bluuebunny/crossref_metadata_2025 huggingface dataset:
The Effects of La Concentration on the Properties of PLT Thin Films: From the Perspective of Dram Applications
Authors: Kang Seong Jun , Ryoo Jeong Seon , Yoon Yung Sup
Published: April 2011

We have studied the effects of La concentration on the dielectric and ferroelectric properties of lead lanthanum titanate (PLT) thin films by using sol-gel method. Both the dielectric and ferroelectric properties were greatly affected by the La concentration. The dielectric constants of the films varied from 340 to 870 with varying La concentration in the range from 15 to 33 mol%. Hysteresis loop became slimmer with the increase of La concentration from 15 to 28 mol% and a little fatter again with the increase of La concentration from 28 to 33 mol%. Among the films investigated in this research, PLT(28) thin film showed the best dielectric properties for the application to the dielectrics of ULSI DRAM's. At the frequency of 100 Hz, the dielectric constant and the loss tangent of PLT(28) thin film were 940 and 0.08, respectively. Its leakage current density at 1.5×10 V/cm was 1×10−6 A/cm2. The comparison between the simulated and the experimental curves for the switching transient characteristics showed that PLT(28) thin film behaved like normal dielectrics.
Electrical and Microstructural Properties of Lead Titanate Thin Films Deposited by Metalorganic Chemical Vapor Deposition
Authors: Vellaikal M. , Kingon A.
Published: April 2011

Lead titanate thin films were deposited on Pt(111)/Ti/SiO2/Si(100) and RuO2/SiO2/Si(100) substrates using metalorganic chemical vapor deposition (MOCVD). Atomic force microscopy revealed that films on ruthenium oxide were rougher than films on platinum. Also the grain size of the film on ruthenium oxide was larger than that on platinum. X-ray analysis revealed that the preferred orientations for films on platinum and ruthenium oxide were different. Hysteresis and fatigue tests were performed to evaluate capacitor structures on these substrates. Films on RuO2 had lower coercive fields than films on platinum. Comparison of polycrystalline and oriented films on platinum indicated that the oriented films were easier to switch and fatigued at a slower rate than the polycrystalline films. But long term property (fatigue, imprint) testing on lead titanate resulted in resistance degradation of these contacts, unlike PZT films.
Electrical Properties of PZT Prepared by Pulsed Laser Ablation on Various Electrodes
Authors: Morimoto Akiharu , Yamanaka Yasuhiro , Minamikawa Toshiharu
Published: April 2011

The effect of various electrodes on the ferroelectric properties of lead-zirconate-titanate (Pb(Zr0.52Ti0.48)O3 PZT) films through the film structure is presented. All the PZT films were deposited by pulsed laser ablation (PLA) using an ArF excimer laser. For electrode materials, YBa2Cu3O7 (YBCO) and Ni-alloy were deposited by pulsed laser ablation and sputtering, respectively. As a result various kinds of PZT films with various film structures were obtained. These experiments revealed that there is no simple correlation between the film structure and the fatigue resistance. The fatigue resistance is, however, found to be improved primarily by decreasing the switched-charge density, although the correlation shows some ambiguity. This suggests that the large polarization reversal accelerates the fatigue but there remained the possibility that the fatigue resistance is improved by the optimization of the film structure and film-substrate interface.
Strontium Barium Niobate Thin Films Prepared by Pulsed Laser Deposition
Authors: Liu Y. , Ong C.W. , Chan P.W. , Choy C.L.
Published: April 2011

Strontium barium niobate Sr0.55Ba0.45Nb2O6 thin films were prepared on Si (111) substrates by pulsed laser deposition (PLD). The film composition was determined as a function of the fluence φ and wavelength λ of the laser beam, the oxygen ambient pressure Po2 and the substrate temperature Ts. The results show that the film composition is very close to that of the target, and is almost independent of φ from 1 to 8 J cm−2, λ = 355, 532 and 1064 nm, Po2 from 0 to 150 mTorr, and Ts from 25 to 700°C. These results suggest that PLD is excellent for preparing SBN films with compositions congruent to that of the target. The x-ray diffraction data show that all the samples deposited at room temperature are amorphous. The x-ray diffraction results also indicate that the samples deposited at 700°C have a tungsten-bronze-(TB-) type structure with preferred crystallite orientation, while the room-temperature-deposited samples after annealing at 800°C for 30 minutes are polycrystalline and have random crystallite orientation.
Preparation and Mechanical Properties of Si3N4 Ceramics With Dispersed NANO Sic Particles
Authors: Yanail Tomohiro , Ishizaki K.
Published: April 2011

The purpose of the present work is to toughen the grain boundary phase of Si3N4 ceramics by forming a nano composite grain boundary phase of SiC particles. The nano SiC particles form through a reaction between the coated carbon and the surface oxidation phase in Si3N4. The carbon is coated through thermal decomposition of CH4 gas. The sintcred bodies arc obtained by hot-pressing at 1800 °C for one h. By increasing the carbon content, both fracture toughness and bending strength initially increase, then reach the maximum value at the same amount of carbon content, and decrease. The carbon content at which the fracture toughness and bending strength exhibit the maximum value increases with the increase in the surface oxygen content. The precipitated SiC particles dispersed in a grain boundary phase, at a Si3N4-Si3N4 interface or in a Si3N4 grain. The locations and size (less than 30 nm) of the SiC particles are examined by TEM and HREM observations. As the grain boundary is toughened by the precipitated nano SiC particles in the grain boundary phase or at the Si3N4-Si3N4 interface to help Si3N4 grain bridging without any glassy phase, these SiC particles block or resist the intergranular fracture.
Fragmentation of Highly Charged Metallic Clusters
Authors: Blaisten-Barojas Estela , Li Yibing , Belenki A.
Published: April 2011

