bluuebunny/crossref_metadata_2025 huggingface dataset:
Morphological Control of Diamond Thin Films: Its Influence on Friction and Wear
Authors: Yee Andrew L. , Ong Hockchun , Chang R. P. H.
Published: April 2011

Microwave plasma enhanced chemical vapor deposition was used to grow diamond films with different morphologies and surface roughnesses. With the proper choice of deposition parameters (111) faceted, octahedral, flat (100) and microcrystalline diamond films were obtained. Scanning electron microscopy, atomic force microscopy and stylus profilometry were used to assess the surface topography for each type of film. Raman spectroscopy and x-ray diffraction were also used to determine the purity of the diamond phase and growth orientation of the films, respectively. Single pass friction and wear tests were conducted on each film in order to determine the effect of surface morphology on the coefficient of friction and wear of the counterface materials and/or diamond films. Counterface materials included alumina, tungsten carbide, zirconia, and the (100) face of a synthetic diamond single crystal. Results showed a decrease in the coefficient of friction as the film roughness decreased. Specific wear of the non-diamond counterface materials showed a marked decrease for the flatter and smoother diamond surfaces. For diamond on diamond, the coefficient of friction also decreased as film topography became smoother. Wear of the diamond films occurred by fracture or shearing of asperity tips which was most severe for the rougher films. Control of diamond morphology is shown to be of paramount importance in tribological applications in order to reduce abrasive wear, material transfer, and diamond film fracturing.
Mechanical Properties of Diamond Fibres
Authors: Everitt N. M. , Shatwell R. A. , Kalaugher E. , Nicholson E.
Published: April 2011

Tungsten and silicon carbide fibres have been coated with diamond using the HFCVD technique. The diamond volume fraction varied between 26% and 73%. Resonance in bending tests gave a Young's modulus of 880 GPa for the diamond coating. Tensile testing indicated that the diamond fracture strength was between 600 MPa and 2000 MPa, depending on the coating thickness, and thus the grain size, of the diamond. The strain to failure of the diamond coating in bending was approximately 0.15% for 25 μm thick films.
Transient And Spatial Radiative Properties Of Patterned Wafers During Rapid Thermal Processing
Authors: Wong Peter Y. , Miaoulis Ioannis N. , Madras Cynthia G.
Published: April 2011

Temperature measurements and processing uniformity continue to be major issues in Rapid Thermal Processing. Spatial and temporal variations in thermal radiative properties of the wafer surface are sources of non-uniformities and dynamic variations. These effects are due to changes in spectral distribution (wafer or heat source), oxidation, epitaxy, silicidation, and other microstructural transformations. Additionally, other variations are induced by the underlying (before processing) and developing (during processing) patterns on the wafer. Numerical simulations of Co silicidation that account for these factors are conducted to determine the radiative properties, heat transfer dynamics, and resultant processing uniformity.
A Universal Thermal Module™ for Clusterable RTP and MOCVD Applications
Authors: Moslehi Mehrdad M. , Omstead Tom , Lee Yong Jin , Kermani Ahmad , Velo Lino , Schaper Charles
Published: April 2011

A Universal Thermal Module™ (UTM™) has been developed for vacuum-integrated cluster RTP and MOCVD as well as stand-alone atmospheric RTP applications. The UTM™ architecture provides highly modular RTP and MOCVD tool configurations for various single-wafer thermal processes. The UTM™ design comprises a temperature-controlled UHV-grade process chamber as well as an ultraclean gearless wafer rotation assembly for improved temperature uniformity and enhanced built-in reliability. The UTM™ RTP employs bottom/backside wafer heating using a multi-zone axisymmetric illuminator and a reflective multi-zone gas showerhead located above the wafer. Precision RTP control is achieved using a multi-zone controller in conjunction with a multipoint sensor system with real-time multi-zone compensations for wafer emissivity and illuminator light interference effects. The RTP temperature measurement and control techniques fully compensate for any axisymmetric or non-axisymmetric wafer emissivity patterns, eliminating the need for pre-RTP wafer backside conditioning. The UTM™ showerhead provides capabilities for ultraclean multi-zone gas injection and in-situ RF plasma for MOCVD and RTCVD processes. The UTM™ MOCVD module meets the most stringent specifications and tool parameters for various metallization and high-K dielectric deposition applications. This module has been used for deposition of low-resistivity copper films with excellent void-free sub-half-micron gap fill for high-performance multilevel interconnects. The UTM™ RTP and MOCVD modules have been implemented based on design optimizations in a virtual reactor environment.
High Temperature Thermal Processing for Ulsi Applications
Authors: Reid Kimberly G. , Sitaram A. R.
Published: April 2011

The diversity of semiconductor manufacturing as well as the decreasing thermal budget for ULSI devices has driven semiconductor equipment manufacturers to develop and improve thermal processing solutions. Recent advances include new temperature measurement systems for rapid thermal processors (RTP), the development of the small batch fast ramp furnace (SBFR), as well as improved capability and load size in the conventional vertical batch furnace (BF). This paper will review the RTP, SBFR, and batch furnace for typical atmospheric front end of the line applications. Throughput and cycle time will be modeled for each type of system. Sematech's cost of ownership model will be employed to evaluate the relative importance of throughput, mean time between failure, and equipment cost. And finally an overview discussion of the issues associated with temperature measurement and system configurations of the RTP will be given.
High Quality Ultrathin Gate Dielectrics Prepared by In-Situ RTP
Authors: Han L. K. , Bhat M. , Yan J. , Wristers D. , Kwong D. L.
Published: April 2011

