bluuebunny/crossref_metadata_2025 huggingface dataset:
Homogenization of the Bilayers of Cu-Al Alloy and Pure Copper to Produce CU-0.3 at.% Al Alloy Films
Authors: Wang Pei-I , Murarka S. P. , Bedell S. , Lanford W. A.
Published: April 2011

Preparation of Cu-0.3 at.% Al alloy films by homogenization anneals of metallic bilayers consisting of Cu/Cu-AI on SiO2 is studied to produce advanced copper based metallization for future ICs. The bilayer films were annealed at temperature in the range of 200°C- 400°C and the depth profiles were obtained using Rutherford Backscattering technique. It is found that Al diffuses through the undoped copper layer to surface - leading to lower Al concentration in the original Al doped Cu layer and apparently increased concentration of Al in undoped Cu (not detectable by RBS). The resistivity of these annealed films ranged from 2.1 to 2.4 μΩ-cm depending on final Al concentration achieved. Electrical stability of such MOS capacitors was also investigated. All these results will be presented and discussed showing that Al-doped copper layers can be used as diffusion barrier/adhesion promoter between the oxide ILD and copper metal.
Ambient Dependence of Agglomeration Stability of Cu/Ta Films
Authors: Hartman J. W. , Atwater H. A. , Hashim Imran , Chin Barry , Chen Fusen
Published: April 2011

We have investigated the effects of oxygen contamination on the agglomeration of thin Cu films fabricated by physical vapor deposition on Ta barriers. Thin Cu films on clean, ultrahigh vacuum-deposited Ta barriers were stable against agglomeration when annealed for several hours at temperatures as high as T=380°C. However, on Ta barriers intentionally contaminated with oxygen, agglomeration of Cu films occurred within minutes when annealed above 300°C. Time-resolved reflectivity was used to study film evolution and agglomeration in situ. Atomic force microscopy was used for post-growth characterization of agglomeration. Characterization of Ta barriers by X-ray photoelectron spectroscopy and Rutherford backscattering spectrometry demonstrated that clean Cu films on contaminated Ta barriers containing as little as 5% oxygen were unstable against agglomeration.
Etching of Platinum Thin Films by High Density Ar/Ci2/Hbr Plasma
Authors: Kim C.-I. , Kim N.-H. , Chang E.-G. , Kwon K.-H. , Yeom G.-Y. , Seo Y.-J.
Published: April 2011

Platinum is widely researched as the electrode material for capacitor of high dielectric films in dynamic random access memory (DRAM) application. However, the dry etching of Pt is difficult because of its chemical stability. So, the dry etching of Pt remains at the preliminary work.

In this work, Pt etching mechanism was investigated by using inductive coupled plasma (ICP) with Ar/Cl2/HBr gas.

The peaks were found due to brominated Pt as well as chlorinated Pt in the XPS (X-ray photoelectron spectroscopy) narrow scan. Ion bombardment effects on the etched surface decreased with increasing HBr/(HBr+Cl2) gas mixing ratio. The maximum etch rate of Pt was 105 nm/min at the HBr/(HBr+Cl2) ratio of 0. And selectivity to SiO2 was good in all samples with various HBr/(HBr+Cl2) gas mixing ratios. These results are consistent with XPS and OES (optical emission spectrometry) and single Langmuir probe.
TiN Diffusion Barrier Formation by Pulsed Source Chemical Vapor Deposition method
Authors: Jeon Hyeongtag , Lee Sangsoo , Ahn Taehang , Uhm Jangwoong
Published: April 2011

TiN film is applied as a diffusion barrier and an adhesion promotion layer in the ultralarge scale integrated circuit (ULSI) devices. These TiN thin films are usually deposited by sputtering and chemical vapor deposition (CVD) methods. The CVD method is now studied intensively due to its satisfiable step coverage and compatibility with current device fabrication process. There are several different CVD methods already proposed such as LPCVD, MOCVD and PECVD. These proposed CVD methods have many disadvantages such as impurity incorporation and particle generation due to gas phase reactions between source and reactant gases. To solve these problems, we propose a new CVD method to reduce impurities and particles which is the pulsed source chemical vapor deposition (PS-CVD) method. In this method, the source, reactant and purge gases are introduced into reaction chamber, separately. TiN films are deposited using TiCl4, NH3 and Ar by alternately introducing into reaction chamber. In detail, TiCl4 source is introduced and adsorbed on Si substrate and then Ar gas purges this source gas. Continuously, NH3 gas in supplied into reaction chamber and adsorbed on the Ti-adsorbed Si substrate and then Ar gas is again introduced to purge NH3 gas. These four steps are one cycle. The main variables in this experiment are source pulse time, source purge time, reactant pulse time, reactant purge time, and so on. The deposition characteristics are also different depending on substrate temperatures. Above the thermal decomposition temperatures, the film thickness is a function of the source pulse time like conventional CVD. Below the thermal decomposition temperatures, the film thickness is saturated and exhibits a constant value in this temperature range. The TiN film thickness depends only on the number of deposition cycle. The process window were determined by experimentally in this temperature range. Process variables were established, and then TiN films were deposited. The characteristics of this TiN diffusion barrier were analyzed. The surface microroughness, the chemical composition and contaminant contents were measured by AFM, SEM and AES. A crystal structure and the phase identification were performed with using XRD and the sheet resistance was measured by a four point probe. These results will be discussed and compared with the results of TiN formed by sputtered and conventional CVD methods.
Integration of Multi-Level Copper Metallization into a High Performance Sub-0.25μM Technology
Authors: Venkatraman R. , Jain A. , Farkas J. , Mendonca J. , Hamilton G. , Capasso C. , Denning D. , Simpson C. , Rogers B. , Frisa L. , Ong T. P. , Herrick M. , Kaushik V. , Gregory R. , Apen E. , Angyal M. , Filipiak S. , Crabtree P. , Sparks T. , Anderson S. , Coronell D. , Islam R. , Smith B. , Fiordalice R. , Kawasaki H. , Klein J. , Venkatesan S. , Weitzman E.
Published: April 2011

