bluuebunny/crossref_metadata_2025_split huggingface dataset:
Chemical Bonding and Si-SiO2Interface Reliability: (A) Minimization of Suboxide Transition Regions, and (B) Monolayer Incorporation of Nitrogen
Authors: Lucovsky G. 
Published: June 2019

ABSTRACTThis paper addresses two aspects of the chemical bonding arrangements at Si-SiO2interfaces that impact significantly on electrical performance and reliability of devices with ultrathin gate dielectrics with oxide equivalent thicknesses, toxeq, in the regime of direct tunneling; i.e., toxeq< 3 nm. These are i) minimization of suboxide bonding arrangements that contribute to roughness in an interfacial transition region, and ii) monolayer nitrogen atom incorporation.
The Energy Release Rate for Decohesion in Thin Multilayered Films on Substrates
Authors: He Ming. Y. , Xu Guanghai , Clarke David R. , Ma Qing , Fujimoto H. 
Published: June 2019

ABSTRACTThe strain energy release rates for the converging decohesion crack in a multilayered film on a substrate have been calculated using the finite element method. The results for the energy release rate as a function of the intrinsic stress, the thickness of the superlayer and the modulus ratio will be presented. A simple functional form for the results will be shown. The effects of plasticity of the thin metal layer on the energy release rate have been examined. The results show that the effect of plastic deformation is not significant for the converging decohesion crack. The effects of the line width have also been addressed. The results show that for two-layer films the energy release rate for steady-state decohesion cracks decreases dramatically as B/h decreases, in the range B/h<40, where B is the line width and h is the thickness of the superlayer. For narrow lines the plane strain solutions overestimate the energy release rate. The numerical results are consistent with the experimental observations on lines with different width.
Characterization of Hole Traps Generated by Electron Injection in Thin SiO2 Films
Authors: Brożek Tomasz , Lum Eric B. , Viswanathan Chand R. 
Published: June 2019

ABSTRACTMOS device stability can be significantly affected by charge trapping in the gate oxide, which changes device parameters and causes serious reliability problems in transistors and memory cells. Hole traps, generated by high-field electron injection, are studied in this work in devices with thermal oxides less than 10 nm thick. PMOS transistors, after various doses of positive and negative Fowler-Nordheim injection and post-stress annealing, are subjected to substrate hot hole injection to investigate hole trapping kinetics. Parameters of hole traps, generated under the stress, are studied as a function of gate oxide thickness and electron injection dose.
Micromechanics Measurements Applied to Integrated Circuit Microelectronics
Authors: Clarke David R. 
Published: June 2019

ABSTRACTAs in other engineered structures, fracture occasionally occurs in integrated microelectronic circuits. Fracture can take a number of forms including voiding of metallic interconnect lines, decohesion of interfaces, and stress-induced microcracking of thin films. The characteristic feature that distinguishes such fracture phenomena from similar behaviors in other engineered structures is the length scales involved, typically micron and sub-micron. This length scale necessitates new techniques for measuring mechanical and fracture properties. In this work, we describe non-contact optical techniques for probing strains and a microscopic “decohesion” test for measuring interface fracture resistance in integrated circuits.
Scanning Stiffness Microscopy - A Novel Technique for Detecting Sub-Surface Cracks
Authors: Saha Ranjana , Tsui Ting Y. , Ross C. A. , Nix William D. 
Published: June 2019

ABSTRACTThin film delamination and sub-surface cracking represent important reliability issues for the semiconductor and thin film magnetic hard disk industries. Detecting such defects is often difficult and requires complicated specimen cross-sectioning and imaging. Because the sample preparation process itself may cause crack growth, such a method may be used only as a qualitative tool for defect characterization. In the present work, we introduce an in-situ non-destructive technique for detecting sub-surface cracks by continuously monitoring the contact stiffness while dragging a probe across a smooth surface at an ultra light load. As the probe encounters a sub-surface crack, the local contact stiffness decreases dramatically. The amount of reduction in contact stiffness depends on the crack size and geometry and the position of the crack relative to the surface. Results of the scanning stiffness microscopy experiments conducted on hard carbon and chromium thin films are described and discussed.
Adhesion Measurement of Interfaces in Multilayer Interconnect Structures
Authors: Ma Qing , Bumgarner John , Fujimoto Harry , Lane Michael , Dauskardt Reinhold H. 
Published: June 2019

