bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mechanisms of Inelastic Deformation and Stress Relaxation in Thin Metallizations Bonded to Hard Substrates
Authors: Korhonen M. A. , Brørgesen P. , Li Che-Yu 
Published: March 2011

ABSTRACTThe yield strength of metallic thin films bonded to hard substrates can be significantly higher than is customary for bulk samples of the same metal. This is related to the constrained nature of the deformation. The constrained deformation, as well as the commonly observed crystallographic texture of thin films, places restrictive conditions on the mechanisms of deformation that produce stress relaxation. In narrow aluminum based metallizations used as interconnects in large scale integrated circuits thermal stress induced voiding provides an effective means for stress relaxation. For these interconnects, the stress state is tensile after excursions to higher temperatures; the stresses relax mainly by dislocation glide and grain boundary sliding during the cooldown, while the longer term relaxation is governed by stress-induced voiding and dislocation creep.
Stress Induced Void Nucleation in Narrow Aluminum Alloy Lines
Authors: Børgesen P. , Korhonen M. A. , Basa C. , LaFontaine W. R. , Land B. , Li C.-Y. 
Published: March 2011

ABSTRACTThe stress induced failure of passivated aluminum based metallizations is the combined result of the stress induced void nucleation and growth of voids. The present work investigates the dependence of the void nucleation on aging temperature and cooling rate. Narrow Al, Al(0.2%Cu) and Al(2%Si) lines of different widths were fabricated by lift-off and passivated with various thicknesses of Si3N4. After a 400°C anneal, the specimens were cooled directly to the selected aging temperature and aged for up to 1100 hours. Void nucleation was found to occur predominantly during the initial cool-down. The rate of nucleation varied in quite different ways with the combination of aging temperature and cooling rate for the different alloys, which is consistent with a grain boundary sliding controlled nucleation mechanism.
Creep-Fatigue Behavior of Microelectronic Solder Joints
Authors: Ross R. G. , Wen L. C. , Mon G. R. , Jetter E. , Winslow J. 
Published: March 2011

ABSTRACTEven at room temperature, solder joints exhibit both creep and fatigue behavior that is strongly dependent on solder joint configuration, the thermal environment, and the solder alloy properties. The microstructures of solder joints with up to 25 years of aging have been studied using SEM/EDS and metallographic techniques. Data are presented on grain growth and metallurgical composition versus aging time. A special non-linear finite element creep-fatigue simulation model has been developed, based on measured strain-rate hardness relationships, and used to analytically predict the effects of observed metallurgical changes and the effects of lead stiffness in solder joint creepfatigue interaction. To corroborate the analytical results, a special bi-metallic test fixture has been developed to accelerate the thermo-mechanical loading of solder joints in thermal cycling environments. Measured time-to-failure data for various electronicpackage lead configurations/stiffnesses, including gullwing and J-lead, are presented and shown to be in reasonable agreement with the analytical results.
Industrial Perspective on Reliability of VLSI Devices
Authors: Ghate P. B. 
Published: March 2011

ABSTRACTThe reliability of silicon integrated circuits (ICs) has improved significantly in the last decade. The complexity of ICs continues to increase. The semiconductor industry is actively working to a) improve the reliability of very large scale (VLSI) ICs, and b) reduce the failure rates to a value closer to 0.1 FIT by the year 2000. This paper summarizes the current status of quality and reliability of ICs. Some of the reliability limiting factors are described. Inadequacy of conventional accelerated test methods to verify the reliability of VLSI devices is highlighted. A challenging VLSI reliability goal with a failure rate approaching 0.1 FIT requires a) an understanding of the root causes of failure mechanisms, b) a translation of the lessons learned into a set of design rules for the circuit designers, c) appropriate materials and process specifications consistent with manufacturing capabilities, and d) in-process reliability test structures and test procedures. A VLSI failure rate goal of 0.1 FIT presents an exciting challenge for the materials scientists.
Thermal Stability of Sputter Deposited Tantallum Silicide Films
Authors: Dixit G. A. , Sundaresan R. , Chen F. S. , Lin Y. S. , Wei C. C. , Liou F. T. 
Published: March 2011