Multiply charged metal clusters undergo fission at a certain size. This critical size can be predicted by the liquid drop model when some modifications are taken into consideration. In this work we revise the asymmetric liquid drop model (ALD) and modify it for the alkali metals. This modification addresses those fragmentation channels in which a parent cluster with charge Ze fissions into two fragments. One of the fragments is small and singly charged whereas the second fragment is large and carries the rest of the charge. A different energetic balance equation is presented in which the ionization energy of a single atom and the energy of formation of a small cluster are included. Results and comparison to experiments is provided for Na and Cs clusters. Prediction of the critical size of Na and Cs clusters with Ze>7 is part of the discussion.
Oxidative Catalytic Decomposition of Toxic Gases Using Hydroxyapatite and Fluorhydroxyapatite
Authors: Palucka Timothy P. , Eror Nicholas G. , Mcnamara Thomas A.
Published: April 2011

An oxidative catalytic route for the decomposition of nerve gases was investigated using hydroxyapatite (HA, chemical composition Ca10(PO4)6(OH)2) and its partially fluorinated analog fluorhydroxyapatite (FHA, Ca10(PO4)6Fx(OH)2−x). Samples were prepared with surface areas ranging from 34 to 238 m2/g to study surface area effects; 1.2 wt. % platinum was deposited on one substrate to investigate the effect of a transition metal on activity and selectivity. Reaction studies were performed using dimethyl methylphosphonate (DMMP), a nerve gas simulant, in a stream of 80 percent nitrogen and 20 percent oxygen at 573 K and atmospheric pressure. High surface area FHA samples showed an increase in the "protection period" (period of 100% conversion) with increasing fluorine substitution; such an increase was not seen for low surface area FHA samples. In the absence of platinum, the reaction products were methanol and dimethyl ether; with platinum, CO2 was also obtained.
Computer Simulation of Diffusion and Adsorption in Pillared Clays
Authors: YI Xiaohua , Sahimi Muhammad , Shing Katherine S.
Published: April 2011

We developed a model to describe the morphology and energetics of pillared clays. Grand- Canonical Ensemble Monte Carlo and Molecular Dynamics simulations are used to study diffusion and adsorption of finite-size molecules in such systems, and the effect of various factors on these processes is investigated.
Point Defects and Cation Tracer Diffusion in (CrxFe1-x)3-δO4 Spinels
Authors: TÖpfer J. , Dieckmann R.
Published: April 2011

The cation diffusion in the spinel solid solution (CrxFe1-x)3-δO4 (0 ≤ x ≤ 0.5) was experimentally investigated at 1200 °C as a function of oxygen activity, aO2 (= PO2/P°with P° = 1 bar) and cationic composition, x. Cation tracer diffusion coefficients, DMe' of Me = Co, Cr, Fe and Mn, were determined using the radioactiveisotopes Co-60, Cr-51, Fe-59 and Mn-54. For each cationic composition V-shaped log DMe vs. log aO2 plots were obtained. The observed oxygen activity dependences indicate that the cation diffusion is determined by different point defect species prevailing at high and low oxygen activities, respectively. The observed oxygen activity dependences, in comparison with considerations based on point defect thermodynamics, suggest that cations diffuse via cation vacancies at high aO2' while at low aO2 cation interstitials prevail in the cation diffusion. In addition, new experimental data for tihe deviation from stoichiometry ≤in (CrxFe1-x)3-≤O4 are presented and discussed.
Cation Conductivity in Mixed Sulfate-Based and Mixed Iodide-Based Solids with Phase Transitions
Authors: Secco E. A.
Published: April 2011

The ac electrical conductivity versus temperature dependence of solids undergoing phase transitions incorporating various guest ions, viz isovalent cations and anions, ions with different ionic radius, ions with different polarizability, in Na2SO4-based, Ag2SO4-based, Li2SO4-based and U02SO4-based compositions along with MxTl(1x)I compositions for 1 ≤ x ≤ 0.13, whose M = K, Rb, Cs, are reported. An overview is given of the interplay of various factors, structural and non-structural, with their contribution limits impacting on locking-in the fast cation conductivity phase and the interpretation of fast-ion conductivity in the context of a percolation-type of ionstransport mechanism.
Interfacial Zone Percolation in Concrete: Effects of Interfacial Zone Thickness and Aggregate Shape
Authors: Bentz D.P. , Hwang J.T.G. , Hagwood C. , Garboczi E.J. , Snyder K.A. , Buenfeld N. , Scrivener K.L.
Published: April 2011

Previously, a hard core/soft shell computer model was developed to simulate the overlap and percolation of the interfacial transition zones surrounding each aggregate in a mortar or concrete. The aggregate particles were modelled as spheres with a size distribution representative of a real mortar or concrete specimen. Here, the model has been extended to investigate the effects of aggregate shape on interfacial transition zone percolation, by modelling the aggregates as hard ellipsoids, which gives a dynamic range of shapes from plates to spheres, to fibers. For high performance concretes, the interfacial transition zone thickness will generally be reduced, which will also affect their percolation properties. This paper presents results from a study of the effects of interfacial transition zone thickness and aggregate shape on these percolation characteristics.
Surface Core-Level Photoelectron Diffraction of Surface Reconstructions
Authors: Rotenberg Eli , Denlinger J. D. , Kevan S. D. , Tonner B. P.
Published: April 2011

Experimental surface core-level shifts (SCLSs) aid in understanding the roles of altered electronic and screening properties at reconstructed semiconductor surfaces.1 Because of unresolved theoretical issues, the assignment of SCLSs has often remained controversial even though the surface geometry has been completely determined with traditional probes.

