bluuebunny/crossref_metadata_2025 huggingface dataset:
Stability and Oxidation Behavior of Ir Thin Film Electrodes on Si and SiO2
Authors: Saenger K.L. , Grill A. , Shaw T.M. , Neumayer D.A. , Lin Chenting , Wang Y.Y.
Published: April 2011

This paper examines factors affecting the oxidation behavior of Ir thin film electrodes and the stability of bilayer Ir/Ir-Ir-O-Si electrodes on silicon substrates. We first examine the morphology and texture of faceted IrO2 extrusions formed on the Ir films during thermal oxidation, and show that an Ir grain-growth anneal in N2 at 650°C for 5 min prior to the oxidation treatment increases both the areal density of IrO2 extrusions and the IrO2<110> x-ray diffraction intensity while decreasing apparent film roughness. We then examine the stability of bilayer lr(100 nm)/Ir(20 nm) films on polycrystalline silicon and show how fairly mild oxygen anneals of the Ir(20 nm)/Si structures can provide an in-situ formed Ir-O-Si barrier that protects the subsequently deposited Ir(100 nm) layer from silicidation reactions during annealing in N2 ambients at 750°C. Transmission electron microscopy indicates that this in-situ formed barrier at the Ir/Si interface has a two layer structure comprising an IrSix underlayer in contact with the silicon substrate and an SiO2 overlayer directly below the remaining Ir.
Simple Electrode-Barrier Structure Using Ir for Integration of PZT-Based High-Density Nonvolatile Memories
Authors: Lee Kwang B. , Tirumala S. , Song Y. , Ryu Sang O. , Desu Seshu B.
Published: April 2011

We have investigated the electrode-barrier properties of Ir for PZT-based nonvolatile memories. Ir layer was rf-sputtered onto a poly-Si coated Si wafer. PZT thin films were deposited on Ir/poly-Si/SiO2/Si by means of sol-gel spin coating. Highly c-axis oriented perovskite PZT thin films were obtained, which might be due to the interface-controlled growth. We found that Ir in itself acted as an oxygen barrier, which was confirmed from the measurement of P-E hysteresis loops with the electrical contact between top-electrode and bottom-poly-Si. Remanent polarization and coercive field of 1rO2/PZT/Ir/poly-Si capacitor were 20 μC/cm2and 30 kV/cm, respectively and the capacitor showed negligible polarization fatigue up to 1011 switching repetitions. However, the leakage current density at the field of larger than 80 kV/cm was high, which was believed to be related to the unknown phase in PZT caused by the reaction of PbO with bottom-Ir. Such high leakage current behavior could be successively improved by the insertion of vacuum-annealed IrOx buffer layer between PZT/Ir. The electrical properties of IrOx/PZT/annealed-IrO2Ir/poly-Si capacitors are also discussed.
Surface Roughness and Growth Texture of (Ba,Sr)TiO3 Thin Films Formed by MOCVD
Authors: Gao Y. , Alluri P. , He S. , Engelhard M. , Lea A.S. , Finder J. , Melnick B. , Hance R. L.
Published: April 2011

Metalorganic chemical vapor deposition (MOCVD) has been used to grow (Ba,Sr)TiO3 thin films on Ir/SiO2/Si substrates. β-diketonates of Ba, Sr, and Ti were used as the precursors, and delivered to the reactor via direct-liquid injection. Growth rate and film thickness were monitored by in-situ spectroscopic ellipsometry, and determined after growth. Film growth was studied as a function of film thickness, composition, substrate temperature, and mixture of O2 and N2O with and without microwave plasma enhancement. Dense, mirror-like films were obtained under all conditions except when pure oxygen plasma enhancement was used. Surface roughness of the films appears strongly dependent on film thickness and composition. Film composition and growth temperature determine growth texture of the films. This paper describes these results as well as the correlation between these results and dielectric properties.
Low Temperature Crystallization of SrBi2Ta2O9 Film by Excimer Laser Irradiation
Authors: Seol K.S. , Hiramatsu H. , Ohki Y. , Shin D.-S. , Choi I.-H. , Kim Y-T.
Published: April 2011

Using a KrF or ArF excimer laser as an irradiation photon source, we have succeeded in crystallizing amorphous SrBi2Ta2O9 films at 200-290°C, quite lower temperatures than the conventional crystallization temperature. The crystallization is enhanced when the substrate temperature, irradiation time, or the laser power density is higher.
Studies of Dielectric Properties of Pulsed Laser Deposited (Ba, Sr)TiO3 Films Using LaNiO3 as Conductive Electrode
Authors: Srivastava Anuranjan , Kumar D. , Singh Rajiv K.
Published: April 2011

LaNiO3 (LNO) films were used as conductive bottom and top electrodes for the fabrication of (Ba0.5Sr0.5) TiO3 (BST) capacitors on silicon substrates. LNO as well as BST films were grown in-situ using a pulsed laser deposition technique with no subsequent heating or oxygenation treatments. Capacitance and leakage current measurements of BST films were carried out using LNO/BST/LNO/Si structures. Using these measurements, the dielectric constant and leakage current of BST films were found to be ∼250 and ∼10−8 A/cm2, respectively. The results obtained in the present study suggest that LNO is a good contact electrode material for BST films in the fabrication of BST capacitors with good structural and electrical properties.
Electrical Properties of Fully Epitaxial PZT/MgO/Si Stacked Structures for Nonvolatile Future Memory Devices
Authors: Senzaki J. , Ueno T.
Published: April 2011