We report the integration of six levels of Cu interconnects using dual inlaid patterning in a 0.2 μm logic technology. A review of process technology as well as device performance shortcomings using conventional aluminum metallization has been presented. Two tantalum based barriers, TaNx and Ta-Si-N as well as a titanium based barrier, CVD TiN, have been evaluated for their applicability. The use of embedded barriers wherein the barrier is formed below the surface of the dielectric has also been discussed as a potential option. No degradation to the device front-end parametrics were found with the choice of an appropriate barrier. Planarization by Cu CMP introduces surface topography that needs to be minimized in order to process multiple levels of interconnects within specified sheet resistance distributions for a range of line widths. Excellent results with highly planarized levels of metallization have consistently been achieved through an optimization of the unit processes and device integration.
Electrochemical and Material Study of Electroless Ternary Barriers for Copper Interconnects
Authors: Lopatin S. , Kim Y. , Shacham-Diamand Y.
Published: April 2011

Electroless cobalt-rich CoWP ternary alloys with a low weight percent of tungsten (∼ 2 percent) and a high phosphorus content (∼11 weight percent) have been deposited in basic solution onto copper and cobalt in integrated Cu damascene structures. A capability of the electroless CoWP deposition to form conformal barrier/protection films was demonstrated. Conformal 10 nm thick CoWP layer was also formed on the sidewalls of 30–40 nm wide seam of aspect ratio about 5:1 on the top of 0.4 μm wide in-laid Cu line.
Metal - Gan Contact Technology
Authors: Lau S. S.
Published: April 2011

In this talk, we summarize the experimental results obtained on metal-GaN interactions in our laboratory. These interactions include the epitaxial growth of metal thin films on chemically cleaned GaN surfaces, metal silicides for Schottky contacts and metallization schemes for ohmic contacts. We found that many fcc and hcp metals can grow epitaxially on (0001) GaN surfaces at room temperature without in-situ surface cleaning. Metal silicide contacts (such as PtSi) may be more suitable for high temperature applications than elemental contacts, due to the thermal stability of silicides. The intrinsic mechanisms for ohmic behavior for various metal contacts are not well understood at present. More consistent barrier height values measured experimentally can shed light on this issue. Due to the defective nature of the GaN layers, carrier transport across the metal/GaN interface can be due to a number of transport mechanisms, thus making accurate determination of the barrier height difficult. In spite of these difficulties, it seems possible to draw certain general conclusions on the electrical behavior of metal contacts on n-GaN.
PVD Ti-Si-N Films Process Development for Copper Interconnect Applications
Authors: Zhang Jiming , Venkatraman Ram , Wilson Terri , Fiordalice Robert , Gregory Rich , Weitzman Elizabeth
Published: April 2011

A process has been developed for the deposition of amorphous Ti-Si-N films using reactive ion sputtering of a TiSi target. The Ti-Si-N films have been extensively characterized over a wide range of process parameters. Resistivities of the films less than 300 μΩ-cm have been achieved. Stress measurements on Ti-Si-N films indicate that the film stress changes from tensile to compressive as the nitrogen composition is increased. Near-zero film stresses were achieved by choice of optimum nitrogen N2 flow. SIMS analysis of Cu diffusion through blanket PVD Ti-Si-N (300Å) after an anneal at 390°C/3 hour showed a near overlap of the Cu profile compared to the profile of an unannealed SiO2/PVD Ti-Si-N /Cu film stack, indicating that the Cu did not diffuse significantly through the barrier after anneal. Low contact resistance (0.8 Ω) and low (< 10−11 A) leakage were obtained using a dual inlaid structure with a 300 Å Ti-Si-N processed with optimized conditions. These results showed that Ti-Si-N could be used as a potential barrier for copper metallization.
Barriers For Copper Interconnections
Authors: Wong S. Simon , Ryu Changsup , Lee Haebum , Kwon Kee-Won
Published: April 2011

The integration of Cu interconnections will require sophisticated structures to prevent Cu from coming into contact with devices. The barriers for Cu also must have good adhesion with dielectric and Cu, and yield desirable microstructure of Cu. This paper discusses several critical barrier requirements and compares the properties of Ta and Ti/TiN barrier systems.
Microstructure Evolution of Al-1.5% Cu Alloy as a Function of Resistance Change Due to Isothermal DC Stressing
Authors: Lee T , Schade M , Merino A , Lee J , Christenson C , Varker C , Evans K
Published: April 2011

