bluuebunny/crossref_metadata_2025 huggingface dataset:
Fracture Strength of A1203 Insulating Thin Film for High Density Wiring Substrate
Authors: Jono Masahiro , Sugeta Atsushi
Published: March 2011

Fracture strength of amorphous A1203 insulating thin film coated on a Fe-42%Ni base metal was Investigated under static and cyclic loadings by using four point bending apparatus. It was found that the both static and cyclic fracture strength of thin film decreased with increasing coating thickness and also fracture under cyclic loading occurred at a strain below the static fracture strength. Observations In detail by the optical and scanning electron microscopes revealed that the splash particles deposited in coating process caused crack initiation origins. Evaluation method of fracture strength of thin films was discussed based on the fracture mechanics approach.
A Micromechanical Analysis of the Signal Propagation in Composite Materials
Authors: Chen C. S.
Published: March 2011

Microstructure of composite materials can have a profound effect upon the performance of microelectronics composed of those composite materials. Conventional analysis based on quasi-homogeneous models neglecting the structural details of the composites is inadequate. Micromechanical analysis is more complex but can provide a more realistic treatment. We have investigated the propagation of a signal in a periodic composite to examine the essential of a micromechanical analysis. By analyzing the state of the composite material just before and after the wave front as well as on both sides right next to the interfaces, we have determined the strength of the propagating signal. The results show that the property differential between material components is critical in determining the energy dissipation. In composite materials made of dissipative components such as polymers,structural details of the composite materials contribute further to the energy dissipation.
A New Approach to Evaluate the Delayed Fracture Behavior of an Optical Glass Fiber
Authors: Muraoka M. , AbÉ H.
Published: March 2011

The method for the direct measurement of subcritical crack growth in silica optical fiber with 125μm in diameter was developed. The obtained crack velocity da/dt as a function of stress intensity factor KI was expressed by means of log da/dt vs log KI linear relation with slope n. The obtained value of n showed 22.6 (25 °C,60%r.h.) with small standard deviation 0.7. These results indicate that the postulated crack growth law used for the lifetime prediction is valid and the present approach can solve the problem in the conventional method for evaluating the value of n where the evaluated value has been widely scattered.
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.
The Effect of Line Geometry on Void Growth in Thin, Narrow Aluminum Lines
Authors: Borgesen P. , Lee J. K. , Korhonen M. A. , Li C.-Y.
Published: March 2011

The stress induced growth of individual voids in passivated Al-lines at room temperature was monitored in-situ without removing the passivation. The kinetics was strongly influenced by variations in line gec.etry, even over distances of many Am, indicating variations in the stress relaxation as well.
A Comparison of the Metallurgical Behavior of Gold and Copper Wires in Ball Bonding
Authors: Uno Tomohiro , Tatsumi K. , Mizuno K. , Kitamura O. , Ohno Y.
Published: March 2011

A comparison was made of gold and copper wires used in ball bonding in terms of their mechanical properties, bondability and the reliability of their bond interfaces in elevated temperature environments. The ball bondability of copper and gold was evaluated through clarification of the factors which govern ball deformability. Moreover a bonding method to suppress the generation of silicon cracks was proposed for ball bonding of copper wire. As to the reliability of the heat affected zone and the bond interfaces, copper wire was found to be superior to gold wire.
The Effect of Process on Performance and Reliability in a One Step Silver-Glass Die Attach Adhesive
Authors: Conlon A.M. , Cameron C.P. , Lau J.W.
Published: March 2011

Silver-glass die attach adhesives provide a cost effective means of producing high reliability parts which can withstand the environmental testing required of electronic components. One step processing of these adhesives provides the additional advantages of increased throughput and processing flexibility compared to eutectically bonded assemblies.

This paper describes the performance of a one step silver-glass die attach adhesive processed under various time and temperature conditions. The effect of peak firing temperature and dwell time on the ultimate tensile strength of the adhesive will be discussed. Tensile data from parts subjected to thermal shock, thermal cycle and high temperature aging will be presented as an indication of the material's long term reliability.
Numerical Analysis of the Bali. Forming Process in Copper Ball Bonding
Authors: Iiongyuan Fang , Yiyu Oian , Yihong Jiang
Published: March 2011

In this paper, the forming process of copper wire ball in copper ball bonding has been studied by numerical analysis. By means of calculation of temperature field, speed field and displacement field for ultrafine copper wire under a miniarc, the regular pattern of copper wire ball formation has been clarified. In this paper, the calculating result of displacement field has also been tested and verified.
Mechanical Behavior of Encapsulants in Microelectronic Packaging
Authors: Wong C.P.
Published: March 2011

A modern electronic device is a complex 3-dimensional structure that consists of millions of components for each single IC chip. This complex and delicate device requires effective encapsulation and packaging to ensure its long-term reliability. The device encapsulant requires not only excellent electrical, physical properties, but also suitable mechanical properties for the hostile and extreme temperature cycling requirements. Hence, the mechanical behavior of the encapsulant plays a critical role in the device reliability.