ABSTRACTTantallum silicide films were sputter deposited from targets with different Si/Ta stoichiometries. The films were then subjected to thermal treatments. Silicon precipitation was observed on films deposited from silicon rich targets. The effects of silicon precipitates on device characteristics was studied. A method to suppress silicon precipitation is reported.
TEM Investigation of Arsenic Precipitates in Semi-Insulating GaAs
Authors: Yegnasubramanian S. , Shahid M. A. 
Published: March 2011

ABSTRACTThis paper presents a TEM investigation of undoped, semi-insulating GaAs crystals grown by the VGF (vertical gradient freeze) technique for microstructure and defects characterization. Energy dispersive X-ray spectrometry (EDS) and selected area electron diffraction (SAD) were used to characterize for composition and lattice spacings, respectively. TEM images of dislocations decorated with precipitate particles are presented. The particles were found to be arsenic rich. Regions of fine particulates were identified and a Moire pattern analysis was carried out. The occurrence of such defects in the low dislocation density VGF GaAs of the present study suggests that these are material related and not necessarily dependent on the growth technique.
Synchrotron X-Ray Topographic Study of the Behavior of Defects in High Carbon-Content Si Wafers during RTP
Authors: Fanning Thomas , Dudley Michael , Wang Franklyn F.Y. , Gordon-Smith David , Hodul David T. 
Published: March 2011

ABSTRACTCzochralski (CZ) grown Si wafers, specially prepared with unusually high carbon content (ranging from 3 to 7 ppma), were subjected to a rapid thermal processing (RTP) treatment at 1050°C for 60s. Synchrotron white beam x-ray topography in transmission geometry was used to study defect structures in these Si wafers, both prior and subsequent to this RTP treatment. Observations of both the partial relaxation of the strain fields of precipitates and widespread nucleation and propagation of dislocations accompanying RTP are presented and discussed. Results are contrasted with those from parallel studies previously conducted on low carbon content wafers.
Investigation of Surface Ion Failure Mechanisms by Corona Discharge
Authors: Comizzoli Robert B. 
Published: March 2011

ABSTRACTIn this paper, the use of corona discharges to investigate and monitor surface ion failure mechanisms in devices is reviewed. The physical mechanisms resulting in surface ioninduced failures are first described. Then, some of the traditional design features and testing methods to minimize these failures are summarized. After presenting the general features of surface charge deposition on devices by a corona discharge, several examples of the application of this technique for design verification, process improvement and control, and failure analysis are given.
Effect of Moisture and Contaminants on the Dielectric Constant of Thin-Film Alumina Substrates
Authors: Chatterjee Indira , Misra Manoranjan , Warren Garry W. , Neve Cathy 
Published: March 2011

ABSTRACTThe dielectric properties of substrate materials constitute key parameters that determine the selection, reliability and design of sophisticated modern electronic devices. Two important factors affecting the reliability of electronic devices are the adsorption of moisture from the atmosphere, and contaminants like airborne particles (dust), flux residues, gaseous pollutants, residues from rinsing and cleaning unit operations etc. Any variation in the dielectric properties due to moisture and/or contaminants would be detrimental to the performance of an electronic package.Among the inorganic materials, alumina represents an optimal combination of electrical properties for many low and high-frequency applications. In this paper, the dielectric constant of thin-film alumina substrates has been measured over a wide frequency range (100 Hz to 3 GHz) as a function of relative humidity. The changes in the dielectric constant when the alumina substrates are contaminated with different contaminants like CuC12, CuSO4, organic acids etc. and exposed to various relative humidity levels for different lengths of time have also been measured. The effect on the dielectric constant when the contaminated substrates are treated with surfactants like oleic acid and dodecyl amine and exposed to different relative humidity levels is also presented. An important observation is that at a relative humidity level of approximately 70% there is a sudden increase in the dielectric constant of the contaminated alumina substrates. Results are also presented for the measured moisture adsorption using Thermo-Gravimetric Analysis in pure alumina, alumina contaminated with CuCI2 and contaminated alumina treated with dodecyl amine. It is shown that the measured dielectric constant is consistent with the amount of moisture adsorption that decreases on treatment with the surfactant.
Stress and Electromigration in Thin Film Metallisation
Authors: Ross C. A. 
Published: March 2011