Fully epitaxial Pb (Zr,Ti)O3(PZT)/MgO/Si(001) stacked structures, one of the potential components of ferroelectric-gate FETs, have been fabricated and characterized. According to the structural and electrical characterization of MgO/Si structures, epitaxially grown MgO thin films on the Si substrates showed a small leakage current of ∼ 10−8 A/cm2 at the electric field of 1 MV/cm. In the C-V measurements of the as-grown MgO/Si heteroepitaxial interfaces, injection-type hysteresis was observed because of the crystal defects in the MgO film adjacent to the interface. Using oxygen annealing with a temperature of 400 °C, it showed no hysteresis and a lower interface trap density of the order of 1011 cm−2eV−1 could be achieved with no formation of a low dielectric layer at the MgO/Si interface. These results indicate that the epitaxial MgO thin films are applicable as the gate insulators of FETs. After the PZT film was deposited on the MgO/Si structure, the C-V characteristic of the stacked structure showed a ferroelectric hysteresis curve and the low interface trap density of 5 × 1011 cm−2eV−1 A maximum memory window width of 1.2 V could be obtained in the PZT thin film on the Si substrate with a MgO intermediate layer.
Piezoelectric Characterisation of Ferroelectric PZT Thin Films Using an Improved Vibrating Beam Method
Authors: Defay E. , Baboux N. , Malhaire C. , Kleimann P. , Barbier D.
Published: April 2011

This study proposes an improvement of the free vibrating beam method allowing characterization of the d31 coefficients of piezoelectric thin films. Preparation and piezoelectric characterization of PZT thin films are shown. An analytical model of the beam and the thin film is developed. Finite element modeling allows for definition of the validity conditions of the model. A numerical fitting of the model to the experimental values exhibits an excellent overlap. We obtain d31 values from 10 pC/N to 14 pC/N. Advantages of this method are shown compared to the first maximum voltage method.
Electromechanical Properties of Lead-Based Ferroelectric Thin Films
Authors: Kholkin A. L. , Brooks K. G. , Taylor D. V. , Setter N. , Safari A.
Published: April 2011

Piezoelectric properties of Pb(Zr,Ti)O3 (PZT) and PbMg1/3Nb2/3O3-PbTiO3 (PMN-PT) films are investigated by interferometric technique combined with conventional dielectric and polarization measurements. It is shown that the piezoelectric d33 coefficient of both materials can be expressed based on their polarization and dielectric constant values using an equation for the electrostriction biased by the polarization. The obtained values of electrostriction coefficients are nearly field-independent and significantly smaller than in bulk materials of the same composition. Polarization offset is observed in PZT films subjected to bipolar fatigue, UV illumination and poling at high temperature, and is explained based on the pinning of ferroelectric domains in preferred orientations. The piezoelectric properties of rhombohedral PZT films are found to depend on their texture. The highest piezoelectric coefficient is observed in (100) oriented films, which have smaller polarization as compared to films having (111) preferred orientation. This difference is explained by the different values of electrostriction coefficients in materials with different textures.
Fabrication and Characterization of Pzt Thin-Film on Bulk Micromachined Si Motion Detectors
Authors: Garino T.J. , Tuttle B.A. , Laguna G. , Clem P.
Published: April 2011

Motion detectors consisting of Pb(ZrxTi(1−x))O3 (PZT) thin films, between platinum electrodes, on micromachined silicon compound clamped-clamped or cantilever beam structures were fabricated using either hot KOH or High Aspect Ratio Silicon Etching (HARSE) to micromnachine the silicon. The beams were designed such that a thicker region served as a test mass that produced stress at the top of the membrane springs that supported it when the object to which the detector was mounted moved. The PZT film devices were placed on these membranes to generate a charge, or a voltage, in response to the stress through the piezoelectric effect. Issues of integration of the PZT device fabrication process with the two etching processes are discussed. The effects of PZT composition and device geometry on the response of the detectors to motion is reported and discussed.
Fabrication and Characterization of Lithium Tantalate / PZT Composite Thick Film Ultrasonic Transducers
Authors: Chen Y. , Sayer M. , Zou L. , Jen C.-K.
Published: April 2011

Lithium tantalate (LiTaO3)/PZT ceramic films with thickness above 50 µm have been deposited on stainless steel substrates using a modified sol-gel process. LT powders are dispersed in a PZT sol-gel matrix to form 0-3 ceramic/ceramic composites. The dielectric and impedance response of the LiTaO3/PZT films supported by the substrates has been studied. The pulse echo response of the films as ultrasonic transducers demonstrates a broadband frequency response. The transducers can operate at least up to a temperature of 368°C.
Rf Magnetron Sputtering Epitaxially Grown (Pb,La)TiO3 Thin Films on (0001) A12O3 and (001) SrTiO3 for Nonlinear Optical Applications
Authors: Rabibisoa U. , Agius B.
Published: April 2011

Ferroelectrics are known to be excellent materials for nonlinear optics. Miniaturization of circuits using these materials requires an optimization of structural and morphological properties of thin films, to minimize optical losses. The first condition is the use of epitaxially grown thin films. The second one is the optimization of the morphological properties, in particular the roughness at the air/film and film/substrate interfaces must be the lowest possible.

