bluuebunny/crossref_metadata_2025_split huggingface dataset:
Comparison of Ru/Ta and Ru/TaN as Barrier Stack for Copper Metallization
Authors: Qu Xin-Ping , Tan Jing-Jing , Zhou Mi , Chen Tao , Ru Guo-Ping , Li Bing-Zong 
Published: April 2011

AbstractThe diffusion barrier properties for ultrathin Ru/Ta and Ru/TaN bilayer structure as the copper diffusion barrier are compared. Cu, Ru, Ta and TaN thin films are deposited by using the ion beam sputtering technique. The experimental results show that the thermal stability of the Cu/Ru/Ta or TaN /Si structure is much more improved than that of the Cu/Ru/Si structure without the interlayer. However, the Cu/Ru/TaN/Si shows better thermal stability than the Cu/Ru/Ta/Si structure, which should be attributed to the amorphous nature of the TaN interlayer. The microstructure evolution of the Cu/Ru/Ta (TaN)/Si structure during annealing is discussed. The results show that the Ru/TaN bilayer can be a very promising diffusion barrier in the future seedless Cu interconnect technology.
Low Temperature Plasma Etching of Copper for Minimizing Size Effects in sub-100 nm Features
Authors: Kulkarni Nagraj S , Tamirisa Prabhakar , Levitin Galit , Kasica Richard J , Hess Dennis W 
Published: April 2011

AbstractA low temperature plasma etching process for patterning copper interconnects is proposed as a solution to the size effect issue in the resistivity of copper. Key features of this etching process based on a previous thermochemical analysis of the Cu-Cl-H system are discussed. Potential benefits of a subtractive etching scheme based on this process in comparison with the damascene scheme for copper-based interconnect processing in sub-100 nm features are presented in the context of the ITRS roadmap. Preliminary experimental work on plasma etching of Cu thin films using the proposed process is discussed.
Determination of Poisson's Ratio of Thin low-k Films using Bidirectional Thermal Expansion Measurement
Authors: Ye Jiping , Shimizu Satoshi , Sato Shigeo , Kojima Nobuo , Noro Junnji 
Published: April 2011

AbstractA recently developed bidirectional thermal expansion measurement (BTEM) method was applied to different types of low-k films to substantiate the reliability of the Poisson's ratio found with this technique and thereby to corroborate its practical utility. In this work, the Poisson's ratio was determined by obtaining the temperature gradient of the biaxial thermal stress from substrate curvature measurements, the temperature gradient of the whole thermal expansion strain along the film thickness from x-ray reflectivity (XRR) measurements, and reduced modulus of the film from nanoindentation measurements. For silicon oxide-based SiOC film having a thickness of 382.5 nm, the Poisson's ratio, Young's modulus and thermal extension coefficient (TEC) were determined to be Vf = 0.26, αf =21 ppm/K and Ef =9,7 GPa. These data are close to the levels of metals and polymers rather than the levels of fused silicon oxide, which is characterized by Vf = 0.17 and Er = 69.6 GPa. The alkyl component in the silicon oxide-based framework is thought to act as an agent in reducing the modulus and elevating the Poisson's ratio in SiOC low-k materials. In the case of an organic polymer SiLK film with a thickness of 501.5 nm, the Poisson's ratio, Young's modulus and TEC were determined to be Vf = 0.39, αf =74 ppm/K and Er =3.1 GPa, which are in the typical range of V= 0.34~0.47 with E =1.0~10 GPa for polymer materials. From the viewpoint of the relationship between the Poisson's ratio and Young's modulus as classified by different material types, the Poisson's ratios found for the silicon oxide-based SiOC and organic SiLK films are reasonable values, thereby confirming that BTEM is a reliable and effective method for evaluating the Poisson's ratio of thin films.
The Role of Arginine as a Complexing Agent in Copper CMP
Authors: Moganty Surya Sekhar , Srinivasan Ramanathan 
Published: April 2011

