bluuebunny/crossref_metadata_2025 huggingface dataset:
Microfields Induced by Random Compensated Charge Pairs in Ferroelectric Materials
Authors: Crowne Frank J. , Tidrow Steven C. , Potrepka Daniel M. , Tauber Arthur
Published: June 2019

The dc and microwave responses of the BaxSr1-x (X,Y)yTi1-yO3 family of ferroelectric compounds with various substitutional additives X3+, Y5+ are analyzed by combining the random-field technique with the mean-field (Landau-Devonshire) theory of ferroelectricity, along with a self-consistent computation of the dielectric constant of the host material in the presence of the impurity fields. The fields in the material are assumed to arise from charge compensation at the Ti4+ sites, leading to permanent dipoles made up of the resulting positive and negative ions separated by a few lattice constants. It is shown that whereas completely random placement of positive and negative ions generates a Holtsmark distribution of electric field, with infinite second moment and hence extremely large fluctuations in field strength, the association of ionized impurities into permanent dipoles leads to much lower fluctuations in field and a distribution with finite second moment, which makes a self-consistent dielectric constant meaningful.
An S-Band Reflection-Type Phase Shifter - A Design Example Using Ferroelectrics
Authors: Kim Dongsu , Choi Yoonsu , Allen Mark G. , Kenney J. Stevenson , Stollberg David W. , Kiesling David
Published: June 2019

One of the challenges faced in using ferroelectrics in high frequency devices is how to effectively use the material in a circuit design. A compact reflection-type phase shifter fabricated on sapphire substrates coated with ferroelectric barium strontium titanate (BST) thin-films has been built which shows the promise of using BST thin films in the design of tunable microwave devices. The phase shifter, fabricated as one monolithic assembly, consists of a 3dB coupler, meandered line inductors and tunable interdigital capacitors. A continuously variable phase shift range of more than 100° using the branch-line coupler was obtained at a center frequency of 2.95 GHz, and more than 90° phase shift over 200 MHz bandwidth with a bias voltage range from 0 V to 175 V. The phase shifter using the Lange coupler has over 700 MHz bandwidth centered at 2.2 GHz with a phase shift of more than 90° and an insertion loss less than 2 dB and return loss of greater than 14 dB, over a bias voltage range from 0 V to 160 V. The loss of the BST phase shifter presented in this work is on the order of other commercially available RF front-end components, such as bandpass filters and RF switches. This holds promise for the practical realization of smart antenna systems in cellular handsets and wireless LAN cards.
The Dependence of Dielectric Properties on Composition Variation in Ba0.6Sr0.4(YTa)yTi1-2yO3
Authors: Potrepka Daniel , Tidrow Steven , Tauber Arthur , Kirchner Kevin , Ervin Matthew , Deb Krishna , Rod Bernard , Crowne Frank
Published: June 2019

Ba0.6Sr0.4(YTa)yTi1-2yO3 has been shown to have properties which are promising for tunable applications requiring low dielectric constant [1]. Ba0.6Sr0.4(YTa)yTi1-2yO3 with y ≤ 0.10 has been synthesized and well-characterized using x-ray diffraction, EDAX, and Raman Spectroscopy. The dependence of the dielectric properties on concentration, y, of Y and Ta are discussed along with implications for improved performance in device applications.
Dielectric and Room Temperature Tunable Properties of Mg-doped Ba0.96Ca0.04Ti0.84Zr0.16O3 Thin Films on Pt/MgO
Authors: Kalkur T.S. , Yi Woo-Chul , Philofsky Elliott , Kammerdine Lee
Published: June 2019

Mg- doped Ba0.96 Ca0.04 Ti0.84Zr0.16O3 (BCTZ) thin films were fabricated on Pt/MgO substrate by metallorganic decomposition method. The structure of the films were analyzed by x-ray diffraction. The electrical measurements were performed on metal-ferroelectric-metal capacitors with platinum as the top and bottom electrode. The dielectric properties were improved after the capacitors were post annealed at 700 °C in oxygen atmosphere for 30 min. A high dielectric constant of 504 and a dissipation factor of less than 4% was obtained at 1 MHz. The Pt/BCTZ/Pt/MgO capacitors exhibited high tunability of 55% at an applied field of 55 kV/cm.
Microwave Phase Shifters Using Ferroelectric (Ba,Sr)TiO3 Films
Authors: Kim Won-Jeong , Kim Eun-Kyoung , Moon Seung-Eon , Han Seok-Kil , Lee Su-Jae , Kang Kwang-Yong
Published: June 2019

The ferroelectric (Ba0.6Sr0.4)TiO3 (BST) films were prepared on (001) MgO single crystals by pulsed laser deposition. Coplanar waveguide (CPW) type phase shifters controlled by external dc bias field were fabricated on BST films using a 2 μm thick metal layer to reduce metal loss. Microwave properties of the CPW phase shifter were measured using a HP 8510C vector network analyzer from 0.1 – 20 GHz. The fabricated CPW phase shifters (8 mm long) exhibited differential phase angle of 100 ° at 10 GHz with a dc bias field of less than 80 kV/cm between center and ground conductors. Furthermore, a stable differential phase angle (102 ± 3.5 o) was observed from another CPW while changing the power of incident microwave from -10 to +30 dBm. Gap size dependent dielectric constant of the BST film was observed and a simple correction method was suggested in the paper. These results demonstrate the possible application of ferroelectric tunable devices on a high power tunable wireless telecommunication.
Extracellular Matrix Molecules Involved in Barnacle Shell Mineralization
Authors: Fernández María S. , Vergara Italo , Oyarzún Alejandro , Arias José I. , Rodríguez Renato , Wiff Juan P. , Fuenzalida Víctor M. , Arias José L.
Published: June 2019