Angular- and energy-dependent x-ray photoelectron diffraction (XPD) of each chemically resolved surface core-level electron can be used to discriminate the structure around each chemically shifted species. However, this technique requires tunability, high energy resolution to separate the SCLSs from the bulk core-levels, and high photon flux in order to gather large amounts of data in a reasonable time. Using the newly commissioned spectromicroscopy beamline 7.0 at the Advanced Light Source, we have acquired chemically-resolved XPD data for Si(111) 7×7 for several photon energies, and by examination of forward-focusing peaks we can draw tentative conclusions about the atomic origins of each core-level shifted peak.
Modeling Valence-Band Images from Synchrotron-Radiation Studies Using Display Analyzers: Lithium Fluoride and Graphite
Authors: Shirley Eric L. , Terminello Louis J. , Klepeis John E. , Himpsel F. J.
Published: April 2011

We present simulated photoelectron angular distributions (PAD's) for LiF and graphite. The results describe electron photocurrent versus photon energy, electron initial-state energy, and emission angles (leading to identification of two, or three, components of a valence electron's initial crystal momentum). Results are displayed in a fashion greatly facilitated by display analyzers. Earlier experimental results for LiF are confirmed in great detail. We discuss statistical comparison of theoretical and experimental PAD's. Effects of Bragg- diffraction on outgoing photoelectrons and uncertainty in crystal momentum normal to a surface are analyzed. In graphite, the observed lowering of symmetry, from that in a periodic-zone band structure to that seen in the PAD's, is modeled and explained.
Synchrotron X-ray Scattering Studies at Mineral-Water Interfaces
Authors: Chiarello Ronald P. , Sturchio Neil C.
Published: April 2011

Synchrotron X-ray scattering techniques provide a powerful tool for the in situ study of atomic scale processes occurring at solid-liquid interfaces. We have applied these techniques to characterize and study reactions at mineral-water interfaces. Here we present two examples. The first is the characterization of the calcite (CaCO3) (1014) cleavage surface, in equilibrium with deionized water, by crystal truncation rod measurements. The second is the in situ study of the heteroepitaxial growth of otavite (CdCO3) on the calcite (1014) cleavage surface. The results of such studies will lead to significant progress in understanding mineral-water interface geochemistry.
A Quantitative Crystallization Study of Thin Amorphous Fe80B20 Films Via Empirical Modeling of Exafs Data
Authors: Harris V. G. , Oliver S. A. , Ayers J. D. , Das B. N. , Koon N. C.
Published: April 2011

Thin amorphous films (t=200Å) of Fe80B20 were annealed at temperatures ranging from 473K–823K and studied using extended X-ray absorption fine structure to investigate the evolution of local structure around the Fe atoms during crystallization. Modeling of the local environment around Fe using empirical standards was employed to determine the relative fraction of the crystalline phases present in annealed samples. Results illustrate the sensitivity of EXAFS in detecting the onset of crystallization in thin amorphous films and its ability to quantitatively measure the relative fraction of crystalline phases present in partially crystallized thin film samples.
The Morphology of Blends of Linear and Branched Polyethylenes by Small-Angle Neutron and X-Ray Scattering
Authors: Londono J. D. , Wignall G. D. , Alamo R. G. , Mandelkern L. , S.Lin J.
Published: April 2011

The solid-state morphology and liquid-state homogeneity of blends of high-density polyethylene (HDPE) and low-density polyethylene (LDPE) were investigated by small-angle neutron and x-ray scattering (SANS and SAXS). The solid state morphology was investigated as a function of composition and cooling rate from the melt. After slow cooling, the evidence indicated that the mixtures were either completely (HDPE-rich blends) or almost completely (LDPE-rich blends) phase separated into separate HDPE and LDPE lamellae over the whole compositional range. In contrast, for rapidly quenched blends the components are extensively co-crystallized for all concentrations, though the SANS data indicated that the branched component had a tendency to be preferentially located in the inter-lamellar regions. In the liquid state, the blends were homogenous at all compositions, showing that the solid state morphology is not determined by the melt structure, but is a function of the crystallization kinetics. Further evidence for blend homogeneity in the liquid is presented. In particular we examine the hypothesis that a phase separated mixture might give a scattering pattern similar to a homogenous blend if the domain sizes were larger that the maximum spatial resolution of the SANS experiment (D > 2π/Qmin ~ 2000Å). In this scenario, the differential scattering cross section dΣ/dΩ(Q) ~ Q-2, though phase separation decreases the cross section in this Q-range with respect to the homogenous blend. For HDPE/LDPE blends in the melt, this decrease in intensity was not observed, thus ruling out the possibility of phase separation.
Possible Standard Specimens for Neutron Diffraction Residual Stress Measurements
Authors: Brand P.C. , Prask H.J. , Blackburn J. , Fields R.J. , Proctor T.M.
Published: April 2011

Increasingly, sub-surface residual stress measurements by means of neutron diffraction are being conducted at various laboratories around the world. Unlike X-ray diffraction residual stress measurement setups, neutron instruments in use worldwide vary widely in design, neutron flux, and level of dedication towards residual stress measurements. Although confidence in the neutron technique has increased within the materials science and engineering communities, no demonstration of standardization or consistency between laboratories has been made. One of the steps in the direction of such standardization is the development of standard specimens, that have well characterized residual stress states and which could be examined worldwide.