This paper reports on the formation of high quality ultrathin oxynitride gate dielectric by in-situ rapid thermal multiprocessing. Four such gate dielectrics are discussed here; (i) in-situ NO-annealed SiO2, (ii) N2O- or NO- or O2-grown bottom oxide/RTCVD SiO2/thermal oxide, (iii) N2O-grown bottom oxide/Si3N4/N2O-oxide (ONO) and (iv) N2O-grown bottom oxide/RTCVD SiO2/N2O-oxide. Results show that capacitors with NO-based oxynitride gate dielectrics, stacked oxynitride gate dielectrics with varying quality of bottom oxide (O2/N2O/NO), and the ONO structures show high endurance to interface degradation, low defect-density and high charge-to-breakdown compared to thermal oxide. The N2O-last reoxidation step used in the stacked dielectrics and ONO structures is seen to suppress charge trapping and interface state generation under Fowler-Nordheim injection. The stacked oxynitride gate dielectrics also show excellent MOSFET performance in terms of transconductance and mobility. While the current drivability and mobilities are found to be comparable to thermal oxide for N-channel MOSFET's, the hot-carrier immunity of N-channel MOSFET's with the N2O-oxide/CVD-SiO2/N2O-oxide gate dielectrics is found to be significantly enhanced over that of conventional thermal oxide.
Temperature Dependence of Nitrogen Accumulation at SiO2/Si by N2O- and by NO-Oxidation
Authors: Weidner G. , Kröger D. , Weidner M. , Tittelbach-Helmrich K.
Published: April 2011

This paper investigates conditions of low thermal budget N2O and NO oxidation with simultaneous accumulation of 0.5 to 1 at% nitrogen at the SiO2/Si interface of thin oxide layers. A nitrogen accumulation model is presented. It is concluded that the nitrogen accumulation should be realized with oxidizing conditions at the interface to silicon and it is proposed to control the NO partial pressure in reactor gas for the desired nitrogen amount at tolerable thermal budget.
Initial Growth of Polycrystalline Si and GeSi Alloys in an RTP System
Authors: Rem J. B. , Salm C. , Klootwijk J. H. , Weusthof M. H. H. , Holleman J. , Verweij J. F.
Published: April 2011

The initial growth of polycrystalline silicon (Si) and germanium-silicon alloys (GexSi1−x) from SiH4 and GeH4, where x is in the range of 0-0.4, in an RTMP reactor has been investigated using an in situ monitoring technique called reflectometry. An inhibition time is found which, for poly-Si in the temperature range of 550–650°C decreases with increasing temperature and for poly-GexSi1−x in the temperature range of 500–625°C shows the same behavior. The effect of total pressure, ranging from 0.10–1.20 mbar, is even stronger: an increasing pressure sharply decreases the inhibition time. For a selective deposition a low SiH4 and GeH4 partial pressure seems favorable, while for a non-selective deposition of poly-GexSi1−x alloys on (gate) oxides (for Thin Film Transistor applications) a high pressure or a pressure pulse at the start of the deposition process can be used.
Successful Preparation of High Frequency HBT by Integrated RTCVD Processes
Authors: Ritter G. , Tillack B. , Knoll D.
Published: April 2011

Complete epitaxial Si-SiGe-Si- stacks with a defined doping profile for each component have been deposited on Si substrates from the system SiH4, GeH4, H2, B2H6, PH3 by RTCVD. The deposition has been carried out at a temperature of 650°C for Si and of 500°C for SiGe, respectively, both at a pressure of 2 mbar. The developed epitaxial process including an effective H2 in-situ preclean annealing has been integrated in a simple double mesa technology for the preparation of SiGe base heterojunction bipolar transistors (HBT). Despite the simplicity of the technology and the lithographical level allowing emitter dimensions of 2.3×2.5 μm2 only, test devices on 4” wafers reached transit frequencies fT and maximum oscillation frequencies fmax of higher than 60 GHz and 30 GHz, respectively. Besides, a low base current has been measýnl as proof for a good layer quality.
Rapid Isothermal Annealing of Doped and Undoped Spin-on Glass Films
Authors: Slaoui A. , Ventura L. , Lachiq A. , Monna R. , Muller J. C.
Published: April 2011

The rapid thermal annealing of doped (SOD) and undoped (SOG) glass films spinned onto silicon from diluted or undiluted solutions has been investigated. The dilution performed by methanol has allowed to obtain oxide films as thin as 10 nm.

The optical measurements of annealed SOG films have shown that good oxide films without oxygen deficiency are achievable. The electrical characteristics of Al-gate capacitors assessed by Capacitance-voltage measurements have shown a great dependence of the water content in the range of 600–850°C before reaching a typical dielectric constant value near 3.8 at higher temperatures. Low Interface state densities values obtained at temperature up to 900°C confirm the curing effect of a rapid thermal annealing.

