bluuebunny/crossref_metadata_2025_split huggingface dataset:
Thin Film Transistors Made From Hydrogenated Microcrystalline Silicon
Authors: Wang K. C. , Chen B. Y. , Hsu K. C. , Yew T. R. , Hwang H. L. 
Published: March 2011

ABSTRACTMicrocrystalline silicon films were deposited by diluted-hydrogen method and hydrogen-atom-treatment method at 250°C in a plasma enhanced chemical vapor deposition system and they were characterized by nuclear magnetic resonance, Raman spectroscopy, and optical bandgap Measurements. One-Mask a-Si:H thin film transistors (TFT's) were fabricated with those microcrystalline materials as the channel layer. The highest electron mobilities of the TFT's fabricated by diluted-hydrogen method and hydrogen-atom-treatment method were 1.23 and 1.04 cm2/V•s, respectively without any thermal treatment steps.
Stress Relaxation In Metals And Polymers: Theory, Experiment And Computer Simulations
Authors: Brostow Witold , Kubát Josef , Kubát Michael J. 
Published: March 2011

ABSTRACTThere exist large amounts of experimental evidence on stress relaxation for metals and their alloys, synthetic and natural polymers, glasses and frozen non-polymeric organic liquids. The results, typically presented as curves a (log t) of relaxation of stress aas a function of logarithmic time t, exhibit common features, apparently independent of the type of Material. All curves consist of three regions: initial, nearly horizontal, starting at σ0; central, descending approximately linearly; and final, corresponding to the internal stress σi = σ(>). We discuss briefly the experimental evidence as well as the main features of the cooperative theory which does not involve specific features of different classes of Materials. The bulk of the paper deals with computer simulations. Simulation results obtained with the method of molecular dynamics are reported for ideal metal lattices, Metal lattices with defects, and for polymeric systems. In agreement with both experiments and the cooperative theory, the simulated σ (log t) curves exhibit the same three regions. In agreement with the theory, the slope of the simulated central part is proportional to the initial effective stress σ0* = σ0 - σi. The time range taken by the central part is strongly dependent on the defect concentration: the lower the defect concentration, the shorter the range. IMposition in the beginning of a high strain ε destroys largely the resistance of a material to deformation, resulting in low values of the internal stress σo. Since the cooperative theory assumes for particles (atoms, polymer chain segments) the existence of two states, unrelaxed and relaxed, and has a formal connection to the Bose-Einstein (B-E) distribution, we first simulate B-E systems, recording the formation of relaxed clusters of particles of different sizes. Differences in cluster sizes predicted from a B-E Model and those obtained from the simulations are recorded and analyzed. On the joint basis of experimental, theoretical
The Effect of Substrate on the Microstructure and Mechanical Behavior of Eutectic Indium-Tin
Authors: Goldstein J. L. Freer , Morris J. W. 
Published: March 2011

AbstractThis study was conducted in order to determine and understand the effect of substrate on eutectic In-Sn. Samples for mechanical testing were produced with either bare Cu or Ni on Cu substrates. Both the microstructure and the mechanical behavior are strongly dependent on substrate, with In-Sn on Cu having a non-uniform and irregular microstructure and In-Sn on Ni having a uniform, normal colony-based eutectic. Deformation is more uniform in the In-Sn on Ni, while it is concentrated along the length of the joint in the In-Sn on Cu. This is reflected in the different shapes of stress-strain curves between In-Sn on Cu and In-Sn on Ni. The stress exponents and activation energies for creep also vary with substrate. Creep deformation is governed by the In-rich γ phase for In-Sn on Cu and by the Sn-rich y phase for In-Sn on Ni. If In-Sn on Ni samples are aged, the microstructure coarsens and the mechanical behavior changes to resemble that of the as-cast In-Sn on Cu.
Mössbauer Parameters Describing Several Intermetallic Phases in Tin-Containing Solders
Authors: Reno Robert C. , Takacs Laszlo 
Published: March 2011