In this paper we will examine two options for a neutron stress standard specimen. 1) A steel ring-plug specimen with very well defined diametrical interference. 2) A spot weld in a High Strength Low Alloy steel disk. The results of neutron residual stress measurements on these specimens will be discussed and conclusions as to their usefulness as neutron stress standards will be presented.
Investigation of Portland Cement and Pure C3S Using 1-D Sans
Authors: Berliner R. , Heuser B. J. , Popovici M.
Published: April 2011

The effect of contrast matching in ordinary Portland cement (OPC) and pure C3S has been investigated as a function of time after hydration using the 1-D small-angle scattering technique. The observed scattering response of OPC hydrated with 100% D2O increased in time, while the response of OPC hydrated with a null water mixture did not. The increase in scattering is therefore attributed to the formation of bubbles in the water-filled pores of the hydrating cement paste. The addition of 1% CaCl2 to OPC increased the kinetics of bubble formation considerably. Based on similar contrast measurements, we have concluded that bubbles do not form in pure C3S. However, the addition of 1% CaCl2 was found to induce bubble formation in the hydrated C3S compound.
Characterization of Metal/Si1-xGex/Si Diodes Fabricated by Cryogenic Processing
Authors: He L. , Li E. , Shi Z.Q. , Jiang R.L. , Liu J. L. , Shi Y. , Zheng Y.D.
Published: April 2011

Schottky diodes were fabricated by evaporating metal thin layers on p-Si1-xGex by cryogenic processing. The cryogenic processing, with substrate temperature cooled to as low as 77K (LT), has been successfully used to enhance metal/III-V semiconductor Schottky barrier height[1]. The electrical characteristics of the diodes were investigated by current-voltage (IV) and current-temperature (I-T) measurements. In order to study the effect of silicide formation on diode characteristics, furnace annealing was performed in nitrogen atmosphere at 450°C and 550°C, respectively. Two kinds of samples with gemanium composition x of 0.17 and 0.20 were used. The electrical characteristics showed the barrier height фB decreased with the increase of the gemanium composition. The annealing temperatures up till to 550°C did not affect the I-V characteristics at room temperature, however, the conduction mechanism showed obvious difference comparing to the as-deposited diodes by I-V-T analysis. For Pd as Schottky metal, very similar results were obtained for the LT as-deposited diodes and the ordinary room temperature (RT) deposited diodes after 550° annealing, they both showed thermionic emission dominated conduction mechanism.
Local Measurements of Surfaces Stress
Authors: Twesten Ray D. , Gibson J. Murray
Published: April 2011

We have recently developed a method of local stress measurement that can be applied at the submicron level to measure differences in intrinsic stress at both free surfaces and buried interfaces. The method exploits the fact that transmission electron microscopy readily reveals local bulk strain fields produced by surface or interfacial stress differences. Using quantitative image analysis and simulation, we can determine the value of this stress difference. We have successfully applied this technique to the clean Si(111) surface during 7×7-1×1 phase coexistence and have determined the stress difference to be 30±5 meV/Å2.
Plasma-Enhanced Chemical Vapor Deposition of Metal and Metal Silicide Films
Authors: Hess Dennis W.
Published: April 2011

Plasma-enhanced CVD (PECVD) has been widely used for the deposition of insulating and semiconducting thin films. In recent years, interest has arisen in the use of PECVD to form metal layers for barrier, contact, and interconnect applications. Plasma deposition conditions that result in the formation of conducting films of transition metals, transition metal silicides, and transition metal nitrides are discussed. Particular attention is given to the as-deposited resistivities of these films, and their relationship to the gas phase reactants. The effects of postdeposition heat treatments are also discussed.
Laser Beam Lithography of Metal Oxide Electrodes for PZT Memory Applications
Authors: Norton Jarrod L. , Mansour Said A. , Liedl G. L. , Bement Arden L. , Slamovich Elliott B. , Venkatraman C.
Published: April 2011

Current metal/metal oxide patterning techniques typically involve photolithography, an expensive, time-consuming process, and/or a vacuum system, which also adds significantly to the cost. In this study, fabrication of metal oxide upper electrodes for Pb(ZrxTi1-x)O3 (PZT) memories by metallorganic decomposition (MOD) was coupled with laser beam patterning. Metal oxide organic precursors were treated with an absorption-enhancing dye and were spun on to ferroelectric PZT films followed by selective area laser beam exposure. This technique was employed to pattern RuO2 and (La,Sr)CoO3 electrodes. A variety of patterns (dot, line, and circular) were prepared which demonstrates the suitability of laser patterning for a variety of applications. The minimum power density required to generate a continuous conductive oxide pattern was found to be approximately 2.5 kW/cm2 at a scan speed of 25 mm/min. Resistivity values for the patterned lines were 660 Ω-cm for RuO2 and 59 mΩ-cm for LSCO.
Process Integration Of Low-Dielectric-Constant Materials
Authors: Jeng Shin-Puu , Taylor Kelly , Chang Mi-Chang , Ting Larry , Lee Charles , Mcanally Peter , Seha Tom , Numata Ken , Tanaka Tsuyoshi , Havemann Robert H.
Published: April 2011

