bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mechanical Modeling of Stress Generation During Cure of Encapsulating Resins
Authors: Lagasse R. R. , Chambers R. S. , Guess T. R. , Plazek D. J. , Bero C. 
Published: March 2011

ABSTRACTWe have developed a numerical model for calculating stresses generated during cure of shrinking encapsulating resins. Mechanical modeling of polymer encapsulated electronic devices usually focusses on stress generated during cooling after cure. The stress developed during cure, due to shrinkage of the encapsulant, is normally neglected. That assumption is valid if both the shear and bulk moduli of the encapsulant at the cure temperature are negligible with respect to the moduli at lower temperatures. Our measurements on a model epoxy encapsulant show that the shear modulus during cure, varying from 0 to 6 MPa, is at least 100 times smaller than that at ambient temperature. In contrast, the bulk modulus at the cure temperature is only 2.5 times smaller. Since the bulk modulus during cure cannot be neglected, significant stress can be produced if volume shrinkage is constrained by a stiff mold or embedded elements. In fact, mechanical failure of encapsulating materials during cure has been evident in some of our experiments. Using measurements of shear and bulk moduli plus volume shrinkage as inputs to a finite element model, we have successfully predicted the shrinkage strains and stresses developed during cure of a model epoxy resin inside a cylindrical tube. Consideration of cure shrinkage stress has led to a process modification that appears to reduce mechanical failures in a real encapsulated device.
Texture and Microstructure Effects on Electromigration Behavior of Aluminum Metallization
Authors: Knorr D. B. , Rodbell K. P. , Tracy D. P. 
Published: March 2011

ABSTRACTPure aluminum films are deposited under a variety of conditions to vary the crystallographic texture. After patterning and annealing at 400°C for 1 hour, electromigration tests are performed at several temperatures. Failure data are compared on the basis of t50 and standard deviation. Microstructure is quantified by transmission electron microscopy for grain size and grain size distribution and by X-ray diffraction for texture. A strong (111) texture significantly improves the electromigration lifetime and decreases the standard deviation in time to failure. This improvement correlates with both the fraction and sharpness of the (111) texture component.
Computer Simulation of Grain Growth in Thin-film Interconnect Lines
Authors: Walton D. T. , Frost H. J. , Thompson C. V. 
Published: March 2011

ABSTRACTMicrostructural evolution in thin-film strips is of interest due to the direct effect of grain structure on integrated circuit interconnect reliability and resistance to electromigration-induced failure. We have explored the evolution of interconnect grain structure via a two-dimensional grain growth simulation. We focus on the strip's transformation to the bamboo structure, in which individual grains traverse the width of the strip. We find that the approach to a fully bamboo structure is exponential, and that the rate of transformation is inversely proportional to the square of the strip width. When the simulation is extended to model grain boundary pinning due to grooving at grain boundary – free surface intersections, we find that there exists a maximum strip width to thickness ratio beyond which the transformation to the bamboo structure does not proceed to completion. By using our simulation results in conjunction with a “failure unit” model for electromigration-induced failure [4] we are able to reproduce the experimentally observed abrupt increase in time-to-failure below a critical strip width, and also model the reliability as a function of annealing conditions.
High-Energy Backscattered Electron Imaging of Voids in Aluminum Metallizations
Authors: Follstaedt D. M. , Van Den Avyle J. A. , Romig A. D. , Knapp J. A. 
Published: March 2011

ABSTRACTBackscattered electron imaging of microcircuits in scanning transmission electron microscopes at 120 kV is shown to produce improved images of voids in passivated Al metallization lines relative to those obtained with scanning electron microscopes at ≤ 40 kV. At 120 kV, resolutions of about 0.1 μm are achieved for voids imaged beneath 1.0 μm glass overlayers. This technique allows improved characterization of microstructures for basic investigations of void formation and more accurate counting of voids in microcircuits without removing glass overlayers. Smaller voids should also be detectable with the higher voltage.
Intermetallic Reactions Between Copper and Magnesium as an Adhesion / Barrier Layer
Authors: Arcot Binny , Cabral C. , Harper J. M. E. , Murarka S. P. 
Published: March 2011

