bluuebunny/crossref_metadata_2025 huggingface dataset:
Prediction of Residual Stresses in an Autofrettaged Thick–Walled Cylinder
Authors: Chen Peter C. T.
Published: March 2011

Most of the earlier results for residual stresses are based on the assumption of elastic unloading. In this paper, the prediction of residual stresses for the case of reverse yielding including the combined Bauschinger and hardening effect will be reported for an autofrettaged thick-walled cylinder. The Bauschinger effect factor is varying as a function of overstrain. The strain-hardening effect is considered with different parameters used for loading and unloading process. The new results indicate that the influence of the combined Bauschinger and hardening effect on residual stress distribution is significant.
Stress Analysis of a Beveled Diamond Anvil
Authors: Bruno M. S. , Dunn K. J.
Published: March 2011

A finite element stress analysis has been performed on a brilliant cut high pressure diamond anvil. The analysis includes the presence of a metal gasket. A perfectly cohesive interface is assumed to exist between the diamond and metal. Different configurations of the anvil face were studied. The stress distribution resulting from various beveled angles has been analyzed. It has been found that for a flat anvil, with a center normal pressure of about 210 kbar, an octahedral shearing stress of about 90 kbar is present near the center and monotonically increases radially to about 208 kbar along the outer edge. When the anvil surface is beveled, the octahedral shearing stress at the outer corner decreases significantly. The optimum beveled angle necessary to minimize these stresses seems to lie in the neighborhood of 15 degrees. The assumptions made and other stress considerations are discussed.
Predicting Catastrophic OD Initiated Fatigue Failure of Thick-Walled Cylinders Using Low Cycle Fatigue Data
Authors: Kapp Joseph A.
Published: March 2011

A procedure is presented to predict fatigue failure of thick-walled cylinders containing discontinuities at the OD. Both crack initiation life and crack growth are considered. The elastic-plastic strains at an OD discontinuity are estimated using an elastic analysis and stress concentration factors. The strain estimates are then used in conjunction with low cycle fatigue data to determine the initiation life. Crack growth life is estimated by integration of a power law relationship. The results obtained by using this analysis method compared to measured fatigue life data for several OD initiated failures in thick-walled cylinders agrees to within about 10 percent.
High Pressure Sealing Characteristics of Metallic Sleeve Seals
Authors: Dean T.J. , Elligsen R.A. , Mohaupt U.H.
Published: March 2011

Close tolerance metallic sleeves may be used as seals for reciprocating pumps or intensifiers operating at pressures up to 700 MPa. Seals of this type may be designed to provide a low friction sealing action which minimizes the usual wear problems. This paper presents the high pressure performance characteristics of such seals and examines the influence of parameters such as seal geometry, initial clearance, working pressure and fluid viscosity and temperature on leakage rates. Experimental results are compared with theoretical data generated using a computer model.
Very High Pressure Generation at the Deep Sea
Authors: Suito Kaichi , Yasukawa Katsumi
Published: March 2011

In the deep sea, truely hydrostatic pressure is produced in a very large area. This pressure may be used as natural resources. By utilizing these resources, very high pressures can be generated using a 6–8 type split-sphere high pressure apparatus. A preliminary experiment to generate very high pressure was undertaken in the deep sea at a depth of about 1000 m. Pressures of about 8.5 GPa were generated in the central part of the high pressure apparatus.
A Method to Determine the Pressure Dependent Distortion of a Simple Piston Gage Based on Dimensional Metrology
Authors: Welch B.E. , Bean Vern E.
Published: March 2011

Elastic distortion of the piston and cylinder is the leading cause of inaccuracy in piston gages at higher pressures. The distortion depends upon the pressure profile between the piston and the cylinder. One possible method of determining the pressure profile is demonstrated.
Compression of CCl4 at High Pressures
Authors: Wood Sharrill D. , Bean Vern E.
Published: March 2011