As device geometries and operating voltage continue to scale while functional density increases, it is imperative to reduce the RC time delay. The replacement of Si0 2 as an intermetal dielectric with an insulator of lower dielectric constant is a particularly attractive solution since it provides immediate performance improvement through reduction in capacitance. An embedded polymer integration scheme improves the interconnect performance through line-to-line capacitance reduction by using polymer only between tightly spaced lines. The gapfill polymeric materials do not degrade the electromigration performance of standard multilayered TiN/Al/TiN interconnects. Embedded polymers alleviate many of the integration and reliability problems associated with polymer integration, and can be easily adopted into a standard production process.
The Formation Al2O3/V2O3 Multilayer Structures by High-Dose Ion Implantation
Authors: Gea Laurence A. , Boatner L. A. , Rankin Janet , Budai J. D.
Published: April 2011

High-resolution TEM, RBS-channeling and x-ray-diffraction techniques have been used to characterize multilayered structures formed by the high-dose co-implantation of vanadium and oxygen into single crystals of cx-A1203. Thin, two-dimensional multilayered structures have been formed by implanting c -axis and a -axis-oriented single crystals of A1203 at room temperature with vanadium (1017 ions/cm2 at 300 keV) and oxygen (2 × 1017 ions/cm 2, 120 keV) followed by a rapid anneal at 1000ºC. Cross-sectional TEM studies showed thatthis process produced a buried layer of V2O3 located about 120 nm below the A12O3 surface. X-raydiffraction investigations revealed that this layer is epitaxially oriented in three dimensions with respect to the host A12O3 lattice. The orientational relationship was subsequently confirmed by RBS/ channeling techniques. V2O3 exhibits a first-order phase transition at about 155 K that is accompanied by striking changes in its electrical and opticalproperties, and this phase transition was observed through in-situ TEM cooling studies ofcross-sectional samples.
High-Resolution Transmission Electron Microscopy Study of Metallic Spin-Glass/Amorphous Silicon Multilayers
Authors: Howell David A. , Crimp Martin A. , Hoines Lilian M. , Bass J.
Published: April 2011

High-resolution transmission electron microscopy has been used to investigate the structure and growth behavior of three separate multilayer systems composed of spin-glass alloys(AuFe.03,CuMn.15, and AgMn.09) alternating with amorphous silicon. Each of the three systems was fabricated with two different sample configurations. The first consisted of bilayers with 3 nm spinglass alloy and 7 nm amorphous siliconlayers. The second consisted of 7 nm spin-glass alloy and 7 nm amorphous silicon layers. HRTEM images of ion-milled cross-sectioned samples revealed variations in the degree of crystallinity of the spin-glass material. Variations in the amount and symmetry of interlayer formation were also observed. Systematic studies of such variations should help to explain differences in their measured spin-glass properties.
Imaging Cross Section of X-ray Multilayer Mirror by Scanning Tunneling Microscope
Authors: Wang QI , Knight L. V. , Thorne M. J.
Published: April 2011

Multilayers are used in x-ray optics as mirrors.1 They usually consist of a stack of bi-layers of two different materials. For x-ray optics, the thickness of the bi-layer, or the d-spacing of the multilayer, ranges from 2 nm to 20 nm. Since x-ray multilayers are usually made by evaporation or sputtering technique, most of materials in multilayers are amorphous or polycrystalline.
Interference Effects In X-Ray Specular Reflectivity from Thin Films
Authors: Lagomarsino S. , Fonzo S. Di , Jark W. , Muller B. , Cedola A. , Pelka G.
Published: April 2011

A strong resonance effect in the specular reflectivity of a C layer deposited on a Ni surface has been measured. The e.m. field intensity distribution has been monitored by measuring the fluorescence intensity of an ultra-thin Ti layer placed in the C film. The reflected intensity and the fluorescence yield of Ti and Ar (this last trapped in the film because of the deposition by sputtering) have been measured in different samples with a different location of the Ti layer. The results show that with this method a nondestructive, accurate determination of the Ti position can be achieved with a relative accuracy of 10−2
Segregation of Si and Cu at AlSiCu / TiN Interfaces
Authors: Kameyama A. , Yaoita A. , Kitano T. , Saito S.
Published: April 2011

The behavior of Cu and Si in the Al-alloy / TiN interface has been demonstrated by techniques of SIMS, GDS, XRD and AES. Cu and Si were observed to segregate at the AlSiCu / TiN interfaces just after sputtered. This segregation occurred to form a layered structure, not an island one. As these materials at the interface remained to exist even after annealing, the distribution of Cu and Si after annealing would be governed by that just as sputtered. The segregation behavior of Cu in A1Cu / TiN structure was the same as that of AlSiCu / TiN.
In-Situ resistance Measurements During Rapid Thermal Annealing for Process Characterization
Authors: Colgan E. G. , Cabral C. , Clevenger L. A. , Harper J. M. E.
Published: April 2011