ABSTRACTThis paper reviews the experimentally established relationship between electromigration and mechanical stress in thin films. A model will be described which calculates the development of stress around sites of electromigration flux divergence in a metallisation track and it is shown how the model can be used to predict the time before electromigration damage occurs. The effect of passivation on the stress state within a metal track is discussed and the behaviour of metallisation under pulsed current testing is interpreted in terms of mechanical stress generation and relaxation.
Microstructural Analysis of Electromigration-Induced Voids and Hillocks
Authors: Sanchez John E. , Morris J. W. 
Published: March 2011

ABSTRACTInterconnect reliability is of continuing concern in modem VLSI circuits. This work presents analyses of the microstructural detail in electromigration-induced damage in Al and Al-Cu unpassivated interconnects. Such failure analysis is crucial for the characterization of the fundamental processes responsible for failure. Results, via TEM, SEM and focussed-ion beam techniques, suggest possible second phase precipitate-void growth interactions, show slit-like open circuit failures in narrow interconnects, and illustrate the microstructures of hillocks and whiskers formed during accelerated electromigration testing. These results are discussed in terms of existing models for electromigration failure processes and lifetimes. The results are further intended to suggest mechanisms for future modelling and to direct the design of more reliable interconnect material systems.
1/f2 Noise and Electromigration in Al-Cu Interconnects
Authors: Dreyer Michael L. 
Published: March 2011

ABSTRACTElectromigration in Al-1.5%Cu interconnects was studied using a direct current (d.c.) induced 1/f2 noise spectrum. The interconnects were fabricated with a multi-step sputter deposition process, with deposition temperatures of 25°C, 300° C, and 475°C. The resulting microstructures were analyzed using SEM and TEM, and grain size distribution parameters were measured. The minimum temperature at which 1/f2 noise could be detected was found to depend on the deposition temperature; for the 25°C, 300°C, and 475°C depositions the lowest temperature at which 1/f2 noise could be measured was 190°C, 220°C, and 265°C, respectively. The activation energy of 1/f2 noise was measured and compared with the electromigration activation energy. The noise activation energy was found to depend on deposition temperature; 0.56 eV, 0.64 eV, and 0.96 eV for the 25°C, 300°C, and 475° C depositions, respectively. SEM analysis of the samples after measurement show initial stages of void and hillock formation. Corresponding electromigration activation energies, 0.56 eV, 0.69 eV, and 1.04 eV were also dependent on deposition temperature. Noise measurements of interconnects made prior to electromigration testing were highly correlated with the electromigration failure times.
Characterization Study of Al-Plug Technology
Authors: Hoang H. H. , Chen F. S. , Turner T. E. , Lin Y. S. , Dixit G. A. , Liou F. T. 
Published: March 2011

ABSTRACTThis work investigates the reliability issues associated with an aluminum sputter process, called the Al-plug process, that results in the complete filling of submicron contacts and vias of various sizes. The state-of-the-art Al-plug technology has proven its superiority over conventional processes due to its process simplicity and complete elimination of metal step-coverage problems and dielectric voiding over contacts/vias, resulting in higher reliability. Materials and electrical characterization of this metal process are presented.
Experimental Evaluation of Mechanical Behavior of GaAs Wafer Material
Authors: Hu Jun Ming , Pecht Michael , Barker Donald 
Published: March 2011

AbstractThe mechanical behavior of non-metalized GaAs wafer material at different temperatures were evaluated. The material properties of GaAs, including the modulus of elasticity, the modulus of rupture, the critical value of stress intensity factor, and the coefficient of thermal expansion, were experimentally determined over various temperature ranges.
New Developments in the Dynamic Mechanical Analysis of Thin-Layer Materials
Authors: Berry B.S. , Pritchet W.C. 
Published: March 2011