Austromegabalanus psittacusis a large (normally up to 30 cm high) sessile balanomorph barnacle from the coast of Chile and South Peru. Its hard shell is composed of twelve calcareous side plates, six parietes and six radii, joined in the form of a truncated cone opened at the top. Plates rest on a basal disk firmly cemented to the substratum. Although the crystalline microstructure of barnacle's shell has been studied to some extent, its organic composition and the mechanisms governing the biomineralization of such highly ordered nanocomposite have remained obscure. By using X-ray diffraction, infrared spectrometry, SEM and TEM electron microscopy, histochemistry, immuno-histochemistry and -ultrastructure, biochemistry and a crystallization assay, we have studied the cell-shell interactions, the crystalline microstructure of the inorganic moiety and the localization of particular macromolecules, and tested their influence on crystallization.The mineral of the plates and basal disk was calcite showing a (104) preferential orientation. Plates were not solid but porous. While parietes have longitudinal canals (from the base to the apex), radii have transversal canals arranged parallel to the base. These canals are not in the center of the plates but displaced to the outside of the shell delimiting a thinner solid outer lamina and a thicker inner one. The inner lamina consisted of parallel calcified layers separated by organic sheets. These sheets showed autofluorescence and consisted of chitin surrounded by proteoglycans and other minor proteins, which seems to be responsible for the fluorescent behaviour. These organic sheets were also organized as several concentric rings around the canals. The shell matrix obtained after decalcification, which surrounded the crystals, also contained a loose net of such proteoglycans. Mantle epithelial cells covered the entire surface of the inner side of the inner lamina and extend to the plate canals. While isolated chitin did not promote or alter calcite crystallization, the proteoglycan-rich fraction dramatically modified crystal morphology and size. As we have demonstrated in another model of biomineralization, such as the eggshell, hereby we suggest that these structured polyanionic proteoglycan moieties could also be part of the regulatory mechanisms of the barnacle shell mineralization.
Mechanical and Microstructural Properties of Stratum Corneum
Authors: Wu Kenneth S. , Osdol William W. Van , Dauskardt Reinhold H.
Published: June 2019

A mechanics approach is presented to study the intercellular delamination resistance and mechanical behavior of stratum corneum (SC) tissue in the direction normal to the skin surface. The effects of temperature and hydration on debonding behavior were also explored. Such understanding, which includes the relationship of mechanical behavior to the underlying SC cellular structure, is essential for emerging transdermal drug delivery technologies. Fracture mechanics-based cantilever-beam specimens were used to determine reproducibly the energy release rates to quantify the cohesive strength of human SC. The debond resistance of fully hydrated SC was found to decrease with increasing temperature, while dehydrated SC exhibited a more complex variation with temperature. Stress-separation tests showed that fracture energies and peak separation stresses decreased with increasing temperature and hydration, although the SC modulus varied only marginally with temperature and hydration. Results are described in terms of microstructural changes associated with hydrophilic regions and intercellular lipid phase transitions.
In Vitro Vascular Cell Adhesion and Proliferation on Alkaline Degraded Poly-lactic/glycolic Acid Polymers
Authors: Webster Thomas J. , Miller Derick C. , Thapa Anil , Haberstroh Karen M.
Published: June 2019

The objective of the present in vitro study was to determine vascular endothelial and smooth muscle cell responses to poly(lactic-co-glycolic acid) (PLGA) films that were exposed apriori to various degrees of alkaline degradation. To model the alkaline environment of blood in arteries, PLGA films were separately soaked in select concentrations (from 0.1 – 10 N) of NaOH for various periods of time (from 10 minutes to 1 hour). Vascular endothelial and smooth muscle cells were then separately allowed to adhere and/or proliferate on the different PLGA degraded surfaces. Results provided the first evidence that smooth muscle adhesion and proliferation increased with larger amounts of alkaline PLGA degradation. In contrast, endothelial cell adhesion and proliferation decreased with increasing amounts of alkaline PLGA degradation. In this manner, the present in vitro study suggests a possible mechanism for insufficient endothelialization on PLGA vascular implants in vivo.
Formation, Characterization, Protein Resistance, and Reactivity of Cl3Si(CH2)11(OCH2CH2)3OH Self-Assembled Monolayers
Authors: Seong Jiehyun , Lee Seok-Won , Laibinis Paul E.
Published: June 2019