ABSTRACTThe reliability of copper multilevel interconnections requires good adhesion and the prevention of copper diffusion into the interlevel dielectric. Magnesium is a candidate for an adhesion layer and diffusion barrier for copper due to the high heats of formation of magnesium oxides, fluorides and sulfides and the formation of low resistivity compounds of Mg with copper. An investigation of the interactions in thin films of copper and magnesium has been carried out in the temperature range of 25°C to 500°C. The results of these reactions leading to phase formation in Cu/Mg bilayers deposited on Si3N4 or SiO2 using X-ray diffraction, in situ sheet resistance, and Rutherford backscattering measurements are presented in this paper. It was found that the Mg-rich phase CuMg2 is the first phase to form on annealing to approximately 215°C, followed by the formation of the Cu-rich phase Cu2Mg at about 380°C in the presence of excess Cu.
Investigations on a New Failure Model for Electromigration
Authors: Kitchin J. , Lloyd J. R. 
Published: March 2011

A new statistical model for electromigration failure in fine-line thin film conductors is developed in [1] by extending [2] to incorporate the statistics of microstructure and concomitant variations in the activation energy for grain boundary diffusion. The resulting distribution of time t to failure is well-approximated bywhere N is the number of line segments that are potential independent failure elements, 1μ and σ are, respectively, the mean and standard deviation of an assumed normal distribution of activation energy in grain boundaries, γ is a scaling constant, T is in degrees Kelvin, j is the current density in the line, p1 is the fraction of line segments for which exactly one grain boundary occurs between two blocking boundaries, and Φ is the standard normal cumulative distribution function. (Note: .)
Shadow Step Structures for CV Dot Formation and Evaluation
Authors: Shah Nitin B. , Rosvold Warren C. 
Published: March 2011

ABSTRACT“Shadow Step Structures” (3S) [1] are pre-patterned mesa-type geometries which are electrically self-isolating when overlayed with conducting thin films. This structure has been successfully implemented to generate CV dot structures. This CV dot structure eliminates the need for screen or photomasking after the oxide growth, thus eliminating manual handling, poor definition of dots due to “shadow screens”, and eliminates the possibility of contamination from screens and/or chemicals. This technique is very useful to qualify metal coaters as opposed to conventional techniques which involve patterning after metal deposition and has the advantage of fast turnaround and inherent cost savings. Measurement fidelity has been demonstrated via a large statistical sampling and is shown to give CV results consistently more accurate and superior to CV structures generated using the conventional techniques of metal shadow screens or photo masking.
Oxidized Porous Silicon Moisture Sensors for Evaluation of Microelectronic Packaging
Authors: Kelly M. J. , Guilinger T. R. , Peterson D. W. , Tuck M. R. , Sweet J. N. 
Published: March 2011

ABSTRACTAccurate moisture measurements in microelectronic assemblies are crucial in assessing reliability of integrated circuits (ICs). We describe the fabrication and use of a silicon-based device for evaluation of moisture barrier coatings. The capacitive moisture sensors use oxidized porous silicon (OPS) as the sensing element. Porous silicon (PS) is formed by anodization of Si in hydrofluoric acid (HF). Oxidation of PS in oxygen produces OPS, which is also porous if an appropriate starting microstructure and oxidation treatment are selected. Metallization layers on the OPS and the wafer back complete the capacitor structure. The capacitance of OPS sensors is functionally related to the moisture content of the surrounding atmosphere. For example, the capacitance of one sensor changed from 4 nF/cm2when exposed to a moisture level of 300 ppm by volume (ppmv) to 36 nF/cm2at 10,000 ppmv. In addition to this excellent sensitivity, capacitor response to step changes in moisture is rapid and reversible. The sensors are also rugged, as demonstrated by their consistent performance during accelerated testing at 85% relative humidity and 140°C. A silicon nitride IC moisture barrier coating was deposited on sensors of this type after normal ceramic dual in-line packaging. Sensor operability after coating deposition was confirmed following intentional introduction of a pinhole into the moisture barrier coating.
A Technique for the Examination of Surface Effects in Aluminum Nitride Ceramics
Authors: Norton M. Grant , McKernan Stuart , Carter C. Barry 
Published: March 2011

ABSTRACTA specimen preparation technique for the study of surface reactions and thin-film effects in aluminum nitride ceramic substrates is described. The technique uses specially prepared electron-transparent thin-foil substrates. These substrates can be examined directly in the electron microscope without the need for any further specimen preparation.
Electromigration Behavior in Layered Ti/AlCu/Ti Films and its Dependence on Intermetallic Structure
Authors: Rodbell K. P. , DeHaven P. W. , Mis J. D. 
Published: March 2011