Low stress encapsulants are the preferred choice for microelectronic packaging. Silicone-base materials, with their low modulus and excellent electrical properties, are one of the best encapsulants. However, the intrinsic elastic (to soft gel-like) silicone properties provide weak mechanic protection of the IC device. We have, however, modified the silicone material with a high loading of silica to improve its mechanical and physical properties. This high silica filler loading material improves its mechanical property, but it also increases its modulus. This modified high modulus silicone material tends to have microcracks during the high temperature cycling testing. In this paper, I will describe a modified version of the enhanced mechanical property silicone-base encapsulant, the materials formulation, the curing and the thermal mechanical protecting mechanism and its application to AT&T's No. 5 Electronic Switching System (ESS) Gated Diode Crosspoint (GDX) hybrid IC supplemental insulating layer (SIL) materials.
Elastomeric Conductors for Electrical Contacts
Authors: Zhu Mingguang , Chung D.D.L.
Published: March 2011

Two new elastomeric electrical conductors were developed. One is silicone infiltrated tin foam containing 14 vol.% tin. The other is short nickel fiber silicone-matrix composites containing 3-12 vol.% fibers, fabricated by the impregnation of silicone into a nickel fiber preform. Both exhibited volume electrical resistivity of the order 10-4 ohm.cm.
Rigid-Rod And Segmented Rigid-Rod Polyimides: GEL/SOL And Liquid Crystalline Transitions, Fibers And Films
Authors: Cheng Stephen Z. D. , Arnold Fred E. , Eashoo Mark , Lee Song-Koo , Hsu Steve L. C. , Lee Chul Joo , Harris Frank W.
Published: March 2011

Organo-soluble rigid-rod and segmented rigid-rod polyimides and their copolyimides exhibit isotropic solutions in hot m-cresol, but form gels upon cooling. A lyotropic liquid crystal phase is observed below the gel/sol transition. Mechanical gel formation is caused by liquid-liquid phase separation, while the liquid crystal phase may be formed through a nucleation process after gelation. High performance fibers can be spun from the hot isotropic solutions using a dry-jet wet spinning method. After the fibers are drawn at high temperatures, they display tensile strength higher than 3.2 GPa and an initial modulus higher than 130 GPa. In particular, the fibers retain relatively high mechanical properties at elevated temperatures. Solution casted films exhibit very low thermal expansion coefficients and dielectric constants. Their structure, morphology and property relationships will also be discussed.
Physical Characterization Of Microelectronic Polymeric Thin Films
Authors: Senturia Stephen D. , Noe Susan C. , Pan Jeffrey Y.
Published: March 2011

The measurement of the mechanical properties and adhesion of polymeric thin films and coatings poses a number of technical problems. Elastic and viscoelastic properties, residual stress, adhesion, the effects of extended cure, and the effects of adsorbed moisture and process reagents are all critical. A particular challenge is to develop measurement methods which can be used with actual samples, preferably non-destructively. This paper examines a number of methods which have been developed to make these measurements, with emphasis on methods which are sensitive enough to look at the effects of process variation and the effects of moisture exposure. Suspended-membrane methods for measuring elastic and viscoelastic properties, residual stress, and adhesion are combined with optical methods for determining index of refraction and birefringence to yield a family of techniques for performing physical characterization. Recent results on the effects of extended cure and moisture uptake on elastic properties, residual stress, and optical properties will be presented.
Internal Stress Development In Spin Coated Polyimide Films
Authors: Pottiger Michael T. , Coburn John
Published: March 2011

The effect of processing on the development of internal stresses in spin coated polyimide films was investigated. The internal stresses are a result of the coefficient of thermal expansion (CTE) mismatch between the polymer and the substrate. Birefringence and CTE were used to characterize the in-plane molecular orientation. In-plane orientation was shown to be sensitive to processing conditions. Increasing the spin speed results in higher in-plane orientation as observed by an increase in birefringence and a corresponding decrease in CTE. Heating rate during cure was observed to have a significant effect on in-plane orientation. Faster heating rates during cure resulted in a lower birefringence. The lower birefringence is attributed to relaxation effects that can occur during a rapid cure. The decrease in orientation was accompanied by an increase in internal stress.
Polyimide Planarization With Polystyrene By Rie Etch-Back
Authors: Ng Hung Y. , Lii T. , Jaso M.
Published: March 2011

This paper reports the results of a planarization process of polyimide which has been utilized as a passivation material in multilevel interconnection. The degree of planarization with spin-coated polyimide over metal topography is only 10–20% due to crosslinking and shrinking of the polymer during the curing process. Polystyrene used as sacrificial planarizing film can achieve <95% planarity over 100μm metal pad with 1μm height. A conformal polystyrene film can be spin-coated onto the polyimide surface without adhesion promoter. The topography of polyimide over the metal pattern can be planarized with thermal reflow of the polystyrene by baking the film below 250°C. The planarity of this sacrificial film, polystyrene, can be transferred to polyimide by etch-back without degrading the polyimide surface properties which has been examined by X-ray photoelectron spectroscopy.
Unsymmetrical Spacers: A New Concept For Synthesis Of Main–Chain Liquid Crystalline Polymers
Authors: Kosfeld R. , Poersch G. , Hess M.
Published: March 2011

12 polyesters with branched spacers and 7 polyesters with linear spacers were synthesized and characterized.
Preparation Of Moisture Resistant Polylmide Films By Plasma Treatment
Authors: Petrich Mark A. , Lu Hsueh Yi
Published: March 2011