This paper investigates Cu segregation and void morphology along AlCu alloy metal lines as a function of resistance change resulting from isothermal DC stressing at 225°C and a current density of J=2×106 A/cm2. The Al-1.5wt.%Cu alloy was deposited via DC magnetron sputtering onto a Si substrate at 525°C with a 1500Å TiW barrier layer. NIST test structures (length = 800µm, thickness = 1.2µm, width = 5 and 10 µm) were utilized in this study. BPSG was used as the insulation layer between Si substrate and conductor. The surface passivation layer was composed of Si3N4/PSG. Various failure criteria were selected to explore the correlation between Cu segregation and void morphology along the metal line and the relative percent resistance change (ΔR/R). The log-normal plots, mean-times-to-failure, and sigmas at each ΔR/R ( -−%, 2%, 5%, 10%, 20%, 100%, 250%) were plotted and listed. The microstructural evolution in terms of void morphology was monitored using SEM. SEM-EDS was used to analyze the Cu concentrations along metal lines tested at various %ΔR criteria.
Modelling Electromigration and Stress Migration Damage in Advanced Interconnect Structures
Authors: Brown Dirk
Published: April 2011

Physical and statistical models have been used extensively to understand and improve electromigration and stress migration induced damage in narrow metal interconnects. As devices continue to shrink, and the interconnect delay becomes a more important fraction of overall circuit delay, the semiconductor industry has begun to make several important changes to the ‘standard’ Al-based interconnect technologies, including (i) a move from metal deposition and metal etch to metal deposition into damascene and dual-damascene structures, (ii) a move from Al-based to Cu-based metallizations, and (iii) a move from oxide to low-k dielectrics between the metal interconnects. The dominant electromigration and stress migration failure mechanisms associated with these advanced interconnect structures are typically different from the failure mechanisms associated with standard Al-based interconnects. In this work, physical and statistical models are used in conjunction with reliability data to compare the failure mechanisms in standard, Al-based interconnects with Cu-based, damascene interconnects. Methods are discussed for determining the dominant failure mechanisms and improving reliability in both types of interconnect.
Early Detection of the Metallization Quality Using Moderately Accelerated Electromigration Stress Conditions
Authors: Scorzoni A. , De Munari I. , Impronta M. , Balboni R. , Kelaidis N. , Foley S. , Forde M.
Published: April 2011

In this work we use a wafer-level, High Resolution Resistance Measuring Technique (HRRMT) to detect fabrication faults of Al-Cu interconnections. Experiments have been performed on two distinct sets of metal lines. The first set includes two lots of 4 μm wide lines which, once tested at moderately accelerated stress conditions, gave largely different life times. A microstructural analysis confirmed a major defectivity of the lot with shorter life time. An accurate examination of the early resistance variations revealed the presence of two distinct and subsequent phases, namely an initial pseudo-parabolic resistance increase followed by a linear resistance drop. Significant differences between the resistance behaviour of the two lots were detected during the first stage, lasting a few hours. Measurable differences could even be detected in the first few minutes. A second group of experiments was launched in order to assess the capability of HRRMT as in-line monitors. Samples from four wafers, one reference wafer and three wafers with intentional process variations, have been tested using our HRRMT at constant temperature and current, simulating an in-line production test. The standard life time of the four wafers have also been collected. Preliminary measurements highlight that a change of life time due to process variation corresponds to changes of the resistance behaviour in the first hours of test. These results pave the way for a new application of high resolution methods to assess the quality of a metallization system in a reasonable amount of time.
Model for Estimation of Metallization Lifetime Including Electromigration and Thermo-Mechanical Stress Relaxation
Authors: Roloff Herbert F. , Fellinger Johannes
Published: April 2011

Future semiconductor technologies with structural dimensions less than 0.35 µm and four or more metallization layers impede the realization of the reliability requirements due to their complexity and increasing operating conditions (>5 mA/µm2). Therefore it is necessary to provide reliability appraisal methods which ensure the operation lifetimes (up to 30 years) required by the market.
Electromigration Damage in Aluminum Alloys Studied by 1/f Noise
Authors: Kruelle C.A. , Ochs E. , Stoll H. , Seeger A. , Bloom I.
Published: April 2011

The electromigration damage in polycrystalline AlSiCu lines caused by dc current densities of the order of magnitude 1010 Am −2 at 500 K has been investigated by long-time high-resolution ac noise measurements over a wide range of temperatures. A multiple-probe setup allowed us to monitor the electrical resistance increase along the line and to show that sudden enhancements of the noise power and the resistance occurred in the same line segment. The peak in the distribution function N(E) of the activation energies E for the defect motion responsible for 1/f noise was found to shift from E0 = 0.7 eV with Gaussian width ΔE = 0.1 eV in the undamaged samples to E0 = 1.0 eV and ΔE = 0.2 eV in the damaged samples. The latter values are compatible with the Cu diffusivity along intermediate-misfit grain boundaries in Al, indicating that the damage process depends not only on the composition but also on the microstructure of the lines. It is proposed that electromigration causes Cu atoms to drift towards and get trapped in grain boundaries, that their thermally activated motion in the boundaries contributes substantially to the 1/f noise, and that eventually the Cu atoms assemble on the anode side of the sample. The dependence of the diffusivity on the grain-boundary mismatch may cause flux divergencies at boundary junctions and thus lead to void formation.
In-Situ X-ray Photoemission Spectromicroscopy of Electromigration in Patterned Al-Cu Lines With Maximum
Authors: Solak H.H. , Lorusso G.F. , Singh S. , Cerrina F. , Underwood J.H. , Batson P.
Published: April 2011