The aim of this work is to study the effect of the deposition atmosphere on these properties for PLT thin films grown on (0001) A12O3 and (001) SrTiO3.
Crystallinity and Surface Morphology of Epitaxial (Sr,Ba)Nb2O6 Thin Film Prepared by Pulsed Laser Deposition with Two-Step Growth Sequence
Authors: Nakagawara Osamu , Shimuta Toni , Tanaka Katsuhiko , Katayama Yuzo
Published: April 2011

We have prepared epitaxially grown SBN thin film with c-axis orientation by an ArF pulsed laser deposition on SrTiO3(100). Pole figures show that the SBN film has a twin structure aligned at ±18.4: with the a-axis of SrTiO3. The epitaxial relationship of SBN<310> //SrTiO3 < 100 > is determined. The lattice mismatch between SBN and SrTiO3 is approximately 0.9%, which contributes to the desirable crystallinity of the SBN thin film. Furthermore, we have tried to form the SBN film with a two-step growth sequence in order to improve surface morphology. The amorphous initial growth region of 5 monolayers (2 nm thickness) is prepared with no substrate heating followed by post-annealing treatment at 720°C and additional growth on the initially crystallized layer. RHEED patterns of the SBN film with the two-step growth sequence have remained streaky throughout the film formation, compared with spotty patterns observed from films prepared by a conventional sequence. Atomic force microscope (AFM) images show that both the initial stage and final stage have extremely flat surfaces of rms≦ lnm which is a remarkably improved figure compared with the roughness rms ≧3nm for the film deposited at 720°C from the initial stage. These results suggest that the two-step growth sequence makes it possible to improve surface morphology to a nanometer level.
Structural Characterization of Pulsed Laser Deposited Ktn Thin Films
Authors: Savvinov A. A. , Siny I. G. , Katiyar R. S. , Pumarol M. , Mourad H. A. , Fernandez F. E.
Published: April 2011

The renewed interest in KTa1−xNbxO (KTN) mixed perovskite materials, especially in thin films of a high quality, is connected with their remarkable dielectric properties in the dilute compositions. Off-center Nb ions in the highly polarizable KTaO3 lattice provide a drastic increase in the dielectric peak up to 20 times in comparison with pure KTaO3 and KNbO3. We prepared KTN thin films with several Nb concentrations in the range of 0 ≤ x ≤ 1 by pulsed laser deposition from semented KTaO3, KNbO3 and KNO3 targets. The effect of the substrate and symmetry-breaking defects was studied by micro-Raman spectroscopy. An anomalous residual intensity of the forbidden first-order scattering modes in the cubic paraelectric phase of the KTN films was connected with the formation of polar microregions even far above the bulk Tc value. On the whole, the KTN film behavior shows the existence of specific defects enlarging the perovskite unit cell in the film so that the activity of off-center Nb ions increases in producing larger electric dipoles and extending the precursor phase above Tc.
Anomalous Diffusion in Membranes
Authors: Granek R. , Pierrat S. , Zilman A. G.
Published: April 2011

We study the undulations and the transverse diffusion of a tagged membrane point in both physical (passive) membranes and active biomembranes. In physical membranes thermal undulations generate a transverse subdiffusive motion, 〈r2〉 ∼ t2/3. Active biomembranes include active sites that use chemical energy to pump ions or molecules from one side to the other. In this case we find a few regimes which show a strongly enhanced diffusion, 〈r2〉 ∼ tα with 1 < α > 2.
Dielectric and Mechanical Relaxation of Glass-Forming Liquids in Nanopores
Authors: Wendt H. , Richert R.
Published: April 2011

We have measured the time resolved phosphorescence of different probe molecules in glassforming solvents under the condition of geometrical confinement in porous glasses. This solvation dynamics technique probes the local dielectric relaxation in the case of a dipolar chromophore in polar liquids. In the absence of dipolar interactions, the observed Stokes shifts reflect the local density or mechanical responses. Therefore, both orientational and translational modes of molecular motions can be measured for liquids imbibed in porous silica glasses. The effect of confinement on the relaxations of supercooled liquids is strongly dependent on the surface chemistry and can be rationalized on the basis of the cooperativity concept. As in the bulk case, we find that the relaxations in nano-confined liquids display heterogeneous dynamics. The density relaxation turns out to be more sensitive to the thermal history relative to the orientational features of molecular motion. By selectively positioning the chromophores at the liquid/solid interface, we observe also that the structural relaxation of the liquid in the immediate vicinity of the glass surface is slowed down but not entirely blocked.
Rotational Diffusion of Microconfined Liquids
Authors: Loughnane Brian J. , Farrer Richard A. , Fourkas John T.
Published: April 2011

The orientational behavior of liquids confined in nanoporous glasses has been studied using ultrafast Optical Kerr Effect spectroscopy. We discuss the detailed microscopic behavior of a weakly wetting liquid (methyl iodide) and a strongly wetting liquid (acetonitrile) confined in these glasses. We demonstrate that the behavior of methyl iodide is dominated by geometrical effects while the behavior of acetonitrile is dominated by surface interactions. We provide evidence that molecular exchange into the bulk is an important channel for the reorientation of strongly wetting liquids at interfaces.
Comparative Thermodynamic Behavior of Physically Restricted Cyclohexane and Cyclohexanone in Porous Silica
Authors: Amanuel S. , Malhotra V. M.
Published: April 2011

We undertook comparative differential scanning calorimeter (DSC) measurements on cyclohexane (C6H12) and cyclohexanone (C6H10O), physically confined in porous silica of pore radius 4, 7.5, 15, 30, and 62.5 nim, with a view to ascertain how guest fluid-surface host interactions affected the thermodynamic properties of the confined fluids. Our results can be summarized as follows: (a) No distinct signature of freezing or melting transition was observed for the physically confined cyclohexanone, irrespective of whether the bulk was present outside the pores. However, this was not the case for cyclohexane. (b) The solid-to-solid transition temperature of cyclohexane and cyclohexanone inversely scaled with the pore radius of the host porous silica. (c) The cubic-to-orthorhombic transition of cyclohexanone was strongly influenced by whether the bulk fluid was present outside the pores. In the absence of the bulk, the transition temperature was considerably suppressed relative to the bulk transition temperature. However, in the presence of the bulk, the confined and the bulk transitions occurred at the same temperature.
Nano-Scale Mechanical Characterization of Plasma Treated Polymer Surfaces
Authors: Dahl S. , Klemberg-Sapieha J. E
Published: April 2011