We report a method for generating tri(ethylene glycol)-terminated-n-alkyltrichlorosiloxane monolayers on SiO2 surfaces. These chemisorbed films, with a thickess of ∼2-3 nm, provide an oligo(ethylene glycol) surface that reduces the nonspecific adsorption of proteins and hydroxyl attachment sites for covalently immobilizing biomolecules to the substrate. These mono-molecular films were formed by adsorbing an acetoxy-tri(ethylene glycol)-terminated n-alkyltrichlorosilane, CH3(C=O)O(CH2CH2O)3(CH2)11SiCl3, onto glass and Si/SiO2 substrates, where the terminal acetate provided a protecting group for the hydroxyl functionality during self-assembly of the film. After formation of the monolayer, the acetate functionality was reduced chemically to form films exposing a covalently attached -(OCH2CH2)3OH terminus at a density of ∼3[.dotmath]1014 molecules/cm2. Protein adsorption studies verified that the films exhibited notable resistances against the non-specific adsorption of various proteins. Chemical modification of the -(OCH2CH2)3OH surface with protein A provided a non-adsorbing surface for selective immobilization of immunoglobulins.
Effects of Ionic Flow and Amelogenins on the Lengthwise Growth of Octacalcium Phosphate Crystals in a Model System of Tooth Enamel Formation
Authors: Iijima M. , Moriwaki Y. , Wen H.B. , Takagi T. , Fincham A.G. , Moradian-Oldak J.
Published: June 2019

This paper briefly reviews our recent studies, which aimed to investigate the effects of 1) the Ca2+and PO43-ions flow and 2) amelogenins on the lengthwise growth of octacalcium phosphate (OCP), which is a potent precursor of enamel apatite crystal. OCP crystals were grown at 37°C in a dual membrane system under various amount of ionic inflow into a reaction space, using 1) 5-30mM Ca and PO4solutions as ionic sources and 2) extracted bovine amelogenin and recombinant murine amelogenins (rM179, rM166). With an increase in the amount of Ca2+and/or PO43-ions flow, the length of OCP crystal increased, while the width decreased. As a result, the length to width (L/W) ratio of crystal changed from 3 to 95, while the width to thickness (W/T) ratio from 32 to 9. The effect of amelogenins was unique, regardless of the type of amelogenins: Rod-like and prism-like OCP crystals with large L/W (61∼107) and small W/T (1.3∼2.2) ratios were formed in 10% amelogenin gels. In contrast, characteristic ribbon-like OCP crystals grew without protein and with gelatin, albumin, polyacrylamide gel and agarose gel. Specific interaction of amelogenins with OCP crystal was ascribed to the self-assembly property of amelogenin molecules and their hydrophobic nature. It was suggested that ionic flow and amelogenins play some critical roles in the elongated growth of enamel crystals.
Spatio-Temporal Patterns in Ferritin Crystal Growth
Authors: Gliko Olga , Vekilov Peter G.
Published: June 2019

We investigate the unsteady kinetics and the formation of spatio-temporal patterns during the ferritin crystal growth, which is controlled by the rate of supply of material. For this, we apply a novel phase-shifting interferometry technique. We find that the growth rate and local slope fluctuate by up to 100% of their average values as a result of step bunching. The fluctuation amplitudes decrease with higher supersaturation and larger crystal size, as well as with increasing distance from the step sources. Since these are parameters that govern the protein supply field, we conclude that fluctuations are rooted in the coupling of the interfacial processes of growth to the bulk transport in the solution. Analysis of the step velocity dependence on local slope indicates a very weak interaction between the steps. Hence, in transport-controlled systems with non-interacting or weakly interacting steps the step bunches decay and step train tends towards its stable, equidistant state.
Tissue Engineering of Fibroblast Constructs and Anisotropic Collagen Gels
Authors: Calve Sarah , Arruda Ellen , Dennis Robert , Grosh Karl , Pasyk Krystyna
Published: June 2019

The creation of anin vitrofunctional tendon construct will enable testing of the influence of mechanics and nutrients on the development and remodeling of tendon under known controlled stimuli which is difficult to achievein vivo. Tendon constructs were engineeredin vitrovia stress-mediated self organization of fibroblasts and ECM on a laminin coated elastomer substrate. Varying the laminin density and the amount of fetal bovine serum on the substrate affected the ability of tendon fibroblasts to form a confluent cell layer and the time to layer delamination. Understanding the factors that promote self-assembly of tendon constructs will enable their combination with already developedin vitromuscle constructs.
Synthesis of biocompatible surfaces by different techniques
Authors: Garreta E. , Fernández T. , Borrós S. , Esteve J. , Colominas C. , Kempf L.
Published: June 2019

In the present work, a sol-gel method of HA synthesis has been developed using different calcium and phosphorous precursors. In order to make a porous scaffold, HA aerogel formation and HA liofilization processes have been studied. The liofilized HA and the HA aerogels have been characterized by SEM-EDX and X-Ray difraction. Finally, so as to improve the biocompatibility and the bioadhesion of the HA scaffolds, different plasma polymerization techniques have been studied. Acrylic acid has been polymerized using plasma polymerization with a radiofrequency source. Different radiofrequency source powers and reactor designs have been tryed. The kinetics of the thin film growth have been studied and the optimal polymerization conditions have been established. Polymeric layers have been characterized by IR and XPS.
Ac Impedance Spectroscopy Study of Modified Proton-Exchange Membrane Nanocomposites
Authors: Damay Françoise , Klein Lisa C.
Published: June 2019

The dielectric and electrical behaviors of a NafionTM membrane, a NafionTM/7SiO2-2P2O5-ZrO2 gel composite, and a NafionTM/ZrP particle composite were investigated using ac impedance spectroscopy at different relative humidities and temperatures. Only NafionTM/7SiO2-2P2O5-ZrO2 showed a slightly higher conductivity than NafionTM at high temperature. For NafionTM/ZrP, proton mobility was significantly lower, particularly at high relative humidity. The results suggest that improvement in fuel cell performance, previously measured on composite membranes, does not merely result from increased hydrophilic properties.
Polymer Nanocomposite Foams Prepared by Supercritical Fluid Foaming Technology
Authors: Lee L. James , Zeng Changchun , Han Xiangmin , Tomasko David L. , Koelling Kurt W.
Published: June 2019