We report the application of a unique photoemission spectromicroscope (MAXIMUM) to the study of electromigration phenomena in Al-Cu interconnects. MAXIMUM is a scanning type photoemission microscope that uses multilayer-coated optics to focus 130 eV x-rays to a sub-0.1 µm spot. An electron energy analyzer collects photoelectrons in a chosen spectral region of interest to form an image of the sample that is sensitive to chemical states of elements on the sample surface. Al-Cu lines were characterized by spectromicroscopy techniques before and after electromigration stressing in the UHV environment of the microscope chamber. We present spectro-micrographs showing the chemical and structural changes on Al-Cu line surfaces as a result of the electromigration process.
Silicon Strength Testing for Mesoscale Structural Applications
Authors: Chen Kuo-Shen , Ayon Arturo A. , Spearing S. Mark
Published: April 2011

The development of power MEMS, such as the Microengine being developed at MIT, requires highly stressed structures to achieve high power densities. Material strength is, therefore, a critical issue for the design of such devices. Due to the stochastic nature of the strength of brittle materials, the length scales of the test specimens should be close to those of the structure in order to avoid excessive extrapolation of the test data. In this paper, strength characterization and supporting analysis of mesoscale biaxial flexure and radiused hub flexure single crystal silicon specimens are presented. The Weibull reference strength' of planar biaxial flexure specimens was found to lie in the range 1.2 to 4.6 GPa, depending on the surface quality. The local strength at stress concentrations was obtained by testing radiused hub flexure specimens. For the case of deep reactive ion etched (DRIE) specimens, the strength at fillet radii was found to be significantly lower than that measured from planar biaxial flexure specimens due to the inferior surface quality in such regions. It was found that strength could be significantly increased by the introduction of an additional isotropic etch after the DRIE step. The test results reported herein have important implications for the development of highly stressed microfabricated structures. The sensitivity of the mechanical strength to surface processing and etching techniques must be accounted for in the design cycle, particular with regard to the selection of the appropriate fabrication route. Furthermore, in the design of highly stressed MEMS devices, it is important to account for the stochastic nature of the material strength.
The Surface Modification with Fluorocarbon Thin Films for the Prevention of Stiction in Mems
Authors: Lee Sang-Ho , Kwon Myong-Jong , Park Jin-Goo , Kim Yong-Kweon , Shin Hyung-Jae
Published: April 2011

Highly hydrophobic fluorocarbon films were prepared by the vapor phase (VP) deposition method in a vacuum chamber using both liquid (3M's FC40, FC722) and solid sources (perfluorodecanoic acid (CF3(CF2)8COOH), perfluorododecane (C12F26)) on Al, Si and oxide coated wafers. The highest static contact angles of water were measured on films deposited on aluminum substrate. But relatively lower contact angles were obtained on the films on Si and oxide wafers. The advancing and receding contact angle analysis using a captive drop method showed a large contact angle hysteresis (ΔH) on the VP deposited fluorocarbon films. AFM study showed poor film coverage on the surface with large hysteresis. FTIR-ATR analysis positively revealed the stretching band of CF2 groups on the VP deposited substrates. The thermal stability of films was measured at 150°C in air and nitrogen atmospheres as a function of time. The rapid decrease of contact angles was observed on VP deposited FC and PFDA films in air. However, no decrease of contact angle on them was observed in N2.
Mechanical and Metallographic Characterization of Liga Fabricated Nickel and 80%Ni-20%Fe Permalloy
Authors: Christenson T.R. , Buchheit T.E. , Schmale D.T. , Bourcier R.J.
Published: April 2011

A table top servohydraulic load frame equipped with a laser displacement measurement system was constructed for the mechanical characterization of LIGA fabricated electroforms. A drop-in tensile specimen geometry which includes a pattern to identify gauge length via laser scanning has proven to provide a convenient means to monitor and characterize mechanical property variations arising during processing. In addition to tensile properties, hardness and metallurgical data were obtained for nickel deposit specimens of current density varying between 20 and 80 mA/cm2 from a sulfamate based bath. Data from 80/20 nickel/iron deposits is also presented for comparison. As expected, substantial mechanical property differences from bulk metal properties are observed as well as a dependence of material strength on current density which is supported by grain size variation. While elastic modulus values of the nickel electrodeposit are near 160 GPa, yield stress values vary by over 60%. A strong orientation in the metal electrodeposits as well as variations in nucleating and growth morphology present a concern for anisotropic and geometry dependent mechanical properties within and between different LIGA components.
Heating Effects on The Young's Modulus of Films Sputtered onto Micromachined Resonators
Authors: Kahn H. , Huff M.A. , Heuer A.H.
Published: April 2011

Surface-micromachined polysilicon lateral resonant structures were fabricated and used to determine the temperature dependence of the Young's modulus of the polysilicon. This is done by passing a dc current through the beams during resonance testing, resulting in Joule-heating. The temperatures are calibrated by increasing the dc current until the melting point of silicon is attained. The calculated Young's moduli agree well with reported values for single crystal silicon.

In addition, metal films were sputter-deposited onto the polysilicon resonators, and similar experiments performed on the composite devices to determine the temperature dependence of the modulus of the sputtered films. Ni films demonstrate a linear decrease in Young's modulus with temperature. TiNi films demonstrate two distinct modulus values with an intermediate transition region, due to the temperature-induced reversible phase transformation exhibited by TiNi.
Observations of Low Cycle Fatigue of Al Thin Films for Mems Applications
Authors: Cornella G. , Vinci R.P. , Iyer R. Suryanarayanan , Dauskardt R.H. , Bravman J.C.
Published: April 2011