Polyimides are an important class of polymeric materials used in microelectronics fabrication. These polymers could be used even more extensively if it were possible to improve their moisture resistance. We are using plasma processing techniques to modify the moisture resistance of polyimide films. Films are exposed to nitrogen trifluoride plasmas to introduce fluorine into the surface of the polyimide. Fluorination is monitored with x-ray photoelectron spectroscopy and Fourier transform infrared absorption spectroscopy. Water contact angle measurements are used to assess the hydrophobicity of the treated surfaces. Thus far, we have demonstrated that this plasma treatment is a good way of introducing fluorine into the polyimide surface, and that these treatments do enhance the hydrophobic nature of polyimide.
The Role Of Surface Modification On Adhesion At The Metal/Polymer Interface
Authors: Berry M. J. , Turlik I. , Smith P. L. , Adema G. M.
Published: March 2011

This paper presents studies of surface modifications of benzocyclobutene (BCB) using reactive ion etching (RIE), ion implantation, and combinations of those in conjunction with liftoff processing steps. It was found that O2/N2 RIE treatments of the BCB surface improve the adhesion of subsequently evaporated chromium and copper. Implant treatments with C+, O+, Si+, As+, and Sb+, were also investigated. The implant treated samples exhibited improved adhesion prior to subsequent heat treatments in the Cr/BCB structures and some improvement subsequent to heat treating in the Cu/BCB structures. Combinations of the surface modification treatments were seen to have the greatest benefit, even after heat treatments.
A Study Of The Interface Between Polyimide And Plated Copper
Authors: Morihiro Yoshiyuki , Miyake Kurumi , Mori Mitsumasa , Kurokawa Hiroshi , Kohara Masanobu , Nunoshita Masahiro
Published: March 2011

A polyimide (PI) surface is analyzed by XPS at each electroless-copper-plating step. Zn ions are adsorbed on the PI surface, and subsequently replaced with Pd ions. Cu is deposited on the PI surface catalyzed by these Pd ions, As the surface concentration of Pd ions increases, the adhesive strength of the plated Cu to the PI surface increases.

In the case of PI fabrication onto a plated Cu, no significant PI degradation is observed.
Chain Conformations Of Aromatic Polvimides And Their Ordering In Thin Films.
Authors: Yoon D. Y. , Parrish W. , Depero L. E. , Ree M.
Published: March 2011

We have investigated the conformation – order relationships of four aromatic polyimides prepared by thermal imidization of the precursor poly(amic acids) in thin films. They are: (i) PMDA-4,4′-ODA polyimide from pyromellitic dianhydride (PMDA) and 4,4′-oxydianiline (ODA) monomers; (ii) PMDA-PDA polyimide from PMDA andp-phenylene diamine (PDA); (iii) PMDA-Benzidine polyimide from PMDA and benzidine and (iv) BPDA-PDA polyirnide from biphenylene tetracarboxylicdianhydride (BPDA) and PDA. X-ray diffraction results and their analyses by molecular modeling show that all the four polyimides exhibit extended chain conformations in various smectic-type ordered structures that form monomer repeat layers but differ in the details of interchain packing. Furthermore, the polyimide chains are highly aligned along the film plane.
Property Control Of New Fluorinated Copolyimides And Their Applications
Authors: Sasaki S. , Matsuura T. , Nishi S. , Ando S.
Published: March 2011

New fluorinated copolyimides are synthesized with 2,2′-bis(trifluoromethyl)-4,4′- diaminobiphenyl (TFDB) and a mixture of 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA) and pyromellitic dianhydride (PMDA). The thermal expansion coefficient decreases with decreasing 6FDA content, because the hexafluoroisopropylidene group makes the main chain flexible. The refractive index decreases with increasing 6FDA content, because the fluorine content increases. The thermal expansion coefficient can be controlled between -0.5 × 10−5 and 8×10−5 /°C, and the refractive index can be controlled between 1.556 and 1.647 at 589.3 nm, by changing the 6FDA content. The polyimides and copolyimides from TFDB can be used in optical filters because of their high optical transparency and low thermal expansion coefficient. They are expected to be used in optical waveguides because of their high optical transparency and refractive index control.
Highly Temperature Resistant Silicone Ladder Polymers
Authors: Adachi Hiroshi , Adachi Etsushi , Yamamoto Shigeyoshi , Kanegae Hirozho
Published: March 2011

High purity high molecular weight poly (phenylsilsesquioxane) (PPSQ) has been synthesized and specimen films prepared by a solvent casting method. The decomposition temperature of the material is 550°C in air. A PPSQ specimen cured at 350°C for 60 min has a weight loss of 1% when held at 460°C for 60 min. A specimen initially dried at 200°C for 30 min then held at 460°C loses twice as much. The main constituent of the volatile material from PPSQ pyrolyzed at 500 °C for 60 min is benzene, which is 5.7% of the specimen weight. The tensile strength for the cured specimen is 8.0 × 109 dyne/cm2 at 25 °C, and 5.5 × 109 dyne/cm2 at 250°C. The strength of the dried specimen is 4.0 × 109 dyne/cm2 at 250°C and about one half that at 25°C. The thermal expansion coefficient for the cured specimen is 11−14 × 10−5 /°C over a temperature range from 5°C to 350°C. Residual stress is 2.8 × 108 dyne/cm2 at 25°C and one order lower at 350°C.
Electrooptic Materials Requirements for Optical Information Processing and Computing
Authors: Asthana Praveen , Herbulock Edward , Karim Zaheed , Kyriakakis Chris , Nordin Gregory P. , Tanguay Armand R.
Published: March 2011