Recent advances in atomic force microscopy (AFM) allow one to perform complex analysis of materials surfaces and near-surface regions with a nanometer scale resolution; this includes the imaging of surface topography and the measurements of stiffness, elasticity, hardness and nano-tribological characteristics. Understanding of the complex AFM response is still in its early stage, and it frequently requires the use of multiple complementary techniques. In the present work we have applied AFM for the study of the surface and nearsurface mechanical properties of plasma-treated polycarbonate. The results from AFM analysis, such as the stiffness and the relative Young modulus, were compared with the hardness values obtained by depth-sensing indentation and by the micro-scratch technique. The characteristics of the observed hardened surface layer are discussed with respect to the role of the “interphase” in adhesion en1hancement of plasma-deposited films on polymers.
H-Atom Assisted jet Vapor Deposition of Parylene-n polymer
Authors: Halpern B. L. , Komarenko P. , Graves R. F. , Fuqua P. D. , Mcdonald J. F. , Yang G.-R. , Wang L. , Lu T. M. , Tomozawa M. , Maitthew I.
Published: April 2011

We describe a new approach to deposition of Parylene N thin films. It utilizes a small scale, sonic speed, Jet Vapor DepositionTM (JVDTM) process technology in place of the conventional larger scale, slow flow, Gorham apparatus. It employs a simple but powerful strategy to promote radical polymerization: exposure of the growing film, during deposition, to a high flux of atomic hydrogen. We believe that H atoms have two effects: they clean oxygen from the substrate, and they promote crosslinking in the Parylene film by abstraction of H atoms from the Parylene ring or side groups. With “H atom assisted JVD” Parylene N deposits and adheres even on warm substrates; it has reduced index of refraction and dielectric constant.
Characterization of Plasma-Deposited Au/Fluoropolymer Nanocomposite Films for Nonlinear Optical Application
Authors: Dalacu D. , Brown A. P. , Klemberg-Sapieha J. E. , Martinu L. , Wertheimer M. R. , Najafi S. I. , Andrews M. A.
Published: April 2011

Nanocomposite films consisting of gold nanoclusters embedded in a fluorocarbon matrix were prepared by simultaneous plasma polymerization of a fluorocarbon gas and magnetron sputtering of a gold target. The optical constants of the films were determined using variable angle spectroscopic ellipsometry (VASE). The Maxwell-Garnett (M-G) effective medium theory (EMT) was used to extract the microstructural characteristics (gold volume fraction, cluster size). The predictions of the M-G EMT were compared with the results from x-ray photoelectron spectroscopy. Angle-resolved measurements suggest the presence of a carbonaceous layer at the cluster surface. The presence of such a layer is discussed in the context of its influence on the validity of the optical model
Low k Film Etch in Applied Materials eMxP+ Chamber
Authors: Yu Melissa , Shan Hongching , Taylor Ashley
Published: April 2011

The materials with lower dielectric constant ( low k ) have been attracting attention recently because the low k material has the potential to be used in place of SiO2 in ULSI. In this work, we focused on evaluating organic low k material performance with plasma etch in the Applied Material's eMxP+ anisotropic etch chamber. The films studied were Dow Chemical BCB and Silk, Allied Signal Flare 2.0, and Du Pont FPI. The feature sizes of the wafer s were 0.25 to 1 micron trenches.
Du Pont FPI resulted in the highest achieved etch rate of more than lum/min, followed by BCB, and Flare. The microloading study indicated that the etch rate microloading is less than 10% between lum and 0.25 urn feature sizes, which suggests that the chance of etch stop for a high aspect ratio features will be small. The profile could vary from bowing to vertical, to tapering by using different process conditions, mainly by temperature. The FP1 profile was more tapered than those of BCB and Flare when the same process was used to etch the same type of patterned wafer having these three different low k films. The detailed study showed that the trend of etch rate and profile for BCB and Flare film etch were similar, but that the absolute value for profile, as well as the trend of etch rate uniformity and profile were somewhat different. In conclusion, low k materials can be etched in AMAT traditional dielectric chamber (eMxP+) with a good etch rate and profile control.
The Effects of Strain Rate and Minor Baron Addition on Brittle-to-Ductile Transition Temperature in Gamma TiAl Alloy
Authors: Lin(T. L. Lin) Dongliang , Wang Yu , Liu Junliang , Law Chi C.
Published: April 2011

Brittle-to-ductile transition (BDT) temperature (TBD) was evaluated according to temperature dependence of tensile properties under different strain rates from 10−5to 10−1s−1in two-phase Ti-47Al-2Mn-2Nb and Ti-47A1–2Mn-2Nb-0.8 TiB2alloys with nearly lamellar microstructure. Based on the strain rate dependence of the determined TBD values, apparent BDT activation energies were determined using Zener-Hollomon factor. Tensile fracture surfaces were observed using a scanning electron microscope while deformation substructures were investigated by transmission electron microscopy. It was found that the BDTT of both alloys increased sharply with the strain rate and that the minor addition of 0.8 vol% TiB2reduced TBD by about 100K at the same strain rate. The TiB2addition also decreases the apparent BDT activation energy from 324 to 256 kJ/mol. Both of these values approximate to self- or inter-diffusion of Ti and Al atoms in TiAl phase. Transgranular fracture and dimple fracture were found dominant in fracture surfaces below and above TBD, respectively. The most common 1/2<110] ordinary dislocations were found to begin climb at mound TBD. All this evidence, as well as a theoretical calculation using the Nabarro Model, add up to a conclusion that the BDT is controlled by dislocation climb in both alloys.
Microstructure of Rolled Ti-46.5Al-4(CrNb,Ta,B)
Authors: Inkson B. J. , Clemens H.
Published: April 2011