Polystyrene (PS) clay nanocomposites were synthesized and used to prepare foams in both batch and continuous extrusion process. It was found that the addition of a small amount of clay could greatly reduce cell size and increase cell density. Once exfoliated, the nanocomposite foam exhibits the highest cell density and the smallest cell size at the same particle concentration. Exfoliated microcellular nanocomposite foams with good surface quality was successfully produced using supercritical carbon dioxide.
Carbon Nanofiber Reinforced Composites for Enhanced Conductivity, Strength, and Tensile Modulus
Authors: Tibbetts Gary G. , Finegan Ioana C. , Kwag Choongyong
Published: June 2019

Carbon nanofibers of diameter 200 nm may be used as an additive to thermoplastics for applications requiring electrical conductivity and enhanced mechanical properties. The electrical properties of nanofiber in thermoplastics such as nylon and polypropylene and are very attractive compared with those provided by other conventional conducting additives. Because of the low diameter of the nanofibers used, the onset of electrical conductivity (percolation threshold) can be below 1 volume %. Because of the highly conductive nature of the fibers, particularly after a graphitization step, the composites can reach resistivities as low as 0.15 Ohm cm. These conducting composites may be used for applications such as radio frequency interference shielding, primerless electrostatic painting, and static discharge. In order to make composites having excellent mechanical properties, good adhesion between fiber and matrix is essential. Carbon nanofiber-matrix adhesion was studied after surface treating the fibers using a variety of methods. Among as-grown fibers, those produced with longer gas phase feedstock residence times in the fiber growth reactor were less graphitic but adhered to a polypropylene matrix better, giving improved tensile strength and modulus Two chemical treatments were found to be somewhat effective in increasing tensile strength, but both decreased the modulus.. A modest degree of oxidation was also found to increase adhesion to the matrix and increase composite tensile strength, while extended oxidation attacked the fibers sufficiently to decrease composite properties.
The Formation of Ordered Nanoporous Structure with Controlled Micelle Size
Authors: Chang Jeongho , Shin Yongsoon , Wang Li-Qiong , Exarhos Gregory J.
Published: June 2019

Selected MPEG-b-PDLLA block copolymers have been synthesized with systematic variation of the chain lengths of the resident hydrophilic and hydrophobic blocks. The size and shape of the micelles that spontaneously form in solution are then controlled by the characteristics of the copolymer template. Formation of nanoporous silica at room temperature with short-preparation time is demonstrated and silica-containing materials evolve with uniform pore shape and wall structure. The formation mechanism of these nanoporous structures obtained by controlling the micelle size has been confirmed using both liquid and solid state 13C and 29Si NMR techniques.
Nanocomposite Films derived from Alkoxysilane Terminated Amide Acid Oligomers and Carbon Nanotubes
Authors: Smith Joseph G. , Connell John W. , Lillehei Peter , Watson Kent A. , Thompson Craig M.
Published: June 2019

Low color, space environmentally stable, polymeric materials with sufficient electrical conductivity for static charge dissipation are of interest for potential applications on Gossamer spacecraft. One method of imparting electrical conductivity while maintaining optical clarity is through the use of single wall carbon nanotubes (SWNTs). Both theory and research on SWNTs have shown them to be conductive. However, SWNTs are very difficult to uniformly disperse in a polymer. The approach described herein was to use oligomers endcapped with functional groups that could condense with functionalities present on purified, laser ablated SWNTs. Low color, radiation resistant amide acid oligomers endcapped with trialkoxysilane groups were combined with SWNTs. Since the SWNTs were purified by an oxidative process (nitric/sulfuric acid treatment), they have functionalities such as hydroxyl and carboxylic acid groups that can condense with the terminal alkoxysilane groups. After mixing at room temperature, the mixtures were used to cast films that were subsequently stage-cured up to 300°C for 1 hour in air. During this thermal treatment, imidization and condensation occurred. The chemistry, physical, and mechanical properties of the resulting nancomposite films will be presented.
Particle size and density control in magnetic polymer nanocomposites
Authors: Millan Angel , Palacio Fernando , Falqui Andrea , Etienne Snoeck , Serin Virginie
Published: June 2019

Magnetic nanocomposites formed by metal oxide nanoparticles and organic polymers can be produced from a polymer-metal ion complex material by a soft thermal treatment. With only slight variations in the preparation procedure it is possible to obtain: 1) different iron oxide phases, e.g., hematite (antiferromagnetic), goethite and akaganeite (both canted antiferromagnets), and maghemite (ferrimagnetic); 2) nanocomposites with a different particle size, in a range from 2 nm to 20 nm; and 3) different particle density. In this contribution the preparation and properties of maghemite nanoparticles in polyvinyl pyridine composites are reported.
Three-DimensionalWafer Process Model for Nanotopography
Authors: Yoshida Takafumi
Published: June 2019

This paper proposes a three-dimensional wafer process model for nanotopography. This model allows us to predict the effect and behavior of nanotopography on the wafer processes especially for the wafer Mechanical/Chemical Lapping (MLP/CLP), wafer Single/Double Side Polishing (SSP/DSP) and device Chemical Mechanical Polishing (CMP).
A Model of Chemical Mechanical Polishing: The Role of Inhibitors
Authors: Paul Ed
Published: June 2019