AbstractThe vibrating-membrane configuration represents an important new approach to the dynamic mechanical analysis of thin-layer materials. The method offers a convenient capability for high-resolution stress measurements over a wide temperature range, and can be combined if desired with internal friction measurements for the detection of defect-related relaxation peaks. Illustrative results are given for the thermomechanical behavior of silicon, silicon carbide, and synthetic diamond membranes, and for the moisture swelling of polyimide films. A detailed study of hydrogen-boron point defects in silicon is in progress, using both internal stress and internal friction measurements, and work on membranes has been supplemented significantly by the use of vibrating-string and ultra-thin vibrating-reed samples.
Isothermal Fatigue of 62Sn–36Pb–2Ag Solder
Authors: Vaynhan Semyon , Fine Morris E. 
Published: March 2011

AbstractThis paper discusses the effects of the most important variables during isothermal fatigue such as strain range, ramp time, tensile and compressive hold times, and temperature on fatigue life of near–eutectic 62Sn–36Pb–2Ag solder at strain ranges below 3.0%. The Coffin-Manson relation does not hold for 62Sn–36Pb–2Ag solder below 1% strain range. Decreasing frequency below 10-2 in no-hold tests reduces the number of cycles to failure. Tensile hold time or compressive hold time alone in the cycle dramatically reduce the number of cycles to failure. Increase of hold time over a few minutes leads to saturation of Nf. Combined tensile and compressive hold times affect the fatigue life of this solder less than either tensile or compressive hold alone. The effect of hold times on fatigue life is much stronger than the effect of ramp time. Practically no ramp time effect was observed in tests with tensile hold times. Very little effect of temperature over the range 25 to 80°C on fatigue life of 62Sn–36Pb–2Ag solder was observed when tested at total strain range of 1%.
Thermal Expansion Model for Multiphase Electronic Packaging Materials
Authors: Allred Ronald E. , Warren William E. 
Published: March 2011

AbstractControl of thermal expansion is often necessary in the design and selection of electronic packages. In some instances, it is desirable to have a coefficient of thermal expansion intermediate between values readily attainable with single or two phase materials. The addition of a third phase in the form of fillers, whiskers, or fibers can be used to attain intermediate expansions. To help design the thermal expansion of multiphase materials for specific applications, a closed form model has been developed that accurately predicts the effective elastic properties of isotropic filled materials and transversely isotropic lamina. Properties of filled matrix materials are used as inputs to the lamina model to obtain the composite elastic properties as a function of the volume fraction of each phase. Hybrid composites with two or more fiber types are easily handled with this model. Results for glass, quartz, and Kevlar fibers with beta-eucryptite filled polymer matrices show good agreement with experimental results for X, Y, and Z thermal expansion coefficients.
Stereoimaging Determination of Strains in Surface Mounted Components and Plated Through Holes Resulting from Thermal Cycung
Authors: Davidson David L. 
Published: March 2011

AbstractThe experimental mechanics of microelectronics components requires high spatial resolution measurements that are best obtained by using the scanning microscope because of the high spacial resolution and depth of field obtained using this instrument. This paper describes how measurements made from photographs taken in the scanning electron microscope have been used successfully to determine the strains which develop due to differences in coefficient of thermal between various parts of microelectronic components. Results are presented for thermal strains in the solder joints of a surface mounted component and in a printed circuit board plated through hole.
Void Growth as a Function of Residual Stress Level in Thin, Narrow Aluminum Lines
Authors: Korhonen M.A. , Børgesen P. , Paszkiet C.A. , Lee J.K. , Li Che-Yu 
Published: March 2011

AbstractHigh tensile stresses develop in passivated aluminum line metallizations on silicon substrates after excursion to elevated temperatures. The principal mechanisms to relax these stresses at room temperature are plastic deformation and grain boundary void growth. It is shown that stress relaxation and void growth are intimately connected.
Thermal Modeling of Plastic Ic Packages
Authors: Bar-Cohen A. , Mix Devin E. 
Published: March 2011