ABSTRACTA sputtered aluminum-low copper (Cu concentration < 2wt.%Cu), multilayered, submicron, device interconnect metallurgy consisting of two TiAl3 layers (∼,0.1μm thick) under and over an Al-Cu alloy conductor (0.95μm thick) with either an Al-Cu or TiN cap layer (0.05μm thick) has been developed. These films were patterned by reactive ion etching, and showed both a low susceptibility to corrosion and a low resistivity. Electromigration lifetime data on Al, Al-Cu, and both dc magnetron sputtered and electron gun evaporated multilayered fine lines, fabricated and tested in the same laboratory, are included for a direct comparison. Outstanding electromigration behavior was measured for sputtered, multilayered, submicron films with copper concentrations between 0.12 – 2wt.%Cu. In contrast, electromigration lifetimes of evaporated, multilayered films were found to degrade rapidly at < 2wt.%Cu. This anomalous electromigration behavior was attributed to structural differences in the Ti-Al intermetallics formed. It is proposed that defects present in the Ti-Al superlattice phase cause decreased electromigration performance compared to films in which TiAl3 exclusively forms. Multilevel structures, consisting of CVD W interlevel vias, were also investigated and found to have significantly degraded electromigration performance compared to planar samples. This was attributed to geometric and material flux divergences at the via/conductor interfaces.
The Effects of Stress on the Interdiffusion in Si1-xGex/Si Superlattices
Authors: Prokes S.M. 
Published: March 2011

AbstractThe effects of grown-in stress and applied external stress on the interdiffusion behavior in long-period Si0.7Ge0.3/Si is examined using x-ray diffraction and Raman Spectroscopy. Both symmetrically and asymmetrically–strained superlattices have been examined, and an activation energy for interdiffusion of 3.9 eV and 4.6eV have been obtained, respectively. In addition, an enhanced interdiffusion has also been measured when the asymmetrically–strained superlattice was subjected to an external tensile stress during annealing. In both cases, enhanced interdiffusion has been measured whenever the Si barrier layers experience tensile stress during annealing. The Raman results indicate that enhanced Ge diffusion into the Si barriers occur when these barriers are put under tensile stress. This result will be discussed in terms of the kinetics of defect formation and motion in the strained Si barriers.
Crystal Plasticity Analysis of Thermal Deformation and Dislocation Accumulation in Gaas/Si Patterned Structure
Authors: Ohashi Tetsuya , Honda Naoyuki 
Published: March 2011

AbstractPlastic slip deformation in patterned.GaAs films on Si substrate during cooling from film deposition temperature are numerically simulated under a continuum mechanics approximation. The plastic slip is assumed to take place on (111) <110> slip systems and activation condition of the slip systems is given by the Schmid's law. The critical resolved shear stresses for the activation of slip systems are expressed as a function of accumulated dislocation densities, which are evaluated by models for their movement and interaction. A three dimensional finite element computer program is developed, in which strain hardening behaviour is given a quantitative expression by the models for dislocations. Results of the simulation reveal process of plastic slip and dislocation accumulation in GaAs film. Residual stress evaluated by the simulation agreed well with results obtained by photo-luminescent experiments.
Stress in Metal Foils During Processing and Thermal Cycling.
Authors: Jagota A. , Lemon M.F. , Hu Y.H. 
Published: March 2011

AbstractThe vibrational technique for stress measurement in films has been used to study silver foils, silver-based conductor pastes, and aluminum foil. During cooling, a tensile stress develops in the films due to thermal expansion mismatch with the substrate. Because the stress is limited by the yield stress, these experiments furnish data for the yield stress of the materials over a wide range of temperature at fixed state. Experiments with silver specimens pre-annealed to different grain sizes show that the yield stress follows the Hall-Petch relationship. The full vibrational analysis is used to extract the stiffness of the foils.
Growth and Microstructure of Aluminum Nitride Thin Films
Authors: Norton M. Grant , Kotula Paul G. , Li Jian , Mckernan Stuart , Cracknell Kathryn P.B. , Carter C. Barry , Mayer James W. 
Published: March 2011

AbstractThe synthesis of aluminum nitride thin films by pulsed-laser ablation is demonstrated. The films were formed on single-crystal sapphire and graphite substrates. A number of techniques were used to characterize the films: transmission and scanning electron microscopy, Rutherford backscattering spectrometry and x-ray diffraction.
Relaxation of Thermal Stresses in Al-Films
Authors: Bohn H.G. , Pill W. , Robrock K.-H , Schilling W. 
Published: March 2011