On the other hand, we have demonstrated that the efficiency of rapid thermal diffusion from boron or phosphorus SOD films deposited on Si wafers depends on the source composition and its thickness. In particular, we have shown that it is possible to control the junction depth, the surface concentration and the minority-carrier diffusion length by varying the amount of dopant concentration in the solution, the thickness of the doped oxide film and the rapid thermal processing parameters. Futhermore, the remaining doped SOG film can play the role of an efficient oxide passivation layer.
Formation of Ultra-Shallow Junctions in Silicon by Rapid Thermal Vapor Phase Doping in an Ultrahigh Vacuum Rapid Thermal Processing System
Authors: O'neil Patricia A. , Violeite Katherine E. , Öztürk Mehmet C. , Ivanov Igor C.
Published: April 2011

In this work, we have studied the formation of ultra-shallow p-type junctions by rapid vapor phase doping. The doping process was performed in an ultra high vacuum rapid thermal processing system using 0.1 l/min of a B2H6/H2 mixture. The B2H6 content of the mixture was only. 500 ppm corresponding to a B2H6 flow of 50 μl/min. In contrast, previous work in conventional and rapid thermal processing systems used B2H6 flows as high as 0.1 l/min which tend to form either pure boron or boron silicide layers depending on the processing conditions. In this study we exposed 4″, (100) oriented, n- and p-type silicon wafers to the B2H6/H2 mixture for varying growth conditions. Boron junction profiles were obtained at temperatures ranging from 650°C to 850°C. Boron dose, peak concentration, and junction depth were found as a function of growth temperature and time. Our results show that ultra-shallow (≤ 500 Å) boron profiles with surface concentrations above 1020 cm−3 can be obtained in Si at temperatures as low as 650°C. Typical process times range from 15 to 90 seconds making the process a good candidate for single wafer manufacturing in rapid thermal processing systems.
Ultra-Shallow Raised P+N Junctions with Self-Aligned Titanium Silicide Contacts formed by Boron Outdiffusion from Selectively Deposited Silicon Epitaxial Layers
Authors: Shih H. T. , Violette K. E. , Öztürk M. C.
Published: April 2011

In this study, we have fabricated ultra-shallow p+n junctions by boron outdiffusion from selectively deposited Si epitaxial layers. The undoped layers (900 – 1000 Å) were selectively deposited on active areas in a UHV-RTCVD reactor using Si2H6 and Cl2 at 800°C and at a total pressure less than 30 mTorr. Junctions were formed by BF2 ion-implantation into epitaxial layers with and without Ge preamorphization followed by RTA at 1000°C and 1050°C for 10 s in Ar. Junction depths ranging from 400 Å to 700 Å were formed at a background concentration of l×1016 cm−3. Abrupt boron profiles with epitaxy/substrate interface concentrations on the order of 1020 cm-3 were formed. Self-aligned TiSi2 was formed at four different thicknesses by evaporating 100, 200, 300 or 400 Å thick Ti followed by a two-step RTA cycle with a selective etch between to remove the unreacted Ti on Si02. Our results show that raised junctions with a Ti thickness of 400 Å (corresponding to a TiSi2 thickness over 900 Å and consumption of the entire epitaxial layer) exhibit a reverse leakage of less than 10 pA for a device area of 800×800 μm2. This corresponds to areal and peripheral leakage current densities of 67 pA/cm2 and 4 pA/cm. Therefore, thick silicide layers can be used on raised junctions reducing the junction sheet resistance and eliminating the possibility of silicide agglomeration. Furthermore, implantation damage in substrate is eliminated by confining the implant into the raised region which is later consumed during silicide formation.
Silicon Etching in Rapid Thermal Chemical Vapor Deposition of Tisi2
Authors: Ren Xiaowei , Gladden Dannellia B. , Öztürk Mehmet C. , Batchelor A. Dale
Published: April 2011

Downscaling of microelectronics devices into the deep submicron regime requires ultrashallow junctions with reliable, low-resistivity contacts. The conventional self-aligned TiSi2 technology exhibits a serious limitation in forming contacts to ultra-shallow junctions due to silicon substrate consumption. Selective chemical vapor deposition of TiSi2 is being investigated because of its potential for overcoming this difficulty. In this process Si and Ti are supplied from the gas phase. The standard source gas for Ti has been TiCl4 while several gases including SiH4, Si2H6 and SiH2Cl2 are available for Si. The reports on this process indicate that optimized process conditions can deliver TiSi2 films without substrate consumption. Although this promise is significant, the deposition has a complicated chemistry involving processes such as silicon etching, silicon consumption or silicon pedestal deposition taking place along with TiSi2 deposition. Although, suppression of Si-substrate etching by excess H2 has been reported previously, a broad quantitative analysis has been lacking up until this reporting. In this work, we have examined silicon etching trends as a function of temperature for different H2:TiCl4 flow ratios using thermodynamic equilibrium calculations. We have also performed experiments in a lamp heated rapid thermal chemical vapor deposition reactor to study substrate etching over the temperature range of 600°C to 800°C and for H2 flows from 0 to 1000 sccm. A silicon conversion efficiency is defined as a measure of the amount of Si converted to TiSi2 relative to total Si used from the substrate and it is evaluated via both thermodynamic calculations and experiments with good agreement between the two. Our calculations suggest that at high temperatures, etching occurs mainly via formation of SiCl2. Addition of H2 into the reaction chemistry encourages formation of HCl reducing the amount of Cl available for SiCl2 formation responsible for substrate etching. Our results show that by optimizing the H2 flow rate and the process temperature silicon substrate etching can be effectively suppressed.
Monte-Carlo simulation of the deposition process in PVD-technology
Authors: Lugscheider E. , Knotek O. , Löffler F. , Schnaut U. , Eckert P.
Published: April 2011

The Magnetron Sputter Ion Plating (MSIP) technology has been applied in a wide range of modern technological fields, due to the virtually unlimited potential of coating and substrate materials. However, up to now, the development of optimization has been depending mainly on empiricism and experiments.