AbstractChemical mechanical polishing (CMP) of copper was investigated in hydrogen peroxide and arginine slurries. Arginine was found to be a complexing agent for the copper in peroxide based slurries, in the alkaline region. The copper polish rate was measured in a Struers LaboPol-5 and LaboForce-3 CMP polishing tool. Static etch rate experiments of copper discs (25.4 mm Dia × 10 mm) were carried in 200 ml beakers with different combinations of hydrogen peroxide and arginine concentrations. Peroxide concentration was varied from 0 to 10 vol%, while the arginine concentration was varied from 0 to 1 wt% for both static etch and polish rate experiments. Fumed silica used as the abrasive medium for polishing.The electrochemical processes involved in oxidative dissolution of copper were investigated by the Tafel corrosion plots and OCP measurements, using the Princeton Applied Research potentiostat. Three electrode corrosion flat cell was used for the electrochemical measurements. Corrosion current density and open circuit potentials (OCP) were used to elucidate the oxidative behavior of peroxide and the complexing role of arginine. Surface characteristics of the polished copper surface were analyzed with the Digital Instruments NanoScope AFM. Polishing with these chemicals resulted in smooth finish.These results indicated that the arginine curtails the formation of oxidative layer on the copper surface and the removal rate was increased by forming complex with the copper.
A Novel Optical Technique to Measure Pad-Wafer Contact Area in Chemical Mechanical Planarization
Authors: Elmufdi Carolina L. , Muldowney Gregory P. 
Published: April 2011

AbstractReal contact area between a CMP pad and wafer is a key factor in local contact pressure, friction and pad wear, all of which impact material removal and defect formation. A new optical method is introduced that quantifies the real contact area during polishing. Confocal reflectance interference contrast microscopy (C-RICM) uses a single focal plane to image the pad-wafer contact interface. A sapphire cover slip is used to provide optical transparency and to match the refractive index of the pad. Imaging the pad surface through the cover slip reveals areas of no reflection (pad-cover slip contact), areas of reflection (non-contact), and interference fringes (near contact). The C-RICM method was validated using micro-fabricated pads having uniform arrays of cylindrical surface structures of known contact area. Experiments conducted on porous polyurethane pads revealed that the real contact area is less than 10% of the total presented area. However Greenwood-Williamson (G-W) theory, widely used in CMP material removal models, predicts a contact area at least a factor of ten smaller. The discrepancy was found to result at least in part because the individual contact zones are not elliptical as assumed in G-W theory. In fact many contacting structures are crescents located at the perimeter of individual pores. These findings underscore the need for accurate control of pore density and morphology in polishing pads, in both initial manufacture and surface conditioning during CMP. The C-RICM method allows non-destructive benchmarking of polishing media in terms of pad-wafer contact, essential for developing improved pad architectures that achieve lower CMP defect levels.
Evaluation of Inhibitors for ECMP of Copper Using Electrochemical Quartz Crystal Microbalance (EQCM) Technique
Authors: Muthukumaran Ashok , Lowalekar Viral , Raghavan Srini 
Published: April 2011

AbstractChemical formulations for the electrochemical mechanical planarization (ECMP) of copper must contain constituents that are stable at anodic potentials. A key component of the formulation is a corrosion inhibitor, which is required to protect low lying areas while higher areas are selectively removed. Organic compounds, which adsorb on copper at low overpotentials and form a film by oxidation at higher overpotentials, may be particularly useful for ECMP. The objective of this work is to evaluate the effect of two inhibitors on copper dissolution in oxalic acid based systems using an electrochemical quartz crystal microbalance (EQCM) technique. By recording current as well as mass changes during the application of potential to electrodeposited copper films, the extent and mechanism of inhibition of sulfhydryl based acid (SBA) inhibitor has been explored.
Simple Detection of Binding Events Using an Anchoring Transition of Liquid Crystals on the Immobilized oligoDNAs
Authors: Kim Hak-Rin , Choi Min-Geon , Kim Joo-Eun , Choi Eui-Yul , Oh Sang-Wook , Kim Jae-Hoon 
Published: April 2011