The compression of carbon tetrachloride has been measured along twelve isotherms covering a pressure range of 0.1 to 200 MPa and a temperature range of 254 to 298 K. Volume changes were measured with an automated capacitance bridge–one side of the bellows containing the sample serving as one plate of the capacitor. Data were obtained in the liquid, face-centered cubic (fcc), and rhombohedral phases, during melting, during freezing into the fcc phase and during the fcc to rhombohedral phase change. Premelting behavior was observed for both solids. The disappearance of the fcc phase at approximately 273 K and the existence of dual melting curves for the fcc and rhombohedral phases were reaffirmed.
Molecular Thermodynamics of Supercritical Fluid Mixtures
Authors: Eckert Charles A.
Published: March 2011

Supercritical fluid extraction uses a dense gas as a solvent at a temperature only slightly above its critical temperature and a pressure of a few hundred bars. The process offers the advantages of both conventional distillation and solvent extraction, and permits the facile achievement of difficult separations by highly selective absorption and desorption of various solutes. A valid thermodynamic model is essential for the rational design of such processes. We have made extensive solubility measurements at pressures to about half a kilobar, and we interpret the results in terms of perturbed hard-sphere equations of state. In this, we characterize solution nonidealities in terms of enhancement factors, which are often in the range of 103−108. Even better information about the specific solvent-solute interactions are available from measurements of partial molal volumes in supercritical solutions. These are very difficult measurements, as the effects are most pronounced precisely where the solvent compressibility is greatest, and accurate data are possible only because of the advent of the high-pressure vibrating tube densitometer, which converts density determinations to highly accurate frequency measurements for determinations to a precision of ±0.0001 g/cc. The solute partial molal volumes are many liters negative in the critical region, and these data are interpreted in terms of various equations of state.
Single-Pulse Coherent Raman Spectroscopy in Shock-Compressed Benzene
Authors: Moore D. S. , Schmidt S. C. , Schiferl D. , Shaner J. W.
Published: March 2011

Single-pulse backwards stimulated Raman and reflected broadband coherent anti-Stokes Raman spectroscopy (BSRS and RBBCARS) have been used to measure the vibrational frequency shifts of the 992 cm−1 ring-stretching mode of liquid benzene shock-compressed to pressures up to 1.2 GPa. The resulting shifts of ∼7.5 cm−1/GPa in the dynamic experiments are compared to spontaneous Raman scattering measurements of heated samples compressed in a diamond-anvil cell. RBBCARS was used to simultaneously measure the ring-stretching mode vibrational frequencies of liquid benzene / liquid perdeuterobenzene mixtures shock-compressed to pressures up to 1.53 GPa. Additional experiments that demonstrate the difficulty of using polarization sensitive coherent Raman techniques, such as Raman-induced Kerr effect spectroscopy (RIKES), in shock-compressed samples are described.
Growth of GexSi1−X/Si Alloys on Si (100), (110) and (111) Surfaces
Authors: Hull R. , Bean J. C. , Peticolas L. , Xie Y. H. , Hsieh Y. F.
Published: March 2011

We compare and contrast GexSi1−x alloys grown on Si (100), (110) and (111) surfaces. The geometry of interfacial misfit dislocations are observed to be different on these three surfaces, as the intersections of available ♣111} glide planes are of different symmetries for the different interfaces. In addition, angular factors resolving the applied and line tension stresses onto misfit dislocations vary over the different surfaces, producing different effective stresses for identical layer thicknesses, compositions and microstructures. Finally, markedly different dislocation microstructures are observed on the different surfaces, as geometrical considerations show that partial dislocations may separately propagate on the (110) and (111) surfaces, in contrast to the (100) surface.
Measurement of Valence Band Offset in Strained GexSi1−x/Si Heterojunctions
Authors: Khorram S. , Chern C. H. , Wang K. L.
Published: March 2011

The valence band discontinuity ΔEV in the coherently strained GexSi1−x/Si heterostruc-ture is determined using I-V-T measurement. The electrical measurements of the band discontinuity of the pseudomorphic layers are difficult due to the thin layer imposed by the strain. Recently, low temperature growth of thick layer (>100 nm) of coherently strained GexSi1−x on Si has been achieved and thus made it possible for an accurate electrical measurement of band offset. The results obtained are in good agreement with the theoretical calculations by pseudopotential method.
Low Threading Dislocation Densities in Thick, Relaxed Si1−xGex Buffer Layers
Authors: Tuppen C. G. , Gibbings C. J. , Hockly M.
Published: March 2011