AbstractThe time and temperature dependent mechanisms underlying the relaxation of thermally induced stresses in Al-films on quartz substrates have been investigated for film thicknesses in the range between 0.4 and 4.2 μm. Film stresses were determined by a high resolution capacitive technique from the bending displacement of the specimens. By employing a lamp furnace heating rates of 10°C/sec could be achieved. This test equipment allowed the investigation of thermally induced film stresses between room temperature and 450°C and in the time range between 10 sec and several hours. Similar temperature programms were run in situ in a scanning electron microscope in order to observe the concommitant changes of the surface morphologies.The experiments show that a major fraction of 50 to 70% of the thermal stress recovers instantaneously by plastic flow. This defines a yield stress for the Al-films which is found to be inversely proportional to the film thickness and to vary linearly with temperature. The magnitude of the yield strength under tension is larger by a factor 1.7 compared to that under compression.
Fracture Behavior of Silicon Cut with a High Power Laser
Authors: Chao C.C. , Chleboski R. , Henderson E.J. , Holmes C.K. , Kalejs J.P. , Gross T.S. 
Published: March 2011

AbstractThe fracture twist test is used to obtain the statistical fracture strength distribution for 10-cm square single crystal and polycrystalline silicon wafers cut with a high-power Nd:YAG laser. Tensile wafer edge stresses at fracture are calculated using nonlinear finite element analysis, and the model results are used to examine the limitations of linear torsion and plate theories. The basic hypothesis is that fracture strength of laser-cut wafers is limited by microcracks formed by large residual tensile stresses produced in the cut edge upon cooling after cutting. Differences are found between single crystal CZ and polycrystalline EFG silicon material Weibull parameters characterizing the fracture strength distribution. These indicate that there is a statistical influence of material variables on the fracture strength of the EFG silicon, which lowers its strength and increases the variance of fracture response in comparison to single crystal silicon.
The Singular Behavior of the Lattice Hardness of Bismuth Cuprates Under Thermocycling
Authors: Belomestnykh V.N. , Khasanov O.L. , Pokholkov Yu.P. , Bush A.A. 
Published: March 2011

AbstractTemperature depepdences of ultrasound velocity V and sound attenuation Q−1,the unit cell parameters a, b, c, and volume W were studied between 77 and 800 K for bismuth cuprates like Bi2Sr2Can−1 CUnO2n+2+8 with n = 1,2,3 (phases: 2201, 2212, and 2223). Acoustic spectra of textured and isotropic samples show anomalies (bending points,extrema, breaks, and splitting of resonance frequency) which are considered as a result of thermostimulated processes - phase transitions of I and II kinds, emergence of substructures in the cuprate lattices - in a system of solid solutions of the mentioned phases. Mechanical properties of the studied systems are observed to be very sensitive to a thermal prehistory (temperature and time ranges of thermocycling).
Testing of Fracture Resistance of Materials
Authors: Ni Beta Y. , Zhang T. Y. , Li J. C. M. 
Published: March 2011

AbstractBoth energy and load required to fracture the material are important quantities and they are not necessarily related to each other as suggested by the fracture mechanics of brittle materials. For example, the difference of the failure behavior between the semi-brittle ABS polymer and the ductile Al 6061-TO can be well characterized by a pre-fracture energy E0 (Joule/m) and a fracture energy Ef (Joule/m2 ). Al 6061-TO has much higher values of E0 and EF than the ABS polymer. This accounts for the ductility of Al 6061-TO. However, the applied stress intensity factor KIapp for both materials are similar. The reason is that their plastic zones have similar shielding effects, even though Aluminum has dislocations and the ABS polymer has cavities and crazes.
The Effect of A Passivation Over-Layer on the Mechanisms of Stress Relaxation in Continuous Films and Narrow Lines of Aluminum
Authors: Paszkiet C. A. , Korhonen M. A. , Li Che-Yu 
Published: March 2011

AbstractStress relaxation was studied in bare and nitride-covered continuous films and narrow lines of aluminum. The rate of relaxation in unpassivated metallizations is shown to be consistent with a dislocation-controlled mechanism. Relaxation in passivated lines appears to depend on grain boundary diffusion-controlled void growth. In passivated continuous films, two rate-controlling mechanisms appear to operate in sequence.
Evaluation on Electromigration and Stressmigration of Metal Interconnections by Hardness Measurements
Authors: Nakagawa T. , Miyatake H. , Maeda T. , Kuroda K. , Tokushige N. , Inoue R. , Kudo J. , Ashida T. 
Published: March 2011