Photorefractive materials comprise an important category of electrooptic materials, and are important constituent elements in a wide range of devices designed specifically for use in optical information processing and computing systems. Critical issues affecting the development and applicability of photorefractive materials are examined from the perspective of photonic neural network implementations that incorporate photorefractive volume holographic interconnections.
Applications of Organic Electro-Optic Materials in High Speed
Electronic Processors
Authors: Lipscomb G. F. , Lytel R. S. , Ticknor A. J. , Kenney J. , Eck T. E. Van , Girton D. G. , Binkley E.
Published: March 2011

The exceptional electro-optic properties of poled polymer films, coupled
with the power and flexibility of thin film fabrication and
photolithographic processing, may make possible a new class of integrated
optic systems combining the processing power of VLSI with a dense, high
bandwidth, photonic interconnection and switching network. We report on the
recent development and initial test results of two electro-optic polymer
based integrated optic devices for optical interconnection applications. The
first is an optical railtap for the distribution of many different optical
signals from a single CW laser diode, and the second is a traveling wave
Mach-Zehnder integrated optic modulator, which was modulated at frequencies
up to 20 GHz.
Room-Temperature CW Operation of SQW Lasers on Si Grown with
AiGaAs/AlGaP Intermediate Layers by MoCVD
Authors: Egawa T. , Hayashi Y. , George T. , Soga T. , Jimbo T. , Umeno M.
Published: March 2011

The heterointerfaces of single quantum wells (SQWs) and the characteristics
of SQW lasers on Si substrates grown with Al0.5 Ga0
5As/Al0.55Ga0.45P intermediate layers
(AlGaAs/AlGaP ILs) entirely by MOCVD are reported. The surface morphology
and the heterointerfaces of SQWs grown on Si substrates with the
AlGaAs/AlGaP ILs are smoother than those of the two-step-grown sample. The
two-dimensional growth of the AlGaAs/AlGaP ILs on a Si substrate contributes
to obtain the smooth heterointerface. The excellent lasing characteristics
are obtained by the AlGaAs/AlGaP ILs, which are caused by the smooth
heterointerfaces. The lasers grown with the AlGaAs/AlGaP ILs show the
averaged threshold current density of 1.83 kA/cm2 and the
averaged differential quantum efficiency of 51.9 % under cw condition at
room temperature.
Photoconductive Properties Of A GaAs-A1GaAs Quantumwell Infrared
Photodetector
Authors: Ueda Toshiyuki , Shinohara Koji , Miyamoto Yoshihiro
Published: March 2011

We investigated the conduction mechanism and performance of GaAs-A1GaAs
quantum-well infrared photodetectors and proposed a conduction model
consisting of Poole-Frenkel-like emission from wells and carrier relaxation
wells. The model agrees with the measured photocurrent and dark current. The
detector's noise current is given by a simple shot noise formula. Analysis
has shown that the photocurrent and the noise current are inversely
proportional to the barrier width, while the dark current is inversely
proportional to the square of the barrier width.
Growth Condition Dependence Of Rheed Pattern From GaAs (111)B
Surface
Authors: Yang K. , Li W. , Taylor A. P. , Xiao Q.-F. , Schowalter L. J. , Laurich B. K. , Smith D. L.
Published: March 2011

A 3-dimensional phase diagram is introduced to describe the dependence of
the RHEED pattern from GaAs(111)B surface on growth conditions. The 2×2,
transitional(1×1), and √19×,√19 surface reconstructions correspond to
different zones in the phase diagram. A equation is given for the planes
that separate these zones, which fit experimental data well. Homoepitaxial
films on GaAs(111)B grown in the 2×2 region generally have bad crystal
quality as determined by the ion channeling, and growth in the √19×√19
region generally yields rough surface morphology. At higher substrate
temperatures (∼ 650 °C), featureless films with minimum ion channeling
yields of less than 4% are achieved.
Quest for Compact Blue Lasers for Optical
Memories
Authors: Bhargava R. N.
Published: March 2011

A short wavelength laser offers unique opportunities in high density optical
recording as well as in laser printing. To achieve a compact blue laser, the
current effort worldwide is primarily concentrated on achieving
well-conducting p-type ZnSe and fabricating quantum well heterostructures so
as to achieve a low threshold laser at room temperature. The recent
milestone ‘an injection blue laser below room temperature’ gives us
confidence that indeed we are on the right path. In photopumped lasers in
various II-VI heterostructures, thresholds at room temperature comparable to
the theoretical limit have been reported. This not only reinforces that
indeed a room temperature injection laser is possible but when combined with
earlier electron-beam pumped laser results, a scanned compact laser is also
feasible.

In recent years several breakthroughs have demonstrated that an infrared
emitting GaAs laser can be used to generate blue light through efficient
second harmonic generation (SHG) in certain non-linear optical materials.
Recent exciting results on SHG of GaAs lasers in KTP grating waveguides
resulted in a blue laser with output power in the range of several
milliwatts. Alternative schemes such as upconversion lasers and SHG in III-V
quantum wells structures are presented.