ABSTRACTInterface decohesion is increasingly becoming a reliability concern in multilayer interconnect structures. It is therefore necessary to provide adhesion tests as a part of materials characterization procedures and to study the fundamental material properties that affect interface toughness. A sandwich structure 4-point bend test was developed for measuring the adhesion between interlayer dielectric and metal interfaces. This technique offers well defined and easily controllable fracture processes and simple analyses based rigorously on fracture mechanics. Using this technique, a number of interfaces were studied. For conventional interconnect systems consisting of Al lines and SiO2 as the interlayer dielectric, the focus was to improve the interface fracture toughness through structure design and process engineering. Potential low dielectric constant materials, such as polymers and porous SiO2, were also studied as candidates for interlayer dielectric materials in the future. Interface strengthening effects of both mechanical and chemical origin, including interface roughness and thin film plasticity, as well as alteration of chemical bonding were explored.
Simulation of the Effect of Dielectric Air Gaps on Interconnect Reliability
Authors: Bassman L. C. , Vinci R. P. , Shieh B. P. , Kim D.-K. , McVittie J. P. , Saraswat K. C. , Deal M. D. 
Published: June 2019

ABSTRACTWe present a modeling strategy for assessing the reliability cost for improved performance from modified interconnect structures. We have studied air gaps which have been deliberately introduced in the passivation between aluminum interconnect lines as a means for increasing transmission speed by decreasing dielectric capacitance. The models allow examination of tradeoffs between improved circuit performance and decreased reliability due to dielectric cracking. Stresses in the dielectric due to electromigration in the metal were modeled using finite element analysis. These stresses were used to compute an estimate of the mean time to failure relative to the case with no air gap using an electromigration failure model from MIT.
Adhesion Assessment of Copper Thin Films
Authors: Kriese M. D. , Moody N. R. , Gerberich W. W. 
Published: June 2019

ABSTRACTNano-indentation testing has been used to quantitatively assess the adhesion of thin copper films, sputtered to thicknesses of 150 nm to 1500 nm. Copper films of low residual stress were deposited via RF diode cathode sputtering onto SiO2/Si substrates. Overlayers of DC magnetron sputtered high residual stress tungsten, 850 nm thick, were additionally used to provide a driving force for delamination. All films tested exhibited buckle-driven delamination, from which the interfacial toughness was estimated to be 0.2 – 2 J/m2, which is comparable to the thermodynamic work of adhesion. The use of an overlayer requires extensions of existing models, but otherwise does not change the interfacial adhesion, allowing measurements of films that would not otherwise delaminate.
Nanoindentation Hardness of Soft Films on Hard Substrates: Effects of the Substrate
Authors: Tsui T. Y. , Ross C. A. , Pharr G. M. 
Published: June 2019

ABSTRACTThe ability to accurately measure the mechanical properties of thin metallic films is important in the semiconductor industry as it relates to device reliability issues. One popular technique for measuring thin film mechanical properties is nanoindentation. This technique has the advantage of being able to measure properties such as hardness and elastic modulus without removing a film from its substrate. However, according to a widely-held rule of thumb, intrinsic film properties can be measured in a manner which is not influenced by the substrate only if the indentation depth is kept to less than 10% of the film thickness, which is often not practical. In this work, a method for making substrate independent hardness measurements of soft metallic films on hard substrates is proposed. The primary issue to be addressed is the substrate-induced enhancement of indentation pile-up and the ways in which this pile-up influences the contact area determined from analyses of nanoindentation load-displacement data. Based on experimental observations of soft aluminum films on silicon, glass, and sapphire substrates, a simple empirical relationship is derived which relates the amount of pile-up to the contact depth. From this relationship, a simple method is developed which allows the intrinsic hardness of the film to be measured by nanoindentation methods even when the indenter penetrates through the film into the substrate.
Electrostatic Adhesion Testing for the Evaluation of Metallization Adhesion
Authors: Yang H. S. , Brotzen F. R. , Callahan D. L. , Dunn C. F. 
Published: June 2019