This paper addresses tension-tension (R=0) low cycle fatigue behavior of thin film Al structures released from a substrate. Al beam specimens 2 µm thick, 50 µm wide and 500 µm long (gauge length) were micromachined over a window in a Si substrate. Cyclic load-displacement behavior was investigated using a multiple step test method, in which each specimen was cycled with several blocks of constant maximum displacement amplitude. Load, displacement and temperature were recorded continuously. A load drop and a corresponding stabilized state were observed for each displacement block. Monotonic tension tests to failure were also performed for comparison. Evidence of cyclic creep was observed. SEM images revealed fatigue markings on cyclically loaded specimens but not on monotonically loaded beams.
Silicon Oxynitride Membrane for Chemical Sensor Application
Authors: Astle S. , Scheid E. , Gue A.M. , Guillemet J.P. , Lescouzeres L.
Published: April 2011

Tin oxide gas sensor can detect various gases by using the conductivity changes due to adsorption and desorption processes of gaseous molecules on its surface. The reduction of the power consumption especially for batteries back-up operation, is one of the challenge for SnO2 gas sensors. We propose a new solution using a silicon oxynitride membrane (SiOxNy) to reach this objective. Thin films of SiOxNy with different compositions have been studied. Their composition, residual stress, Young modulus and mechanical strength have been evaluated. As a result, we propose an optimized silicon oxynitride membrane with a low residual stress (-50 MPa), giving above 95% fabrication yield and low power consumption (65 mW / 450°C). A new sensors generation has been successfully fabricated and its mechanical strength and thermal performances have been evaluated. Moreover, an equation is derived, which describes the variation of the Young modulus as a function of the silicon oxynitride composition.
Characterization of Epoxy-Functionalized Silsesquioxanes as Potential Underfill Encapsulants
Authors: Lin E. K. , Snyder C. R. , Mopsik F. I. , Wallace W. E. , Wu W. L. , Zhang C. X. , Laine R. M.
Published: April 2011

In electronics packaging, underfill encapsulants are needed to improve package reliability in flip-chip devices. The underfill generally consists of an epoxy resin highly filled with silica particles and is designed to reduce the stress arising from the difference in the thermal expansion between the solder bumps and the substrate. Currently, concerns about the flow of the silica particles and surface phenomena are arising as electronics packages reduce in size. Newly developed epoxy-functionalized octameric silsesquioxanes provide an intriguing alternative to current formulations. These single-phase inorganic/organic hybrid materials may have properties similar to filled materials without the complications from the rheology of filled materials. The physical properties of the functionalized silsesquioxanes are measured with respect to the critical parameters for underfill materials. Measurements of properties such as the coefficient of thermal expansion and density are performed to evaluate the suitability of these materials as potential underfill encapsulants.
29Si Nmr Study of Hydrolyzed Teos-Rteos (R: Methyl, Ethyl, Phenyl) Systems
Authors: Mendez-Vivar J. , Mendoza-Bandala A. , Gutierrez A. , Cao G.
Published: April 2011

Sols composed of Tetraethoxysilane (TEOS) and RTEOS (R: methyl, ethyl, phenyl) catalyzed with HCl were prepared. The molar ratios TEOS :RTEOS:EtOH:H20:HC1 were (1.0-0.8947):(5.26×10−2-0.1579):0.95:1.0:7×10−4, respectively. The sols were analyzed by 29 Si NMR immediately after mixing the reagents in order to study the hydrolysis and condensation reactions. A predominant self-condensation was observed in the TEOS-ETEOS sol, compared to cross-condensation. This result was opposite to the behaviour of the TEOS-MTEOS and TEOS-PTEOS sols.
Processing of Inorganic-Organic Hybrids From Metal Alkoxides and Phenyltriethoxysilane
Authors: Yoshinaga Ikuko , Yamada Noriko , Katayama Shingo , Claflin B. , Lucovsky G.
Published: April 2011

In the synthesis of inorganic-organic hybrids from metal alkoxides and phenyltriethoxysilane (PTES), metal alkoxides were found to influence the phenyl siloxane network formation. The presence of metal alkoxides in the initial stage of hydrolysis and condensation of PTES promote the formation of phenyl siloxane networks to provide a dense hybrid. However, the presence of metal alkoxides in the stage of hydrolyzed PTES provide a loose structure of phenyl siloxane networks involving a number of silanol groups.
Barrier Properties of Inorganic-Organic Polymers
Authors: Hoffmann M. , Amberg-Schwab S. , Claflin B. , Lucovsky G.
Published: April 2011

The oxygen barrier properties of sol-gel derived inorganic-organic polymer coatings were investigated. By systematic variation of the ratios of the starting compounds and of the curing conditions, materials with different inorganic and organic network densities were obtained. The network densities were characterized using 29Si solid-state NMR and FT-Raman spectroscopy. It was found that the oxygen transmission rates decrease with increasing inorganic as well as organic network density.
Development of Some Promising Approaches for The Toughening of High-Temperature Polymers
Authors: Kumudinie C. , Premachandra J. K. , Mark J. E. , Dang T. D. , Unroe M. R. , Arnold F. E. , Claflin B. , Lucovsky G. , Claflin B. , Lucovsky G.
Published: April 2011

High-temperature poly(arylene ether) and hydroxypolybenzoxazole polymers were toughened using dispersed rubbery phases. This rubbery phase was a hybrid material which was in-situ generated within the polymer matrix using mixtures of partially-hydrolyzable trialkoxy and dialkoxy organosilanes with a fully hydrolyzable tetraalkoxysilane. The resulting materials were characterized with regard to their structures, mechanical properties (modulus, ultimate strength, maximum extensibility, and toughness), thermal properties, optical properties, and tendencies to absorb water. Some of the results are presented here.
Synthesis and Characterization of Surface Protected Nanocrystalline Particles of Titania
Authors: Scolan E. , Sanchez C.
Published: April 2011