A previously presented model of CMP is extended to include the role of inhibitors. In CMP, a chemical reaction forms a surface film which is removed mechanically by abrasives. When inhibitor molecules bond to the surface film, the mechanical abrasion rate is reduced. The general model will be discussed, and then applied to W-CMP explaining differences in the reduction of polishing rates for different inhibitors.
Slurry Utilization Efficiency Studies in Chemical Mechanical Planarization
Authors: Philipossian Ara , Mitchell Erin
Published: June 2019

The residence time distribution of slurry in the pad-wafer interface was experimentally determined and used to calculate the slurry utilization efficiency (η) of the CMP process. Slurry utilization efficiency represents the percentage of slurry that actually participates in the polish by entering the region bounded between the wafer and the pad. Results show that η ranges from 2 to 22 percent, depending on operating conditions such as applied wafer pressure, relative pad wafer velocity, slurry flow rate and pad surface texture (i.e. type of pad grooving).
News from the M in CMP - Viscosity of CMP Slurries, a Constant?
Authors: Lortz W. , Menzel F. , Brandes R. , Klaessig F. , Knothe T. , Shibasaki T.
Published: June 2019

It is well known and accepted that the viscosity of CMP-slurries has an effect on polishing results. Even though the literature on rheology recognizes that viscosity is not always constant and the slurry can show non-Newtonian behavior or even dilatant effects, all calculations have been performed with constant viscosity.

However, the “real” viscosity of a CMP-slurry during polishing can change significantly with shear rate.

The typical equipment for viscosity measurement is based on a rotating cylinder or a plate. But even with a plate system it is only possible to reach a shear rate range up to 50,000 1/sec. A calculation of the shear rate between the wafer and the polishing pad is based on a relative velocity of 1 m/sec and a distance between the wafer and the pad of 20 μm; this correlates to a shear rate of 50,000 1/sec. If parts of the polishing pad come closer to the wafer or especially closer to the edge of structures on the wafer (for example 1 μm), the shear rate will increase locally to 1,000,000 1/sec.

When the shear rate is high enough, viscosity depends mostly on hydrodynamic factors like viscosity of continuos phase, solids content, particle size, particle size distribution and shape of the particles.

The shape of fumed metal oxides is controlled during the synthesis in the flame process. But the slurry-making process is also responsible for particle size distribution, shape of the particle and the high shear rate viscosity of the CMP-slurry.

The high shear rate viscosity of different silica slurries in dependence from BET-surface area, used milling energy, concentration and preparation direction was measured in this investigation.
Atomistic Mechanisms Underlying Chemical Mechanical Planarization of Copper
Authors: Ye Y.Y. , Biswas R. , Bastawros A. , Chandra A.
Published: June 2019

With an aim to understanding the fundamental mechanisms underlying chemical mechanical planarization (CMP) of copper, we simulate the nanoscale polishing of a copper surface with molecular dynamics utilizing the embedded atom method. Mechanical abrasion produces rough planarized surfaces with a large chip in front of the abrasive particle, and dislocations in the bulk of the crystal. The addition of chemical dissolution leads to very smooth planarized copper surfaces and considerably smaller frictional forces that prevent the formation of bulk dislocations. This is a first step towards understanding the interplay between mechanistic material abrasion and chemical dissolution in chemical mechanical planarization of copper interconnects.
The Effect of Pad Properties on Planarity in a CMP Process
Authors: Kim Hoyoung , Park Dong-Woon , Hong Chang-Ki , Han Woo-Sung , Moon Joo-Tae
Published: June 2019

This study presents the effect of pad properties, such as elastic modulus and surface roughness, on planarity in a CMP process. A systematic method to measure planarization length, which represents the die-scale planarity in a quantitative manner, has been proposed. It has been shown that the planarization length is highly dependent on the bulk modulus of the pad. The effect of elastic modulus and roughness of the pad on dishing amount, which represents the feature-scale planarity, has been shown. Dishing amount is determined by the elastic modulus of the superficial layer of the pad, which is typically tens of microns thick, rather than by the bulk elastic modulus of the pad. A double layer pad model has been proposed based on the observed results, which can explain that the dishing amount is reduced by increasing elastic modulus of the pad superficial layer, or by decreasing the surface roughness of the pad.
Pad Degradation During CMP Process: Effect of Soak in Slurry and Water on Thermal and Mechanical Properties of the CMP Pads
Authors: Tregub A. , Ng G. , Moinpour M.
Published: June 2019

Soak of polyurethane-based CMP pads in tungsten slurry and de-ionized water and its effect on retention of thermal and mechanical properties of the pads was studied using Dynamic Mechanical Analysis (DMA), Thermal Mechanical Analysis (TMA), Thermal Gravimetric Analysis (TGA), and Modulated Differential Scanning Calorimetry (MDSC). Simultaneous cross-linking and plastisizing due to soak were established using DMA and MDSC analysis. The stable operating temperature range and its dependence on soak time were determined using TMA analysis. Substantial difference in diffusion behavior of the “soft” and “hard” pads was discovered: diffusion into the hard pads followed Fickian law [1], while diffusion into the multi-layer soft pads was dominated by the fast filling of the highly porous pad surface with liquid.