A series of relaxed Si1−xGex alloy layers with germanium contents up to 70% has been deposited on silicon. Although direct deposition ot these highly mismatched layers on silicon gave dislocation densities of 109-1010cm2 and poor morphology, it was found that the use of a linear grade enabled completely relaxed Si.3Ge.7 layers with defect densities of ∼3.105cm−2 to be obtained. However, if the grading was too rapid the dislocation density was much higher. The role of dislocation nucleation and propagation in determining the required thickness of graded layer is discussed.
Intensity Modulation of Glancing Angle X-Ray Diffraction Spectra of GexSi1−x/Si Superlattices
Authors: Wang Xun , Zhou G. L. , Sheng C. , Yu M. R.
Published: March 2011

The glancing angle x-ray diffraction spectra of GexSi1−x/Si superlattices grown by MBE under different temperatures are investigated. Three different types of the intensity distributions of diffraction peaks are observed, which are believed to be corresponded with different situations of interfaces. If all the interfaces in superlattice structure are highly flat, up to 17 orders diffraction peaks are identified with their intensities modulated by a periodical envelope function, otherwise the distribution of diffraction intensities follows simply a decaying function. A quantitative analysis using computer simulation based on the modified Bragg's law and the optical multilayer theory is used to derive the structural parameters including the thicknesses of Si and GexSi1−x layers, superlattice period, Ge content x and the degree of interfacial roughness.
Temperature Dependence of Critical Thickness for Two Dimensional Growth of GexSi1−x on Si Substrate
Authors: Wang Xun , Zhou G. L. , Zhou T. C. , Sheng C. , Yu M. R.
Published: March 2011

For obtaining good structural perfection, the molecular beam epitaxial (MBE) growth of GexSi1−x on Si substrate should not only be kept in the pseudomorphic form but also in layer-by-layer growth stage. We found that the two dimensional layer-by-layer growth of GexSi1−x on Si could persist to a certain deposition thickness, beyond that the transition to islanding growth occurs. The transition thickness is significantly dependent on the growth temperature and germanium content, and is always smaller than the critical thickness of pseudomorphic growth. In order to obtain good crystalline quality in growing GexSi1−x superlattices on Si substrates, the thickness of GexSi1−x layers should be controlled below the transition thickness and lower growth temperature is favorable.
High Definition Mesa Growth by Silicon MBE
Authors: Hammerl E. , Wittmann F. , Messarosch J. , Eisele I. , Huber V. , Oppolzer H.
Published: March 2011

A novel epitaxial growth method for fabricating mesa patterns on a micrometer scale has been investigated. Electrical devices have been prepared employing this technique and their characteristics are in good agreement with those of mesa etched devices.
Residual Strain and Defect Analysis in as Grown and Annealed SiGe Layers
Authors: Powell A. R. , Kubiak R. A. , Whall T. E. , Parker E. H. C. , Bowen D. K.
Published: March 2011

In this paper we address the problem of producing SiGe buffer layers of acceptable quality for the growth of symmetrically strained SiGe structures. Initially we consider SiGe layers grown to well beyond the metastable critical thickness and examine the degree of residual strain both as - grown and post anneal. The defect levels in metastable SiGe layers following high temperature anneal were also studied. A buffer layer was grown consisting of stacked metastable SiGe layers each of which is annealed in situ prior to the growth of the next layer and terminating with a 0.45 SiGe alloy. This produces nearly fully relaxed 1.15pim thick structures with threading dislocation densities of 4 × 106cm−2. Limited area growth on Si suggests that elastically relaxed material free of both threading and misfit dislocations can be produced.
Photoreflectance and Resonant Raman Scattering in Short Period Si/Ge Superlattices on Ge (001) and Si (001)
Authors: Menczigar U. , Eberl K. , Abstreiter G.
Published: March 2011