An industrial Ti-46.5A1–4(CrNb,Ta) alloy, with and without boron additions, has been successfully rolled to sheet 1.5mm thick. The microstructure of the sheet material has been characterised as a function of boron content and subsequent heat treatments. It is observed that rod-like (Ti-Ta)B precipitates are effective in refining the grain structure in both as-rolled and subsequently heat treated material. As-rolled microstructures rapidly cooled from the α + γ phase field contain unstable α2, which transforms to B2 phase on annealing below the α + γ tranus. Annealing in the α-phase field can result in a designed fully lamellar microstructure.
Infrared Joining of Titanium Aluminides by Using Ti-15Ni-15Cu Foil
Authors: Lee S. J. , Wu S. K.
Published: April 2011

The infrared joining of titanium-aluminides Ti50A150, Ti60Al40and Ti70A130at Tw= 1100∼1200°C for 30–60sec using Ti-15Cu-15Ni foil as brazing filler-metal was investigated. Multilayered structures are formed by isothermal solidification following solid-state interdiffusion. The diffusion of Al atoms is the main controlling factor pertaining to the microstructural evolution of the joint interface. Seven characteristic zones at Twcan be distinguished in the Ti50Al50joint: γ-TiAl (I and II), α + β two-phase mixed, high Al% α-phase, α2-Ti3Al, β-Ti and residual liquid filler-metal. Five characteristic zones at Tw, are obtained in the Ti70A130joint: α2-Ti3Al, α2+ β two-phase mixed, α + β two-phase mixed, β-Ti and residual liquid filler-metal. The observed joint microsturctures at room temperature are obtained from the phase transformation of these well-established high-temperature phases during cooling. A step-by-step microstructural evolution mechanism at Tw= 1150°C is proposed individually for Ti50A150and Ti70A130alloys. These steps are in good agreement with the observed microstructures and are consistent with the multiphase diffusion theories in solid-state systems. The microstructural evolution of Ti60A140joint interfaces can also be explained by the proposed step mechanisms for Ti50A150and Ti70A130alloys.
Electron Diffraction Study on the Crystal Structure of a Ternary Intermetallic Compound Co3AICx
Authors: Mishima Yoshinao , Hwang Keurn-Yeon , Wei Fu-Gao
Published: April 2011

Intermetallic compound Co3A1Cx, or called ic-phase, has been reported to assume the E21, or Perovskite structure. In the present work its crystal structure is critically reinvestigated in the two-phase alloys containing κ-phase in the Co primary solid solution matrix, α(Co), using conventional electron diffraction. It is shown that the crystal structure of κ-phase is a derivative of E21 being a cubic structure composed of eight E21 sub-unit cells in a half of which the body center sites are not occupied by carbon atoms. As a result, its space group is Fm3m and the chemical formula should be Co3AIC0.5. It is also found that the lattice parameter of the phase is about twice as large as that of α(Co). Orientation relationship of the κ-phase with the matrix α(Co) is found to be similar to the case for the γ' phase with the fcc γmatrix in a Ni-base superalloy since three orthogonal axes of κ-phase are parallel to those of α(Co). Lattice misfit under this orientation relationship between the two phases is found to be about 2.5%.
A T.E.M. Study of the Microstructure of a Ti48Al48Cr2Nb2 Alloy
Authors: Zghal S. , Thomas M. , Naka S. , Couret A.
Published: April 2011

The microstructures of as cast and air quenched Ti48Al48Cr2Nb2 alloys are analysed by transmission electron microscopy. Statistical analyses on the orientation variants and on the orientation relationships at the interfaces are presented. The results are used to have a better understanding on the formation mechanism of the lamellar microstructure.
Strength and Fracture Behavior of Aluminide Matrix Composites with Ceramic Fibers
Authors: Inoue M. , Suganuma K. , Niihara K.
Published: April 2011

This paper investigates the fracture behavior of FeAl and Ni3AI matrix composites with ceramic continuous fibers 8.5–10 μm in diameter. When stress is applied to these composites, multiple-fracture of fibers predominately occurs before matrix cracking, because the load carried by the fibers reaches their fracture strength. Fragments which remain longer than the critical length can provide significant strengthening through load bearing even though fiber breaking has occurred. The ultimate fracture strength of the composites also depends on stress relaxation by plastic deformation of the matrix at a crack tip in the multiple-fractured fibers. Ductilizing of the matrix by B doping improves the ultimate strength at ambient temperatures in both composites. However, their mechanical properties at elevated temperatures are quite different. In the case of Ni3AI matrix composites, embrittlement of the matrix is undesirable for high strength and reliability at 873–973 K.
Microstructure and Mechanical Properties of Nb-Al-N and Nb-Si-B Powder Compacts Produced by Spark Plasma Sintering
Authors: Murakamia T. , Kitaharab A. , Kawahara M. , Takahashid Y. , Inui H. , Yamaguchie M.
Published: April 2011

