bluuebunny/crossref_metadata_2025_split huggingface dataset:
Enhanced Scratch Resistance of Nanocomposite Gelatin Films
Authors: Chen Quan , Schadler Linda S. , Siegel Richard W. , Irvin Glen C. , Mendel John 
Published: June 2019

AbstractNanocomposites were made using deionized gelatin filled with well-dispersed nanoscale alumina particles. Scratch tests on the nanocomposite films showed substantially improved scratch resistance. Tensile tests revealed increases in both modulus and tensile strength of the nano-filled gelatin films accompanied by a decrease in strain-to-failure. The increase in modulus and strength reduced the degree of plastic deformation during scratch testing, but the onset of periodic cracking in the scratch track was unaffected. Optical transmittance measurements of the gelatin composite showed that the films retained transparency in the visible light range.
Mechanical Behavior of Intercalated Polycarbonate Layered-Silicate Nanocomposites
Authors: Hsieh Alex J. , Harris Donovan , Moy Paul , Song John W. 
Published: June 2019

AbstractThe effect of layered-silicates on the mechanical response of intercalated polycarbonate (PC) nanocomposites subjected to quasi-static tensile, compressive and ballistic impact testing conditions has been investigated. These nanocomposites were melt-processed, in which good dispersion of nanoclays and adequate adhesive bonding between the nanoclay and PC matrix are achieved. However, their ductility upon tensile loading is significantly affected; a transition from ductile to brittle deformation occurs at clay loading of about 3 wt.%. Stress whitening is evident in the tensile- and ballistic-tested 1.5, 2.5, and 3.5 wt.% clay nanocomposites, and is attributed to the light scattering by microvoids, which are presumably formed from either crazing of PC or debonding of the nanoclay tactoids upon mechanical deformation. The effect of clay loading on the ballistic impact strength of the monolithic PC nanocomposites and layered PC/PC-nano/PC composites is determined. Compressive yield strength measurements are obtained at strain rate of 0.001/s for the monolithic PC nanocomposites and are utilized to correlate with the ballistic impact strength of the layered PC/PC-nano/PC composites. Thermal degradation is noted in these PC nanocomposites, and its effect on the mechanical deformation is briefly discussed.
Analysis of Carbon Nanotube Pull-out from a Polymer Matrix*
Authors: Frankland S. J. V. , Harik V. M. 
Published: June 2019

AbstractMolecular dynamics (MD) simulations of carbon nanotube (NT) pull-out from a polymer matrix are carried out. As the NT pull-out develops in the simulation, variations in the displacement and velocities of the NT are monitored. The existence of a carbon-ring-based period in NT sliding during pull-out is identified. Linear trends in the NT velocity-force relation are observed and used to estimate an effective viscosity coefficient for interfacial sliding at the NT/polymer interface. As a result, the entire process of NT pull-out is characterized by an interfacial friction model that is based on a critical pull-out force, and an analog of Newton's friction law used to describe the NT/polymer interfacial sliding.
Dynamic Contact Characteristics During Chemical Mechanical Polishing (CMP)
Authors: Choi Wonseop , Lee Seung-Mahn , Singh Rajiv K. 
Published: June 2019

AbstractIn chemical mechanical polishing (CMP), it is critical to understand dynamic contact at the pad-particles-wafer interface for desired CMP performance. The dynamic contact is dependent on process variables (platen velocity and down pressure) and particle characteristics (size and concentration), which in turn affect friction force. In this study, we have characterized the dynamic contact at the pad-particles-wafer interface as a function of platen velocity and down pressure. In situ lateral friction force measurements were carried out for silica slurry / sapphire wafer system in order to investigate the dynamic contact during polishing. As solids loading increases, the slope in the friction force vs. platen velocity curve changes from a negative to a positive value. Friction force increases with down pressure for different solids loading conditions. Consequently, friction force is determined as a function of down pressure and platen velocity, validating a dynamic contact mechanism during CMP.
Re-Examining The Physical Basis of Pattern Density and Step Height CMP Models
Authors: Xie Xiaolin , Park Tae , Lee Brian , Tugbawa Tamba , Cai Hong , Boning Duane 
Published: June 2019