AbstractTo detect biological events, biosensors require a transducer part where specific biomolecular binding events at a bioreceptor part is converted to measurable quantitative signals. Currently, most of biosensors adopt a fluorescent or radioactive probing technique as a transducer. However, such approaches require expensive and sophisticated analysis procedures with laboratory-based equipment.In this work, we propose a novel method for optically detecting hybridization results in a deoxyribonucleic acid (DNA) chip using an anchoring transition of liquid crystal (LC) alignment. To investigate the effects of structural changes of DNA on the LC alignment, we used a functional substrate on which single-stranded oligonucleotide DNA (ssDNA) was selectively immobilized to a Biotin Chip substrate. In our experiment, we used a 19-mer oligoDNA or p53 tumor suppressor as a bioreceptor and its complementary partner oligoDNA as a target material.Before hybridization, surface nematic LC (NLC) molecules on the immobilized ssDNAs are homeotropically aligned by a steric interaction between the freely penetrated NLC molecules and the ssDNA. After hybridization, the penetration of the NLC molecules is hindered by the double strand DNA (dsDNA) due to their increased packing density. Such an interface condition makes the surface ordering of the NLC molecules very weak, as a result, the NLC in the bulk has a planar inhomogeneous orientation. Although hybridization events of the DNA and the subsequent molecular interaction between the immobilized DNA and the NLC molecules takes place within a layer whose thickness is in the tens of nm, such binding events can be communicated to the NLC bulk beyond a distance of tens of μm though the long-range elastic deformation of the NLC molecules. Thus, the hybridization event is converted to amplified optical signals via birefringent nature of the NLC between crossed polarizers. Our NLC-based DNA chip array showed that the extinction ratio of transmitted light depending on the hybridization results was approximately four, which could be read by the naked eye. Since such anchoring behaviors on the immobilized DNA are very similar to those on the conventional amphiphilic homeotropic surfactant of LCs, it is expected that quantitative analysis of hybridization events can be explored with our simple system.
On the Role of Oxygen Vacancies in the Determination of the Gas-Sensing Properties of Tin-Oxide Nanowires
Authors: Mosca Roberto , Zha Mingzheng , Calestani Davide , Lazzarini Laura , Salviati Giancarlo , Zappettini Andrea , Zanotti Lucio , Comini Elisabetta , Sberveglieri Giorgio 
Published: April 2011

AbstractSnO2 nanowires have been recently employed in the “gas-sensors” field and excellent results of conductometric and optical tests on SnO2 nanowires-based gas sensors have been reported.However, the mechanism that controls the gas-sensing effect in metal oxides nanowires is not fully understood yet. Here the authors present the first results of an in-depth study about the influence of post growth treatments on the physical and gas sensing properties of SnO2 nanowires.In particular, SnO2 nanowires grown by a vapour transport technique were annealed in a oxygen-rich atmosphere and then characterized by different techniques to assess the influence of the treatment on the nanowires properties.The annealing in oxygen atmosphere is shown to strongly affect the PL and CL spectra, the electrical resistivity as well as the gas sensing properties of the nanowires. The obtained results are consistent with a reduction of the oxygen vacancies concentration induced by the O2 treatment and seem to confirm the role of these defects in affecting the gas response of SnO2 nanowires-based sensors.
A Computational Study on SnO2 Au-Doped Grains: CO Adsorption
Authors: Mazzone Anna 
Published: April 2011

AbstractIn this study an analysis is made of the adsorption properties of nanocrystalline SnO2 containing a metallic dopant. The analysis is based on semi-empirical Hartree-Fock and scattering theories and the structures considered are SnO2 grains with a rutile lattice and a size comparable with the experimental ones. The grains contain rows of gold atoms located on the grain surface or in an endohedral position, in the grain interior, and the adsorbed system is generated by depositing a CO molecule on the grain surface. The calculations illustrate the dependence of the binding energies and ofthe conductance on the grain size, on the location of the metallic additives in both the clean and in the CO-adsorbed grains. New mechanisms of adsorption and of current transport are proposed.
Thermal Stability of Supported Noble Metal Nanoclusters
Authors: Kutluk Galif , Yagi Shinya , Sumida Hirosuke , Namatame Hirofumi , Taniguchi Masaki 
Published: April 2011