Measurement of resistance in-situ during rapid thermal annealing is a powerful technique for process characterization and optimization. A major advantage of in-situ resistance measurements is the very rapid process learning. With silicides, in-situ resistance measurements can quickly determine an appropriate thermal process in which a low resistance silicide phase is formed without the agglomeration or inversion of silicide/polycrystalline silicon structures. One example is an optimized two step anneal for CoSi2 formation which was developed in less than one day. Examples of process characterization include determining the phase formation kinetics of TiSi2 (C49 and C54), Co2Si, and CoSi2 using in-situ ramped resistance measurements. The stability of TiSi2 or CoSi2/poly-Si structures has also been characterized by isothermal measurements. Resistance measurements have been made at heating rates from 1 to 100°C/s and temperatures up to 1000°C. The sample temperature was calibrated by melting Ag, Al, or Au/Si eutectics.
Modeling of Aspect Ratio Dependent Etching in an Inductively Coupled Plasma
Authors: Han J.S. , McVittie J.P.
Published: April 2011

SPEEDIE is used to simulate aspect ratio dependent etching of silicon dioxide in an inductively coupled plasma. Overhang test structures and standard via/trench structures are etched in the system under standard processing conditions. Results from the overhang test structure yield information about the ion angular distribution and aid in the development of the model. The simultaneous etching and deposition model includes such effects as ion enhanced polymer deposition, angle dependent polymer sputtering, Langmuir adsorption saturation model, and surface dependent sticking probability. The model is able to capture all the lag trends, defined as the difference in etch rate for different aspect ratios, and profiles accurately.
Dynamic Simulation of Ultra-Shallow Implantation Profiles in Single-Crystalline Silicon
Authors: Posselt Matthias
Published: April 2011

The binary collision code Crystal-TRIM is applied to simulate 15 keV BF+2 and As+ implantations into channeling and "random" directions, at different doses. The buildup of radiation damage is described by assuming statistical creation of local amorphous regions and formation of amorphous zones if the density and/or size of the local amorphous regions exceeds a critical value. Damage accumulation during ion bombardment causes enhanced dechanneling and, therefore, the alteration of the shape of range and damage profiles. The depth profiles calculated by Crystal-TRIM show a good agreement with experimental data. The thickness of the amorphous layers formed at high doses is also in accordance with measurements.
A New Flexible Rapid Thermal Processing System
Authors: Saraswat K. C. , Chen Y. , Degertekin L. , Khuri-Yakub B. T.
Published: April 2011

A highly flexible Rapid Thermal Multiprocessing (RTM) reactor is described. This flexibility is the result of several new innovations: a lamp system, an acoustic thermometer and a real-time control system. The new lamp has been optimally designed through the use of a “virtual reactor” methodology to obtain the best possible wafer temperature uniformity. It consists of multiple concentric rings composed of light bulbs with horizontal filaments. Each ring is independently and dynamically controlled providing better control over the spatial and temporal optical flux profile resulting in excellent temperature uniformity over a wide range of process conditions. An acoustic thermometer non-invasively allows complete wafer temperature tomography under all process conditions - a critically important measurement never obtained before. For real-time equipment and process control a model based multivariable control system has been developed. Extensive integration of computers and related technology for specification, communication, execution, monitoring, control, and diagnosis demonstrates the programmability of the RTM.
In-Situ Resistance Measurements During Rapid Thermal Annealing for Process Characterization
Authors: Colgan E.G. , Cabral C. , Clevenger L.A. , Harper J.M.E.
Published: April 2011

Measurement of resistance in-situ during rapid thermal annealing is a powerful technique for process characterization and optimization. A major advantage of in-situ resistance measurements is the very rapid process learning. With silicides, in-situ resistance measurements can quickly determine an appropriate thermal process in which a low resistance silicide phase is formed without the agglomeration or inversion of silicide/polycrystalline silicon structures. One example is an optimized two step anneal for CoSi2 formation which was developed in less than one clay. Examples of process characterization include determining the phase formation kinetics of TiSi2 (C49 and C54), Co2Si, and CoSi2 using in-situ ramped resistance measurements. The stability of TiSi2 or CoSi2/poly-Si structures has also been characterized by isothermal measurements. Resistance measurements have been made at heating rates from 1 to 100°C/s and temperatures up to 1000°C. The sample temperature was calibrated by melting Ag, Al, or Au/Si eutectics.
Design-Coupled Manufacturing
Authors: Lemnios Zachary J.
Published: April 2011

A new approach to semiconductor manufacturing is necessary to decouple end product cost from factory volume. The economy of scale model for manufacturing semiconductor integrated circuits is leading to factories that cost in excess of $1 billion and with costs anticipated to increase nonlinearly. Perhaps of greater concern is that process development and integration costs are of the same magnitude. The Advanced Research Projects Agency (ARPA) has funded several stand-alone research programs to explore new ways of designing and fabricating leading-edge semiconductors. The next steps are to tightly couple design and manufacturing through powerful new frameworks and embedded intelligence with tools. This new manufacturing capability based on flexible, intelligent equipment coupled to a powerful design framework could lead to a leading-edge manufacturing capability, but at a fraction of the cost of a conventional factory. Furthermore, this manufacturing model supports innovation and could lead to a new generation of ICs and systems. The key elements necessary to enable this new semiconductor fabrication environment is described.
Monte-Carlo simulation of the deposition process in PVD-technoIogy
Authors: Lugscheider E. , Knotek O. , Löffler F. , Schnaut U. , Eckert P.
Published: April 2011

The Magnetron Sputter Ion Plating (MSIP) technology has been applied in a wide range of modem technological fields, due to the virtually unlimited potential of coating and substrate materials. However, up to now, the development of optimization has been depending mainly on empiricism and experiments.