AbstractOur group has proposed several chip-scale CMP models, with key assumptions including the notion of planarization length in the pattern density model [1], and step height dependent polishing rate in the density step height model [2]. In the effective density model, planarization length is the characteristic length of an elliptic weighting function based on the long-range pad deformation and pressure distribution during CMP. This semi-physical model is often adequate and usually gives a fitting error of a few hundred angstroms. As ever-shrinking device size pushes for tighter control of post CMP uniformity, however, we need a chip-scale CMP model with better accuracy.In this work, we re-examine the physical basis for averaging weighting functions and step height dependence, particularly in the context of contact mechanics based model formulations. The comparison of the two models confirms that the analytical density and step height models can be viewed as approximations to the contact wear model. The study also suggests a new dependence of contact height on line space and pattern density.
Study of Slurry Composition Transition in a Rotary Copper CMP Process
Authors: Hegde Sharath , Patri Udaya B. , Jindal Anurag , Babu S.V. 
Published: June 2019

AbstractThe polishing pad is one of the prime components in a typical Chemical Mechanical Polishing (CMP) process. The structure and transport properties of a polishing pad are critical in determining the particle and chemical utilization in a conventional CMP process. Our earlier paper investigated the particle retention and transport on two different polishing pads, IC-1400 and Suba-500, during copper polishing. In this paper, the results of chemical retention and transport of IC-1400 and Suba-500 pads during copper polishing are presented. The polish rate results from slurry-step-flow experiments with H2O2-glycine based slurries, where the concentrations of chemicals in the slurry are altered in steps during polishing, are correlated to the chemical retention and transport characteristics of these pads. It is found that IC-1400 has a higher chemical transport capability than Suba-500 pad, which is shown to affect the polish rates of copper.
Single Asperity Chemical Mechanical Wear Studied by Atomic Force Microscopy
Authors: Stevens Forrest , Langford Steve , Dickinson J. Thomas 
Published: June 2019

AbstractNanometer scale wear caused by a single asperity of silicon nitride was examined by measuring the wear caused by atomic force microscope tips translated against sodium trisilicate glass, soda-lime glass, or fused silica in aqueous solutions. As a function of contact force, FN, and scan duration, t, the wear to both tip and substrate scales approximately as (FNt)0.5. Substrate wear was independent of temperature from 5°C to 60°C, whereas tip wear showed a temperature dependence on soda-lime glass corresponding to an activation energy of 60 kJ/mol on soda-lime glass.
Multi-Scale Characterization of Pad Role on Material Removal Rate in CMP
Authors: Gouda Sunil D. , Bastawros Ashraf , Chandra Abhijit 
Published: June 2019

AbstractA combined experimental and theoretical approach has been devised to understand the mechanical behavior of CMP pad. The pad response is examined at different length scale utilizing a nano-indentation with a conical tip and a flat-punch. The experimentally observed trends showed the competition between the local contact field of the abrasive particle and the global porous pad cell deformation. From the experiments, the local particle-level contact, cell bending, long range pad surface asperity contact as well as the bulk response of the pad can be integrated into mechanism-based models for better understanding the applied force partitioning and to predict the characteristics of the material removal rates.
Effect of Pad Surface Texture and Slurry Abrasive Concentration on Tribological and Kinetic Attributes of ILD CMP
Authors: Philipossian Ara , Olsen Scott 
Published: June 2019

AbstractReal-time coefficient of friction (COF) analysis is used to determine the extent of normal and shear forces during CMP and identify the lubrication regimes associated with the process. Pads with different surface textures and slurries with varying abrasive concentrations are used to polish ILD films over a wide range of operating parameters. Results show that by varying abrasive concentration and pad surface texture, one can cause the process tribology to change from ‘boundary lubrication’ to ‘partial lubrication’, to ‘hydrodynamic lubrication’. A two-phase model relating average coefficient of friction and Preston's constant is presented. At abrasive concentrations up to 9 percent, material removal is proportional to the extent of contact between the abrasives and the wafer. At abrasive concentrations between 9 to 25 percent, removal rate is directly influenced by average COF. A new parameter termed the ‘tribological mechanism indicator’ is defined and extracted from the data, which coupled with the information on COF and ILD removal rate, results in a series of ‘universal’ correlations. A qualitative model based on pad storage modulus is used to explain the trends.
Effect of Ceria Particle-Size Distribution and Pressure Interactions in Chemo-Mechanical Polishing (CMP) of Dielectric Materials
Authors: Chandrasekaran Naga , Taylor Ted , Sabde Gundu 
Published: June 2019