ABSTRACTQuantitative measurement of the adhesion strength of thin film metallizations has been achieved by a novel technique employing electrostatic forces to generate delaminating stresses. This technique has been used in testing the adhesion of Al-Cu, Cu, and Al multilayer films deposited on Si. Micro-blister-type failure is revealed by scanning electron microscopy. The delamination process and the geometry of the blister are discussed. The measured adhesion data fit a Weibull distribution function.
Failure Lifetime Prediction Of Cracked Concrete Structures
Authors: Barpi F. , Chille' F. , Imperato L. , Valente S. 
Published: June 2019

ABSTRACTThis paper presents the results of creep tests on three notched dam models made with three type of concrete. In order to characterise the time-dependent behaviour of the process zone, a series of tensile tests was performed for each kind of concrete. On the basis of the law obtained in this way, crack propagation was simulated numerically through the Cohesive Crack model.
The Future Of Nde Applications To RPV Embrittlement Measurements
Authors: Vassilaros M. G. 
Published: June 2019

ABSTRACTAssuring the integrity of nuclear power plant reactor pressure vessels (RPV) is of upmost importance to the U.S. Nuclear Regulatory Commission since there is no backup or redundancy to this component. These vessels must maintain high toughness in order to assure integrity despite the fact the vessel toughness decreases with neutron irradiation from the running of the plant. Currently the toughness loss of the RPV is inferred from generic equations or the change in measured toughness of samples irradiated in the RPV. A nondestructive evaluation technique
to monitor the toughness of the RPV would enhance integrity assessments of the vessel. Such an NDE technique must have the ability to measure the microstructural changes resulting from irradiation that effect the toughness of the RPV steel. Additionally the technique must be able to investigate the RPV through the thickness without removing the stainless steel weld cladding on the surface. Although the development of such an NDE technique may be difficult the U. S. NRC is supporting such research in hopes of developing more information concerning the toughness of U. S. RPVs.
The Riddle Of Nde For Embrittlemient Detection
Authors: Blaszkiewicz M. 
Published: June 2019

ABSTRACTThe ability to nondestructively determine the level of irradiation induced degradation in nuclear reactor pressure vessels (RPVs) would enhance the integrity assessment currently used by the nuclear industry. Presently, destructive testing of Charpy specimens from surveillance capsules is used to approximate the RPV upper shelf energy and the ductile-to-brittle transition temperature, and approved models and guidelines are used to determine the state of embrittlement. However, these models and surveillance programs do not always provide enough accurate information to support decisions for premature RPV life termination, life continuation to license expiration, or life renewal and extension by means of annealing. Effective nondestructive techniques would extend the usefulness of the surveillance material by reducing the amount of material used for destructive studies, and ultimately by allowing tests to be performed directly on the RPV. Nondestructive techniques, ranging from electrical resistivity to hyperfine interactions, have been, and continue to be, explored for use in embrittlement assessment. The current states of these various techniques are discussed, and future directions for research are suggested.
Preliminary Results On Ultrasonic Attenuation Detection Of Neutron Irradiation Embrittlement Of Nuclear Reactor Steel
Authors: Hiser A. L. , Green R. E. 
Published: June 2019

ABSTRACTNeutron bombardment of reactor pressure vessel (RPV) steels causes reductions in fracture toughness in these steels, termed neutron irradiation embrittlement. Currently there are no accepted methods for nondestructive determination of the extent of the irradiation embrittlement nor the actual fracture toughness of the reactor pressure vessel. This paper provides preliminary results of an effort addressing the use of ultrasonic attenuation as a suitable parameter for nondestructive determination of irradiation embrittlement in RPV steels.
Ultrasonic Nde Of Radiation Damage
Authors: Tittmann B. R. 
Published: June 2019

ABSTRACTIrradiation degrades the fracture toughness of reactor pressure vessel steels. To date no satisfactory method has been developed to nondestructively measure the loss of fracture toughness. Metal embrittlement is often associated with impurity pinning of dislocations. A review is presented of the interaction of dislocations with ultrasonic waves to give rise to attenuation or internal friction. The emphasis is on amplitude dependent attenuation due to dislocation breakaway from pinning points. Recommendations for future work are provided.
Service Life Prediction And Choice Of Repair Strategy For Rc Structures
Authors: Henriksen Carsten 
Published: June 2019