Energies and the directions of the particles sputtered with various ejection angles and initial energies from the target surface are changed due to collisions with gas atoms during their movement within the sputtering chamber. Therefore the particles have a distribution of incident energies and angles which have a great influence on structure and properties of thin film coatings. This paper describes computer investigations to simulate the motions of the particles from target to substrate using a Monte-Carlo method and a binary collision approximation. The applied model takes into account non-uniform sputtering effects of the target in the MSIP process due to the magnetic field and the erosion zone.
Deposition Profile Simulation: Topological Effects
Authors: Wang Yun Biao , Teyssandier Francis
Published: April 2011

There is a considerable amount of evidence for the dependence of microstructure and surface morphology of films obtained by conventional thermally activated chemical vapor deposition on mass transport phenomena. This paper addresses the simulation of the influence of conveclive-diffusivc transport phenomena as well as homogeneous reactions on the deposition profile of silicon films in the case of some characteristic topological effects. For that purpose, the Si-H chemical system including both homogeneous and heterogeneous reactions is used. The evolution of the deposition profile during vapor growth is simulated for various surface defects such as a step or a trench. The influence of basic processing parameters such as temperature or flowrate is discussed.
Elastic Analysis of Twinning in Misfitting Thin Films
Authors: Sridhar N. , Rickman J.M. , SroIovitz D.J.
Published: April 2011

We examine the conditions under which a misfitting thin film on a substrate will twin and the pattern of the twin microstructure that will form. Using linear elasticity theory, we present exact analytical results for the energy released due to the formation of a periodic array of twinned domains as well as that for a single embedded twin domain. While the analysis is applicable to general misfit strain tensors, we specifically analyze the energetics of twinned domain formation for a tetragonal film on a cubic substrate. The analysis shows that for a periodic distribution of twins, the equilibrium width of the domains of the two variants are identical. Our results also show that the equilibrium periodicity of the microstructure scales inversely with film thickness for large film thickness and decays exponentially with increasing film thickness for small film thicknesses.
Simulation Studies of TiN PVD and CVD Thin Films for Contact/Via Liners
Authors: Bang D.S. , McVittie J.P. , Saraswat K.C. , Iacoponi J.A. , Gray J , Krivokapic Z. , Littau K. A.
Published: April 2011

TiN PVD and CVD models have been incorporated in the SPEEDIE topography simulator. A parameter extraction methodology is presented which allows engineers to locally calibrate their process to the SPEEDIE simulator. The calibration requires no special equipment or modifications to the PVD or CVD equipment. Parameter extraction is demonstrated with Applied Materials deposition equipment.
Carbon Atom, Dimer and Trimer Chemistry on Diamond Surfaces from Molecular Dynamics Simulations
Authors: Valone Steven M.
Published: April 2011

Spectroscopic investigations of various atmospheres appearing in diamond film synthesis suggest evidence for carbon atoms, dimers or trimers. Molecular dynamics simulations with the Brenner hydrocarbon potential are being used to investigate the elementary reactions of these species on a hydrogen-terminated diamond (111) surface. In principle these types of simulations can be extended to simulations of growth morphologies, in the 1-2 monolayer regime presently.
Residual Stresses in Tungsten Lines: Analysis of Experimental- (Micro-Raman Spectroscopy, Xrd) and Numerical Results
Authors: De Wolf I. , Maes H.E. , Moffet J. , Ignat M.
Published: April 2011

Micro-Raman spectroscopy, XRD, and analytical modelling are used to study stresses in and surrounding tungsten lines of different widths and spacing. The stress in the lines and in the adjacent substrate is calculated using a concentrated- and a distributed edge force model. Both models are adapted such that the substrate-stress components can also be calculated for an array of lines. The results from XRD and micro-Raman spectroscopy and the results from the distributed edge force model are in agreement. The combination of data from the two experimental techniques is shown to give some important feed-back to the theoretical models.
Current-Stress-Induced Interface States in p-Si Mos Diodes Detected by a.c. Conductance Measurement
Authors: Inoue Masao , Shirafuji Junji
Published: April 2011

Effect of Fowler-Nordheim current stress on (100) p-Si metal/oxide/semiconductor diodes have been studied by means of a.c. conductance measurement. Growth of two distinct peaks are observed in the depletion and the inversion resions corresponding to the generation of two kinds of defects in the upper and lower halves of the bandgap. These defects show different behaviors against the current stress in the energy profiles of the density and the capture cross section. The degradation of the Si/SiO2 interface is discussed in relation to the defect creation.
Thermal Stability of Platinum Silicide in Deep Sub-Micron Lines
Authors: Xu Dan-Xia , Das Suhit R. , Erickson Lynden , Naem Abdalla
Published: April 2011

The properties of platinum silicide have been evaluated in the form of blanket films and confined lines with linewidth down to 0.15 μm. Pt films, ranging in thickness from 150Å to 1000Å, were prepared by sputter-deposition onto Si (100) blanket substrates or substrates patterned with windows of various sizes in SiO2. The samples were then annealed in a rapid thermal annealing system up to 550°C to form PtSi. The sheet resistance of silicide lines did not change significantly with linewidth. The thermal stability of the sheet resistance of PtSi was also measured for different linewidths and film thicknesses. The sheet resistance remained stable on annealing up to 850°C for a silicide film made of 250Å Pt and did not appear to be sensitive to the linewidth. The thickness dependence of the thermal stability of resistance was also evaluated.