In summary, various efforts to achieve compact blue lasers and their
availability in the near future are presented.
P-type Conduction in Bulk ZnSe by Nitrogen
Ion-Implantation
Authors: Jin M. K. , Yasuda T. , Shahzad K. , Merz J. L.
Published: March 2011

P-type conduction in bulk ZnSe has been achieved using 1×1016
cm−2 nitrogen (N) ionimplantation followed by a high
temperature rapid thermal annealing. Room temperature Hall effect
measurements of the sample show that the hole concentration is
∼1×1017 cm−3, and the mobility is ∼30
cm2/V-s. Photoluminescence (PL) measurements were performed to
study the optical behavior of the samples, and the results show that the ion
implantation damage can be partially repaired by thermal annealing at 900°C
or higher. Thermal degradation and recovery of the ion-implantation damage
were studied as a function of the annealing temperature.
Optoelectronic Memory Element with the Application of
Photoconducting and Electroluminescent thin Film Devices
Authors: Porada Zbigniew W.
Published: March 2011

An optoelectronic memory element was constructed from two photoconducting
(PC) and two electroluminescent (EL) devices. Between one EL device and one
PC device an optical feedback was provided, so that these two components
constituted a bi-stable system. Experimental details of preparation of the
PC-EL type thin film systems and results of investigations of the memory
element are presented.
Measurements of Photo-Induced Changes in Conjugated
Polymers
Authors: Seager Carleton H. , Sinclair Michael B. , Branch D. Mc , Heeger A. J. , Baker G. L.
Published: March 2011

We have used the highly sensitive technique of Photothermal Deflection
Spectroscopy (PDS) to measure changes in the infra-red absorption spectra of
MEHPPV, P3HT and Polydiacetylene-4BCMU induced by pumping these polymers
with light above the π - π* transition energy. In contrast to previous
chopped light transmission measurements of these effects, the PDS technique
can directly measure the buildup or decay of the absorption coefficient, m,
on the time scale of seconds to days. In the case of MEHPPV we observe that
above-gap light causes the appearance of a broad infra-red peak in α, which
continues to grow-in hours after the pump light is first applied. For this
polymer the general shape of the absorption spectra in the unpumped state
mimics the photo-induced changes, suggesting that remnant photo-induced
states determine the maximum transparency observed under normal experimental
conditions. For P3HT and to a lesser extent, MEHPPV, we also observe
irreversible photo-induced absorption components which we tentatively
identify with photo-induced oxidation of the polymer matrix.
Subgap Absorption in Conjugated Polymers
Authors: Sinclair M. , Seager C. H. , McBranch D. , Heeger A. J. , Baker G. L.
Published: March 2011

Along with χ(3), the magnitude of the optical absorption in the
transparent window below the principal absorption edge is an important
parameter which will ultimately determine the utility of conjugated polymers
in active integrated optical devices. With an absorptance sensitivity of
< 10-5, Photothermal Deflection Spectroscopy (PDS) is ideal
for determining the absorption coefficients of thin films of “transparent”
materials. We have used PDS to measure the optical absorption spectra of the
conjugated polymers poly[1,4-phenylenevinylene] (and derivitives) and
polydiacetylene-4BCMU in the spectral region from 0.55 eV to 3 eV. Our
spectra show that the shape of the absorption edge varies considerably from
polymer to polymer, with polydiacetylene-4BCMU having the steepest
absorption edge. The minimum absorption coefficients measured varied
somewhat with sample age and quality, but were typically in the range 1
cm-1 to 10 cm-1. In the region below 1 eV,
overtones of C-H stretching modes were observed, indicating that further
improvements in transparency in this spectral region might be achieved via
deuteration or fluorination.
Vibrational Overtone Spectra in Polymeric Thin
Films
Authors: Skumanich Andrew , Moylan Christopiier
Published: March 2011

With the enhanced sensitivity of Photothermal Deflection Spectroscopy (PDS),
vibrational overtone spectra have been obtained in organic thin films for
the first time, covering the range from the near IR to the visible (0.4 - 2
eV). The absorption spectra of polycarbonate, for instance, exhibits C-I1
stretch modes for Δn> I where n is the
vibrational quantum level. Previous measurements were constrained to either
long fibers, which pose the problem of various scattering losses not related
to absorption, or to a restricted wavelength region in the visible
accessible by dye laser sources. The unparalleled sensitivity of PDS allows
precise determination of frequency, lineshape and intensity of the various
modes, even for films ∼10μm thick over a broad energy range. The overtone
spectra can be used as a probe of various basic molecular properties. In a
manner similar to NMR spectroscopy, it is possible to study specific atomic
bonds.
Scanning Tunneling Microscopy Studies of Metal/Metal Epitaxial Growth.
Authors: Chambliss David D. , Chiang Shirley , Wilson Robert J.
Published: March 2011

The morphologies of submonolayer films of Ni, Fe, Au, and Ag deposited on Au(111) at room temperature are studied using scanning tunneling microscopy (STM). The structures of steps and islands on length scales up to ˜3000Å are examined to determine processes of atomic motion and island nucleation. In all cases the deposited atoms move rapidly at room temperature and their aggregation is affected by the Au(111) “herringbone” reconstruction. Ni and Fe aggregate to form island arrays with regular spacing, which are nucleated at “elbow” sites of the herringbone pattern. Au forms fewer islands, showing these atoms are less likely to stick at these elbow sites. Ag forms a complex structure of monolayer-high fingers which reflect the interaction of diffusion-controlled aggregation with energetic differences defined by the reconstruction. These studies make it clear that the final structure of an ultrathin metal film can depend sensitively on fine details of atomic structure in the substrate.
Molecular Dynamics Study of Thermal Disorder in a Bicrystal Model
Authors: Nguyen Tue , Ho Paul S. , Kwok Thomas , Nitta Cynthia , Yip Sidney
Published: March 2011