Nb-Al-N and Nb-Si-B powder compacts were prepared by spark plasma sintering, and their microstructure, mechanical properties and oxidation behavior were investigated. Adding nitrogen was easily done by blending or mechanically alloying Nb and AIN powders and then sintering them. The addition of nitrogen caused the formation of Nb2N in all the Nb-Al-N compacts and Nb2N and Nb3Al2N in compacts with high aluminum and nitrogen contents. The highest room-temperature hardness and the highest yield stress at 1473K were observed for compacts consisting of Nb2N and Nb3Al2N and those consisting of Nb2N and Nb2Al, respectively. Nb-Si-B compacts were prepared from elemental powders. Two or three of NbB2, Nb5Si3, Nb5Si3B2 and NbSi2 phases were identified as constituent phases of Nb-Si-B compacts depending on composition unless a large amount of silicon is consumed by forming SiO2. Contributions of NbB2, NbSi3 and Nb5Si3B2 phases to room-temperaturehardness and yield stress at 1973K were much larger than those of NbSi2. However, the oxidation resistance of Nb-Si-B compacts increased with increasing the volume fraction of NbSi2.The oxidation resistance of NbSi3B2 was better than that of NbSi3, but was not as good as that of NbSi2.
Hydrogen Sites In The α(TiCrSiO) 1/1 Approximant Phase
Authors: Kim J. Y. , Kim W. J. , Yelon W. B. , Gibbons P. C. , Kelton K. F.
Published: April 2011

Crystal approximant phases are important because they are believed to have a similar local atomic structure to corresponding quasicrystals. Interstitial hydrogen is used as a probe of the local structures of the Ti-based quasicrystals and crystal approximants. Phase pure samples of ct(TiCrSiO), a Mackay type 1/1 crystal approximant, which were plasma etched and coated with a thin layer of Pd, were loaded with deuterium from the gas phase to a maximum deuterium atom to metal atom ratio (D/M) of 0.26. After deuteration, the sample becomes a fine powder and remains single-phase. A Rietveld structural refinement of powder x-ray and neutron diffraction data was made to determine the location of the interstitial sites. For the fully deuterated sample the deuterium atoms sit at both octahedral and tetrahedral sites. The octahedral sites are formed by six Ti atoms in the first and second shells of the icosahedra. Deuterium atoms are also located at the tetrahedral interstitial sites formed between the clusters along <100> directions. In the partially loaded samples with DiM = 0.11, the deuterium atoms occupy only octahedral sites, demonstrating a preference for these sites.
Chemical Disorder And Columnar Vacancies In Ideal Decagonal AL-NI-CO Quasicrystals
Authors: Yan Yanfa , Pennycook S. J. , Tsai A.-P.
Published: April 2011

Abstruct

Atomic-resolution Z-contrast images provide conclusive evidence for chemical disorder in an ideal Al-Ni-Co quasicrystal. The so-called basic Ni-rich, high-temperature, quasiperiodic structure exhibits chemical disorder at the center of the 2 nm diameter clusters that involves both the Al and Ni(Co) atoms. The atomic structure of the 2 nm clusters is derived directly from the images and differs from previous models. The presence of closely-spaced, half-occupied atomic columns (or columnar vacancies) in specific rings within the clusters is directly observed. We propose that these columnar vacancies mediate the phason flips necessary for transformation to random tiling.
Nano-Quasicrystalline Particles In Mn-Ion Implanted GaAs
Authors: Sun K. , Zhu S. , Kuo K. H.
Published: April 2011

Both icosahedral and decagonal quasicrystalline particles of a few tens of nanometers in size have been found in Mn-ion implanted GaAs single crystals with a dose of 8×1016 Mn+/cm2 by high resolution electron microscopy (HREM). The identity of these quasicrystals was confirmed by the Fourier transforms made from these HREM images and their composition measured by micro-probe X-ray analysis and electron energy loss spectroscopy was 38–45 at.%Mn, the rest being Ga. The orientation relations among the icosahedral quasicrystal (i), the decagonal quasicrystal (d), and the GaAs matrix found by both HREM images and their Fourier transforms are: i- 5 // d-10 // GaAs[110] or [114]. In addition, nano-particles of a cubic, a hexagonal, and an orthorhombic Ga-Mn crystalline approximant have also been found in the GaAs matrix.
Bulk Mechanical Properties Of Quasicrystals
Authors: Takeuchi S.
Published: April 2011

Elastic moduli, anharmonicity, hardness and high temperature plastic behavior of icosahedral and decagonal quasicrystals are reviewed. Elastic properties are discussed in relation to the bonding nature of the quasicrystals. The plastic deformation behavior at high temperatures is discussed based on the characteristics of the dislocation mechanism in the quasiperiodic lattice. A Peierls potential, a phason relaxation and a dragging stress due to production of a defect field are considered as the controlling factors for the thermally activated dislocation glide; a dislocation in quasiperiodic lattice is accompanied not only by the elastic (phonon) strain field but also by the phason strain field which is difficult to be relaxed completely with the dislocation glide.
The Activation Parameters And The Mechanisms Of Plastic Deformation Of Al-Pd-Mn Single Quasicrystals
Authors: MessersChmidt U. , Geyer B. , Bartsch M. , Feuerbacher M. , Urban K.
Published: April 2011

In situ straining experiments on Al-Pd-Mn single quasicrystals in a high-voltage electron microscope between 675 °C and 750°C showed viscously moving dislocations with segments oriented in preferred directions. First measurements from video recordings indicate that dislocations on parallel traces move at two different velocities. For the first time, macroscopic samples were deformed in compression below 680 °C. Above a transition temperature of about 635°C for specimens of a fivefold compression axis and a strain rate of 10−5 s−1, the specimens show a yield point followed by a range of steady state deformation. Below that temperature, they are brittle. However, plastic deformation was achieved down to 555°C by using a lower strain rate and performing stress relaxation tests before the fracture stress was reached. The samples then show very strong work-hardening. The rapid decrease of the activation volume with decreasing temperature, which is characteristic of the high-temperature range, does not continue at low temperatures.The results are interpreted by dislocation generation and recovery and by the cluster friction mechanism controlling the dislocation mobility.
Ferroelectric Liquid Crystals For Non-Display Applications
Authors: Haase W. , Ganzke D. , Pozhidaev E. P.
Published: April 2011