AbstractHighly dispersive and size controlled Pd and Pt nanoclusters have been synthesized by gas condensation and Arc plasma source. The morphology, crystallographic structures, electronic structure and the temperature dependence of chemical states of nanocluster were investigated by using TEM, AFM, EXAFS and XPS, respectively. The results show that non-passivized Pd nanoclusters with the size of 1.5~ 5.7nm are consisted with pure Pd core covered by highly oxidized PdO2 thin layer. The dioxide state PdO2 layers start to converting to Pd at 120°C and vanishing at 180°C in a reduction atmosphere.
Effect of Calcination Temperature on Interface Properties Between In2O3 and Au Electrode in Micro Gap Semiconductor Gas Sensors
Authors: Tamaki Jun , Niimi Jun , Konishi Satoshi 
Published: April 2011

AbstractThe In2O3 thin film nanosensors were fabricated by dropping In(OH)3 sol on nano gap electrode with 0.1-2.5 micron of gap size, dried, and calcined at various temperatures. The grain size of In2O3 and thus the number of In2O3 grains were changed by calcining at 600-850 °C. The size of grain was increased from 15 nm at 600 °C to 55 nm at 850 °C, and thus the number of grains in 0.3 micron gap was decreased from 19 to 5.3. Contrary to the expectation, the small resistance changes to both 1 ppm Cl2 (resistance increase) and 0.5 ppm Cl2 (resistance decrease) were obtained for In2O3 nanosensors calcined at 700-850 °C. These were contributed to the changes in the surface and interface chemical state to suppress the adsorption of or substitution with Cl2 molecule.
Investigation of the humidity effects on SnO2-based sensors in CO detection
Authors: Malagu' Cesare , Benetti Michele , Carotta Maria Cristina , Giberti Alessio , Guidi Vincenzo , Milano Luciano , Martinelli Giuliano 
Published: April 2011

AbstractAn algorithm for compensating water vapor pressure in CO detection is proposed here and tested on SnO2 thick-film gas sensors. For each sensor working at a fixed temperature, the conductance, G, is fitted by an analytical surface, whose expression can be inverted to determine the CO concentration once the water partial pressure is measured. As soon as the rate of water-vapor pressure change is slower than about 300 Pa/min, G is a function of the temperature, water vapor and CO concentration. If quicker water vapor variations occur instead, the sensing film undergoes a non-negligible transitory phenomenon during which G assumes different values even at fixed water vapor pressure and temperature. This phenomenon prevents the compensation from working properly. An explanation of the behavior is offered by the interpretation of kinetics equations at surface.
The Strain Status of the Buried Self-assembled InAs quantum dots using MeV technique
Authors: Wang Hsing-Yeh , Chen C.H. , Niu H. , Wu S.C. , Lee C.P. 
Published: April 2011

AbstractThe strain status of the buried InAs self-assembled quantum dot was comprehended by measurement first time. Results show the in-plane strain is compressive and lattice in the growth direction is lager than the lattice of GaAs. The strain of the sample annealed at 650 degree relaxes in the growth direction. The growth and the lateral direction become relaxed in the sample annealed at 750 degree.
Luminescence properties of newly developed red-emitting phosphors M2Si2O7:Eu3+ (M=La, Y) under UV/VUV excitation
Authors: Zhang Zhiya , Wang Yuhua 
Published: April 2011

AbstractThe red-emitting phosphors of Eu3+ doped M2Si2O7 (M=La, Y) were synthesized by a solid-state reaction method and their luminescence properties in UV-VUV region have been studied. On the excitation spectra, the Eu3+-O2- CT band is of higher intensity for La2Si2O7, while for Y2Si2O7, the absorption around 150nm is much stronger and this can be assigned to the Y3+-O2- CT band in company with the Si-O group absorption. The emission spectra show higher intensity and better color purity for La2Si2O7:Eu3+ under 254nm excitation due to Eu3+ occupying the non-centrosymmetric site. Under 147nm excitation, Y2Si2O7:Eu3+ exhibits stronger emission with purer red, which can be corresponded to the absorption of Y3+-O2- CT in the VUV region.
Selective Area Heteroepitaxy of Nano-AlGaN UV Excitation Sources for Biofluorescence Application
Authors: Jindal Vibhu , Grandusky James , Shahedipour-Sandvik Fatemeh , LeBoeuf Steven , Balch Joleyn , Tolliver Todd 
Published: April 2011