ABSTRACTThe accumulating damage to concrete structures during the last years has led to an increasing need for repair work.The need for concrete repairs is not likely to change in the future, not until all old concrete structures have been repaired or rehabilitated through preventive maintenance.Both repair and preventive maintenance of a concrete structure require economic investment, not only at present, but also in the future. A repair does not last forever and preventive measures (e.g. surface treatment) require regular maintenance. Society does not have unlimited resources for the repair and maintenance of concrete structures. Consequently, there is a need for optimization of the resources, i.e. using few resources in the best way at the right time.It is therefore necessary to base the repair/maintenance on technical and (in particular) economic evaluations.The following describes a model for evaluation of the technical and economic need for repair/maintenance of concrete structures.
Fiber Optic Sensing the Behavior of Prestressed-Prism-Reinforced Composite Concrete Beams for Bridge Deck Application
Authors: Nawy Edward G. , P. E.  
Published: June 2019

ABSTRACTThis investigation involves the identification and use of a novel type of fiber optic sensors in monitoring the deformation behavior of critical sections of the structural concrete elements and transforming them into smart systems. Basic operating principles of the Bragg-grating sensors identified in this work are proved to be feasible. Deformational behavior was studied of high performance concrete composite beams reinforced with prestressed prisms and instrumented with Bragg Grating fiber optic sensors. The experimental techniques using those sensors for evaluating their behavior at service load stages, and the potential of this technique for on-line, real-time monitoring of existing constructed concrete structures are presented.
Non-Invasive Monitoring of Acute Intracranial Mass Lesions Using Ultrasonic Fingerprinting
Authors: Nagy P. B. , Rosenberg W. S. , Stankovits L. M. 
Published: June 2019

ABSTRACTPotentially dangerous neurological changes in shock-trauma patients are currently monitored by computer-aided X-ray tomography which is prohibitively expensive and even dangerous for long-term, e.g., comatose, patients. By ultrasound, only low-frequency “diffuse” ultrasonic inspection is feasible through the skull so that the details are irreversible lost in the essentially random scattering process. In order to overcome this inherent limitation, we adapted a continuous computer-controlled ultrasonic monitoring system based on the ultrasonic fingerprinting method originally developed for materials characterization purposes in the nuclear, civil engineering, and aerospace industries. An ultrasonic detector directed at the general area of interest can be used to record and repeatedly update the personal signature of the patient, which is then used as an “ultrasonic fingerprint.” Any abrupt change in this signature indicates the immediate need for further investigation by CT or other sophisticated diagnostic tools. Experimental studies were conducted on both a human skull/gelatin phantom and 5 intact human cadavers. Ultrasonic fingerprinting could detect the secondary effects of volumetric changes occurring at multiple locations and the average detectable volumes of mass lesions were found to be lower than indications for surgical intervention.
A Digital Mems-based Strain Gage for Structural Health Monitoring
Authors: Maclean B. J. , Mladejovsky M. G. , Whitaker M. R. , Olivier M. , Jacobsen S. C. 
Published: June 2019

ABSTRACTOne approach for structural health monitoring of aging aircraft is to take discrete airframe strain measurements and record the flight loads history. A complementary method consists of measuring changes in dynamic response due to fatigue crack growth. The challenge in implementing such methods is the need for inexpensive networks of distributed strain sensors which possess high resolution with no drift over time. The Uni-Axial Strain Transducer (UAST) has been developed as a digital, absolute encoding device to address these very issues. The UAST is a micro-electromechanical system (MEMS) which exploits the capacitive coupling between an array of electrostatic field emitters and an array of 64 field detectors on a CMOS IC chip. The slightly different array element spacings form a vernier scale and digital signal processing of the detector outputs is used to calculate the absolute translational displacement of the emitter array relative to the CMOS detector chip. The UAST provides a dynamic range of 11,500 μ-strain and displacements of 2.5 nm are easily resolved. The sensor sampling rate is dynamically configurable for 150, 290, 540, 1000, 1600 or 2500 Hz, providing 15, 14, 13, 12, 11, or 10 bits of resolution (equal to 0.35, 0.7, 1.4, 2.8, 5.6, or 11.4 μ-strain), respectively. The sensor network can communicate with up to 128 UASTs on a common 5-wire digital bus, eliminating the need for shielding and considerably reducing the number of wires which will have to be routed through the airframe. A network technology demonstration is being conducted on a 1/2 scale F-I 8 vertical tail where dynamic loads are applied to evaluate network performance related to monitoring of fatigue crack growth or rivet-line failures. Application of the UAST in a helicopter rotor health usage and monitoring system, and the design of a bi-axial transducer under development, are also mentioned.
Application Of Dielectric Analysis To The Study Of Ageing In Adhesive Bonded Structures
Authors: Pethrick Richard A. , Joshi Sadanand B. , Hayward David , Li Zhi-Cheng , Halliday Steven , Banks William M. , Gilmore Ray , Yates Lawrence W. 
Published: June 2019