During a traditional CMP process, which involves application of polishing pads and slurry, the pad properties can be substantially and irreversibly changed as the result of slurry/rinse water absorption.

The retention of the pad properties after exposure was monitored using such thermal and mechanical techniques, as Thermal Mechanical Analysis (TMA), Dynamical Mechanical Analysis (DMA), Modulated Differential Scanning Calorimetry (MDSC), Thermal Gravimetric Analysis (TGA).
Ta/low-κ CMP with Colloidal Silica Particles
Authors: Beaud Patrice , Bouvet Didier , Fazan Pierre , Jacquinot Eric , Aoki Hiroyuki , Aoki Tomoko
Published: June 2019

Low-κ/Cu interconnect integration achievement is one of the key issues for the future sub-100 nm technologies. Nowadays, no definitive integration scheme has been reported. Low-κ integration is especially difficult because the trench/via etching and CMP processes can damage its properties. In the present work, we present results on different materials that could be used in such integration. We focused our study on the barrier (Ta/TaN) and on a low-κ material (dense and porous), that is a spin-on-dielectric (SOD) of the methylsilsesquioxane (MSQ) type. CMP slurries were made from monodisperse colloidal silica particles. In a first approach, the slurries compositions mainly differed by their pH and abrasive characteristics. The particle size ranged from 12 to 80 nm, with a pH varying between 2 and 11. The sensitivity of the Ta/TaN and low-κ removal rates will also be reported. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) of the different films were carried out in order to evaluate the impact of CMP on their surface quality. Measurements did not show any surface degradation or/and scratches, and no delamination has been observed. Post-CMP κ value measurements have been carried out to highlight possible damage on the low-ê dielectric materials.
Chemical-Mechanical Planarization of Copper: The Effect of Inhibitor and Complexing Agent
Authors: Luo Ying , Du Tianbao , Desai Vimal
Published: June 2019

The present investigation was focused on understanding of the oxidation, dissolution and modification of Cu surface in slurries at various pH using hydrogen peroxide as oxidizer, glycine as complexing agent and 3-amino-triazol (ATA) as inhibitor during Cu-CMP. The electrochemical process involved in the oxidative dissolution of copper was investigated by potentiodynamic polarization studies. Surface modification of copper was investigated using Xray photoelectron spectroscopy to understand the interaction of Cu-H2O2-glycine-ATA during CMP. In the absence of glycine and ATA, the copper removal rate is found to be high in a slurry with 5% H2O2 at pH 2, then it decreases with increasing pH and reaches the minimum at pH 6, it continuously increases at alkaline condition. In the presence of 0.01M glycine, the removal rate of copper decreases in acidic slurries while increases significantly in alkaline slurries. With the further addition of ATA, the copper removal rate was reduced. However, better surface planarity was obtained. The present investigation enhanced understanding of the mechanism of Cu CMP in the presence of oxidizer, complexing agent and inhibitor for formulation of a highly effective CMP-slurry.
Electrochemical Measurements Demonstrate Performance of BTAH and Alternative Passivating Agents on Copper in a Hydroxylamine CMP System
Authors: Carter Melvi Keith , Small Robert
Published: June 2019

Organic passivating agents have been measured by a galvanostatic method during abrasive free Chemical Mechanical Planarization (CMP) of copper coated silicon wafers. CMP process steps include (a) removal of the passivation layer to expose the metal surface, (b) wet chemical oxidation of the metal surface and (c) mechanical removal of the oxidation products by means of the pad with a colloidal polishing aid such as silica or alumina1. CMP of necessity seeks to establish a unique equilibrium between little or no metal removal due to corrosion effects and rapid metal removal resulting from a mechanically aided chemical oxidation or polishing. Chemical oxidizing agents can corrode the metal surface during polishing and non-polishing steps alike so protective passivation agents are necessary to inhibit or block surface corrosion. Historically, benzotriazole (BTAH) has been the copper protective agent of choice because it performed well at concentrations of 50 to 500ppm, however BTAH can scratch copper. Self-assembly of monolayers was reported by Sung et al2 demonstrating a tendency toward organizational energy of molecular surface protection. Cho et al3 have reported formation of a flat, well ordered BTAH based monolayer on copper supporting a three dimensional BTAH stack above it. Metrikos-Hukovic et al4 reported evidence for a monolayer of a CuBTA compound and additional adsorption/crystallization layers of 7nm thickness5 were measured. Discussions in this work refer to the combined adsorption/chelation layers on copper as passivation providing measurements that distinguish between them. It will be shown that addition of BTAH forms a thin layer of CuBTA covered by a second layer creating a protective film with relatively high electrical resistance. The purpose of this electrochemical effort is to measure the effect of BTAH during a non-Prestonian, slurry free CMP process, to affect a direct measure of bi-layer passivation and to identify other organic compounds that may also provide protection of the copper surface against corrosion.
Slurries for Copper Damascene Patterning: Similarities and Differences
Authors: Jindal A. , Rajagopalan G. , Gupta M. , Lu J.-Q. , Rose K. , Gutmann R.J.
Published: June 2019