AbstractWe report here on the Mbssbauer parameters of two intermetallic phases expected to be present in composite solders: the Cu9Sn3Ni phase present in some forms of eutectic Sn-Pb solders and the Ag-Sn (ζ) phase which may be present in lead-free solders containing appreciable amounts of silver. Both samples were prepared by mechanical alloying techniques.Our results show that the isomer shift of the Ag-Sn ζ phase is + 2.13 mm/sec relative to SnO2 and the phase has a room-temperature recoilless fraction that is 36% of that of SnO2. The results for Cu9 Sn3Ni are an isomer shift of + 1.78 mm/sec and a recoilless fraction 58 % of that of SnO2.
Fluence Dependence of Excimer Laser Ablation of Ain
Authors: Lumpp Janet K. , Coretsopoulos Christopher N. , Allen Susan D. 
Published: March 2011

AbstractAluminum nitride has been ablated with a KrF excimer laser (248 nm) at fluences from 1 to 60 J/cm2. Ablation depth, emission spectra and photothermal beam deflection were detected as a function of fluence. An ablation rate of 0.2 μm/pulse was achieved above 30 J/cm2 in vacuum. Ablation rate decreased with decreasing, fluence. Irradiated surfaces have a conductive metallic layer of reduced aluminum nitride. At low fluences, the metallic surface layer was spotty within the area of the laser beam. Below the fluence threshold for producing the metallized surface, emission spectra and photothermal beam deflection were still detected. Emission lines from Al, Al+ and Al-N were observed. Photothermal deflection data was used to calculate supersonic velocities for shock waves propagating from the sample surface. Shock waves resulted from rapid heating near the surface and expansion of ablated material from the laser spot.
Material and Reliability Considerations for Anisotropically Conductive Adhesive Based Interconnects
Authors: Dion J. , Borgesen P. , Yost B. , Lilienfeld D. A. , Li C.-Y. 
Published: March 2011

AbstractAn adhesive based interconnect design in which the contact force between a bumped die and substrate is maintained by the shrinkage stress of the adhesive was investigated for use in high performance applications. In general, heating will reduce the contact force because of the differential thermal expansions and load relaxation in the adhesive. Special experimental techniques have been developed to measure the relevant materials properties. The potential for optimization in terms of materials selection is discussed.
High Temperature Polyimide Nanofoams
Authors: Charlier Y. , Russell T. P. , Hedrick J. L. 
Published: March 2011

AbstractA means of generating high temperature polymer foams which leads to pore size in the nanometer regime has been developed. Nanofoams were prepared by casting block copolymers comprised of a thermally stable block and a thermally labile material, where the thermally stable material forms the matrix in which thermally labile material is dispersed. Triblock copolymers comprised of high Tg, amorphous polyimide matrices with poly(propylene oxide), as the thermally decomposable coblock, were prepared. The copolymer synthesis was carried out through either the poly(amic alkyl ester) or poly(amic acid) precursor and subsequent cyclodehydration to the polyimide by either thermal or chemical means, respectively. Microphase separated morphologies were observed for all copolymers, irrespective of the block lengths surveyed, by dynamic mechanical analysis. Upon heating, the poly(propylene oxide) underwent thermolysis leaving pores where the size and shape of the pores were dictated by the initial copolymer morphology. A 5 to 15% reduction in density was observed consistent with the generation of a foam.
Electrical Characterization of Low Dielectric Constant LCP Composite Films
Authors: Walpita L. M. , Lundberg G. , Stamatoff J. 
Published: March 2011

AbstractA variety of low dielectric constant composites have been made into films and characterized. These composites were blends of liquid crystalline polymers (LCPs), hollow glass spheres (HGS) and polytetrafluoroethylene (PTFE). By adjusting the percentage compositions of the various components of the composites, the dielectric constant could be adjusted in the range 2.4 to 3.4. Measurement of the dielectric constant by Time Domain Reflectometry (TDR) and Frequency Domain Reflectometry (FDR) are discussed. Dielectric anisotropy is also discussed. The experimentally observed results are compared with those derived theoretically.
Moisture Absorption and its Effects on the Performance of Printed Circuit Materials
Authors: Liu P. C. , Wang D. W. , Fuerniss S. J. , Poliks M. D. , Obrzut J. , Siperko L. M. , Chen W. T. , Havens R. D. , Murcko R. M. 
Published: March 2011