ABSTRACTDielectric techniques have the potential of allowing observation of changes in the dipole mobility within an adhesive joint structure as a result of its exposure to a warm humid environment. Water molecules absorbed by an adhesive resin will exhibit a series of distinct relaxation features, which are characteristic of the environment in which the molecules are located. Hydration of the surface oxide of an aluminium-epoxy joint will produce a distinctive dielectric relaxation at approximately 1 MHz which is quantitatively related to the amount of hydroxide formed. Data on aged adhesive joints indicates that the dielectric technique has potential for the study of the changes occurring within the joints and the technique may be also used for studies of carbon fibre - epoxy - carbon fibre structures.
Fiber Breakage In Polymer-Matrix Composites During Static And Fatigue Loading, Observed By Electrical Resistance Measurement
Authors: Wang Xiaojun , Chung D. D. L. 
Published: June 2019

ABSTRACTBy measuring the electrical resistance of a continuous unidirectional carbon fiber epoxy-matrix composite along the fiber direction during loading in this direction, fiber breakage was progressively monitored in real time. Fiber breakage occurred in spurts involving 1000 fibers or more. It started at about half of the failure strain during static tensile loading and at about half of the fatigue life during tensiontension fatigue testing. Immediately before static failure, 35% of the fibers were broken. Immediately before fatigue failure, 18% of the fibers were broken. The fiber breakage was accompanied by decrease in modulus.
Strategies For Nde Of Fiber Reinforced Polymer Structural Components
Authors: Duke John C. 
Published: June 2019

ABSTRACTA strategy for selecting and developing nondestructive evaluation (NDE) methodologies for fiber reinforced polymer composite structural components to be used in civil infrastructure applications is described. Conventional and innovative evaluation approaches are discussed.Actual experience with NDE of hybrid carbon and glass fiber reinforced vinyl ester pultruded
beams that are installed in a bridge carrying automotive traffic is described.
Epoxy Cure Monitoring With An Interdigitated Gate Electrode Field Effect Transistor (IGEFET)
Authors: Kolesar E. S. , Wiseman J. M. 
Published: June 2019

ABSTRACTAn interdigitated gate electrode field-effect transistor (IGEFET) was designed, fabricated and used to monitor the cure of a common epoxy. The IGEFET sensor consists of an interdigitated gate electrode structure which is coupled to the gate contact of a conventional metal-oxide-semiconductor field-effect transistor (MOSFET). The epoxy was deposited on the interdigitated gate electrode, and the IGEFET's electrical performance was observed as the epoxy cured. The cross-linking chemical reaction during epoxy cure caused electrical impedance changes that were quantified when the IGEFET was operated with a periodic voltage pulse signal. Charge transferred through the chemically-active epoxy is manifested as a temporally-dependent potential applied to the MOSFET's gate contact. By operating the MOSFET as a linear amplifier, a potential corresponding to the temporally-dependent gate voltage was directly measured at the amplifier's output. The Fourier transform of the IGEFET's time-domain response at specific time increments was computed. The resulting epoxy cure spectra were compared to a reproducible baseline spectrum, and an ensemble of difference spectra were computed to reveal the epoxy's chemical state at specific instances of time. The difference spectra features yield valuable information concerning the state of the epoxy's cure.