Short period Si/Ge superlattices have been grown on Ge (001) and Si (001) substrates by molecular beam epitaxy. The optical properties of the superlattices have been studied with photoreflectance. (PR) and resonant Raman scattering (RRS). With PR we are able to observe new, structural induced transitions for all superlattices which are related to E0-and E1-like gaps. The analysis of PR spectra is complicated by an optical etalon effect if the samples are sufficently thick. The E1-like transitions in the range between 1.9eV and 2.7eV are also studied with RRS. Due to the confinement of the optical phonons in the Ge and Si layers RRS is able to probe the bandstructure in each layer seperately. Localized electronic states in the Ge layers can be observed with RRS for a Si4Ge18 superlattice and are compared with PR measurements.
The Extraction of Minority Carrier Lifetime from the Current-Voltage Characteristics of Si/Si1−xGex Devices
Authors: Ghani T. , Hoyt J. L. , Noble D. B. , Gibbons J. F. , Turner J. E. , Kamins T. I.
Published: March 2011

The extraction of recombination lifetime from the current-vol tage characteristics of diode structures containing Si1−xGex strained layers is discussed. Electrical measurements are used in conjunction with computer simulations to extract minority carrier lifetime in Si1−xGex layers with various oxygen concentrations. The minority carrier lifetime in Si1−xGex increases from several psec at an oxygen concentration of 2×1020 cm−3, to greater than 0.5 μs at concentrations below 3×1017 cm−3. The structures are analyzed for sensitivity of the current characteristics to Si1−xGex minority carrier lifetime. Calculations predict that the maximum lifetime which can be extracted from such structures is greater than 100 μsec. However, due to limitations imposed by perimeter currents, the maximum lifetime which can be extracted from our diode structures is on the order of 3 μsec. Maximizing area to perimeter ratio of the diode structures and moving the Si1−xGex-SiO2 interface away from the active device region is required in order to increase the maximum extracted lifetime from such structures.
Si/Si1−xGex p-Channel Mosfets Fabricated Using a Gate Quality Dielectric Process
Authors: Kesan V. P. , Subbanna S. , Tejwani M. J. , Restle P. J. , Iyer S. S.
Published: March 2011

The use of Si1−xGex alloys for p-channel high transconductance MOSFETs requires a high quality dielectric system. Direct oxidation of Si1−xGex alloys or even low temperature deposition of SiO2 directly on Si1−xGex results in a very high interface state density. We show that low interface state densities (below 1011 eV−1cm−2) can be obtained using both thermal and PECVD oxides through the use of a thin (6–8 nm) Si cap between the oxide and the Si1-xGex layer. The Si cap layer leads to a sequential turn-on of the Si1−xGex channel and the Si cap channel, as clearly observed in low temperature C-V curves. We show that this dual channel structure can be designed to suppress the parasitic Si cap channel. High quality, fully isolated Si1−xGex p-channel MOSFETs have been fabricated in an integrable, low Dt process using both thermal or PECVD gate oxides and selective UHV/CVD for the Si/ Si1−xGex channels. We show that optimally designed Si/Si1−xGex MOSFETs exhibit up to 70% higher transconductance at 300K than control Si devices fabricated on n-doped 1017/cm3 Si substrates. Si/Si1−xGex p-channel MOSFETs with thermal and PECVD gate oxides show comparable device characteristics.
Integrated Rib Waveguide-Photodetector Using Si/Si1−xGex Multiple Quantum Wells for Long Wavelenghts
Authors: Kesan V. P. , May P. G. , Treyz G. V. , Bassous E. , Iyer S. S. , Halbout J. -M.
Published: March 2011

We have investigated the structural, electrical, and optical quality of epitaxial Si and Si1−xGex films grown by MBE on SIMOX (Separation by IMplanted OXygen) silicon substrates. Epitaxial films grown on these SOI substrates have been characterized using planar and cross-sectional TEM, high resolution X-ray diffraction, SIMS, and Seeco chemical etching to delineate defects. We have fabricated Si/SiGe P-i-N photodetectors integrated with Si waveguides on SOI for long wavelength applications. Low reverse leakage current densities were seen in these device structures. The photodetector exhibited an internal quantum efficiency of 50% at 1.1 μm with a frequency response bandwidth of 2 GHz.
Equipment for Monitoring and Controlling Rheed-Oscillations
Authors: Larsson M. , Björklund L. -E. , Hansson G. V.
Published: March 2011

