oxide Cathode Materials
Authors: Voigt J. A. , Boyle T. J. , Doughty D. H. , Hernandez B. A. , Johnson B. J. , Levy S.C. , Tafoya C. J. , Rosay M. 
Published: April 2011

ABSTRACTA nonaqueous coprecipitation process has been developed to prepare controlled stoichiometry lithium manganese oxalate precipitates. The process involved mixing a methanolic Li-Mn nitrate solution with a methanolic solution containing tetramethylammonium oxalate as the precipitating agent. The resulting oxalates were readily converted to a variety of phase pure lithium manganese oxides at moderate temperatures (≤600°C), where the phase formed was determined by the initial Li/Mn ratio in the starting solution. Metal cation dopants have been incorporated into the oxalate precipitate by dissolving the appropriate metal nitrate in the Li-Mn precursor solution The various starting solutions, oxalate precipitates, and calcined oxides have been extensively characterized using a variety of techniques, including 7Li NMR, TGA/DTA, SEM, and XRD. Results indicate that a strong interaction occurs between Li and Mn in the nitrate solution which carries over into the oxalate phase during precipitation. The morphology and the crystallite size of the oxide powders were shown to be controlled by the morphology of the oxalate precursor and the oxalate calcination temperature, respectively. The results of initial cathode performance tests with respect to dopant type (Al, Ni, Co) and concentration for LiMn2O4 are also reported.
Development of a Model of on-Board Pemfc Powered Locomotive with a Metal Hydride Cylinder
Authors: Hasegawa H. , Ohki Y. 
Published: April 2011

ABSTRACTThis paper presents a phase-zero evaluation case of installing on-off-board hybrid powered Electric Motor Vehicle (EMV) in existing and new local line and reports development of a model fuel cell powered locomotive. EMV such as electric car and locomotive are a new conceptual EMV using hybrid power between off-board substation and on-board Regenerative Fuel Cell (RFC) power system with Metal Hydride (MH) stored hydrogen generated with water electrolyzer by off-board surplus power. In this study, it is estimated a possibility to close power gap over 30 % in placing the new conceptual vehicle. The Locomotive is a 110 cm long locomotive powered by a 20 W PEMFC configured with 20 cells and supplied with about 2 g hydrogen, from a cylinder of 100 g metal hydride, and natural convection air (02). Measuring 50 cm (W), 50 cm (H), and weighting 25.9 kgf, the locomotive has a permanent magnet motor with a rated power 38 W (12 V, 3 A) and ran on railway that has a gauge of 126 mm (3'6“/8.5=4.94”), a length of 100 m. The performance of this train was acceleration of 0.5 m/s, cruising speed of 4.1 m/s at traction force of 15.8 N (1.6 kgf), average rolling friction of 5 N (460 gf).
Evaluation of the Humidification Requirements of New Proton Exchange Membranes for Fuel Cells
Authors: Grot Stephen A. , Hedstrom J.C. , Vanderborgh N.E. 
Published: April 2011

ABSTRACTMeasurements of PEM fuel cell device performance were made with different gas inlet temperatures and relative humidity using a newly-designed test fixture. Significant improvement in device performance was observed when the fuel inlet temperature was increased above the operating temperature of the cell. These measurements were then correlated to a model to describe energy and mass transport processes.
Effects of the Electrolyte Composition on the Electrode Characteristics of Rechargeable Lithium Batteries
Authors: Morita Masayuki , Ishikawa Masashi , Matsuda Yoshiharu 
Published: April 2011

ABSTRACTA variety of organic solvent-based electrolytes have been studied for ambient temperature, rechargeable lithium (ion) batteries. The ionic behavior of the electrolyte system was investigated through conductivity measurements. The electrochemical characteristics of carbon-based materials (carbon fiber and graphite) as the negative electrode were examined in different compositions of the organic electrolytes. The electrolyte composition as well as the structure of the electrode material greatly influenced the charge/discharge profiles of the electrode.
Effect of CO2 on the Cycleability of Lithium Metal Anode
Authors: Momma Toshiyuki , Matsumoto Yasuhiro , Osaka Tetsuya 
Published: April 2011