AbstractPolymers have found wide usage in microelectronics industry. Their moisture absorption properties cause the concern of reliability without hermeticity (RwoH). For printed circuit packages, the lamination process, the components assembly, and the field performance of final product are strongly influenced by the presence of high level moisture content. For instance, moisture is an important factor in the development of internal shorts through metal migration when printed circuit package is in service. Moisture can also cause dimensional changes in printed circuit cores and delamination during the soldering processes in components assembly, resulting in manufacturing yield loss and defects. Understanding moisture properties of resins and the resin glass composites are therefore important in developing a strategy to control the moisture content of final products. This paper will discuss the moisture fundamental properties of two resins and their resin glass systems. These properties will be related to their assembly and reliability performance.
Factors Affecting Metal/Polymer Interface Durability in Microelectronics Packaging: Chemistry and Water Uptake
Authors: Clearfleld H. M. , Furman B. K. , Callegari A. , Graham T. , Purushothaman S. 
Published: March 2011

AbstractDurability of metal/polymer interfaces is essential for the long-term reliability of high performance microelectronics packages. Such interfaces undergo stresses during production and in service. In this work, we report on the durability of interfaces formed between reactive metals and polyimides (PI) that have been subjected to stresses simulating both types of environment. The P1 surfaces were treated by Ar RF plasmas prior to metal deposition, and durability was determined by measuring the 90 degree peel strength as a function of environmental exposure. The durability of Cr and Ti/PMDA-ODA interfaces through processing stresses (i.e., large thermal excursions) depends on the PI surface modification and the metal reactivity. For both, we observed interfacial degradation due to oxidation of the metal–the cause is water absorbed by the polyimide. These studies, coupled with water transport measurements, suggest that the physical structure of the interface is the dominant factor. To determine the durability under service environmental stresses (e.g., temperature/humidity), we correlated peel strengths with interfacial chemistry and water uptake. In this case, Ar and O2plasmas were used. For Ta/BPDA-PDA, the durability depends on the type of plasma treatment. Ar-treated specimens maintain strength through 500 hours T/H stressing whereas those treated by O2plasma alone fail at 165 hours. The differences here can be explained by the interfacial chemistry–Ta/Ar-etched surfaces form a stable TaG-like structure whereas the Ta/O2-etched surfaces form a metastable, sub-oxide structure that transforms to Ta2O5during stressing. Ta/PMDA-ODA interfaces fail readily under these conditions due to the increased water uptake of the PI.
Investigations of Curing Chemistry and Hydrolytic Stability of Polyimide - on - Metal Interfaces
Authors: Cumpston B. H. , Nagarkar P. V. , Cornella G. , Volfson D. , Trusell F. , Jensen K. F. , Senturia S. D. 
Published: March 2011

AbstractPolyimide-on-metal interfaces relevant to electronics packaging applications have been studied by Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). Two polyimides with different backbone structures were considered: (i) biphenyltetracarboxylic dianhydride (BPDA) - p-phenylene diamine (PDA) and (ii) 4,4′-(hexafluroisopropylidene)-bis(phthalic anhydride) (6FDA) - 4,4′-bis(4-aminophenoxy) biphenyl (APBP). Thin polymer films (10–100 nm) were cured on Al, Cr and Cu surfaces at different temperatures to allow probing of chemical interactions by surface spectroscopies. Anhydride intermediates were detected on all three substrates for both polyimides. Carboxylate intermediates were detected in BPDA-PDA films on Cr and Cu and resulted in increased adhesion at these interfaces. XPS data revealed a nitrogen deficiency at the BPDAPDA/Cr interface. A mechanism explaining the formation of this intermediate and the deficiency of nitrogen is proposed. Hydrolytic stability of the interface was investigated using ex situ total internal reflection FTIR spectroscopy and XPS. The results show that the fluorinated polyimide, 6FDA-APBP, is more stable than BPDA-PDA when treated at 85 °C and 85% relative humidity for 100 hours.
Theoretical Modelling of Polymer Metallization: an Assessment of Bonding Mechanisms that Effect the Formation of Stable Metal Overlayers
Authors: Jansen S. , Palmieri M. , Grabania S. , Whitwell G. 
Published: March 2011