A Light Oscillation Control Unit System (LOCUS) has been developed for the purpose of monitoring Reflexion High Energy Electron Diffraction (RHEED) oscillations and to use the oscillations to control the crystal growth with single atomic layer resolution. The system can be used for phase-locked epitaxy, i.e., shutters controlling the growth are actuated when monolayers are completed. To reduce the usual damping of the RHEED-oscillations, the system can also use the method of synchronization of nucleation, i.e., periodically varying the surface supersaturation by changing the substrate surface temperature during each oscillation. Four shutters can be operated automatically and the superlattice composition can be chosen in a number of different ways. LOCUS gives fast response on intensity oscillation maxima and minima beyond a programmable discrimination level. Relevant crystal growth parameters can be changed during the run of the program, which implies that even quasi-periodic superlattices can be grown. There is also a possibility to switch from automatic to manual control. The shutters and substrate heater have been designed to reduce the influence of shifts of the diffraction pattern as the growth conditions are changed.
Growth of CoSi2 on CaF2/Si (111) Heterostructures
Authors: Adamski C. , Schäffer C.
Published: March 2011

In order to produce an epitaxial metal/insulator/semiconductor structure we investigated the growth of CoSi2 on CaF2/Si (111) heterostructures. We demonstrate the possibility to grow epitaxial CoSi2 on CaF2 films by utilization of the template technique. The fabrication of these structures will be presented. The properties of such heterostructures were determined by means of RHEED, LEED, AES, SIMS, RBS and resistivity measurements.
Studies of SiH2Ci2/H2 Gas Phase Chemistry for Selective Thin Film Growth of Crystalline Silicon, c-Si, Using Remote Plasma Enhanced Chemical Vapor Deposition
Authors: Theil J. A. , Lucovsky G. , Hattangady S. V. , Fountain G. G. , Markunas R. J.
Published: March 2011

Conventional high temperature, >800°C, CVD processes, utilizing SiH2Ci2 promote selective deposition of c-Si onto c-Si, but not on SiO2 surfaces. We show that low temperature, 300°C remote PECVD, with rf-excited He plasmas, and SiH2Ci2 and H2 injected downstream, also selectively deposits c-Si on c-Si and not SiO2 surfaces. This preliminary study employs in-situ mass spectrometry, MS, to determine the species responsible for selective deposition process reaction pathways. These MS studies suggest that species responsible for film deposition are Si-containing fragments of the SiH2Ci2 molecule, e.g., SiH2Ci, SiCi2H, etc., while the species responsible for inhibiting deposition on the SiO2 surfaces are by-products of the break-up of the SiH2Ci2 molecule in the gas phase, e.g., H-atoms, HCI and H2Ci+ ions.
Last Developments in Luminescence of Porous Silicon
Authors: Bsiesy A. , Gaspard F. , Hereino R. , Ugeon M. , Muller F. , Romestain R. , Vial J. C.
Published: March 2011

It is shown that visible photoluminescence and electroluminescence can be obtained from porous silicon layers. Room temperature photoluminescence is readily obtained from as-formed high porosity samples. Light emission at wavelengths as short as 560 nm can be observed after further thinning of the silicon pore walls by dissolution in HF under illumination. Silicon walls can also be thinned by an electrochemical oxidation process, this method allowing to use layers of rather low porosities (65%) which thus gives good mechanical properties to the samples. The thinning of the already very small size crystallites of porous silicon leads to quantum size effects which are at the origin of the light emission far above the band gap of silicon. Photoluminescence decay characteristics suggest that a tunnelling effect could be involved in the recombination mechanism of photogenerated charge carriers. Bright electroluminescence during anodic oxidation of porous silicon has been also evidenced. The influence of the porosity, of the layer thickness and of the anodic current density on the integrated electroluminescence intensity are described in detail.
Schottky - Barrier Tunnelling Spectroscopy of Si:B Delta Layers
Authors: Biswas R. G. , Braithwaite G. , Phillips P. J. , Kubiak R. A. , Parker E. H. C. , Whall T. E. , Wood A. , O'Neill A.
Published: March 2011