Energies and the directions of the particles sputtered with various ejection angles and initial energies from the target surface are changed due to collisions with gas atoms during their movement within the sputtering chamber. Therefore the particles have a distribution of incident energies and angles which have a great influence on structure and properties of thin film coatings. This paper describes computer investigations to simulate the motions of the particles from target to substrate using a Monte-Carlo method and a binary collision approximation. The applied model takes into account non-uniform sputtering effects of the target in the MSIP process due to the magnetic field and the erosion zone.
Effects of ECR N2O-Plasma Nitridation on Thermal Oxide Characteristics
Authors: Lee Jin-Woo , Lee Jung-Yeal , Choi Deuk-Sung , Hur Sung-Hoi , Kim Choong-Ki , Han Chul-Hi
Published: April 2011

The effects of electron cyclotron resonance (ECR) N2O-plasma nitridation on the characteristics of thermal SiO2 have been investigated. Although the ECR N2O-plasma nitridation was performed at low-temperature(≤400°C), it was found that oxynitride layer can be successfully grown at the Si/SiO2 interface. The atomic concentration of nitrogen near the Si/SiO2 interface was comparable to that of high temperature N2O annealing. The ECR N2O-plasma nitrided thermal SiO2 exhibits higher breakdown field characteristics, higher time-to-breakdown and charge-to-breakdown values in comparison with those of thermal SiO2. In addition, ECR N2O-plasma nitrided thermal SiO2 shows improved charge trapping properties
Stress and Electromigration
Authors: Lloyd J.R.
Published: April 2011

The interdependence of mechanical stress and electromigration behavior has been recognized for quite some time, but has only begun to be fully appreciated and dealt with in a meaningful
manner. There have been a number of recent advances in understanding that also may lead to a change in the way that electromigration failure is viewed in real applications.
A1/A1-Oxide Interface Diffusion During Electromigration
Authors: Augur R.A. , Wolters R.A.M. , Schmidt W. , Kordić S.
Published: April 2011

This paper presents new results concerning diffusion at the interface between Al and its oxide, due to electromigration in Al interconnects. The results show that the phenomenon is an important and general one. Significant large-scale modification of the surface of Alalloy conductors was observed after electromigration stress under a wide range of different conditions: 1) in a number of different alloys (Al-Si, Al-Cu, Al-Si-V & Al-Si-V-Pd), 2) with and without passivation, 3) over an extended temperature range, 4) over an extended range of current density, and 5) with a number of different underlayers (SiO2, W-Ti (no vacuum-break before Al deposition) and W-Ti (oxidized surface before Al deposition)). After electromigration stressing, the surface showed height variations: at certain locations the original thickness remained, while at adjacent locations the thickness was reduced; as much as 150nm in 2500 hrs, for Al-Si on oxidized W-Ti metallization. Damage by thinning has received little attention in the past. Based on the results presented, a model for the underlying mechanism is proposed. In this model Al atoms diffuse concurrently along the interface between the Al-metal and its oxide, and through the grain boundaries, even at low stress conditions and in non-bamboo lines.
A Macroscopic Model of Electromigration: Comparison with Experiment
Authors: Kime Yolanda J.
Published: April 2011

Comparison of theory and experiment is critical in microelectronic reliability. In this work, a model which has been previously used for electromigration time to failure predictions (developed by Harrison) is extended to include predictions for numbers of voids and void sizes. Predictions from the model are compared to experimental measurements. The model makes reasonable predictions for mean lifetimes, numbers of voids, and void areas with very few free parameters. The model, however, does not adequately reproduce the range of lifetimes found in experiment.
The Influence of Tiw Barrier Layer on Reliability of AlCu and AlSiCu Interconnects
Authors: Kordic S. , Wolters R.A.M. , Augur R.A. , Dirks A.G.
Published: April 2011

The influence of a TiW barrier layer on the stress-voiding behavior of AlCu and AlSiCu interconnects is investigated. The results are compared to the same alloys deposited on SiO2- In both cases, AlCu exhibits a notably better voiding behavior compared to AlSiCu. In the case in which the alloys are directly deposited on the TiW barrier without breaking vacuum between TiW and Al(Si)Cu depositions, a significant improvement of the voiding behavior of both alloys is observed. Compared to AlCu, AlSiCu shows worse voiding behavior due to the presence of Si precipitates, which introduce significant extra dislocations and defects in the Al grains. These dislocations and defects are diffusion paths which assist stress relaxation and void formation. In the presence of a TiW barrier part of the Si content of the AlSiCu is consumed during the anneal by the Al-TiW interface, which results in a decreased number of dislocations and defects within the Al grains, and an improved voiding behavior compared to AlSiCu on SiO2-Furthermore, W and Ti diffuse into the grain boundaries of both alloys. The presence of W and Ti in the grain boundaries reduces the amount of Cu depletion from within the grains, which makes both alloys more resistant to stress voiding. The above is supported by Auger and TEM results. The electromigration results of the alloys in question are presented. These show that also with respect to electromigration AlCu is the preferred alloy both on TiW and SiO2.
Metallization Systems on Cvd-Diamond Substrates for Application in Multichip Modules
Authors: Brown W. D. , Naseem H. A. , Malshe A. P. , Glezen J. H. , Hinshaw W. D.
Published: April 2011