AbstractIt is well known that the grain size of interconnections made from aluminum alloys affects electromigration and stressmigration tolerance. The hardness of three kinds of aluminum alloys is measured and it is shown that it has a strong correlation between the grain size of the aluminum alloy films. Stressmigration testing is done for those aluminum alloy films and it is found that the SM tolerance of aluminum films can be judged by the hardness of the films. Electromigration testing is also done and the results also confirm the correlation between EM tolerance and hardness of the aluminum films. Hardness measurements are simple and have the possibility of rough estimation of EM and SM tolerance. This method have the merit of saving time for life test.
Real-Time FT-IR Studies Of The Reaction Kinetics For The Polymerization Of Divinyl Siloxane Bis-Benzocyclobutene Monomers
Authors: Stokich T. M. , Lee W. M. , Peters R. A. 
Published: March 2011

ABSTRACTThe thermal polymerization reaction of divinyl siloxane bis-benzocyclobutene (DVS bis-BCB) was monitored in-situ with FT-IR spectroscopy in order to follow specific chemical changes and determine the reaction order and rate constants at temperatures from 150° to 210°C. FT-IR spectra were obtained at regular intervals throughout the reaction with a Nicolet 170SX spectrophotometer.Monomeric DVS bis-BCB contains mixed stereo and positional isomers of 1,3- bis(2-bicyclo[4.2.0]octa-1, 3, 5-trien-3-ylethenyl)-1, 1, 3, 3-tetramethyl disiloxane (CAS 117732-87-3). It polymerizes via Diels-Alder cycloaddition reactions between vinyl groups and an intermediate o-quinodimethane formed by first-order, thermally initiated ring openings of the benzocyclobutene rings. Gaseous byproducts are not produced; therefore, the cure is easier to manage than are cures for polyimides which evolve water in polycondensation reactions. The DVS bis-BCB has four reactive elements per monomer unit and, thus, polymerizes into a very highly cross linked and solvent resistant network.With the FT-IR methodology, the reaction was easily monitored through the points of gel formation and vitrification. With the exception of DSC (i.e., calorimetry) which does not sense specific chemistry, other methods were not successful in following the reaction after a gel was formed. We have found that the polymerization was first-order until vitrification occurs; the gelation alone had no apparent effect on the reaction rate.DVS bis-BCB is under development at Dow as high performance dielectric material for multilayer interconnect coating applications for the microelectronics industry. Methodology reported here is employed in developing effective cure management strategies.
CT Fluorescence And Molecular Aggregation Of A Polyimide As Function Of Imidization Condition.
Authors: Hasegawa M. , Arai H. , Horie K. , Yokota R. , Mita I. 
Published: March 2011

ABSTRACTThe emission mechanisms of solid PI(BPDA/PDA) derived from biphenyltetracarboxylic dianhydride (BPDA) and p-phenylenediamine (PDA) were examined with the absorption and fluorescence. spectra of model compounds (denoted by M). M(BPDA/CHA) (CHA: cyclohexyl amine) fluoresces at ca. 430 nm in hexafluoro-2-propanol(HFP) solution, while M(BPDA/AN) (AN: aniline) does not. PI(BPDA/PDA) film does not show the monomer fluorescence of biphenyldiimide unit, but shows only intermolecular CT fluorescence peaking at 530–540 nm. This suggests that for PI(BPDA/PDA) film and PI(BPDA/AN) in solution the local excited state of biphenyldiimide units is deactivated owing to intramolecular charge-transfer(CT).The intermolecular CT fluorescence reflecting sensitively molecular packing of PI chains was used to monitor isothermal imidization process of poly(amic acid)(PAA) of BPDA/PDA. The fluorescence of PAA(BPDA/PDA) peaking at 490 nm decreases rapidly and disappears at 30–40% conversion, then the fluorescence of PI(BPDA/PDA) peaking at 540 nm increases gradually during isothermal imidization. The fluorescence intensity at 540 nm increases rapidly as imidization proceeds when imidized at higher temperature. A kinetic study on isothermal imidization shows that the vitrification is strongly related to the reorientation of polymer chains and the final PI structures.