AbstractEffect of ceria particle-size distribution and pressure interactions in CMP of dielectric materials and the subsequent surface generation mechanisms is investigated in detail. The removal rate is observed to correlate primarily with the slurry mean particle-size distribution (D50) and reach early rate saturation with decreasing particle size. Slurries with tighter particlesize distribution exhibit a logarithmic relationship with pressure, while a linear relationship is observed for wider distribution slurries. In contrast to the removal rate, surface roughness and degree of microscratches depend primarily on the tail distribution (D99) and increase with increasing particle size. The addition of a selective component to the slurry increases the rate differential between the slurries.
Planarisation of Patterned Aluminium/Diamond Surfaces for SAWdevices
Authors: Holland Anthony S. , Reeves Geoffrey K. , Leech Patrick W. 
Published: June 2019

AbstractA novel method for forming interdigitated electrodes for GHz Surface acoustic wave (SAW) devices on diamond using a damascene-like polishing technique is described. Low aspect ratio Al electrodes are recessed into the diamond substrates to create a near planar surface. This allows the deposition of higher quality oriented ZnO. CVD diamond samples were ion-beam etched with groove widths in the range 1-5μm to a depth of 80-120nm. Al (120nm thick) was sputter deposited on to the etched diamond and was polished using either (i) a solution of 0.05μm silica on a neoprene polishing cloth or (ii) using a ∼0.12mm thick PVDF (polyvinylidene difluoride) filter pad with colloidal solutions of silica. Using AFM scans and optical microscopy it was observed that the combination of method (i) with the small sample size resulted in significant hollowing-out of the Al electrodes and complete removal of Al from over 90% of the pad-interconnect area. The alternative technique in (ii) demonstrated far less Al removal and better uniformity in the electrode patterns.
Supramolecular Abrasive-free System for Cu CMP
Authors: Keleher Jason , Rushing Ken , Zhao Joe , Wojtczak Bill , Li Yuzhuo 
Published: June 2019

AbstractKey issues in CMP today include reduction of surface defectivity and enhancement of planarization efficiency. More specifically, the polished surface should be free of defects such as scratches, pits, corrosion spots, trench copper loss, and residue particles. For copper/low k CMP, one of the most promising strategies to accomplishing these goals is an Abrasive-Free Process (AFP). By eliminating abrasive particles from the process, either free or fixed to the pad, it has been anticipated and realized that defects such as severe scratching, particle contamination and slurry instability via particle aggregation or settling will be significantly reduced. In addition, with proper formulation, an abrasive free process can also yield an excellent over polishing window and desired step function of pressure for material removal rate. Coupled with a supramolecular design, some of the characteristic advantages seen in abrasive containing system such as step height reduction efficiency can be realized without the side effects often introduced from solid particles. In this presentation, some designing principles for an abrasive free system will be first presented. The potential advantages of a supramolecular design for copper CMP will be illustrated. The CMP performance on a set of testing blanket and patterned wafers will be discussed.
Electrochemical Studies of Copper Chemical Mechanical Polishing Mechanism: Effects of Oxidizer Concentration
Authors: Lu J. , Garland J.E. , Petite C.M. , Babu S.V. , Roy D. 
Published: June 2019

AbstractThe process of copper chemical-mechanical planarization (CMP) can be considered as an erosion corrosion process. Such a process can be efficiently studied by in situ and ex situ electrochemical techniques, such as potentiodynamic scan and electrochemical impedance spectroscopy (EIS). Using a copper disk as the working electrode in an electrochemical cell, slurries with different oxidizer concentrations have been investigated with the aforementioned techniques. Corresponding dissolution tests were also studied and compared. It is shown that changing the oxidizer concentration leads to the formation of surface films with different structure and composition on the copper surface during CMP process. The nature of these films controls the rate of copper corrosion. These results could be used to explain the change of copper removal rate in different oxidizer concentration, as well as to understand the copper CMP mechanism.
Mechanisms of Passivation of Copper in CMP Slurries Containing Peroxide and Glycine
Authors: Wang Ling , Doyle Fiona M. 
Published: June 2019