This work studies a (310) θ = 36.86° <001> symmetrical-tilt bicrystal model using an Embedded Atom Method aluminum potential. Based on explicit results obtained from the simulations regarding structural order, energy, and mobility, we find that our bicrystal model shows no evidence of pre-melting (complete melting below Tm). Both the surface and the grain-boundary interface exhibit thermal disorder at temperatures below Tm, with complete melting occurring only at, or very near, Tm. Concerning the details of the onset of melting, the data show considerable disordering in the interfacial region starting at about 0.93 Tm. The interfaces exhibit metastable behavior in this temperature range, and the temperature variation of the interfacial thickness suggests that the disordering induced by the interface is a continuous transition, a behavior that has been predicted by a theoretical analysis.
Correlations Between Grain Boundary Structure and Energy
Authors: Merkle K. L. , Wolf D.
Published: March 2011

High-resolution electron-microscopy (HREM) and computer simulations of <110> tilt grain boundaries (GBs) in Au are used to investigate correlations between atomic-scale GB structure and energy. The energies calculated for a variety of symmetric and asymmetric GBs suggest that asymmetric GB-plane orientations are often preferred over symmetric ones. The experimentally observed faceting behavior agrees with the computed energies. Computer simulations indicate general interrelations between GB energy and (i) volume expansion and (ii) the number of broken bonds per unit area of GB. These atomic-scale microstructural GB parameters, as evaluated from HREM observations, are compared to simulation results.
The Mechanical Behavior of a Grain Boundary-Rich (Nanocrystalline) Metal
Authors: Mayo M. J.
Published: March 2011

Nanocrystalline copper has been produced by two different techniques -- gas phase condensation and mechanical wear. Both nanocrystalline coppers have hardnesses and strain rate sensitivities that are greater than those of conventional, large-grained copper. These properties differences are tentatively explained on the basis of the two routes by which grain boundaries traditionally influence plastic deformation: by acting as barriers to dislocation glide, and by providing the vacancy sources and sinks necessary to facilitate diffusional flow. Additionally, there are notable differences in the mechanical properties of the two nanocrystalline coppers. Although the materials appear quite similar microstructurally, nanoindentation experiments show that the wear debris is 50% harder and 3 times more strain rate sensitive than the gas phase condensation-produced copper. These differences indicate that the microstructures are probably not as similar as first perceived, and that a previously overlooked microstructural feature may be influencing deformation in one or both of the materials.
Analysis of Brittle Intergranular Crack Propagation During Stress Corrosion
Authors: Jones Russell H.
Published: March 2011

Crack growth rates during intergranular stress corrosion, in materials such as Fe in Ca(NO3)2 at +750 mV (SCE), appear to exceed rates which can occur by dissolution and ion transport within the crack. Brittle crack jumps induced by a corrosion or stress corrosion process, and which magnify the dissolution supported crack velocity by a factor of up to 103, could explain this behavior. Hydrogen can induce these very fast crack growth rates, but these rates have been obtained at electrochemical potentials where H reduction is not thermodynamically possible. Other possible mechanisms for this accelerated crack growth include: 1) intergranularcorrosion altered tearing modulus, 2) grain boundary dealloying, or 3) adsorption induced brittle fracture. Examination of each of these mechanisms suggests that intergranular corrosion could reduce the tearing modulus through changes in the crack shape. However, crack opening analysis clearly shows that the crack tip is shielded from the applied stress intensity and that an embrittlement process which reduces the interface toughness is need for brittle intergranular crack jumps to occur. Further research is in progress to identify the source of this embrittlement.
Structural Relaxation by Precipitation in Al-Li I. Growth Kinetics of Precipitates
Authors: Kamel R. , Gobran N. K. , Danial M. M.
Published: March 2011

Changes in electrical resistance measured by the four probe method was adopted as a structure sensitive physical property used to trace changes in the atomic microstructure below and above the δ'-solvus line in the Al-Li binary alloys. The kinetics of the growth and dissolution of δ' phase (Al3Li) and the formation of δ phase (AlLi), below and above δ'-solvus line, during the coarsening process were studied by isochronal and isothermal investigations. The diffusional growth of δ'-phase, below the δ'-solvus line, was found to be activated by 0.24 eV. Interpretation of the results showed that this energy involved two events during the coarsening process. The first event seemed to be a breakdown of the bonding between the vacancy-Lithium pair and the second event involved the transport of Li atoms to Al-particles to coarsen δ'; (Al3Li) particles. Furthermore, the study of the temperature dependence of electrical resistance of the stable phases δ' and δ of Al-Li alloys was found to be accompanied by difference in the temperature coefficient of the electrical resistance and was attributed to the change in structure of the two phases considered.
Precipitation at Transformation Interfaces
Authors: Khalid F. A. , Edmonds D. V.
Published: March 2011