A brief review of non-display devises based on ferroelectric liquid crystals (FLC‘s) is presented. The development of ferroelectric liquid crystal materials and corresponding electrooptical elements for non-display applications have been considered.
Colorless High Dielectric Compounds for Low Voltage Liquid Crystal Application
Authors: Wu Shin-Tson , Schwartz Robert N. , Zhang Qing T. , Marder Seth , Hsu Chain-Shu
Published: April 2011

Several colorless compounds with dielectric anisotropy in the 10-50 range were studied. The absorption spectra, phase transition temperature, birefringence, dielectric anisotropy and visco-elastic coefficient of these compounds were measured.
Advances in Holographic Polymer Dispersed Liquid Crystal Technology
Authors: Bowley C. C. , Fontecchio A. K. , Lin J.-J. , Yuan H. , Crawford G. P.
Published: April 2011

We discuss recent advances in reflective holographically-formed polymer dispersed liquid crystal materials in the context of their suitability for reflective display applications. A dual-domain phenomenon resulting in a broadened reflection peak is presented. A simple phenomenological model is developed to explain this unusual effect The effect of monomer functionality on the reflectance characteristics of these materials is also discussed. Monomers of effective functionality ∼4.5 yield the brightest holograms, however, the data suggests that these systems are currently far from optimal.
Characterization of Plated Cu Thin Film Microstructures
Authors: Gignac L. M. , Rodbell K. P. , Cabral C. , Andricacos P. C. , Rice P. M. , Beyers R. B. , Locke P. S. , Klepeis S. J.
Published: April 2011

Electroplated Cu was found to have a fine as-plated microstructure, 0.05 ±0.03 μm, with multiple grains through the film thickness and evidence of twins and dislocations within grains. Over time at room temperature, the grains grew to greater than 1 μm in size. Studied as a function of annealing temperature, the recrystallized grains were shown to be 1.6 ± 1.0 μm in size, columnar and highly twinned. The grain growth was directly related to the time dependent decrease in sheet resistance. The initial grain structure was characterized using scanning transmission electron microscopy (STEM) from a cross-section sample prepared by a novel focused ion beam (FIB) and lift-out technique. The recrystallized grain structures were imaged using FIB secondary electron imaging. From these micrographs, the grain boundary structures were traced, and an image analysis program was used to measure the grain areas. A Gaussian fit of the log-normal distribution of grain areas was used to calculate the mean area and standard deviation. These values were converted to grain size diameters by assuming a circular grain geometry.
Bath Additive and Current Density Effects on Copper Electroplating Fill of Cu Damascene Structures
Authors: Mikkola Robert D. , Jiang Qing-Tang , Carpio Ronald , Carpenter Brad
Published: April 2011

Copper electroplating has become the leading technology for gap fill of damascene structures on advanced interconnects. A key to developing a robust electroplating process that produces deposits free of voids and seams is understanding the role of the additive components, i.e., levelers, brighteners and wetting agents, and their relative diffusion/adsorption characteristics. Additionally, obtaining insight about the cathodic current/potential relationship is critical for maximizing the effectiveness of the additive components.

Our results indicate that bath additive composition and the plating parameters (plating pulse frequency, and current density) play critical roles in the outcome of the Cu fill. SEM cross sectional analysis of timed partial electroplating fill studies show two types of fill, 1) conformal and 2) bottom-up. Conformal fill of features smaller than 0.25 μm with an aspect ratio (AR) of 4.0 tends to form seam voids in the center of the structure. These seam voids can lead to early electromigration failures. On the other hand, bottom-up fill leads to a void free Cu deposit within the feature.
The Study of Oxide Planarization Using a Grindstone
Authors: Yano Hiroyuki , Okumura Katsuya , Shoji Fumito , Wada Yutaka , Hiyama Hirokuni , Kimura Norio
Published: April 2011

Oxide planarization using a specially fabricated “grindstone” was investigated. Using the grindstone, better planarity compared with the conventional CMP technique was demonstrated. Interestingly, it was also found that the oxide removal rate became very slow after the oxide surface became planar. This self-stop was thought to be influenced by the isolated abrasives from the grindstone. The dependence on the tool structure and the conditioning was investigated to prove the model. Also the defect issue is presented in this paper.
CMP Fundamentals and Challenges
Authors: Oliver Michael R.
Published: April 2011

Chemical Mechanical Polishing (CMP) as a semiconductor polishing technology has grown dramatically during the past decade. It has been a key enabling technology, facilitating the development of high density multilevel interconnects. Its widespread application has exceeded the growth of the scientific understanding.

Models for silicon dioxide polishing mechanisms have built upon the work originally done for glass polishing. Recent work has augmented our insight, but our understanding is far from complete. A quantitative picture of the basic interaction mechanisms for silicon dioxide polishing does not yet exist. The models for metal polishing are now an active area of investigation. Recent work has demonstrated that more work is need to adequate explain the CMP of metals. The metal CMP mechanisms appear to be substantially more complex than originally assumed.