AbstractCopper has been observed to passivate in CMP slurries containing glycine, when hydrogen peroxide is used as an oxidant, even under acidic conditions where no solid oxidized phases appear on the potential-pH diagram. This passivation behavior is highly desirable for effective CMP. In contrast, passivation is not seen in slurries of similar pH and complexing agent concentration, where the potential is increased electrochemically. In order to model the effects of chemistry on CMP rates, we are endeavoring to better understand the mechanisms responsible for passivation in slurries containing hydrogen peroxide. Here we report tests that characterize the development and degree of passivation seen in slurries with a reasonably wide range of compositions.
The pH Effect On Chemical Mechanical Planarization Of Copper
Authors: Du Tianbao , Desai Vimal 
Published: June 2019

AbstractThis study explores the effect of pH on the chemical mechanical polishing (CMP) characteristics of copper in H2O2 and KIO3 based slurries under various dynamic and static conditions. High purity copper disc was used to study the dissolution and oxidation kinetics at various pH (2 to 10) with 5% H2O2 or 0.1M KIO3. Electrochemical techniques were used to investigate the dissolution/passivation behavior of Cu. The affected surface layers of the statically etched Cu-disc were investigated using X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). In 5% H2O2, the Cu removal rate decreases with an increase in pH and reaches minimum at pH 6, and then increases under alkaline conditions. XPS results indicate that the surface oxide formed at various pH values was responsible for this CMP trend. However, with 0.1M KIO3, the CMP removal rates were found to be lower at pH 2. The maximum was observed at pH 4, then the removal rate decreased with the increase of pH. The lower value of removal rate at pH2 was due to the fast interaction between Cu and KIO3 and the precipitation of CuI on the pad, which makes the pad glassy, resulting in lowered removal rates. This was confirmed by XPS measurements. The decreased CMP removal rates when the pH is higher than 4 might be due to the weaker oxidation power of KIO3 with the increase of pH.
A New Cleaning Technique for Corrosion Protection in Aluminum Metallization
Authors: Kodera Masako , Uekusa Shin-ichiro , Matsui Yoshitaka , Miyashita Naoto , Shigeta Atsushi , Takahashi Shinya , Kawai Murato , Kawamoto Hiroshi , Tsujimura Manabu 
Published: June 2019

AbstractA new cleaning technique using gas dissolved water has been found to be effective in protecting against corrosion in aluminum metallization, which is also useful in post-cleaning of Cu CMP as already reported. Corrosion can be a significant concern in aluminum as well as in copper metallization. In Al CMP process, corrosion often occurs in contact with DIWbecause of the big potential difference between Al and the barrier metal. In this study, it has been confirmed that gas dissolved water is able to change the potential of various metal films, and that following Al CMP, post-cleaning using gas dissolved water instead of DIW can successfully protect against corrosion.Furthermore this technique is also effective in the post-cleaning process of Al wiring formed by RIE, which contains a slight amount of Cu. Because segregation of copper at the side-wall of wiring often occurs during RIE and the following processes, Al-Cu wiring is easily corroded during the DIW rinsing step in wet cleaning, which may cause killer defects. Gas dissolved water can remarkably decrease the potential difference between Al-Cu alloy and segregated Cu, as well as Al-Cu alloy and the Ti/TiN used as a barrier metal. Moreover, because it seems that a reaction occurs between cathode water and Ti/TiN, where electrons may be supplied there to corrosive sites, corrosion can be prevented.
Delamination Behavior of Cu-Low-k Stack Under Different Slurries
Authors: Sikder A. K. , Thagella S. , Zantye P. B. , Kumar Ashok 
Published: June 2019