The stress of the silicide films was measured using a laser deflection system. The asdeposited metal films were under compressive stress, but the stress turned into tensile upon annealing when silicide started to form. After PtSi was formed, the stress remained stable with annealing temperature until approximately 900°C when the stress exhibited a sharp decrease. Unlike electrical conductance, however, the breakdown temperature for stress did not strongly depend on the film thickness.
A Comparative Study on Electromigration Failure Mechanism Between Near-Bamboo and Bamboo Al(Cu) Two-Level Structure
Authors: Wang P.-H. , Lee C. , jawarani D. , kawasaki H. , ho P. S.
Published: April 2011

As the interconnect line width reduces to the sub-micron range, the grain distribution of Al(Cu) alloy lines reaches a bamboo structure. Understanding of the electromigration resistance of near-bamboo and bamboo structures is essential to the sub-micron reliability issue. In this study, the mass transport and failure mechanism of 1 μm wide Al(1%Cu) two-level lines with near-bamboo and bamboo structures were investigated by a drift velocity technique [1]. Our results show that interfacial (A10X/A1 interface) diffusion coupled with grain boundary diffusion determines the failure mechanism of bamboo lines.
Reliability Aspects of Thin Dielectric Films Used in NVM ICs
Authors: Kotov Alexander E.
Published: April 2011

The behavior of small MOS structures with polycrystalline silicon gates subjected to stresses caused by electron injection was analyzed. A nature of degradation in MOS structures is more clearly and reliably extracted from the investigations of the microstructures with active areas less than 10 μm2. NVM cells with floating gate are convenient objects for such investigations. Due to the high current sensitivity and range of described novel techniques (10-17 - 10-7 A), small tunnel oxide area in memory cell (1-5 μm2) and temperature measurements (120 - 438 K) some new results in oxide degradation have been found.

In this work the following chain of degradation processes during electron injection was experimentally detected: conversion from planar to local injection (area of localization~10-3 um2) => appearance of percolated path for low field leakage (it is defined by sufficient amount of generated deep level traps in dielectric Nt~ 1020 cm-3) => development of leakage channel into the breakdown region. TDDB method usually developed on large MOS structures with electrostatic energy more than critical value 107 eV is not able to distinguish this chain and correctly evaluate degradation. Taking into account a localization of electron injection, it was found that the charge to the leakage channel generation is about 104 -105 Cl/cm2 for cells without fabrication defects. A kinetics of localization is very sensitive to the tunnel oxidation process.

Degradation stages of NVM cells, subjected to different electric stresses and anneals, have been investigated in wide current and temperature ranges. Polaron and Trap Model for the I-V leakage characteristics of degraded SiO2 films is presented.
Effect of Surface and Grain-Boundary Diffusion on Interconnect Reliability
Authors: Klinger L. M. , Glickman E. E. , Fradkov V. E. , Mullins W. W. , Bauer C. L.
Published: April 2011

The effect of surface and grain-boundary diffusion on interconnect reliability is addressed by extending the theory of thermal grooving to arbitrary grain-boundary flux. For a periodic array of grain boundaries, three regimes are identified: (1) equilibrium, (2) global steady state, and (3) local steady state. These regimes govern the stability of polycrystalline materials subjected to large electric (electromigration) or mechanical (stress voiding) fields, especially in thin films where grain size approximates film thickness.
The Detrimental Effect of a Passivation on the Electromigration Lifetime of Narrow Al-Si-Cu Lines
Authors: Witvrouw A. , Roussel Ph. , Deweerdt B. , Maex K.
Published: April 2011

2 mm long, 0.8 μm wide and 0.8 μ thick Al-Si-Cu lines, passivated with a 1.14 μm thick PETEOS SiO2 were found to have a lower electromigration lifetime compared to identical unpassivated lines. The high tensile stress in the passivated lines is assumed to accelerate electromigration failure. This is confirmed by the very low activation energy for electromigration failure in the passivated lines and by the multiple events of recovery during and after electromigration testing, suggesting failure sites are slit voids.
Line Length Dependence of Small, Electromigration Induced Resistance Changes in Aluminum
Authors: Kraayeveld J.R. , Verbruggen A.H. , Willemsen A.W-J. , Radelaar S.
Published: April 2011

Two series of experiments were carried out to investigate the line length dependence of changes in the electrical resistance caused by passing a DC current through thin film Al conductors. First, the effect of adding side branches with a spacing of 5 μ m to 150 μ m long lines was studied. Experiments performed at T = 148 °C and at a DC current density of 0.5 MA/cm2 showed three effects due to adding the side branches: i) the magnitude of the resistance changes is reduced, ii) the resistance changes saturate on a time scale of one hour, and iii) the resistance changes fully recover after switching off the current. In the second series of experiments the current, temperature and line length dependence of resistance changes induced in short (3-100 μ m) lines between bonding pads were studied. For current densities smaller than a certain length dependent critical value the resistance saturates after applying the current and relaxes back to the original value after removing the current. The time to relax back, which is comparable to the time to reach saturation, is proportional to the sample length squared. This and the activation energy derived from the temperature dependence of the relaxation process suggest strongly that the observed time dependence of the resistance changes is determined by grain boundary diffusion (electromigration) along the whole length of the line.
A Simple Analysis of Average Mechanical Behavior and Strain Energy Density of Misoriented Grains in a Textured Film
Authors: Vinci R.P. , Weihs T.P. , Zielinski E.M. , Barbee T.W. , Bravman J.C.
Published: April 2011