Alloy carbide precipitation associated with the transformation interface between austenite and ferrite, and austenite and pearlite in steels can result in a fine particle dispersion that can contribute significantly to strength in a wide range of commercial carbon steels. Studies of this precipitation reaction are hindered by the fact that the transformation interface is lost upon cooling to room temperature, either by further transformation or by decomposition of the residual austenite phase to martensite. In the present work this has been avoided by developing an alloy in which the precipitation reaction occurs, but in which the austenite is stabilised to room temperature, thus allowing a detailed examination by TEM and APFIM techniques of the interfacial region.
Grain Boundary Chemistry in Al-Cu Metallizations as Determined by Analytical Electron Microscopy
Authors: Michael J. R. , Romig A. D. , Frear D. R.
Published: March 2011

Al with additions of Cu is commonly used as the conductor metallizations for integrated circuits (ICs). As the packing density of ICs increases, interconnect lines are required to carry ever higher current densities. Consequently, reliability due to electromigration failure becomes an increasing concern. Cu has been found to increase the lifetimes of these conductors, but the mechanism by which electromigration is improved is not yet fully understood. In order to evaluate certain theories of electromigration it is necessary to have a detailed description of the Cu distribution in the Al microstructure, with emphasis on the distribution of Cu at the grain boundaries. In this study analytical electron microscopy (AEM) has been used to characterize grain boundary regions in an Al-2 wt.% Cu thin film metallization on Si after a variety of thermal treatments. The results of this study indicate that the Cu distribution is dependent on the thermal annealing conditions. At temperatures near the θ phase (CuAl2) solvus, the Cu distribution may be modelled by the collector plate mechanism, in which the grain boundary is depleted in Cu relative to the matrix. At lower temperatures, Cu enrichment of the boundaries occurs, perhaps as a precursor to second phase formation. Natural cooling from the single phase field produces only grain boundary depletion of Cu consistent with the collector-plate mechanism. The kinetic details of the elemental segregation behavior derived from this study can be used to describe microstructural evolution in actual interconnect alloys.
Grain Boundary Structure and Diffusion Induced Grain Boundary Migration
Authors: King A. H.
Published: March 2011

We present a review of systematic studies of diffusion induced grain boundary migration (DIGM). The results are compared with structural models for the grain boundaries in order to assess the effects of structure upon DIGM. The nucleation of DIGM is also assessed in the light of grain boundary structure and it is demonstrated that changes of grain boundary solute concentration can induce large enough energy changes to drive novel grain boundary dissociation reactions.
Ultra-Fast Melting and Solidification Behaviour of Amorphous and Crystalline Silicon
Authors: Cullis A.G. , Webber H.C. , Chew N.G.
Published: March 2011

Subnanosecond ultra-violet radiation pulses are used to produce relatively thick, large area amorphous layers onSi crystals by transient melting and solidification. The different behaviours of (001) and (111) Si orientations are highlighted. Observations of crystal growth phenomena during solidification at velocities lower than required for amorphization are correlated with theoretical predictions. Computer modelling of heat flow in amorphous silicon is refined.
Raman Scattering in Ultra Heavily Doped Si and Ge: The Dependence on Free Carrier and Substitutional Dopant Densities
Authors: Compaan A. , Contreras G. , Cardona M. , Axmann A.
Published: March 2011

We present the results of a systematic study of phonon softening due to free electrons and holes in extremely heavily doped Si and Ge. Metastable concentrations of Bi, Sb, As, P, Al and B were implanted and pulsed laser annealed (ruby or XeCl) to produce substitutional concentrations up to 4×1021 cm−3 . We find softening of the zone center optic phonon of as much as ˜5% in p-type Ge, ˜5.4% in p-type Si, and 2% in n-type Si. The shifts are explained by phonon coupling to single particle electronic excitations. In addition we discuss the density dependence of the Raman-active vibrational local modes of P and Al in Ge and of B in Si which we demonstrate can provide a convenient measure of substitutional concentrations of these low mass dopants.
Instability at the Melting Threshold of Laser Irradiated Silicon as the Underlying Origin of the Ripples Formation
Authors: Combescot M. , Bok J. , Guillaume C. Benoit A La
Published: March 2011

The increase of reflectivity associated with a strong decrease of the laser penetration depth at the melting threshold of laser irradiated silicon induces a symmetry breaking with formation of a mixture of solid and liquid regions. We present a steady state solution in the case of solid and liquid stripes and we show that the liquid regions are slightly hotter than solid ones in contradiction with the previous idea of an undercooled liquid. The pattern size has to be smaller than a critical value of the order of the laser penetration depth, and can be selected by additional interference and diffraction effects.
Initial Obsevation of the Crystal-Amorphous Transition and the Formation of Ripple Patterns on Silicon Induced by 7 ps Pulses at 1.05 µm
Authors: Boyd Ian W. , Moss Steven C. , Boggess Thomas F. , Smirl Arthur L.
Published: March 2011

We describe our preliminary observations of the interaction of short pulse 1 µm radiation with crystalline silicon. In particular we find that for 7 ps pulses, but not for 46 ps pulses, the crystal-amorphous transition can be induced on the Si surface. Additionally, we have measured the single shot melting threshold for c-Si to be 0.6 ± 0.2 J cm-2 for 7 ps pulses. The formation of ripple patterns and other surface structures with pulses as short as 4 ps is also reported.
Wetting Angles and Surface Tension in the Crystallization of Thin Liquid Films
Authors: Yablonovitch Eli , Gmitter T.
Published: March 2011