AbstractIn this work, we present a systematic approach to the problems in polymer metallization. There are three main components to our study which include: assessment of the limits of metal polymer interaction, consideration of metal-metal interaction or aggregration at the interface limit, and modification of the copper surfaces to increase reactivity. All of these phenomena are assessed through application of semi-empirical electronic structure calculations with the ultimate objective being to effect a strategy for better metal deposition with the primary metal being copper. Polymer models include polyimide, epoxy resins, polyolefin ketones, and nitrile functionalized polymers. In the first component study, orbital interactions which affect adhesion are compared for a variety of polymer models and transition metals. This initial study is then extended to consider the potential for metallization by consideration of competition of metal-polymer interactions and metal-metal interactions as a metal lattice “grows” at the metal/polymer interface. Finally modification of the metal/polymer interface is assessed by considering the effect of oxidation or codeposition of dissimilar metals to augment the electronic properties and thus affinity of copper for the polymer. The general trends produced in this work are consistent with experimental measurements of adhesion and have been validated by spectral measurements. This work clearly shows the molecular level limitations of polymer-metal interactions for a series of important systems.
An Adhesion Study of Copper and Chromium Films to Polyimide
Authors: Chung T. G. , Yu Jin , Kim Y.-H. , Ahn E. C. , Park I. S. 
Published: March 2011

AbstractAdhesion of Cu and Cr to polyimide was studied by 90° peel test, AES, and X-ray diffraction. The two necessary conditions of the high adhesion strength were the presence of Cr interlayer and the preactivation of the polymer surface by RF plasma treatment. The Cr is thought to react with activated polyimide to form carbide-like bonds which enhance the adhesion strength drastically. Correlations between the peel strength and C260/Cr527 Auger PHR from the peeled metal strip were good. Qualitatively, the peel strength is related to the amount of plastic deformation done on the metal strip during peeling.
Micromechanical Testing of Electronic Packaging Components and Materials
Authors: Li C.-Y. , Yost B. , Korhonen M. A. , Dion J. 
Published: March 2011

AbstractMechanical modelling of microelectronic packages for design optimization requires the quantitative knowledge of a large number of physical parameters. Because of the composite nature of many components, and because relevant materials properties in the microscale often deviate from the bulk values, there is therefore a need for a variety of micromechanical testing techniques. These techniques include tension, compression, shear, bending, and fatigue testing of samples with sizes in the 10 micron range. A novel technique has been developed for the testing the z-direction properties of thin films with displacements in the sub-micron range. Mechanical properties of thin films and surface regions may advantageously be probed by a continuous microindentation tester. All elastic properties of both isotropic and anisotropic packaging materials and components may be evaluated directly by the above methods, and the inelastic deformation behavior determined over many orders of magnitude of strain rate by load relaxation measurements. The above techniques and examples of their application will be discussed.
Mechanical and Accelerated Testing of Flip Chip Interconnect Systems
Authors: Subrahmanyan Ravi 
Published: March 2011

AbstractFlip chip interconnect systems are becoming increasingly popular in the electronics industry due to their low profile and high densities. During temperature cycles, the differential expansions between various assembly members of a flip chip interconnect system produce mechanical stresses that are the driving force for failures. Such failures can be a significant reliability concern.Accelerated test methodologies for flip chip interconnect systems assess the reliability of existing interconnects and identify potential reliability concerns in future interconnect designs. Traditionally, such methodologies have relied on test methods such as temperature cycling to determine the mechanical integrity of the flip chip interconnect. However, application of such methods to new interconnect materials, geometry and processes requires characterization of basicmechanical behavior of the interconnect system.In this work, the feasibility of using a micromechanical test methodology for flip chip applications is examined. 90PbSn solders is used as an example. The data obtained from such flip chip solder interconnects is validated using a damage integral methodology. The measured data is shown to adequately describe published thermal stress profiles and thermal fatigue life data measured using solder joints of the same composition. Finally, some considerations in the application of micromechanical measurements to determination of acceleration factors and development of accelerated test methods are discussed.
Characterization of Mems Actuators Via Nanoindentation
Authors: Glumac D. E. , Rizq R. N. , Robbins W. P. , Polla D. L. , Nelson J. C. 
Published: March 2011