AbstractWe report on the selective area heteroepitaxy and facet evolution of AlGaN nanostructures on GaN/sapphire substrate using various mask materials. We also report on the challenges associated with selection of an appropriate mask material for selective area heteroepitaxy of AlGaN with varying Al composition. The shape and the growth rate of the nanostructures are observed to be greatly affected by the mask material. The evolution of the AlGaN nanostructures and Al incorporation were studied exhaustively as a function of growth parameters; including temperature, pressure, NH3 flow, total alkyl flow and TMAl/(TMAl+TMGa) ratio. The growth rate of nanostructures was reduced drastically when higher Al percentage AlGaN nanostructures were grown. The growth rates were increased for higher Al percentage AlGaN using a surfactant which resulted in a high quality pyramidal structure. As indicated by high resolution x-ray diffraction (XRD) and cathodoluminescence (CL) spectroscopy, composition of Al in the AlGaN nanostructure is significantly different from that of a thin film grown under the same growth conditions.
Area Selective Atomic Layer Deposition by Soft Lithography
Authors: Chen Rong , Porter David W. , Kim Hyoungsub , McIntyre Paul C. , Bent Stacey F. 
Published: April 2011

AbstractArea selective HfO2 thin film growth through atomic layer deposition (ALD) has been achieved on octadecyltrichlorosilane (ODTS) patterned Si substrates. Patterned hydrophobic self-assembled monolayers (SAMs) were first transferred to Si substrates by micro-contact printing. Using hafnium-tetrachloride or tetrakis(dimethylamido) hafnium(IV) and water as ALD precursors, amorphous HfO2 layers were then grown selectively on the SAM-free regions of the surface where native hydroxyl groups nucleate growth from the vapor phase. The HfO2 pattern was readily observed through scanning electron microscopy and scanning Auger imaging, demonstrating that soft lithography is a simple and promising method to achieve area selective ALD. To evaluate the selectivity, the resolution of the soft lithography based method was compared with that of area selective ALD of HfO2 by selective surface modification of patterned silicon oxide obtained using long-time SAM exposure. It was found that the selective surface modification showed much higher spatial resolution and selectivity, an observation consistent with previous studies indicating that highly ordered and densely packed ODTS films were important to achieve complete deactivation.
Phase Change Materials - From Structures to Kinetics
Authors: Wuttig Matthias , Welnic Wojciech , Detemple Ralf , Dieker Henning , Kalb Johannes , Wamwangi Daniel , Steimer Christoph 
Published: April 2011

AbstractPhase change materials possess a unique combination of properties which include a pronounced property contrast between the amorphous and crystalline state, i.e. a high electrical and optical contrast. In particular the latter observation is indicative for a considerable structural difference between the amorphous and crystalline state. At the same time the crystallization of the amorphous state proceeds on a fast time scale. This raises the question how structure, properties and kinetics are related in phase change alloys. It will be demonstrated that only a small group of covalent semiconductors with octahedral-like coordination has the required property combination. This is related to their thermodynamic properties which govern the kinetics of crystallization.
Thermal Analysis and Structural Design of Phase Change Random Access Memory
Authors: Zhao Rong , Lim Ler Ming , Shi Luping , Lee Hock Koon , Yang Hongxin , Chong Tow Chong 
Published: April 2011

AbstractA thermal modeling based on Finite Element Method (FEM) was used to simulate Phase Change Random Access Memory (PCRAM) cells. The factors affecting temperature distribution of a PCRAM cell structure such as geometry, device structure and the properties of the individual materials were investigated. The results of the analysis provided the fundamental design of a novel cell structure which has a better performance and reliability.