Two first-step copper damascene slurries and one commercial second-step slurry are characterized in terms of their intrinsic properties and CMP performance. A prototype first-step slurry with high static etch rate (∼150 nm/min) yielded higher dishing in the copper lines (∼200 nm in 100 μm lines) compared to a commercial first-step slurry with negligible static etch rate. In both the cases, dishing in copper lines is observed to be a strong function of line width and radial position on the wafer. High static etch rate of the prototype slurry is believed to be responsible for the high dishing. Non-selective second-step polishing removes the liner layer while maintaining planarity.
Light Emitting Polymermaterials: the Working Base for Flexible Full Color Displays
Authors: Becker Heinrich , Breuning Esther , Büsing Arne , Falcou Aurelie , Heun Susanne , Parham Amir , Spreitzer Hubert , Steiger Jürgen , Stösse Philipp
Published: June 2019

In the last few years, industrial research into materials fulfilling the needs of the maturing OLED display industry has intensified considerably. A first generation of polymers (phenyl- PPVs) is now being commercially exploited in first monochrome polymer LED display applications. Based on these materials, non-planar displays have already been demonstrated. However, those proof of concept devices have been monochrome. Especially the RGB materials need considerable improvement to be suitable for flexible full color displays.

We will therefore report on the progress in the development of polymers for red, green, and blue emission. Our main focus here is on improving the properties of various polymers derived from the spiro-bifluorene core.

Depending on the color, the main issues vary strongly: For BLUE polymers, efficiency, color coordinates, and processibility are already at a commercial level while operational lifetime still needs strong improvement. RED materials are in an almost contrary situation: here, the operational lifetime is excellent, whereas the efficiency and the driving current are requiring further improvement. For GREEN, achieving saturated emission, whilst maintaining the other properties (high efficiency, long operational lifetime), is still challenging. We will demonstrate the current status of material development within Covion.

In addition, we achieved advances in full-color patterning, especially techniques based on Ink-Jet printing. This technology potentially allows the efficient manufacturing of high resolution RGB devices on a variety of substrates, including flexible layers.
Super-elastic Gold Conductors on Elastomeric Substrates
Authors: Chambers Catriona , Lacour Stéphanie P. , Wagner Sigurd , Suo Zhigang , Huang Zhenyu
Published: June 2019

3-D displays, sensor skins, mechatronic structures, and e-textiles will rely on deformable and stretchable electronic circuits. It is likely that such circuits will be made of rigid semiconductor islands interconnected with one-time deformable or even elastic metallization. However, free-standing metal films fracture at tensile strains in the order of one percent, well short of the approximately ten-percent extension needed for deformable circuits. We have discovered that flat metal lines made on an elastomeric substrate can be stretched reversibly by ten percent without losing electrical conduction. While this phenomenon of “super-elastic” conductive films is as of yet unexplained, it appears to originate in the diversion of mechanical strain around cracks in the film and through the elastomer substrate. We fabricated 1mm thick poly-dimethylsiloxane (PDMS) membranes with up to 50-nm thick, 1-mm wide gold lines deposited by electron beam evaporation. Then we evaluated the structure of the gold films by optical and scanning electron microscopy, and measured the electro-mechanical characteristics in a strain tester, with contact electrodes applied to the film. We find that 50 nm thick lines retain their electrical conduction up to 30 percent strain. Also, when the tensile strain is cycled between 0 and 10 percent, the electrical resistance in the stressed and relaxed states are reproducible. We will describe substrate and conductor preparation, and their structural and electro-mechanical properties.
Island Edge Coverage By Metal Interconnects for Three Dimensional Circuits
Authors: Bhattacharya Rabin , Wagner Sigurd
Published: June 2019

Three-dimensional integrated circuits is a new and exciting field that has been spurred on by the need for conformal displays and detector arrays. These circuits are fabricated by interconnecting rigid sub-circuit islands made on a flat, deformable substrate. To prepare for interconnects, we apply a patterned deformable sacrificial material over the flat substrate. We then deform the substrate, with the sub-circuit islands and the sacrificial pattern on it, to a spherical surface. Following deformation, we evaporate interconnect metal and then liftoff the sacrificial material, leaving only the metal lines that interconnect the islands. The maximum size for a circuit island to remain intact is proportional to the island's thickness. The larger the island has to be, the thicker it must be made to prevent it from cracking. For 50 μm thick Kapton E substrates, it was found that 40 μm square SiNx islandsmust be at least 0.5 μm thick.With such thick islands, sidewall coverage during evaporation of the interconnect metal becomes difficult because of the dome shape of the substrate. Moreover, during substrate deformation, there is delamination that occurs at the island-substrate interface. This delamination forms a gap between the edge of the island, and the substrate. Thick metalization that covers both sidewall and islandsubstrate gap, produces a yield of 97% for 10 micrometer wide aluminum lines.
Ultra-Low Temperature Poly-Si Thin Film by Excimer Laser Recrystallization For Flexible Substrates
Authors: Han Sang-Myeon , Lee Min-Cheol , Kang Su-Hyuk , Shin Moon-Young , Han Min-Koo
Published: June 2019

An ultra-low temperature (< 200°C) polycrystalline silicon (poly-Si) film is fabricated for the plastic substrate application using inductively coupled plasma chemical vapor deposition (ICP-CVD) and excimer laser annealing. The precursor active layer is deposited using the SiH4/He mixture at 150°C (substrate). The deposited silicon film consists of crystalline component as well as hydrogenated amorphous component. The hydrogen content in the precursor layer is less than 5 at%. The grain size of the precursor active silicon film is about 200nm and it is increased up to 500nm after excimer laser irradiation.
High Performance Polysilicon Thin Film Transistor Circuits On Flexible Stainless Steel Foils
Authors: Afentakis Themis , Hatalis Miltiadis K. , Voutsas Apostolos T. , Hartzell John W.
Published: June 2019

In recent years, there has been an increased interest in the use of flexible substrates in microelectronic fabrication. Flexible substrates, such as polymers and metals have the potential to be utilized in roll-to-roll processing, resulting in low cost, rugged systems. Thin flexible stainless steel foils offer a number of advantages over polymers for device and circuit fabrication, most significantly in the increased thermal budget tolerance that they provide. This enables the utilization of high temperature processes in the fabrication and the production of high performance devices and circuits.