Monodisperse non-aggregated nanoparticles of titania are obtained through hydrolysis at 60°C of titanium butoxide in the presence of acetylacetone and para-toluene sulfonic acid. After drying the resulting xerosols can be dispersed without aggregation in water-alcoholic or alcoholic solutions. The characterizations of the nanoparticles have been carried out by using quasi-elastic light scattering (QELS), 13C 1H in solution and X-ray diffraction, TEM, TG-DTA, 13C CP-MAS NMR in the solid state. The mean size of the anatase oxide core can be adjusted in the I to 5 nanometer range by a careful tuning of the synthetic conditions. The anatase particles are surrounded by acetylacetonato ligands, para-toluene sulfonate based species and water.
Structural and Rheological Properties of Zirconia-Pmma Sol-Gel System
Authors: Messaddeq S.H. , Pulcinelli S.H. , Santilli C.V.
Published: April 2011

The influence of polymethylmetacrylate on the rheological and structural characteristics of zirconia sols was analyzed by shear stress versus shear rate measurements, quasi elastic light scattering and infrared spectra. The thickness of coated film determined by profilometry increases linearly with the relative volume of PMMA. The addition of PMMA led to the polycondensation reaction and the formation and growth of zirconia particles.
Templating Nanoporosity in Organosilicates Using Well-Defined Branched Macromolecules
Authors: Hedrick L. , Hawker C. J. , Trollsås M. , Remenar J. , Yoon D. Y. , Miller R. D.
Published: April 2011

A general route to organic-inorganic hybrids with nanophase morphologies has been elaborated with the objective of ultimately templating nanoporosity in organosilicates. A key feature of the hybrids is the preparation of well-defined macromolecules bearing significant functionality to interact with the organosilicates. The use of living polymerization methods allows the synthesis of polymers with accurate control of molecular weight, polydispersity, and chain ends. We have demonstrated living polymerizations from dendritic and hyperbranched initiators to produce controlled branched, star and hyperstar macromolecules. These polymers are used as structure directing agents to organize organosilicates into nanostructures. Once the macromolecular species has templated or organized the inorganic component, the organic polymer can be selectively removed by thermolysis to produce a nanoporous inorganic structure. The size and shape of the pores are similar to those of the initial hybrid morphology. A significant reduction in the dielectric constant of these insulating materials is achieved simply by replacing a portion of the glass matrix with air which has a dielectric constant of 1.
Amorphous Microporous Mixed Oxides of Tailored Polarity and their Application in Membrane Catalyzed Hydrogenation Reactions
Authors: Maier Wilhelm F. , Lange Christian
Published: April 2011

Amorphous microporous mixed oxides (AMM) are materials characterized by a narrow micropore distribution, high porosity, definable surface polarity and homogeneous elemental distribution (absence of domains). They are prepared by a modified Sol-Gel procedure in a single preparation step. Membranes prepared from these materials are selective heterogeneous catalysts, whose microstructural properties can be adjusted to the reaction conditions. Here it is shown, how the surface polarity of the membrane affects the hydrogenation properties.
Failure Analysis Using Voltage Contrast and Ebic
Authors: Rice Larry , Chen Wei
Published: April 2011

As ULSI device critical dimensions continue to shrink to submicron sizes, electron microscopy techniques such as electron beam induced current (EBIC) and voltage contrast are finding more applications towards pinpointing failure sites for subsequent cross sectioning or deprocessing. In addition to the traditional use of EBIC for junction delineation, EBIC has been applied to locate leakage sites in capacitor structures and silicon-on-insulator (SOI) devices as well. Similarly, voltage contrast has been applied to identify single or multiple opens in via chains which consist of thousands of vias. In addition to a brief revisit of the basic principles of EBIC and voltage contrast, focus will be placed on the application of EBIC and voltage contrast in failure analysis of semiconductor devices. Examples of using voltage contrast combined with precision cross section focused ion beam (XFIB) for identifying the failure mechanism of 0.8μm vias will be presented. Also, the use of EBIC for identifying leakage sites in SOI and bipolar devices and subsequent FIB/scanning electron microscopy (SEM) analysis will be presented.
Energy-Filtered Transmission Electron Microscopy of Multilayers in Semiconductors
Authors: Liu C. P. , Boothroyd C. B. , Humphreys C. J.
Published: April 2011

Knowledge about compositional profiles on an atomic scale is important for semiconductor multilayers. In this paper, we attempt to quantify the Ti atomic fraction in a TixAll–xN multilayer and the total As concentrations in As δ-doped layers using energy-filtered imaging. These two materials represent materials where the characteristic energy loss edges are located in widely different energy losses with the L edge of Ti being above 450eV and that of As around 1350eV. The accuracy of the Ti atomic fraction in TixAll–xN is found to be around 10at% for specimens of uniform thickness made by focused ion beam milling, whereas the resolution and As concentration for the As containing δ-layer is found to be dominated by the signal to noise ratio.
Installing and Operating Fegtem's
Authors: Hetherington C. J. D. , Cullis A. G. , Walker S. , Turner J. , Nelson E.C. , O'Keefe M.A.
Published: April 2011