The challenges for CMP have been to improve the performance of the technology, and increasingly this needs a foundation of scientific understanding to achieve the needed gains. We can expect that, as the scientific foundation grows, it will contribute significantly to manufacturing improvements as has been the case in other areas of semiconductor technology.
Development of High Purity One Atm Ozone Source - Its Application to Ultrathin SiO2 Film Formation on Si Substrate
Authors: Koike Kunihiko , Inoue Goichi , Ichimura Shingo , Nakamura Ken , Kurokawa Akira , Nonaka Hidehiko
Published: April 2011

A high-concentration ozone generator operating at atmospheric pressure has been developed for fabrication of ultra thin silicon oxide films. The generator can supply atmospheric pressure of ozone jet with ozone concentration up to 80 vol%. The ozone jet is generated by desorbing ozone at nearbyn room temperature, which has been condensed on silica-gel by passing ozone/oxygen mixture gas from a commercial ozonizer at a low temperature (<-50°C); at the temperature ozone is more selectively adsorbed on silica-gel than oxygen. The high purity ozone jet with a concentration of 25 vol% at a pressure of 1 × 105 Pa had so large oxidation power that SiO2 film as thick as 3.3 nm grew on a Si surface after 60 min exposure at 375°C. The density of the film was equivalent to that of the film formed by a conventional thermal oxidation process, judging from etching rate with dilute HF solution.
Modeling Soft Breakdown of Ultra-Thin Gate Oxide Layers
Authors: Houssa Michel , Mertens P.W. , Heyns M.M.
Published: April 2011

The time-dependent dielectric breakdown of MOS capacitors with ultra-thin gate oxide layers is investigated. After the occurrence of soft breakdown, the gate current increases by 3 to 4 orders of magnitudes and behaves like a power law of the applied gate voltage. It is shown that this behavior can be explained by assuming that a percolation path is formed between the electron traps generated in the gate oxide layer during electrical stress of the capacitors. The time dependence of the gate voltage signal after soft breakdown is next analysed. It is shown that the fluctuations in the gate voltage are non-gaussian as well as that long-range correlations exist in the system after soft breakdown. These results can be explained by a dynamic percolation model, taking into account the trapping-detrapping of charges within the percolation cluster formed at soft breakdown.
Effect of Thermal Stability and Roughness on Electrical Properties of Tantalum Oxide Gates
Authors: Alers G.B. , Stirling L.A. , Vandover R.B. , Chang J.P. , Werder D.J. , Urdahl R. , Rajopalan R.
Published: April 2011

Gate dielectrics with an effective SiO2 thickness of 1.6 nm (100 Hz) have been fabricated using chemical vapor deposition of tantalum oxide directly on silicon. A low temperature plasma anneal process was used to passivate excess traps in the oxide layer and to avoid degradation of capacitance and leakage after high temperature processing. Stable capacitance-voltage characteristics were obtained after the plasma anneal with an interface state density of ∼ 1012 cm−2 before post metallization anneal. We have examined the impact of high temperature processes and crystallization on the roughness for 10nm – 50nm films of Ta2O5 films on Si and SiN. The impact of roughness on capacitance and leakage current is examined through calculations assuming a Gaussian distribution of thickness across the capacitor with two conductive contacts. It is found that when the rms roughness exceeds about 20% of the film thickness then an increase in capacitance is observed that can be mistaken as an effective dielectric constant increase. The increase in capacitance due to roughness is accompanied by an exponential increase in leakage currents that ultimately degrades the charge storage capacity of the oxide.
Photo-Induced CVD of Tantalum Pentoxide Dielectric Films Using an Injection Liquid Source
Authors: Zhang J.-Y. , Boyd I.W. , Mooney M.B. , Hurley P.K. , O'sullivan B.J. , Beechinor J.T. , Kelly P.V. , Crean G.M. , Senateur J.-P.
Published: April 2011

In this paper the new technique of ultraviolet-assisted injection liquid source (UVILS) chemical vapour deposition (CVD) of thin tantalum pentoxide films on p-type Si (100) wafers is presented. This method involves the use of a krypton chloride (KrCl*) excimer lamp, radiating at 222 nm, and a novel injection liquid source capable of delivering precisely controllable quantities of a novel high-volatility liquid metalorganic precursor into the CVD chamber. The physical and chemical properties of the films formed have been studied using spectroscopic ellipsometry and Fourier transform infrared spectroscopy measurements while the electrical properties of the films were determined by surface charge analysis, capacitancevoltage, and current-voltage measurements. Simple metal/oxide/silicon capacitor structures incorporating this tantalum pentoxide have been fabricated. Refractive index values of 2.09±0.07, dielectric constant values of 18-24, fixed oxide charge content of < 1 × 1011 cm−2 and breakdown fields higher than 2 MV/cm can be readily obtained in the as-deposited films.
Effect of Al, Ta, and O Precursors on Growth and Properties of Al2O3 and Ta2O5 Thin Films Deposited by Triode PECVD
Authors: Klein Tonya , Niu Dong , Parsons Gregory
Published: April 2011

In this article, the properties of plasma deposited Al2O3 and Ta2O5 thin films (k ≈ 12 and 25 respectively) are discussed as possible high k alternatives to SiO2. The films were formed in a 4” compatible triode plasma CVD reactor using Ta(V)ethoxide for Ta2O5 and Al acetylacetonate, Al tri-sec-butoxide, Al triisopropoxide, and triethyldialuminum tri-sec-butoxide metal organic precursors for Al2O3. Precursors were heated to 150 °C and delivered to the reactor with He and Ar carrier gases downstream from the plasma. For Ta2O5 films, film properties were strongly dependent on the oxygen precursor, with O2 resulting in higher growth rates, better uniformity, and better stability to water exposure than films deposited using N2O. For Al2O3, distinct differences in OH and C incorporation were observed for the various Al and O precursors studied. In particular, films deposited from alkoxides had higher concentrations of OH and C, and had higher leakage currents. For films deposited with triethydialuminum tri-sec-butoxide, the N2O plasma O atom source resulted in smaller leakage currents and less C than an O2 plasma. Temperature dependence of the deposition rates and the leakage currents was also observed.