Thin film transistors have been fabricated on thin stainless steel foils using a variety of crystallization and gate dielectric approaches. N-channel devices with average effective mobility values of 250cm2/Vs and p-channel devices with effective mobility values in the region of 90cm2/Vs were successfully fabricated. Both digital and analog circuits, such as operational amplifiers, ring oscillators and a variety of shift register designs were also fabricated, and their basic performance characteristics will be presented in this paper. The characteristics of ring oscillators having 19 inverter stages operating with speeds of 15MHz or higher, along with the characteristics of various shift register architectures with maximum operating frequencies above 1MHz, will be reported. The impact of process and design parameters on their operation was evaluated and will be addressed in this paper.

The results that are presented in this paper constitute the first successful implementation of high performance circuitry having a high degree of scalability and complexity on thin metal foils, thus making the fabrication of efficient, inexpensive and versatile systems on flexible foils for a large variety of applications a realistic prospect.
All-organic field effect transistors
Authors: Parashkov R. , Becker E. , Ginev G. , Schneider D. , Metzdorf D. , Dobbertin T. , Johannes H-H. , Kowalsky W.
Published: June 2019

In this work we present fully patterned organic transistors based on selective electropolymerization of conducting polymers that enables simple fabrication of micron scale features. It involves fabrication of pentacene field effect transistors in which the conducting, insulating parts as well as the substrate are all made of polymers. We have fabricated drain and source electrodes by electropolymerization of 3,4- ethylenedioxythiophene and gate by spin coating of commercially available poly( 3,4- ethylenedioxythiophene) (PEDOT:PSS) aqueous dispersion, polyvinylalcohol for the gate dielectric layer, and pentacene for the organic active layer. We have built a top-gate structure with gate dielectric layer and gate placed on the top of the pentacene layer, and in a such way obtained protection of the active layer could permit enhancement of the operating time of devices. Carrier mobility as large as 0,01 cm2/V s was measured. Functional all- organic transistors have been realised using a simple and potentially inexpensive technology.
Organic Light Emitting Diodes and Photo Detectors Fabricated on a Polymeric Substrate for Flexible Optical Integrated Devices
Authors: Ohmori Yutaka , Kajii Hirotake , Taneda Takayuki , Kaneko Masamitsu
Published: June 2019

Direct fabrication of organic light emitting diodes (OLED) on a polymeric substrate, i.e., polymeric waveguide substrate to form a flexile optical integrated devices has been realized. The OELD was fabricated by organic molecular beam deposition (OMBD) technique on a polymeric substrate and a glass substrate, for comparison. The device fabricated on a polymeric substrate shows similar device characteristics to that on a glass substrate. Optical signal of faster than 100 MHz has been created by applying pulsed voltage directly to the OLED with emissive layers utilizing rubrene or porphine doped in 8-hydoxyquinolinum aluminum derivatives. Optical signal transmission with OLED fabricated on a polymeric waveguide with optical connectors has been successfully realized. Optical photo detectors (OPD) utilizing phthalocyanine derivatives with superlattice structure provide increased pulse response with input optical signals, and the OPD with 5 MHz of cut-off frequency has been realized with superlattice structure under reverse bias voltage to the OPD.
Effective Jet Printing of Organic Semiconducting Polymers
Authors: Paul Kateri E. , Wong William S. , Ready Steven E.
Published: June 2019

Organic semiconducting polymers are an attractive alternative to conventional inorganic materials because of the ability to process the polymers from solution and apply them to flexible substrates using lower temperatures and at a lower cost. Direct writing of these materials has the potential to reduce processing steps and material waste. While printing of semiconductors for organic light emitting diodes (OLEDs) is well known, little has been reported on printing semiconductors for organic thin-film transistors (OTFTs). We have developed a process to fabricate TFTs and arrays using jet printing to eliminate all photolithographic patterning. Active layers of the polymeric semiconductor are jet-printed for the active layer. Many factors are found to affect the characteristics of devices having a jet-printed semiconductor layer, including the substrate temperature, surface energy, device geometry, and drop size and overlap. We will discuss the printing conditions that lead to performance similar to that of devices fabricated by spin coating.
Thermal Vibration in nAgI-3Ag2O-2V2O5 Glasses
Authors: Thazin A. , Fujishima Y. , Arai M. , Sakuma T. , Takahashi H.
Published: June 2019

The X-ray diffraction measurement for superionic conducting glasses nAgI-3Ag2O-2V2O5 (n = 2, 5, 10) has been performed at 12, 100, 200 and 290 K. The temperature dependence of structure factor S(Q) of nAgI-3Ag2O-2V2O5 has been discussed based on the theoretical treatment including the thermal vibration of atoms in noncrystalline materials. The effective overall Debye-Waller temperature parameter B increases with the increase of temperature and also with AgI concentration.