The latest transmission electron microscopes with field emission guns and imaging filters now provide much of the microanalysis and imaging necessary in applications such as ULSI device development. The installation and operating environment of the instruments are critical to their successful operation. Information from two such installations is presented here, one in a purpose built facility and the other in an existing building. Ground vibration, acoustic noise, stray electromagnetic fields, air flow and temperature variation are considered, and the measures implemented to achieve desirable levels of each parameter are discussed. The physical layout of an installation is also shown.
Relaxation of Metamorphic III-V Heterostructures Studied by Digital Processing of HREM Images
Authors: Rocher André , Snoeck Etienne , Goldstein Léon , Jacquet Joël , Fortin Catherine
Published: April 2011

The crystalline structure of metamorphic heterostructures grown by epitaxy has been studied by digital processing of High Resolution Electron Microscopy (HREM) images. Two systems have been investigated: the GaSb/(001)GaAs, known to be fully relaxed by a perfect Lomer dislocation network and the GaAs/(001)InP relaxed by partial and 60° dislocations randomly distributed. A transition zone can be defined between the perfect substrate and the relaxed epitaxial layer: its thickness is less than 20Å in GaSb/GaAs and more than 80Å in GaAs/InP. These results indicate that the misfit dislocations are only one of the elements involved in the relaxation of misfit stress.
HRTEM Study of Structure and Evolution of Highly Mismatched Heteroepitaxial Interface, GaSe/GaAs(100)
Authors: Dai Z.R. , Chegwidden S. R. , Ohuchi F. S.
Published: April 2011

The microstructural evolution of the GaSe/GaAs(100) thin film system was characterized by high resolution transmission electron microscopy (HRTEM). The relationship of crystallographic orientation between the GaSe thin film and the GaAs substrate is [011]GaAs ‖ [1100]GaSe/(100)GaAs ‖ (0001)GaSe, with the dominant polytype for the GaSe thin film being a γ-type which has a 3R-rhombohedral structure with R3m space group. An intermediate layer was observed between the GaAs substrate and the GaSe thin film, with a structure distinct from that of either GaAs or GaSe. The result of a fast Fourier transform (FFT) of the lattice image corresponding to the intermediate layer indicated that its crystal structure was associated with that of α-Ga2Se3. A new vacancy ordered structural model of β-Ga2Se3 was suggested.
Application of Tem on Sub-Half Micron Semiconductor Devices
Authors: Zhang Hong
Published: April 2011

Application of transmission electron microscopy on sub-half micron devices has been illustrated in terms of process evaluation and failure analysis. For process evaluation, it is emphasized that a large number of features need to be examined in order to have reliable conclusions about the processes, while for failure analysis, the goal is to pin-point a single process step causing failure or a single source introducing the particle defect.
Growth And Structure Of Nanometric Iron Oxide Films
Authors: Guiot E. , Gota S. , Henriot M. , Gautier-Soyer M. , Lefebvre S.
Published: April 2011

Nanometric films of iron oxides (Fe3O4, α and γ Fe2O3) of high crystalline order and purity are epitaxially grown on α-A12O3(0001) by atomic oxygen assisted MBE. A complete characterization of the films structure has been performed by in situ LEED and RHEED, and ex situ GIXRD using synchrotron radiation. The films grown at room temperature and post annealed at 400°C and 700°C (po2=10−6 Torr) are respectively metastable γ-Fe2O3 (111) and α-Fe2O3 (0001). For a substrate temperature of 450°C during growth, Fe3O4 (111) is directly obtained. GIXRD shows an in-plane expansion of the films, which decreases with thickness (0.8 and 0.2% for film thickness of 20 and 80 Å, respectively).
Degree of Crystallinity and Strain in B4C and SiC Thin Films as a Function of Processing Conditions
Authors: Hershberger J. , Rek Z. U. , Kustas F. , Yalisove S. M. , Bilello J. C.
Published: April 2011

Amorphous and crystalline content in sputtered B4C and SiC thin films has been analyzed by synchrotron grazing incidence x-ray scattering (GIXS). GIXS provided quantitative information on the average structure while TEM was used to find inhomogeneities such as small volume fraction phases. GIXS results were compared to simulations to determine average particle size or bond length for crystalline or amorphous phases respectively. In this work, we compared results from films deposited with, and without, an RF bias applied to the substrate during deposition. Results indicated that SiC can be described as strained polycrystalline material with particle size of approximately 13 Å for biased samples and 9Å for unbiased samples. Boron carbide deposited without bias was completely crystalline with a particle size of approximately 30 Å, while the data suggested that B4C deposited with bias is amorphous. The scattering from the biased materials was Fourier transformed to yield radial distribution functions (RDF). This provided nearest neighbor distances, and it was demonstrated that the technique can be used to determine full three-dimensional strain tensors in amorphous thin films.
Direct Correlation of Solar Cell Performance with Metal Impurity Distributions in Polycrystalline Silicon using Synchrotron-Based X-ray Analysis
Authors: McHugo S. A. , Thompson A. C. , Lamble G. , MacDowell A. , Celestre R. , Padmore H. , Imaizumi M. , Yamaguchi M. , Perichaud I. , Martinuzzi S. , Werner M. , Rinio M. , Moller H. J. , Sopori B. , Hieslmair H. , Flink C. , Istratov A. , Weber E. R.
Published: April 2011