Delta doping in MBE has attracted considerable attention since its inception in 1980 [1], as a vehicle for studies of 2D phenomena and for its potential applications in, for example, FET devices [2] and I.R. detectors [3]. Boron delta doping in silicon is a recent development [4]. In previous papers we have reported on the growth, TEM, CV profiling, SIMS profiling and XRD characterisation of B delta layers [4,5,6]. It is of interest to know if the present growth method [4] produces a dopant sheet a monolayer wide or, in any event, what is the true width. Previous techniques [4,5,6] have yielded values between 0.4nm and 3nm for the width. Schottky barrier tunnelling spectroscopy provides further information on this question, but is also of interest for a study of the electronic structure of the delta layer. It has been used previously for a study of delta doping in III-V materials [7] and also for Sb delta doping in Si [8,9], but there have so far been no reports of its application to Si:B delta layers.
Aspects of Crystal Quality of Si (100) Films Grown by Molecular Beam Epitaxy
Authors: Ni W. -X. , Henry A. , Ekberg J. O. , Hansson G. V.
Published: March 2011

Silicon layers grown by molecular beam epitaxy, using both direct resistive heating and indirect radiant heating of the substrate, have been evaluated by photoluminescence measurements, diode I-V characterization, and chemical etching tests. The results show that large densities of defects could be introduced when resistively heated substrates were experiencing thermo-mechanical stress. Films with good crystal quality were grown using a carefully designed radiant type heater.
Electromigration Lifetime and Step Coverage in Al/Cu/Si Thin Film Conductors
Authors: Kisselgof Larisa , Elliott L. J. , Maziarz J. J. , Lloyd J. R.
Published: March 2011

Electromigration-induced failure was investigated in Al/Cu/Si conductor stripes deposited over trenches cut into an oxide layer and compared with those deposited onto flat areas. The results indicate a reduction in lifetime which is proportional to the size of the step to be covered and this reduction is in excess of what is expected from simple current density scaling. In addition, the electromigration performance of conductors deposited over topology did not correlate well with the performance on flat structures.
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

The 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

The 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

Even 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

The 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

Tantallum 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

This 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

Czochralski (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

In 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

The 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

This 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

Interconnect 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

Electromigration 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

This 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

The 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

The 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

This 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

Control 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

The 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

High 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

The 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.
A Study of Polyamic-Acid Interchange Reactions
Authors: Kreuz John A. , Goff David L.
Published: March 2011

C. C. Walker[1] first demonstrated that size exclusion chromatography (SEC) is an effective analytical technique for observing molecular weight distribution changes (MWD) of polyamic-acids with time. The specific polyamic-acid studied was that based on pyromellitic dianhydride and 4,4′- oxydianiline (PMDA/ODA), and the MWD narrowed on aging. Essentially, a decrease occurred in the weight average molecular weight (Mw), but no change took place in the number average molecular weight (Mn). Redistribution of molecular weight was postulated to be due to an equilibration reaction arising from the reversibility of amic-acids[2]. Additional data on Mw decreases with time of polyamicacids other than PMDA/ODA have been reported by Miwa and Numata[3] and Kreuz[4], and although trends are similar, rates of equilibrations of various polyamic-acids appeared to be partially due to backbone structure. The dianhydrides of 3,3′,4,4′-biphenyl dianhydride (BPDA) and 3,3′,4,4′- oxydiphthalic anhydride (ODPA) tended to give more stable polyamic-acid solutions.
Intramolecular Charge Transfer In Aromatic Polyimides
Authors: Salley Joseph M. , Miwa Takao , Frank Curtis W.
Published: March 2011

The 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

Isothermal 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.