AbstractNanoindentation has been used to characterize polycrystalline silicon serpentine structures which will become the “framework” for piezoelectric meander line microactuators. These structures are fabricated using silicon wafer surface micromachining processing techniques, and they are suspended about 1 micron above the wafer surface. Normally, nanoindentation equipment is used for materials scratch-testing; however, this equipment was modified so that a probe tip could make contact to the sides of the meander lines, thus enabling known forces to be applied parallel to the wafer surface. For one type of device, the nanoindentaion technique yielded a spring constant of 400 N/m, while simple beam theory gave 1300 N/m and the finite element analysis software ANSYS gave 1200 N/m. This measurement technique holds the promise of being able to apply a known force and then countering that force with piezoelectric actuation to determine the forces that future piezoelectric microactuators will be able to provide.
Determination of Shear Stress at a Solder Paste/Stencil Interface
Authors: Head Linda M. , Rogers Vincent , Sahay Chitteranjan , Constable James 
Published: March 2011

AbstractTo create a model for the release process of solder paste during stencil printing for surface mount applications it is necessary to determine the shear stress developed at the interface between the solder paste and stencil sidewall. An experiment has been developed to determine the value of the shear stress for solder paste samples. For the purpose of this experiment a Micro-mechanical tester has been adapted and programmed to provide both a shear thinning cycle and a pull-off cycle that simulate aperture fill and stencil lift-off. The shear stress developed at the solder/stencil-sidewall interface is estimated from the data obtained during the pull-off portion of the Micro-mechanical test procedure. The micro-mechanical tester is fitted with a set of parallel plates that can be adjusted for plate separation and surface roughness.The experiment consists of two parts: (1) the shear thinning cycle and (2) the horizontal pull-off. After application of the solder paste and adjustment of plate separation, a back and forth movement of the upper plate provides shear thinning of the paste. This step is necessary to simulate the shear thinning that occurs from the application of squeege pressure during aperture fill. The horizontal pull-off then simulates the lift-off step of the stencil printing procedure. During the horizontal pull-off data is. taken which allows calculation of the force developed as the upper plate is pulled away from the lower. Results from this experiment show the values of shear stress that develop during pull-off with a variation of surface treatments and plate separations.This paper will present the experimental set-up, a description of the relationship between this experiment and the actual stencil lift-off process, and shear stress data that has been acquired for a variety of solder pastes and plate separations.
The Use of Gravure Offset Printing in the Realisation of Fine Line Thick Film Conductors
Authors: LeppÄvuori S. , VÄÄnÄnen J. , Lahti M. , Kukkola K. , UusimÄki A. 
Published: March 2011

ABSTRACTThe use of gravure offset printing to transfer film patterns from an inked plate to the substrate by a silicone rubber pad has been shown to have promising advantages in fine line and multilayer production. The technology is now moving into the field of electronics manufacturing. By optimising the printing parameters and ink characteristics in the gravure offset technique, lines and spaces as narrow as 50 μtm were achieved and even finer lines are possible. Commercially available fine line thick film Au and Ag pastes were modified for this purpose. The thickness of sintered conductors ranged from about 2 to 11 μtm depending on ink viscosity, control of printing equipment and repetition of prints. When compared with films deposited by conventional thick film technology, the conductivity and adhesion on alumina were similr. The small interconnections between conductors through the insulator layer necessary in multilayer techniques were realised using gravure offset printing to coat excimer laser drilled vias. Interconnection diameters of less than 100 μtm were achieved.
In situ and Ex situ Applications of Spectroscopic Ellipsometry
Authors: Woollam John A. , Johs Blaine , McGahan William A. , Snyder Paul G. , Hale Jeffrey , Yao Huade Walter 
Published: March 2011

AbstractWe briefly review the optics of ellipsometry, followed by discussions of a series of example applications of the technique including single films on a substrate; multilayer stacks common to silicon integrated circuit fabrication; flat panel display materials, and in situ semiconductor growth and deposition control.