The work presented here directly measures metal impurity distributions and their chemical state in as-grown and fully processed polycrystalline silicon used for terrestrial-based solar cells. The goal was to determine if a correlation exists between poorly performing regions of solar cells and metal impurity distributions as well as to ascertain the chemical state of the impurities. Synchrotron-based x-ray fluorescence mapping and x-ray absorption spectroscopy, both with a spatial resolution of lμm, were used to measure impurity distributions and chemical state, respectively, in poorly performing regions of polycrystalline silicon. The Light Beam Induced Current method was used to measure minority carrier recombination in the material in order to identify poor performance regions. We have detected iron, chromium, nickel, gold and copper impurity precipitates and we have recognized a direct correlation between impurity distributions and poor performing regions in both as-grown and fully processed material. Furthermore, from x-ray absorption studies, we have initial results, indicating that the Fe in this material is in oxide form, not FeSi2,. These results provide a fundamental understanding into the efficiency-limiting factors of polycrystalline silicon solar cells as well as yielding insight for methods of solar cell improvement.
Amorphous Semiconductor Sample Preparation For Transmission Exafs Measurements
Authors: Ridgway M. C. , Glover C. J. , Tan H. H , Clark A. , Karouta F. , Foran G. J , Lee T. W. , Moon Y. , Yoon E. , Hansen J. L. , Nylandsted-Larsen A. , Clerc C. , Chaumont J.
Published: April 2011

A novel methodology has been developed for the preparation of amorphous semiconductor samples for use in transmission extended x-ray absorption fine structure (EXAFS) measurements. Epitaxial heterostructures were fabricated by metal organic chemical vapour deposition (group III-Vs) or molecular beam epitaxy (group IVs). An epitaxial layer of ∼2 μm thickness was separated from the underlying substrate by selective chemical etching of an intermediate sacrificial layer. Ion implantation was utilised to amorphise the epitaxial layer either before or after selective chemical etching. The resulting samples were both stoichiometric and homogeneous in contrast to those produced by conventional techniques. The fabrication of amorphous GaAs, InP, In0.53Ga0.47As and SixGe1-x samples is described. Furthermore, EXAFS measurements comparing both fluorescence and transmission detection, and crystalline and amorphised GaAs, are shown.
Synchrotron Radiation Hard X-Ray Microprobe by Multilayer Fresnel Zone Plate
Authors: Tamura S. , Ohtani K. , Yasumoto M. , Murali K. , Kamuo N. , Kihara H. , Yoshida K. , Suzuki Y.
Published: April 2011

A hard X-ray microbeam with submicrometer spot size from synchrotron radiation (SR) sources is expected to add a new dimension to various X-ray analysis methods. A Fresnel zone plate (FZP) is one of the promising focusing elements for X-rays. In order to develop high performance multilayer FZP for use in the hard X-ray region, Cu/Al concentric multilayers were fabricated by use of a DC sputtering deposition process. Lower Ar gas pressure or higher rotating speed of a wire substrate has been effective in forming smoother multilayer interfaces. From a focusing test of the Cu/Al FZP (100-zones) by the SR (λ= 0.154nm), microbeams of 1.5 μm φ and 0.8 μm φ have been achieved for the first- and third-order focal beams, respectively.
Temperature-Driven Oxidation Behavior of Pure Iron Surface Investigated by Time-Resolved EXAFS Measurements
Authors: Doh S. J. , Lee J. M. , Noh D. Y. , Je J. H.
Published: April 2011

The surface-front oxidation mechanism of iron was investigated by time-resolved, glancingangle Fe K-edge fluorescence EXAFS measurements at various oxidation temperatures of 200-700 C. The glancing angle was chosen according to the depth of the oxide layer, roughly 1500-2000A. The oxidation behavior under rapid heating(up to 600°C within 10 minutes) was compared with the slowly heated oxidation process using the Quick-EXAFS measurements. In the slowly heated process, Fe3O4 was the dominating phase at a relatively low temperature (300-400 C) initially. However, at a relatively high temperature (above 600°C), the Fe2O3 and FeO crystalline phases are gradually enriched as the successive oxidation process involving intrusive oxygen proceeded. Remarkably under a prolonged heat treatment above 600°C, the stable FeO phase that exists in a deep-lying interface structure and Fe2O3 phase eventually dominates the thick front-surface structure. In a quickly heated process, however, Fe3O4 phase is less dominating, which is contradictory to the commonly accepted oxidation models. The EXAFS results are discussed in conjunction with the x-ray diffraction features under the same heat treatment conditions.
Novel Method for Controlling Nano Thin Coatings on Particulate Materials
Authors: Fitz-Gerald J. , Pennycook S. , Gao H. , Krishnamoorthy V. , Marcinka J. , Glenn W. , Singh R.K.
Published: April 2011

Particulate coatings have wide ranging applications in several new technologies such as flat-panel displays, sintering of advanced ceramics, rechargeable batteries, etc. In this paper, we show the feasibility of the pulsed laser ablation technique to make very thin, uniformly distributed and discrete coatings in particulate systems so that the properties of the core particles can be suitably modified. Presently, laser ablation techniques have been primarily applied to deposit thin films on flat substrate materials. To deposit discontinuous particulate coatings, the laser induced plume from the target comes in contact with an agitated bed of core particles. The pressure and nature of the background gas (inert or active) controls the cluster size of the nano particles in the laser plume. Experiments were conducted for laser deposition of Ag nano particles on Al2O3 and SiO2 core particles by pulsed excimer laser (wavelength = 248 nm and pulse duration = 25 nanosecond) irradiation of a Ag sputtering target The surface coverage and coating uniformities of the film were found to depend on the synthesis parameters (energy density, # laser pulses, gas pressure backfill gas, molecular weight) as well as the residence time of the core particles in the plume regime. The films were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), wavelength dispersive x-ray analysis (WDX), scanning transmission electron microscopy (STEM), and x-ray photoelectron spectroscopy (XPS).