AbstractThe successful design of plastic integrated circuit packages for high performance VLSI chips is a crucial element in the development of costeffective packaging technology. Unfortunately, however, most common plastic encapsulating and die-bonding materials provide relatively low thermal conductivities and large thermal expansion coefficients, as well as low mechanical strengths and a limited operating temperature range. These material properties combine to produce a large number of thermally induced package failure modes. Thus, insightful material selection and detailed design, based on extensive thermal modeling/analysis, must be performed to achieve acceptable levels of component reliability.This paper begins with a discussion of the temporal development of the temperature fields inside a plastic IC package and continues with the presentation of transient and steady-state, first-order analytical models for: the chip temperature, the temperature and gradient across the die bond, and the half-thickness encapsulant temperature. The values obtained for a typical PDIP package are discussed and compared to the results of a finite-element analysis of this package. The insights obtained from these analyses are used to develop material Figures-of-Merit that can be used in the selection of die-bond and encapsulant materials for plastic IC packages.
Intramolecular Charge Transfer In Aromatic Polyimides
Authors: Salley Joseph M. , Miwa Takao , Frank Curtis W. 
Published: March 2011

ABSTRACTThe use of polyimides in integrated circuits to planarize complex topography and the need to decrease the dimensions of electronic devices have motivated us to gain a better understanding of the details of the polymer microenvironment. UV/Vis absorption experiments suggest that intramolecular charge transfer (ICT) exists and therefore might utilized as intrinsic, nonperturbing probes. The transfer of charge is believed to occur upon exposure of ultraviolet light as a result of donation from the phenyl ring (from the diamine fragment) to the adjacent imide ring. Furthermore, the transfer of charge should be a function of the torsional angle between the planes of the donor and acceptor segments.In this study, we first investigate the nature of the ICT by conducting UV/Vis absorption measurements on a series of model compounds. A comparative analysis of 10−5 M solutions of the models in dioxane provides evidence that intramolecular charge transfer occurs when the compounds are exposed to 264 nm (ultraviolet) light. Similarly, a comparison of an analogous series of polyimides demonstrates that the same phenomenon occurs in the more complex polymeric systems when spin-cast films are exposed to 326 nm (ultraviolet) light
A Fluorescence Study Of Polyimide Cure Kinetics
Authors: Hoffmann D.A. , Ansari H. , Frank C.W. 
Published: March 2011

ABSTRACTIsothermal annealing studies reveal long term increases in charge transfer fluorescence in spin-cast BTDA-ODA/MPD films. Due to the amorphous nature of these materials, the increase in charge transfer complex (CTC) population is attributed to thermally activated hindered rotation leading to local segmental correlations. This ordering process is driven by the non-equilibrium structure of the initially imidized film. Increased in-plane orientation at higher spin speeds produces a stress activation effect, lowering the energy barrier for segmental rotation.
Structure And Properties Of BPDA-PDA Polyimide From Its Poly(Amic Acid) Precursor Complexed With An Aminoalkyl Methacrylate
Authors: Ree Moonhor , Nunes Thomas L. , Chen K.-J. Rex , Czornyj George 
Published: March 2011

ABSTRACTBPDA-PDA poly(amic acid) precursor was functionalized through its carboxylic acid groups being linked with a crosslinkable aminoalkyl methacrylate, 2-(dimethylamino)ethyl methacrylate (DMAEM), by acid/base complexation. BPDA-PDA polyimide films, which were thermally imidized from the precursors complexed with various amounts of DMAEM, were characterized by means of wide angle x-ray diffraction, stress-strain analysis, and residual stress analysis. The structure and properties of the BPDA-PDA polyimide film were dependent upon the history of the precursor, that is, the complexation of the poly(amic acid) precursor with DMAEM. The molecular packing order was enhanced with the history of DMAEM loading while the molecular order along the chain axis was disrupted. Overall, physical properties, such as mechanical properties and residual stress, were degraded with DMAEM loading. The moisture induced stress relaxation behavior was sensitive to the history of DMAEM loading, whereas the creep induced stress relaxation was varied little due to its high Tg. These properties are understood in terms of structure/property relationships, as well as microvoids, which were possibly generated by outgassing the bulky DMAEM pendent groups during thermal imidization.