Differences in strain energy density between grains of different orientation within a thin film may drive morphological changes such as abnormal grain growth, hillocking, and sunken grains. Models of these morphological changes generally assume that the behavior of each grain is the same as that of a blanket film of corresponding orientation. In order to investigate this assumption as it applies to the behavior of a (100)-oriented grain within a {111}-fiber textured copper film, simple continuum analytical and finite element models are applied to the case of a film on a rigid substrate subjected to temperature changes. The simple models indicate that the behavior of a misoriented grain does not simply duplicate that of a blanket film of the same orientation; the behavior of the surrounding grains must also be considered. The strain energy density difference between the grain and the surrounding film is less than that predicted by blanket film behavior. An elasticity equation is presented which describes the average stress-temperature behavior of widely dispersed misoriented grains within a textured film.
Recent Developments in Fuel Cell Materials
Authors: Appleby A. J.
Published: April 2011

Chemical and physical requirements limit the choice of fuel cell electrolytes to strong aqueous acids and alkalis, (pyro)phosphoric acid, carbonate melts, and solid oxides (O= conductors, with rare H+ conductors). The choice of electrolytes and operating temperatures is therefore limited, controlling the choice of other materials (anode catalysts, cathode catalysts, current collectors, and construction materials), which are determined by the properties of the electrolyte, the temperature, the electrode potentials, the gas atmospheres, and thermodynamic and kinetic considerations. The families of state-of-the art and new materials for each class of electrolyte are reviewed. The area of greatest activity is the solid oxide fuel cell (500°C-1000°C). In a review of this length, the extensive list of new solid oxide developments can only be given by way of introduction.
Fabrication of a Polymer Battery based on Polypyrrole Electrodes and a Polymer Gel Electrolyte
Authors: Killian Jeffrey G. , Coffey B.M. , Poehler T.O. , Searson P.C.
Published: April 2011

The electronic conductivity and redox behavior of conjugated polymers make them suitable for charge storage applications. We present preliminary results for an all polymer system consisting of a p-doped polypyrrole cathode and pseudo n-doped polypyrrole/polystyrenesulfonate anode. Using a thin film construction technique, electrodes were assembled into cells using a polymer gel electrolyte based on polyacrylonitrile, which has a high room temperature conductivity. Charge capacities of 13 mAh g−1 based on the mass of the electroactive polymer in the cathode have been obtained for over 100 cycles.
The Role of Sei in Lithium and Lithium Ion Batteries
Authors: Peled E. , Golodnttsky D. , Ardel G. , Menachem C. , Bar Tow D. , Eshkenazy V.
Published: April 2011

This paper presents and discusses fundamental processes taking place at the lithium and LixC6 electrode/electrolyte interphases and models for these interphases. We deal with both nonaqueous and polymer (dry and gel) electrolytes, graphitized and nongraphitized carbonaceous materials as anodes for Li-ion batteries. Each electrode/electrolyte combination has its own unique features and problems but there are some general phenomena common to all of them. Issues to be reviewed include SEI composition, morphology and formation reactions, graphite surface modifications including chemical bonded SEI and micro channels formation, electrode degradation processes, lithium deposition-dissolution and intercalation-deintercalation mechanisms, rate-determining steps (RDS), electrolyte and electrode parameters and conditions affecting the above mentioned processes. Technologyrelated issues are emphasized.
Sn-Substituted LaNi5 Alloys For Metal Hydride Electrodes
Authors: Wasz Margot L. , Schwarz Ricardo B. , Srinivasan Supramaniam , Sridhar Kumar M. P.
Published: April 2011

Our research examines the efficacy of tin additions to LaNi5 in improving the hydrogen storage capacity of the material during charging/discharging. Alloys were prepared using high energy ball milling (mechanical alloying), a technique superior to arc casting for alloying elements with a wide disparity in melting points. Characterization by x-ray diffraction and Rietveld analysis shows that tin preferentially occupies the Ni(3g) sites in the LaNi5 structure, and the unit cell volume increases linearly with tin content to the maximum tin solubility of 7.33 atomic percent (LaNi4.56Sn0.44). We found that powders prepared by mechanical alloying and not exposed to air require no activation to induce hydrogen absorption. The hydrogen storage capacity in the gas and electrochemical phase was measured as a function of tin content. We found that with increasing tin, the plateau pressure decreases logarithmically, whereas the hydrogen storage capacity decreases linearly.
The Effect of Ru on Unsupported Pt-Ru Alloys for Methanol Electro-Oxidation at Different Temperatures
Authors: Chu Deryn , Walker Charles , Gilman Sol
Published: April 2011

Unsupported different atomic ratios of platinum-ruthenium bulk alloys were prepared. The alloys were characterized by cyclic voltammetry, X-ray diffraction and energy dispersive X-ray spectroscopy. These alloys were also tested as anodes for methanol electro-oxidation in sulfuric acid over a range of temperatures. Ruthenium is inactive for methanol electro-oxidation at 25 °C, but becomes active at higher temperatures. When a comparison is made on the basis of “true” (hydrogen adsorption) surface area, a 30 atomic percent Ru electrocatalyst provides the highest activity for methanol electro-oxidation as measured at either 0.4 or 0.5V vs. RHE at both 25 and 60 °C.
Carbonaceous Materials Containing Silicon as Anodes for Lithium-Ion Cells
Authors: Wilsons A.M. , Dahn J.R. , Xue J.S. , Gao Y. , Feng X.H.
Published: April 2011