Because of its high thermal conductivity, free-standing CVD-diamond is an extremely attractive material for application as the substrate in multichip modules (MCMs). However, this material does present some technological challenges, one being the development of reliable metallization systems. In this work, adherent metallization systems, such as Au/Ti, Au/Ti-W, Au/Ni-Cr, Au/Cr and Cu/Cr have been produced at low temperatures. Thin adhesion/seed metal layers were deposited using sputtering and evaporation techniques. Gold and copper metallization of several microns thickness was accomplished by electroplating over the thin metal layer. Post-deposition annealing of both the adhesion/seed layer and plated metallization systems were performed at temperatures up to 500°C in an effort to enhance adhesion and determine the impact of subsequent high temperature operations on reliability issues such as intermetallic diffusion, delamination, and the impact of surface microcavities. Extremely adherent Au/Cr and Cu/Cr metallization systems appropriate for use in MCM technology were developed.
Formation of Ultra-Thin Silicon Oxynitride Films by Low-Energy Nitrogen Implantation.
Authors: Diniz J. A. , Tatsch P. J. , Kretly L. C. , Queiroz J. E. C. , Godoy Fo J.
Published: April 2011

Oxynitrides (SiOxNy) have been used as gate insulators for submicron devices [1]. The present work reports the oxynitride formation at SiO2/Si structure by N2+ implantation at low energies. Si substrates were implanted with N2+ ion beams (energy = 5.6 keV and dose =1×10 ions/cm2), annealed at 950°C for 30 min in N2 ambient, oxidized at 950°C in O2 + 1% TCE environment and annealed at 950°C for 30 min in N2. After these process steps, the oxynitride formation was investigated by FTIR, SIMS and ellipsometric analysis. These physical characterizations revealed the presence of Si-0 and Si-N bonds. The film thicknesses and refractive indexes were 7 nm and 1.62, respectively. The dielectric constant = 4.39 and effective charge density = 7xl010 cm–2 were determined by C-V, indicating that the SiOxNy films formed are suitable gate insulators for MOS devices.
Persistent Photoconductivity Study on Ion Irradiated Carbon Films
Authors: Bhattacharyya Somnath , Kanjilal D. , Subramanyam S.V.
Published: April 2011

Conducting carbon films are irradiated by high energy ion beam and persistent photoconductivity has been found from the irradiated samples. A complex distribution of traps created mostly by random displacement of carbon atoms by energetic ion beam from its polymeric matrix showed a persistent photoconductivity at low temperatures down to 50K. From the photo decay constants and the magnitude of photocurrent the density of traps and the corresponding activation energies have been calculated.
Ion Beam Modification of PVDC and Pe Polymers
Authors: Evelyn A. L. , Ila D. , Fisher J. , Poker D. B.
Published: April 2011

The electronic and nuclear stopping effects produced by MeV ion bombardment in polyvinylidine chloride (PVDC) and polyethylene (PE) are separated by stacking thin films of the polymers. The resulting multi-layer laminates of each polymer were bombarded with 3.5 MeV alpha particles. The energy of the incident ions was selected, using TRIM, such that the first layers experienced most of the effects of the electronic energy deposited and the last layers received most of the effects of the nuclear stopping power. The changes in the conductance and the chemical structure of each layer were measured by direct resistivity measurements and Raman microprobe analysis.
Mev Ion Beam Induced Index of Refraction Changes in Layered GaAs/AlGaAs Waveguides
Authors: Taylor T. , Ila D. , Zimmerman R. L. , Ashley P. R. , Poker D. B.
Published: April 2011

Previously, we showed that localized optical modifications could be produced without subsequent post thermal annealing in selectively masked planar GaAs/Al 4Ga6As waveguide structures using 10 MeV oxygen ions. In our present investigation, irradiation experiments were performed on masked GaAs/Al 4Ga6As waveguide samples at 298 K using 10 MeV oxygen and 8 MeV carbon ions. The two ion incident energies were chosen to yield the maximum electronic stopping power near the interface septing the top cladding layer and the guiding layer. This localized modification process emphasizes the crucial role that the electronic energy transfer plays on the degree to which the refractive index of the guiding layer is altered. Propagation loss measurements on the fabricated channel waveguides were performed by end fire coupling a laser diode source at a wavelength of 1.3 μm. Observation of the extracted propagation loss values reveal that further optimization of the ion beam pmeters are required before practical applications can be achieved. The relative efficiency of the various ions to induce optically altered regions which serve as lateral confinement barriers of laser light shows that this fabrication process is sensitive to the ion beam current.
Vibrational and Electronic Transition in InAs Quantum Dots Formed by Sequential Implantation of in and as in a-SiO2
Authors: Ueda A. , Henderson D.O. , Mu R. , Tung Y.-S. , Hall C. , Zhu Jane G. , White C.W. , Zuhr R.A.
Published: April 2011

The optical, structural, and thermodynamic properties of materials can be changed by reducing their dimensions. We sequentially implanted In and As into fused silica windows in order to investigate the formation and properties of InAs nano-particles. The UV/VIS/NIR, FTIR in mid-IR, and far-IR spectroscopy were mainly used to study the change in electronic transitions and in vibrational modes (phonons) of the nanoparticle InAs. The phonons can be confined to the surface of nanoparticles and have frequencies falling between the transverse and longitudinal optical modes of the bulk material. Thermal annealing developed the formation of InAs quantum dots from as-implanted In+As system. At a certain annealing temperature, we observed a change in UV/VIS transmission spectra and IR reflectance spectra indicating the formation of InAs quantum dots. This is particularly evident from the absorption in the IR, and surface phonon bands are observed confirming the presence of quantum confined InAs.