AbstractLower mechanical strength, reduced cohesive strength and lack of compatibility with other interconnect materials, are the major challenges involved in chemical mechanical polishing (CMP) of Cu metallization with ultra low-k materials as interlayer dielectrics. In this study we have investigated the polishing behavior of patterned Cu samples with underneath different low-k materials using two different slurries and a wide range of machine parameters. CMP micro tribometer was used to polish the samples with different rotations of platen (50 to 250 RPM) and down forces (1-6 PSI). Friction co-efficient and wear behavior were also investigated at different conditions. Optical and scanning electron microscopy was used to investigate the polished surface. It was observed that the two different Cu slurries used for polishing have marked effects on the polishing of Cu-low-k stack with respect to wear and delamination.
Integration Challenges for Chemical Mechanical Polishing of Cu/Low-κ Interconnects
Authors: Lee Jeffrey A. , Moinpour Mansour , Liou Huey-Chiang , Abell Thomas 
Published: June 2019

AbstractThe drive for improved performance of microelectronic devices has led to the prevalence of copper metallization and the aggressive development of low-permittivity (low-κ) dielectric materials for use as interlayer dielectrics in BEOL interconnect structures. Progressive scaling of metal line widths coupled with the need to incorporate ultra low-κ (ULK) dielectrics, with κ<2.2, presents numerous challenges for integration and reliability. Perhaps the most significant challenge for the 90nm technology node and beyond is successful planarization of Cuinterconnect structures by chemical mechanical polishing (CMP). The present paper will discuss the general integration challenges and key structural reliability issues for chemical mechanical polishing of Cu-interconnects incorporating ULK dielectric materials.
Laser-Crystallized High Quality ITO on Plastic Substrates for Flexible Displays
Authors: Chung Wonsuk , Wickboldt Paul , Toet Daniel , Carey Paul G. , Thompson Michael O. 
Published: June 2019

AbstractIn the study presented here, we successfully demonstrated that high quality ITO films could be obtained on plastic substrates using Excimer laser crystallization. ITO films were first deposited at 10 °C on PEN substrates by DC magnetron sputtering, and then irradiated using a homogenized pulsed XeCl excimer laser beam (308 nm, 35 ns pulse duration) in a vacuum chamber. It was possible to reliably attain Type I ITO films with sheet resistances down to 35 Ω/΢, combined with 80 % optical transmittance in visible range. Well defined 2 μm lines could be obtained using simple HCl etchant at room temperature. We also developed Type II ITO films with a sheet resistance of 15 Ω/΢ and an optical transmittance of 80 % by means of laser annealing on plastic substrates, although these materials were found inferior to Type I in etching properties.
Development of High Permeability Core Materials for Embeddable Inductors in Flexible Organic Substrates
Authors: Liu C. K. , Cheng P. L. , Leung S. Y. Y. , Law T. W. , Lam D. C. C. 
Published: June 2019

AbstractCapacitors, resistors and inductors are surface mounted components on circuit boards, which occupy up to 70% of the circuit board area. For selected applications, these passives are packaged inside green ceramic tape substrates and sintered at temperatures over 700°C in a co-fired process. These high temperature processes are incompatible with organic substrates, and low temperature processes are needed if passives are to be embedded into organic substrates. A new high permeability dual-phase Nickel Zinc Ferrite (DP NZF) core fabricated using a low temperature sol-gel route was developed for use in embedded inductors in organic substrates. Crystalline NZF powder was added to the sol-gel precursor of NZF. The solution was deposited onto the substrates as thin films and heat-treated at different temperatures. The changes in the microstructures were characterized using XRD and SEM. Results showed that addition of NZF powder induced low temperature transformation of the sol-gel NZF phase to high permeability phase at 250°C, which is approximately 350°C lower than transformation temperature for pure NZF sol gel films. Electrical measurements of DP NZF cored two-layered spiral inductors indicated that the inductance increased by three times compared to inductors without the DP NZF cores. From microstructural observations, the increase is correlated with the changes in microstructural connectivity of the powder phase.
Dielectric Properties of Layer Polymer Films
Authors: Sakai W. , Yoshiji T. , Tsutsumi N. , Chiang C. K. 
Published: June 2019

AbstractThe dielectric and thermal properties of three-layer structured films were studied. The two outer layers were about 1 μm and the thickness of the middle layer was varied. We measured the thickness dependence of the dielectric constant of the three-layer structured films. The dielectric results were evaluated with a simple serial three-capacitance model. Local thermal property of these polymer films were also measured using a micro-tip local thermal analysis method. Local glass transition of the film was compared with the one expected from bulk data.