Graphite and pregraphitic carbons capable of reversibly reacting with lithium ions are hosts commonly used in Li-ion cells. As a continuation of previous work, we have used chemical vapour deposition of benzene and silicon-containing precursors to prepare carbons containing nanodispersed silicon. The silicon resides within the unorganized regions in the pregraphitic carbons. These materials reversibly react with lithium in electrochemical cells and the reversible specific capacity has been known to increase from -300 mAhg−1, in the absence of silicon, to near 500 mAhg−1 as silicon is added. We also report on Si-O-C materials which have been shown to reversibly react with Li in electrochemical cells with reversible specific capacities as high as 770mAhg−1. These materials have been made by thermal pyrolysis of siloxane polymers and epoxy-silane composites prepared from hardened mixtures of epoxy novolac resin and epoxy-functional silane. These materials all show promise for use as anode materials in advanced rechargeable lithium batteries.
Electrochemical Behavior of Carbon Aerogels Derived From Different Precursors
Authors: Pekala R.W. , Alviso C.T. , Nielsen J.K. , Tran T.D. , Reynolds G.A.M. , Dresselhaus M.S.
Published: April 2011

The ability to tailor the structure and properties of porous carbons has led to their increased use as electrodes in energy storage devices. Our research focuses on the synthesis and characterization of carbon aerogels for use in electrochemical double layer capacitors. Carbon aerogels are formed from the sol-gel polymerization of (1) resorcinol-formaldehyde or (2) phenolic-furfural, followed by supercritical drying from carbon dioxide, and subsequent pyrolysis in an inert atmosphere. These materials can be produced as monoliths, composites, thin films, powders, or microspheres. In all cases, the aerogels have an open-cell structure with an ultrafine pore size (<100 nm), high surface area (400-1100 m2/g), and a solid matrix composed of interconnected particles, fibers, or platelets with characteristic dimensions of 10 nm. This paper examines the effects of the carbon precursor and processing conditions on electrochemical performance in aqueous and organic electrolytes.
Transient Behavior of Ultracapacitors and Supercapacitors
Authors: Huggins Robert A.
Published: April 2011

Several different mechanisms can be used to provide short term high power pulses from electrochemical systems. Their fundamental characteristics and applicability to the different types of transient output requirements will be discussed. When significant amounts of energy must be delivered, the most favorable materials operate by means of insertion reactions. The methods that can be employed to quantitatively evaluate the critical materials parameters will be described. Spreadsheet techniques are especially useful for modelling the transient transport behavior of components containing such materials under various boundary conditions. LaPlace transform methods can then be used to convert information about the parameters of individual components into the dynamic response of the total system.
Ionic Conductivity in Laco1-XMgX03-δ: A Potential Cathode Material for Solid Oxide Fuel Cells
Authors: Yu Anbin , Haile Sossina M.
Published: April 2011

A serious concern with present designs of solid oxide fuel cells is the requirement that “triple-point junctions” exist, sites at which the cathode, electrolyte and oxidizing gas are in simultaneous contact. Only at these junctions can the cathode catalyze the reduction of oxygen into 0= ions and initiate their subsequent transport through the electrolyte. Enhanced ionic conductivity in the cathode material may increase the surface area over which reduction can take place and relax the triple-point constraint. To this end, we have examined the electrical and structural properties of LaCo1-xMgx03-δ materials under various atmospheres. Oxygen ion transport in this and related ABO3 perovskites takes place via oxygen vacancy migration. We have opted to investigate the effect of Mg doping on the transition metal site in an effort to maintain a significant oxygen vacancy concentration in oxidizing atmospheres (as would be encountered during fuel cell operation) and to isolate the effects of A- and B-site doping.
A Basic Thin Film Study of Spinel Limn204As a Possible Cathode Material for Lithium Secondary Cells
Authors: Miura Takashi , Kishi Tomiya
Published: April 2011

In a series of fundamental studies on the cathode active materials for a lithium secondary cell using geometrically well-defined sample electrodes, thin films of spinel LiMn204on a platinum plate were investigated in this work in an LiCl04/propylene carbonate solution. These pyrolytically prepared films exihibit reversible extraction/insertion behavior for lithium under galvanostatic charge/discharge cycling between 4.3-3.5 V. The chemical diffusion coefficient of lithium in LixMn204determined by the galvanostatic intermittent titration technique (GITT) was in the order of 10−7-10−10cm2- s−1within a spinel single-phase region of 0.6<x<1.0 and increased with increasingx.
Gas Diffusion-Type Oxygen Electrode Using Perovskite-Type Oxides for Metal-Air Batteries
Authors: Hyodo Takeo , Miura Norio , Yamazoe Noboru
Published: April 2011

In order to develop an air cathode of metal-air batteries, oxygen reduction behavior of gas diffusion-type carbon electrodes loaded with perovskite-type oxides, Lai-xA'xFe03(A'=Ca, Sr, Ba, 0<x<1.0), was examined in 8 M KOH at 60 °C. Among the oxide catalysts tested, La0.5Sr0.5Fe03(specific surface area : 21.5 m2.g−1) gave the highest electrode performance. On the basis of electrode reaction kinetics, H2O2decomposition rates, and temperature programed desorption of oxygen, it was concluded that such a performance was attributable to the active sites of the oxide for the direct 4-electron reduction of oxygen. Moreover, the electrode using Lao.5Sro.5FeO3was found to be rather stable in a short-term operation for 90 h at 300 mA-cm−2.
In sito Ion Beam Analysis of Radiation Damage Kinetics in MgTiO3 Single Crystals at 170-470 K
Authors: Yu Ning , Mitchell Jeremy N. , Sickafus Kurt E. , Nastasi Michael
Published: April 2011