ABSTRACTThe lithium metal anode electrodeposited on nickel was studied by charge-discharge test coupled with in-situ ac impedance measurement. The test gives information about lithium anode interface and the modified interface of electrodeposited lithium by CO2 is confirmed to enhance the lithium cycleability. Also the CO2 protects the lithium interface in the presence of H20 impurity during cycling test.
Material Requirements for Lithium-Ion Batteries
Authors: Xie Like , Fouchard David , Megahed Sid 
Published: April 2011

ABSTRACTLithium-ion (or ‘rocking-chair’) batteries with lithiated oxide cathodes and carbon anodes are finding increasing acceptance in many electronic applications including low rates (e.g., memory backup, real time clock, bridge function) and high rates (e.g., laptop computers, cellular phones, camcorders, etc.). This technology offers significant improvements in safety relative to cells using lithium metal anodes, with only a modest reduction in energy density. In general, materials for lithium-ion cells are chosen to minimize the energy density penalties associated with replacing the lithium electrode with an intercalation electrode. In this review paper, we describe the properties of the cathode, anode and electrolyte, and discuss requirements for improved materials for advanced lithium-ion systems. Consideration is given to energy density, rate capability, cycleability and thermal stability.
Carbon Surface Conditioning Produces an Anode Suitable for Heavy-Duty Discharge in Li Secondary Batteries
Authors: Takamura Tsutomu , Kikuchi Masahiro , Awano Hidekazu , Ura Tetsuya , Ikezawa Yasunari 
Published: April 2011

ABSTRACTCarbon fibers prepared at 1000 °C from mesophase pitch were treated with trimethyl silazane for modifying surface -OH group into trimethyl silyl group. The irreversible reduction current on the first cathodic sweep was diminished. Low-temperature carbon fibers prepared at 700°C and active carbon fibers were evaluated for electrochemical lithium doping and undoping reaction in propylenecarbonate(PC)/ethylene carbonate or PC/dimethyl carbonate mixtures(l:l) containing 1 M LiClO4 at room temperature.Pristine samples prepared at 700 °C gave very poor reversibility and capacity on cyclic voltammograms(cv), but a constant current charge/discharge with a very low current gave a capacity over 400 mAh/g. After prolonged heating at 700°C, the cv characteristics were gradually improved. Partial oxidation in a mild oxidizing atmosphere at 700 °C for a few minutes was found to be quite effective in improving the cv characteristics remarkably. The charge/discharge capacity, however, was very similar to that obtained for the pristine sample at a very low consatant current. This indicates that the heat treatments effectively increase the electrochemical reaction rate of lithium doping and undoping, but have no effect on the intrinsic capacity.Active carbon fibers were found to have considerable capacity after repeated oxidation/reduction cycles in solution. Partial oxidation treatment was also effective in increasing the charge/discharge current. The capacity after the treatment was over 400mAh/g, which is far larger than that of the double layer capacity of the sample.The improvement due to the heat treatment is elucidated based on the removal of a surface inhibiting layer through the treatment.
Use of Submicron Carbon Filaments in Place of Carbon Black as a Porous Reduction Electrode in Lithium Batteries With a Catholyte Comprising Bromine Chloride in Thionyl Chloride
Authors: Frysz Christine A. , Shui Xiaoping , Chung D. D. L. 
Published: April 2011

ABSTRACTSubmicron carbon filaments used in place of carbon black as porous reduction electrodes in carbon limited lithium batteries in plate and jellyroll configurations with the BCX (bromine chloride in thionyl chloride) catholyte gave a specific capacity (at 2 V cut-off) of up to 8700 mAh/g carbon, compared to a value of up to 2900 mAh/g carbon for carbon black. The high specific capacity per g carbon (demonstrating superior carbon efficiency) for the filament electrode is partly due to the filaments' processability into sheets as thin as 0.2 mm with good porosity and without a binder, and partly due to the high catholyte absorptivity and high rate of catholyte absorption of the filament electrode.