The behaviour of thin liquid films is known to be dominated by surface tension forces. We show that the crystallization of thin liquid films requires that two wetting angle conditions be simultaneously satisfied: (i) relating to the liquid–vapour interface and (ii) relating to the crystal–liquid interface. The balance between capillary pressure and thermal gradient forces shows that the equilibrium freezing point of thin films is actually depressed below the bulk freezing point. The magnitude of the effect is 1°K in an 800 Å thick film. These observations suggest that small–scale thickness fluctuations may be responsible for the initiation of sub–grain boundaries in the growth of crystalline silicon films.
Formation of Buried Oxide in Silicon by High-Dose Oxygen Implantation, and Application of this Technology to CMOS Devices
Authors: Izumi K. , Omura Y. , Nakashima S.
Published: March 2011

SIMOX (Separation by Implanted Oxygen) technology has been developed for realization of oxygen-ion implanted SOI. The distribution of implanted oxygen was analyzed by Auger electron spectroscopy and Rutherford backscattering spectroscopy. The properties of the silicon oxide formed by oxygenion implantation were investigated by infrared spectra, capacitance-voltage characteristics, dielectric strength, and dielectric constants. The crystallinity of the top layer silicon and of the epitaxially-grown silicon layer was deter mined by electron-beam diffraction. An electric-field-shielding effect was observed in the polycrystalline silicon region which was formed between the top layer silicon and the buried oxide. High-speed digital and high-voltage analogue CMOS LSIs, a 1kb CMOS RAM and a BSH LSI, were successfully fabricated using SIMOX technology.
Comparison of Pulsed Laser and Furnace Annealing of Nitrogen Implanted Silicon
Authors: Smith T. P. , Stiles P. J. , Augustyniak W. M. , Brown W. L. , Jacobson D. C. , Kant R. A.
Published: March 2011

Formation of buried insulating layers and redistribution of impurities during annealing are important processes in new semiconductor device technologies. We have studied pulsed ruby laser and furnace annealing of high dose (D>1017 N/cm2) 50 KeV nitrogen implanted silicon. Using He Back scattering and channeling, X-ray diffraction, transmission electron microscopy, and infrared transmission spectroscopy, we have compared liquid and solid phase regrowth, diffusion, impurity segregation and nitride formation. As has been previously reported, during furnace annealing at or above 1200C nitrogen redistributes and forms a polycrystalline silicon nitride (Si3N4 ) layer. [1–4] In contrast, pulsed laser annealing produces a buried amorphous silicon nitride layer filled with voids or bubbles below a layer of polycrystalline silicon.
CW Laser Crystallization of Soi Thermal analysis of the most critical parameters
Authors: Hode J.M. , Joly J.P. , Jeuch P.
Published: March 2011

We present an overview of the thermal modeling of CW laser induced crystallization of SOI. The dynamical case for a three-layer structure is derived. Effects of the phase change (increase in reflectivity, latent heat) are also treated. Analytical expressions are given and the models are compared to experiment.
Electron-Beam Recrystallization of Silicon Layers on Silicon Dioxide
Authors: Inoue Tomoyasu , Shibata Kenji , Kato Koichi , Yoshii Toshio , Higashinakagawa Iwao , Taniguchi Kenji , Kashiwagi Masahiro
Published: March 2011

Recent progress of SOI growth by electron beam recrystallization is described. Transient temperature profile on the recrystallizing sample surface was analyzed experimentally by direct observation with a thermovision, which is essential for the understanding of crystal growith mechanism. SOI growth was performed by a spot beam annealing and a pseudo-line shaped beam annealing. The line shaped electron beam has been proved to be useful for large area crystallization.

Emphasis was placed on lateral seeded recrystallization of silicon layer evaporated in an ultra high vacuum. Silicon layers with the seed area grown epitaxially during the evaporation and above 1 μm thickness were successfully recrystallized, resulting in reproducible lateral epitaxiy. The pseudo-line shaped electron beam formed by very high frequency oscillation enabled dimensional enlargement of lateral epitaxial growth. crystalline properties were characterized by analyses of Rutherford backscattering and electron channeling pattern.
Preparation of GaAs Soi and its Laser Recrystallization
Authors: Xiqiang LI , Zhihao Chen , Chenglu Lin , Weiyuan Wang
Published: March 2011

GaAs SOI consisting of a sputtered GaAs film on a SiO2 −Si or sapphire substrate is irradiated by CW Ar+ laser beam with a view to investigating its recrystallization. Using AES, x-ray diffraction, TEM and ED, we have studied the compositions, crystal orientations and grain size of the laser-irradiated GaAs films. The possible application of GaAs SOI to devices is discussed on the basis of the experimental results.
Luminescence Spectroscopy on Highly Excited Si - Experimental Determination of the Plasma Drift Velocity
Authors: Laurich B. , Forchel A.
Published: March 2011

The emission spectra of the electron-hole plasma created at the surface of a Si sample by intense laser pulses (65 ns or 400 ps) are investigated. It is shown that the plasma drift is necessary for a consistent interpretation of the luminescence line shape and the energetic position of the line. We determine average densities up to 2.1019 cm−3 for 300K and typical drift velocities up to 4.106 cm/s.