Radiation damage kinetics in synthetic MgTiO3 (geikielite) single crystals have been studied using the in situ ion beam facility at Los Alamos National Laboratory. The geikielite samples were irradiated at temperatures of 170, 300, and 470 K with 400 keV xenon ions and the radiation damage was sequentially measured with Rutherford backscattering using a 2 MeV He ion beam along a channeling direction. Threshold doses of 1 and 5×1015 Xe/cm2 were determined for the crystalline-to-amorphous transformation induced by Xe ion irradiation at 170 and 300 K, respectively. However, geikielite retained its crystallinity up to a dose of 2.5x1016 Xe/cm2 at the irradiation temperature of 470 K. This study has shown that MgTiO3, which has a corundum derivative structure, is another radiation resistant material that has the potential for use in radiation environments.
Effect of Cascade Remnants on Freely Migrating Defects in Cu -1 % Au Alloys
Authors: Iwase A. , Rehn L. E. , Baldo P. M. , Funk L.
Published: April 2011

The effects of cascade remnants on Freely Migrating Defects (FMD) were studied by measuring Radiation-Induced Segregation (RIS) in Cu-l%Au at 400°C during simultaneous irradiation with 1.5-MeV He and (400-800)-keV heavy ions (Ne, Ar or Cu). The large RIS observed during 1.5-MeV He-only irradiation was dramatically suppressed under simultaneous heavy ion irradiation. For Cu simultaneous irradiation, the suppression disappeared immediately after the Cu irradiation ceased, while for simultaneous inert gas (Ne or Ar) irradiation, the suppression persisted after the ion beam was turned off. These results demonstrate that the displacement cascades created by heavy ions introduce additional annihilation sites, which reduce the steady-state FMD concentrations. As the cascade remnants produced by Cu ions are thermally unstable at 400°C, the RIS suppression occurs only during simultaneous irradiation. On the other hand, the inert gas atoms which accumulate in the specimen apparently stabilize the cascade remnants, allowing the suppression to persist.
Effects of ion beam irradiation on the crystallization of Copper films
Authors: Hishita Shunichi , Oyoshi Keiji , Suehara Shigeru , Aizawa Takashi
Published: April 2011

Radiation effects of 2 MeV Ar+ ions on the crystallization of copper films were investigated with or without oxygen adsorption. Metal copper films of 1-5 nm thickness deposited on SrTiO3 (100) at 300K. by evaporation consisted of fine crystals with random orientation. The crystals were grown without epitaxial relationship to the substrate by ion irradiation. The epitaxial growth of copper crystals was achieved by the combined use of oxygen adsorption and ion irradiation. The epitaxial relationship between the film and the substrate was determined Cu (100) // SrTiO3( 100) and Cu [001] // SrTiO3 [001].
Ion Induced Damage and their Annealing in LiTaO3 Single Crystal
Authors: Zhang Z , Rusakova I.A. , Chu W.K.
Published: April 2011

LiTaO3 single crystals have been implanted with 100 keV oxygen ions at room temperature with doses of 1×1014 /cm2,6xl014/cm2,1.2x1015/cm2, 6xl015/cm2, and 2xl016/cm2. Annealing temperatures ranged from 550 °C to 1075 °C. RBS-channeling and TEM were used for characterization. For partially damaged samples, complete recovery of the crystalline structure was achieved after annealing at 550 °C, which is below the Curie temperature. For totally amorphized samples, thermal annealing induced multidomain growth. These domains extend beyond the original amorphous/crystal interface deep into bulk (1 – 1.5 μm ).
Versatile Applications of Ion Implanted Polymers
Authors: Giedd R.E. , Wang Y.Q. , Moss M.G. , Kaufmann J.
Published: April 2011

Ion beam implantation of polymers has been shown to modify electrical and mechanical properties near the surface of the material. A complete understanding of the mechanism of modification and type of microstructure remaining as a result of this process has not yet been achieved. In this paper, we will discuss how recent advances in our understanding of these fundamental mechanisms and material processing techniques has led to a number ot prototypical applications. Specifically, the fundamentals of using ion implanted polymers as high value, small geometry resistors, temperature, strain, and vacuum sensing materials and as protective surfaces in chemically reactive environments.
Proton Modification of Ultra High Molecular Weight Polyethylene to Promote Crosslinking for Enhanced Chemical and Physical Properties
Authors: Wilson J.F. , Liu J.R. , Romero-Borja F. , Chu W.K.
Published: April 2011

Crosslinking onset was investigated for ultra high molecular weight polyethylene(UHMW-PE) implanted with 2.6 MeV H+ ions at low doses from 6×1011-3×1013 ions/cm2. Crosslinking in the near surface region(20–40μm) was determined from gel permeation chromatography(GPC) of 1,2,4 trichlorobenzene sol fractions and increased with dose. Fourier transform infrared spectroscopy(FTIR) showed irradiation resulted in increased free radicals confirmed from increased carbonyl groups. Hydrogen annealing after ion implantation resulted in 38–49% decrease in FTIR peak associated with carbonyl.